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融合波模和射线理论的矿井电波传播模型 被引量:8
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作者 霍羽 徐钊 刘逢雪 《电子学报》 EI CAS CSCD 北大核心 2013年第1期110-116,共7页
本文提出了电波在煤矿井巷内传播的融合模型:利用波导波模理论修正射线模型,确定巷道内源射线的个数及其离开发射机的方向;通过几何光学基本定律证明矩形巷道内射线传播路径投影的反射定律和夹角定律,推导出射线到达接收天线所在巷道截... 本文提出了电波在煤矿井巷内传播的融合模型:利用波导波模理论修正射线模型,确定巷道内源射线的个数及其离开发射机的方向;通过几何光学基本定律证明矩形巷道内射线传播路径投影的反射定律和夹角定律,推导出射线到达接收天线所在巷道截面的位置、经历的反射次数、路径长度等与射线离开角的关系,以改进主动射线跟踪法,简化计算;运用接收球原理判断各射线经反射后能否到达接收机.经仿真并与实测数据比较,验证了模型的正确性. 展开更多
关键词 波导波模 射线发射 射线跟踪 射线数量 离开角 巷道
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Application of 3D stereotomography to the deep-sea data acquired in the South China Sea:a tomography inversion case 被引量:2
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作者 邢逢源 杨锴 +2 位作者 薛冬 汪小将 陈宝书 《Applied Geophysics》 SCIE CSCD 2017年第1期142-153,191,192,共14页
A 3D stereotomography algorithm, which is derived from the 3D Cartesian coordinate, is applied for the first time to the deep-sea data acquired in the LH area, South China Sea, to invert a macro velocity model for pre... A 3D stereotomography algorithm, which is derived from the 3D Cartesian coordinate, is applied for the first time to the deep-sea data acquired in the LH area, South China Sea, to invert a macro velocity model for pre-stack depth migration. The successful implementation of stereotomography is highly dependent on the correct extraction of slowness components and the proper application of regularization terms. With the help of the structure tensor algorithm, a high-quality 3D stereotomography data space is achieved in a very efficient manner. Then, considering that the horizontal slowness in cross-line direction is usually unavailable for 3D narrow-azimuth data, the regularization terms must be enhanced to guarantee a stable convergence of the presented algorithm. The inverted model serves as a good model for the 3D pre-stack depth migration. The synthetic and real data examples demonstrated the robustness and effectiveness of the presented algorithm and the related schemes. 展开更多
关键词 3D stereotomography structure tensor extraction of horizontal components of slowness REGULARIZATION
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Microstructures and compressive properties of AZ91D/fly-ash cenospheres composites 被引量:2
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作者 黄志求 于思荣 李慕勤 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2010年第B07期458-462,共5页
Novel AZ91D Mg alloy/fly-ash cenospheres(AZ91D/FACs)composites were fabricated by melt stir technique.Fly-ash cenosphere particles with 4%,6%,8%,10%in mass fraction and 100μm in size were used.Hardness and compressiv... Novel AZ91D Mg alloy/fly-ash cenospheres(AZ91D/FACs)composites were fabricated by melt stir technique.Fly-ash cenosphere particles with 4%,6%,8%,10%in mass fraction and 100μm in size were used.Hardness and compressive strength of the composites were measured.The effects of mass fraction of cenospheres on the microstructure and compressive properties were characterized.The results show that the cenospheres are uniformly distributed in the matrix and there is no sign of cenosphere cluster or residual pore.The densities of the composites are 1.85-1.92 g/cm 3 .By comparing with matrix,the compressive yield strength of the composites is improved,and the cenospheres is filled with Mg matrix alloy.SEM,XRD and EDX results of the composites show clear evidence of reaction product at cenosphere/matrix interface.On the basis of XRD and EDX,composition, structure and thermodynamic analysis,the main interfacial phase between the cenosphere and AZ91D Mg alloy was identified to be MgAl2O4. 展开更多
关键词 fly ash cenosphere microstructure compressive properties interface
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Evaluation of wind vectors observed by HY-2A scatterometer using ocean buoy observations,ASCAT measurements,and numerical model data 被引量:5
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作者 李大伟 申辉 《Chinese Journal of Oceanology and Limnology》 SCIE CAS CSCD 2015年第5期1191-1200,共10页
The first Chinese microwave ocean environment satellite HY-2A was launched successfully in August, 201 I. This study presents a quality assessment of HY-2A scatterometer (HYSCAT) data based on comparison with ocean ... The first Chinese microwave ocean environment satellite HY-2A was launched successfully in August, 201 I. This study presents a quality assessment of HY-2A scatterometer (HYSCAT) data based on comparison with ocean buoy data, the Advanced Scatterometer (ASCAT) data, and numerical model data from the National Centers for Environmental Prediction (NCEP). The in-situ observations include those from buoy arrays operated by the National Data Buoy Center (NDBC) and Tropical Atmosphere Ocean (TAO) project. Only buoys located offshore and in deep water were analyzed. The temporal and spatial collocation windows between HYSCAT data and buoy observations were 30 min and 25 km, respectively. The comparisons showed that the wind speeds and directions observed by HYSCAT agree well with the buoy data. The root-mean-squared errors (RMSEs) of wind speed and direction for the HYSCAT standard wind products are 1.90 m/s and 22.80°, respectively. For the HYSCAT-ASCAT comparison, the temporal and spatial differences were limited to 1 h and 25 km, respectively. This comparison yielded RMSEs of 1.68 m/s for wind speed and 19.1° for wind direction. We also compared HYSCAT winds with reanalysis data from NCEP. The results show that the RMSEs of wind speed and direction are 2.6 m/s and 26°, respectively. The global distribution of wind speed residuals (HYSCAT-NCEP) is also presented here for evaluation of the HYSCAT-retrieved wind field globally. Considering the large temporal and spatial differences of the collocated data, it is concluded that the HYSCAT-retrieved wind speed and direction met the mission requirements, which were 2 rn/s and 20° for wind speeds in the range 2-24 m/s. These encouraging assessment results show that the wind data obtained from HYSCAT will be useful for the scientific community. 展开更多
关键词 HY-2A SCATTEROMETER wind fields EVALUATION
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Study on absorption coefficients of dual-energy γ-rays in determining phase fractions of multiphase flows
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作者 李志彪 李东晖 吴应湘 《Journal of Zhejiang University-Science A(Applied Physics & Engineering)》 SCIE EI CAS CSCD 2005年第12期1416-1419,共4页
This paper discusses the principle and mathematical method to measure the phase fractions of multiphase flows by using a dual-energy gamma-ray system. The dual-energy gamma-ray device is composed of radioactive isotop... This paper discusses the principle and mathematical method to measure the phase fractions of multiphase flows by using a dual-energy gamma-ray system. The dual-energy gamma-ray device is composed of radioactive isotopes of 241Am and 137Cs with emission energies of 59.5 keV and 662 keV respectively. A rational method to calibrate the absorption coefficient was introduced in detail. The statistical error has been analyzed on the basis of the accurate absorption coefficient which enables determination phrase fractions almost independent of the flow regime. Improvement has been achieved on the measurement accuracy of phase fractions. 展开更多
关键词 Absorption coefficient γ-rays DUAL-ENERGY Phase fraction
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Exact solutions to the Klein-Gordon equation in the vicinity of Schwarzschild black holes 被引量:1
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作者 QIN YiPing 《Science China(Physics,Mechanics & Astronomy)》 SCIE EI CAS 2012年第3期381-384,共4页
We find exact solutions to the Klein-Gordon equation in the vicinity of Schwarzschild black holes.For particles with a zero angular momentum,the convergence range of the solution is r < 4M.One of the solutions desc... We find exact solutions to the Klein-Gordon equation in the vicinity of Schwarzschild black holes.For particles with a zero angular momentum,the convergence range of the solution is r < 4M.One of the solutions describes an exponential enhancement of the density of particles in the vicinity of Schwarzschild black holes,which might be the mechanism of gamma-ray bursts. 展开更多
关键词 general relativity Schwarzschild black holes quantum effects
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The gamma-ray spectral index changes for blazars 被引量:3
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作者 YANG JiangHe FAN JunHui +1 位作者 NIE JianJun YANG RuShu 《Science China(Physics,Mechanics & Astronomy)》 SCIE EI CAS 2012年第11期2179-2185,共7页
Based upon Fermi 1FGL and EGRET 3EG samples, a sample including 79 blazars (53 FSRQs, 26 BL Lacs) is presented. It is investigated that the correlations between the ratio of EGRET to Fermi blazars g-ray flux densiti... Based upon Fermi 1FGL and EGRET 3EG samples, a sample including 79 blazars (53 FSRQs, 26 BL Lacs) is presented. It is investigated that the correlations between the ratio of EGRET to Fermi blazars g-ray flux densities and the spectral index differ for EGRET to Fermi blazars for three subclasses of high-frequency peaked BL Lacertae objects-HBL, low-frequency peaked BL Lacertae objects-LBL, and flat spectrum radio quasars-FSRQs. There is a consistent relationship between the ratio of the two γ-ray flux densities and the spectral index difference for the three subclasses. It suggests that the spectrum changed with the source brightness in the gamma-ray band. Both the spectral index difference and the correlation slopes follow a continuous sequence from FSRQs to LBLs to HBLs, which is consistent with the noted blazar sequence. 展开更多
关键词 active galactic nuclei (AGN) BLAZARS gamma-ray emission spectral index
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