Summary of Built-In Variables With Reserved Names
This section is an overview of the built-in elements of the following categories as defined by the underlying COMSOL language:
•
Constants
•
Variables
•
Functions
These language elements are built-in or user-defined. In addition there are operators that cannot be user-defined, and expressions, which are always user-defined.
具有保留名称的内置变量摘要
本节概述了由基础COMSOL语言定义的以下类别的内置元素：
•常量•变量•功能
这些语言元素是内置的或用户定义的。 此外，还有不能由用户定义的运算符，以及始终由用户定义的表达式。
About Reserved Names关于预留名称
Built-in variables have reserved names, names that cannot be redefined by the user. It is not recommended to use a reserved variable name for a user-defined variable, parameter, or function. For some of the most common reserved variable names, such as pi, i, and j, the text where you enter the name turns orange and you get a tooltip message if you select the text string. Reserved function names are reserved only for function names, which means that such names can be used for variable and parameter names, and vice versa. The following tables list most built-in elements and hence those reserved names.
内置变量具有保留名称，用户无法重新定义。 不建议对用户定义的变量，参数或函数使用保留的变量名。 对于一些最常见的保留变量名称，例如pi，i和j，输入名称变为橙，如果选择文本字符串，则会得到工具提示消息。 保留的函数名称仅作为函数名保留，这意味着
此类名称可用于变量和参数名称，反之亦然。 下表列出了大多数内置元素，因此列出了这些保留名称。
Constants and Parameters常量和参数
There are three different types of constants: built-in mathematical and numerical constants, built-in physical constants, and parameters. Parameters are user-defined constants that can vary over parameter sweeps. Constants are scalar valued. The following table lists the built-in physical constants. Constants and parameters can have units.
有三种不同类型的常数：内置的数学和数值常数，内置的物理常数和参数。 参数是用户定义的常量，可以随参数扫描而变化。 常量是标量值。 下表列出了内置物理常量。 常量和参数可以有单位。
Built-in Physical Constants内置物理常数
Table 5-12: Built-in Physical Constants
Name
Description描述
g_const
Acceleration of gravity
N_A_const
Avogadro constant
k_B_const
Boltzmann constant
Z0_const
Characteristic impedance of vacuum (impedance of free space)
真空的特性阻抗（自由空间的阻抗）
me_const
Electron mass电子质量
e_const
Elementary charge元电荷
F_const
Faraday constant法拉第常数
alpha_const
Fine-structure constant精细结构常数
G_const
Gravitational constant万有引力常量
V_m_const
Molar volume of ideal gas (at 273.15 K and 1 atm)
理想气体的摩尔体积（在273.15K和1atm下）
mn_const
Neutron mass中子质量
mu0_const
Permeability of vacuum (magnetic constant)
真空的磁导率（磁常数）
epsilon0_const
Permittivity of vacuum (electric constant)
真空介电常数（电常数）
h_const
Planck’s constant普朗克常数
hbar_const
Planck’s constant over 2 pi超过2 pi的普朗克常数
mp_const
Proton mass质子质量
variable used in lambda
c_const
Speed of light in vacuum真空中的光速
sigma_const
Stefan-Boltzmann constant斯蒂芬－玻尔兹曼常数
R_const
Universal gas constant通用气体常数
b_const
Wien displacement law constant维恩位移常数
Built-in Mathematical Functions内置数学函数