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Appl. Sci., Volume 8, Issue 3 (March 2018)

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Cover Story (view full-size image) The objective of this study is to investigate the feasibility of ball-milled graphene oxide [...] Read more.
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Editorial

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Open AccessEditorial Advances in Vibroacoustics and Aeroacustics of Aerospace and Automotive Systems
Appl. Sci. 2018, 8(3), 366; https://doi.org/10.3390/app8030366
Received: 23 February 2018 / Revised: 26 February 2018 / Accepted: 27 February 2018 / Published: 3 March 2018
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Open AccessEditorial Special Issue on Solid State Lasers Materials, Technologies and Applications
Appl. Sci. 2018, 8(3), 460; https://doi.org/10.3390/app8030460
Received: 13 March 2018 / Revised: 15 March 2018 / Accepted: 15 March 2018 / Published: 17 March 2018
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Abstract
Even though more than half a century has already passed since the first demonstration of laser action in ruby crystal, solid-state lasers are still a hot research topic.[...] Full article

Research

Jump to: Editorial, Review

Open AccessFeature PaperArticle Quasi-Static Elastography and Ultrasound Plane-Wave Imaging: The Effect of Beam-Forming Strategies on the Accuracy of Displacement Estimations
Appl. Sci. 2018, 8(3), 319; https://doi.org/10.3390/app8030319
Received: 22 December 2017 / Revised: 15 February 2018 / Accepted: 17 February 2018 / Published: 26 February 2018
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Abstract
Quasi-static elastography is an ultrasound method which is widely used to assess displacements and strain in tissue by correlating ultrasound data at different levels of deformation. Ultrafast plane-wave imaging allows us to obtain ultrasound data at frame rates over 10 kHz, permitting the
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Quasi-static elastography is an ultrasound method which is widely used to assess displacements and strain in tissue by correlating ultrasound data at different levels of deformation. Ultrafast plane-wave imaging allows us to obtain ultrasound data at frame rates over 10 kHz, permitting the quantification and visualization of fast deformations. Currently, mainly three beam-forming strategies are used to reconstruct radio frequency (RF) data from plane-wave acquisitions: delay-and-sum (DaS), and Lu’s-fk and Stolt’s-fk operating in the temporal-spatial and Fourier spaces, respectively. However, the effect of these strategies on elastography is unknown. This study investigates the effect of these beam-forming strategies on the accuracy of displacement estimation in four transducers (L7-4, 12L4VF, L12-5, MS250) for various reconstruction line densities and apodization/filtering settings. A method was developed to assess the accuracy experimentally using displacement gradients obtained in a rotating phantom. A line density with multiple lines per pitch resulted in increased accuracy compared to one line per pitch for all transducers and strategies. The impact on displacement accuracy of apodization/filtering varied per transducer. Overall, Lu’s-fk beam-forming resulted in the most accurate displacement estimates. Although DaS in some cases provided similar results, Lu’s-fk is more computationally efficient, leading to the conclusion that Lu’s-fk is most optimal for plane wave ultrasound-based elastography. Full article
(This article belongs to the Special Issue Ultrafast Ultrasound Imaging)
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Open AccessArticle Failure Monitoring and Condition Assessment of Steel-Concrete Adhesive Connection Using Ultrasonic Waves
Appl. Sci. 2018, 8(3), 320; https://doi.org/10.3390/app8030320
Received: 12 February 2018 / Revised: 17 February 2018 / Accepted: 22 February 2018 / Published: 26 February 2018
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Abstract
Adhesive bonding is increasingly being incorporated into civil engineering applications. Recently, the use of structural adhesives in steel-concrete composite systems is of particular interest. The aim of the study is an experimental investigation of the damage assessment of the connection between steel and
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Adhesive bonding is increasingly being incorporated into civil engineering applications. Recently, the use of structural adhesives in steel-concrete composite systems is of particular interest. The aim of the study is an experimental investigation of the damage assessment of the connection between steel and concrete during mechanical degradation. Nine specimens consisted of a concrete cube and two adhesively bonded steel plates were examined. The inspection was based on the ultrasound monitoring during push-out tests. Ultrasonic waves were excited and registered by means of piezoelectric transducers every two seconds until the specimen failure. To determine the slip between the steel and concrete a photogrammetric method was applied. The procedure of damage evaluation is based on the monitoring of the changes in the amplitude and phase shift of signals measured during subsequent phases of degradation. To quantify discrepancies between the reference signal and other registered signals, the Sprague and Gears metric was applied. The results showed the possibilities and limitations of the proposed approach in diagnostics of adhesive connections between steel and concrete depending on the failure modes. Full article
(This article belongs to the Section Acoustics)
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Open AccessFeature PaperArticle Characteristic Analysis of Compact Spectrometer Based on Off-Axis Meta-Lens
Appl. Sci. 2018, 8(3), 321; https://doi.org/10.3390/app8030321
Received: 18 January 2018 / Revised: 14 February 2018 / Accepted: 23 February 2018 / Published: 26 February 2018
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Abstract
Ultra-compact spectrometers with high-resolution and/or broadband features have long been pursued for their wide application prospects. The off-axis meta-lens, a new species of planar optical instruments, provides a unique and feasible way to realize these goals. Here we give a detailed investigation of
[...] Read more.
Ultra-compact spectrometers with high-resolution and/or broadband features have long been pursued for their wide application prospects. The off-axis meta-lens, a new species of planar optical instruments, provides a unique and feasible way to realize these goals. Here we give a detailed investigation of the influences of structural parameters of meta-lens-based spectrometers on the effective spectral range and the spectral resolution using both wave optics and geometrical optics methods. Aimed for different usages, two types of meta-lens based spectrometers are numerically proposed: one is a wideband spectrometer working at 800–1800 nm wavelengths with the spectral resolution of 2–5 nm and the other is a narrowband one working at the 780–920 nm band but with a much higher spectral resolution of 0.15–0.6 nm. The tolerance for fabrication errors is also discussed in the end. These provides a prominent way to design and integrate planar film-based spectrometers for various instrumental applications. Full article
(This article belongs to the Special Issue Metasurfaces: Physics and Applications)
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Open AccessArticle Attosecond Time Delay in Photoionization of Noble-Gas and Halogen Atoms
Appl. Sci. 2018, 8(3), 322; https://doi.org/10.3390/app8030322
Received: 5 February 2018 / Revised: 18 February 2018 / Accepted: 20 February 2018 / Published: 26 February 2018
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Abstract
Ultrafast processes are now accessible on the attosecond time scale due to the availability of ultrashort XUV laser pulses. Noble-gas and halogen atoms remain important targets due to their giant dipole resonance and Cooper minimum. Here, we calculate photoionization cross section, asymmetry parameter
[...] Read more.
Ultrafast processes are now accessible on the attosecond time scale due to the availability of ultrashort XUV laser pulses. Noble-gas and halogen atoms remain important targets due to their giant dipole resonance and Cooper minimum. Here, we calculate photoionization cross section, asymmetry parameter and Wigner time delay using the time-dependent local-density approximation (TDLDA), which includes the electron correlation effects. Our results are consistent with experimental data and other theoretical calculations. The asymmetry parameter provides an extra layer of access to the phase information of the photoionization processes. We find that halogen atoms bear a strong resemblance on cross section, asymmetry parameter and time delay to their noble-gas neighbors. Our predicted time delay should provide a guidance for future experiments on those atoms and related molecules. Full article
(This article belongs to the Special Issue Extreme Time Scale Photonics)
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Open AccessArticle Applicability of Emotion Recognition and Induction Methods to Study the Behavior of Programmers
Appl. Sci. 2018, 8(3), 323; https://doi.org/10.3390/app8030323
Received: 22 December 2017 / Revised: 7 February 2018 / Accepted: 24 February 2018 / Published: 26 February 2018
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Abstract
Recent studies in the field of software engineering have shown that positive emotions can increase and negative emotions decrease the productivity of programmers. In the field of affective computing, many methods and tools to recognize the emotions of computer users were proposed. However,
[...] Read more.
Recent studies in the field of software engineering have shown that positive emotions can increase and negative emotions decrease the productivity of programmers. In the field of affective computing, many methods and tools to recognize the emotions of computer users were proposed. However, it has not been verified yet which of them can be used to monitor the emotional states of software developers. The paper describes a study carried out on a group of 35 participants to determine which of these methods can be used during programming. During the study, data from multiple sensors that are commonly used in methods of emotional recognition were collected. The participants were extensively questioned about the sensors’ invasiveness during programming. This allowed us to determine which of them are applicable in the work of programmers. In addition, it was verified which methods are suitable for use in the work environment and which are only suitable in the laboratory. Moreover, three methods for inducing negative emotions have been proposed, and their effectiveness has been verified. Full article
(This article belongs to the Special Issue Socio-Cognitive and Affective Computing)
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Open AccessArticle Improvement of RF Wireless Power Transmission Using a Circularly Polarized Retrodirective Antenna Array with EBG Structures
Appl. Sci. 2018, 8(3), 324; https://doi.org/10.3390/app8030324
Received: 14 December 2017 / Revised: 5 February 2018 / Accepted: 22 February 2018 / Published: 26 February 2018
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Abstract
This paper presents the performance improvement of a circularly polarized (CP) retrodirective array (RDA) through the suppression of mutual coupling effects. The RDA is designed based on CP Koch-shaped patch antenna elements with an inter-element spacing as small as 0.4λ for a
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This paper presents the performance improvement of a circularly polarized (CP) retrodirective array (RDA) through the suppression of mutual coupling effects. The RDA is designed based on CP Koch-shaped patch antenna elements with an inter-element spacing as small as 0.4 λ for a compact size ( λ is the wavelength in free space at the designed frequency of 5.2 GHz). Electromagnetic band gap (EBG) structures are applied to reduce the mutual coupling between the antenna elements, thus improving the circular polarization characteristic of the RDA. Two CP RDAs with EBGs, in the case 5 × 5 and 10 × 10 arrays, are used as wireless power transmitters to transmit a total power of 50 W. A receiver is located at a distance of 1 m away from the transmitter to harvest the transmitted power. At the broadside direction, the simulated results demonstrate that the received powers are improved by approximately 11.32% and 12.45% when using the 5 × 5 and 10 × 10 CP RDAs with the EBGs, respectively, as the transmitters. Full article
(This article belongs to the Section Computer Science and Electrical Engineering)
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Open AccessArticle Flexural Performance of Transparent Plastic Bar Reinforced Concrete
Appl. Sci. 2018, 8(3), 325; https://doi.org/10.3390/app8030325
Received: 17 December 2017 / Revised: 20 February 2018 / Accepted: 21 February 2018 / Published: 26 February 2018
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Abstract
In this study, experiments were conducted to derive a mix design for improving the flexural performance of light transparent concrete, which is attracting much attention and interest as an interior and exterior material for buildings, so that it could be easily applied in
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In this study, experiments were conducted to derive a mix design for improving the flexural performance of light transparent concrete, which is attracting much attention and interest as an interior and exterior material for buildings, so that it could be easily applied in the field as a non-structural element by securing a lightweight, workability, and economic efficiency through the improvement of the concrete mix design and the use of economical materials for promoting its practical use. It was found that the mixing of polyvinyl alcohol (PVA) fiber was effective in improving the consistency by preventing the aggregate from floating due to the mixing of lightweight aggregate with a low specific gravity. The flexural performance test results showed that the load transfer factor (LTF) from the concrete matrix to the fiber was highest in the test specimens without plastic bars, followed by those with 5 and 10 mm plastic bars, respectively. Full article
(This article belongs to the Section Materials)
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Open AccessFeature PaperArticle Capacity Enhancement of Few-Mode Fiber Transmission Systems Impaired by Mode-Dependent Loss
Appl. Sci. 2018, 8(3), 326; https://doi.org/10.3390/app8030326
Received: 24 January 2018 / Revised: 16 February 2018 / Accepted: 17 February 2018 / Published: 26 February 2018
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Abstract
Space-division multiplexing over few-mode fibers is a promising solution to increase the capacity of the future generation of optical transmission systems. Mode-dependent loss (MDL) is known to have a detrimental impact on the capacity of few-mode fiber systems. In the presence of MDL,
[...] Read more.
Space-division multiplexing over few-mode fibers is a promising solution to increase the capacity of the future generation of optical transmission systems. Mode-dependent loss (MDL) is known to have a detrimental impact on the capacity of few-mode fiber systems. In the presence of MDL, spatial modes experience different attenuations which results in capacity reduction. In this work, we propose a digital signal processing solution and an optical solution to mitigate the impact of MDL and improve the channel capacity. First, we show that statistical channel state information can be used for a better power allocation for spatial modes instead of equal launch power to increase the system capacity. Afterwards, we propose a deterministic mode scrambling strategy to efficiently reduces the impact of MDL and improves few-mode fiber systems capacity. This scrambling strategy can be efficiently combined with the optimal power allocation to further enhance the capacity. Through numerical simulations of the average and outage capacities, we show that the proposed techniques bring significant capacity gains. Full article
(This article belongs to the Special Issue DSP for Next Generation Fibre Communication Systems)
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Open AccessArticle Surface Decorated Zn0.15Cd0.85S Nanoflowers with P25 for Enhanced Visible Light Driven Photocatalytic Degradation of Rh-B and Stability
Appl. Sci. 2018, 8(3), 327; https://doi.org/10.3390/app8030327
Received: 22 January 2018 / Revised: 10 February 2018 / Accepted: 17 February 2018 / Published: 26 February 2018
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Abstract
Decoration of Zn0.15Cd0.85S nanoflowers with P25 for forming P25/Zn0.15Cd0.85S nanocomposite has been successfully synthesized with fine crystallinity by one-step low temperature hydrothermal method. Photocatalytic efficiency of the as-prepared P25/Zn0.15Cd0.85S for the
[...] Read more.
Decoration of Zn0.15Cd0.85S nanoflowers with P25 for forming P25/Zn0.15Cd0.85S nanocomposite has been successfully synthesized with fine crystallinity by one-step low temperature hydrothermal method. Photocatalytic efficiency of the as-prepared P25/Zn0.15Cd0.85S for the degradation of Rh-B is evaluated under the visible light irradiation. The synthesized composite is completely characterized with XRD, FESEM, TEM, BET, and UV-vis DRS. TEM observations reveal that P25 is closely deposited on the Zn0.15Cd0.85S nanoflowers with maintaining its nanoflower morphology. The photocatalytic activity of the as-obtained photocatalyst shows that the P25/Zn0.15Cd0.85S exhibits very high catalytic activity for degradation of Rh-B under visible light irradiation due to an increasing of the active sites and enhancing the catalyst stability because of the minimum recombination of the photo-induced electrons and holes. Moreover, it is found that the nanocomposite retains its photocatalytic activity even after four cycles. In addition, to explain the mechanism of degradation, scavengers are used to confirm the reactive species. Photo-generated holes and OH play a significant role in the visible light of P25/Zn0.15Cd0.85S nanocomposite induced degradation system, but electrons play the most important role. Full article
(This article belongs to the Section Chemistry)
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Open AccessArticle Multi-Agent Decision Support Tool to Enable Interoperability among Heterogeneous Energy Systems
Appl. Sci. 2018, 8(3), 328; https://doi.org/10.3390/app8030328
Received: 30 December 2017 / Revised: 8 February 2018 / Accepted: 17 February 2018 / Published: 26 February 2018
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Abstract
Worldwide electricity markets are undergoing a major restructuring process. One of the main reasons for the ongoing changes is to enable the adaptation of current market models to the new paradigm that arises from the large-scale integration of distributed generation sources. In order
[...] Read more.
Worldwide electricity markets are undergoing a major restructuring process. One of the main reasons for the ongoing changes is to enable the adaptation of current market models to the new paradigm that arises from the large-scale integration of distributed generation sources. In order to deal with the unpredictability caused by the intermittent nature of the distributed generation and the large number of variables that contribute to the energy sector balance, it is extremely important to use simulation systems that are capable of dealing with the required complexity. This paper presents the Tools Control Center (TOOCC), a framework that allows the interoperability between heterogeneous energy and power simulation systems through the use of ontologies, allowing the simulation of scenarios with a high degree of complexity, through the cooperation of the individual capacities of each system. A case study based on real data is presented in order to demonstrate the interoperability capabilities of TOOCC. The simulation considers the energy management of a microgrid of a real university campus, from the perspective of the network manager and also of its consumers/producers, in a projection for a typical day of the winter of 2050. Full article
(This article belongs to the Section Energy)
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Open AccessArticle Artificial Flora (AF) Optimization Algorithm
Appl. Sci. 2018, 8(3), 329; https://doi.org/10.3390/app8030329
Received: 9 January 2018 / Revised: 12 February 2018 / Accepted: 17 February 2018 / Published: 26 February 2018
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Abstract
Inspired by the process of migration and reproduction of flora, this paper proposes a novel artificial flora (AF) algorithm. This algorithm can be used to solve some complex, non-linear, discrete optimization problems. Although a plant cannot move, it can spread seeds within a
[...] Read more.
Inspired by the process of migration and reproduction of flora, this paper proposes a novel artificial flora (AF) algorithm. This algorithm can be used to solve some complex, non-linear, discrete optimization problems. Although a plant cannot move, it can spread seeds within a certain range to let offspring to find the most suitable environment. The stochastic process is easy to copy, and the spreading space is vast; therefore, it is suitable for applying in intelligent optimization algorithm. First, the algorithm randomly generates the original plant, including its position and the propagation distance. Then, the position and the propagation distance of the original plant as parameters are substituted in the propagation function to generate offspring plants. Finally, the optimal offspring is selected as a new original plant through the selection function. The previous original plant becomes the former plant. The iteration continues until we find out optimal solution. In this paper, six classical evaluation functions are used as the benchmark functions. The simulation results show that proposed algorithm has high accuracy and stability compared with the classical particle swarm optimization and artificial bee colony algorithm. Full article
(This article belongs to the Special Issue Swarm Robotics)
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Open AccessArticle Compact 6 dB Two-Color Continuous Variable Entangled Source Based on a Single Ring Optical Resonator
Appl. Sci. 2018, 8(3), 330; https://doi.org/10.3390/app8030330
Received: 26 January 2018 / Revised: 22 February 2018 / Accepted: 24 February 2018 / Published: 26 February 2018
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Abstract
Continuous-variable entangled optical beams at the degenerate wavelength of 0.8 μm or 1.5 μm have been investigated extensively, but separately. The two-color entangled states of these two useful wavelengths, with sufficiently high degrees of entanglement, still lag behind. In this work, we analyze
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Continuous-variable entangled optical beams at the degenerate wavelength of 0.8 μm or 1.5 μm have been investigated extensively, but separately. The two-color entangled states of these two useful wavelengths, with sufficiently high degrees of entanglement, still lag behind. In this work, we analyze the various limiting factors that affect the entanglement degree. On the basis of this, we successfully achieve 6 dB of two-color quadrature entangled light beams by improving the escape efficiency of the nondegenerate optical amplifier, the stability of the phase-locking servo system, and the detection efficiency. Our entangled source is constructed only from a single ring optical resonator, and thus is highly compact, which is suitable for applications in long-distance quantum communication networks. Full article
(This article belongs to the Section Optics and Lasers)
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Open AccessArticle Granular Activated Carbon from Grape Seeds Hydrothermal Char
Appl. Sci. 2018, 8(3), 331; https://doi.org/10.3390/app8030331
Received: 7 November 2017 / Revised: 13 February 2018 / Accepted: 15 February 2018 / Published: 27 February 2018
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Abstract
A two-stage conversion process for the production of a valuable product from biomass waste, i.e., grape seeds activated carbon (GSAC) was investigated. Such process involved hydrothermal carbonization (HTC) of grape seeds, followed by chemical activation with potassium hydroxide (KOH). Different HTC temperatures (T
[...] Read more.
A two-stage conversion process for the production of a valuable product from biomass waste, i.e., grape seeds activated carbon (GSAC) was investigated. Such process involved hydrothermal carbonization (HTC) of grape seeds, followed by chemical activation with potassium hydroxide (KOH). Different HTC temperatures (THTC = 180–250 °C), as well as different KOH:hydrochar ratios (R = 0.25:1–1:1), were explored. The samples that were obtained from both stages of the biomass conversion process were analyzed in terms of textural characterization (apparent total and micro-pore surface areas, total and micro-pore volumes, pore size distribution), proximate and ultimate compositions, thermal stability, surface morphology (via SEM), and surface chemistry characterization (via FTIR). Overall yields of approximately 35% were achieved, which are comparable to those obtained with the state-of-art one-stage process. In a wide range of operating conditions, the higher THTC and R, the higher was the surface area of the GSAC, which was maximal (above 1000 m2/g) for THTC = 250 °C and R = 0.5. At such optimal conditions, around 90% of the total porosity was due to micro-pores. Such a trend was not fulfilled at the most severe operating conditions (THTC = 250 °C; R = 1), which resulted in larger pore size, causing surface area reduction. A proper selection of the process parameters of both the process stages gives great opportunities of tuning and optimizing the overall process. The produced GSACs showed a remarkable thermal stability, and their surface appeared rather free of functional groups. Full article
(This article belongs to the Section Chemistry)
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Open AccessArticle Comparative Spectroscopic Investigation of Tm3+:Tellurite Glasses for 2-μm Lasing Applications
Appl. Sci. 2018, 8(3), 333; https://doi.org/10.3390/app8030333
Received: 10 January 2018 / Revised: 13 February 2018 / Accepted: 21 February 2018 / Published: 27 February 2018
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Abstract
We performed a comparative spectroscopic analysis on three novel Tm3+:tellurite-based glasses with the following compositions Tm2O3:TeO2-ZnO (TeZnTm), Tm2O3:TeO2-Nb2O5 (TeNbTm), and Tm3+:TeO2-K2
[...] Read more.
We performed a comparative spectroscopic analysis on three novel Tm3+:tellurite-based glasses with the following compositions Tm2O3:TeO2-ZnO (TeZnTm), Tm2O3:TeO2-Nb2O5 (TeNbTm), and Tm3+:TeO2-K2O-Nb2O5 (TeNbKTm), primarily for 2-μm laser applications. Tellurite glasses were prepared at different doping concentrations in order to investigate the effect of Tm3+ ion concentration as well as host composition on the stimulated emission cross sections and the luminescence quantum efficiencies. By performing Judd–Ofelt analysis, we determined the average radiative lifetimes of the 3H4 level to be 2.55 ± 0.07 ms, 2.76 ± 0.03 ms and 2.57 ± 0.20 ms for the TeZnTm, TeNbTm and TeNbKTm samples, respectively. We clearly observed the effect of the cross-relaxation, which becomes significant at higher Tm2O3 concentrations, leading to the quenching of 1460-nm emission and enhancement of 1860-nm emission. Furthermore, with increasing Tm2O3 concentrations, we observed a decrease in the fluorescence lifetimes as a result of the onset of non-radiative decay. For the 3H4 level, the highest obtained quantum efficiency was 32% for the samples with the lowest Tm2O3 ion concentration. For the 1860-nm emission band, the average emission cross section was determined to measure around 6.33 ± 0.34 × 10−21 cm2, revealing the potential of thulium-doped tellurite gain media for 2-μm laser applications in bulk and fiber configurations. Full article
(This article belongs to the Special Issue Rare-Earth Doping for Optical Applications)
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Open AccessArticle Minkowski Island and Crossbar Fractal Microstrip Antennas for Broadband Applications
Appl. Sci. 2018, 8(3), 334; https://doi.org/10.3390/app8030334
Received: 4 February 2018 / Revised: 22 February 2018 / Accepted: 24 February 2018 / Published: 27 February 2018
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Abstract
The paper presents microstrip patch antennas, which are based on the fractal antenna concept, and use planar periodic geometries, providing improved characteristics. The properties of the fractal structure were used in a single-fractal layer design as well as in a design, which employs
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The paper presents microstrip patch antennas, which are based on the fractal antenna concept, and use planar periodic geometries, providing improved characteristics. The properties of the fractal structure were used in a single-fractal layer design as well as in a design, which employs fractals on both the upper and bottom layers of the antenna. The final structure, i.e., a double-fractal layer antenna has been optimized to enhance bandwidth and gain of the microstrip antenna. The proposed geometry significantly improved antenna performance. The antenna could support an ultra-wide bandwidth ranging from 4.1 to 19.4 GHz, demonstrating higher gain with an average value of 6 dBi over the frequency range, and a radiation capability directed in the horizontal plane of the antenna. Full article
(This article belongs to the Special Issue Metasurfaces: Physics and Applications)
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Open AccessArticle REV Application in DEM Analysis of Non-Vibrational Rock Splitting Method to Propose Feasible Borehole Spacing
Appl. Sci. 2018, 8(3), 335; https://doi.org/10.3390/app8030335
Received: 12 February 2018 / Revised: 19 February 2018 / Accepted: 21 February 2018 / Published: 27 February 2018
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Abstract
Most of the tunnel excavation methods involve the use of explosion and vibration techniques that is not feasible in urban areas due to unavoidable production of noise, vibration, and dust. The environmental considerations of tunneling projects in urban areas demand the use of
[...] Read more.
Most of the tunnel excavation methods involve the use of explosion and vibration techniques that is not feasible in urban areas due to unavoidable production of noise, vibration, and dust. The environmental considerations of tunneling projects in urban areas demand the use of excavation methods in which minimum noise, vibration, and dust is produced. In this study, non-vibrational rock splitting method is introduced that involves the fragmentation of rock segments using a split-wedge system inserted into already drilled boreholes. The main objective of this study is the investigation of important parameters involved in the non-vibrational rock splitting method for improving its efficiency. Discrete element analysis of this method was performed using Particle Flow Code (PFC2D) and the concept of Representative Elementary Volume (REV) was used to simulate intact rocks based on their unconfined compressive strength and modulus ratio concept. Maximum borehole spacing values were obtained using the numerical simulation of rock splitting process in intact rocks. The numerical analysis results show that increased borehole spacing values can be used for all intact rock types in cases of average modulus ratio and high modulus ratio and also that decreasing the borehole depth generally results in the use of increased borehole spacing. Full article
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Open AccessFeature PaperArticle Radiation Pressure-Driven Plasma Surface Dynamics in Ultra-Intense Laser Pulse Interactions with Ultra-Thin Foils
Appl. Sci. 2018, 8(3), 336; https://doi.org/10.3390/app8030336
Received: 8 December 2017 / Revised: 7 February 2018 / Accepted: 17 February 2018 / Published: 27 February 2018
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Abstract
The dynamics of the plasma critical density surface in an ultra-thin foil target irradiated by an ultra-intense (∼6 × 1020 Wcm2) laser pulse is investigated experimentally and via 2D particle-in-cell simulations. Changes to the surface motion are diagnosed as
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The dynamics of the plasma critical density surface in an ultra-thin foil target irradiated by an ultra-intense (∼6 × 10 20 Wcm 2 ) laser pulse is investigated experimentally and via 2D particle-in-cell simulations. Changes to the surface motion are diagnosed as a function of foil thickness. The experimental and numerical results are compared with hole-boring and light-sail models of radiation pressure acceleration, to identify the foil thickness range for which each model accounts for the measured surface motion. Both the experimental and numerical results show that the onset of relativistic self-induced transparency, in the thinnest targets investigated, limits the velocity of the critical surface, and thus the effectiveness of radiation pressure acceleration. Full article
(This article belongs to the Special Issue Laser-Driven Particle Acceleration)
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Open AccessArticle MOVICLOUD: Agent-Based 3D Platform for the Labor Integration of Disabled People
Appl. Sci. 2018, 8(3), 337; https://doi.org/10.3390/app8030337
Received: 18 January 2018 / Revised: 22 February 2018 / Accepted: 23 February 2018 / Published: 27 February 2018
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Abstract
Agent-Based Social Simulation (ABSS), used in combination with three-dimensional representation, makes it possible to do near-reality modeling and visualizations of changing and complex environments. In this paper, we describe the design and implementation of a tool that integrates these two techniques. The purpose
[...] Read more.
Agent-Based Social Simulation (ABSS), used in combination with three-dimensional representation, makes it possible to do near-reality modeling and visualizations of changing and complex environments. In this paper, we describe the design and implementation of a tool that integrates these two techniques. The purpose of this tool is to assist in creating a work environment that is adapted to the needs of people with disabilities. The tool measures the degree of accessibility in the place of work and identifies the architectural barriers of the environment by considering the activities carried out by workers. Thus, thanks to the use of novel mechanisms and simulation techniques more people with disabilities will have the opportunity to work and feel comfortable in the environment. To validate the developed tool, a case study was performed in a real environment. Full article
(This article belongs to the Special Issue Multi-Agent Systems)
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Open AccessArticle MAP-MRF-Based Super-Resolution Reconstruction Approach for Coded Aperture Compressive Temporal Imaging
Appl. Sci. 2018, 8(3), 338; https://doi.org/10.3390/app8030338
Received: 10 January 2018 / Revised: 10 February 2018 / Accepted: 24 February 2018 / Published: 27 February 2018
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Abstract
Coded Aperture Compressive Temporal Imaging (CACTI) can afford low-cost temporal super-resolution (SR), but limits are imposed by noise and compression ratio on reconstruction quality. To utilize inter-frame redundant information from multiple observations and sparsity in multi-transform domains, a robust reconstruction approach based on
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Coded Aperture Compressive Temporal Imaging (CACTI) can afford low-cost temporal super-resolution (SR), but limits are imposed by noise and compression ratio on reconstruction quality. To utilize inter-frame redundant information from multiple observations and sparsity in multi-transform domains, a robust reconstruction approach based on maximum a posteriori probability and Markov random field (MAP-MRF) model for CACTI is proposed. The proposed approach adopts a weighted 3D neighbor system (WNS) and the coordinate descent method to perform joint estimation of model parameters, to achieve the robust super-resolution reconstruction. The proposed multi-reconstruction algorithm considers both total variation (TV) and 2 , 1 norm in wavelet domain to address the minimization problem for compressive sensing, and solves it using an accelerated generalized alternating projection algorithm. The weighting coefficient for different regularizations and frames is resolved by the motion characteristics of pixels. The proposed approach can provide high visual quality in the foreground and background of a scene simultaneously and enhance the fidelity of the reconstruction results. Simulation results have verified the efficacy of our new optimization framework and the proposed reconstruction approach. Full article
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Open AccessFeature PaperArticle Metaheuristic Algorithm for Photovoltaic Parameters: Comparative Study and Prediction with a Firefly Algorithm
Appl. Sci. 2018, 8(3), 339; https://doi.org/10.3390/app8030339
Received: 31 December 2017 / Revised: 15 February 2018 / Accepted: 20 February 2018 / Published: 27 February 2018
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Abstract
In this paper, a Firefly algorithm is proposed for identification and comparative study of five, seven and eight parameters of a single and double diode solar cell and photovoltaic module under different solar irradiation and temperature. Further, a metaheuristic algorithm is proposed in
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In this paper, a Firefly algorithm is proposed for identification and comparative study of five, seven and eight parameters of a single and double diode solar cell and photovoltaic module under different solar irradiation and temperature. Further, a metaheuristic algorithm is proposed in order to predict the electrical parameters of three different solar cell technologies. The first is a commercial RTC mono-crystalline silicon solar cell with single and double diodes at 33 °C and 1000 W/m2. The second, is a flexible hydrogenated amorphous silicon a-Si:H solar cell single diode. The third is a commercial photovoltaic module (Photowatt-PWP 201) in which 36 polycrystalline silicon cells are connected in series, single diode, at 25 °C and 1000 W/m2 from experimental current-voltage. The proposed constrained objective function is adapted to minimize the absolute errors between experimental and predicted values of voltage and current in two zones. Finally, for performance validation, the parameters obtained through the Firefly algorithm are compared with recent research papers reporting metaheuristic optimization algorithms and analytical methods. The presented results confirm the validity and reliability of the Firefly algorithm in extracting the optimal parameters of the photovoltaic solar cell. Full article
(This article belongs to the Special Issue Computational Intelligence in Photovoltaic Systems)
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Open AccessArticle An Integrated Open Approach to Capturing Systematic Knowledge for Manufacturing Process Innovation Based on Collective Intelligence
Appl. Sci. 2018, 8(3), 340; https://doi.org/10.3390/app8030340
Received: 3 February 2018 / Revised: 17 February 2018 / Accepted: 22 February 2018 / Published: 27 February 2018
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Abstract
Process innovation plays a vital role in the manufacture realization of increasingly complex new products, especially in the context of sustainable development and cleaner production. Knowledge-based innovation design can inspire designers’ creative thinking; however, the existing scattered knowledge has not yet been properly
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Process innovation plays a vital role in the manufacture realization of increasingly complex new products, especially in the context of sustainable development and cleaner production. Knowledge-based innovation design can inspire designers’ creative thinking; however, the existing scattered knowledge has not yet been properly captured and organized according to Computer-Aided Process Innovation (CAPI). Therefore, this paper proposes an integrated approach to tackle this non-trivial issue. By analyzing the design process of CAPI and technical features of open innovation, a novel holistic paradigm of process innovation knowledge capture based on collective intelligence (PIKC-CI) is constructed from the perspective of the knowledge life cycle. Then, a multi-source innovation knowledge fusion algorithm based on semantic elements reconfiguration is applied to form new public knowledge. To ensure the credibility and orderliness of innovation knowledge refinement, a collaborative editing strategy based on knowledge lock and knowledge–social trust degree is explored. Finally, a knowledge management system MPI-OKCS integrating the proposed techniques is implemented into the pre-built CAPI general platform, and a welding process innovation example is provided to illustrate the feasibility of the proposed approach. It is expected that our work would lay the foundation for the future knowledge-inspired CAPI and smart process planning. Full article
(This article belongs to the Special Issue Smart Sustainable Manufacturing Systems)
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Open AccessArticle Disentangling Long Trajectory Contributions in Two-Colour High Harmonic Generation
Appl. Sci. 2018, 8(3), 341; https://doi.org/10.3390/app8030341
Received: 18 January 2018 / Revised: 20 February 2018 / Accepted: 23 February 2018 / Published: 28 February 2018
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Abstract
This work investigates High Harmonic Generation (HHG) in gas targets, induced by intense two-colour driving fields. We compared classical trajectory Monte Carlo simulations based on a semiclassical model of strong field tunnel ionisation of helium to experimental HHG spectra, and investigated the relative
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This work investigates High Harmonic Generation (HHG) in gas targets, induced by intense two-colour driving fields. We compared classical trajectory Monte Carlo simulations based on a semiclassical model of strong field tunnel ionisation of helium to experimental HHG spectra, and investigated the relative contribution of long trajectories to low harmonic orders. This phenomenon can be found even when the experimental setup is chosen to suppress long trajectories and favour phase matching for short trajectories. Full article
(This article belongs to the Special Issue Extreme Time Scale Photonics)
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Open AccessArticle Tackling Area Coverage Problems in a Reconfigurable Floor Cleaning Robot Based on Polyomino Tiling Theory
Appl. Sci. 2018, 8(3), 342; https://doi.org/10.3390/app8030342
Received: 22 January 2018 / Revised: 13 February 2018 / Accepted: 22 February 2018 / Published: 28 February 2018
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Abstract
Whilst Polyomino tiling theory has been extensively studied as a branch of research in mathematics, its application has been largely confined to multimedia, graphics and gaming domains. In this paper, we present a novel application of Tromino tiling theory, a class of Polyomino
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Whilst Polyomino tiling theory has been extensively studied as a branch of research in mathematics, its application has been largely confined to multimedia, graphics and gaming domains. In this paper, we present a novel application of Tromino tiling theory, a class of Polyomino with three cells in the context of a reconfigurable floor cleaning robot, hTromo. The developed robot platform is able to automatically generate a global tiling set required to cover a defined space while leveraging on the Tromino tiling theory. Specifically, we validated the application of five Tromino tiling theorems with our hTromo robot. Experiments performed clearly demonstrate the efficacy of the proposed approach resulting in very high levels of area coverage performance in all considered experimental cases. This paper also presents the system architecture of our hTromo robot and a detailed description of the five tiling theorems applied in this study. Full article
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Open AccessArticle Using a Combination of Spectral and Textural Data to Measure Water-Holding Capacity in Fresh Chicken Breast Fillets
Appl. Sci. 2018, 8(3), 343; https://doi.org/10.3390/app8030343
Received: 24 January 2018 / Revised: 19 February 2018 / Accepted: 22 February 2018 / Published: 28 February 2018
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Abstract
The aim here was to explore the potential of visible and near-infrared (Vis/NIR) hyperspectral imaging (400–1000 nm) to classify fresh chicken breast fillets into different water-holding capacity (WHC) groups. Initially, the extracted spectra and image textural features, as well as the mixed data
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The aim here was to explore the potential of visible and near-infrared (Vis/NIR) hyperspectral imaging (400–1000 nm) to classify fresh chicken breast fillets into different water-holding capacity (WHC) groups. Initially, the extracted spectra and image textural features, as well as the mixed data of the two, were used to develop partial least square-discriminant analysis (PLS-DA) classification models. Smoothing, a first derivative process, and principle component analysis (PCA) were carried out sequentially on the mean spectra of all samples to deal with baseline offsets and identify outlier data. Six samples located outside the confidence ellipses of 95% confidence level in the score plot were defined as outliers. A PLS-DA model based on the outlier-free spectra provided a correct classification rate (CCR) value of 78% in the prediction set. Then, seven optimal wavelengths selected using a successive projections algorithm (SPA) were used to develop a simplified PLS-DA model that obtained a slightly reduced CCR with a value of 73%. Moreover, the gray-level co-occurrence matrix (GLCM) was implemented on the first principle component image (with 98.13% of variance) of the hyperspectral image to extract textural features (contrast, correlation, energy, and homogeneity). The CCR of the model developed using textural variables was less optimistic with a value of 59%. Compared to results of models based on spectral or textural data individually, the performance of the model based on the mixed data of optimal spectral and textural features was the best with an improved CCR of 86%. The results showed that the spectral and textural data of hyperspectral images together can be integrated in order to measure and classify the WHC of fresh chicken breast fillets. Full article
(This article belongs to the Special Issue Hyperspectral Chemical Imaging for Food Authentication)
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Open AccessArticle Safety Design and Development of a Human-Robot Collaboration Assembly Process in the Automotive Industry
Appl. Sci. 2018, 8(3), 344; https://doi.org/10.3390/app8030344
Received: 20 December 2017 / Revised: 13 February 2018 / Accepted: 17 February 2018 / Published: 28 February 2018
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Abstract
Human-robot collaboration (HRC) is a complex procedure in manufacturing due to the problems posed by compatibility and operational safety among humans and robots, and by task definitions among them in a collaborative order. In this paper, the research results of the human-robot collaboration
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Human-robot collaboration (HRC) is a complex procedure in manufacturing due to the problems posed by compatibility and operational safety among humans and robots, and by task definitions among them in a collaborative order. In this paper, the research results of the human-robot collaboration study for the case of an automotive brake disc assembly is presented. The analytic hierarchy process (AHP) is proposed as a decision-making method for the human-robot collaboration system, and detailed hierarchical task analysis (HTA) is applied to allocate operational tasks to humans and robots, thus reducing the chance of duty interference. Additionally, a virtual environment software (Tecnomatix Process Simulate, version 11.1,80, Siemens, Munich, BY, Germany, 2012) is used to model the assembly workstation, providing an opportunity to evaluate the feasibility of the process through different scenarios. Finally, an experimental test is conducted to evaluate the performance of the assembly procedure. This research proves that, although human-robot collaboration increases the total process time slightly, this collaboration improves human ergonomics considerably and reduces the operator injury risk. Full article
(This article belongs to the Section Mechanical Engineering)
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Open AccessArticle Characterization of Control-Dependent Variable Stiffness Behavior in Discrete Muscle-Like Actuators
Appl. Sci. 2018, 8(3), 346; https://doi.org/10.3390/app8030346
Received: 5 February 2018 / Revised: 20 February 2018 / Accepted: 22 February 2018 / Published: 28 February 2018
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Abstract
This paper presents the modeling, characterization and validation for a discrete muscle-like actuator system composed of individual on–off motor units with complex dynamics inherent to the architecture. The dynamics include innate hardening behavior in the actuator with increased length. A series elastic actuator
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This paper presents the modeling, characterization and validation for a discrete muscle-like actuator system composed of individual on–off motor units with complex dynamics inherent to the architecture. The dynamics include innate hardening behavior in the actuator with increased length. A series elastic actuator model is used as the plant model for an observer used in feedback control of the actuator. Simulations are performed showing the nonlinear nature of the changing stiffness as well as how this affects the dynamics, clearly observed in the phase portrait. Variable-stiffness hardening behavior is evaluated in experiment and shows good agreement with the model. Full article
(This article belongs to the Special Issue Bio-Inspired Robotics)
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Open AccessArticle Dimensionless Energy Conversion Characteristics of an Air-Powered Hydraulic Vehicle
Appl. Sci. 2018, 8(3), 347; https://doi.org/10.3390/app8030347
Received: 11 February 2018 / Revised: 22 February 2018 / Accepted: 23 February 2018 / Published: 28 February 2018
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Abstract
Due to the advantages of resource conservation and less exhaust emissions, compressed air-powered vehicle has attracted more and more attention. To improve the power and efficiency of air-powered vehicle, an air-powered hydraulic vehicle was proposed. As the main part of the air-powered hydraulic
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Due to the advantages of resource conservation and less exhaust emissions, compressed air-powered vehicle has attracted more and more attention. To improve the power and efficiency of air-powered vehicle, an air-powered hydraulic vehicle was proposed. As the main part of the air-powered hydraulic vehicles, HP transformer (short for Hydropneumatic transformer) is used to convert the pneumatic power to higher hydraulic power. In this study, to illustrate the energy conversion characteristics of air-powered hydraulic vehicle, dimensionless mathematical model of the vehicle’s working process was set up. Through experimental study on the vehicle, the dimensionless model was verified. Through simulation study on the vehicle, the following can be obtained: firstly, the increase of the hydraulic chamber orifice and the area ratio of the pistons can lead to a higher output power, while output pressure is just the opposite. Moreover, the increase of the output pressure and the aperture of the hydraulic chamber can lead to a higher efficiency, while area ratio of the pistons played the opposite role. This research can be referred to in the performance and design optimization of the HP transformers. Full article
(This article belongs to the Special Issue Power Transmission and Control in Power and Vehicle Machineries)
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Open AccessArticle Intelligent Video Surveillance Platform for Wireless Multimedia Sensor Networks
Appl. Sci. 2018, 8(3), 348; https://doi.org/10.3390/app8030348
Received: 18 January 2018 / Revised: 14 February 2018 / Accepted: 23 February 2018 / Published: 28 February 2018
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Abstract
Wireless multimedia sensor networks (WMSNs) are increasingly being deployed for surveillance and monitoring applications. WMSNs applications produce large amount of data, which require high transmission rates. An efficient and seamless delivery of multimedia services in WMSNs is still a challenging task. This article
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Wireless multimedia sensor networks (WMSNs) are increasingly being deployed for surveillance and monitoring applications. WMSNs applications produce large amount of data, which require high transmission rates. An efficient and seamless delivery of multimedia services in WMSNs is still a challenging task. This article proposes an intelligent video surveillance platform (IVSP) for wireless multimedia sensor networks. IVSP presents the design of a networked system for joint rate control and error control of video over resource-constrained embedded devices. First, a combination of two different congestion indicators is introduced to differentiate between congestion levels and handle them accordingly. Second, a feedback-based rate controller is developed to maximize received video quality, in which sensor nodes can adaptively adjust their sending rates. Finally, a different retransmission mechanism for different packets is proposed. Lost packets can be stored temporarily and resend when free channel is available to avoid congestion. The core component of IVSP is an open source hardware platform, which is based on Raspberry Pi sensor nodes. IVSP is extensively evaluated on 7 Raspberry Pi sensor nodes. We present the results of 7-node real-world deployment of IVSP in a video surveillance application and show that it works well in long-term deployments. Full article
(This article belongs to the Section Computer Science and Electrical Engineering)
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Open AccessArticle Using Multispectral Airborne LiDAR Data for Land/Water Discrimination: A Case Study at Lake Ontario, Canada
Appl. Sci. 2018, 8(3), 349; https://doi.org/10.3390/app8030349
Received: 13 January 2018 / Revised: 23 February 2018 / Accepted: 24 February 2018 / Published: 28 February 2018
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Abstract
Coastal areas are environmentally sensitive and are affected by nature events and human activities. Land/water interaction in coastal areas changes over time and, therefore, requires accurate detection and frequent monitoring. Multispectral Light Detection and Ranging (LiDAR) systems, which operate at different wavelengths, have
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Coastal areas are environmentally sensitive and are affected by nature events and human activities. Land/water interaction in coastal areas changes over time and, therefore, requires accurate detection and frequent monitoring. Multispectral Light Detection and Ranging (LiDAR) systems, which operate at different wavelengths, have become available. This new technology can provide an effective and accurate solution for the determination of the land/water interface. In this context, we aim to investigate a set of point features based on elevation, intensity, and geometry for this application, followed by a presentation of an unsupervised land/water discrimination method based on seeded region growing algorithm. The multispectral airborne LiDAR sensor, the Optech Titan, was used to acquire LiDAR data at three wavelengths (1550, 1064, and 532 nm) of a study area covering part of Lake Ontario in Scarborough, Canada for testing the discrimination methods. The elevation- and geometry-based features achieved an average overall accuracy of 75.1% and 74.2%, respectively, while the intensity-based features achieved 63.9% accuracy. The region growing method succeeded in discriminating water from land with more than 99% overall accuracy, and the land/water boundary was delineated with an average root mean square error of 0.51 m. The automation of this method is restricted by having double returns from water bodies at the 532 nm wavelength. Full article
(This article belongs to the Special Issue Laser Scanning)
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Open AccessArticle Smart Control System to Optimize Time of Use in a Solar-Assisted Air-Conditioning by Ejector for Residential Sector
Appl. Sci. 2018, 8(3), 350; https://doi.org/10.3390/app8030350
Received: 25 January 2018 / Revised: 23 February 2018 / Accepted: 23 February 2018 / Published: 28 February 2018
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Abstract
The present work provides a series of theoretical improvements of a control strategy in order to optimize the time of use of solar air-conditioning by an ejector distributed in multiple solar collectors of vacuum tubes for the residential sector, which will allow us
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The present work provides a series of theoretical improvements of a control strategy in order to optimize the time of use of solar air-conditioning by an ejector distributed in multiple solar collectors of vacuum tubes for the residential sector, which will allow us to reduce carbon-dioxide emissions, costs and electrical energy consumption. In a solar ejector cooling system, the instability of the solar source of energy causes an operational conflict between the solar thermal system and ejector cooling cycle. A fuzzy control structure for the supervisory ejector cycle and multi-collector control system is developed: the first control is applied to control the mass flow of the generator and the evaporator for different cooling capacities (3, 3.5, 4, 4.5 and 5 kW) and set a temperature reference according to the operating conditions; the second is applied to keep a constant temperature power source that feeds the low-grade ejector cooling cycle using R134aas refrigerant. For the present work, the temperature of the generator oscillates between 65 °C and 90 °C, a condenser temperature of 30 °C and an evaporator temperature of 10 °C. For the purpose of optimization, there are different levels of performance for time of use: the Mode 0 (economic) gives a performance of 17.55 h, Mode 5 (maximum cooling power) 14.86 h and variable mode (variable mode of capacities) 16.25 h, on average. Simulations are done in MATLAB-Simulink applying fuzzy logic for a mathematical model of the thermal balance. They are compared with two different types of solar radiation: real radiation and disturbed radiation. Full article
(This article belongs to the Special Issue Smart Home and Energy Management Systems)
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Open AccessFeature PaperArticle A Vector Printing Method for High-Speed Electrohydrodynamic (EHD) Jet Printing Based on Encoder Position Sensors
Appl. Sci. 2018, 8(3), 351; https://doi.org/10.3390/app8030351
Received: 11 February 2018 / Revised: 26 February 2018 / Accepted: 26 February 2018 / Published: 28 February 2018
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Abstract
Electrohyrodynamic (EHD) jet printing has been widely used in the field of direct micro-nano patterning applications, due to its high resolution printing capability. So far, vector line printing using a single nozzle has been widely used for most EHD printing applications. However, the
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Electrohyrodynamic (EHD) jet printing has been widely used in the field of direct micro-nano patterning applications, due to its high resolution printing capability. So far, vector line printing using a single nozzle has been widely used for most EHD printing applications. However, the application has been limited to low-speed printing, to avoid non-uniform line width near the end points where line printing starts and ends. At end points of line vector printing, the deposited drop amount is likely to be significantly large compared to the rest of the printed lines, due to unavoidable acceleration and deceleration. In this study, we proposed a method to solve the printing quality problems by producing droplets at an equally spaced distance, irrespective of the printing speed. For this purpose, an encoder processing unit (EPU) was developed, so that the jetting trigger could be generated according to user-defined spacing by using encoder position signals, which are used for the positioning control of the two linear stages. Full article
(This article belongs to the Special Issue Printed Electronics 2017)
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Open AccessArticle A Lattice Boltzmann Method and Asynchronous Model Coupling for Viscoelastic Fluids
Appl. Sci. 2018, 8(3), 352; https://doi.org/10.3390/app8030352
Received: 21 January 2018 / Revised: 23 February 2018 / Accepted: 26 February 2018 / Published: 28 February 2018
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Abstract
The numerical algorithms of viscoelastic flows can appear a tremendous challenge as the Weissenberg number (Wi) enlarged sufficiently. In this study, we present a generalized technique of time-stably advancing based on the coupled lattice Boltzmann method, in order to improve the
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The numerical algorithms of viscoelastic flows can appear a tremendous challenge as the Weissenberg number (Wi) enlarged sufficiently. In this study, we present a generalized technique of time-stably advancing based on the coupled lattice Boltzmann method, in order to improve the numerical stability of simulations at a high Wi number. The mathematical models of viscoelastic fluids include both the equation of the solvent and the Oldroyd-B constitutive equation of the polymer. In the two-dimensional (2D) channel flow, the coupled method shows good agreements between the corresponding exact results and the numerical results obtained by our method. In addition, as the Wi number increased, for the viscoelastic flows through contractions, we show that the prediction of our presented method can reproduce the same numerical results that were reported by previous studies. The main advantage of current method is that it can be applied to simulate the complex phenomena of the viscoelastic fluids. Full article
(This article belongs to the Special Issue Development and Applications of Kinetic Solvers for Complex Flows)
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Open AccessArticle Oxygen Vacancy-Mediated ZnO Nanoparticle Photocatalyst for Degradation of Methylene Blue
Appl. Sci. 2018, 8(3), 353; https://doi.org/10.3390/app8030353
Received: 4 December 2017 / Revised: 9 January 2018 / Accepted: 14 January 2018 / Published: 28 February 2018
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Abstract
ZnO nanoparticles (NPs) are synthesized by deoxidizing ZnO powder in a vacuum drying process. This process reduces the size of the NPs and increases the concentration of oxygen vacancies on their surfaces. ZnO NPs with sufficient oxygen vacancies are highly effective for the
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ZnO nanoparticles (NPs) are synthesized by deoxidizing ZnO powder in a vacuum drying process. This process reduces the size of the NPs and increases the concentration of oxygen vacancies on their surfaces. ZnO NPs with sufficient oxygen vacancies are highly effective for the photodecomposition of methylene blue (MB) dye in water under ultraviolet irradiation. The MB degradation efficiency exceeds 99 percent after 50 min of light irradiation, and the catalytic property of the NPs remains stable over several complete degradation cycles. It is revealed that the concentration of oxygen vacancies on the surface, and the photocatalytic activity, are both higher for smaller NPs. Oxygen vacancies reduce the recombination rate of photo-generated charge carriers by capturing the electrons and hence, improve the efficiency of redox reactions. In addition, a smaller particle size leads to a larger specific surface area and a higher photonic efficiency for the ZnO NPs. Full article
(This article belongs to the Special Issue Nanostructured Photodetectors and Photovoltaic Devices)
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Open AccessFeature PaperArticle Application of Auxetic Foam in Sports Helmets
Appl. Sci. 2018, 8(3), 354; https://doi.org/10.3390/app8030354
Received: 18 February 2018 / Accepted: 19 February 2018 / Published: 1 March 2018
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Abstract
This investigation explored the viability of using open cell polyurethane auxetic foams to augment the conformable layer in a sports helmet and improve its linear impact acceleration attenuation. Foam types were compared by examining the impact severity on an instrumented anthropomorphic headform within
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This investigation explored the viability of using open cell polyurethane auxetic foams to augment the conformable layer in a sports helmet and improve its linear impact acceleration attenuation. Foam types were compared by examining the impact severity on an instrumented anthropomorphic headform within a helmet consisting of three layers: a rigid shell, a stiff closed cell foam, and an open cell foam as a conformable layer. Auxetic and conventional foams were interchanged to act as the helmet’s conformable component. Attenuation of linear acceleration was examined by dropping the combined helmet and headform on the front and the side. The helmet with auxetic foam reduced peak linear accelerations (p < 0.05) relative to its conventional counterpart at the highest impact energy in both orientations. Gadd Severity Index reduced by 11% for frontal impacts (38.9 J) and 44% for side impacts (24.3 J). The conformable layer within a helmet can influence the overall impact attenuating properties. The helmet fitted with auxetic foam can attenuate impact severity more than when fitted with conventional foam, and warrants further investigation for its potential to reduce the risk of traumatic brain injuries in sport specific impacts. Full article
(This article belongs to the Special Issue Sports Materials)
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Open AccessArticle Temperature Dependence on Density, Viscosity, and Electrical Conductivity of Ionic Liquid 1-Ethyl-3-Methylimidazolium Fluoride
Appl. Sci. 2018, 8(3), 356; https://doi.org/10.3390/app8030356
Received: 29 January 2018 / Revised: 25 February 2018 / Accepted: 27 February 2018 / Published: 1 March 2018
PDF Full-text (1247 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Ionic liquids are considered environmentally friendly media for various industrial applications. Basic data on physicochemical properties are significant for a new material, in terms of developing its potential applications. In this work, 1-ethyl-3-methylimidazolium fluoride ([EMIm]F) ionic liquid was synthesized via an anion metathesis
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Ionic liquids are considered environmentally friendly media for various industrial applications. Basic data on physicochemical properties are significant for a new material, in terms of developing its potential applications. In this work, 1-ethyl-3-methylimidazolium fluoride ([EMIm]F) ionic liquid was synthesized via an anion metathesis process. Physical properties including the density, viscosity, electrical conductivity, and thermal stability of the product were measured. The results show that the density of [EMIm]F decreases linearly with temperature increases, while dynamic viscosity decreases rapidly below 320 K and the temperature dependence of electrical conductivity is in accordance with the VFT (Vogel–Fulcher–Tammann) equation. The temperature dependence of the density, conductivity, and viscosity of [EMIm]F can be expressed via the following equations: ρ = 1.516 − 1.22 × 10−3 T, σm = 4417.1exp[−953.17/(T − 166.65)] and η = 2.07 × 10−7exp(−5.39 × 104/T), respectively. [EMIm]F exhibited no clear melting point. However, its glass transition point and decomposition temperature are −71.3 °C and 135 °C, respectively. Full article
(This article belongs to the Section Materials)
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Open AccessArticle A Biomimetic Approach for Designing a Full External Breast Prosthesis: Post-Mastectomy
Appl. Sci. 2018, 8(3), 357; https://doi.org/10.3390/app8030357
Received: 4 January 2018 / Revised: 9 February 2018 / Accepted: 27 February 2018 / Published: 1 March 2018
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Abstract
This work presents the design of a new breast prosthesis using the biomimetic technique for cases of complete mastectomy to address the problem of the increasing number of women diagnosed with breast cancer in Mexico who are candidates for a mastectomy. The designed
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This work presents the design of a new breast prosthesis using the biomimetic technique for cases of complete mastectomy to address the problem of the increasing number of women diagnosed with breast cancer in Mexico who are candidates for a mastectomy. The designed prosthesis considers the morphology of a real breast regarding its internal structure to obtain authentic mobility and feel. In order to accomplish this, a model was obtained in 3D CAD using a coordinate measuring machine (CMM) that can be scalable without losing its qualities, and which can be used in any type of patient; afterwards, a finite element model was developed and a static analysis performed with suggested load cases to evaluate the sensitivity and naturalness of the prosthesis; and finally, a modal analysis was conducted. The results obtained in displacements and in distribution of stress for the load cases assessed are consistent with those of a real breast: there were smooth contours and there was natural mobility in the prosthesis designed by means of the biomimetic technique. Full article
(This article belongs to the Special Issue Biofabrication: from Additive Bio-Manufacturing to Bioprinting)
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Open AccessArticle Bloch-Surface-Polariton-Based Hybrid Nanowire Structure for Subwavelength, Low-Loss Waveguiding
Appl. Sci. 2018, 8(3), 358; https://doi.org/10.3390/app8030358
Received: 1 December 2017 / Revised: 17 January 2018 / Accepted: 26 February 2018 / Published: 1 March 2018
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Abstract
Surface plasmon polaritons (SPPs) have been thoroughly studied in the past decades for not only sensing but also waveguiding applications. Various plasmonic device structures have been explored due to their ability to confine their optical mode to the subwavelength level. However, with the
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Surface plasmon polaritons (SPPs) have been thoroughly studied in the past decades for not only sensing but also waveguiding applications. Various plasmonic device structures have been explored due to their ability to confine their optical mode to the subwavelength level. However, with the existence of metal, the large ohmic loss limits the propagation distance of the SPP and thus the scalability of such devices. Therefore, different hybrid waveguides have been proposed to overcome this shortcoming. Through fine tuning of the coupling between the SPP and a conventional waveguide mode, a hybrid mode could be excited with decent mode confinement and extended propagation distance. As an effective alternative of SPP, Bloch surface waves have been re-investigated more recently for their unique advantages. As is supported in all-dielectric structures, the optical loss for the Bloch surface wave is much lower, which stands for a much longer propagating distance. Yet, the confinement of the Bloch surface wave due to the reflections and refractions in the multilayer structure is not as tight as that of the SPP. In this work, by integrating a periodic multilayer structure that supports the Bloch surface wave with a metallic nanowire structure, a hybrid Bloch surface wave polariton could be excited. With the proposed hybrid nanowire structure, a hybrid mode is demonstrated with the deep subwavelength mode confinement and a propagation distance of tens of microns. Full article
(This article belongs to the Special Issue Surface Waves on Planar Photonic Crystals)
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Open AccessArticle Numerical Analysis to Improve the Ballistic Trajectory of an Air-Based Material Density Separator System
Appl. Sci. 2018, 8(3), 359; https://doi.org/10.3390/app8030359
Received: 2 February 2018 / Revised: 23 February 2018 / Accepted: 27 February 2018 / Published: 1 March 2018
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Abstract
A material density separator utilizes a high velocity channel of air with a ballistic trajectory to separate materials based on their different densities and sizes. Light materials are carried with the airflow, leaving behind the separated heavy materials. A vibrating bed is then
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A material density separator utilizes a high velocity channel of air with a ballistic trajectory to separate materials based on their different densities and sizes. Light materials are carried with the airflow, leaving behind the separated heavy materials. A vibrating bed is then used to collect both heavy and light plastic materials for further separation and recycling processes. The effectiveness of the separation process mainly depends on the ballistic trajectory of the air stream and the slanting position of the vibrating bed. In this study, flow characteristics inside the density separation system were investigated to optimize the ballistic trajectory of air and the slanting position of the vibrating bed to improve the separation process. Various inlet air velocities, duct shapes, and the slanting angles of the mechanical separators were used to study their effects on flow properties (velocity magnitude, pressure, shear stress, and vorticity). Results show that the ballistic trajectory of air strongly depends on the diameter and shape of the duct hole, the inclination angle of the vibrating bed, and the air inlet velocity. The selection of the suitable values of these parameters is necessary to improve the plastic separation process. Full article
(This article belongs to the Section Mechanical Engineering)
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Open AccessArticle A Self-Consistent Physical Model of the Bubbles in a Gas Solid Two-Phase Flow
Appl. Sci. 2018, 8(3), 360; https://doi.org/10.3390/app8030360
Received: 27 November 2017 / Revised: 5 February 2018 / Accepted: 23 February 2018 / Published: 2 March 2018
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Abstract
We develop a self-consistent physical model of bubbles in a gas solid two-phase flow. Using the Peng-Robonson state equation and a detailed specific heat ratio equation of bubbles, we obtain the kinetic equations of the bubbles on the basis of the Ergun equation,
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We develop a self-consistent physical model of bubbles in a gas solid two-phase flow. Using the Peng-Robonson state equation and a detailed specific heat ratio equation of bubbles, we obtain the kinetic equations of the bubbles on the basis of the Ergun equation, thermodynamic equations, and kinetic equations. It is found that the specific heat ratio of bubbles in such systems strongly depends on bubble pressures and temperatures, which play an important role in the characteristics of the bubbles. The theoretical studies show that with increasing height in the systems, the gas flow rate shows a downward trend. Moreover, the larger particles in the gas solid flows are, the greater the gas velocity is. The bubble sizes increase with the increasing heights of the gas solid systems, and then decrease. The bubble velocity is affected by the gas velocity and the bubble size, which gradually increase and eventually quasi-stabilize. This shows that gas and solid phases in a gas solid two-phase flow interact with each other and a self-consistent system comes into being. The theoretical results have exhibited important value as a guide for understanding the properties and effects of bubbles in gas solid two-phase flows. Full article
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Open AccessArticle An Experimental Study of a Data Compression Technology-Based Intelligent Data Acquisition (IDAQ) System for Structural Health Monitoring of a Long-Span Bridge
Appl. Sci. 2018, 8(3), 361; https://doi.org/10.3390/app8030361
Received: 11 January 2018 / Revised: 13 February 2018 / Accepted: 27 February 2018 / Published: 2 March 2018
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Abstract
There has recently been an increase in interest in structural health monitoring (SHM) using wireless sensor networks. For SHM, in particular, it is important to accurately and efficiently measure the dynamic acceleration response using wireless sensor networks in real-time. For the purpose, a
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There has recently been an increase in interest in structural health monitoring (SHM) using wireless sensor networks. For SHM, in particular, it is important to accurately and efficiently measure the dynamic acceleration response using wireless sensor networks in real-time. For the purpose, a CAFB (cochlea-inspired artificial filter bank) has been developed in a previous study, which is a dynamic data compression technology. Since the developed CAFB can select and compress only the interested range of frequency signals from an entire response of a structure, it efficiently provides a real-time dynamic response based on wireless networking. CAFB of the previous study is optimized to selectively acquire low-frequency signals of sub-10 Hz, which is required for SHM of long and large-scale structures. According to the CAFB’s optimization using an El-Centro seismic waveform, six band-pass filters, 1.0 Hz interval, and 0.6 Hz bandwidth have been adapted. This article is to evaluate dynamic acceleration response performance of civil structures using the CAFB developed in the previous study. To achieve the purpose, the optimally-designed CAFB was embedded in an intelligent data acquisition (IDAQ) system. To evaluate the performance of the IDAQ system with the embedded CAFB, the real-time dynamic response was investigated for a model cable-stayed bridge, measured by a wire-measuring system and the CAFB-based IDAQ system simultaneously. The results show excellent agreement between the compressed dynamic response acquired by the CAFB-based IDAQ system and that acquired by the wire measuring system. In addition, the measurement from the CAFB-based IDAQ system revealed the modal information of the model bridge. The developed CAFB can determine and reconstruct the entire dynamic response from compression with modal information only; its efficient operation illustrates its potential to be utilized in real-time structural health monitoring. Full article
(This article belongs to the Special Issue Advanced Internet of Things for Smart Infrastructure System)
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Open AccessArticle Preventive Effects of Lactobacillus Plantarum YS4 on Constipation Induced by Activated Carbon in Mice
Appl. Sci. 2018, 8(3), 363; https://doi.org/10.3390/app8030363
Received: 29 January 2018 / Revised: 23 February 2018 / Accepted: 28 February 2018 / Published: 2 March 2018
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Abstract
This study was designed to analyze the effects of Lactobacillus plantarum YS4 (LP-YS4) on activated carbon-induced constipation in ICR (Institute of Cancer Research) mice. The mice were fed on YS4 and LB (Lactobacillus bulgaricus), followed by inducing constipation. The results of
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This study was designed to analyze the effects of Lactobacillus plantarum YS4 (LP-YS4) on activated carbon-induced constipation in ICR (Institute of Cancer Research) mice. The mice were fed on YS4 and LB (Lactobacillus bulgaricus), followed by inducing constipation. The results of the experiment suggested that anti-gastric acid and bile salt activities of LP-YS4 were more effective than LB. It was conclusive that LP-YS4 could inhibit the weight loss induced by constipation and had an effect on fecal weight, particle number and further decrease in water content initiated by constipation. At the same time, LP-YS4 could increase gastrointestinal (GI) transit rate and limit the time of the first black stool defecation. It could also raise the motilin (MTL), endothelin (ET), acetylcholinesterase (AChE), substance P (SP), and vasoactive intestinal peptide (VIP) serum levels and reduce the somatostatin (SS) level in constipated mice as compared to the mice in control group. LP-YS4 could reduce myeloperoxidase (MPO), nitric oxide (NO), and malondialdehyde (MDA) levels in small intestinal tissue of mice and raise glutathione (GSH) levels as compared to the control group mice. By H&E (hematoxylin-eosin) assay, we determined that LP-YS4 could reduce the small intestinal tissue injury by activated carbon. Real-Time Quantitative Polymerase Chain Reaction (RT-qPCR) experiment data demonstrated that LP-YS4 has the capability to increase c-Kit, stem cell factor (SCF), glial cellline-derived neurotrophic factor (GDNF) mRNA (messenger RNA) expressions and decrease transient receptor potential vanilloid 1 (TRPV1), nitric oxide synthase (NOS) expressions in small intestine tissue of constipated mice. High concentration of LP-YS4 exhibited much better effects than that of LB. From these results, LP-YS4 could be considered as an effective substance that actively inhibits constipation. Full article
(This article belongs to the Section Chemistry)
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Open AccessArticle Analysis of Mechanical Properties of Self Compacted Concrete by Partial Replacement of Cement with Industrial Wastes under Elevated Temperature
Appl. Sci. 2018, 8(3), 364; https://doi.org/10.3390/app8030364
Received: 29 January 2018 / Revised: 23 February 2018 / Accepted: 24 February 2018 / Published: 7 March 2018
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Abstract
Self-Compacting Concrete (SCC) differs from the normal concrete as it has the basic capacity to consolidate under its own weight. The increased awareness regarding environmental disturbances and its hazardous effects caused by blasting and crushing procedures of stone, it becomes a delicate and
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Self-Compacting Concrete (SCC) differs from the normal concrete as it has the basic capacity to consolidate under its own weight. The increased awareness regarding environmental disturbances and its hazardous effects caused by blasting and crushing procedures of stone, it becomes a delicate and obvious issue for construction industry to develop an alternative remedy as material which can reduce the environmental hazards and enable high-performance strength to the concrete, which would make it durable and efficient for work. A growing trend is being established all over the world to use industrial byproducts and domestic wastes as a useful raw material in construction, as it provides an eco-friendly edge to the construction process and especially for concrete. This study aims to enlighten the use and comparative analysis for the performance of concrete with added industrial byproducts such as Ground Granulated Blast Furnace Slag (GGBFS), Silica fumes (SF) and Marble Powder (MP) in the preparation of SCC. This paper deals with the prediction of mechanical properties (i.e., compressive, tensile and flexural Strength) of self-compacting concrete by considering four major factors such as type of additive, percentage additive replaced, curing days and temperature using Artificial Neural Networks (ANNs). Full article
(This article belongs to the Special Issue Soft Computing Techniques in Structural Engineering and Materials)
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Open AccessArticle Influence of Size Reduction of Fly Ash Particles by Grinding on the Chemical Properties of Geopolymers
Appl. Sci. 2018, 8(3), 365; https://doi.org/10.3390/app8030365
Received: 8 January 2018 / Revised: 20 February 2018 / Accepted: 27 February 2018 / Published: 4 March 2018
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Abstract
Chemical properties of geopolymers were evaluated from the reduction of fly ash particle size by grinding. X-ray diffraction determined that at early curing ages new crystalline phases appear in the matrix of the geopolymer and they remain for 28 days, with increases in
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Chemical properties of geopolymers were evaluated from the reduction of fly ash particle size by grinding. X-ray diffraction determined that at early curing ages new crystalline phases appear in the matrix of the geopolymer and they remain for 28 days, with increases in intensities up to 60%. In Fourier transform infrared spectroscopy, displacements were identified in the main band of the geopolymers at higher wavenumbers, attributed to the greater rigidity in the structures of the aluminosilicate gel due to the increase of the reaction products in the geopolymers obtained through fly ashsubjected to previous grinding, which is observable in the geopolymers matrix. Results indicate that the reduction of fly ash particle size by grinding has an influence on the chemical properties of geopolymers. Full article
(This article belongs to the Section Chemistry)
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Open AccessArticle Polyimide Encapsulation of Spider-Inspired Crack-Based Sensors for Durability Improvement
Appl. Sci. 2018, 8(3), 367; https://doi.org/10.3390/app8030367
Received: 2 January 2018 / Revised: 27 February 2018 / Accepted: 1 March 2018 / Published: 3 March 2018
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Abstract
In mechanical sensory systems, encapsulation is one of the crucial issues to take care of when it comes to protection of the systems from external damage. Recently, a new type of a mechanical strain sensor inspired by spider’s slit organ has been reported,
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In mechanical sensory systems, encapsulation is one of the crucial issues to take care of when it comes to protection of the systems from external damage. Recently, a new type of a mechanical strain sensor inspired by spider’s slit organ has been reported, which has incredibly high sensitivity, flexibility, wearability, and multifunctional sensing abilities. In spite of many of these advantages, the sensor is still vulnerable in harsh environments of liquids and/or high temperature, because it has heat-vulnerable polyethylene terephthalate (PET) substrate without any encapsulation layer. Here, we present a mechanical crack-based strain sensor with heat, water and saline solution resistance by alternating the substrate from polyester film to polyimide film and encapsulating the sensor with polyimide. We have demonstrated the ability of the encapsulated crack-based sensor against heat, water, saline solution damage through experiments. Our sensor exhibited reproducibility and durability with high sensitivity to strain (gauge factor above 10,000 at strain of two percent). These results show a new potential of the crack-based sensory system to be used as a wearable voice/motion/pulse sensing device and a high-temperature strain sensor. Full article
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Open AccessArticle Quillaja saponaria Saponins with Potential to Enhance the Effectiveness of Disinfection Processes in the Beverage Industry
Appl. Sci. 2018, 8(3), 368; https://doi.org/10.3390/app8030368
Received: 3 January 2018 / Revised: 15 February 2018 / Accepted: 28 February 2018 / Published: 3 March 2018
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Abstract
This study examines the in vitro effect of Quillaja saponaria extracts on Asaia spp. planktonic cells and biofilms, in comparison and combination with two disinfectants: peracetic acid and N-ethyl-N,N-dimethylhexadecylammonium bromide. The growth of six bacterial strains was evaluated
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This study examines the in vitro effect of Quillaja saponaria extracts on Asaia spp. planktonic cells and biofilms, in comparison and combination with two disinfectants: peracetic acid and N-ethyl-N,N-dimethylhexadecylammonium bromide. The growth of six bacterial strains was evaluated spectrophotometrically. Biofilm eradication was determined using the plate count method and luminometry. The planktonic cells were characterized by relatively high resistance to peracetic acid and higher sensitivity to N-ethylo-N,N-dimethylohexadecylioamonium bromide. In almost all the tested strains, growth was inhibited by 0.125% (v/v) peracetic acid and 0.0313% (w/v) quaternary ammonium compound. However, combinations of cell pretreatment using saponin and peracetic acid action were the most efficient against both planktonic and biofilm cells. The minimum inhibitory concentrations for peracetic acid were 4–8 times lower than those for bacterial strains without preliminary saponin action. Eradication of Asaia spp. biofilms reduced the number of living cells by 4–5 logarithmic units. These results demonstrate the synergetic action of saponin extract and disinfectant, and could be useful in the development of industrial strategies against Asaia spp. biofilms. Full article
(This article belongs to the Section Chemistry)
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Open AccessArticle Finger Angle-Based Hand Gesture Recognition for Smart Infrastructure Using Wearable Wrist-Worn Camera
Appl. Sci. 2018, 8(3), 369; https://doi.org/10.3390/app8030369
Received: 8 February 2018 / Revised: 26 February 2018 / Accepted: 28 February 2018 / Published: 3 March 2018
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Abstract
The arising of domestic robots in smart infrastructure has raised demands for intuitive and natural interaction between humans and robots. To address this problem, a wearable wrist-worn camera (WwwCam) is proposed in this paper. With the capability of recognizing human hand gestures in
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The arising of domestic robots in smart infrastructure has raised demands for intuitive and natural interaction between humans and robots. To address this problem, a wearable wrist-worn camera (WwwCam) is proposed in this paper. With the capability of recognizing human hand gestures in real-time, it enables services such as controlling mopping robots, mobile manipulators, or appliances in smart-home scenarios. The recognition is based on finger segmentation and template matching. Distance transformation algorithm is adopted and adapted to robustly segment fingers from the hand. Based on fingers’ angles relative to the wrist, a finger angle prediction algorithm and a template matching metric are proposed. All possible gesture types of the captured image are first predicted, and then evaluated and compared to the template image to achieve the classification. Unlike other template matching methods relying highly on large training set, this scheme possesses high flexibility since it requires only one image as the template, and can classify gestures formed by different combinations of fingers. In the experiment, it successfully recognized ten finger gestures from number zero to nine defined by American Sign Language with an accuracy up to 99.38%. Its performance was further demonstrated by manipulating a robot arm using the implemented algorithms and WwwCam to transport and pile up wooden building blocks. Full article
(This article belongs to the Special Issue Advanced Internet of Things for Smart Infrastructure System)
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Open AccessArticle Wireless Sensors and IoT Platform for Intelligent HVAC Control
Appl. Sci. 2018, 8(3), 370; https://doi.org/10.3390/app8030370
Received: 28 January 2018 / Revised: 14 February 2018 / Accepted: 27 February 2018 / Published: 3 March 2018
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Abstract
Energy consumption of buildings (residential and non-residential) represents approximately 40% of total world electricity consumption, with half of this energy consumed by HVAC systems. Model-Based Predictive Control (MBPC) is perhaps the technique most often proposed for HVAC control, since it offers an enormous
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Energy consumption of buildings (residential and non-residential) represents approximately 40% of total world electricity consumption, with half of this energy consumed by HVAC systems. Model-Based Predictive Control (MBPC) is perhaps the technique most often proposed for HVAC control, since it offers an enormous potential for energy savings. Despite the large number of papers on this topic during the last few years, there are only a few reported applications of the use of MBPC for existing buildings, under normal occupancy conditions and, to the best of our knowledge, no commercial solution yet. A marketable solution has been recently presented by the authors, coined the IMBPC HVAC system. This paper describes the design, prototyping and validation of two components of this integrated system, the Self-Powered Wireless Sensors and the IOT platform developed. Results for the use of IMBPC in a real building under normal occupation demonstrate savings in the electricity bill while maintaining thermal comfort during the whole occupation schedule. Full article
(This article belongs to the Special Issue Smart Home and Energy Management Systems)
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Open AccessArticle Measurement of Strain and Strain Rate during the Impact of Tennis Ball Cores
Appl. Sci. 2018, 8(3), 371; https://doi.org/10.3390/app8030371
Received: 28 January 2018 / Revised: 1 March 2018 / Accepted: 1 March 2018 / Published: 4 March 2018
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Abstract
The aim of this investigation was to establish the strains and strain rates experienced by tennis ball cores during impact to inform material characterisation testing and finite element modelling. Three-dimensional surface strains and strain rates were measured using two high-speed video cameras and
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The aim of this investigation was to establish the strains and strain rates experienced by tennis ball cores during impact to inform material characterisation testing and finite element modelling. Three-dimensional surface strains and strain rates were measured using two high-speed video cameras and corresponding digital image correlation software (GOM Correlate Professional). The results suggest that material characterisation testing to a maximum strain of 0.4 and a maximum rate of 500 s−1 in tension and to a maximum strain of −0.4 and a maximum rate of −800 s−1 in compression would encapsulate the demands placed on the material during impact and, in turn, define the range of properties required to encapsulate the behavior of the material during impact, enabling testing to be application-specific and strain-rate-dependent properties to be established and incorporated in finite element models. Full article
(This article belongs to the Special Issue Sports Materials)
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Open AccessArticle Effects of Heat Treatment on the Tribological Properties of Sicp/Al-5Si-1Cu-0.5Mg Composite Processed by Electromagnetic Stirring Method
Appl. Sci. 2018, 8(3), 372; https://doi.org/10.3390/app8030372
Received: 29 January 2018 / Revised: 26 February 2018 / Accepted: 1 March 2018 / Published: 4 March 2018
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Abstract
This paper investigated the influence of heat treatment (T6) on the dry sliding wear behavior of SiCp/Al-5Si-1Cu-0.5Mg composite that was fabricated by electromagnetic stirring method. The wear rates and friction coefficients were measured using a pin-on-disc tribometer under loads of 15–90 N at
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This paper investigated the influence of heat treatment (T6) on the dry sliding wear behavior of SiCp/Al-5Si-1Cu-0.5Mg composite that was fabricated by electromagnetic stirring method. The wear rates and friction coefficients were measured using a pin-on-disc tribometer under loads of 15–90 N at dry sliding speeds of 100 r/min, 200 r/min, and 300 r/min, over a sliding time of 15 min. The worn surfaces and debris were examined using a scanning electron microscope and was analyzed with an energy dispersive spectrometer. The experimental results revealed that SiCp/Al-5Si-1Cu-0.5Mg alloy treated with T6 exhibited lower wear rate and friction coefficient than the other investigated alloys. As the applied load increased, the wear rate and friction coefficient increased. While, the wear rate and friction coefficient decreased with the sliding speed increasing. The morphology of the eutectic silicon was spheroidal after the T6 heat treatment. SiCp particles and Al2Cu phase can be considered as the main raisons for improving the wear behavior. Abrasion and oxidation were the wear mechanisms at low load levels. However, the wear mechanisms at high load levels were plastic deformation and delamination. Full article
(This article belongs to the Special Issue Mechanical Behaviour of Aluminium Alloys)
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Open AccessArticle Hybrid Genetic Algorithm Fuzzy-Based Control Schemes for Small Power System with High-Penetration Wind Farms
Appl. Sci. 2018, 8(3), 373; https://doi.org/10.3390/app8030373
Received: 2 February 2018 / Revised: 21 February 2018 / Accepted: 1 March 2018 / Published: 4 March 2018
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Abstract
Wind is a clean, abundant, and inexhaustible source of energy. However, wind power is not constant, as windmill output is proportional to the cube of wind speed. As a result, the generated power of wind turbine generators (WTGs) fluctuates significantly. Power fluctuation leads
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Wind is a clean, abundant, and inexhaustible source of energy. However, wind power is not constant, as windmill output is proportional to the cube of wind speed. As a result, the generated power of wind turbine generators (WTGs) fluctuates significantly. Power fluctuation leads to frequency deviation and voltage flicker inside the system. This paper presents a new methodology for controlling system frequency and power. Two decentralized fuzzy logic-based control schemes with a high-penetration non-storage wind–diesel system are studied. First, one is implemented in the governor of conventional generators to damp frequency oscillation, while the other is applied to control the pitch angle system of wind turbines to smooth wind output power fluctuations and enhance the power system performance. A genetic algorithm (GA) is employed to tune and optimize the membership function parameters of the fuzzy logic controllers to obtain optimal performance. The effectiveness of the suggested controllers is validated by time domain simulation for the standard IEEE nine-bus three-generator test system, including three wind farms. The robustness of the power system is checked under normal and faulty operating conditions. Full article
(This article belongs to the Special Issue Renewable Energy 2018)
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Open AccessArticle Symmetry-Breaking Effect on the Electromagnetic Properties of Plasmonic Trimers Composed of Graphene Nanodisks
Appl. Sci. 2018, 8(3), 374; https://doi.org/10.3390/app8030374
Received: 26 January 2018 / Revised: 19 February 2018 / Accepted: 28 February 2018 / Published: 5 March 2018
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Abstract
Plasmonic trimers composed of equal-sized graphene nanodisks are proposed in this paper. The symmetry-breaking effect on the electromagnetic properties of the nanostructure is numerically investigated by studying plasmon energy diagrams and optical scattering spectra in mid-infrared range with a gradient vertex angle. The
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Plasmonic trimers composed of equal-sized graphene nanodisks are proposed in this paper. The symmetry-breaking effect on the electromagnetic properties of the nanostructure is numerically investigated by studying plasmon energy diagrams and optical scattering spectra in mid-infrared range with a gradient vertex angle. The degenerate plasmonic modes are lifted and new modes appear with increased vertex angle. The energy diagrams are consistent with scattering extinction spectra, about which the dipole moment distribution of the proposed structure is discussed to demonstrate the coupling strength of the collective plasmonic modes of the trimer. More specifically, the frequency tunability of the plasmonic trimer is pointed out by modifying the chemical potential of the graphene nanodisks without varying the geometric configuration. The proposed structure might find applications such as light-matter interaction, single molecule detection, and high-sensitivity chemical sensing. Full article
(This article belongs to the Section Nanotechnology and Applied Nanosciences)
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Open AccessArticle Effects of Shot-Peening and Stress Ratio on the Fatigue Crack Propagation of AL 7475-T7351 Specimens
Appl. Sci. 2018, 8(3), 375; https://doi.org/10.3390/app8030375
Received: 23 January 2018 / Revised: 24 February 2018 / Accepted: 28 February 2018 / Published: 5 March 2018
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Abstract
Shot peening is an attractive technique for fatigue enhanced performance of metallic components, because it increases fatigue crack initiation life prevention and retards early crack growth. Engineering design based on fatigue crack propagation predictions applying the principles of fracture mechanics is commonly used
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Shot peening is an attractive technique for fatigue enhanced performance of metallic components, because it increases fatigue crack initiation life prevention and retards early crack growth. Engineering design based on fatigue crack propagation predictions applying the principles of fracture mechanics is commonly used in aluminum structures for aerospace engineering. The main purpose of present work was to analyze the effect of shot peening on the fatigue crack propagation of the 7475 aluminum alloy, under both constant amplitude loading and periodical overload blocks. The tests were performed on 4 and 8 mm thickness specimens with stress ratios of 0.05 and 0.4. The analysis of the shot-peened surface showed a small increase of the micro-hardness values due to the plastic deformations imposed by shot peening. The surface peening beneficial effect on fatigue crack growth is very limited; its main effect is more noticeable near the threshold. The specimen’s thickness only has marginal influence on the crack propagation, in opposite to the stress ratio. Periodic overload blocks of 300 cycles promotes a reduction of the fatigue crack growth rate for both intervals of 7500 and 15,000 cycles. Full article
(This article belongs to the Special Issue Mechanical Behaviour of Aluminium Alloys)
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Open AccessArticle The Improvement of Mechanical Properties, Thermal Stability, and Water Absorption Resistance of an Eco-Friendly PLA/Kenaf Biocomposite Using Acetylation
Appl. Sci. 2018, 8(3), 376; https://doi.org/10.3390/app8030376
Received: 30 January 2018 / Revised: 26 February 2018 / Accepted: 28 February 2018 / Published: 5 March 2018
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Abstract
As a result of industrialization and environmental pollution, increasing importance is being given to eco-friendly materials and technology. In particular, eco-friendly biocomposites using polylactic acid (PLA) have attracted great interest. In this work, fiber-reinforced composites were investigated in order to enhance the mechanical
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As a result of industrialization and environmental pollution, increasing importance is being given to eco-friendly materials and technology. In particular, eco-friendly biocomposites using polylactic acid (PLA) have attracted great interest. In this work, fiber-reinforced composites were investigated in order to enhance the mechanical properties and improve the economic efficiency of PLA. Specifically, composite materials using natural fibers, such as kenaf were actively studied. In the utilization of natural fibers, such as kenaf, the treatment method for increasing the bonding force between the fiber and the matrix is very important. In this study, the surface of kenaf was treated using an acetylation technique, and the PLA composite material was prepared using surface-treated kenaf. Changes in fiber properties were observed with acetylation treatment time. The mechanical properties, thermal stability, and water absorption resistance of the acetylated kenaf and PLA composites prepared for each condition were evaluated. Finally, was concluded that acetylation treatment is effective for improving the performance of PLA/kenaf composites. This behavior was found to relate to the surface cleaning of acetylated kanaf, in addition to the efficient modification of the hydrophilic characteristics of kenaf. Full article
(This article belongs to the Section Materials)
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Open AccessArticle Aesthetics and Survival of Immedia