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According to theorem of motion of centre of mass and theorem of moment of momentum about centre of mass , we derive the theorem of moment of momentum about instantaneous center of rotation.

从质心运动定理和相对质心的动量矩定理出发，导出了相对瞬心的动量矩定理。

The first kind is 0-equation model. It only includes mass and momentum conservation equations. Great progresses have been made in improving this model. It has successfully been applied to many natural rivers with complicated boundary geometry. The second kind is κ-ε model. The κ equation and ε equation are needed, besides mass and momentum conservation equations. Many researchers have studied the depth-averaged mathematical models of turbulence in recent years. However, the models were used mostly in regular artificial canals or natural water areas with simple boundaries.

对于宽浅型河流，采用深度平均法进行流场计算时，用得较多的有两类模型：一类是不增加任何脉动量的偏微分方程的模型，这类模型已在适体坐标下运用得较多且较成功；另一类是κ-ε二方程模型，它是近几十年来广泛应用的一类湍流模型，并发展了许多具体的形式，但大多数只对顺直河道进行了研究，对弯曲较大的河道研究不多，本文运用适体坐标，采用正交交错网格及非正交交错网格，把此模型运用到了弯曲较大的河段及具有汇流的河段，取得了较大的成功。

With this angular momentum, according to the three laws of planetary motion proposed by Kepler, a certain amount of angular momentum will create a certain path of movement.

根据喀卜勒的行星三大定律，一定的角动量会产生一定的运动轨道。

The absence of net charge and momentum would follow from accepted physical laws ( Gauss's law and the non-divergence of the stress-energy-momentum pseudotensor , respectively), if the universe were finite.

如果没有净电荷和势头将遵循公认的物理定律（高斯的法律和非分歧应力能量动量pseudotensor分别），如果宇宙是有限的

The mathematical form of material energy-momentum tensor is the same as a sum of the energymomentum tensor in elastic material and the Maxwell stress tensor in electromagnetic field Moreover, under infinitesimal symmetrical transformations, the infinitesimal invariance condition gives a balance of the field variables and material energy-momentum tensor.

另外，在无穷小对称变换条件下，它指出—种场变量与物质能量-动量张量的平衡关系。

By expressing 4-angular momentum of the high-speed particular in the form of tensor ,and by Lorentz transformation,we can get the conversion equation of 3-dimension angular momentum and auxiliary vector.

高速运动质点的4-角动量表示成张量Jμv 的形式，通过对Jμv进行洛伦兹变换可以得到3维角动量L的变换关系以及辅助量G的变换关系，在经典过渡下，前者与角动量的伽利略变换相符合，后者恰好反映加速度a是伽利略变换的不变量。

The two-cycle variation in side force per 360° of roll under small bleed momentum is gradually evolved to one-cycle variation under large bleed momentum.

模型上的侧向力随模型滚转从小吹气量下的双周期变化逐渐演化成为大吹气量下的单周期变化，利用该渐变规律可以实现对非对称背涡流场的主动控制，提出了微量吹气扰动控制概念。

Because of the space is uniform,So that the momentum conservation is occurrence in nature,it explain the momentum conservation is a attribute of the space.

由空间的均匀性而导出的动量守恒，说明动量守恒是物质空间的一个基本属性，动量守恒在整个物理学的框架中应具有定律的基础地位。

In this paper, in the momentum space , the angular momentum operator and the boost vector operator, i.

在动量表象下对非零质量带自旋粒子的角动量算符和推动矢量算符也即Lorentz变换生成元进行了讨论，得到了它们按轨道和自旋两部分分拆的新的表达

Choose a gear that allows you to hold the ideal body position on the climb too easy a gear will give you a fast cadence forcing you into the saddle and preventing from using your legs to absorb shocks on the other hand too hard a gear lead to a loss of momentum if you hit an obstacle a common error is riders who shift the little chambering too soon when approaching a hill climb this can cost a loss of momentum at the base of the climb when they need it the most.

选择适合的齿数来让你保持理想的爬坡姿势，用太轻的齿数，会导致踩踏转数过快，这会迫使你紧贴座垫，同时也会使你的双腿失去避震的作用。另一方面，在碰到障碍物时，若使用过重的齿轮组合，则会让你失去动力。

Through comparing with the results by simulation to study the effects of theprojectile"s final velocity, the angle of rotation and the ballistic trajectory"s migration withdifferent projectile"s rotating speeds, different target"s moving speeds and differentpenetration angles.

通过比较数值模拟的结果来研究不同弹头转速、目标速度、侵彻角对侵彻过程中弹头最终速度、翻转角度和弹道偏移的影响。

I love stationery and all the accoutrement of writing.

我爱文具以及所有的书写的工具装备。