低温下纤维束及束增强复合材料的应力集中

基于剪滞理论，采用一种六角形纤维束模型，以玻璃纤维和碳纤维束为例，计算了在低温下一纤维束内的纤维应力集中因子，并将此结果与常温下的计算结果进行比较，证实了随着温度的降低，玻璃纤维和碳纤维束中的应力集中会有不同程度改变的结论．采用修正的剪滞分析模型，研究了低温下单向玻璃和碳纤维束增强复合材料由纤维束断裂而导致的应力集中，得到的结果比现有常温下的计算结果更具实际意义，也证实了本文结果的合理性和精确性。     

THE PERIODIC CAPACITATED ARC ROUTING PROBLEM LINEAR PROGRAMMING MODEL, METAHEURISTIC AND LOWER BOUNDS

1. Introduction The Capacitated Arc Routing Problem(CARP) is defined on an undirected network inwhich a fleet of identical vehicles with limitedcapacity is based at a depot node. Each edge hasa non-negative traversal cost and can betraversed any number…     

动物体形结构的对称性

首先对两个具体的物理系统进行分析，揭示了结构对称与能量最小之间的关系，在此基础上分析和解释了动物体形结构的对称性。并认为动物体形结构的对称性是由最小能量原理决定的。     

陶瓷抛光砖粉制备蒸压硅酸盐制品研究

研究利用陶瓷抛光砖粉制备蒸压硅酸盐制品，并与粉煤灰对比。试验采用了IR、XRD、SEM以及EDS等测试方法研究其水热特性、水化产物的组成和形貌，并测试其强度。研究结果表明：陶瓷抛光砖粉在蒸压条件下有较高的火山灰活性；在相同配比条件下，抛光砖粉中参与反应的活性SiO2远比粉煤灰多，生成较低Ca/Si的水化产物，其蒸压制品强度高于粉煤灰；当石灰∶抛光砖粉＝1∶3时其蒸压制品强度较高。利用陶瓷抛光砖粉制备蒸压硅酸盐制品有广阔应用前景。     

21世纪的科技发展趋势及对策研究

21世纪科技的发展将对人类的生存空间、物质进步产生重大的影响,人类只有积极地应对科技,才能实现人类的全面发展.本文就此问题展开讨论.     

Nova Geminorum 1912 and the origin of the idea of gravitational lensing

Einstein’s early calculations of gravitational lensing, contained in a scratch notebook and dated to the spring of 1912, are reexamined. A hitherto unknown letter by Einstein suggests that he entertained the idea of explaining the phenomenon of new stars by gravitational lensing in the fall of 1915 much more seriously than was previously assumed. A reexamination of the relevant calculations by Einstein shows that, indeed, at least some of them most likely date from early October 1915. But in support of earlier historical interpretation of Einstein’s notes, it is argued that the appearance of Nova Geminorum 1912 (DN Gem) in March 1912 may, in fact, provide a relevant context and motivation for Einstein’s lensing calculations on the occasion of his first meeting with Erwin Freundlich during a visit in Berlin in April 1912. We also comment on the significance of Einstein’s consideration of gravitational lensing in the fall of 1915 for the reconstruction of Einstein’s final steps in his path towards general relativity.     

The DNA concentration effect on DNA radiation damage induced by <Superscript>7</Superscript>Li ions and γ rays

To evaluate the influence of the DNA concentration in the aqueous solution on DNA radiation damage, the plasmid DNA in the presence or absence of Mannitol （scavenger of free radical OH.） was irradiated by ^7Li ions and γ rays at various DNA concentrations. Gel electrophoresis analysis revealed that the DNA damage of single and double strand breaks induced by irradiation became more severe at lower DNA concentration. In the condition of γ-ray irradiation, most of double strand breaks （DSB） damage was neutralized and less associated with DNA concentration in the presence of mannitol. However, under ^7Li irradiation, DSB damage could not be cleared by mannitol but was gradually aggravated with decreasing DNA concentrations. These findings imply that under low-LET irradiation, most of the DSB damage is generated by free radical OH·diffusion, and thus may be counteracted by scavengers, while at higher-LET irradiation, quite a fraction of DSB induction is caused by direct ionizing energy deposition of heavy ions, which cannot be eliminated. This work also indicates that the proportion between free radical damage and direct ionizing damage is s constant which is independent of DNA concentration when the DNA concentration is under a certain value （50ng/μL）. Our study sheds light on the un- derlying mechanisms in the DNA radiation damage process.     

Influence of Monitoring Method and Control Complexity on Operator Performance in Manually Controlled Spacecraft Rendezvous and Docking

This study focuses on the influence of the monitoring method and control complexity on the operator performance in manually controlled spacecraft rendezvous and docking (RVD).Two one-factor experiments were designed on a simulated RVD system.One examined the video guidance and periscope monitoring methods,and the other examined three control complexity levels using one-axis RVD control,twoaxis RVD control,and three-axis RVD control.Eighteen male volunteers aged 22-35 participated in the experiments.The results show that the RVD operating time increases with control complexity.Based on the operators' findings,the two-axis control is the easiest.The monitoring method has no significant influence on failure rate with the low complexity using one-axis RVD control.     

A Binary Integer Program to Maximize the Agreement Between Partitions

This research note focuses on a problem where the cluster sizes for two partitions of the same object set are assumed known; however, the actual assignments of objects to clusters are unknown for one or both partitions. The objective is to find a contingency table that produces maximum possible agreement between the two partitions, subject to constraints that the row and column marginal frequencies for the table correspond exactly to the cluster sizes for the partitions. This problem was described by H. Messatfa (Journal of Classification, 1992, pp. 5–15), who provided a heuristic procedure based on the linear transportation problem. We present an exact solution procedure using binary integer programming. We demonstrate that our proposed method efficiently obtains optimal solutions for problems of practical size. We would like to thank the Editor, Willem Heiser, and an anonymous reviewer for helpful comments that resulted in improvements of this article.