Effect of increased linings on micro-pressure waves in a high-speed railway tunnel

A micro-pressure wave (MPW) is generated when a train enters a tunnel at high speed, which causes a strong impact on the environment around the tunnel. The increased lining used to repair damage in high-speed railway tunnels changes cross-sections and has a strong influence on the MPW at the tunnel exit. In this paper, the methods of full-scale measurement, numerical simulation and moving-model experiments are used to study the MPW generated in a tunnel whose lining is increased. The rules governing the effect of increased linings on MPWs are obtained, which can be used as a reference for the Tunnel Damage Regulation Project in China.     

标准CMOS工艺在高速模拟电路和数模混合电路中的应用展望

从速度、集成度、功耗和成本等几个方面深入的分析了利用标准CMOS工艺来设计开发高速模拟器件和混合处理芯片的现状及发展潜力。     

电子类EDA教学中引入MPW计划的研究与实践

EDA技术的快速发展，给我国高校电子技术教学带来严峻挑战。如何使高校培养的EDA人才符合市场需求，是现代EDA教学改革的目标。论文首先分析了现代EDA教学现状，介绍了MPW的基本概念及国内外MPW计划的实施情况，然后提出在本科电子类EDA教学中结合科研项目，引入MPW计划的必要性和可行性，并以多年来我校工程实践和毕业设计实践说明MPW计划在现代电子设计教学和人才培养中的作用。     

Wave formation mechanism in magnetic pulse welding

Wavy interface morphology is observed in Magnetic Pulse Welding (MPW) similarly to that of the Explosion Welding process (EXW). It is recognized that interfacial waves are formed in a periodic manner and have well defined wavelength and amplitude. The phenomenon of wave formation in EXW has been subjected to extensive investigations in which empirical and numerical models have been published. In the present study, a wave formation mechanism for MPW is presented. This wave-creation mechanism was studied by evaluating the influence of sample geometry on wave morphology using stereoscopic optical microscopy. It was found that interfacial waves are formed in a Kelvin–Helmholtz instability mechanism. Reflected shock waves interact with the welding collision point at the weld interface, where interferences are the source for the wave's initiation. The collision energy, impact angle, and the geometry of the joint, were found to have the most significant influence on the waves' characteristics. An empirical relationship between interfacial wavelength and the free moving distance of the shock waves in the welded tubular parts was found.     

考虑缺陷率模型的多项目晶圆布图规划算法

针对随机缺陷会降低多项目晶圆实际产出的问题,提出一种新的多项目晶圆布图规划算法。通过在布图规划中引入缺陷率模型的方法,增加芯片产量的裕量,降低因随机缺陷造成的产量损失。同时优化模拟退火流程,使得在布图尺寸约束条件下,布图规划过程能够跳出局部最优解陷阱。对工业实例进行布图规划的结果表明,该算法能够接受不满足布图尺寸约束条件的中间结果,从而遍历解空间,得到全局最优的布图,并且相对已有算法,使用相同数量晶圆进行切割时,算法的布图结果增加了137%的芯片产量的总裕量,同时,降低了25%的工作芯片所需要生产的晶圆数量。     

利用光刻机挡板优化MPW光罩布局

伴随着国内市场竞争的日趋激烈,常规的MPW(多项目晶圆)布局也不能满足客户的要求,同时也不能最大限度地降低设计公司的研发成本,也不利于国内foundry厂市场的开拓.鉴于此,文章着重提出了利用光刻机挡板把光罩进行区域划分,在不增加流片和满足客户要求的前提下,使光罩得到最大限度的利用,降低了客户的流片费用.通过在15cm...     

电磁轴承功率放大器参数设计

由于功率放大器处于电磁轴承系统的执行环节,其动态性能将直接影响系统的性能。为了提高电磁轴承系统的性能,针对电流响应速度、力的响应速度、同频允许的最大振幅和不平衡量控制等指标,以采用最小脉宽开关功率放大器的电磁轴承系统为例,从系统的频响角度出发,分析了满足实际工况下功率放大器参数设计要求。从而在保证系统运行性的同时,通过合理设计功率放大器的主要个数,节省设备制造成本。在经过理论分析和仿真试验之后,给出一些设计的实例,从而对实际电磁轴承功率放大器的设计提供了指导依据。     

Pyrolytic liquid fuel: A source of renewable electricity generation in Makkah

Millions of Muslims from all over the world visit the Holy Cities of Saudi Arabia: Makkah and Madinah every year to worship in form of Pilgrimage (Hajj) and Umrah. The rapid growth in local population, urbanization, and living standards in Makkah city along with continually increasing number of visitors result in huge municipal solid waste generation every year. Most of this waste is disposed to landfills or dumpsites without material or energy recovery, thus posing substantial environmental and health risks. The municipal plastic waste is the second largest waste stream (up to 23% of total municipal waste) that is comprised of plastic bottles, water cups, food plates, and shopping bags. The sustainable disposal of plastic waste is challenging task due to its clogging effects, very slow biodegradation rates, and presence of toxic additives and dyes. Pyrolysis is one of the promising waste-to-energy technology for converting municipal plastic waste into energy (liquid fuel) and value-added products like char. The produced liquid fuel has the potential to be used in several energy-related applications such as electricity generation, transportation fuel, and heating purposes. It has been estimated that the plastic waste in Makkah city in 2016 can produce around 87.91 MW of electricity. This is projected to increase up to around 172.80 MW of electricity by 2040. A global warming potential of 199.7 thousand Mt.CO₂ eq. will be achieved with savings of 7.9 thousand tons emission of CH₄, if pyrolysis technology is developed in Makkah city. Furthermore, a total savings of 297.52 million SAR from landfill diversion, electricity generation, and carbon credits would be possible to achieve in 2016 from pyrolysis. These economic benefits will increase every year and will reach up to 584.83 million SAR in 2040.     

Measurement and analysis technologies for magnetic pulse welding: established methods and new strategies

Magnetic pulse welding (MPW) is a fast and clean joining technique that offers the possibility to weld dissimilar metals, e.g., aluminum and steel. The high-speed collision of the joining partners is used to generate strong atomic bonded areas. Critical brittle intermetallic phases can be avoided due to the absence of external heat. These features attract the notice of industries performing large scale productions of dissimilar metal joints, like automotive and plant engineering. The most important issue is to guarantee a proper weld quality. Numerical simulations are often used to predict the welding result a priori. Nevertheless, experiments and the measurement of process parameters are needed for the validation of these data. Sensors nearby the joining zone are exposed to high pressures and intense magnetic fields which hinder the evaluation of the electrical output signals. In this paper, existing analysis tools for process development and quality assurance in MPW are reviewed. New methods for the process monitoring and weld characterization during and after MPW are introduced, which help to overcome the mentioned drawbacks of established technologies. These methods are based on optical and mechanical measuring technologies taking advantage of the hypervelocity impact flash, the impact pressure and the deformation necessary for the weld formation.     

Application of high velocity impact welding at varied different length scales

Three complementary impact welding technologies are described in this paper. They are explosive welding, magnetic pulse welding, and laser impact welding, which have been used to provide metallurgical bonds between both similar and dissimilar metal pairs. They share the physical principle that general impact-driven welding can be carried out by oblique impact but are used at different length scales from meters to sub-millimeter. The different length scales require different kinds of systems to drive the process, and the scales themselves can give different weld morphologies. Metallographic analysis on cross-sections shows a wavy interface morphology which is likely the result of an instability associated with jetting, which scours the surfaces clean during impact. The normalized period and amplitude of the undulations increase with increasing impact energy density. Microhardness testing results show the impact welded interface has a much greater hardness than the base metals. This can lead to weldments that have strengths equal to or greater than that of the weakest base material.