以服务带动销售?

波音的客户支援服务方式正在发生转变,目的是使其客户可以获得更快的响应,这种新型关系的建立,也应用到了波音787飞机上。     

孔、轮廓和表面(十)

第七章座标镗床的运行操作 (一) 下面仅就机床的操作实践问题作一概括的介绍。当然,本文不可能完全预计到各类具体工件的所有要求和条件。工件的装夹——工件装夹在机床工作台上以后,就构成了工件相对于机床测量系统及主轴的几何关系。虽然装夹的形式可能是多种多样的,但应该确保的共同要求有如下几点: 1.工件表面或轴线对机床工作台的平行度以及工件边缘或轴线与工作台运动方向的找正。     

用于卫星运载火箭的最佳Q制导法

研究一种以最佳Q制导为基础的闭合回路控制逻辑.这种制导系统控制卫星运载火箭沿着二维或三维轨道飞行,以将有效载荷送入指定的圆周轨道.改进后的Q制导算法使用所需的最佳速度矢量,使火箭从现有位置经两次推进加速转移到最终轨道上所需要的总冲减少到最小.所需的速度矢量可以看作是,在经过第一次推进加速后火箭在假想的转移轨道上的瞬时速度.针对这种最佳转移轨道,推导出一种简单明了的Q矩阵表达法,并概要论述大周期和小周期制导算法及形成操纵指令的原理.     

FLOW OF A VISCOUS FLUID PAST A FLEXIBLE MEMBRANE

This paper treats the numerical calculation of a steady two-dimensional viscous flow past a flexible membrane. Both edges of the membrane are fixed in the flow and its chord is set normal to the flow. The numerical calculations of the Navier-Stokes equation based on a finite difference method and a relaxation method are carried out for several values of the membrane tension in cases when the Reynolds numbers are 5, 10 and 20. It is found that the membrane tension has a minimum value below which there is no steady shape of the membrane. Two different shapes of the membrane are possible at a given value of tension: the one is of small deformation, while the other a large deformation. There appear twin vortices in the concave region of the membrane shape if its deformation increases to a certain extent.     

The effect of hypokinesia on lipid metabolism in adipose tissue

The increase of nonesterified fatty acid (NEFA) concentration in plasma was observed in rats subjected to hypokinesia for 1-60 days. In the period of recovery (7 and 21 days after 60 days immobilization) the content of NEFA returned to control values. The increase of fatty acid release from adipose tissue was observed in hypokinetic rats, however the stimulation of lipolysis by norepinephrine was lower in rats exposed to hypokinesis. The decrease of the binding capacity and a diminished number of beta-adrenergic receptors were found in animals after hypokinesia. The augmentation of the incorporation of glucose into lipids and the marked increase in the stimulation of lipogenesis by insulin were found in adipose tissue of rats subjected to long-term hypokinesia. These results showed an important effect of hypokinesia on lipid mobilization, on lipogenesis and on the processes of hormone regulation in adipose tissue.     

第一部分 前言与基本定律

1.1 前言振动本质上是一种很实际的现象。尽管振动分析和理论已非常广泛,但是人们一般认为,在实践中实际遇到的振动问题要比能用理论予示的或阐明的振动问题要多得多。因此,振动特性的实验测量几乎在机械和结构振动的每一研究中都起着主要作用。