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Appl. Sci., Volume 8, Issue 9 (September 2018) – 294 articles

Cover Story (view full-size image): Halloysite nanotubes were used to selectively incorporate anionic surfactant micelles and an organic solvent to generate a cleaning system to be applied in Cultural Heritage restoration. The application of this prepared emulsion for the controlled cleaning of a marble artifact is demonstrated. This work represents a further step toward the opportunity to extend the use of emulsions for cleaning protocols for stone-based artifacts. View this paper.
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15 pages, 3232 KiB  
Article
Effect of Cavity Vacuum Pressure Diminution on Thermal Performance of Triple Vacuum Glazing
by Saim Memon, Farukh Farukh and Karthikeyan Kandan
Appl. Sci. 2018, 8(9), 1705; https://doi.org/10.3390/app8091705 - 19 Sep 2018
Cited by 10 | Viewed by 5568
Abstract
Long-term durability of the vacuum edge seal plays a significant part in retrofitting triple vacuum glazing (TVG) to existing buildings in achieving progress towards a zero-energy building (ZEB) target. Vacuum pressure decrement with respect to time between panes affects the thermal efficiency of [...] Read more.
Long-term durability of the vacuum edge seal plays a significant part in retrofitting triple vacuum glazing (TVG) to existing buildings in achieving progress towards a zero-energy building (ZEB) target. Vacuum pressure decrement with respect to time between panes affects the thermal efficiency of TVG. This study reports a 3D finite element model, with validated mathematical methods and comparison, for the assessment of the influence of vacuum pressure diminution on the thermal transmittance (U value) of TVG. The centre-of-pane and total U values of TVG are calculated to be 0.28 Wm−2 K−1 and 0.94 Wm−2 K−1 at the cavity vacuum pressure of 0.001 Pa. The results suggest that a rise in cavity pressure from 0.001 Pa to 100 kPa increases the centre-of-pane and total U values from 0.28 Wm−2 K−1 and 0.94 Wm−2 K−1 to 2.4 Wm−2 K−1 and 2.58 Wm−2 K−1, respectively. The temperature descent on the surfaces of TVG between hot and cold sides increases by decreasing the cavity vacuum pressure from 50 kPa to 0.001 Pa. Nonevaporable getters will maintain the cavity vacuum pressure of 0.001 Pa for over 20 years of life span in the cavity of 10-mm wide edge-sealed triple vacuum glazing, and enable the long-term durability of TVG. Full article
(This article belongs to the Special Issue Zero-Energy Buildings)
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11 pages, 432 KiB  
Article
Creative Chord Sequence Generation for Electronic Dance Music
by Darrell Conklin, Martin Gasser and Stefan Oertl
Appl. Sci. 2018, 8(9), 1704; https://doi.org/10.3390/app8091704 - 19 Sep 2018
Cited by 6 | Viewed by 5536
Abstract
This paper describes the theory and implementation of a digital audio workstation plug-in for chord sequence generation. The plug-in is intended to encourage and inspire a composer of electronic dance music to explore loops through chord sequence pattern definition, position locking and generation [...] Read more.
This paper describes the theory and implementation of a digital audio workstation plug-in for chord sequence generation. The plug-in is intended to encourage and inspire a composer of electronic dance music to explore loops through chord sequence pattern definition, position locking and generation into unlocked positions. A basic cyclic first-order statistical model is extended with latent diatonicity variables which permits sequences to depart from a specified key. Degrees of diatonicity of generated sequences can be explored and parameters for voicing the sequences can be manipulated. Feedback on the concepts, interface, and usability was given by a small focus group of musicians and music producers. Full article
(This article belongs to the Special Issue Digital Audio and Image Processing with Focus on Music Research)
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20 pages, 2164 KiB  
Article
Low Cost Omnidirectional Sound Source Utilizing a Common Directional Loudspeaker for Impulse Response Measurements
by Nikolaos M. Papadakis and Georgios E. Stavroulakis
Appl. Sci. 2018, 8(9), 1703; https://doi.org/10.3390/app8091703 - 19 Sep 2018
Cited by 16 | Viewed by 12961
Abstract
Alternative low-cost sources (e.g., balloons, gun fires) are used for impulse response measurements when a dodecahedron speaker is not available. This study sets to explore the applicability of a method utilizing a common directional loudspeaker as a sound source. For this purpose measurements [...] Read more.
Alternative low-cost sources (e.g., balloons, gun fires) are used for impulse response measurements when a dodecahedron speaker is not available. This study sets to explore the applicability of a method utilizing a common directional loudspeaker as a sound source. For this purpose measurements were performed in three spaces with three different common directional loudspeakers. Different placements of the loudspeakers were performed (twelve positions similar to the twelve positions of the faces of a dodecahedron speaker, different rotations of the loudspeakers for a total sum of twenty six and fourteen positions). The impulse responses obtained were added up creating a single impulse response for each case. Comparisons of the acoustic parameters measured with the proposed method and with a dodecahedron speaker are presented and suggest the expected mean absolute error and standard deviation for similar measurements. Reverberation time measurements show a mean absolute error of less than 0.08 s, as compared with measurements with a dodecahedron speaker. The proposed method can be the primary method for measuring impulse responses when a dodecahedron speaker is not available. Suggested improvements may lead to better omnidirectionality as compared with a dodecahedron loudspeaker, and set the method applicable to be utilized for auralization purposes. Full article
(This article belongs to the Section Acoustics and Vibrations)
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19 pages, 6147 KiB  
Article
Noise-Canceling Office Chair with Multiple Reference Microphones
by László Sujbert and Attila Szarvas
Appl. Sci. 2018, 8(9), 1702; https://doi.org/10.3390/app8091702 - 19 Sep 2018
Cited by 3 | Viewed by 5804
Abstract
Office employees are exposed to acoustic noise, especially in an open office environment. Passive or active headsets sufficiently reduce the level of noise, but their long-time wear is uncomfortable. The paper presents an active headrest system built into a chair. Feedforward control is [...] Read more.
Office employees are exposed to acoustic noise, especially in an open office environment. Passive or active headsets sufficiently reduce the level of noise, but their long-time wear is uncomfortable. The paper presents an active headrest system built into a chair. Feedforward control is utilized with multiple reference microphones, and flexible gooseneck microphones serve as error sensors. The reference sensors surround the chair, allowing the suppression of sound waves arriving from any direction. The concept of multiple reference control has been tested by extensive experiments showing that multiple reference signals help to increase the suppression in normal rooms where reverberation occurs, even if only one noise source is present. The preliminary experiments are completed by a series of simulations aiming to explore the zones of quiet at the user’s ears. The paper introduces the construction details of the noise-canceling chair: The two loudspeakers are controlled by the signals of two error microphones and four reference signals. The controller is based on the normalized filtered error least mean squared algorithm, implemented on an Analog Devices ADSP-21262 signal processor-based hardware. Experimental results are reported that show the efficient suppression of tonal, as well as broadband disturbances. Full article
(This article belongs to the Special Issue Active and Passive Noise Control)
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24 pages, 9541 KiB  
Article
Study on Hysteresis Model of Welding Material in Unstiffened Welded Joints of Steel Tubular Truss Structure
by Yaqi Suo, Wenwei Yang and Peng Chen
Appl. Sci. 2018, 8(9), 1701; https://doi.org/10.3390/app8091701 - 19 Sep 2018
Cited by 9 | Viewed by 7606
Abstract
The weld form of intersecting joints in a steel tubular truss structure changes with the various intersecting curves. As the key role of joints in energy dissipation and seismic resistance, the weld is easy to damage, as a result the constitutive behavior of [...] Read more.
The weld form of intersecting joints in a steel tubular truss structure changes with the various intersecting curves. As the key role of joints in energy dissipation and seismic resistance, the weld is easy to damage, as a result the constitutive behavior of the weld is different from that of the base metal. In order to define the cumulative damage characteristic and study the constitutive behavior of welded metal with the influence of damage accumulation, low-cycle fatigue tests were carried out to evaluate overall response characteristics and to quantify variation of cyclic stress amplitude, unloading stiffness and energy dissipation capacity. The results show that the cyclic softening behavior of welding materials is apparent, however, the steel shows hardening behavior with the increase of cyclic cycles, while the cyclic stress amplitude, unloading stiffness, and energy dissipation capacity of the welding materials degenerate gradually. Based on the Ramberg–Osgood model and introducing the damage variable D, a hysteretic model of welding material with the effect of damage accumulation was established, including an initial loading curve, cyclic stress-strain curve, and hysteretic curve model. Further, the evolution equation of D was also built. The parameters reflecting the damage degradation were fitted by the test data, and the simulation results of the model were proved to be in good agreement with the test results. Full article
(This article belongs to the Special Issue Emerging Construction Materials and Sustainable Infrastructure)
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17 pages, 8990 KiB  
Article
Design and Research of Double-Sided Linear Switched Reluctance Generator for Wave Energy Conversion
by Yan Chen, Min Cao, Chunyan Ma and Zhigang Feng
Appl. Sci. 2018, 8(9), 1700; https://doi.org/10.3390/app8091700 - 19 Sep 2018
Cited by 7 | Viewed by 5188
Abstract
As a clean and renewable energy source, wave energy is of great significance in solving primary energy shortages and environmental pollution. Direct-drive wave power systems consisting of linear generators have attracted the attention of researchers from various countries. Linear Switched Reluctance Generator has [...] Read more.
As a clean and renewable energy source, wave energy is of great significance in solving primary energy shortages and environmental pollution. Direct-drive wave power systems consisting of linear generators have attracted the attention of researchers from various countries. Linear Switched Reluctance Generator has the advantages of simple structure, sturdiness, reliable operation, suitable for harsh environments, and easy maintenance, aiming at the problem of single-sided magnetic pull force and serious coupling of phase winding of traditional linear switched reluctance generator, a Double-sided Linear Switched Reluctance Generator (DLSRG) for wave power generation is designed, and its electromagnetic characteristics (including coupling characteristics, magnetic saturation characteristics, and magnetic tension characteristics) are analyzed to verify the rationality of the structure and parameter selection. Finally, the power generation performance is studied. The joint simulation results show that the structure design of DLSRG is reasonable, overcomes the problem of single-sided magnetic pull force, the phase-to-phase coupling is negligible, and it has continuous power generation capability, and the power generation efficiency is as high as 80.6%. Therefore, DLSRG designed in this paper is suitable for wave power generation. Full article
(This article belongs to the Section Energy Science and Technology)
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18 pages, 6394 KiB  
Article
Electro-Aero-Mechanical Model of Piezoelectric Direct-Driven Flapping-Wing Actuator
by Takashi Ozaki and Kanae Hamaguchi
Appl. Sci. 2018, 8(9), 1699; https://doi.org/10.3390/app8091699 - 19 Sep 2018
Cited by 12 | Viewed by 6569
Abstract
We present an analytical model of a flapping-wing actuator, including its electrical, aerodynamic, and mechanical systems, for estimating the lift force from the input electrical power. The actuator is modeled as a two-degree-of-freedom kinematic system with semi-empirical quasi-steady aerodynamic forces and the electromechanical [...] Read more.
We present an analytical model of a flapping-wing actuator, including its electrical, aerodynamic, and mechanical systems, for estimating the lift force from the input electrical power. The actuator is modeled as a two-degree-of-freedom kinematic system with semi-empirical quasi-steady aerodynamic forces and the electromechanical effect of piezoelectricity. We fabricated actuators of two different scales with wing lengths of 17.0 and 32.4 mm and measured their performances in terms of the stroke/pitching angle, average lift force, and average consumed power. The experimental results were in good agreement with the analytical calculation for both types of actuators; the errors in the evaluated characteristics were less than 30%. The results indicated that the analytical model well simulates the actual prototypes. Full article
(This article belongs to the Special Issue Piezoelectric Actuators)
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23 pages, 3090 KiB  
Article
Integrated Transport Efficiency and Its Spatial Convergence in China’s Provinces: A Super-SBM DEA Model Considering Undesirable Outputs
by Fei Ma, Wenlin Wang, Qipeng Sun, Fei Liu and Xiaodan Li
Appl. Sci. 2018, 8(9), 1698; https://doi.org/10.3390/app8091698 - 19 Sep 2018
Cited by 21 | Viewed by 4695
Abstract
Undesirable outputs, such as carbon emissions and loss of property due to traffic accidents, hold great significance for the sustainable development of the transport industry. In this study, we applied a super-efficiency data envelopment analysis model with a slack-based measure (Super-SBM DEA) considering [...] Read more.
Undesirable outputs, such as carbon emissions and loss of property due to traffic accidents, hold great significance for the sustainable development of the transport industry. In this study, we applied a super-efficiency data envelopment analysis model with a slack-based measure (Super-SBM DEA) considering undesirable outputs to measure the integrated transport efficiency (ITE) of 31 provinces in China during the period of 2009–2016. Following this, we used a spatial autocorrelation model to test and verify the spatial autocorrelation of the ITEs at the level of the 31 provinces, and further to explore the aggregating features. Finally, considering the spatial effects that emerged, we constructed a β-convergence model to analyze the convergence characteristics of China’s ITEs and investigate its conditional factors. The research results show that the average ITE demonstrated a linear growth trend; the effective decision-making units (the ITE value was greater than 1) are only 11 provinces, accounting for about 35% by 2016. The mean of ITEs was also found to present a law of decreasing order of Eastern, Central and Western Zones. However, the Central Zone and Western Zone have a better efficiency improvement trend compared to the Eastern Zone. The Moran’s I index was bigger than zero, indicating that the ITEs formed a spatial autocorrelation phenomenon. The Moran scatter plots further showed that the provincial ITEs mainly followed the patterns of high–high, high–low and low–low aggregation. The ITE of the 31 provinces was found to have a clear absolute β-convergence and conditional β-convergence characteristics. Moreover, the level of economic development, household per capita traffic consumption, transport industry scale, technology advancement and transport intensity were all seen to have an important impact on the convergence of integrated transport efficiency. It is hoped that the findings of this study may contribute further insights and practical knowledge to effectively measuring the development level of China’s integrated transport efficiency, and to understanding future changes in the ITE gap among Chinese provinces. Full article
(This article belongs to the Section Environmental Sciences)
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12 pages, 2348 KiB  
Article
Structure and Photoelectrical Properties of Natural Photoactive Dyes for Solar Cells
by Qian Liu, Nan Gao, Dejiang Liu, Jinglin Liu and Yuanzuo Li
Appl. Sci. 2018, 8(9), 1697; https://doi.org/10.3390/app8091697 - 19 Sep 2018
Cited by 23 | Viewed by 5052
Abstract
A series of natural photoactive dyes, named as D1–D6 were successfully extracted from six kinds of plant leaves for solar cells. The photoelectrical properties of dyes were measured via UV-Vis absorption spectra, cyclic voltammetry as well as photovoltaic measurement. To theoretically reveal the [...] Read more.
A series of natural photoactive dyes, named as D1–D6 were successfully extracted from six kinds of plant leaves for solar cells. The photoelectrical properties of dyes were measured via UV-Vis absorption spectra, cyclic voltammetry as well as photovoltaic measurement. To theoretically reveal the experimental phenomena, the chlorophyll was selected as the reference dye, where the ground and excited state properties of chlorophyll were calculated via density functional theory (DFT) and time-dependent density functional theory (TD-DFT). The experimental results show that the absorption peaks of those dyes are mainly distributed in the visible light regions of 400–420 nm and 650–700 nm, which are consistent with the absorption spectrum of chlorophyll. The photoelectrical conversion efficiencies of the solar cells sensitized by the six kinds of natural dyes are in the order of D1 > D4 > D2 > D5 > D6 > D3. The dye D1 performance exhibits the highest photoelectrical conversion efficiency of 1.08% among the investigated six natural dyes, with an open circuit voltage of 0.58 V, a short-circuit current density of 2.64 mA cm−2 and a fill factor of 0.70. Full article
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29 pages, 1513 KiB  
Review
A Review of the Synthesis and Applications of Polymer–Nanoclay Composites
by Feng Guo, Saman Aryana, Yinghui Han and Yunpeng Jiao
Appl. Sci. 2018, 8(9), 1696; https://doi.org/10.3390/app8091696 - 19 Sep 2018
Cited by 295 | Viewed by 20424
Abstract
Recent advancements in material technologies have promoted the development of various preparation strategies and applications of novel polymer–nanoclay composites. Innovative synthesis pathways have resulted in novel polymer–nanoclay composites with improved properties, which have been successfully incorporated in diverse fields such as aerospace, automobile, [...] Read more.
Recent advancements in material technologies have promoted the development of various preparation strategies and applications of novel polymer–nanoclay composites. Innovative synthesis pathways have resulted in novel polymer–nanoclay composites with improved properties, which have been successfully incorporated in diverse fields such as aerospace, automobile, construction, petroleum, biomedical and wastewater treatment. These composites are recognized as promising advanced materials due to their superior properties, such as enhanced density, strength, relatively large surface areas, high elastic modulus, flame retardancy, and thermomechanical/optoelectronic/magnetic properties. The primary focus of this review is to deliver an up-to-date overview of polymer–nanoclay composites along with their synthesis routes and applications. The discussion highlights potential future directions for this emerging field of research. Full article
(This article belongs to the Special Issue Nanoclays for Technological Applications)
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14 pages, 933 KiB  
Article
A Heterogeneous Ensemble Approach for Activity Recognition with Integration of Change Point-Based Data Segmentation
by Qin Ni, Lei Zhang and Luqun Li
Appl. Sci. 2018, 8(9), 1695; https://doi.org/10.3390/app8091695 - 19 Sep 2018
Cited by 18 | Viewed by 4628
Abstract
One of the main topics of Smart Home (SH) research is the recognition of activities performed by its inhabitants, which is considered to be one of the bases to foster new technological solutions inside the home, including services to prolong independent living of [...] Read more.
One of the main topics of Smart Home (SH) research is the recognition of activities performed by its inhabitants, which is considered to be one of the bases to foster new technological solutions inside the home, including services to prolong independent living of the elderly. However, current activity recognition proposals still find problems when considering all the different types of activities that can be performed at home, namely static, dynamic, and transitional activities. In this paper, we consider recognition of transitional activities, which is often ignored in most studies. In addition, we propose a novel dynamic segmentation method based on change points in data stream and construct an ensemble of heterogeneous classifiers to recognize twelve activities (of all types). The experiment is conducted on the dataset collected over ten hours by a wearable accelerometer placed on the person’s wrist. The base classifiers selected to form this ensemble are support vector machine (SVM), decision tree (DT) and k-nearest neighbors (KNN). As a result, the proposed approach has achieved an overall classification accuracy equal to 96.87% with 10-fold cross-validation. Moreover, all activity types considered have been similarly well identified. Full article
(This article belongs to the Special Issue Body Area Networks)
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18 pages, 2528 KiB  
Article
Electrokinetic Characterization of Natural Stones Coated with Nanocomposites for the Protection of Cultural Heritage
by Marco Roveri, Simona Raneri, Sabrina Bianchi, Francesca Gherardi, Valter Castelvetro and Lucia Toniolo
Appl. Sci. 2018, 8(9), 1694; https://doi.org/10.3390/app8091694 - 19 Sep 2018
Cited by 8 | Viewed by 4394
Abstract
Protective coatings, in recent years also from nanocomposite formulations, are commonly applied onto architectural stone and stone artefacts, mainly to prevent absorption of condensed water and dissolved atmospheric pollutants into the porous stone structure. While standard protocols to assess a coating’s performance are [...] Read more.
Protective coatings, in recent years also from nanocomposite formulations, are commonly applied onto architectural stone and stone artefacts, mainly to prevent absorption of condensed water and dissolved atmospheric pollutants into the porous stone structure. While standard protocols to assess a coating’s performance are available, understanding the response of the coating-stone system is a complex task, due to the interplay of various factors determining the overall behaviour. Characterization techniques allowing one to correlate the extent and nature of surface modification upon treatment with the most relevant physical properties (i.e., water absorption and surface wettability) are thus of great interest. Electrokinetic analysis based on streaming current measurements, thanks to its sensitivity towards even minor changes in the surface chemical composition, may fulfil such requirement. Indeed, by involving the interaction with a testing aqueous electrolyte solution, this technique allows one to probe not only the outer surface, but also the outermost layer of the pore network, which plays a crucial role in the interaction of the stone with condensed atmospheric water. In this work, a correlation was found between the extent of surface modification, as determined by streaming current measurements, surface wettability and capillary water absorption, for three lithotypes with different mineralogical and microstructural properties treated with two nanocomposite formulations (one water based and one in alcoholic solvent) containing organosilica precursors and titania nanoparticles. Full article
(This article belongs to the Special Issue Nanoclays for Technological Applications)
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24 pages, 3373 KiB  
Article
Data Analysis and Forecasting of Tuberculosis Prevalence Rates for Smart Healthcare Based on a Novel Combination Model
by Jiyang Wang, Chen Wang and Wenyu Zhang
Appl. Sci. 2018, 8(9), 1693; https://doi.org/10.3390/app8091693 - 18 Sep 2018
Cited by 15 | Viewed by 5942
Abstract
In recent years, healthcare has attracted much attention, which is looking for more and more data analytics in healthcare to relieve medical problems in medical staff shortage, ageing population, people living alone, and quality of life. Data mining, analysis, and forecasting play a [...] Read more.
In recent years, healthcare has attracted much attention, which is looking for more and more data analytics in healthcare to relieve medical problems in medical staff shortage, ageing population, people living alone, and quality of life. Data mining, analysis, and forecasting play a vital role in modern social and medical fields. However, how to select a proper model to mine and analyze the relevant medical information in the data is not only an extremely challenging problem, but also a concerning problem. Tuberculosis remains a major global health problem despite recent and continued progress in prevention and treatment. There is no doubt that the effective analysis and accurate forecasting of global tuberculosis prevalence rates lay a solid foundation for the construction of an epidemic disease warning and monitoring system from a global perspective. In this paper, the tuberculosis prevalence rate time series for four World Bank income groups are targeted. Kruskal–Wallis analysis of variance and multiple comparison tests are conducted to determine whether the differences of tuberculosis prevalence rates for different income groups are statistically significant or not, and a novel combined forecasting model with its weights optimized by a recently developed artificial intelligence algorithm—cuckoo search—is proposed to forecast the hierarchical tuberculosis prevalence rates from 2013 to 2016. Numerical results show that the developed combination model is not only simple, but is also able to satisfactorily approximate the actual tuberculosis prevalence rate, and can be an effective tool in mining and analyzing big data in the medical field. Full article
(This article belongs to the Special Issue Data Analytics in Smart Healthcare)
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10 pages, 3843 KiB  
Article
Post-Sputtering Heat Treatments of Molybdenum on Silicon Wafer
by Xuguang Jia, Ziyun Lin, Terry Chien-Jen Yang, Binesh Puthen-Veettil, Lingfeng Wu, Gavin Conibeer and Ivan Perez-Wurfl
Appl. Sci. 2018, 8(9), 1692; https://doi.org/10.3390/app8091692 - 18 Sep 2018
Cited by 18 | Viewed by 6147
Abstract
This paper investigated the property evolutions of Mo thin films that were subjected to post-sputtering heat treatments from 700 °C to 1100 °C. It was found that, after annealing, the use of Si wafers eliminated crack formations found in previously reported Mo thin [...] Read more.
This paper investigated the property evolutions of Mo thin films that were subjected to post-sputtering heat treatments from 700 °C to 1100 °C. It was found that, after annealing, the use of Si wafers eliminated crack formations found in previously reported Mo thin films sputtered on fused silica substrates. The recrystallization of the Mo thin film was found to start at 900 °C, which led to rearrangements of the preferred crystalline orientation and enhancement of grain size when the annealing temperature was further increased. The electrical conductivity of the Mo thin films was majorly affected by the increase of Mo crystallite size as the annealing temperature was increased. Overall, the improvement of material sustainability and compatibility in the high temperature annealing process has made it positive to implement a Mo-Si contact-substrate scheme for vertical structured Si QDs solar cells. Full article
(This article belongs to the Special Issue Next Generation Photovoltaic Solar Cells)
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11 pages, 4896 KiB  
Article
Investigation of Flame Evolution in Heavy Oil Boiler Bench Using High-Speed Planar Laser-Induced Fluorescence Imaging
by Jiangbo Peng, Zhen Cao, Xin Yu, Yang Yu, Guang Chang and Zhiqiang Wang
Appl. Sci. 2018, 8(9), 1691; https://doi.org/10.3390/app8091691 - 18 Sep 2018
Cited by 5 | Viewed by 3817
Abstract
Over recent years, much attention has been paid to the performance evaluation of industrial-type burners. The ignition and stable combustion process are of great significance in assessing the quality of burner. The planar laser-induced fluorescence (PLIF) technique can be applied to heavy oil [...] Read more.
Over recent years, much attention has been paid to the performance evaluation of industrial-type burners. The ignition and stable combustion process are of great significance in assessing the quality of burner. The planar laser-induced fluorescence (PLIF) technique can be applied to heavy oil boilers, extending this technique to engineering applications. Considering the complex environment of the bench test, measures such as temperature control and moisture proofing are made to improve the possibility of detection using PLIF. In this paper, an experimental investigation of flame growth following ignition is reported. A wrinkled structure could be observed from the configuration of the ignition flame; its trajectory will be depicted. The results showed that the wrinkled structure developed downward, i.e., by deviation from the direction of the airflow. The displacement velocity of the flame was used to describe the combustion rate. Good agreement was obtained for the flame shapes of both forced ignition and autoignition. In addition, the center of combustion deviated from the center of boiler, possibly due to some irregularity in the burner’s assembly which was critical to the design of the combustion chamber. Full article
(This article belongs to the Section Optics and Lasers)
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12 pages, 4884 KiB  
Article
Excimer Laser Three-Dimensional Micromachining Based on Image Projection and the Optical Diffraction Effect
by Yu-Hsuan Hung, Hung-Liang Chien and Yung-Chun Lee
Appl. Sci. 2018, 8(9), 1690; https://doi.org/10.3390/app8091690 - 18 Sep 2018
Cited by 5 | Viewed by 5001
Abstract
An excimer laser three-dimensional (3D) micromachining system is proposed based on a mask image projection method and the optical diffraction effect. The effects of optical diffraction on the laser machining rate are evaluated using a hole-arrayed mask pattern with various feature sizes and [...] Read more.
An excimer laser three-dimensional (3D) micromachining system is proposed based on a mask image projection method and the optical diffraction effect. The effects of optical diffraction on the laser machining rate are evaluated using a hole-arrayed mask pattern with various feature sizes and hole-area opening ratios. The practical feasibility of the proposed method is demonstrated by machining conical, trihedral, and pyramidal 3D microstructures on polycarbonate substrates. The proposed method greatly simplifies the photo-mask design and preparation task in traditional excimer laser 3D micromachining systems and provides a powerful technique for achieving large-area 3D microstructures with complex patterns and atypical profiles. Full article
(This article belongs to the Section Optics and Lasers)
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46 pages, 16823 KiB  
Review
Frequency Selective Surfaces: A Review
by Rana Sadaf Anwar, Lingfeng Mao and Huansheng Ning
Appl. Sci. 2018, 8(9), 1689; https://doi.org/10.3390/app8091689 - 18 Sep 2018
Cited by 226 | Viewed by 48631
Abstract
The intent of this paper is to provide an overview of basic concepts, types, techniques, and experimental studies of the current state-of-the-art Frequency Selective Surfaces (FSSs). FSS is a periodic surface with identical two-dimensional arrays of elements arranged on a dielectric substrate. An [...] Read more.
The intent of this paper is to provide an overview of basic concepts, types, techniques, and experimental studies of the current state-of-the-art Frequency Selective Surfaces (FSSs). FSS is a periodic surface with identical two-dimensional arrays of elements arranged on a dielectric substrate. An incoming plane wave will either be transmitted (passband) or reflected back (stopband), completely or partially, depending on the nature of array element. This occurs when the frequency of electromagnetic (EM) wave matches with the resonant frequency of the FSS elements. Therefore, an FSS is capable of passing or blocking the EM waves of certain range of frequencies in the free space; consequently, identified as spatial filters. Nowadays, FSSs have been studied comprehensively and huge growth is perceived in the field of its designing and implementation for different practical applications at frequency ranges of microwave to optical. In this review article, we illustrate the recent researches on different categories of FSSs based on structure design, array element used, and applications. We also focus on theoretical breakthroughs with fabrication techniques, experimental verifications of design examples as well as prospects and challenges, especially in the microwave regime. We emphasize their significant performance parameters, particularly focusing on how advancement in this field could facilitate innovation in advanced electromagnetics. Full article
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12 pages, 2681 KiB  
Article
No-reference Automatic Quality Assessment for Colorfulness-Adjusted, Contrast-Adjusted, and Sharpness-Adjusted Images Using High-Dynamic-Range-Derived Features
by Jinseong Jang, Hanbyol Jang, Taejoon Eo, Kihun Bang and Dosik Hwang
Appl. Sci. 2018, 8(9), 1688; https://doi.org/10.3390/app8091688 - 18 Sep 2018
Cited by 2 | Viewed by 3872
Abstract
Image adjustment methods are one of the most widely used post-processing techniques for enhancing image quality and improving the visual preference of the human visual system (HVS). However, the assessment of the adjusted images has been mainly dependent on subjective evaluations. Also, most [...] Read more.
Image adjustment methods are one of the most widely used post-processing techniques for enhancing image quality and improving the visual preference of the human visual system (HVS). However, the assessment of the adjusted images has been mainly dependent on subjective evaluations. Also, most recently developed automatic assessment methods have mainly focused on evaluating distorted images degraded by compression or noise. The effects of the colorfulness, contrast, and sharpness adjustments on images have been overlooked. In this study, we propose a fully automatic assessment method that evaluates colorfulness-adjusted, contrast-adjusted, and sharpness-adjusted images while considering HVS preferences. The proposed method does not require a reference image and automatically calculates quantitative scores, visual preference, and quality assessment with respect to the level of colorfulness, contrast, and sharpness adjustment. The proposed method evaluates adjusted images based on the features extracted from high dynamic range images, which have higher colorfulness, contrast, and sharpness than that of low dynamic range images. Through experimentation, we demonstrate that our proposed method achieves a higher correlation with subjective evaluations than that of conventional assessment methods. Full article
(This article belongs to the Special Issue Intelligent Imaging and Analysis)
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13 pages, 3761 KiB  
Article
Frequency Enhancement of Oil Whip and Oil Whirl in a Ferrofluid–Lubricated Hydrodynamic Bearing–Rotor System by Magnetic Field with Permanent Magnets
by Liao-Yong Luo, Yi-Hua Fan, Jyh-Haw Tang, Ting-Yu Chen, Nai-Rong Zhong, Pin-Chieh Feng and Yu-Chun Kao
Appl. Sci. 2018, 8(9), 1687; https://doi.org/10.3390/app8091687 - 18 Sep 2018
Cited by 3 | Viewed by 5344
Abstract
The article describes the effect of a magnetic field applied to a ferrofluid–lubricated hydrodynamic journal bearing–rotor system. A rotor with a single journal bearing in one end was built to be the test rig. The experimental results showed that 3 to 8 permanent [...] Read more.
The article describes the effect of a magnetic field applied to a ferrofluid–lubricated hydrodynamic journal bearing–rotor system. A rotor with a single journal bearing in one end was built to be the test rig. The experimental results showed that 3 to 8 permanent magnets, arranged by different methods, can all increase the instability threshold of the oil bearing. Especially, the magnetic field formed by eight magnets has the optimal effect. The whirl speed and the whip speed can be increased from 3024 rpm to 4480 rpm, and from 3184 rpm to 5268 rpm. Full article
(This article belongs to the Section Mechanical Engineering)
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17 pages, 3535 KiB  
Article
Study on Structural Robustness of Isolated Structure Based on Seismic Response
by Wenwei Yang, Chao Bao, Xiaotong Ma and Shangrong Zhang
Appl. Sci. 2018, 8(9), 1686; https://doi.org/10.3390/app8091686 - 18 Sep 2018
Cited by 8 | Viewed by 4202
Abstract
The qualitative analysis for structural robustness study subjected to severe earthquakes is unable to meet engineering requirements, and a quantitative analysis method for structural robustness is needed to be proposed. The existing analysis methods, such as Incremental Dynamic Analysis Method and Pushover method, [...] Read more.
The qualitative analysis for structural robustness study subjected to severe earthquakes is unable to meet engineering requirements, and a quantitative analysis method for structural robustness is needed to be proposed. The existing analysis methods, such as Incremental Dynamic Analysis Method and Pushover method, only study the response of the structure directly from the macroscopic view, rather than focusing on the response of a single component on the structure. Especially for the construction of isolated structure, the impact of accidental bearing failure on the isolated structure and the impact of progressive collapse cannot be considered. In this paper, based on the Alternative Load Path Method, the quantitative analysis method for structural robustness analysis under earthquake is proposed. The structural robustness of some different vertical irregular isolated structures under different earthquakes is studied. Full article
(This article belongs to the Special Issue Emerging Construction Materials and Sustainable Infrastructure)
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14 pages, 5657 KiB  
Article
Fluctuations of 1/f Noise in Damaging Structures Analyzed by Acoustic Emission
by Alberto Carpinteri, Giuseppe Lacidogna and Federico Accornero
Appl. Sci. 2018, 8(9), 1685; https://doi.org/10.3390/app8091685 - 18 Sep 2018
Cited by 18 | Viewed by 4496
Abstract
It is well known in literature that frequency fluctuations of different physical quantities clearly show 1/f noise power spectra. In the present work, the authors observe that in some brittle materials, such as concrete, masonry, and mortar, Acoustic Emission (AE) signals, generating [...] Read more.
It is well known in literature that frequency fluctuations of different physical quantities clearly show 1/f noise power spectra. In the present work, the authors observe that in some brittle materials, such as concrete, masonry, and mortar, Acoustic Emission (AE) signals, generating from brittle fracture phenomena, exhibit a frequency fluctuation approaching to 1/f. Acoustic Emission data obtained from laboratory tests on concrete samples, and from in-situ monitoring of some important Italian historical buildings are reported in terms of spectral density vs. frequency. It is shown that in structural elements subjected to different load conditions, the frequency fluctuations are 1/f like. The study and interpretation of these phenomena through the use of the AE technique can be therefore very useful for identifying the transition from the critical conditions of a structure to those that involve an incipient collapse. Full article
(This article belongs to the Section Acoustics and Vibrations)
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16 pages, 3701 KiB  
Article
Stochastic Wind Curtailment Scheduling for Mitigation of Short-Term Variations in a Power System with High Wind Power and Electric Vehicle
by Jaehee Lee, Jinyeong Lee, Young-Min Wi and Sung-Kwan Joo
Appl. Sci. 2018, 8(9), 1684; https://doi.org/10.3390/app8091684 - 18 Sep 2018
Cited by 7 | Viewed by 3972
Abstract
Occasionally, wind curtailments may be required to avoid an oversupply when wind power, together with the minimum conventional generation, exceed load. By curtailing wind power, the forecast uncertainty and short-term variations in wind power can be mitigated so that a lower spinning reserve [...] Read more.
Occasionally, wind curtailments may be required to avoid an oversupply when wind power, together with the minimum conventional generation, exceed load. By curtailing wind power, the forecast uncertainty and short-term variations in wind power can be mitigated so that a lower spinning reserve is sufficient to maintain the operational security of a power system. Additionally, the electric vehicle (EV) charging load can relieve the oversupply of wind power generation and avoid uneconomical wind power curtailments. This paper presents a stochastic generation scheduling method to ensure the operation security against wind power variation as well as against forecast uncertainty considering the stochastic EV charging load. In the paper, the short-term variations of wind power that are mitigated by the wind curtailment are investigated, and incorporated into a generation scheduling problem as the mixed-integer program (MIP) forms. Numerical results are also presented in order to demonstrate the effectiveness of the proposed method. Full article
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19 pages, 6488 KiB  
Article
Nonlocal Damage Mechanics for Quantification of Health for Piezoelectric Sensor
by A. Habib, A. Shelke, U. Amjad, U. Pietsch and S. Banerjee
Appl. Sci. 2018, 8(9), 1683; https://doi.org/10.3390/app8091683 - 18 Sep 2018
Cited by 6 | Viewed by 3224
Abstract
In this paper, a novel method to quantify the incubation of damage on piezoelectric crystal is presented. An intrinsic length scale parameter obtained from nonlocal field theory is used as a novel measure for quantification of damage precursor. Features such as amplitude decay, [...] Read more.
In this paper, a novel method to quantify the incubation of damage on piezoelectric crystal is presented. An intrinsic length scale parameter obtained from nonlocal field theory is used as a novel measure for quantification of damage precursor. Features such as amplitude decay, attenuation, frequency shifts and higher harmonics of guided waves are commonly-used damage features. Quantification of the precursors to damage by considering the mentioned features in a single framework is a difficult proposition. Therefore, a nonlocal field theory is formulated and a nonlocal damage index is proposed. The underlying idea of the paper is that inception of the damage at the micro scale manifests the evolution of damage at the macro scale. In this paper, we proposed a nonlocal field theory, which can efficiently quantify the inception of damage on piezoelectric crystals. The strength of the method is demonstrated by employing the surface acoustic waves (SAWs) and longitudinal bulk waves in Lithium Niobate (LiNbO3) single crystal. A control damage was introduced and its manifestation was expressed using the intrinsic dominant length scale. The SAWs were excited and detected using interdigital transducers (IDT) for healthy and damage state. The acoustic imaging of microscale damage in piezoelectric crystal was conducted using scanning acoustic microscopy (SAM). The intrinsic damage state was then quantified by overlaying changes in time of flight (TOF) and frequency shift on the angular dispersion relationship. Full article
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14 pages, 4024 KiB  
Article
Data Fusion Based on Adaptive Interacting Multiple Model for GPS/INS Integrated Navigation System
by Chuang Zhang, Chen Guo and Daheng Zhang
Appl. Sci. 2018, 8(9), 1682; https://doi.org/10.3390/app8091682 - 17 Sep 2018
Cited by 22 | Viewed by 4918
Abstract
The extended Kalman filter (EKF) as a primary integration scheme has been applied in the Global Positioning System (GPS) and inertial navigation system (INS) integrated system. Nevertheless, the inherent drawbacks of EKF contain not only instability caused by linearization, but also massive calculation [...] Read more.
The extended Kalman filter (EKF) as a primary integration scheme has been applied in the Global Positioning System (GPS) and inertial navigation system (INS) integrated system. Nevertheless, the inherent drawbacks of EKF contain not only instability caused by linearization, but also massive calculation of Jacobian matrix. To cope with this problem, the adaptive interacting multiple model (AIMM) filter method is proposed to enhance navigation performance. The soft-switching characteristic, which is provided by interacting multiple model algorithm, permits process noise to be converted between upper and lower limits, and the measurement covariance is regulated by Sage adaptive filtering on-line Moreover, since the pseudo-range and Doppler observations need to be updated, an updating policy for classified measurement is considered. Finally, the performance of the GPS/INS integration method on the basis of AIMM is evaluated by a real ship, and comparison results demonstrate that AIMM could achieve a more position accuracy. Full article
(This article belongs to the Special Issue Signal Processing for Satellite Positioning Systems)
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10 pages, 16228 KiB  
Article
The Intra-Class and Inter-Class Relationships in Style Transfer
by Xin Cui, Meng Qi, Yi Niu and Bingxin Li
Appl. Sci. 2018, 8(9), 1681; https://doi.org/10.3390/app8091681 - 17 Sep 2018
Cited by 3 | Viewed by 4214
Abstract
Neural style transfer, which has attracted great attention in both academic research and industrial engineering and demonstrated very exciting and remarkable results, is the technique of migrating the semantic content of one image to different artistic styles by using convolutional neural network (CNN). [...] Read more.
Neural style transfer, which has attracted great attention in both academic research and industrial engineering and demonstrated very exciting and remarkable results, is the technique of migrating the semantic content of one image to different artistic styles by using convolutional neural network (CNN). Recently, the Gram matrices used in the original and follow-up studies for style transfer were theoretically shown to be equivalent to minimizing a specific Maximum Mean Discrepancy (MMD). Since the Gram matrices are not a must for style transfer, how to design the proper process for aligning the neural activation between images to perform style transfer is an important problem. After careful analysis of some different algorithms for style loss construction, we discovered that some algorithms consider the relationships between different feature maps of a layer obtained from the CNN (inter-class relationships), while some do not (intra-class relationships). Surprisingly, the latter often show more details and finer strokes in the results. To further support our standpoint, we propose two new methods to perform style transfer: one takes inter-class relationships into account and the other does not, and conduct comparative experiments with existing methods. The experimental results verified our observation. Our proposed methods can achieve comparable perceptual quality yet with a lower complexity. We believe that our interpretation provides an effective design basis for designing style loss function for style transfer methods with different visual effects. Full article
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18 pages, 2901 KiB  
Article
Dynamic Optimization Using Local Collocation Methods and Improved Multiresolution Technique
by Jisong Zhao and Teng Shang
Appl. Sci. 2018, 8(9), 1680; https://doi.org/10.3390/app8091680 - 17 Sep 2018
Cited by 4 | Viewed by 3849
Abstract
Dynamic optimization has wide applications in scientific and industrial researches. Multiresolution techniques provide an efficient way to solve dynamic optimization problems but have some disadvantages. An improved multiresolution technique is developed in this paper to overcome these disadvantages. The proposed technique consists of [...] Read more.
Dynamic optimization has wide applications in scientific and industrial researches. Multiresolution techniques provide an efficient way to solve dynamic optimization problems but have some disadvantages. An improved multiresolution technique is developed in this paper to overcome these disadvantages. The proposed technique consists of local collocation methods and a multiresolution-based mesh refinement method. New, generalized dyadic meshes are proposed to overcome the dyadic limitation, and the mesh refinement method is improved so that it can start with the coarsest generalized dyadic mesh. Additionally, the proposed technique involves a mesh refinement algorithm to remove the redundant mesh points in the constant control regions by analyzing the control slopes. The technique is applied to three chemical process control optimization problems and compared with other methods to demonstrate its effectiveness. Numerical results show that the proposed technique can solve chemical process control optimization problems accurately and efficiently and has advantages over other methods. Full article
(This article belongs to the Section Chemical and Molecular Sciences)
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12 pages, 6688 KiB  
Article
Combined Mie Resonance Metasurface for Wideband Terahertz Absorber
by Jie Hu, Tingting Lang, Changyu Shen and Liyang Shao
Appl. Sci. 2018, 8(9), 1679; https://doi.org/10.3390/app8091679 - 17 Sep 2018
Cited by 9 | Viewed by 5379
Abstract
In this paper, we propose a combined metasurface consisting of an aluminum substrate and an array of TiO2 blocks to achieve a wideband terahertz absorber. We incorporated several similar dielectric blocks with different side length into each unit cell. Each dielectric block [...] Read more.
In this paper, we propose a combined metasurface consisting of an aluminum substrate and an array of TiO2 blocks to achieve a wideband terahertz absorber. We incorporated several similar dielectric blocks with different side length into each unit cell. Each dielectric block could cause magnetic-resonance-inducing absorption effect with different peak wavelengths. Thus, our combined metasurface could achieve wider absorption frequency band than the traditional design when these dielectric blocks were properly designed. The absorption bandwidth could be widened nearly 2.5 times and 5 times compared to a single block case when there were four and nine blocks, respectively, andcouldbe further improved by increasing the number of combinations in structures (variable parameters included number, spacing, dimensions etc.). For both TE00 (the electric fields of the light polarized along the y-axis) and TM00 (the electric fields of the light polarized along the x-axis) polarization states, the absorption bandwidth could be widened effectively; even when the incident angle was 45°, the absorption rate could still reach about 75%. This structure is simple and easy to fabricate, and this design concept can also be used in various other application fields. Full article
(This article belongs to the Special Issue Optical Nanoantennas)
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17 pages, 5328 KiB  
Article
Research on a Surface Defect Detection Algorithm Based on MobileNet-SSD
by Yiting Li, Haisong Huang, Qingsheng Xie, Liguo Yao and Qipeng Chen
Appl. Sci. 2018, 8(9), 1678; https://doi.org/10.3390/app8091678 - 17 Sep 2018
Cited by 264 | Viewed by 17833
Abstract
This paper aims to achieve real-time and accurate detection of surface defects by using a deep learning method. For this purpose, the Single Shot MultiBox Detector (SSD) network was adopted as the meta structure and combined with the base convolution neural network (CNN) [...] Read more.
This paper aims to achieve real-time and accurate detection of surface defects by using a deep learning method. For this purpose, the Single Shot MultiBox Detector (SSD) network was adopted as the meta structure and combined with the base convolution neural network (CNN) MobileNet into the MobileNet-SSD. Then, a detection method for surface defects was proposed based on the MobileNet-SSD. Specifically, the structure of the SSD was optimized without sacrificing its accuracy, and the network structure and parameters were adjusted to streamline the detection model. The proposed method was applied to the detection of typical defects like breaches, dents, burrs and abrasions on the sealing surface of a container in the filling line. The results show that our method can automatically detect surface defects more accurately and rapidly than lightweight network methods and traditional machine learning methods. The research results shed new light on defect detection in actual industrial scenarios. Full article
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11 pages, 5282 KiB  
Article
Fault Detection of Stator Inter-Turn Short-Circuit in PMSM on Stator Current and Vibration Signal
by Hong Liang, Yong Chen, Siyuan Liang and Chengdong Wang
Appl. Sci. 2018, 8(9), 1677; https://doi.org/10.3390/app8091677 - 16 Sep 2018
Cited by 49 | Viewed by 6681
Abstract
The stator inter-turn short circuit fault is one of the most common and key faults in permanent magnet synchronous motor (PMSM). This paper introduces a time–frequency method for inter-turn fault detection in stator winding of PMSM using improved wavelet packet transform. Both stator [...] Read more.
The stator inter-turn short circuit fault is one of the most common and key faults in permanent magnet synchronous motor (PMSM). This paper introduces a time–frequency method for inter-turn fault detection in stator winding of PMSM using improved wavelet packet transform. Both stator current signal and vibration signal are used for the detection of short circuit faults. Two different experimental data from a three-phase PMSM were processed and analyzed by this time–frequency method in LabVIEW. The feasibility of this approach is shown by the experimental test. Full article
(This article belongs to the Special Issue Fault Detection and Diagnosis in Mechatronics Systems)
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21 pages, 420 KiB  
Article
Associative Memories to Accelerate Approximate Nearest Neighbor Search
by Vincent Gripon, Matthias Löwe and Franck Vermet
Appl. Sci. 2018, 8(9), 1676; https://doi.org/10.3390/app8091676 - 16 Sep 2018
Cited by 6 | Viewed by 4511
Abstract
Nearest neighbor search is a very active field in machine learning. It appears in many application cases, including classification and object retrieval. In its naive implementation, the complexity of the search is linear in the product of the dimension and the cardinality of [...] Read more.
Nearest neighbor search is a very active field in machine learning. It appears in many application cases, including classification and object retrieval. In its naive implementation, the complexity of the search is linear in the product of the dimension and the cardinality of the collection of vectors into which the search is performed. Recently, many works have focused on reducing the dimension of vectors using quantization techniques or hashing, while providing an approximate result. In this paper, we focus instead on tackling the cardinality of the collection of vectors. Namely, we introduce a technique that partitions the collection of vectors and stores each part in its own associative memory. When a query vector is given to the system, associative memories are polled to identify which one contains the closest match. Then, an exhaustive search is conducted only on the part of vectors stored in the selected associative memory. We study the effectiveness of the system when messages to store are generated from i.i.d. uniform ±1 random variables or 0–1 sparse i.i.d. random variables. We also conduct experiments on both synthetic data and real data and show that it is possible to achieve interesting trade-offs between complexity and accuracy. Full article
(This article belongs to the Special Issue Advanced Intelligent Imaging Technology)
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