In allusion to the limitations of the traditional attitude measurement system consisting of a three-axis magnetic sensor and two accelerometers on high-spinning projectile, a new scheme comprised of two magnetic senso...In allusion to the limitations of the traditional attitude measurement system consisting of a three-axis magnetic sensor and two accelerometers on high-spinning projectile, a new scheme comprised of two magnetic sensors and two accelerometers installed in a particular way is given. The configuration of the sensors is described. The calculation method and the mathematical model of the projectile attitude based on the sensor configuration are discussed. The basic calculation method including the Magsonde Window, the proof of the ratios of maximums and minimums and the calculation of the attitude angles are analyzed in theory. Finally, the system is simulated under the given conditions. The simulation result indicates that the estimated attitude angles are in agreement with the true attitude angles.展开更多
The sinusoid curve fit is widely applied in the evaluation of digitized measurement equipment, such as data acquisition system, digital storage oscilloscope, waveform recorder and A/D converter,etc. Because of the di...The sinusoid curve fit is widely applied in the evaluation of digitized measurement equipment, such as data acquisition system, digital storage oscilloscope, waveform recorder and A/D converter,etc. Because of the distortion and noise of sinusoid signal generator, the digitizing and the non linearity errors in measurement, it is impossible to avoid the distortion and the noise in sinusoid sampling series. The distortion and the noise limit the accuracy of curve fit results. Therefore, it is desirable to find a filter that can filter out both distortion and noise of the sinusoid sampling series, and in the meantime, the filter doesn′t influence the amplitude, the frequency, the phase and DC bias of fitting curve of the sine wave. And then, the uncertainty of fitting parameter can be reduced. This filter is designed and realized. Its realization in time domain is described and its transfer function in frequency domain is presented.展开更多
A digital predistorted class-F power amplifier （PA） using Cree GaN HEMT CGH40010 operating at 2. 12 GHz is presented to obtain high efficiency and excellent linearity for wideband code-division multiple access （ WC...A digital predistorted class-F power amplifier （PA） using Cree GaN HEMT CGH40010 operating at 2. 12 GHz is presented to obtain high efficiency and excellent linearity for wideband code-division multiple access （ WCDMA ） applications. Measurement results with the continuous wave （CW） signals indicate that the designed class-F PA achieves a peak power-added efficiency （PAE） of 75. 2% with an output power of 39.4 dBm. The adjacent channel power ratio （ACPR） of the designed PA after digital predistortion （DPD） decreases from -28. 3 and -27. 5 dBc to -51.9 and -54. 0 dBc, respectively, for a 4-carrier 20 MHz WCDMA signal with 7. 1 dB peak to average power ratio （PAPR）. The drain efficiency （DE） of the PA is 37. 8% at an average output power of 33. 3 dBm. The designed power amplifier can be aoolied in the WCDMA system.展开更多
Both theoretical and field observations were examined to study the close relationship between soil degeneration and the evolution of grassland vegetation. A general n-species model of equal competition under different...Both theoretical and field observations were examined to study the close relationship between soil degeneration and the evolution of grassland vegetation. A general n-species model of equal competition under different degrees of soil degradation was applied to field data in order to probe the dynamic processes and mechanisms of vegetation evolution due to the effects of the soil's ecological deterioration on grassland vegetation. Comparisons were made between the theoretical results and the practical surveys with satisfactory results.展开更多
A vegetation evolution model influenced by a degeneration of soil ecological functions was set up. Three ideal communities of a) trees, b) shrubs, and c) herbage populations were first simulated. Then numerical simula...A vegetation evolution model influenced by a degeneration of soil ecological functions was set up. Three ideal communities of a) trees, b) shrubs, and c) herbage populations were first simulated. Then numerical simulations of the evolutionary and developmental processes of a natural forest community, which is composed of over 100 species,were conducted. Results of the study showed that a) in all communities, soil degeneration not only drove some weaker species to extinction, but also a few dominant ones; b) there were different response scales with species in an ideal tree metapopulation that could persist as long as a thousand years, with shrubs in an ideal shrub metapopulation that could persevere for several hundred years, and with species in an ideal herbage metapopulation that could become extinct within 10 years; and c) each metapopulation experienced three evolutionary stages during adaptation to the environment: a) the stage of compelled adaptation or resistance, b) the adjusted stage, and c) the stabilized stage.展开更多
Most injection molded parts are three-dimensional, with complex geometrical configurations and thick/thin wall sections. The change of the thickness of parts has significant influence on flow during injection molding....Most injection molded parts are three-dimensional, with complex geometrical configurations and thick/thin wall sections. The change of the thickness of parts has significant influence on flow during injection molding. This paper presents a 3D finite element model to deal with the three-dimensional flow, which can more accurately predict the filling process than a 2.5D model. In this model, equal-order velocity-pressure interpolation method is successfully employed and the relation between velocity and pressure is obtained from the discretized momentum equation in order to derive the pressure equation. A 3D control volume scheme is employed to track the flow front. The validity of the model has been tested through the analysis of the flow in a cavity.展开更多
Based on the effective structure of the self-mixing interference effects,a general model for the self-mixing interference effects in the LD pumped solid-state laser has been established for the first time.The numerica...Based on the effective structure of the self-mixing interference effects,a general model for the self-mixing interference effects in the LD pumped solid-state laser has been established for the first time.The numerical simulation of the self-mixing interference signal has been done,the results show that when the external cavity length is integral times of 1/2,1/3,2/3,1/4,3/4 of the effective cavity length,the intensity of the self-mixing interference signals reach maximum in value.While that of single mode laser is integral times of half of the effective cavity length,the measuring precision of displacement of single mode laser is λ/2.A conclusion can be drawn from the above results that the measuring precision of displacement of multi-mode laser is higher than that of single mode laser.展开更多
The numeric al simulation study on the temperature distribution of underground field for the ground coupled heat pump (GCHP) with vertical spira l coil was carried out by using finite element. The distribution and rec...The numeric al simulation study on the temperature distribution of underground field for the ground coupled heat pump (GCHP) with vertical spira l coil was carried out by using finite element. The distribution and recovery of undergroun d field temperature under different operation ratio and the optimal operation ratio were simulated.The performance parameters, i.e. inlet and outlet temperature of the ground spiral coil in heating and cooling modes were tested, the heat extracted or emitted by the heat pump to the ground was calculated, and the coefficients of performance (COP) of GCHP at heat ing and cooling modes were analyzed.展开更多
Utilizing the improved model with quasi-coherent two-quantum state and new Hamiltonian containing an additional interaction term [Phys. Rev. E62 (2000) 6989 and Euro. Phys. J. B19 (2001) 297] we study numerically the ...Utilizing the improved model with quasi-coherent two-quantum state and new Hamiltonian containing an additional interaction term [Phys. Rev. E62 (2000) 6989 and Euro. Phys. J. B19 (2001) 297] we study numerically the influences of the quantum and disorder effects including distortion of the sequences of masses of amino acid molecules and fluctuations of force constant of molecular chains, and of exciton-phonon coupled constants and of the dipole-dipole interaction constant and of the ground state energy on the properties of the solitons transported the bio-energy in the protein molecules by Runge-Kutta method. The results obtained show that the new soliton is robust against these structure disorders, especially for stronger disorders in the sequence of masses spring constants and coupling constants,except for quite larger fluctuations of the ground state energy and dipole-dipole interaction constant. This means that the new soliton in the improved model is very stable in normal cases and is possibly a carrier of bio-energy transport in the protein molecules.展开更多
The structure and single-particle motion of a two-dimensional dusty plasma have been investigated. Pair correlation function, mean square displacement, velocity autocorrelation function, and the corresponding spectrum...The structure and single-particle motion of a two-dimensional dusty plasma have been investigated. Pair correlation function, mean square displacement, velocity autocorrelation function, and the corresponding spectrum function have been computed by molecular dynamical simulation. The results show that the coagulation of a two-dimensional dusty plasma system is strongly affected by particle density and temperature, which are discussed in details.展开更多
With PSU/NCAR nonhydrostatic mesoscale model MM5, the rainfall process of tropical storm Fitow(0114) is simulated for 00:00 UTC 31 Aug. – 00:00 UTC 2 Sept. 2001. Mesoscale separation is performed on the results with ...With PSU/NCAR nonhydrostatic mesoscale model MM5, the rainfall process of tropical storm Fitow(0114) is simulated for 00:00 UTC 31 Aug. – 00:00 UTC 2 Sept. 2001. Mesoscale separation is performed on the results with the filtering scheme. Analyses show that the MM5 model well reproduced the position and intensity of heavy rain. Mesoscale characteristics of heavy rain were well represented in rainfall time scale, rainfall area, stream field and divergence at lower and upper levels. The interaction between inverted typhoon troughs and the mesoscale systems lead to heavy rain occurrence. The distribution of divergence fields at lower and upper levels can have a kind of indication for the rainfall. Heavy rains are closely associated with topography and land-sea distribution in South China. Weak instability is favorable to the generation of heavy rain.展开更多
Long-span roof with span larger than height always has a complicated three-dimensional curve. Wind pressure on the roof is often influenced not only by the atmospheric turbulence, but also by the “signature” turbule...Long-span roof with span larger than height always has a complicated three-dimensional curve. Wind pressure on the roof is often influenced not only by the atmospheric turbulence, but also by the “signature” turbulence provoked in the wind by the structure itself. So it is necessary to study characteristics of flows around the roof. In this paper, three-dimensional numerical simulation of wind-induced pressure has been periormed on a long-span flat roof by means of Computational Fluid Dynamics （CFD） software ——FLUENT. The flow characteristics are studied by considering some parameters, such as wind direction, span-height ratio, roof pitch, flow characteristics, roughness of terrain. The simulation is based upon the Reynolds-averaged equations, in which Reynolds stress equation model （RSM） and SIMPLE technology, （Semi-Implieit Method for Pressure-Linked Equations） have been used. Compared with wind tunnel tests, the computational results have good agreement with the experimental data. It is proved that the results are creditable and the method is feasible.展开更多
文摘In allusion to the limitations of the traditional attitude measurement system consisting of a three-axis magnetic sensor and two accelerometers on high-spinning projectile, a new scheme comprised of two magnetic sensors and two accelerometers installed in a particular way is given. The configuration of the sensors is described. The calculation method and the mathematical model of the projectile attitude based on the sensor configuration are discussed. The basic calculation method including the Magsonde Window, the proof of the ratios of maximums and minimums and the calculation of the attitude angles are analyzed in theory. Finally, the system is simulated under the given conditions. The simulation result indicates that the estimated attitude angles are in agreement with the true attitude angles.
文摘The sinusoid curve fit is widely applied in the evaluation of digitized measurement equipment, such as data acquisition system, digital storage oscilloscope, waveform recorder and A/D converter,etc. Because of the distortion and noise of sinusoid signal generator, the digitizing and the non linearity errors in measurement, it is impossible to avoid the distortion and the noise in sinusoid sampling series. The distortion and the noise limit the accuracy of curve fit results. Therefore, it is desirable to find a filter that can filter out both distortion and noise of the sinusoid sampling series, and in the meantime, the filter doesn′t influence the amplitude, the frequency, the phase and DC bias of fitting curve of the sine wave. And then, the uncertainty of fitting parameter can be reduced. This filter is designed and realized. Its realization in time domain is described and its transfer function in frequency domain is presented.
基金The National Natural Science Foundation of China(No.60702163)the National Science and Technology Major Project(No.2010ZX03007-002-01,2011ZX03004-003)
文摘A digital predistorted class-F power amplifier （PA） using Cree GaN HEMT CGH40010 operating at 2. 12 GHz is presented to obtain high efficiency and excellent linearity for wideband code-division multiple access （ WCDMA ） applications. Measurement results with the continuous wave （CW） signals indicate that the designed class-F PA achieves a peak power-added efficiency （PAE） of 75. 2% with an output power of 39.4 dBm. The adjacent channel power ratio （ACPR） of the designed PA after digital predistortion （DPD） decreases from -28. 3 and -27. 5 dBc to -51.9 and -54. 0 dBc, respectively, for a 4-carrier 20 MHz WCDMA signal with 7. 1 dB peak to average power ratio （PAPR）. The drain efficiency （DE） of the PA is 37. 8% at an average output power of 33. 3 dBm. The designed power amplifier can be aoolied in the WCDMA system.
文摘Both theoretical and field observations were examined to study the close relationship between soil degeneration and the evolution of grassland vegetation. A general n-species model of equal competition under different degrees of soil degradation was applied to field data in order to probe the dynamic processes and mechanisms of vegetation evolution due to the effects of the soil's ecological deterioration on grassland vegetation. Comparisons were made between the theoretical results and the practical surveys with satisfactory results.
基金Project supported by the National Natural Science Foundation of China (No. 40371108) the National "211" Key Project of China: The environmental evolution and ecological construction on multi-spatio-temporal scales.
文摘A vegetation evolution model influenced by a degeneration of soil ecological functions was set up. Three ideal communities of a) trees, b) shrubs, and c) herbage populations were first simulated. Then numerical simulations of the evolutionary and developmental processes of a natural forest community, which is composed of over 100 species,were conducted. Results of the study showed that a) in all communities, soil degeneration not only drove some weaker species to extinction, but also a few dominant ones; b) there were different response scales with species in an ideal tree metapopulation that could persist as long as a thousand years, with shrubs in an ideal shrub metapopulation that could persevere for several hundred years, and with species in an ideal herbage metapopulation that could become extinct within 10 years; and c) each metapopulation experienced three evolutionary stages during adaptation to the environment: a) the stage of compelled adaptation or resistance, b) the adjusted stage, and c) the stabilized stage.
文摘Most injection molded parts are three-dimensional, with complex geometrical configurations and thick/thin wall sections. The change of the thickness of parts has significant influence on flow during injection molding. This paper presents a 3D finite element model to deal with the three-dimensional flow, which can more accurately predict the filling process than a 2.5D model. In this model, equal-order velocity-pressure interpolation method is successfully employed and the relation between velocity and pressure is obtained from the discretized momentum equation in order to derive the pressure equation. A 3D control volume scheme is employed to track the flow front. The validity of the model has been tested through the analysis of the flow in a cavity.
文摘Based on the effective structure of the self-mixing interference effects,a general model for the self-mixing interference effects in the LD pumped solid-state laser has been established for the first time.The numerical simulation of the self-mixing interference signal has been done,the results show that when the external cavity length is integral times of 1/2,1/3,2/3,1/4,3/4 of the effective cavity length,the intensity of the self-mixing interference signals reach maximum in value.While that of single mode laser is integral times of half of the effective cavity length,the measuring precision of displacement of single mode laser is λ/2.A conclusion can be drawn from the above results that the measuring precision of displacement of multi-mode laser is higher than that of single mode laser.
文摘The numeric al simulation study on the temperature distribution of underground field for the ground coupled heat pump (GCHP) with vertical spira l coil was carried out by using finite element. The distribution and recovery of undergroun d field temperature under different operation ratio and the optimal operation ratio were simulated.The performance parameters, i.e. inlet and outlet temperature of the ground spiral coil in heating and cooling modes were tested, the heat extracted or emitted by the heat pump to the ground was calculated, and the coefficients of performance (COP) of GCHP at heat ing and cooling modes were analyzed.
文摘Utilizing the improved model with quasi-coherent two-quantum state and new Hamiltonian containing an additional interaction term [Phys. Rev. E62 (2000) 6989 and Euro. Phys. J. B19 (2001) 297] we study numerically the influences of the quantum and disorder effects including distortion of the sequences of masses of amino acid molecules and fluctuations of force constant of molecular chains, and of exciton-phonon coupled constants and of the dipole-dipole interaction constant and of the ground state energy on the properties of the solitons transported the bio-energy in the protein molecules by Runge-Kutta method. The results obtained show that the new soliton is robust against these structure disorders, especially for stronger disorders in the sequence of masses spring constants and coupling constants,except for quite larger fluctuations of the ground state energy and dipole-dipole interaction constant. This means that the new soliton in the improved model is very stable in normal cases and is possibly a carrier of bio-energy transport in the protein molecules.
文摘The structure and single-particle motion of a two-dimensional dusty plasma have been investigated. Pair correlation function, mean square displacement, velocity autocorrelation function, and the corresponding spectrum function have been computed by molecular dynamical simulation. The results show that the coagulation of a two-dimensional dusty plasma system is strongly affected by particle density and temperature, which are discussed in details.
基金The National Natural Science Foundation of China (No. 40375036) the Base Condition Flat Roof Item of the Ministry of Science and Technology (No.2003DIB4J145)
文摘With PSU/NCAR nonhydrostatic mesoscale model MM5, the rainfall process of tropical storm Fitow(0114) is simulated for 00:00 UTC 31 Aug. – 00:00 UTC 2 Sept. 2001. Mesoscale separation is performed on the results with the filtering scheme. Analyses show that the MM5 model well reproduced the position and intensity of heavy rain. Mesoscale characteristics of heavy rain were well represented in rainfall time scale, rainfall area, stream field and divergence at lower and upper levels. The interaction between inverted typhoon troughs and the mesoscale systems lead to heavy rain occurrence. The distribution of divergence fields at lower and upper levels can have a kind of indication for the rainfall. Heavy rains are closely associated with topography and land-sea distribution in South China. Weak instability is favorable to the generation of heavy rain.
文摘Long-span roof with span larger than height always has a complicated three-dimensional curve. Wind pressure on the roof is often influenced not only by the atmospheric turbulence, but also by the “signature” turbulence provoked in the wind by the structure itself. So it is necessary to study characteristics of flows around the roof. In this paper, three-dimensional numerical simulation of wind-induced pressure has been periormed on a long-span flat roof by means of Computational Fluid Dynamics （CFD） software ——FLUENT. The flow characteristics are studied by considering some parameters, such as wind direction, span-height ratio, roof pitch, flow characteristics, roughness of terrain. The simulation is based upon the Reynolds-averaged equations, in which Reynolds stress equation model （RSM） and SIMPLE technology, （Semi-Implieit Method for Pressure-Linked Equations） have been used. Compared with wind tunnel tests, the computational results have good agreement with the experimental data. It is proved that the results are creditable and the method is feasible.
