A tabu search algorithm for the minmax regret minimum spanning tree problem with interval data

This paper deals with the strongly NP-hard minmax regret version of the minimum spanning tree problem with interval costs. The best known exact algorithms solve the problem in reasonable time for rather small graphs. In this paper an algorithm based on the idea of tabu search is constructed. Some properties of the local minima are shown. Exhaustive computational tests for various classes of graphs are performed. The obtained results suggest that the proposed tabu search algorithm quickly outputs optimal solutions for the smaller instances, previously discussed in the existing literature. Furthermore, some arguments that this algorithm performs well also for larger instances are provided.     

On the existence of an FPTAS for minmax regret combinatorial optimization problems with interval data

The general problem of minimizing the maximal regret in combinatorial optimization problems with interval costs is considered. Some results are proven that allow to obtain a fully polynomial time approximation scheme (FPTAS) for the problem under the assumption that a pseudopolynomial algorithm is given.     

Influence of the random dynamic parameters of the human body on the dynamic characteristics of the coupled system of structure-crowd

The presence of human occupants may change the dynamic behaviour of structures considerably. While this effect is considered in mechanical engineering (e.g. interaction between driver seat and driver) and biomechanics (potentially damaging effects of vibrations) by using equivalent mass-spring-damper systems for the human body, the design practice in civil engineering still often clings to the so-called mass-only model, i.e. the occupants are considered only as additional masses when analysing the dynamic behaviour of floor slabs and stand structures. Recent research efforts aim to improve this situation by recommending averaged models for the human body. This approach seems to be reasonable for large crowds; however, for smaller groups, the question arises whether the random scatter in the dynamic characteristics of the human body leads to random scatter in the effective natural frequency and the effective damping of the coupled structure-crowd system. Based on a probabilistic model for the dynamic characteristics of the human body, an extensive study is presented in this paper. The key variables are the natural frequency of the bare structure, the ratio of the crowd’s mass to the structure mass and the group size. The scatter in the effective dynamic characteristics of the coupled system is revealed by the 90%-confidence interval. Furthermore, the maximum span of the respective bounds is used to identify cases where the averaged model fails to predict the real behaviour of the coupled system.     

Thermostressed State of a Hollow Glass Cylinder under the Action of Electromagnetic Radiation

We present a method for solving the problem of finding the thermostressed state of a hollow glass cylinder subjected to the action of electromagnetic radiation of the infrared frequency range. In the approximation of a nonradiating body, we derive a system of equations for determining the spectral densities of the energy fluxes of the effective radiation from the surfaces and the corresponding relations for heat generation. We present the results of numerical simulations.     

A randomized algorithm for the min-max selecting items problem with uncertain weights

This paper deals with the min-max version of the problem of selecting p items of the minimum total weight out of a set of n items, where the item weights are uncertain. The discrete scenario representation of uncertainty is considered. The computational complexity of the problem is explored. A randomized algorithm for the problem is then proposed, which returns an O(ln K)-approximate solution with a high probability, where K is the number of scenarios. This is the first approximation algorithm with better than K worst case ratio for the class of min-max combinatorial optimization problems with unbounded scenario set.     

随机激励下结构的非线性分析

针对随机时间序列载荷激励下的非线性系统,提出一种基于Z变换的递归方法．对于所获得的响应时间序列的识别,建议了一种离散小波变换（DWT）的技术．