Search results for: Meng Zhang

Authors: Sara Kamalisiahroudi, Jun Huang, Zhe Li, Jianbo Zhang

Abstract:

Two types of commercial cylindrical lithium ion batteries (Panasonic 3.4 Ah NCR-18650B and Samsung 2.9 Ah INR-18650), were investigated experimentally. The capacities of these samples were individually measured using constant current-constant voltage (CC-CV) method at different ambient temperatures (-10 ℃, 0 ℃, 25 ℃). Their internal resistance was determined by electrochemical impedance spectroscopy (EIS) and pulse discharge methods. The cells with different configurations of parallel connection NCR-NCR, INR-INR and NCR-INR were charged/discharged at the aforementioned ambient temperatures. The results showed that the difference of internal resistance between cells much more evident at low temperatures. Furthermore, the parallel connection of NCR-NCR exhibits the most uniform temperature distribution in cells at -10 ℃, this feature is quite favorable for the safety of the battery pack.

Keywords: batteries in parallel connection, internal resistance, low temperature, temperature difference, current distribution

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Authors: Mengxiao Li, Johnson Zhang

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Currently, topology optimization technique is widely used to define the layout design of structures that are presented as truss-like topologies. However, due to the difficulty in combining optimization technique with more realistic material models where their nonlinear properties should be considered, the achieved optimized topologies are commonly unable to apply straight towards the practical design problems. This study presented an optimization procedure of composite structures where different elastic stiffness, yield criteria, and hardening models are assumed for the candidate materials. From the results, it can be concluded that a more explicit modeling has the significant influence on the resulting topologies. Also, the isotropic or kinematic hardening is important for elastoplastic structural optimization design. The capability of the proposed optimization procedure is shown through several cases.

Keywords: topology optimization, material composition, nonlinear modeling, hardening rules

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Authors: Guanghua Zhang, Fubao Wang, Weijun Duan

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Convolution neural network (CNN) has attracted more and more attention on recent years. Especially in the field of computer vision and image classification. However, unsupervised learning with CNN has received less attention than supervised learning. In this work, we use a new powerful tool which is deep convolutional generative adversarial networks (DCGANs) to generate images from Sloan Digital Sky Survey. Training by various star and galaxy images, it shows that both the generator and the discriminator are good for unsupervised learning. In this paper, we also took several experiments to choose the best value for hyper-parameters and which could help to stabilize the training process and promise a good quality of the output.

Keywords: convolution neural network, discriminator, generator, unsupervised learning

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Authors: Zhengyang Ma, Zhiyao Li, Jiayi Zhang

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This article examines the prospect theory’s arguments about decision-making through two case studies, the First Gulf War and Russia’s annexation of Crimea. The article uses the methods of comparative case analysis and process tracing to investigate the prospect theory’s fundamental arguments. Through evidence derived from existing primary and secondary sources, this paper argues that both former U.S. President Bush and Russian President Putin viewed their situations as a domain of loss and made risky decisions to prevent further deterioration, which attests the arguments of the prospect theory. After the two case studies, this article also discusses how the prospect theory could be used in analyzing the decision-making process that led to the current Russia-Ukraine War.

Keywords: the prospect theory, international relations, the first gulf war, the crimea crisis

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Authors: Dezhi Li, Peng Cui, Bo Zhang, Tengyuan Chang

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In order to solve the housing problem for the low-income families, the construction of affordable housing is booming in China. However, due to various reasons, the service facilities and systems in the indemnificatory residential community meet many problems. This article established a Satisfaction Evaluation System of the Fundamental Public Services for Large-scale Indemnificatory Residential Community based on the national standards and local criteria and developed evaluation methods and processes. At last, in the case of Huagang project in Nanjing, the satisfaction of basic public service is calculated according to a survey of local residents.

Keywords: indemnificatory residential community, public services, satisfaction evaluation, structural equation modeling

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Authors: Xu Runzhang, Yang Yanbing, Niu Yi, Zhang Mingyou, Liu Yu

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For a class of semilinear parabolic equations with linear dynamical boundary conditions in a bounded domain, we obtain both global solutions and finite time blow-up solutions when the initial data varies in the phase space H1(Ω). Our main tools are the comparison principle, the potential well method and the concavity method. In particular, we discuss the behavior of the solutions with the initial data at critical and high energy level.

Keywords: high energy level, critical energy level, linear dynamical boundary condition, semilinear parabolic equation

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Authors: Yu-Yao Wang, Xiao-Meng Hu, Joanne Yeung, Xiao-Yan Li

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The high private cost and unquantified external cost limit the development of reclaimed water. In this study, an integrated framework comprising life cycle assessment (LCA), quantitative microbial risk assessment (QMRA), and life cycle costing (LCC) was developed to evaluate both costs of reclaimed water supply in water systems of various scales. LCA assesses the environmental impacts, and QMRA estimates the associated pathogenic impacts. These impacts are monetized as external costs and analyzed with the private cost by LCC to count the total life cycle cost. The framework evaluated the Hong Kong urban water system in the baseline scenario (BS) and five wastewater reuse scenarios (RS). They are RSI: substituting freshwater for toilet flushing only, RSII: substituting both freshwater and seawater for toilet flushing, RSIII: using reclaimed water for all non-potable uses, RSIV: using reclaimed water for all non-potable uses and indirect potable uses, and RSV: non-potable use and indirect potable use by conveying 100% reclaimed water to recharge the reservoirs. The results show that substituting freshwater and seawater for toilet flushing has the least total life cycle cost, exhibiting that it is the most cost-effective option for Hong Kong. Meanwhile, the evaluation results show that the external cost of each scenario is comparable to the corresponding private cost, indicating the importance of the inclusion of comprehensive external cost evaluation in private cost assessment of water systems with reclaimed water supply.

Keywords: life cycle assessment, life cycle costing, quantitative microbial risk assessment, water reclamation, reclaimed water, alternative water resources

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Authors: Khoi A. Nguyen, Rodney A. Stewart, Hong Zhang

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‘Water-related energy’ is energy use which is directly or indirectly influenced by changes to water use. Informatics applying a range of mathematical, statistical and rule-based approaches can be used to reveal important information on demand from the available data provided at second, minute or hourly intervals. This study aims to combine these two concepts to improve the current water end use disaggregation problem through applying a wide range of most advanced pattern recognition techniques to analyse the concurrent high-resolution water-energy consumption data. The obtained results have shown that recognition accuracies of all end-uses have significantly increased, especially for mechanised categories, including clothes washer, dishwasher and evaporative air cooler where over 95% of events were correctly classified.

Keywords: deep learning network, smart metering, water end use, water-energy data

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Authors: Gong Zhang, Hong Cai, Bin Dong, Jifang Tao, Aiqun Liu, Dim-Lee Kwong, Yuandong Gu

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An on-chip refractive index sensor with high sensitivity and large measurement range is demonstrated in this paper. The sensing structures are based on Mach-Zehnder interferometer configuration, built on the SOI substrate. The wavelength sensitivity of the sensor is estimated to be 3129 nm/RIU. Meanwhile, according to the interference pattern period changes, the measured period sensitivities are 2.9 nm/RIU (TE mode) and 4.21 nm/RIU (TM mode), respectively. As such, the wavelength shift and the period shift can be used for fine index change detection and larger index change detection, respectively. Therefore, the sensor design provides an approach for large index change measurement with high sensitivity.

Keywords: Mach-Zehnder interferometer, nanotechnology, refractive index sensing, sensors

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Authors: Guofan Shao, Lina Tang, Hao Zhang

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The values of image classification accuracy are affected by class size distributions and classification schemes, making it difficult to compare the performance of classification algorithms across different remote sensing data sources and classification systems. Based on the term efficacy from medicine and pharmacology, we have developed the metrics of image classification efficacy at the map and class levels. The novelty of this approach is that a baseline classification is involved in computing image classification efficacies so that the effects of class statistics are reduced. Furthermore, the image classification efficacies are interpretable and comparable, and thus, strengthen the assessment of image data classification methods. We use real-world and hypothetical examples to explain the use of image classification efficacies. The metrics of image classification efficacy meet the critical need to rectify the strategy for the assessment of image classification performance as image classification methods are becoming more diversified.

Keywords: accuracy assessment, efficacy, image classification, machine learning, uncertainty

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Authors: Ling Zhang, Feng Liu

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A matrix is called a ray pattern matrix if its entries are either 0 or a ray in complex plane which originates from 0. A ray pattern A of order n is called spectrally arbitrary if the complex matrices in the ray pattern class of A give rise to all possible nth degree complex polynomial. Otherwise, it is said to be spectrally non-arbitrary ray pattern. We call that a spectrally arbitrary ray pattern A of order n is minimally spectrally arbitrary if any nonzero entry of A is replaced, then A is not spectrally arbitrary. In this paper, we find that is not spectrally arbitrary when n equals to 4 for any θ which is greater than or equal to 0 and less than or equal to n. In this article, we give several ray patterns A(θ) of order n that are not spectrally arbitrary for some θ which is greater than or equal to 0 and less than or equal to n. by using the nilpotent-Jacobi method. One example is given in our paper.

Keywords: spectrally arbitrary, nilpotent matrix , ray patterns, sign patterns

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Authors: Idrees Khan, Zhang Baoliang

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Kaolin clay (KC) supported Zinc oxide (ZnO/KC) and ZnO nanoparticles (NPs) were prepared by a chemical reduction process and used for the photodegradation of methyl red (MR) as photocatalysts. Due to the interlayered porous structure of KC, we achieved a perfect association between ZnO NPs and KC. SEM image showed the irregular morphology of ZnO NPs, while ZnO/KC NCs were predominately round-shaped. Moreover, in both cases, NPs were present in dispersed and agglomerated forms with an average particle size way below 100 nm. The results acquired from photodegradation analyses showed that ZnO NPs and ZnO/KC NCs degraded about 82% and 99% of MR under UV light in a short irradiation time within 10 min. The recovered and re-recovered ZnO NPs and ZnO/KC NCs were also considerably photodegraded MR in an aqueous medium. The same NPs also exhibit promising bioactivities against two pathogenic bacteria, i.e., Citrobacter and Providencia. ZnO/KC NCs' antioxidant activity reached a reasonable 70% compared to the 88% activity of the standard ascorbic acid.

Keywords: nanoparticles, photocatalyst, photodegradation, zinc oxide, methyl red

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Authors: Jing Zhang, Yongqin Chang, Yongwei Wang, Xiaolin Li, Shaoning Jiang, Farong Wan, Yi Long

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Microstructural and hardening changes of Fe-0.2wt.%V alloy and pure Fe irradiated with 100 keV hydrogen ions at room temperature were investigated. It was found that dislocation density varies dramatically after irradiation, ranging from dislocation free to dense areas with tangled and complex dislocation configuration. As the irradiated Fe-0.2wt.%V samples were annealed at 773 K, the irradiation-induced dislocation loops disappear, while many small precipitates with enriched C distribute in the matrix. Some large precipitates with enriched V were also observed. The hardness of Fe-0.2wt.%V alloy and pure Fe increases after irradiation, which ascribes to the formation of dislocation loops in the irradiated specimens. Compared with pure Fe, the size of the irradiation-introduced dislocation loops in Fe-0.2wt.%V alloy decreases and the density increases, the change of the hardness also decreases.

Keywords: irradiation, Fe-0.2wt.%V alloy, microstructures, hardness

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Authors: Pengfei Meng, Shuangcheng Jia, Qian Li

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We proposed a real-time high-precision semantic segmentation network based on a multi-resolution feature fusion module, the auxiliary feature extracting module, upsampling module, and atrous spatial pyramid pooling (ASPP) module. We designed a feature fusion structure, which is integrated with sufficient features of different resolutions. We also studied the effect of side-branch structure on the network and made discoveries. Based on the discoveries about the side-branch of the network structure, we used a side-branch auxiliary feature extraction layer in the network to improve the effectiveness of the network. We also designed upsampling module, which has better results than the original upsampling module. In addition, we also re-considered the locations and number of atrous spatial pyramid pooling (ASPP) modules and modified the network structure according to the experimental results to further improve the effectiveness of the network. The network presented in this paper takes the backbone network of Bisenetv2 as a basic network, based on which we constructed a network structure on which we made improvements. We named this network deep multiple-resolution bilateral networks for real-time, referred to as DMBR-Net. After experimental testing, our proposed DMBR-Net network achieved 81.2% mIoU at 119FPS on the Cityscapes validation dataset, 80.7% mIoU at 109FPS on the CamVid test dataset, 29.9% mIoU at 78FPS on the COCOStuff test dataset. Compared with all lightweight real-time semantic segmentation networks, our network achieves the highest accuracy at an appropriate speed.

Keywords: multi-resolution feature fusion, atrous convolutional, bilateral networks, pyramid pooling

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Authors: Anqi Wang, Linye Zhang

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With the proliferation and development of mobile devices, various mobile apps have appeared to satisfy people’s needs. Metro, with the feature of convenient, punctuality and economic, is one of the most popular modes of transportation in cities. Yet, there are still some inconveniences brought by various factors, impacting tourists’ riding experience. The aim of this study is to help tourists to shorten the time of purchasing tickets, to provide them clear metro information and direct navigation, detailed schedule as well as a way to collect metro cards as souvenir. The study collects data through three phases, including observation, survey and test. Data collected from 106 tourists totally in Wuhan metro stations are discussed in the study. The result reflects tourists’ demand when they take the metro. It also indicates the feasibility of using mobile technology to improve passenger’s experience.

Keywords: mobile app, metro, public transportation, ticket, mobile payment, indoors positioning, tourists

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Authors: Meng H. Lean, Wei-Ping L. Chu

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The effects of ferroelectric nanofiller size, shape, loading, and polarization, on bipolar charge injection, transport, and recombination through amorphous and semicrystalline polymers are studied. A 3D particle-in-cell model extends the classical electrical double layer representation to treat ferroelectric nanoparticles. Metal-polymer charge injection assumes Schottky emission and Fowler-Nordheim tunneling, migration through field-dependent Poole-Frenkel mobility, and recombination with Monte Carlo selection based on collision probability. A boundary integral equation method is used for solution of the Poisson equation coupled with a second-order predictor-corrector scheme for robust time integration of the equations of motion. The stability criterion of the explicit algorithm conforms to the Courant-Friedrichs-Levy limit. Trajectories for charge that make it through the film are curvilinear paths that meander through the interspaces. Results indicate that charge transport behavior depends on nanoparticle polarization with anti-parallel orientation showing the highest leakage conduction and lowest level of charge trapping in the interaction zone. Simulation prediction of a size range of 80 to 100 nm to minimize attachment and maximize conduction is validated by theory. Attached charge fractions go from 2.2% to 97% as nanofiller size is decreased from 150 nm to 60 nm. Computed conductivity of 0.4 x 1014 S/cm is in agreement with published data for plastics. Charge attachment is increased with spheroids due to the increase in surface area, and especially so for oblate spheroids showing the influence of larger cross-sections. Charge attachment to nanofillers and nanocrystallites increase with vol.% loading or degree of crystallinity, and saturate at about 40 vol.%.

Keywords: nanocomposites, nanofillers, electrical double layer, bipolar charge transport

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Authors: Xiaobing Liu, Bo Zhang, Xiaolong Zhao

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The square-dancing is one of the most popular new physical activities in China in recent years, which has become a hotspot of Chinese landscape research. This paper collects 749 news reports from four authoritative newspapers in Harbin for 3 years, and probes into the space use needs of participants and non-participants of square-dancing. In this paper, the research results are compared with the contents of three related planning and design codes in China, and some modification or supplementary suggestions are proposed from three aspects, such as decision-making process, total-quantity control, and site design. Different from the traditional research, this research does not use the data from interviews and the questionnaires, but uses the traditional media report content for analyzing. To some extent, it avoids the research result being excessively subjective, enhances objectivity and the authority.

Keywords: China, landscape, space design, square-dancing

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Authors: Yanheng Zhang, Lu Feng, Yilan Kang, Donghui Fu, Qian Zhang, Qiu Li, Wei Qiu

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Diamond-reinforced Ni matrix composite has been widely applied in engineering for coating large-area structural parts owing to its high hardness, good wear resistance and corrosion resistance compared with those features of pure nickel. The mechanical properties of Ni-diamond composite coating can be promoted by the high incorporation and uniform distribution of diamond particles in the nickel matrix, while the distribution features of particles are affected by electrodeposition process parameters, especially the additives in the plating bath. Glycine has been utilized as an organic additive during the preparation of pure nickel coating, which can effectively increase the coating hardness. Nevertheless, to author’s best knowledge, no research about the effects of glycine on the Ni-diamond co-deposition has been reported. In this work, the diamond reinforced Ni nanocomposite coatings were fabricated by a co-electrodeposition technique from a modified Watt’s type bath in the presence of glycine. After preparation, the SEM morphology of the composite coatings was observed combined with energy dispersive X-ray spectrometer, and the diamond incorporation was analyzed. The surface morphology and roughness were obtained by a three-dimensional profile instrument. 3D-Debye rings formed by XRD were analyzed to characterize the nickel grain size and orientation in the coatings. The average coating thickness was measured by a digital micrometer to deduce the deposition rate. The microhardness was tested by automatic microhardness tester. The friction coefficient and wear volume were measured by reciprocating wear tester to characterize the coating wear resistance and cutting performance. The experimental results confirmed that the presence of glycine effectively improved the surface morphology and roughness of the composite coatings. By optimizing the glycine concentration, the incorporation of diamond particles was increased, while the nickel grain size decreased with increasing glycine. The hardness of the composite coatings was increased as the glycine concentration increased. The friction and wear properties were evaluated as the glycine concentration was optimized, showing a decrease in the wear volume. The wear resistance of the composite coatings increased as the glycine content was increased to an optimum value, beyond which the wear resistance decreased. Glycine complexation contributed to the nickel grain refinement and improved the diamond dispersion in the coatings, both of which made a positive contribution to the amount and uniformity of embedded diamond particles, thus enhancing the microhardness, reducing the friction coefficient, and hence increasing the wear resistance of the composite coatings. Therefore, additive glycine can be used during the co-deposition process to improve the mechanical properties of protective coatings.

Keywords: co-electrodeposition, glycine, mechanical properties, Ni-diamond nanocomposite coatings

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Authors: Hui-Fang Lee, Hsuan-Jung Hsieh, Wen-Chi Lu, Meng-Chu Liu

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The purpose of the study was to examine abnormal BMI students of Chien Hsin University of Science and Technology, implement teaching aerobics course through elementary and advanced curriculum design, dietary education and three-day dietary record, analyze participant fitness improvement, an 10-week course as well as pre-test and post-test were carried out to evaluate the effect of the aerobics course on the fitness ability. The actual participate elementary and advanced courses each of 40 people, with low participation deduction course unfinished fitness testing, access to elementary curriculum valid samples 35 (87.5%) people, advanced courses valid samples 38(95%) people, 16 students participated in two consecutive courses. The fitness activities included sit-bending, one-minute sit-ups, standing long jump, and three minutes to board the stage. Analysis and comparison to the average three-day dietary record difference, an independent samples t-test was conducted to analyze the differences in the four activities between pre-test and post-test. The results showed that the elementary course had significant effects on females’ sit-bending and one minute sit-ups, the females also had high fat intake in three-day dietary record. The advanced course had significant effects on males’ sit-bending and on females’ BMI, sit-bending and standing long jump, males and females in three-day dietary record carbohydrate intake slightly low, slightly higher protein and fat intake. In conclusion, aerobics course teaching, dietary education and three-day, dietary record implementation can significantly enhance the physical fitness indicators, and continued to participate in advanced courses better. In the practice of sport should be the future course planning elementary and advanced courses, while introducing dietary education, achieve concrete results in improving physical fitness.

Keywords: physical fitness, aerobics course, dietary education, three-day dietary record

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Authors: Shiming Li, Qingwang Liu, Honggan Wu, Jianbing Zhang

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Plantation forests are useful for timber production, recreation, environmental protection and social development. Stands height is an important parameter for the estimation of forest volume and carbon stocks. Although lidar is suitable technology for the vertical parameters extraction of forests, but high costs make it not suitable for operational inventory. With the development of computer vision and photogrammetry, aerial photos from unmanned aerial system can be used as an alternative solution for height mapping. Structure-from-motion (SfM) photogrammetry technique can be used to extract DSM and DEM information. Canopy height model (CHM) can be achieved by subtraction DEM from DSM. Our result shows that overlapping aerial photos is a potential solution for plantation forests height mapping.

Keywords: forest height mapping, plantation forests, structure-from-motion photogrammetry, UAS

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Authors: Wanda Luen-Wun Siu, Xiaowen Zhang

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The COVID-19 pandemic has presented an opportune time for China to deploy its health diplomacy around the world. This paper focused on China’s health diplomacy along the path of its Health Silk Road, with particular emphasis on the Middle East and Europe amid COVID-19. This paper employed a retrospective literature review, analyzed China’s health diplomacy in such regions to cultivate bilateral and multilateral relationships. And findings argued that such health diplomacy is a success, and Beijing has assumed a leadership role in the world’s health governance. This research contributes to the literature in health diplomacy and suggests that amid the ever changing international order, China has exerted great effort in its health diplomacy and established itself as a responsible world power.

Keywords: china’s health silk road, COVID-19, europe, middle east

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Authors: Liang Zhang, Yuanfu Lu, Yuming Dong, Guohua Jiao, Wei Chen, Jiancheng Lv

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We demonstrated an interferometric demodulation scheme using a mode-locked fiber laser. The mode-locked fiber laser is launched into a two-beam interferometer. When the ratio between the fiber path imbalance of interferometer and the laser cavity length is close to an integer, an interferometric fringe emerges as a result of vernier effect, and then the phase shift of the interferometer can be demodulated. The mode-locked fiber laser provides a large bandwidth and reduces the cost for wavelength division multiplexion (WDM). The proposed interferometric demodulation scheme can be further applied in multi-point sensing system such as fiber optics hydrophone array, seismic wave detection network with high sensitivity and low cost.

Keywords: fiber sensing, interferometric demodulation, mode-locked fiber laser, vernier effect

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Authors: Linghui Meng, James Atlas, Deborah Munro

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There is an increasing demand for prosthetics capable of mimicking natural limb movements and hand gestures, but precise movement control of prosthetics using only electrode signals continues to be challenging. This study considers the implementation of machine learning as a means of improving accuracy and presents an initial investigation into hand gesture recognition using models based on electromyographic (EMG) signals. EMG signals, which capture muscle activity, are used as inputs to machine learning algorithms to improve prosthetic control accuracy, functionality and adaptivity. Using logistic regression, a machine learning classifier, this study evaluates the accuracy of classifying two hand gestures from the publicly available Ninapro dataset using two-time series feature extraction algorithms: Time Series Feature Extraction (TSFE) and Convolutional Neural Networks (CNNs). Trials were conducted using varying numbers of EMG channels from one to eight to determine the impact of channel quantity on classification accuracy. The results suggest that although both algorithms can successfully distinguish between hand gesture EMG signals, CNNs outperform TSFE in extracting useful information for both accuracy and computational efficiency. In addition, although more channels of EMG signals provide more useful information, they also require more complex and computationally intensive feature extractors and consequently do not perform as well as lower numbers of channels. The findings also underscore the potential of machine learning techniques in developing more effective and adaptive prosthetic control systems.

Keywords: EMG, machine learning, prosthetic control, electromyographic prosthetics, hand gesture classification, CNN, computational neural networks, TSFE, time series feature extraction, channel count, logistic regression, ninapro, classifiers

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Authors: Caihong Sun, Xizi Zhang

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Rating prediction is an important problem for recommender systems. The task is to predict the rating for an item that a user would give. Most of the existing algorithms for the task ignore the effect of negative ratings rated by users on items, but the negative ratings have a significant impact on users’ purchasing decisions in practice. In this paper, we present a rating prediction algorithm based on factorization machines that consider the effect of negative ratings inspired by Loss Aversion theory. The aim of this paper is to develop a concave and a convex negative disgust function to evaluate the negative ratings respectively. Experiments are conducted on MovieLens dataset. The experimental results demonstrate the effectiveness of the proposed methods by comparing with other four the state-of-the-art approaches. The negative ratings showed much importance in the accuracy of ratings predictions.

Keywords: factorization machines, feature engineering, negative ratings, recommendation systems

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Authors: Wanda Luen-Wun Siu, Xiaowen Zhang

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The outbreak of the COVID-19 epidemic has caused great difficulties for South-South cooperation, but there are also opportunities. China’s health diplomacy has changed from dispatching medical teams, assisting in the construction of hospitals, and encouraging medical investment in the Africa health sector. This paper adopted a retrospective review of China’s health diplomacy in Africa from 1963 to 2020. Findings suggested that China has a preference for aiding Africa health infrastructure and sending medical teams to African countries. China’s health diplomacy in Africa is a success and has established secure diplomatic relations with African countries, thanks to the medical and health assistance to Africa over 60 years. This research contributes to the literature of health diplomacy and foreign relations and indicates that China’s health aid has fostered cooperation at the medical and diplomatic levels.

Keywords: Africa, china’s health diplomacy, COVID-19, bilateral relations

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Authors: Serge B. Provost, Yishan Zhang

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A moment-based adjustment to the saddlepoint approximation is introduced in the context of density estimation. First applied to univariate distributions, this methodology is extended to the bivariate case. It then entails estimating the density function associated with each marginal distribution by means of the saddlepoint approximation and applying a bivariate adjustment to the product of the resulting density estimates. The connection to the distribution of empirical copulas will be pointed out. As well, a novel approach is proposed for estimating the support of distribution. As these results solely rely on sample moments and empirical cumulant-generating functions, they are particularly well suited for modeling massive data sets. Several illustrative applications will be presented.

Keywords: empirical cumulant-generating function, endpoints identification, saddlepoint approximation, sample moments, density estimation

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Authors: Jisong Zhang, Yinghua Zhao

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The present study investigated the mechanical properties and microstructure of Ultra-High Performance Concrete (UHPC) containing supplementary cementitious materials (SCMs), such as fly ash (FA) and silica fume (SF), and to verify the synergistic effect in the ternary system. On the basis of 30% fly ash replacement, the incorporation of either 10% SF or 20% SF show a better performance compared to the reference sample. The efficiency factor (k-value) was calculated as a synergistic effect to predict the compressive strength of UHPC with these SCMs. The SEM of micrographs and pore volume from BJH method indicate a high correlation with compressive strength. Further, an artificial neural networks model was constructed for prediction of the compressive strength of UHPC containing these SCMs.

Keywords: artificial neural network, fly ash, mechanical properties, ultra-high performance concrete

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Authors: N. Zhang, J. S. Kuang, S. Mogili

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To investigate seismic performance of beam-column knee joints, four full-scale reinforced concrete beam-column knee joints, which were fabricated to simulate those in as-built RC frame buildings designed to ACI 318-14 and ACI-ASCE 352R-02, were tested under reversed cyclic loading. In the experimental programme, particular emphasis was given to the effect of horizontal reinforcement (in format of inverted U-shape bars) on the shear strength and ductility capacity of knee joints. Test results are compared with those predicted by four seismic design codes, including ACI 318-14, EC8, NZS3101 and GB50010. It is seen that the current design codes of practice cannot accurately predict the shear strength of seismically designed knee joints.

Keywords: large-scale tests, RC beam-column knee joints, seismic performance, shear strength

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Authors: Z. H. Shi, T. J. Dou, H. Zhang, H. X. Huang, N. Zeng

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The contamination of significant quantities of soils and sediments with uranium and other actinide elements as a result of nuclear activity poses many environmental risks. The electrokinetic process is one of the most promising remediation techniques for sludge, sediment, and saturated or unsaturated soils contaminated with heavy metals and radionuclides. However, secondary waste is a major concern for soil contaminated with nuclides. To minimize the generation of secondary wastes, this study used the anion and cation exchange membranes to improve the performance of the experimental apparatus. Remediation experiments of uranium-contaminated soil were performed with different agents. The results show that using acetic acid and EDTA as chelating agents clearly enhances the migration ability of the uranium. The ion exchange membranes (IEMs) used in the experiments not only reduce secondary wastes, but also, keep the soil pH stable.

Keywords: electrokinetic remediation, ion exchange membranes, soil, uranium

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Authors: Zhang Zijian

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Nowadays, spherical robots have played an important role in many fields, but the insufficient ability of obstacle surmounting limits their wider application fields. To solve this problem, a jumping system of a spherical robot is designed based on Archimedes helix. The jumping system of the robot utilizes the characteristics of Archimedes helix and isovelocity helix to achieve constant speed and stable contraction, which ensures the stability of the system. Also, the jumping action of the robot is realized by instantaneous release of elastic potential energy. In order to verify the effectiveness of the jumping system, we designed a spherical robot and its jumping system. The experimental results show that the jumping system has the advantages of light weight, small size, high energy conversion efficiency, and can realize the spherical jumping function.

Keywords: hopping mechanism, Archimedes' Helix, hopping robot, spherical robot

Procedia PDF Downloads 135