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#: ../../source/behavior/equations/equations.rst:2
msgid "Equations"
msgstr "方程"

#: ../../source/behavior/equations/equations.rst:4
msgid ""
"Although equations are probably the single most important mathematical "
"aspect of Modelica, they are also the simplest to explain."
msgstr "尽管方程可能是Modelica语言中第一重要的数学元素，但是Modelica中的方程仍然是最易于解释的。\ "

#: ../../source/behavior/equations/equations.rst:8
msgid "Basic Equations"
msgstr "基本方程"

#: ../../source/behavior/equations/equations.rst:10
msgid ""
"There are really no complicated semantics to explain about equations. All "
"equations are composed of a left hand expression and a right hand expression"
" separated by an equals sign, *i.e.,*"
msgstr "关于方程真的没有复杂的语义需要解释。\ "
"所有的方程都是由左边一个表达式和右边一个表达式组成，中间被等号隔开。\ "
"例如："

#: ../../source/behavior/equations/equations.rst:18
msgid ""
"Through the examples presented in this chapter, the reader has been exposed "
"to this pattern over and over again in each example.  The only real "
"deviation from the syntax shown above is the case where a description of the"
" equation is included as well, *e.g.,*"
msgstr "通过本章中的实例，读者可以反复接触每个例子中的这种格式。\ "
"上面展示的唯一真实存在的语法偏差是关于方程的描述应该如下，例如："

#: ../../source/behavior/equations/equations.rst:28
msgid ""
"As was pointed out previously, the left hand and right hand sides of an "
"equation in Modelica are expressions, not assignments.  In other words (and "
"in contrast to most programming languages), the left hand side does **not** "
"have to be a variable (as we can see in the case of Newton's law above)."
msgstr ""
"正如我们先前指出的那样，在Modelica语言中，方程的左边和右边是表达式，而不是赋值。\ "
"换句话说（对比大多数的程序语言），方程的左边\ **不**\ 一定要包含变量\ "
"（正如上面牛顿第一定律中看到的那样）。\ "

#: ../../source/behavior/equations/equations.rst:35
msgid "Initial Equations"
msgstr "初始方程"

#: ../../source/behavior/equations/equations.rst:37
msgid ""
"As we saw in many of the examples in this chapter, it is possible to specify"
" equations within a model to be used to solve for initial conditions.  This "
"entire topic of initialization will be discussed in detail in the next "
"section, titled :ref:`initialization`.  For now, all we will say on this "
"topic is that if an equation is to be applied *only* to solve for initial "
"conditions, the ``equation`` section must be qualified by the ``initial`` "
"keyword as follows:"
msgstr ""
"正如在本章中看到的许多例子一样。\ "
"在一个模型中指定方程用于求解初始状态是可能的。\ "
"关于初始化的整个主题将会在下章中详细讨论，标题就是\ :ref:`initialization`\ 。"
"目前在本章中要说的是如果方程\ **仅仅**\ 用于求解初始化，\ ``equation``\ "
"区域必须冠以\ ``initial``\ （初始）关键词。\ "

#: ../../source/behavior/equations/equations.rst:51
msgid "Conditional Equations"
msgstr "带条件的方程"

#: ../../source/behavior/equations/equations.rst:53
msgid ""
"In the next chapter, we'll discuss how to use ``if`` statements to represent"
" conditional behavior.  It is worth getting ahead of ourselves a little bit "
"to point out that equations can be conditional.  There are really two forms "
"of conditional equations. The first is the balanced form, *e.g.,*"
msgstr ""
"下一章将讨论如何应用\ ``if``\ "
"（如果）命令表示有条件的行为。\ "
"值得提前指出的是方程可以是有条件的。\ "
"条件方程有两种形式。\ "
"第一种是平衡形式。\ "
"例如："

#: ../../source/behavior/equations/equations.rst:67
msgid ""
"In the balanced case, the number of equations is always the same (1 in the "
"code above), but *which* equation can change.  This is important because to "
"simulate a model in Modelica, the number of variables must equal the number "
"of equations and the number of equations must be fixed during the "
"simulation."
msgstr ""
"在平衡的情况下，方程的数量总是一致的（上述代码中都为1）。\ "
"但是要使用\ *哪条*\ 方程这点可以改变。\ "
"这个很重要，因为要在Modeliaca中模拟一个模型，变量的数量必须等于方程的数量。\ "
"而且，在模拟的过程中方程的数量必须是固定的。\ "

#: ../../source/behavior/equations/equations.rst:73
msgid ""
"The other type of conditional equations are ones where the number of "
"equations is unbalanced.  This means that the number of equations on the "
"``if`` side may not be equal to the number of equations on the ``else`` side"
" (like it was in the balanced case, previously)."
msgstr ""
"另外一种条件方程的类型是方程的数量是不平衡的。\ "
"这意味着方程的数量在\ ``if``\ 和\ ``else``\ 的两侧可能是不相等的\ "
"（不像此前的平衡情况那样）。\ "

#: ../../source/behavior/equations/equations.rst:80
msgid ""
"But remember, the number of equations cannot change during a simulation.  So"
" how is it then that the number of equations can be different from the "
"``if`` side to the ``else`` side?  It can only happen if **the value of the "
"conditional expression cannot change during the simulation**.  In order to "
"be able to ensure that the conditional expression can never change, it is "
"necessary that all variables in the conditional expression have so-called "
"*parametric variability*."
msgstr ""
"但是请记得，方程的数量在模拟过程中不能改变。\ "
"那么是如何做到\ ``if``\ 和\ ``else``\ "
"两侧的方程数量是不同的呢？只有一种情况\ **模拟过程中条件表达式的值不能改变。**\ "
"为了确保条件表达式永不改变，条件表达式中所有的变量必须拥有所谓的\ *参数级别的可变性*\ 。\ "

#: ../../source/behavior/equations/equations.rst:89
msgid ""
"Remember in our discussion of :ref:`variability` the fact that variables "
"with the ``parameter`` qualifier cannot change during a simulation?  If a "
"variable with the ``parameter`` qualifier cannot change during a simulation "
"and all the variables in an expression have this parametric variability then"
" the entire expression must also have parametric variability (*i.e.,* the "
"value of the expression cannot change during a simulation)."
msgstr ""
"还记得讨论\ :ref:`variability`\ 的时候，带有\ ``parameter``\ "
"（参数）限定词的变量在模拟过程中不能改变的事实吗？如果带有\ ``parameter``\ "
"（参数）限定词的变量在模拟过程中不能改变，且表达式中的所有变量都拥有这个参数级别的可变性，\ "
"那么整个表达式一定也拥有参数级别的可变性（亦即表达式的值在模拟过程中不能改变）。\ "

#: ../../source/behavior/equations/equations.rst:97
msgid ""
"At this point, you might be asking yourself why this unbalanced case would "
"be useful?  Again, we are getting ahead of ourselves here, but one use case "
"would be the conditional application of initial equations, *e.g.,*"
msgstr "关于这个问题，你一定会质疑，这种不平衡的情况有用吗？再次提前指出，其中一种应用是在带条件的初始方程，例如："

#: ../../source/behavior/equations/equations.rst:112
msgid ""
"In other words, if the Boolean parameter ``steady_state`` is true, then the "
"initial equations are enforced.  But if the parameter is false, they are "
"not.  The conditional expression here clearly has parametric variability "
"because the expression contains only a variable and that variable is a "
"parameter."
msgstr ""
"换句话说，如果布尔参数\ ``steady_state``\ "
"（稳定状态）为真，那么初始方程是有效的。\ "
"但是如果参数为假，它们就无效。\ "
"这里的条件表达式具有参数级别的可变性是因为，表达式仅仅包含一个变量，而这个变量是个参数。\ "

#: ../../source/behavior/equations/equations.rst:118
msgid ""
"That's all we'll say on this topic for now, since discrete and conditional "
"behavior will be discussed in detail in the :ref:`next chapter <discrete-"
"behavior>`."
msgstr "这些就是本节所要讨论的，离散和有条件的行为将在\ :ref:`\ 下一章\ <discrete-behavior>`\ 中讨论"
