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Water storage changes in the North China Plain from 2004 to 2019

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Science China(Technological Sciences) 2023年第7期66卷 2036-2046页

作者： CHEN MinLan xu YuYue PAN hang WANG LuHan School of Geography and Ocean Science Nanjing UniversityNanjing 210023China Jiangsu Provincial Key Laboratory of Geographic Information Science and Technology Nanjing UniversityNanjing 210023China Frontiers Science Center for Critical Earth Material Cycling Nanjing UniversityNanjing 210023China National Earth System Science Data Center National Science and Technology Infrastructure of ChinaBeijing 100101China

In the past few decades,the irrational use of water resources has resulted in many issues such as land subsidence in the North China Plain(NCP),hindering its socio-economic *** accurate understanding of water resource changes is important for the allocation of water resources in the *** this study,we employed Gravity Recovery and Climate Experiment(GRACE) satellite data to monitor the total water storage(TWS) change in the NCP during 2004–***,precipitation,and runoff during 2004–2019 were sequentially examined,using the water balance formula(WBF),to retrieve TWS ***,the soil moisture,snow water equivalent,and canopy water storage from the Global Land Data Assimilation System were used to calculate the natural component of the TWS variations.A comparison of these results revealed the drivers of the changes in water *** results showed that:(1) overall TWS retrieved by GRACE decreased substantially as a consequence of human activity,while TWS obtained by WBF fluctuated periodically around zero under the impact of three natural drivers;(2) TWS in the NCP fell at a remarkable rate of-12.39 mm/y from 2004 to 2019,and the natural part of TWS experienced two significant declines,during 2004–2010 and 2013–2016;(3) variations in runoff,precipitation,and evapotranspiration from 2004 to 2019 were not significant,but human activities contributed more to the decreasing TWS than natural *** study provides a reference for water resource management and groundwater exploitation across the NCP under climate change.

关键词： North China Plain water storage GRACE human activities climatic factor

Automatic Requirement Dependency Extraction Based on Integrated Active Learning Strategies

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Machine Intelligence Research 2024年第5期21卷 993-1010页

作者： Hui Guan Guorong Cai hang xu Department of Computer Science and Technology Shenyang University of Chemical TechnologyShenyang110142China Key Laboratory of Industrial Intelligence Technology on Chemical Process Shenyang110142China

Since requirement dependency extraction is a cognitively challenging and error-prone task,this paper proposes an automatic requirement dependency extraction method based on integrated active learning *** this paper,the coefficient of variation method was used to determine the corresponding weight of the impact factors from three different angles:uncertainty probability,text similarity difference degree and active learning variant prediction divergence *** combining the three factors with the proposed calculation formula to measure the information value of dependency pairs,the top K dependency pairs with the highest comprehensive evaluation value are selected as the optimal *** the optimal samples are continuously added into the initial training set,the performance of the active learning model using different dependency features for requirement dependency extraction is rapidly ***,compared with other active learning strategies,a higher evaluation measure of requirement dependency extraction can be achieved by using the same number of ***,the proposed method using the PV-DM dependency feature improves the weight-F1 by 2.71%,the weight-recall by 2.45%,and the weight-precision by 2.64%in comparison with other strategies,saving approximately 46%of the labelled data compared with the machine learning approach.

关键词： Requirement dependency dependency extraction dependency features integrated active learning strategies coefficient of variation

Free Vibration Analysis of Moderately-Thick Laminated Doubly-Curved Shells with the Modified Higher-Order Theory

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Acta Mechanica Solida Sinica 2023年第1期36卷 132-142页

作者： Yuan Tao Jie xu xuegang Yuan hang Yin School of Mathematics Boda College of Jilin Normal UniversitySiping 136000China Department of Mechanics Northeastern UniversityShenyang 110819China School of Science Dalian Minzu UniversityDalian 116600China

In this work,the free vibration properties ofmoderately-thick laminated doubly-curved shells are *** model of the natural frequency of the simply-supported laminated doubly-curved shell is formulated via the variational *** on the numerical solutions,the influences of the shell type,the aspect ratio,the lamination angle and the layer number on the free vibration are *** obtained results show that,for the symmetrically laminated curved shells with fixed thickness,when the layer number is greater than 4,the increasing number has no impact on the natural frequency;however,the lamination angle plays a key role in the fundamental frequency of the spherical shell,while it has little effect on the hyperbolic paraboloid ***,a higher-order shear deformation theory with modified parameters is developed for the moderately-thick laminated doubly-curved shells in this work,i.e.,the geometrically nonlinear strain–displacement relationships are derived with a stricter series expansion form,which are more suitable for the moderately-thick curved shells.

关键词： Vibration analysis Laminated doubly-curved shell Modified displacement fields Higher-order shear deformation

A Coordinate-Free Approach to the Design of Generalized Griffis-Duffy Platforms

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Chinese Journal of Mechanical Engineering 2024年第3期37卷 95-103页

作者： Chengwei Shen xu Pei Lubin hang Jingjun Yu College of Optical Mechanical and Electrical EngineeringZhejiang A&F UniversityHangzhou 311300China School of Mechanical Engineering and Automation Beihang UniversityBeijing 100191China School of Mechanical and Automotive Engineering Shanghai University of Engineering ScienceShanghai 201620China

Architectural singularity belongs to the Type II singularity,in which a parallel manipulator(PM)gains one or more degrees of freedom and becomes *** remaining permanently in a singularity are beneficial for linearto-rotary motion ***-Duffy(GD)platform is a mobile structure admitting a Bricard *** this paper,we present a coordinate-free approach to the design of generalized GD platforms,which consists in determining the shape and attachment of both the moving platform and the fixed *** generalized GD platform is treated as a combination of six coaxial single-loop mechanisms under the same *** to the inversion,hidden in the geometric structure of these single-loop mechanisms,the mapping from a line to a circle establishes the geometric transformation between the fixed base and the moving platform based on the center of inversion,and describes the shape and attachment of the generalized GD ***,the center of inversion not only identifies the location of rotation axis,but also affects the shape of the platform mechanism.A graphical construction of generalized GD platforms using inversion,proposed in the paper,provides geometrically feasible solutions of the manipulator design for the requirement of the location of rotation axis.

关键词： Generalized Griffis-Duffy platforms Self-motion Inversion Coordinate-free determination Manipulator design

Metal–organic frameworks with aggregation-induced emission

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Aggregate

Aggregate 2024年第3期5卷 127-141页

作者： hang xu Peng Cheng Key Laboratory of Advanced Energy Materials Chemistry(MOE)and Frontiers Science Center for New Organic Matter College of ChemistryNankai UniversityTianjinChina

Aggregation-induced emission(AIE)materials exhibit remarkable emission in the aggregated or solid state while demonstrating minimal emission in dilute *** contrast to conventional luminescent materials,AIE luminogens(AIEgens)offer several advantages in the aggregate state,including high quantum yield,excel-lent photostability,and low background signals,making them highly promising for diverse *** AIEgens into designable metal–organic frame-works(MOFs)enables tunable and well-ordered AIE materials,allowing for precise control over photophysical properties and deeper exploration of AIE *** AIE MOFs have been constructed and investigated,and several reviews focus on their structure design and applications in sensing and *** review highlights the state-of-the-art advancements in AIE MOFs,including mech-anisms,design strategies,and applications in chemical sensing,bioimaging,and disease *** challenges associated with practical applications of AIE MOFs are also addressed,with an emphasis on their large-scale production involved interdisciplinary *** comprehensive review aims at guiding further development of AIE MOFs and promoting their practical applications in analysis,healthcare,and other luminescence relatedﬁelds.

关键词： aggregation-induced emission luminescent materials metal–organic frameworks

Squeeze flow of interstitial Herschel-Bulkley fluid between two rigid spheres

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Particuology 2010年第4期8卷 360-364页

作者： Chunhui xu Li Yuan Yong xu Wenbin hang College of Science China Agricultural University Beijing 100083 China

Interaction between two spheres with an interstitial fluid is crucial in discrete element modeling for simulating the behaviors of ＇wet＇ particulate materials. The normal viscous force of squeeze flow between two arbitrary rigid spheres with an interstitial HerscheI-Bulkley fluid was studied on the basis of Reynolds＇ lubrication theory, resulting in analytical integral expressions of pressure distribution and the viscous force between the two spheres. According to the variation of shear stress, the fluid was divided into yielding and unyielding regions, followed by a discussion on the thickness of the two regions. The result of this paper could be reduced to either the power-law fluid or the Bingham fluid case.

关键词： Wet granuleDiscrete element method Herschel-Bulldey fluid Viscous force

Entanglement and Teleportation of Pair Cat States in Amplitude Decoherence Channel

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Communications in Theoretical Physics 2009年第7期52卷 45-49页

作者： xu hang-Shi xu Jing-Bo Zhejiang Institute of Modern Physics and Physics Department Zhejiang University Hangzhou 310027 China

The dynamic behavior of the entanglement for the pair cat states in the amplitude decoherence channel isstudied by adopting the entanglement of formation determined by the ***,we consider the teleportationby using joint measurements of the photon-number sum and phase difference with the pair cat states as an entangleresource and discuss the influence of amplitude decoherence on the mean fidelity of the teleportation.

关键词： entanglement teleportation pair cat states

A Maple Package on Symbolic Computation of Hirota Bilinear Form for Nonlinear Equations

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Communications in Theoretical Physics 2009年第11期52卷 801-807页

作者： YANG xu-Dong RUAN hang-Yu Department of Physics Ningbo University Ningbo 315211 China

An improved algorithm for symbolic computation of Hirota bilinear forms of KdV-type equations withlogarithmic transformations is *** the algorithm,the general assumption of Hirota bilinear form is successfullyreduced based on the property of uniformity in ***,we discard the integral operation in the *** software package HBFTrans is written in Maple and its running effectiveness is tested by a variety solitonequations.

关键词： Hirota bilinear form nonlinear equation, symbolic algebra

Learning practically feasible policies for online 3D bin packing

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Science China(Information Sciences) 2022年第1期65卷 175-191页

作者： hang ZHAO Chenyang ZHU Xin xu Hui HUANG Kai xu School of Computer Science National University of Defense Technology College of Intelligence Science and Technology National University of Defense Technology College of Computer Science and Software Engineering Shenzhen University

We tackle the online 3 D bin packing problem(3 D-BPP), a challenging yet practically useful variant of the classical bin packing problem. In this problem, the items are delivered to the agent without informing the full sequence information. The agent must directly pack these items into the target bin stably without changing their arrival order, and no further adjustment is permitted. Online 3 D-BPP can be naturally formulated as a Markov decision process(MDP). We adopt deep reinforcement learning, in particular, the on-policy actor-critic framework, to solve this MDP with constrained action space. To learn a practically feasible packing policy, we propose three critical designs. First, we propose an online analysis of packing stability based on a novel stacking tree. It attains a high analysis accuracy while reducing the computational complexity from O(N2) to O(N log N), making it especially suited for reinforcement learning training. Second, we propose a decoupled packing policy learning for different dimensions of placement which enables high-resolution spatial discretization and hence high packing precision. Third, we introduce a reward function that dictates the robot to place items in a far-to-near order and therefore simplifies the collision avoidance in movement planning of the robotic arm. Furthermore, we provide a comprehensive discussion on several key implemental issues. The extensive evaluation demonstrates that our learned policy outperforms the state-of-the-art methods significantly and is practically usable for real-world applications.

关键词： bin packing problem online 3D-BPP reinforcement learning