From March 19 to 27,four outstanding young people from Chengdu went on a trip to Perth,Australia,as the winners of the Perth Professional Development and Internship Competition,an innovative campaign for Chengdu and i...From March 19 to 27,four outstanding young people from Chengdu went on a trip to Perth,Australia,as the winners of the Perth Professional Development and Internship Competition,an innovative campaign for Chengdu and its sister city Perth,which has had fruitful student exchanges.The competition was designed to select four展开更多
英语作文习作范例点评写怍第一节Dear Jenny,I really like the idea of adding a new column to our English newspaper.In my opinion.I prefer the"Fun at my school"column.The reasons why I choose it are as follows.F...英语作文习作范例点评写怍第一节Dear Jenny,I really like the idea of adding a new column to our English newspaper.In my opinion.I prefer the"Fun at my school"column.The reasons why I choose it are as follows.First of all,this column can enhance students'comprehension,through which,the bonds between students and school can be strengthened.What's more,this column not only broadens students horizons,but also adds color to school life.Last butnot least.it can relieve stress.which benefits menta!health.展开更多
Fish are the oldest and most diverse vertebrates on the planet,living in waters around the world,and are very important for maintaining ecological balance,as well as providing rich food resources for human beings.Perh...Fish are the oldest and most diverse vertebrates on the planet,living in waters around the world,and are very important for maintaining ecological balance,as well as providing rich food resources for human beings.Perhaps as far as common people are concerned,fish can be divided into two kinds,edible and non-edible.In fact,there are more than 20,000 fish species in the world,some of which are highly skilled and make people broaden their horizons.展开更多
Two-dimensional(2D)organic-inorganic hybrid perovskites(OIHPs)have been developed as promising candidates for photodetection,owing to their excellent semiconducting features and structural tunability.However,as an imp...Two-dimensional(2D)organic-inorganic hybrid perovskites(OIHPs)have been developed as promising candidates for photodetection,owing to their excellent semiconducting features and structural tunability.However,as an important parameter for photodetection,the photoresponsive range of 2D OIHPs is usually modulated by finite metal-halide combinations,constraining their further development.The emerging aromatic amine-based alternating-cations-interlayered(A-ACI)hybrid perovskites that exhibit excellent charge transport and additional interlayered structural designability,provide an extra solution for achieving ideal photoresponsive range.Herein,for the first time,the photoresponsive range is successfully broadened in A-ACI hybrid perovskites(NMA)_(4)(FA)_(2)Pb_(3)Br_(12)(2)remolding from(NMA)_(4)(MA)_(2)Pb_(3)Br_(12)(1)(NMA=N-methylbenzylaminium,FA=formamidinium and MA=methylammonium).Particularly,1 and 2adopt an unprecedented configuration that NMA and MA/FA are alternately arranged in the interlayer in a 4:2 manner.Importantly,2 exhibits a narrower bandgap than 1,which can be ascribed to the lowlying conduct band composed of intercalation FAπ*orbitals.Meanwhile,2 possesses a shorter interlayer distance and flatter inorganic skeleton,synergistically facilitating the wider photo-absorption range and further endowing a broadening photoresponsive range(70 nm).This research not only enriches the perovskite family but also provides insights into structure-property relationships.展开更多
Energy resolution calibration is crucial for gamma-ray spectral analysis,as measured using a scintillation detector.A locally constrained regularization method was proposed to determine the resolution calibration para...Energy resolution calibration is crucial for gamma-ray spectral analysis,as measured using a scintillation detector.A locally constrained regularization method was proposed to determine the resolution calibration parameters.First,a Monte Carlo simulation model consistent with an actual measurement system was constructed to obtain the energy deposition distribution in the scintillation crystal.Subsequently,the regularization objective function is established based on weighted least squares and additional constraints.Additional constraints were designed using a special weighting scheme based on the incident gamma-ray energies.Subsequently,an intelligent algorithm was introduced to search for the optimal resolution calibration parameters by minimizing the objective function.The most appropriate regularization parameter was determined through mathematical experiments.When the regularization parameter was 30,the calibrated results exhibited the minimum RMSE.Simulations and test pit experiments were conducted to verify the performance of the proposed method.The simulation results demonstrate that the proposed algorithm can determine resolution calibration parameters more accurately than the traditional weighted least squares,and the test pit experimental results show that the R-squares between the calibrated and measured spectra are larger than 0.99.The accurate resolution calibration parameters determined by the proposed method lay the foundation for gamma-ray spectral processing and simulation benchmarking.展开更多
We propose a near-field thermophotovoltaic system utilizing magnetic Weyl semimetals,which exhibit a distinct gyrotropic effect originating from their intrinsic axion field.Critically,we demonstrate that intentional b...We propose a near-field thermophotovoltaic system utilizing magnetic Weyl semimetals,which exhibit a distinct gyrotropic effect originating from their intrinsic axion field.Critically,we demonstrate that intentional band dislocation,achieved by layer-specific tuning of the chemical potential,significantly enhances the energyconversion efficiency.This effect arises from the formation of quasi-flat bands in momentum space,which broaden the spectral heat flux and amplify photon tunneling above the bandgap.At optimized chemical potential mismatches,the system achieves a 65%Carnot efficiency and a power density of 7×10^(4)W·m^(-2),surpassing symmetric configurations by 7%.The optimization of the Weyl semimetals thickness further demonstrates a clear tuning window where both the output power and energy-conversion efficiency are significantly improved.These results establish chemical-potential engineering toward high-efficiency near-field thermophotovoltaics for waste heat recovery and infrared energy applications.展开更多
China will enter WTO in the near future. The great shock to uncompleted reform and excessive protection firstly means challenges and opportunities. The way to deal with this situation is to regard entering WTO as the ...China will enter WTO in the near future. The great shock to uncompleted reform and excessive protection firstly means challenges and opportunities. The way to deal with this situation is to regard entering WTO as the second reform and open. By upholding opening - door policy, we can stride forward towards internationalization and really merge into world market. By expending the reform, we can actively push forward marketization, and further improve system of enterprise, market construction and governmetnt’s function. All industries should take different strategies and pay much attention to improving core technology and international competitiveness.展开更多
Semiconductor photocatalysis can be operated over a narrow pH range for wastewater treatment. In this study, a simulated solar-light-mediated bismuth tungstate (SSL/Bi2WO6) process is found to be effective for norflox...Semiconductor photocatalysis can be operated over a narrow pH range for wastewater treatment. In this study, a simulated solar-light-mediated bismuth tungstate (SSL/Bi2WO6) process is found to be effective for norfloxacin degradation over a narrow pH range. To broaden the operating pH range of the SSL/Bi2WO6 process, an NH4+ buffer system and an Fe3+ salt were introduced under extremely basic and acidic pH conditions, respectively. The NH4+ buffer system continuously supplied hydroxyl ions to generate ·OH radicals and prevented acidification of the solution, resulting in improved norfloxacin removal and mineralization removal under alkaline conditions. In contrast, the Fe3+ salt offered an additional homogeneous photo-sensitization pathway. The former treatment assisted in norfloxacin decay and the latter increased the collision frequency between the photo-generated hole and hydroxyl ions. Moreover, the effect of parameters such as pH and Fe3+ dosage was optimized.展开更多
The inhomogeneous broadening parameter and the internal loss of green LDs are determined by experiments and theoretical fitting. It is found that the inhomogeneous broadening plays an important role on the threshold c...The inhomogeneous broadening parameter and the internal loss of green LDs are determined by experiments and theoretical fitting. It is found that the inhomogeneous broadening plays an important role on the threshold current density of green LDs. The green LD with large inhomogeneous broadening even cannot lase. Therefore, reducing inhomogeneous broadening is a key issue to improve the performance of green LDs.展开更多
To carry out accurate burnup calculations for a pebble-bed fluoride-salt-cooled high-temperature reactor,the energy-dependent cross-sectional model based on the Doppler broadening rejection correction method has been ...To carry out accurate burnup calculations for a pebble-bed fluoride-salt-cooled high-temperature reactor,the energy-dependent cross-sectional model based on the Doppler broadening rejection correction method has been proposed to develop the energy-dependent elastic scattering cross-sectional model. In this study, the Monte Carlo continuous energy code PSG2/Serpent was used to examine the difference between the constant cross-sectional model and the energy-dependent cross-sectional model during burnup. For the cases analyzed in this study,numerical simulations show that the multiplication coefficient was improved by hundreds pcm and ^(239)Pu concentration was improved by approximately 1–2% during burnup when the energy-dependent elastic scattering crosssectional model is considered.展开更多
We have studied the effect of the spontaneously generated coherence （SGC） on gain of lasing without inversion （LWI） in a closed three-level A-type atomic system with Doppler broadening. It is shown that, regardles...We have studied the effect of the spontaneously generated coherence （SGC） on gain of lasing without inversion （LWI） in a closed three-level A-type atomic system with Doppler broadening. It is shown that, regardless of the driving and probe fields being co- or counter-propagating, at a suitable value of the Doppler width, we can obtain a much larger LWI gain with SGC than that without SGC; and the region of the LWI gain spectrum with SGC is obviously larger than that without SGC. When the Doppler width takes a constant value, the gain does not monotonically decrease or increase with increasing strength of SGC, the largest LWI gain can be obtained by adjusting strength of SGC. Generally speaking, the co-propagating probe and driving fields is favourable to obtain a larger LWI gain.展开更多
ZnS thin films were prepared by sulfuring zinc thin films at different sulfuration temperatures.The crystal structure,surface morphology,defects,and optical properties of the thin films were characterized by x-ray dif...ZnS thin films were prepared by sulfuring zinc thin films at different sulfuration temperatures.The crystal structure,surface morphology,defects,and optical properties of the thin films were characterized by x-ray diffraction(XRD),scanning electron microscopy(SEM),positron annihilation Doppler broadening,and UV-Vis spectrophotometer,respectively.It was found that the(200)-plane preferred orientation of the ZnS thin films changed to(111)-plane with increasing sulfidation temperature.Moreover,a number of large holes were generated at 420?C and eliminated at 440?C.The concentration of defects was lowest when the sulfuration temperature was 440?C.The optical transmission of all samples was maintained at 60%–80%in the wavelength range of 400 nm–800 nm,and the band energy of the ZnS thin films was approximately3.5 e V for all treatment temperatures except 430?C.展开更多
We theoretically study the nonlinear compression of a 20-rnJ, 1030-nm picosecond chirped pulse from the thin-disk amplifier in a krypton gas-filled hollow-core fiber. The chirp from the thin-disk amplifier system has ...We theoretically study the nonlinear compression of a 20-rnJ, 1030-nm picosecond chirped pulse from the thin-disk amplifier in a krypton gas-filled hollow-core fiber. The chirp from the thin-disk amplifier system has little influence on the initial pulse, however, it shows an effect on the nonlinear compression in hollow-core fiber. We use a large diameter hollow waveguide to restrict undesirable nonlinear effects such as ionization; on the other hand, we employ suitable gas pressure and fiber length to promise enough spectral broadening; with 600-μm, 6-bar (1 bar = 105 Pa), 1.8-m hollow fiber, we obtain 31.5-fs pulse. Moreover, we calculate and discuss the optimal fiber lengths and gas pressures with different initial durations induced by different grating compression angles for reaching a given bandwidth. These results are meaningful for a compression scheme from picoseconds to femtoseconds.展开更多
Emission spectra of a semiconductor bridge （SCB） plasma in a visible range was studied in air. The electron density was measured in a conventional way from the broadening of the Al Ⅰ 394.4 nm Stark width. Based on ...Emission spectra of a semiconductor bridge （SCB） plasma in a visible range was studied in air. The electron density was measured in a conventional way from the broadening of the Al Ⅰ 394.4 nm Stark width. Based on the Saha equation, a system for recording the intensity of Si Ⅰ 390.5 nm and Si Ⅱ 413.1 nm was designed. With this technique, the SCB plasma electron density was measured well and accurately. Moreover, the electron density distribution Vs time was acquired from one SCB discharge. The individual result from the broadening of the Al Ⅰ 394.4 nm Stark width and Saha equation was all in the range of 1015 cm^-3 to 1016 cm^-3. Finally the presumption of the local thermodynamic equilibrium （LTE） condition was validated.展开更多
An Autler-Townes（AT） spectroscopy based on phase conjugate six-wave mixing（SWM） is proposed to detect AT doublet of high-lying state in a Doppler-broadened cascade four-level system.It is found that the SWM spectr...An Autler-Townes（AT） spectroscopy based on phase conjugate six-wave mixing（SWM） is proposed to detect AT doublet of high-lying state in a Doppler-broadened cascade four-level system.It is found that the SWM spectrum is dependent strongly on the ratios between the magnitudes of the wave vectors.We discuss how the Doppler broadening affects the SWM spectrum from a time-domain viewpoint and find that,due the atomic motion,the atomic polarizations acquire different phases for atoms with different velocities as time evolves.The Doppler free SWM spectrum can be obtained only when the atomic polarization can be rephasing again at certain time after the interactions of all the incident fields.展开更多
Spectroscopic properties of flashlamp pumped Nd^3＋：YAG laser are studied as a function of temperature in a range from-30℃ to 60℃. The spectral width and shift of quasi three-level 946.0-nm inter-Stark emission wit...Spectroscopic properties of flashlamp pumped Nd^3＋：YAG laser are studied as a function of temperature in a range from-30℃ to 60℃. The spectral width and shift of quasi three-level 946.0-nm inter-Stark emission within the respective intermanifold transitions of ^4F3/2→^4I9/2are investigated. The 946.0-nm line shifts toward the shorter wavelength and broadens. In addition, the threshold power and slope efficiency of the 946.0-nm laser line are quantified with temperature.The lower the temperature, the lower the threshold power is and the higher the slope efficiency of the 946.0-nm laser line is,thus the higher the laser output is. This phenomenon is attributed to the ion-phonon interaction and the thermal population in the ground state.展开更多
We report spectroscopic studies on plasma electron number density of laser-induced plasma produced by ns-Nd：YAG laser light pulses on an aluminum sample in air at atmospheric pressure. The effect of different laser e...We report spectroscopic studies on plasma electron number density of laser-induced plasma produced by ns-Nd：YAG laser light pulses on an aluminum sample in air at atmospheric pressure. The effect of different laser energy and the effect of different laser wavelengths were compared. The experimentally observed line profiles of neutral aluminum have been used to extract the excitation temperature using the Boltzmann plot method, whereas the electron number density has been determined from the Stark broadened as well as using the Saha-Boltzmann equation （SBE）. Each approach was also carried out by using the AI emission line and Mg emission lines. It was observed that the,SBE method generated a little higher electron number density value than the Stark broadening, method, but within the experimental uncertainty range. Comparisons of Ne determined by the two methods show the presence of a linear relation which is independent of laser energy or laser wavelength. These results show the applicability of the SBE method for Are determination, especially when the system does not have any pure emission lines whose electron impact factor is known, Also use of Mg lines gives superior results than Al lines.展开更多
On-the-fly Doppler broadening of cross sections is important in Monte Carlo simulations,particularly in Monte Carlo neutronics-thermal hydraulics coupling simulations.Methods such as Target Motion Sampling(TMS)and win...On-the-fly Doppler broadening of cross sections is important in Monte Carlo simulations,particularly in Monte Carlo neutronics-thermal hydraulics coupling simulations.Methods such as Target Motion Sampling(TMS)and windowed multipole as well as a method based on regression models have been developed to solve this problem.However,these methods have limitations such as the need for a cross section in an ACE format at a given temperature or a limited application energy range.In this study,a new on-the-fly Doppler broadening method based on a Back Propagation(BP)neural network,called hybrid windowed networks(HWN),is proposed to resolve the resonance energy range.In the HWN method,the resolved resonance energy range is divided into windows to guarantee an even distribution of resonance peaks.BP networks with specially designed structures and training parameters are trained to evaluate the cross section at a base temperature and the broadening coefficient.The HWN method is implemented in the Reactor Monte Carlo(RMC)code,and the microscopic cross sections and macroscopic results are compared.The results show that the HWN method can reduce the memory requirement for cross-sectional data by approximately 65%;moreover,it can generate keff,power distribution,and energy spectrum results with acceptable accuracy and a limited increase in the calculation time.The feasibility and effectiveness of the proposed HWN method are thus demonstrated.展开更多
The signal-to-noise ratio （SNR） of seismic reflection data in many areas is rather poor and conventional two-dimensional filters designed to suppress noise with different moveout from the signal tend to generate art...The signal-to-noise ratio （SNR） of seismic reflection data in many areas is rather poor and conventional two-dimensional filters designed to suppress noise with different moveout from the signal tend to generate artifacts. We have extended a method of multichannel filtering, based on the hypothesis that signals on adjacent channels are similar, for enhancing the SNR on stacked sections. Using only the mid-range frequencies where the SNR is highest, the event trend is found for overlapping windows on the section and the average signal vector is calculated. Then the data from the full bandwidth section are projected onto the spatially varying unit similarity vectors and the results are merged for the overlapping windows. Application of the method to synthetic data containing steeply dipping events and to a stacked section for a marine 2D line has produced good results. The modifications we have introduced carry a small overhead in computing time but they should enable the method to be used effectively even on sections containing steep dips.展开更多
文摘From March 19 to 27,four outstanding young people from Chengdu went on a trip to Perth,Australia,as the winners of the Perth Professional Development and Internship Competition,an innovative campaign for Chengdu and its sister city Perth,which has had fruitful student exchanges.The competition was designed to select four
文摘英语作文习作范例点评写怍第一节Dear Jenny,I really like the idea of adding a new column to our English newspaper.In my opinion.I prefer the"Fun at my school"column.The reasons why I choose it are as follows.First of all,this column can enhance students'comprehension,through which,the bonds between students and school can be strengthened.What's more,this column not only broadens students horizons,but also adds color to school life.Last butnot least.it can relieve stress.which benefits menta!health.
文摘Fish are the oldest and most diverse vertebrates on the planet,living in waters around the world,and are very important for maintaining ecological balance,as well as providing rich food resources for human beings.Perhaps as far as common people are concerned,fish can be divided into two kinds,edible and non-edible.In fact,there are more than 20,000 fish species in the world,some of which are highly skilled and make people broaden their horizons.
基金financially supported by the National Natural Science Foundation of China(Nos.22435005,22193042,21921001,52202194,22305105,22201284)the Key Research Program of Frontier Sciences of the Chinese Academy of Sciences(No.ZDBSLY-SLH024)。
文摘Two-dimensional(2D)organic-inorganic hybrid perovskites(OIHPs)have been developed as promising candidates for photodetection,owing to their excellent semiconducting features and structural tunability.However,as an important parameter for photodetection,the photoresponsive range of 2D OIHPs is usually modulated by finite metal-halide combinations,constraining their further development.The emerging aromatic amine-based alternating-cations-interlayered(A-ACI)hybrid perovskites that exhibit excellent charge transport and additional interlayered structural designability,provide an extra solution for achieving ideal photoresponsive range.Herein,for the first time,the photoresponsive range is successfully broadened in A-ACI hybrid perovskites(NMA)_(4)(FA)_(2)Pb_(3)Br_(12)(2)remolding from(NMA)_(4)(MA)_(2)Pb_(3)Br_(12)(1)(NMA=N-methylbenzylaminium,FA=formamidinium and MA=methylammonium).Particularly,1 and 2adopt an unprecedented configuration that NMA and MA/FA are alternately arranged in the interlayer in a 4:2 manner.Importantly,2 exhibits a narrower bandgap than 1,which can be ascribed to the lowlying conduct band composed of intercalation FAπ*orbitals.Meanwhile,2 possesses a shorter interlayer distance and flatter inorganic skeleton,synergistically facilitating the wider photo-absorption range and further endowing a broadening photoresponsive range(70 nm).This research not only enriches the perovskite family but also provides insights into structure-property relationships.
基金supported by the National Natural Science Foundation of China(No.41804141)。
文摘Energy resolution calibration is crucial for gamma-ray spectral analysis,as measured using a scintillation detector.A locally constrained regularization method was proposed to determine the resolution calibration parameters.First,a Monte Carlo simulation model consistent with an actual measurement system was constructed to obtain the energy deposition distribution in the scintillation crystal.Subsequently,the regularization objective function is established based on weighted least squares and additional constraints.Additional constraints were designed using a special weighting scheme based on the incident gamma-ray energies.Subsequently,an intelligent algorithm was introduced to search for the optimal resolution calibration parameters by minimizing the objective function.The most appropriate regularization parameter was determined through mathematical experiments.When the regularization parameter was 30,the calibrated results exhibited the minimum RMSE.Simulations and test pit experiments were conducted to verify the performance of the proposed method.The simulation results demonstrate that the proposed algorithm can determine resolution calibration parameters more accurately than the traditional weighted least squares,and the test pit experimental results show that the R-squares between the calibrated and measured spectra are larger than 0.99.The accurate resolution calibration parameters determined by the proposed method lay the foundation for gamma-ray spectral processing and simulation benchmarking.
基金supported by the National Natural Science Foundation of China(Grant Nos.12125504 and 12305050)the National Key R&D Program of China(Grant No.2022YFA1404400)+2 种基金the Hundred Talents Program of the Chinese Academy of Sciences,the Natural Science Foundation of Jiangsu Higher Education Institutions of China(Grant No.23KJB140017)the Opening Project of Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology(Grant No.Ammt2023B-1)the Guangdong University of Technology SPOE Seed Foundation(Grant No.SF2024111502).
文摘We propose a near-field thermophotovoltaic system utilizing magnetic Weyl semimetals,which exhibit a distinct gyrotropic effect originating from their intrinsic axion field.Critically,we demonstrate that intentional band dislocation,achieved by layer-specific tuning of the chemical potential,significantly enhances the energyconversion efficiency.This effect arises from the formation of quasi-flat bands in momentum space,which broaden the spectral heat flux and amplify photon tunneling above the bandgap.At optimized chemical potential mismatches,the system achieves a 65%Carnot efficiency and a power density of 7×10^(4)W·m^(-2),surpassing symmetric configurations by 7%.The optimization of the Weyl semimetals thickness further demonstrates a clear tuning window where both the output power and energy-conversion efficiency are significantly improved.These results establish chemical-potential engineering toward high-efficiency near-field thermophotovoltaics for waste heat recovery and infrared energy applications.
文摘China will enter WTO in the near future. The great shock to uncompleted reform and excessive protection firstly means challenges and opportunities. The way to deal with this situation is to regard entering WTO as the second reform and open. By upholding opening - door policy, we can stride forward towards internationalization and really merge into world market. By expending the reform, we can actively push forward marketization, and further improve system of enterprise, market construction and governmetnt’s function. All industries should take different strategies and pay much attention to improving core technology and international competitiveness.
基金supported by the National Science Foundation of China(41877481,41503102)the open project of the State Key Laboratory of Loess and Quaternary Geology,Institute of Earth Environment,Chinese Academy of Science(SKLLQG1729)+2 种基金the China Postdoctoral Science Foundation(2018M643669)the Fundamental Research Funds for the Central Universities(2018249)the "Hundred Talent Program" of the Chinese Academy of Sciences~~
文摘Semiconductor photocatalysis can be operated over a narrow pH range for wastewater treatment. In this study, a simulated solar-light-mediated bismuth tungstate (SSL/Bi2WO6) process is found to be effective for norfloxacin degradation over a narrow pH range. To broaden the operating pH range of the SSL/Bi2WO6 process, an NH4+ buffer system and an Fe3+ salt were introduced under extremely basic and acidic pH conditions, respectively. The NH4+ buffer system continuously supplied hydroxyl ions to generate ·OH radicals and prevented acidification of the solution, resulting in improved norfloxacin removal and mineralization removal under alkaline conditions. In contrast, the Fe3+ salt offered an additional homogeneous photo-sensitization pathway. The former treatment assisted in norfloxacin decay and the latter increased the collision frequency between the photo-generated hole and hydroxyl ions. Moreover, the effect of parameters such as pH and Fe3+ dosage was optimized.
基金supported by the National Key Research and Development Program of China(Grant Nos.2017YFB0405000,2016YFB0401803)the National Natural Science Foundation of China(Grant Nos.61834008,61574160,and 61704184)support of the Chinese Academy of Science Visiting Professorship for Senior International Scientists (Grant No.2013T2J0048)
文摘The inhomogeneous broadening parameter and the internal loss of green LDs are determined by experiments and theoretical fitting. It is found that the inhomogeneous broadening plays an important role on the threshold current density of green LDs. The green LD with large inhomogeneous broadening even cannot lase. Therefore, reducing inhomogeneous broadening is a key issue to improve the performance of green LDs.
基金supported by the National Natural Science Foundation of China(Nos.11675057 and 11705195)the Hunan Provincial Education Department Project of China(No.15C1176)the General Financial Grant from the China Postdoctoral Science Foundation(No.2017M622697)
文摘To carry out accurate burnup calculations for a pebble-bed fluoride-salt-cooled high-temperature reactor,the energy-dependent cross-sectional model based on the Doppler broadening rejection correction method has been proposed to develop the energy-dependent elastic scattering cross-sectional model. In this study, the Monte Carlo continuous energy code PSG2/Serpent was used to examine the difference between the constant cross-sectional model and the energy-dependent cross-sectional model during burnup. For the cases analyzed in this study,numerical simulations show that the multiplication coefficient was improved by hundreds pcm and ^(239)Pu concentration was improved by approximately 1–2% during burnup when the energy-dependent elastic scattering crosssectional model is considered.
基金Project supported by the National Natural Science Foundation of China （Grant No 10675076）, the Natural Science Foundation of Shandong Province, China （Grant No Y2006A21） and the State Key Laboratory of High Field Laser Physics, Shanghai Institute of 0ptics and Fine Mechanics, Chinese Academy of Sciences.
文摘We have studied the effect of the spontaneously generated coherence （SGC） on gain of lasing without inversion （LWI） in a closed three-level A-type atomic system with Doppler broadening. It is shown that, regardless of the driving and probe fields being co- or counter-propagating, at a suitable value of the Doppler width, we can obtain a much larger LWI gain with SGC than that without SGC; and the region of the LWI gain spectrum with SGC is obviously larger than that without SGC. When the Doppler width takes a constant value, the gain does not monotonically decrease or increase with increasing strength of SGC, the largest LWI gain can be obtained by adjusting strength of SGC. Generally speaking, the co-propagating probe and driving fields is favourable to obtain a larger LWI gain.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11705212 and 11675188)
文摘ZnS thin films were prepared by sulfuring zinc thin films at different sulfuration temperatures.The crystal structure,surface morphology,defects,and optical properties of the thin films were characterized by x-ray diffraction(XRD),scanning electron microscopy(SEM),positron annihilation Doppler broadening,and UV-Vis spectrophotometer,respectively.It was found that the(200)-plane preferred orientation of the ZnS thin films changed to(111)-plane with increasing sulfidation temperature.Moreover,a number of large holes were generated at 420?C and eliminated at 440?C.The concentration of defects was lowest when the sulfuration temperature was 440?C.The optical transmission of all samples was maintained at 60%–80%in the wavelength range of 400 nm–800 nm,and the band energy of the ZnS thin films was approximately3.5 e V for all treatment temperatures except 430?C.
基金Project supported by the National Basic Research Program of China(Grant No.2011CB808101)the Funds from the Chinese Academy of Sciences,and the National Natural Science Foundation of China(Grant Nos.11127901,10734080,61221064,60908008,and 61078037)
文摘We theoretically study the nonlinear compression of a 20-rnJ, 1030-nm picosecond chirped pulse from the thin-disk amplifier in a krypton gas-filled hollow-core fiber. The chirp from the thin-disk amplifier system has little influence on the initial pulse, however, it shows an effect on the nonlinear compression in hollow-core fiber. We use a large diameter hollow waveguide to restrict undesirable nonlinear effects such as ionization; on the other hand, we employ suitable gas pressure and fiber length to promise enough spectral broadening; with 600-μm, 6-bar (1 bar = 105 Pa), 1.8-m hollow fiber, we obtain 31.5-fs pulse. Moreover, we calculate and discuss the optimal fiber lengths and gas pressures with different initial durations induced by different grating compression angles for reaching a given bandwidth. These results are meaningful for a compression scheme from picoseconds to femtoseconds.
基金supported by National Major Base Projects of China
文摘Emission spectra of a semiconductor bridge （SCB） plasma in a visible range was studied in air. The electron density was measured in a conventional way from the broadening of the Al Ⅰ 394.4 nm Stark width. Based on the Saha equation, a system for recording the intensity of Si Ⅰ 390.5 nm and Si Ⅱ 413.1 nm was designed. With this technique, the SCB plasma electron density was measured well and accurately. Moreover, the electron density distribution Vs time was acquired from one SCB discharge. The individual result from the broadening of the Al Ⅰ 394.4 nm Stark width and Saha equation was all in the range of 1015 cm^-3 to 1016 cm^-3. Finally the presumption of the local thermodynamic equilibrium （LTE） condition was validated.
基金Project supported by the National Basic Research Program of China(Grant No.2013CB922002)the National Natural Science Foundation of China(Grant Nos.11274376 and 61308011)the National High Technology Research and Development Program of China(Grant No.2011AA120102)
文摘An Autler-Townes（AT） spectroscopy based on phase conjugate six-wave mixing（SWM） is proposed to detect AT doublet of high-lying state in a Doppler-broadened cascade four-level system.It is found that the SWM spectrum is dependent strongly on the ratios between the magnitudes of the wave vectors.We discuss how the Doppler broadening affects the SWM spectrum from a time-domain viewpoint and find that,due the atomic motion,the atomic polarizations acquire different phases for atoms with different velocities as time evolves.The Doppler free SWM spectrum can be obtained only when the atomic polarization can be rephasing again at certain time after the interactions of all the incident fields.
基金Project supported by Estahban Branch,Islamic Azad University
文摘Spectroscopic properties of flashlamp pumped Nd^3＋：YAG laser are studied as a function of temperature in a range from-30℃ to 60℃. The spectral width and shift of quasi three-level 946.0-nm inter-Stark emission within the respective intermanifold transitions of ^4F3/2→^4I9/2are investigated. The 946.0-nm line shifts toward the shorter wavelength and broadens. In addition, the threshold power and slope efficiency of the 946.0-nm laser line are quantified with temperature.The lower the temperature, the lower the threshold power is and the higher the slope efficiency of the 946.0-nm laser line is,thus the higher the laser output is. This phenomenon is attributed to the ion-phonon interaction and the thermal population in the ground state.
文摘We report spectroscopic studies on plasma electron number density of laser-induced plasma produced by ns-Nd：YAG laser light pulses on an aluminum sample in air at atmospheric pressure. The effect of different laser energy and the effect of different laser wavelengths were compared. The experimentally observed line profiles of neutral aluminum have been used to extract the excitation temperature using the Boltzmann plot method, whereas the electron number density has been determined from the Stark broadened as well as using the Saha-Boltzmann equation （SBE）. Each approach was also carried out by using the AI emission line and Mg emission lines. It was observed that the,SBE method generated a little higher electron number density value than the Stark broadening, method, but within the experimental uncertainty range. Comparisons of Ne determined by the two methods show the presence of a linear relation which is independent of laser energy or laser wavelength. These results show the applicability of the SBE method for Are determination, especially when the system does not have any pure emission lines whose electron impact factor is known, Also use of Mg lines gives superior results than Al lines.
基金supported by the Science Challenge Project(No.TZ2018001)the National Natural Science Foundation of China(Nos.11775126,11545013,11775127)+1 种基金Young Elite Scientists Sponsorship Program by CAST(No.2016QNRC001)Tsinghua University Initiative Scientific Research Program。
文摘On-the-fly Doppler broadening of cross sections is important in Monte Carlo simulations,particularly in Monte Carlo neutronics-thermal hydraulics coupling simulations.Methods such as Target Motion Sampling(TMS)and windowed multipole as well as a method based on regression models have been developed to solve this problem.However,these methods have limitations such as the need for a cross section in an ACE format at a given temperature or a limited application energy range.In this study,a new on-the-fly Doppler broadening method based on a Back Propagation(BP)neural network,called hybrid windowed networks(HWN),is proposed to resolve the resonance energy range.In the HWN method,the resolved resonance energy range is divided into windows to guarantee an even distribution of resonance peaks.BP networks with specially designed structures and training parameters are trained to evaluate the cross section at a base temperature and the broadening coefficient.The HWN method is implemented in the Reactor Monte Carlo(RMC)code,and the microscopic cross sections and macroscopic results are compared.The results show that the HWN method can reduce the memory requirement for cross-sectional data by approximately 65%;moreover,it can generate keff,power distribution,and energy spectrum results with acceptable accuracy and a limited increase in the calculation time.The feasibility and effectiveness of the proposed HWN method are thus demonstrated.
文摘The signal-to-noise ratio （SNR） of seismic reflection data in many areas is rather poor and conventional two-dimensional filters designed to suppress noise with different moveout from the signal tend to generate artifacts. We have extended a method of multichannel filtering, based on the hypothesis that signals on adjacent channels are similar, for enhancing the SNR on stacked sections. Using only the mid-range frequencies where the SNR is highest, the event trend is found for overlapping windows on the section and the average signal vector is calculated. Then the data from the full bandwidth section are projected onto the spatially varying unit similarity vectors and the results are merged for the overlapping windows. Application of the method to synthetic data containing steeply dipping events and to a stacked section for a marine 2D line has produced good results. The modifications we have introduced carry a small overhead in computing time but they should enable the method to be used effectively even on sections containing steep dips.
