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When a tree model meets texture baking:an approach for quality-preserving lightweight visualization in virtual 3D scene construction

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International Journal of Digital Earth 2023年第1期16卷 645-670页

作者： Chen Zhang Biao He Renzhong Guo Ding Ma School of Resource and Environmental Sciences Wuhan UniversityWuhanPeople’s Republic of China research institute for smart cities Shenzhen UniversityShenzhenPeople’s Republic of China

Three-dimensional(3D)high-fidelity surface models play an important role in urban scene ***,the data quantity of such models is large and places a tremendous burden on *** applications must balance the visual quality of the models with the rendering *** study provides a practical texture baking processing pipeline for generating 3D models to reduce the model complexity and preserve the visually pleasing ***,we apply a mesh simplification to the original model and use texture baking to create three types of baked textures,namely,a diffuse map,normal map and displacement *** simplified model with the baked textures has a pleasing visualization effect in a rendering ***,we discuss the influence of various factors in the process on the results,as well as the functional principles and characteristics of the baking *** proposed approach is very useful for real-time rendering with limited rendering hardware as no additional memory or computing capacity is required for properly preserving the relief details of the *** step in the pipeline is described in detail to facilitate the realization.

关键词： Texture baking tree modeling natural scene construction lightweight visualization 3D real scene

Numerical modeling of solute transport in deformable unsaturated layered soil

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Water Science and Engineering 2017年第3期10卷 184-196页

作者： Sheng Wu Dong-sheng Jeng cities research institute Griffith School of EngineeringGriffith UniversitySouthport 4222Australia

The effect of soil stratification was studied through numerical investigation based on the coupled model of solute transport in deformable unsaturated soil. The theoretical model implied two-way coupled excess pore pressure and soil deformation based on Biot's consolidation theory as well as a one-way coupled volatile pollutant concentration field developed from the advection-diffusion theory. Embedded in the model, the degree of saturation, fluid compressibility, self-weight of the soil matrix, porosity variance, longitudinal dispersion, and linear sorption were computed. Based on simulation results of a proposed three-layer landfill model using the finite element method, the multi-layer effects are discussed with regard to the hydraulic conductivity, shear modulus, degree of saturation, molecular diffusion coefficient, and thickness of each layer. Generally speaking, contaminants spread faster in a stratified field with a soft and highly permeable top layer; soil parameters of the top layer are more critical than the lower layers but controlling soil thicknesses will alter the results. This numerical investigation showed noticeable impacts of stratified soil properties on solute migration results, demonstrating the importance of correctly modeling layered soil instead of simply assuming the averaged properties across the soil profile.

关键词： Solute transport Layered soil Consolidation Unsaturated soil Deformable media

Impedance Analysis of Grid Forming Control Based Modular Multilevel Converters

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Journal of Modern Power Systems and Clean Energy 2023年第3期11卷 967-979页

作者： Rongcai Pan Guangfu Tang Shan Liu Zhiyuan He China Electric Power research institute Beijing 100192China State Grid smart Grid research institute Beijing 102209China

Grid-forming control(GFC)is promising for power electronics based power systems with high renewable energy ***,the impedance modeling for GFC is necessary and has gained significant attention ***,most of the impedance analyses for GFC are based on a twolevel converter(TLC)rather than a modular multilevel converter(MMC).MMC differs from TLC with respect to its dominant multi-frequency *** is necessary to analyze the impedance of GFC-based MMC owing to its superiority in highvoltage direct current(HVDC)transmission to interlink two weak AC systems with high renewable energy *** the main contribution,this paper presents the AC-and DC-side impedance analyses for the GFC-based MMC with both power and DC voltage control using the harmonic transfer function(HTF),and compares the impedances of GFC-based MMC and *** is inferred that although the impedance is mainly influenced within 200 Hz,the instability still could occur owing to negative resistance triggered by relatively larger *** difference in AC-side impedance with power and DC voltage control is not apparent with proper parameters,while the DC-side impedance differs *** generalized Nyquist criterion is necessary for AC-side stability owing to the relatively large coupling terms under ***,the coupling between AC-and DC-side impedances is noneligible,especially considering the DC-side resonance around the system resonant *** effects of parameters,system strength,and virtual impedance on the impedance shaping are analyzed and verified through simulations.

关键词： Sequence impedance modular multilevel converter(MMC) grid-forming control(GFC) harmonic transfer function generalized Nyquist criterion

R&D and application of voltage sourced converter based high voltage direct current engineering technology in China

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Journal of Modern Power Systems and Clean Energy 2014年第1期2卷 1-15页

作者： Guangfu TANG Zhiyuan HE Hui PANG State Grid smart Grid research institute Beijing 102200China

As a new generation of direct current(DC)transmission technology,voltage sourced converter(VSC)based high voltage direct current(HVDC)has been widely developed and applied all over the *** has also carried out a deep technical research and engineering application in this area,and at present,it has been stepped into a fast growing *** paper gives a general review over China’s VSC based HVDC in terms of engineering technology,application and future *** comprehensively analyzes the technical difficulties and future development orientation on the aspects of the main configurations of VSC based HVDC system,topological structures of converters,control and protection technologies,flexible DC cables,converter valve tests,*** introduces the applicable fields and current status of China’s VSC based HVDC projects,and analyzes the application trends of VSC based HVDC projects both in China and all over the world according to the development characteristics and demands of future power grids.

关键词： Voltage sourced converter based high voltage direct current(VSC based HVDC) Two-level converter Modular multi-level converter(MMC) Direct current grid(DC grid)

Understanding urban structures and crowd dynamics leveraging large-scale vehicle mobility data

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Frontiers of Computer Science 2020年第5期14卷 77-88页

作者： Zhihan Jiang Yan Liu Xiaoliang Fan Cheng Wang Jonathan Li Longbiao Chen Fujian Key Laboratory of Sensing and Computing for smart cities School of Information Science and EngineeringXiamen UniversityXiamen361005China

A comprehensive understanding of city structures and urban dynamics can greatly improve the efficiency and quality of urban planning and management,while the traditional approaches of which,such as manual surveys,usually incur substantial labor and *** this paper,we propose a data-driven framework to sense urban structures and dynamics from large-scale vehicle mobility ***,we divide the city into fine-grained grids,and cluster the grids with similar mobility features into structured urban areas with a proposed distance-constrained clustering algorithm(DCCA).Second,we detect irregular mobility traffic patterns in each area leveraging an ARIMA-based anomaly detection algorithm(ADAM),and correlate them to the urban social and emergency ***,we build a visualization system to demonstrate the urban structures and crowd *** evaluate our framework using real-world datasets collected from Xiamen city,China,and the results show that the proposed framework can sense urban structures and crowd comprehensively and effectively.

关键词： vehicle mobility big data spatial clustering event detection urban computing ubiquitous computing

A joint model of infrastructure planning and smart charging strategies for shared electric vehicles

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Green Energy and Intelligent Transportation 2024年第4期3卷 44-58页

作者： Junbei Liu Xiong Yang Chengxiang Zhuge Department of Land Surveying and Geo-Informatics The Hong Kong Polytechnic UniversityHung HomKowloonHong KongChina The Hong Kong Polytechnic University Shenzhen research institute ShenzhenChina smart cities research institute The Hong Kong Polytechnic UniversityHong KongChina

This paper presents a data-driven joint model designed to simultaneously deploy and operate infrastructure for shared electric vehicles(SEVs).The model takes into account two prevalent smart charging strategies:the Time-of-Use(TOU)tariff and Vehicle-to-Grid(V2G)*** specifically quantify infrastructural demand and simulate the travel and charging behaviors of SEV users,utilizing spatiotemporal and behavioral data extracted from a SEV trajectory *** findings indicate that the most cost-effective strategy is to deploy slow chargers exclusively at rental *** SEV operators,the use of TOU and V2G strategies could potentially reduce charging costs by 17.93%and 34.97%*** the scenarios with V2G applied,the average discharging demand is 2.15kWh per day per SEV,which accounts for 42.02%of the actual average charging demand of *** findings are anticipated to provide valuable insights for SEV operators and electricity companies in their infrastructure investment decisions and policy formulation.

关键词： Electric carsharing Charging infrastructure smart charging Big data Micro-simulation

Randomized Latent Factor Model for High-dimensional and Sparse Matrices from Industrial Applications

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IEEE/CAA Journal of Automatica Sinica 2019年第1期6卷 131-141页

作者： Mingsheng Shang Xin Luo Zhigang Liu Jia Chen Ye Yuan MengChu Zhou the Chongqing Engineering research Center of Big Data Application for smart cities and Chongqing Key Laboratory of Big Data and Intelligent ComputingChongqing Institute of Green and Intelligent TechnologyChinese Academy of Sciences the School of Computer Science and Engineering Beihang University the Department of Electrical and Computer Engineering New Jersey Institute of Technology

Latent factor(LF) models are highly effective in extracting useful knowledge from High-Dimensional and Sparse(HiDS) matrices which are commonly seen in various industrial applications. An LF model usually adopts iterative optimizers,which may consume many iterations to achieve a local optima,resulting in considerable time cost. Hence, determining how to accelerate the training process for LF models has become a significant issue. To address this, this work proposes a randomized latent factor(RLF) model. It incorporates the principle of randomized learning techniques from neural networks into the LF analysis of HiDS matrices, thereby greatly alleviating computational burden. It also extends a standard learning process for randomized neural networks in context of LF analysis to make the resulting model represent an HiDS matrix *** results on three HiDS matrices from industrial applications demonstrate that compared with state-of-the-art LF models, RLF is able to achieve significantly higher computational efficiency and comparable prediction accuracy for missing data.I provides an important alternative approach to LF analysis of HiDS matrices, which is especially desired for industrial applications demanding highly efficient models.

关键词： Big data high-dimensional and sparse matrix latent factor analysis latent factor model randomized learning

High Frequency Stability Constraints Based MMC Controller Design Using NSGA-III Algorithm

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CSEE Journal of Power and Energy Systems 2023年第2期9卷 623-633页

作者： Ke Ji Weiming Chen Xueguang Wu Hui Pang Jingxuan Hu Shan Liu Fan Cheng Guangfu Tang China Electric Power research institute Beijing 100192China Chen is with State Grid Fujian Electric Power research institute Fuzhou 350007China State Grid smart Grid research institute Beijing 102211China

The occurrence of high frequency resonances(HFRs)has been frequently observed in several MMC-HVDC *** avoid these HFRs,the controller design of an MMC must satisfy two requirements:1)The controller should remain stable while in the high frequency range,and 2)MMC impedance should not possess a negative real part in the high frequency *** far,majority of the related studies on MMC controller design have been unable to address these requirements *** paper first describes the simplified high frequency MMC impedance model developed indigenously by the ***,the driving mechanism of two kinds of HFRs is revealed using the said developed model,including:1)MMC controller instability,and 2)Interaction instability between MMC and AC ***,the mathematical expressions outlining the controller stability constraint and positive damping constraint are ***,NSGA-III based multi-objective optimization algorithm is adopted,to identify the region most suitable for satisfying the proposed stability constraints under the MMC controller *** proposed controller design method is capable of effectively evading the HFRs triggered by the incompatible *** detailed time-domain simulations generated using PSCAD/EMTDC software validate the proposed designed method and endorse the improved results.

关键词： AC cable controller parameter optimization harmonic resonance MMC NSGA-III offshore wind power integration

Distributed Robust Energy and Reserve Dispatch for Coordinated Transmission and Active Distribution Systems

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Journal of Modern Power Systems and Clean Energy 2023年第5期11卷 1494-1506页

作者： Yongli Ji Qingshan Xu Yuanxing Xia smart Grid research institute Nanjing Institute of TechnologyNanjing 211167China School of Electrical Engineering Southeast UniversityNanjing 210096China

The increasing penetration of renewable energy sources introduces higher requirements for the operation flexibility of transmission system(TS) and connected active distribution systems(DSs). This paper presents an efficient distributed framework for the TS and DSs to work cooperatively yet independently. In addition to conventional power interaction, upward and downward reserve capacities are exchanged to form the feasible access regions at the boundaries that apply to different system operation situations. A distributed robust energy and reserve dispatch approach is proposed under this framework. The approach utilizes the supply-and demand-side resources in different systems to handle various uncertainties and improve overall efficiency and reliability. In particular, integrated as aggregated virtual energy storage(AVES) devices, air-conditioning loads are incorporated into the optimal dispatch. In addition, a reserve model with charging/discharging-state elasticity is developed for AVESs to enhance system flexibility and provide additional reserve support. Different cases are compared to verify the effectiveness and superiority of the proposed approach.

关键词： Air-conditioning load distributed coordination feasible access region interregional energy and reserve support transmission and active distribution system