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  PhysicalQuantity

Sigma KEE - PhysicalQuantity
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物理量
PhysicalQuantity是一种用来衡量建模世界上的 一些可以量度的部分,例如:「地球的直径」(长度固定)和「装满了可变形的固体的应力」(应力的衡量,它是一个有 三个空间坐标的函数)。 PhysicalQuantity 要不是 ConstantQuantity,就是 FunctionQuantityConstantQuantity 的实例需要有一个 UnitOfMeasure,而 FunctionQuantity 的实例是要靠一个 Function, 它把 ConstantQuantity 的实例和其它 ConstantQuantity 的实例联系在一起(举例说, TimeDependentQuantity 属于 FunctionQuantity)。 PhysicalQuantity 这个名字和定义是借用物 理理论,但是 PhysicalQuantity 不一定是指物质上的。 除了长度、时间和速度等这些尺度以外,非物理尺寸如 货币也是可行的。因此,金钱会是 PhysicalQuantity 的实例。 PhysicalQuantity 和纯 Number 的区别在于前者附有一个衡量的尺度。
Relationships      
Parents 数量 Any specification of how many or how much of something there is. Accordingly, there are two subclasses of Quantity: Number (how many) and PhysicalQuantity (how much).
Children 恒量A ConstantQuantity is a PhysicalQuantity that has a constant value, e.g. 3 Meters and 5 HourDurations. The magnitude (see MagnitudeFn) of every ConstantQuantity is a RealNumber. ConstantQuantity is distinguished from FunctionQuantity, in that each instance of the latter is formed through the mapping of one PhysicalQuantity to another PhysicalQuantity. Each instance of ConstantQuantity is expressed with the BinaryFunction MeasureFn, which takes a Number and a UnitOfMeasure as arguments. For example, 3 Meters is expressed as (MeasureFn 3 Meter). Instances of ConstantQuantity form a partial order (see PartialOrderingRelation) with the lessThan relation, since lessThan is a RelationExtendedToQuantities and lessThan is defined over the RealNumbers. The lessThan relation is not a total order (see TotalOrderingRelation) over the class ConstantQuantity since elements of some subclasses of ConstantQuantity (such as length quantities) are incomparable to elements of other subclasses of ConstantQuantity (such as mass quantities).
 函数量A FunctionQuantity is a PhysicalQuantity that is returned by a Function that maps from one or more instances of ConstantQuantity to another instance of ConstantQuantity. For example, the velocity of a particle would be represented by a FunctionQuantity relating values of time (which are instances of ConstantQuantity) to values of distance (also instances of ConstantQuantity). Note that all elements of the range of the Function corresponding to a FunctionQuantity have the same physical dimension as the FunctionQuantity itself.
 性能指标
 测量单位A standard of measurement for some dimension. For example, the Meter is a UnitOfMeasure for the dimension of length, as is the Inch. There is no intrinsic property of a UnitOfMeasure that makes it primitive or fundamental, rather, a system of units (e.g. SystemeInternationalUnit) defines a set of orthogonal dimensions and assigns units for each.


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