We propose a method to determine the optimal power of the microwave resonance transition that simultaneously improves the signal-to-noise ratio and reduces line width based on saturation broadening theory and experime...We propose a method to determine the optimal power of the microwave resonance transition that simultaneously improves the signal-to-noise ratio and reduces line width based on saturation broadening theory and experiment. Saturation broadening spectra of the ground state hyperfine transition of trapped 199Hg＋ ions are measured and analyzed. The value of the optimal microwave power is obtained by using the proposed method and is verified. Rabi oscillations decay spectra of trapped 199Hg＋ ions are observed and the optimal microwave irradiation time for the maximum transition signal intensity is determined. This work will help to improve the short-term frequency stability of the mercury ion microwave frequency standard.展开更多
Compared with non-gray model,equivalent gray model has equal calculation accuracy but much higher computing speed.To solve the existing problems of the equivalent gray method,sole ternary model was developed.In the mo...Compared with non-gray model,equivalent gray model has equal calculation accuracy but much higher computing speed.To solve the existing problems of the equivalent gray method,sole ternary model was developed.In the model,coupling solving process of energy balance equations is omitted and the model zone is real closed.Meanwhile,the full furnace temperature and heat flow calculations are avoided,which makes it easier to find the relationship between the equivalent gray gas radiation characteristic parameter and the initial conditions.The radiation characteristic parameter was calculated with different temperature combinations,different model zone sizes and different partial pressures of absorbent gas.The results show the similar variations in the absorption coefficient and emissivity for the equivalent gray model,which both decrease with the increase of the gas temperature and the surface temperature（especially the former one）as well as the model zone size while increase with the increase of the partial pressure of absorbent gas.展开更多
The development of space telecommunications in recent years has necessitated the design and the realization of compact, high-performance equipment operating at increasingly high frequencies. The use of high-precision ...The development of space telecommunications in recent years has necessitated the design and the realization of compact, high-performance equipment operating at increasingly high frequencies. The use of high-precision radars for surveillance, detection and mobile communication systems orients research toward the antennas to electronic sweep. In this article, we present a microstrip leaky-wave antenna with periodic patches. Its design is based on an integral formulation solved by software using HFSS finite elements. A parametric study of this antenna is validated by simulations and compared with other results found in the literature. Analysis of the antenna’s radiation parameters shows that the main beam direction and levels of minor’s lobes can be controlled from these geometrical parameters. The interest of this study is to meet the requirements of antennas dedicated telecommunications systems.展开更多
Objective: The purpose of this study was to compare the dose distribution and dose volume histogram (DVH) of the planning target volume (PTV) and organs at risk (OARs) among conventional radiation therapy (CR), three-...Objective: The purpose of this study was to compare the dose distribution and dose volume histogram (DVH) of the planning target volume (PTV) and organs at risk (OARs) among conventional radiation therapy (CR), three-dimensional conformal radiation therapy (3DCRT), two-step intensity-modulated radiation therapy (TS-IMRT) and direct machine parameter optimization intensity-modulated radiation therapy (DMPO-IMRT) after breast-conserving surgery. Methods: For each of 20 randomly chosen patients, 4 plans were designed using 4 irradiation techniques. The prescribed dose was 50 Gy/2 Gy/25 f, 95% of the planning target volume received this dose. The cumulated DVHs and 3D dose distributions of CR, 3DCRT, TS-IMRT and DMPO-IMRT plans were compared. Results: For the homogeneity indices, no statistically significant difference was observed among CR, 3DCRT, TS-IMRT and DMPO-IMRT while the difference of the conformality indices were statistically significant. With regard to the organs at risk, IMRT and 3DCRT showed a significantly fewer exposure dose to the ipsilateral lung than CR in the high-dose area while in the low-dose area, IMRT demonstrated a significant increase of exposure dose to ipsilateral lung, heart and contralateral breast compared with 3DCRT and CR. In addition, the monitor units (MUs) for DMPO-IMRT were approximately 26% more than those of TS-IMRT and the segments of the former were approximately 24% less than those of the latter. Conclusion: Compared with CR, 3DCRT and IMRT improved the homogeneity and conformity of PTV, reduced the irradiated volume of OARs in high dose area but IMRT increased the irradiated volume of OARs in low dose area. DMPO-IMRT plan has fewer delivery time but more MUs than TS-IMRT.展开更多
We present an exercise that intends to establish a relationship between the strength of nebular emission lines and optical stellar features in the spectrum of a galaxy. After accurately subtracting the stellar continu...We present an exercise that intends to establish a relationship between the strength of nebular emission lines and optical stellar features in the spectrum of a galaxy. After accurately subtracting the stellar continuum and the underlying stellar absorption, we made reliable measurements of the emission lines of all the galaxies in the Sloan Digital Sky Survey Data Release 2 (SDSS DR2). More than 4000 star-forming galaxies with high S/N ratio of both the stellar spectrum and the emission lines are selected. These galaxy spectra are fitted with the 10 PCs of Yip et al., after all the emission line regions have been filtered out. We find that the flux of hydrogen Balmer emission lines, Ha and Hβ can be well recovered from the PCs, while the metal lines are not well reproduced. The fluxes of Ha and Hβ measured from the PC-reconstructed spectra and from the observed spectra agree well with an rms scatter of only - 0.1 dex. This result suggests that, with moderate spectral resolution and S/N ratio, the optical stellar spectrum of a galaxy can serve as an indicator of star formation rate.展开更多
This paper explores the time-dependent magnetohydrodynamics(MHD)micropolar fluid flow over a three-dimensional variable stretching surface in the occurrence of radiation effect.The model time-dependent partial differe...This paper explores the time-dependent magnetohydrodynamics(MHD)micropolar fluid flow over a three-dimensional variable stretching surface in the occurrence of radiation effect.The model time-dependent partial differential equations(PDE’s)in three independent variables are transformed into ordinary differential equations(ODE’s)by the suitable selfsimilarity variables.Homotopy perturbation method(HPM)and Runge-Kutta(RK)4^(th) order method along with shooting technique are used in the present model.And also,HPM results are compared with Runge-Kutta(RK)4^(th) order method along with the shooting technique.The velocity,micro rotation in x and y directions,temperature,skin friction factor and heat transfer rates are examined for the emerging parameters.The velocity profiles and momentum boundary layer thickness intensification with increasing values of the vortex viscosity parameter.The higher value of a magnetic parameter declines the skin friction coefficient.This type of investigation may be profitable to the polymer fluids,exotic lubricants,electronic chips,artificial fibers,drawing of copper wires,etc.展开更多
This work provides a comprehensive theoretical analysis of MHD unsteady free convection viscoelastic fluid flow through a porous medium. The medium is treated as incompressible and optically transparent. The flow of t...This work provides a comprehensive theoretical analysis of MHD unsteady free convection viscoelastic fluid flow through a porous medium. The medium is treated as incompressible and optically transparent. The flow of the fluid is initiated by shearing action of the moving wall with time dependent suction. Radiative heat flow is considered in temperature equation. The coupled nonlinear problem has been solved asymptotically. Approximate solutions have been obtained for the mean velocity, mean temperature using multi parameter perturbation technique. The originality of the present study is to investigate the effect of viscoelastic property of the fluid（Walters B？ model） on the flow and heat transfer phenomena when the flow is permeated through a porous medium with uniform porous matrix subject to transverse magnetic field and time dependent fluctuative suction at the boundary surface. The case of viscous flow has been discussed as a particular case on comparison with the result reported earlier and it is in good agreement. Flow reversal is indicated incase of viscoelastic fluid with high heat capacity in the presence of magnetic field. The higher cooling of the plate in case of viscoelastic flow also causes a flow reversal.展开更多
A parameterized radiation and cloud model developed at the University of Utah,U.S.A.has been used to compute the atmospheric radiative properties in Zhangye area during the pilot experiment of HEIFE in September of 19...A parameterized radiation and cloud model developed at the University of Utah,U.S.A.has been used to compute the atmospheric radiative properties in Zhangye area during the pilot experiment of HEIFE in September of 1988.Some characteristics of atmospheric radiative heating fields during the autumn in Zhangye area have been analysed,and some questions that merit attention in the future observation are also discussed in this paper.展开更多
基金Supported by the National Natural Science Foundation of China under Grant Nos 11074282 and 11474320
文摘We propose a method to determine the optimal power of the microwave resonance transition that simultaneously improves the signal-to-noise ratio and reduces line width based on saturation broadening theory and experiment. Saturation broadening spectra of the ground state hyperfine transition of trapped 199Hg＋ ions are measured and analyzed. The value of the optimal microwave power is obtained by using the proposed method and is verified. Rabi oscillations decay spectra of trapped 199Hg＋ ions are observed and the optimal microwave irradiation time for the maximum transition signal intensity is determined. This work will help to improve the short-term frequency stability of the mercury ion microwave frequency standard.
基金Sponsored by National Science and Technology Support Plan of China(2011AA060104)
文摘Compared with non-gray model,equivalent gray model has equal calculation accuracy but much higher computing speed.To solve the existing problems of the equivalent gray method,sole ternary model was developed.In the model,coupling solving process of energy balance equations is omitted and the model zone is real closed.Meanwhile,the full furnace temperature and heat flow calculations are avoided,which makes it easier to find the relationship between the equivalent gray gas radiation characteristic parameter and the initial conditions.The radiation characteristic parameter was calculated with different temperature combinations,different model zone sizes and different partial pressures of absorbent gas.The results show the similar variations in the absorption coefficient and emissivity for the equivalent gray model,which both decrease with the increase of the gas temperature and the surface temperature（especially the former one）as well as the model zone size while increase with the increase of the partial pressure of absorbent gas.
文摘The development of space telecommunications in recent years has necessitated the design and the realization of compact, high-performance equipment operating at increasingly high frequencies. The use of high-precision radars for surveillance, detection and mobile communication systems orients research toward the antennas to electronic sweep. In this article, we present a microstrip leaky-wave antenna with periodic patches. Its design is based on an integral formulation solved by software using HFSS finite elements. A parametric study of this antenna is validated by simulations and compared with other results found in the literature. Analysis of the antenna’s radiation parameters shows that the main beam direction and levels of minor’s lobes can be controlled from these geometrical parameters. The interest of this study is to meet the requirements of antennas dedicated telecommunications systems.
文摘Objective: The purpose of this study was to compare the dose distribution and dose volume histogram (DVH) of the planning target volume (PTV) and organs at risk (OARs) among conventional radiation therapy (CR), three-dimensional conformal radiation therapy (3DCRT), two-step intensity-modulated radiation therapy (TS-IMRT) and direct machine parameter optimization intensity-modulated radiation therapy (DMPO-IMRT) after breast-conserving surgery. Methods: For each of 20 randomly chosen patients, 4 plans were designed using 4 irradiation techniques. The prescribed dose was 50 Gy/2 Gy/25 f, 95% of the planning target volume received this dose. The cumulated DVHs and 3D dose distributions of CR, 3DCRT, TS-IMRT and DMPO-IMRT plans were compared. Results: For the homogeneity indices, no statistically significant difference was observed among CR, 3DCRT, TS-IMRT and DMPO-IMRT while the difference of the conformality indices were statistically significant. With regard to the organs at risk, IMRT and 3DCRT showed a significantly fewer exposure dose to the ipsilateral lung than CR in the high-dose area while in the low-dose area, IMRT demonstrated a significant increase of exposure dose to ipsilateral lung, heart and contralateral breast compared with 3DCRT and CR. In addition, the monitor units (MUs) for DMPO-IMRT were approximately 26% more than those of TS-IMRT and the segments of the former were approximately 24% less than those of the latter. Conclusion: Compared with CR, 3DCRT and IMRT improved the homogeneity and conformity of PTV, reduced the irradiated volume of OARs in high dose area but IMRT increased the irradiated volume of OARs in low dose area. DMPO-IMRT plan has fewer delivery time but more MUs than TS-IMRT.
基金Supported by the National Natural Science Foundation of China.
文摘We present an exercise that intends to establish a relationship between the strength of nebular emission lines and optical stellar features in the spectrum of a galaxy. After accurately subtracting the stellar continuum and the underlying stellar absorption, we made reliable measurements of the emission lines of all the galaxies in the Sloan Digital Sky Survey Data Release 2 (SDSS DR2). More than 4000 star-forming galaxies with high S/N ratio of both the stellar spectrum and the emission lines are selected. These galaxy spectra are fitted with the 10 PCs of Yip et al., after all the emission line regions have been filtered out. We find that the flux of hydrogen Balmer emission lines, Ha and Hβ can be well recovered from the PCs, while the metal lines are not well reproduced. The fluxes of Ha and Hβ measured from the PC-reconstructed spectra and from the observed spectra agree well with an rms scatter of only - 0.1 dex. This result suggests that, with moderate spectral resolution and S/N ratio, the optical stellar spectrum of a galaxy can serve as an indicator of star formation rate.
基金The author,S.R.R.Reddy wishes to thanks the Center for Nonlinear Systems,Chennai Institute of Technology,India,vide funding number CIT/CNS/2021/RD/064 for partially funded of this work。
文摘This paper explores the time-dependent magnetohydrodynamics(MHD)micropolar fluid flow over a three-dimensional variable stretching surface in the occurrence of radiation effect.The model time-dependent partial differential equations(PDE’s)in three independent variables are transformed into ordinary differential equations(ODE’s)by the suitable selfsimilarity variables.Homotopy perturbation method(HPM)and Runge-Kutta(RK)4^(th) order method along with shooting technique are used in the present model.And also,HPM results are compared with Runge-Kutta(RK)4^(th) order method along with the shooting technique.The velocity,micro rotation in x and y directions,temperature,skin friction factor and heat transfer rates are examined for the emerging parameters.The velocity profiles and momentum boundary layer thickness intensification with increasing values of the vortex viscosity parameter.The higher value of a magnetic parameter declines the skin friction coefficient.This type of investigation may be profitable to the polymer fluids,exotic lubricants,electronic chips,artificial fibers,drawing of copper wires,etc.
文摘This work provides a comprehensive theoretical analysis of MHD unsteady free convection viscoelastic fluid flow through a porous medium. The medium is treated as incompressible and optically transparent. The flow of the fluid is initiated by shearing action of the moving wall with time dependent suction. Radiative heat flow is considered in temperature equation. The coupled nonlinear problem has been solved asymptotically. Approximate solutions have been obtained for the mean velocity, mean temperature using multi parameter perturbation technique. The originality of the present study is to investigate the effect of viscoelastic property of the fluid（Walters B？ model） on the flow and heat transfer phenomena when the flow is permeated through a porous medium with uniform porous matrix subject to transverse magnetic field and time dependent fluctuative suction at the boundary surface. The case of viscous flow has been discussed as a particular case on comparison with the result reported earlier and it is in good agreement. Flow reversal is indicated incase of viscoelastic fluid with high heat capacity in the presence of magnetic field. The higher cooling of the plate in case of viscoelastic flow also causes a flow reversal.
文摘A parameterized radiation and cloud model developed at the University of Utah,U.S.A.has been used to compute the atmospheric radiative properties in Zhangye area during the pilot experiment of HEIFE in September of 1988.Some characteristics of atmospheric radiative heating fields during the autumn in Zhangye area have been analysed,and some questions that merit attention in the future observation are also discussed in this paper.
