查询词典 if and only if

A user wants to decrypt if and only if his attributes sets in each authority are satisfied the access structure of corresponding authority.

只有用户在每个认证服务器上的属性集合满足该服务器上的密文规则，用户才能解密密文。

When F is an algebraically closed field char F≠2, A is similar over F to an orthogonal matrix if and only if ( 1 ) the invariant factors of A aer self-reciprocal (2) the elementary divi sors of A of the form x...

ii当F为一个代数闭域且char≠2时，F相似于一个正交矩阵的充要条件为(1)A的不变因子是自反的。(2)A的形为(X±1)~(2k)的初等因子出现偶数次。

Then R is an Archimedean domain if and only if a is contained in some minimal prime ideal of R for every nonzero nonunit a.

则有R是阿基米德整环当且仅当a含在R的某个极小素理想中。

We introduce the notion of characteristic pairs and give the definition of dual characteristic pairs of Dirac structures on Lie bialgebroids. Using the dual characteristic pairs, we give the if and only if conditions for which a maximally isotropic subbundle of the double of a Lie bialgebroid is a Dirac structure.

本文在李双代数胚上，引入了Dirac结构的特征对并给出对偶特征对的概念，利用对偶特征对，给出李双代数胚double的极大迷向子丛是Dirac结构的充要条件；其次，分别利用特征对与对偶特征对，将可约Dirac结构分为第一类可约与第二类可约，在此基础上，建立Poisson流形的两类对应约化定理。

Specially, when k≥2 and the generating spaces are spacelike or timelike, they are totally geodesic if and only if they are totally umbilical.

特别，若M的生成空间是类空的或类时的，则当k≥2时，M全测地与全脐等价。

By means of moving frame, some properties of ruled surfaces are obtained, including the surfaces being minimal, totally geodesic, totally developableand totally umbilical. Some equivalent conditions in which the ruled surfaces are totally developable are obtained. It is abtained that (k+1)-dimensional ruled surfaces are totally geodesic if and only if they are minimal and totally developable.

利用活动标架法研究了直纹面的一些性质，包括极小性，全可展性，全测地性和全脐性，给出了直纹面是全可展性的一组充要条件，同时得到，R(上标 n+1 下标 v)中的k+1维直纹面M是全测地的充要条件是它是极小的且全可展的。

On the Hardy space and Bergman space with parameter 1, we find that the weighted composition operators are compact if and only if they are weakly compact.

对于参数为1的Hardy空间H〓和Bergman空间L〓，证明了其上定义的加权复合算子的紧性与弱紧性是等价的。

It is true for two structures if and only if the structures\nare the same type and their corresponding fields are equal.

当且仅当两个结构是同类型而且各字段都相等时它们相等。

"The objects can be thought of as points in space, with the distance between points given by a distance formula, such that:(1) the distance from point A to point B is zero if and only if A and B are identical ,"

可以把这些对象想成是空间中的点，两点之间的距离由距离公式给定，于是：(1)只有当A和B是重合的时候，A到B的距离才为零

It drops a packet probabilistically if and only if the average queue size lies between the minth and maxth thresholds.

只有当平均伫列尺寸位於最小和最大限额之间时，会或然性的舍弃封包。

Breath, muscle contraction of the buttocks; arch body, as far as possible to hold his head, right leg straight towards the ceiling (peg-leg knee in order to avoid muscle tension).

呼气，收缩臀部肌肉；拱起身体，尽量抬起头来，右腿伸直朝向天花板（膝微屈，以避免肌肉紧张）。

The cost of moving grain food products was unchanged from May, but year over year are up 8%.

粮食产品的运输费用与5月份相比没有变化，但却比去年同期高8％。