小孔

Battista della Porta in1589, but it was not until1611 that Kepler compared a lens of glass to the lens in the eye and showed that rays from each point of an object were brought to a focus at each corresponding point of an image on the retina.

透镜可以集结更多的光束，并且依然可以象小孔一样成相，但是有一点两者不同，在小孔摄影机里，无论胶片与小孔的距离远近，光线都可以相成同样清晰的影像。

After comparing the laser intensity absorbed due to the inverse Bremsstrahlung absorption of the plasma with that absorbed due to the Fresnel absorption on the keyhole wall, the different effects of the two energy absorption mechanisms on forming and keeping the keyhole were analyzed.

通过比较小孔内等离子体的反韧致辐射吸收的激光功率密度和小孔孔壁上的多次反射吸收的激光功率密度，分析了两种能量吸收机制在小孔形成和维持过程中所起的不同作用。

Opening a bucket down a hole when a part of the steam discharged from the holes and the other part of theREDUCING VALVES condensation of water vapor generation inverted bucket to lose buoyancy by its own weight goes down inverted bucket connecting lever to open the valve spool driven cycle work intermittent drainage.

倒吊桶上开有一小孔，当一部份蒸汽从小孔排出，另一部份蒸汽产生凝结水，倒吊桶失去浮力，靠自身重量向下沉，倒吊桶连接杠杆带动阀芯开启阀门，循环工作，间断排水。

The pore capacity is becoming smaller with increasingthe vitrinite content. 2. Micro-porosity is dominated in the total pore capacity, which takes more than50%. There is not relationship among pore capacity and specific surface with otherfactors such as Maceral and R0, which shows that the distribution and shapes of poreare not influenced by the composition of the coal. 3. The pore is opened for the coal of Ordos Basin, the order is from durain to clarainthen samples to vitrain. Others are belong to half-opened and thin throat. 4. The adsorption content of gas is increasing with the higher pressure, and the freegas content is decreasing;The adsorption content of gas is decreasing with thehigher temp, and the free gas content is increasing;The adsorption content of gas isincreasing with higher vitrinite content for the kennel coal when temp.

总空隙主要由小孔孔容构成，小孔孔容占了50%以上；镜质组含量和惰性组含量等物质以及镜煤反射率均与孔容、比表面未表现出明显的相关性，说明孔隙分布特征不受物质组成的影响 3、鄂尔多斯地区的空隙呈现开放状态为主，空隙开放的次序为暗煤-亮煤-煤样-镜煤，其他盆地则为半封闭和细瓶颈空隙 4、随压力增加，煤对气体的吸附量增加，煤中所含游离气的量随之减小；随温度增加，煤对气体的吸附量减小，而煤中所含游离气的量随之增加；在相同的温压条件下，同是长焰煤的样品，吸附量在孔容中所占的比例随镜质组含量增加而增加。

The principal of buffer is described as follows.At impulsing down,the piston moves down and vacates the annular space.The pressure in respiratory cavity decreases to a certain level and the traveling valve opens.At that time,the liquids enter into traveling valve and cavity and the plunger is impulsed upward to carry out the gentle transient at the sudden change.When the upward impulsing begins,the respiratory cavity is subjected to pressure and the traveling valve closes.During the gradual pressure rising,the liquids in respiratory cavity effuse from the upper ventage and the sudden change of force-summing direction of plunger is relieved relying on the resistance of ventage.

其原理大致是：下冲程时，活塞向下运动，让出环形空间的体积，呼吸腔内压力下降，下降到一定水平后，游动阀打开，此时，游动阀和小孔同时进液，使柱塞在从上死点处突然改变方向向上运动时得到缓冲，实现了柔和过渡；当上冲程开始时，呼吸腔受压，游动阀关闭，在压力逐渐上升的过程中，呼吸腔内的液体从上部的小孔流出，并依靠小孔的阻力使柱塞受力突然换向得到缓冲。

The method is :there are two perpendicular axes whose distance are controlled ,one is the axis of work table, the other is fixed with a microscope for aiming.

该测量方法是：两个相互垂直且间距可调的数控回转轴，一轴与工件的回转中心重合，另一轴上固定可移动的瞄准显微镜，当显微镜瞄准被测孔时，两轴的转角由各自的圆光栅测出，两轴之间的角度位置确定曲面壳体零件上小孔的孔位置，同时采用CCD摄像头，利用图象处理技术实现小孔的尺寸测量。

The studied results show that the radial dimension of keyhole increases with laser power for partial penetration, while it is nearly unvaried when the workpi ece is fully penetrated.

通过对小孔同轴视觉图像的处理提取出小孔径向尺寸，研究了小孔径向尺寸随焊接规范参量变化的动特性。

The emission of N_2 in discharge gap is detected using optical emission spectrophy. The discharge reactor was put in lightproof box to avoid the disturbance from outside lights. A small hole was drilled in one sidewall of the box, and the fibre was mounted coupling to the inlet (1mm) into the hole. A tube with the inner diameter of 1.1mm was set in the front of the hole. In this way, only the light from a certain direction emitted from the discharge reactor could transfer into the inlet through the tube. The reactor could be moved in the vertical direction of the fibre, and the spectrometry can collect the total emission along the fibre inlet in single-shot measurement.

利用光学发射光谱仪对多针对板电晕放电中放电间隙内的N_2发射光谱进行测量，放电反应器置于暗箱中以避免外界对光谱测量的影响，将光谱仪的光纤耦合入口固定在暗箱侧壁的小孔内，小孔孔径为光纤耦合入口直径，在小孔前方安装孔径为1.1mm的细直管，只采集与光纤耦合入口在同一直线上的发光，避免放电区其它区域的发光被同时接收。

There is no essential difference between the two, as the pool of metal around the hole surrounded by molten metal gravity and surface tension have to make holes to bridge the trend, while the metal vapor is generated by a continuous attempt to maintain the existence of holes.

从机理上看，这两种焊接方法的前提都是焊接时存在小孔，两者没有本质的区别，小孔周围为熔池金属所包围，熔化金属的重力及表面张力有使小孔弥合的趋势，而连续产生的金属蒸气则力图维持小孔的存在。

At the same time, the gas flow acting on the keyhole is simulated by finite element method. The gas flow fields of pneumatic circumferential motion and pressure distribution nephograms around and in the keyhole are obtained. Analysis shows that when plasma is blown backwards i.e., in direction towards the trailing edge of the weld pool, plasma can be eliminated better.

利用有限元法对激光焊接时保护气体在小孔内部和表面气流状况进行了数值模拟，通过对不同焊接条件下模拟形成的小孔气动扰流的气流场和压力分布云图的分析，解释了采用逆向侧吹保护气体吹除等离子体的方法，可以更有效地抑制等离子体云的产生，防止小孔塌陷，有利于维持小孔的稳定性。

I didn't watch TV last night, because it .

昨晚我没有看电视，因为电视机坏了。

Since this year, in a lot of villages of Beijing, TV of elevator liquid crystal was removed.

今年以来，在北京的很多小区里，电梯液晶电视被撤了下来。