改进遗传算法求解有时间窗车辆路由问题

为了有效求解带有时间窗的车辆路由问题,在标准遗传算法的基础上,引入两代竞争近距淘汰选择算子,用欧氏距离来判断个体之间的距离作为个体的相似程度,相似程度高且适应度差的个体被淘汰,并辅以循环交叉算子和插入变异算子,构造出了一种改进的遗传算法.仿真实验表明,改进的算法在迭代过程中能有效保持群体的多样性,避免出现早熟现象而陷入局部极值点,提高遗传算法的内在并行性.同时通过竞争淘汰,使局部搜索能力得到加强,加快了搜索速度.改进算法所计算出的结果优于用轮盘赌和自适应选择作为选择算子的遗传算法的结果.     

固液流化床中不同粒径粒子群的滑流速度

在稳定的流动状态下,实验考察了铅直管内粒径不同的两组分粒子群的滑流速度,并与每一组分单独存在时的值进行了对比.相对于单组分时的滑流速度,两组分场合的每一组分的滑流速度都会发生偏离并相互接近,偏离的程度受两个粒子群的粒径比、浓度比以及总粒子浓度的影响.通过对两个粒子群之间的相互影响因素的定量分析,以单成分的空隙方程式为基础,建立了在多种操作条件下直接计算滑流速度的模型.     

基于USB双机通信的设计与实现

USB由于其速度快、支持热插拔、稳定性好、用户使用方便、支持即插即用等优点,现已成为PC机的标准总线接口。介绍了一种利用USB总线接口来实现的双PC机互联的技术方案。     

The utilization of two‐metre Countryside Stewardship Scheme grass margins by the gatekeeper Pyronia tithonus (L)

The utilization of 2‐m Countryside Stewardship Scheme (CSS) grass margins by Pyronia tithonus was investigated during the period 1997–2000 at three farms in Essex, UK. The aims of the research were to investigate whether 2‐m grass margins established using the CSS would provide suitable habitat for P. tithonus. Overall, there was no significant difference between P. tithonus abundance on the 2‐m grass margins and the control sections without margins, but significantly more P. tithonus were observed on the 2‐m grass margins in 2000 than in 1997. There was a strong relationship between P. tithonus abundance and the presence of hedgerows, and significantly more P. tithonus were recorded on 2‐m grass margins next to hedgerows than on 2‐m grass margins established in areas without adjacent hedgerows. It was suggested that P. tithonus would benefit most from habitats with 2‐m grass margins sown with a seed mixture containing a range of fine‐leaved grasses and wildflowers, next to a hedgerow, and managed in accordance with current practices.     

从Techné特刊看现代西方技术哲学的转向

在国际技术哲学学会(SPT)成立35周年、Techné创刊15周年之际,Techné在2010年第2期组织了一期特刊,回顾了SPT的建制化发展历程,考察了技术哲学过去35年的历史演变,总结了在这一时期取得的主要成就,并对未来技术哲学的新动向做了展望。这有助于我们更好地了解现代技术哲学的发展状况,对我国技术哲学今后的发展有重要的启示意义。     

Gas-liquid phase coexistence and finite-size effects in a two-dimensional Lennard-Jones system

The gas-liquid phase coexistence in a two-dimensional Lennard-Jones system is investigated using Maxwell construction method together with molecular dynamics simulations.The results of phase coexistence in different truncations of the potential are compared with data obtained from the literature,and the corresponding critical properties calculated.The crossover from Ising-like to mean field behavior is observed and confirmed as the temperature approaches the critical point from below.Performing simulations on systems with different sizes,we find that a finite size effect is more significant than those shown in most of the previous results,and a lower critical temperature is obtained when the full extent of this finite size effect is considered.     

跳分形过程下延展期权定价

当标的资产遵循跳分形过程时, 构建了延展期权的评估框架. 首先, 在风险中性环境里, 对标的资产发生跳跃次数的收益求条件期望现值, 导出了延展一期的看涨期权解析定价公式, 并探讨了公式的一些特殊情形. 然后, 将定价公式延展到\,$M$\,期, 该延展期权价值在\,$M$\,趋于无穷极限状态时, 将收敛于永久延展期权. 提出了一种简单有效的两点外推法求极限. 最后, 提供数值结果, 阐述了定价表达式的简单实用.     

中心二次曲线的一个轨迹特征

证明了平面曲线c是中心二次曲线的充要条件为:c是到两定点连线的斜率之积为一非零常数的点的轨迹,并就此常数的变化与轨迹类型和图形形状的关系进行了讨论.     

拉氏（Laguerre）双曲型有核圆汇的一个性质及其应用

本文得到了拉氏(Laguerre)双曲型有核圆汇的一个性质,即拉氏双曲型有核圆汇δ(Z-Z_0)=-k(k>0)可以看成由抛物型线性圆列族lⅠ(α,β)和lⅡ(α,β)所构成。构造出lⅠ(α,β)和lⅡ(α,β)的矩阵方程,并用代数法和作图法解决了如何寻求一个双曲型有核圆汇和两个抛物型有核圆汇的公共圆问题。