This paper reports the current-voltage characteristics of [001]-oriented AlAs/InxGa1-xAs/GaAs resonant tunnelling diodes （RTDs） as a function of uniaxial external stress applied parallel to the [110] and the [1^-10]...This paper reports the current-voltage characteristics of [001]-oriented AlAs/InxGa1-xAs/GaAs resonant tunnelling diodes （RTDs） as a function of uniaxial external stress applied parallel to the [110] and the [1^-10] orientations, and the output characteristics of the GaAs pressure sensor based on the pressure effect on the RTDs. Under [110] stress, the resonance peak voltages of the RTDs shift to more positive voltages. For [1^-10] stress, the peaks shift toward more negative voltages. The resonance peak voltage is linearly dependent on the [110] and [1^-0] stresses and the linear sensitivities are up to 0.69 mV/MPa, -0.69 mV/MPa respectively. For the pressure sensor, the linear sensitivity is up to 0.37 mV/kPa.展开更多
The charge transport behavior of barium fluoride nanocrystals is investigated by in situ impedance measurement up to 35 GPa. It is found that the parameters change discontinuously at about 6.9 GPa, corresponding to th...The charge transport behavior of barium fluoride nanocrystals is investigated by in situ impedance measurement up to 35 GPa. It is found that the parameters change discontinuously at about 6.9 GPa, corresponding to the phase transition of BaF2 nanocrystals under high pressure. The charge carriers in BaF2 nanocrystals include both Fions and electrons. Pressure makes the electronic transport more difficult. The defects at grains dominate the electronic transport process. Pressure could make the charge-discharge processes in the Fm3m phase more difficult.展开更多
The calculations presented in this paper are based on the Sanchez-Lacombe（SL）lattice fluid theory.The interaction energy parameter,g12/k,required in this approach was obtained by fitting the cloud points of polystyr...The calculations presented in this paper are based on the Sanchez-Lacombe（SL）lattice fluid theory.The interaction energy parameter,g12/k,required in this approach was obtained by fitting the cloud points of polystyrene（PS）/methylcyclohexane（MCH）polymer solutions under pressure.The SL lattice fluid theory was used to calculate the spinodals,the binodals,and the Flory-Huggins（FH）interaction parameter of the solutions.The calculated results show that the SL lattice fluid theory can describe the dependences of thermodynamics of PS/MCH solutions on temperature and pressure very well.However,the calculated enthalpy and the excess volume changes indicate that the Clausius-Clapeyron equation cannot be suitable to describe pressure effect on PS/MCH solutions.Further analysis on the thermodynamics of this system under pressure shows that the role of entropy is more important than the excess volume in the present case.展开更多
The evaporation behaviors are crucial for the flame location estimation in liquid rocketengines.This work,for the first time,experimentally reports the sub-millimeter droplet evaporationcharacteristics of the corrosiv...The evaporation behaviors are crucial for the flame location estimation in liquid rocketengines.This work,for the first time,experimentally reports the sub-millimeter droplet evaporationcharacteristics of the corrosive dinitrogen tetroxide(NTO,one prevailing hypergolic oxidizer)athigh ambient pressure up to 4.5 MPa.An in-house corrosion-resistant droplet generator is usedto generate isolated flying droplets of sub-millimeter size,which are then exposed in a gas environ-ment with temperatures between 1010 K and 1210 K and pressures in the range between 2.0 MPaand 4.5 MPa,provided by an optical rapid compression machine.Parallelly,a theoretical modelconsidering both the droplet ambient convection and the NTO dissociation is developed.Resultsindicate that firstly,the present theoretical model that considers the transient droplet-ambient con-vection as well as the temperature and pressure dependent rate of dissociation shows good agree-ment with the experimentally observed droplet lifetime.In addition,the flying droplets velocityregress gradually due to momentum exchange with the ambient,which is more prominent at higherpressure.The evaporation caused droplet size reduction is consistent with the classical D^(2)-law pre-diction,in the present temperature and pressure range.Finally,higher temperature and pressureaccelerate the evaporation and an empirical correlation for the temperature and pressure dependentevaporation rate constant is proposed,which shows good agreement with experiment and simula-tion results.展开更多
Changes in barometric pressure can affect the micro-dynamic state of groundwater level.The groundwater level data carry a lot of important information of tectonic activity and earthquakes.It is very significant to eli...Changes in barometric pressure can affect the micro-dynamic state of groundwater level.The groundwater level data carry a lot of important information of tectonic activity and earthquakes.It is very significant to eliminate the barometric pressure effects from the groundwater level data in order to recognize seismic anomalies effectively.With the analysis of the main influential constituents of barometric pressure and their changes,we can have a better understanding of the changes of the aquifer medium,which can provide useful information for earthquake prediction.Taking the May 12,2008 Wenchuan earthquake as an example,this paper deals with the influence of barometric pressure on groundwater level based on observational data from Nanxi,Qionglai and Chaohu wells.The methods of the linear regression and the deconvolution regression were employed to remove the barometric pressure from the groundwater level data.The harmonic analysis and the spectral analysis were used to recognize the main influential waves of barometric pressure effect.A comparison was conducted on the main influential waves before and after the earthquake.The results showed that the main influential waves of barometric pressure effect changed and the amplitudes of all constituents also changed.This phenomenon may result from the characteristics of the influential constituents of pressure,or from the changes of the aquifer medium,which were caused by the earthquake.展开更多
Various strategies for thermoelectric material optimization have been widely studied and used for promoting electrical transport and suppressing thermal transport.As a nontraditional method,pressure has shown great po...Various strategies for thermoelectric material optimization have been widely studied and used for promoting electrical transport and suppressing thermal transport.As a nontraditional method,pressure has shown great potential,as it has been applied to obtain a high thermoelectric figure of merit,but the microscopic mechanisms involved have yet to be fully explored.In this study,we focus on r-GeTe,a lowtemperature phase of GeTe,and investigate the pressure effects on the electronic structure,electrical transport properties and anharmonic lattice dynamics based on density functional theory(DFT),the Boltzmann transport equations(BTEs)and perturbation theory.Electronic relaxation times are obtained based on the electron-phonon interaction and the constant relaxation time approximation.The corresponding electrical transport properties are compared with those obtained from previous experiments.Hydrostatic pressure is shown to increase valley degeneracy,decrease the band effective mass and enhance the electrical transport property.At the same time,the increase in the low-frequency phonon lifetime and phonon group velocity leads to an increase in lattice thermal conductivity under pressure.This study provides insight into r-GeTe under hydrostatic pressure and paves the way for a high-pressure strategy to optimize transport properties.展开更多
The kinetic effects of pressure, solvent, and substituent on the thermal isomerization from 2 oxospiro[diazirine 3,3 indoline] to 3 diazo 2 oxo indoline have been examined. The rate constants of the thermal is...The kinetic effects of pressure, solvent, and substituent on the thermal isomerization from 2 oxospiro[diazirine 3,3 indoline] to 3 diazo 2 oxo indoline have been examined. The rate constants of the thermal isomerization increased with increasing external pressure and were related to the σ + P substituent constant of Hammett correlation. The results suggest that the thermal isomerization proceeds via a dipolar transition state involving heterolytic bond fission. However, the kinetic solvent effects on the thermal isomerization were not observed. The special solvent effects were discussed on the basis of the linear free energy relationship.展开更多
Effects of pressure and/or magnetism on the critical superconducting temperature（Tc） of δ-Mo N single crystal were investigated using a Maglab system. The δ-Mo N single crystal was synthesized at extreme condition...Effects of pressure and/or magnetism on the critical superconducting temperature（Tc） of δ-Mo N single crystal were investigated using a Maglab system. The δ-Mo N single crystal was synthesized at extreme conditions of high pressure and high temperature. The carrier density of δ-Mo N single crystal as a function of applied pressure was determined using Hall coefficient measurement.展开更多
The heavy fuel compression ignition engines are widely equipped as aircraft piston engines. The fuel injection system is one of the key technologies that determines the performance of engine. One of the main challenge...The heavy fuel compression ignition engines are widely equipped as aircraft piston engines. The fuel injection system is one of the key technologies that determines the performance of engine. One of the main challenges is to precisely control the injected fuel quantity and flow rate in the presence of pressure fluctuation. This challenge is even more serious for heavy fuel. An original design for electrically controlled high pressure fuel injection system called Multi-Pumppressure-reservoirs fuel injection System(MPS) was demonstrated to reduce the pressure fluctuation and help keep injection stable. MPS was compared with an ordinary high pressure Common Rail fuel injection System(CRS). This work established one-dimensional AMESim and mathematical models for both CRS and MPS to study the effect of different structures and geometric parameters on the pressure fluctuations. The calculations show that the average fuel pressure fluctuation of MPS can be reduced by 57% for the crankshaft speed of 1900 r/min, and the pressure fluctuation before injection reduced by 100%. It is concluded that the pressure performance of MPS is less sensitive to pressure reservoir volume than that of CRS, and there is an opportunity for further volume reduction.展开更多
The effect of nitrogen pressure on optical properties of hydrogen-free diamond-like carbon (DLC) films deposited by pulsed laser ablation graphite in different background pressures of nitrogen is reported. By varying ...The effect of nitrogen pressure on optical properties of hydrogen-free diamond-like carbon (DLC) films deposited by pulsed laser ablation graphite in different background pressures of nitrogen is reported. By varying nitrogen pressures from 0.05 to 15.00 Pa, the photoluminescence is gradually increased and optical transmittance is gradually decreased. Atomic force microscopy (AFM) is used to observe the surface morphology of the DLC films. The results indicate that the surface becomes unsmoothed and there a...展开更多
Under high pressure, the long believed single-phase material CaB6 was latterly discovered to have a new phase tI56. Based on the density-functional theory, the pressure effects on the structural and elastic properties...Under high pressure, the long believed single-phase material CaB6 was latterly discovered to have a new phase tI56. Based on the density-functional theory, the pressure effects on the structural and elastic properties of CaB6 are obtained. The calculated bulk, shear, and Young’s moduli of the recently synthesized high pressure phase tI56-CaB6 are larger than those of the low pressure phase. Moreover, the high pressure phase of CaB6 has ductile behaviors, and its ductility increases with the increase of pressure. On the contrary, the calculated results indicate that the low pressure phase of CaB6 is brittle. The calculated Debye temperature indicates that the thermal conductivity of CaB6 is not very good. Furthermore, based on the Christoffel equation, the slowness surface of the acoustic waves is obtained.展开更多
The structural stability and electrical properties of AlB2-type MnB2 were studied based on high pressure angledispersive x-ray diffraction, in situ electrical resistivity measured in a diamond anvil cell(DAC) and firs...The structural stability and electrical properties of AlB2-type MnB2 were studied based on high pressure angledispersive x-ray diffraction, in situ electrical resistivity measured in a diamond anvil cell(DAC) and first-principles calculations under high pressure. The x-ray diffraction results show that the structure of AlB2-type MnB2 remains stable up to 42.6 GPa. From the equation of state of MnB2, we obtained a bulk modulus value of 169.9±3.7 GPa with a fixed pressure derivative of 4, which indicates that AlB2-type MnB2 is a hard and incompressible material. The electrical resistance undergoes a transition at about 19.3 GPa, which can be explained by a transition of manganese 3d electrons from localization to delocalization under high pressure.展开更多
Based on the 3D electron's radial wave function of Co 2+ free ion,a Nephelauxetic effect modifying factor to modify the radial wave function is introduced when Co 2+ cations are put into the crystal fie...Based on the 3D electron's radial wave function of Co 2+ free ion,a Nephelauxetic effect modifying factor to modify the radial wave function is introduced when Co 2+ cations are put into the crystal field of Zn 1-x Co x Se.With the modified wave functions,the optical transitions for Zn 1-x Co x Se crystals are calculated.Moreover,based on the first principle of physics,the influences of high pressure to the Nephelauxetic effect modifying factor is considered,and the high pressure blue shift for the Zn 1-x Co x Se crystal absorption spectra are calculated and a shift rate of d E /d p =0 45meV/GPa is obtained.展开更多
We consider a Ginzburg-Landau modified model of layered high-temperature superconductor under pressure. We have theoretically studied the relation between the pressure and the temperature of layered high-temperature s...We consider a Ginzburg-Landau modified model of layered high-temperature superconductor under pressure. We have theoretically studied the relation between the pressure and the temperature of layered high-temperature superconductor. If the pressure is not a constant, we have a relation of quadratic equation between the pressure and the temperature of layered high-temperature superconductor. In a special case, we find the critical temperature decreases with further increasing pressure. In another special ease, the critical temperature increases with further increasing pressure.展开更多
Atmospheric pressure fluctuations can result in long-period noise(T>10 s)in gravity observations,and it is crucial to remove the atmospheric pressure effect for observing weak dynamic signals using superconducting ...Atmospheric pressure fluctuations can result in long-period noise(T>10 s)in gravity observations,and it is crucial to remove the atmospheric pressure effect for observing weak dynamic signals using superconducting gravimeters.This paper focuses on analyzing the impact of the atmospheric pressure on observing the Slichter mode signal.We analyze the effect of local atmospheric pressure fluctuations on gravity observations,yielding a correlation of over 90%between the atmospheric pressure and gravity in the Slichter mode band(0.04—0.09 mHz).To better remove the atmospheric pressure effect on observing the Slichter mode,we use coherence analysis methods and refer to the Slichter mode reference degenerate frequency(0.0502 m Hz)obtained by other researchers to compute the atmospheric admittance in the frequency domain.Taking the MW9.1 Tohoku earthquake that occurred in Japan on March 11,2011,as an example,we analyze the noise level in the Slichter mode band after atmospheric pressure correction using gravity and atmospheric pressure data from superconducting gravimeter(SG)stations with simultaneous sampling at the same location.The results show that the coherence analysis method for calculating frequency domain admittance significantly affects correcting pressure noise,but detecting Slichter mode remains challenging.The noise level in the gravity is still much higher than the Slichter mode signal level.Other noise signals,such as ocean tidal noise and hydrological effect,may also affect observations of the Slichter mode.Future research needs to further analyze the effects of these types of noise.展开更多
Objective The study aim was to investigate the effects of exposure to multiple environmental organic pollutants on cardiopulmonary health with a focus on the potential mediating role of oxidative stress.Methods A repe...Objective The study aim was to investigate the effects of exposure to multiple environmental organic pollutants on cardiopulmonary health with a focus on the potential mediating role of oxidative stress.Methods A repeated-measures randomized crossover study involving healthy college students in Beijing was conducted.Biological samples,including morning urine and venous blood,were collected to measure concentrations of 29 typical organic pollutants,including hydroxy polycyclic aromatic hydrocarbons(OH-PAHs),bisphenol A and its substitutes,phthalates and their metabolites,parabens,and five biomarkers of oxidative stress.Health assessments included blood pressure measurements and lung function indicators.Results Urinary concentrations of 2-hydroxyphenanthrene(2-OH-PHE)(β=4.35%[95%confidence interval(CI):0.85%,7.97%]),3-hydroxyphenanthrene(β=3.44%[95%CI:0.19%,6.79%]),and 4-hydroxyphenanthrene(4-OH-PHE)(β=5.78%[95%CI:1.27%,10.5%])were significantly and positively associated with systolic blood pressure.Exposures to 1-hydroxypyrene(1-OH-PYR)(β=3.05%[95%CI:−4.66%,−1.41%]),2-OH-PHE(β=2.68%[95%CI:−4%,−1.34%]),and 4-OH-PHE(β=3%[95%CI:−4.68%,−1.29%])were negatively associated with the ratio of forced expiratory volume in the first second to forced vital capacity.These findings highlight the adverse effects of exposure to multiple pollutants on cardiopulmonary health.Biomarkers of oxidative stress,including 8-hydroxy-2'-deoxyguanosine and extracellular superoxide dismutase,mediated the effects of multiple OH-PAHs on blood pressure and lung function.展开更多
To study the relative sensitivity of permeability to pore pressure Pp and confining pressure Pc for clay-rich rocks, permeability measurements were performed on samples of four clay-rich sandstones. A new method （her...To study the relative sensitivity of permeability to pore pressure Pp and confining pressure Pc for clay-rich rocks, permeability measurements were performed on samples of four clay-rich sandstones. A new method （hereafter denoted the ＂slide method＂） was developed and used for analyzing the permeability data obtained. The effective pressure coefficients for permeability nk were calculated. The values of nk were found to be greater than 1.0 and insensitive to changes in pressure. These results confirmed observations previously made on clay-rich rocks. Also, the coefficients nk obtained had different characteristics for different samples because of differences in the types of clay they contained. The effective pressure law （σeff=Pc-nkPp） determined using the slide method gave better results about k（oefr） than classic Terzaghi＇s law （σeff=Pc-nkPp）.展开更多
Based on the elastic-plastic, large-deformation finite element method, burst capacity of steel pipeline with longitudinal corrosion defect subjected to internal pressure is studied. The appropriate stress-based criter...Based on the elastic-plastic, large-deformation finite element method, burst capacity of steel pipeline with longitudinal corrosion defect subjected to internal pressure is studied. The appropriate stress-based criterion is used to predict the failure pressure of finite element model of corroded pipeline under internal pressure. By considering the pipe steel grades and geometries of corrosion defects, a series of finite element analyses is conducted. The effects of corrosion depth, length and width on burst capacity are also discussed. A specific failure pressure solution for the assessment of corrosion defects in moderate-to-high strength pipeline is proposed on the base of numerical results. The failure pressures predicted by the proposed method are in better agreement with the experimental results than the results by the other methods.展开更多
The thermal decomposition of 2, 2'-azobis (isobutyronitrile) (AIBN) in supercritical CO2 with cosolvent methanol or cyclohexane has been studied by using UV/Vis spectroscopic method at 335.15 K and at 12.0 MPa and...The thermal decomposition of 2, 2'-azobis (isobutyronitrile) (AIBN) in supercritical CO2 with cosolvent methanol or cyclohexane has been studied by using UV/Vis spectroscopic method at 335.15 K and at 12.0 MPa and 14.0 MPa. Both of the cosolvents can accelerate the decomposition rate, and the effect of methanol is more significant than that of the cyclohexane.展开更多
基金Project supported by the National Natural Science Foundation of China （Grant Nos 50405025 and 50375050）.
文摘This paper reports the current-voltage characteristics of [001]-oriented AlAs/InxGa1-xAs/GaAs resonant tunnelling diodes （RTDs） as a function of uniaxial external stress applied parallel to the [110] and the [1^-10] orientations, and the output characteristics of the GaAs pressure sensor based on the pressure effect on the RTDs. Under [110] stress, the resonance peak voltages of the RTDs shift to more positive voltages. For [1^-10] stress, the peaks shift toward more negative voltages. The resonance peak voltage is linearly dependent on the [110] and [1^-0] stresses and the linear sensitivities are up to 0.69 mV/MPa, -0.69 mV/MPa respectively. For the pressure sensor, the linear sensitivity is up to 0.37 mV/kPa.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11374131,11674404,11404137 and 61378085the Program for New Century Excellent Talents in University under Grant No NCET-13-0824+1 种基金the Program for the Development of Science and Technology of Jilin Province under Grant Nos 201201079 and 20150204085GXthe Twentieth Five-Year Program for Science and Technology of Education Department of Jilin Province under Grant No 20150221
文摘The charge transport behavior of barium fluoride nanocrystals is investigated by in situ impedance measurement up to 35 GPa. It is found that the parameters change discontinuously at about 6.9 GPa, corresponding to the phase transition of BaF2 nanocrystals under high pressure. The charge carriers in BaF2 nanocrystals include both Fions and electrons. Pressure makes the electronic transport more difficult. The defects at grains dominate the electronic transport process. Pressure could make the charge-discharge processes in the Fm3m phase more difficult.
基金Supported by the National Natural Science Foundation of China(Nos.20574069,20490220,50303017,50373044and50340420392)Programs of the Chinese Academy of Sciences(No.KJCX2-SW-H07)the National Basic Research Program ofChina(No.2003CB615600).
文摘The calculations presented in this paper are based on the Sanchez-Lacombe（SL）lattice fluid theory.The interaction energy parameter,g12/k,required in this approach was obtained by fitting the cloud points of polystyrene（PS）/methylcyclohexane（MCH）polymer solutions under pressure.The SL lattice fluid theory was used to calculate the spinodals,the binodals,and the Flory-Huggins（FH）interaction parameter of the solutions.The calculated results show that the SL lattice fluid theory can describe the dependences of thermodynamics of PS/MCH solutions on temperature and pressure very well.However,the calculated enthalpy and the excess volume changes indicate that the Clausius-Clapeyron equation cannot be suitable to describe pressure effect on PS/MCH solutions.Further analysis on the thermodynamics of this system under pressure shows that the role of entropy is more important than the excess volume in the present case.
基金supported by the Natural Science Foundation of China(No.52236001)The support from Research Grants Council of Hong Kong,China(No.CityU 15218820)was also appreciated。
文摘The evaporation behaviors are crucial for the flame location estimation in liquid rocketengines.This work,for the first time,experimentally reports the sub-millimeter droplet evaporationcharacteristics of the corrosive dinitrogen tetroxide(NTO,one prevailing hypergolic oxidizer)athigh ambient pressure up to 4.5 MPa.An in-house corrosion-resistant droplet generator is usedto generate isolated flying droplets of sub-millimeter size,which are then exposed in a gas environ-ment with temperatures between 1010 K and 1210 K and pressures in the range between 2.0 MPaand 4.5 MPa,provided by an optical rapid compression machine.Parallelly,a theoretical modelconsidering both the droplet ambient convection and the NTO dissociation is developed.Resultsindicate that firstly,the present theoretical model that considers the transient droplet-ambient con-vection as well as the temperature and pressure dependent rate of dissociation shows good agree-ment with the experimentally observed droplet lifetime.In addition,the flying droplets velocityregress gradually due to momentum exchange with the ambient,which is more prominent at higherpressure.The evaporation caused droplet size reduction is consistent with the classical D^(2)-law pre-diction,in the present temperature and pressure range.Finally,higher temperature and pressureaccelerate the evaporation and an empirical correlation for the temperature and pressure dependentevaporation rate constant is proposed,which shows good agreement with experiment and simula-tion results.
基金supported by the National Natural Science Foundation of China (Grant No. 40930637)Special Project for Earthquake Science(Grant No. 200808079)Subject Foundation of Ministry of Education for Doctor Candidates in Universities (Grant No. 20100022110001)
文摘Changes in barometric pressure can affect the micro-dynamic state of groundwater level.The groundwater level data carry a lot of important information of tectonic activity and earthquakes.It is very significant to eliminate the barometric pressure effects from the groundwater level data in order to recognize seismic anomalies effectively.With the analysis of the main influential constituents of barometric pressure and their changes,we can have a better understanding of the changes of the aquifer medium,which can provide useful information for earthquake prediction.Taking the May 12,2008 Wenchuan earthquake as an example,this paper deals with the influence of barometric pressure on groundwater level based on observational data from Nanxi,Qionglai and Chaohu wells.The methods of the linear regression and the deconvolution regression were employed to remove the barometric pressure from the groundwater level data.The harmonic analysis and the spectral analysis were used to recognize the main influential waves of barometric pressure effect.A comparison was conducted on the main influential waves before and after the earthquake.The results showed that the main influential waves of barometric pressure effect changed and the amplitudes of all constituents also changed.This phenomenon may result from the characteristics of the influential constituents of pressure,or from the changes of the aquifer medium,which were caused by the earthquake.
基金supported by the Research Grants Council of Hong Kong(17201019)the National Natural Science Foundation of China(11934007,11874194and 11874313)+3 种基金the Guangdong Provincial Key Laboratory of Energy Materials for Electric Power(NO.2018B030322001)the Science and Technology Innovation Committee Foundation of Shenzhen(KQTD2016022619565991)the Zhejiang Provincial Natural Science Foundation(LR19A040001)SL acknowledges the support from the startup fund of Nanjing University of Posts and Telecommunications(NY220096).
文摘Various strategies for thermoelectric material optimization have been widely studied and used for promoting electrical transport and suppressing thermal transport.As a nontraditional method,pressure has shown great potential,as it has been applied to obtain a high thermoelectric figure of merit,but the microscopic mechanisms involved have yet to be fully explored.In this study,we focus on r-GeTe,a lowtemperature phase of GeTe,and investigate the pressure effects on the electronic structure,electrical transport properties and anharmonic lattice dynamics based on density functional theory(DFT),the Boltzmann transport equations(BTEs)and perturbation theory.Electronic relaxation times are obtained based on the electron-phonon interaction and the constant relaxation time approximation.The corresponding electrical transport properties are compared with those obtained from previous experiments.Hydrostatic pressure is shown to increase valley degeneracy,decrease the band effective mass and enhance the electrical transport property.At the same time,the increase in the low-frequency phonon lifetime and phonon group velocity leads to an increase in lattice thermal conductivity under pressure.This study provides insight into r-GeTe under hydrostatic pressure and paves the way for a high-pressure strategy to optimize transport properties.
文摘The kinetic effects of pressure, solvent, and substituent on the thermal isomerization from 2 oxospiro[diazirine 3,3 indoline] to 3 diazo 2 oxo indoline have been examined. The rate constants of the thermal isomerization increased with increasing external pressure and were related to the σ + P substituent constant of Hammett correlation. The results suggest that the thermal isomerization proceeds via a dipolar transition state involving heterolytic bond fission. However, the kinetic solvent effects on the thermal isomerization were not observed. The special solvent effects were discussed on the basis of the linear free energy relationship.
基金Project supported by the Natural Science Foundation of Hebei Province,China(Grant No.A2014501010)the Youth Foundation of the Chinese Academy of Sciences(Grant No.Y4VX047X61)the Chinese Academy of Sciences Project(Grant No.XDB07000000)
文摘Effects of pressure and/or magnetism on the critical superconducting temperature（Tc） of δ-Mo N single crystal were investigated using a Maglab system. The δ-Mo N single crystal was synthesized at extreme conditions of high pressure and high temperature. The carrier density of δ-Mo N single crystal as a function of applied pressure was determined using Hall coefficient measurement.
文摘The heavy fuel compression ignition engines are widely equipped as aircraft piston engines. The fuel injection system is one of the key technologies that determines the performance of engine. One of the main challenges is to precisely control the injected fuel quantity and flow rate in the presence of pressure fluctuation. This challenge is even more serious for heavy fuel. An original design for electrically controlled high pressure fuel injection system called Multi-Pumppressure-reservoirs fuel injection System(MPS) was demonstrated to reduce the pressure fluctuation and help keep injection stable. MPS was compared with an ordinary high pressure Common Rail fuel injection System(CRS). This work established one-dimensional AMESim and mathematical models for both CRS and MPS to study the effect of different structures and geometric parameters on the pressure fluctuations. The calculations show that the average fuel pressure fluctuation of MPS can be reduced by 57% for the crankshaft speed of 1900 r/min, and the pressure fluctuation before injection reduced by 100%. It is concluded that the pressure performance of MPS is less sensitive to pressure reservoir volume than that of CRS, and there is an opportunity for further volume reduction.
基金supported by the Natural Science Foundationof Shandong Province (Grant No. Y2002A09).
文摘The effect of nitrogen pressure on optical properties of hydrogen-free diamond-like carbon (DLC) films deposited by pulsed laser ablation graphite in different background pressures of nitrogen is reported. By varying nitrogen pressures from 0.05 to 15.00 Pa, the photoluminescence is gradually increased and optical transmittance is gradually decreased. Atomic force microscopy (AFM) is used to observe the surface morphology of the DLC films. The results indicate that the surface becomes unsmoothed and there a...
文摘Under high pressure, the long believed single-phase material CaB6 was latterly discovered to have a new phase tI56. Based on the density-functional theory, the pressure effects on the structural and elastic properties of CaB6 are obtained. The calculated bulk, shear, and Young’s moduli of the recently synthesized high pressure phase tI56-CaB6 are larger than those of the low pressure phase. Moreover, the high pressure phase of CaB6 has ductile behaviors, and its ductility increases with the increase of pressure. On the contrary, the calculated results indicate that the low pressure phase of CaB6 is brittle. The calculated Debye temperature indicates that the thermal conductivity of CaB6 is not very good. Furthermore, based on the Christoffel equation, the slowness surface of the acoustic waves is obtained.
基金Project supported by the National Basic Research Program of China （Grant No. 2011CB808200）, the Program for Changjiang Scholars and Innovative Re- search Team in University, China （Grant No. IRT1132）, the National Natural Science Foundation of China （Grant Nos. 51032001, 11074090, 10979001, and 51025206）, and the U.S. Department of Energy, Office of Science, and Office of Basic Energy Sciences （Grant No. DE-AC02-98CH 10886）.
文摘The structural stability and electrical properties of AlB2-type MnB2 were studied based on high pressure angledispersive x-ray diffraction, in situ electrical resistivity measured in a diamond anvil cell(DAC) and first-principles calculations under high pressure. The x-ray diffraction results show that the structure of AlB2-type MnB2 remains stable up to 42.6 GPa. From the equation of state of MnB2, we obtained a bulk modulus value of 169.9±3.7 GPa with a fixed pressure derivative of 4, which indicates that AlB2-type MnB2 is a hard and incompressible material. The electrical resistance undergoes a transition at about 19.3 GPa, which can be explained by a transition of manganese 3d electrons from localization to delocalization under high pressure.
文摘Based on the 3D electron's radial wave function of Co 2+ free ion,a Nephelauxetic effect modifying factor to modify the radial wave function is introduced when Co 2+ cations are put into the crystal field of Zn 1-x Co x Se.With the modified wave functions,the optical transitions for Zn 1-x Co x Se crystals are calculated.Moreover,based on the first principle of physics,the influences of high pressure to the Nephelauxetic effect modifying factor is considered,and the high pressure blue shift for the Zn 1-x Co x Se crystal absorption spectra are calculated and a shift rate of d E /d p =0 45meV/GPa is obtained.
文摘We consider a Ginzburg-Landau modified model of layered high-temperature superconductor under pressure. We have theoretically studied the relation between the pressure and the temperature of layered high-temperature superconductor. If the pressure is not a constant, we have a relation of quadratic equation between the pressure and the temperature of layered high-temperature superconductor. In a special case, we find the critical temperature decreases with further increasing pressure. In another special ease, the critical temperature increases with further increasing pressure.
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB41000000)National Natural Science Foundation of China(Grant Nos:42394113,42174108,41874094,42192535,and 42242015)+1 种基金the Young Top-notch Talent Cultivation Program of Hubei ProvinceThe Project Supported by the Open Fund of Hubei Luojia Laboratory(No.220100033)。
文摘Atmospheric pressure fluctuations can result in long-period noise(T>10 s)in gravity observations,and it is crucial to remove the atmospheric pressure effect for observing weak dynamic signals using superconducting gravimeters.This paper focuses on analyzing the impact of the atmospheric pressure on observing the Slichter mode signal.We analyze the effect of local atmospheric pressure fluctuations on gravity observations,yielding a correlation of over 90%between the atmospheric pressure and gravity in the Slichter mode band(0.04—0.09 mHz).To better remove the atmospheric pressure effect on observing the Slichter mode,we use coherence analysis methods and refer to the Slichter mode reference degenerate frequency(0.0502 m Hz)obtained by other researchers to compute the atmospheric admittance in the frequency domain.Taking the MW9.1 Tohoku earthquake that occurred in Japan on March 11,2011,as an example,we analyze the noise level in the Slichter mode band after atmospheric pressure correction using gravity and atmospheric pressure data from superconducting gravimeter(SG)stations with simultaneous sampling at the same location.The results show that the coherence analysis method for calculating frequency domain admittance significantly affects correcting pressure noise,but detecting Slichter mode remains challenging.The noise level in the gravity is still much higher than the Slichter mode signal level.Other noise signals,such as ocean tidal noise and hydrological effect,may also affect observations of the Slichter mode.Future research needs to further analyze the effects of these types of noise.
基金supported by the National Key Research&Development Program of the Ministry of Science and Technology of China(2022YFE0134900,2023YFC3708305,2023YFC3708302)Strategy Priority Research Program(Category B)of the Chinese Academy of Sciences(No.XDB0750300)National Natural Science Foundation of China(Grant No.42477455,42077390).
文摘Objective The study aim was to investigate the effects of exposure to multiple environmental organic pollutants on cardiopulmonary health with a focus on the potential mediating role of oxidative stress.Methods A repeated-measures randomized crossover study involving healthy college students in Beijing was conducted.Biological samples,including morning urine and venous blood,were collected to measure concentrations of 29 typical organic pollutants,including hydroxy polycyclic aromatic hydrocarbons(OH-PAHs),bisphenol A and its substitutes,phthalates and their metabolites,parabens,and five biomarkers of oxidative stress.Health assessments included blood pressure measurements and lung function indicators.Results Urinary concentrations of 2-hydroxyphenanthrene(2-OH-PHE)(β=4.35%[95%confidence interval(CI):0.85%,7.97%]),3-hydroxyphenanthrene(β=3.44%[95%CI:0.19%,6.79%]),and 4-hydroxyphenanthrene(4-OH-PHE)(β=5.78%[95%CI:1.27%,10.5%])were significantly and positively associated with systolic blood pressure.Exposures to 1-hydroxypyrene(1-OH-PYR)(β=3.05%[95%CI:−4.66%,−1.41%]),2-OH-PHE(β=2.68%[95%CI:−4%,−1.34%]),and 4-OH-PHE(β=3%[95%CI:−4.68%,−1.29%])were negatively associated with the ratio of forced expiratory volume in the first second to forced vital capacity.These findings highlight the adverse effects of exposure to multiple pollutants on cardiopulmonary health.Biomarkers of oxidative stress,including 8-hydroxy-2'-deoxyguanosine and extracellular superoxide dismutase,mediated the effects of multiple OH-PAHs on blood pressure and lung function.
基金supported by a grant from the National Natural Science Foundation of China(Grant No.50774064)the Open Fund PLN0802 of the State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation(Southwest Petroleum University)
文摘To study the relative sensitivity of permeability to pore pressure Pp and confining pressure Pc for clay-rich rocks, permeability measurements were performed on samples of four clay-rich sandstones. A new method （hereafter denoted the ＂slide method＂） was developed and used for analyzing the permeability data obtained. The effective pressure coefficients for permeability nk were calculated. The values of nk were found to be greater than 1.0 and insensitive to changes in pressure. These results confirmed observations previously made on clay-rich rocks. Also, the coefficients nk obtained had different characteristics for different samples because of differences in the types of clay they contained. The effective pressure law （σeff=Pc-nkPp） determined using the slide method gave better results about k（oefr） than classic Terzaghi＇s law （σeff=Pc-nkPp）.
基金financially supported by Ministry of Science and Technology of China(Grant No.2011CB013702)the Program for New Century Excellent Talents in University(Grant No.NCET-11-0051)
文摘Based on the elastic-plastic, large-deformation finite element method, burst capacity of steel pipeline with longitudinal corrosion defect subjected to internal pressure is studied. The appropriate stress-based criterion is used to predict the failure pressure of finite element model of corroded pipeline under internal pressure. By considering the pipe steel grades and geometries of corrosion defects, a series of finite element analyses is conducted. The effects of corrosion depth, length and width on burst capacity are also discussed. A specific failure pressure solution for the assessment of corrosion defects in moderate-to-high strength pipeline is proposed on the base of numerical results. The failure pressures predicted by the proposed method are in better agreement with the experimental results than the results by the other methods.
文摘The thermal decomposition of 2, 2'-azobis (isobutyronitrile) (AIBN) in supercritical CO2 with cosolvent methanol or cyclohexane has been studied by using UV/Vis spectroscopic method at 335.15 K and at 12.0 MPa and 14.0 MPa. Both of the cosolvents can accelerate the decomposition rate, and the effect of methanol is more significant than that of the cyclohexane.
