A comparison of peak and plate electrodes in electrical resistivity tomography: application to the chalky groundwater of the Beauvais aquifer (northern part of the Paris basin,France)   总被引：1，自引：0，他引：1  

Lahcen Zouhri  Pascale Lutz 《水文研究》2010,24(21):3040-3052

Electrical resistivity tomography was used in order to explore an experimental site of the LaSalle Beauvais Polytechnic Institute (France). The test was conducted along a profile line of 315 m length, using 64 electrodes deployed at an inter‐electrode spacing of 5 m, and the data were recorded using gradient, Wenner and pole–dipole arrays. The performance of plate electrodes (non‐conventional flat‐based) is compared with the performance of peak electrodes (conventional spike). The hydrogeophysical investigation of the chalk aquifer system of Beauvais shows that the performance of plate electrodes is satisfactory, leading to inversions of small root‐mean‐square errors. Peak and the plate electrodes were tested before and after injection of a salt tracer in the piezometer of the experimental site. The study demonstrates the usefulness of plate electrodes (efficient, less time consuming) and the possibility of aquifer characterization by a salt tracer. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

双重曲柄活塞机构动力学分析     

汤锦基 《广东海洋大学学报》1992,(1)

分析和研究了双重曲柄活塞机构的运动和受力情况,并与传统曲柄连杆机构相比较,提出了双重曲柄活塞机构具有运动传递稳定,振动较小,机械效率提高等优点。  相似文献   

Seismic Hazard Mapping and Microzonation in the Sikkim Himalaya through GIS Integration of Site Effects and Strong Ground Motion Attributes   总被引：2，自引：1，他引：1  

Sankar Kumar Nath 《Natural Hazards》2004,31(2):319-342

The seismic ground motion hazard is mapped in the Sikkim Himalaya with local and regional site conditions incorporated through geographic information system. A strong motion network in Sikkim comprising of 9 digital accelerographs recorded more than 100 events during 1998–2002, of which 41 events are selected with signal-to-noise ratio 3 for the estimation of site response (SR), peak ground acceleration (PGA) and predominant frequency (PF) at all stations. With these and inputs from IRS-1C LISS III digital data, topo-sheets, geographical boundary of the State of Sikkim, surface geological maps, soil taxonomy map in 1:50,000 scale and seismic refraction profiles, the seismological and geological thematic maps, namely, SR, PGA, PF, lithology, soil class, %slope, drainage, and landslide layers are generated. The geological themes are united to form the basic site condition coverage of the region. The seismological themes are assigned normalized weights and feature ranks following a pair-wise comparison hierarchical approach and later integrated to evolve the seismic hazard map. When geological and seismological layers are integrated together through GIS, microzonation map is prepared. The overall site response, PGA and predominant frequency show an increasing trend in the NW–SE direction peaking at Singtam in the lesser Himalaya. As Main Boundary Thrust (MBT) is approached, the attribute value increases further. A quasi-probabilistic seismic hazard index has been proposed based on site response, peak ground acceleration and predominant frequency. Six seismic hazard zones are marked with percent probability <22%, 22–37%, 37–52%, 52–67%, 67–82%, >82% at 3 Hz and <20%, 20–34%, 34–48%, 48–61%, 61–75%, >75% at 9 Hz. In the microzonation vector layer of integrated seismological and geological themes also six major zones are mapped, with percent probability <15%, 15–31%, 31–47%, 47–63%, 63–78%, >78% at low frequency end. The maximum risk is attached to the probability greater than 78% in the Singtam and its adjoining area. These maps are generally better spatial representation of seismic hazard including site-specific analysis.  相似文献   

Particle acceleration in shocks     

L. O. Drury 《Astrophysics and Space Science》1995,233(1-2):251-260

The mechanism of particle acceleration by shocks is reviewed, and the resulting modifications of the shock structure contrasted with those which occur in molecular shocks with magnetic precursors. The danger associated with the use of steady models is emphasised and the applicability of the theory to cosmic ray acceleration in supernova remnants briefly discussed.  相似文献   

Centaurus A as a source of extragalactic cosmic rays with arrival energies well beyond the GZK cutoff     

Gustavo E. Romero  Jorge A. Combi  Santiago E. Perez Bergliaffa  Luis A. Anchordoqui 《Astroparticle Physics》1996,5(3-4)

The ultra-high energy cosmic rays recently detected by several air shower experiments could have an extragalactic origin. In this case, the nearest active galaxy Centaurus A might be the source of the most energetic particles ever detected on Earth. We have used recent radio observations in order to estimate the arrival energy of the protons accelerated by strong shock fronts in the outer parts of this southern radio source. We expect detections coresponding to particles with energies up to 2.2 × 10²¹ eV and an arrival direction of (l ≈ 310°, b ≈ 20°) in galactic coordinates. The future Southern Hemisphere Pierre Auger Observatory might provide a decisive test for extragalactic models of the origin of the ultra-high energy cosmic rays.  相似文献   

Calibration of the anchizone: a critical comparison of illite 'crystallinity'scales used for definition   总被引：7，自引：0，他引：7  

H. J. KISCH 《Journal of Metamorphic Geology》1990,8(1):31-46

Instrumental settings for determination of illite/muscovite 'crystallinity'(half-height width of the 10-Å X-ray diffraction peak) and the limits of the anchimetamorphic zone adopted by various authors fall into several groups.
The variation in the limiting peak widths between the authors that have adopted Kubler's Neuchâtel boundary values of 0.42° and 0.25°Δ2θ can be interpreted in terms of variation in the instrumental settings. The choice of time constants higher than those given by the formula causes peak broadening; this effect is particularly marked at high scan rates. The peak broadening is by constant increments that are virtually independent of the absolute peak width.
The differences between the Kubler (Neuchâtel)-derived limiting values and some other scales are appreciably greater than can be accounted for by these differences in instrumental settings: many of these scales are not equivalent. In particular, the limits adopted by Dunoyer de Segonzac (1969) and subsequent workers at Strasbourg are too broad; their anchizone represents a range of grades of metamorphism lower than that of Kubler, widely overlapping the latter's 'diagenetic'zone. Those adopted by some other, mainly French, authors are too narrow.
The limits of the anchizone should be calibrated by inter-laboratory standards, and the instrumental settings should be specified in full.  相似文献   

SUMER - Solar Ultraviolet Measurements of Emitted Radiation     

K. Wilhelm  W. Curdt  E. Marsch  U. Schühle  P. Lemaire  A. Gabriel  J. -C. Vial  M. Grewing  M. C. E. Huber  S. D. Jordan  A. I. Poland  R. J. Thomas  M. Kühne  J. G. Timothy  D. M. Hassler  O. H. W. Siegmund 《Solar physics》1995,162(1-2):189-231

The instrument SUMER - Solar Ultraviolet Measurements of Emitted Radiation is designed to investigate structures and associated dynamical processes occurring in the solar atmosphere, from the chromosphere through the transition region to the inner corona, over a temperature range from 10⁴ to 2 × 10⁶ K and above. These observations will permit detailed spectroscopic diagnostics of plasma densities and temperatures in many solar features, and will support penetrating studies of underlying physical processes, including plasma flows, turbulence and wave motions, diffusion transport processes, events associated with solar magnetic activity, atmospheric heating, and solar wind acceleration in the inner corona. Specifically, SUMER will measure profiles and intensities of EUV lines; determine Doppler shifts and line broadenings with high accuracy; provide stigmatic images of the Sun in the EUV with high spatial, spectral, and temporal resolution; and obtain monochromatic maps of the full Sun and the inner corona or selected areas thereof. SUMER will be flown on the Solar and Heliospheric Observatory (SOHO), scheduled for launch in November, 1995. This paper has been written to familiarize solar physicists with SUMER and to demonstrate some command procedures for achieving certain scientific observations.  相似文献   

STUDY ON THE CORROSION PEAK OF CARBON STEEL IN MARINE SPLASH ZONE   总被引：3，自引：0，他引：3  

朱相荣  黄桂桥  梁采凤 《中国海洋湖沼学报》1997,15(4):378-380

lNTRODUCTI0NSincetheoonceptofrnarinesplashzone(MSZ)wasfirstproposedbyHumble,rnanyresearchesprovedthatthecorrosionofsteelinthesplashzoneisthemostseriousinthemarineenvironninetandthatthisMSZcorrosionhasapeak(Zhu,l995).Howevertheenvironmentalfactorscatisingthecorrosionpeakwasnotkn0wnthen(Niat0,l975,Atsushi,l994)andtherangeoftheMSZwasnotyetdeariydefinedopzkaki,l985).ThispaperexplainsthemaincauseofthecormsionpeakanddefinestheexaCtrangeoftheMSZinsomeofChina'sharbours.MATERIALSANDMET…  相似文献   

Charge state behaviour of projectiles under an acceleration mechanism in a hot plasma     

L. del Peral  M. D. Rodríguez-Frías  R. Gmez-Herrero  J. Rodríguez-Pacheco  J. Gutirrez 《Astroparticle Physics》2002,17(4):215-420

We have studied the ionization states of most ions in solar flares when a stochastic acceleration mechanism is present. Calculations using a computer code (ESCAPE) designed to find the charge states of heavy and light ions under stochastic acceleration have shown an energy dependence on the ionization states, stronger for heavy ions. Moreover the charge states depend on source parameters as density or temperature, but if an acceleration mechanism is taken into account in impulsive solar energetic particles events, the same source temperature may not be inferred for all the ions.  相似文献   

北京市夏季臭氧变化特征的观测研究   总被引：9，自引：0，他引：9  

吴瑞霞浦一芬  张美根寿绍文 《南京气象学院学报》2005,28(5):690-694

利用2002年7月至8月325m气象塔资料研究了北京市夏季近地层臭氧浓度变化特征及其与气象因子的关系。结果表明：北京市夏季边界层臭氧浓度日变化显著．臭氧浓度随高度增加而增加；臭氧多数为单峰型分布，双峰型仅分布在底层；臭氧峰值出现时间与气温峰值出现时间基本一致，或略有落后。  相似文献