The modified sum-peak method estimates radioactivity by using only the peak and the sum-peak count rates.To verify the modified sum-peak method,the dependence of the full energy peak efficiency on the source-to-detect...The modified sum-peak method estimates radioactivity by using only the peak and the sum-peak count rates.To verify the modified sum-peak method,the dependence of the full energy peak efficiency on the source-to-detector distance in a high-purity germanium detector system was studied using a Geant4 Monte Carlo simulation.The effect of the deadlayer in the germanium crystal was estimated by reference to experiments on 241 Am and the relative efficiency of the detector.The peak efficiency dependence on the source-to-detector distance was compared between the simulation and measurements.The modified sum-peak method is discussed with respect to these peak efficiencies.展开更多
In this paper, simulation of InAs/GaAs quantum dot (QD) laser is performed based upon a set of eight rate equations for the carriers and photons in five energy states. Carrier dynamics in these lasers were under analy...In this paper, simulation of InAs/GaAs quantum dot (QD) laser is performed based upon a set of eight rate equations for the carriers and photons in five energy states. Carrier dynamics in these lasers were under analysis and the rate equations are solved using 4th order Runge-Kutta method. We have shown that by increasing injected current to the active medium of laser, switching-on and stability time of the system would decrease and power peak and stationary power will be increased. Also, emission in any state will start when the lower state is saturated and remain steady. The results including P-I characteristic curve for the ground state (GS), first excited state (ES1), second excited state (ES2) and output power of the QD laser will be presented.展开更多
The objective of this ongoing joint research program is to determine how 3D/4D modeling, simulation and visualization of Products (buildings), Organizations and Processes (POP) can support lean construction. Initial f...The objective of this ongoing joint research program is to determine how 3D/4D modeling, simulation and visualization of Products (buildings), Organizations and Processes (POP) can support lean construction. Initial findings suggest that Process Design Pattern may have the potential to intuitively support ICT based lean construction. We initiated a 'Process Archeology' in order to reveal the requirements for tools that can support the planning, simulation and control of lean construction methods. First findings show that existing tools provide only limited support and therefore, we started to develop new methodologies and technologies to overcome these shortcomings. Through the introduction of Process Design Patterns, we intent to establish process thinking in the interdisciplinary POP design. Optimized construction processes may be synthesized with semi-automatic methods by applying Process Design Patterns on building structures. By providing process templates that integrate problem solution and expert knowledge, Process Design Patterns may have the potential to ensure high quality process models.展开更多
The uniformity of microstructure distribution across the transverse section of a Ti-6AI-4 V bar afler stepwise radial forging process is a relevant index to the quality of the foaled bar. In this work, hot deformatio...The uniformity of microstructure distribution across the transverse section of a Ti-6AI-4 V bar afler stepwise radial forging process is a relevant index to the quality of the foaled bar. In this work, hot deformation chamcteristics of Ti-6Al-4 V bar in the stepwise radial forging process were investigated in the or+p and g range 6etween 940℃ and 1000℃. Various flow curves and microstructures were obtained by using Gleeble simulation. The deformation process of a bar from initial diameter to a desired reduction in cross section was simulated by using a FEM code ABAQUS combined with the constitutive models obtained from physical simulation. Heat onduction model was coupled to the computation. The principal stresses and final strain istribution of the bar after forging were predicted by the contours obtained from FEM analysis. Together with the results obtained from Gleeble simulation, a map of microstructure distribu- tion on the cross section of the forged bar was constructed. According to the map,recrystallized zone in the center region of the bar was predicted to be approximately 50 to 65% of the total cross section area.展开更多
The Coulomb barrier and electron screening cause difficulties in directly measuring nuclear reaction cross sections of charged particles at astrophysical energies. The Trojan-horse method （THM） has been introduced t...The Coulomb barrier and electron screening cause difficulties in directly measuring nuclear reaction cross sections of charged particles at astrophysical energies. The Trojan-horse method （THM） has been introduced to solve the difficulties as a powerful indirect tool. In order to understand experimentM spectra better, Geant4 is employed to simulate the method. Validity and reliability of simulation data are examined by comparing the experimental data with simulated results. The Geant4 simulation of THM future related experiments. improves data analysis and is beneficial to the design for展开更多
文摘The modified sum-peak method estimates radioactivity by using only the peak and the sum-peak count rates.To verify the modified sum-peak method,the dependence of the full energy peak efficiency on the source-to-detector distance in a high-purity germanium detector system was studied using a Geant4 Monte Carlo simulation.The effect of the deadlayer in the germanium crystal was estimated by reference to experiments on 241 Am and the relative efficiency of the detector.The peak efficiency dependence on the source-to-detector distance was compared between the simulation and measurements.The modified sum-peak method is discussed with respect to these peak efficiencies.
文摘In this paper, simulation of InAs/GaAs quantum dot (QD) laser is performed based upon a set of eight rate equations for the carriers and photons in five energy states. Carrier dynamics in these lasers were under analysis and the rate equations are solved using 4th order Runge-Kutta method. We have shown that by increasing injected current to the active medium of laser, switching-on and stability time of the system would decrease and power peak and stationary power will be increased. Also, emission in any state will start when the lower state is saturated and remain steady. The results including P-I characteristic curve for the ground state (GS), first excited state (ES1), second excited state (ES2) and output power of the QD laser will be presented.
文摘The objective of this ongoing joint research program is to determine how 3D/4D modeling, simulation and visualization of Products (buildings), Organizations and Processes (POP) can support lean construction. Initial findings suggest that Process Design Pattern may have the potential to intuitively support ICT based lean construction. We initiated a 'Process Archeology' in order to reveal the requirements for tools that can support the planning, simulation and control of lean construction methods. First findings show that existing tools provide only limited support and therefore, we started to develop new methodologies and technologies to overcome these shortcomings. Through the introduction of Process Design Patterns, we intent to establish process thinking in the interdisciplinary POP design. Optimized construction processes may be synthesized with semi-automatic methods by applying Process Design Patterns on building structures. By providing process templates that integrate problem solution and expert knowledge, Process Design Patterns may have the potential to ensure high quality process models.
文摘The uniformity of microstructure distribution across the transverse section of a Ti-6AI-4 V bar afler stepwise radial forging process is a relevant index to the quality of the foaled bar. In this work, hot deformation chamcteristics of Ti-6Al-4 V bar in the stepwise radial forging process were investigated in the or+p and g range 6etween 940℃ and 1000℃. Various flow curves and microstructures were obtained by using Gleeble simulation. The deformation process of a bar from initial diameter to a desired reduction in cross section was simulated by using a FEM code ABAQUS combined with the constitutive models obtained from physical simulation. Heat onduction model was coupled to the computation. The principal stresses and final strain istribution of the bar after forging were predicted by the contours obtained from FEM analysis. Together with the results obtained from Gleeble simulation, a map of microstructure distribu- tion on the cross section of the forged bar was constructed. According to the map,recrystallized zone in the center region of the bar was predicted to be approximately 50 to 65% of the total cross section area.
基金Supported by National Natural Science Foundation of China(11075218,10575132)Beijing Natural Science Foundation(1122017)
文摘The Coulomb barrier and electron screening cause difficulties in directly measuring nuclear reaction cross sections of charged particles at astrophysical energies. The Trojan-horse method （THM） has been introduced to solve the difficulties as a powerful indirect tool. In order to understand experimentM spectra better, Geant4 is employed to simulate the method. Validity and reliability of simulation data are examined by comparing the experimental data with simulated results. The Geant4 simulation of THM future related experiments. improves data analysis and is beneficial to the design for
