The valuation relation of potential difference with discharging time in Electrical Discharge Machining (EDM) is analyzed theoretically and tested and verified by experiments designed in this paper and the relation bet...The valuation relation of potential difference with discharging time in Electrical Discharge Machining (EDM) is analyzed theoretically and tested and verified by experiments designed in this paper and the relation between potential difference and spark location is induced and analyzed, and proceed by experiments under the condition of onedimension.展开更多
美国SPARK(The Sports Play Active Recreation for Kids即儿童的运动、游戏和体育活动)课程是致力于改善儿童肥胖状况,促进儿童终身体育健康的一门体育课程。通过对它的培训和教学实践,再与国内体育教学相比,它先进的课程理念、科学的...美国SPARK(The Sports Play Active Recreation for Kids即儿童的运动、游戏和体育活动)课程是致力于改善儿童肥胖状况,促进儿童终身体育健康的一门体育课程。通过对它的培训和教学实践,再与国内体育教学相比,它先进的课程理念、科学的课程结构以及丰富多彩的教学内容和富有创造性的教学方法给我们留下深刻印象和极大的启示。展开更多
In order to develop AlN composites suitable for high average power electronic tube, AlN-W materials were prepared by spark plasma sintering. The effects of manufacture parameters on dielectric loss tangent and permitt...In order to develop AlN composites suitable for high average power electronic tube, AlN-W materials were prepared by spark plasma sintering. The effects of manufacture parameters on dielectric loss tangent and permittivity constant were investigated, which include powder-mixed method, milling time of high-energy ball milling, starting powder particle size, sintering temperature and holding time and adding amount of the conductive second phase. The results showed that A1N-W materials sintered at the temperature of 1700℃ holding for 5 min with 10 vol.% W showed the best dielectric loss tangent larger than 0.81 at the frequency 1 kHz-1 MHz. In addition, magnetic stirring mixed powder and lower sintering temperature led to the better propelties because of the higher porosity. The samples sintered from the starting AlN powder with smaller particle size also had the better properties.展开更多
文摘The valuation relation of potential difference with discharging time in Electrical Discharge Machining (EDM) is analyzed theoretically and tested and verified by experiments designed in this paper and the relation between potential difference and spark location is induced and analyzed, and proceed by experiments under the condition of onedimension.
文摘美国SPARK(The Sports Play Active Recreation for Kids即儿童的运动、游戏和体育活动)课程是致力于改善儿童肥胖状况,促进儿童终身体育健康的一门体育课程。通过对它的培训和教学实践,再与国内体育教学相比,它先进的课程理念、科学的课程结构以及丰富多彩的教学内容和富有创造性的教学方法给我们留下深刻印象和极大的启示。
文摘In order to develop AlN composites suitable for high average power electronic tube, AlN-W materials were prepared by spark plasma sintering. The effects of manufacture parameters on dielectric loss tangent and permittivity constant were investigated, which include powder-mixed method, milling time of high-energy ball milling, starting powder particle size, sintering temperature and holding time and adding amount of the conductive second phase. The results showed that A1N-W materials sintered at the temperature of 1700℃ holding for 5 min with 10 vol.% W showed the best dielectric loss tangent larger than 0.81 at the frequency 1 kHz-1 MHz. In addition, magnetic stirring mixed powder and lower sintering temperature led to the better propelties because of the higher porosity. The samples sintered from the starting AlN powder with smaller particle size also had the better properties.
