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On Local Convexity of Quadratic Transformations

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Journal of the Operations Research Society of China 2014年第3期2卷 341-350页

作者： yong xia State Key Laboratory of Software Development Environment LMIB of the Ministry of EducationSchool of Mathematics and System SciencesBeihang UniversityBeijing 100191China

In this paper,we improve Polyak’s local convexity result for quadratic *** and open problems are also presented.

关键词： Convexity Quadratic transformation Joint numerical range

New semidefinite programming relaxations for box constrained quadratic program

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Science China Mathematics 2013年第4期56卷 877-886页

作者： xia yong State Key Laboratory of Software Development Environment LMIB of the Ministry of EducationSchool of Mathematics and System SciencesBeihang University

We establish in this paper optimal parametric Lagrangian dual models for box constrained quadratic program based on the generalized D.C.(difference between convex) optimization approach,which can be reformulated as se... 详细信息

关键词： box constrained quadratic program Lagrangian dual semidefinite programming D.C. optimiza- tion lower bound zonotope

A Survey of Hidden Convex Optimization

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Journal of the Operations Research Society of China 2020年第1期8卷 1-28页

作者： yong xia Key Laboratory of Mathematics Informatics and Behavioral Semantics of the Ministry of EducationSchool of Mathematics and System SciencesBeihang UniversityBeijing 100191China

Motivated by the fact that not all nonconvex optimization problems are difficult to solve,we survey in this paper three widely used ways to reveal the hidden convex structure for different classes of nonconvex optimiz... 详细信息

关键词： Convex programming Quadratic programming Quadratic matrix programming Fractional programming Lagrangian dual Semidefinite programming

A Note on Legendre–Fenchel Conjugate of the Product of Two Positive-Definite Quadratic Forms

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Journal of the Operations Research Society of China 2013年第3期1卷 333-338页

作者： yong xia State Key Laboratory of Software Development Environment Key Laboratory of MathematicsInformatics and Behavioral Semantics of the Ministry of EducationSchool of Mathematics and System SciencesBeihang UniversityBeijing 100191P.R.China

The Legendre–Fenchel conjugate of the product of two positive-definite quadratic forms was posted as an open question in the field of nonlinear analysis and optimization by Hiriart-Urruty[‘Question 11’in SIAM Review 49,255–273,2007].Under a convexity assumption on the function,it was answered by Zhao[SIAM *** Analysis&Applications 31(4),1792–1811,2010].In this note,we answer the open question without making the convexity assumption.

关键词： Legendre-Fenchel conjugate Quadratic form

Vibration of Timoshenko beam on hysteretically damped elastic foundation subjected to moving load

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Science China(Physics,Mechanics & Astronomy) 2015年第8期58卷 58-66页

作者： LUO WeiLi xia yong WENG Shun Department of Civil and Environmental Engineering The Hong Kong Polytechnic University School of Civil Engineering & Mechanics Huazhong University of Science and Technology

The vibration of beams on foundations under moving loads has many applications in several fields, such as pavements in highways or rails in railways. However, most of the current studies only consider the energy dissipation mechanism of the foundation through viscous behavior; this assumption is unrealistic for soils. The shear rigidity and radius of gyration of the beam are also usually excluded. Therefore, this study investigates the vibration of an infinite Timoshenko beam resting on a hysteretically damped elastic foundation under a moving load with constant or harmonic amplitude. The governing differential equations of motion are formulated on the basis of the Hamilton principle and Timoshenko beam theory, and are then transformed into two algebraic equations through a double Fourier transform with respect to moving space and time. Beam deflection is obtained by inverse fast Fourier transform. The solution is verified through comparison with the closed-form solution of an Euler-Bernoulli beam on a Winkler foundation. Numerical examples are used to investigate:(a) the effect of the spatial distribution of the load, and(b) the effects of the beam properties on the deflected shape, maximum displacement, critical frequency, and critical velocity. These findings can serve as references for the performance and safety assessment of railway and highway structures.

关键词： vibration beam-foundation system moving load

A novel technique for measuring 3D deformation of adhesively bonded single lap joint

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Science China(Physics,Mechanics & Astronomy) 2016年第1期59卷 58-65页

作者： Bing Pan LuJun Ma yong xia Institute of Solid Mechanics Beihang University State Key Lab of Automotive Safety and Energy Tsinghua University

An easy-to-implement yet practical single-camera microscopic stereo-digital image correlation(stereo-DIC) technique is proposed for surface three-dimensional(3D) deformation measurement of singe lap joint(SLJ) samples subjected to mechanical loads. The basic principles, optical configurations and implementation procedures of the proposed technique are described in detail. Compared with existing single-camera 2D-DIC technique, which has been regularly used for in-plane deformation measurement of a SLJ specimen, the proposed technique offers the special merit of simultaneously determining all the three displacement components by simply adding two additional optical elements to existing single-camera 2D-DIC systems. The accuracy and effectiveness of the proposed technique is demonstrated by measuring the 3D deformation of a SLJ specimen subjected to quasi-static tensile loads.

关键词： digital image correlation single lap joint deformation measurement

Optimal dividend and capital injection problem with a random time horizon and a ruin penalty in the dual model

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Applied Mathematics(A Journal of Chinese Universities) 2015年第3期30卷 325-339页

作者： ZHAO yong-xia YAO Ding-jun School of Statistics Qufu Normal University School of Finance Nanjing University of Finance and Economics

In the dual risk model, we consider the optimal dividend and capital injection problem, which involves a random time horizon and a ruin penalty. Both fixed and proportional costs from the transactions of capital injection are considered. The objective is to maximize the total value of the expected discounted dividends, and the penalized discounted both capital injections and ruin penalty during the horizon, which is described by the minimum of the time of ruin and an exponential random variable. The explicit solutions for optimal strategy and value function are obtained, when the income jumps follow a hyper-exponential ***, some numerical examples are presented to illustrate our results.

关键词： dual model transaction cost dividend capital injection HJB equation

Comparative study of mechanical-electrical-thermal responses of pouch, cylindrical, and prismatic lithium-ion cells under mechanical abuse

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Science China(Technological Sciences) 2018年第10期61卷 1472-1482页

作者： LI Wei xia yong CHEN GuanHua SAHRAEI Elham State Key Laboratory of Automotive Safety and Energy Department of Automotive Engineering Tsinghua University Impact and Crashworthiness Lab Massachusetts Institute of Technology Electric Vehicle Safety Lab The George Mason University

In the study, mechanical abuse tests mainly in the form of indentation were performed on the cylindrical cell, pouch cell, and prismatic cell. The mechanical force-displacement response, open circuit voltage(OCV), and temperature distribution were recorded and compared. In spherical head indentation tests of the pouch and prismatic cell and lateral indentation of the cylindrical cell, the peak force is strongly correlated with OCV drop and local temperature increase. However, in flat-end cylinder indentation tests, the internal mechanical damage is progressively developed, and the OCV drop and the temperature increase occur before the peak force. The fracture surfaces of the post-mortem samples were examined to investigate the correlation between fracture patterns and internal short circuit(ISC) behaviors(OCVand temperature distribution). Two distinct fracture patterns were observed that the in-plane fracture induced by biaxial stretching and inter-layers' fracture induced by shearing. A strong correlation is observed between the number of shear fractures and OCV drop. An increase in the number of inter-layers' fractures increases the rate of OCV drop. Additionally, the fracture patterns influence the ISC area and location,thereby affecting the heat generation and conduction as well as the temperature distribution.

关键词： mechanical abuse fracture pattern mechanical-electrical-thermal response lithium-ion battery

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青少年双相障碍患者高尿酸血症的相关因素

中国心理卫生杂志 2025年第1期39卷 32-36页

作者：孙裕勇刘晓妍崔文静郭鹏飞夏泳浙江大学医学院附属精神卫生中心/杭州市第七人民医院杭州310013

目的:了解青少年双相障碍患者高尿酸血症(HUA)的相关因素。方法:选取青少年双相障碍患者59名及健康对照60名。收集一般人口学资料和临床资料,检测血清尿酸(UA)、甘油三酯(TG)、总胆固醇(TC)、高密度脂蛋白胆固醇(HDL-C)、低密度脂蛋白... 详细信息

目的:了解青少年双相障碍患者高尿酸血症(HUA)的相关因素。方法:选取青少年双相障碍患者59名及健康对照60名。收集一般人口学资料和临床资料,检测血清尿酸(UA)、甘油三酯(TG)、总胆固醇(TC)、高密度脂蛋白胆固醇(HDL-C)、低密度脂蛋白胆固醇(LDL-C)、空腹血糖(FPG)、果糖胺(FA)水平等生理指标。采用汉密顿抑郁量表-17 (HAMD-17)、Bech-Rafaelsen躁狂量表(BRMS)评估患者的情绪症状。结果:青少年双相障碍患者的HUA检出率高于健康对照组(30.5%vs.18.3%,P<0.05),青少年双相障碍躁狂发作期HUA的检出率高于抑郁发作期(48.2%vs.20.8%,P<0.05)。非条件logistic回归分析显示,高TG和高体质指数是青少年双相障碍患者HUA的危险因素(OR=2.51、1.34)。结论:本研究发现,青少年双相障碍患者较健康对照可能有更高的高尿酸血症风险,其发生与高甘油三酯和高体质指数相关。

关键词：青少年双相障碍高尿酸血症体质指数代谢综合征甘油三酯