为解决增压中冷车用柴油机瞬态工况排气烟度恶化问题,建立了基于实时数据采集的高压射流辅助能量供给(H igh Pressure A ir Spray Assistant Power Supp ly,HPAS)试验系统,研究了不同HPAS控制策略对发动机瞬态性能的影响规律。试验结果...为解决增压中冷车用柴油机瞬态工况排气烟度恶化问题,建立了基于实时数据采集的高压射流辅助能量供给(H igh Pressure A ir Spray Assistant Power Supp ly,HPAS)试验系统,研究了不同HPAS控制策略对发动机瞬态性能的影响规律。试验结果表明采用工况瞬变前2 s开始补气、油门稳定后即停止补气的预补气策略时HPAS对瞬态性能改善并不明显;采用油门增加即开始补气、回油门时停止补气的全程补气策略和油门增加到一半时开始补气、回油门时停止补气的中间补气两种策略对瞬态性能改善明显且幅值相近。考虑到实车应用的方便性确定了全程补气作为最终控制策略。展开更多
Abrasive waterjets （AWJs） can be used in extreme mining conditions for hard rock destruction, due to their ability to effectively cut difficult-to-machine materials with an absence of dust formation. They can also b...Abrasive waterjets （AWJs） can be used in extreme mining conditions for hard rock destruction, due to their ability to effectively cut difficult-to-machine materials with an absence of dust formation. They can also be used for explosion, intrinsic, and fire safety. Every destructible material can be considered as either ductile or brittle in terms of its fracture mechanics. Thus, there is a need for a method to predict the efficiency of cutting with AWJs that is highly accurate irrespective of material. This problem can be solved using the energy conservation approach, which states the proportionality between the material removal volume and the kinetic energy of AWJs. This paper describes a method based on this approach, along with recommendations on reaching the most effective level of destruction. Recommendations are provided regarding rational ranges of values for the relation of abrasive flow rate to water flow rate, standoff distance, and size of abrasive particles. I also provide a parameter to establish the threshold conditions for a material＇s destruction initiation based on the temporary-structural approach of fracture mechanics.展开更多
AIM:To evaluate the efficacy of Stretta procedure with gastroesophageal reflux disease(GERD)based on symptom control,medication changes and oesophagitis grade.METHODS:Ninety patients with a history of GERD underwent S...AIM:To evaluate the efficacy of Stretta procedure with gastroesophageal reflux disease(GERD)based on symptom control,medication changes and oesophagitis grade.METHODS:Ninety patients with a history of GERD underwent Stretta procedure from June 2007 to March 2010.All patients with GERD diagnosed by the pres-ence of endoscopically evidenced oesophagitis or abnormal esophageal pH testing.We evaluated GERD-health-related quality of life,satisfaction,medication use and endoscopy at baseline,6,12 mo after treatment.Complications of the procedure were analyzed.RESULTS:We found that patients experienced significant changes in symptoms of GERD after Stretta proce-dure.The onset of GERD symptom relief was less than 2 mo(70.0%)or 2 to 6 mo(16.7%).The mean GERD-HRQL score was 25.6(baseline),7.3(6 mo,P<0.01),and 8.1(12 mo,P<0.01).The mean heartburn scorewas 3.3(baseline),and 1.2(12 mo,P<0.05).The percentage of patients with satisfactory GERD control improved from 31.1%at baseline to 86.7%after treat-ment,and patient satisfaction improved from 1.4 at baseline to 4.0 at 12 mo(P<0.01).Medication usage decreased significantly from 100%of patients on pro-ton pump inhibitors therapy at baseline to 76.7%of patients showing elimination of medications or only as needed use of antacids/H2-RA at 12 mo.An improvement in endoscopic grade of oesophagitis was seen in 33 of the 41 patients.All patients had either no erosions or only mild erosive disease(grade A)at 6 mo.CONCLUSION:The experience with Stretta procedure confirms that it is well tolerated,safe,effective and durable in the treatment of GERD.The Stretta procedure provides the drug-refractory patients with a new mini-mally invasive method.展开更多
Volumetric fraction distribution measurement is a constituent part of process tomography system in oil-water-gas multiphase flow. With the technological development of nuclear radial inspection, dual-energy γ-ray tec...Volumetric fraction distribution measurement is a constituent part of process tomography system in oil-water-gas multiphase flow. With the technological development of nuclear radial inspection, dual-energy γ-ray techniques make it possible to investigate the concentration of the different components on the cross-section of oil-water-gas multiphase pipe-flow. The dual-energy gamma-ray technique is based on materials attenuation coefficients measurement comprised of two radioactive isotopes of 241Am and 241Cs which have emission energies at 59.5 keV and 662 keV in this project. Nuclear instruments and data acquisition system were designed to measure the material’s attenuation dose rate and a number of static tests were conducted at the Multiphase Laboratory, Institute of Mechanics, Chinese Academy of Sciences. Three phases of oil-water-gas media were inves- tigated for their possible use to simulate different media volumetric fraction distributions in experimental vessels. Attenuation intensities were measured, and the arithmetic of linear attenuation coefficients and the equations of volumetric fractions were studied. Investigation of an unexpected measurement error from attenuation equations revealed that a modified arithmetic was involved and finally the system achieved acceptable accuracy in experimental research.展开更多
Turbulent kinetic energy budgets are presented for a highly curved flow generated by the collision of plane wall turbulent jet with a low-velocity boundary layer. The different terms are obtained in the vertical plane...Turbulent kinetic energy budgets are presented for a highly curved flow generated by the collision of plane wall turbulent jet with a low-velocity boundary layer. The different terms are obtained in the vertical plane of symmetry by quadratic interpolation of the LDV （Laser Doppler Velocimetry） measurements, for a wall jet-to-boundary layer velocity ratio of 2. The results, which have relevance to flows encountered in powered-lift aircraft operating in ground effect, quantify the structure of the complex ground vortex flow. The analysis of turbulent energy equation terms using the measured data revealed that production by normal and shear stresses are both very important to the turbulent structure of the impact zone of the ground vortex. This is an indication that the modeling of turbulence of a ground vortex requires a good representation of the production by normal stresses which is most important in the collision zone.展开更多
Laser-induced fluorescence excitation spectra of jet-cooled NiC1 molecules were recorded in the energy range of 12900-15000 cm-1. Six vibronic bands with rotational structure have been observed and assigned to the [13...Laser-induced fluorescence excitation spectra of jet-cooled NiC1 molecules were recorded in the energy range of 12900-15000 cm-1. Six vibronic bands with rotational structure have been observed and assigned to the [13.0]2II3/2（v＇=0-5）-X2II3/2（v＂=0） transition progression. The relevant rotational constants, significant isotopic shifts, and （equilibrium） molecular parameters have been determined. In addition, the lifetimes of the observed bands have also been measured.展开更多
This paper discusses the principle and mathematical method to measure the phase fractions of multiphase flows by using a dual-energy gamma-ray system. The dual-energy gamma-ray device is composed of radioactive isotop...This paper discusses the principle and mathematical method to measure the phase fractions of multiphase flows by using a dual-energy gamma-ray system. The dual-energy gamma-ray device is composed of radioactive isotopes of 241Am and 137Cs with emission energies of 59.5 keV and 662 keV respectively. A rational method to calibrate the absorption coefficient was introduced in detail. The statistical error has been analyzed on the basis of the accurate absorption coefficient which enables determination phrase fractions almost independent of the flow regime. Improvement has been achieved on the measurement accuracy of phase fractions.展开更多
We present computational results on the evolution of the shock-accelerated heavy bubbles surrounded by nitrogen with the Atwood number At = 0.497–0.677 and the emphasis is on the jet phenomenon caused by the shock fo...We present computational results on the evolution of the shock-accelerated heavy bubbles surrounded by nitrogen with the Atwood number At = 0.497–0.677 and the emphasis is on the jet phenomenon caused by the shock focusing. The multi-fluid Eulerian equation is solved by a finite volume method based on MUSCL-Hancock approach. Based on the numerical schlieren and the distributions of density and pressure, it is found that there are three typical jet structures(outward jet, no jet, inward jet) for different combinations of gas mixture inside the bubble which determine the position of shock focusing relative to the downstream pole of the heavy bubble(upstream of the pole, at the pole, downstream the pole). Compared with the inward jet, the velocity of outward jet is obviously larger. As At increases, the moment of jet formation is postponed, and the maximal values and magnifications of pressure and density increase distinctly. Therefore, the energy convergence effects are heavily enhanced with the increase of bubble gas density.展开更多
文摘为解决增压中冷车用柴油机瞬态工况排气烟度恶化问题,建立了基于实时数据采集的高压射流辅助能量供给(H igh Pressure A ir Spray Assistant Power Supp ly,HPAS)试验系统,研究了不同HPAS控制策略对发动机瞬态性能的影响规律。试验结果表明采用工况瞬变前2 s开始补气、油门稳定后即停止补气的预补气策略时HPAS对瞬态性能改善并不明显;采用油门增加即开始补气、回油门时停止补气的全程补气策略和油门增加到一半时开始补气、回油门时停止补气的中间补气两种策略对瞬态性能改善明显且幅值相近。考虑到实车应用的方便性确定了全程补气作为最终控制策略。
文摘Abrasive waterjets （AWJs） can be used in extreme mining conditions for hard rock destruction, due to their ability to effectively cut difficult-to-machine materials with an absence of dust formation. They can also be used for explosion, intrinsic, and fire safety. Every destructible material can be considered as either ductile or brittle in terms of its fracture mechanics. Thus, there is a need for a method to predict the efficiency of cutting with AWJs that is highly accurate irrespective of material. This problem can be solved using the energy conservation approach, which states the proportionality between the material removal volume and the kinetic energy of AWJs. This paper describes a method based on this approach, along with recommendations on reaching the most effective level of destruction. Recommendations are provided regarding rational ranges of values for the relation of abrasive flow rate to water flow rate, standoff distance, and size of abrasive particles. I also provide a parameter to establish the threshold conditions for a material＇s destruction initiation based on the temporary-structural approach of fracture mechanics.
文摘AIM:To evaluate the efficacy of Stretta procedure with gastroesophageal reflux disease(GERD)based on symptom control,medication changes and oesophagitis grade.METHODS:Ninety patients with a history of GERD underwent Stretta procedure from June 2007 to March 2010.All patients with GERD diagnosed by the pres-ence of endoscopically evidenced oesophagitis or abnormal esophageal pH testing.We evaluated GERD-health-related quality of life,satisfaction,medication use and endoscopy at baseline,6,12 mo after treatment.Complications of the procedure were analyzed.RESULTS:We found that patients experienced significant changes in symptoms of GERD after Stretta proce-dure.The onset of GERD symptom relief was less than 2 mo(70.0%)or 2 to 6 mo(16.7%).The mean GERD-HRQL score was 25.6(baseline),7.3(6 mo,P<0.01),and 8.1(12 mo,P<0.01).The mean heartburn scorewas 3.3(baseline),and 1.2(12 mo,P<0.05).The percentage of patients with satisfactory GERD control improved from 31.1%at baseline to 86.7%after treat-ment,and patient satisfaction improved from 1.4 at baseline to 4.0 at 12 mo(P<0.01).Medication usage decreased significantly from 100%of patients on pro-ton pump inhibitors therapy at baseline to 76.7%of patients showing elimination of medications or only as needed use of antacids/H2-RA at 12 mo.An improvement in endoscopic grade of oesophagitis was seen in 33 of the 41 patients.All patients had either no erosions or only mild erosive disease(grade A)at 6 mo.CONCLUSION:The experience with Stretta procedure confirms that it is well tolerated,safe,effective and durable in the treatment of GERD.The Stretta procedure provides the drug-refractory patients with a new mini-mally invasive method.
文摘Volumetric fraction distribution measurement is a constituent part of process tomography system in oil-water-gas multiphase flow. With the technological development of nuclear radial inspection, dual-energy γ-ray techniques make it possible to investigate the concentration of the different components on the cross-section of oil-water-gas multiphase pipe-flow. The dual-energy gamma-ray technique is based on materials attenuation coefficients measurement comprised of two radioactive isotopes of 241Am and 241Cs which have emission energies at 59.5 keV and 662 keV in this project. Nuclear instruments and data acquisition system were designed to measure the material’s attenuation dose rate and a number of static tests were conducted at the Multiphase Laboratory, Institute of Mechanics, Chinese Academy of Sciences. Three phases of oil-water-gas media were inves- tigated for their possible use to simulate different media volumetric fraction distributions in experimental vessels. Attenuation intensities were measured, and the arithmetic of linear attenuation coefficients and the equations of volumetric fractions were studied. Investigation of an unexpected measurement error from attenuation equations revealed that a modified arithmetic was involved and finally the system achieved acceptable accuracy in experimental research.
文摘Turbulent kinetic energy budgets are presented for a highly curved flow generated by the collision of plane wall turbulent jet with a low-velocity boundary layer. The different terms are obtained in the vertical plane of symmetry by quadratic interpolation of the LDV （Laser Doppler Velocimetry） measurements, for a wall jet-to-boundary layer velocity ratio of 2. The results, which have relevance to flows encountered in powered-lift aircraft operating in ground effect, quantify the structure of the complex ground vortex flow. The analysis of turbulent energy equation terms using the measured data revealed that production by normal and shear stresses are both very important to the turbulent structure of the impact zone of the ground vortex. This is an indication that the modeling of turbulence of a ground vortex requires a good representation of the production by normal stresses which is most important in the collision zone.
基金This work was supported by the National Natural Science Foundation of China （No.21273212, No.20873133, and No.21173205）, the National Key Basic Research Program of China （No.2010CB923302）, the Chinese Academy of Sciences （No.KJCX2-YW-N24）, the FRFCUC （No.WK2340000012）, and the USTC-NSRL Joint Funds （No.KY2340000021）.
文摘Laser-induced fluorescence excitation spectra of jet-cooled NiC1 molecules were recorded in the energy range of 12900-15000 cm-1. Six vibronic bands with rotational structure have been observed and assigned to the [13.0]2II3/2（v＇=0-5）-X2II3/2（v＂=0） transition progression. The relevant rotational constants, significant isotopic shifts, and （equilibrium） molecular parameters have been determined. In addition, the lifetimes of the observed bands have also been measured.
文摘This paper discusses the principle and mathematical method to measure the phase fractions of multiphase flows by using a dual-energy gamma-ray system. The dual-energy gamma-ray device is composed of radioactive isotopes of 241Am and 137Cs with emission energies of 59.5 keV and 662 keV respectively. A rational method to calibrate the absorption coefficient was introduced in detail. The statistical error has been analyzed on the basis of the accurate absorption coefficient which enables determination phrase fractions almost independent of the flow regime. Improvement has been achieved on the measurement accuracy of phase fractions.
基金supported by the National Natural Science Foundation of China(Grant Nos.11172278,11302201,11472253 and 11202195)Science Foundation of China Academy of Engineering Physics(Grant No.2014B0201017)
文摘We present computational results on the evolution of the shock-accelerated heavy bubbles surrounded by nitrogen with the Atwood number At = 0.497–0.677 and the emphasis is on the jet phenomenon caused by the shock focusing. The multi-fluid Eulerian equation is solved by a finite volume method based on MUSCL-Hancock approach. Based on the numerical schlieren and the distributions of density and pressure, it is found that there are three typical jet structures(outward jet, no jet, inward jet) for different combinations of gas mixture inside the bubble which determine the position of shock focusing relative to the downstream pole of the heavy bubble(upstream of the pole, at the pole, downstream the pole). Compared with the inward jet, the velocity of outward jet is obviously larger. As At increases, the moment of jet formation is postponed, and the maximal values and magnifications of pressure and density increase distinctly. Therefore, the energy convergence effects are heavily enhanced with the increase of bubble gas density.
