Band structure of wurtzite （WZ） GaAs nanowires （NWs） is investigated by using photoluminescenee measurements under hydrostatic pressure at 6 K. We demonstrate that WZ GaAs NWs have a direct bandgap transition with...Band structure of wurtzite （WZ） GaAs nanowires （NWs） is investigated by using photoluminescenee measurements under hydrostatic pressure at 6 K. We demonstrate that WZ GaAs NWs have a direct bandgap transition with an emission energy of 1.53eV, corresponding to the optical transition between conduction band Г7c and valence band Г9v in WZ GaAs. The direct-to-pseudodirect bandgap transition can be observed by applying a pressure approximately above 2.5 GPa.展开更多
The utilization of pressure vessels in aerospace applications is manifold.In this work,fnite element analysis（FEA）has been carried out using ANSYS software package with 2D axisymmetric model to access the failure pr...The utilization of pressure vessels in aerospace applications is manifold.In this work,fnite element analysis（FEA）has been carried out using ANSYS software package with 2D axisymmetric model to access the failure pressure of cylindrical pressure vessel made of ASTM A36 carbon steel having weld-induced residual stresses.To fnd out the effect of residual stresses on failure pressure,frst an elasto-plastic analysis is performed to fnd out the failure pressure of pressure vessel not having residual stresses.Then a thermo-mechanical fnite element analysis is performed to assess the residual stresses developed in the pressure vessel during welding.Finally one more elasto-plastic analysis is performed to assess the effect of residual stresses on failure pressure of the pressure vessel having residual stresses.This analysis indicates reduction in the failure pressure due to unfavorable residual stresses.展开更多
Deep-water jacket skirt pile grouting is a critical step in ocean platform construction. Because of the complexity of the skirt pile structure and grouting pipeline, the calculation of grouting pressure and the contro...Deep-water jacket skirt pile grouting is a critical step in ocean platform construction. Because of the complexity of the skirt pile structure and grouting pipeline, the calculation of grouting pressure and the control of output pressure are involved. Beginning with the jacket skirt pile grouting construction scheme, grouting pressure is estimated on the basis of engineering fluid mechanics theory and variable frequency control technique. Programmable logic controller is the center of grouting pressure control system, which accomplishes the flow control of cement buffer tank, water buffer tank, additive buffer tank, cement metering tank, water metering tank, additive metering tank, mixer and agitator. Based on PROFIBUS-DP network, the output pressure of the slurry pump is controlled by the inverter. This method has been applied successfully in JZ20-2 Nor. high spot jacket platform construction.展开更多
The characteristics of a hybrid hydraulic vehicle driven by the hydraulic common rail propulsion system with a hydraulic free-piston engine and a hydraulic transformer were studied.A mathematical model of the propulsi...The characteristics of a hybrid hydraulic vehicle driven by the hydraulic common rail propulsion system with a hydraulic free-piston engine and a hydraulic transformer were studied.A mathematical model of the propulsion system was established and a control method of the propulsion system was proposed.Extensive simulation results of hybrid hydraulic vehicles with the hydraulic common rail propulsion system were presented.The hydraulic common rail propulsion system achieved the switch power control and the constant power propulsion.The control method based on the propulsion,break and speed limit requirement was verified.Our results showed that the hydraulic common rail propulsion system gained an ideal acceleration process.展开更多
Water inrush and mud gushing are one of the biggest hazards in tunnel construction. Unfavorable geological sections can be observed in almost all railway tunnels under construction or to be constructed, and vary in ex...Water inrush and mud gushing are one of the biggest hazards in tunnel construction. Unfavorable geological sections can be observed in almost all railway tunnels under construction or to be constructed, and vary in extent. Furthermore, due to the different heights of mountains and the lengths of tunnels, the locations of the unfavorable geological sections cannot be fully determined before construction, which increases the risk of water inrush and mud gushing. Based on numerous cases of water inrush and mud gushing in railway tunnels, the paper tries to classify water inrush and mud gushing in railway tunnels in view of the conditions of the surrounding rocks and meteorological factors associated with tunnel excavation. In addition, the causes of water inrush and mud gushing in combination of macroand micromechanisms are summarized, and site-specifc treatment method is put forward. The treatment methods include choosing a method of advance geological forecast according to risk degrees of different sections in the tunnel, determining the items of predictions, and choosing the appropriate methods, i.e. draining-oriented method, blocking-oriented method or draining-and-blocking method. The treatment technologies of railway water inrush and mud gushing are also summarized, including energy relief and pressure relief technology, advance grouting technology, and advance jet grouting technology associated with their key technical features and applicable conditions. The results in terms of treatment methods can provide reference to the prevention and treatment of tunnel water inrush and mud gushing.展开更多
Metal-organic frameworks(MOFs)and covalent organic frameworks(COFs)with highly ordered porous structure,tunable bandgap,large specific surface area and structural diversity,provide an appealing platform for the develo...Metal-organic frameworks(MOFs)and covalent organic frameworks(COFs)with highly ordered porous structure,tunable bandgap,large specific surface area and structural diversity,provide an appealing platform for the development of stimulus response,sensing,imaging and optoelectronics.Among various tuning methods,pressure engineering using the diamond anvil cell is a highly powerful in-situ technique,which can efficiently modulate the structural and optical properties of MOFs/COFs.This is beyond the realization of traditional chemical methods.This review outlines the research progress in the experimentoriented discovery of new phases or unique properties under high pressure,including phase transition,abnormal compression,photoluminescence(PL)discoloration and enhancement.Notably,the improvement of PL quantum yield in MOFs could be achieved by pressure-treated engineering and hydrogen-bonding cooperativity effect.We also propose and establish the relationship between structure and optical properties under high pressure.Finally,the challenge and outlook of the current fields are summarized.We hope that this review will supply guidance for comprehending the development of high-pressure MOF/COF-related research fields,and offer novel strategies for designing more high-performance MOF/COF materials to ultimately expand their applications.展开更多
Tungsten disulfide(WS_(2))has been reported to show negligible stacking dependence under ambient conditions,impeding its further explorations on physical properties and potential applications.Here,we realize efficient...Tungsten disulfide(WS_(2))has been reported to show negligible stacking dependence under ambient conditions,impeding its further explorations on physical properties and potential applications.Here,we realize efficient modulation of interlayer coupling in bilayer WS_(2)with 3R and 2H stackings by high pressure,and find that the pressure-triggered interlayer coupling and pressure-induced resonant-to-nonresonant transition exhibit prominent stacking dependence,which are experimentally observed for the first time in WS2.Our work may unleash the stacking degree of freedom in designing WS_(2)devices with tailored properties correlated to interlayer coupling.展开更多
This paper presents a new idea to reduce the solidity of low-pressure turbine(LPT) blade cascades,while remain the structural integrity of LPT blade.Aerodynamic performance of a low solidity LPT cascade was improved b...This paper presents a new idea to reduce the solidity of low-pressure turbine(LPT) blade cascades,while remain the structural integrity of LPT blade.Aerodynamic performance of a low solidity LPT cascade was improved by increasing blade trailing edge thickness(TET).The solidity of the LPT cascade blade can be reduced by about12.5% through increasing the TET of the blade without a significant drop in energy efficiency.For the low solidity LPT cascade,increasing the TET can decrease energy loss by 23.30% and increase the flow turning angle by1.86% for Reynolds number(Re) of 25,000 and freestream turbulence intensities(FSTT) of 2.35%.The flow control mechanism governing behavior around the trailing edge of an LPT cascade is also presented.The results show that appropriate TET is important for the optimal design of high-lift load LPT blade cascades.展开更多
基金Supported by the National Natural Science Foundation of China under Grant No 11474275
文摘Band structure of wurtzite （WZ） GaAs nanowires （NWs） is investigated by using photoluminescenee measurements under hydrostatic pressure at 6 K. We demonstrate that WZ GaAs NWs have a direct bandgap transition with an emission energy of 1.53eV, corresponding to the optical transition between conduction band Г7c and valence band Г9v in WZ GaAs. The direct-to-pseudodirect bandgap transition can be observed by applying a pressure approximately above 2.5 GPa.
文摘The utilization of pressure vessels in aerospace applications is manifold.In this work,fnite element analysis（FEA）has been carried out using ANSYS software package with 2D axisymmetric model to access the failure pressure of cylindrical pressure vessel made of ASTM A36 carbon steel having weld-induced residual stresses.To fnd out the effect of residual stresses on failure pressure,frst an elasto-plastic analysis is performed to fnd out the failure pressure of pressure vessel not having residual stresses.Then a thermo-mechanical fnite element analysis is performed to assess the residual stresses developed in the pressure vessel during welding.Finally one more elasto-plastic analysis is performed to assess the effect of residual stresses on failure pressure of the pressure vessel having residual stresses.This analysis indicates reduction in the failure pressure due to unfavorable residual stresses.
基金Supported by Key Research Project of China Offshore Oil Engineering Co,Ltd.
文摘Deep-water jacket skirt pile grouting is a critical step in ocean platform construction. Because of the complexity of the skirt pile structure and grouting pipeline, the calculation of grouting pressure and the control of output pressure are involved. Beginning with the jacket skirt pile grouting construction scheme, grouting pressure is estimated on the basis of engineering fluid mechanics theory and variable frequency control technique. Programmable logic controller is the center of grouting pressure control system, which accomplishes the flow control of cement buffer tank, water buffer tank, additive buffer tank, cement metering tank, water metering tank, additive metering tank, mixer and agitator. Based on PROFIBUS-DP network, the output pressure of the slurry pump is controlled by the inverter. This method has been applied successfully in JZ20-2 Nor. high spot jacket platform construction.
基金Supported by the National Ministry Fundamental Research Foundation of China(A2220060053)
文摘The characteristics of a hybrid hydraulic vehicle driven by the hydraulic common rail propulsion system with a hydraulic free-piston engine and a hydraulic transformer were studied.A mathematical model of the propulsion system was established and a control method of the propulsion system was proposed.Extensive simulation results of hybrid hydraulic vehicles with the hydraulic common rail propulsion system were presented.The hydraulic common rail propulsion system achieved the switch power control and the constant power propulsion.The control method based on the propulsion,break and speed limit requirement was verified.Our results showed that the hydraulic common rail propulsion system gained an ideal acceleration process.
文摘Water inrush and mud gushing are one of the biggest hazards in tunnel construction. Unfavorable geological sections can be observed in almost all railway tunnels under construction or to be constructed, and vary in extent. Furthermore, due to the different heights of mountains and the lengths of tunnels, the locations of the unfavorable geological sections cannot be fully determined before construction, which increases the risk of water inrush and mud gushing. Based on numerous cases of water inrush and mud gushing in railway tunnels, the paper tries to classify water inrush and mud gushing in railway tunnels in view of the conditions of the surrounding rocks and meteorological factors associated with tunnel excavation. In addition, the causes of water inrush and mud gushing in combination of macroand micromechanisms are summarized, and site-specifc treatment method is put forward. The treatment methods include choosing a method of advance geological forecast according to risk degrees of different sections in the tunnel, determining the items of predictions, and choosing the appropriate methods, i.e. draining-oriented method, blocking-oriented method or draining-and-blocking method. The treatment technologies of railway water inrush and mud gushing are also summarized, including energy relief and pressure relief technology, advance grouting technology, and advance jet grouting technology associated with their key technical features and applicable conditions. The results in terms of treatment methods can provide reference to the prevention and treatment of tunnel water inrush and mud gushing.
基金supported by the National Natural Science Foundation of China(12304261,12274177)。
文摘Metal-organic frameworks(MOFs)and covalent organic frameworks(COFs)with highly ordered porous structure,tunable bandgap,large specific surface area and structural diversity,provide an appealing platform for the development of stimulus response,sensing,imaging and optoelectronics.Among various tuning methods,pressure engineering using the diamond anvil cell is a highly powerful in-situ technique,which can efficiently modulate the structural and optical properties of MOFs/COFs.This is beyond the realization of traditional chemical methods.This review outlines the research progress in the experimentoriented discovery of new phases or unique properties under high pressure,including phase transition,abnormal compression,photoluminescence(PL)discoloration and enhancement.Notably,the improvement of PL quantum yield in MOFs could be achieved by pressure-treated engineering and hydrogen-bonding cooperativity effect.We also propose and establish the relationship between structure and optical properties under high pressure.Finally,the challenge and outlook of the current fields are summarized.We hope that this review will supply guidance for comprehending the development of high-pressure MOF/COF-related research fields,and offer novel strategies for designing more high-performance MOF/COF materials to ultimately expand their applications.
基金supported by the National Natural Science Foundation of China(Grant Nos.T2325007,62250073,U21A20459,62004026,61774029,62104029,12104086,62150052,U23A20570,and 51902346)the Sichuan Science and Technology Program(Grant Nos.2021JDTD0028,2023NSFSC1334,24NSFSC5852,and 24NSFSC5853)the Science and Technology Innovation Program of Hunan Province(Grant No.2021RC3021)。
文摘Tungsten disulfide(WS_(2))has been reported to show negligible stacking dependence under ambient conditions,impeding its further explorations on physical properties and potential applications.Here,we realize efficient modulation of interlayer coupling in bilayer WS_(2)with 3R and 2H stackings by high pressure,and find that the pressure-triggered interlayer coupling and pressure-induced resonant-to-nonresonant transition exhibit prominent stacking dependence,which are experimentally observed for the first time in WS2.Our work may unleash the stacking degree of freedom in designing WS_(2)devices with tailored properties correlated to interlayer coupling.
基金supported by the National Foundation for Innovative Research Groups of China(Grant No.51421063)
文摘This paper presents a new idea to reduce the solidity of low-pressure turbine(LPT) blade cascades,while remain the structural integrity of LPT blade.Aerodynamic performance of a low solidity LPT cascade was improved by increasing blade trailing edge thickness(TET).The solidity of the LPT cascade blade can be reduced by about12.5% through increasing the TET of the blade without a significant drop in energy efficiency.For the low solidity LPT cascade,increasing the TET can decrease energy loss by 23.30% and increase the flow turning angle by1.86% for Reynolds number(Re) of 25,000 and freestream turbulence intensities(FSTT) of 2.35%.The flow control mechanism governing behavior around the trailing edge of an LPT cascade is also presented.The results show that appropriate TET is important for the optimal design of high-lift load LPT blade cascades.
