This paper describes an experimental study investigating the effects of sinusoidal pulsed injection on the combustion mode transition in a dual-mode supersonic combustor.The results are obtained under inflow condition...This paper describes an experimental study investigating the effects of sinusoidal pulsed injection on the combustion mode transition in a dual-mode supersonic combustor.The results are obtained under inflow conditions of 2.9 MPa stagnation pressure,1900 K stagnation temperature,and Mach number of 3.0.It has been observed that,at the same equivalence ratio,the combustion mode and flow field structure undergo irreversible changes from a weak combustion state to a strong combustion state at a specific pulsed jet frequency compared to steady jet.For steady jet,the combustion mode is dual-mode.As the frequency of the unsteady jet changes,the combustion mode also changes:it becomes a transition mode at frequencies of 171 Hz and 260 Hz,and a ramjet mode at 216 Hz.Combustion instability under steady jet manifests as a transition in flame stabilization mode.In contrast,under pulsed jet,combustion instability appears either as a transition in flame stabilization mode or as flame blow-off and flashback.The flow field oscillation frequency in the non-reacting flow is 171 Hz,which may resonate with the 171 Hz pulsed jet frequency,making the combustion oscillations most pronounced at this frequency.When the jet frequency is increased to 216 Hz,the combustion intensity significantly increases,and the combustion mode transfers to the ramjet mode.However,further increasing the frequency to 260 Hz results in a decrease in combustion intensity,returning to the transition mode.The frequency of the flow field oscillations varies with the coupling of the pulsed injection frequency,shock wave,and flame,and if the system reaches an unstable state,that is,pre-combustion shock train moves far upstream of the isolator during the pulsed jet period,strong combustion state can be achieved,and this process is irreversible.展开更多
Traditional in situ biogeochemical transformation suffers from competition among crucial microorganisms and inadequate formation of reactive minerals,thus leading to the accumulation of toxic intermediates.In this stu...Traditional in situ biogeochemical transformation suffers from competition among crucial microorganisms and inadequate formation of reactive minerals,thus leading to the accumulation of toxic intermediates.In this study,three regulation schemes were proposed to solve these problems from the perspective of engineering mode.Results showed intermittent injection mode effectively reduced the accumulation of toxic intermediates but the reduction rate of tetrachloroethylene was decreased.And periodical supplementation of carbon and sulfur sources accelerated the removal of tetrachloroethylene but failed to reduce the accumulation of toxic products.While,regular supplementation of sulfate effectively weakened the competition of methanogens and increased the iron sulfide proportion on the surface of the minerals,thus reducing the accumulation of toxicity.Based on the results,this study obtained an effective engineering approach for practical site application.In addition,the main forms of active minerals capable ofβ-eliminating contaminants during biogeochemical transformation were identified in this study,including FeS,FeS_(2),and Fe_(3)S_(4).Furthermore,the engineered regulatory mechanism of this study was summarized through the analysis of microbial community structure and mineral morphology.The amendment promotes the production of minerals and thus controls the transformation pathway of contaminants by altering the abundance of sulfate-reducing bacteria and dissimilatory iron reducing bacteria.This mechanism can provide a basis for subsequent theoretical studies.展开更多
To achieve the electric field strength and the induced currents in equivalence in susceptibility tests with the high-level field radiation above 400 MHz,a double differential-mode(DM) current injection method based on...To achieve the electric field strength and the induced currents in equivalence in susceptibility tests with the high-level field radiation above 400 MHz,a double differential-mode(DM) current injection method based on directional couplers is proposed.Two cascaded symmetrical directional couplers compose a coupling device to inject the DM currents.When the coupling device is used,two devices are necessary to achieve the equivalence between radiation and injection,i.e.the equivalence between the injected voltages and the field strength,which is linear,regardless of the characteristics of the equipment under test(EUT).The results are verified by experiments using typical coaxial cables and nonlinear devices,where the equivalence between the nonlinear EUT responses induced by radiation and injection at both ends is achieved by using two coupling devices.At a frequency up to 1.75 GHz,the maximal experimental error is only 3.39%.The experimental results confirm the accuracy of the proposed method even both the EUTs work in the nonlinear region.The proposed method is applicable for radiated susceptibility(RS) testing of interconnected systems in the microwave frequency band.展开更多
The mathematical models of the flow of polymer foam in porous media under three injection modes are established and the relevant numerical calculation methods are given. The profiles of the liquid phase saturation, th...The mathematical models of the flow of polymer foam in porous media under three injection modes are established and the relevant numerical calculation methods are given. The profiles of the liquid phase saturation, the pressure drop and the number density of the flowing HPAM foam in artificial sandstone cores with the dimensionless distance under three injection modes are numerically calculated and analyzed. The results show that, compared with the injection mode 2 and 3, HPAM foam flows in a piston-like fashion in the artificial sandstone core under the injection mode 1 and produces the biggest pressure drop. Obviously, the flood efficiency is the highest under the injection mode 1.展开更多
There are the application scope limits for single differential-mode current injection test method, so in order to carry out injection susceptibility test for two-pieces equipment interconnected with both ends of a cab...There are the application scope limits for single differential-mode current injection test method, so in order to carry out injection susceptibility test for two-pieces equipment interconnected with both ends of a cable simultaneously, a double differential-mode current in- jection test method (DDMCI) is proposed. The method adopted the equivalence source wave theorem and Baum-Liu-Tesche(BLT) equation as its theory foundation. The equivalent corresponding relation between injection voltage and radiation electric field intensity is derived, and the phase relation between the two injection voltage sources is confirmed. The results indicate that the amplitude and phase of the equivalent injection voltage source is closely related to the S parameter of directional coupling device, the transmission line length, and the source vector in BLT equation, but has nothing to do with the reflection coefficient between the two equipment pieces. Therefore, by choosing the right amplitude and phase of the double injection voltage sources, the DDMCI test is equivalent to the radiation test for two interconnected equipment of a system.展开更多
The general strategy and method of constructing universal calibration model for levofioxacin injections by near-infrared spectroscopy have been investigated and discussed. Firstly, a constant-temperature homogeneous l...The general strategy and method of constructing universal calibration model for levofioxacin injections by near-infrared spectroscopy have been investigated and discussed. Firstly, a constant-temperature homogeneous liquid calibration model for levofloxacin hydrochloride injections with the same composition but different active principal ingredient （API） content was established as the basic unit for universal model. Then, samples of levofloxacin hydrochloride injections containing propylene glycol or levofloxacin lactate injections were added to develop a primary constant-temperature liquid universal model. Temperature- amended final universal model was established to apply to samples under different temperatures. The final model was built from 61 calibration samples and 77 validation samples. The value of the root mean square error of cross validation （RMSECV） and coefficient of determination （r2） of leave-one-out cross-validation （LOOCV） were 0.792 and 0.9993, respectively, the root mean square error of prediction （RMSEP） of test set validation （TSV） was 0.87, and the average relative deviation was 1.44%. According to the ICH guidelines, the universal calibration model was evaluated. Based on the experimental statistical results, the recommended number of calibration samples for a constant-temperature homogeneous liquid quantitative model was no less than 15.展开更多
With complex fractured-vuggy heterogeneous structures, water has to be injected to facilitate oil pro- duction. However, the effect of different water injection modes on oil recovery varies. The limitation of existing...With complex fractured-vuggy heterogeneous structures, water has to be injected to facilitate oil pro- duction. However, the effect of different water injection modes on oil recovery varies. The limitation of existing numerical simulation methods in representing fractured- vuggy carbonate reservoirs makes numerical simulation difficult to characterize the fluid flow in these reservoirs. In this paper, based on a geological example unit in the Tahe Oilfield, a three-dimensional physical model was designed and constructed to simulate fluid flow in a fractured-vuggy reservoir according to similarity criteria. The model was validated by simulating a bottom water drive reservoir, and then subsequent water injection modes were optimized. These were continuous （constant rate）, intermittent, and pulsed injection of water. Experimental results reveal that due to the unbalanced formation pressure caused by pulsed water injection, the swept volume was expanded and consequently the highest oil recovery increment was achieved. Similar to continuous water injection, intermit- tent injection was influenced by factors including the connectivity of the fractured-vuggy reservoir, well depth, and the injection-production relationship, which led to a relative low oil recovery. This study may provide a constructive guide to field production and for the devel- opment of the commercial numerical models specialized for fractured-vuggy carbonate reservoirs.展开更多
In this paper, the effect of injected energy on low energy single longitudinal mode (SLM) pre-lase Q-switched is analyzed and the optimization procedure is shown in detail. Here, taking the Pr:YLF laser as an example ...In this paper, the effect of injected energy on low energy single longitudinal mode (SLM) pre-lase Q-switched is analyzed and the optimization procedure is shown in detail. Here, taking the Pr:YLF laser as an example of low energy laser, and the parameters of Pr:YLF laser by using pre-lase have been shown. Compared with normal Q-switched laser, the single pulse energy reaches 60.16% and the pulse width exceeds 39.73% when the same maximum energy is injected and SLM is achieved in pre-lase. The analysis results show that pre-lase is suitable for low energy laser to obtain SLM and there be an optimal performance to achieve the optimal energy output.展开更多
Exohiss is a low-frequency structureless whistler-mode emission potentially contributing to the precipitation loss of radiation belt electrons outside the plasmasphere. Exohiss is usually considered the plasmaspheric ...Exohiss is a low-frequency structureless whistler-mode emission potentially contributing to the precipitation loss of radiation belt electrons outside the plasmasphere. Exohiss is usually considered the plasmaspheric hiss leaked out of the dayside plasmapause.However, the evolution of exohiss after the leakage has not been fully understood. Here we report the prompt enhancements of exohiss waves following substorm injections observed by Van Allen Probes. Within several minutes, the energetic electron fluxes around 100 keV were enhanced by up to 5 times, accompanied by an up to 10-time increase of the exohiss wave power. These substorm-injected electrons are shown to produce a new peak of linear growth rate in the exohiss band(< 0.1 f_(ce)). The corresponding path-integrated growth rate of wave power within 10° latitude of the magnetic equatorial plane can reach 13.4, approximately explaining the observed enhancement of exohiss waves. These observations and simulations suggest that the substorm-injected energetic electrons could amplify the preexisting exohiss waves.展开更多
During the operation of a high-power neutral beam injection (NBI) system on theHL-1M tokamak, an optical diagnostic means using CCD camera was developed to characterize theNBI performance. The vacuum valve opening pro...During the operation of a high-power neutral beam injection (NBI) system on theHL-1M tokamak, an optical diagnostic means using CCD camera was developed to characterize theNBI performance. The vacuum valve opening process and NBI period in the HL-1M experimentwere displayed by a lot of photos taken with this means. Thus, the Hα emission profiles of theneutral beam (NB) and its interaction with plasma were given. Finally, the reason possible forplasma breakdown during NBI mode Ⅱ discharge was investigated. Therefore, this in-situ diagnosiscan provide more information of the NBI.展开更多
In the Ruhrstahl-Heraeus （RH） refining process, liquid steel flow pattern in a ladle is controlled by the fluid flow behavior in the vacuum chamber. Potassium chloride solution and NaOH solution saturated with CO2 w...In the Ruhrstahl-Heraeus （RH） refining process, liquid steel flow pattern in a ladle is controlled by the fluid flow behavior in the vacuum chamber. Potassium chloride solution and NaOH solution saturated with CO2 were respectively used as a tracer to investigate the liquid and gas flow behaviors in the vacuum chamber. Principal compo nent and comparative analysis were made to show the factors controlling mixing and circulation flow rate. The liquid level and bubble behavior in the vacuum chamber greatly affect fluid flow in RH process. Experiments were performed to investigate the effects of liquid steel level, gas flow rate, bubble residence time, and gas injection mode on mixing, decarburization, and void fraction. The results indicate that the mixing process can be divided into three regions： the flow rate affected zone, the concentration gradient-affected zone, and their combination. The liquid steel level in the vacuum chamber of 300 mm is a critical point in the decarburization transition. For liquid level lower than 300 mm, liquid steel circulation controls decarburization, while for liquid level higher than 300mm, bubble behavior is the main controlling factor. During the RH process, it is recommended to use the concentrated bubble injection mode for low gas flow rates and the uniform bubble injection mode for high gas flow rates.展开更多
Based on the oil,gas and water distribution characteristics of Khasib reservoir in Halfaya oilfield,Iraq,a core displacement experiment is designed to evaluate the influence of different displacement methods and displ...Based on the oil,gas and water distribution characteristics of Khasib reservoir in Halfaya oilfield,Iraq,a core displacement experiment is designed to evaluate the influence of different displacement methods and displacement parameters on oil displacement efficiency.The research shows that,in the displacement method with water injected from the edge of the reservoir,early depletion production is conducive to the elastic expansion of the gas cap,forming the three-dimensional displacement of"upper pressure and lower pushing",and the oil displacement effect is good.When gas injection at the top and water injection at the edge are used for synergistic displacement,the injection timing has different influences on the oil displacement effects of high and low parts.Considering the overall oil displacement efficiency,the injection pressure should be greater than the bubble point pressure of crude oil.Two displacement methods are recommended with the reasonable injection time at 20–25 MPa.The injection speed has the same influence on different injection media.Appropriately reducing the injection speed is conducive to the stability of the displacement front,delaying the breakthrough of injection media and improving the oil displacement effect.The reasonable injection rate of water flooding is 0.075 mL/min,the reasonable injection rates of water and gas are 0.15 mL/min and 0.10 mL/min,respectively in gas-water synergistic displacement.Gas-water synergistic displacement is conducive to the production of crude oil at high position,and has crude oil recovery 5.0%–14.8%higher than water flooding from the edge,so it is recommended as the development mode of Khasib reservoir at the middle and late stages.展开更多
Research on dual-fuel(DF)engines has become increasingly important as engine manufacturers seek to reduce carbon dioxide emissions.There are significant advantages of using diesel pilot-ignited natural gas engines as ...Research on dual-fuel(DF)engines has become increasingly important as engine manufacturers seek to reduce carbon dioxide emissions.There are significant advantages of using diesel pilot-ignited natural gas engines as DF engines.However,different combustion modes exist due to variations in the formation of the mixture.This research used a simulation model and numerical simulations to explore the combustion characteristics of high-pressure direct injection(HPDI),partially premixed compression ignition(PPCI),and double pilot injection premixed compression ignition(DPPCI)combustion modes under a low-medium load.The results revealed that the DPPCI combustion mode provides higher gross indicated thermal efficiency and more acceptable total hydrocarbon(THC)emission levels than the other modes.Due to its relatively good performance,an experimental study was conducted on the DPPCI mode engine to evaluate the impact of the diesel dual-injection strategy on the combustion process.In the DPPCI mode,a delay in the second pilot ignition injection time increased THC emissions(a maximum value of 4.27g/(kW·h)),decreased the emission of nitrogen oxides(a maximum value of 7.64 g/(kW·h)),increased and then subsequently decreased the gross indicated thermal efficiency values,which reached 50.4%under low-medium loads.展开更多
The degradation mechanism of enhancement-mode Al Ga N/Ga N high electron mobility transistors（HEMTs） fabricated by fluorine plasma ion implantation technology is one major concern of HEMT＇s reliability. It is obser...The degradation mechanism of enhancement-mode Al Ga N/Ga N high electron mobility transistors（HEMTs） fabricated by fluorine plasma ion implantation technology is one major concern of HEMT＇s reliability. It is observed that the threshold voltage shows a significant negative shift during the typical long-term on-state gate overdrive stress. The degradation does not originate from the presence of as-grown traps in the Al Ga N barrier layer or the generated traps during fluorine ion implantation process. By comparing the relationships between the shift of threshold voltage and the cumulative injected electrons under different stress conditions, a good agreement is observed. It provides direct experimental evidence to support the impact ionization physical model, in which the degradation of E-mode HEMTs under gate overdrive stress can be explained by the ionization of fluorine ions in the Al Ga N barrier layer by electrons injected from 2DEG channel.Furthermore, our results show that there are few new traps generated in the Al Ga N barrier layer during the gate overdrive stress, and the ionized fluorine ions cannot recapture the electrons.展开更多
In this paper, we observe experimentally the optical bistability induced by the side-mode injection power and wave- length detuning in a single mode Fabry-P6rot laser diode （SMFP-LD）. Results show that the bistabili...In this paper, we observe experimentally the optical bistability induced by the side-mode injection power and wave- length detuning in a single mode Fabry-P6rot laser diode （SMFP-LD）. Results show that the bistability characteristics of the dominant and injected modes are strongly dependent on the injected input optical power and wavelength detuning in an SMFP-LD. We observe three types of hysteresis loops： counterclockwise, clockwise, and butterfly hysteresis with various loop widths. In the case of a bistability loop caused by injection power, the transition from counterclockwise to clockwise in the hysteresis direction with the wavelength detuning from 0.028 nm to 0.112 nm is observed in a way of butterfly hys- teresis for the dominant mode by increasing the wavelength detuning. The width of hysteresis loop, induced by wavelength detuning is also changed while the injection power is enhanced from -7 dBm to -5 dBm.展开更多
基金supported by the Program of Key Laboratory of Cross-Domain Flight Interdisciplinary Technology,China(No.2023-ZY0205)。
文摘This paper describes an experimental study investigating the effects of sinusoidal pulsed injection on the combustion mode transition in a dual-mode supersonic combustor.The results are obtained under inflow conditions of 2.9 MPa stagnation pressure,1900 K stagnation temperature,and Mach number of 3.0.It has been observed that,at the same equivalence ratio,the combustion mode and flow field structure undergo irreversible changes from a weak combustion state to a strong combustion state at a specific pulsed jet frequency compared to steady jet.For steady jet,the combustion mode is dual-mode.As the frequency of the unsteady jet changes,the combustion mode also changes:it becomes a transition mode at frequencies of 171 Hz and 260 Hz,and a ramjet mode at 216 Hz.Combustion instability under steady jet manifests as a transition in flame stabilization mode.In contrast,under pulsed jet,combustion instability appears either as a transition in flame stabilization mode or as flame blow-off and flashback.The flow field oscillation frequency in the non-reacting flow is 171 Hz,which may resonate with the 171 Hz pulsed jet frequency,making the combustion oscillations most pronounced at this frequency.When the jet frequency is increased to 216 Hz,the combustion intensity significantly increases,and the combustion mode transfers to the ramjet mode.However,further increasing the frequency to 260 Hz results in a decrease in combustion intensity,returning to the transition mode.The frequency of the flow field oscillations varies with the coupling of the pulsed injection frequency,shock wave,and flame,and if the system reaches an unstable state,that is,pre-combustion shock train moves far upstream of the isolator during the pulsed jet period,strong combustion state can be achieved,and this process is irreversible.
基金supported by the National Natural Science Foundation of China(No.42277057).
文摘Traditional in situ biogeochemical transformation suffers from competition among crucial microorganisms and inadequate formation of reactive minerals,thus leading to the accumulation of toxic intermediates.In this study,three regulation schemes were proposed to solve these problems from the perspective of engineering mode.Results showed intermittent injection mode effectively reduced the accumulation of toxic intermediates but the reduction rate of tetrachloroethylene was decreased.And periodical supplementation of carbon and sulfur sources accelerated the removal of tetrachloroethylene but failed to reduce the accumulation of toxic products.While,regular supplementation of sulfate effectively weakened the competition of methanogens and increased the iron sulfide proportion on the surface of the minerals,thus reducing the accumulation of toxicity.Based on the results,this study obtained an effective engineering approach for practical site application.In addition,the main forms of active minerals capable ofβ-eliminating contaminants during biogeochemical transformation were identified in this study,including FeS,FeS_(2),and Fe_(3)S_(4).Furthermore,the engineered regulatory mechanism of this study was summarized through the analysis of microbial community structure and mineral morphology.The amendment promotes the production of minerals and thus controls the transformation pathway of contaminants by altering the abundance of sulfate-reducing bacteria and dissimilatory iron reducing bacteria.This mechanism can provide a basis for subsequent theoretical studies.
基金supported by National Basic Research Program of China(973 Program)
文摘To achieve the electric field strength and the induced currents in equivalence in susceptibility tests with the high-level field radiation above 400 MHz,a double differential-mode(DM) current injection method based on directional couplers is proposed.Two cascaded symmetrical directional couplers compose a coupling device to inject the DM currents.When the coupling device is used,two devices are necessary to achieve the equivalence between radiation and injection,i.e.the equivalence between the injected voltages and the field strength,which is linear,regardless of the characteristics of the equipment under test(EUT).The results are verified by experiments using typical coaxial cables and nonlinear devices,where the equivalence between the nonlinear EUT responses induced by radiation and injection at both ends is achieved by using two coupling devices.At a frequency up to 1.75 GHz,the maximal experimental error is only 3.39%.The experimental results confirm the accuracy of the proposed method even both the EUTs work in the nonlinear region.The proposed method is applicable for radiated susceptibility(RS) testing of interconnected systems in the microwave frequency band.
文摘The mathematical models of the flow of polymer foam in porous media under three injection modes are established and the relevant numerical calculation methods are given. The profiles of the liquid phase saturation, the pressure drop and the number density of the flowing HPAM foam in artificial sandstone cores with the dimensionless distance under three injection modes are numerically calculated and analyzed. The results show that, compared with the injection mode 2 and 3, HPAM foam flows in a piston-like fashion in the artificial sandstone core under the injection mode 1 and produces the biggest pressure drop. Obviously, the flood efficiency is the highest under the injection mode 1.
基金Project supported by Arm Pre-research Program （51333040101）, National Defense 973 Program （6131380301 ）, National Natural Science Foundation of China （61040003）.
文摘There are the application scope limits for single differential-mode current injection test method, so in order to carry out injection susceptibility test for two-pieces equipment interconnected with both ends of a cable simultaneously, a double differential-mode current in- jection test method (DDMCI) is proposed. The method adopted the equivalence source wave theorem and Baum-Liu-Tesche(BLT) equation as its theory foundation. The equivalent corresponding relation between injection voltage and radiation electric field intensity is derived, and the phase relation between the two injection voltage sources is confirmed. The results indicate that the amplitude and phase of the equivalent injection voltage source is closely related to the S parameter of directional coupling device, the transmission line length, and the source vector in BLT equation, but has nothing to do with the reflection coefficient between the two equipment pieces. Therefore, by choosing the right amplitude and phase of the double injection voltage sources, the DDMCI test is equivalent to the radiation test for two interconnected equipment of a system.
基金National Science and Technology Major Project of the Ministry of Science and Technology of China(Grant No. 2010ZX09401-403)
文摘The general strategy and method of constructing universal calibration model for levofioxacin injections by near-infrared spectroscopy have been investigated and discussed. Firstly, a constant-temperature homogeneous liquid calibration model for levofloxacin hydrochloride injections with the same composition but different active principal ingredient （API） content was established as the basic unit for universal model. Then, samples of levofloxacin hydrochloride injections containing propylene glycol or levofloxacin lactate injections were added to develop a primary constant-temperature liquid universal model. Temperature- amended final universal model was established to apply to samples under different temperatures. The final model was built from 61 calibration samples and 77 validation samples. The value of the root mean square error of cross validation （RMSECV） and coefficient of determination （r2） of leave-one-out cross-validation （LOOCV） were 0.792 and 0.9993, respectively, the root mean square error of prediction （RMSEP） of test set validation （TSV） was 0.87, and the average relative deviation was 1.44%. According to the ICH guidelines, the universal calibration model was evaluated. Based on the experimental statistical results, the recommended number of calibration samples for a constant-temperature homogeneous liquid quantitative model was no less than 15.
基金supported by China National Science and Technology Major Project(2011ZX05009-004,2011ZX05014-003)National Key Basic Research and Development Program(973 Program),China(2011CB201006)Science Foundation of China University of Petroleum,Beijing(2462014YJRC053)
文摘With complex fractured-vuggy heterogeneous structures, water has to be injected to facilitate oil pro- duction. However, the effect of different water injection modes on oil recovery varies. The limitation of existing numerical simulation methods in representing fractured- vuggy carbonate reservoirs makes numerical simulation difficult to characterize the fluid flow in these reservoirs. In this paper, based on a geological example unit in the Tahe Oilfield, a three-dimensional physical model was designed and constructed to simulate fluid flow in a fractured-vuggy reservoir according to similarity criteria. The model was validated by simulating a bottom water drive reservoir, and then subsequent water injection modes were optimized. These were continuous （constant rate）, intermittent, and pulsed injection of water. Experimental results reveal that due to the unbalanced formation pressure caused by pulsed water injection, the swept volume was expanded and consequently the highest oil recovery increment was achieved. Similar to continuous water injection, intermit- tent injection was influenced by factors including the connectivity of the fractured-vuggy reservoir, well depth, and the injection-production relationship, which led to a relative low oil recovery. This study may provide a constructive guide to field production and for the devel- opment of the commercial numerical models specialized for fractured-vuggy carbonate reservoirs.
文摘In this paper, the effect of injected energy on low energy single longitudinal mode (SLM) pre-lase Q-switched is analyzed and the optimization procedure is shown in detail. Here, taking the Pr:YLF laser as an example of low energy laser, and the parameters of Pr:YLF laser by using pre-lase have been shown. Compared with normal Q-switched laser, the single pulse energy reaches 60.16% and the pulse width exceeds 39.73% when the same maximum energy is injected and SLM is achieved in pre-lase. The analysis results show that pre-lase is suitable for low energy laser to obtain SLM and there be an optimal performance to achieve the optimal energy output.
基金supported by National Natural Science Foundation of China grants 41631071, 41774170, 41274174, 41174125, 41131065, 41421063, 41231066 and 41304134Chinese Academy of Sciences grants KZCX2-EW-QN510 and KZZD-EW-01-4+2 种基金CAS Key Research Program of Frontier Sciences grant QYZDB-SSWDQC015National Key Basic Research Special Foundation of China Grant No. 2011CB811403Fundamental Research Funds for the Central Universities WK2080000077
文摘Exohiss is a low-frequency structureless whistler-mode emission potentially contributing to the precipitation loss of radiation belt electrons outside the plasmasphere. Exohiss is usually considered the plasmaspheric hiss leaked out of the dayside plasmapause.However, the evolution of exohiss after the leakage has not been fully understood. Here we report the prompt enhancements of exohiss waves following substorm injections observed by Van Allen Probes. Within several minutes, the energetic electron fluxes around 100 keV were enhanced by up to 5 times, accompanied by an up to 10-time increase of the exohiss wave power. These substorm-injected electrons are shown to produce a new peak of linear growth rate in the exohiss band(< 0.1 f_(ce)). The corresponding path-integrated growth rate of wave power within 10° latitude of the magnetic equatorial plane can reach 13.4, approximately explaining the observed enhancement of exohiss waves. These observations and simulations suggest that the substorm-injected energetic electrons could amplify the preexisting exohiss waves.
文摘During the operation of a high-power neutral beam injection (NBI) system on theHL-1M tokamak, an optical diagnostic means using CCD camera was developed to characterize theNBI performance. The vacuum valve opening process and NBI period in the HL-1M experimentwere displayed by a lot of photos taken with this means. Thus, the Hα emission profiles of theneutral beam (NB) and its interaction with plasma were given. Finally, the reason possible forplasma breakdown during NBI mode Ⅱ discharge was investigated. Therefore, this in-situ diagnosiscan provide more information of the NBI.
基金Item Sponsored by National Natural Science Foundation of China(51404022)Doctoral Fund of Ministry of Education of China(20130006110023)Ph.D Early Development Program of Taiyuan University of Science and Technology of China(20152008,20142001)
文摘In the Ruhrstahl-Heraeus （RH） refining process, liquid steel flow pattern in a ladle is controlled by the fluid flow behavior in the vacuum chamber. Potassium chloride solution and NaOH solution saturated with CO2 were respectively used as a tracer to investigate the liquid and gas flow behaviors in the vacuum chamber. Principal compo nent and comparative analysis were made to show the factors controlling mixing and circulation flow rate. The liquid level and bubble behavior in the vacuum chamber greatly affect fluid flow in RH process. Experiments were performed to investigate the effects of liquid steel level, gas flow rate, bubble residence time, and gas injection mode on mixing, decarburization, and void fraction. The results indicate that the mixing process can be divided into three regions： the flow rate affected zone, the concentration gradient-affected zone, and their combination. The liquid steel level in the vacuum chamber of 300 mm is a critical point in the decarburization transition. For liquid level lower than 300 mm, liquid steel circulation controls decarburization, while for liquid level higher than 300mm, bubble behavior is the main controlling factor. During the RH process, it is recommended to use the concentrated bubble injection mode for low gas flow rates and the uniform bubble injection mode for high gas flow rates.
基金Supported by the Scientific Research and Technology Development Project of CNPC(2019D-4410)。
文摘Based on the oil,gas and water distribution characteristics of Khasib reservoir in Halfaya oilfield,Iraq,a core displacement experiment is designed to evaluate the influence of different displacement methods and displacement parameters on oil displacement efficiency.The research shows that,in the displacement method with water injected from the edge of the reservoir,early depletion production is conducive to the elastic expansion of the gas cap,forming the three-dimensional displacement of"upper pressure and lower pushing",and the oil displacement effect is good.When gas injection at the top and water injection at the edge are used for synergistic displacement,the injection timing has different influences on the oil displacement effects of high and low parts.Considering the overall oil displacement efficiency,the injection pressure should be greater than the bubble point pressure of crude oil.Two displacement methods are recommended with the reasonable injection time at 20–25 MPa.The injection speed has the same influence on different injection media.Appropriately reducing the injection speed is conducive to the stability of the displacement front,delaying the breakthrough of injection media and improving the oil displacement effect.The reasonable injection rate of water flooding is 0.075 mL/min,the reasonable injection rates of water and gas are 0.15 mL/min and 0.10 mL/min,respectively in gas-water synergistic displacement.Gas-water synergistic displacement is conducive to the production of crude oil at high position,and has crude oil recovery 5.0%–14.8%higher than water flooding from the edge,so it is recommended as the development mode of Khasib reservoir at the middle and late stages.
基金Project(2017YFE0102800)supported by the National Key R&D Program of ChinaProject(19JCYBJC21200)supported by the Tianjin Natural Science Foundation,China。
文摘Research on dual-fuel(DF)engines has become increasingly important as engine manufacturers seek to reduce carbon dioxide emissions.There are significant advantages of using diesel pilot-ignited natural gas engines as DF engines.However,different combustion modes exist due to variations in the formation of the mixture.This research used a simulation model and numerical simulations to explore the combustion characteristics of high-pressure direct injection(HPDI),partially premixed compression ignition(PPCI),and double pilot injection premixed compression ignition(DPPCI)combustion modes under a low-medium load.The results revealed that the DPPCI combustion mode provides higher gross indicated thermal efficiency and more acceptable total hydrocarbon(THC)emission levels than the other modes.Due to its relatively good performance,an experimental study was conducted on the DPPCI mode engine to evaluate the impact of the diesel dual-injection strategy on the combustion process.In the DPPCI mode,a delay in the second pilot ignition injection time increased THC emissions(a maximum value of 4.27g/(kW·h)),decreased the emission of nitrogen oxides(a maximum value of 7.64 g/(kW·h)),increased and then subsequently decreased the gross indicated thermal efficiency values,which reached 50.4%under low-medium loads.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61334002,61106106,and 61474091)the Opening Project of Science and Technology on Reliability Physics and Application Technology of Electronic Component Laboratory(Grant No.ZHD201206)+1 种基金the New Experiment Development Funds for Xidian University,China(Grant No.SY1213)the Scientific Research Foundation for the Returned Overseas Chinese Scholars
文摘The degradation mechanism of enhancement-mode Al Ga N/Ga N high electron mobility transistors（HEMTs） fabricated by fluorine plasma ion implantation technology is one major concern of HEMT＇s reliability. It is observed that the threshold voltage shows a significant negative shift during the typical long-term on-state gate overdrive stress. The degradation does not originate from the presence of as-grown traps in the Al Ga N barrier layer or the generated traps during fluorine ion implantation process. By comparing the relationships between the shift of threshold voltage and the cumulative injected electrons under different stress conditions, a good agreement is observed. It provides direct experimental evidence to support the impact ionization physical model, in which the degradation of E-mode HEMTs under gate overdrive stress can be explained by the ionization of fluorine ions in the Al Ga N barrier layer by electrons injected from 2DEG channel.Furthermore, our results show that there are few new traps generated in the Al Ga N barrier layer during the gate overdrive stress, and the ionized fluorine ions cannot recapture the electrons.
基金supported by the National Natural Science Foundation of China(Grant No.61205111)the Open Foundation of State Key Laboratory of Millimeter Waves,China(Grant No.K201219)the Natural Science Foundation of Chongqing Normal University,China(Grant No.2011XLZ06)
文摘In this paper, we observe experimentally the optical bistability induced by the side-mode injection power and wave- length detuning in a single mode Fabry-P6rot laser diode （SMFP-LD）. Results show that the bistability characteristics of the dominant and injected modes are strongly dependent on the injected input optical power and wavelength detuning in an SMFP-LD. We observe three types of hysteresis loops： counterclockwise, clockwise, and butterfly hysteresis with various loop widths. In the case of a bistability loop caused by injection power, the transition from counterclockwise to clockwise in the hysteresis direction with the wavelength detuning from 0.028 nm to 0.112 nm is observed in a way of butterfly hys- teresis for the dominant mode by increasing the wavelength detuning. The width of hysteresis loop, induced by wavelength detuning is also changed while the injection power is enhanced from -7 dBm to -5 dBm.
