工程实践中的体系与系统

 介绍了国际上通行的体系概念，通过实例阐述了常见的体系类型，从多个维度描述了系统与体系的区别，根据实践总结，提出体系与系统的核心界定准则，并结合工程实践进行了详细描述。     

Predicting Initial Formation Temperature for Deep Well Engineering with a New Method

With the progress of science and technology, human beings explore the energy under-ground with thousands of meters. As a thermophysical parameter, initial formation temperature (IFT) plays an essential...     

Effect of Y_2O_3 content in the pack mixtures on microstructure and oxidation resistance of B–Y modified silicide coating

B–Y modified silicide coatings were prepared on Nb–Si based alloy by pack cementation at 1300 ℃ for 10 h. The effect of Y_2O_3 content in the pack mixtures on microstructure and oxidation resistance of the coatings was investigated. The results show that the four coatings have similar structures, which possess a(Nb,X)Si_2 outer layer and a(Nb,X)_5Si_3 transitional layer. Y_2O_3 content in the pack mixtures has an obvious effect on the Si content in the coating. The mass gains of the coatings prepared with 0.5, 1, 2 and 3 wt% Y_2O_3 in pack mixtures are 2.33, 1.96, 2.05 and 2.86 mg/cm~2 after oxidation at 1250 ℃ for 100 h, respectively. The coating prepared with 1 wt% Y_2O_3 exhibits the best oxidation resistance due to the formation of a dense glass-like borosilicate scale.     

Effect of Mo content on microstructure and stress-rupture properties of a Ni-base single crystal superalloy

The additional 1.5 wt% Mo was added in a Ni-base single crystal(SC) alloy with the composition of Ni–6.5Al–8.0Mo–2.4Cr–6.2Ta–4.9Co–1.5Re–(0.01–0.05)Y(wt%) to study the effect of Mo content on the microstructure and stress-rupture properties. The creep and stress-rupture tests under the conditions of 850 °C/500 MPa and 1100 °C/130 MPa were conducted, and the microstructure of as-cast, heat treated and stress ruptured specimens were analyzed. It was found that the 1.5 wt% Mo addition enhanced the stress-rupture lives at both intermediate(850 °C) and high(1100 °C)temperatures. The microstructure analysis showed that adding 1.5 wt% Mo in the basic alloy affected the microstructure dramatically, i.e., the Mo-rich phases formed in the specimens of as-cast and stress-ruptured specimens. It is considered that the improvement of the stress-rupture lives is duo to the strengthening effect of Mo to both γ and γ'phases and the decrease of stacking fault energy, diffusion constant and dislocation spacing. The Mo-rich phases precipitated under condition of 1100 °C/130 MPa did not affect the creep and stress-rupture properties obviously in the present study.     

Atomic-scale segregation behavior of Sn/Ti and O at Σ3[11¯0](111) grain boundary in niobium

First-principle calculation was performed to illustrate the atomic arrangement and segregation behavior of Sn/Ti and O in View the MathML source grain boundary, and the interaction of oxygen interstitials with Sn/Ti atoms on the grain boundary was studied. The analyses on the segregation energies and geometric positions, and the electron densities show that Sn, Ti and O atoms segregate at the Σ3 grain boundary. And the preferred segregation sites of the impurities at View the MathML source were determined. When Sn segregates at grain boundary plane, the O atom prefers to the bulk-like site and shows no segregation tendency at grain boundary, whereas the segregated Ti atom can slightly enhance oxygen segregation at the grain boundary.     

大众化再解读视角的我国高等教育发展思考

大众化在本质意义上是高等教育适应经济社会发展规律及其自身发展规律的重大变革和调整.它绝非意味着高等教育质量整体水平的降低,而是蕴涵着高等教育质量结构及其特点发生重大调整和变化;绝非意味着某一类型或某些层面的高校规模片面地发展,而是意味着高校结构整体的重大调整和创新;绝非仅仅意味着适龄青年接受高等教育比例的提高,还意味着为社会公众提供更多的终身教育机会.     

云计算环境中优化遗传算法的资源调度策略

资源调度是云计算的核心问题,传统遗传算法(GA)、Sufferage算法等都可以用于云计算环境中的资源调度,但传统遗传算法存在收敛慢、易早熟等缺点,Sufferage算法则不适用于多聚类环境的密集型任务调度.本文在充分考虑云计算环境的动态异构性和大规模任务处理特性的基础上,提出了一种基于染色体编码方式和适应度函数的改进遗传算法(IGA),并在云仿真器CloudSim上对3种算法进行了仿真.仿真结果表明,该算法在性能和服务质量QoS(Qualityof Service)方面都优于传统遗传算法和Sufferage,能更好地适用于大规模任务下的云计算环境资源调度.     

船体结构粘弹性夹层阻抑振动波传递特性研究

基于波动理论分析了含粘弹性材料夹层的船体板架中振动波传递特性,给出粘弹性夹层对弯曲波的隔声量公式.同时将粘弹性夹层引入转角含阻振质量的典型船舶L型结构中,通过多次构造阻抗失配有效地阻断船体振动噪声主分量的传递.在此基础上,将这种复合隔振技术引入到动力舱段声学设计中并开展相应的数值实验.结果表明:粘弹性夹层对船体结构波具有较强的阻抑作用,夹层隔振性能随其杨氏模量降低及尺度增加而增大,夹层杨氏模量对隔声量的影响较其尺度更为显著,在刚性隔振基础上联合应用较小尺度的聚氨酯夹层可显著增加隔振效果并有效拓宽了隔振频带,具有较高的效费比.     

关于我国新一轮环保科技体制改革的若干思考

作为科技体制的部门延伸,环保科技体制是促进环保科技发展、应对我国严峻环境问题的重要条件和保障。本文通过问卷调查,剖析了我国当前环保科技体制存在的主要问题及产生原因,并为新一轮环保科技体制改革的启动提供了相应的政策建议。     

基于广义能量法的车辆制动稳定性分析

运用广义能量法和能量相平面方法分析了车辆转弯制动过程中的非稳态特性和能量转换特性.结合魔术公式轮胎模型,建立了考虑载荷转移的车辆9DOF非线性动力学模型.基于VBOX惯性测量技术搭建车载稳定性测量系统验证了模型的可靠性,运用广义能量法和相平面分析方法建立了车辆能量转换分析模型.在Matlab环境下仿真分析了转弯制动工况下车辆能量时变及转换特性.结果表明,车辆制动初始时间区域为车辆失稳和施加控制的关键区域,在较小转向角制动时以横摆控制为主,转向角较大时应兼顾侧向控制和横摆控制.