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Appl. Sci., Volume 7, Issue 11 (November 2017)

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Cover Story (view full-size image) Getting inspiration from nature snake, we find that a snake-like robot should have as many or more [...] Read more.
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Open AccessArticle ECG Identification Based on Non-Fiducial Feature Extraction Using Window Removal Method
Appl. Sci. 2017, 7(11), 1205; https://doi.org/10.3390/app7111205
Received: 12 October 2017 / Revised: 10 November 2017 / Accepted: 20 November 2017 / Published: 22 November 2017
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Abstract
This study proposes electrocardiogram (ECG) identification based on non-fiducial feature extraction using window removal method, nearest neighbor (NN), support vector machine (SVM), and linear discriminant analysis (LDA). In the pre-processing stage, Daubechies 4 is used to remove the baseline wander and noise of
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This study proposes electrocardiogram (ECG) identification based on non-fiducial feature extraction using window removal method, nearest neighbor (NN), support vector machine (SVM), and linear discriminant analysis (LDA). In the pre-processing stage, Daubechies 4 is used to remove the baseline wander and noise of the original signal. In the feature extraction and selection stage, windows are set at a time interval of 5 s in the preprocessed signal, while autocorrelation, scaling, and discrete cosine transform (DCT) are applied to extract and select features. Thereafter, the window removal method is applied to all of the generated windows to remove those that are unrecognizable. Lastly, in the classification stage, the NN, SVM, and LDA classifiers are used to perform individual identification. As a result, when the NN is used in the Normal Sinus Rhythm (NSR), PTB diagnostic, and QT database, the results indicate that the subject identification rates are 100%, 99.40% and 100%, while the window identification rates are 99.02%, 97.13% and 98.91%. When the SVM is used, all of the subject identification rates are 100%, while the window identification rates are 96.92%, 95.82% and 98.32%. When the LDA is used, all of the subject identification rates are 100%, while the window identification rates are 98.67%, 98.65% and 99.23%. The proposed method demonstrates good results with regard to data that not only includes normal signals, but also abnormal signals. In addition, the window removal method improves the individual identification accuracy by removing windows that cannot be recognized. Full article
(This article belongs to the Special Issue Smart Environment and Healthcare)
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Open AccessArticle EigenScape: A Database of Spatial Acoustic Scene Recordings
Appl. Sci. 2017, 7(11), 1204; https://doi.org/10.3390/app7111204
Received: 23 October 2017 / Revised: 21 November 2017 / Accepted: 8 November 2017 / Published: 22 November 2017
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Abstract
The classification of acoustic scenes and events is an emerging area of research in the field of machine listening. Most of the research conducted so far uses spectral features extracted from monaural or stereophonic audio rather than spatial features extracted from multichannel recordings.
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The classification of acoustic scenes and events is an emerging area of research in the field of machine listening. Most of the research conducted so far uses spectral features extracted from monaural or stereophonic audio rather than spatial features extracted from multichannel recordings. This is partly due to the lack thus far of a substantial body of spatial recordings of acoustic scenes. This paper formally introduces EigenScape, a new database of fourth-order Ambisonic recordings of eight different acoustic scene classes. The potential applications of a spatial machine listening system are discussed before detailed information on the recording process and dataset are provided. A baseline spatial classification system using directional audio coding (DirAC) techniques is detailed and results from this classifier are presented. The classifier is shown to give good overall scene classification accuracy across the dataset, with 7 of 8 scenes being classified with an accuracy of greater than 60% with an 11% improvement in overall accuracy compared to use of Mel-frequency cepstral coefficient (MFCC) features. Further analysis of the results shows potential improvements to the classifier. It is concluded that the results validate the new database and show that spatial features can characterise acoustic scenes and as such are worthy of further investigation. Full article
(This article belongs to the Special Issue Sound and Music Computing) Printed Edition available
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Open AccessCommunication Magnetic-Responsive Microparticles that Switch Shape at 37 °C
Appl. Sci. 2017, 7(11), 1203; https://doi.org/10.3390/app7111203
Received: 6 October 2017 / Accepted: 14 November 2017 / Published: 22 November 2017
Cited by 1 | PDF Full-text (1431 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Shape-memory polymers have seen tremendous research efforts driven by the need for better drug carries and biomedical devices. In contrast to these advancements, fabrication of shape-memory particles which actuate at body temperature remains scarce. We developed a shape-memory microparticle system with dynamically tunable
[...] Read more.
Shape-memory polymers have seen tremendous research efforts driven by the need for better drug carries and biomedical devices. In contrast to these advancements, fabrication of shape-memory particles which actuate at body temperature remains scarce. We developed a shape-memory microparticle system with dynamically tunable shapes under physiological temperature. Temperature-responsive poly(ε-caprolactone) (PCL) microparticles were successfully prepared by an in situ oil-in-water (o/w) emulsion polymerization technique using linear telechelic and tetra-branched PCL macromonomers. By optimizing the mixing ratios of branched PCL macromonomers, the crystal-amorphous transition temperature was adjusted to the biological relevant temperature. The particles with a disk-like temporal shape were achieved by compression. The shape recovery from the disk to spherical shape was also realized at 37 °C. We also incorporated magnetic nanoparticles within the PCL microparticles, which can be remote-controllable by a magnet, in such a way that they can be actuated and manipulated in a controlled way. Full article
(This article belongs to the Special Issue Shape Memory Polymers)
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Open AccessArticle A Comparison between Horizontal and Vertical Interchannel Decorrelation
Appl. Sci. 2017, 7(11), 1202; https://doi.org/10.3390/app7111202
Received: 22 September 2017 / Accepted: 17 November 2017 / Published: 22 November 2017
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Abstract
The perceptual effects of interchannel decorrelation on perceived image spread have been investigated subjectively in both horizontal and vertical stereophonic reproductions, looking specifically at the frequency dependency of decorrelation. Fourteen and thirteen subjects graded the horizontal and vertical image spreads of a pink
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The perceptual effects of interchannel decorrelation on perceived image spread have been investigated subjectively in both horizontal and vertical stereophonic reproductions, looking specifically at the frequency dependency of decorrelation. Fourteen and thirteen subjects graded the horizontal and vertical image spreads of a pink noise sample, respectively. The pink noise signal had been decorrelated by a complementary comb-filter decorrelation algorithm, varying the frequency-band, time-delay and decorrelation factor for each sample. Results generally indicated that interchannel decorrelation had a significant effect on auditory image spread both horizontally and vertically, with spread increasing as correlation decreases. However, it was found that the effect of vertical decorrelation was less effective than that of horizontal decorrelation. The results also suggest that the decorrelation effect was frequency-dependent; changes in horizontal image spread were more apparent in the high frequency band, whereas those in vertical image spread were in the low band. Furthermore, objective analysis suggests that the perception of vertical image spread for the low and middle frequency bands could be associated with a floor reflection; whereas for the high band, the results appear to be related to spectral notches in the ear input signals. Full article
(This article belongs to the Section Acoustics)
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Open AccessArticle Short-Pulse-Width Repetitively Q-Switched ~2.7-μm Er:Y2O3 Ceramic Laser
Appl. Sci. 2017, 7(11), 1201; https://doi.org/10.3390/app7111201
Received: 16 October 2017 / Accepted: 17 November 2017 / Published: 22 November 2017
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Abstract
A short-pulse-width repetitively Q-switched 2.7-μm Er:Y2O3 ceramic laser is demonstrated using a specially designed mechanical switch, a metal plate carved with slits of both slit-width and duty-cycle optimized. With a 20% transmission output coupler, stable pulse trains with durations (full-width
[...] Read more.
A short-pulse-width repetitively Q-switched 2.7-μm Er:Y2O3 ceramic laser is demonstrated using a specially designed mechanical switch, a metal plate carved with slits of both slit-width and duty-cycle optimized. With a 20% transmission output coupler, stable pulse trains with durations (full-width at half-maximum, FWHM) of 27–38 ns were generated with a repetition rate within the range of 0.26–4 kHz. The peak power at a 0.26 kHz repetition rate was ~3 kW. Full article
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Open AccessArticle A Non-Reference Image Denoising Method for Infrared Thermal Image Based on Enhanced Dual-Tree Complex Wavelet Optimized by Fruit Fly Algorithm and Bilateral Filter
Appl. Sci. 2017, 7(11), 1190; https://doi.org/10.3390/app7111190
Received: 19 October 2017 / Revised: 13 November 2017 / Accepted: 13 November 2017 / Published: 22 November 2017
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Abstract
To eliminate the noise of infrared thermal image without reference and noise model, an improved dual-tree complex wavelet transform (DTCWT), optimized by an improved fruit-fly optimization algorithm (IFOA) and bilateral filter (BF), is proposed in this paper. Firstly, the noisy image is transformed
[...] Read more.
To eliminate the noise of infrared thermal image without reference and noise model, an improved dual-tree complex wavelet transform (DTCWT), optimized by an improved fruit-fly optimization algorithm (IFOA) and bilateral filter (BF), is proposed in this paper. Firstly, the noisy image is transformed by DTCWT, and the noise variance threshold is optimized by the IFOA, which is enhanced through a fly step range with inertia weight. Then, the denoised image will be re-processed using bilateral filter to improve the denoising performance and enhance the edge information. In the experiment, the proposed method is applied to eliminate both addictive noise and multiplicative noise, and the denoising results are compared with other representative methods, such as DTCWT, block-matching and 3D filtering (BM3D), median filter, wiener filter, wavelet decomposition filter (WDF) and bilateral filter. Moreover, the proposed method is applied as pre-processing utilization for infrared thermal images in a coal mining working face. Full article
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Open AccessArticle Fault Diagnosis Model of Photovoltaic Array Based on Least Squares Support Vector Machine in Bayesian Framework
Appl. Sci. 2017, 7(11), 1199; https://doi.org/10.3390/app7111199
Received: 30 September 2017 / Revised: 8 November 2017 / Accepted: 20 November 2017 / Published: 21 November 2017
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Abstract
With the rapid development of the photovoltaic industry, fault monitoring is becoming an important issue in maintaining the safe and stable operation of a solar power station. In order to diagnose the fault types of photovoltaic array, a fault diagnosis method that is
[...] Read more.
With the rapid development of the photovoltaic industry, fault monitoring is becoming an important issue in maintaining the safe and stable operation of a solar power station. In order to diagnose the fault types of photovoltaic array, a fault diagnosis method that is based on the Least Squares Support Vector Machine (LSSVM) in the Bayesian framework is put forward. First, based on the elaborate analysis of the change rules of the output electrical parameters and the equivalent circuit internal parameters of photovoltaic array in different fault states, the input variables of the photovoltaic array fault diagnosis model are determined. Second, through the LSSVM algorithm in the Bayesian framework, the fault diagnosis model based on the output electrical parameters and the equivalent circuit internal parameters of the photovoltaic array is built, which can effectively detect the photovoltaic array faults of short circuit, open circuit, and abnormal aging. Then, the simulation model is built to verify the validity of the LSSVM algorithm in the Bayesian framework by comparing it with the model of LSSVM and the Support Vector Machine (SVM). Moreover, a 5 × 3 photovoltaic array and a reference photovoltaic string are established and experimentally tested to validate the performance of the proposed method. Full article
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Open AccessArticle An Experimental and Analytical Study on the Deflection Behavior of Precast Concrete Beams with Joints
Appl. Sci. 2017, 7(11), 1198; https://doi.org/10.3390/app7111198
Received: 13 September 2017 / Revised: 7 November 2017 / Accepted: 20 November 2017 / Published: 21 November 2017
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Abstract
The use of precast concrete modular construction in the replacement and rebuilding of old structures has recently increased. However, the joints between modules in this type of construction exhibit special behavior that should be considered when analyzing the behavior of modular members. Both
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The use of precast concrete modular construction in the replacement and rebuilding of old structures has recently increased. However, the joints between modules in this type of construction exhibit special behavior that should be considered when analyzing the behavior of modular members. Both stability and serviceability should be studied; however, existing research has only addressed the former. Research regarding serviceability, involving deflection and crack development and propagation, is lacking. This study considers the difference in strength between on-site cast and precast segmental concrete to accurately evaluate the deflection of precast concrete flexural members with joints within the lapped splice. In addition, to reflect an initial crack, the deflection is calculated and evaluated by reflecting the effect of tension-stiffening and subsequently redefining the attached transmission lengths of the left and right sides of the cracked surface as a new cracked region. As a result of explicitly including joint behavior which is considered attached transmission length and characteristic by concrete strength, a more accurate calculation of deflection is developed. Full article
(This article belongs to the Section Materials)
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Open AccessArticle Identifying Single Trial Event-Related Potentials in an Earphone-Based Auditory Brain-Computer Interface
Appl. Sci. 2017, 7(11), 1197; https://doi.org/10.3390/app7111197
Received: 20 October 2017 / Accepted: 17 November 2017 / Published: 21 November 2017
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Abstract
As brain-computer interfaces (BCI) must provide reliable ways for end users to accomplish a specific task, methods to secure the best possible translation of the intention of the users are constantly being explored. In this paper, we propose and test a number of
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As brain-computer interfaces (BCI) must provide reliable ways for end users to accomplish a specific task, methods to secure the best possible translation of the intention of the users are constantly being explored. In this paper, we propose and test a number of convolutional neural network (CNN) structures to identify and classify single-trial P300 in electroencephalogram (EEG) readings of an auditory BCI. The recorded data correspond to nine subjects in a series of experiment sessions in which auditory stimuli following the oddball paradigm were presented via earphones from six different virtual directions at time intervals of 200, 300, 400 and 500 ms. Using three different approaches for the pooling process, we report the average accuracy for 18 CNN structures. The results obtained for most of the CNN models show clear improvement over past studies in similar contexts, as well as over other commonly-used classifiers. We found that the models that consider data from the time and space domains and those that overlap in the pooling process usually offer better results regardless of the number of layers. Additionally, patterns of improvement with single-layered CNN models can be observed. Full article
(This article belongs to the Special Issue Sound and Music Computing) Printed Edition available
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Open AccessArticle Impact of Alloying on Stacking Fault Energies in γ-TiAl
Appl. Sci. 2017, 7(11), 1193; https://doi.org/10.3390/app7111193
Received: 21 October 2017 / Revised: 13 November 2017 / Accepted: 15 November 2017 / Published: 21 November 2017
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Abstract
Microstructure and mechanical properties are key parameters influencing the performance of structural multi-phase alloys such as those based on intermetallic TiAl compounds. There, the main constituent, a γ-TiAl phase, is derived from a face-centered cubic structure. Consequently, the dissociation of dislocations and
[...] Read more.
Microstructure and mechanical properties are key parameters influencing the performance of structural multi-phase alloys such as those based on intermetallic TiAl compounds. There, the main constituent, a γ -TiAl phase, is derived from a face-centered cubic structure. Consequently, the dissociation of dislocations and generation of stacking faults (SFs) are important factors contributing to the overall deformation behavior, as well as mechanical properties, such as tensile/creep strength and, most importantly, fracture elongation below the brittle-to-ductile transition temperature. In this work, SFs on the { 111 ) plane in γ -TiAl are revisited by means of ab initio calculations, finding their energies in agreement with previous reports. Subsequently, stacking fault energies are evaluated for eight ternary additions, namely group IVB–VIB elements, together with Ti off-stoichiometry. It is found that the energies of superlattice intrinsic SFs, anti-phase boundaries (APBs), as well as complex SFs decrease by 20–40% with respect to values in stoichiometric γ -TiAl once an alloying element X is present in the fault plane having thus a composition of Ti-50Al-12.5X. In addition, Mo, Ti and V stabilize the APB on the (111) plane, which is intrinsically unstable at 0 K in stoichiometric γ -TiAl. Full article
(This article belongs to the Special Issue Mechanical Behaviour of Aluminium Alloys)
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Open AccessArticle Performance Evaluation of a Novel Propulsion System for the Spherical Underwater Robot (SURIII)
Appl. Sci. 2017, 7(11), 1196; https://doi.org/10.3390/app7111196
Received: 28 September 2017 / Revised: 19 November 2017 / Accepted: 17 November 2017 / Published: 20 November 2017
Cited by 1 | PDF Full-text (6575 KB) | HTML Full-text | XML Full-text
Abstract
This paper considers a novel propulsion system for the third-generation Spherical Underwater Robot (SURIII), the improved propulsion system is designed and analyzed to verify its increased stability compared to the second-generation Spherical Underwater Robot (SURII). With the new propulsion system, the robot is
[...] Read more.
This paper considers a novel propulsion system for the third-generation Spherical Underwater Robot (SURIII), the improved propulsion system is designed and analyzed to verify its increased stability compared to the second-generation Spherical Underwater Robot (SURII). With the new propulsion system, the robot is not only symmetric on the X axis but also on the Y axis, which increases the flexibility of its movement. The new arrangement also reduces the space constraints of servomotors and vectored water-jet thrusters. This paper also aims to the hydrodynamic characteristic of the whole robot. According to the different situations of the surge and heave motion, two kinds of methods are used to calculate the drag coefficient for the SURIII. For surge motion, the drag coefficient can be determined by the Reynolds number. For heave motion, considering about the influences of edges and gaps of the SURIII, the drag coefficient needs to be calculated by the dynamic equation. In addition, the Computational Fluid Dynamics (CFD) simulation is carried out to estimate some parameters which cannot be measured. The pressure contours, velocity vectors and velocity streamlines for different motions are extracted from the post-processor in the CFD simulation. The drag coefficients of surge and heave motion are both calculated by the simulation results and compared with the chosen one by Reynolds number. Finally, an experiment is also conducted for measure the propulsive force of the multi-vectored water-jet thrusters by using a 6-DoF load cell. The experimental results demonstrate the propulsive force is better than a previous version. Thus, the propulsive performance is better than before. Full article
(This article belongs to the Special Issue Bio-Inspired Robotics)
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Open AccessArticle Design and Tests of a High-Performance Long-Wave Infrared Refractive Thermal Imager: Freeform Lens in Coaxial System
Appl. Sci. 2017, 7(11), 1195; https://doi.org/10.3390/app7111195
Received: 18 October 2017 / Accepted: 10 November 2017 / Published: 20 November 2017
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Abstract
In this paper, we used a freeform lens in a long-wave, un-cooled, refractive infrared (IR) thermal imager and present the design strategy and test results. This optical system is composed of only one freeform lens and several spheres. It can correct the distortion
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In this paper, we used a freeform lens in a long-wave, un-cooled, refractive infrared (IR) thermal imager and present the design strategy and test results. This optical system is composed of only one freeform lens and several spheres. It can correct the distortion issue inherent to wide field-of-view systems more effectively, and achieve a better thermal imaging performance simultaneously compared to traditional aspheric optical lenses. Such a design model can alleviate the calculation load and cater for the demand of the ultra-precision turning on single crystal germanium. It satisfies the design idea of freeform surfaces with machining feasibility. The refractive freeform IR imager can be realized from the theoretical design to the engineering applications. The research contents of this paper are helpful for the further application of the freeform lens to a more complex cooled infrared refractive thermal imager. Full article
(This article belongs to the Section Optics and Lasers)
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Open AccessArticle Multi-Party Optimal Operation for Distribution Networks Containing DC-Linked Microgrids: Integrated Network Reconfigurations and Energy Sharing
Appl. Sci. 2017, 7(11), 1194; https://doi.org/10.3390/app7111194
Received: 14 October 2017 / Revised: 10 November 2017 / Accepted: 16 November 2017 / Published: 20 November 2017
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Abstract
With the development of Microgrids (MG) in distribution networks, how to coordinate the reconfiguration of distribution networks with the energy sharing of Direct Current (DC)-linked multi-MG is an unsolved problem. In this paper, a multi-party optimization framework is proposed, the involving parties include
[...] Read more.
With the development of Microgrids (MG) in distribution networks, how to coordinate the reconfiguration of distribution networks with the energy sharing of Direct Current (DC)-linked multi-MG is an unsolved problem. In this paper, a multi-party optimization framework is proposed, the involving parties include the Distribution Network Operator (DNO), the Multi-MG Coalition Operator (MCO), and the MG operator. For the DC-linked MGs, the MCO is obligated to coordinate the energy sharing, a stochastic optimal scheduling model for the MG coalition is formulated, considering the uncertainties of Photovoltaic (PV), Wind Turbines (WT), and load power. Moreover, a billing mechanism is designed to distribute the cost of each MG participated in the energy sharing. For the distribution network, an event triggered dynamic reconfiguration model is proposed. Based on the scheduling results of MCO, the decisions of switch operations are finally co-decided by the expected exchanging power of the MGs and the real-time errors caused by uncertainty factors. Finally, a modified IEEE-33 nodes distribution system are used to test and verify the effectiveness of the method. Full article
(This article belongs to the Section Energy)
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Open AccessArticle Laboratory and On-Site Tests for Rapid Runway Repair
Appl. Sci. 2017, 7(11), 1192; https://doi.org/10.3390/app7111192
Received: 15 October 2017 / Revised: 8 November 2017 / Accepted: 16 November 2017 / Published: 19 November 2017
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Abstract
The attention to rapid pavement repair has grown fast in recent decades: this topic is strategic for the airport management process for civil purposes and peacekeeping missions. This work presents the results of laboratory and on-site tests for rapid runway repair, in order
[...] Read more.
The attention to rapid pavement repair has grown fast in recent decades: this topic is strategic for the airport management process for civil purposes and peacekeeping missions. This work presents the results of laboratory and on-site tests for rapid runway repair, in order to analyse and compare technical and mechanical performances of 12 different materials currently used in airport. The study focuses on site repairs, a technique adopted most frequently than repairs with modular elements. After describing mechanical and physical properties of the examined materials (2 bituminous emulsions, 5 cement mortars, 4 cold bituminous mixtures and 1 expanding resin), the study presents the results of carried out mechanical tests. The results demonstrate that the best performing material is a one-component fast setting and hardening cement mortar with graded aggregates. This material allows the runway reopening 6 h after the work. A cold bituminous mixture (bicomponent premixed cold asphalt with water as catalyst) and the ordinary cement concrete allow the reopening to traffic after 18 h, but both ensure a lower service life (1000 coverages) than the cement mortar (10,000 coverages). The obtained results include important information both laboratory level and field, and they could be used by airport management bodies and road agencies when scheduling and evaluating pavement repairs. Full article
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Open AccessArticle Research on the Rational Yield Ratio of Isolation System and Its Application to the Design of Seismically Isolated Reinforced Concrete Frame-Core Tube Tall Buildings
Appl. Sci. 2017, 7(11), 1191; https://doi.org/10.3390/app7111191
Received: 10 October 2017 / Revised: 14 November 2017 / Accepted: 15 November 2017 / Published: 19 November 2017
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Resilience-based seismic design of reinforced concrete (RC) tall buildings has become an important trend in earthquake engineering. Seismic isolation technology is an effective and important method to improve the resiliency of RC frame-core tube tall buildings located in high seismic regions. However, the
[...] Read more.
Resilience-based seismic design of reinforced concrete (RC) tall buildings has become an important trend in earthquake engineering. Seismic isolation technology is an effective and important method to improve the resiliency of RC frame-core tube tall buildings located in high seismic regions. However, the traditional design method for this type of building does not focus on the key design parameter, namely, the yield ratio of the isolation system and has therefore been proved to be highly inefficient. To address these issues, the rational yield ratio of isolation system for such buildings is investigated based on 28 carefully designed cases, considering the influences of total heights, yield ratios and seismically isolated schemes. The rational range of the yield ratio is recommended to be 2-3%. Based on this, a high-efficiency design method is proposed for seismically isolated RC frame-core tube tall buildings. Subsequently, a seismically isolated RC frame-core tube tall building with a height of 84.1 m is designed using the proposed design method. The rationality, reliability and efficiency of the proposed method are validated. The research outcome can serve as a reference for further development of the seismic design method for seismically isolated RC frame-core tube tall buildings. Full article
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Open AccessArticle Utilizing Downdraft Fixed Bed Reactor for Thermal Upgrading of Sewage Sludge as Fuel by Torrefaction
Appl. Sci. 2017, 7(11), 1189; https://doi.org/10.3390/app7111189
Received: 31 October 2017 / Revised: 13 November 2017 / Accepted: 15 November 2017 / Published: 18 November 2017
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Abstract
A lab-scale downdraft fixed bed reactor was used for the study of sewage sludge, a non-lignocellulosic biomass, torrefaction to enhance the thermochemical properties of sewage sludge. The torrefaction was carried out for a temperature range of 200–350 °C and a residence time of
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A lab-scale downdraft fixed bed reactor was used for the study of sewage sludge, a non-lignocellulosic biomass, torrefaction to enhance the thermochemical properties of sewage sludge. The torrefaction was carried out for a temperature range of 200–350 °C and a residence time of 0–50 min. Degree of torrefaction, torrefaction index, chemical exergy, gas analysis, and molar ratios were taken into account to analyze the torrefied product with respect to torrefaction temperature. The effect of torrefaction temperature was very pronounced and the temperature range of 250–300 °C was considered to be the optimum torrefaction temperature range for sewage sludge. Chemical exergy, calorific value and torrefaction index were significantly influenced by the change in the relative carbon content resulting in decrease of the O/C and H/C molar ratios. Full article
(This article belongs to the Special Issue Renewable Energy 2018)
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Open AccessArticle Elastic Stability of Perforated Plates Strengthened with FRP under Uniaxial Compression
Appl. Sci. 2017, 7(11), 1188; https://doi.org/10.3390/app7111188
Received: 18 October 2017 / Revised: 8 November 2017 / Accepted: 13 November 2017 / Published: 18 November 2017
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Abstract
Openings are frequently introduced in plates for the purpose of inspection, maintenance, service, etc. The presence of openings reduces the buckling and ultimate capacity significantly, and pasting fiber-reinforced polymers (FRP) is an ideal technique for postponing the buckling and increasing the ultimate capacity
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Openings are frequently introduced in plates for the purpose of inspection, maintenance, service, etc. The presence of openings reduces the buckling and ultimate capacity significantly, and pasting fiber-reinforced polymers (FRP) is an ideal technique for postponing the buckling and increasing the ultimate capacity of the plates. In this paper, the finite element (FE) method has been employed to study the buckling stress of the perforated plates strengthened with FRP under uniaxial compression, and several parameters are considered: material’s geometrical and mechanical properties, boundary conditions, plate aspect ratio, hole sizes, and hole position. Then a method of calculating the buckling stress is proposed and modified based on the theory of composite plate and the numerical results. The study shows that, the stiffness modified factor αD, which considers the orthotropic properties of FRP are a function of the reinforcement index ω and hole size d/b for Boundary conditions (BCs) of 4S and 3S1F. And it is recommended to place the big hole close to the middle area of the plate in x-axis. It also shows that for a small hole size, there is little effect of the hole position ey/b on buckling coefficient Ku regardless of the BCs, and that effect becomes more pronounced as d/b increases, so it is recommended to put the holes near the middle of the plate for 4S and the simple support edge for 3S1F in y-axis. Full article
(This article belongs to the Special Issue Soft Computing Techniques in Structural Engineering and Materials)
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Open AccessArticle Input–Output Finite Time Stabilization of Time-Varying Impulsive Positive Hybrid Systems under MDADT
Appl. Sci. 2017, 7(11), 1187; https://doi.org/10.3390/app7111187
Received: 31 August 2017 / Revised: 23 October 2017 / Accepted: 7 November 2017 / Published: 17 November 2017
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Abstract
Time-varying impulsive positive hybrid systems based on finite state machines (FSMs) are considered in this paper, and the concept of input–output finite time stability (IO-FTS) is extended for this type of hybrid system. The IO-FTS analysis of the single linear time-varying system is
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Time-varying impulsive positive hybrid systems based on finite state machines (FSMs) are considered in this paper, and the concept of input–output finite time stability (IO-FTS) is extended for this type of hybrid system. The IO-FTS analysis of the single linear time-varying system is given first. Then, the sufficient conditions of IO-FTS for hybrid systems are proposed via the mode-dependent average dwell time (MDADT) technique. Moreover, the output feedback controller which can stabilize the non-autonomous hybrid systems is derived, and the obtained results are presented in a linear programming form. Finally, a numerical example is provided to show the theoretical results. Full article
(This article belongs to the Special Issue Modeling, Simulation, Operation and Control of Discrete Event Systems)
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Open AccessArticle Optimal Cluster Expansion-Based Intrusion Tolerant System to Prevent Denial of Service Attacks
Appl. Sci. 2017, 7(11), 1186; https://doi.org/10.3390/app7111186
Received: 3 November 2017 / Revised: 16 November 2017 / Accepted: 15 November 2017 / Published: 17 November 2017
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Abstract
In this study, we propose an optimal cluster expansion-based intrusion-tolerant system (ITS) that can maintain quality of service (QoS) under a massive denial of service (DoS) attack. Our proposed scheme conserves resources while maintaining good QoS by optimally increasing and decreasing cluster size.
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In this study, we propose an optimal cluster expansion-based intrusion-tolerant system (ITS) that can maintain quality of service (QoS) under a massive denial of service (DoS) attack. Our proposed scheme conserves resources while maintaining good QoS by optimally increasing and decreasing cluster size. To evaluate the performance of the proposed scheme, we use a CloudSim simulator and compare our proposed scheme with an existing conventional adaptive cluster transformation (ACT) scheme. Our simulation results show that the proposed scheme outperforms the conventional ACT scheme in terms of better QoS and lower resource consumption. Full article
(This article belongs to the Section Computer Science and Electrical Engineering)
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Open AccessArticle Enhanced Photocatalytic Activity of Iron-Doped ZnO Nanowires for Water Purification
Appl. Sci. 2017, 7(11), 1185; https://doi.org/10.3390/app7111185
Received: 2 October 2017 / Revised: 14 November 2017 / Accepted: 14 November 2017 / Published: 17 November 2017
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Abstract
In order to improve the photocatalytic efficiency of ZnO nanowires, iron-doped ZnO nanowires (ZnO:Fe NWs) were successfully synthesized. The morphology, optical properties and photocatalytic performance of ZnO:Fe NWs were studied by scanning electron microscopy (SEM), UV-Visible spectrophotometry and photoluminescence spectroscopy (PL), respectively. The
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In order to improve the photocatalytic efficiency of ZnO nanowires, iron-doped ZnO nanowires (ZnO:Fe NWs) were successfully synthesized. The morphology, optical properties and photocatalytic performance of ZnO:Fe NWs were studied by scanning electron microscopy (SEM), UV-Visible spectrophotometry and photoluminescence spectroscopy (PL), respectively. The SEM observations showed that the morphology of the ZnO NWs was not modified by iron doping, but the band gap was reduced from 3.29 eV for ZnO NWs to 3.25 eV for ZnO:Fe NWs. This band gap reduction allows the semiconductor to harvest more photons to excite more electrons in the valence band; subsequently, resulting in an improvement of the degradability of the understudied organic dyes: methylene blue (MB), methyl orange (MO), and acid red 14 (AR14). The photocatalytic study showed that the photo-degradation rate of the MB, MO, and AR14 was improved 9%, 20%, and 5% respectively by 1% iron doping in the ZnO NWs. Full article
(This article belongs to the Special Issue Nanotechnology in Wastewater Treatment Technology)
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Open AccessArticle NIRExpNet: Three-Stream 3D Convolutional Neural Network for Near Infrared Facial Expression Recognition
Appl. Sci. 2017, 7(11), 1184; https://doi.org/10.3390/app7111184
Received: 28 September 2017 / Revised: 26 October 2017 / Accepted: 6 November 2017 / Published: 17 November 2017
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Abstract
Facial expression recognition (FER) under active near-infrared (NIR) illumination has the advantages of illumination invariance. In this paper, we propose a three-stream 3D convolutional neural network, named as NIRExpNet for NIR FER. The 3D structure of NIRExpNet makes it possible to extract automatically,
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Facial expression recognition (FER) under active near-infrared (NIR) illumination has the advantages of illumination invariance. In this paper, we propose a three-stream 3D convolutional neural network, named as NIRExpNet for NIR FER. The 3D structure of NIRExpNet makes it possible to extract automatically, not just spatial features, but also, temporal features. The design of multiple streams of the NIRExpNet enables it to fuse local and global facial expression features. To avoid over-fitting, the NIRExpNet has a moderate size to suit the Oulu-CASIA NIR facial expression database that is a medium-size database. Experimental results show that the proposed NIRExpNet outperforms some previous state-of-art methods, such as Histogram of Oriented Gradient to 3D (HOG 3D), Local binary patterns from three orthogonal planes (LBP-TOP), deep temporal appearance-geometry network (DTAGN), and adapt 3D Convolutional Neural Networks (3D CNN DAP). Full article
(This article belongs to the Section Computer Science and Electrical Engineering)
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Open AccessArticle Gap-Dependent Localized High Energy Multiple Dipolar Modes in Passive Silver-Coated Silica Nanoparticle Antennas
Appl. Sci. 2017, 7(11), 1183; https://doi.org/10.3390/app7111183
Received: 24 October 2017 / Accepted: 2 November 2017 / Published: 17 November 2017
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Abstract
The gap-induced plasmonic response of metallic nanoparticles drastically changes the near and far-field properties of nanoparticle antenna. Similar to a pair of metallic nanostructures, the two nanoparticles, with a dielectric core and silver shell in close proximity, exhibit multiple high energy plasmonic resonances
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The gap-induced plasmonic response of metallic nanoparticles drastically changes the near and far-field properties of nanoparticle antenna. Similar to a pair of metallic nanostructures, the two nanoparticles, with a dielectric core and silver shell in close proximity, exhibit multiple high energy plasmonic resonances at the short wavelength end of their optical spectrum. In this article, we have overwhelmingly investigated the disparity in the electric field of a core–shell dimer antenna when the gap between nanoparticles within the dimer becomes sub-nanometer in length. We used an electromagnetic planewave to excite the core–shell nanoparticles within the dimer. Frequency domain Finite Element Method (FEM) was employed for the numerical optical analysis of a dimer comprised of two silver-coated silica (SCS) nanoparticles in close proximity, using Computer Simulation Technology (CST) Microwave Studio. A modified Drude model has been used to predict the optical properties of the system with incorporating the size effects. The SCS dimer was numerically analyzed in the visible frequency band, and anomalies in near-field plasmonic coupling were investigated in detail. The inter-surface gap g between nanoparticles within the dimer varied in a range from 0.1 to 402 nm. Full article
(This article belongs to the Special Issue Nano-Antennas)
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Open AccessFeature PaperReview State of the Art: Bipedal Robots for Lower Limb Rehabilitation
Appl. Sci. 2017, 7(11), 1182; https://doi.org/10.3390/app7111182
Received: 5 October 2017 / Revised: 3 November 2017 / Accepted: 3 November 2017 / Published: 16 November 2017
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Abstract
The bipedal robot is one of the most attractive robots types given its similarity to the locomotion of human beings and its ability to assist people to walk during rehabilitation. This review summarizes the chronological historical development of bipedal robots and introduces some
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The bipedal robot is one of the most attractive robots types given its similarity to the locomotion of human beings and its ability to assist people to walk during rehabilitation. This review summarizes the chronological historical development of bipedal robots and introduces some current popular bipedal robots age. Then, the basic theory-stability control and key technology-motion planning of bipedal robots are introduced and analyzed. Bipedal robots have a wide range of applications in the service, education, entertainment, and other industries. After that, we specifically discuss the applications of bipedal robots in lower limb rehabilitation, including wearable exoskeleton robots, rehabilitation equipment, soft exoskeleton robots, and unpowered exoskeleton robots, and their control methods. Lastly, the future development and the challenges in this field are discussed. Full article
(This article belongs to the Special Issue Bio-Inspired Robotics)
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Open AccessArticle Viscoelastic Dampers for Rotors: Modeling and Validation at Component and System Level
Appl. Sci. 2017, 7(11), 1181; https://doi.org/10.3390/app7111181
Received: 20 October 2017 / Revised: 10 November 2017 / Accepted: 13 November 2017 / Published: 16 November 2017
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Abstract
The aim of this paper is to propose a methodology for the modelling, testing, and the parameter identification of viscoelastic supports for rotating machines at the component and system level. Although the use of this type of dampers is common in rotordynamic applications,
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The aim of this paper is to propose a methodology for the modelling, testing, and the parameter identification of viscoelastic supports for rotating machines at the component and system level. Although the use of this type of dampers is common in rotordynamic applications, the strict dependence on the working frequency of the material parameters makes their behavior hard to predict and recommends grounding the design on experimental data of the characteristics. A dedicated test rig is adopted to characterize the supports and validate the modelling approach at component level. A parameter identification procedure is carried out from the experimental results to extract the mechanical properties of the supports. To this end, a Genetic Algorithm (GA) is adopted to search the most fitting values of damping and stiffness of the reference model. The choice of GA is motivated by the need of adopting a technique that can be easily implemented on industrial control units, being that the dedicated machine is supposed to be used in production lines for testing procedures. The results are obtained in terms of complex stiffness as a function of the frequency and are then translated in classical stiffness and damping components that are commonly used in rotordynamics. Afterwards, they are introduced in the model of a turbo-molecular pump adopted as a case study to evaluate the correctness of the proposed methodology at system level at stand-still and with the pump in rotation. The proposed approach is effective, showing a good match between the numerical model and the experimental results even with a relatively low order model of the viscoelastic supports and on a complex rotordynamic system. Full article
(This article belongs to the Section Acoustics)
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Open AccessArticle Performance of Time Reversal Based Underwater Target Detection in Shallow Water
Appl. Sci. 2017, 7(11), 1180; https://doi.org/10.3390/app7111180
Received: 30 September 2017 / Accepted: 13 November 2017 / Published: 16 November 2017
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Abstract
In this paper, a scheme based on the time reversal technique is proposed to improve the detection performance for detecting a cylindrical object bottoming at the seafloor in shallow water. When the time reversal technique is applied to the response of the clutter
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In this paper, a scheme based on the time reversal technique is proposed to improve the detection performance for detecting a cylindrical object bottoming at the seafloor in shallow water. When the time reversal technique is applied to the response of the clutter with the strong time-varying characteristic of shallow water, it is difficult to obtain a high peak response. However, in the case where a cylindrical object is placed on the seafloor because the time-invariant property of the target response is stronger than the time-varying property of the reverberation by the clutters, the time reversal technique can be applied to enhance the target signal. In this paper, it is demonstrated that the peak due to the target that is contacted at the seabed becomes higher when applying the time reversal technique. The performance is investigated by using numerical computation of the probability of detection for various probabilities of false alarm and computer simulation. Full article
(This article belongs to the Section Acoustics)
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Open AccessFeature PaperArticle Sound Synthesis of Objects Swinging through Air Using Physical Models
Appl. Sci. 2017, 7(11), 1177; https://doi.org/10.3390/app7111177
Received: 12 October 2017 / Accepted: 10 November 2017 / Published: 16 November 2017
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Abstract
A real-time physically-derived sound synthesis model is presented that replicates the sounds generated as an object swings through the air. Equations obtained from fluid dynamics are used to determine the sounds generated while exposing practical parameters for a user or game engine to
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A real-time physically-derived sound synthesis model is presented that replicates the sounds generated as an object swings through the air. Equations obtained from fluid dynamics are used to determine the sounds generated while exposing practical parameters for a user or game engine to vary. Listening tests reveal that for the majority of objects modelled, participants rated the sounds from our model as plausible as actual recordings. The sword sound effect performed worse than others, and it is speculated that one cause may be linked to the difference between expectations of a sound and the actual sound for a given object. Full article
(This article belongs to the Special Issue Sound and Music Computing) Printed Edition available
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Open AccessArticle Determination of the Constants of GTN Damage Model Using Experiment, Polynomial Regression and Kriging Methods
Appl. Sci. 2017, 7(11), 1179; https://doi.org/10.3390/app7111179
Received: 8 October 2017 / Revised: 9 November 2017 / Accepted: 10 November 2017 / Published: 15 November 2017
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Abstract
Damage models, particularly the Gurson–Tvergaard–Needleman (GTN) model, are widely used in numerical simulation of material deformations. Each damage model has some constants which must be identified for each material. The direct identification methods are costly and time consuming. In the current work, a
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Damage models, particularly the Gurson–Tvergaard–Needleman (GTN) model, are widely used in numerical simulation of material deformations. Each damage model has some constants which must be identified for each material. The direct identification methods are costly and time consuming. In the current work, a combination of experimental, numerical simulation and optimization were used to determine the constants. Quasi-static and dynamic tests were carried out on notched specimens. The experimental profiles of the specimens were used to determine the constants. The constants of GTN damage model were identified through the proposed method and using the results of quasi-static tests. Numerical simulation of the dynamic test was performed utilizing the constants obtained from quasi-static experiments. The results showed a high precision in predicting the specimen’s profile in the dynamic testing. The sensitivity analysis was performed on the constants of GTN model to validate the proposed method. Finally, the experiments were simulated using the Johnson–Cook (J–C) damage model and the results were compared to those obtained from GTN damage model. Full article
(This article belongs to the Special Issue Soft Computing Techniques in Structural Engineering and Materials)
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Open AccessArticle Modified Local Linear Embedding Algorithm for Rolling Element Bearing Fault Diagnosis
Appl. Sci. 2017, 7(11), 1178; https://doi.org/10.3390/app7111178
Received: 11 September 2017 / Revised: 14 November 2017 / Accepted: 13 November 2017 / Published: 15 November 2017
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Abstract
Due to the noise accompanied with rolling element bearing fault signal, it can reduce the accuracy of faulty diagnoses. In order to improve the robustness of a faulty diagnosis, this study proposed a fault diagnosis model based on modified local linear embedding (M-LLE)
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Due to the noise accompanied with rolling element bearing fault signal, it can reduce the accuracy of faulty diagnoses. In order to improve the robustness of a faulty diagnosis, this study proposed a fault diagnosis model based on modified local linear embedding (M-LLE) algorithm. Aiming at the characteristics of rolling element bearing fault data, the vibration signal was first analyzed in time domain and frequency domain to construct high dimension eigenvectors. Next, the high-dimensional eigenvectors can be reduced to low-dimensional eigenvectors by M-LLE algorithm. In the M-LLE algorithm, the Mahalanobis distance (MD) metric is adopted to replace Euclidean distance in traditional neighborhood construction and L1-norm is used to standardize weight matrix, which can enhance the anti-noise ability of the Local Linear Embedding (LLE) algorithm. Finally, fault diagnosis results can be obtained when low-dimensional rolling element bearing fault data is classified by K-Nearest Neighbor (KNN) classifier. By simulating the noisy artificial data sets in different degrees, the proposed algorithm can get the perfect local structure of manifolds. The effectiveness of M-LLE algorithm can be proved. In addition, experimental results of real rolling element bearing data which provided by the University of Cincinnati show that the accuracies of all kinds of faults can reach 100%. It can be deemed that the proposed fault diagnosis model can effectively improve the accuracy of fault diagnosis. Full article
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Open AccessEditorial Smart Healthcare
Appl. Sci. 2017, 7(11), 1176; https://doi.org/10.3390/app7111176
Received: 13 November 2017 / Revised: 14 November 2017 / Accepted: 14 November 2017 / Published: 15 November 2017
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Abstract
Medicine is undergoing a sector-wide transformation thanks to the advances in computing and networking technologies [...]
Full article
(This article belongs to the Special Issue Smart Healthcare) Printed Edition available
Open AccessReview Recent Advances in the Synthesis of Graphene-Based Nanomaterials for Controlled Drug Delivery
Appl. Sci. 2017, 7(11), 1175; https://doi.org/10.3390/app7111175
Received: 29 September 2017 / Revised: 30 October 2017 / Accepted: 13 November 2017 / Published: 15 November 2017
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Abstract
Graphene-based nanomaterials have exhibited wide applications in nanotechnology, materials science, analytical science, and biomedical engineering due to their unique physical and chemical properties. In particular, graphene has been an excellent nanocarrier for drug delivery application because of its two-dimensional structure, large surface area,
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Graphene-based nanomaterials have exhibited wide applications in nanotechnology, materials science, analytical science, and biomedical engineering due to their unique physical and chemical properties. In particular, graphene has been an excellent nanocarrier for drug delivery application because of its two-dimensional structure, large surface area, high stability, good biocompatibility, and easy surface modification. In this review, we present the recent advances in the synthesis and drug delivery application of graphene-based nanomaterials. The modification of graphene and the conjugation of graphene with other materials, such as small molecules, nanoparticles, polymers, and biomacromolecules as functional nanohybrids are introduced. In addition, the controlled drug delivery with the fabricated graphene-based nanomaterials are demonstrated in detail. It is expected that this review will guide the chemical modification of graphene for designing novel functional nanohybrids. It will also promote the potential applications of graphene-based nanomaterials in other biomedical fields, like biosensing and tissue engineering. Full article
(This article belongs to the Special Issue Graphene and Graphene Oxide in Biomedical Application)
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