利用核对软件降低MARK IV格式磁带回放数据的误码率     

LU Chunmei 《中国科学院上海天文台年刊》2003,(1)

由于磁带回放的不稳定性及磁带与处理机的不匹配 ,导致由磁带导入硬盘的数据误码率很高 ,影响了送入处理机的数据可用率。结果显示 ,采用核对软件能将数据可用率提高一个数量级  相似文献   

Spectroscopic identification of the infrared counterpart to GX5-1     

R. M. Bandyopadhyay  T. Shahbaz  P. A. Charles 《Monthly notices of the Royal Astronomical Society》2003,340(3):L13-L16

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Palaeotemperature reconstructions of the European permafrost zone during marine oxygen isotope Stage 3 compared with climate model results     

Ko van Huissteden  Jef Vandenberghe  David Pollard 《第四纪科学杂志》2003,18(5):453-464

A palaeotemperature reconstruction based on periglacial phenomena in Europe north of approximately 51 °N, is compared with high‐resolution regional climate model simulations of the marine oxygen isotope Stage 3 (Stage 3) palaeoclimate. The experiments represent Stage 3 warm (interstadial), Stage 3 cold (stadial) and Last Glacial Maximum climatic conditions. The palaeotemperature reconstruction deviates considerably for the Stage 3 cold climate experiments, with mismatches up to 11 °C for the mean annual air temperature and up to 15 °C for the winter temperature. However, in this reconstruction various factors linking climate and permafrost have not been taken into account. In particular a relatively thin snow cover and high climatic variability of the glacial climate could have influenced temperature limits for ice‐wedge growth. Based on modelling the 0 °C mean annual ground temperature proves to be an appropriate upper temperature limit. Using this limit, mismatches with the Stage 3 cold climate experiments have been reduced but still remain. We therefore assume that the Stage 3 ice wedges were generated during short (decadal time‐scale) intervals of extreme cold climate, below the mean temperatures indicated by the Stage 3 cold climate model simulations. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

On the Spectral Index－Flux Density Relation for Large Samples of Radio Sources     

W.Reich  P.Reich  R.Wielebinski 《中国天文和天体物理学报》2003,3(4):347-358

We present new statistical results on the spectral index-flux density relation for large samples of radio sources using archival data of the most sensitive surveys, such as 6C, Miyun, WENSS, B3, NVSS, GB87. Instrumental selection effects and the completeness of the catalogs are discussed. Based on the spectral indices calculated for about 200 000 sources from the WENSS (327 MHz) and NVSS (1.4 GHz) catalogs, we obtained (1) The median spectral index increases from amed --0.9 toαmed --0.8 (Svαvα), while S327 flux densities decrease from 0.1 Jy down to 25mJy. The median spectral indices nearly show no variation within the error bars when the flux density is larger than 0.1 Jy. (2) A dependence of the fraction of ultra-steep spectrum sources (USS, -1.5 <α<-1.0), steep spectrum sources (SSS, -1.0 <α< -0.5) and flat spectrum sources (FSS, -0.5≤α≤0.0) is partly responsible for the spectral flattening. Another contribution to the spectral flattening comes from the variation of αmed of steep spectrum so  相似文献   

Gamma-rays and cosmic rays from a pulsar in Cygnus OB2     

W. Bednarek 《Monthly notices of the Royal Astronomical Society》2003,345(3):847-853

We argue that γ-ray sources observed in the direction of the Cygnus OB2 association in the GeV and TeV energy range are due to a pulsar that was created by a supernova a few tens of thousands of years ago. The GeV emission is produced by a middle-aged pulsar, a factor of 2 older than the Vela pulsar. The TeV emission is produced by high-energy hadrons and/or leptons accelerated in pulsar wind nebulae. We suggest, moreover, that the excess of cosmic rays at ∼10¹⁸ eV observed from the direction of the Cygnus region can also be related to the appearance of this very energetic pulsar in the Cyg OB2 association. Some of the relativistic hadrons, captured in strong magnetic fields of a high-density region of Cyg OB2, produce neutrons and γ-rays in collisions with matter. These neutrons can arrive from Cyg OB2, creating an excess of cosmic rays.  相似文献   

Water transport from the North-east Irish Sea to western Scottish coastal waters: Further observations from time-trend matching of Sellafield radiocaesium     

W.A. McKay  M.S. Baxter 《Estuarine, Coastal and Shelf Science》1985,21(4):471-480

Radiocaesium isotopes, discharged into the North-east Irish Sea from the Sellafield (formerly Windscale) nuclear fuel reprocessing plant in Cumbria, have been employed as flow monitors to update and extend the record of coastal water movement from the Irish Sea to the Clyde Sea area and, further north, to Loch Etive. The temporal trends in radiocaesium levels have been used to determine the extent of water mixing en route and to define mean advection rates. Flow conditions from the Irish Sea have changed considerably since the mid-1970s, the residence time of northern Irish Sea waters being ～12 months during 1978–1980 inclusive. Average transport times of four and six months are estimated for the Sellafield to Clyde and Sellafield to Etive transects respectively. Sellafield ¹³⁷Cs levels in seawater were diluted by factors of 27 and 50 respectively during current movement to the Clyde and Etive areas. The decrease in salinity-corrected ¹³⁷Cs concentrations between the Clyde and Etive suggests that dilution by Atlantic water occurs, the latter mainly entering the Firth of Lorne from the west. The majority (～94%) of the radiocaesium supply to Loch Etive enters the Firth of Lorne via the portion of the coastal current circulating west of Islay, only ～6% arriving via the Sound of Jura.  相似文献   

Short-term Climate Characteristics at Ny-(A)lesund over the Arctic Tundra Area     

Deng Haibin  Lu Longhua  Bian Lingen 《极地研究(英文版)》2005,16(2)

Based on the Germany Koldwey Station's 1994-2003 conventional observation hourly data, this paper conducts a statistical analysis on the short-term climate characteristics for an arctic tundra region (Ny-(A)lesund island) where our first arctic expedition station (Huanghe Station) was located. Affected by the North Atlantic warming current, this area has a humid temperate climate, and the air temperature at Ny-(A)lesund rose above 0 ℃ even during deep winter season during our research period. The wind speed in this area was low and appeared most at southeast direction. We find that the temperature at Ny-(A)lesund rose in the faster rate (0.68 ℃/10 a) than those at the whole Arctic area. Compared with the floating ices where our expedition conducted in the Arctic, Ny-(A)lesund was warmer and more humid and had lower wind speed. Comparison of the near surface air temperature derived by NCEP/NCAR reanalysis to the conventional measurements conducted at the Koldwey site in Ny-(A)lesund area shows a good agreement for winter season and a significant difference for summer season.  相似文献   

Interpretation of transient electromagnetic soundings over three-dimensional structures for the central-loop configuration   总被引：2，自引：0，他引：2  

Gregory A. Newman  Walter L. Anderson  Gerald W. Hohmann 《Geophysical Journal International》1987,89(3):889-914

Summary. An assessment is made of the bias of fitting constrained layered-earth models to transient electromagnetic data obtained over 3-D structures. In this assessment we use the central-loop configuration and show that accurate estimates of the depth of burial of 3-D structures can be obtained with layered-earth model fitting. However, layered-earth interpretations are not reliable for estimating depth extents and resistivities of 3-D structures. When layered earths are used for interpretation, it is advantageous in some cases to use data based on the magnetic field instead of the voltage. A magnetic-field definition of apparent resistivity, in contrast to a definition based on the voltage, eliminates apparent-resistivity overshoots and undershoots in the data. A resistivity undershoot in the data can produce an extraneous and misleading layer in an interpretation of a 3-D resistive structure. Due to 3-D effects, apparent-resistivity soundings (magnetic field and voltage) may rise so steeply at late times that it may not be possible to fit a sounding to a reasonable layered-earth model. Truncating such a sounding, over a buried conductor, allows for a reasonable layered-earth fit and an accurate estimate of the depth to the conductor. However, the resistivity of the conductor is overestimated.
Measurements of the horizontal field in the central-loop configuration can map 3-D structures, provided the sensor is located accurately at the centre of the transmitting loop. Horizontal-field calculations show that the transients peak on the flanks of a 3-D structure, but are depressed over the structure's centre. Weak transient responses flanked by two large transient responses, which are opposite in sign, locate the structure. The sign reversal is caused by a corresponding reversal in the currents that are channelled through or deflected away from conductive or resistive structures, respectively.  相似文献   

The Effect of Solar Activity on the Annual Precipitation in the Beijing Area   总被引：3，自引：0，他引：3  

Juan Zhao  Yan-Ben Han  Zhi-An LiDepartment of Astronomy  Beijing Normal University Beijing  zj@bnu.edu.cnNational Astronomical Observatories  Chinese Academy of Sciences  Beijing 《中国天文和天体物理学报》2004,4(2):189-197

Using continuous wavelet transform, we examine the relationship between solar activity and the annual precipitation in the Beijing area. The results indicate that the annual precipitation is closely related to the variation of sunspot numbers, and that solar activity probably plays an important role in influencing the precipitation on land.  相似文献   

2001-2002年上海天文台卫星激光测距观测报告     

杨福民  张忠萍  陈婉珍  陈菊平 《中国科学院上海天文台年刊》2003,(1)

介绍了 2 0 0 1- 2 0 0 2年上海天文台卫星激光测距观测概况和亚厘米级精度的测距实验  相似文献