Is Empty Spacetime a Physical Thing?

This article deals with empty spacetime and the question of its physical reality. By “empty spacetime” we mean a collection of bare spacetime points, the remains of ridding spacetime of all matter and fields. We ask whether these geometric objects—themselves intrinsic to the concept of field—might be observable through some physical test. By taking quantum-mechanical notions into account, we challenge the negative conclusion drawn from the diffeomorphism invariance postulate of general relativity, and we propose new foundational ideas regarding the possible observation—as well as conceptual overthrow—of this geometric ether.     

Theoretical study of synthetic reaction of tetrazole and tetrazolate anion

Tetrazole (H₂CN₄) and tetrazolate anion (HCN$_{4}^{-}$) are high‐energy compounds with a five‐membered ring‐type structures, which can be easily synthesized by HCN and HN₃ and by HCN and N$_{3}^{-}$, respectively, in an irreversible reaction. The ab initio methods including MP2/6‐31G**, B3LYP/6‐31G**, B3LYP/6‐311+G(2d,p), and CBS/QB3 from Gaussian 98 program are employed to study the thermochemistry and reaction mechanism. The transition states of both HCN + HN₃ → H₂CN₄ and HCN + N$_{3}^{-}$ → HCN$_{4}^{-}$ reaction are investigated, and it is found that the latter reaction is more favored than the former one in view of the chemical kinetics and thermodynamics, thus indicating that tetrazole (H₂CN₄) and tetrazolate anion (HCN$_{4}^{-}$) are formed more easily in an alkali environment than in other systems. Pentazole (HN₅) is an unknown high‐energy compound and has not yet been synthesized. For comparison, HN₅ and N$_{5}^{-}$, both which have similar type of synthetic reactions to the above‐mentioned reactions, are studied. © 2000 John Wiley & Sons, Inc. Int J Quant Chem 80: 27–37, 2000     

A tabu search procedure for multicommodity location/allocation with balancing requirements

We propose a tabu search heuristic for the location/allocation problem with balancing requirements. This problem typically arises in the context of the medium term management of a fleet of containers of multiple types, where container depots have to be selected, the assignment of customers to depots has to be established for each type of container, and the interdepot container traffic has to be planned to account for differences in supplies and demands in various zones of the geographical territory served by a container shipping company. It is modeled as a mixed integer program, which combines zero-one location variables and a multicommodity network flow structure. Extensive computational results on a set of benchmark problems and comparisons with an efficient dual ascent procedure are reported. These show that tabu search is a competitive approach for this class of problems.     

Tensile Properties and Morphology of Oil Palm Empty Fruit Bunch Regenerated Cellulose Biocomposite Films

The regenerated cellulose (RC)biocomposite films were prepared using casting method where oil palm empty fruit bunch (OPEFB) and microcrystalline cellulose (MCC) were dissolved in N-dimethylacetamide/lithium chloride (DMAc/LiCl)solution. The increasing of OPEFB contents up to 2 wt% increased the tensile strength and modulus of elasticity of RC biocomposite films while the elongation at break decreased. However, at 3 and 4 wt% of OPEFB content, the tensile strength and modulus of elasticity decreased with increases OPEFB content, but elongation at break increased. The increment of tensile strength and modulus of elasticity at 2 wt% is due to the OPEFB fiber that partially dissolved and dispersed with the OPEFB matrix. The morphology studies illustrate that at 2 wt% of OPEFB content of biocomposite films surface consists less voids and agglomerations than at 4 wt%. This can be considered the RC filler was partially dispersed with the RC matrix in the biocomposite films.     

综放孤岛面空巷加固措施

探讨了综放孤岛面空巷的加固方案,阐述了对综放孤岛面空巷进行加固的施工工艺,包括打锚索加固、注玛丽散加固、充超高水材料等,以保证综采工作面顺利通过空巷。     

基于自适应变异粒子群算法的铁路空车调配

提出一种用于求解铁路空车调配的自适应变异粒子群算法.该算法在迭代过程中加入了变异操作,根据群体适应度方差调整变异概率的大小,并通过调整惯性权重因子来增强算法跳出局部最优的能力.将自适应变异粒子群算法用于铁路空车调配,建立以空车总走行距离最小为目标的数学模型,并在此基础上设计相应的算法.算例结果表明,应用自适应变异粒子群...     

MSEM增压系统一维非定常流计算模型的改进

对ＭＳＥＭ增压系统一维非定常流数值模拟中影响计算精度的四个主要因素：气阀端、变截面段、质量添加段及计算时间步长进行了分析，并提出了改进措施。计算结果表明，流量误差得到显著减小。     

关爱“空巢老人”——社区图书馆亟待关注的社会课题

随着社会的发展,我国的老龄化问题越来越严重,尤其是＂空巢＂老人的问题更是值得人们关注。针对＂空巢＂老人的问题,分析了社区图书馆为空巢老人服务的必要性,提出了社区图书馆开展人性化服务的对策措施。