Sequence Independent Lifting in Mixed Integer Programming

We investigate lifting, i.e., the process of taking a valid inequality for a polyhedron and extending it to a valid inequality in a higher dimensional space. Lifting is usually applied sequentially, that is, variables in a set are lifted one after the other. This may be computationally unattractive since it involves the solution of an optimization problem to compute a lifting coefficient for each variable. To relieve this computational burden, we study sequence independent lifting, which only involves the solution of one optimization problem. We show that if a certain lifting function is superadditive, then the lifting coefficients are independent of the lifting sequence. We introduce the idea of valid superadditive lifting functions to obtain good aproximations to maximum lifting. We apply these results to strengthen Balas' lifting theorem for cover inequalities and to produce lifted flow cover inequalities for a single node flow problem.     

CET阅读理解题:问题与方法(二)

本文通过对CET阅读理解考题、提问(问题)以及原文和提问中一些关键词语之间的内含百分比进行分析和对比,探索如何准确解题的方法与捷径。     

Welfare Rigidity,the Composition of Public Expenditure and the Welfare Trap

Welfare expenditure is characterized by rigidity, i.e., it goes up easily but is very hard to get down. We introduced welfare rigidity into an endogenous growth model that includes government expenditure to analyze the impact of welfare rigidity and the composition of public expenditure on economic growth and family utility. Our findings show that welfare spending and economic growth have a non-monotonic relationship that is negative or inverted U-shaped depending on cross-country differences. Higher welfare rigidity reduces long-term economic growth and household utility. According to the estimated optimal size of welfare expenditure, China, as a developing country with a large population, has to do all it can to improve people’s livelihood but must at the same time weigh its limited resources so that its welfare expenditure does not fall into a “welfare trap.”     

Risk minimization for an insurer with investment and reinsurance via g-expectation

Abstract

This paper is devoted to the study of a risk-based optimal investment and proportional reinsurance problem. The surplus process of the insurer and the risky asset process in the financial market are assumed to be general jump-diffusion processes. We use a convex risk measure generated by g-expectation to describe the risk of the terminal wealth with investment and reinsurance. Under the aim of minimizing the risk, the problem is solved by using techniques of stochastic maximum principles. Two interesting special cases are studied and the explicit expressions for optimal strategies and corresponding minimal risks are derived.     

海尔集团基于网络营销导向的网站建设研究

以海尔集团为例，从网络营销的角度对大中型企业电子商务网站的相关问题进行研究。对海尔网站的各部分要素进行了详尽的分析，对海尔网站的网络设计优化进行了诊断，从中发现海尔网站的成功与不足之处，并进而揭示出我国大中型企业在此方面存在的共性问题，旨在使各大中型企业加深对网络营销导向的企业网站建设的认识，并为正在进行网络营销导向的网站建设的各大中型企业提供一定的参考与借鉴。     

"两个口号"论争与俄苏文学文论传播中的期刊

"两个口号"的论争与俄苏文学和文论在中国的传播有关,而这又受制于论争参与者的价值观念与期刊对俄苏文学和文论译介的互动。1934年至1936年,国民党系统的期刊译介俄苏文艺,一般以作品为主,且与"民族主义文艺运动"的主题相关。同人期刊译介俄罗斯文学名家名作,也积极译介无产阶级文学和苏联文艺动态。左翼的期刊译介了大量有关"社会主义现实主义创作方法"和苏联文艺政策的文章。它表明中国的文艺界进一步向苏联的文艺思想看齐,因而"两个口号"论争的理性色彩也进一步加强,但同时也使论争中的"宗派主义"和"关门主义"现象无法完全克服。     

在英语教学中发展学生思维能力方法初探

在英语教学中,学生的思维能力对其英语综合能力的提高有重要影响,本文结合教学实践,提出培养和发展学生思维能力的四种方法.     

印度高等教育规模扩充的驱动因素分析

高等教育规模扩充受多重因素的驱动。在1950—1970年的20年间，印度的高等教育经历了大规模的扩充，持续扩充背后的驱动因素有哪些？本文从不同的角度出发，分析了驱动印度高等教育规模扩充的深层因素。