Due to the slim hole at the lower part of the ultra-deep and deep wells, the eccentricity and rotation of drill string and drilling fluid properties have great effects on the annular pressure drop. This leads to the f...Due to the slim hole at the lower part of the ultra-deep and deep wells, the eccentricity and rotation of drill string and drilling fluid properties have great effects on the annular pressure drop. This leads to the fact that conventional computational models for predicting circulating pressure drop are inapplicable to hydraulics design of deep wells. With the adoption of helical flow theory and H-B rheological model, a computational model of velocity and pressure drop of non-Newtonian fluid flow in the eccentric annulus was established for the cases where the drill string rotates. The effects of eccentricity, rotation of the drill string and the dimensions of annulus on pressure drop in the annulus were analyzed. Drilling hydraulics was given for an ultra-deep well. The results show that the annular pressure drop decreases with an increase in eccentricity and rotary speed, and increases with a decrease in annular flow area. There is a great difference between static mud density and equivalent circulating density during deep well drilling.展开更多
Growth of a black hole requires the participation of a near-by accretion disk if it is to occur at a significant rate. The Kerr solution of Einstein’s equation is a vacuum solution, but the center of a realistic Kerr...Growth of a black hole requires the participation of a near-by accretion disk if it is to occur at a significant rate. The Kerr solution of Einstein’s equation is a vacuum solution, but the center of a realistic Kerr black hole is not a vacuum, so the predicted disk singularity does not exist. Instead, the center of a black hole is occupied by an ultra-dense, spheroidal core whose diameter is greater than that of the theoretical disk singularity. The surface of a black hole’s core is continually bombarded by energetic particles from the external universe. Hence the cold remnant of a gravitationally-collapsed star that has often been assumed to be present at the center of a black hole must be replaced conceptually by a quark-gluon plasma whose temperature is of the order of 1012 K or more. The gravitational potential well of a black hole is extremely deep (TeV), but the number of discrete energy levels below the infinite-red-shift surface is finite. Information can be conveyed to observers in the external universe by thermally-excited fermions that escape from levels near the top of a black hole potential well.展开更多
In this paper,the etching characteristics of the ultra-high resistivity silicon（UHRS） by using the Bosch process were investigated.The experimental results indicated that the sulfur hexafluoride flux,the temperature...In this paper,the etching characteristics of the ultra-high resistivity silicon（UHRS） by using the Bosch process were investigated.The experimental results indicated that the sulfur hexafluoride flux,the temperature of the substrate,the platen power and the etching intermittence had important influence on the etching rate and the etching morphology of the UHRS.The profiles and morphologies of sidewall were characterized with scanning electron microscopy（SEM）.By using an improved three-stage Bosch process,380-μm deep through holes were fabricated on the UHRS with the average etching rate of about 3.14 μm/min.Meanwhile,the fabrication mechanism of deep through holes on the UHRS by using the three-stage Bosch process was illustrated on the basis of the experimental results.展开更多
基金supported by the National 863 Program (2006AA06A19-2)
文摘Due to the slim hole at the lower part of the ultra-deep and deep wells, the eccentricity and rotation of drill string and drilling fluid properties have great effects on the annular pressure drop. This leads to the fact that conventional computational models for predicting circulating pressure drop are inapplicable to hydraulics design of deep wells. With the adoption of helical flow theory and H-B rheological model, a computational model of velocity and pressure drop of non-Newtonian fluid flow in the eccentric annulus was established for the cases where the drill string rotates. The effects of eccentricity, rotation of the drill string and the dimensions of annulus on pressure drop in the annulus were analyzed. Drilling hydraulics was given for an ultra-deep well. The results show that the annular pressure drop decreases with an increase in eccentricity and rotary speed, and increases with a decrease in annular flow area. There is a great difference between static mud density and equivalent circulating density during deep well drilling.
文摘Growth of a black hole requires the participation of a near-by accretion disk if it is to occur at a significant rate. The Kerr solution of Einstein’s equation is a vacuum solution, but the center of a realistic Kerr black hole is not a vacuum, so the predicted disk singularity does not exist. Instead, the center of a black hole is occupied by an ultra-dense, spheroidal core whose diameter is greater than that of the theoretical disk singularity. The surface of a black hole’s core is continually bombarded by energetic particles from the external universe. Hence the cold remnant of a gravitationally-collapsed star that has often been assumed to be present at the center of a black hole must be replaced conceptually by a quark-gluon plasma whose temperature is of the order of 1012 K or more. The gravitational potential well of a black hole is extremely deep (TeV), but the number of discrete energy levels below the infinite-red-shift surface is finite. Information can be conveyed to observers in the external universe by thermally-excited fermions that escape from levels near the top of a black hole potential well.
基金Project supported by the National Natural Science Foundation of China(Nos.61574108,61574112,61504099)
文摘In this paper,the etching characteristics of the ultra-high resistivity silicon（UHRS） by using the Bosch process were investigated.The experimental results indicated that the sulfur hexafluoride flux,the temperature of the substrate,the platen power and the etching intermittence had important influence on the etching rate and the etching morphology of the UHRS.The profiles and morphologies of sidewall were characterized with scanning electron microscopy（SEM）.By using an improved three-stage Bosch process,380-μm deep through holes were fabricated on the UHRS with the average etching rate of about 3.14 μm/min.Meanwhile,the fabrication mechanism of deep through holes on the UHRS by using the three-stage Bosch process was illustrated on the basis of the experimental results.
