在工程技术领域内，经常会遇到两类典型的问题。其中的第一类问题，可以归结为有限个已知单元体的组合。例如，材料力学中的连续梁、建筑结构框架和桁架结构。我们把这类问题，称为离散系统。如图1-1所示平面桁架结构，是由6个承受轴向力的“杆单元”组成。尽管离散系统是可解的，但是求解图1-2所示这类复杂的离散系统，要依靠计算机技术

材料在外力作用下所呈现的有关强度和变形方面的特 性,称为材料的力学性能。 材料力学性能是构件强度、刚度和稳定计算的重要组成部分, 也是合理选用材料和从事新材料研究的重要依据。 材料的力学性能都要通过试验来测定。 本节主要介绍工程中常用材料在拉伸和压缩时的力学性能

这些连接件除主要发生剪切变形以外,在 受剪面pn, 受压现象(如上图)构件在较小的局部区域到 剪力QH, ua相应的压力叫挤压力(mngt挤压面mn 的应力叫挤压应力( bearing stress)记为or挤压加P=H 因连接件的受力和变形很复杂不能用材 故连接件的强度计算一般采用工程实用计算

1.BASE Power dissipation 2. COLLECTOR pcm:1.5w(tamb=25℃)

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These circuits consist of four independent, high TSSOP14 (Thin Shrink Small Outline e Package) gain, intemally frequency compensated operation al amplifiers. They operate from a single power supply over a wide range of voltages. Operation

General Description de range of applica is local on card bypassing is needed only if the regulator is located far from 9 gulation, eliminating the distribution problems associated the filter capacitor of the power supply

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TWO-Terminal Ic DEVICES Temperature Transducer AD590 FEATURES PIN DESIGNATIONS Linear Current Output: 1 HA/K Wide Range:-55C to+150C Probe Compatible Ceramic Sensor Package

General Description hese devices need only one external com ation capacitor at the output. Tthe LM? aged in the to-220 power package and is capable applications requiring other voltages, see LM137 data 4 supplying 1.5A of output current These regulators employ internal current limiting safe area Features a Thermal, short circuit and sa tually all overload conditions