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Convexification of Hybrid AC-DC Optimal Power Flow with Line-Commutated Converters

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CSEE j.urnal of Power and Energy Systems 2024年第2期10卷 617-628页

作者： Hongyuan Liang Zhigang Li j.H.Zheng Q.H.wu School of Electric Power Engineering South China University of TechnologyGuangzhou 510641China

Line-commutated converter (LCC)-based high-voltage DC (HVDC) systems have been integrated with bulk AC power grids for interregional transmission of renewable power. The nonlinear LCC model brings additional nonconvexity to optimal power flow (OPF) of hybrid AC-DC power grids. A convexification method for the LCC station model could address such nonconvexity but has rarely been discussed. We devise an equivalent reformulation for classical LCC station models that facilitates second-order cone convex relaxation for the OPF of LCC-based AC-DC power grids. We also propose sufficient conditions for exactness of convex relaxation with its proof. Equivalence of the proposed LCC station models and properties, exactness, and effectiveness of convex relaxation are verified using four numerical simulations. Simulation results demonstrate a globally optimal solution of the original OPF can be efficiently obtained from relaxed model.

关键词： AC-DC power system convex relaxation linecommutated converter optimal power flow second-order cone programming

Attitude control of multi-spacecraft systems on SO(3)with stochastic links failure

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Chinese j.urnal of Aeronautics 2024年第3期37卷 320-331页

作者： KANG Zeyu SHEN Qiang wu Shufan Chris j.DAMAREN MU Zhongcheng School of Aeronautics and Astronautics Shanghai Jiao Tong UniversityShanghai 200240China Institute for Aerospace Studies University of TorontoTorontoOntario M3H 5T6Canada

In this paper,for Multi-Spacecraft System(MSS)with a directed communication topology link and a static virtual leader,a controller is proposed to realize attitude consensus and attitude stabilization with stochastic links failure and actuator ***,an MSS attitude error model suitable for a directed topology link and with a static virtual leader based on SO(3)is derived,which considers that the attitude error on SO(3)cannot be defined based on algebraic ***,we design a controller to realize the MSS on SO(3)with attitude consensus and attitude stabilization under stochastic links failure and actuator ***,the simulation results of a multi-spacecraft system with stochastic links failure and a static virtual leader spacecraft are demonstrated to illustrate the efficiency of the attitude controller.

关键词： Multi-spacecraft systems Attitude consensus Attitude stabilization Stochastic links failure Super-martingale convergence

Semitransparent organic solar cells with high light utilization efficiency and color rendering index

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Science China Chemistry 2024年第7期67卷 2248-2256页

作者： Ni Gao Haij.n Bin Shangrong wu RenéA.j.j.nssen Yongfang Li Laboratory of Advanced Optoelectronic Materials Suzhou Key Laboratory of Novel Semiconductor Materials and DevicesCollege of ChemistryChemical Engineering and Materials ScienceSoochow UniversitySuzhou 215123China j.angsu Key Laboratory of Advanced Negative Carbon Technologies Soochow UniversitySuzhou 215123China Molecular Materials and Nanosystems&Institute for Complex Molecular Systems Eindhoven University of TechnologyEindhoven 5600 MBthe Netherlands

Semitransparent organic solar cells(ST-OSCs)have garnered considerable attention as promising renewable energy technology for integrating photovoltaics into ***,there is a trade-off between power conversion efficiency(PCE)and average visible transmittance(AVT),which hinders the achievement of a high light utilization efficiency(LUE).In this study,we propose a valuable method to address this challenge by replacing the transparent top electrode,Ag,with a 20 nm layer of *** ST-OSCs based on the 20 nm Au electrode demonstrate superior exciton extraction,more efficient charge collection,and higher color-rendering index(CRI)due to their smoother surface,higher conductivity,and enhanced visible light transmittance,resulting in a significantly higher PCE of 13.67%and an enhanced AVT of 30.17%,contributing to a high LUE of 4.15%.Additionally,optically transparent dielectric layers,applied on the front and back sides of the ST-OSCs to further boost performance,delivered an impressive LUE of 4.93%,with PCE and AVT values reaching 14.44%and 34.12%,***,the champion ST-OSCs also exhibited a favorable CRI value of *** achievements represent the bestperforming ST-OSCs to date with both high LUE and CRI and hold significant implications for the prospective commercialization of ST-OSCs.

关键词： semitransparent organic solar cells power conversion efficiency average visible transmittance light utilization efficiency color-rendering index

GraphFlow+:Exploiting Conversation Flow in Conversational Machine Comprehension with Graph Neural Networks

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Machine Intelligence Research 2024年第2期21卷 272-282页

作者： j.ng Hu Lingfei wu Yu Chen Po Hu Mohammed j.Zaki School of Computer Science Central China Normal UniversityWuhan 430079China Pinterest San Francisco 94016USA Meta Mountain View 94039USA Rensselaer Polytechnic Institute Troy 12180USA

The conversation machine comprehension(MC)task aims to answer questions in the multi-turn conversation for a single ***,recent approaches don’t exploit information from historical conversations effectively,which results in some references and ellipsis in the current question cannot be *** addition,these methods do not consider the rich semantic relationships between words when reasoning about the passage *** this paper,we propose a novel model GraphFlow+,which constructs a context graph for each conversation turn and uses a unique recurrent graph neural network(GNN)to model the temporal dependencies between the context graphs of each ***,we exploit three different ways to construct text graphs,including the dynamic graph,static graph,and hybrid graph that combines the *** experiments on CoQA,QuAC and DoQA show that the GraphFlow+model can outperform the state-of-the-art approaches.

关键词： Conversational machine comprehension(MC) reading comprehension question answering graph neural networks(GNNs) natural language processing(NLP)

Granger causal representation learning for groups of time series

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Science China(Information Sciences) 2024年第5期67卷 56-68页

作者： Ruichu CAI Yunj.n wu Xiaokai HUANG Wei CHEN Tom Z.j.FU Zhifeng HAO School of Computer Science Guangdong University of Technology Peng Cheng Laboratory College of Science Shantou University

Discovering causality from multivariate time series is an important but challenging *** existing methods focus on estimating the Granger causal structures among multivariate time series,while ignoring the prior knowledge of these time series, e.g., the group of the time series. Focusing on discovering the Granger causal structures among groups of time series, we propose a Granger causal representation learning method to solve this problem. First, we use the multiset canonical correlation analysis method to learn the Granger causal representation of each group of time series. Then, we model the Granger causal relationships among the learned Granger causal representations using a recurrent neural network with temporal information. Finally, we formulate the above two stages into one unified optimization problem, which is efficiently solved using the augmented Lagrangian method. We conduct extensive experiments on synthetic and real-world datasets to validate the correctness and effectiveness of the proposed method.

关键词： Granger causal discovery Granger causal representation learning time series data recurrent neural network multiset canonical correlation analysis

Observability Analysis of Integrated Electricity and Heating Systems with Thermal Quasi-dynamics in Pipelines

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CSEE j.urnal of Power and Energy Systems 2024年第3期10卷 1145-1158页

作者： Zhigang Li Wenj.an Zheng j.nbo Zhao j.H.Zheng Q.H.wu School of Electric Power Engineering South China University of TechnologyGuangzhou 510641China Fuzhou Changle District Power Supply Company of State Grid Fuj.an Electric Power Co. Ltd.Fuzhou 350000China Department of Electrical and Computer Engineering University of ConnecticutStorrsCT 06269USA CSEE IEEE

Observability analysis(OA)is vital to obtaining the available input measurements of state estimation(SE)in an integrated electricity and heating system(IEHS).Considering the thermal quasi-dynamics in pipelines,the measurement equations in heating systems are dependent on the estimated results,leading to an interdependency between OA and *** OA methods require measurement equations be known exactly before SE is performed,and they are not applicable to *** bridge this gap,a scenario-based OA scheme for IEHSs is devised that yields reliable analysis results for a predefined set of time-delay scenarios to cope with this *** its core procedure,the observable state identification and observability restoration are formulated in terms of integer linear *** tests are conducted to demonstrate the validity and superiority of the proposed formulation.

关键词： Integrated electricity and heating system measurement observability analysis state estimation thermal quasi-dynamics

Effects of different ratios of soluble to insoluble dietary fiber on growth performance and intestinal health of piglets

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ANIMAL NUTRITION 2024年第3期18卷 257-271页

作者： Feng, Luya Luo, Zhenfu Wang, j.ng wu, Kunfu Wang, Wenliang Liu, Zhimou Wen, j.ping Wang, Zhenbin Duns, Gregory j. Ma, Xiaokang Tan, Bi'e Hunan Agr Univ Coll Anim Sci & Technol Hunan Prov Key Lab Prod Qual Regulat Livestock & P Changsha 410128 Peoples R China Yuelushan Lab Changsha 410128 Peoples R China Hunan Nuoze Biol Technol Co Ltd Yiyang 413001 Peoples R China

This study investigated the impact of different ratios of soluble to insoluble dietary fiber (SDF:IDF) formulations by sugar beet pulp (SBP) supplementation on piglet growth performance, nutrient digestibility, immune function, intestinal morphology, intestinal microbiota and intestinal health. A total of 60 crossbred piglets (Duroc x [Landrace x Yorkshire]) at 40 d old with body weight of 10.0 +/- 0.3 kg were randomly assigned to 5 treatments with 6 replicates per treatment and 2 piglets per replicate in a 21d trial. The dietary treatments included a corn-soybean meal diet (0% SBP supplementation; CON), and diets supplemented with 2%, 4%, 6%, and 8% SBP, representing different SDF:IDF ratios at 10.16%, 13.53%, 16.79%, 19.86%, and 24.81%, respectively. The results indicated that the 8% SBP treatment had a negative effect on feed-to-gain ratio (linear, P = 0.009) compared with the CON treatment (P = 0.021). The apparent total tract digestibility (ATTD) of crude protein was lower in treatments supplemented with SBP (P = 0.002) and showed a linear decrease (P = 0.001), while the ATTD of IDF showed a linear increase (P = 0.037) in four SBP treatments compared to the CON treatment. The 4% SBP treatment increased serum concentrations of triglyceride (quadratic, P = 0.019) and K (linear, P < 0.0037), and decreased alanine transaminase concentration (quadratic, P = 0.015) compared with the CON treatment. The concentrations of Cit, Cys, Ile, Leu, Orn, Arg, taurine, urea, 1-methylhistidine, a-aminoadipic acid, aaminobutyric acid and cystathionine in the 4% SBP treatment were highest among all treatments (P < 0.05). The serum concentrations of interleukin-6, interleukin-8, interleukin-10, transforming growth factor-b, and tumor necrosis factor-a in the 6% SBP treatment were higher than those in the CON treatment (P < 0.05), which also increased mucin-2 and G protein-coupled receptor 41 mRNA expression (P < 0.05) in colonic mucosa compared with the CON treatment and improved th

关键词： Soluble dietary fiber Insoluble dietary fiber Sugar beet pulp Growth performance Intestinal health Piglet SUGAR-BEET PULP CHAIN FATTY-ACIDS NUTRIENT DIGESTIBILITY MICROBIOTA COMPOSITION FECAL MICROBIOTA BARRIER FUNCTION WEANING STRESS AMINO-ACIDS WHEAT METABOLISM

Addressable structured light system using metasurface optics and an individually addressable VCSEL array

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Photonics Research 2024年第6期12卷 1129-1137页

作者： CHENYANG wu XUANLUN HUANG YIPENG j. TINGYU CHENG j.AXING WANG NAN CHI SHAOHUA YU CONNIE j.CHANG-HASNAIN School of Information Science and Technology Fudan UniversityShanghai 200433China Berxel Photonics Co. Ltd.Shenzhen 518071China Peng Cheng Laboratory Shenzhen 518055China Chinese University of Hong Kong Shenzhen 518172China

Structured-light(SL)based 3D sensors have been widely used in many *** SL is the most widely deployed among all SL sensors due to its light weight,compact size,fast video rate,and low *** transmitter(known as the dot proj.ctor)consists of a randomly patterned vertical-cavity surface-emitting laser(VCSEL)array multiplicated by a diffractive optical element(DOE)with a fixed repeated *** that the separation of any two speckles is only one known and fixed number(albeit random),there are no other known scales to cal-ibrate or ***,typical SL sensors require extensive in-factory calibrations,and the depth resolution is limited to 1 mm at-60 cm *** this paper,to the best of our knowledge,we propose a novel dot proj.ctor and a new addressable SL(ASL)3D sensor by using a regularly spaced,individually addressable VCSEL array,multiplicated by a metasurface-DOE(MDOE)into a random pattern of the *** turning on or off the VCSELs in the array provides multiple known distances between neighboring speckles,which is used as a“built-in caliper”to achieve higher accuracy of *** as a precise“vernier caliper,”the addressable VCSEL array enables fine control over speckle positions and high detection *** experimentally dem-onstrated that the proposed method can result in sub-hundred-micron level *** new concept opens new possibilities for applications such as 3D computation,facial recognition,and wearable devices.

关键词： speckle light surface

The variation of DOM during long distance water transport by the China South to North Water Diversion Scheme and impact on drinking water treatment

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Frontiers of Environmental Science & Engineering 2024年第5期18卷 85-100页

作者： Hankun Yang Yuj.an Li Hongyu Liu Nigel j.D.Graham Xue wu j.awei Hou Mengj.e Liu Wenyu Wang Wenzheng Yu State Key Laboratory of Environmental Aquatic Chemistry Key Laboratory of Drinking Water Science and TechnologyResearch Center for Eco-Environmental SciencesChinese Academy of SciencesBeijing100085China School of Environment and Municipal Engineering Qingdao Technological UniversityQingdao266033China Colleges of Forestry Northeast Forestry UniversityHarbin150006China Department of Civil and Environmental Engineering Imperial College LondonSouth Kensington CampusLondonSW7 2AZUK School of Chemistry and Chemical Engineering Beijing Institute of TechnologyBeijing100081China State Key Laboratory of Separation Membrane Processes School of Environment Science and EngineeringTiangong UniversityTianjin300387China

In this study,samples were taken from three locations,upstream to downstream,along the central route proj.ct of the China South to North Water Diversion(SNWD)scheme in summer and *** were used to reveal the variations of dissolved organic matter(DOM)during the water transfer process,and the effects of these variations on drinking water treatment and disinfection by-products formation potential(DBPs-FP).The results showed that polysaccharides accumulate in summer and reduce in winter with flow distance,which has an important effect on the overall properties of DOM,as well as on the performance of coagulation,ultrafiltration,and the formation of *** substances,and their hydrophilic content,also increased in summer and decreased in winter with flow *** contrast,the concentration of small organic substances(MW≤1000 Da)increased in both summer and winter with flow distance,which affected both nanofiltration(NF)membrane fouling and *** results provide a useful case study of spatial and temporal changes in raw water DOM during long distance water transfer and their impact on the treatment and quality of drinking water from the SNWD.

关键词： Long-distance water transfer The China South to North Water Diversion Scheme Coagulation Membrane filtration Disinfection by-products