The Derivation and Solution of Indicator Equations for Seismometer-Galvanometer Combinations Including the Effect of Seismometer Inductance     

R. A. Savill  E. W. Carpenter  J. K. Wright 《Geophysical Journal International》1962,6(4):409-425

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Coring experiments with cryogenic water and carbon dioxide ices—toward planetary surface operations     

J.R.C Garry  I.P Wright 《Planetary and Space Science》2004,52(9):823-831

As a prelude to the design of sampling devices able to extract materials from the icy surfaces of comets, outer-planet satellites, and the martian poles, it is necessary to understand some of the physical properties of these ices. To this end we have investigated the mechanical resistance displayed by two ices subjected to coring operations at low temperatures and under vacuum. The ices used in this study were water ice, frozen from liquid water, and carbon dioxide ice grown from its vapour. The coring tool employed had dimensions and required power levels that were comparable to a sample extraction system designed for a present-day spacecraft lander. The specific cutting strength, a parameter that measures the toughness of the material, has been measured while coring these two ices. For water ice this property rose from at an ice temperature of , to at . At the lower temperature of , pore-free carbon dioxide ice has also been measured to have a specific cutting strength approximately half that of water ice at the same temperature. These laboratory-based measurements may be used as guides for the power levels needed to core solid water and CO₂ ices at certain rates.  相似文献   

Space Plasma Exploration by Active Radar (SPEAR): an overview of a future radar facility   总被引：1，自引：0，他引：1  

D. M. Wright  J. A. Davies  T. R. Robinson  P. J. Chapman  T. K. Yeoman  E. C. Thomas  M. Lester  S. W. H. Cowley  A. J. Stocker  R. B. Horne  F. Honary 《Annales Geophysicae》2000,18(9):1248-1255

SPEAR is a new polar cap HF radar facility which is to be deployed on Svalbard. The principal capabilities of SPEAR will include the generation of artificial plasma irregularities, operation as an all-sky HF radar, the excitation of ULF waves, and remote sounding of the magnetosphere. Operation of SPEAR in conjunction with the multitude of other instruments on Svalbard, including the EISCAT Svalbard radar, and the overlap of its extensive field-of-view with that of several of the HF radars in the SuperDARN network, will enable in-depth diagnosis of many geophysical and plasma phenomena associated with the cusp region and the substorm expansion phase. Moreover, its ability to produce artificial radar aurora will provide a means for the other instruments to undertake polar cap plasma physics experiments in a controlled manner. Another potential use of the facility is in field-line tagging experiments, for coordinated ground-satellite experiments. Here the scientific objectives of SPEAR are detailed, along with the proposed technical specifications of the system.  相似文献   

Metamorphism and aqueous alteration in low petrographic type ordinary chondrites     

Derek W. G. Sears  Andrew D. Morse  Robert Hutchison  R. Kyle Guimon  Lu Jie  C. M. O'D. Alexander  Paul H. Benoit  Ian Wright  Colin Pillinger  Tian Xie  Michael E. Lipschutz 《Meteoritics & planetary science》1995,30(2):169-181

Abstract— In order to investigate the relative importance of dry metamorphism and aqueous alteration in the history of chondrules, chondrules were hand-picked from the Semarkona (petrographic type 3.0), Bishunpur (3.1), Chainpur (3.4), Dhajala (3.8) and Allegan (5) chondrites, and matrix samples were extracted from the first three ordinary chondrites. The thermoluminescence (TL) properties of all the samples were measured, and appropriate subsets of the samples were analyzed by electron-microprobe and radiochemical neutron activation and the water and H-isotopic composition determined. The TL data for chondrules from Semarkona and Bishunpur scatter widely showing no unambiguous trends, although group B1 chondrules tend to have lower sensitivities and lower peak temperatures compared with group A5 chondrules. It is argued that these data reflect the variety of processes accompanying chondrule formation. The chondrules show remarkably uniform contents of the highly labile elements, indicating mineralogical control on abundance and volatile loss from silicates and loss and recondensation of mobile chalcophiles and siderophiles in some cases. Very high D/H values (up to ～8000‰ SMOW) are observed in certain Semarkona chondrules, a confirmation of earlier work. With increasing petrographic type, mean TL sensitivities of the chondrules increase, the spread of values within an individual meteorite decreases, and peak temperatures and peak widths show trends indicating that the TL is mainly produced by feldspar and that dry, thermal metamorphism is the dominant secondary process experienced by the chondrules. The TL sensitivities of matrix samples also increase with petrographic type. Chainpur matrix samples show the same spread of peak temperatures and peak widths as Chainpur chondrules, indicating metamorphism-related changes in the feldspar are responsible for the TL of the matrix. The TL data for the Semarkona and Bishunpur matrix samples provide, at best, only weak evidence for aqueous alteration, but the matrix contains H with approximately terrestrial D/H values, even though it contains much water. Secondary processes (probably aqueous alteration) presumably lowered the D/H of the matrix and certain chondrules. While chondrule properties appear to be governed primarily by formation processes and subsequent metamorphism, the matrix of Semarkona has a more complex history involving aqueous alteration as a meteorite-wide process.  相似文献   

Numerical classification applied to certain Jamaican eocene nummulitids     

Raymond M. Wright  Paul Switzer 《Mathematical Geology》1971,3(3):297-311

Eighty-eight specimens of Eocene nummulitids from the Yellow Limestone Formation of northwestern Jamaica are classified according to quantitative measurements of morphologic parameters that are generally considered to be taxonomically useful. The specimens are grouped into homogeneous classes by the computer screening of differently oriented data projections. By this method, the use of similarity coefficients and the question of a priori weighting of characters, for which numerical taxonomy has been heavily criticized, are both avoided. The stability of the classes thus obtained is validated by discriminant analysis. These techniques provide an objective view of phenetic differences among specimens and show how the measured characters produce those differences. Tightness of coiling and total number of whorls, prove to be the most useful features in discriminating between groups but seem to have taxonomic value only at the specific and not at the generic level. This suggests that the generaOperculinoides andNummulites are synonymous.  相似文献   

Preliminary deep reflection studies in the Arunta Block, Central Australia     

B.R. Goleby  C. Wright  B.L.N. Kennett 《Geophysical Journal International》1987,89(1):437-442

Summary. In 1985, near-vertical incidence reflection profiling was carried out across the Arunta Block in Central Australia. This region consists of exposed Proterozoic metasediments, granites and granulites. There is usually a limited sedimentary coverage generated by deep weathering. The seismic sections for the deep crust are markedly different from those previously recorded in Eastern Australia where there is extensive sedimentary cover. One of the striking features is the presence of energy with frequencies as high as 100 Hz at two-way times of 5-6 s. Reflections are found throughout the crust, and there is no zone that can be characterised as non-reflective. The strongest reflectors commonly lie in the intervals around 4-6 s and 8–11 s and display significant dip. Individual shot records show fairly rapid variations in amplitude and waveform within a reflection band and the correlation between records from adjacent shots can also be somewhat limited. Such features are not well suited to the application of standard processing techniques designed for subhorizontal structures, and call into question the utility of conventional stacking. The character of the reflections changes markedly with varying frequency which suggests that they arise by interference phenomena, probably associated with laterally varying lamellar structures.  相似文献   

Mantle structure and composition to 800-km depth beneath southern Africa and surrounding oceans from broadband body waves     

R. E. Simon  C. Wright  M. T. O. Kwadiba  E. M. Kgaswane   《Lithos》2003,71(2-4):353-367

Average one-dimensional P and S wavespeed models from the surface to depths of 800 km were derived for the southern African region using travel times and waveforms from earthquakes recorded at stations of the Kaapvaal and South African seismic networks. The Herglotz–Wiechert method combined with ray tracing was used to derive a preliminary P wavespeed model, followed by refinements using phase-weighted stacking and synthetic seismograms to yield the final model. Travel times combined with ray tracing were used to derive the S wavespeed model, which was also refined using phase-weighted stacking and synthetic seismograms. The presence of a high wavespeed upper mantle lid in the S model overlying a low wavespeed zone (LWZ) around 210- to 345-km depth that is not observed in the P wavespeed model was inferred.

The 410-km discontinuity shows similar characteristics to that in other continental regions, but occurs slightly deeper at 420 km. Depletion of iron and/or enrichment in aluminium relative to other regions are the preferred explanation, since the P wavespeeds throughout the transition zone are slightly higher than average. The average S wavespeed structure beneath southern Africa within and below the transition zone is similar to that of the IASP91 model. There is no evidence for discontinuity at 520-km depth. The 660-km discontinuity also appears to be slightly deeper than average (668 km), although the estimated thickness of the transition zone is 248 km, similar to the global average of 241 km. The small size of the 660-km discontinuity for P waves, compared with many other regions, suggests that interpretation of the discontinuity as the transformation of spinel to perovskite and magnesiowüstite may require modification. Alternative explanations include the presence of garnetite-rich material or ilmenite-forming phase transformations above the 660-km discontinuity, and the garnet–perovskite transformation as the discontinuity.  相似文献   

An integrated water balance model for assessing water scarcity in a data-sparse interfluve in eastern India     

Shreyashi Santra Mitra  Jim Wright  Abhisek Santra  A.R. Ghosh 《水文科学杂志》2013,58(10):1813-1827

Abstract

The objective of this study is to measure the balance of water demand versus water resource availability in an interfluve of West Bengal, India to support water resource planning, particularly of inter-basin transfers. Surface water availability was modelled using the US Soil Conservation Service curve number (SCS-CN) approach, whilst groundwater availability was modelled based on water-level fluctuations and the rainfall infiltration method. Water use was modelled separately for the agricultural, industrial, and domestic sectors using a predominantly normative approach and water use to availability ratios calculated for different administrative areas within the interfluve. Overall, the approach suggested that the interfluve receives 327 × 10⁶ m³ year^-1 of excess water after satisfying these sectoral demands, but that the eastern part of the study area is in deficit. However, a sensitivity analysis carried on the approach to several assumptions in the model suggested changed circumstances would produce surplus/deficit ranging from ?215 × 10⁶ to 435 × 10⁶ m³ year^-1 . The approach could have potential for localised water balance modelling in other Indian catchments.