Global Approximation of Solutions of Time-Dependent Variational Inequalities

We consider a class of parametric variational inequalities where both the operator and the convex set depend on time. This kind of variational inequalities are useful to model many time dependent equilibrium problems. We study the Lipschitz continuity of the solutions with respect to the time parameter and construct approximations for them which minimize the average worst case error. Some improved estimates of the Lipschitz constant for this class of problems are given. In order to illustrate our procedure, we study a classical network equilibrium problem.     

The convenient setting for quasianalytic Denjoy-Carleman differentiable mappings

For quasianalytic Denjoy-Carleman differentiable function classes CQ where the weight sequence Q=(Qk) is log-convex, stable under derivations, of moderate growth and also an L-intersection (see (1.6)), we prove the following: The category of CQ-mappings is cartesian closed in the sense that CQ(E,CQ(F,G))≅CQ(E×F,G) for convenient vector spaces. Applications to manifolds of mappings are given: The group of CQ-diffeomorphisms is a regular CQ-Lie group but not better.     

Effect of Side Chains and Sulfonic Groups on the Performance of Polycarboxylate-Type Superplasticizers in Concentrated Cement Suspensions

Polycarboxylate-type superplasticizers (PCs) containing different side chains and sulfonic groups have been synthesized, and the effect of side chains and sulfonic groups on their performance in cementitious systems has been intensively investigated by measuring zeta potential, thickness of absorption layer, paste fluidity, rheological properties as well as the setting time in this paper. Results show that the PC containing both short poly(ethylene oxide) (PEO) side chains and long PEO side chains with the molar ratio of 1:1 has a better dispersibility than the PC containing only short PEO side chains or only long PEO side chains in cement suspensions. The shorter the side chain of the PC, the longer the setting time of cement paste incorporating it. An appropriate increase of sulfonic group content is beneficial for the improvement of dispersibility for the PC and leads to no obvious change for the setting time. It also suggests that there is a geometrical balance between the PEO side chains and sulfonic groups for the performance of PC. This work is not only helpful for understanding the relationship of molecular structure of PCs and their performance, but also further designing optimum molecular structure of PC to meet the requirement in different concrete system.     

高等级公路路线方案的多目标量化优选

应用最小二乘法准则,并改进了层次分析法判断矩阵的构成,获得考虑专家评价水平的诸影响因素权向量;基于集值统计法和属性数学原理,建立了对高等级公路路线方案量化综合评价优选模型,并给出了计算实例.     

Optimal Operations Management and Network Planning of a District Heating System with a Combined Heat and Power Plant

District heating plants are becoming more common in European cities. These systems make it possible to furnish users with warm water while locating the production plants in the outskirts having the double benefit of lowering the impact of pollution on the center of the city and achieving better conversion performances. In order to amortize the costs throughout the year, the system often includes a combined heat and power (CHP) plant, to exploit the energy during the summer as well, when the demand for warm water decreases. A linear programming model for the optimal resource management of such a plant is presented and some results for a real case are reported. A distribution network design problem is also addressed and solved by means of mixed integer linear programming.     

Approximation algorithms for scheduling unrelated parallel machines

We consider the following scheduling problem. There arem parallel machines andn independent jobs. Each job is to be assigned to one of the machines. The processing of jobj on machinei requires timep _ij . The objective is to find a schedule that minimizes the makespan.Our main result is a polynomial algorithm which constructs a schedule that is guaranteed to be no longer than twice the optimum. We also present a polynomial approximation scheme for the case that the number of machines is fixed. Both approximation results are corollaries of a theorem about the relationship of a class of integer programming problems and their linear programming relaxations. In particular, we give a polynomial method to round the fractional extreme points of the linear program to integral points that nearly satisfy the constraints.In contrast to our main result, we prove that no polynomial algorithm can achieve a worst-case ratio less than 3/2 unlessP = NP. We finally obtain a complexity classification for all special cases with a fixed number of processing times.A preliminary version of this paper appeared in theProceedings of the 28th Annual IEEE Symposium on the Foundations of Computer Science (Computer Society Press of the IEEE, Washington, D.C., 1987) pp. 217–224.     

考虑专家水平的土木工程质量综合评估模型

应用加权集值统计、属性数学和最小方差等方法 ,建立了考虑专家水平的量化综合评估模型 ,对土木工程质量进行多目标多人的综合评估 ,并给出计算实例 .     

Interruptible Exact Sampling in the Passive Case

We establish, for various scenarios, whether or not interruptible exact stationary sampling is possible when a finite-state Markov chain can only be viewed passively. In particular, we prove that such sampling is not possible using a single copy of the chain. Such sampling is possible when enough copies of the chain are available, and we provide an algorithm that terminates with probability one.     

A lattice boltzmann model for compressible perfect gas

A new lattice Boltzmann model for compressible perfect gas is proposed. The numerical example shows that it can be used to simulate shock wave and contact discontinuity. The results are comparable with those obtained by traditional methods. The ratio of specific heats γ may be chosen according to the requirement of problems. The project supported by the National Natural Science Foundation of China     

结构体系的非概率可靠性分析方法

结构体系的可靠性与结构的失效模式有关。在非概率条件下 ,结构体系的可靠性取决于非概率可靠性指标最小的最危险失效模式。最危险失效模式的识别及相应极限状态方程的建立是结构体系非概率可靠性计算的关键问题。文中考虑了结构参数及强度、外载荷等参量的不确定性 ,基于随机可靠性方法中常用的优化准则法 ,提出了非概率结构体系主要失效模式的枚举准则。可在只需枚举出少量主要失效模式的情况下 ,不漏掉最危险失效模式。并提出用区间增量载荷法生成主要失效模式的极限状态方程。算例分析表明文中方法是实用和有效的。