西北地区中小城市空间扩展及其动力机制研究

本文分析了西北地区中小城市空间扩展的现状特征及其动力机制,并通过与英国城镇空间扩展和人口集聚特征的对比分析,提出中国西北地区城市空间扩展范式,即：不同类型城市规模均持续扩大背景下的空间形态结构分异,迁往主要中心城市大背景下的中小城市人口集聚,大城市及特大城市仍处于能量集聚背景下的城镇区域＂虚多中心＂发展。     

隧道管片真空吸盘机真空吸附力的分析与计算

隧道管片真空吸盘机是盾构法施工中管片生产的关键设备之一,作者在借鉴国外公司管片生产专用设备的基础上,结合我国管片生产的实际情况,创新设计并研制成功了具有吸吊管片(管片自重5000kg)和任意角度(0～180)°翻转管片功能的真空吸盘翻转机。同时,详细分析了被吸吊管片在任意姿态下的动态受力情况,并分别对相应姿态下的真空吸附力进行了详细的计算,得到了被吸吊管片在水平、垂直两个典型工位及任意角度工位下真空吸附力的计算公式,从而为真空吸盘机的设计和应用提供了科学的设计依据,为我国自主创新设计及开发系列管片真空吸盘翻转机奠定了理论基础。     

缠绕螺旋线斜拉索气动性能的数值模拟

为研究螺旋线对斜拉索气动性能的影响,采用Fluent软件的LES模块对光拉索和缠绕螺旋线拉索进行数值模拟。首先,建立了光拉索和缠绕螺旋线拉索的数值计算模型,并在拉索轴向布置9个截面的风压和风速监测点;然后,采用Fluent软件的大涡模拟模块进行了数值计算;最后,在数值模拟数据的基础上,研究了螺旋线对拉索平均阻力系数、脉动升力系数、旋涡脱落频率、风压和风速的轴向相关性、绕流流场等的影响。研究结果表明:在风雨激振发生的雷诺数范围内,缠绕螺旋线能减小拉索的平均阻力系数;破坏规则的旋涡脱落,减小脉动升力系数,降低气动力在拉索轴向方向的相关性。     

Determination of forces in high speed blanking using FEM and experiments

The increasing demand for micro-formed and stamped parts such as connectors in the electronic industry is forcing manufacturers to push the speed limit of conventional press technologies to improve throughput. Designing dies/tooling for higher speeds and obtaining extended tool life requires a thorough understanding of the process. This paper discusses an experimental study of the interaction between punch, stripper plate and sheet material at various blanking velocities up to 1600 mm/s. The effect of velocity on punching force is also studied. A methodology to obtain high strain and strain rate dependent material flow stress data using blanking test and finite element modelling is presented.     

Circumventing mental health stigma by embracing the warrior culture: Lessons learned from the Defender's Edge program.

Despite considerable efforts on the part of the Department of Defense, Department of Veterans Affairs, and the wider mental health community, mental health stigma continues to be a significant barrier to seeking help by service members, highlighting the need for newer modes of thought. A significant factor contributing to this stigma is the fundamental difference between traditional mental health approaches and the warrior culture. As a mental health prevention initiative, the Defender's Edge (DEFED) program was specifically developed to fit within the United States Air Force Security Forces (SF) charged with ground combat operations while deployed to Iraq. DEFED adopted a strengths-based philosophy and integrated a psychologist into the SF culture. Evaluative feedback from 192 program participants is presented, demonstrating high programmatic acceptability and feasibility suggestive of success in circumventing mental health stigma. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Modelling of temperature and forces when orthogonally machining hardened steel

This paper initially considers heat generation in single-point metal cutting and the direct/indirect techniques employed to measure cutting temperatures. The development of analytical models of the cutting process is briefly reviewed, including more recent work involving finite element (FE) methods. Details are given of the different FE packages and formulation methods used by different researchers. Following on from this, an FE model is presented using FORGE 2® to simulate cutting forces and temperature distributions when orthogonal turning a hardened hot work die steel, AISI H13 (52HRC), with polycrystalline cubic boron nitride (PCBN) tooling. Experimental data from infrared chip surface temperature measurements and cutting force output are used to validate the model. Good correlation was obtained between experimental and modelled results for temperature; however, the FE analysis underestimated feed force results due to a lack of adequate workpiece property data and simplistic tool/chip friction assumptions.     

Kinetic and kinematic responses of post mortem human surrogates and the Hybrid III ATD in high-speed frontal sled tests

Despite improvements in vehicle design and safety technologies, frontal automotive collisions continue to result in a substantial number of injuries and fatalities each year. Although a considerable amount of research has been performed on PMHSs and ATDs, matched dynamic whole-body frontal testing with PMHSs and the current ATD aimed at quantifying both kinetic and kinematic data in a single controlled study is lacking in the literature. Therefore, a total of 4 dynamic matched frontal sled tests were performed with three male PMHSs and a Hybrid III 50th percentile male ATD (28.6 g, Δv = 40 kph). Each subject was restrained using a 4 kN load limiting, driver-side, 3-point seatbelt. Belt force was measured for the lap belt and shoulder belt. Reaction forces were measured at the seat pan, seat back, independent foot plates, and steering column. Linear head acceleration, angular head acceleration, and pelvic acceleration were measured for all subjects. Acceleration of C7, T7, T12, both femurs, and both tibias were also measured for the PMHSs. A Vicon motion analysis system, consisting of 12 MX-T20 2 megapixel cameras, was used to quantify subject 3D motion (±1 mm) at a rate of 1 kHz. Excursions of select anatomical regions were normalized to their respective initial positions and compared by test condition and between subject types. Notable discrepancies were observed in the responses of the PMHSs and the ATD. The reaction forces and belt loading for the ATD, particularly foot plate, seat back, steering column, and lap belt forces, were not in agreement with those of the PMHSs. The forward excursions of the ATD were consistently within those of the PMHSs with the exception of the left upper extremity. This could potentially be due to the known limitations of the Hybrid III ATD shoulder and chest. The results presented herein demonstrate that there are some limitations to the current Hybrid III ATD under the loading conditions evaluated in the current study. Overall, this study presents a comprehensive data set of belt forces, reaction forces, accelerations, and bilateral displacement data that can be used to evaluate the performance of ATDs and validate computational models.     

Model of slice-push cutting forces of stacked thin material

Adding slicing to push cutting processes can significantly reduce cutting forces. Creating an appropriate model for the calculation of forces is necessary to completely understand manufacturing processes. In this investigation, a model detailing the cutting forces of stacked thin material using an asymmetrical knife is developed. Equilibrium of forces and frictional effects at the cutting edge are analyzed to determine the components in vertical and horizontal direction of the total cutting force, and their dependency on the slice-push ratio. The friction effects of the new model are based on Coulomb friction. For comparison purposes, an existing shear friction model is extended to discuss the new presented Coulomb friction model. To support the findings, the newly developed model is experimentally verified.     

Discrete element method (DEM) modelling of evolving mill liner profiles due to wear. Part I: DEM validation

Since the early 1990s the discrete element method (DEM) gained considerable success in its ability to predict the power draw and the load behaviour in mills as affected by operating conditions. The DEM can also be used to design milling equipment and predict the breakage of particles. A detailed validation of this method is required in order to produce accurate results. In this paper, we assess the ability of the DEM to predict forces exerted by the mill charge on liners. Data obtained on an experimental two-dimensional mill designed in order to record the normal and tangential forces exerted on an instrumented lifter bar was available. The measured results are compared to the DEM simulated results. Good agreement has been found in terms of amplitude of forces and positions of shoulder and toe at low speed.     

半圆形防波堤抗滑移稳定浅析

基于二维随机波浪对半圆形防波堤作用的物理模型试验和相关理论，分析不同水深下影响半圆形防波堤抗滑稳定的因素，找出堤体滑移失稳破坏和不同水深下滑移方向不同的原因。