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Goodness-of-fit tests for multi-dimensional copulas:Expanding application to historical drought data

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Water Science and Engineering 2013年第1期6卷 18-30页

作者： Ming-wei MA Li-liang REN Song-bai SONG Jia-li SONG shan-hu jiang State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering Hohai University College of Water Resources and Architectural Engineering Northwest A&F University Business School Hohai University

The question of how to choose a copula model that best fits a given dataset is a predominant limitation of the copula approach, and the present study aims to investigate the techniques of goodness-of-fit tests for multi-dimensional copulas. A goodness-of-fit test based on Rosenblatt＇s transformation was mathematically expanded from two dimensions to three dimensions and procedures of a bootstrap version of the test were provided. Through stochastic copula simulation, an empirical application of historical drought data at the Lintong Gauge Station shows that the goodness-of-fit tests perform well, revealing that both trivariate Gaussian and Student t copulas are acceptable for modeling the dependence structures of the observed drought duration, severity, and peak. The goodness-of-fit tests for multi-dimensional copulas can provide further support and help a lot in the potential applications of a wider range of copulas to describe the associations of correlated hydrological variables. However, for the application of copulas with the number of dimensions larger than three, more complicated computational efforts as well as exploration and parameterization of corresponding copulas are required.

关键词： goodness-of-fit test, multi-dimensional copulas, stochastic simulation Rosenblatt'stransformation, bootstrap approach," drought data

Evaluation of high-resolution satellite precipitation products with surface rain gauge observations from Laohahe Basin in northern China

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Water Science and Engineering 2010年第4期3卷 405-417页

作者： shan-hu jiang Li-liang REN Bin YONG Xiao-li YANG Lin SHI State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering Hohai University Nanjing 210098 P. R. China

Three high-resolution satellite precipitation products, the Tropical Rainfall Measuring Mission （TRMM） standard precipitation products 3B42V6 and 3B42RT and the Climate Precipitation Center＇s （CPC） morphing technique precipitation product （CMORPH）, were evaluated against surface rain gauge observations from the Laohahe Basin in northern China. Widely used statistical validation indices and categorical statistics were adopted. The evaluations were performed at multiple time scales, ranging from daily to yearly, for the years from 2003 to 2008. The results show that all three satellite precipitation products perform very well in detecting the occurrence of precipitation events, but there are some different biases in the amount of precipitation. 3B42V6, which has a bias of 21%, fits best with the surface rain gauge observations at both daily and monthly scales, while the biases of 3B42RT and CMORPH, with values of 81% and 67%, respectively, are much higher than a normal receivable threshold. The quality of the satellite precipitation products also shows monthly and yearly variation： 3B42RT has a large positive bias in the cold season from September to April, while CMORPH has a large positive bias in the warm season from May to August, and they all attained their best values in 2006 （with 10%, 50%, and -5% biases for 3B42V6, 3B42RT, and CMORPH, respectively）. Our evaluation shows that, for the Laohahe Basin, 3B42V6 has the best correspondence with the surface observations, and CMORPH performs much better than 3B42RT. The large errors of 3B42RT and CMORPH remind us of the need for new improvements to satellite precipitation retrieval algorithms or feasible bias adjusting methods.

关键词： satellite precipitation product TRMM 3B42RT TRMM 3B42V6 CMORPH surface rain gauge observation Laohahe Basin

Initiatives to clarify mechanisms of hydrological evolution in human-influenced Yellow River Basin

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Water Science and Engineering 2023年第2期16卷 117-121页

作者： Li-liang Ren shan-shui Yuan Xiao-li Yang shan-hu jiang Gui-bao Li Qiu-an Zhu Xiu-qin Fang Yi Liu Yi-qi Yan State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering Hohai UniversityNanjing 210098China College of Hydrology and Water Resources Hohai UniversityNanjing 210098China Yangtze Institute for Conservation and Development Hohai UniversityNanjing 210098China Chinese Hydraulic Engineering Society Beijing 100053China Hydrology Bureau Yellow River Conservancy CommissionMinistry of Water ResourcesZhengzhou 450003China

Significant changes in water cycle elements/processes have created serious challenges to regional sustainability and high-quality development in the Yellow River Basin in *** is necessary to investigate the impacts of climate change and human activities on hydrological evolution and disaster risk from a holistic perspective of the *** study developed initiatives to clarify the mechanisms of hydrological evolution in the human-influenced Yellow River *** proposed research method includes:(1)a tool to simulate multiple factors and a multi-scale water cycle using a grid-based spatiotemporal coupling approach,and(2)a new algorithm to separate the responses of the water cycle to climate change and human impacts,and de-couple the eco-environmental effects using artificial intelligence *** this research framework,key breakthroughs are expected to be made in the understanding of the impacts of land cover change on the water cycle and blue/green water *** outcomes of this research project are expected to provide theoretical support for ecological protection and water governance in the basin.

关键词： Climate change human activities Hydrological evolution Runoff change Yellow River Basin

Construction of Pd-doped RuO_(2) nanosheets for efficient and stable acidic water oxidation

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Green Energy & Environment 2024年第6期9卷 937-948页

作者： Yibo Liu Xing hu Chenxi Liu shan Zhu Kezhu jiang Feng Liu Shijian Zheng Tianjin Key Laboratory of Materials Laminating Fabrication and Interface Control Technology College of Materials Science and EngineeringHebei University of TechnologyTianjin300401China Yunnan Precious Metals Lab Co. LTDKunming650100China

RuO_(2) has been considered a potential alternative to commercial IrO_(2) for the oxygen evolution reaction(OER)due to its superior intrinsic ***,its inherent structure dissolution in acidic environments restricts its commercial *** this study,we report a novel Pd-doped ruthenium oxide(Pd–RuO_(2))nanosheet catalyst that exhibits improved activity and stability through a synergistic effect of Pd modulation of Ru electronic structure and the two-dimensional *** catalyst exhibits excellent performance,achieving an overpotential of only 204 mVat a current density of 10 mA cm^(-2).Impressively,after undergoing 8000 cycles of cyclic voltammetry testing,the overpotential merely decreased by 5 *** PEM electrolyzer with Pd0.08Ru0.92O_(2) as an anode catalyst survived an almost 130 h operation at 200 mA cm^(-2).To elucidate the underlying mechanisms responsible for the enhanced stability,we conducted an X-ray photoelectron spectroscopy(XPS)analysis,which reveals that the electron transfer from Pd to Ru effectively circumvents the over-oxidation of Ru,thus playing a crucial role in enhancing the catalyst's ***,density functional theory(DFT)calculations provide compelling evidence that the introduction of Pd into RuO_(2) effectively modulates electron correlations and facilitates the electron transfer from Pd to Ru,thereby preventing the overoxidation of ***,the application of the two-dimensional structure effectively inhibited the aggregation and growth of nanoparticles,further bolstering the structural integrity of the catalyst.

关键词： Oxygen evolution reaction Pd-doped ruthenium oxide Two-dimensional structure Electron transfer Stability

A whole-net cooperative positioning method based on CDGNSS and inter-vehicle ranging

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Chinese Journal of Aeronautics 2024年第2期37卷 401-416页

作者： shan hu Hongbo ZHAO Chen ZhuANG School of Electronics and Information Engineering Beihang UniversityBeijing 100191China

Relative positioning is recognized as an important issue for vehicles in urban ***-vehicle Cooperative Positioning(CP)techniques which fuse the Global Navigation Satellite System(GNSS)and inter-vehicle ranging have attracted attention in improving the performance of baseline estimation between ***,current CP methods estimate the baselines separately and ignore the interactions among the positioning information of different *** interactions are called’information coupling’.In this work,we propose a new multivehicle precise CP framework using the coupled information in the network based on the Carrier Differential GNSS(CDGNSS)and inter-vehicle *** demonstrate the benefit of the coupled information by deriving the Cramer-Rao Lower Bound(CRLB)of the float estimation in *** fully use this coupled information,we propose a Whole-Net CP(WN-CP)method which consists of the Whole-Net Extended Kalman Filter(WN-EKF)as the float estimation filter,and the Partial Baseline Fixing(PBF)as the ambiguity resolution *** WN-EKF fuses the measurements of all baselines simultaneously to improve the performance of float estimation,and the PBF strategy fixes the ambiguities of the one baseline to be estimated,instead of full ambiguity resolution,to reduce the computation load of ambiguity *** tests involving four vehicles were conducted in urban *** results show that the proposed WN-CP method can achieve better performance and meanwhile maintain a low computation load compared to the existing methods.

关键词： GNSS Cooperative positioning Baseline Ambiguity resolution Information coupling

An Enhanced Conic Reformulation for Capacity-Constrained Assortment Optimization Under the Mixture of Multinomial Logit Model

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Journal of the Operations Research Society of China 2024年第3期12卷 757-771页

作者： shan jiang Ka-Meng Nip School of Management Xiamen UniversityXiamen361005FujianChina School of Mathematical Sciences Xiamen UniversityXiamen361005FujianChina

In this work,we study the conic quadratic mixed-integer formulation for assortment optimization problem under the mixture of multinomial logit(MMNL)*** MMNL model generalizes the widely studied multinomial logit choice model and can approximate any random utility model with an arbitrary additive *** important operational decision problem in revenue management is assortment optimization problem,which aims to find a subset of products to make available to customers that maximizes the expected revenue of the *** is known that assortment optimization problem under the MMNL model is NP-hard and inapproximable within any constant performance *** used methods for solving such problem are heuristical approaches or customized combinatorial optimization *** the meanwhile,studies related to global optimization approaches are relatively *** propose an enhanced conic quadratic mixed-integer formulation for solving assortment optimization problem under the MMNL model with a higher computational ***,we conduct extensive numerical experiments to demonstrate that the proposed reformulation significantly outperforms the existing conic reformulations for assortment optimization under the MMNL model.

关键词： Assortment optimization MMNL model Conic reformulation Capacitated constrained

NextPolish2:A Repeat-aware Polishing Tool for Genomes Assembled Using HiFi Long Reads

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Genomics, Proteomics & Bioinformatics 2024年第1期22卷 105-109页

作者： jiang hu Zhuo Wang Fan Liang shan-Lin Liu Kai Ye De-Peng Wang School of Automation Science and Engineering Faculty of Electronic and Information EngineeringXi’an Jiaotong UniversityXi’an 710049China GrandOmics Biosciences Beijing 102206China Department of Entomology College of Plant ProtectionChina Agricultural UniversityBeijing 100193China

The high-fidelity(HiFi)long-read sequencing technology developed by PacBio has greatly improved the base-level accuracy of genome ***,these assemblies still contain base-level errors,particularly within the error-prone regions of HiFi long *** genome polishing tools usually introduce overcorrections and haplotype switch errors when correcting errors in genomes assembled from HiFi long ***,we describe an upgraded genome polishing tool-NextPolish2,which can fix base errors remaining in those“highly accurate”genomes assembled from HiFi long reads without introducing excessive overcorrections and haplotype switch *** believe that NextPolish2 has a great significance to further improve the accuracy of telomere-to-telomere(T2T)***2 is freely available at https://***/Nextomics/NextPolish2.

关键词： Telomere-to-telomere Genome assembly Genome polishing Error correction HiFi long read

Microlensing bias on the detection of strong lensing gravitational wave

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Science China(Physics,Mechanics & Astronomy) 2024年第6期67卷 156-165页

作者： Xikai shan Xuechun Chen Bin hu Guoliang Li Institute for Frontier in Astronomy and Astrophysics Beijing Normal UniversityBeijing 102206China Department of Astronomy Beijing Normal UniversityBeijing 100875China Purple Mountain Observatory Chinese Academy of SciencesNanjing 210023China

Identifying strong lensing gravitational wave(SLGW)events is of utmost importance in astrophysics as we approach the historic first detection of SLGW amidst the growing number of gravitational wave(GW)***,one crucial method for identifying SLGW signals involves assessing the overlap of parameters between two ***,the distribution of discrete matter,such as stars and sub-halos,within the strong lensing galaxy can imprint a wave optical(WO)effect on the SLGW *** frequency dependent imprints introduce biases in parameter estimation and impact SLGW *** this study,we assess the influence of the stellar microlensing field embedded in a strong lensing *** findings demonstrate that the WO effect reduces the detection efficiency of SLGW by 5%-50%for various false alarm probabilities per pair(FAPper pair).Specifically,at an FAPper pairof 10^(-5),the detection efficiency decreases from~10%to~5%.Consequently,the presence of the microlensing field can result in missing half of the strong lensing ***,the microlensing WO effect introduces a noticeable bias in intrinsic parameters,particularly for chirp mass and mass ***,it has tiny influence on extrinsic *** all parameters,~30%of events exhibit a 1σparameter bias,~12%exhibit a 2σparameter bias,and~5%exhibit a 3σparameter bias.

关键词： gravitational wave gravitational strong lensing gravitational micro lensing wave optical effect

Energy-Efficient Traffic Offloading for RSMA-Based Hybrid Satellite Terrestrial Networks with Deep Reinforcement Learning

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China Communications 2024年第2期21卷 49-58页

作者： Qingmiao Zhang Lidong Zhu Yanyan Chen shan jiang National Key Laboratory of Science and Technology on Communications University of Electronic Science and Technology of ChinaChengdu 611731China The Higher Educational Key Laboratory for Flexible Manufacturing Equipment Integration of Fujian Province Xiamen Institute of TechnologyXiamen 361021China China Mobile(jiangxi)Communications Group Co. LtdYichun 336000China

As the demands of massive connections and vast coverage rapidly grow in the next wireless communication networks, rate splitting multiple access(RSMA) is considered to be the new promising access scheme since it can provide higher efficiency with limited spectrum resources. In this paper, combining spectrum splitting with rate splitting, we propose to allocate resources with traffic offloading in hybrid satellite terrestrial networks. A novel deep reinforcement learning method is adopted to solve this challenging non-convex problem. However, the neverending learning process could prohibit its practical implementation. Therefore, we introduce the switch mechanism to avoid unnecessary learning. Additionally, the QoS constraint in the scheme can rule out unsuccessful transmission. The simulation results validates the energy efficiency performance and the convergence speed of the proposed algorithm.

关键词： deep reinforcement learning energy efficiency hybrid satellite terrestrial networks rate splitting multiple access traffic offloading