Lecture D33: Forced Vibration Fosinwt m Spring Force Fs =-kx, k>0 Dashpot Fd =-ci, c>0 Forcing Fext Fo sin wt Newton's Second Law (mix =CF) mx+cx+kx= Fo sin wt =k/m,=c/(2mwn)

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

So far we have used Newton's second law= ma to establish the instantaneous relation between the sum of the forces acting on a particle and the acceleration of that particle. Once the acceleration is known,the velocity (or position) is obtained by integrating the expression of the acceleration (or velocity). There are two situations in which the cumulative effects of unbalanced forces acting on a particle are of interest to us. These involve:

In this lecture we will consider the equations that result from integrating Newtons second law, F=ma, in time. This will lead to the principle of linear impulse and momentum. This principle is very useful when solving problems in which we are interested in determining the global effect of a force acting on a particle over a time interval Linear momentum We consider the curvilinear motion of a particle of mass, m, under the influence of a force F. Assuming that

is a vector equation that relates the magnitude and direction of the force vector, to the magnitude and direction of the acceleration vector. In the previous lecture we derived expressions for the acceleration vector expressed in cartesian coordinates. This expressions can now be used in Newton's second law, to produce the equations of motion expressed in cartesian coordinates

例题2-5求例题2-4中所示薄壁圆环在内压力 b p=2MPa作用下的径向应变和圆环直径的改变量。 已知材料的弹性模量E=210GPa p 解:在例题2-4中已经求出圆环在任一横截面 上的正应力=40MPa,若正应力不超过材料的比 例极限,则可按公式(2-6)算出沿正应力方向 (a) (即沿圆周方向)的线应变为

1. Current Regulations of Agricultural seed Production 2. (1)The Current Seed Law of P.R. China 3.(2)Registration and release of plant cultivars 4.(3) Plant Breeders right 5.()Requirements for the seed Enterprises: Capitalasset; Physical/technical conditions

General Approach to Electrochemical Experiments Identify assumptions Ditusion- ass tran sort +Identify suitable boundary conditions Solye linear diffusion equation (Fick's 2nd law -use Laplace transtorm

10.1 Federal Regulation of Medical Devices 10.1.1 The Law (including amendments) 10.1.2 Organization of FDA 10.1.3 Classification of Devices 10.1.4 Process of Assessment 10.1.4.1 510(k)Substantial Equivalence 10.1.4.2 Premarket Approval 10.1.5 Clinical Trials (Investigational Device Exemption) 10.1.6 Labeling 10.1.7 Tripartite Biocompatibility Guidance 10.1.8 Standards 10.1.9 Good Manufacturing Procedures 10.1.10 Good Laboratory Practices 10.2 Clinical Trial Design

美国的产品责任法主要是州法,而不是联邦统一的立法。各州都有自己的产 品责任法,而且各有差异,为了统一各州的产品责任法,美国商务部在1979年 1月提出了一项《统一产品责任法(草案)》(Draft Uniform ProductLiability Law),供各州采用,但至今尚未被各州采纳