A theory of pressure sensor performance in snow     

Jerome B. Johnson 《水文研究》2004,18(1):53-64

A theory of pressure sensor response in snow is derived and used to examine the sources of measurement errors in snow water equivalent (SWE) pressure sensors. Measurement errors in SWE are caused by differences in the compressibility of the pressure sensor and the adjacent snow layer, which produces a shear stress along the perimeter of the sensor. When the temperature at the base of the snow cover equals 0 °C, differences in the snowmelt rate between the snow–SWE sensor interface and the adjacent snow–soil interface may also produce a shear stress along the sensor's perimeter. This shear stress perturbs the pressure field over the sensor, producing SWE measurement errors. Snow creep acts to reduce shear stresses along the SWE sensor's perimeter at a rate that is inversely proportional to the snow viscosity. For sustained periods of differential snowmelt, a difference in the mass of snow over the sensor compared with the surrounding soil will develop, producing additional permanent errors in SWE measurements. The theory indicates that SWE pressure sensor performance can be improved by designing a sensor with a high Young's modulus (low compressibility), low aspect ratio, large diameter and thermal properties that match those of the surrounding soil. Simulations of SWE pressure sensor errors using the theory are in close agreement with observed errors and may provide a means to correct historical SWE measurements for use in hydrological hindcast or climate studies. Published in 2003 by John Wiley & Sons, Ltd.  相似文献   

The effect of rotational gravity darkening on magnetically torqued Be star discs     

J. C. Brown  D. Telfer  Q. Li  R. Hanuschik  J. P. Cassinelli  A. Kholtygin 《Monthly notices of the Royal Astronomical Society》2004,352(3):1061-1072

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Relativistic models of two low-luminosity radio jets: B2 0326+39and B2 1553+24   总被引：1，自引：0，他引：1  

J.R. Canvin  R. A. Laing 《Monthly notices of the Royal Astronomical Society》2004,350(4):1342-1365

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Helical magnetic fields associated with the relativistic jets of four BL Lac objects     

Denise C. Gabuzda  Éamonn Murray  Patrick Cronin 《Monthly notices of the Royal Astronomical Society》2004,351(4):L89-L93

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Outbursts of young stellar objects     

O. M. Matthews  R. Speith  G. A. Wynn 《Monthly notices of the Royal Astronomical Society》2004,347(3):873-884

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Calibration of Vector Magnetogram with the Nonlinear Least-squares Fitting Technique     

Jiang-Tao Su  Hong-Qi ZhangNational Astronomical Observatories  Chinese Academy of Sciences  Beijing   《中国天文和天体物理学报》2004,4(4):365-376

To acquire Stokes profiles from observations of a simple sunspot with the Video Vector Magnetograph at Huairou Solar Observing Station (HSOS), we scanned the FeI λ5324.19A line over the wavelength interval from 150mA redward of the line center to 150 mA blueward, in steps of 10 mA. With the technique of analytic inversion of Stokes profiles via nonlinear least-squares, we present the calibration coefficients for the HSOS vector magnetic magnetogram. We obtained the theoretical calibration error with linear expressions derived from the Unno-Becker equation under weak-field approximation.  相似文献   

Influence of coronal mass ejection on geomagnetic activity during 1988–1993     

Shrivastava  Pankaj Kumar  Singh  G. N. 《Earth, Moon, and Planets》2002,91(1):1-8

The most rapid and dramatic evolution in the solar corona occurs in events now known as Coronal Mass Ejections (CMEs). There have considerable importance for our understanding of the evolution of the mass and energy injected into the interplanetary medium. In this work, we have studied the relation of CMEs with geomagnetic activity for the period of 1988 to 1993. Not all CMEs are capable of producing geomagnetic disturbances. Our study indicates that the maximum chance of a geomagnetic disturbance occurs two to three days after a CME in association with B-type solar flares.  相似文献   

Type Ia supernovae and remnant neutron stars     

A. R. King  J. E. Pringle  D. T. Wickramasinghe 《Monthly notices of the Royal Astronomical Society》2001,320(3):L45-L48

On the basis of the current observational evidence, we put forward the case that the merger of two CO white dwarfs produces both a Type Ia supernova explosion and a stellar remnant, the latter in the form of a magnetar. The estimated occurrence rates raise the possibility that many, if not most, Type Ia supernovae might result from white dwarf mergers.  相似文献   

浅谈桂林市新解放桥工程地质勘察及桥基处理     

牟春梅 《南方国土资源》2001,14(4):79-82

随着桂林市经济和旅游业的发展 ,交通量大幅度的增加 ,原解放桥所能承受的荷载已远远超过它的设计标准 ,加上桥基和桥面已有不同程度的破损 ,建设新的解放桥已势在必行。文章就新解放桥场地的工程地质条件、存在的工程地质问题及所进行的工程地质评价和桥基处理情况作简要介绍。  相似文献   

滚动轴承内外圈滚道的磁力研磨研究     

张世亮 《广东海洋大学学报》1994,(1)

采用直流励磁装置、磁性磨料及工件共同构成磁加工系统。磁性磨料在磁场的作用下，对轴承内、外圈滚道以磁刷的形式进行研磨。由于磨料的可流动性，加工时既能满足对被加工表面粗糙度的加工要求，又能较好地保持工件原有的形位精度；且加工后在被加工表面形成一定的压应力，使工件的抗疲劳强度提高，使用寿命延长。  相似文献