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Appl. Sci., Volume 7, Issue 1 (January 2017)

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Cover Story (view full-size image) Composites having hydroxyapatite (HAp) nanoparticles are widely employed in biomedical applications [...] Read more.
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Open AccessReview A Comprehensive Review on Handcrafted and Learning-Based Action Representation Approaches for Human Activity Recognition
Appl. Sci. 2017, 7(1), 110; https://doi.org/10.3390/app7010110
Received: 5 September 2016 / Revised: 26 October 2016 / Accepted: 13 January 2017 / Published: 23 January 2017
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Abstract
Human activity recognition (HAR) is an important research area in the fields of human perception and computer vision due to its wide range of applications. These applications include: intelligent video surveillance, ambient assisted living, human computer interaction, human-robot interaction, entertainment, and intelligent driving.
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Human activity recognition (HAR) is an important research area in the fields of human perception and computer vision due to its wide range of applications. These applications include: intelligent video surveillance, ambient assisted living, human computer interaction, human-robot interaction, entertainment, and intelligent driving. Recently, with the emergence and successful deployment of deep learning techniques for image classification, researchers have migrated from traditional handcrafting to deep learning techniques for HAR. However, handcrafted representation-based approaches are still widely used due to some bottlenecks such as computational complexity of deep learning techniques for activity recognition. However, approaches based on handcrafted representation are not able to handle complex scenarios due to their limitations and incapability; therefore, resorting to deep learning-based techniques is a natural option. This review paper presents a comprehensive survey of both handcrafted and learning-based action representations, offering comparison, analysis, and discussions on these approaches. In addition to this, the well-known public datasets available for experimentations and important applications of HAR are also presented to provide further insight into the field. This is the first review paper of its kind which presents all these aspects of HAR in a single review article with comprehensive coverage of each part. Finally, the paper is concluded with important discussions and research directions in the domain of HAR. Full article
(This article belongs to the Special Issue Human Activity Recognition)
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Open AccessArticle The Interphase Influences on the Particle-Reinforced Composites with Periodic Particle Configuration
Appl. Sci. 2017, 7(1), 102; https://doi.org/10.3390/app7010102
Received: 29 November 2016 / Revised: 19 December 2016 / Accepted: 12 January 2017 / Published: 23 January 2017
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Abstract
This work improved upon an effective micromechanical method to analyze the mechanical properties of three-dimensional particle-reinforced composites (PRC) with consideration of the interfacial debonding. By incorporating the interfacial debonding model, Mises yield criterion, and failure theory, the effects of particle shape, particle volume
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This work improved upon an effective micromechanical method to analyze the mechanical properties of three-dimensional particle-reinforced composites (PRC) with consideration of the interfacial debonding. By incorporating the interfacial debonding model, Mises yield criterion, and failure theory, the effects of particle shape, particle volume fraction, and loading condition on the mechanical properties are studied. A comparison of simulation results obtained from the established method and published experimental data is presented. Good consistency can be found in this study. On this basis, the interfacial cohesive strength and particle shape effects on the biaxial failure strength of particle-reinforced composites with interfacial debonding were also studied. The results revealed that both interfacial strength and particle shape have significant effects on biaxial tensile failure strength. However, the different interfacial strength influence on failure envelope can hardly be discerned in biaxial compressive loading. Full article
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Open AccessArticle Microporous Titanium through Metal Injection Moulding of Coarse Powder and Surface Modification by Plasma Oxidation
Appl. Sci. 2017, 7(1), 105; https://doi.org/10.3390/app7010105
Received: 7 December 2016 / Revised: 12 January 2017 / Accepted: 16 January 2017 / Published: 22 January 2017
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Abstract
Titanium is one of the most attractive materials for biomedical applications due to having excellent biocompatibility accompanied by good corrosion resistance. One popular processing technique for Ti is Metal Injection Moulding (MIM). However, there are several issues associated with the use of this
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Titanium is one of the most attractive materials for biomedical applications due to having excellent biocompatibility accompanied by good corrosion resistance. One popular processing technique for Ti is Metal Injection Moulding (MIM). However, there are several issues associated with the use of this technique, such as the high cost of the fine powder used, the high level of contamination and consequent alteration to material properties, as well as the large volume shrinkage that occurs during sintering. In this study, the use of a relatively coarse Ti powder with a mean particle size of 75 μm to process Ti parts with the potential for biomedical applications by MIM will be examined, compared to a commercial Ti feedstock, and subsequently coated using Plasma Electrolytic Oxidation (PEO). The results show that samples produced with the coarse powder shrink 35% less and have a relative density 14% less with an average pore size three-times larger than that of the commercial feedstock. This helps increase the potential competitiveness of MIM in the production of biomedical parts, as it reduces cost, shrinkage and results in more intentionally-induced micropores, such as are desired for biomedical implants. PEO treatment of the samples yields a thick rough coating comprised of a mixture of rutile and anatase with interconnected microporous channels and openings resembling the mouth of a volcanic crater. Full article
(This article belongs to the Special Issue Powder Injection Moulding)
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Open AccessFeature PaperArticle Nondestructive Estimation of Moisture Content, pH and Soluble Solid Contents in Intact Tomatoes Using Hyperspectral Imaging
Appl. Sci. 2017, 7(1), 109; https://doi.org/10.3390/app7010109
Received: 3 December 2016 / Revised: 10 January 2017 / Accepted: 17 January 2017 / Published: 21 January 2017
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Abstract
The objective of this study was to develop a nondestructive method to evaluate chemical components such as moisture content (MC), pH, and soluble solid content (SSC) in intact tomatoes by using hyperspectral imaging in the range of 1000–1550 nm. The mean spectra of
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The objective of this study was to develop a nondestructive method to evaluate chemical components such as moisture content (MC), pH, and soluble solid content (SSC) in intact tomatoes by using hyperspectral imaging in the range of 1000–1550 nm. The mean spectra of the 95 matured tomato samples were extracted from the hyperspectral images, and multivariate calibration models were built by using partial least squares (PLS) regression with different preprocessing spectra. The results showed that the regression model developed by PLS regression based on Savitzky–Golay (S–G) first-derivative preprocessed spectra resulted in better performance for MC, pH, and the smoothing preprocessed spectra-based model resulted in better performance for SSC in intact tomatoes compared to models developed by other preprocessing methods, with correlation coefficients (rpred) of 0.81, 0.69, and 0.74 with root mean square error of prediction (RMSEP) of 0.63%, 0.06, and 0.33% Brix respectively. The full wavelengths were used to create chemical images by applying regression coefficients resulting from the best PLS regression model. These results obtained from this study clearly revealed that hyperspectral imaging, together with suitable analysis model, is a promising technology for the nondestructive prediction of chemical components in intact tomatoes. Full article
(This article belongs to the Special Issue Applications of Hyperspectral Imaging for Food and Agriculture)
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Open AccessArticle Thermal Sensitive Shape Memory Behavior of Epoxy Composites Reinforced with Silicon Carbide Whiskers
Appl. Sci. 2017, 7(1), 108; https://doi.org/10.3390/app7010108
Received: 5 December 2016 / Revised: 13 January 2017 / Accepted: 16 January 2017 / Published: 21 January 2017
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Abstract
A novel shape memory polymer composite was fabricated by introducing various amounts of silicon carbide whiskers (SiCws) into a shape memory epoxy. The relationship between the thermomechanical properties of the system and structural changes were investigated via dynamic mechanical analysis, scanning electron microscopy,
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A novel shape memory polymer composite was fabricated by introducing various amounts of silicon carbide whiskers (SiCws) into a shape memory epoxy. The relationship between the thermomechanical properties of the system and structural changes were investigated via dynamic mechanical analysis, scanning electron microscopy, and bending tests. The results show that the bend strength of composites can improve by 64.1% when SiCw content reaches 12 wt %. The shape transition temperatures of SiCw/epoxy composites decreased slightly with the increase in SiCw content, but it was noted that all of the composites showed excellent shape memory properties. The shape fixity ratio increased as SiCw content increased (>99%), and the shape recovery ratio slightly decreased as SiCw content increased (>95%). All of the composites nearly recovered to their original shape within 2 min (not 100%), and the shape recovery speed significantly improved at a higher temperature. It is anticipated that tagging products will be used in the aerospace industry. Full article
(This article belongs to the Special Issue Shape Memory Polymers)
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Open AccessArticle Damage-Induced Stresses and Remaining Service Life Predictions of Wire Ropes
Appl. Sci. 2017, 7(1), 107; https://doi.org/10.3390/app7010107
Received: 13 December 2016 / Revised: 10 January 2017 / Accepted: 17 January 2017 / Published: 21 January 2017
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Abstract
Wire ropes in marine applications often encounter relatively fast and noticeable wear, a result of the fatigue to which they are exposed coupled with harsh operational conditions. This paper addresses some of the aspects of fatigue damage that occur in wire ropes. Using
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Wire ropes in marine applications often encounter relatively fast and noticeable wear, a result of the fatigue to which they are exposed coupled with harsh operational conditions. This paper addresses some of the aspects of fatigue damage that occur in wire ropes. Using the finite element method, stress and fatigue analysis of three different design types (6 × 7, 7 × 7, 8 × 7) of wire rope is performed. The size of the wire rope cross-section area is varied in order to simulate the progressive damage of the wires so that consequential stress levels and remaining fatigue life can be numerically predicted. The aim was to provide a better understanding of the mechanical behavior of damaged wire ropes under various conditions, since an appropriate choice of wire rope design could then be made from engineering and economic points of view. Additionally, potential failures can be predicted, resulting in effective maintenance and the avoidance of potential risks of rope failure, especially important regarding economical and safety aspects of transportation in the marine industry. Full article
(This article belongs to the Section Materials)
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Open AccessArticle A CMOS Multiplied Input Differential Difference Amplifier: A New Active Device and Its Applications
Appl. Sci. 2017, 7(1), 106; https://doi.org/10.3390/app7010106
Received: 9 November 2016 / Revised: 9 January 2017 / Accepted: 16 January 2017 / Published: 21 January 2017
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Abstract
This paper presents a newly developed active device, referred to as a multiplied input differential difference amplifier (MIDDA), which allows operations of summation/subtraction and multiplication of input signals. It was designed and fabricated using I3T25 0.35 μm ON (ON Semiconductor, Phoenix, AZ, USA)
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This paper presents a newly developed active device, referred to as a multiplied input differential difference amplifier (MIDDA), which allows operations of summation/subtraction and multiplication of input signals. It was designed and fabricated using I3T25 0.35 μm ON (ON Semiconductor, Phoenix, AZ, USA) Semiconductor technology. The achieved results, which describe the experimentally verified behaviour of the fabricated device, are introduced, as well as the simple applications of MIDDA with electronically controllable parameters, useful for analogue signal processing. Moreover, the paper discusses an interesting example of nonlinear application to a double-sideband amplitude modulator, based on the utilization of multiplication and summation of particular signals. The laboratory experimental results which are achieved through the use of a fabricated prototype (both in time and frequency domain), confirm the workability of the concept. Full article
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Open AccessArticle 3D Ear Normalization and Recognition Based on Local Surface Variation
Appl. Sci. 2017, 7(1), 104; https://doi.org/10.3390/app7010104
Received: 30 September 2016 / Revised: 28 November 2016 / Accepted: 9 January 2017 / Published: 21 January 2017
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Abstract
Most existing ICP (Iterative Closet Point)-based 3D ear recognition approaches resort to the coarse-to-fine ICP algorithms to match 3D ear models. With such an approach, the gallery-probe pairs are coarsely aligned based on a few local feature points and then finely matched using
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Most existing ICP (Iterative Closet Point)-based 3D ear recognition approaches resort to the coarse-to-fine ICP algorithms to match 3D ear models. With such an approach, the gallery-probe pairs are coarsely aligned based on a few local feature points and then finely matched using the original ear point cloud. However, such an approach ignores the fact that not all the points in the coarsely segmented ear data make positive contributions to recognition. As such, the coarsely segmented ear data which contains a lot of redundant and noisy data could lead to a mismatch in the recognition scenario. Additionally, the fine ICP matching can easily trap in local minima without the constraint of local features. In this paper, an efficient and fully automatic 3D ear recognition system is proposed to address these issues. The system describes the 3D ear surface with a local feature—the Local Surface Variation (LSV), which is responsive to the concave and convex areas of the surface. Instead of being used to extract discrete key points, the LSV descriptor is utilized to eliminate redundancy flat non-ear data and get normalized and refined ear data. At the stage of recognition, only one-step modified iterative closest points using local surface variation (ICP-LSV) algorithm is proposed, which provides additional local feature information to the procedure of ear recognition to enhance both the matching accuracy and computational efficiency. On an Inter®Xeon®W3550, 3.07 GHz work station (DELL T3500, Beijing, China), the authors were able to extract features from a probe ear in 2.32 s match the ear with a gallery ear in 0.10 s using the method outlined in this paper. The proposed algorithm achieves rank-one recognition rate of 100% on the Chinese Academy of Sciences’ Institute of Automation 3D Face database (CASIA-3D FaceV1, CASIA, Beijing, China, 2004) and 98.55% with 2.3% equal error rate (EER) on the Collection J2 of University of Notre Dame Biometrics Database (UND-J2, University of Notre Dame, South Bend, IN, USA, between 2003 and 2005). Full article
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Open AccessArticle Use of Ferritin-Based Metal-Encapsulated Nanocarriers as Anticancer Agents
Appl. Sci. 2017, 7(1), 101; https://doi.org/10.3390/app7010101
Received: 24 November 2016 / Revised: 28 December 2016 / Accepted: 16 January 2017 / Published: 21 January 2017
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Abstract
The ability of ferritin to bind and deliver metals and metal-based drugs to human neuroblastoma SH-SY5Y cells was studied. We used heavy chain (H) ferritin-based metal-containing nanocarriers to test whether these constructs, which are able to cross the blood-brain barrier, may be used
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The ability of ferritin to bind and deliver metals and metal-based drugs to human neuroblastoma SH-SY5Y cells was studied. We used heavy chain (H) ferritin-based metal-containing nanocarriers to test whether these constructs, which are able to cross the blood-brain barrier, may be used for the delivery of toxic molecules to brain cells, and to study their effect on the viability and cellular redox homeostasis of human neuroblastoma cells. We show that metal-containing nanocarriers are efficiently captured by SH-SY5Y cells. Iron-containing nanocarriers have a proliferative effect, while silver and cisplatin-encapsulated nanocarriers determine concentration-dependent neuroblastoma cell death. This work is a proof of concept for the use of ferritins for the delivery of toxic molecules to brain tumors. Full article
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Open AccessArticle A Real-Time Computation Model of the Electromagnetic Force and Torque for a Maglev Planar Motor with the Concentric Winding
Appl. Sci. 2017, 7(1), 98; https://doi.org/10.3390/app7010098
Received: 4 October 2016 / Revised: 12 December 2016 / Accepted: 12 January 2017 / Published: 20 January 2017
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Abstract
The traditional model of the electromagnetic force and torque does not take the coil corners into account, which is the major cause for the motor fluctuation. To reduce the fluctuation, a more accurate real-time computation model, which considers the influence of the coil
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The traditional model of the electromagnetic force and torque does not take the coil corners into account, which is the major cause for the motor fluctuation. To reduce the fluctuation, a more accurate real-time computation model, which considers the influence of the coil corners, is proposed in this paper. Three coordinate systems respectively for the stator, the mover, and the corner are established. The first harmonic of the magnetic flux density distribution of a Halbach magnet array is taken into account in this model. The coil is divided into the straight coil segment and the corner coil segment based on its structure. For the straight coil segment, the traditional Lorenz force method can be used to compute its electromagnetic force and torque, which is a function of the mover position. For the corner coil segment, however, the numerical calculation method can be used to get its respective electromagnetic force and torque. Based on the above separate analysis, an electromagnetic model can be derived, which is suitable for practical application. Compared with the well-known harmonic model, the proposed real-time computation model is found to have less model inaccuracy. Additionally, the real-time ability of the maglev planar motor model and the decoupling computation is validated by NI PXI platform (Austin, TX, USA). Full article
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Open AccessArticle Strong Aftershock Study Based on Coulomb Stress Triggering—A Case Study on the 2016 Ecuador Mw 7.8 Earthquake
Appl. Sci. 2017, 7(1), 88; https://doi.org/10.3390/app7010088
Received: 8 December 2016 / Revised: 10 January 2017 / Accepted: 12 January 2017 / Published: 20 January 2017
Cited by 1 | PDF Full-text (1588 KB) | HTML Full-text | XML Full-text
Abstract
The 2016 Ecuador M 7.8 earthquake ruptured the subduction zone boundary between the Nazca plate and the South America plate. This M 7.8 earthquake may have promoted failure in the surrounding crust, where six M ≥ 6 aftershocks occurred following this mainshock. These
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The 2016 Ecuador M 7.8 earthquake ruptured the subduction zone boundary between the Nazca plate and the South America plate. This M 7.8 earthquake may have promoted failure in the surrounding crust, where six M ≥ 6 aftershocks occurred following this mainshock. These crustal ruptures were triggered by the high coulomb stress changes produced by the M 7.8 mainshock. Here, we investigate whether the six M ≥ 6 aftershocks are consistent with the positive coulomb stress region due to the mainshock. To explore the correlation between the mainshock and the aftershocks, we adopt a recently published high-quality finite fault model and focal mechanisms to study the coulomb stress triggers during the M 7.8 earthquake sequence. We compute the coulomb failure stress changes (ΔCFS) on both of the focal mechanism nodal planes. We compare the ΔCFS imparted by the M 7.8 mainshock on the subsequent aftershocks with the epicenter location of each aftershock. In addition, the shear stress, normal stress, and coulomb stress changes in the focal sources of each aftershock are also computed. Coulomb stress changes in the focal source for the six M ≥ 6 aftershocks are in the range of −2.17–7.564 bar. Only one computational result for the M 6.9 aftershock is negative; other results are positive. We found that the vast majority of the six M ≥ 6 aftershocks occurred in positive coulomb stress areas triggered by the M 7.8 mainshock. Our results suggest that the coulomb stress changes contributed to the development of the Ecuador M 7.8 earthquake sequence. Full article
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Open AccessArticle Wind-Induced Fatigue Analysis of High-Rise Steel Structures Using Equivalent Structural Stress Method
Appl. Sci. 2017, 7(1), 71; https://doi.org/10.3390/app7010071
Received: 24 November 2016 / Revised: 26 December 2016 / Accepted: 5 January 2017 / Published: 20 January 2017
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Abstract
Welded beam-to-column connections of high-rise steel structures are susceptive to fatigue damage under wind loading. However, most fatigue assessments in the field of civil engineering are mainly based on nominal stress or hot spot stress theories, which has the disadvantage of dependence on
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Welded beam-to-column connections of high-rise steel structures are susceptive to fatigue damage under wind loading. However, most fatigue assessments in the field of civil engineering are mainly based on nominal stress or hot spot stress theories, which has the disadvantage of dependence on the meshing styles and massive curves selected. To address this problem, in this paper, the equivalent structural stress method with advantages of mesh-insensitive quality and capability of unifying different stress-life curves (S-N curves) into one is introduced to the wind-induced fatigue assessment of a large-scale complicated high-rise steel structure. The multi-scale finite element model is established and the corresponding wind loading is simulated. Fatigue life assessments using equivalent structural stress method, hot spot stress method and nominal stress method are performed, and the results are verified and comparisons are made. The mesh-insensitive quality is also verified. The results show that the lateral weld toe of the butt weld connecting the beam flange plate and the column is the location where fatigue damage most likely happens. Nominal stress method considers fatigue assessment of welds in a more global way by averaging all the stress on the weld section while in equivalent structural stress method and hot spot method local stress concentration can be taken into account more precisely. Full article
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Open AccessFeature PaperReview Nonlinear Silicon Photonic Signal Processing Devices for Future Optical Networks
Appl. Sci. 2017, 7(1), 103; https://doi.org/10.3390/app7010103
Received: 11 November 2016 / Revised: 16 December 2016 / Accepted: 25 December 2016 / Published: 20 January 2017
Cited by 6 | PDF Full-text (5324 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, we present a review on silicon-based nonlinear devices for all optical nonlinear processing of complex telecommunication signals. We discuss some recent developments achieved by our research group, through extensive collaborations with academic partners across Europe, on optical signal processing using
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In this paper, we present a review on silicon-based nonlinear devices for all optical nonlinear processing of complex telecommunication signals. We discuss some recent developments achieved by our research group, through extensive collaborations with academic partners across Europe, on optical signal processing using silicon-germanium and amorphous silicon based waveguides as well as novel materials such as silicon rich silicon nitride and tantalum pentoxide. We review the performance of four wave mixing wavelength conversion applied on complex signals such as Differential Phase Shift Keying (DPSK), Quadrature Phase Shift Keying (QPSK), 16-Quadrature Amplitude Modulation (QAM) and 64-QAM that dramatically enhance the telecom signal spectral efficiency, paving the way to next generation terabit all-optical networks. Full article
(This article belongs to the Special Issue Silicon Photonics Components and Applications)
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Open AccessFeature PaperArticle Membrane Operations for Process Intensification in Desalination
Appl. Sci. 2017, 7(1), 100; https://doi.org/10.3390/app7010100
Received: 16 December 2016 / Revised: 10 January 2017 / Accepted: 13 January 2017 / Published: 20 January 2017
Cited by 7 | PDF Full-text (1739 KB) | HTML Full-text | XML Full-text
Abstract
Process intensification strategy (PIS) is emerging as an interesting guideline to revolutionize process industry in terms of improved efficiency and sustainability. Membrane engineering has appeared as a strong candidate to implement PIS. The most significant progress has been observed in desalination where substantial
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Process intensification strategy (PIS) is emerging as an interesting guideline to revolutionize process industry in terms of improved efficiency and sustainability. Membrane engineering has appeared as a strong candidate to implement PIS. The most significant progress has been observed in desalination where substantial reduction in overall energy demand, environmental footprint, and process hazards has already been accomplished. Recent developments in membrane engineering are shaping the desalination industry into raw materials and energy production where fresh water will be produced as a byproduct. The present study discusses the current and perspective role of membrane engineering in achieving the objectives of PIS in the field of desalination. Full article
(This article belongs to the Special Issue Membrane Distillation) Printed Edition available
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Open AccessArticle Modeling and Simulation of a Wave Energy Converter INWAVE
Appl. Sci. 2017, 7(1), 99; https://doi.org/10.3390/app7010099
Received: 7 November 2016 / Revised: 21 December 2016 / Accepted: 16 January 2017 / Published: 19 January 2017
Cited by 2 | PDF Full-text (2764 KB) | HTML Full-text | XML Full-text
Abstract
INGINE Inc. developed its own wave energy converter (WEC) named INWAVE and has currently installed three prototype modules in Jeju Island, Korea. This device is an on-shore-type WEC that consists of a buoy, pulleys fixed to the sea-floor and a power take off
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INGINE Inc. developed its own wave energy converter (WEC) named INWAVE and has currently installed three prototype modules in Jeju Island, Korea. This device is an on-shore-type WEC that consists of a buoy, pulleys fixed to the sea-floor and a power take off module (PTO). Three ropes are moored tightly on the bottom of the buoy and connected to the PTO via the pulleys, which are moving back and forth according to the motion of the buoy. Since the device can harness wave energy from all six degrees of movement of the buoy, it is possible to extract energy efficiently even under low energy density conditions provided in the coastal areas. In the PTO module, the ratchet gears convert the reciprocating movement of the rope drum into a uni-directional rotation and determine the transmission of power from the relation of the angular velocities between the rope drum and the generator. In this process, the discontinuity of the power transmission occurs and causes the modeling divergence. Therefore, we introduce the concept of the virtual torsion spring in order to prevent the impact error in the ratchet gear module, thereby completing the PTO modeling. In this paper, we deal with dynamic analysis in the time domain, based on Newtonian mechanics and linear wave theory. We derive the combined dynamics of the buoy and PTO modules via geometric relation between the buoy and mooring ropes, then suggest the ratchet gear mechanism with the virtual torsion spring element to reduce the dynamic errors during the phase transitions. Time domain simulation is carried out under irregular waves that reflect the actual wave states of the installation area, and we evaluate the theoretical performance using the capture width ratio. Full article
(This article belongs to the Special Issue Advancing Grid-Connected Renewable Generation Systems)
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