A dynamic model with substructures for contact-impact analysis of flexible multibody systems

In the fields of science and engineering, many kinds of impact problems of flexible multi-body systems, such as impact of objects on a spacecraft and collision caused by locking of space-craft extension mechanisms, are frequently encountered. They are referred to as contact-impact problems when people are not interested in the local deformation close to contact points but in the transient dynamic response in contact-impact duration. It is necessary to investigate contact- impact dynamics of f…     

宜业尚品——台泥承诺2030年吨水泥排碳量降至585公斤

如何看待"宜业尚品、造福人类"的行业发展新目标对于"宜业尚品、造福人类"的行业发展新目标,我相信每一个台泥人会产生强烈的共鸣。台泥集团长期关注"人与自然环境、工厂与社会"之间的关系,积极推动工厂与社会的对话。全世界现在面临最大的问题是干净的能源以及如何处置社会废弃物。     

Microstructure and mechanical properties of Mg-5Li-1Al sheets prepared by accumulative roll bonding

Ultrafine-grain and high-strength Mg-5Li-1Al sheets were prepared by accumulative roll bonding (ARB) process. Evolution of microstructure and mechanical properties of ARB-processed Mg-5Li-1Al sheets was investigated.Results show that, during ARB process, the evolution of deformation mechanism of t Mg-5Li-1Al alloy is as follows: twinning deformation, shear deformation, forming macro shear zone, and finally dynamic recrystallization (DRX). The grain refining mechanism changes from twin DRX to rotation DRX. With the increase in ARB cycles, strength of the Mg-5Li-1Al sheets is enhanced, whilst elongation varies slightly. With the increase in rolling cycles, anisotropy of mechanical properties decreases. It is conclusive that strain hardening and grain refinement dominate the strengthening mechanism of Mg-5Li-1Al alloy.     

Low Loss,High NA Chalcogenide Glass Fibers for Broadband Mid‐Infrared Supercontinuum Generation

High‐purity Ge–As–Se and Ge–As–S chalcogenide glasses were prepared by modified physical and chemical purification techniques. Using the purified glasses, step‐index fibers with a small core (~5.5 μm) and large numerical aperture (~1.3) were fabricated. When a 13.5‐cm‐long fiber was pumped with 320 fs pulses at a repetition rate of 10.5 MHz at 4.1 μm, supercontinuum spanning from ~1.8 to ~9.8 μm with a dynamic range of ±10 dB and an average power of ~3 mW was generated.     

塑造活力与品质水岸——杭州市滨江区北塘河畔城市设计

随着城市回归滨水地域发展趋势的加快,如何建设具有活力和品质的城市水岸已经成为当前城市规划关注的课题。杭州市滨江区的北塘河畔城市设计以规划理念策略的创新、功能结构的明晰、交通体系的完善、公共利空间的丰富和开发控制引导,完善滨水地区的活力支撑体系;同时,通过突出滨水主题、复合利用土地、满足滨水活动需求、凝练滨水空间意向和构筑特色滨水空间形态,打造高品质的现代城市滨水地域。     

High Brightness 2.2–12 μm Mid‐Infrared Supercontinuum Generation in a Nontoxic Chalcogenide Step‐Index Fiber

An environment friendly nonlinear chalcogenide glass fiber with a Ge‐Sb‐Se core and a Ge‐Se cladding is fabricated for bright broadband mid‐infrared (MIR) supercontinuum (SC) generation. The fabricated Ge‐Sb‐Se/Ge‐Se fiber with a core diameter of 6 μm shows zero group velocity dispersion at ~4.2 μm and ~7.3 μm. By pumping the fiber with a length of 11 cm at 4.485 μm with 330 fs pulses, we achieve a SC covering the 2.2–12 μm spectral range and with an output average power of ~17 mW. This bright broadband SC source is promising for high‐resolution MIR spectroscopy.     

中深孔台阶爆破开挖大型基础坑的方法

高层建筑在岩层中开挖大而深的基础坑，以往是采用深孔爆破。为了加快工程施工速度与降低工程费用需用新方法，为此将采矿技术中深孔台阶爆破应用于基础开挖。文中阐述了应用这种方法的具体技术及适用条件，并提出了爆破槽的概念。     

矿渣粉磨健康状态识别模型及系统设计

提出一种基于数据挖掘的装备健康状态识别模型,实现对矿渣粉磨系统的运行健康预测。首先,利用一种多算法综合的特征筛选方法对工况数据进行挖掘分析,确定影响设备运行健康状态的评估指标参数;其次,以健康运行状态评估指标为对象,开展系统运行工况状态聚类挖掘,分析历史样本运行数据中的健康工况模式分布,以此为依据定义工况的运行状态类别,建立健康工况模式库;然后,将实时运行数据与健康工况模式库比对,利用自回归积分滑动平均算法(auto-regressive integrated moving average,简称ARIMA)训练预测评估模型,对健康评估指标参数的变化趋势进行预测,获取系统健康状态评估结果;最后,基于上述模型开发了矿渣粉磨健康状态识别系统软件,并应用于某生产现场,验证了该模型及系统的有效性和实用性。     

基于Mras的感应电机无速度传感矢量控制研究

利用Simulink软件建立了模型参考自适应无速度传感器矢量控制系统仿真,分析了比例积分转速调节器的缺点,提出在转速调节器中的积分器采用一种模糊控制算法,此算法根据转速偏差和偏差变化来修改积分器的输入,使积分器提前退饱和.仿真结果表明,在转速调节器中采用模糊控制算法使调节器提前退饱和,减小了调速系统超调量和调节时间,提高了系统抗干扰性.     

有限元方法在基础沉降计算中的应用及实例

用有限元方法和理论模型,研究高层及多层建筑的天然地基沉降计算值与分层总和法及实际沉降值的差别。《建筑地基基础规范》(GB50007—2002)推荐使用分层总和法计算地基沉降,并用沉降计算经验系数加以修正,取得较好的结果。用有限元方法计算的地基沉降值与分层总和法的结果比较,能够取得同样良好的结果。有限元方法更适合计算机使用,能得到复杂条件下地基沉降计算值以及地基土的实际应力分布。