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The seasonal dependence of cycle slip occurrence of GPS data over China low latitude region

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Science China(Technological Sciences) 2007年第4期50卷 422-429页

作者： ZHANG DongHe FENG Man XIAO Zuo HAO YongQiang SHI LiQin YANG GuangLin SUO YuCheng Department of Geophysics Peking UniversityBeijing 100871China Center for Space Science and Applied Research Chinese Academy of SciencesBeijing 100080China National Forecasting Center for Space Weather Beijing 100080China China Research Institute for Radio Propagation Xinxiang 453003China

The relationship of daily accumulated cycle slip occurrence with the season is analyzed using the GPS data observed in six GPS stations located in China low latitude region in 2001. It is found that the seasonal dependence of cycle slip oc-currence is evident. The cycle slip mainly occurs during the periods of two equinox months (March to May and September to October), and some correlative changes of the cycle slip occurrences over all six stations are exhibited in some special days. Considering the diurnal dependence of cycle slip, it can be inferred that the cycle slip occurrence with certain elevation limitation is related with the iono-spheric irregularities over this region.

关键词： GPS cycle slip ionospheric irregularities scintillation carrier phase

Design and analysis of the optical transceiver for mobile atmospheric laser communication

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Chinese Optics Letters 2003年第8期1卷 455-458页

作者：马东堂魏急波庄钊文温涛 College of Electronic Science and Engineering National University of Defense Technology Changsha 410073

The concept of mobile atmospheric laser communication (MALC) is introduced in this paper. Atmospheric attenuation, turbulence-induced scintillation and beam wander cause deep fades in the beam power and degrade the optical channel. The optical transceiver presented in this paper is designed for a MALC test system. Currently achievable hardware performance capabilities for the MALC terminals are used as input parameters to the analysis. A novel optical transceiver structure is designed. Link margin is analyzed using the MALC analysis software, our optical link analysis program. Data rate, bit-error rate, prime transmit power requirements, optical link margin, pulse width, background signal, aperture quality and atmospheric effects drive the optical transmitter requirements. Results are displayed as required aperture size, aperture number and the spacing between apertures for a given range and terminal moving speed. The aperture size is parameterized by data rate, transmitting optical power and wavelength. Si-APD and CCD are selected as the main receive detectors. The receiver aperture, detector size (diameter), receiver speed and sensitivity are the main factors to consider in the design of the receiver.

关键词： Bit error rate Charge coupled devices Lenses Probability scintillation

Fast light of CsI(Na) crystals

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Chinese Physics C 2011年第12期35卷 1130-1133页

作者：孙希磊吕军光胡涛周莉曹俊王贻芳占亮俞伯祥蔡啸方建谢宇广安正华王志刚薛镇章爱武吕绮雯宁飞鹏葛永帅刘颖彪 Institute of High Energy Physics CAS Shanxi University

The responses of different common alkali halide crystals to alpha-rays and gamma-rays are tested in this research. It is found that only CsI（Na） crystals have significantly different waveforms between alpha and gamma scintillations, while others do not exhibit this phenomena. The rise time of the fast light is about 5 ns and the decay time is 174-12 ns. It is suggested that the fast light of CsI（Na） crystals arises from the recombination of free electrons with self-trapped holes of the host crystal CsI. Self-absorption limits the emission of fast light of CsI（T1） and NaI（T1） crystals.

关键词： CsI（Na） waveform ionization scintillation exciton self-absorption

Aperture-averaging effects for weak to strong scintillations in turbulent atmosphere

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Chinese Optics Letters 2004年第7期2卷 373-375页

作者：张逸新朱拓陶纯堪 School of Science Southern Yangtze University Wuxi 214036School of Electronic Engineering and Optoelectronic Techniques.Nanjing University of Science and Technology Nanjing 210014 School of Science Southern Yangtze University Wuxi 214036 School of Electronic Engineering and Optoelectronic Techniques. Nanjing University of Science and Technology Nanjing 210014nder the approximations of (1) the received irradiance fluctuations of an optical wave caused by small scale turbulent eddies are multiplicatively modulated by the fluctuations caused by large scale turbulent eddies (2) the scintillations caused by small- and large-scale eddies respectively are statistically independent (3) the Rytov method for optical scintillation collected by the finite-diameter receiving aperture is valid for light wave propagation under weak to saturation fluctuation regime we develop the applicable aperture-averaging analytic formulas in the week-to-strong-fluctuation for the scintillations of plane and spherical waves which include the outer- and inner-scale rules of turbulence.

Under the approximations of (1) the received irradiance fluctuations of an optical wave caused by small scale turbulent eddies are multiplicatively modulated by the fluctuations caused by large scale turbulent eddies; (2) the scintillations caused by small- and large-scale eddies, respectively, are statistically independent; (3) the Rytov method for optical scintillation collected by the finite-diameter receiving aperture is valid for light wave propagation under weak to saturation fluctuation regime, we develop the applicable aperture-averaging analytic formulas in the week-to-strong-fluctuation for the scintillations of plane and spherical waves, which include the outer- and inner-scale rules of turbulence.

关键词： scintillation Turbulent flow

A study of ionospheric scintillation effects on Differential GNSS

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A study of ionospheric scintillation effects on Differential...

A DISCUSSION ON FRESNEL APPROXIMATION IN PHASE SCREEN MODEL

第三届中国卫星导航学术年会

作者： Liu Dun,Deng Zhongxin,Feng Jian,Zhen Weimin China Research Institute of Radiowave Propagation,Qingdao 266107,China

Irregularly structured ionospheric regions can cause diffraction and scattering of trans-ionospheric GNSS signals.When received at an antenna,these signals present random temporal fluctuations in both amplitude and phase,as known ionospheric scintillation.In addition to worsening the signal quality,ionospheric irregularity related to scintillation will break down the spatial correlation structure of ionosphere,leading to a degradation of differential GNSS performance.As the data analysis shows that during a scintillation event,the length of baseline on which DGNSS could be used will be reduced to a much shorter distance comparing with that under undisturbed ionosphere condition.The residual error caused by scintillation related irregularity increases as the length of baseline increase during the scintillation event.The residual error under scintillation could be 2～4 times bigger than that of no scintillation effects.The accuracy of scintillation effected DGNSS is even worse than that of under quiet ionosphere condition for baselines longer than 20km as indicated by our analysis in this paper.

关键词： GNSS Ionosphere scintillation Differential GNSS

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Journal of Electronics(China) 1990年第1期7卷 93-97页

作者：逯贵祯 Beijing Broadcast Institute Beijing

The Fresnel approximation in phase screen model is discussed and the coherencefunction is derived for k>>k.The application condition for Rino’s results is obtained,and it is|▽R△Ne|/R△ne<<1.

关键词： Ionospheric scintillation Power law phase screen model Random media

Study of the Ionospheric Effects of Selected Cases of Solar Flares over Abidjan

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Journal of Physical Science and Application 2018年第3期8卷 18-25页

作者： Jean Baptiste Ackah Olivier Kouadio Obrou Sylvain Malan Ahoua Laboratoire de Physique de l'Atmosphere Universite Felix Houphouet Boigny Abidjan22 B.P.582 Abidjan 22Cote-d'Ivoire

The present study investigates the changes in TEC(total electron content)and ionospheric scintillation index(S4)inferred from the GNSS data recorded at the SCINDA station of Abidjan(Latitude=5.34°N,Longitude=3.90°W)during and after a solar flare.In the course of 2014,a year of high solar activity,three(3)cases of extreme(X1.66)and moderate(M6.23 and M2.13)solar flares recorded in the months of September and December effects on the ionosphere have been studied using the X ray fluxes,the magnetic parameters(Vx,Bz,Dst),the ionospheric scintillation index S4 and TEC and its ROT(time rate of change).The ROT exhibits a prominent peak between ten(10)and twelve(12)minutes after the occurrence of the maximum peak of the time rate of change of the X-ray flux emitted during the flare.The ROT maximum value occurs simultaneously with an enhancement of the S4 index.Deferred perturbations of the solar flare on the TEC in the SCINDA station of Abidjan occur within 42 to 54 hours after an M-class solar flare and within 46 to 58 hours following an X-Class solar flare.The magnetic storms resulted from these flares show an increment of 20%on VTEC observed when compared to the average VTEC()computed from the most five(5)quietest days of the selected months.

关键词： TEC ionospheric scintillation solar flare X-ray

Determination of Full Energy Peak Efficiency of NaI(Tl) Detector Depending on Efficiency Transfer Principle for Conversion Form Experimental Values

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World Journal of Nuclear Science and Technology 2012年第3期2卷 65-72页

作者： Mohamed Abd-Elzaher Mohamed Salem Badawi Ahmed El-Khatib Abouzeid Ahmed Thabet Department of Basic and Applied Science Faculty of Engineering Arab Academy for Science Technology and Maritime Transport Alexandria Egypt Physics Department Faculty of Science Alexandria University Alexandria Egypt

In this work we calibrated the NaI(Tl) scintillation detectors (5.08 × 5.08 cm2 and 7.62 × 7.62 cm2) and the Full Energy Peak Efficiency (FEPE) for these detectors have been calculated for point sources placed at different positions on the detector axis using the analytical approach of the effective solid angle ratio. This approach is based on the direct mathematical method reported by Selim and Abbas [1,2] and has been used successfully before to calibrate the cylindrical, parallelepiped, and 4π NaI(Tl) detectors by using point, plane and volumetric sources. In addition, the present method is free of some major inconveniences of the conventional methods.

关键词： Full Energy Peak Efficiency NaI(Tl) scintillation Efficiency Transfer

Determination of Tritium Concentration in Heavy Water

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World Journal of Nuclear Science and Technology 2014年第3期4卷 170-176页

作者： Reza Pourimani Mehrdad Aghamohammadi Department of Physics Faculty of Science Arak University Arak Iran

In this work, tritium concentration was determined in different D2O enrichment in heavy water samples. Samples were prepared from Arak Heavy Water Production Plant. Tritium concentration was determined utilizing liquid scintillation detector (LSC) system based on β-decay of tritium isotope. In this work instead of simple distillation, the azeotropic distillation method was used. Absorbed spectra and fluorescence spectra were registered by Shimadz spectrometer UV-2100 model and fluorescence spectrometer LS50B model respectively. Tritium concentration was obtained from 1.75 ± 0.80 up 6.16 ± 1.01 Bq/L for 0.35% to 77.50% enrichment of D2O concentration in heavy water samples. Coefficient correlation between tritium concentration and D2O concentration in heavy water R2 = 0.853 was derived. For 99.8% enriched D2O in heavy water, deviation was observed from direct line that caused decreasing of R2.

关键词： Tritium Liquid scintillation Detector Heavy Water Correlation Coefficient Azeotropic Distillation