An abrasive water-jet cutting process is one in which water pressure is raised to a very high pressure and forced through a very small orifice to form a very thin high speed jet beam. This thin jet beam is then direct...An abrasive water-jet cutting process is one in which water pressure is raised to a very high pressure and forced through a very small orifice to form a very thin high speed jet beam. This thin jet beam is then directed through a chamber and then fed into a secondary nozzle, or mixing tube. During this process, a vacuum is generated in the cham- ber, and garnet abrasives and air are pulled into the chamber, through an abrasive feed tube, and mixes with this high speed stream of water. Because of the restrictions introduced by the abrasive feed tube geometry, a vacuum gradient is generated along the tube. Although this phenomenon has been recog- nized and utilized as a way to monitor nozzle condition and abrasive flowing conditions, yet, until now, conditions inside the abrasive feed line have not been completely understood. A possible reason is that conditions inside the abrasive feed line are complicated. Not only compressible flow but also multi- phase, multi-component flow has been involved in inside of abrasive feed tube. This paper explored various aspects of the vacuum creation process in both the mixing chamber and the abrasive feed tube. Based on an experimental exploration, an analytical framework is presented to allow theoretical calculations of vacuum conditions in the abrasive feed tube.展开更多
[提示]母乳喂养,英语叫breast-fed。母乳喂养婴儿,好处可谓多矣!首先在诞生一年之內,婴儿的死亡率就比非母乳喂养者降低了20％。别的好处也很多,比如:Other studies have shown breast-fed babies are less likely to be overweight,hav...[提示]母乳喂养,英语叫breast-fed。母乳喂养婴儿,好处可谓多矣!首先在诞生一年之內,婴儿的死亡率就比非母乳喂养者降低了20％。别的好处也很多,比如:Other studies have shown breast-fed babies are less likely to be overweight,have fewer behavioral problems and may show differences in intelligence.They also may grow up to have lower blood pressure(血压).调查还证明,当今美国母乳喂养的婴儿占婴儿总数之70％!笔者甚至怀疑,我国是否达到了这个标准,尤其是都市年轻母亲。展开更多
基金supported by the National Innovate Research Groups Foundation of China (50621403)National Basic Research Program of China (2009CB724600).
文摘An abrasive water-jet cutting process is one in which water pressure is raised to a very high pressure and forced through a very small orifice to form a very thin high speed jet beam. This thin jet beam is then directed through a chamber and then fed into a secondary nozzle, or mixing tube. During this process, a vacuum is generated in the cham- ber, and garnet abrasives and air are pulled into the chamber, through an abrasive feed tube, and mixes with this high speed stream of water. Because of the restrictions introduced by the abrasive feed tube geometry, a vacuum gradient is generated along the tube. Although this phenomenon has been recog- nized and utilized as a way to monitor nozzle condition and abrasive flowing conditions, yet, until now, conditions inside the abrasive feed line have not been completely understood. A possible reason is that conditions inside the abrasive feed line are complicated. Not only compressible flow but also multi- phase, multi-component flow has been involved in inside of abrasive feed tube. This paper explored various aspects of the vacuum creation process in both the mixing chamber and the abrasive feed tube. Based on an experimental exploration, an analytical framework is presented to allow theoretical calculations of vacuum conditions in the abrasive feed tube.
文摘[提示]母乳喂养,英语叫breast-fed。母乳喂养婴儿,好处可谓多矣!首先在诞生一年之內,婴儿的死亡率就比非母乳喂养者降低了20％。别的好处也很多,比如:Other studies have shown breast-fed babies are less likely to be overweight,have fewer behavioral problems and may show differences in intelligence.They also may grow up to have lower blood pressure(血压).调查还证明,当今美国母乳喂养的婴儿占婴儿总数之70％!笔者甚至怀疑,我国是否达到了这个标准,尤其是都市年轻母亲。
