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Fault ride-through of renewable energy conversion systems during voltage recovery

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Journal of Modern Power Systems and Clean Energy 2016年第1期4卷 28-39页

作者： Ruiqi LI Hua geng geng YANG Department of Automation Tsinghua UniversityBeijing 100084China

Asymmetrical voltage swells during recovery of a short-circuit fault lead to fluctuations in the dc-link voltage of a renewable energy conversion system(RECS),and may induce reversed power flow and even trip the RECS. This paper studies characteristics of both typical causes resulting in the practical asymmetrical voltage swell and the voltage at the point of common coupling(PCC)during the fault recovery. As analyzed, the fault recovery process can be divided into two continuous periods in which different control strategies have to be applied. Also protective measures are necessary in the transient period of the process. Additionally, the asymmetrical high-voltage ride-through capability and the controllability criteria of the RECS are analyzed based on eliminating the fluctuations. Furthermore, an asymmetrical control scheme is proposed to maintain the controllability of the RECS and ride through the entire recovery process. As verified by the simulation, the scheme can promise the RECS to deal with the practical fault recovery period and mitigate the dc-link voltage fluctuations, which improves the reliability of the RECS and the power system.

关键词： Inverter Renewable energy conversion system Asymmetrical grid voltage High-voltage ride-through(HVRT) Limit analysis

Randomized difference-based gradient-free algorithm for distributed resource allocation

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Science China(Information Sciences) 2022年第4期65卷 212-228页

作者： Xiaoxue geng Wenxiao ZHAO Key Laboratory of Systems and Control Institute of Systems Science Academy of Mathematics and Systems ScienceChinese Academy of Sciences School of Mathematical Sciences University of Chinese Academy of Sciences

This paper considers a distributed resource allocation problem over time-varying networks. The objective of each agent in the network is to optimize the sum of separable convex functions subjected to resource constraints by observing its local objective function and the information exchanged with its adjacent neighbors. Thus, the problem lies in a distributed framework. In existing literature dealing with similar problems, the measurement of the gradients/subgradients of the objective functions has been applied in the algorithm design. In this paper, by adding stochastic dithers to the local objective functions and constructing randomized differences, we propose a distributed gradient-free algorithm for solving the problem, and show that the algorithm is strongly convergent; that is, the estimates generated from each agent almost certainly converge to the optimal resource allocation solution of the network. Finally, the effectiveness of the algorithm is validated by conducting numerical experiments.

关键词： resource allocation distributed algorithm randomized difference

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Leukocyte immunoglobulin-like receptor B2 overexpression as a promising therapeutic target and noninvasive screening biomarker for colorectal cancer

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World Journal of Gastroenterology 2023年第37期29卷 5313-5326页

作者： Qian-Qian Wang Lei Zhou geng Qin Chang tan Yuan-Chen Zhou Shu-Kun Yao Department of Gastroenterology Peking University China-Japan Friendship School of Clinical MedicineBeijing 100029China Department of General Surgery China-Japan Friendship HospitalBeijing 100029China Department of Gastroenterology China-Japan Friendship HospitalBeijing 100029China

BACKGROUND Colorectal cancer(CRC)has become the second most deadly malignancy in the world,and the exploration of screening markers and precise therapeutic targets is *** previous research identified leukocyte immunoglobulin-like receptor B2(LILRB2)protein as a characteristic protein of CRC,but the association between LILRB2 expression and clinicopathological features,the internal mechanism related to CRC progression,and screening diagnostic efficacy are not ***,we hypothesized that LILRB2 is significantly highly expressed in CRC tissues,correlated with advanced stage and a poor prognosis,and could be used as a therapeutic target and potential screening biomarker for *** To explore whether LILRB2 can be used as a potential therapeutic target and noninvasive screening biomarker for *** Patients who underwent radical surgery for CRC at China-Japan Friendship Hospital between February 2021 and October 2022 were *** and paracancerous tissues were collected to verify LILRB2 expression,and the association between LILRB2 expression and clinicopathological features was *** was collected from CRC patients,adenoma patients and healthy controls during the same period to assess the diagnostic value of LILRB2 as a noninvasive screening biomarker,and its diagnostic value was further compared with that of the traditional markers carcinoembryonic antigen(CEA)and carbohydrate antigen 19-9(CA19-9).RESULTS A total of 58 CRC patients were included,and LILRB2 protein was significantly overexpressed in cancer tissues compared with paracancerous tissues(Ptant metastasis,advanced tumor-node-metastasis stage and a poor prognosis(P<0.05),which sugg

关键词： Colorectal cancer Leukocyte immunoglobulin-like receptor B2 Angiopoietin-like protein 2 Therapeutic target Noninvasive screening biomarker

Homogenization of Elliptic Problems with Neumann Boundary Conditions in Non-smooth Domains

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Acta Mathematica Sinica,English Series 2018年第4期34卷 612-628页

作者： Jun geng School of Mathematics and Statistics Lanzhou University

We consider a family of second-order elliptic operators {LE } in divergence form with rapidly oscillating and periodic coefficients in Lipschitz and convex domains in Rn. We are able to show that the uniform WI＇p estimate of second order elliptic systems holds for 2n/n＋1-δ〈p〈2n/n-1＋δ where δ 〉 0 is independent of ~ and the ranges are sharp for n = 2, 3. And for elliptic equations in Lipschitz domains,the W1,p estimate is true for 3/2 -δ 〈 p〈 3 ＋ δ ifn ≥ 4, similar estimate was extended to domains, the WI＇p estimate is true for nconvex domains for 1 〈 p 〈 ∞.

关键词： Homogenization elliptic non-smooth

Global Burden of Disease, Injury and Risk Factor Study 2010: Its Policy Implications for China

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Biomedical and Environmental Sciences 2014年第1期27卷 45-48页

作者： YU Shi Cheng tan Feng ZHOU Mai geng LIU Shi Wei ZHU Xiao Jun ZHU Yu Ling Chinese Center for Disease Control and Prevention (China CDC) National Institute for Occupational Health and Poison Control China CDC National Center for Non-communicable Chronic Disease Control China CDC

Results of the Global Burden of Disease, Injury and Risk Factor Study 2010 （GBD 2010） were released on December 13, 2012 in London, a series of papers concerning the project have been published in the Lancet[1]. Research findings of the project have been reported in the United States, the United Kingdom, Indonesia, China[2] and Australia, and widely applied across the world. In addition, the GBD 2010 will see more countries report their project research findings and implement these findings in the near future. The GBD 2010 provides researchers, administrators and policymakers with new and critical sources for their research, teaching and policymaking.

关键词： 2010 Global Burden of Disease Its Policy Implications for China

Ultramicro molybdenum nitride powder prepared using high-energy mechanochemical method

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Rare Metals 2008年第3期27卷 303-307页

作者： AN geng LIU Gaojie Technical Center Jinduicheng Molybdenum Co. Ltd Xi＇an 710075 China School of Materials Science and Engineering Xi＇an Jiaotong University Xi＇an 710049 China

Using the specially designed mechanochemical ball-mill equipment, ultramicro molybdenum nitride powders were prepared from pure molybdenum powders in ammonia atmosphere at room temperature by high-energy ball milling. The structure and the particle size of the powders were investigated by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, and transmission electron microscopy （TEM）. The results show that the mass ratio of grinding media to powder was 8：1, after milling for 30 h the Mo2N of fcc structure was obtained, and the average particle size of the powders was around 100 nm. It is found that the chemisorption of ammonia onto the fresh molybdenum surfaces created by milling was the predominant process during solid-gas reaction, and the energy input due to introduction of highly dense grain boundaries and lattice defects offered the activation energy for the transition from Mo-N chemisorption to molybdenum nitride. In addition, the change of Mo electronic undersaturation induced by the grain refining accelerated the bonding between Mo and N. The mechanism model of whole nitriding reaction was given, During the high-energy ball milling processing, the rotational speed of milling played a critical role in determining the overall reaction speed.

关键词： material preparation molybdenum nitride mechanochemical method ultramicro powder

Soft video parsing by label distribution learning

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Frontiers of Computer Science 2019年第2期13卷 302-317页

作者： Miaogen LING Xin geng Department of Computer Science and Engineering Southeast University Nanjing 211189 China

In this paper, we tackle the problem of segmenting out a sequence of actions from videos. The videos contain background and actions which are usually composed of ordered sub-actions. We refer the sub-actions and the background as semantic units. Considering the possible overlap between two adjacent semantic units, we propose a bidirectional sliding window method to generate the label distributions for various segments in the video. The label distribution covers a certain number of semantic unit labels, representing the degree to which each label describes the video segment. The mapping from a video segment to its label distribution is then learned by a Label Distribution Learning (LDL) algorithm. Based on the LDL model, a soft video parsing method with segmental regular grammars is proposed to construct a tree structure for the video. Each leaf of the tree stands for a video clip of background or sub-action. The proposed method shows promising results on the THUMOST4, MSR-II and UCF101 datasets and its computational complexity is much less than the compared state-of-the-art video parsing method.

关键词： video parsing label distribution learning subactions graduality

Preparation of ultramicro molybdenum carbide powders and study on wear properties of their coating

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Rare Metals 2011年第3期30卷 262-266页

作者： AN geng LIU Gaojie Technical Center Jinduicheng Molybdenum Co. Ltd Xi＇an 710077 China School of Material Science and Engineering Xi＇an Jiaotong University Xi＇an 710049 China

Using specially designed mechanochemical ball-mill equipment, ultramicro molybdenum carbide （MoC） powders were prepared by high-energy ball milling from pure molybdenum powders in civil coal gas atmosphere at room temperature. The structure and the particle size of the powders were investigated by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, and Transmission Electron micros-copy （TEM）. The results showed that after milling for 30 h, the MoC powders of hexagonal structure were obtained, and their average parti-cle size was around 100 nm. It was found that chemisorption of CO in coal gas onto the fresh molybdenum surfaces created by milling was the predominant processes during the solid-gas reaction, and the energy input due to the introduction of highly dense grain boundaries and lattice defects provided the activation energy for the transition from Mo-C chemisorption to MoC. A coating was formed on the 40Cr steel base using plasma spray by mixing Ni60 alloy powders and ultramicro MoC powders of 5 wt.%, 10 wt.%, and 15 wt.%, respectively. Coat-ing abrasion tests under the condition of dry-grinding, 2 h wear time, and 300 N load showed that the wear resistance property of the coating added with ultramicro MoC powders could be improved greatly, and the wear resistance property of the coating increased with the increase of ultramicro MoC content. The wear mechanisms of ultramicro MoC coating is mainly plough wear and flaking wear assisted. In the abra-sion process, the evenly distributed ultramicro MoC particles play a dispersion strengthening and self-lubricating role in the coating.

关键词： powders molybdenum carbide coatings wear resistance ball milling

A Binary Particle Swarm Optimization for the Minimum Weight Dominating Set Problem

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Journal of Computer Science & Technology 2018年第2期33卷 305-322页

作者： geng Lin Jian Guan Department of Mathematics Minjiang University Fuzhou 350121 China Modern Educational Technology Center Minjiang University Fuzhou 350121 China

The minimum weight dominating set problem （MWDSP） is an NP-hard problem with a lot of real-world applications. Several heuristic algorithms have been presented to produce good quality solutions. However, the solution time of them grows very quickly as the size of the instance increases. In this paper, we propose a binary particle swarm optimization （FBPSO） for solving the MWDSP approximately. Based on the characteristic of MWDSP, this approach designs a new position updating rule to guide the search to a promising area. An iterated greedy tabu search is used to enhance the solution quality quickly. In addition, several stochastic strategies are employed to diversify the search and prevent premature convergence. These methods maintain a good balance between the exploration and the exploitation. Experimental studies on 106 groups of 1 060 instances show that FBPSO is able to identify near optimal solutions in a short running time. The average deviation between the solutions obtained by FBPSO and the best known solutions is 0.441%. Moreover, the average solution time of FBPSO is much less than that of other existing algorithms. In particular, with the increasing of instance size, the solution time of FBPSO grows much more slowly than that of other existing algorithms.

关键词： metaheuristics binary particle swarm optimization tabu search dominating set problem combinatorial optimization