与前面不同的是，本章着重于降低系统的变量个数。

The main goal of the chapter is to reduce the number of state variables of systems.

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如果系统的变量都是时间的连续函数，就称为连续变量系统或者模拟系统，其描述方程为微分方程。

The system that all its variables are continuous functions of time is called continuous-variable or analog system; the describing equations are differential equations.

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运用图形CAD系统的变量化设计思想，结合图形特征，基于软件工程中的面向对象设计方法，开发了轮胎胶囊及模具CAD软件系统。

Combined with the characters of the graphics and variational parameters, a CAD system was developed, based on object oriented method for designing tire bladder and its mould.

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So what they do is, they're describing how these thermodynamic properties change, in terms of only state functions and state variables.

他们的作用是描述,随着状态函数和状态变量的变化，系统的热力性质如何变化。

麻省理工公开课 - 热力学与动力学课程节选

So, these on-changing properties that describe the state of the equilibrium state of the system are called state variables.

这些描述,系统平衡态的,变化的属性,就叫做状态变量。

麻省理工公开课 - 热力学与动力学课程节选

These are physical knobs that are available us as experimentalists. And so when we turn these knobs on our system, we want to know how the enthalpy is changing for that system.

这些都是我们做实验可,以得到的物理变量,所以当我们在系统中,改变这些量的时候。

麻省理工公开课 - 热力学与动力学课程节选