投入方面主要是基本建设投资、原料、劳动力等 产出方面主要是产品、服务、生活的改善、时间的节 省及自然环境的改善等 这些要素的状况将取决于两个方面:一是项目将来所处的 环境;二是项目本身的技术方案

CSA是剑桥科学文摘(Cambridge Scientific Abstracts)的简称。它由美国一家著名的私 人信息公司编辑出版,该公司出版科学技术研究文献的文摘和索引工具已有30多年的历 史。目前,CSA通过因特网可提供70多个数据库的检索服务。内容范围包括:生命科 学、环境与水科学、计算机科学、材料科学与工程、航空航天以及人文社会科学

第三篇动力学 静力学研究物体的平衡,而不涉及不平衡物体的运动; 运动学研究物体运动的几何性质,而不追究引起物体运动的原因; 动力学将力与运动联系起来,研究作用于物体上的力与物体机械 运动之间的关系。 动力学知识被广泛地应用于机械的设计、制造,矿山的建设、开采, 房屋建筑、水利工程、航空航天等各个方面

一、1960年11月，日本广岛市一男子因不堪忍受工厂噪声折磨刺杀工厂主。 二、1961年7月，日本东京青年因不堪忍受客货车的噪声自杀身亡。 三、1981年，在美国的现代派露天音乐会。 四、华盛顿时间 1991年4月12日上午11点半，美国南部的迈阿密商业机场上的恐怖试验

In this lecture, we will revisit the application of Newton's second law to a system of particles and derive some useful relationships expressing the conservation of angular momentum. Center of Mass Consider a system made up of n particles. A typical particle, i, has mass mi, and, at the instant considered, occupies the position Ti relative to a frame xyz. We can then define the center of mass, G, as the point

In lecture D9, we saw the principle of impulse and momentum applied to particle motion. This principle was of particular importance when the applied forces were functions of time and when interactions between particles occurred over very short times, such as with impact forces. In this lecture, we extend these principles to two dimensional rigid body dynamics. Impulse and Momentum Equations Linear Momentum In lecture D18, we introduced the equations of motion for a two dimensional rigid body. The linear momen- tum for a system of particles is defined

In this lecture, we consider the motion of a 3D rigid body. We shall see that in the general three dimensional case, the angular velocity of the body can change in magnitude as well as in direction, and, as a consequence, the motion is considerably more complicated than that in two dimensions. Rotation About a Fixed Point We consider first the simplified situation in which the 3D body moves in such a way that there is always a point, O, which is fixed. It is clear that, in this case, the path of any point in the rigid body which is at a

A pendulum is a rigid body suspended from a fixed point (hinge) which is offset with respect to the body's center of mass. If all the mass is assumed to be concentrated at a point, we obtain the idealized simple pendulum. Pendulums have played an important role in the history of dynamics. Galileo identified the pendulum as the first example of synchronous motion, which led to the first successful clock developed

D244BD RIGID BODY DYNAMICS KINETIC EWEGY In echure we derwed am kinenc a susem u dm T= Fere ts the velouty relanve to G. for a nald body we ca wate Uing the vechor nidontklyAxB=Ax

In this lecture, we will consider how to transfer from one orbit, or trajectory, to another. One of the assumptions that we shall make is that the velocity changes of the spacecraft, due to the propulsive effects, occur instantaneously. Although it obviously takes some time for the spacecraft to accelerate to the velocity of the new orbit, this assumption is reasonable when the burn time of the rocket is much smaller than the period of the orbit. In such cases, the Av required to do the maneuver is simply the difference between the