基于ADAMS的钢丝绳建模方法研究

利用ADAMS软件对起重机械进行动力学仿真时,钢丝绳的建模一直是个难点。结合钢丝绳在机械系统中的不同用途,对几种不同的钢丝绳建模方法的优势和局限性进行探讨,着重介绍了Machinery工具栏中Cable工具的钢丝绳建模新方法,并对其仿真结果的精确性进行了理论分析。     

Simplified Calculation Methods for Static Behaviors of Triple-Tower Suspension Bridges and Parametric Study

International Journal of Steel Structures - In this paper, simplified formulas to determine the static behaviors of triple-tower suspension bridges were derived, including the formulas for the...     

混合的记忆

<正>春节少不了同学聚会,而今年恰是我的母校——百年名校雅礼中学的新建教学楼落成后的第一个春节。在大家漫不经心的回忆里,仍旧是斑驳的红砖房与房子后面的那个院子。席间,有人感叹,真是找不到那旧时的影子了。我知道改变一个建筑行为的最终目的大概是将一个平衡改变为另一个平衡。日子的飞奔也大抵是与遗忘成正比的,当多年后的今天,我们能掏出时间来回忆往事,是我们的日子总算开始慢了下来的证据。因为新教学楼大部分是自己的手笔,带着对孩     

港口防波堤的损坏及原因分析

随着港口建设规模的不断扩大,深水防波堤建设项目也逐年增多,防波堤在抵御海浪侵袭等方面具有重要的作用。但近年来不断出现的防波堤损坏事件,给港口水工工程建设造成了一定的困扰。本文就港口防波堤的损坏情况及损坏的原因进行了分析。     

城市交通拥挤收费技术及其应用案例

交通拥挤问题是目前大中城市普遍面临的问题,是城市交通需求系统与交通供给系统发生矛盾的突出表现。而实行交通拥挤收费,是一个缓解城市交通堵塞较为有效的经济手段。从四个方向分别对交通拥挤收费技术进行探讨,分别为基于博弈论的交通拥挤收费分析、最优拥挤收费模型分析、基于自由流时间的交通拥挤收费研究、弹性需求下多类型用户拥挤收费模型研究。并对实施交通拥挤收费的典型案例作简要分析。     

电梯层门耐火性能研究（2）

笔者在《电梯层门耐火性能研究（1）》（刊登于《中国电梯》杂志2013年第24卷第23期）中主要阐述了高层建筑火灾蔓延路径、建筑物构件耐火要求及国内常用电梯层门的耐火试验结果。本文将接续上文继续探讨电梯层门材料、厚度及制作结构等因素对层门耐火性能的影响,继续研究高层住宅电梯候梯厅（前室）防火阻隔及电梯层门耐火性能的技术要求,与广大读者交流和讨论。     

某地下人防商业建筑防火设计分析

为保障战时人员与物资掩蔽、人民防空指挥、医疗救护及经济发展,某市拟建设某地下人商业项目。由于《人民防空工程设计防火规范》与《建筑设计防火规范》对地下商业的消防设计的有关规定存在一定的差距,本着安全、经济的原则,针对某地下人防商业建筑的特点,运用FDS、EVACNET4等软件,从火灾控制、防火分隔、人员疏散及消防系统等方面分析了其消防设计的难点及解决方案。     

城市不平衡发展的分析与探讨

文章在阐述城市空间发展理论的基础上，分析了城市空间不平衡发展的规律，对我国西部大开发战略进行了反思，提出了发展我国不发达地区的思路。     

Kinetic modeling of simultaneous polycondensation and free radical polymerization for polyurethane/poly(methyl methacrylate) interpenetrating polymer network

A comprehensive kinetic Monte Carlo algorithm has been developed to investigate the formation process of a polyurethane/poly(methyl methacrylate) (PU/PMMA) interpenetrating polymer network (IPN), in which a component independent strategy is proposed to perform the simulation of simultaneous polycondensation and free radical polymerization. An empiric diffusion model based on the mass fraction of polymer is used to quantify the effect of diffusional limitations on MMA polymerization. Results show that the presence of acrylic monomers has little impact on the formation rate of PU, but the presence of the PU network can accelerate the polymerization of MMA. In addition, the effects of component mass ratio, acrylic cross-linker concentration, and [NCO]/[OH] ratio on the IPN formation kinetics are investigated based on the kinetic model. It is believed that the as-developed modeling strategy can be extended to other IPN systems and provide a better understanding of the interactions between chemically independent networks.     

A New Ferroelectric Phase of YMnO3 Induced by Oxygen‐Vacancy Ordering

Manganese oxides are good candidates of strongly correlated electron materials due to the uniqueness of electronic structure of manganese and the mobility of oxygen among lattice sites under external impacts. Here, we used electron beam as the excitation source to explore the structural evolution of YMnO₃ and identified a new phase under the radiation of electron beam in the transmission electron microscope. Analyses of the electron energy‐loss spectra reveal that this phase originates from ordered oxygen vacancy. We applied the first principles calculation to pick out the optimized stable structure with a lower polarization, and verified its correctness by electron diffraction and image simulations. Analyses of density of states indicate that weak Y–O covalence is favorable for the existence of ferroelectricity, supporting the electrostatic nature of ferroelectricity in the YMnO₃.