Chinese Foreign Ministry responded to the pressure from U.S.on yuan valuation issue,proclaiming that China is not deliberately seeking for Sino-US trade surplus and will firmly oppose any
China opposes Viet Nam’s exploring oil and gas in China’s jurisdictional area ofthe South China Sea,Foreign Ministry spokeswoman Jiang Yu said on May 28."China’s stance on the South China Sea is clear and cons...China opposes Viet Nam’s exploring oil and gas in China’s jurisdictional area ofthe South China Sea,Foreign Ministry spokeswoman Jiang Yu said on May 28."China’s stance on the South China Sea is clear and consistent.展开更多
Objective To observe the clinical efficacy of opposing needling for the treatment of migraine with the symptom of hyperactivity of liver yang type and its effect on NO level in plasma of patients. Methods Atotal of 60...Objective To observe the clinical efficacy of opposing needling for the treatment of migraine with the symptom of hyperactivity of liver yang type and its effect on NO level in plasma of patients. Methods Atotal of 60 migraine patients with the symptom of hyperactivity of liver yang who met the inclusive criteria were randomly divided into a opposing needling group （group A） and a routine acupuncture group （group B） by using SPSS 15.0 software according to the registration order with 30 patients in each group. Patients in group A were treated with opposing needling. Taich6ng （太冲 LR 3）, Zhongzhu （中渚 TE 3）, ZOlfnqi （足临泣 GB 41） and QiOxu （丘墟 GB 40） in the uninjured side were selected. After deqi, reducing method was used. Then Taixi （太溪 KI 3） in the uninjured side was selected. After deqi, rein forcing method was used. Needles were retained for 30 rain. Patients in group B were treated with routine acupuncture. Local Ash point, Sishncong （ 四神聪EX-HN1）, Yifeng （翳风 TE 17）, Fengchi （风池 GB 20）, Sizhukong （丝竹空 TE 23）, Shuaigu （率谷GB 8）, Hegu （合谷 LI 4） and LiEque （列缺 LU 7） were selected. After puncturing, reducing method was used routinely and needles were retained for 30 rain. After 2 weeks treatment, migraine specific quality of life questionnaire （MSQ）, visual analogue scale （VAS） and nitric oxide （NO） level in plasma of patients in two groups were observed. Results After treatment, the MSQ, VAS and NO of two groups were significantly improved compared with those before treatment. After treatment, score of MSQ functional limitation was 73.41±10.22 in group A and 60.95 ± 10.15 in group B; the score of MSQ dysfunction was 86.11 ±8.22 in group A and 75.45±8.34 in group B; score of MSQ emotion was 80.51±10.16 in group A and 75.01± 10.20 in group B. The improvements of group A were superior to those of group B, and the differences were all statistically significant （all P〈0.05）. After treatment, the VAS score was 0.93 ± 1.25 in group A and 2.17± 1.70 in group B. The improvement of group A was superior to that of group B, and the difference was statistically significant （P〈0.05）. After treatment, blood plasma NO level was （42.15 ± 16.15） μmol/L in group A and （62.76±15.17） μmol/L in group B. The improvement of group A was superior to that of group B, and the difference was statistically significant （P〈0.05）. Overall response rate was 86.7% （26/30） in group A and 53.3% （16/30） in group B, and the difference between two groups was statistically significant （P〈0.05）. Conclusion Opposing needling is an effective method for the treatment of migraine with the symptom of hyperactivity of liver yong. Its mechanism is to regulate the generation of NO in migraine patients, and improve the relaxation and contraction of cerebral vascular smooth muscle, so as to adjust the cerebral circulation.展开更多
Along with the survey on experimental investigations drawing attention to the drag and heat reduction mechanism, the authors simultaneously focus on the recent advances of numerical simulations on the schemes applied ...Along with the survey on experimental investigations drawing attention to the drag and heat reduction mechanism, the authors simultaneously focus on the recent advances of numerical simulations on the schemes applied to supersonic/hypersonic vehicles. The CFD study has evolved as an irreplaceable method in scheme evaluation and aircraft optimization. Similar to our previous experimental survey, the advances in drag and heat reduction schemes are reviewed by similar kinds of mechanism in this article, namely the forward-facing cavity, the opposing jet, the aerospike, the energy deposition and their combinational configurations. This review article puts an emphatic eye on the flow conditions, numerical methods, novel schemes and analytical conclusions given in the simulations. Further, the multi-objective design optimization concept has also been illustrated due to the observable advantages of using CFD over experimental method, especially those performances conducted in drag reduction and thermal protection practice, and this would possess reference value in the design of aircraft system.展开更多
This paper focuses on the usage of the forward-facing cavity and opposing jet combinatorial configuration as the thermal protection system （TPS） for hypersonic vehicles. A hemispherecone nose-tip with the combinator...This paper focuses on the usage of the forward-facing cavity and opposing jet combinatorial configuration as the thermal protection system （TPS） for hypersonic vehicles. A hemispherecone nose-tip with the combinatorial configuration is investigated numerically in hypersonic free stream. Some numerical results are validated by experiments. The flow field parameters, aerodynamic force and surface heat flux distribution are obtained. The influence of the opposing jet stagnation pressure on cooling efficiency of the combinatorial TPS is discussed. The detailed numerical results show that the aerodynamic heating is reduced remarkably by the combinatorial system. The recirculation region plays a pivotal role for the reduction of heat flux. The larger the stagnation pressure of opposing jet is, the more the heating reduction is. This kind of combinatorial system is suitable to be the TPS for the high-speed vehicles which need long-range and long time flight.展开更多
Implementation of an opposing jet in design of a hypersonic blunt body significantly modifies the external flowfield and yields a considerable reduction in the aerodynamic drag.This study aims to investigate the effec...Implementation of an opposing jet in design of a hypersonic blunt body significantly modifies the external flowfield and yields a considerable reduction in the aerodynamic drag.This study aims to investigate the effects of flowfield modeling parameters of injection and freestream on the flow structure and aerodynamics of a blunt body with an opposing jet in hypersonic flow.Reynolds-Averaged Navier-Stokes(RANS)equations with a Shear Stress Transport(SST)turbulence model are employed to simulate the intricate jet flow interaction.Through utilizing a Non-Intrusive Polynomial Chaos(NIPC)method to construct surrogates,a functional relation is established between input modeling parameters and output flowfield and aerodynamic quantities in concern.Sobol indices in sensitivity analysis are introduced to represent the relative contribution of each parameter.It is found that variations in modeling parameters produce large variations in the flow structure and aerodynamics.The jet-to-freestream total-pressure ratio,jet Mach number,and freestream Mach number are the major contributors to variation in surface pressure,demonstrating an evident location-dependent behavior.The penetration length of injection,reattachment angle of the shear layer,and aerodynamic drag are also most sensitive to the three crucial parameters above.In comparison,the contributions of freestream temperature,freestream density,and jet total temperature are nearly negligible.展开更多
Experimental and numerical studies are carried out to validate the potential of opposing Plasma Synthetic Jet(PSJ)for drag reduction for a hemisphere.Firstly,flow field changes of opposing PSJ are analyzed by comparin...Experimental and numerical studies are carried out to validate the potential of opposing Plasma Synthetic Jet(PSJ)for drag reduction for a hemisphere.Firstly,flow field changes of opposing PSJ are analyzed by comparing the experimental schlieren images and simulation results in a supersonic free stream of Mach number 3.As PSJ is a kind of unsteady pulsed jet,the shock standoff distance increases initially and then decreases under the control of PSJ,which corresponds to the change of the strength of PSJ.Accordingly,the amount of drag reduction of the hemisphere increases initially and then decreases.It is found that there is a short period of“drag rise”during the formation of PSJ before the drag reduction,which is induced by the generation of normal shock waves and the area difference of the cavity wall of PSJ Actuator(PSJA).Secondly,the effects of five parameters,including exit diameter,discharge energy of PSJA,Mach number,static pressure of incoming flow and angle of attack,on drag reduction of opposing PSJ were studied in detail by using numerical method.It is found that the Maximum Pressure Ratio(MPR)has a significant impact on the average drag reduction for a configuration-determined PSJA.For the configuration selected in this study,the flow field of opposing PSJ shows typical Short Penetration Mode(SPM)in a control cycle of PSJ when the MPR is less than 0.89.However,the flow field shows typical Long Penetration Mode(LPM)at some time when the MPR is bigger than 0.89.Relatively better drag reduction is achieved in this case.展开更多
In this paper, a Non-Ablative Thermal Protection System(NATPS) with the spiked body and the opposing jet combined configuration is proposed to reduce the aerodynamic heating of the hypersonic vehicle, and the coupled ...In this paper, a Non-Ablative Thermal Protection System(NATPS) with the spiked body and the opposing jet combined configuration is proposed to reduce the aerodynamic heating of the hypersonic vehicle, and the coupled fluid-thermal numerical analysis is performed to study the thermal control performance of the NATPS. The results show that the spiked body pushes the bow shock away from the protected structure and thus reduces the shock intensity and the wall heat flux. In addition, the low temperature gas of the opposing jet separates the high temperature gas behind the shock from the nose cone of the spiked body, ensuring the non-ablative property of the spiked body. Therefore, the NATPS reduces the aerodynamic heating by the reconfiguration of the flow field, and the thermal control efficiency of the system is better than the Thermal Protection System(TPS) with the single spiked body and the single opposing jet. The influencing factors of the NATPS are analyzed. Both increasing the length of the spiked body and reducing the total temperature of the opposing jet can improve the thermal control performance of the NATPS and the nonablative property of the spiked body. However, increasing the heat conductivity coefficient of the spiked body can enhance benefit the non-ablative property of the spiked body, but has little influence on the thermal control performance of the NATPS.展开更多
Opposed multi-burner(OMB)gasification technology is the first large-scale gasification technology developed in China with completely independent intellectual property rights.It has been widely used around the world,in...Opposed multi-burner(OMB)gasification technology is the first large-scale gasification technology developed in China with completely independent intellectual property rights.It has been widely used around the world,involving synthetic ammonia,methanol,ethylene glycol,coal liquefaction,hydrogen production and other fields.This paper summarizes the research and development process of OMB gasification technology from the perspective of the cold model experiment and process simulation,pilotscale study and industrial demonstration.The latest progress of fundamental research in nozzle atomization and dispersion,mixing enhancement of impinging flow,multiscale reaction of different carbonaceous feedstocks,spectral characteristic of impinging flame and particle characteristics inside gasifier,and comprehensive gasification model are reviewed.The latest industrial application progress of ultralarge-scale OMB gasifier and radiant syngas cooler(RSC)combined with quenching chamber OMB gasifier are introduced,and the prospects for the future technical development are proposed as well.展开更多
The three-dimensional Navier Stokes equation and the k-ε viscous model are used to simulate the attack angle characteristics of a hemisphere nose-tip with an opposing jet thermal protection system in supersonic flow ...The three-dimensional Navier Stokes equation and the k-ε viscous model are used to simulate the attack angle characteristics of a hemisphere nose-tip with an opposing jet thermal protection system in supersonic flow conditions. The numerical method is validated by the relevant experiment. The flow field parameters, aerodynamic forces, and surface heat flux distributions for attack angles of 0°, 2°, 5°, 7°, and 10° are obtained. The detailed numerical results show that the cruise attack angle has a great influence on the flow field parameters, aerodynamic force, and surface heat flux distribution of the supersonic vehicle nose-tip with an opposing jet thermal protection system. When the attack angle reaches 10°, the heat flux on the windward generatrix is close to the maximal heat flux on the wall surface of the nose-tip without thermal protection system, thus the thermal protection has failed.展开更多
This pilot study is to assess the feasibility and the effect of a combination therapy of rehabilitation treatment and contralateral needling,which is manipulated at the foot of the unaffected side,for the recovery of ...This pilot study is to assess the feasibility and the effect of a combination therapy of rehabilitation treatment and contralateral needling,which is manipulated at the foot of the unaffected side,for the recovery of the paretic hand post-stroke.This prospective pilot clinical trial will recruit 72 stroke patients with paretic hands and a disease course of 14 to 90 d.Patients will be randomized into two groups:the control group will receive conventional Xingnao Kaiqiao acupuncture and basic treatment for the stroke;based on the control group,the observation group will receive the contralateral needling at the foot of the unaffected side combined with the rehabilitation movement of the paretic hand.12 sessions will be administrated for 2 weeks.The primary outcome,FuglMeyer Assessment,and the secondary outcomes,the handgrip strength,the range of motion,the modified Barthel index,and the Brunnstrom recovery stages,will be measured the recovery of the hand motor function during the 2 weeks'intervention.This study aims to investigate the instant effect of contralateral needling at the foot of the unaffected side combined with the rehabilitation treatment movement for patients with the paretic hand of Poststroke motor dysfunction and provide the previous evidence for the future large sample studies.展开更多
The wavelet approach is introduced to study the influence of the natural convection stagnation point flow of the Williamson fluid in the presence of thermophysical and Brownian motion effects. The thermal radiation ef...The wavelet approach is introduced to study the influence of the natural convection stagnation point flow of the Williamson fluid in the presence of thermophysical and Brownian motion effects. The thermal radiation effects are considered along a permeable stretching surface. The nonlinear problem is simulated numerically by using a novel algorithm based upon the Chebyshev wavelets. It is noticed that the velocity of the Williamson fluid increases for assisting flow cases while decreases for opposing flow cases when the unsteadiness and suction parameters increase, and the magnetic effect on the velocity increases for opposing flow cases while decreases for assisting flow cases. When the thermal radiation parameter, the Dufour number, and Williamson’s fluid parameter increase, the temperature increases for both assisting and opposing flow cases. Meanwhile, the temperature decreases when the Prandtl number increases. The concentration decreases when the Soret parameter increases, while increases when the Schmidt number increases. It is perceived that the assisting force decreases more than the opposing force. The findings endorse the credibility of the proposed algorithm, and could be extended to other nonlinear problems with complex nature.展开更多
Flying condition with angle of attack is inevitable in a hypersonic vehicle,and it may influence the thermal protection system(TPS)performance of opposing jet and its combinations.A 3D Navier–Stokes equation and shea...Flying condition with angle of attack is inevitable in a hypersonic vehicle,and it may influence the thermal protection system(TPS)performance of opposing jet and its combinations.A 3D Navier–Stokes equation and shear stress transfer(SST)k-ωmodel with compressible correction are employed to simulate the angle of attack characteristics of a blunt body with opposing jet and platelet transpiration TPS.The flowfield and heat flux transfer for angles of attack 0°,3°,6°with jet pressure ratio PR=0.1 and 0°,6°,12°with PR=0.2 are obtained.Numerical results show that the flowfield is no longer symmetrical with the effect of the angle of attack.The flowfield and heat transfer in windward and leeward performed adversely.The recompression shock wave in windward is strengthened,which increases local temperature and strengthens heat transfer.The opposing jet fails in thermal protection when the angle of attack reaches critical value;however,the critical angle of attack can be promoted by increasing PR.Finally,the transpiration gas can strengthen the cooling efficiency of windward,thereby,increasing the critical angle of attack.展开更多
Metal additives play an essential role in explosive and propellant formulations. Boron(B) is widely used in propellant applications owing to its high energetic content. The addition of B to explosives and propellants ...Metal additives play an essential role in explosive and propellant formulations. Boron(B) is widely used in propellant applications owing to its high energetic content. The addition of B to explosives and propellants increases their energy density, making them more efficient and powerful. Nevertheless, B forms oxide layers on its surface during combustion, slowing down the combustion rate and reducing rocket motor efficiency. To overcome this issue, other metal additives such as aluminum(Al), magnesium(Mg),and titanium(Ti) are revealed to be effective in boosting the combustion rate of propellants. These additives may improve the combustion rate and therefore enhance the rocket motor’s performance. The present study focused on preparing and investigating the ignition and combustion behavior of pure hydroxyl-terminated polybutadiene(HTPB)-B fuel supplemented with nano-titanium and nanomagnesium. The burn rates of HTPB-B fuel samples were evaluated on the opposed flow burner(OFB)under a gaseous oxygen oxidizer, for which the mass flux ranges from 22 kg/(m^(2)·s) to 86 kg/(m^(2)·s). The addition of Ti and Mg exhibited higher regression rates, which were attributed to the improved oxidation reaction of B due to the synergetic metal combustion effect. The possible combustion/oxidation reaction mechanism of B-Mg and B-Ti by heating the fuel samples at 900℃ and 1100℃ was also examined in a Nabertherm burnout furnace under an oxygen atmosphere. The post-combustion products were collected and further subjected to X-ray diffraction(XRD) and field emission scanning electron microscopy(FE-SEM) analyses to inspect the combustion behavior of B-Ti and B-Mg. It has been observed that the B oxide layer at the interface between B-Ti(B-Mg) is removed at lower temperatures, hence facilitating oxygen transfer from the surroundings to the core B. Additionally, Ti and Mg decreased the ignition delay time of B, which improved its combustion performance.展开更多
To examine the correlation between the sizes of sea breeze fronts and pollutants under the influence of synoptic fields, a numerical simulation was conducted in the southeast coastal area of the Korean Peninsula, wher...To examine the correlation between the sizes of sea breeze fronts and pollutants under the influence of synoptic fields, a numerical simulation was conducted in the southeast coastal area of the Korean Peninsula, where relatively high concentrations of pollutants occur because of the presence of various kinds of industrial developments. Sea breeze and sea breeze front days during the period 2005 09 were identified using wind profiler data and, according to the results, the number of days were 72 and 53, respectively. When synoptic forcing was weak, sea breeze fronts moved fast both in horizontal fields and in terms of wind velocity, while in the case of strong synoptic forcing, sea breeze fronts remained at the coast or moved slowly due to strong opposing flows. In this case, the sea breeze front development function and horizontal potential temperature difference were larger than with weak synoptic forcing. The ozone concentration that moves together with sea breeze fronts was also formed along the frontal surfaces. Ozone advection and diffusion in the case of strong synoptic forcing was suppressed at the frontal surface and the concentration gradient was large. The vertical distribution of ozone was very low due to the Thermal Internal Boundary Layer （TIBL） being low.展开更多
The relationship between the opposing left-turn conflict and the traffic participants was analyzed in this study. Based on the traffic conflict technology, the image data were collected in a real traffic situation. Th...The relationship between the opposing left-turn conflict and the traffic participants was analyzed in this study. Based on the traffic conflict technology, the image data were collected in a real traffic situation. The relationship was investigated under two different conditions. The number of opposing left-turn conflicts was positively correlated with the number of left-turn vehicles while the ratio of left-turn vehicles to opposing vehicles was less than 1, and showed a positive correlation with the number of opposing-through vehicles when the ratio of left-turn vehicles to opposing vehi- cles was more than 1. In other words, the opposing left-turn risk was positively correlated with the number of the minor traffic participants, which had a negative effect on the whole traffic system op- eration.展开更多
In order to meet the requirements of the machining process of cone screw of the Opposed Conical High Pressure Seawater Hydraulic Pump,this work describes the design process to determine the theoretical profile of the ...In order to meet the requirements of the machining process of cone screw of the Opposed Conical High Pressure Seawater Hydraulic Pump,this work describes the design process to determine the theoretical profile of the tool,starting from the surface equation of the cone screw. Along with the expression of the theoretical tool profile,the equation of the contact line between the cone screw and the tool is established based on the coordinate transformation theory and the space meshing theory,as well as the surface equation and the position relationship between the screw and the tool during processing. By solving the contact condition based on the method of numerical discretization analysis via MATLAB,the contact line trajectory and theoretical tool profile curve are derived.The feasibility of the proposed method is verified by an example of tool profile design for machining the screw.展开更多
A set of laboratory experiments are carried out to investigate the effect of following/opposing currents on wave attenuation.Rigid vegetation canopies with aligned and staggered configurations were tested under the co...A set of laboratory experiments are carried out to investigate the effect of following/opposing currents on wave attenuation.Rigid vegetation canopies with aligned and staggered configurations were tested under the condition of various regular wave heights and current velocities,with the constant water depth being 0.60 m to create the desired submerged scenarios.Results show that the vegetation-induced wave dissipation is enhanced with the increasing incident wave height.A larger velocity magnititude leads to a greater wave height attenuation for both following and opposing current conditions.Moreover,there is a strong positive linear correlation between the damping coefficientβand the relative wave height H_(0)/h,especially for pure wave conditions.For the velocity profile,the distributions of U_(min)and U_(max)show different patterns under combined wave and current.The time-averaged turbulent kinetic energy(TKE)vary little under pure wave and U_(c)=±0.05 m/s conditions.With the increase of flow velocity amplitude,the time-averaged TKE shows a particularly pronounced increase trend at the top of the canopy.The vegetation drag coefficients are obtained by a calibration approach.The empirical relations of drag coefficient with Reynolds and Keulegane-Carpenter numbers are proposed to further understand the wave-current-vegetation interaction mechanism.展开更多
文摘Chinese Foreign Ministry responded to the pressure from U.S.on yuan valuation issue,proclaiming that China is not deliberately seeking for Sino-US trade surplus and will firmly oppose any
文摘China opposes Viet Nam’s exploring oil and gas in China’s jurisdictional area ofthe South China Sea,Foreign Ministry spokeswoman Jiang Yu said on May 28."China’s stance on the South China Sea is clear and consistent.
基金Supported by Traditional Chinese Medicine Bureau of Guangdong Province,project number:20141240
文摘Objective To observe the clinical efficacy of opposing needling for the treatment of migraine with the symptom of hyperactivity of liver yang type and its effect on NO level in plasma of patients. Methods Atotal of 60 migraine patients with the symptom of hyperactivity of liver yang who met the inclusive criteria were randomly divided into a opposing needling group （group A） and a routine acupuncture group （group B） by using SPSS 15.0 software according to the registration order with 30 patients in each group. Patients in group A were treated with opposing needling. Taich6ng （太冲 LR 3）, Zhongzhu （中渚 TE 3）, ZOlfnqi （足临泣 GB 41） and QiOxu （丘墟 GB 40） in the uninjured side were selected. After deqi, reducing method was used. Then Taixi （太溪 KI 3） in the uninjured side was selected. After deqi, rein forcing method was used. Needles were retained for 30 rain. Patients in group B were treated with routine acupuncture. Local Ash point, Sishncong （ 四神聪EX-HN1）, Yifeng （翳风 TE 17）, Fengchi （风池 GB 20）, Sizhukong （丝竹空 TE 23）, Shuaigu （率谷GB 8）, Hegu （合谷 LI 4） and LiEque （列缺 LU 7） were selected. After puncturing, reducing method was used routinely and needles were retained for 30 rain. After 2 weeks treatment, migraine specific quality of life questionnaire （MSQ）, visual analogue scale （VAS） and nitric oxide （NO） level in plasma of patients in two groups were observed. Results After treatment, the MSQ, VAS and NO of two groups were significantly improved compared with those before treatment. After treatment, score of MSQ functional limitation was 73.41±10.22 in group A and 60.95 ± 10.15 in group B; the score of MSQ dysfunction was 86.11 ±8.22 in group A and 75.45±8.34 in group B; score of MSQ emotion was 80.51±10.16 in group A and 75.01± 10.20 in group B. The improvements of group A were superior to those of group B, and the differences were all statistically significant （all P〈0.05）. After treatment, the VAS score was 0.93 ± 1.25 in group A and 2.17± 1.70 in group B. The improvement of group A was superior to that of group B, and the difference was statistically significant （P〈0.05）. After treatment, blood plasma NO level was （42.15 ± 16.15） μmol/L in group A and （62.76±15.17） μmol/L in group B. The improvement of group A was superior to that of group B, and the difference was statistically significant （P〈0.05）. Overall response rate was 86.7% （26/30） in group A and 53.3% （16/30） in group B, and the difference between two groups was statistically significant （P〈0.05）. Conclusion Opposing needling is an effective method for the treatment of migraine with the symptom of hyperactivity of liver yong. Its mechanism is to regulate the generation of NO in migraine patients, and improve the relaxation and contraction of cerebral vascular smooth muscle, so as to adjust the cerebral circulation.
基金support from the National Natural Science Foundation of China (Nos.11502291 & 11802340)
文摘Along with the survey on experimental investigations drawing attention to the drag and heat reduction mechanism, the authors simultaneously focus on the recent advances of numerical simulations on the schemes applied to supersonic/hypersonic vehicles. The CFD study has evolved as an irreplaceable method in scheme evaluation and aircraft optimization. Similar to our previous experimental survey, the advances in drag and heat reduction schemes are reviewed by similar kinds of mechanism in this article, namely the forward-facing cavity, the opposing jet, the aerospike, the energy deposition and their combinational configurations. This review article puts an emphatic eye on the flow conditions, numerical methods, novel schemes and analytical conclusions given in the simulations. Further, the multi-objective design optimization concept has also been illustrated due to the observable advantages of using CFD over experimental method, especially those performances conducted in drag reduction and thermal protection practice, and this would possess reference value in the design of aircraft system.
基金co-supported by National Natural Science Foundation of China (No. 90916018)Research Fund for the Doctoral Program of Higher Education of China (No.200899980006)
文摘This paper focuses on the usage of the forward-facing cavity and opposing jet combinatorial configuration as the thermal protection system （TPS） for hypersonic vehicles. A hemispherecone nose-tip with the combinatorial configuration is investigated numerically in hypersonic free stream. Some numerical results are validated by experiments. The flow field parameters, aerodynamic force and surface heat flux distribution are obtained. The influence of the opposing jet stagnation pressure on cooling efficiency of the combinatorial TPS is discussed. The detailed numerical results show that the aerodynamic heating is reduced remarkably by the combinatorial system. The recirculation region plays a pivotal role for the reduction of heat flux. The larger the stagnation pressure of opposing jet is, the more the heating reduction is. This kind of combinatorial system is suitable to be the TPS for the high-speed vehicles which need long-range and long time flight.
文摘Implementation of an opposing jet in design of a hypersonic blunt body significantly modifies the external flowfield and yields a considerable reduction in the aerodynamic drag.This study aims to investigate the effects of flowfield modeling parameters of injection and freestream on the flow structure and aerodynamics of a blunt body with an opposing jet in hypersonic flow.Reynolds-Averaged Navier-Stokes(RANS)equations with a Shear Stress Transport(SST)turbulence model are employed to simulate the intricate jet flow interaction.Through utilizing a Non-Intrusive Polynomial Chaos(NIPC)method to construct surrogates,a functional relation is established between input modeling parameters and output flowfield and aerodynamic quantities in concern.Sobol indices in sensitivity analysis are introduced to represent the relative contribution of each parameter.It is found that variations in modeling parameters produce large variations in the flow structure and aerodynamics.The jet-to-freestream total-pressure ratio,jet Mach number,and freestream Mach number are the major contributors to variation in surface pressure,demonstrating an evident location-dependent behavior.The penetration length of injection,reattachment angle of the shear layer,and aerodynamic drag are also most sensitive to the three crucial parameters above.In comparison,the contributions of freestream temperature,freestream density,and jet total temperature are nearly negligible.
基金co-supported by the National Natural Science Foundation of China(Nos.52075538,12002377,11872374)the Natural Science Foundation of Hunan Province,China(Nos.2020JJ5670,2020JJ2031)+1 种基金the research program of National University of Defense Technology(No.ZK18-03-11)China Postdoctoral Science Foundation(No.2019M652754)。
文摘Experimental and numerical studies are carried out to validate the potential of opposing Plasma Synthetic Jet(PSJ)for drag reduction for a hemisphere.Firstly,flow field changes of opposing PSJ are analyzed by comparing the experimental schlieren images and simulation results in a supersonic free stream of Mach number 3.As PSJ is a kind of unsteady pulsed jet,the shock standoff distance increases initially and then decreases under the control of PSJ,which corresponds to the change of the strength of PSJ.Accordingly,the amount of drag reduction of the hemisphere increases initially and then decreases.It is found that there is a short period of“drag rise”during the formation of PSJ before the drag reduction,which is induced by the generation of normal shock waves and the area difference of the cavity wall of PSJ Actuator(PSJA).Secondly,the effects of five parameters,including exit diameter,discharge energy of PSJA,Mach number,static pressure of incoming flow and angle of attack,on drag reduction of opposing PSJ were studied in detail by using numerical method.It is found that the Maximum Pressure Ratio(MPR)has a significant impact on the average drag reduction for a configuration-determined PSJA.For the configuration selected in this study,the flow field of opposing PSJ shows typical Short Penetration Mode(SPM)in a control cycle of PSJ when the MPR is less than 0.89.However,the flow field shows typical Long Penetration Mode(LPM)at some time when the MPR is bigger than 0.89.Relatively better drag reduction is achieved in this case.
基金supported by the Priority Academic Program Development of Jiangsu Higher Education Institutions
文摘In this paper, a Non-Ablative Thermal Protection System(NATPS) with the spiked body and the opposing jet combined configuration is proposed to reduce the aerodynamic heating of the hypersonic vehicle, and the coupled fluid-thermal numerical analysis is performed to study the thermal control performance of the NATPS. The results show that the spiked body pushes the bow shock away from the protected structure and thus reduces the shock intensity and the wall heat flux. In addition, the low temperature gas of the opposing jet separates the high temperature gas behind the shock from the nose cone of the spiked body, ensuring the non-ablative property of the spiked body. Therefore, the NATPS reduces the aerodynamic heating by the reconfiguration of the flow field, and the thermal control efficiency of the system is better than the Thermal Protection System(TPS) with the single spiked body and the single opposing jet. The influencing factors of the NATPS are analyzed. Both increasing the length of the spiked body and reducing the total temperature of the opposing jet can improve the thermal control performance of the NATPS and the nonablative property of the spiked body. However, increasing the heat conductivity coefficient of the spiked body can enhance benefit the non-ablative property of the spiked body, but has little influence on the thermal control performance of the NATPS.
基金supported by the National Natural Science Foundation of China(21776086,21761132034)。
文摘Opposed multi-burner(OMB)gasification technology is the first large-scale gasification technology developed in China with completely independent intellectual property rights.It has been widely used around the world,involving synthetic ammonia,methanol,ethylene glycol,coal liquefaction,hydrogen production and other fields.This paper summarizes the research and development process of OMB gasification technology from the perspective of the cold model experiment and process simulation,pilotscale study and industrial demonstration.The latest progress of fundamental research in nozzle atomization and dispersion,mixing enhancement of impinging flow,multiscale reaction of different carbonaceous feedstocks,spectral characteristic of impinging flame and particle characteristics inside gasifier,and comprehensive gasification model are reviewed.The latest industrial application progress of ultralarge-scale OMB gasifier and radiant syngas cooler(RSC)combined with quenching chamber OMB gasifier are introduced,and the prospects for the future technical development are proposed as well.
基金Project supported by the National Natural Science Foundation of China (Grant No. 90916018)the Research Fund for the Doctoral Program of Higher Education of China (Grant No. 200899980006)the Natural Science Foundation of Hunan Province,China(Grant No. 09JJ3109)
文摘The three-dimensional Navier Stokes equation and the k-ε viscous model are used to simulate the attack angle characteristics of a hemisphere nose-tip with an opposing jet thermal protection system in supersonic flow conditions. The numerical method is validated by the relevant experiment. The flow field parameters, aerodynamic forces, and surface heat flux distributions for attack angles of 0°, 2°, 5°, 7°, and 10° are obtained. The detailed numerical results show that the cruise attack angle has a great influence on the flow field parameters, aerodynamic force, and surface heat flux distribution of the supersonic vehicle nose-tip with an opposing jet thermal protection system. When the attack angle reaches 10°, the heat flux on the windward generatrix is close to the maximal heat flux on the wall surface of the nose-tip without thermal protection system, thus the thermal protection has failed.
基金the Exploration and Innovation Project from the First Teaching Hospital of Tianjin University of TCM(201921)。
文摘This pilot study is to assess the feasibility and the effect of a combination therapy of rehabilitation treatment and contralateral needling,which is manipulated at the foot of the unaffected side,for the recovery of the paretic hand post-stroke.This prospective pilot clinical trial will recruit 72 stroke patients with paretic hands and a disease course of 14 to 90 d.Patients will be randomized into two groups:the control group will receive conventional Xingnao Kaiqiao acupuncture and basic treatment for the stroke;based on the control group,the observation group will receive the contralateral needling at the foot of the unaffected side combined with the rehabilitation movement of the paretic hand.12 sessions will be administrated for 2 weeks.The primary outcome,FuglMeyer Assessment,and the secondary outcomes,the handgrip strength,the range of motion,the modified Barthel index,and the Brunnstrom recovery stages,will be measured the recovery of the hand motor function during the 2 weeks'intervention.This study aims to investigate the instant effect of contralateral needling at the foot of the unaffected side combined with the rehabilitation treatment movement for patients with the paretic hand of Poststroke motor dysfunction and provide the previous evidence for the future large sample studies.
基金Project supported by the National Natural Science Foundation of China(Nos.51709191,51706149,and 51606130)the Key Laboratory of Advanced Reactor Engineering and Safety,Ministry of Education of China(No.ARES-2018-10)the State Key Laboratory of Hydraulics and Mountain River Engineering of Sichuan University of China(No.Skhl1803)
文摘The wavelet approach is introduced to study the influence of the natural convection stagnation point flow of the Williamson fluid in the presence of thermophysical and Brownian motion effects. The thermal radiation effects are considered along a permeable stretching surface. The nonlinear problem is simulated numerically by using a novel algorithm based upon the Chebyshev wavelets. It is noticed that the velocity of the Williamson fluid increases for assisting flow cases while decreases for opposing flow cases when the unsteadiness and suction parameters increase, and the magnetic effect on the velocity increases for opposing flow cases while decreases for assisting flow cases. When the thermal radiation parameter, the Dufour number, and Williamson’s fluid parameter increase, the temperature increases for both assisting and opposing flow cases. Meanwhile, the temperature decreases when the Prandtl number increases. The concentration decreases when the Soret parameter increases, while increases when the Schmidt number increases. It is perceived that the assisting force decreases more than the opposing force. The findings endorse the credibility of the proposed algorithm, and could be extended to other nonlinear problems with complex nature.
文摘Flying condition with angle of attack is inevitable in a hypersonic vehicle,and it may influence the thermal protection system(TPS)performance of opposing jet and its combinations.A 3D Navier–Stokes equation and shear stress transfer(SST)k-ωmodel with compressible correction are employed to simulate the angle of attack characteristics of a blunt body with opposing jet and platelet transpiration TPS.The flowfield and heat flux transfer for angles of attack 0°,3°,6°with jet pressure ratio PR=0.1 and 0°,6°,12°with PR=0.2 are obtained.Numerical results show that the flowfield is no longer symmetrical with the effect of the angle of attack.The flowfield and heat transfer in windward and leeward performed adversely.The recompression shock wave in windward is strengthened,which increases local temperature and strengthens heat transfer.The opposing jet fails in thermal protection when the angle of attack reaches critical value;however,the critical angle of attack can be promoted by increasing PR.Finally,the transpiration gas can strengthen the cooling efficiency of windward,thereby,increasing the critical angle of attack.
基金the Hindustan Institute of Technology and Science for their support.
文摘Metal additives play an essential role in explosive and propellant formulations. Boron(B) is widely used in propellant applications owing to its high energetic content. The addition of B to explosives and propellants increases their energy density, making them more efficient and powerful. Nevertheless, B forms oxide layers on its surface during combustion, slowing down the combustion rate and reducing rocket motor efficiency. To overcome this issue, other metal additives such as aluminum(Al), magnesium(Mg),and titanium(Ti) are revealed to be effective in boosting the combustion rate of propellants. These additives may improve the combustion rate and therefore enhance the rocket motor’s performance. The present study focused on preparing and investigating the ignition and combustion behavior of pure hydroxyl-terminated polybutadiene(HTPB)-B fuel supplemented with nano-titanium and nanomagnesium. The burn rates of HTPB-B fuel samples were evaluated on the opposed flow burner(OFB)under a gaseous oxygen oxidizer, for which the mass flux ranges from 22 kg/(m^(2)·s) to 86 kg/(m^(2)·s). The addition of Ti and Mg exhibited higher regression rates, which were attributed to the improved oxidation reaction of B due to the synergetic metal combustion effect. The possible combustion/oxidation reaction mechanism of B-Mg and B-Ti by heating the fuel samples at 900℃ and 1100℃ was also examined in a Nabertherm burnout furnace under an oxygen atmosphere. The post-combustion products were collected and further subjected to X-ray diffraction(XRD) and field emission scanning electron microscopy(FE-SEM) analyses to inspect the combustion behavior of B-Ti and B-Mg. It has been observed that the B oxide layer at the interface between B-Ti(B-Mg) is removed at lower temperatures, hence facilitating oxygen transfer from the surroundings to the core B. Additionally, Ti and Mg decreased the ignition delay time of B, which improved its combustion performance.
基金supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF)funded by the Ministry of Education, Science and Technology (Grant No. 2012-0007035)
文摘To examine the correlation between the sizes of sea breeze fronts and pollutants under the influence of synoptic fields, a numerical simulation was conducted in the southeast coastal area of the Korean Peninsula, where relatively high concentrations of pollutants occur because of the presence of various kinds of industrial developments. Sea breeze and sea breeze front days during the period 2005 09 were identified using wind profiler data and, according to the results, the number of days were 72 and 53, respectively. When synoptic forcing was weak, sea breeze fronts moved fast both in horizontal fields and in terms of wind velocity, while in the case of strong synoptic forcing, sea breeze fronts remained at the coast or moved slowly due to strong opposing flows. In this case, the sea breeze front development function and horizontal potential temperature difference were larger than with weak synoptic forcing. The ozone concentration that moves together with sea breeze fronts was also formed along the frontal surfaces. Ozone advection and diffusion in the case of strong synoptic forcing was suppressed at the frontal surface and the concentration gradient was large. The vertical distribution of ozone was very low due to the Thermal Internal Boundary Layer （TIBL） being low.
基金Supported by the Programme of Introducing Talents of Discipline to Universities (B12022)
文摘The relationship between the opposing left-turn conflict and the traffic participants was analyzed in this study. Based on the traffic conflict technology, the image data were collected in a real traffic situation. The relationship was investigated under two different conditions. The number of opposing left-turn conflicts was positively correlated with the number of left-turn vehicles while the ratio of left-turn vehicles to opposing vehicles was less than 1, and showed a positive correlation with the number of opposing-through vehicles when the ratio of left-turn vehicles to opposing vehi- cles was more than 1. In other words, the opposing left-turn risk was positively correlated with the number of the minor traffic participants, which had a negative effect on the whole traffic system op- eration.
基金National Natural Science Foundation of China(No.51075008)
文摘In order to meet the requirements of the machining process of cone screw of the Opposed Conical High Pressure Seawater Hydraulic Pump,this work describes the design process to determine the theoretical profile of the tool,starting from the surface equation of the cone screw. Along with the expression of the theoretical tool profile,the equation of the contact line between the cone screw and the tool is established based on the coordinate transformation theory and the space meshing theory,as well as the surface equation and the position relationship between the screw and the tool during processing. By solving the contact condition based on the method of numerical discretization analysis via MATLAB,the contact line trajectory and theoretical tool profile curve are derived.The feasibility of the proposed method is verified by an example of tool profile design for machining the screw.
基金financially supported by the National Key Research and Development Program of China(2023YFC3208501)the National Natural Science Foundation of China(Grant Nos.U2340225,51979172)+2 种基金the Nanjing Hydraulic Research Institute Special Fund for Basic Scientific Research of Central Public Research Institutes(Y223002,Y220013)the CRSRI Open Research Program(Grant No.CKWV20221007/KY)the Post-Three Gorges Sediment Research Project of MWR(ProjectⅢ:Impact and Countermeasures of the Three Gorges Project on the Stability of the Shoal and Channel and Habitat of Yangtze River Estuary)。
文摘A set of laboratory experiments are carried out to investigate the effect of following/opposing currents on wave attenuation.Rigid vegetation canopies with aligned and staggered configurations were tested under the condition of various regular wave heights and current velocities,with the constant water depth being 0.60 m to create the desired submerged scenarios.Results show that the vegetation-induced wave dissipation is enhanced with the increasing incident wave height.A larger velocity magnititude leads to a greater wave height attenuation for both following and opposing current conditions.Moreover,there is a strong positive linear correlation between the damping coefficientβand the relative wave height H_(0)/h,especially for pure wave conditions.For the velocity profile,the distributions of U_(min)and U_(max)show different patterns under combined wave and current.The time-averaged turbulent kinetic energy(TKE)vary little under pure wave and U_(c)=±0.05 m/s conditions.With the increase of flow velocity amplitude,the time-averaged TKE shows a particularly pronounced increase trend at the top of the canopy.The vegetation drag coefficients are obtained by a calibration approach.The empirical relations of drag coefficient with Reynolds and Keulegane-Carpenter numbers are proposed to further understand the wave-current-vegetation interaction mechanism.
