计算机通信接口与物理实验

在物理实验中引入“计算机应用”是当前教改的任务之一。也是实验教学发展的必然趋势。本通过重力加速度和型材杨氏模量的测量实验，说明计算机通信接口在物理实验中应用的可行性。     

Geodetic VLBI data analysis using VLBI3 software

Summary VLBI (Very Long Baseline Interferometry) geodetic data have been analysed. Baseline, lengths of several thousands kilometers and their time rates have been estimated from a subset of data, spanning three years, of the IRIS project and using VLBI3 software. A weighted-least-squares estimation has been carried out with thea priori standard deviations of the data modified to account for systematic biases due to mismodelling of the clocks and atmosphere. Comparisons with independent analysis show an agreement to the cm level or better both in baseline lengths and rates.     

Strings and branes under microscope

It is shown that in the standard vacuum 5D Kaluza‐Klein gravity there exist wormhole‐like solutions which look like strings attached to two D‐branes. The asymptotic behaviour of the corresponding metric is investigated.     

On the first Laplacian eigenvalue and the center of gravity of compact hypersurfaces

For a closed hypersurface in a space form, this work provides some sharp upper bounds for its first positive Laplacian eigenvalue. These bounds are extrinsic as they rely on the mean curvatures and center(s) of gravity of the hypersurface. Received: May 22, 2000     

一种超高耐久混凝土——梯度结构混凝土

分析超高耐久混凝土的研究现状,提出了一种高耐久、低成本的超高耐久混凝土--梯度结构混凝土(Gradient Structural Concrete,简称GSC),采用电量法和氯离子扩散系数法来评价梯度结构混凝土的抗氯离子渗透性能,最后进行梯度结构混凝土的寿命预测与成本分析.结果表明,高性能混凝土(High Performance Concrete,简称HPC)、无细观界面过渡区水泥基复合材料(Meso-interfacial transition zone-free cement-based materials,简称 MIF)和梯度结构混凝土MIF-HPC的6 h导电量和氯离子扩散系数的排列顺序均为:HPC>MIF-HPC>MIF,其抗氯离子渗透性能排列顺序为:MIF>MIF-HPC>HPC.梯度结构混凝土的成本会有所增加,但由于其氯离子渗透性能大幅降低,其使用寿命得到大幅延长,使得其年损耗费用大幅下降.     

High gravity batch and continuous processes for beer production: Evaluation of fermentation performance and beer quality

This study deals with two innovative brewing processes, high gravity batch and complete continuous beer fermentation systems. The results show a significant influence of the variables such as concentration and temperature on the yield factor of the substrate into ethanol and consequently on the productivity of the high gravity batch process. The technological feasibility of continuous production of beer based on yeast immobilization on cheap alternative carriers was also demonstrated. The influence of process parameters on fermentation performance and quality of the obtained beers was studied by sensorial analysis. No significant difference in the degree of acceptance between the obtained products and some traditional market brands was found. Presented at the 34th International Conference of the Slovak Society of Chemical Engineering, Tatranské Matliare, 21–25 May 2007.     

Selection of a staggered grid for inertia‐gravity waves in shallow water

The problem of accuracy in propagating inertia‐gravity waves on Arakawa grids is investigated. It is shown that the sole analysis of spatial discretization and the recommendation of the B‐grid for coarse resolution models and C‐grid for high resolution models must be re‐analysed when time discretization is taken into account as well. For a chosen time discretization, a coarse C‐grid is shown for example, to increase precision when using larger time‐steps (up to the stability limit) whereas the precision of the B‐grid decreases. Here, an analysis of error for different grids in function of the space–time resolutions and computational costs is presented and some recommendations on the choice of the particular staggered grid for a given application are outlined. Copyright © 2002 John Wiley & Sons, Ltd.     

无粘结力后张预应力钢筋在桥梁建设中的应用

为了解决天津永和斜拉桥主梁块件预制，首次提出在三向预应力块力中竖向预应力篇采用无粘结为预应为粗钢筋，主要解决块件断面较弱制孔困难，压浆串浆，简化施工工序。     

Search space pruning and global optimisation of multiple gravity assist spacecraft trajectories

We introduce and describe the Multiple Gravity Assist problem, a global optimisation problem that is of great interest in the design of spacecraft and their trajectories. We discuss its formalization and we show, in one particular problem instance, the performance of selected state of the art heuristic global optimisation algorithms. A deterministic search space pruning algorithm is then developed and its polynomial time and space complexity derived. The algorithm is shown to achieve search space reductions of greater than six orders of magnitude, thus reducing significantly the complexity of the subsequent optimisation. This work was partially funded under the Ariadna scheme of the European Space Agency, contract number 18138/04/NL/MV.     

Some aspects of gravitational quantum mechanics

String theory, quantum geometry, loop quantum gravity and black hole physics all indicate the existence of a minimal observable length on the order of Planck length. This feature leads to a modification of Heisenberg uncertainty principle. Such a modified Heisenberg uncertainty principle is referred as gravitational uncertainty principle(GUP) in literatures. This proposal has some novel implications on various domains of theoretical physics. Here, we study some consequences of GUP in the spirit of Quantum mechanics. We consider two problem: a particle in an one-dimensional box and free particle wave function. In each case we will solve corresponding perturbational equations and compare the results with ordinary solutions.