从图像上看，它们对应于,用平行于坐标轴的平面横截图像得到的，过程中保持x或y恒定。

And, in terms of a graph, they correspond to slicing by a plane that's parallel to one of the coordinate planes, so that we either keep x constant, or keep y constant.

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齿轮A位于驱动轴的末端，齿轮b在副传动轴上，它们恒定啮合。

Gear a, at the end of the drive shaft, and gear B, on the countershaft, are in constant mesh.

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某舰的螺旋桨尾轴长期处在恒定载荷作用下，虽然尾轴应力在弹性极限范围内，但是尾轴局部还是很容易发生微量的塑性变形。

Tiny deformation will appear in the local of the propeller shaft of certain ship which is endured an invariableness load, although the shaft stress is within the elastic limit range.

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We said, "Let's take, for the simplest case that we can possibly imagine, namely a particle moving in one dimension along the x-axis with a constant acceleration a.

我们说过,"考虑我们可以想象的最简单的情况,即质点在一维空间运动,沿着 x 轴且保持恒定加速度 a

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