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The shifts of precipitation phases and their impacts

Science China Earth Sciences 2025年

作者： xuemei li Tao CHE Yuanlong TANG Huan'e DUAN Guigang WANG Xu ZHANG Chuanming YANG Jun WU Yue ZHANG Lanhai li Faculty of Geomatics Lanzhou Jiaotong University National-Local Joint Engineering Research Center of Technologies and Applications for National Geographic State Monitoring Key Laboratory of Science and Technology in Surveying & Mapping Gansu Province Key Laboratory of Cryospheric Science and Frozen Soil Engineering Heihe Remote Sensing Experimental Research StationNorthwest Institute of Eco-Environment and Resources Chinese Academy of Sciences Xinjiang Key Laboratory of Water Cycle and Utilization in Arid Zone Xinjiang Institute of Ecology and Geography Chinese academy of Sciences Tianshan Snow Cover and Avalanche Observation and Research Station of Xinjiang

Precipitation comes in various phases, including rainfall, snowfall, sleet, and hail. Shifts of precipitation phases, as well as changes in precipitation amount, intensity, and frequency, have significant impacts on regional climate, hydrology,ecology, and the energy balance of the land-atmosphere system. Over the past century, certain progress has been achieved in aspects such as the observation, discrimination, transformation, and impact of precipitation phases. Mainly including:since the1980s, studies on the observation, formation mechanism, and prediction of precipitation phases have gradually received greater attention and reached a certain scale. The estimation of different precipitation phases using new detection theories and methods has become a research focus. Avariety of discrimination methods or schemes, such as the potential thickness threshold method of the air layer, the temperature threshold method of the characteristic layer, and the near-surface air temperature threshold method,have emerged one after another. Meanwhile, comparative studies on the discrimination accuracy and applicability assessment of multiple methods or schemes have also been carried out simultaneously. In recent years, the shift of precipitation from solid to liquid (SPSL) in the mid-to-high latitudes of the Northern Hemisphere has become more pronounced due to global warming and human activities. It leads to an increase in rain-on-snow (ROS) events and avalanche disasters, affecting the speed, intensity, and duration of spring snow-melting, accelerating sea ice and glacier melting, releasing carbon from permafrost, altering soil moisture, productivity, and phenological characteristics of ecosystems, and thereby affecting their structures, processes, qualities, and service functions. Although some progress has been made in the study of precipitation phases, there remains considerable research potential in terms of completeness of basic data, reliability of discrimination schemes,

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Improved grey prediction model based on exponential grey action quantity

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Journal of Systems Engineering and Electronics 2018年第3期29卷 560-570页

作者： YIN Kedong GENG Yan li xuemei School of Economics Ocean University of China Marine Development Studies Institute Ocean University of China

With the passage of time, it has become important to investigate new methods for updating data to better fit the trends of the grey prediction model. The traditional GM（1,1） usually sets the grey action quantity as a constant. Therefore, it cannot effectively fit the dynamic characteristics of the sequence, which results in the grey model having a low precision. The linear grey action quantity model cannot represent the index change law. This paper presents a grey action quantity model, the exponential optimization grey model（EOGM（1,1））, based on the exponential type of grey action quantity; it is constructed based on the exponential characteristics of the grey prediction model. The model can fully reflect the exponential characteristics of the simulation series with time. The exponential sequence has a higher fitting accuracy. The optimized result is verified using a numerical example for the fluctuating sequence and a case study for the index of the tertiary industry＇s GDP. The results show that the model improves the precision of the grey forecasting model and reduces the prediction error.

关键词： exponential of grey action quantity optimal algorithm grey forecasting mathematical modeling

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A Parameter Adaptive Method for Image Smoothing

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Tsinghua Science and Technology 2024年第4期29卷 1138-1151页

作者： Suwei Wang Xiang Ma xuemei li School of Computer Science and Technology Shandong UniversityJinan 250101China School of Software Shandong UniversityJinan 250101China

Edge is the key information in the process of image smoothing. Some edges, especially the weak edges, are difficult to maintain, which result in the local area being over-smoothed. For the protection of weak edges, we propose an image smoothing algorithm based on global sparse structure and parameter adaptation. The algorithm decomposes the image into high frequency and low frequency part based on global sparse structure. The low frequency part contains less texture information which is relatively easy to smoothen. The high frequency part is more sensitive to edge information so it is more suitable for the selection of smoothing parameters. To reduce the computational complexity and improve the effect, we propose a bicubic polynomial fitting method to fit all the sample values into a surface. Finally, we use Alternating Direction Method of Multipliers (ADMM) to unify the whole algorithm and obtain the smoothed results by iterative optimization. Compared with traditional methods and deep learning methods, as well as the application tasks of edge extraction, image abstraction, pseudo-boundary removal, and image enhancement, it shows that our algorithm can preserve the local weak edge of the image more effectively, and the visual effect of smoothed results is better.

关键词： image smoothing parameter adaptation bicubic interpolation polynomial fitting

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Image smoothing based on global sparsity decomposition and a variable parameter

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Computational Visual Media 2021年第4期7卷 483-497页

作者： Xiang Ma xuemei li Yuanfeng Zhou Caiming Zhang Shandong University Jinan 250101China Shandong Co-Innovation Center of Future Intelligent Computing Yantai 264025China Digital Media Technology Key Lab of Shandong Province Jinan 250014China

Smoothing images,especially with rich texture,is an important problem in computer *** an ideal result is difficult due to complexity,irregularity,and anisotropicity of the ***,some properties are shared by the texture and the structure in an *** is a hard compromise to retain structure and simultaneously remove *** create an ideal algorithm for image smoothing,we face three *** images with rich textures,the smoothing effect should be *** should overcome inconsistency of smoothing results in different parts of the *** is necessary to create a method to evaluate the smoothing *** apply texture pre-removal based on global sparse decomposition with a variable smoothing parameter to solve the first two problems.A parametric surface constructed by an improved Bessel method is used to determine the smoothing *** evaluation measures:edge integrity rate,texture removal rate,and gradient value distribution are proposed to cope with the third *** use the alternating direction method of multipliers to complete the whole algorithm and obtain the *** show that our algorithm is better than existing algorithms both visually and *** also demonstrate our method’s ability in other applications such as clip-art compression artifact removal and content-aware image manipulation.

关键词： image smoothing texture removal global sparse decomposition Bessel method

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17.1%-Efficiency organic photovoltaic cell enabled with two higher-LUMO-level acceptor guests as the quaternary strategy

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Science China Chemistry 2020年第4期63卷 490-496页

作者： Kun li Yishi Wu xuemei li Hongbing Fu Chuanlang Zhan Department of Chemistry Capital Normal UniversityBeijing 100048China School of Chemistry&Chemical Engineering Linyi UniversityLinyi 276000China CAS Key Laboratory of Photochemistry Institute of ChemistryChinese Academy of SciencesBeijing 100190China

Quaternary blended organic solar cells utilize four blended material components(one donor plus three acceptors, two donors and two acceptors, or three donors plus one acceptor) as the active layer materials. The use of four material components allows us to have more material selections and more mechanism choices to improve the photon-to-electron conversion efficiency. In this contribution, we present a new case of quaternary material system, that shows 17.1% efficiency obtained by adding IDIC and PC71BM as the guest acceptors of the host binary of PM6:Y6. The lowest unoccupied molecular orbital(LUMO) levels of IDIC and PC71BM are both higher than that of Y6, which is one reason to obtain increased open-circuit voltage(Voc) in the quaternary device. Upon introduction of IDIC and PC71BM as the acceptor guests, the hole and electron mobilities are both increased, which contributes to the increased short-circuit current-density(Jsc). Effects of the weight ratios of the three acceptor components are investigated, which demonstrates that the increased hole and electron mobilities, the accelerated hole-transfer, and the reduced monomolecular recombination are the factors contributing to the increased Jscand fill-factor. This case of quaternary device demonstrates the applicability of the quaternary strategy in increasing the device functions and hence the efficiencies in the field of organic photovoltaic cells.

关键词： quaternary solar cell organic photovoltaic small-molecule acceptor nonfullerene fullerene

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Formula for computing knots with minimum stress and stretching energies

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Science China(Information Sciences) 2018年第5期61卷 171-185页

作者： xuemei li Fan ZHANG Guoning CHEN Caiming ZHANG School of Computer Science and Technology Shandong University School of Computer Science and Technology Shandong Technology and Business University Department of Computer Science University of Houston Shandong Provincial Key Laboratory of Digital Media Technology

Computing knots for a given set of data points in a plane is one of the key steps in the construction of fitting curves with high precision. In this study, a new method is proposed for computing a parameter value(knot) for each data point. With only three adjacent consecutive data points, one may not determine a unique interpolation quadratic polynomial curve, which has one degree of freedom(a variable). To obtain a better curve, the stress and stretching energies are used to optimize this variable so that the quadratic polynomial curve has required properties, which ensure that when the three consecutive points are co-linear, the optimal quadratic polynomial curve constructed is the best. If the position of the mid-point of the three points lies between the first point and the third point, the quadratic polynomial curve becomes a linear polynomial curve. Minimizing the stress and stretching energies is a time-consuming task. To avoid the computation of energy minimization, a new model for simplifying the stress and stretching energies is presented. The new model is an explicit function and is used to compute the knots directly, which greatly reduces the amount of computation. The knots are computed by the new method with minimum stress and stretching energies in the sense that if the knots computed by the new method are used to construct quadratic polynomial,the quadratic polynomial constructed has the minimum stress and stretching energies. Experiments show that the curves constructed using the knots generated by the proposed method result in better interpolation precision than the curves constructed using the knots by the existing methods.

关键词： parameter stress and stretching energies polynomial precision curve construction

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A novel composite(FMC)to serve as a durable 3D-clam-shaped bifunctional cathode catalyst for both primary and rechargeable zinc-air batteries

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Science Bulletin 2017年第17期62卷 1216-1226页

作者： Nengneng Xu xuemei li Haoran li Yanan Wei Jinli Qiao State Key Laboratory for Modification of Chemical Fibers and Polymer Materials State Environmental Protection Engineering Center for Pollution Treatment and Control inTextile IndustryCollege of Environmental Science and EngineeringDonghua UniversityShanghai 201620China

Novel and highly durable air cathode electrocatalyst with three dimensional （3D）-clam-shaped structure, MnO2 nanotubes-supported Fe2O3 （Fe2O3/MnO2） composited by carbon nanotubes （CNTs）（（Fe2O3/ MnO2）3/4-（CNTs）1/4） is synthesized using a facile hydrothermal process and a following direct heat- treatment in the air. The morphology and composition of this catalyst are analyzed using scanning elec- tronic microscopy （SEM）, transmission electron microscopy （TEM）, X-ray diffraction （XRD） and energy dispersive X-ray spectroscopy （EDX）. The morphology characteristics reveal that flower-like Fe2O3 parti- cles are highly dispersed on both MnO2 nanotubes and CNT surfaces, coupling all three components firmly. Electrochemical measurements indicate that the synergy of catalyst exhibit superior bi- functional catalytic activity for both oxygen reduction reaction （ORR） and oxygen evolution reaction （OER） as well as stability than Pt/C and lrO2 catalysts. Using these catalysts for air-cathodes, both primary and rechargeable zinc-air batteries （ZABs） are assembled for performance validation. In a primary ZAB, this 3D-clamed catalyst shows a decent open circuit voltage （OCV, -1.48 V） and a high discharge peak power density （349 mW cm 2）, corresponding to a coulomhic efficiency of 92%. In a rechargeahle ZABs with this bifunctional catalyst, high OCV （〉1.3 V） and small charge-discharge voltage gap （〈1.1 V） are achieved along with high specific capacity （780 mAh g 1 at 30 mA cm-2） and robust cycle-life （1,390 cycles at cycle profile of 20 mA/10 min）.

关键词： Bifunctional composite catalysts ORR and OER Rechargeable ZABs Specific capacity Long durability

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ADVANCE SELliNG IN THE PRESENCE OF PRODUCT DIFFUSION EFFECT

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Journal of Systems Science and Systems Engineering 2017年第1期26卷 77-99页

作者： Xiaoyan Xu xuemei li Yiwen Bian Yanhong Sun School of Management University of Science & Technology of China Hefei 230026 China School of Management Zhejiang University Hangzhou 310058 China SHU-UTS SILC Business School Shanghai University Shanghai 201899 China

Product diffusion refers to the phenomenon that the later demand is dependent on the early sales. To investigate how a firm＇s advance selling strategy is affected by the effect of product diffusion, we consider a monopolist seller who sells a fashionable product in a market that comprises of myopic and strategic consumers over two periods （i.e., the advance selling season and the regular selling season）. For a linear product diffusion effect we fred that, when the effect of product diffusion is positive, the seller may set an extremely high advance selling price to induce the strategic consumers to purchase in the regular selling season, which is counter-intuitive. Moreover, the optimal procurement quantity for the seller may increase in the negative effect of product diffusion and decrease in the amount of strategic consumers. When we extend our model to consider a concave quadratic product diffusion effect, however, the optimal procurement quantity is concave in the amount of strategic consumers. Numerical studies are further presented to discuss the managerial insights.

关键词： Advance selling product diffusion strategic consumer behavior interface on marketing andoperations management

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Combined model based on optimized multi-variable grey model and multiple linear regression

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Journal of Systems Engineering and Electronics 2011年第4期22卷 615-620页

作者： Pingping Xiong Yaoguo Dang Xianghua wu xuemei li College of Economics and Management Nanjing University of Aeronautics and Astronautics Nanjing 210016 P. R. China College of Mathematics and Physics Nanjing University of Information Science and Technology Nanjing 210044 P. R. China

The construction method of background value is improved in the original multi-variable grey model （MGM（1,m）） from its source of construction errors. The MGM（1,m） with optimized background value is used to eliminate the random fluctuations or errors of the observational data of all variables, and the combined prediction model together with the multiple linear regression is established in order to improve the simulation and prediction accuracy of the combined model. Finally, a combined model of the MGM（1,2） with optimized background value and the binary linear regression is constructed by an example. The results show that the model has good effects for simulation and prediction.

关键词： multi-variable grey model (MGM(1,m)) backgroundvalue optimization multiple linear regression combined predic-tion model.

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Sketch simplification guided by complex agglomeration

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Science China(Information Sciences) 2019年第5期62卷 145-160页

作者： Yue liU xuemei li Pengbo BO Xifeng GAO School of Computer Science and Technology Shandong University School of Computer Science and Technology Harbin Institute of Technology School of Software Shandong University Courant Institute of Mathematical Sciences New York University

We propose a novel method for vector sketch simplification based on the simplification of the geometric structure that is extracted from the input vector graph, which can be referred to as a base *** the sets of strokes, which are treated in the existing approaches, a base complex is considered to be a collection of various geometric primitives. Guided by the shape similarity metrics that are defined for the base complex, an agglomeration procedure is proposed to simplify the base complex by iteratively merging a pair of geometric primitives that exhibit the minimum cost into a new one. This simplified base complex is finally converted into a simplified vector graph. Our algorithm is computationally efficient and is able to retain a large amount of useful shape information from the original vector graph, thereby achieving a tradeoff between efficiency and geometric fidelity. Furthermore, the level of simplification of the input vector graph can be easily controlled using a single threshold in our method. We make comparisons with some existing methods using the datasets that have been provided in the corresponding studies as well as using different styles of sketches drawn by artists. Thus, our experiments demonstrate the computational efficiency of our method and its capability for producing the desirable results.

关键词： sketch simplification base complex iterative merging

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