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Appl. Sci., Volume 7, Issue 5 (May 2017)

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Open AccessArticle A Fast Motion Parameters Estimation Method Based on Cross-Correlation of Adjacent Echoes for Wideband LFM Radars
Appl. Sci. 2017, 7(5), 500; doi:10.3390/app7050500
Received: 15 April 2017 / Revised: 7 May 2017 / Accepted: 9 May 2017 / Published: 15 May 2017
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Abstract
In wideband radar systems, the performance of motion parameters estimation can significantly affect the performance of object detection and the quality of inverse synthetic aperture radar (ISAR) imaging. Although the traditional motion parameters estimation methods can reduce the range migration (RM) and Doppler
[...] Read more.
In wideband radar systems, the performance of motion parameters estimation can significantly affect the performance of object detection and the quality of inverse synthetic aperture radar (ISAR) imaging. Although the traditional motion parameters estimation methods can reduce the range migration (RM) and Doppler frequency migration (DFM) effects in ISAR imaging, the computational complexity is high. In this paper, we propose a new fast non-parameter-searching method for motion parameters estimation based on the cross-correlation of adjacent echoes (CCAE) for wideband LFM signals. A cross-correlation operation is carried out for two adjacent echo signals, then the motion parameters can be calculated by estimating the frequency of the correlation result. The proposed CCAE method can be applied directly to the stretching system, which is commonly adopted in wideband radar systems. Simulation results demonstrate that the new method can achieve better estimation performances, with much lower computational cost, compared with existing methods. The experimental results on real radar datasets are also evaluated to verify the effectiveness and superiority of the proposed method compared to the state-of-the-art existing methods. Full article
(This article belongs to the Special Issue Selected Papers from IEEE ICASI 2017)
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Open AccessArticle Swirling Gas Jet-Assisted Laser Trepanning for a Galvanometer-Scanned CO2 Laser
Appl. Sci. 2017, 7(5), 502; doi:10.3390/app7050502
Received: 24 March 2017 / Revised: 30 April 2017 / Accepted: 6 May 2017 / Published: 17 May 2017
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Abstract
Laser-drilled hole arrays are part of an important field that aim to improve efficiency without affecting the quality of laser-drilled holes. In this paper, a swirling gas jet was implemented to assist with laser trepanning for a galvanometer scanned CO2 laser. The
[...] Read more.
Laser-drilled hole arrays are part of an important field that aim to improve efficiency without affecting the quality of laser-drilled holes. In this paper, a swirling gas jet was implemented to assist with laser trepanning for a galvanometer scanned CO2 laser. The proposed swirling gas jet is based on laser trepanning. This swirling gas jet nozzle was composed of four inlet tubes to produce the flow of the vortex. Then, the plume particles were excluded, and spatter on the surface of the workpiece decreased. Thus, this approach can mitigate the problem of overcooling. This study manipulated the appropriate parameter settings, which were simulated by computational fluid dynamics software ANSYS CFX. The proposed swirling gas jet can be used with galvanometer-based scanner systems to keep the laser beam from interference by spatter. In addition, a hollow position of the vortex was achieved by using the four inlet tubes, which resulted in pressure asymmetry in the nozzle and velocity distribution on the surface of the workpiece. The experiment verified that the depth of processing could be enhanced by 110% when trepanning at a scanning speed of 30 mm/s, and that the removal of volume could be enhanced by 71% in trepanning at a diameter of 1 mm by using a swirl assistant compared with a non-assisted condition. Furthermore, the material removal rate of the swirling jet increases when the machining area of the galvanometer-based scanner is larger. Full article
(This article belongs to the Special Issue Selected Papers from the 2016 International Conference on Inventions)
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Open AccessFeature PaperArticle On the Visualization of Gas Metal Arc Welding Plasma and the Relationship Between Arc Length and Voltage
Appl. Sci. 2017, 7(5), 503; doi:10.3390/app7050503
Received: 18 March 2017 / Revised: 25 April 2017 / Accepted: 9 May 2017 / Published: 15 May 2017
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Abstract
In this article, the camera settings for high-speed imaging of the arc, metal transfer, and weld pool in gas metal arc welding (GMAW) are investigated. The results show that by only changing camera exposure times and the selection of narrow bandpass filters, images
[...] Read more.
In this article, the camera settings for high-speed imaging of the arc, metal transfer, and weld pool in gas metal arc welding (GMAW) are investigated. The results show that by only changing camera exposure times and the selection of narrow bandpass filters, images that reveal features of the arc such as the iron vapor-dominated region, metal transfer and weld pool behavior can be produced without the need for external light sources. Using the images acquired, the arc length was measured and the relationship between arc length and arc voltage is discussed. The results show that for low values of current, the measured welding voltage increases with increasing arc length; however, for high current values, the arc voltage increases even though the measured arc length becomes shorter. It is suggested that the increase in arc voltage for high values of welding current is due to the increased evaporation of the wire electrode which decreases the plasma temperature and consequently the arc plasma electrical conductivity. Full article
(This article belongs to the Special Issue Gas Metal Arc Welding)
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Open AccessArticle Advanced Emergency Braking Control Based on a Nonlinear Model Predictive Algorithm for Intelligent Vehicles
Appl. Sci. 2017, 7(5), 504; doi:10.3390/app7050504
Received: 31 December 2016 / Revised: 1 May 2017 / Accepted: 8 May 2017 / Published: 16 May 2017
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Abstract
Focusing on safety, comfort and with an overall aim of the comprehensive improvement of a vision-based intelligent vehicle, a novel Advanced Emergency Braking System (AEBS) is proposed based on Nonlinear Model Predictive Algorithm. Considering the nonlinearities of vehicle dynamics, a vision-based longitudinal vehicle
[...] Read more.
Focusing on safety, comfort and with an overall aim of the comprehensive improvement of a vision-based intelligent vehicle, a novel Advanced Emergency Braking System (AEBS) is proposed based on Nonlinear Model Predictive Algorithm. Considering the nonlinearities of vehicle dynamics, a vision-based longitudinal vehicle dynamics model is established. On account of the nonlinear coupling characteristics of the driver, surroundings, and vehicle itself, a hierarchical control structure is proposed to decouple and coordinate the system. To avoid or reduce the collision risk between the intelligent vehicle and collision objects, a coordinated cost function of tracking safety, comfort, and fuel economy is formulated. Based on the terminal constraints of stable tracking, a multi-objective optimization controller is proposed using the theory of non-linear model predictive control. To quickly and precisely track control target in a finite time, an electronic brake controller for AEBS is designed based on the Nonsingular Fast Terminal Sliding Mode (NFTSM) control theory. To validate the performance and advantages of the proposed algorithm, simulations are implemented. According to the simulation results, the proposed algorithm has better integrated performance in reducing the collision risk and improving the driving comfort and fuel economy of the smart car compared with the existing single AEBS. Full article
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Open AccessArticle An Efficient Compensation Method for Limited-View Photoacoustic Imaging Reconstruction Based on Gerchberg–Papoulis Extrapolation
Appl. Sci. 2017, 7(5), 505; doi:10.3390/app7050505
Received: 29 March 2017 / Revised: 8 May 2017 / Accepted: 9 May 2017 / Published: 17 May 2017
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Abstract
The reconstruction for limited-view scanning, though often the case in practice, has remained a difficult issue for photoacoustic imaging (PAI). The incompleteness of sampling data will cause serious artifacts and fuzziness in those missing views and it will heavily affect the quality of
[...] Read more.
The reconstruction for limited-view scanning, though often the case in practice, has remained a difficult issue for photoacoustic imaging (PAI). The incompleteness of sampling data will cause serious artifacts and fuzziness in those missing views and it will heavily affect the quality of the image. To solve the problem of limited-view PAI, a compensation method based on the Gerchberg–Papoulis (GP) extrapolation is applied into PAI. Based on the known data, missing detectors elements are estimated and the image in the missing views is then compensated using the Fast Fourier Transform (FFT). To accelerate the convergence speed of the algorithm, the total variation (TV)-based iterative algorithm is incorporated into the GP extrapolation-based FFT-utilized compensation method (TV-GPEF). The effective variable splitting and Barzilai–Borwein based method is adopted to solve the optimization problem. Simulations and in vitro experiments for both limited-angle circular scanning and straight-line scanning are conducted to validate the proposed algorithm. Results show that the proposed algorithm can greatly suppress the artifacts caused by the missing views and enhance the edges and the details of the image. It can be indicated that the proposed TV-GPEF algorithm is efficient for limited-view PAI. Full article
(This article belongs to the Special Issue Biomedical Photoacoustic and Thermoacoustic Imaging)
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Open AccessArticle A New Health Assessment Index of Tunnel Lining Based on the Digital Inspection of Surface Cracks
Appl. Sci. 2017, 7(5), 507; doi:10.3390/app7050507
Received: 28 March 2017 / Revised: 26 April 2017 / Accepted: 9 May 2017 / Published: 12 May 2017
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Abstract
The stability assessment of aged tunnel linings are mainly evaluated based on the visual inspection, and the Tunnel-lining Crack Index (TCI) is one of the most widely used tunnel lining health assessment indexes in Japan. However, the intersection and distribution of cracks, which
[...] Read more.
The stability assessment of aged tunnel linings are mainly evaluated based on the visual inspection, and the Tunnel-lining Crack Index (TCI) is one of the most widely used tunnel lining health assessment indexes in Japan. However, the intersection and distribution of cracks, which could influence the stability of tunnel lining greatly, were not considered in TCI. A new method was proposed for the health assessment of tunnel lining, which evaluated the lining states according to the fractal dimension of cracks. Based on the machine vision-based method, the crack image could be extracted efficiently. The fractal dimension of lining cracks in one span could be obtained in a few minutes. A series of comparative tests and field tests were conducted to evaluate the validity of this new method. The comparative tests confirmed that fractal dimension was able to characterize the density, width, and distribution of cracks. The intersection of cracks, which would increase the risk of lining collapse, could also increase the fractal dimension. The fractal dimensions of tunnel lining cracks were obtained according to the digital inspection test of Hidake Tunnel in Japan for all the 65 spans. Moreover, the TCI was obtained through statistical methods. The correlation between fractal dimension and TCI of tunnel lining was studied. The significance of the new evaluation index is that it can identify the unusual spans of tunnel lining and provide a basis for further internal testing. As a complement to the conventional visual inspection method, the fractal dimension of the cracks is a promising health assessment index. Full article
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Open AccessArticle Immobilized TiO2-Polyethylene Glycol: Effects of Aeration and pH of Methylene Blue Dye
Appl. Sci. 2017, 7(5), 508; doi:10.3390/app7050508
Received: 24 February 2017 / Revised: 2 May 2017 / Accepted: 4 May 2017 / Published: 12 May 2017
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Abstract
Immobilized TiO2 and immobilized TiO2-polyethylene glycol (TiO2/PEG) films have been prepared via brush coating method. The formulation of immobilized TiO2 film was prepared by mixing distilled water with P25, while the formulation containing P25 combined with 8%
[...] Read more.
Immobilized TiO2 and immobilized TiO2-polyethylene glycol (TiO2/PEG) films have been prepared via brush coating method. The formulation of immobilized TiO2 film was prepared by mixing distilled water with P25, while the formulation containing P25 combined with 8% PEG in distilled water was used in preparing immobilized TiO2/PEG. A double sided adhesive tape (DSAT) was stacked onto a glass surface prior to coating with the formulations and annealing by a thermal treatment at 100 °C for 15 min. The photocatalytic activity of immobilized photocatalysts was evaluated under photodegradation of methylene blue (MB). It was observed that immobilized TiO2/PEG has showed a higher rate of photocatalytic activity compared to immobilize TiO2. The X-ray photoelectron spectroscopy and Fourier transform infrared (FT-IR) spectra of immobilized TiO2/PEG sample proved that the existence of C=O led to enhanced photoactivity efficiency under normal light and visible light irradiations. The photocatalytic activity performance of immobilized TiO2/PEG was the highest at 75 mL·min−1 aeration rate and pH 11 of MB dye. The correlation between of all these parameters was investigated in this study. Full article
(This article belongs to the Section Chemistry)
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Open AccessArticle Facile Synthesis of α-MnO2 with a 3D Staghorn Coral-like Micro-Structure Assembled by Nano-Rods and Its Application in Electrochemical Supercapacitors
Appl. Sci. 2017, 7(5), 511; doi:10.3390/app7050511
Received: 22 March 2017 / Revised: 20 April 2017 / Accepted: 11 May 2017 / Published: 13 May 2017
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Abstract
Abstract: Manganese oxides with an alpha crystal structure are synthesized via combined solid-state reaction and wet chemical processing, which is a simple and inexpensive synthetic route easy for mass production. The effects of the synthetic reaction duration and the temperature of acid
[...] Read more.
Abstract: Manganese oxides with an alpha crystal structure are synthesized via combined solid-state reaction and wet chemical processing, which is a simple and inexpensive synthetic route easy for mass production. The effects of the synthetic reaction duration and the temperature of acid treatments on crystal structure, morphology, and electrochemical capacitive properties of α-MnO2 are discussed. It is evidenced that the samples treated in acid for a longer time at 25 °C display the uniform nanorods that are aggregated to form micro-buildings with fine features on the surface of rods. This microstructure possesses large surface areas and more active sites that are easy to access electrochemically, leading to a better electrochemical capacitive performance. We expected that these results would provide the practical information for shape- and morphology-controlled synthesis for nanostructured functional materials in supercapacitor applications. Full article
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Open AccessArticle Development of Green Geopolymer Using Agricultural and Industrial Waste Materials with High Water Absorbency
Appl. Sci. 2017, 7(5), 514; doi:10.3390/app7050514
Received: 21 February 2017 / Revised: 17 April 2017 / Accepted: 18 April 2017 / Published: 16 May 2017
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Abstract
Geopolymer is a promising porous material that can be used for evaporative cooling applications. Developing a greener geopolymer using agricultural and industrial wastes is a promising research area. In this study, we utilize rice husk (RH), rice husk ash (RHA), metakaolin (MK), ground
[...] Read more.
Geopolymer is a promising porous material that can be used for evaporative cooling applications. Developing a greener geopolymer using agricultural and industrial wastes is a promising research area. In this study, we utilize rice husk (RH), rice husk ash (RHA), metakaolin (MK), ground granulated blast furnace slag (GGBS), and palm oil fuel ash (POFA) to prepare geopolymer pastes, with alkali liquid as an activator. Many geopolymer samples have been prepared as per the Design of Experimental software (DOE), and its corresponding response surface mode and central composite design and later they were characterized. The samples were cured in an oven for 2 h at 80 °C, and thereafter stored at room temperature (~25–30 °C) prior to being tested for its water absorption and compressive strength. The effect of the different composition of precursors on water absorption, density, porosity, and the compressive strength of the prepared geopolymers have been investigated. The results showed that the compressive strength of geopolymers is directly proportional to the ratio of the alkali liquid. Post-optimization, the best geopolymer paste mixture was confirmed to contain 10% of RH, 15% RHA, 35% MK, 10% POFA and 30% of GGBS, with 72% desirability for maximum water absorption (~38%) and compressive strength (4.9 MPa). The results confirmed its applicability for evaporative cooling. Full article
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Open AccessFeature PaperArticle Detection of Pitting in Gears Using a Deep Sparse Autoencoder
Appl. Sci. 2017, 7(5), 515; doi:10.3390/app7050515
Received: 15 March 2017 / Revised: 5 May 2017 / Accepted: 12 May 2017 / Published: 16 May 2017
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Abstract
In this paper; a new method for gear pitting fault detection is presented. The presented method is developed based on a deep sparse autoencoder. The method integrates dictionary learning in sparse coding into a stacked autoencoder network. Sparse coding with dictionary learning is
[...] Read more.
In this paper; a new method for gear pitting fault detection is presented. The presented method is developed based on a deep sparse autoencoder. The method integrates dictionary learning in sparse coding into a stacked autoencoder network. Sparse coding with dictionary learning is viewed as an adaptive feature extraction method for machinery fault diagnosis. An autoencoder is an unsupervised machine learning technique. A stacked autoencoder network with multiple hidden layers is considered to be a deep learning network. The presented method uses a stacked autoencoder network to perform the dictionary learning in sparse coding and extract features from raw vibration data automatically. These features are then used to perform gear pitting fault detection. The presented method is validated with vibration data collected from gear tests with pitting faults in a gearbox test rig and compared with an existing deep learning-based approach. Full article
(This article belongs to the Special Issue Deep Learning Based Machine Fault Diagnosis and Prognosis)
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Open AccessArticle Fire Damage Assessment of Reinforced Concrete Structures Using Fuzzy Theory
Appl. Sci. 2017, 7(5), 518; doi:10.3390/app7050518
Received: 30 March 2017 / Revised: 4 May 2017 / Accepted: 9 May 2017 / Published: 16 May 2017
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Abstract
Once a reinforced concrete (RC) structure is damaged by fire, the fire damage assessment should proceed to take appropriate post-fire actions, including the decision-making of whether it can be repaired for reuse or not. Since the assessment results of current fire damage diagnosis
[...] Read more.
Once a reinforced concrete (RC) structure is damaged by fire, the fire damage assessment should proceed to take appropriate post-fire actions, including the decision-making of whether it can be repaired for reuse or not. Since the assessment results of current fire damage diagnosis methods, however, highly depend on the subjective judgment of inspectors, it is hard to ensure their objectiveness and reliability. This study, therefore, aims to develop a new fire damage diagnosis system (FDDS) based on fuzzy theory that can provide objective and comprehensive evaluation results by considering all of the damage conditions observed from the inspection on RC structural members exposed to fire. In addition, the FDDS was applied to an actual fire-damaged case reported by the Architectural Institute of Japan (AIJ, 2009), and it appears that the proposed method provides a reasonable estimation on the fire damage grade of the fire-damaged RC members. Full article
(This article belongs to the Special Issue Structural Health Monitoring (SHM) of Civil Structures)
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Open AccessArticle Probing Dynamics in Colloidal Crystals with Pump-Probe Experiments at LCLS: Methodology and Analysis
Appl. Sci. 2017, 7(5), 519; doi:10.3390/app7050519
Received: 4 April 2017 / Revised: 4 May 2017 / Accepted: 8 May 2017 / Published: 19 May 2017
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Abstract
We present results of the studies of dynamics in colloidal crystals performed by pump-probe experiments using an X-ray free-electron laser (XFEL). Colloidal crystals were pumped with an infrared laser at a wavelength of 800 nm with varying power and probed by XFEL pulses
[...] Read more.
We present results of the studies of dynamics in colloidal crystals performed by pump-probe experiments using an X-ray free-electron laser (XFEL). Colloidal crystals were pumped with an infrared laser at a wavelength of 800 nm with varying power and probed by XFEL pulses at an energy of 8 keV with a time delay up to 1000 ps. The positions of the Bragg peaks, and their radial and azimuthal widths were analyzed as a function of the time delay. The spectral analysis of the data did not reveal significant enhancement of frequencies expected in this experiment. This allowed us to conclude that the amplitude of vibrational modes excited in colloidal crystals was less than the systematic error caused by the noise level. Full article
(This article belongs to the Special Issue X-Ray Free-Electron Laser)
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Open AccessArticle Joint Resource Allocation in Secure OFDMA-Based Networks Taking a Base Station as a Two-Way Relay
Appl. Sci. 2017, 7(5), 520; doi:10.3390/app7050520
Received: 21 March 2017 / Revised: 28 April 2017 / Accepted: 12 May 2017 / Published: 21 May 2017
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Abstract
Due to the broadcast nature of wireless media, all nodes in the coverage of a transmitter are capable of capturing its signals, thus wireless transmission is sensitive to wiretapping. Several existing schemes place an emphasis on secrecy rate improvement, under the protocols of
[...] Read more.
Due to the broadcast nature of wireless media, all nodes in the coverage of a transmitter are capable of capturing its signals, thus wireless transmission is sensitive to wiretapping. Several existing schemes place an emphasis on secrecy rate improvement, under the protocols of amplify-and-forward or decode-and-forward, when there are only relay users in the network. We set up a novel communication model in which normal and two-way relay users coexist in the same cell, taking the base station as a relay. Our objective is to maximize the total secrecy rate, taking subcarrier pairing, subcarrier assignment and power allocation into account, when there is one eavesdropper in one cell of the cellular network. Although this problem is very intricate, we reformulate it as a convex optimization problem by means of Lagrange duality. In order to reduce the computational complexity, equal power allocation is proposed. Lastly, the experimental results show the proposed resource allocation scheme can obtain a higher secrecy rate than traditional schemes. Full article
(This article belongs to the Section Computer Science and Electrical Engineering)
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Open AccessArticle Intensified Pozzolanic Reaction on Kaolinite Clay-Based Mortar
Appl. Sci. 2017, 7(5), 522; doi:10.3390/app7050522
Received: 20 February 2017 / Revised: 12 May 2017 / Accepted: 16 May 2017 / Published: 18 May 2017
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Abstract
The objective of this study is to develop and characterize kaolinite clay-based structural mortar. The pozzolanic reaction induced from two mineral additives, i.e., calcium hydroxide and silica fume (SF), and the physical filling effect from SF, were found to be effective on the
[...] Read more.
The objective of this study is to develop and characterize kaolinite clay-based structural mortar. The pozzolanic reaction induced from two mineral additives, i.e., calcium hydroxide and silica fume (SF), and the physical filling effect from SF, were found to be effective on the enhancement of structural properties. Based on several preliminary experiments, 7:3 ratio of kaolinite clay/calcium hydroxide was selected as a basic binder. Then, the amount of SF was chosen as 0%, 7.5%, and 15% of the total binder to consider both the chemical and physical effects. The results showed that compressive strengths of samples with 7.5% and 15% SF are significantly increased by approximately 200% and 350%, respectively, at 28 days compared to the sample without SF. However, based on the results of the sample with 15% SF, it is found that excessive addition of SF causes long-term strength loss, possibly owing to micro cracks. With the careful consideration on this long-term behavior, this suggested new mix design can be further extended to develop sustainable structural materials using natural minerals or waste materials with nonbinding properties. Full article
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Open AccessArticle Combined Operation of Electrical Loads, Air Conditioning and Photovoltaic-Battery Systems in Smart Houses
Appl. Sci. 2017, 7(5), 525; doi:10.3390/app7050525
Received: 11 April 2017 / Revised: 9 May 2017 / Accepted: 11 May 2017 / Published: 18 May 2017
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Abstract
In this paper, a novel Energy Management System (EMS) is proposed for a hybrid energy system with photovoltaic (PV) and energy storage system for a smart house. The EMS is designed to control the shiftable loads, the air conditioning and the electric storage
[...] Read more.
In this paper, a novel Energy Management System (EMS) is proposed for a hybrid energy system with photovoltaic (PV) and energy storage system for a smart house. The EMS is designed to control the shiftable loads, the air conditioning and the electric storage system. The aim is to reduce the electrical energy consumption cost without compromising the end-user comfort. Monte Carlo Simulation (MCS) is used to estimate the optimal size of the hybrid system considering energy saving and investment costs. Simulations results confirm the effectiveness of the proposed EMS in decreasing the electrical energy consumption and costs. The proposed method for the sizing of the hybrid system is also able to select the best size of the PV-battery system in smart houses. Full article
(This article belongs to the Special Issue Smart Home and Energy Management Systems)
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Open AccessArticle Application of Pulsed Laser-TIG Hybrid Heat Source in Root Welding of Thick Plate Titanium Alloys
Appl. Sci. 2017, 7(5), 527; doi:10.3390/app7050527
Received: 17 March 2017 / Revised: 23 April 2017 / Accepted: 26 April 2017 / Published: 18 May 2017
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Abstract
Laser-TIG (tungsten inert gas) hybrid welding process is applied to produce stable back beads in the first layer during one-side multilayer welding. To explain why stable back beads can be formed, a comparison is conducted between single TIG and laser-TIG hybrid welding. Results
[...] Read more.
Laser-TIG (tungsten inert gas) hybrid welding process is applied to produce stable back beads in the first layer during one-side multilayer welding. To explain why stable back beads can be formed, a comparison is conducted between single TIG and laser-TIG hybrid welding. Results indicate that during laser action the arc column is enhanced and deflected to the keyhole, which changes the spatial distribution of plasma by strong attraction. The keyhole plasma possesses extreme electric conductivity. After laser action, the enhanced arc is restituted, the low energy density arc acts on the molten pool, and the bottom of the molten pool is solidified to prevent its collapse. The heat and force are redistributed over the top of molten pool under the alternative action of the enhanced arc and original arc. In this case the thermal distribution and mechanical situation in the molten pool must be more balanced and reasonable, and the back bead appearance is continuous, stable and uniform. This process gives high quality and efficient root welding of the thick plate. Full article
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Open AccessArticle Artwork Identification for 360-Degree Panoramic Images Using Polyhedron-Based Rectilinear Projection and Keypoint Shapes
Appl. Sci. 2017, 7(5), 528; doi:10.3390/app7050528
Received: 24 February 2017 / Revised: 29 April 2017 / Accepted: 17 May 2017 / Published: 19 May 2017
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Abstract
With the increased development of 360-degree production technologies, artwork has recently been photographed without authorization. To prevent this infringement, we propose an artwork identification methodology for 360-degree images. We transform the 360-degree image into a three-dimensional sphere and wrap it with a polyhedron.
[...] Read more.
With the increased development of 360-degree production technologies, artwork has recently been photographed without authorization. To prevent this infringement, we propose an artwork identification methodology for 360-degree images. We transform the 360-degree image into a three-dimensional sphere and wrap it with a polyhedron. On the sphere, several points are located on the polyhedron to determine the width, height, and direction of the rectilinear projection. The 360-degree image is divided and transformed into several rectilinear projected images to reduce the adverse effects from the distorted panoramic image. We also propose a method for improving the identification precision of artwork located at a highly distorted position using the difference of keypoint shapes. After applying the proposed methods, identification precision is increased by 45% for artwork that is displayed on a 79-inch monitor in a seriously distorted position with features that were generated by scale-invariant feature transformations. Full article
(This article belongs to the Special Issue Holography and 3D Imaging: Tomorrows Ultimate Experience)
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Open AccessArticle X-ray Pump–Probe Investigation of Charge and Dissociation Dynamics in Methyl Iodine Molecule
Appl. Sci. 2017, 7(5), 529; doi:10.3390/app7050529
Received: 26 April 2017 / Revised: 15 May 2017 / Accepted: 15 May 2017 / Published: 19 May 2017
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Abstract
Molecular dynamics is of fundamental interest in natural science research. The capability of investigating molecular dynamics is one of the various motivations for ultrafast optics. We present our investigation of photoionization and nuclear dynamics in methyl iodine (CH3I) molecule with an
[...] Read more.
Molecular dynamics is of fundamental interest in natural science research. The capability of investigating molecular dynamics is one of the various motivations for ultrafast optics. We present our investigation of photoionization and nuclear dynamics in methyl iodine (CH3I) molecule with an X-ray pump X-ray probe scheme. The pump–probe experiment was realized with a two-mirror X-ray split and delay apparatus. Time-of-flight mass spectra at various pump–probe delay times were recorded to obtain the time profile for the creation of high charge states via sequential ionization and for molecular dissociation. We observed high charge states of atomic iodine up to 29+, and visualized the evolution of creating these high atomic ion charge states, including their population suppression and enhancement as the arrival time of the second X-ray pulse was varied. We also show the evolution of the kinetics of the high charge states upon the timing of their creation during the ionization-dissociation coupled dynamics. We demonstrate the implementation of X-ray pump–probe methodology for investigating X-ray induced molecular dynamics with femtosecond temporal resolution. The results indicate the footprints of ionization that lead to high charge states, probing the long-range potential curves of the high charge states. Full article
(This article belongs to the Special Issue X-Ray Free-Electron Laser)
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Open AccessArticle Innovation of New Occlusion Devices for Cancers
Appl. Sci. 2017, 7(5), 530; doi:10.3390/app7050530
Received: 24 March 2017 / Revised: 27 April 2017 / Accepted: 9 May 2017 / Published: 19 May 2017
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Abstract
Liver cancer, a life-threatening disease, can be cured if found early. A common treatment for liver tumors that cannot be removed by surgery is hepatic artery embolization. It involves injecting small beads to block the blood flow towards cancer cells. In this paper,
[...] Read more.
Liver cancer, a life-threatening disease, can be cured if found early. A common treatment for liver tumors that cannot be removed by surgery is hepatic artery embolization. It involves injecting small beads to block the blood flow towards cancer cells. In this paper, we propose the world’s first nitinol spherical occlusion device, which can be deployed in the upstream of an artery to reduce the blood flow to the downstream cancer cells. Finite element models were developed to predict the device’s mechanical integrity during manufacturing and deployment. Computational fluid dynamics were applied to simulate the device’s clinical occlusion performance. Simulation results suggested that devices with a metal density of 14–27% would reduce the average blood flow rate by 30–50%. A conceptual prototype was first cut by pulsed-fiber optic laser, and a series of expansions and heat treatments were used to shape the device to its final geometry. Flow experiments were conducted for proof of concept, and results showed that the spherical occlusion device successfully reduced the flow as designed. The occlusion device with the metal density of 27% was able to reduce 44% of flow, which agreed well with the simulation results. Full article
(This article belongs to the Special Issue Selected Papers from the 2016 International Conference on Inventions)
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Open AccessArticle Improved Ultrasonic Computerized Tomography Method for STS (Steel Tube Slab) Structure Based on Compressive Sampling Algorithm
Appl. Sci. 2017, 7(5), 432; doi:10.3390/app7050432
Received: 9 March 2017 / Revised: 20 April 2017 / Accepted: 20 April 2017 / Published: 26 April 2017
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Abstract
This paper developed a new ultrasonic computerized tomography (CT) method for damage inspections of a steel tube slab (STS) structure based on compressive sampling (CS). CS is a mathematic theory providing an approximate recovery for a sparse signal with minimal reconstruction error from
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This paper developed a new ultrasonic computerized tomography (CT) method for damage inspections of a steel tube slab (STS) structure based on compressive sampling (CS). CS is a mathematic theory providing an approximate recovery for a sparse signal with minimal reconstruction error from under-sampled measurements. Considering the natural sparsity of the damage, CS algorithm is employed to image the defect in the concrete-filled steel tube of Shenyang Metro line 9 for reducing the work time. Thus, in the measurement stage, far fewer ultrasonic measurement paths were selected from the dense net of conventional ultrasonic CT techniques to capture the underlying damage information. Then, in the imaging stage, 1-norm minimization algorithm of CS theory is selected to recover the internal damage via fusing measurement data and solving optimization problem. The functionality of the proposed method is validated by three numerical concrete tube models with various conditions. Additionally, both the conventional ultrasonic CT technique and the proposed one are employed for ultrasonic inspection of the STS structure in Shenyang Metro line 9. Both the numerical and experimental results indicate that the proposed ultrasonic CT improved by CS has a great potential for damage detection, which provides an alternative accurate and effective way for non-destructive testing/evaluation (NDT/E). Full article
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Open AccessFeature PaperArticle Infrared Spectroscopy for Studying Structure and Aging Effects in Rhamnolipid Biosurfactants
Appl. Sci. 2017, 7(5), 533; doi:10.3390/app7050533
Received: 23 April 2017 / Revised: 18 May 2017 / Accepted: 19 May 2017 / Published: 22 May 2017
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Abstract
Biosurfactants are produced by microorganisms and represent amphiphilic compounds with polar and non-polar moieties; hence they can be used to stabilize emulsions, e.g., in the cosmetic and food sectors. Their structure and its changes when exposed to light and elevated temperature are yet
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Biosurfactants are produced by microorganisms and represent amphiphilic compounds with polar and non-polar moieties; hence they can be used to stabilize emulsions, e.g., in the cosmetic and food sectors. Their structure and its changes when exposed to light and elevated temperature are yet to be fully understood. In this study, we demonstrate that attenuated total reflection infrared (ATR-IR) spectroscopy is a useful tool for the analysis of biosurfactants, using rhamnolipids produced by fermentation as an example. A key feature is that the analytical method does not require sample preparation despite the high viscosity of the purified natural product. Full article
(This article belongs to the Special Issue Optics and Spectroscopy for Fluid Characterization)
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Open AccessFeature PaperArticle Formation of Boundary Film from Ionic Liquids Enhanced by Additives
Appl. Sci. 2017, 7(5), 433; doi:10.3390/app7050433
Received: 5 March 2017 / Revised: 12 April 2017 / Accepted: 20 April 2017 / Published: 26 April 2017
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Abstract
Room temperature ionic liquids (RTILs) have several properties that make them interesting candidates as base fluids for extreme conditions. However, a lack of compatibility with tribo-improving additives combined with an often overly aggressive nature is limiting their use as base fluids. To overcome
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Room temperature ionic liquids (RTILs) have several properties that make them interesting candidates as base fluids for extreme conditions. However, a lack of compatibility with tribo-improving additives combined with an often overly aggressive nature is limiting their use as base fluids. To overcome these drawbacks, hydrocarbon-imitating RTIL base fluids have recently been developed. In this study, the effects of several common additives in the novel RTIL (P-SiSO) were examined by laboratory tribotesting. A reciprocating steel-steel ball-on-flat setup in an air atmosphere was used, where the lubricant performance was evaluated over a range of loads and temperatures. Surface analyses after testing were carried out using optical profilometry, scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS). Neat P-SiSO displayed high performance in the tribotests. At an elevated load and temperature, a shift in lubrication mode was observed with an accompanying increase in friction and wear. Surface analysis revealed a boundary film rich in Si and O in the primary lubrication mode, while P was detected after a shift to the secondary lubrication mode. An amine additive was effective in reducing wear and friction under harsh conditions. The amine was determined to increase formation of the protective Si–O film, presumably by enhancing the anion activity. Full article
(This article belongs to the Special Issue Lubricant Additives)
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Open AccessArticle A Resonantly Pumped Single-Longitudinal Mode Ho:Sc2SiO5 Laser with Two Fabry–Perot Etalons
Appl. Sci. 2017, 7(5), 434; doi:10.3390/app7050434
Received: 5 February 2017 / Revised: 7 April 2017 / Accepted: 18 April 2017 / Published: 25 April 2017
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Abstract
We present a single-longitudinal-mode Ho:Sc2SiO5 (Ho:SSO) laser pumped by a Tm:YAP laser for the first time. Two intra-cavity Fabry–Perot etalons were used to realize the single-longitudinal mode of operation. The maximum output power of 590 mW at 2111.91 nm was
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We present a single-longitudinal-mode Ho:Sc2SiO5 (Ho:SSO) laser pumped by a Tm:YAP laser for the first time. Two intra-cavity Fabry–Perot etalons were used to realize the single-longitudinal mode of operation. The maximum output power of 590 mW at 2111.91 nm was obtained with the incident power of 10.2 W, when the slope efficiency was 9.7% and the optical conversion efficiency was 5.8%. The M2 factor of the single longitudinal mode Ho:SSO laser was measured to be 1.17. Full article
(This article belongs to the Section Optics and Lasers)
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Open AccessArticle A TSVD-Based Method for Forest Height Inversion from Single-Baseline PolInSAR Data
Appl. Sci. 2017, 7(5), 435; doi:10.3390/app7050435
Received: 28 January 2017 / Revised: 20 April 2017 / Accepted: 21 April 2017 / Published: 25 April 2017
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Abstract
The random volume over ground (RVoG) model associates vegetation vertical structure parameters with multiple complex interferometric coherence observables. In this paper, on the basis of the RVoG model, a truncated singular value decomposition (TSVD)-based method is proposed for forest height inversion from single-baseline
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The random volume over ground (RVoG) model associates vegetation vertical structure parameters with multiple complex interferometric coherence observables. In this paper, on the basis of the RVoG model, a truncated singular value decomposition (TSVD)-based method is proposed for forest height inversion from single-baseline polarimetric interferometric synthetic aperture radar (PolInSAR) data. In addition, in order to improve the applicability of TSVD for this issue, a new truncation method is proposed for TSVD. Differing from the traditional three-stage method, the TSVD-based inversion method estimates the pure volume coherence directly from the complex interferometric coherence, and estimates the forest height from the estimated pure volume coherence with a least-squares method. As a result, the TSVD-based method can adjust the contributions of the polarizations in the estimation of the model parameters and avoid the null ground-to-volume ratio assumption. The simulated experiments undertaken in this study confirmed that the TSVD-based method performs better than the three-stage method in forest height inversion. The TSVD-based method was also applied to E-SAR P-band data acquired over the Krycklan Catchment, Sweden, which is covered with mixed pine forest. The results showed that the TSVD-based method improves the root-mean-square error by 48.6% when compared to the three-stage method, which further validates the performance of the TSVD-based method. Full article
(This article belongs to the Special Issue Polarimetric SAR Techniques and Applications)
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Open AccessArticle Improved Image Denoising Algorithm Based on Superpixel Clustering and Sparse Representation
Appl. Sci. 2017, 7(5), 436; doi:10.3390/app7050436
Received: 21 February 2017 / Revised: 14 April 2017 / Accepted: 21 April 2017 / Published: 26 April 2017
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Abstract
Good learning image priors from the noise-corrupted images or clean natural images are very important in preserving the local edge and texture regions while denoising images. This paper presents a novel image denoising algorithm based on superpixel clustering and sparse representation, named as
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Good learning image priors from the noise-corrupted images or clean natural images are very important in preserving the local edge and texture regions while denoising images. This paper presents a novel image denoising algorithm based on superpixel clustering and sparse representation, named as the superpixel clustering and sparse representation (SC-SR) algorithm. In contrast to most existing methods, the proposed algorithm further learns image nonlocal self-similarity (NSS) prior with mid-level visual cues via superpixel clustering by the sparse subspace clustering method. As the superpixel edges adhered to the image edges and reflected the image structural features, structural and edge priors were considered for a better exploration of the NSS prior. Next, each similar superpixel region was regarded as a searching window to seek the first L most similar patches to each local patch within it. For each similar superpixel region, a specific dictionary was learned to obtain the initial sparse coefficient of each patch. Moreover, to promote the effectiveness of the sparse coefficient for each patch, a weighted sparse coding model was constructed under a constraint of weighted average sparse coefficient of the first L most similar patches. Experimental results demonstrated that the proposed algorithm achieved very competitive denoising performance, especially in image edges and fine structure preservation in comparison with state-of-the-art denoising algorithms. Full article
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Open AccessArticle Hybrid Electric Vehicle Performance with Organic Rankine Cycle Waste Heat Recovery System
Appl. Sci. 2017, 7(5), 437; doi:10.3390/app7050437
Received: 6 February 2017 / Revised: 16 April 2017 / Accepted: 20 April 2017 / Published: 26 April 2017
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Abstract
This study examines the implementation of a waste heat recovery system on an electric hybrid vehicle. The selected waste heat recovery method operates on organic Rankine cycle principles to target the overall fuel consumption improvement of the internal combustion engine element of a
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This study examines the implementation of a waste heat recovery system on an electric hybrid vehicle. The selected waste heat recovery method operates on organic Rankine cycle principles to target the overall fuel consumption improvement of the internal combustion engine element of a hybrid powertrain. This study examines the operational principle of hybrid electric vehicles, in which the internal combustion engines operates with an electric powertrain layout (electric motors/generators and batteries) as an integral part of the powertrain architecture. A critical evaluation of the performance of the integrated powertrain is presented in this paper whereby vehicle performance is presented through three different driving cycle tests, offering a clear assessment of how this advanced powertrain configuration would benefit under several different, but relevant, driving scenarios. The driving cycles tested highlighted areas where the driver could exploit the full potential of the hybrid powertrain operational modes in order to further reduce fuel consumption. Full article
(This article belongs to the Special Issue Internal Combustion Engines (ICE) for Ground Transport)
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Open AccessArticle Novel Genetic Algorithm-Based Energy Management in a Factory Power System Considering Uncertain Photovoltaic Energies
Appl. Sci. 2017, 7(5), 438; doi:10.3390/app7050438
Received: 25 February 2017 / Revised: 17 April 2017 / Accepted: 21 April 2017 / Published: 26 April 2017
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Abstract
The demand response and accommodation of different renewable energy resources are essential factors in a modern smart microgrid. This paper investigates the energy management related to the short-term (24 h) unit commitment and demand response in a factory power system with uncertain photovoltaic
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The demand response and accommodation of different renewable energy resources are essential factors in a modern smart microgrid. This paper investigates the energy management related to the short-term (24 h) unit commitment and demand response in a factory power system with uncertain photovoltaic power generation. Elastic loads may be activated subject to their operation constraints in a manner determined by the electricity prices while inelastic loads are inflexibly fixed in each hour. The generation of power from photovoltaic arrays is modeled as a Gaussian distribution owing to its uncertainty. This problem is formulated as a stochastic mixed-integer optimization problem and solved using two levels of algorithms: the master level determines the optimal states of the units (e.g., micro-turbine generators) and elastic loads; and the slave level concerns optimal real power scheduling and power purchase/sale from/to the utility, subject to system operating constraints. This paper proposes two novel encoding schemes used in genetic algorithms on the master level; the point estimate method, incorporating the interior point algorithm, is used on the slave level. Various scenarios in a 30-bus factory power system are studied to reveal the applicability of the proposed method. Full article
(This article belongs to the Special Issue Computational Intelligence in Photovoltaic Systems)
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Open AccessArticle A New Robust Tracking Control Design for Turbofan Engines: H/Leitmann Approach
Appl. Sci. 2017, 7(5), 439; doi:10.3390/app7050439
Received: 28 December 2016 / Revised: 10 April 2017 / Accepted: 19 April 2017 / Published: 27 April 2017
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Abstract
In this paper, a H/Leitmann approach to the robust tracking control design is presented for an uncertain dynamic system. This new method is developed in the following two steps. Firstly, a tracking dynamic system with simultaneous consideration of parameter uncertainty and
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In this paper, a H /Leitmann approach to the robust tracking control design is presented for an uncertain dynamic system. This new method is developed in the following two steps. Firstly, a tracking dynamic system with simultaneous consideration of parameter uncertainty and noise is modeled based on a linear system and a reference model. Accordingly, a “nominal system” from the tracking system is defined and controlled by a H control to obtain the asymptotical stability and noise resistance. Secondly, by making use of a Lyapunov function and the norm boundedness, a new robust control with the “Leitmann approach” is designed to cope with the uncertainty. The two controls collaborate with each other to achieve “uniform tracking boundedness” and “uniform ultimate tracking boundedness”. The new approach is then applied to an aircraft turbofan control design, and the numerical simulation results show the prescribed performances of the closed-loop system and the advantage of the developed approach. Full article
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Open AccessArticle Improvement of Interfacial Adhesion of Incorporated Halloysite-Nanotubes in Fiber-Reinforced Epoxy-Based Composites
Appl. Sci. 2017, 7(5), 441; doi:10.3390/app7050441
Received: 20 February 2017 / Revised: 10 April 2017 / Accepted: 22 April 2017 / Published: 27 April 2017
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Abstract
The heart of composite materials depends on the characteristics of their interface. The physical properties of composite materials are often described by the rule of mixtures, representing the average physical properties of the reinforcement and the matrix resin. However, in practical applications there
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The heart of composite materials depends on the characteristics of their interface. The physical properties of composite materials are often described by the rule of mixtures, representing the average physical properties of the reinforcement and the matrix resin. However, in practical applications there are situations which arise where the rule of mixtures is not followed. This is because when an external energy applied to the composite material is transferred from the matrix to the reinforcement, the final physical properties are affected by the interface between them rather than the intrinsic properties of both the reinforcement and the matrix. The internal bonding strength of the interface of these composites can be enhanced by enhancing the bonding strength by adding a small amount of material at the interface. In this study, the mechanical properties were evaluated by producing a carbon fiber-reinforced composite material and improved by dispersing halloysite nanotubes (HNTs) and the epoxy resin using an ultrasonic homogenizer. The interfacial bond strength increased with the addition of HNT. On the other hand, the addition of HNTs more than 3 wt % did not show the reinforcing effect by HNT agglomeration. Full article
(This article belongs to the Special Issue Surface Modification of Halloysite Nanotubes)
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Open AccessFeature PaperArticle Polarization Properties of Laser Solitons
Appl. Sci. 2017, 7(5), 442; doi:10.3390/app7050442
Received: 13 March 2017 / Revised: 19 April 2017 / Accepted: 22 April 2017 / Published: 27 April 2017
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Abstract
The objective of this paper is to summarize the results obtained for the state of polarization in the emission of a vertical-cavity surface-emitting laser with frequency-selective feedback added. We start our research with the single soliton; this situation presents two perpendicular main orientations,
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The objective of this paper is to summarize the results obtained for the state of polarization in the emission of a vertical-cavity surface-emitting laser with frequency-selective feedback added. We start our research with the single soliton; this situation presents two perpendicular main orientations, connected by a hysteresis loop. In addition, we also find the formation of a ring-shaped intensity distribution, the vortex state, that shows two homogeneous states of polarization with very close values to those found in the soliton. For both cases above, the study shows the spatially resolved value of the orientation angle. It is important to also remark the appearance of a non-negligible amount of circular light that gives vectorial character to all the different emissions investigated. Full article
(This article belongs to the Special Issue Guided-Wave Optics)
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Open AccessArticle Chemical Constituents and Biological Activities of Essential Oils of Hydnora africana Thumb Used to Treat Associated Infections and Diseases in South Africa
Appl. Sci. 2017, 7(5), 443; doi:10.3390/app7050443
Received: 21 September 2016 / Revised: 22 November 2016 / Accepted: 1 December 2016 / Published: 27 April 2017
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Abstract
Hydnora africana (HA) Thumb is a member of the genus Hydnora. The roots are used in the treatment of infectious diseases in South Africa folk medicine. Though the root extracts are used to treat various human diseases including inflamed throat, there
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Hydnora africana (HA) Thumb is a member of the genus Hydnora. The roots are used in the treatment of infectious diseases in South Africa folk medicine. Though the root extracts are used to treat various human diseases including inflamed throat, there is a dearth of scientific data on the biological activities of essential oil isolated from this plant in the literature. Therefore, the present study was conducted to determine the chemical components and certain biological activities of the essential oil using standard bioassay methods. The plant essential oil exhibited a moderate free radical scavenging activity that was dependent on the radical species. Similarly, the essential oil was active against the growth of all thirteen opportunistic bacteria apart from Salmonella typhimurium, Pseudomonas aeruginosa and Proteus vulgaris. The essential oil was also active against Aspergillus niger among all the nine fungi selected. In addition, the species is typified by substantial amounts of classes of compounds including; carboxylic acids (30.68%), terpenes (10.70%), alkyl aldehydes (4.86%) and esters (0.82%), identified as antioxidant and antimicrobial agents. The essential oil of H. africana could be said to have pharmacological properties, and these agents in the essential oil of H. africana could justify the folklore usage of this plant in the treatment of infections and related diseases. Full article
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Open AccessArticle Improved Imaging of Magnetically Labeled Cells Using Rotational Magnetomotive Optical Coherence Tomography
Appl. Sci. 2017, 7(5), 444; doi:10.3390/app7050444
Received: 20 January 2017 / Revised: 13 April 2017 / Accepted: 14 April 2017 / Published: 27 April 2017
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Abstract
In this paper, we present a reliable and robust method for magnetomotive optical coherence tomography (MM-OCT) imaging of single cells labeled with iron oxide particles. This method employs modulated longitudinal and transverse magnetic fields to evoke alignment and rotation of anisotropic magnetic structures
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In this paper, we present a reliable and robust method for magnetomotive optical coherence tomography (MM-OCT) imaging of single cells labeled with iron oxide particles. This method employs modulated longitudinal and transverse magnetic fields to evoke alignment and rotation of anisotropic magnetic structures in the sample volume. Experimental evidence suggests that magnetic particles assemble themselves in elongated chains when exposed to a permanent magnetic field. Magnetomotion in the intracellular space was detected and visualized by means of 3D OCT as well as laser speckle reflectometry as a 2D reference imaging method. Our experiments on mesenchymal stem cells embedded in agar scaffolds show that the magnetomotive signal in rotational MM-OCT is significantly increased by a factor of ~3 compared to previous pulsed MM-OCT, although the solenoid’s power consumption was 16 times lower. Finally, we use our novel method to image ARPE-19 cells, a human retinal pigment epithelium cell line. Our results permit magnetomotive imaging with higher sensitivity and the use of low power magnetic fields or larger working distances for future three-dimensional cell tracking in target tissues and organs. Full article
(This article belongs to the Special Issue Development and Application of Optical Coherence Tomography (OCT))
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Open AccessArticle A Multi-View Stereo Algorithm Based on Homogeneous Direct Spatial Expansion with Improved Reconstruction Accuracy and Completeness
Appl. Sci. 2017, 7(5), 446; doi:10.3390/app7050446
Received: 12 February 2017 / Revised: 14 April 2017 / Accepted: 21 April 2017 / Published: 29 April 2017
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Abstract
Reconstruction of 3D structures from multiple 2D images has wide applications in such fields as computer vision, cultural heritage preservation, etc. This paper presents a novel multi-view stereo algorithm based on homogeneous direct spatial expansion (MVS-HDSE) with high reconstruction accuracy and completeness. It
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Reconstruction of 3D structures from multiple 2D images has wide applications in such fields as computer vision, cultural heritage preservation, etc. This paper presents a novel multi-view stereo algorithm based on homogeneous direct spatial expansion (MVS-HDSE) with high reconstruction accuracy and completeness. It adopts many unique measures in each step of reconstruction, including initial seed point extraction using the DAISY descriptor to increase the number of initial sparse seed points, homogeneous direct spatial expansion to enhance efficiency, initial value modification via a conditional-double-surface-fitting method before optimization and adaptive consistency filtering after optimization to ensure high accuracy, processing using a multi-level image pyramid to further improve completeness and efficiency, etc. As demonstrated by experiments, owing to above measures the proposed algorithm attained much improved reconstruction completeness and accuracy. Full article
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Open AccessArticle Dual-Branch Deep Convolution Neural Network for Polarimetric SAR Image Classification
Appl. Sci. 2017, 7(5), 447; doi:10.3390/app7050447
Received: 9 March 2017 / Revised: 23 April 2017 / Accepted: 24 April 2017 / Published: 27 April 2017
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Abstract
The deep convolution neural network (CNN), which has prominent advantages in feature learning, can learn and extract features from data automatically. Existing polarimetric synthetic aperture radar (PolSAR) image classification methods based on the CNN only consider the polarization information of the image, instead
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The deep convolution neural network (CNN), which has prominent advantages in feature learning, can learn and extract features from data automatically. Existing polarimetric synthetic aperture radar (PolSAR) image classification methods based on the CNN only consider the polarization information of the image, instead of incorporating the image’s spatial information. In this paper, a novel method based on a dual-branch deep convolution neural network (Dual-CNN) is proposed to realize the classification of PolSAR images. The proposed method is built on two deep CNNs: one is used to extract the polarization features from the 6-channel real matrix (6Ch) which is derived from the complex coherency matrix. The other is utilized to extract the spatial features of a Pauli RGB (Red Green Blue) image. These extracted features are first combined into a fully connected layer sharing the polarization and spatial property. Then, the Softmax classifier is employed to classify these features. The experiments are conducted on the Airborne Synthetic Aperture Radar (AIRSAR) data of Flevoland and the results show that the classification accuracy on 14 types of land cover is up to 98.56%. Such results are promising in comparison with other state-of-the-art methods. Full article
(This article belongs to the Special Issue Polarimetric SAR Techniques and Applications)
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Open AccessArticle Experimental Study on Heat Transfer Performance of Vacuum Tube Heat Collector with Thermal Storage
Appl. Sci. 2017, 7(5), 448; doi:10.3390/app7050448
Received: 11 March 2017 / Revised: 25 April 2017 / Accepted: 25 April 2017 / Published: 28 April 2017
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Abstract
This experimental study is intended to explore the heat performance of a novel vacuum tube heat collector with thermal storage. In order to enhance the heat transfer performance, we add radial metal fins to the U-tube which is used as the heat transfer
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This experimental study is intended to explore the heat performance of a novel vacuum tube heat collector with thermal storage. In order to enhance the heat transfer performance, we add radial metal fins to the U-tube which is used as the heat transfer channel of water. Meanwhile, in order to increase the thermal capacity of the heat collector, the heat collector model is designed to be larger than the general collector and is filled with the phase change materials (PCMs). In the U-tube, paraffin is chosen as the PCM. Then, during the experiment, to study the energy absorption and desorption characteristics of the heat collector, we chose to test during the day and night in the summer and the transition season. The experimental results show that, at night, the outlet water temperature of the vacuum tube heat collector has been enhanced by using PCM. The outlet water temperature decreases with the increase of flow rate. Full article
(This article belongs to the Special Issue Advances in Thermal System Analysis and Optimization)
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Open AccessArticle Evaluation of a Simplified Method to Estimate the Peak Inter-Story Drift Ratio of Steel Frames with Hysteretic Dampers
Appl. Sci. 2017, 7(5), 449; doi:10.3390/app7050449
Received: 4 March 2017 / Revised: 10 April 2017 / Accepted: 20 April 2017 / Published: 27 April 2017
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Abstract
In this paper, a simplified method is proposed to estimate the peak inter-story drift ratios of steel frames with hysteretic dampers. The simplified method involved the following: (1) the inelastic spectral displacement is estimated using a single-degree-of-freedom (SDOF) system with multi-springs, which is
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In this paper, a simplified method is proposed to estimate the peak inter-story drift ratios of steel frames with hysteretic dampers. The simplified method involved the following: (1) the inelastic spectral displacement is estimated using a single-degree-of-freedom (SDOF) system with multi-springs, which is equivalent to a steel frame with dampers and in which multi-springs represent the hysteretic behavior of dampers; (2) the first inelastic mode vector is estimated using a pattern of story drifts obtained from nonlinear static pushover analysis; and (3) the effects of modes higher than the first mode are estimated by using the jth modal period, jth mode vector, and jth modal damping ratio obtained from eigenvalue analysis. The accuracy of the simplified method is estimated using the results of nonlinear time history analysis (NTHA) on a series of three-story, six-story, and twelve-story steel moment resisting frames with steel hysteretic dampers. Based on the results of a comparison of the peak inter-story drift ratios estimated by the simplified method and that computed via NTHA using an elaborate analytical model, the accuracy of the simplified method is sufficient for evaluating seismic demands. Full article
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Open AccessArticle Shear Strengths of Different Bolt Connectors on the Large Span of Aluminium Alloy Honeycomb Sandwich Structure
Appl. Sci. 2017, 7(5), 450; doi:10.3390/app7050450
Received: 19 January 2017 / Revised: 24 March 2017 / Accepted: 24 April 2017 / Published: 27 April 2017
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Abstract
This study investigates the shear capacity of aluminum alloy honeycomb sandwich plates connected by high-strength, ordinary, or self-tapping bolts. For that purpose, experimental tests and finite elements are carried out. The failure of a high-strength bolt connector is driven by bending deformations developed
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This study investigates the shear capacity of aluminum alloy honeycomb sandwich plates connected by high-strength, ordinary, or self-tapping bolts. For that purpose, experimental tests and finite elements are carried out. The failure of a high-strength bolt connector is driven by bending deformations developed in the bolt that deform connection plate and pad openings. In the case of ordinary bolt connectors, stress concentration on the bolt shear surface causes a large shear deformation that finally leads to failure. In the case of self-tapping bolt connectors, the insufficient mechanical bite force of the screw thread yields the bolt misalignment and concentrates shear deformation. As a result, the high-strength bolt connector is the most efficient design solution. If the bolt hole edge distance is more than 1.5 times as much as the bolt diameter, the connection performance becomes insensitive to this parameter. The practical formula for evaluating the connector shear capacity is derived from experimental data. Full article
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Open AccessArticle Using Acoustic Emission Methods to Monitor Cement Composites during Setting and Hardening
Appl. Sci. 2017, 7(5), 451; doi:10.3390/app7050451
Received: 28 February 2017 / Revised: 24 April 2017 / Accepted: 24 April 2017 / Published: 28 April 2017
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Abstract
Cement-based composites belong among the basic building materials used in civil engineering. Their properties are given not only by their composition but also by their behaviour after mixing, as well as by the methods of curing. Monitoring the processes and phenomena during the
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Cement-based composites belong among the basic building materials used in civil engineering. Their properties are given not only by their composition but also by their behaviour after mixing, as well as by the methods of curing. Monitoring the processes and phenomena during the early stages of setting is vital for determining the resulting properties and durability. The acoustic emission method is a unique non-destructive method that can detect structural changes as a cement-based composite is setting. It can also detect the onset and growth of cracks during the service life of a cement-based composite since the moment it has been mixed. The paper discusses the use of the acoustic emission method with a focus on the early stage of the lifespan of a cement-based composite including the measures necessary for its use and description of the parameters of acoustic emission signals. Full article
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Open AccessArticle Texture Analysis and Land Cover Classification of Tehran Using Polarimetric Synthetic Aperture Radar Imagery
Appl. Sci. 2017, 7(5), 452; doi:10.3390/app7050452
Received: 9 March 2017 / Revised: 20 April 2017 / Accepted: 21 April 2017 / Published: 29 April 2017
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Abstract
Land cover classification of built-up and bare land areas in arid or semi-arid regions from multi-spectral optical images is not simple, due to the similarity of the spectral characteristics of the ground and building materials. However, synthetic aperture radar (SAR) images could overcome
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Land cover classification of built-up and bare land areas in arid or semi-arid regions from multi-spectral optical images is not simple, due to the similarity of the spectral characteristics of the ground and building materials. However, synthetic aperture radar (SAR) images could overcome this issue because of the backscattering dependency on the material and the geometry of different surface objects. Therefore, in this paper, dual-polarized data from ALOS-2 PALSAR-2 (HH, HV) and Sentinel-1 C-SAR (VV, VH) were used to classify the land cover of Tehran city, Iran, which has grown rapidly in recent years. In addition, texture analysis was adopted to improve the land cover classification accuracy. In total, eight texture measures were calculated from SAR data. Then, principal component analysis was applied, and the first three components were selected for combination with the backscattering polarized images. Additionally, two supervised classification algorithms, support vector machine and maximum likelihood, were used to detect bare land, vegetation, and three different built-up classes. The results indicate that land cover classification obtained from backscatter values has better performance than that obtained from optical images. Furthermore, the layer stacking of texture features and backscatter values significantly increases the overall accuracy. Full article
(This article belongs to the Special Issue Polarimetric SAR Techniques and Applications)
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Open AccessArticle Damage Index Calibration of Frame-Supported Concealed Multi-Ribbed Wall Panels with Energy-Efficient Blocks
Appl. Sci. 2017, 7(5), 453; doi:10.3390/app7050453
Received: 14 March 2017 / Revised: 23 April 2017 / Accepted: 26 April 2017 / Published: 28 April 2017
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Abstract
In this paper, we carry out low-reversed cyclic loading tests on differently-structured frame-supported concealed multi-ribbed wall panels with energy-efficient blocks. Models for evaluating damage performance are introduced for comparative study, in an effort to identify the preferable model for such a structure. To
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In this paper, we carry out low-reversed cyclic loading tests on differently-structured frame-supported concealed multi-ribbed wall panels with energy-efficient blocks. Models for evaluating damage performance are introduced for comparative study, in an effort to identify the preferable model for such a structure. To this end, the paper uses OpenSees, a nonlinear finite element software that can accurately depict the mechanical performance of a structure, both to calculate the necessary mechanical parameters and to verify the damage model of interest. In this paper, we determine the numerical ranges for the damage index at different stages of accumulative damage, attaching detailed descriptions on a stage-by-stage basis. Then, we offer suggestions for structure restoration according to these indices. Full article
(This article belongs to the Section Materials)
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Open AccessArticle Energy-Saving Network Ventilation Technology of Extra-Long Tunnel in Climate Separation Zone
Appl. Sci. 2017, 7(5), 454; doi:10.3390/app7050454
Received: 21 January 2017 / Revised: 16 April 2017 / Accepted: 23 April 2017 / Published: 28 April 2017
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Abstract
Saving energy is a major challenge for the development and safety of the world. Researchers at home and abroad have been continuously working on energy saving technology in the tunnel ventilation for decades. Based on segmented longitudinal ventilation for extra-long road tunnels, the
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Saving energy is a major challenge for the development and safety of the world. Researchers at home and abroad have been continuously working on energy saving technology in the tunnel ventilation for decades. Based on segmented longitudinal ventilation for extra-long road tunnels, the main ventilation mode and utilization method of natural wind energy in extra-long road tunnel were analyzed in this paper. In addition, the possible velocity distribution of natural wind in each section under wind pressure was investigated. Principles of natural wind in each tunnel section were studied based on long-term monitored meteorological factors. Accordingly, a fan equipment configuration method with high guaranteed rate during tunnel operation was proposed. A calculation method for energy-saving network ventilation in the tunnels was established. A feasible and efficient optimized energy-saving ventilation strategy was proposed, which utilizes natural wind and reduces the operation energy consumption. Thus, the annual energy saving in ventilation can reach up to 43.2% compared to previous energy costs when the intelligent ventilation system works. The research results can properly combine natural wind energy with mechanical ventilation to realize the smart self-energy saving in extra-long tunnels. Full article
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Open AccessArticle Inverse Identification of the Frequency-Dependent Mechanical Parameters of a Viscoelastic Core Layer Based on the Vibration Response
Appl. Sci. 2017, 7(5), 455; doi:10.3390/app7050455
Received: 21 March 2017 / Revised: 25 April 2017 / Accepted: 25 April 2017 / Published: 28 April 2017
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Abstract
The identification of the mechanical parameters of the viscoelastic core layer is of great significance for the modeling and damping design of the constrained layer damping (CLD) composite structure. In this study, based on the measured frequency vibration response of a CLD plate,
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The identification of the mechanical parameters of the viscoelastic core layer is of great significance for the modeling and damping design of the constrained layer damping (CLD) composite structure. In this study, based on the measured frequency vibration response of a CLD plate, an inverse approach was developed to identify the aforementioned parameters. Then, on the basis of considering both the viscoelastic material damping and the remaining equivalent viscous damping, the equation of motion of the CLD plate under base excitation was established and a method to obtain the vibration response was also presented. Further, a matching calculation based on sensitivity was proposed, to achieve the identification of the mechanical parameters. Finally, a CLD aluminum plate with a ZN_1 viscoelastic core layer was chosen to demonstrate the proposed method. In addition, the identification results were also introduced into the vibration response analysis and the rationality of the identified parameters were verified by comparing the vibration responses obtained by theoretical calculations and the experiment. Full article
(This article belongs to the Section Mechanical Engineering)
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Open AccessArticle The Experimental Realization of an Acoustic Cloak in Air with a Meta-Composite Shell
Appl. Sci. 2017, 7(5), 456; doi:10.3390/app7050456
Received: 10 March 2017 / Revised: 16 April 2017 / Accepted: 25 April 2017 / Published: 29 April 2017
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Abstract
Anisotropic cloak shells can be used for the spatial transformation of a space to alter the propagation of acoustic waves by redirecting them along a pre-determined path. This paper outlines the design, fabrication, and experimental analysis of a circular acoustic cloak shell made
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Anisotropic cloak shells can be used for the spatial transformation of a space to alter the propagation of acoustic waves by redirecting them along a pre-determined path. This paper outlines the design, fabrication, and experimental analysis of a circular acoustic cloak shell made of meta-composite material for in-air applications. Based on the three-dimensional coordinate transformation, we first designed an anisotropic circle meta-composite cloak shell according to its impedance values. The cloak shell comprises various layered structures with cavities and tubes, respectively, providing acoustic mass and compliance for the provision of anisotropic material properties. Secondly, we conducted numerical and experimental analyses under practice working conditions to demonstrate the efficacy of the acoustic cloak. The structure of the cloak shell, fabricated by three-dimensional printing (3D printing), is experimentally evaluated in a semi-anechoic room with a free-field environment. The simulation and experimental results demonstrate the acoustic cloaking effects in the scattering far field. Besides the scattering field, the sound field measurement results obtained with the region enclosed by the shell also shows the abilities of the cloak shell in altering the direction of wave propagation along a pre-determined path in air. Full article
(This article belongs to the Section Acoustics)
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Open AccessArticle Intent-Estimation- and Motion-Model-Based Collision Avoidance Method for Autonomous Vehicles in Urban Environments
Appl. Sci. 2017, 7(5), 457; doi:10.3390/app7050457
Received: 2 March 2017 / Revised: 23 April 2017 / Accepted: 26 April 2017 / Published: 30 April 2017
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Abstract
Existing collision avoidance methods for autonomous vehicles, which ignore the driving intent of detected vehicles, thus, cannot satisfy the requirements for autonomous driving in urban environments because of their high false detection rates of collisions with vehicles on winding roads and the missed
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Existing collision avoidance methods for autonomous vehicles, which ignore the driving intent of detected vehicles, thus, cannot satisfy the requirements for autonomous driving in urban environments because of their high false detection rates of collisions with vehicles on winding roads and the missed detection rate of collisions with maneuvering vehicles. This study introduces an intent-estimation- and motion-model-based (IEMMB) method to address these disadvantages. First, a state vector is constructed by combining the road structure and the moving state of detected vehicles. A Gaussian mixture model is used to learn the maneuvering patterns of vehicles from collected data, and the patterns are used to estimate the driving intent of the detected vehicles. Then, a desirable long-term trajectory is obtained by weighting time and comfort. The long-term trajectory and the short-term trajectory, which are predicted using a constant yaw rate motion model, are fused to achieve an accurate trajectory. Finally, considering the moving state of the autonomous vehicle, collisions can be detected and avoided. Experiments have shown that the intent estimation method performed well, achieving an accuracy of 91.7% on straight roads and an accuracy of 90.5% on winding roads, which is much higher than that achieved by the method that ignores the road structure. The average collision detection distance is increased by more than 8 m. In addition, the maximum yaw rate and acceleration during an evasive maneuver are decreased, indicating an improvement in the driving comfort. Full article
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Open AccessArticle Perfect Light Absorbers Made of Tungsten-Ceramic Membranes
Appl. Sci. 2017, 7(5), 458; doi:10.3390/app7050458
Received: 8 March 2017 / Revised: 21 April 2017 / Accepted: 26 April 2017 / Published: 29 April 2017
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Abstract
Plasmonic materials are expanding their concept; in addition to noble metals that are good conductors even at optical frequencies and support surface plasmon polaritons at the interface, other metals and refractory materials are now being used as plasmonic materials. In terms of complex
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Plasmonic materials are expanding their concept; in addition to noble metals that are good conductors even at optical frequencies and support surface plasmon polaritons at the interface, other metals and refractory materials are now being used as plasmonic materials. In terms of complex permittivity at optical frequencies, these new plasmonic materials are, though not ideal, quite good to support surface plasmons. Numerical investigations of the optical properties have been revealing new capabilities of the plasmonic materials. On the basis of the precise computations for electromagnetic waves in artificially designed nanostructures, in this article, we address membrane structures made of tungsten and silicon nitride that are a typical metal and ceramic, respectively, with high-temperature melting points. The membranes are applicable to low-power-consuming thermal emitters operating at and near the visible range. We numerically substantiate that the membranes serve as perfect light absorbers, in spite of the subwavelength thickness, that is, 200–250 nm thickness. Furthermore, we clarify that the underlying physical mechanism for the unconventional perfect absorption is ascribed to robust impedance matching at the interface between air and the membranes. Full article
(This article belongs to the Special Issue Guided-Wave Optics)
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Open AccessArticle An Initial Load-Based Green Software Defined Network
Appl. Sci. 2017, 7(5), 459; doi:10.3390/app7050459
Received: 28 March 2017 / Revised: 21 April 2017 / Accepted: 25 April 2017 / Published: 2 May 2017
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Abstract
Software defined network (SDN) is a new network architecture in which the control function is decoupled from the data forwarding plane, that is attracting wide attentions from both research and industry sectors. However, SDN still faces the energy waste problem as do traditional
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Software defined network (SDN) is a new network architecture in which the control function is decoupled from the data forwarding plane, that is attracting wide attentions from both research and industry sectors. However, SDN still faces the energy waste problem as do traditional networks. At present, research on energy saving in SDN is mainly focused on the static optimization of the network with zero load when new traffic arrives, changing the transmission path of the uncompleted traffic which arrived before the optimization, possibly resulting in route oscillation and other deleterious effects. To avoid this, a dynamical energy saving optimization scheme in which the paths of the uncompleted flows will not be changed when new traffic arrives is designed. To find the optimal solution for energy saving, the problem is modeled as a mixed integer linear programming (MILP) problem. As the high complexity of the problem prohibits the optimal solution, an improved heuristic routing algorithm called improved constant weight greedy algorithm (ICWGA) is proposed to find a sub-optimal solution. Simulation results show that the energy saving capacity of ICWGA is close to that of the optimal solution, offering desirable improvement in the energy efficiency of the network. Full article
(This article belongs to the Special Issue Green Wireless Networks)
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Open AccessArticle Automated Diatom Classification (Part B): A Deep Learning Approach
Appl. Sci. 2017, 7(5), 460; doi:10.3390/app7050460
Received: 8 March 2017 / Revised: 21 April 2017 / Accepted: 21 April 2017 / Published: 2 May 2017
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Abstract
Diatoms, a kind of algae microorganisms with several species, are quite useful for water quality determination, one of the hottest topics in applied biology nowadays. At the same time, deep learning and convolutional neural networks (CNN) are becoming an extensively used technique for
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Diatoms, a kind of algae microorganisms with several species, are quite useful for water quality determination, one of the hottest topics in applied biology nowadays. At the same time, deep learning and convolutional neural networks (CNN) are becoming an extensively used technique for image classification in a variety of problems. This paper approaches diatom classification with this technique, in order to demonstrate whether it is suitable for solving the classification problem. An extensive dataset was specifically collected (80 types, 100 samples/type) for this study. The dataset covers different illumination conditions and it was computationally augmented to more than 160,000 samples. After that, CNNs were applied over datasets pre-processed with different image processing techniques. An overall accuracy of 99% is obtained for the 80-class problem and different kinds of images (brightfield, normalized). Results were compared to previous presented classification techniques with different number of samples. As far as the authors know, this is the first time that CNNs are applied to diatom classification. Full article
(This article belongs to the Special Issue Automated Analysis and Identification of Phytoplankton Images)
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Open AccessArticle Jointly Production and Correlated Maintenance Optimization for Parallel Leased Machines
Appl. Sci. 2017, 7(5), 461; doi:10.3390/app7050461
Received: 8 March 2017 / Revised: 23 April 2017 / Accepted: 25 April 2017 / Published: 30 April 2017
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Abstract
This paper deals with a preventive maintenance strategy optimization correlated to production for a manufacturing system made by several parallel machines under lease contract. In order to minimize the total cost of production and maintenance by reducing the production system interruptions due to
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This paper deals with a preventive maintenance strategy optimization correlated to production for a manufacturing system made by several parallel machines under lease contract. In order to minimize the total cost of production and maintenance by reducing the production system interruptions due to maintenance activities, a correlated group preventive maintenance policy is developed using the gravity center approach (GCA). The aim of this study is to determine an economical production plan and an optimal group preventive maintenance interval Tn at which all machines are maintained simultaneously. An analytical correlation between failure rate of machines and production level is considered and the impact of the preventive maintenance policy on the production plan is studied. Finally, the proposed maintenance policy GPM is compared with an individual simple strategy approach IPM in order to illustrate its efficiency. Full article
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Open AccessFeature PaperArticle Influence of the Origin of Polyamide 12 Powder on the Laser Sintering Process and Laser Sintered Parts
Appl. Sci. 2017, 7(5), 462; doi:10.3390/app7050462
Received: 3 April 2017 / Revised: 24 April 2017 / Accepted: 25 April 2017 / Published: 30 April 2017
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Abstract
Different features of polymer powders influence the process of laser sintering (LS) and the properties of LS-parts to a great extent. This study investigates important aspects of the “powder/process/part”-property relationships by comparing two polyamide 12 (PA12) powders commercially available for LS, with pronounced
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Different features of polymer powders influence the process of laser sintering (LS) and the properties of LS-parts to a great extent. This study investigates important aspects of the “powder/process/part”-property relationships by comparing two polyamide 12 (PA12) powders commercially available for LS, with pronounced powder characteristic differences (Duraform® PA and Orgasol® Invent Smooth). Due to the fact that the primary influence factor on polymer behaviour, the chemical structure of the polymer chain, is identical in this case, the impacts resulting from powder distribution, particle shape, thermal behaviour, and crystalline and molecular structure, can be studied in detail. It was shown that although both systems are PA12, completely different processing conditions must be applied to accomplish high-resolution parts. The reason for this was discovered by the different thermal behaviour based on the powder production and the resulting crystalline structure. Moreover, the parts built from Orgasol® Invent Smooth unveil mechanical properties with pronounced anisotropy, caused from the high melt viscosity and termination of polymer chains. Further differences are seen in relation to the powder characteristics and other significant correlations could be revealed. For example, the study demonstrated how the particle morphology and shape impact the surface roughness of the parts. Full article
(This article belongs to the Special Issue Materials for 3D Printing)
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Open AccessArticle Experimental Studies on the Behavior of a Newly-Developed Type of Self-Insulating Concrete Masonry Shear Wall under in-Plane Cyclic Loading
Appl. Sci. 2017, 7(5), 463; doi:10.3390/app7050463
Received: 26 February 2017 / Revised: 16 April 2017 / Accepted: 26 April 2017 / Published: 30 April 2017
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Abstract
This study aimed to investigate the inelastic behavior of a newly-developed type of self-insulating concrete masonry shear wall (SCMSW) under in-plane cyclic loading. The new masonry system was made from concrete blocks with special configurations to provide a stronger bond between units than
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This study aimed to investigate the inelastic behavior of a newly-developed type of self-insulating concrete masonry shear wall (SCMSW) under in-plane cyclic loading. The new masonry system was made from concrete blocks with special configurations to provide a stronger bond between units than ordinary concrete masonry units. A total of six fully-grouted SCMSWs were prepared with different heights (1.59 to 5.78 m) and different vertical steel configurations. The developed masonry walls were tested under in-plane cyclic loading and different constant axial load ratios. In addition, the relationship between the amount of axial loading, the amount of the flexural reinforcement and the wall aspect ratios and the nonlinear hysteretic response of the SCMSW was evaluated. The results showed that the lateral load capacity of SCMSW increases with the amount of applied axial load and the amount of vertical reinforcement. However, the lateral load capacity decreases as the wall aspect ratio increases. The existence of the boundary elements at the SCMSW ends increases the ductility and the lateral load capacity. Generally, the SCMSW exhibited predominantly flexural behavior. These results agreed with those reported in previous research for walls constructed with ordinary units. Full article
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Open AccessArticle Failure Response of Simultaneously Pre-Stressed and Laser Irradiated Aluminum Alloys
Appl. Sci. 2017, 7(5), 464; doi:10.3390/app7050464
Received: 22 February 2017 / Revised: 21 April 2017 / Accepted: 25 April 2017 / Published: 29 April 2017
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Abstract
The failure response of aluminum alloys (Al-6061 and Al-7075) under the condition of simultaneously pre-stressing and laser heating was investigated. Specimens were subjected to predetermined preloading states and then irradiated by continuous wave fiber (Yb) laser. For all specimens, it was found that
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The failure response of aluminum alloys (Al-6061 and Al-7075) under the condition of simultaneously pre-stressing and laser heating was investigated. Specimens were subjected to predetermined preloading states and then irradiated by continuous wave fiber (Yb) laser. For all specimens, it was found that the yield stress decreased with increasing laser power density. This implies that the load-bearing capacity of the specimens reduced under increased thermal or tensile loading. Consequently, the specimen’s failure time was shortened by increasing either laser power density or preloaded speed. For Al-6061, a remarkable reduction in failure time by the increase of laser power density is found. However, for Al-7075, under higher preloaded speeds, comparatively smaller impact of laser power density on the failure time is reported. Moreover, for Al-6061, relatively a more non-uniform variation in the average failure time with the increase of laser power density or preloaded speed is observed. The failure mode of Al-6061 turned from brittle to ductile at higher laser power densities; whereas for Al-7075, it changed from quasi-brittle to ductile. At higher preloaded speeds, a greater degree of melting and ablation phenomenon can be seen due to relatively higher temperatures and higher heating rates. Full article
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Open AccessArticle Control of Corner Separation with Plasma Actuation in a High-Speed Compressor Cascade
Appl. Sci. 2017, 7(5), 465; doi:10.3390/app7050465
Received: 31 March 2017 / Revised: 25 April 2017 / Accepted: 25 April 2017 / Published: 29 April 2017
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Abstract
The performances of modern highly loaded compressors are limited by the corner separations. Plasma actuation is a typical active flow control methodology, which has been proven to be capable of controlling the corner separations in low-speed compressor cascades. The main purpose of this
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The performances of modern highly loaded compressors are limited by the corner separations. Plasma actuation is a typical active flow control methodology, which has been proven to be capable of controlling the corner separations in low-speed compressor cascades. The main purpose of this paper is to uncover the flow control law and the mechanism of high-speed compressor cascade corner separation control with plasma actuations. The control effects of the suction surface as well as the endwall plasma actuations in suppressing the high-speed compressor cascade flow separations are investigated with numerical methods. The main flow structures within the high-speed compressor cascade corner separation and the development of the corresponding flow loss are investigated firstly. Next, the performances of plasma actuations in suppressing the high-speed compressor cascade corner separation are studied. At last, the mechanisms behind the control effects of the suction surface and the endwall plasma actuations are discussed. Both the suction surface and the endwall plasma actuations can improve the high-speed compressor cascade static pressure rise coefficient, while reducing the corresponding total pressure loss and blockage coefficients. The suction surface plasma actuation can suppress not only the high-speed compressor cascade corner separation vortex but also the airfoil separation, so, compared to the endwall plasma actuation, the suction surface plasma actuation is more efficient in reducing the total pressure loss of the high-speed compressor cascade. However, through suppressing the development of the passage vortex, the endwall plasma actuation is more efficient in reducing the flow blockage and improving the static pressure rise of the high-speed compressor cascade. Full article
(This article belongs to the Special Issue Active Flow Control Technologies for Energy and Propulsive Systems)
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Open AccessArticle Subsidence Evolution of the Leizhou Peninsula, China, Based on InSAR Observation from 1992 to 2010
Appl. Sci. 2017, 7(5), 466; doi:10.3390/app7050466
Received: 2 March 2017 / Revised: 21 April 2017 / Accepted: 26 April 2017 / Published: 29 April 2017
PDF Full-text (8886 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Over the past two decades, the Leizhou Peninsula has suffered from many geological hazards and great property losses caused by land subsidence. However, the absence of a deformation map of the whole peninsula has impeded the government in making the necessary decisions concerning
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Over the past two decades, the Leizhou Peninsula has suffered from many geological hazards and great property losses caused by land subsidence. However, the absence of a deformation map of the whole peninsula has impeded the government in making the necessary decisions concerning hazard prevention and mitigation. This study aims to provide the evolution of land deformation (subsidence and uplift) in the whole peninsula from 1992 to 2010. A modified stacking procedure is proposed to map the surface deformation with JERS, ENVISAT, and ALOS1 images. The map shows that the land subsidence mainly occurs along the coastline with a maximum velocity of 32 mm/year and in a wide range of inland arable lands with a velocity between 10 and 19 mm/year. Our study suggests that there is a direct correlation between the subsidence and the surface geology. Besides, the observed subsidence in urban areas, caused by groundwater overexploitation for domestic and industrial use, is moving from urban areas to suburban areas. In nonurban areas, groundwater extraction for aquaculture and arable land irrigation are the main reason for land subsidence, which accelerates saltwater intrusion and coastline erosion if regular surface deformation measurements and appropriate management measures are not taken. Full article
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Open AccessArticle Graph-Based Semi-Supervised Learning for Indoor Localization Using Crowdsourced Data
Appl. Sci. 2017, 7(5), 467; doi:10.3390/app7050467
Received: 29 March 2017 / Revised: 26 April 2017 / Accepted: 26 April 2017 / Published: 29 April 2017
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Abstract
Indoor positioning based on the received signal strength (RSS) of the WiFi signal has become the most popular solution for indoor localization. In order to realize the rapid deployment of indoor localization systems, solutions based on crowdsourcing have been proposed. However, compared to
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Indoor positioning based on the received signal strength (RSS) of the WiFi signal has become the most popular solution for indoor localization. In order to realize the rapid deployment of indoor localization systems, solutions based on crowdsourcing have been proposed. However, compared to conventional methods, lots of different devices are used in crowdsourcing system and less RSS values are collected by each device. Therefore, the crowdsourced RSS values are more erroneous and can result in significant localization errors. In order to eliminate the signal strength variations across diverse devices, the Linear Regression (LR) algorithm is proposed to solve the device diversity problem in crowdsourcing system. After obtaining the uniform RSS values, a graph-based semi-supervised learning (G-SSL) method is used to exploit the correlation between the RSS values at nearby locations to estimate an optimal RSS value at each location. As a result, the negative effect of the erroneous measurements could be mitigated. Since the AP locations need to be known in G-SSL algorithm, the Compressed Sensing (CS) method is applied to precisely estimate the location of the APs. Based on the location of the APs and a simple signal propagation model, the RSS difference between different locations is calculated and used as an additional constraint to improve the performance of G-SSL. Furthermore, to exploit the sparsity of the weights used in the G-SSL, we use the CS method to reconstruct these weights more accurately and make a further improvement on the performance of the G-SSL. Experimental results show improved results in terms of the smoothness of the radio map and the localization accuracy. Full article
(This article belongs to the Section Computer Science and Electrical Engineering)
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Open AccessArticle Optimal System Frequency Response Model and UFLS Schemes for a Small Receiving-End Power System after Islanding
Appl. Sci. 2017, 7(5), 468; doi:10.3390/app7050468
Received: 14 March 2017 / Revised: 19 April 2017 / Accepted: 26 April 2017 / Published: 2 May 2017
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Abstract
Large frequency deviations after islanding are exceedingly critical in small receiving-end power systems. The under-frequency load shedding (UFLS) scheme is an efficient protection step for preventing system black outs. It is very important to get an exact model to design the UFLS schemes.
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Large frequency deviations after islanding are exceedingly critical in small receiving-end power systems. The under-frequency load shedding (UFLS) scheme is an efficient protection step for preventing system black outs. It is very important to get an exact model to design the UFLS schemes. In this paper, an optimization model to achieve the system frequency response (SFR) model either from the full-scale power system or from test records was proposed. The optimized SFR model took into account the response of governors-prime movers and the dynamic characteristics of loads developed in the modern power system. Then the UFLS schemes were designed via the optimized SFR model and particle swarm optimization (PSO) method. The time-domain simulation with the actual small receiving-end power system was presented to investigate the validity of the presented model and the developed technique. Full article
(This article belongs to the Special Issue Distribution Power Systems)
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Open AccessArticle Multi-Objective Climb Path Optimization for Aircraft/Engine Integration Using Particle Swarm Optimization
Appl. Sci. 2017, 7(5), 469; doi:10.3390/app7050469
Received: 29 January 2017 / Revised: 21 April 2017 / Accepted: 26 April 2017 / Published: 30 April 2017
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Abstract
In this article, a new multi-objective approach to the aircraft climb path optimization problem, based on the Particle Swarm Optimization algorithm, is introduced to be used for aircraft–engine integration studies. This considers a combination of a simulation with a traditional Energy approach, which
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In this article, a new multi-objective approach to the aircraft climb path optimization problem, based on the Particle Swarm Optimization algorithm, is introduced to be used for aircraft–engine integration studies. This considers a combination of a simulation with a traditional Energy approach, which incorporates, among others, the use of a proposed path-tracking scheme for guidance in the Altitude–Mach plane. The adoption of population-based solver serves to simplify case setup, allowing for direct interfaces between the optimizer and aircraft/engine performance codes. A two-level optimization scheme is employed and is shown to improve search performance compared to the basic PSO algorithm. The effectiveness of the proposed methodology is demonstrated in a hypothetic engine upgrade scenario for the F-4 aircraft considering the replacement of the aircraft’s J79 engine with the EJ200; a clear advantage of the EJ200-equipped configuration is unveiled, resulting, on average, in 15% faster climbs with 20% less fuel. Full article
(This article belongs to the Special Issue Gas Turbines Propulsion and Power)
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Open AccessArticle Four-Dimensional Thermal Analysis of 888 nm Pumped Nd:YVO4 Dual-Rod Acousto-Optic Q-Switched Laser
Appl. Sci. 2017, 7(5), 470; doi:10.3390/app7050470
Received: 14 March 2017 / Revised: 9 April 2017 / Accepted: 27 April 2017 / Published: 8 May 2017
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Abstract
A theoretical analysis upon the four-dimensional (4D) spatio-temporal temperature dependent dynamics of 888 nm pumped Nd:YVO4 dual-rod laser is established, which is valid in both continuous-wave (CW) and acousto-optic (AO) Q-switched pulse lasers conditions. Our model can accurately solve the 4D thermal
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A theoretical analysis upon the four-dimensional (4D) spatio-temporal temperature dependent dynamics of 888 nm pumped Nd:YVO 4 dual-rod laser is established, which is valid in both continuous-wave (CW) and acousto-optic (AO) Q-switched pulse lasers conditions. Our model can accurately solve the 4D thermal generation and temperature evolution not only in the steady Q-switched state, but also in the first few unstable giant or dwarf pulses region. Factors including ground state depletion (GSD), energy transfer upconversion (ETU), fluorescence branching ratios, temperature-dependent cross sections and nonradiative relaxations processes are comprehensively considered for precisely estimating thermal effects, valid in both the steady pulse region and the unstable region at the beginning. Moreover, temporal and spatial temperature profiles and their coupling effect on output properties at different repetition-rates are discussed. Experiments of high-power high-repetition-rate 888 nm end-pumped Nd:YVO 4 dual-rod CW and AO Q-switched lasers are also firstly presented and the experimental results enjoy good consistency with our theory. Full article
(This article belongs to the Section Optics and Lasers)
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Open AccessArticle An Improved Differential Quadrature Time Element Method
Appl. Sci. 2017, 7(5), 471; doi:10.3390/app7050471
Received: 10 March 2017 / Revised: 26 April 2017 / Accepted: 26 April 2017 / Published: 3 May 2017
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Abstract
A Differential Quadrature Time Element Method (DQTEM) was proposed by the author and co-worker, its drawback is the need of larger storage capacity since the dimension of the coefficients matrix for solution is the product of both spatial degrees of freedom and temporal
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A Differential Quadrature Time Element Method (DQTEM) was proposed by the author and co-worker, its drawback is the need of larger storage capacity since the dimension of the coefficients matrix for solution is the product of both spatial degrees of freedom and temporal degrees of freedom. To solve this problem, an improved DQTEM is developed in this work, in which the differential quadrature method is used to discretize both spatial and time domains, sequentially, and the dimension of the coefficients matrix is greatly reduced without losing solution accuracy. Theoretical studies demonstrate the improved DQTEM features superiorities including higher-order accuracy, adequate stability and symplectic characteristics. The improvement of DQTEM is validated by extensive comparisons of the present DQTEM with the original DQTEM. Full article
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Open AccessArticle Single Mode Air-Clad Single Crystal Sapphire Optical Fiber
Appl. Sci. 2017, 7(5), 473; doi:10.3390/app7050473
Received: 16 March 2017 / Revised: 14 April 2017 / Accepted: 30 April 2017 / Published: 3 May 2017
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Abstract
The observation of single mode propagation in an air-clad single crystal sapphire optical fiber at wavelengths at and above 783 nm is presented for the first time. A high-temperature wet acid etching method was used to reduce the diameter of a 10 cm
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The observation of single mode propagation in an air-clad single crystal sapphire optical fiber at wavelengths at and above 783 nm is presented for the first time. A high-temperature wet acid etching method was used to reduce the diameter of a 10 cm length of commercially-sourced sapphire fiber from 125 micrometers to 6.5 micrometers, and far-field imaging provided modal information at intervals as the fiber diameter decreased. Modal volume was shown to decrease with decreasing diameter, and single mode behavior was observed at the minimum diameter achieved. While weakly-guiding approximations are generally inaccurate for low modal volume optical fiber with high core-cladding refractive index disparity, consistency between these approximations and experimental results was observed when the effective numerical aperture was measured and substituted for the theoretical numerical aperture in weakly-guiding approximation calculations. With the demonstration of very low modal volume in sapphire at fiber diameters much larger than anticipated by legacy calculations, the resolution of sapphire fiber distributed sensors may be increased and other sensing schemes requiring very low modal volume, such as fiber Bragg gratings, may be realized in extreme environment applications. Full article
(This article belongs to the Special Issue Distributed Optical Fiber Sensors)
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Open AccessArticle A Fast and Cost-Effective Detection of Melamine by Surface Enhanced Raman Spectroscopy Using a Novel Hydrogen Bonding-Assisted Supramolecular Matrix and Gold-Coated Magnetic Nanoparticles
Appl. Sci. 2017, 7(5), 475; doi:10.3390/app7050475
Received: 8 March 2017 / Revised: 27 April 2017 / Accepted: 27 April 2017 / Published: 3 May 2017
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Abstract
A fast and cost-effective melamine detection approach has been developed based on surface enhanced Raman spectroscopy (SERS) using a novel hydrogen bonding-assisted supramolecular matrix. The detection utilizes Fe3O4/Au magnetic nanoparticles coated with 5-aminoorotic acid (AOA) as a SERS active
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A fast and cost-effective melamine detection approach has been developed based on surface enhanced Raman spectroscopy (SERS) using a novel hydrogen bonding-assisted supramolecular matrix. The detection utilizes Fe3O4/Au magnetic nanoparticles coated with 5-aminoorotic acid (AOA) as a SERS active substrate (Fe3O4/Au–AOA), and Rhodamine B (RhB) conjugated AOA as a Raman reporter (AOA–RhB). Upon mixing the reagents with melamine, a supramolecular complex [Fe3O4/Au–AOA•••melamine•••AOA–RhB] was formed due to the strong multiple hydrogen bonding interactions between AOA and melamine. The complex was separated and concentrated to a pellet by an external magnet and used as a supramolecular matrix for the melamine detection. Laser excitation of the complex pellet produced a strong SERS signal diagnostic for RhB. The logarithmic intensity of the characteristic RhB peaks was found to be proportional to the concentration of melamine with a limit of detection of 2.5 µg/mL and a detection linearity range of 2.5~15.0 µg/mL in milk. As Fe3O4 nanoparticles and AOA are thousands of times less expensive than the monoclonal antibody used in a traditional sandwich immunoassay, the current assay drastically cut down the cost of melamine detection. The current approach affords promise as a biosensor platform that cuts down sample pre-treatment steps and measurement expense. Full article
(This article belongs to the Special Issue Biological Applications of Magnetic Nanoparticles)
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Open AccessArticle Vibration Control of a Power Transmission Tower with Pounding Tuned Mass Damper under Multi-Component Seismic Excitations
Appl. Sci. 2017, 7(5), 477; doi:10.3390/app7050477
Received: 7 March 2017 / Revised: 22 April 2017 / Accepted: 2 May 2017 / Published: 5 May 2017
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Abstract
In this paper, the two-dimensional vibration controls of a power transmission tower with a pounding tuned mass damper (PTMD) under multi-component seismic excitations are analyzed. A three-dimensional finite element model of a practical power transmission tower is established in ABAQUS (Dassasult Simulia Company,
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In this paper, the two-dimensional vibration controls of a power transmission tower with a pounding tuned mass damper (PTMD) under multi-component seismic excitations are analyzed. A three-dimensional finite element model of a practical power transmission tower is established in ABAQUS (Dassasult Simulia Company, Providence, RI, USA). The TMD (tuned mass damper) and PTMD are simulated by the finite element method. The response of the transmission tower with TMD and PTMD are analyzed, respectively. To achieve optimal design, the influence of the mass ratio, ground motion intensity, gap, and incident angle of seismic ground motion are investigated, respectively. The results show that the PTMD is very effective in reducing the vibration of the transmission tower in the longitudinal and transverse directions. The reduction ratio increases with the increase of the mass ratio. The ground motion intensity and gap have no obvious influence on the reduction ratio. However, the incident angle has a significant influence on the reduction ratio. Full article
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Open AccessArticle A Novel Technique for Designing High Power Semiconductor Optical Amplifier (SOA)-Based Tunable Fiber Compound-Ring Lasers Using Low Power Optical Components
Appl. Sci. 2017, 7(5), 478; doi:10.3390/app7050478
Received: 1 April 2017 / Revised: 28 April 2017 / Accepted: 3 May 2017 / Published: 5 May 2017
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Abstract
A simple, stable and inexpensive dual-output port widely tunable semiconductor optical amplifier (SOA)-based fiber compound-ring laser structure is demonstrated. This unique nested ring cavity enables high optical power to split into different branches where amplification and wavelength selection are achieved by using low-power
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A simple, stable and inexpensive dual-output port widely tunable semiconductor optical amplifier (SOA)-based fiber compound-ring laser structure is demonstrated. This unique nested ring cavity enables high optical power to split into different branches where amplification and wavelength selection are achieved by using low-power SOAs and a tunable filter. Furthermore, two Sagnac loop mirrors, which are spliced at the two ends of the compound-ring cavity not only serve as variable reflectors but also channel the optical energy back to the same port without using any high optical power combiner. We propose and discuss how the demonstrated fiber compound-ring laser structure can be extended in order to achieve a high power fiber laser source by using low power optical components, such as N × N couplers and (N > 1) number of SOAs. A coherent beam-combining efficiency of over 98% for two parallel nested fiber ring resonators is achieved over the C-band tuning range of 30 nm. Optical signal-to-noise ratio (OSNR) of +45 dB, and optical power fluctuation of less than ±0.02 dB are measured over three hours at room temperature. Full article
(This article belongs to the Section Optics and Lasers)
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Open AccessFeature PaperArticle Construction and Commissioning of PAL-XFEL Facility
Appl. Sci. 2017, 7(5), 479; doi:10.3390/app7050479
Received: 23 March 2017 / Revised: 20 April 2017 / Accepted: 26 April 2017 / Published: 17 May 2017
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Abstract
The construction of Pohang Accelerator Laboratory X-ray Free-Electron Laser (PAL-XFEL), a 0.1-nm hard X-ray free-electron laser (FEL) facility based on a 10-GeV S-band linear accelerator (LINAC), is achieved in Pohang, Korea by the end of 2016. The construction of the 1.11 km-long building
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The construction of Pohang Accelerator Laboratory X-ray Free-Electron Laser (PAL-XFEL), a 0.1-nm hard X-ray free-electron laser (FEL) facility based on a 10-GeV S-band linear accelerator (LINAC), is achieved in Pohang, Korea by the end of 2016. The construction of the 1.11 km-long building was completed by the end of 2014, and the installation of the 10-GeV LINAC and undulators started in January 2015. The installation of the 10-GeV LINAC, together with the undulators and beamlines, was completed by the end of 2015. The commissioning began in April 2016, and the first lasing of the hard X-ray FEL line was achieved on 14 June 2016. The progress of the PAL-XFEL construction and its commission are reported here. Full article
(This article belongs to the Special Issue X-Ray Free-Electron Laser)
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Open AccessArticle A Study of the Transient Response of Duct Junctions: Measurements and Gas-Dynamic Modeling with a Staggered Mesh Finite Volume Approach
Appl. Sci. 2017, 7(5), 480; doi:10.3390/app7050480
Received: 20 March 2017 / Revised: 28 April 2017 / Accepted: 2 May 2017 / Published: 8 May 2017
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Abstract
Duct junctions play a major role in the operation and design of most piping systems. The objective of this paper is to establish the potential of a staggered mesh finite volume model as a way to improve the description of the effect of
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Duct junctions play a major role in the operation and design of most piping systems. The objective of this paper is to establish the potential of a staggered mesh finite volume model as a way to improve the description of the effect of simple duct junctions on an otherwise one-dimensional flow system, such as the intake or exhaust of an internal combustion engine. Specific experiments have been performed in which different junctions have been characterized as a multi-port, and that have provided precise and reliable results on the propagation of pressure pulses across junctions. The results obtained have been compared to simulations performed with a staggered mesh finite volume method with different flux limiters and different meshes and, as a reference, have also been compared with the results of a more conventional pressure loss-based model. The results indicate that the staggered mesh finite volume model provides a closer description of wave dynamics, even if further work is needed to establish the optimal calculation settings. Full article
(This article belongs to the Special Issue Internal Combustion Engines (ICE) for Ground Transport)
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Open AccessArticle Variable Pole Pitch Electromagnetic Propulsion with Ladder-Slot-Secondary Double-Sided Linear Induction Motors
Appl. Sci. 2017, 7(5), 481; doi:10.3390/app7050481
Received: 28 February 2017 / Revised: 27 April 2017 / Accepted: 28 April 2017 / Published: 6 May 2017
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Abstract
In this paper, we propose a novel variable pole pitch (VPP) electromagnetic (EM) propulsion technique using a series of ladder-slot-secondary double-sided linear induction motors (LS-secondary DLIMs). An equivalent circuit is developed for the LS-secondary DLIM, which considers the distribution of the eddy current
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In this paper, we propose a novel variable pole pitch (VPP) electromagnetic (EM) propulsion technique using a series of ladder-slot-secondary double-sided linear induction motors (LS-secondary DLIMs). An equivalent circuit is developed for the LS-secondary DLIM, which considers the distribution of the eddy current in the ladders and the end effect. This equivalent circuit forms the basis for the subsequent design, numerical analysis, and optimization. The primary purpose of the VPP EM propulsion system is to address several obstacles encountered in high-speed large-thrust applications of LIMs, such as power factor improvement, optimization considering supply frequency constraint and operating kinetics, etc. The equivalent circuit of the LS-secondary DLIM, i.e., the theoretical foundation of the VPP EM propulsion, has been validated via simulation and experimentation on a small-scale platform, which proves that the numerical analysis of the VPP EM propulsion is effective. Full article
(This article belongs to the Section Energy)
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Open AccessArticle Development of Height Indicators using Omnidirectional Images and Global Appearance Descriptors
Appl. Sci. 2017, 7(5), 482; doi:10.3390/app7050482
Received: 9 March 2017 / Revised: 2 May 2017 / Accepted: 4 May 2017 / Published: 6 May 2017
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Abstract
Nowadays, mobile robots have become a useful tool that permits solving a wide range of applications. Their importance lies in their ability to move autonomously through unknown environments and to adapt to changing conditions. To this end, the robot must be able to
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Nowadays, mobile robots have become a useful tool that permits solving a wide range of applications. Their importance lies in their ability to move autonomously through unknown environments and to adapt to changing conditions. To this end, the robot must be able to build a model of the environment and to estimate its position using the information captured by the different sensors it may be equipped with. Omnidirectional vision sensors have become a robust option thanks to the richness of the data they capture. These data must be analysed to extract relevant information that permits estimating the position of the robot taking into account the number of degrees of freedom it has. In this work, several methods to estimate the relative height of a mobile robot are proposed and evaluated. The framework we present is based on the global appearance of the scenes, which has emerged as an efficient and robust alternative comparing to methods based on local features. All the algorithms have been tested with some sets of images captured under real working conditions in several indoor and outdoor spaces. The results prove that global appearance descriptors provide a feasible alternative to estimate topologically the relative altitude of the robot. Full article
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Open AccessFeature PaperArticle Late Reverberation Synthesis Using Filtered Velvet Noise
Appl. Sci. 2017, 7(5), 483; doi:10.3390/app7050483
Received: 15 March 2017 / Revised: 2 May 2017 / Accepted: 3 May 2017 / Published: 6 May 2017
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Abstract
This paper discusses the modeling of the late part of a room impulse response by dividing it into short segments and approximating each one as a filtered random sequence. The filters and their associated gain account for the spectral shape and decay of
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This paper discusses the modeling of the late part of a room impulse response by dividing it into short segments and approximating each one as a filtered random sequence. The filters and their associated gain account for the spectral shape and decay of the overall response. The noise segments are realized with velvet noise, which is sparse pseudo-random noise. The proposed approach leads to a parametric representation and computationally efficient artificial reverberation, since convolution with velvet noise reduces to a multiplication-free sparse sum. Cascading of the differential coloration filters is proposed to further reduce the computational cost. A subjective test shows that the resulting approximation of the late reverberation often leads to a noticeable difference in comparison to the original impulse response, especially with transient sounds, but the difference is minor. The proposed method is very efficient in terms of real-time computational cost and memory storage. The proposed method will be useful for spatial audio applications. Full article
(This article belongs to the Special Issue Spatial Audio)
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Open AccessArticle Numerical Simulation of Red Blood Cell-Induced Platelet Transport in Saccular Aneurysms
Appl. Sci. 2017, 7(5), 484; doi:10.3390/app7050484
Received: 2 March 2017 / Revised: 3 May 2017 / Accepted: 4 May 2017 / Published: 6 May 2017
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Abstract
We present a numerical simulation of blood flow in two aneurysmal vessels. Using a multicomponent continuum approach, called mixture theory, the velocity fields and spatial distribution of the red blood cells (RBCs) and the plasma are predicted. Platelet migration is described by a
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We present a numerical simulation of blood flow in two aneurysmal vessels. Using a multicomponent continuum approach, called mixture theory, the velocity fields and spatial distribution of the red blood cells (RBCs) and the plasma are predicted. Platelet migration is described by a convection-diffusion equation, coupled to the RBC concentration field. The model is applied to study a two-dimensional straight vessel and multiple two-dimensional aneurysm vessels with different neck sizes. The model accurately predicts the enrichment of the platelets near the wall in the straight vessel, agreeing with the experimental measurement quantitatively. The numerical results also show that the near-wall enrichment of the platelets in the parent vessel highly influences the platelet concentration within the aneurysm. The results also indicate that the platelet concentration within the aneurysm increases with Reynolds number and decreases with a smaller neck size. This might have significance on the formation of thrombus (blood clot) within the aneurysm, which in turn may have a protective effect on preventing ruptures. Based on the success with the problems studied, we believe the current model can be a useful tool for analyzing the blood flow and platelets transport within patient specific aneurysms in the future. Full article
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Open AccessArticle Optimization of Hybrid Ultrasonic Frequency Pulsed VP-GTAW Process Parameters on Tensile Properties of AA 5456 Alloy
Appl. Sci. 2017, 7(5), 485; doi:10.3390/app7050485
Received: 17 March 2017 / Revised: 18 April 2017 / Accepted: 5 May 2017 / Published: 8 May 2017
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Abstract
Tensile properties optimization of AA 5456 aluminum alloy was carried out with hybrid ultrasonic frequency pulsed variable polarity gas tungsten arc wending (HPVP-GTAW). An orthogonal method was employed to conduct the experiments, and the tensile properties of AA 5456 aluminum alloy welded joints
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Tensile properties optimization of AA 5456 aluminum alloy was carried out with hybrid ultrasonic frequency pulsed variable polarity gas tungsten arc wending (HPVP-GTAW). An orthogonal method was employed to conduct the experiments, and the tensile properties of AA 5456 aluminum alloy welded joints were measured and analyzed. Regression models were developed based on the least square estimation by taking tensile strength, yield strength, percent elongation, and ratio of reduction in area as response functions of variable polarity frequency fL, pulse frequency fH and a dimensionless parameter ψ, which were calculated by background current Ib, peak current Ip, and pulse duration δ, respectively. The developed regression equations were checked for validity by coefficient of correlation r2 and confirmatory experiments. Optimum parameters of HPVP-GTAW were achieved through the discussion on response surfaces and contour plots drawn using the regression equations. Full article
(This article belongs to the Special Issue Gas Tungsten Arc Welding)
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Open AccessArticle Relationship between Amount of Daily Movement Measured by a Triaxial Accelerometer and Motor Symptoms in Patients with Parkinson’s Disease
Appl. Sci. 2017, 7(5), 486; doi:10.3390/app7050486
Received: 20 January 2017 / Revised: 3 May 2017 / Accepted: 4 May 2017 / Published: 9 May 2017
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Abstract
The aim of this study was to analyze the association between the amount of daily movement measured with a triaxial accelerometer (MIMAMORI-Gait) and motor symptoms in patients with Parkinson’s disease (PD). The subjects were 50 consecutive patients with untreated PD free of dementia.
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The aim of this study was to analyze the association between the amount of daily movement measured with a triaxial accelerometer (MIMAMORI-Gait) and motor symptoms in patients with Parkinson’s disease (PD). The subjects were 50 consecutive patients with untreated PD free of dementia. The amount of overall movement over 24 h was measured with the portable MIMAMORI-Gait device and its association with the modified Hoehn and Yahr stage and UPDRS part II and III scores was analyzed. In patients with PD, the amount of overall movement measured with MIMAMORI-Gait was significantly associated with the UPDRS part II score (β = −0.506, p < 0.001) and part III score (β = −0.347, p = 0.010), but not with the modified Hoehn and Yahr stage. The amount of overall movement measured with MIMAMORI-Gait can potentially be used for evaluation of motor symptoms and ADL in PD patients. Full article
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Open AccessArticle Decision Optimization for Power Grid Operating Conditions with High- and Low-Voltage Parallel Loops
Appl. Sci. 2017, 7(5), 487; doi:10.3390/app7050487
Received: 15 March 2017 / Revised: 26 April 2017 / Accepted: 5 May 2017 / Published: 9 May 2017
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Abstract
With the development of higher-voltage power grids, the high- and low-voltage parallel loops are emerging, which lead to energy losses and even threaten the security and stability of power systems. The multi-infeed high-voltage direct current (HVDC) configurations widely appearing in AC/DC interconnected power
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With the development of higher-voltage power grids, the high- and low-voltage parallel loops are emerging, which lead to energy losses and even threaten the security and stability of power systems. The multi-infeed high-voltage direct current (HVDC) configurations widely appearing in AC/DC interconnected power systems make this situation even worse. Aimed at energy saving and system security, a decision optimization method for power grid operating conditions with high- and low-voltage parallel loops is proposed in this paper. Firstly, considering hub substation distribution and power grid structure, parallel loop opening schemes are generated with GN (Girvan-Newman) algorithms. Then, candidate opening schemes are preliminarily selected from all these generated schemes based on a filtering index. Finally, with the influence on power system security, stability and operation economy in consideration, an evaluation model for candidate opening schemes is founded based on analytic hierarchy process (AHP). And a fuzzy evaluation algorithm is used to find the optimal scheme. Simulation results of a New England 39-bus system and an actual power system validate the effectiveness and superiority of this proposed method. Full article
(This article belongs to the Special Issue Energy Saving)
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Open AccessFeature PaperArticle Design Optimization of a District Heating Network Expansion, a Case Study for the Town of Kiruna
Appl. Sci. 2017, 7(5), 488; doi:10.3390/app7050488
Received: 28 March 2017 / Revised: 2 May 2017 / Accepted: 5 May 2017 / Published: 10 May 2017
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Abstract
The urbanization of new areas beyond the existing perimeter of a town implies the expansion of several infrastructures, including the district heating network. The main variables involved in the design of the district heating network expansion are the layout of the new pipes,
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The urbanization of new areas beyond the existing perimeter of a town implies the expansion of several infrastructures, including the district heating network. The main variables involved in the design of the district heating network expansion are the layout of the new pipes, their diameters, and the capacity of the new heat production sites that are required to satisfy the increased demand of room heating and hot tap water. In this paper, a multi-objective evolutionary algorithm is applied to the minimization of the costs related to the expansion of the district heating network of the town of Kiruna, in northern Sweden. The results show that the spectrum of the optimal design compromises between investment costs for the new pipes and the new heat generation site on one side, and operating costs due to overall fuel consumption and pumping power in the network on the other. The presented methodology is a tool meant for the decision makers in the company who own the district heating network, to evaluate all the possible best design alternatives before making a decision. Full article
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Open AccessArticle Mechanical Performance Monitoring for Prestressed Concrete Piles Used in a Newly-Built High-Piled Wharf in a Harbor with Fiber Bragg Grating Sensor Technology When Pile Driving
Appl. Sci. 2017, 7(5), 489; doi:10.3390/app7050489
Received: 24 March 2017 / Revised: 20 April 2017 / Accepted: 26 April 2017 / Published: 10 May 2017
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Abstract
Mechanical performance monitoring of civil infrastructure using fiber Bragg grating (FBG) sensors has received significant public attention in recent years. However, there is currently little research on the mechanical performance monitoring of piles used in high-piled wharfs in coastal ports during pile driving
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Mechanical performance monitoring of civil infrastructure using fiber Bragg grating (FBG) sensors has received significant public attention in recent years. However, there is currently little research on the mechanical performance monitoring of piles used in high-piled wharfs in coastal ports during pile driving using the FBG sensor technique. Based on the properties of precast prestressed concrete piles used in high-piled wharfs in coastal ports and servicing seawater environments, and the benefits of FBG sensors, the mechanical performance monitoring for precast prestressed concrete piles used in a newly-built high-piled wharf in the Tianjin Port of China is devised and deployed with the FBG sensor technique. To conduct performance monitoring of the precast prestressed concrete pile, a state-of-the-art FBG strain sensor, which is less thermosensitive and does not require temperature compensation, was used to monitor the strain status of different locations of the pile. In one pile, three of this kind of strain sensor were set near the head, middle and tip of the pile, and one FBG angle sensor was set near the head of the pile to measure the dip angle of the pile. During the testing, data were recorded for all of the details of the pile driving process. According to the data analysis, it is clear that the compressive strain at the middle of the pile during driving is larger than that near the head and tip of the pile. Therefore, the middle of the prestressed concrete pile is the key location that should be preferentially monitored during pile driving. Meanwhile, when the hammer impacts the pile continuously, the obvious tension strain at the tip of the pile increases and the maximum dynamic tension strain reaches 56 με, which approaches the tension ultimate strain. This occurs because the frictional resistance of soil is small in the middle of the pile when the tip meets the significant supporting soil layer. This study can provide a reference for the mechanical performance monitoring deployment of precast prestressed concrete piles used in high-piled wharf structures in coastal ports. Full article
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