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Novel Materials and Their Synthesis

Yuping Wu, Guoxiu Wang, Shiyou Guan
2014 Chemistry International  
Yuping Wu and Prof. Shiyou Guan's labs were in charge of the local organization activities.  ...  Novel Materials and Their Synthesis by Yuping Wu, Guoxiu Wang and Shiyou Guan The IUPAC International Conference on Novel Materials and Synthesis (NMS) was initiated in 2005 in Shanghai.  ... 
doi:10.1515/ci.2014.36.2.26 fatcat:hfoyup3fyndwrcn26k6z7khiga

Terahertz Spiral Spatial Filtering Imaging

Hui Liu, Shiyou Wu, Meng Zhao, Chao Li, XiaoJun Liu, Guangyou Fang
2021 Applied Sciences  
In this paper, we propose a terahertz (THz) spiral spatial filtering (SSF) imaging method that can enable image contrast enhancement. The related theory includes three main steps: (1) the THz image of the target is Fourier transformed to the spatial spectrum distribution; (2) the spatial spectrum is modulated by a spiral phase at the Fourier plane; (3) the filtered spatial spectrum is inverse Fourier transformed to the desired THz image. Meanwhile, analytic expression of the final THz image is
more » ... erived. Due to the unique nature of the spiral phase, THz image contrast enhancement can be achieved and verified by various simulated target images with different contrasts. In our designed THz SSF imaging system, Fourier transform is carried out by the lens, and the spiral phase is acquired by the spiral phase plate (SPP). Proof-of-principle experiments with three different types of targets (carved metal letters, a high-density polyethylene (HDPE) piece with a scratch, and a leaf) were carried out, and the effectiveness of contrast enhancement and edge extraction on the THz reconstruction images was validated.
doi:10.3390/app11062526 fatcat:nsmsmkxisvbunlw3j5x2u4ugd4

How Good are Child Vulnerability Assessment Tools in China?

Di Qi, Shiyou Wu
2020 Social Sciences  
The research team then examined the codes together, and discussed any inconsistencies, in order to ensure the accuracy of the codes (Wu et al. 2016 ).  ... 
doi:10.3390/socsci9070118 fatcat:c5betja5bbdj3mzsqmxncihj54

Welfare Participation and Time Use in China

Qin Gao, Shiyou Wu, Fuhua Zhai
2014 Social Indicators Research  
Based on previous research on Dibao (Du & Park, 2007; Gao, Garfinkel, & Zhai, 2009; Gustafsson & Deng, 2011; Wang, 2007; Wu & Ramesh, 2014) , this study uses household heads' individual characteristics  ...  characteristics that are predictive of Dibao receipt include poor health or disability, unemployment, low education, large household size, and living in a less developed region Gustafsson & Deng, 2011; Wu  ... 
doi:10.1007/s11205-014-0826-0 fatcat:rw257hot5fa6vcgkiwt7ul2lva

One Objective for All Models – Self-supervised Learning for Topic Models [article]

Zeping Luo, Cindy Weng, Shiyou Wu, Mo Zhou, Rong Ge
2022 arXiv   pre-print
Self-supervised learning has significantly improved the performance of many NLP tasks. In this paper, we highlight a key advantage of self-supervised learning -- when applied to data generated by topic models, self-supervised learning can be oblivious to the specific model, and hence is less susceptible to model misspecification. In particular, we prove that commonly used self-supervised objectives based on reconstruction or contrastive samples can both recover useful posterior information for
more » ... eneral topic models. Empirically, we show that the same objectives can perform competitively against posterior inference using the correct model, while outperforming posterior inference using misspecified model.
arXiv:2203.03539v1 fatcat:g6kxid254vc45lwmnd3np7dpyy

Energy scavenging based on a single-crystal PMN-PT nanobelt

Fan Wu, Wei Cai, Yao-Wen Yeh, Shiyou Xu, Nan Yao
2016 Scientific Reports  
Self-powered nanodevices scavenging mechanical energy require piezoelectric nanostructures with high piezoelectric coefficients. Here we report the fabrication of a single-crystal (1 − x)Pb(Mg 1/3 Nb 2/3 ) O 3 − xPbTiO 3 (PMN-PT) nanobelt with a superior piezoelectric constant (d 33 = ~550 pm/V), which is approximately ~150%, 430%, and 2100% of the largest reported values for previous PMN-PT, PZT and ZnO nanostructures, respectively. The high d 33 of the single-crystalline PMN-PT nanobelt
more » ... s from the precise orientation control during its fabrication. As a demonstration of its application in energy scavenging, a piezoelectric nanogenerator (PNG) is built on the single PMN-PT nanobelt, generating a maximum output voltage of ~1.2 V. This value is ~4 times higher than that of a single-CdTe PNG, ~13 times higher than that of a single-ZnSnO 3 PNG, and ~26 times higher than that of a single-ZnO PNG. The profoundly increased output voltage of a lateral PNG built on a single PMN-PT nanobelt demonstrates the potential application of PMN-PT nanostructures in energy harvesting, thus enriching the material choices for PNGs. Piezoelectric nanogenerators (PNG) have attracted extensive attention because they can harvest ubiquitous mechanical energies from ambient environment at any time 1 , for self-powered nanosystems that enable continuous operations of implantable biodevices, micro-electrochemical systems, wireless sensors and portable/wearable electronics, without the trouble of charging and replacing power sources 2 . At first, PNGs were based on vertically aligned nanowires of different materials, including ZnO 3 , AlGaN 1 , GaN 1,4,5 , InN 1,6 , PZT 7 , and CdS 8 . The rubbing of the electrode and the nanowire in vertical configuration results in mechanical instability, which is undesirable and avoided by the creation of a "lateral PNG" 9 in 2009, using a lateral piezoelectric nanowire with both ends fixed to a flexible substrate. Since then, various materials have been selected for such lateral PNGs, including ZnO 9,10 , ZnSnO 3 11 and CdTe 12 nano/microwires. However, the piezoelectric coefficients (d 33 ) of these materials are not high enough (e.g. 12.4 pm/V for ZnO 13 , and 11.06 pm/V for ZnSnO 3 14 ) , resulting to small output voltages and limited application of lateral PNGs based on a single nanostructure. Therefore the major challenge is to find alternative materials with higher piezoelectric coefficients for lateral PNGs, such that their output voltage can be profoundly increased 15 . Among the intensively studied piezoelectric materials, relaxor ferroelectric (1 − x)Pb (Mg 1/3 Nb 2/3 )O 3 − x PbTiO 3 (PMN-PT) is highly desirable as a next-generation piezoelectric material due to its excellent piezoelectric properties (a d 33 up to 2500 pm/V 16 for PMN-PT bulk). The difficulty of fabricating PMN-PT nanostructures with excellent piezoelectric performances, readily available for PNG device assembling lies in the fact that the piezoelectric properties of PMN-PT will be weakened by up to 92% 17 if deviated from the optimum composition and orientation. The first synthesis of 1-D PMN-PT nanostructures was reported in 2012 by Xu et al. 15 , who successfully used a bottom-up (hydrothermal) method to obtain single-crystal piezoelectric PMN-PT nanowires. However, the composition and orientation of each individual PMN-PT nanowire can not be precisely controlled by that bottom-up approach 15 , making it impractical to guarantee the excellent piezoelectric performance of each individual PMN-PT nanowire. For the same reason, a lateral PNG based on a single PMN-PT nanostructure, though theoretically promising for a high output voltage, has never been realized. In this paper, we report the unprecedented fabrication of a single-crystal PMN-PT nanobelt by a top-down method. The crystal orientation, dimension and composition of the PMN-PT nanobelt are precisely controlled during fabrication to enhance the piezoelectric properties. The resultant d 33 of the obtained nanobelt reaches ~550 pm/V, which is ~150%, 430%, and 2100% of the largest reported values for previous PMN-PT 15 , PZT 18 , and ZnO 19 nanostructures. A lateral PNG based on a single PMN-PT nanobelt is designed and built to demonstrate the PMN-PT nanobelt's efficient application in harvesting mechanical energies. During transportation and device
doi:10.1038/srep22513 pmid:26928788 pmcid:PMC4772540 fatcat:olmx4v3g55gkrovzniwxhxizje

Human Respiration Localization Method Using UWB Linear Antenna Array

Yuan Liu, Shiyou Wu, Jie Chen, Guangyou Fang, Hejun Yin
2015 Journal of Sensors  
Human respiration is the basic vital sign in remote monitoring. There has been remarkable progress in this area, but some challenges still remain to obtain the angle-of-arrival (AOA) and distinguish the individual signals. This paper presents a 2D noncontact human respiration localization method using Ultra-Wideband (UWB) 1D linear antenna array. The imaging reconstruction based on beamforming is used to estimate the AOA of the human chest. The distance-slow time 2D matrix at the estimated AOA
more » ... s processed to obtain the distance and respiration frequency of the vital sign. The proposed method can be used to isolate signals from individual targets when more than one human object is located in the surveillance space. The feasibility of the proposed method is demonstrated via the simulation and experiment results.
doi:10.1155/2015/601926 fatcat:yjzyrnqy3ngcbighjkq7kuvvze

Exploring Factors for Achieving Successful Educational Attainment among Chinese Doctoral Students in the United States

Shiyou Wu, Qi Wu, Xiaojiang Wei, Sarah E. Bledsoe, David Ansong
2020 Journal of International Students  
SHIYOU WU, MSW, PhD, is an Assistant Professor in the School of Social Work at Arizona State University.  ...  Wu, 2010; S. Wu & Wu, 2013) because of the current hukou policy. These policies force students from underdeveloped areas to remain or return to their hometown for higher education.  ... 
doi:10.32674/jis.v10i2.844 fatcat:husnwj5afzgaxk74k4huk4a2ou

Building Near-Isogenic Introgression Lines of Elite Maintainer Gangxiang B and Identifying Some Specific Traits

Yeqing Xiao, Xiaoyan Wu, Lanxiang Hu, Wenchang Wu, Shiyou Luo, Wei Deng, Dazhou Chen
2012 Rice Genomics and Genetics  
Xiaoyan Wu, Lanxiang Hu, Wenchang Wu, Shiyou Luo and Wei Deng involved in doing research work.  ... 
doi:10.5376/rgg.2012.03.0002 fatcat:qkcgvwh5enbttfokpahjhc3ryy

Adaptive ISAR Imaging of Maneuvering Targets Based on a Modified Fourier Transform

Binbin Wang, Shiyou Xu, Wenzhen Wu, Pengjiang Hu, Zengping Chen
2018 Sensors  
Focusing on the inverse synthetic aperture radar (ISAR) imaging of maneuvering targets, this paper presents a new imaging method which works well when the target's maneuvering is not too severe. After translational motion compensation, we describe the equivalent rotation of maneuvering targets by two variables-the relative chirp rate of the linear frequency modulated (LFM) signal and the Doppler focus shift. The first variable indicates the target's motion status, and the second one represents
more » ... he possible residual error of the translational motion compensation. With them, a modified Fourier transform matrix is constructed and then used for cross-range compression. Consequently, the imaging of maneuvering is converted into a two-dimensional parameter optimization problem in which a stable and clear ISAR image is guaranteed. A gradient descent optimization scheme is employed to obtain the accurate relative chirp rate and Doppler focus shift. Moreover, we designed an efficient and robust initialization process for the gradient descent method, thus, the well-focused ISAR images of maneuvering targets can be achieved adaptively. Human intervention is not needed, and it is quite convenient for practical ISAR imaging systems. Compared to precedent imaging methods, the new method achieves better imaging quality under reasonable computational cost. Simulation results are provided to validate the effectiveness and advantages of the proposed method. Sensors 2018, 18, 1370 2 of 16 blurring problem arises in the ISAR image. In order to solve this problem, the range instantaneous Doppler (RID) algorithm [17, 18] is proposed. The RID algorithm can be divided into two categories. One is based on the time-frequency representations [19, 20] . The most commonly-used ones include the short-time Fourier transform (STFT) [21] , the Wigner-Ville distribution (WVD) [22] , the smoothed pseudo-WVD (SPWVD) [23], the reassigned smoothed pseudo-Wigner-Ville distribution (RSPWVD) [24] , and so on. STFT is free from the cross-term interference but its resolution is poor. The others belong to the bilinear transform and suffer from the tradeoff between the time frequency concentration and the interference of cross-terms. The second category is based on the parameter estimation of signal model. When the maneuvering of the target is not too severe, the target's motion could be regarded as a uniform accelerated rotation after translational motion compensation. Additionally, each scatterer brings about a linear frequency modulated (LFM) signal [25, 26] . The parameters of the LFM signal, namely the centroid frequency and chirp rate, can be estimated by many effective methods, such as the Radon-Wigner transform (RWT) [27], the fractional Fourier transform (FrFT) [28], etc. However, these methods require estimating the parameters of each LFM component, which are computationally inefficient and inaccurate. Additionally, these RID methods do not consider the possible residual error of translational motion compensation. In this paper, we study the ISAR imaging of targets with not too severe maneuvering motion, and propose an adaptive imaging method based on modified Fourier transform. After translational motion compensation, the maneuvering motion can be regarded as uniform accelerated rotation and can be described by the rotational angular velocity and acceleration. The jerk of the target is very small and can be neglected. For targets with rigid body, the relative chirp rate of LFM signal is the same for all scatterers and only depends on target's motion status. Additionally, considering the possible residual error of translational motion compensation, a new variable called Doppler focus shift is defined to describe the shift of the equivalent rotation axis in the azimuth direction. With the relative chirp rate and the Doppler focus shift, both the quadratic phase terms of LFM signals and the rotation axis shift could be compensated in the modified Fourier transform matrix. Then the blurring in ISAR images is effectively eliminated. On this basic, ISAR imaging of maneuvering targets is converted into a parameter optimization problem. The optimal relative chirp rate and Doppler focus shift are obtained through a two-dimensional gradient descent method according to the optimal imaging quality. Moreover, we design an efficient and robust initialization process for the gradient descent method, thus, optimal imaging result could be obtained adaptively without human intervention. This is very helpful and convenient for practical ISAR imaging system. Except for the advantages of clear imaging result, robustness, and automation, the proposed method does not require heavy computation. The rest of the paper is organized as follows: In Section 2, the ISAR imaging geometry and signal model are presented; the principles of the newly-proposed method are elaborated in Section 3; experimental results based on simulation are provided in Section 4; and, finally, Section 5 draws the conclusions of this paper.
doi:10.3390/s18051370 pmid:29702626 pmcid:PMC5981441 fatcat:5cnn7uac7na3fizoodrmuipu7u

Edge detection by spiral phase contrast imaging at terahertz frequencies

Hui Liu, Shiyou Wu, Meng Zhao, Shen Zheng, Chao Li, Guangyou Fang
2021 Electronics Letters  
This paper proposes the spiral phase contrast (SPC) imaging at terahertz (THz) frequencies to achieve the target edge detection. The THz SPC imaging is built based on a classical 4f imaging system, and a spiral phase plate is placed in the Fourier plane to generate the spiral phase. Owing to the unique nature of the spiral phase, edge detection can be achieved. The THz SPC imaging mechanism is analysed by the scalar diffraction theory, and its corresponding analytic expression is derived. A
more » ... le target is simulated and the resultant image shows a remarkable edge detection. A proof-of-principle experiment is carried out using our designed THz SPC imaging system and the effectiveness of target edge extraction on the THz images is validated. A circle same as the simulation is imaged firstly, which is consistent with the simulated result. And the letter "Z" with more edges is imaged later. All edges in experiments are extracted perfectly, which are extremely consistent with the THz SPC imaging theory.
doi:10.1049/ell2.12167 fatcat:pniyor5xefbr5i4javpwvapefe

Experimental Study of Wireless Monitoring of Human Respiratory Movements Using UWB Impulse Radar Systems

Xiaolin Liang, Yuankai Wang, Shiyou Wu, Thomas Gulliver
2018 Sensors  
This paper analyzes and discusses the capability of human being detection using impulse ultra-wideband (UWB) radar with an improved detection algorithm. The multiple automatic gain control (AGC) technique is employed to enhance the amplitudes of human respiratory signals. Two filters with seven values averaged are used to further improve the signal-to-noise ratio (SNR) of the human respiratory signals. The maximum slope and standard deviation are used for analyzing the characteristics of the
more » ... eived pulses, which can provide two distance estimates for human being detection. Most importantly, based on the two distance estimates, we can accurately judge whether there are human beings in the detection environments or not. The data size can be reduced based on the defined interested region, which can improve the operation efficiency of the radar system for human being detection. The developed algorithm provides excellent performance regarding human being detection, which is validated through comparison with several well-known algorithms.
doi:10.3390/s18093065 pmid:30213122 pmcid:PMC6165135 fatcat:l4rjjhuwr5d4zjtunfiqd2iygi

Improved Intra-pulse Modulation Phase Calibration Algorithm with Accelerated Entropy Minimization Optimization

Yue Lu, Shiyou Xu, Yue Zhang, Qi Wu, Zengping Chen.
2019 IEEE Access  
SHIYOU XU was born in Hebei, China, in 1978. He received the B.S. and Ph.D. degrees from the National University of Defense Technology, Changsha, China, in 2001 and 2008, respectively.  ...  ) | 2 ∂θ k = g * (θ) · ∂g (θ) ∂θ k + g (θ) · ∂g (θ) ∂θ k * = g * (θ) · ∂g (θ) ∂θ k + g * (θ) · ∂g (θ) ∂θ k * Based on the principle that a + a * = 2Re {a} (45) where a is a complex number, (30) QI WU  ... 
doi:10.1109/access.2019.2953065 fatcat:nxno5iezyrgqjd2rjmoyak2s2y

Detection of Quasi-Static Trapped Human Being Using Mono-Static UWB Life-Detection Radar

Kun Yan, Shiyou Wu, Guangyou Fang
2021 Applied Sciences  
In practical situations such as hostage rescue, earthquake and other similar events, the ultra-wideband (UWB) life-detection radar echo response from the respiration motion of the trapped person is always quasi-/non-periodic in respiration frequency or very weak in respiration amplitude, which can be called quasi-static vital sign. Although it is an extremely difficult task, considering the economic cost, the detection ability of the traditional UWB life-detection radars with only a pair of
more » ... sceiver antennas is desired to be enhanced for locating the quasi-static trapped human being. This article proposes two different detection methods for quasi-static trapped human beings through the single/multiple observation points, which corresponds to the single-/multi-station radar operating mode, respectively. Proof-of-principle experiments were carried out by our designed radar prototypes, validating the effectiveness of the proposed methods.
doi:10.3390/app11073129 fatcat:hh7lnmpkvnhwreyyo6ct2vtnci

Multifractality and cross-correlation analysis of streamflow and sediment fluctuation at the apex of the Pearl River Delta

Yao Wu, Yong He, Menwu Wu, Chen Lu, Shiyou Gao, Yanwen Xu
2018 Scientific Reports  
The fluctuation and distribution of hydrological signals are highly related to the fluvial and geophysical regime at estuarine regions. Based on the long daily streamflow and sediment data of Makou (MK) and Sanshui (SS) stations at the apex of the Pearl River Delta, the scaling behavior of the streamflow and sediment is explored by multifractal detrended fluctuation analysis (MF-DFA). The results indicated that there was significant multifractal structure present in the fluctuations of
more » ... w and sediment. Meanwhile, the multifractal degree and complexity of sediment were much stronger than streamflow. Although the scaling exponents of streamflow were larger than sediment at both MK and SS, no evident differences have been found on the scaling properties of streamflow and sediment for the ratios MK/SS. Moreover, the cross-correlation between streamflow and sediment is further detected by Multifractal Detrended Cross-Correlation Analysis (MF-DXA). The multifractal response between streamflow and sediment at small timescale is characterized by long-range correlations whereas it exhibits random behavior at large timescale. The interaction of the broadness of probability density function and the long-range correlations should be responsible for the multifractal properties of hydrological time series as the multifractal degree of surrogate and shuffled data was significantly undermined. The fluctuation of fluvial dynamic and sediment structure, associated with the identification of various geophysical and hydrological characteristics, can exert substantial control on the natural system of alluvial deltas and estuaries 1,2 . Due to distinct regional regime and anthropic interference, the hydrological phenomena generally display self-affine and self-similar fractal behaviors over multiple time scales 3 . As recommended by the National Research Council, substantial attention should be paid to the invariance property across scales in the hydrological processes, which contribute considerably to the management of water resource and the predication of morphological evolution 4,5 . The streamflow fluctuation with dynamical input (precipitation) and output (evaporation) is generally characterized by long-range power-law correlation. Analogously, the sediment fluctuation is closely intertwined with the pattern of depletion (deposition) and supply (proximal/distal erosion) 6,7 , implicating the fractal properties of the underling sediment dynamics 8 . Exploration and determination of such correlation are of help to the understanding of the intrinsic behavior of the corresponding hydrological fluctuation and to predict their future events. More than half a century ago, Hurst first proposed that the annual streamflow records in the Nile River exhibited "long-range statistical dependencies". Similar long-range correlations have also been found in a remarkably wide variety of natural phenomena in later researches 9,10 . However, the intrinsic fluctuations of hydrological process are fairly vulnerable to the non-linearity and non-stationarity such as artificial noises and trend patterns, which may lead to spurious or at least unreliable results in the analysis of the long-range correlations. Hurst's original R/S analysis was thus criticized, since it failed to distinguish trend from the hydrological fluctuations 11,12 . In order to obtain a robust detection of the long-range correlations associated with the fractal behavior of the hydrological alteration, detrended fluctuation analysis (DFA) was introduced to analyze non-stationary time Published: xx xx xxxx OPEN
doi:10.1038/s41598-018-35032-z pmid:30410076 pmcid:PMC6224538 fatcat:vldx2xsrifh7toxitcqwxcceaa
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