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The basic approach of protecting people from being hurt or killed in an accident is to improve crashworthiness of vehicles. This paper starts with discussing theories and methods for vehicle passive safety design, which included experiential methods, analytic methods, multi-body dynamics methods, crash test methods and the finite element method. Emphasis will be paid to the basic FEM theories and algorithms of impact problems. Topics discussed include the governing equation, element discretization, hourglass control, time integration, material model, shell element algorithms and contact-impact algorithms. For more reliable simulation results, this paper then conducts study on how to accurately get material model parameters by combining the FEM method with experimental method, and develops relevant material test machine and parameter calculating software. Based on that, basic typical impact simulation and test validation study are conducted. On the basis of the above work, the paper studies the thin-shell structures'crashworthiness, which was affected by the following factors: spot-weld features, shell thickness, cross-section and pre-deformation. As to vehicle parts'crashworthiness, the paper conducts simulation study of designing energy-absorbing steering system and adaptive airbag system. A practical energy-absorbing steering wheel is designed as an example. In further depth research, the paper suggests several inverse quantificational methods for vehicle crashworthiness design based on the ideal crash characteristics. The above theories and methods are applied with good results through several practical vehicles' crashworthiness design and improvement.

文中对汽车碰撞安全性的设计理论和方法进行了归类和总结，其中包括经验法、解析法、多刚体动力学法、试验法以及有限元方法等；重点介绍了碰撞有限元法的基本理论和有关算法，涉及到有限元求解控制方程、单元离散、沙漏模态控制、时间积分、材料模型和应力修正、薄壳单元算法以及接触碰撞界面算法等，探讨了有限元计算中的材料模型参数获取技术，开发了相应的材料试验装置及材料模型参数反求软件，在此基础上进行了基本的碰撞仿真算例和试验对比研究；文中通过应用有限元方法研究了薄壁构件的碰撞吸能特性，指出了设计薄壁吸能构件时需要考虑的几个主要影响因素，即焊点、壁厚、横截面和预变形等；在关于车辆部件的碰撞安全性能设计中进行了吸能转向机构和自适应安全气囊的仿真研究，提出了吸能转向机构和自适应安全气囊的仿真研究方法；文中最后探讨了整车碰撞性能的设计与改进方法，提出了以理想碰撞特性为目标，采用分段加速度或者根据碰撞时间进行设计的反推设计法、部件吸能仿真优化设计法等量化设计方法，并通过综合应用文中所讨论的相关技术进行了整车碰撞性能的设计与改进实例研究，所选定的车型是大众化的普通轿车和碰撞安全性基础较差的微型面包车，研究结果表明，本文所提出的设计与改进方法是适用而有效的，具有重要的工程实用意义和价值。

In section 2, we use skills in analytic geometry to study the theory of the companion centers of nonisosceles triangles.

在第二节中，我们用解析几何中的技巧研究非等腰三角形的伴心理论。

Conics is a difficult section in the Analytic Geometry for senior high school students.

圆锥曲线是高中生解析几何学习中的一个难点。

In the third section, we come to the analytic method of the heavy-ion collision.

在第三部分我们介绍了重离子碰撞的分析理论。

Golden Section in mathematics is relative to many architectures, solid geometry acknowledgements are often used in architectural design and construction, and the calculations in space analytic geometry are often used irregular construction.

无可厚非的数学在这片领域上占有密不可分的关系。数学中的黄金分割与许多建筑有关，建筑设计与施工中常用到的立体几何的知识，不规则形状的施工建筑中，还常常需要空间解析几何的计算。

In the third section, there are six types of the method of geographical textual research, logic, reason, comparison, elimination, comprehensiveness and the method of giving evidence for ancientness in modern times.

第三部分总结张守节的地理考证方法，将其分为逻辑推理法、事理推证法、比较法、以今证古法、排除法和综合考证法等六种方法。

Some Andalusite crystals have carbonaceous inclusions, arranged so that in cross-section they form a dark cross.

某些红柱石晶体含有碳质包裹体，正是这种结构导致了她的横截面有一个黑十字。

This section concentrates on features of particular relevance to the anesthetist.

本部分将集中探讨与麻醉医生相关的方面。

It comprises an in-put shaft hinged to its yoke through one axis, and an out-put shaft also hinged to its yoke through another axis, and these two yokes (13) were combined together by only one axis position, perpendicular to that two yoke axes like a cross, so that this combined axis will bend just like the angle bisector of that two shafts to maintain its constant velocity by a few methods, firstly, by using a section of gear teeth mesh at both ends of the shafts' teeth were so polished so that it can turn longitudinally as usual gear, and also sideways, to provide a larger solid angle of turning from ordinary 45 degrees into 60 or even more.

它包括输入轴，其通过一根轴铰链连接于叉形支架，和输出轴，其通过另一根轴也铰链连接于其叉形支架。并且这两个叉形支架(13)只需用一根相对垂直铰链轴相连而组合在一起，使得这种组合的轴总能形成这两个轴的角平分线，以通过少数几种方法保持其恒速，首先，通过用啮合在轴的两端的一段齿轮齿抛光为以能够像普通齿轮一样纵向转动，并且还能够侧向转动，以提供较大的转向立体角，从通常的45度变成60度或更大。

SaiMei mainly deals in all ranges of hardware fittings with advanced technology and equipments e.g. slotted angle, shelving, bracket, belt steel, steel pipe, laminate, galvanized steel plate, galvanized steel pipe, TV shelf, warehouse shelf, nails, wire, wire net, furniture, section steel, ect. The technology in steel rolling, auto pressing, moulding, surface treatment keeps ahead of the world.

公司主营万能角钢、货架、支架、电视架、仓储货架、置物架、优质带钢、钢管、层板、镀锌钢板、镀锌钢管、钉子，铁丝，铁丝网、家具、型材等五金制品，技术力量雄厚、生产设备先进，其中轧钢镀锌、自动冲压、滚压成型和表面处理等技术领先世界水平。

You can buy sweetened beverages, if that suits you.

你若喜欢的话，可以买些含有糖精的混合饮料。

As many of you are probably aware, Nick and Vanessa were recently faced with an embarrasing sex scandal after naked pictures of the two getting jiggy with it in a hot tub surfaced the net.

正如很多你可能知道，尼克和 Vanessa 最近面临一个尴尬的绯闻事件后，赤裸裸的图片两个越来越jiggy与它在浴缸中的一个热点浮现净。