小直径薄壁管直接拉伸方法研究

大学材料性能实验教学通常以棒料单向拉伸为主要内容,而未能兼顾各种型材在服役状态下的几何属性对材料属性的影响。研究小直径薄壁管直接拉伸实验技术和方法,并将其引入实验教学,使学生通过实验自主地分析塞头装配、试样类型及加载速率对拉伸结果的影响,取得了良好的实践教学效果,对管形状态下材料力学性能的准确获取与促进管材塑性成形理论研究具有重要学术意义。     

大学校长之背景特征与大学绩效分析——基于高阶理论的视角

为发现大学校长对大学绩效影响的共性背景特征,本文以高阶理论为理论依据,全面分析大学校长的人口统计学背景、教育背景、工作背景和学术背景对大学绩效的影响。通过对2007-2010年期间大学进步较快与退步较快两组样本的对比,本研究发现了两组大学校长在教育背景、工作背景方面诸多不同于直觉的实证结论,而在人口统计学背景、学术背景方面无明显差别。     

西辽河流域的古代都市——辽上京临潢府（上）

西拉木伦河流域是西辽河的主要干流,10世纪初由契丹人在西拉木伦河流域建立起来的辽上京城成为辽王朝的统治中心。这是中国古代北方民族继北魏之后所建立的最壮观最辉煌的一座特殊都市。自金朝灭亡后,辽上京城渐渐淡出人们的视野。清康熙至嘉庆年间,由编写＂大清一统志＂的文人们发现并确认了辽上京城的所在位置。以往中外学术界一直认为,辽上京城的重新发现是清道光年间蒙古学者张穆所撰写的《蒙古游牧纪》一书,这种观点是错误的。其实最迟在《嘉庆重修大清一统志》中已经有明确记载。此外,契丹人所修建的辽上京城从＂二元＂理念出发,采用了＂北朝南市＂的二元体制,分为南北二城。北城即皇城,为辽朝皇帝的临政之所;南城即所谓汉城则是以容纳汉人为主体的包括契丹人之外的各族人的生产、生活、市易、井肆、居住的场所。辽上京城是西辽河流域古代都市文明的标志,对东北亚乃至内陆亚洲的文化交流与传布,商品贸易的往来等都产生了不可估量的作用。     

Dynamic analysis of a high-speed train operating on a curved track with failed fasteners

A high-speed train-track coupling dynamic model is used to investigate the dynamic behavior of a high-speed train operating on a curved track with failed fasteners. The model considers a high-speed train consisting of eight vehicles coupled with a ballasted track. The vehicle is modeled as a multi-body system, and the rail is modeled with a Timoshenko beam resting on the discrete sleepers. The vehicle model considers the effect of the end connections of the neighboring vehicles on the dynamic behavior. The track model takes into account the lateral, vertical, and torsional deformations of the rails and the effect of the discrete sleeper support on the coupling dynamics of the vehicles and the track. The sleepers are assumed to move backward at a constant speed to simulate the vehicle running along the track at the same speed. The train model couples with the track model by using a Hertzian contact model for the wheel/rail normal force calculation, and the nonlinear creep theory by Shen et al. (1984) is used for wheel/rail tangent force calculation. In the analysis, a curved track of 7000-m radius with failed fasteners is selected, and the effects of train operational speed and the number of failed fasteners on the dynamic behaviors of the train and the track are investigated in detail. Furthermore, the wheel/rail forces and derailment coefficient and the wheelset loading reduction are analyzed when the high-speed train passes over the curved track with the different number of continuously failed fasteners at different operational speeds. Through the detailed numerical analysis, it is found that the high-speed train can operate normally on the curved track of 7000-m radius at the speeds of 200 km/h to 350 km/h.     

How history becomes a cross-border matter: death foretold of a French–German–Swiss textbook

The middle of the 1990s saw the creation of a French–German–Swiss history textbook supported by the European Commission. Disseminated to school instructors in the Upper Rhine, it received generally positive reviews, but ended up on the dusty shelves of school libraries. This result was due to several factors, which are analysed in this article. This acknowledgement of failure leads to the argument that European cross-border cooperation is constrained by a key paradox, referred to as ‘low gravity’, i.e. the attraction of small projects toward the local and regional levels, while major projects are pushed up to the national level.     

皮带煤仓转载工程施工体会

本文介绍了开滦钱家营矿业分公司八采区皮带煤仓转载工程的卸载硐室、煤仓、给煤机硐室的施工工艺,采用合理、先进的施工方案,实现了安全、优质、高效。     

长江上游流域径流变化与分布式水文模拟

研究长江洪水和水资源问题,对于长江流域的可持续发展极为重要。本文以长江上游流域16个主要控制站径流观测数据为基础,对长江上游流域径流变化及其影响原因进行分析。结果表明,除金沙江流域径流微弱增加外,其他流域径流都有一定程度的减少趋势,其中岷江流域高场、横江流域横江、沱江流域李家湾、嘉陵江流域小河坝、武胜、北碚等站的径流显著减少,长江上游干流控制站寸滩站径流则微弱减少。针对流域气候变化与人类活动对水资源量的变化影响,建立大尺度分布式月水量平衡模型,将模型应用于长江上游的7个区间,模拟结果表明模型精度较高。最后应用分布式月水量平衡模型定量识别气候变化及人类活动对流域径流变化的贡献率,长江上游寸滩站径流减少,气候变化是主要影响因素,贡献率为71.43%;而岷江和嘉陵江流域的径流减小,人类活动贡献率大约占到一半。     

Java的多线程动画技术

讨论了网络教学软件中原始图像的加载问题,给出了一种高效正确的多线程解决方案和其例程片断。     

采煤工作面瓦斯治理技术的探讨与应用——煤矿井下采煤工作面上隅角瓦斯治理装置

煤矿井下采煤工作面上隅角瓦斯治理输送装置,它是一种治理煤矿井下壁式采煤工作面上隅角瓦斯积聚的设备。主要解决现有煤矿井下采煤工作面上隅角存在的瓦斯积聚而超标易造成瓦斯爆炸和治理费用昂贵的技术难点。本装置属于环保节能型,具有技术先进,科学合理、治理瓦斯有效、治理费用低和经济效益好等优点,能有效解决和治理采煤工作面上隅角瓦斯积聚问题,从而达到煤矿井下采煤工作面安全生产的目的。     

考虑装船机联机作业的煤炭出口码头装船作业调度优化

为提高煤炭出口码头作业效率和服务水平,对装船作业调度进行优化。在考虑装船机联机作业的前提下,以最小化煤炭出口码头作业线运行能耗成本和船舶在港时间成本为目标,综合考虑作业流程约束和泊位、垛位和作业线的作业唯一性约束,建立混合整数规划模型,并设计基于仿真解码方案的遗传算法求解。用实例验证模型的可行性和算法的有效性。结果表明,研究成果可为具有工艺流程复杂、装船机联机作业等特点的煤炭出口码头装船作业调度问题提供较好的解决方案。