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
Pulse echo accumulation is commonly employed in coherent Doppler wind LiDAR(light detection and ranging)under the assumption of steady wind.Here,the measured spectral data are analyzed in the time dimension and freque...Pulse echo accumulation is commonly employed in coherent Doppler wind LiDAR(light detection and ranging)under the assumption of steady wind.Here,the measured spectral data are analyzed in the time dimension and frequency dimension to cope with the temporal wind shear and achieve the optimal accumulation time.A hardware-efficient algorithm combining the interpolation and cross-correlation is used to enhance the wind retrieval accuracy by reducing the frequency sampling interval and then reduce the spectral width calculation error.Moreover,the temporal broadening effect and spatial broadening effect are decoupled according to the strategy we developed.展开更多
We present a high-resolution study on the B^(2)Π-X^(2)Πelectronic origin band spectrum of the C_(6)H radical with its center at~18990 cm^(-1).The C_(6)H radicals are produced in a pulsed supersonic slit-jet discharg...We present a high-resolution study on the B^(2)Π-X^(2)Πelectronic origin band spectrum of the C_(6)H radical with its center at~18990 cm^(-1).The C_(6)H radicals are produced in a pulsed supersonic slit-jet discharge source and detected in direct absorption by sensitive cavity ring-down spectroscopy.By using a home-made narrow linewidth nanosecond pulsed laser source,the experimental spectrum allows to resolve the A-type doublet fine structures in high-J rotational lines.A set of improved B21I state constants,including the Atype doubling parameters of p'=-1.16(9)×10^(-3)cm^(-1),Q=-1.22(7)×10^(-4)cm^(-1),are determined from analysis of the experimental spectrum.An analysis on the spectral line profile has resulted in a significant linwidth broadening of-0.05±0.01 cm^(-1),corresponding to a B^(2)Πtatelife time of~100+20 ps.The short lifetime of the excited B^(2)Πstate is proposed due to fast internal vibronic couplings to high-lying vibronic levels of lower electronic states.展开更多
This work reports pressure-broadening line-wing and line-core of the lithium Li(2p←2s)resonance line perturbed by ground sodium Na(3s)atoms.In far-wing regions,the calculations are performed quantum-mechanically and ...This work reports pressure-broadening line-wing and line-core of the lithium Li(2p←2s)resonance line perturbed by ground sodium Na(3s)atoms.In far-wing regions,the calculations are performed quantum-mechanically and are intended to examine the photoabsorption coefficients at diverse temperatures.The results show the existence of three satellites,in the blue wing near the wavelengths 470 nm and in the red wing around 862 nm and 1070 nm.For the line-core region,by adopting the simplified Baranger model,the line-width and line-shift rates are determined,and their variation law with temperature is examined.No published data were found to compare these results with.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
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
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
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
A 3D viscoelastic-plastic thermal-mechanical coupled finite element model was built on the basis of the secondary development of the commercial software MSC.Marc. Numerical simulations were performed to study slab bro...A 3D viscoelastic-plastic thermal-mechanical coupled finite element model was built on the basis of the secondary development of the commercial software MSC.Marc. Numerical simulations were performed to study slab broadening in the secondary cooling zone. The effects of slab width and thickness on slab broadening were considered. The obtained results reveal that the width broadening is noticeable, and the ratio of ultimate broadening slightly increases with the increase of slab width. This agrees well with the measured data in practice. There is no obvious increase in ultimate broadening when the thickness of slabs increases.展开更多
In order to check the general existence of broadening of slab and the reasons of formation,the broadening of slab was investigated on the basis of several industrial manufactures of continuous casting.The results show...In order to check the general existence of broadening of slab and the reasons of formation,the broadening of slab was investigated on the basis of several industrial manufactures of continuous casting.The results show that slab broadening commonly exists in the process of continuous casting.The causes of broadening were ruled out of the consideration of the change of mold size or the change of technical parameters.The results reveal that the broadening of slab probably results from the static pressure of molten steel and the force from driving rolls.At the same time,online observations of three grades of steel in the process of continuous casting reveal that the ratio of ultimate broadening of slab ranges from 1.27% to 3.00%,and even arrives at 4.4%.展开更多
Full quantum calculations are performed to investigate the broadening profiles of the atomic lithium Li（2s-2p） resonance line induced by interactions with ground Ne（2s^22p^6） perturbers in the spectral wings and c...Full quantum calculations are performed to investigate the broadening profiles of the atomic lithium Li（2s-2p） resonance line induced by interactions with ground Ne（2s^22p^6） perturbers in the spectral wings and core. The X^2Σ~＋, A^2Π,and B^2Σ~＋ potential-energy curves of the two first low lying Li Ne molecular states, as well as the corresponding transition dipole moments, are determined with ab initio methods based on the SA-CASSCF-MRCI calculations. The emission and absorption coefficients in the wavelength range 550-800 nm and the line-core width and shift are investigated theoretically for temperatures ranging from 130 K to 3000 K. Their temperature dependence is analyzed, and the obtained results are compared with the previous experimental measurements and theoretical works.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
This paper studies the propagation effect in a closed lambda-type three-level atomic system with Doppler broadening. It is shown that, Doppler broadening due to atomic motion and propagation effect associated with dri...This paper studies the propagation effect in a closed lambda-type three-level atomic system with Doppler broadening. It is shown that, Doppler broadening due to atomic motion and propagation effect associated with driving field depletion along the active medium decreases obviously the gain and output of the lasing without inversion （LWI）; the relative phase between the probe and driving fields has a remarkable modulation role to the propagation effect on LWI when Doppler broadening presents; by choosing suitable value of the relative phase, we can get the largest gain and output of LWI.展开更多
In this paper we study influences of Doppler broadening, spontaneously generated coherence, and other system parameters on propagation effect in a quasi lambda-type four-level atomic system. It is shown that when the ...In this paper we study influences of Doppler broadening, spontaneously generated coherence, and other system parameters on propagation effect in a quasi lambda-type four-level atomic system. It is shown that when the Doppler broadening is present, generally speaking, the values of gain and intensity of lasing without inversion （i.e. the probe field） in the co-propagating probe and driving fields case are much larger than those in the counter-propagating case; considerably larger gain and intensity of lasing without inversion than those without the Doppler broadening can be obtained by choosing appropriate values of the Doppler broadening width and spontaneously generated coherence strength. The gain and intensity of lasing without inversion increase with the increase of spontaneously generated coherence strength; when spontaneously generated coherence is present, much larger gain and intensity of lasing without inversion than those in the case without spontaneously generated coherence can be obtained. Choosing suitable values of the probe detuning, Rabi frequencies of the driving and pump fields at the entrance of the medium also can remarkably enhance the gain and intensity of lasing without inversion.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
Determination of both the electron density and temperature simultaneously in a cold argon arc-plasma jet by analyzing the Stark broadening of two different emission lines is presented. This method is based on the fact...Determination of both the electron density and temperature simultaneously in a cold argon arc-plasma jet by analyzing the Stark broadening of two different emission lines is presented. This method is based on the fact that the Stark broadening of different lines has a different dependence on the electron density and temperature. Therefore, a comparison of two or more line broadenings allows us to diagnose the electron density and temperature simultaneously. In this study we used the first two Balmer series hydrogen lines Ha and Ha for their large broadening width. For this purpose, a small amount of hydrogen was introduced into the discharge gas. The results of the Gigosos-Cardenoso computational model, considering more relevant processes for the hydrogen Balmer lines, is used to process the experimental data. With this method, we obtained reliable electron density and temperature, 1.88 × 1015 cm^-3 and 13000 K, respectively. Possible sources of error were also analyzed.展开更多
The electron density within the volume of the tungsten divertor of the Experimental Advanced Superconducting Tokamak （EAST） is calculated based on Dε line （396.9 nm） Stark broadening （SB） measurements. The quas...The electron density within the volume of the tungsten divertor of the Experimental Advanced Superconducting Tokamak （EAST） is calculated based on Dε line （396.9 nm） Stark broadening （SB） measurements. The quasistatic approximation is employed in the SB calculation of the Dε line. The influences of other broadening mechanisms on the calculation error of electron density have been evaluated. The SB method is applied to the study of spatial distribution and time evolution of the electron density in the W divertor. Two electron density bands are observed in the detached divertor plasma during an L-mode discharge sustained by low hybrid wave （LHW） heating, which could be related to the striated particle flux distribution induced by LHW. After the onset of detachment, the upper electron density band corresponding to outer strike point firstly increases then decreases, while the lower density band corresponding to striated particle flux increases continually although the electron densities from Langmuir Probes at the divertor plate keep a descending trend. This could indicate a downward movement of the radiation region that approximately moves along the magnetic field lines after the onset of detachment.展开更多
In this article we will present an attempt to measure the Stark broadening parameter of the Zn I-line at 636.23 nm utilizing the optical emission spectroscopy (OES) technique, taking into consideration the possibility...In this article we will present an attempt to measure the Stark broadening parameter of the Zn I-line at 636.23 nm utilizing the optical emission spectroscopy (OES) technique, taking into consideration the possibility of existence of self absorption. This method is standing on comparison of the Lorentzian FWHM and spectral line intensity of the unknown Stark broadening parameter line (Zn I-636.23 nm—in our case) to a well known Stark parameter line (e.g. Zn I-lines at 472.2, 481 and 468 nm) at a reference electron density of 2.7 × 1017 cm-3 and temperature of 1 eV. We have utilized the emission spectral data acquired from well diagnosed plasma produced by the interaction of Nd: YAG laser at wavelength of 1064 nm with ZnO nanomaterial target in open air. The results indicates that the Stark broadening of the Zn I-line at 636.23 nm is centered at 5.06 ± 0.03 ? with a 25% uncertainty at the given reference plasma parameters. The knowledge of the Stark broadening parameter of the 636.23 nm line may be important in the diagnostics of the laser plasma experiments especially in the absence of the Hα-line.展开更多
Full quantum mechanical calculations are performed to determine the broadening in the far wings of the cesium D1 and D2 line shapes arising from elastic collisions of Cs atom with inert helium atoms. The potential ene...Full quantum mechanical calculations are performed to determine the broadening in the far wings of the cesium D1 and D2 line shapes arising from elastic collisions of Cs atom with inert helium atoms. The potential energy curves of the low-lying CsHe molecular states, as well as the related transition dipole moments, are carefully computed from ab initio methods based on state-averaged complete active space self-consistent field-multireference configuration interaction(SACASSCF-MRCI) calculations, involving the spin-orbit effect, and taking into account the Davidson and BSSE corrections.The absorption and emission reduced coefficients are determined in the temperature and wavelength ranges of 323-3000 K and 800-1000 nm, respectively. Both profiles of the absorption and the emission are dominated by the free-free transitions,and exhibit a satellite peak in the blue wing near the wavelength 825 nm, attributed to B^2Σ1/2^+→ X^2Σ1/2^+/transitions. The results are in good agreement with previous experimental and theoretical works.展开更多
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Project supported by the Shanghai Science and Technology Innovation Action(Grant No.22dz1208700).
文摘Pulse echo accumulation is commonly employed in coherent Doppler wind LiDAR(light detection and ranging)under the assumption of steady wind.Here,the measured spectral data are analyzed in the time dimension and frequency dimension to cope with the temporal wind shear and achieve the optimal accumulation time.A hardware-efficient algorithm combining the interpolation and cross-correlation is used to enhance the wind retrieval accuracy by reducing the frequency sampling interval and then reduce the spectral width calculation error.Moreover,the temporal broadening effect and spatial broadening effect are decoupled according to the strategy we developed.
基金supported by the National Natural Foundation of China(No.21827804,No.22103075,No.22173089)the National Key R&D Program of China(No.2021YFA0716801,No.2017YFA0303502)。
文摘We present a high-resolution study on the B^(2)Π-X^(2)Πelectronic origin band spectrum of the C_(6)H radical with its center at~18990 cm^(-1).The C_(6)H radicals are produced in a pulsed supersonic slit-jet discharge source and detected in direct absorption by sensitive cavity ring-down spectroscopy.By using a home-made narrow linewidth nanosecond pulsed laser source,the experimental spectrum allows to resolve the A-type doublet fine structures in high-J rotational lines.A set of improved B21I state constants,including the Atype doubling parameters of p'=-1.16(9)×10^(-3)cm^(-1),Q=-1.22(7)×10^(-4)cm^(-1),are determined from analysis of the experimental spectrum.An analysis on the spectral line profile has resulted in a significant linwidth broadening of-0.05±0.01 cm^(-1),corresponding to a B^(2)Πtatelife time of~100+20 ps.The short lifetime of the excited B^(2)Πstate is proposed due to fast internal vibronic couplings to high-lying vibronic levels of lower electronic states.
基金realized within the framework of the PNR project 8/423/4388support from the Algerian Ministry of Higher Education and ANDRU。
文摘This work reports pressure-broadening line-wing and line-core of the lithium Li(2p←2s)resonance line perturbed by ground sodium Na(3s)atoms.In far-wing regions,the calculations are performed quantum-mechanically and are intended to examine the photoabsorption coefficients at diverse temperatures.The results show the existence of three satellites,in the blue wing near the wavelengths 470 nm and in the red wing around 862 nm and 1070 nm.For the line-core region,by adopting the simplified Baranger model,the line-width and line-shift rates are determined,and their variation law with temperature is examined.No published data were found to compare these results with.
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 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 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 Key Projects in the National Science & Technology Pillar Program during the 11th Five-Year Plan Period of China (No.2006BAE03A04)
文摘A 3D viscoelastic-plastic thermal-mechanical coupled finite element model was built on the basis of the secondary development of the commercial software MSC.Marc. Numerical simulations were performed to study slab broadening in the secondary cooling zone. The effects of slab width and thickness on slab broadening were considered. The obtained results reveal that the width broadening is noticeable, and the ratio of ultimate broadening slightly increases with the increase of slab width. This agrees well with the measured data in practice. There is no obvious increase in ultimate broadening when the thickness of slabs increases.
基金Item Sponsored by National Science and Technology Support Program for 11th Five-Year Plan of China(2006BAE03A04)
文摘In order to check the general existence of broadening of slab and the reasons of formation,the broadening of slab was investigated on the basis of several industrial manufactures of continuous casting.The results show that slab broadening commonly exists in the process of continuous casting.The causes of broadening were ruled out of the consideration of the change of mold size or the change of technical parameters.The results reveal that the broadening of slab probably results from the static pressure of molten steel and the force from driving rolls.At the same time,online observations of three grades of steel in the process of continuous casting reveal that the ratio of ultimate broadening of slab ranges from 1.27% to 3.00%,and even arrives at 4.4%.
文摘Full quantum calculations are performed to investigate the broadening profiles of the atomic lithium Li（2s-2p） resonance line induced by interactions with ground Ne（2s^22p^6） perturbers in the spectral wings and core. The X^2Σ~＋, A^2Π,and B^2Σ~＋ potential-energy curves of the two first low lying Li Ne molecular states, as well as the corresponding transition dipole moments, are determined with ab initio methods based on the SA-CASSCF-MRCI calculations. The emission and absorption coefficients in the wavelength range 550-800 nm and the line-core width and shift are investigated theoretically for temperatures ranging from 130 K to 3000 K. Their temperature dependence is analyzed, and the obtained results are compared with the previous experimental measurements and theoretical works.
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.
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)
文摘This paper studies the propagation effect in a closed lambda-type three-level atomic system with Doppler broadening. It is shown that, Doppler broadening due to atomic motion and propagation effect associated with driving field depletion along the active medium decreases obviously the gain and output of the lasing without inversion （LWI）; the relative phase between the probe and driving fields has a remarkable modulation role to the propagation effect on LWI when Doppler broadening presents; by choosing suitable value of the relative phase, we can get the largest gain and output of LWI.
基金supported by the National Natural Science Foundation of China (Grant No.10875072)
文摘In this paper we study influences of Doppler broadening, spontaneously generated coherence, and other system parameters on propagation effect in a quasi lambda-type four-level atomic system. It is shown that when the Doppler broadening is present, generally speaking, the values of gain and intensity of lasing without inversion （i.e. the probe field） in the co-propagating probe and driving fields case are much larger than those in the counter-propagating case; considerably larger gain and intensity of lasing without inversion than those without the Doppler broadening can be obtained by choosing appropriate values of the Doppler broadening width and spontaneously generated coherence strength. The gain and intensity of lasing without inversion increase with the increase of spontaneously generated coherence strength; when spontaneously generated coherence is present, much larger gain and intensity of lasing without inversion than those in the case without spontaneously generated coherence can be obtained. Choosing suitable values of the probe detuning, Rabi frequencies of the driving and pump fields at the entrance of the medium also can remarkably enhance the gain and intensity of lasing without inversion.
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.
文摘Determination of both the electron density and temperature simultaneously in a cold argon arc-plasma jet by analyzing the Stark broadening of two different emission lines is presented. This method is based on the fact that the Stark broadening of different lines has a different dependence on the electron density and temperature. Therefore, a comparison of two or more line broadenings allows us to diagnose the electron density and temperature simultaneously. In this study we used the first two Balmer series hydrogen lines Ha and Ha for their large broadening width. For this purpose, a small amount of hydrogen was introduced into the discharge gas. The results of the Gigosos-Cardenoso computational model, considering more relevant processes for the hydrogen Balmer lines, is used to process the experimental data. With this method, we obtained reliable electron density and temperature, 1.88 × 1015 cm^-3 and 13000 K, respectively. Possible sources of error were also analyzed.
基金supported by National Key Research and Development Program of China (No. 2017YFA0402500)National Natural Science Foundation of China (Nos. 11575243, 11605238, and 11575242)
文摘The electron density within the volume of the tungsten divertor of the Experimental Advanced Superconducting Tokamak （EAST） is calculated based on Dε line （396.9 nm） Stark broadening （SB） measurements. The quasistatic approximation is employed in the SB calculation of the Dε line. The influences of other broadening mechanisms on the calculation error of electron density have been evaluated. The SB method is applied to the study of spatial distribution and time evolution of the electron density in the W divertor. Two electron density bands are observed in the detached divertor plasma during an L-mode discharge sustained by low hybrid wave （LHW） heating, which could be related to the striated particle flux distribution induced by LHW. After the onset of detachment, the upper electron density band corresponding to outer strike point firstly increases then decreases, while the lower density band corresponding to striated particle flux increases continually although the electron densities from Langmuir Probes at the divertor plate keep a descending trend. This could indicate a downward movement of the radiation region that approximately moves along the magnetic field lines after the onset of detachment.
文摘In this article we will present an attempt to measure the Stark broadening parameter of the Zn I-line at 636.23 nm utilizing the optical emission spectroscopy (OES) technique, taking into consideration the possibility of existence of self absorption. This method is standing on comparison of the Lorentzian FWHM and spectral line intensity of the unknown Stark broadening parameter line (Zn I-636.23 nm—in our case) to a well known Stark parameter line (e.g. Zn I-lines at 472.2, 481 and 468 nm) at a reference electron density of 2.7 × 1017 cm-3 and temperature of 1 eV. We have utilized the emission spectral data acquired from well diagnosed plasma produced by the interaction of Nd: YAG laser at wavelength of 1064 nm with ZnO nanomaterial target in open air. The results indicates that the Stark broadening of the Zn I-line at 636.23 nm is centered at 5.06 ± 0.03 ? with a 25% uncertainty at the given reference plasma parameters. The knowledge of the Stark broadening parameter of the 636.23 nm line may be important in the diagnostics of the laser plasma experiments especially in the absence of the Hα-line.
文摘Full quantum mechanical calculations are performed to determine the broadening in the far wings of the cesium D1 and D2 line shapes arising from elastic collisions of Cs atom with inert helium atoms. The potential energy curves of the low-lying CsHe molecular states, as well as the related transition dipole moments, are carefully computed from ab initio methods based on state-averaged complete active space self-consistent field-multireference configuration interaction(SACASSCF-MRCI) calculations, involving the spin-orbit effect, and taking into account the Davidson and BSSE corrections.The absorption and emission reduced coefficients are determined in the temperature and wavelength ranges of 323-3000 K and 800-1000 nm, respectively. Both profiles of the absorption and the emission are dominated by the free-free transitions,and exhibit a satellite peak in the blue wing near the wavelength 825 nm, attributed to B^2Σ1/2^+→ X^2Σ1/2^+/transitions. The results are in good agreement with previous experimental and theoretical works.
