Theoretical model and solutions on power line harmonic radiation (PLHR) propagating in the ground, air, and anisotropic homogeneous ionosphere are presented, The theoretical model is verified by the PLHR events obse...Theoretical model and solutions on power line harmonic radiation (PLHR) propagating in the ground, air, and anisotropic homogeneous ionosphere are presented, The theoretical model is verified by the PLHR events observed by the DEMETER satellite. Some propagation characteristics of PLHR based on the model are obtained. This paper is bene- ficial to quantitatively interpret the formation mechanism of PLHR phenomenon.展开更多
Surface plasmon polaritons excited by an electron beam can be transformed into coherent and tunable light radiation waves with power enhancement in the simple structure of a metal film with a dielectric medium loading...Surface plasmon polaritons excited by an electron beam can be transformed into coherent and tunable light radiation waves with power enhancement in the simple structure of a metal film with a dielectric medium loading. In this paper, the process of the radiation transformation of this radiation, and the dependencies of the radiation characteristics on the parameters of the structure and the electron beam are studied in detail. The radiation power enhancement is greatly influenced by the beam energy and the film thickness in the infrared to ultraviolet frequency region. Up to 122 times radiation power enhancement and 6.5% radiation frequency tuning band can be obtained by optimizing the beam energy and the parameters of the film.展开更多
We compute the characteristic parameters of the magneto-dipole radiation of a neutron star undergoing torsional seismic vibrations under the action of Lorentz restoring force about an axis of a dipolar magnetic field ...We compute the characteristic parameters of the magneto-dipole radiation of a neutron star undergoing torsional seismic vibrations under the action of Lorentz restoring force about an axis of a dipolar magnetic field experiencing decay. After a brief outline of the general theoretical background of the model of a vibration-powered neutron star, we present numerical estimates of basic vibration and radiation characteristics, such as frequency, lifetime and luminosity, and investigate their time dependence on magnetic field decay. The presented analysis suggests that a gradual decrease in frequencies of pulsating high-energy emission detected from a handful of currently monitored AXP/SGR-like X-ray sources can be explained as being produced by the vibration-powered magneto-dipole radiation of quaking magnetars.展开更多
A type of silicon detector known as AXUV (absolute extreme ultraviolet) photodiodes is successfully used to measure the radiated power in EAST. The detector is characterized by compact structure, fast temporal respo...A type of silicon detector known as AXUV (absolute extreme ultraviolet) photodiodes is successfully used to measure the radiated power in EAST. The detector is characterized by compact structure, fast temporal response (〈0.5 s) and flat spectral sensitivity in the range from ultra-violet to X-ray. Two 16-channel AXUV arrays are installed in EAST to view the whole poloidal cross-section of plasma. Based on the diagnostic system, typical radiation distributions for both limiter and divertor plasma are obtained and compared. As divertor detachment occurs, the radiation distribution in X-point region is observed to vary distinctly. The total radiation power losses in discharges with different plasma parameters are briefly analyzed.展开更多
The air breakdown in the high-power antenna near-field region limits the enhancement of the radiated power. A model coupling the field equivalent principle and the electron number density equation is presented to stud...The air breakdown in the high-power antenna near-field region limits the enhancement of the radiated power. A model coupling the field equivalent principle and the electron number density equation is presented to study the breakdown process in the near-field region of the circular aperture antenna at atmospheric pressure. Simulation results show that, although the electric field in the near-field region is nonuniform, the electron diffusion has small influence on the breakdown process when the initial electron number density is uniform in space. The field magnitude distribution on the aperture plays an important role in the maximum radiated power above which the air breakdown occurs. The maximum radiated power also depends on the phase difference of the fields at the center and edge of the aperture, especially for the uniform field magnitude distribution.展开更多
An experiment was performed on the Shenguang III prototype laser facility to continue the study on hohlraum radiation source with approximately constant radiation temperature using a continuously shaped laser pulse.A ...An experiment was performed on the Shenguang III prototype laser facility to continue the study on hohlraum radiation source with approximately constant radiation temperature using a continuously shaped laser pulse.A radiation source with a flattop temperature of about130 e V that lasted about 5 ns was obtained.The previous analytical iteration method based on power balance and self-similar solution of ablation was modified taking into account the plasma movements and it was used to design the laser pulse shape for experiment.A comparison between experimental results and simulation is presented and better agreement was achieved using the modified method.Further improvements are discussed.展开更多
<strong>Context and Background:</strong><span><span><span style="font-family:;" "=""><span style="font-family:Verdana;"> The product of the electr...<strong>Context and Background:</strong><span><span><span style="font-family:;" "=""><span style="font-family:Verdana;"> The product of the electromagnetic (EM) wave’s power </span><i><span style="font-family:Verdana;">P</span></i><span style="font-family:Verdana;"> times its period </span><i><span style="font-family:Verdana;">τ</span></i><span style="font-family:Verdana;">, </span><i><span style="font-family:Verdana;">i.e.</span></i> <i><span style="font-family:Verdana;">Pτ</span></i><span style="font-family:Verdana;">, is the amount of energy conserved in EM wave’s absorption in matter. Whether </span><i><span style="font-family:Verdana;">Pτ</span></i><span style="font-family:Verdana;"> is the amount of energy conserved in the emission of EM waves from matter is not assessed. </span><b><span style="font-family:Verdana;">Motivation:</span></b><span style="font-family:Verdana;"> In this </span><span><span style="font-family:Verdana;">research, we perform a computational study to explore the ability of </span><i><span style="font-family:Verdana;">Pτ</span></i> </span><span style="font-family:Verdana;">to repr</span><span style="font-family:Verdana;">esent the amount of energy conserved in EM wave’s emission from</span><span style="font-family:Verdana;"> matter. </span><b><span style="font-family:Verdana;">Hypothesis:</span></b><span style="font-family:Verdana;"> Since the magnitude of the power </span><i><span style="font-family:Verdana;">P</span></i><span style="font-family:Verdana;"> of emitted EM waves computed through Larmor’s formula for a rotating dipole is excessively small, we alternatively hypothesize that </span><i><span style="font-family:Verdana;">Pτ</span></i><span style="font-family:Verdana;"> and the law of conservation of energy can lead to a realistic estimation of </span><i><span style="font-family:Verdana;">P</span></i><span style="font-family:Verdana;">. </span><b><span style="font-family:Verdana;">Methods:</span></b><span style="font-family:Verdana;"> We estimate the power </span><i><span style="font-family:Verdana;">P</span></i><sub><span style="font-family:Verdana;">AME</span></sub><span style="font-family:Verdana;"> of the anomalous microwave emission (AME), a well-characterized radiation generated in the interstellar medium (ISM) by spinning dust grains, and one </span><span style="font-family:Verdana;">possible source of contamination of the cosmic microwave background (CMB). </span><span style="font-family:Verdana;">For our estimation of </span><i><span style="font-family:Verdana;">P</span></i><sub><span style="font-family:Verdana;">AME</span></sub><span style="font-family:Verdana;">, we assume the AME to be generated in a molecular cloud mostly populated by spinning silicate nanoparticles (SSNs) or polycyclic aromatic hydrocarbon (PAH) spinning dust grains. Indeed, SSNs and PAHs are listed among the most probable sources of AME, and their characteristics are well-known. We discriminate between realistic and non-realistic values of </span><i><span style="font-family:Verdana;">P</span></i><sub><span style="font-family:Verdana;">AME</span></sub><span style="font-family:Verdana;"> based upon the magnitude of two parameters that depend on </span><i><span style="font-family:Verdana;">P</span></i><sub><span style="font-family:Verdana;">AME</span></sub><span style="font-family:Verdana;">: the significant distance </span><i><span style="font-family:Verdana;">z</span></i><span style="font-family:Verdana;">, and the time of photon production </span><i><span style="font-family:Verdana;">T</span></i><span style="font-family:Verdana;">. The parameter z is the space interval from the spinning dust grain within which the spinning dust grain’s electric field is effective. </span><b><span style="font-family:Verdana;">Results: </span></b><span style="font-family:Verdana;">Using the information available for AME, SSNs and PAHs, we estimate the power </span><i><span style="font-family:Verdana;">P</span></i><sub><span style="font-family:Verdana;">AME</span></sub><span style="font-family:Verdana;"> using both Larmor’s formula and </span><i><span style="font-family:Verdana;">Pτ</span></i><span style="font-family:Verdana;">. We compare and comment the results obtained for </span><i><span style="font-family:Verdana;">z</span></i><span style="font-family:Verdana;"> and </span><i><span style="font-family:Verdana;">T</span></i><span style="font-family:Verdana;">. </span><b><span style="font-family:Verdana;">Conclusions: </span></b><span style="font-family:Verdana;">Our study highlights the effectiveness of </span><i><span style="font-family:Verdana;">Pτ </span></i><span style="font-family:Verdana;">over Larmor’s formula in providing a realistic value of </span><i><span style="font-family:Verdana;">P</span></i><sub><span style="font-family:Verdana;">AME</span></sub><span style="font-family:Verdana;">. This finding might have consequences in quantum technology of single photon detection and production.</span></span></span></span>展开更多
We investigate the Terahertz (THz) plasma waves in a two-dimensional (2D) electron gas in a nanometer field effect transistor (FET) with quantum effects, the electron scattering, the thermal motion of electrons ...We investigate the Terahertz (THz) plasma waves in a two-dimensional (2D) electron gas in a nanometer field effect transistor (FET) with quantum effects, the electron scattering, the thermal motion of electrons and electron exchange-correlation. We find that, while the elec- tron scattering, the wave number along y direction and the electron exchange-correlation suppress the radiation power, but the thermal motion of electrons and the quantum effects can amplify the radiation power. The radiation frequency decreases with electron exchange-correlation con- tributions, but increases with quantum effects, motion of electrons. It is worth mentioning that radiation frequency. These properties could be plasma oscillations in nanometer FET. the wave number along y direction and thermal the electron scattering has scarce influence on the of great help to the realization of practical THz展开更多
The plasma wave instability in rectangle field effect transistors (FETs) is studied with electron diffusion current density by quantum hydrodynamic model in this paper. General dispersion relation including effects ...The plasma wave instability in rectangle field effect transistors (FETs) is studied with electron diffusion current density by quantum hydrodynamic model in this paper. General dispersion relation including effects of electrical thermal motion, external friction associated with electron scattering effect, electron exchange-correlation contributions and quantum effects were obtained for rectangle FETs. The electron diffusion current density term is considered for further analysis in this paper. It is found that the quantum effects, the electron diffusion current density and electrical thermal motion enhance the radiation power and frequencies. But the electron exchange- correlation effects and the electron scattering effects reduce the radiation power and frequencies. Results showed that a transistor has advantages for the realization of practical terahertz sources.展开更多
The instability of terahertz(THz)plasma waves in two-dimensional(2D)quantum electron gas in a nanometer field effect transistor(FET)with asymmetrical boundary conditions has been investigated.We analyze THz plas...The instability of terahertz(THz)plasma waves in two-dimensional(2D)quantum electron gas in a nanometer field effect transistor(FET)with asymmetrical boundary conditions has been investigated.We analyze THz plasma waves of two parts of the 2D quantum electron gas:gated and ungated regions.The results show that the radiation frequency and the increment(radiation power)in 2D ungated quantum electron gas are much higher than that in 2D gated quantum electron gas.The quantum effects always enhance the radiation power and enlarge the region of instability in both cases.This allows us to conclude that 2D quantum electron gas in the transistor channel is important for the emission and detection process and both gated and ungated parts take part in that process.展开更多
A power radiation monitoring system based on thermoelectric MEMS microwave power sensors is studied. This monitoring system consists of three modules: a data acquisition module, a data processing and display module, ...A power radiation monitoring system based on thermoelectric MEMS microwave power sensors is studied. This monitoring system consists of three modules: a data acquisition module, a data processing and display module, and a data sharing module. It can detect the power radiation in the environment and the date information can be processed and shared. The measured results show that the thermoelectric MEMS microwave power sensor and the power radiation monitoring system both have a relatively good linearity. The sensitivity of the thermoelectric MEMS microwave power sensor is about 0.101 mV/mW, and the sensitivity of the monitoring system is about 0.038 V/mW. The voltage gain of the monitoring system is about 380 times, which is relatively consistent with the theoretical value. In addition, the low-frequency and low-power module in the monitoring system is adopted in order to reduce the electromagnetic pollution and the power consumption, and this work will extend the application of the thermoelectric MEMS microwave power sensor in more areas.展开更多
An infrared imaging bolometer diagnostic has been upgraded recently to be adapted for the complications of the signal-to-noise ratio arising from the low level of plasma radiation and high reflectivity of low energy p...An infrared imaging bolometer diagnostic has been upgraded recently to be adapted for the complications of the signal-to-noise ratio arising from the low level of plasma radiation and high reflectivity of low energy photon(〈6.2 eV).It utilizes a platinum foil,blackened on both sides with graphite spray,as the bolometer detector.The advantage of the blackened foil is the light absorption extending into the infrared.After a careful calibration of the foil,the incident power density distribution on the foil is determined by solving the heat diffusion equation with a numerical technique.The local plasma radiated power density is reconstructed with a minimum fisher information regularization method by assuming plasma emission toroidal symmetry.Comparisons of the results and the profiles measured by an ordinary bolometric detector demonstrate that this method is good enough to provide the plasma radiated power pattern.The typical plasma radiated power density distribution before and after high mode(H-mode) transition is firstly reconstructed with the infrared imaging bolometer.Moreover,during supersonic molecular beam injection(SMBI),an enhanced radiation region is observed at the edge of the plasma.展开更多
Sound radiation of thin plates is a common problem in engineering. Hashimoto proposed the discrete calculation method(DCM) to deal with the problem. The calculation of the radiation impedance of the rectangular elemen...Sound radiation of thin plates is a common problem in engineering. Hashimoto proposed the discrete calculation method(DCM) to deal with the problem. The calculation of the radiation impedance of the rectangular element is more cumbersome than that of the circular one, so the discrete rectangular radiation element is approximated by the circular one. However, error is also introduced. The formula developed by Sha has been employed to get self- and mutual-radiation impedances of rectangular radiation element. Numerical study was performed to verify error introduced by the approximation Hashimoto adopted. Experimental researches on sound radiation of a 2 mm-thick and a 4 mm-thick magnesium alloy plates were also carried out to evaluate the errors introduced by the approximation. The experimental results indicate that the circular approximation Hashimoto adopted overestimates the sound radiation efficiency. The maximum error levels of the radiation efficiencies of the2 mm-thick and 4 mm-thick magnesium alloy plates are up to 0.15 and 0.12, respectively. The effect of element aspect ratio on the sound radiation efficiency is also remarkable.展开更多
Based on the piezo-optic effect of medium, the refractive index of medium is the function of its density, and so it's also the function of acoustic pressure. Therefore, acoustic pressure in the optical path everyw...Based on the piezo-optic effect of medium, the refractive index of medium is the function of its density, and so it's also the function of acoustic pressure. Therefore, acoustic pressure in the optical path everywhere can be determined absolutely by laser-interferometric technique and relative distribution of pressure in the middle and far acoustic field, which can be obtained from theory or experiment respectively. Theory and experiment of measurement of pressure in acoustic field with laser-interferometer are introduced. Distribution of pressure radiated by a power ultrasonic transducer is determined by laser interferometric technique. The theoretical and experimental results are in good agreement. The receiving sensitivity of a PVDF (Polyvinylidene fluoride) transducer in free field is also calibrated absolutely due to above results and its sensitivity is -118.5 dB.展开更多
An easy-to-implement scheme called Enhanced High Gain Harmonic Generation is expected to be able to significantly enhance the performance of HG-FEL. In this paper we investigate the effects of the system parameters in...An easy-to-implement scheme called Enhanced High Gain Harmonic Generation is expected to be able to significantly enhance the performance of HG-FEL. In this paper we investigate the effects of the system parameters in the new scheme, including the electron energy detuning, initial electron-beam energy spread, seeding laser power, dispersive field strength and amount of the phase shift, etc. The numerical results from GENESIS (3D-code) are presented and show that the new scheme has acceptable parameters tolerance requirements and is no more or even less sensitive to the system parameters than that of the existing scheme; With the electron energy above the resonance, the efficiency is enhanced for both the new scheme and the existing scheme compared with the resonant energy case.展开更多
In this paper, a general formula for calculating the complex strengths of secondary sources is derived from the minimization criterion of total acoustic power output when both of the primary and secondary sources are ...In this paper, a general formula for calculating the complex strengths of secondary sources is derived from the minimization criterion of total acoustic power output when both of the primary and secondary sources are directional. Then specific properties of active sound attenuation are presented for some commonly used typical directional sources and the rule for distributing directional secondary sources is given.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant No.51207006)the Natural Science Foundation of Beijing,China(Grant No.3123038)
文摘Theoretical model and solutions on power line harmonic radiation (PLHR) propagating in the ground, air, and anisotropic homogeneous ionosphere are presented, The theoretical model is verified by the PLHR events observed by the DEMETER satellite. Some propagation characteristics of PLHR based on the model are obtained. This paper is bene- ficial to quantitatively interpret the formation mechanism of PLHR phenomenon.
基金Project supported by the National Basic Research Program of China(Grant No.2014CB339801)the National Natural Science Foundation of China(Grant Nos.61231005,11305030,and 612111076)the National High Technology Research and Development Program of China(Grant No.2011AA010204)
文摘Surface plasmon polaritons excited by an electron beam can be transformed into coherent and tunable light radiation waves with power enhancement in the simple structure of a metal film with a dielectric medium loading. In this paper, the process of the radiation transformation of this radiation, and the dependencies of the radiation characteristics on the parameters of the structure and the electron beam are studied in detail. The radiation power enhancement is greatly influenced by the beam energy and the film thickness in the infrared to ultraviolet frequency region. Up to 122 times radiation power enhancement and 6.5% radiation frequency tuning band can be obtained by optimizing the beam energy and the parameters of the film.
基金supportde by the National Natural Science Foundation of China(Grant Nos.10935001 and 10973002)the National Basic Research Program of China(Grant No.2009CB824800)the John Templeton Foundation
文摘We compute the characteristic parameters of the magneto-dipole radiation of a neutron star undergoing torsional seismic vibrations under the action of Lorentz restoring force about an axis of a dipolar magnetic field experiencing decay. After a brief outline of the general theoretical background of the model of a vibration-powered neutron star, we present numerical estimates of basic vibration and radiation characteristics, such as frequency, lifetime and luminosity, and investigate their time dependence on magnetic field decay. The presented analysis suggests that a gradual decrease in frequencies of pulsating high-energy emission detected from a handful of currently monitored AXP/SGR-like X-ray sources can be explained as being produced by the vibration-powered magneto-dipole radiation of quaking magnetars.
基金supported by National Natural Science Foundation of China (No. 10935004)National Magnetic Confinement Fusion Science Program of China (Nos. 2010GB106000, 2010GB106004)
文摘A type of silicon detector known as AXUV (absolute extreme ultraviolet) photodiodes is successfully used to measure the radiated power in EAST. The detector is characterized by compact structure, fast temporal response (〈0.5 s) and flat spectral sensitivity in the range from ultra-violet to X-ray. Two 16-channel AXUV arrays are installed in EAST to view the whole poloidal cross-section of plasma. Based on the diagnostic system, typical radiation distributions for both limiter and divertor plasma are obtained and compared. As divertor detachment occurs, the radiation distribution in X-point region is observed to vary distinctly. The total radiation power losses in discharges with different plasma parameters are briefly analyzed.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61501358,11622542,61431010,and 61627901)the Fundamental Research Funds for the Central Universities,China
文摘The air breakdown in the high-power antenna near-field region limits the enhancement of the radiated power. A model coupling the field equivalent principle and the electron number density equation is presented to study the breakdown process in the near-field region of the circular aperture antenna at atmospheric pressure. Simulation results show that, although the electric field in the near-field region is nonuniform, the electron diffusion has small influence on the breakdown process when the initial electron number density is uniform in space. The field magnitude distribution on the aperture plays an important role in the maximum radiated power above which the air breakdown occurs. The maximum radiated power also depends on the phase difference of the fields at the center and edge of the aperture, especially for the uniform field magnitude distribution.
文摘An experiment was performed on the Shenguang III prototype laser facility to continue the study on hohlraum radiation source with approximately constant radiation temperature using a continuously shaped laser pulse.A radiation source with a flattop temperature of about130 e V that lasted about 5 ns was obtained.The previous analytical iteration method based on power balance and self-similar solution of ablation was modified taking into account the plasma movements and it was used to design the laser pulse shape for experiment.A comparison between experimental results and simulation is presented and better agreement was achieved using the modified method.Further improvements are discussed.
文摘<strong>Context and Background:</strong><span><span><span style="font-family:;" "=""><span style="font-family:Verdana;"> The product of the electromagnetic (EM) wave’s power </span><i><span style="font-family:Verdana;">P</span></i><span style="font-family:Verdana;"> times its period </span><i><span style="font-family:Verdana;">τ</span></i><span style="font-family:Verdana;">, </span><i><span style="font-family:Verdana;">i.e.</span></i> <i><span style="font-family:Verdana;">Pτ</span></i><span style="font-family:Verdana;">, is the amount of energy conserved in EM wave’s absorption in matter. Whether </span><i><span style="font-family:Verdana;">Pτ</span></i><span style="font-family:Verdana;"> is the amount of energy conserved in the emission of EM waves from matter is not assessed. </span><b><span style="font-family:Verdana;">Motivation:</span></b><span style="font-family:Verdana;"> In this </span><span><span style="font-family:Verdana;">research, we perform a computational study to explore the ability of </span><i><span style="font-family:Verdana;">Pτ</span></i> </span><span style="font-family:Verdana;">to repr</span><span style="font-family:Verdana;">esent the amount of energy conserved in EM wave’s emission from</span><span style="font-family:Verdana;"> matter. </span><b><span style="font-family:Verdana;">Hypothesis:</span></b><span style="font-family:Verdana;"> Since the magnitude of the power </span><i><span style="font-family:Verdana;">P</span></i><span style="font-family:Verdana;"> of emitted EM waves computed through Larmor’s formula for a rotating dipole is excessively small, we alternatively hypothesize that </span><i><span style="font-family:Verdana;">Pτ</span></i><span style="font-family:Verdana;"> and the law of conservation of energy can lead to a realistic estimation of </span><i><span style="font-family:Verdana;">P</span></i><span style="font-family:Verdana;">. </span><b><span style="font-family:Verdana;">Methods:</span></b><span style="font-family:Verdana;"> We estimate the power </span><i><span style="font-family:Verdana;">P</span></i><sub><span style="font-family:Verdana;">AME</span></sub><span style="font-family:Verdana;"> of the anomalous microwave emission (AME), a well-characterized radiation generated in the interstellar medium (ISM) by spinning dust grains, and one </span><span style="font-family:Verdana;">possible source of contamination of the cosmic microwave background (CMB). </span><span style="font-family:Verdana;">For our estimation of </span><i><span style="font-family:Verdana;">P</span></i><sub><span style="font-family:Verdana;">AME</span></sub><span style="font-family:Verdana;">, we assume the AME to be generated in a molecular cloud mostly populated by spinning silicate nanoparticles (SSNs) or polycyclic aromatic hydrocarbon (PAH) spinning dust grains. Indeed, SSNs and PAHs are listed among the most probable sources of AME, and their characteristics are well-known. We discriminate between realistic and non-realistic values of </span><i><span style="font-family:Verdana;">P</span></i><sub><span style="font-family:Verdana;">AME</span></sub><span style="font-family:Verdana;"> based upon the magnitude of two parameters that depend on </span><i><span style="font-family:Verdana;">P</span></i><sub><span style="font-family:Verdana;">AME</span></sub><span style="font-family:Verdana;">: the significant distance </span><i><span style="font-family:Verdana;">z</span></i><span style="font-family:Verdana;">, and the time of photon production </span><i><span style="font-family:Verdana;">T</span></i><span style="font-family:Verdana;">. The parameter z is the space interval from the spinning dust grain within which the spinning dust grain’s electric field is effective. </span><b><span style="font-family:Verdana;">Results: </span></b><span style="font-family:Verdana;">Using the information available for AME, SSNs and PAHs, we estimate the power </span><i><span style="font-family:Verdana;">P</span></i><sub><span style="font-family:Verdana;">AME</span></sub><span style="font-family:Verdana;"> using both Larmor’s formula and </span><i><span style="font-family:Verdana;">Pτ</span></i><span style="font-family:Verdana;">. We compare and comment the results obtained for </span><i><span style="font-family:Verdana;">z</span></i><span style="font-family:Verdana;"> and </span><i><span style="font-family:Verdana;">T</span></i><span style="font-family:Verdana;">. </span><b><span style="font-family:Verdana;">Conclusions: </span></b><span style="font-family:Verdana;">Our study highlights the effectiveness of </span><i><span style="font-family:Verdana;">Pτ </span></i><span style="font-family:Verdana;">over Larmor’s formula in providing a realistic value of </span><i><span style="font-family:Verdana;">P</span></i><sub><span style="font-family:Verdana;">AME</span></sub><span style="font-family:Verdana;">. This finding might have consequences in quantum technology of single photon detection and production.</span></span></span></span>
基金supported by National Natural Science Foundation of China(No.10975114)
文摘We investigate the Terahertz (THz) plasma waves in a two-dimensional (2D) electron gas in a nanometer field effect transistor (FET) with quantum effects, the electron scattering, the thermal motion of electrons and electron exchange-correlation. We find that, while the elec- tron scattering, the wave number along y direction and the electron exchange-correlation suppress the radiation power, but the thermal motion of electrons and the quantum effects can amplify the radiation power. The radiation frequency decreases with electron exchange-correlation con- tributions, but increases with quantum effects, motion of electrons. It is worth mentioning that radiation frequency. These properties could be plasma oscillations in nanometer FET. the wave number along y direction and thermal the electron scattering has scarce influence on the of great help to the realization of practical THz
基金supported by National Natural Science Foundation of China (No. 10975114)Research Projects of Higher Education of Gansu Province (2017A-016)
文摘The plasma wave instability in rectangle field effect transistors (FETs) is studied with electron diffusion current density by quantum hydrodynamic model in this paper. General dispersion relation including effects of electrical thermal motion, external friction associated with electron scattering effect, electron exchange-correlation contributions and quantum effects were obtained for rectangle FETs. The electron diffusion current density term is considered for further analysis in this paper. It is found that the quantum effects, the electron diffusion current density and electrical thermal motion enhance the radiation power and frequencies. But the electron exchange- correlation effects and the electron scattering effects reduce the radiation power and frequencies. Results showed that a transistor has advantages for the realization of practical terahertz sources.
基金supported by National Natural Science Foundation of China(No.10975114)
文摘The instability of terahertz(THz)plasma waves in two-dimensional(2D)quantum electron gas in a nanometer field effect transistor(FET)with asymmetrical boundary conditions has been investigated.We analyze THz plasma waves of two parts of the 2D quantum electron gas:gated and ungated regions.The results show that the radiation frequency and the increment(radiation power)in 2D ungated quantum electron gas are much higher than that in 2D gated quantum electron gas.The quantum effects always enhance the radiation power and enlarge the region of instability in both cases.This allows us to conclude that 2D quantum electron gas in the transistor channel is important for the emission and detection process and both gated and ungated parts take part in that process.
基金supported by the National Natural Science Foundation of China(No.11304158)the Province Natural Science Foundation of Jiangsu(No.BK20140890)+1 种基金the Open Research Fund of the Key Laboratory of MEMS of Ministry of Education,Southeast University(No.3206005302)the Scientific Research Foundation of Nanjing University of Posts and Telecommunications(Nos.NY213024,NY215139)
文摘A power radiation monitoring system based on thermoelectric MEMS microwave power sensors is studied. This monitoring system consists of three modules: a data acquisition module, a data processing and display module, and a data sharing module. It can detect the power radiation in the environment and the date information can be processed and shared. The measured results show that the thermoelectric MEMS microwave power sensor and the power radiation monitoring system both have a relatively good linearity. The sensitivity of the thermoelectric MEMS microwave power sensor is about 0.101 mV/mW, and the sensitivity of the monitoring system is about 0.038 V/mW. The voltage gain of the monitoring system is about 380 times, which is relatively consistent with the theoretical value. In addition, the low-frequency and low-power module in the monitoring system is adopted in order to reduce the electromagnetic pollution and the power consumption, and this work will extend the application of the thermoelectric MEMS microwave power sensor in more areas.
基金supported by National Natural Science Foundation of China(Nos.10805016 and 11175061)the Chinese National Fusion Projectfor ITER(No.2014GB109001)
文摘An infrared imaging bolometer diagnostic has been upgraded recently to be adapted for the complications of the signal-to-noise ratio arising from the low level of plasma radiation and high reflectivity of low energy photon(〈6.2 eV).It utilizes a platinum foil,blackened on both sides with graphite spray,as the bolometer detector.The advantage of the blackened foil is the light absorption extending into the infrared.After a careful calibration of the foil,the incident power density distribution on the foil is determined by solving the heat diffusion equation with a numerical technique.The local plasma radiated power density is reconstructed with a minimum fisher information regularization method by assuming plasma emission toroidal symmetry.Comparisons of the results and the profiles measured by an ordinary bolometric detector demonstrate that this method is good enough to provide the plasma radiated power pattern.The typical plasma radiated power density distribution before and after high mode(H-mode) transition is firstly reconstructed with the infrared imaging bolometer.Moreover,during supersonic molecular beam injection(SMBI),an enhanced radiation region is observed at the edge of the plasma.
基金the National Technology Research and Development Program in the 12th Five Year Plan of China(No.2011BAE22B05)the Canada-ChinaUSA Collaborative Research and Development Project(No.2011DFA50900)
文摘Sound radiation of thin plates is a common problem in engineering. Hashimoto proposed the discrete calculation method(DCM) to deal with the problem. The calculation of the radiation impedance of the rectangular element is more cumbersome than that of the circular one, so the discrete rectangular radiation element is approximated by the circular one. However, error is also introduced. The formula developed by Sha has been employed to get self- and mutual-radiation impedances of rectangular radiation element. Numerical study was performed to verify error introduced by the approximation Hashimoto adopted. Experimental researches on sound radiation of a 2 mm-thick and a 4 mm-thick magnesium alloy plates were also carried out to evaluate the errors introduced by the approximation. The experimental results indicate that the circular approximation Hashimoto adopted overestimates the sound radiation efficiency. The maximum error levels of the radiation efficiencies of the2 mm-thick and 4 mm-thick magnesium alloy plates are up to 0.15 and 0.12, respectively. The effect of element aspect ratio on the sound radiation efficiency is also remarkable.
基金National Natural Science Foundation of China!(No.59738150)
文摘Based on the piezo-optic effect of medium, the refractive index of medium is the function of its density, and so it's also the function of acoustic pressure. Therefore, acoustic pressure in the optical path everywhere can be determined absolutely by laser-interferometric technique and relative distribution of pressure in the middle and far acoustic field, which can be obtained from theory or experiment respectively. Theory and experiment of measurement of pressure in acoustic field with laser-interferometer are introduced. Distribution of pressure radiated by a power ultrasonic transducer is determined by laser interferometric technique. The theoretical and experimental results are in good agreement. The receiving sensitivity of a PVDF (Polyvinylidene fluoride) transducer in free field is also calibrated absolutely due to above results and its sensitivity is -118.5 dB.
文摘An easy-to-implement scheme called Enhanced High Gain Harmonic Generation is expected to be able to significantly enhance the performance of HG-FEL. In this paper we investigate the effects of the system parameters in the new scheme, including the electron energy detuning, initial electron-beam energy spread, seeding laser power, dispersive field strength and amount of the phase shift, etc. The numerical results from GENESIS (3D-code) are presented and show that the new scheme has acceptable parameters tolerance requirements and is no more or even less sensitive to the system parameters than that of the existing scheme; With the electron energy above the resonance, the efficiency is enhanced for both the new scheme and the existing scheme compared with the resonant energy case.
文摘In this paper, a general formula for calculating the complex strengths of secondary sources is derived from the minimization criterion of total acoustic power output when both of the primary and secondary sources are directional. Then specific properties of active sound attenuation are presented for some commonly used typical directional sources and the rule for distributing directional secondary sources is given.