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Computation of satellite clock-ephemeris augmentation parameters for dual-frequency multi-constellation satellite-based augmentation system 被引量:3
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作者 CHEN Jie HUANG Zhigang LI Rui 《Journal of Systems Engineering and Electronics》 SCIE EI CSCD 2018年第6期1111-1123,共13页
Dual-frequency multi-constellation(DFMC) satellitebased augmentation system(SBAS) does not broadcast fast correction, which is important in reducing range error in L1-only SBAS.Meanwhile, the integrity bound of a sate... Dual-frequency multi-constellation(DFMC) satellitebased augmentation system(SBAS) does not broadcast fast correction, which is important in reducing range error in L1-only SBAS.Meanwhile, the integrity bound of a satellite at low elevation is so loose that the service availability is decreased near the boundary of the service area. Therefore, the computation of satellite clockephemeris(SCE) augmentation parameters needs improvement.We propose a method introducing SCE prediction to eliminate most of the SCE error resulting from global navigation satellite system GNSS broadcast message. Compared with the signal-inspace(SIS) after applying augmentation parameters broadcast by the wide area augmentation system(WAAS), SIS accuracy after applying augmentation parameters computed by the proposed algorithm is improved and SIS integrity is ensured. With global positioning system(GPS) only, the availability of category-I(CAT-I)with a vertical alert level of 15 m in continental United States is about 90%, while the availability in the other part of the WAAS service area is markedly improved. With measurements made by the stations from the crustal movement observation network of China,users in some part of China can obtain CAT-I(vertical alert limit is 15 m) service with GPS and global navigation satellite system(GLONASS). 展开更多
关键词 dual-frequency multi-constellation(DFMC) satellitebased augmentation system(SBAS) orbit determination integrity
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Understanding the spatial interaction of ultrasounds based on three-dimensional dual-frequency ultrasonic field numerical simulation
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作者 Zhao-yang Yin Qi-chi Le +3 位作者 Yan-chao Jiang Da-zhi Zhao Qi-yu Liao Qi Zou 《China Foundry》 SCIE EI CAS CSCD 2024年第1期29-43,共15页
A transient 3D model was established to investigate the effect of spatial interaction of ultrasounds on the dual-frequency ultrasonic field in magnesium alloy melt.The effects of insertion depth and tip shape of the u... A transient 3D model was established to investigate the effect of spatial interaction of ultrasounds on the dual-frequency ultrasonic field in magnesium alloy melt.The effects of insertion depth and tip shape of the ultrasonic rods,input pressures and their ratio on the acoustic field distribution were discussed in detail.Additionally,the spacing,angle,and insertion depth of two ultrasonic rods significantly affect the interaction between distinct ultrasounds.As a result,various acoustic pressure distributions and cavitation regions are obtained.The spherical rods mitigate the longitudinal and transversal attenuation of acoustic pressure and expand the cavitation volume by 53.7%and 31.7%,respectively,compared to the plate and conical rods.Increasing the input pressure will enlarge the cavitation region but has no effect on the acoustic pressure distribution pattern.The acoustic pressure ratio significantly affects the pressure distribution and the cavitation region,and the best cavitation effect is obtained at the ratio of 2:1(P15:P20). 展开更多
关键词 dual-frequency ultrasonic numerical model acoustic pressure spatial interaction magnesium alloy
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Degradation of 4-Chlorophenol Solution by Synergetic Effect of Dual-frequency Ultrasound with Fenton Reagent 被引量:8
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作者 赵德明 徐新华 +1 位作者 雷乐成 汪大翚 《Chinese Journal of Chemical Engineering》 SCIE EI CAS CSCD 2005年第2期204-210,共7页
4-Chlorophenol (4-CP) solution was treated by dual-frequency ultrasound inconjunction with Fenton reagent, and obvious improvement in the 4-CP degradation rate was observedin this advanced oxidation process. Experimen... 4-Chlorophenol (4-CP) solution was treated by dual-frequency ultrasound inconjunction with Fenton reagent, and obvious improvement in the 4-CP degradation rate was observedin this advanced oxidation process. Experimental results showed that ultrasonic intensity,saturating gas and pH value affected greatly the 4-CP removal rate. Among four different saturatinggases (Ar, O_2, air and N_2), 4-CP degradation with Ar-saturated solution was the best. However, inthe view of practical wastewater treatment, using oxygen as the saturating gas would be moreeconomical. The addition of Fenton reagent followed the first-order kinetics and increased the 4-CPdegradation rate. The 4-CP removal rate increased by around 126% within 15 min treatment. Thesynergetic effect of dual-frequency ultrasound with Fenton reagent on 4-CP degradation was obviouslyobserved. 展开更多
关键词 dual-frequency ultrasound with Fenton reagent advanced oxidation process synergetic effect
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Design and preliminary test of a 105/140 GHz dual-frequency MW-level gyrotron 被引量:3
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作者 Linlin HU Dimin SUN +11 位作者 Qili HUANG Tingting ZHUO Guowu MA Yi JIANG Shenggang GONG Zaojin ZENG Zixing GUO Chaohai DU Fanhong LI Hongbin CHEN Fanbao MENG Hongge MA 《Plasma Science and Technology》 SCIE EI CAS CSCD 2022年第3期162-169,共8页
A dual-frequency(105/140 GHz)MW-level continuous-wave gyrotron was developed for fusion application at Institute of Applied Electronics,China Academy of Engineering Physics.This gyrotron employs a cylindrical cavity w... A dual-frequency(105/140 GHz)MW-level continuous-wave gyrotron was developed for fusion application at Institute of Applied Electronics,China Academy of Engineering Physics.This gyrotron employs a cylindrical cavity working in the TE18,7 mode at 105 GHz and the TE24,9 mode at 140 GHz.A triode magnetron injection gun and a built-in quasi-optical mode converter were designed to operate at these two frequencies.For the proof-test phase,the gyrotron was equipped with a single-disk boron nitride window to achieve radio frequency output with a power of~500 k W for a short-pulse duration.In the preliminary short-pulse proof-test in the first quarter of2021,the dual-frequency gyrotron achieved output powers of 300 k W at 105 GHz and 540 k W at140 GHz,respectively,under 5 Hz 1 ms continuous pulse-burst operations.Power upgrade and pulse-width extension were hampered by the limitation of the high-voltage power supply and output window.This gyrotron design was preliminarily validated. 展开更多
关键词 GYROTRON MEGAWATT plasma heating fusion application dual-frequency
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Analytical Expressions of Dual-Frequency Plasma Diagnostic Theory 被引量:3
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作者 程立 时家明 许波 《Plasma Science and Technology》 SCIE EI CAS CSCD 2012年第1期37-39,共3页
Based on the fundamental ideas concerning microwave attenuation in plasma, we obtain a new expression of transmission attenuation of microwaves as a function of the incident wave frequency. And with reasonable hypothe... Based on the fundamental ideas concerning microwave attenuation in plasma, we obtain a new expression of transmission attenuation of microwaves as a function of the incident wave frequency. And with reasonable hypothesis, analytical forms of the electron density and the electron-neutral collision frequency are derived from the equations of the transmission attenuation of microwaves at two near frequencies. This method gives an effective and easy approach to diagnose the unmagnetized plasma. 展开更多
关键词 PLASMA diagnosis dual-frequency ATTENUATION electron density electron-neutral collision frequency
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Optical feedback characteristics in a dual-frequency laser during laser cavity tuning 被引量:2
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作者 刘刚 张书练 +1 位作者 李岩 朱钧 《Chinese Physics B》 SCIE EI CAS CSCD 2005年第10期1984-1989,共6页
The optical feedback characteristics in a Zeeman-birefringence dual-frequency laser are studied during the laser cavity tuning in three different kinds of optical feedback conditions: (i) only //-light is fed back;... The optical feedback characteristics in a Zeeman-birefringence dual-frequency laser are studied during the laser cavity tuning in three different kinds of optical feedback conditions: (i) only //-light is fed back; (ii) only ⊥-light is fed back; (iii) both lights are fed back. A compact displacement sensor is designed using the experimental result that there is a nearly 90 degrees phase delay between the two lights' cosine optical feedback signals when both lights are fed back into the laser cavity. The priority order that the two lights' intensity curves appear can be used for direction discrimination. The resolution of the displacement sensor is at least 79 rim, and the sensor can discriminate the target's moving direction easily. 展开更多
关键词 dual-frequency laser optical feedback SELF-MIXING displacement sensor
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DEFORMATION MEASUREMENT USING DUAL-FREQUENCY PROJECTION GRATING PHASE-SHIFT PROFILOMETRY 被引量:2
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作者 Yanming Chen Yuming He Eryi Hu Hongmao Zhu 《Acta Mechanica Solida Sinica》 SCIE EI 2008年第2期110-115,共6页
2π phase ambiguity problem is very important in phase measurement when a deformed object has a large out of plane displacement. The dual-frequency projection grating phaseshifting profilometry (PSP) can be used to ... 2π phase ambiguity problem is very important in phase measurement when a deformed object has a large out of plane displacement. The dual-frequency projection grating phaseshifting profilometry (PSP) can be used to solve such an issue. In the measurement, two properchosen frequency gratings are utilized to synthesize an equivalent wavelength grating which ensures the computed phase in a principal phase range. Thus, the error caused by the phase unwrapping process with the conventional phase reconstruct algorithm can be eliminated. Finally, experimental result of a specimen with large plastic deformation is given to prove that the proposed method is effective to handle the phase discontinuity. 展开更多
关键词 dual-frequency phase-shift profilometry projection grating phase unwrapping DEFORMATION
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EXPERIMENTAL STUDY ON SOIL MOISTURE USING DUAL-FREQUENCY MICROWAVE RADIOMETER 被引量:2
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作者 GUAN Zhi ZHAO Kai SONG Dong-sheng 《Chinese Geographical Science》 SCIE CSCD 2006年第1期83-86,共4页
An experiment of measuring soil moisture was carried out by using dual-frequency microwave radiometer designed by the authors. The measured data were analyzed by using statistical regression method and the empirical r... An experiment of measuring soil moisture was carried out by using dual-frequency microwave radiometer designed by the authors. The measured data were analyzed by using statistical regression method and the empirical regression model of retrieving soil moisture in L-band and C-band was developed. The soil moisture in a rainfall event was retrieved using the experiential regression model, which is consistent well with the field sampling value. The results show that when soil moisture is lower than 75%, the brightness temperature is linear with soil moisture. However, when soil moisture is higher than 75%, the brightness temperature is not linear with soil moisture, so it is difficult for microwave radiometer to measure the changes of soil moisture. The experiment verifies the effectiveness and feasibility of microwave remote sensing soil moisture. Although this method for linear regression based on the data measured with the radiometer is simple, and has strong adaptability, generally it has only local application value, and lacks universal applicability for different areas and different conditions. 展开更多
关键词 soil moisture dual-frequency microwave radiometer brightness temperature
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The Performance of Dual-Frequency Polarimetric Scatterometer in Sea Surface Wind Retrieval 被引量:1
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作者 LIU Shubo WEI Enbo +2 位作者 JIN Xu LV Ailing DANG Hongxing 《Journal of Ocean University of China》 SCIE CAS CSCD 2019年第5期1051-1060,共10页
The wind retrieval performance of HY-2 A scanning scatterometer operating at Ku-band in HH and VV polarizations has been well evaluated in the wind speed range of 0–25 m s^-1.In order to obtain more accurate ocean wi... The wind retrieval performance of HY-2 A scanning scatterometer operating at Ku-band in HH and VV polarizations has been well evaluated in the wind speed range of 0–25 m s^-1.In order to obtain more accurate ocean wind field,a potential extension of dual-frequency(C-band and Ku-band)polarimetric measurements is investigated for both low and very high wind speeds,from 5 to 45 m s^-1.Based on the geophysical model functions of C-band and Ku-band,the simulation results show that the polarimetric measurements of Ku-band can improve the wind vector retrieval over the entire scatterometer swath,especially in nadir area,with the wind direction root-mean-square error(RMSE)less than 12?in the wind speed range of 5–25 m s^-1.Furthermore,the results also show that C-band cross-polarization plays a very important role in improving the wind speed retrieval,with the wind speed retrieval accuracy better than 2 m s^-1 for all wind conditions(0–45 m s^-1).For extreme winds,the C-band HH backscatter coefficients modeled by CMOD5.N(H)and the ocean co-polarization ratio model at large incidence are used to retrieve sea surface wind vector.This result reveals that there is a big decrease of wind direction retrieval RMSE for extreme wind fields,and the retrieved result of C-band HH polarization is nearly the same as that of C-band VV polarization for low-to-high wind speed(5–25 m s^-1).Thus,to improve the wind retrieval for all wind conditions,the dual-frequency polarimetric scatterometer with C-band and Ku-band horizontal polarization in inner beam,and C-band horizontal and Ku-band vertical polarization in outer beam,can be used to measure ocean winds.This study will contribute to the wind retrieval with merged satellites data and the future spaceborne scatterometer. 展开更多
关键词 dual-frequency polarimetric SCATTEROMETER WIND VECTOR RETRIEVAL
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Difference-frequency ultrasound generation from microbubbles under dual-frequency excitation 被引量:1
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作者 马青玉 邱媛媛 +2 位作者 黄蓓 章东 龚秀芬 《Chinese Physics B》 SCIE EI CAS CSCD 2010年第9期437-442,共6页
The difference-frequency (DF) ultrasound generated by using parametric effect promises to improve detection depth owing to its low attenuation, which is beneficial for deep tissue imaging. With ultrasound contrast a... The difference-frequency (DF) ultrasound generated by using parametric effect promises to improve detection depth owing to its low attenuation, which is beneficial for deep tissue imaging. With ultrasound contrast agents infusion, the harmonic components scattered from the microbubbles, including DF, can be generated due to the nonlinear vibration. A theoretical study on the DF generation from microbubbles under the dual-frequency excitation is proposed in formula based on the solution of the RPNNP equation. The optimisation of the DF generation is discussed associated with the applied acoustic pressure, frequency, and the microbubble size. Experiments are performed to validate the theoretical predictions by using a dual-frequency signal to excite microbubbles. Both the numerical and experimental results demonstrate that the optimised DF ultrasound can be achieved as the difference frequency is close to the resonance frequency of the microbubble and improve the contrast-to-tissue ratio in imaging. 展开更多
关键词 difference-frequency MICROBUBBLE dual-frequency excitation parametric effect
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Effect of Low-frequency Power on F, CF_2 Relative Density and F/CF_2 Ratio in Fluorocarbon Dual-Frequency Plasmas 被引量:1
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作者 黄宏伟 叶超 +3 位作者 徐轶君 袁圆 施国峰 宁兆元 《Plasma Science and Technology》 SCIE EI CAS CSCD 2010年第5期566-570,共5页
Effect of low-frequency power on F, CF2 relative density and F/CF2 ratio, in C2F6, C4F8 and CHF3 dual-frequency capacitively couple discharge driven by the power of 13.56 MHz/2 MHz, was investigated by using optical e... Effect of low-frequency power on F, CF2 relative density and F/CF2 ratio, in C2F6, C4F8 and CHF3 dual-frequency capacitively couple discharge driven by the power of 13.56 MHz/2 MHz, was investigated by using optical emission spectroscopy. High F, CF2 relative density and high F/CF2 ratio were obtained in a CHF3 plasma. But for C2F6 and C4Fs plasmas, the F, CF2 relative density and F/CF2 ratio all decreased significantly due to the difference in both reactive paths and reactive energy. The increase of LF power caused simultaneous increase of F and CF2 radical relative densities in C4Fs and CHF3 plasmas, but led to increase of F with the decrease in CF2 relative densities in C2F6 plasma due to the increase of lower energy electrons and the decrease of higher energy electrons in electron energy distribution function (EEDF). 展开更多
关键词 fluorocarbon plasma dual-frequency discharge low-k films etching
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Improved Double-Probe Technique for Spatially Resolved Diagnosis of Dual-Frequency Capacitive Plasmas 被引量:1
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作者 陆文琪 蒋相站 +6 位作者 刘永新 杨烁 张权治 李小松 徐勇 朱爱民 王友年 《Plasma Science and Technology》 SCIE EI CAS CSCD 2013年第6期511-515,共5页
The conventional double-probe technique was improved with a combination of selfpowering and radio-frequency(RF) choking.RF perturbations in dual-frequency capacitively coupled discharge were effectively eliminated,a... The conventional double-probe technique was improved with a combination of selfpowering and radio-frequency(RF) choking.RF perturbations in dual-frequency capacitively coupled discharge were effectively eliminated,as judged by the disappearance of self-bias on the probes.The improved technique was tested by spatially resolved measurements of the electron temperature and ion density in both the axial and radial directions of a dual-frequency capacitive plasma.The measured data in the axial direction were compared with simulation results,and they were excellently consistent with each other.The measured radial distributions of the ion density and electron temperature were influenced significantly by the lower frequency(LF) power.It was shown that superposition of the lower frequency to the higher frequency(HF) power shifted the maximum ion density from the radial center to the edge region,while the trend for the electron temperature profile was the opposite.The changing feature of the ion density distribution is qualitatively consistent with that of the optical emission intensity reported. 展开更多
关键词 dual-frequency capacitive plasma double probe plasma diagnosis
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Investigation of Capacitively Coupled Argon Plasma Driven by Dual-Frequency with Different Frequency Configurations 被引量:1
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作者 虞一青 辛煜 +1 位作者 陆文琪 宁兆元 《Plasma Science and Technology》 SCIE EI CAS CSCD 2011年第5期571-574,共4页
Low pressure argon dual-frequency (DF) capacitively coupled plasma (CCP) is generated by using different frequency configurations, such as 13.56/2, 27/2, 41/2, and 60/2 MHz. Characteristics of the plasma are inves... Low pressure argon dual-frequency (DF) capacitively coupled plasma (CCP) is generated by using different frequency configurations, such as 13.56/2, 27/2, 41/2, and 60/2 MHz. Characteristics of the plasma are investigated by using a floating double electrical probe and optical emission spectroscopy (OES). It is shown that in the DF-CCPs, the electron temperature Te decreases with the increase in exciting frequency, while the onset of 2 MHz induces a sudden increase in Te and the electron density increases basically with the increase in low frequency (LF) power. The intensity of 750.4 nm emission line increases with the LF power in the case of 13.56/2 MHz, while different tendencies of line intensity with the LF power appear for other configurations. The reason for this is also discussed. 展开更多
关键词 dual-frequency capacitively coupled plasma double probe optical emission spectroscopy
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Effect of Discharge Parameters on Properties of Diamond-Like Carbon Films Prepared by Dual-Frequency Capacitively Coupled Plasma Source 被引量:1
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作者 杨磊 辛煜 +2 位作者 徐海鹏 虞一青 宁兆元 《Plasma Science and Technology》 SCIE EI CAS CSCD 2010年第1期53-58,共6页
Diamond-like carbon (DLC) films were prepared with CH4-Ar using a capacitively coupled plasma enhanced chemical vapor deposition (CCP-CVD) method driven by dual-frequency of 41 MHz and 13.56 MHz in combination. Du... Diamond-like carbon (DLC) films were prepared with CH4-Ar using a capacitively coupled plasma enhanced chemical vapor deposition (CCP-CVD) method driven by dual-frequency of 41 MHz and 13.56 MHz in combination. Due to a coupling via bulk plasma, the self-bias voltage depended not only on the radiofrequency (RF) power of the corresponding electrode but also on another RF power of the counter electrode. The influence of the discharge parameters on the deposition rate, optical and Raman properties of the deposited films was investigated. The optical band decreased basically with the increase in the input power of both the low frequency and high frequency. Raman measurements show that the deposited films have a maximal sp3 content with an applied negative self-bias voltage of -150 V, while high frequency power causes a continuous increase in the sp3 content. The measurement of atomic force microscope (AFM) shows that the surface of the deposited films under ion-bombardment becomes smoother than those with non-intended self-bias voltage. 展开更多
关键词 dual-frequency capacitively coupled discharge DLC Raman spectroscopy
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Deposition of organosilicone thin film from hexamethyldisiloxane(HMDSO)with 50kHz/33MHz dual-frequency atmospheric-pressure plasma jet 被引量:1
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作者 李娇娇 袁强华 +3 位作者 常小伟 王勇 殷桂琴 董晨钟 《Plasma Science and Technology》 SCIE EI CAS CSCD 2017年第4期92-98,共7页
The deposition of organosilicone thin films from hexamethyldisiloxane(HMDSO) by using a dual-frequency (50 kHz/33 MHz) atmospheric-pressure micro-plasma jet with an admixture of a small volume of HMDSO and Ar was ... The deposition of organosilicone thin films from hexamethyldisiloxane(HMDSO) by using a dual-frequency (50 kHz/33 MHz) atmospheric-pressure micro-plasma jet with an admixture of a small volume of HMDSO and Ar was investigated.The topography was measured by using scanning electron microscopy.The chemical bond and composition of these films were analyzed by Fourier transform infrared spectroscopy (FTIR) and x-ray photoelectron spectroscopy.The results indicated that the as-deposited film was constituted by silicon,carbon,and oxygen elements,and FTIR suggested the films are organosilicon with the organic component (-CHx) and hydroxyl functional group(-OH) connected to the Si-O-Si backbone.Thin-film hardness was recorded by an MH-5-VM Digital Micro-Hardness Tester.Radio frequency power had a strong impact on film hardness and the hardness increased with increasing power. 展开更多
关键词 organosilicone thin film HEXAMETHYLDISILOXANE dual-frequency atmospheric-pressureplasma jet
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Effect of Low-Frequency Power on Etching Characteristics of 6H-SiC in C4F8/Ar Dual-Frequency Capacitively Coupled Plasma 被引量:1
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作者 XU Yijun WU Xuemei YE Chao 《Plasma Science and Technology》 SCIE EI CAS CSCD 2013年第10期1066-1070,共5页
Dry etching of 6H silicon carbide (6H-SiC) wafers in a C4Fs/Ar dual-frequency capacitively coupled plasma (DF-CCP) was investigated. Atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) wer... Dry etching of 6H silicon carbide (6H-SiC) wafers in a C4Fs/Ar dual-frequency capacitively coupled plasma (DF-CCP) was investigated. Atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) were used to measure the SiC surface structure and compositions, respectively. Optical emission spectroscopy (OES) was used to measure the relative concentration of F radicals in the plasma. It was found that the roughness of the etched SiC surface and the etching rate are directly related to the power of low-frequency (LF) source. At lower LF power, a smaller surface roughness and a lower etching rate are obtained due to weak bombardment of low energy ions on the SiC wafers. At higher LF power the etching rate can be efficiently increased, but the surface roughness increases too. Compared with other plasma dry etching methods, the DF-CCP can effectively inhibit CχFγ films' deposition, and reduce surface residues. 展开更多
关键词 SIC plasma etching dual-frequency capacitively coupled plasma X-ray photoelectron spectroscopy optical emission spectroscopy
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Study of numerical simulation on dual-frequency IP method with FEM 被引量:2
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作者 LIN Jiayong DIN Maobin +1 位作者 TANG Jingtian YAN Hong 《Global Geology》 2010年第2期99-103,共5页
Using the finite element method and Cole-Cole model for dual-frequency IP method to research numerical simulation, the authors introduced the fundamental principle of the dual-frequency IP method and the boundary valu... Using the finite element method and Cole-Cole model for dual-frequency IP method to research numerical simulation, the authors introduced the fundamental principle of the dual-frequency IP method and the boundary value problem and variational equations, then replaced the complex resistivity of the model with the Cole-Cole model's parameters under ignoring the EM effect. Through solving the last linear equations, electric potentials of all the model's points were obtained. With changing model's parameters, the authors got different curves of the Fs and phases. According to the results of the simulation, the algorithm is proved to be correct and adaptable. 展开更多
关键词 dual-frequency IP numerical simulation frequency domain FEM
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Dual-Frequency Operation of Bow-Tie Microstrip Antenna
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作者 钟顺时 张需溥 《Journal of Shanghai University(English Edition)》 CAS 2005年第3期234-236,共3页
Characteristics of a single-feed dual-frequency bow-tie microstrip antenna are studied. By using the variation method, simple formulas for resonant frequencies of the bow-tie microstrip antenna are derived. It is show... Characteristics of a single-feed dual-frequency bow-tie microstrip antenna are studied. By using the variation method, simple formulas for resonant frequencies of the bow-tie microstrip antenna are derived. It is shown that the dual-frequency ratio can be controlled easily by choosing the parameters of the antenna. This design gives compact antenna size and simple antenna structure. Experimental results are presented, verifying the validity of the design. 展开更多
关键词 microstrip antennas resonant frequency dual-frequency miniature design.
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A Physics-Based Dual-Frequency Approach for Altimeter Wind Speed Retrieval
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作者 LI Shuiqing ZHOU Liangming +3 位作者 LI Zhanbin MIAO Qingsheng MOU Lin WANG Aifang 《Journal of Ocean University of China》 SCIE CAS 2014年第4期579-583,共5页
The altimeter normalized radar cross section(NRCS) has been used to retrieve the sea surface wind speed for decades, and more than a dozen of wind speed retrieval algorithms have been proposed. Despite the continuing ... The altimeter normalized radar cross section(NRCS) has been used to retrieve the sea surface wind speed for decades, and more than a dozen of wind speed retrieval algorithms have been proposed. Despite the continuing efforts to improve the wind speed measurements, a bias dependence on wave state persists in all wind algorithms. On the basis of recent evidence that short waves are essentially modulated by local winds and much less affected by wave state, we proposed a physics-based approach to retrieve the wind speed from the dual-frequency difference in terms of the mean square slope of short waves. A collocated dataset of coincident altimeter/buoy measurements were used to develop and validate the approach. Validation against buoy measurements indicates that the approach is almost unbiased and has an overall root mean square error of 1.24 m s-1, which is 5.3% lower than the single-parameter algorithm in operational use(Witter and Chelton, 1991) and 2.4% lower than another dual-frequency approach(Chen et al., 2002). Furthermore, the results indicate that the new approach significantly improves the wave-dependent bias compared to the single-parameter algorithm. The capacity of altimeter to retrieve sea surface wind speed appears to be limited for the case of winds below 3 m s-1. The validity of the approach at high winds needs to be further examined in the future study. 展开更多
关键词 ALTIMETER mean square slope dual-frequency wind speed retrieval
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Effects of HF frequency on plasma characteristics in dual-frequency helium discharge at atmospheric pressure by fluid modeling
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作者 Yinan WANG Shuaixing LI +3 位作者 Li WANG Ying JIN Yanhua ZHANG Yue LIU 《Plasma Science and Technology》 SCIE EI CAS CSCD 2018年第11期76-83,共8页
On the basis of the fluid theory and the drift-diffusion approximation, a numerical model for dual-frequency atmospheric pressure helium discharge is established, in order to investigate the effects of the high freque... On the basis of the fluid theory and the drift-diffusion approximation, a numerical model for dual-frequency atmospheric pressure helium discharge is established, in order to investigate the effects of the high frequency source (HF) on the characteristics of dual-frequency atmospheric pressure helium discharge. The numerical results showed that the electron heating rate increases with enhancing HF frequency, as well as the particles densities, electron dissipation rate, current density, net electron generation and bulk plasma region. Moreover, it is also observed that the efficient electron heating region moves when the HF frequency has been changed. The plasma parameters are not linear change with the HF frequency linearly increasing. 展开更多
关键词 dual-frequency numerical study electron energy mechanisms
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