Because single trigger system is unreliable for shock wave overpressure test, this paper presents a multi-trigger overpressure test system. The large memory capacity is divided into parts to achieve data acquisition a...Because single trigger system is unreliable for shock wave overpressure test, this paper presents a multi-trigger overpressure test system. The large memory capacity is divided into parts to achieve data acquisition and storage with multiple triggers. Compared with conventional single-shot storage test system, this system can prevent false trigger and improve reliability of the test. By using explosion time to extract valid signal segments, it improves the efficiency of data recovery. These characteristics of the system contribute to multi-point test. After the dynamic characteristics of the system are calibrated, the valid data can be obtained in explosion experiments. The results show that the multi-trigger test system has higher reliability than single trigger test system.展开更多
Turbulent combustion in a DLR (German Aerospace Center) Scramjet engine was simulated using the newly-proposed Partially Resolved Numerical Simulation (PRNS) procedure. The PRNS procedure uses temporal filtering to de...Turbulent combustion in a DLR (German Aerospace Center) Scramjet engine was simulated using the newly-proposed Partially Resolved Numerical Simulation (PRNS) procedure. The PRNS procedure uses temporal filtering to define large-scale turbulence, and the model developed to account for unresolved scales is grid independent. No problem about inner commutation error and inconsistencies will arise from the PRNS, while such issues are of concern in traditional Large Eddy Simulation (LES) methods. The mean results have good agreement with the experiment data and the flow structures with small scales are well resolved.展开更多
This paper analyzes the physicochemical properties of supercritical C02, the characteristic of shale gas and shale gas reservoirs. The technologies of drilling, production, fracturing using the supercritical CO2 in sh...This paper analyzes the physicochemical properties of supercritical C02, the characteristic of shale gas and shale gas reservoirs. The technologies of drilling, production, fracturing using the supercritical CO2 in shale gas explo- ration are proposed, to increase the penetration rate, decrease the damage to formation while fracturing, and enhance the recovery of shale gas. It is believed that the huge economic benefits of shale gas exploration with the supercritical CO2 fluid will be obtained, and it also can initiate a new technology field of CO2 in the petroleum engineering.展开更多
The scramjet and maglev engineering technology development and trends at home and abroad are firstly presented in this paper. A new launch mode of space transportation system is proposed based on scramjet and magnetic...The scramjet and maglev engineering technology development and trends at home and abroad are firstly presented in this paper. A new launch mode of space transportation system is proposed based on scramjet and magnetic suspension technologies, and its key technologies required are given. This paper also makes analysis on using scramjet and magnetic suspension technologies to launch a reusable rocket, and the results show that a normal temperature conductor maglev launch system is feasible.展开更多
Modeling vapor pressure is crucial for studying the moisture reliability of microelectronics, as high vapor pressure can cause device failures in environments with high temperature and humidity. To minimize the impact...Modeling vapor pressure is crucial for studying the moisture reliability of microelectronics, as high vapor pressure can cause device failures in environments with high temperature and humidity. To minimize the impact of vapor pressure, a super-hydrophobic(SH) coating can be applied on the exterior surface of devices in order to prevent moisture penetration. The underlying mechanism of SH coating for enhancing device reliability, however, is still not fully understood. In this paper, we present several existing theories for predicting vapor pressure within microelectronic materials. In addition, we discuss the mechanism and effectiveness of SH coating in preventing water vapor from entering a device, based on experimental results. Two theoretical models, a micro-mechanics-based whole-field vapor pressure model and a convection-diffusion model, are described for predicting vapor pressure. Both methods have been successfully used to explain experimental results on uncoated samples. However, when a device was coated with an SH nanocomposite, weight gain was still observed, likely due to vapor penetration through the SH surface. This phenomenon may cast doubt on the effectiveness of SH coatings in microelectronic devices. Based on current theories and the available experimental results, we conclude that it is necessary to develop a new theory to understand how water vapor penetrates through SH coatings and impacts the materials underneath. Such a theory could greatly improve microelectronics reliability.展开更多
Hypersonic flow-field measurement techniques have been studied for about 50 years. Despite truly remarkable progress with a probe or other device to measure the temperature, pressure or velocity, there are still serio...Hypersonic flow-field measurement techniques have been studied for about 50 years. Despite truly remarkable progress with a probe or other device to measure the temperature, pressure or velocity, there are still serious problems for these "intrusive" techniques. The intrusive measurement techniques introduce unexpected shock waves or flow-field structures, even make the boundary layer transition earlier and show a converse result. In recent years, nonintrusive diagnostics have been in urgent demand to give a more accurate and comprehensive flow-field for hypersonic testing. In this paper, an overview of some advanced nonintrusive measurement techniques such as embedded thermocouples for heat flux measurement, Pressure Sensitive Paint(PSP), Particle Image Velocimetry(PIV), infrared thermographs, and focusing Schlieren system are introduced. All of these techniques are nonintrusive and provide measurement of various parameters such as temperature, static pressure, dynamic pressure, flow velocity and visualization of flow structure, which gives us an exact and direct understanding of the hypersonic flow.展开更多
Leakage power is the dominant source of power dissipation for Sub-100 nm VLSI （very large scale integration） circuits. Various techniques were proposed to reduce the leakage power at nano-scale; one of these techniq...Leakage power is the dominant source of power dissipation for Sub-100 nm VLSI （very large scale integration） circuits. Various techniques were proposed to reduce the leakage power at nano-scale; one of these techniques is MTV （multi-threshold voltage） In this paper, the exact and optimal value of threshold voltage （Vth） for each transistor in any sequential circuit in the design is found, so that the value of the total leakage current in the design is at the minimum. This could be achieved by applying AI （artificial intelligence） search algorithm. The proposed algorithm is called LOAIS （leakage optimization using AI search）. LOAIS exploits the total slack time of each transistor＇s location and their contributions in the leakage current. It is introduced by AI heuristic search algorithms under 22 nm BSIM4 predictive technology model. The proposed approach saves around 80% of the sub-threshold leakage current without degrading the performance of the circuit.展开更多
In this paper, some preliminary calculations and the experiments were performed to figure out the flow field, in which some rods were normally inserted into the main flow surrounded by a porous cavity. As a result, it...In this paper, some preliminary calculations and the experiments were performed to figure out the flow field, in which some rods were normally inserted into the main flow surrounded by a porous cavity. As a result, it is found that the starting shock wave severely interacts with the rods, the bow shock wave, its reflections, and the porous wall, which are numerically well predicted at some conditions. Moreover, inserting the rods makes the pressure on the upper wall in the porous region increase when the main flow in the porous region is completely supersonic. The calculations also suggest that three rods cause the widest suction area.展开更多
The major problems for the development of an ultra micro gas turbine system were discussed briefly from the stand point of the internal flow and the performance characteristics. Following to these, the development of ...The major problems for the development of an ultra micro gas turbine system were discussed briefly from the stand point of the internal flow and the performance characteristics. Following to these, the development of ultra micro centrifugal compression systems for the ultra micro gas turbine is explained with the design and the manufacturing processes. The measured results of ultra micro centrifugal compressors are shown.展开更多
The transverse injection flow field has an important impact on the flowpath design of scramjet engines. At present a combination of the transverse injection scheme and any other flame holder has been widely employed i...The transverse injection flow field has an important impact on the flowpath design of scramjet engines. At present a combination of the transverse injection scheme and any other flame holder has been widely employed in hypersonic propulsion systems to promote the mixing process between the fuel and the supersonic freestream; combustion efficiency has been improved thereby, as well as engine thrust. Research on mixing techniques for the transverse injection flow field is summarized from four aspects, namely the jet-to-crossflow pressure ratio, the geometric configuration of the injection port, the number of injection ports, and the injection angle. In conclusion, urgent investigations of mixing techniques of the transverse injection flow field are pro- posed, especiaUy data mining in the quantitative analytical results for transverse injection flow field, based on results from multi-objective design optimization theory.展开更多
Conventional PCC pile technique has been widely used as embankment piles for highway construction in China. To further improve the PCC pile capacity, the expansive concrete technique has been applied to the PCC pile t...Conventional PCC pile technique has been widely used as embankment piles for highway construction in China. To further improve the PCC pile capacity, the expansive concrete technique has been applied to the PCC pile to replace the normal concrete recently. The use of expansive concrete for the PCC pile could increase the pile diameter as well as the contact pressure at the pile-soil interface due to the expansion process of concrete, which allows the improved PCC pile to provide higher capacity than the conventional PCC pile. This paper presents a theoretical model for the new improved PCC pile using expansive concrete technique. The model is formulated by assuming the PCC pile installation process as large strain undrained cylindrical cavity expansion and the subsequent pile shaft expansion combined with soil consolidation process is simulated by the small strain cylindrical cavity expansion combined with strain-controlled consolidation. Then, similarity solution technique is used to solve the problem of cavity expansion in modified cam Clay （MCC） model, while the strain-controlled consolidation is calculated through the finite difference method （FDM）. Subsequently, the suitability of the cavity expansion solution in the interpretation of the PCC pile installation is verified by comparing the calculated excess pore pressure with the measured value in an instrumented field test. The stress changes and excess pore pressure during the PCC pile installation and subsequent pile shaft expansion are investigated by means of parametric study. The proposed theoretical model first reveals and quantifies the fundamental mechanism of the PCC pile using expansive concrete technique and it provides a theoretical basis for developing design methods of the new improved PCC pile in the future.展开更多
Several recently developed analytical techniques, based on high-end mass spectrometry and chromatography, for dealing with challenges in petroleum characterization are reported. Folded flight path time-of-flight mass ...Several recently developed analytical techniques, based on high-end mass spectrometry and chromatography, for dealing with challenges in petroleum characterization are reported. Folded flight path time-of-flight mass spectrometry provides resolving power up to 100000, enabling accurate mass measurement for molecular formula determination with high confidence. Atmos- pheric pressure chemical ionization （APCI） can be used in both gas chromatography （GC, as APGC） and liquid chromatog- raphy （LC） for analyzing non-polar hydrocarbons as well as polar compounds. The improvement in chromatography facilitates the mass spectrometric analysis through online coupling. Comprehensive two-dimensional gas chromatography （GCxGC） re- solves overlapping components, rendering accurate identification and quantitation. Supercritical fluid extraction has been de- veloped as an alternative method to replace traditional solvent extraction methods and eliminate the use of large volumes of solvents that can be harmful to health and environment. Supercritical fluid chromatography （SFC） has been developed as a convergence of GC and LC chromatographic techniques. The use of SFC for heavy oils and residua has been demonstrated. Prospective developments in the use of mass spectrometric and chromatographic methods for petroleum characterization are also described.展开更多
文摘Because single trigger system is unreliable for shock wave overpressure test, this paper presents a multi-trigger overpressure test system. The large memory capacity is divided into parts to achieve data acquisition and storage with multiple triggers. Compared with conventional single-shot storage test system, this system can prevent false trigger and improve reliability of the test. By using explosion time to extract valid signal segments, it improves the efficiency of data recovery. These characteristics of the system contribute to multi-point test. After the dynamic characteristics of the system are calibrated, the valid data can be obtained in explosion experiments. The results show that the multi-trigger test system has higher reliability than single trigger test system.
基金Project supported by the National Natural Science Foundation of China (No. 90405003)the China Postdoctoral Science Founda-tion (No. 20060390339)
文摘Turbulent combustion in a DLR (German Aerospace Center) Scramjet engine was simulated using the newly-proposed Partially Resolved Numerical Simulation (PRNS) procedure. The PRNS procedure uses temporal filtering to define large-scale turbulence, and the model developed to account for unresolved scales is grid independent. No problem about inner commutation error and inconsistencies will arise from the PRNS, while such issues are of concern in traditional Large Eddy Simulation (LES) methods. The mean results have good agreement with the experiment data and the flow structures with small scales are well resolved.
基金Key Project of Chinese National Programs for Fundamental Research and Development(973 Program) (No. 2010CB226704)Chinese National Natural Science Foundation (No. 51034007 )+1 种基金the China National Petroleum Corporation Key Project Foundation (No. 2011A-4205)China Postdoctoral Science Foundation(No. 2011M500492)
文摘This paper analyzes the physicochemical properties of supercritical C02, the characteristic of shale gas and shale gas reservoirs. The technologies of drilling, production, fracturing using the supercritical CO2 in shale gas explo- ration are proposed, to increase the penetration rate, decrease the damage to formation while fracturing, and enhance the recovery of shale gas. It is believed that the huge economic benefits of shale gas exploration with the supercritical CO2 fluid will be obtained, and it also can initiate a new technology field of CO2 in the petroleum engineering.
文摘The scramjet and maglev engineering technology development and trends at home and abroad are firstly presented in this paper. A new launch mode of space transportation system is proposed based on scramjet and magnetic suspension technologies, and its key technologies required are given. This paper also makes analysis on using scramjet and magnetic suspension technologies to launch a reusable rocket, and the results show that a normal temperature conductor maglev launch system is feasible.
基金the support of the National High-Tech Research and Development Program of China (863 Program) (2015AA03A101)
文摘Modeling vapor pressure is crucial for studying the moisture reliability of microelectronics, as high vapor pressure can cause device failures in environments with high temperature and humidity. To minimize the impact of vapor pressure, a super-hydrophobic(SH) coating can be applied on the exterior surface of devices in order to prevent moisture penetration. The underlying mechanism of SH coating for enhancing device reliability, however, is still not fully understood. In this paper, we present several existing theories for predicting vapor pressure within microelectronic materials. In addition, we discuss the mechanism and effectiveness of SH coating in preventing water vapor from entering a device, based on experimental results. Two theoretical models, a micro-mechanics-based whole-field vapor pressure model and a convection-diffusion model, are described for predicting vapor pressure. Both methods have been successfully used to explain experimental results on uncoated samples. However, when a device was coated with an SH nanocomposite, weight gain was still observed, likely due to vapor penetration through the SH surface. This phenomenon may cast doubt on the effectiveness of SH coatings in microelectronic devices. Based on current theories and the available experimental results, we conclude that it is necessary to develop a new theory to understand how water vapor penetrates through SH coatings and impacts the materials underneath. Such a theory could greatly improve microelectronics reliability.
文摘Hypersonic flow-field measurement techniques have been studied for about 50 years. Despite truly remarkable progress with a probe or other device to measure the temperature, pressure or velocity, there are still serious problems for these "intrusive" techniques. The intrusive measurement techniques introduce unexpected shock waves or flow-field structures, even make the boundary layer transition earlier and show a converse result. In recent years, nonintrusive diagnostics have been in urgent demand to give a more accurate and comprehensive flow-field for hypersonic testing. In this paper, an overview of some advanced nonintrusive measurement techniques such as embedded thermocouples for heat flux measurement, Pressure Sensitive Paint(PSP), Particle Image Velocimetry(PIV), infrared thermographs, and focusing Schlieren system are introduced. All of these techniques are nonintrusive and provide measurement of various parameters such as temperature, static pressure, dynamic pressure, flow velocity and visualization of flow structure, which gives us an exact and direct understanding of the hypersonic flow.
文摘Leakage power is the dominant source of power dissipation for Sub-100 nm VLSI （very large scale integration） circuits. Various techniques were proposed to reduce the leakage power at nano-scale; one of these techniques is MTV （multi-threshold voltage） In this paper, the exact and optimal value of threshold voltage （Vth） for each transistor in any sequential circuit in the design is found, so that the value of the total leakage current in the design is at the minimum. This could be achieved by applying AI （artificial intelligence） search algorithm. The proposed algorithm is called LOAIS （leakage optimization using AI search）. LOAIS exploits the total slack time of each transistor＇s location and their contributions in the leakage current. It is introduced by AI heuristic search algorithms under 22 nm BSIM4 predictive technology model. The proposed approach saves around 80% of the sub-threshold leakage current without degrading the performance of the circuit.
文摘In this paper, some preliminary calculations and the experiments were performed to figure out the flow field, in which some rods were normally inserted into the main flow surrounded by a porous cavity. As a result, it is found that the starting shock wave severely interacts with the rods, the bow shock wave, its reflections, and the porous wall, which are numerically well predicted at some conditions. Moreover, inserting the rods makes the pressure on the upper wall in the porous region increase when the main flow in the porous region is completely supersonic. The calculations also suggest that three rods cause the widest suction area.
文摘The major problems for the development of an ultra micro gas turbine system were discussed briefly from the stand point of the internal flow and the performance characteristics. Following to these, the development of ultra micro centrifugal compression systems for the ultra micro gas turbine is explained with the design and the manufacturing processes. The measured results of ultra micro centrifugal compressors are shown.
基金supported by the Science Foundation of National University of Defense Technology (No. JC11-01-02)the Hunan Provincial Natural Science Foundation of China (No.12jj4047)
文摘The transverse injection flow field has an important impact on the flowpath design of scramjet engines. At present a combination of the transverse injection scheme and any other flame holder has been widely employed in hypersonic propulsion systems to promote the mixing process between the fuel and the supersonic freestream; combustion efficiency has been improved thereby, as well as engine thrust. Research on mixing techniques for the transverse injection flow field is summarized from four aspects, namely the jet-to-crossflow pressure ratio, the geometric configuration of the injection port, the number of injection ports, and the injection angle. In conclusion, urgent investigations of mixing techniques of the transverse injection flow field are pro- posed, especiaUy data mining in the quantitative analytical results for transverse injection flow field, based on results from multi-objective design optimization theory.
基金supported by the National Natural Science Foundation of China(Grant No.51420105013)
文摘Conventional PCC pile technique has been widely used as embankment piles for highway construction in China. To further improve the PCC pile capacity, the expansive concrete technique has been applied to the PCC pile to replace the normal concrete recently. The use of expansive concrete for the PCC pile could increase the pile diameter as well as the contact pressure at the pile-soil interface due to the expansion process of concrete, which allows the improved PCC pile to provide higher capacity than the conventional PCC pile. This paper presents a theoretical model for the new improved PCC pile using expansive concrete technique. The model is formulated by assuming the PCC pile installation process as large strain undrained cylindrical cavity expansion and the subsequent pile shaft expansion combined with soil consolidation process is simulated by the small strain cylindrical cavity expansion combined with strain-controlled consolidation. Then, similarity solution technique is used to solve the problem of cavity expansion in modified cam Clay （MCC） model, while the strain-controlled consolidation is calculated through the finite difference method （FDM）. Subsequently, the suitability of the cavity expansion solution in the interpretation of the PCC pile installation is verified by comparing the calculated excess pore pressure with the measured value in an instrumented field test. The stress changes and excess pore pressure during the PCC pile installation and subsequent pile shaft expansion are investigated by means of parametric study. The proposed theoretical model first reveals and quantifies the fundamental mechanism of the PCC pile using expansive concrete technique and it provides a theoretical basis for developing design methods of the new improved PCC pile in the future.
文摘Several recently developed analytical techniques, based on high-end mass spectrometry and chromatography, for dealing with challenges in petroleum characterization are reported. Folded flight path time-of-flight mass spectrometry provides resolving power up to 100000, enabling accurate mass measurement for molecular formula determination with high confidence. Atmos- pheric pressure chemical ionization （APCI） can be used in both gas chromatography （GC, as APGC） and liquid chromatog- raphy （LC） for analyzing non-polar hydrocarbons as well as polar compounds. The improvement in chromatography facilitates the mass spectrometric analysis through online coupling. Comprehensive two-dimensional gas chromatography （GCxGC） re- solves overlapping components, rendering accurate identification and quantitation. Supercritical fluid extraction has been de- veloped as an alternative method to replace traditional solvent extraction methods and eliminate the use of large volumes of solvents that can be harmful to health and environment. Supercritical fluid chromatography （SFC） has been developed as a convergence of GC and LC chromatographic techniques. The use of SFC for heavy oils and residua has been demonstrated. Prospective developments in the use of mass spectrometric and chromatographic methods for petroleum characterization are also described.
