检索结果-南通市图书馆

Biasing transition rate method based on direct MC simulation for probabilistic safety assessment

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Nuclear Science and Techniques 2017年第7期28卷 91-96页

作者： xiao-Lei Pan Jia-qun wang Run Yuan Fang wang Han-Qing Lin Li-Qin Hu Jin wang University of Science and Technology of China Hefei 230027 China Key Laboratory of Neutronics and Radiation Safety Institute of Nuclear Energy Safety Technology Chinese Academic of Sciences Hefei 230031 China

Direct Monte Carlo(MC) simulation is a powerful probabilistic safety assessment method for accounting dynamics of the *** it is not efficient at simulating rare events.A biasing transition rate method based on direct MC simulation is proposed to solve the problem in this *** method biases transition rates of the components by adding virtual components to them in series to increase the occurrence probability of the rare event,hence the decrease in the variance of MC *** cases are used to benchmark this *** results show that the method is effective at modeling system failure and is more efficient at collecting evidence of rare events than the direct MC *** performance is greatly improved by the biasing transition rate method.

关键词： MC模拟发生概率安全评估偏置仿真跃迁安全评价方法稀有事件

Differences and relations of objectives, constraints, and decision parameters in the optimization of individual heat exchangers and thermal systems

在线全文

学校读者我要写书评

暂无评论

Science China(Technological Sciences) 2016年第7期59卷 1071-1079页

作者： CHEN qun wang YiFei Key Laboratory for Thermal Science and Power Engineering of Ministry of Education Department of Engineering MechanicsTsinghua University

Performance improvement of heat exchangers and the corresponding thermal systems benefits energy conservation, which is a multi-parameters, multi-objectives and multi-levels optimization problem. However, the optimized results of heat exchangers with improper decision parameters or objectives do not contribute and even against thermal system performance improvement. After deducing the inherent overall relations between the decision parameters and designing requirements for a typical heat exchanger network and by applying the Lagrange multiplier method, several different optimization equation sets are derived, the solutions of which offer the optimal decision parameters corresponding to different specific optimization objectives, respectively. Comparison of the optimized results clarifies that it should take the whole system, rather than individual heat exchangers, into account to optimize the fluid heat capacity rates and the heat transfer areas to minimize the total heat transfer area, the total heat capacity rate or the total entropy generation rate, while increasing the heat transfer coefficients of individual heat exchangers with different given heat capacity rates benefits the system performance. Besides, different objectives result in different optimization results due to their different intentions, and thus the optimization objectives should be chosen reasonably based on practical applications, where the inherent overall physical constraints of decision parameters are necessary and essential to be built in advance.

关键词： energy conservation thermal system physical constraint decision parameter optimization objectives

Reproduction of the Sedimentary Disturbance Phenomenon of the Diexi Ancient Landslide-Dammed Lake under Earthquake

在线全文

学校读者我要写书评

暂无评论

Journal of Mountain Science 2015年第5期12卷 1181-1188页

作者： WEI Yu-feng wang xiao-qun SHENG Man ZHOU Zhou YUAN Yong State Key Laboratory of Geohazard Prevention & Geoenvironment Protection Chengdu University of Technology

Valuable geological and environmental information can be obtained from the 200 m thick lacustrine sediments in the Diexi lake(an ancient landslide-dammed lake) of the Minjiang River. The shaking table test method was employed to study the disturbance phenomena which occurred in the Diexi lake sediments. The results show that the disturbance phenomena were caused by liquefaction-induced flows in the unconsolidated lacustrine sediments, due to triggering by earthquakes. The deformations only occurred in unconsolidated sediment layers and not in consolidated layers. This means that a consolidated layer cannot be liquefied and disturbed again by an earthquake for a second time. The disturbance on one layer corresponds to only one earthquake. The temporal occurrence of earthquakes could be determined by disturbance layers generated at different ages. In total, 10 disturbed layers were found in the lacustrine sediments of the Diexi lake. The experiments showed that there were more than 10 earthquakes between 30 ka B.P. and 15 ka B.P. in the Diexi lake area based on the dating of the disturbed sediment layers.

关键词： Minjiang River Diexi lake Landslide Earthquake disturbance deformation Simulatingexperiment

Effect ofαphase on fatigue crack growth of Ti-6242 alloy

在线全文

学校读者我要写书评

暂无评论

Journal of Iron and Steel Research International 2017年第8期24卷 811-822页

作者： Hang-wei Zhou Hui-qun Liu Dan-qing Yi Yu xiao xiao-long Zhao Jian wang Qi Gao School of Materials Science and Engineering Central South UniversityChangsha 410088HunanChina Key Laboratory of Nonferrous Materials Ministry of EducationCentral South UniversityChangsha 410083HunanChina BAOTI Group Ltd. Baoji 721014ShanxiChina

Fatigue crack growth as a function ofαphase volume fraction in Ti-6Al-2Sn-4Zr-2Mo（Ti-6242）alloy was investigated using fatigue testing,optical microscopy,scanning electron microscopy,and transmission electron ***α＋βannealing treatments with different solid solution temperatures and cooling rates were conducted in order to tailor microstructure with differentαphase features in the Ti-6242 alloy,and fatigue crack growth mechanism was discussed after detailed microstructure *** results showed that fatigue crack growth rate of Ti-6242 alloy decreased with the decrease in volume fraction of the primaryαphase（αp）.Samples with a large-sizedαgrain microstructure treated at high solid solution temperature and slow cooling rate have lower fatigue crack growth *** appearance of secondaryαphase（αs）with the increase of solid solution temperature led to crack ***,a fatigue crack growth transition phenomenon was observed in the Paris regime of Ti-6242 alloy with 29.8% αp（typical bi-modal microstructure）and large-sizedαgrain microstructure,owing to the change of fatigue crack growth mechanism.

关键词： Ti-6242 alloy Microstructure tailoring Fatigue crack growth α phase Fatigue crack growth rate Crack propagation transition

Scaling of weighted spectral distribution in weighted small-world networks

在线全文

学校读者我要写书评

暂无评论

Chinese Physics B 2017年第2期26卷 536-545页

作者： Bo Jiao xiao-qun Wu Luoyang Electronic Equipment Test Center Luoyang 471003 China School of Mathematics and Statistics Wuhan University Wuhan 430072 China

Many real-world systems can be modeled by weighted small-world networks with high clustering coefficients. Recent studies for rigorously analyzing the weighted spectral distribution（W SD） have focused on unweighted networks with low clustering coefficients. In this paper, we rigorously analyze the W SD in a deterministic weighted scale-free small-world network model and find that the W SD grows sublinearly with increasing network order（i.e., the number of nodes） and provides a sensitive discrimination for each input of this model. This study demonstrates that the scaling feature of the W SD exists in the weighted network model which has high and order-independent clustering coefficients and reasonable power-law exponents.

关键词： weighted spectral distribution weighted small-world network scaling

On two actuarial quantities for the compound Poisson risk model with tax and a threshold dividend strategy

在线全文

学校读者我要写书评

暂无评论

Applied Mathematics(A Journal of Chinese Universities) 2013年第1期28卷 27-39页

作者： wang Wen-yuan xiao Li-qun MING Rui-xing HU Yi-jun College of Science Shantou University School of Mathematics and Statistics Wuhan University School of Mathematical Sciences University of Science and Technology of China School of Statistics and Mathematics Zhejiang Gongshang University

In this paper, we consider a compound Poisson risk model with taxes paid according to a loss-carry-forward system and dividends paid under a threshold strategy. First, the closed-form expression of the probability function for the total number of taxation periods over the lifetime of the surplus process is derived. Second, analytical expression of the expected accumulated discounted dividends paid between two consecutive taxation periods is provided. In addition, explicit expressions are also given for the exponential individual claims.

关键词： Compound Poisson risk model total number of taxation periods expected accumulated discounted dividends.

Isometric Immersions of Higher Codimension in to the Product S~κ×H^(n+p-k)

在线全文

学校读者我要写书评

暂无评论

Acta Mathematica Sinica,English Series 2014年第12期30卷 2146-2160页

作者： Xing xiao LI Tian qun ZHANG Department of Mathematics He'nan Normal University Luoyang No.43 Middle School

In this paper,we obtain a sufficient and necessary condition for a simply connected Riemannian manifold（M^n,g） to be isometrically immersed,as a submanifold with codimension p 〉 1,into the product S^k×H^n＋p＋k of... 详细信息

关键词： Isometric immersions of higher codimension product structure spheres and hyperboloids

Standard triple therapy for Helicobacter pylori infection in China: A meta-analysis

在线全文

学校读者我要写书评

暂无评论

World Journal of Gastroenterology 2014年第40期20卷 14973-14985页

作者： Ben wang Zhi-Fa Lv You-Hua wang Hui wang xiao-qun Liu Yong Xie xiao-Jiang Zhou Department of Gastroenterology The First Affiliated Hospital of Nanchang University

AIM: To assess the efficacy and safety of standard triple therapy compared with other pre-existing and new therapies in China.

关键词： Helicobacter pylori Eradication Combination drug therapy Amoxicillin Clarithromycin Adverse effects Meta-analysis

A multiobjective evolutionary optimization method based critical rainfall thresholds for debris flows initiation

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Mountain Science 2020年第8期17卷 1860-1873页

作者： YAN Yan ZHANG Yu HU wang GUO xiao-jun MA Chao wang Zi-ang ZHANG qun Key Laboratory of High-Speed Railway Engineering MOE/School of Civil EngineeringSouthwest Jiao tong UniversityChengdu 610031China Institute of Geographic Sciences and Natural Resources Research Chinese Academy of SciencesBeijing 100101China School of Computer Science and Engineering University of Electronic Science and Technology of ChinaChengdu 611731China Key Laboratory of Mountain Surface Process and Hazards/Institute of Mountain Hazards and Environment Chinese Academy of SciencesChengdu 610041China School of Soil and Water Conservation Beijing Forestry UniversityBeijing 100083China Sichuan Institute of Land and Space Ecological Restoration and Geological Hazard Prevention Chengdu 610081China

At present,most researches on the critical rainfall threshold of debris flow initiation use a linear model obtained through *** relatively weak fault tolerance,this method not only ignores nonlinear effects but also is susceptible to singular noise samples,which makes it difficult to characterize the true quantization relationship of the rainfall ***,the early warning threshold determined by statistical parameters is susceptible to negative samples(samples where no debris flow has occurred),which leads to uncertainty in the reliability of the early warning results by the regression *** overcome the above limitations,this study develops a data-driven multiobjective evolutionary optimization method that combines an artificial neural network(ANN)and a multiobjective evolutionary optimization implemented by particle swarm optimization(PSO).Firstly,the Pareto optimality method is used to represent the nonlinear and conflicting critical thresholds for the rainfall intensity I and the rainfall duration *** ANN is used to construct a dual-target(dual-task)predictive surrogate model,and then a PSO-based multiobjective evolutionary optimization algorithm is applied to train the ANN and stochastically search the trained ANN for obtaining the Pareto front of the I-D surrogate prediction model,which is intended to overcome the limitations of the existing linear regression-based threshold ***,a double early warning curve model that can effectively control the false alarm rate and negative alarm rate of hazard warnings are proposed based on the decision space and target space *** study provides theoretical guidance for the early warning and forecasting of debris flows and has strong applicability.

关键词： Debris flow Critical rainfall thresholds Multiobjective evolutionary optimization Artificial neural network Pareto optimality