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Efficient Dual Algorithms for Image Segmentation Using TV-Allen-Cahn Type Models

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Communications in Computational Physics 2011年第4期9卷 859-877页

作者： Li-lian Wang Ying gu Division of Mathematical Sciences School of Physical and Mathematical SciencesNanyang Technological University637371Singapore

Variational image segmentation based on the Mumford and Shah model[31],together with implementation by the piecewise constant level-set method(PCLSM)[26],leads to fully nonlinear Total Variation(TV)-Allen-Cahn *** commonlyused numerical approaches usually suffer from the difficulties not only with the nondifferentiability of the TV-term,but also with directly evolving the discontinuous piecewise constant-structured *** this paper,we propose efficient dual algorithms to overcome these *** use of a splitting-penalty method results in TVAllen-Cahn type models associated with different"double-well"potentials,which allow for the implementation of the dual algorithm of Chambolle[8].Moreover,we present a new dual algorithm based on an edge-featured penalty of the dual variable,which only requires to solve a vectorial Allen-Cahn type equation with linear∇(div)-diffusion rather than fully nonlinear diffusion in the Chambolle’s ***,more efficient numerical algorithms such as time-splitting method and Fast Fourier Transform(FFT)can be *** numerical tests show that two dual algorithms are much faster and more stable than the primal gradient descent approach,and the new dual algorithm is at least as efficient as the Chambolle’s algorithm but is more *** demonstrate that the new method also provides a viable alternative for image restoration.

关键词： Variational models image segmentation TV-Allen-Cahn type equations dual algorithms splitting-penalty methods FFT.

Finite element response sensitivity analysis of three-dimensional soil-foundation-structure interaction (SFSI) systems

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Earthquake Engineering and Engineering Vibration 2018年第3期17卷 555-566页

作者： gu quan Liu Yongdou Li Yong Lin Chun School of Architecture and Civil Engineering Xiamen University Department of Civil and Environmental Engineering University of Alberta

The nonlinear finite element（FE） analysis has been widely used in the design and analysis of structural or geotechnical *** response sensitivities（or gradients） to the model parameters are of significant importance in these realistic engineering *** the sensitivity calculation has lagged behind,leaving a gap between advanced FE response analysis and other research hotspots using the response *** response sensitivity analysis is crucial for any gradient-based algorithms,such as reliability analysis,system identification and structural *** various sensitivity analysis methods,the direct differential method（DDM） has advantages of computing efficiency and accuracy,providing an ideal tool for the response gradient *** paper extended the DDM framework to realistic complicated soil-foundation-structure interaction（SFSI） models by developing the response gradients for various constraints,element and materials *** enhanced framework is applied to three-dimensional SFSI system prototypes for a pilesupported bridge pier and a pile-supported reinforced concrete building frame structure,subjected to earthquake loading *** DDM results are verified by forward finite difference method（FFD）.The relative importance（RI） of the various material parameters on the responses of SFSI system are investigated based on the DDM response sensitivity *** FFD converges asymptotically toward the DDM results,demonstrating the advantages of DDM（e.g.,accurate,efficient,insensitive to numerical noise）.Furthermore,the RI and effects of the model parameters of structure,foundation and soil materials on the responses of SFSI systems are investigated by taking advantage of the sensitivity analysis *** extension of DDM to SFSI systems greatly broaden the application areas of the d gradient-based algorithms,*** model updating and nonlinear system identification of complicated SFSI systems.

关键词： finite element method response sensitivity analysis direct differentiation method finite difference method soil-foundation-structure interaction

Distributed Harmonic Power Sharing with Voltage Distortion Suppression in Islanded Microgrids Considering Non-linear Loads

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CSEE Journal of Power and Energy Systems 2024年第1期10卷 117-128页

作者： guannan Lou Shanlin Li Wei gu quan Yang School of Electrical Engineering Southeast UniversityNanjingJiangsu 210096China the Jiangsu Provincial Key Laboratory of Smart Grid Technology and Equipment Southeast University Dongguan Power Supply Bureau of guangdong Power Grid Company Guangdong 523000China

In contemporary power grids or microgrids,harmonic distortion has emerged as one of the critical power quality issues for utility power grids,which has escalated especially due to the high penetration of power-electronic-converter-interfaced distributed generation(DG).This paper first illustrates the prevalent dispute revolving around the harmonic power sharing and distortion restraint,and subsequently proposes a consensusbased framework that facilitates an accurate sharing of harmonics among multi-DGs connected in parallel,with an effective suppression of the output voltage *** with the majority of existing studies addressing the issue of voltage harmonics at the point of common coupling(PCC),our method primarily emphasizes on the output voltage distortion since the power quality requirement for certain local critical loads is often known to be *** the help of adaptive regulation,the overall distortion produced at the output terminals of DGs can be retained within an acceptable *** working principle of the proposed control method,which is not only easy to implement but also independent of model parameters,is further described in *** the small-signal dynamic model,the system stability and robustness are *** hardware-in-the-loop(HIL)simulations aid in determining the outcome of the proposed strategy in microgrid control.

关键词： Distributed generation droop control harmonic power sharing microgrid voltage distortion mitigation

EXPERT DISCOVERY AND KNOWLEDGE MINING IN COMPLEX MULTI-AGENT SYSTEMS

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Journal of Systems Science and Systems Engineering 2007年第2期16卷 222-234页

作者： Minjie ZHANG Xijin TANG quan BAI Jifa gu School of Computer Science and Software Engineering University of Wollongong Wollongong NSW 2522 Australia Instttute of System Sctence Chinese Academy of Sciences Beijing 100080 China

Complex problem solving requires diverse expertise and multiple techniques. In order to solve such problems, complex multi-agent systems that include both of human experts and autonomous agents are required in many application domains. Most complex multi-agent systems work in open domains and include various heterogeneous agents. Due to the heterogeneity of agents and dynamic features of working environments, expertise and capabilities of agents might not be well estimated and presented in these systems. Therefore, how to discover useful knowledge from human and autonomous experts, make more accurate estimation for experts＇ capabilities and find out suitable expert（s） to solve incoming problems （＂Expert Mining＂） are important research issues in the area of multi-agent system. In this paper, we introduce an ontology-based approach for knowledge and expert mining in hybrid multi-agent systems. In this research, ontologies are hired to describe knowledge of the system. Knowledge and expert mining processes are executed as the system handles incoming problems. In this approach, we embed more self-learning and self-adjusting abilities in multi-agent systems, so as to help in discovering knowledge of heterogeneous experts of multi-agent systems.

关键词： Knowledge discovery knowledge mining expert mining multi-agent system

Experimental study of wind loads on gable roofs of low-rise buildings with overhangs

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Frontiers of Structural and Civil Engineering 2018年第3期12卷 300-317页

作者： Peng HUANG Ling TAO Ming gu Yong quan i University Shanghai 200092China

Gable roofs with overhangs （eaves） are the common constructions of low-rise buildings on the southeastern coast of China, and they were vulnerable to typhoons from experience. The wind pressure distributions on gable roofs of low-rise buildings are investigated by a series of wind tunnel tests which consist of 99 test cases with various roof pitches, height-depth ratios and width-depth ratios. The block pressure coefficients and worst negative （block） pressure coefficients on different roof regions of low-rise buildings are proposed for the main structure and building envelope, respectively. The effects of roof pitch, height-depth ratio, and width-depth ratio on the pressure coefficients of each region are analyzed in detail. In addition, the pressure coefficients on the roofs for the main structure and building envelope are fitted according to roof pitch, height-depth ratio and width-depth ratio of the low-rise building. Meanwhile, the rationality of the fitting formulas is verified by comparing the fitting results with the codes of different countries. Lastly, the block pressure coefficients and worst negative pressure coefficients are recommended to guide the design of low-rise buildings in typhoon area and act as references for the future＇s modification of wind load codes.

关键词： low-rise building gable roof wind loads wind tunnel test block pressure coefficient load code

Covering α-Fe2O3 protection layer on the surface of p-Si micropillar array for enhanced photoelectrochemical performance

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Frontiers of Environmental Science & Engineering 2017年第6期11卷 119-127页

作者： Jing gu Hongtao Yu Xie quan Shuo Chen Key Laboratory of Industrial Ecology and Environmental Engineering (Ministry of Education) School of Environmental Science and Technology Dalian University of Technology Dalian 116024 China

The spontaneous oxidation process of pristine silicon （Si） limits its application as photocatalyst or electrode in aqueous solution or moist air. Covering a protection layer on Si surface is an effective approach to overcome this disadvantage. In this paper, α-Fe2O3 is demonstrated to be an excellent alternative as a protection material, α-Fe2O3 layer was deposited around each p-type Si micropillar （SiMP） in well-ordered array by chemical bath ＂deposition ＂method. The diameter of SiMP was 3 μm and the thickness of α-Fe2O3 layer was about 20 nm. The photoeletrochemical stability of SiMP/α-Fe2O3 was proved by 10 circles cyclic voltammetr7 testing. Compared with SiMP, its optical absorption and photocurrent density improved 2 times and 4 times, respectively, and its onset potential for hydrogen evolution moved positively about 0.4 V. These improved performances could be ascribed to the enhanced photogenemted-charge-separation efficiency deriving from built-in electric field at the interface between Si and α-Fe2O3. The above results show an effective strategy to utilize Si material as photocatalyst or electrode in aqueous solution or moist air.

关键词： Si α-Fe2O3 Photoelectrochemistry Photogenemted charge separation

Synthesis and ion exchange properties for Cs^+ of ammonium-type mordenite

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Rare Metals 2015年第10期34卷 752-756页

作者： Dian-quan Dong Jian-guo Zheng Xian-lian Han College of Chemical Engineering School of Qingdao University of Science and Technology

Cesium content in the seawater is 3.0 9 10-4 mg·L-1, and ammonium-type mordenite was used to exchange cesium from cesium source. K-type mordenite was obtained by hydrothermal synthesis method. After ammonium-modified, ion exchange properties such as saturated ion exchange capacities and selectivity coefficients for alkali metal ions were determined. At the same time, ion exchange isothermal curves of ammonium-type mordenite for Cs+ and NH4+ were determined at 25°*** electrolyte solution theory was used to work out activity coefficients of the system, and the Kielland diagram of the ion exchange system was obtained. The calculated equilibrium constant(Ka) and ion free enthalpy(DG0) of mordenite for Cs+ and NH4+ are 1.455 and -930.3J·mol-1, respectively, indicating that ion exchange process of ammonium-type mordenite for cesium is a spontaneous process.

关键词： Ion exchange Thermodynamics Mordenite Cesium

In-situ SEM Observation of Monotonic and Cyclic Deformed Structure in Ti-2A1-2.5Zr Alloy

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Journal of Materials Science & Technology 2001年第1期17卷 37-38页

作者： Zhentao YU lian ZHOU Haichen gu Ju DENG Northwest institute for Nonferrous Metal Research P.O.Box 51Xi’an 710016China Materials Science and Engineering College Xi’an Jiaotong UniversityXi’an 710049China

The SEM observation in situ of monotonic and cyclic deformed structure in Ti-ZA1-2.5Zr alloy was performed. The regularity of slippage, crack nucleation, propagation and the typical dislocation configuration were also investigated. The twin and twist play an important role in maintaining homogeneous deformation in the final plastic deformation stage.

关键词： plastic deformation in situ

Preface: Advances in OpenSees Applications to Civil Engineering

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Computer Modeling in Engineering & Sciences 2019年第9期120卷 467-470页

作者： Joel Conte Frank McKenna quan gu Department of Structural Engineering University of California at San DiegoLa JollaCA 92093USA NHERI SimCenter University of CaliforniaBerkeleyRichmond Field StationRichmondCA 94804USA School of Architecture and Civil Engineering Xiamen UniversityXiamenChina.

This special issue is dedicated to the memory of a world-renowned expert in earthquake engineering,Professor Stephen ***(October 16,1946-February 10,2018),for his educational efforts and visionary research contributions that spanned theory,numerical modeling,computer simulation,laboratory experiments,field testing,and design code *** decades of prolific,enthusiastic,and selfless service to the academia,profession and industry as well as his friendship will be remembered *** his capacity as the Director of the Pacific Earthquake Engineering Research(PEER)Center(2009-2015),Professor Mahin was steadfast in supporting the development and application of OpenSees(i.e.,Open System for Earthquake Engineering Simulation).To recognize his great efforts,this special issue is about the applications of OpenSees in civil engineering,and Computer Modeling in Engineering&Sciences(CMES)is a suitable journal for this special issue.

关键词： earthquake Director supporting