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Soft-capacitated Facility Location Game

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Acta Mathematicae Applicatae Sinica 2010年第1期26卷 93-98页

作者： Yu Li Da-chuan xu Department of Mathematics School of Science Beijing Jiaotong University Beijing 100044 China Department of Applied Mathematics College of Applied Sciences Beijing University of Technology Beijing 100124 China

We study the soft-capacitated facility location game which is an extension of the facility location game of Pa1 and Tardos. We propose a 6-approximate cross-monotonic cost-sharing method. Numerical tests indicate that... 详细信息

关键词： Facility location game cross-monotonic competitive approximate cost recovery

On the Local Solvability and Stability for the Inverse Spectral Problem of the Generalized Dirichlet–Regge Problem

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Acta Mathematica Sinica,English Series 2022年第7期38卷 1229-1240页

作者： Xiao chuan xu Natalia Pavlovna BONDARENKO School of Mathematics and Statistics Nanjing University of Information Science and TechnologyNanjing 210044P.R.China Department of Applied Mathematics and Physics Samara National Research UniversityMoskovskoye Shosse 34Samara 443086Russia Department of Mechanics and Mathematics Saratov State UniversityAstrakhanskaya 83Saratov 410012Russia

For the generalized Dirichlet–Regge problem with complex coefficients,we prove the local solvability and stability for the inverse spectral problem,which indicates an improved result of the previous work([Journal of ... 详细信息

关键词： Dirichlet-Regge problem inverse spectral problem local solvability stability reconstruction algorithm

Nonlinear Extrapolation Estimates of π

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Acta Mathematicae Applicatae Sinica 2024年第1期40卷 91-108页

作者： Wen-qing xu Sha-sha Wang Da-chuan xu Beijing Institute for Scientific and Engineering Computing Beijing University of TechnologyBeijing100124China Department of Mathematics and Statistics California State UniversityLong BeachCalifornia90840USA Department of Mathematics and Physics Shijiazhuang Tiedao UniversityShijiazhuang050043China

The classical Archimedean approximation of π uses the semiperimeter or area of regular polygons inscribed in or circumscribed about a unit circle in R~2 and it is well-known that by using linear combinations of these basic estimates,modern extrapolation techniques can greatly speed up the approximation ***,when n vertices are randomly selected on the circle,the semiperimeter and area of the corresponding random inscribed and circumscribing polygons are known to converge to π almost surely as n→∞,and by further applying extrapolation processes,faster convergence rates can also be achieved through similar linear combinations of the semiperimeter and area of these random *** this paper,we further develop nonlinear extrapolation methods for approximating π through certain nonlinear functions of the semiperimeter and area of such *** focus on two types of extrapolation estimates of the forms χ_n=S_n~αA_n~β and Y_n(p)=(αS_n~p+βA_n~p)~(1/p) where α+β=1,p≠0,and Sn and An respectively represents the semiperimeter and area of a random n-gon inscribed in the unit circle in R~2,and Xn may be viewed as the limit of Y_n(p) when p→*** deriving probabilistic asymptotic expansions with carefully controlled error estimates for Xn and Y_n(p),we show that the choice α=4/3,β=-1/3 minimizes the approximation error in both cases,and their distributions are also asymptotically normal.

关键词： Archimedean polygons random polygons approximations ofπ extrapolation processes asymptotic convergence

An Improved Approximation Algorithm for the k-Level Facility Location Problem with Soft Capacities

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Acta Mathematicae Applicatae Sinica 2017年第4期33卷 1015-1024页

作者： Chen-chen WU Da-chuan xu College of Science Tianjin 300384 China Department of Information and Operations Research College of Applied Sciences Beijing University of Tech-nology Beijing 100124 China

We consider the k-level facility location problem with soft capacities （k-LFLPSC）. In the k- LFLPSC, each facility i has a soft capacity ui along with an initial opening cost fi ≥O, i.e., the capacity of facility i is an integer multiple of ui incurring a cost equals to the corresponding multiple of fi. We firstly propose a new bifactor （ln（1/β）/（1 -β）, 1 ＋ 2/（1 - β））-approximation algorithm for the k-level facility location problem （k-LFLP）, where β∈（0, 1） is a fixed constant. Then, we give a reduction from the k-LFLPSC to the k-LFLP. The reduction together with the above bifactor approximation algorithm for the k-LFLP imply a 5.5053-approximation algorithm for the k-LFLPSC which improves the previous 6-approximation.

关键词： facility location approximation algorithm soft capacity

Robust Solutions of Uncertain Complex-valued Quadratically Constrained Programs

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Acta Mathematica Sinica,English Series 2008年第8期24卷 1279-1290页

作者： Da chuan xu Zheng Hai HUANG Department of Applied Mathematics College of Applied Sciences Beijing University of Technology 100 Pingleyuan Chaoyang District Beijing 100022 P. R. China Department of Mathematics School of Science Tianjin University Tianjin 300072 P. R. China

In this paper, we discuss complex convex quadratically constrained optimization with uncertain data. Using S-Lemma, we show that the robust counterpart of complex convex quadratically constrained optimization with ellipsoidal or intersection-of-two-ellipsoids uncertainty set leads to a complex semidefinite program. By exploring the approximate S-Lemma, we give a complex semidefinite program which approximates the NP-hard robust counterpart of complex convex quadratic optimization with intersection-of-ellipsoids uncertainty set.

关键词： robust optimization quadratically constrained program complex semidefinite program S-Lemma

Evolution of Microstructure,Mechanical Properties and Corrosion Resistance of Ultrasonic Assisted Welded-Brazed Mg/Ti Joint

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Journal of Materials Science & Technology 2016年第12期32卷 1253-1259页

作者： chuan xu Guangmin Sheng xuezhen Cao Xinjian Yuan College of Materials Science and Engineering Chongqing University

Ultrasonic vibration with different powers from 0 k W to 1.6 k W was applied during the tungsten inert gas welding-brazing of Mg/*** microstructures,mechanical properties and corrosion resistance of the ultrasonic assisted tungsten inert gas（U-TIG） welded-brazed Mg/Ti joint were *** results showed that,without being subjected to ultrasonic vibration,coarse columnar α-Mg grains occurred in the fusion zone of Mg/Ti ***,with ultrasonic power of 1.2 k W,the average grain size of columnar α-Mg grains was refined from 200 μm to about 50 μm and the tensile strength of joints increased^18% up to 228 ***,high fraction of grain boundaries was introduced by grain refinement,contributing to improve the corrosion resistance in two ways：（i） accelerating the formation of Mg（OH）2protective layer and（ii） reducing the mismatch and disorder between Mg（OH）2 protective layer and Mg alloy surface.

关键词： Magnesium alloy Titanium alloy Microstructure Mechanical properties Corrosion resistance Ultrasonic vibration

Effect of CO_2 partial pressure on SCC behavior of welded X80 pipeline in simulated soil solution

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Acta Metallurgica Sinica(English Letters) 2011年第1期24卷 65-74页

作者： Ming WU xu CHEN chuan HE Jun XIAO College of Petroleum Engineering Liaoning Shihua University Eushun 113001 China

The stress corrosion cracking （SCC） behavior of welded X80 pipeline steel in simulated Ku＇erle soil solution was studied by means of electrochemical impedance spectroscopy （EIS） and slow strain rate tests （SSRT）. The microstructure of the welded steel was observed by optical microscopy （OM）. It is demonstrated that the microstructure of the weld metal consists of acicular ferrite and grain boundary ferrite, while that of heat affected zone （HAZ） is a mixture of acicular ferrite and bainitic ferrite micro- constituents. The microstructure of the base steel is composed of ferrite and pearlite. The anodic dissolution of X80 pipeline steel in simulated Ku＇erle soil solution could be enhanced and the SCC sensitivity increased with the increase of CO2 partial pressure. The SCC mechanism of X80 pipeline is a mixing mechanism of hydrogen embrittlement combined with anodic dissolution, and the hydrogen embrittlement plays a leading role. The higher SCC sensitivity of the weld metal was attributed to the metallurgical transformation, local hardening and residual stress.

关键词： X80 steel Weld metal CO2 partial pressure SCC

Load balancing routing for single-layered satellite networks

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The Journal of China Universities of Posts and Telecommunications 2010年第2期17卷 92-99页

作者： RAO Yuan WANG Ru-chuan xu Xiao-long College of Computer Nanjing University of Posts and Telecommunications Nanjing 210003 China

The varying population density leads to imbalanced utilization rate of satellites. To ensure an intelligent engineering of traffic over satellite networks, a distributed routing scheme for single-layered satellite network, load balancing routing protocol based on mobile agent （LBRP-MA） is proposed. For LBRP-MA, mobile agents explore route by migrating autonomously. Upon arriving at destination, mobile agents migrate back. On each intermediate satellite, mobile agents evaluate path cost considering satellite geographical position as well as inter-satellite link （ISL） cost, and finally take ISL congestion index into account to update routing tables. Through simulations on the Courier-like constellation, the proposed approach is shown to achieve guaranteed end-to-end delay bound and decrease packet loss ratio with better throughput, which is especially suitable for data transferring in case of high traffic load. Moreover, results of the complexity analysis demonstrate that LBRP-MA can have low onboard signaling, storage and computation requirements. Furthermore, issues of LBRP-MA such as ISL congestion index and cost modification factor are discussed.

关键词： load balancing mobile agent satellite networks routing

Steady characteristic investigation on passive residual heat removal system of Chinese advanced PWR

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Nuclear Science and Techniques 2008年第1期19卷 58-64页

作者： XIAO Zejun xu chuan ZHUO Wenbin CHEN Bingde National Key Laboratory of Bubble Physics ＆ Natural Circulation Nuclear Power Institute of China Chengdu 610041 China

Thermal-hydraulic characteristic investigation on passive residual heat removal system (PRHRS) of Chinese advanced PWR was conducted to provide input data for PRHRS design and to demonstrate the feasibility of unique design features. A total of 237 sets of test data at steady state have been obtained and the main influence factors on the two-phase natural circulation flow rate and residual heat removal capability were identified. On the basis of theory analysis, a correlation of two-phase natural circulation was obtained, and relative errors of 95% test data were less than ±16%. There is a considerable effect of the system status parameters on the threshold of height between heat source and heat sink, and its correlation of two-phase natural circulation system has been obtained. The steady characteristic research shows that PRHRS has the capability of removing the core decay power through natural circulation.

关键词：反应堆核反应能源管理消除系统