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351.
The National Optical Astronomy Observatories (NOAO) proposes to build 8 m telescopes at two locations. The Northern Hemisphere location is on Mauna Kea, Hawaii, and the Southern Hemisphere location is within the existing boundary of the Cerro Tololo Inter-American Observatory. This paper describes the sites under consideration and the facilities that support the operation of each telescope, namely, the telescope enclosure, the control facility, and the recoating facility.Paper presented at the Symposium on the JNLT and Related Engineering Developments, Tokyo, November 29–December 2, 1988.Operated by the Association of Universities for Research in Astronomy Inc., under contract with the National Science Foundation. 相似文献
352.
353.
James E. Cloern Andrea E. Alpine Brian E. Cole Raymond L.J. Wong James F. Arthur Melvin D. Ball 《Estuarine, Coastal and Shelf Science》1983,16(4):415-429
Phytoplankton dynamics in the upper reach of the northern San Francisco Bay estuary are usually characterized by low biomass dominated by microflagellates or freshwater diatoms in winter, and high biomass dominated by neritic diatoms in summer. During two successive years of very low river discharge (the drought of 1976-77), the summer diatom bloom was absent. This is consistent with the hypothesis that formation of the diatom population maximum is a consequence of the same physical mechanisms that create local maxima of suspended sediments in partially-mixed estuaries: density-selective retention of particles within an estuarine circulation cell. Because the estuary is turbid, calculated phytoplankton growth rates are small in the central deep channel but are relatively large in lateral shallow embayments where light limination is less severe. When river discharge falls within a critical range (100–350 m3 s?1) that positions the suspended particulate maximum adjacent to the productive shallow bays, the population of neritic diatoms increases. However, during periods of high discharge (winter) or during periods of very low discharge (drought), the suspended particulate maximum is less well-defined and is uncoupled (positioned downstream or upstream) from the shallow bays of the upper estuary, and the population of neritic diatoms declines. Hence, the biomass and community composition of phytoplankton in this estuary are controlled by river discharge. 相似文献
354.
Alan M. Wong Arch M. Reid Stuart A. Hall Virgil L. Sharpton 《Meteoritics & planetary science》2001,36(11):1443-1455
Abstract— In Leon County, Texas, USA, the Marquez Dome, an approximately circular 1.2 km diameter zone of disturbed Cretaceous rocks surrounded by shallow dipping Tertiary sediments, has been interpreted by Gibson and Sharpton (1989) and Sharpton and Gibson (1990) as the surface expression of a buried complex impact crater. New gravity and magnetic anomaly data collected over the Marquez Dome have been combined with well‐log and seismic reflection information to develop a better estimate of the overall geometry of the structure. A three‐dimensional model constructed to a depth of 2000 m from all available information indicates a complex crater 13 km in diameter with an uplift in the center of at least 1120 m. The zone of deformation associated with the cratering event is limited to a depth of <1720 m. No impact breccias were recovered in drilling at two locations, 1.1 and 2 km from the center of the structure, and the central uplift may be the only prominent remnant of this impact into unconsolidated, water‐rich sediments. The magnetic anomaly field shows no correlation with the location and extent of the structure. 相似文献
355.
Ron C. K. Wong 《国际地质力学数值与分析法杂志》2001,25(2):131-153
Oil sands are dense granular materials with interlocked structure and clay shales are heavily overconsolidated clays. They are classified as structured soil or weak rock, exhibiting high peak strength with severe softening and dilation, particularly at low confining stress. The triaxial compression test results indicate that both materials yield linear Mohr–Coulomb envelopes with an apparent cohesion for peak and residual strengths. However, the strength components mobilized from these two materials are very different. This paper investigates if these strength parameters are intrinsic properties or responses derived in triaxial compression conditions. Computer tomography scanning technique is used to aid in examining the micro‐structural features of the sheared specimens such as shear banding pattern, shear band thickness, spatial porosity distributions inside and outside shear bands. These micro‐structural features are used to explain the macro‐deformation response observed in the triaxial compression tests. Mobilization of strength components derived from interlocked structure, cementation, dilation, rolling and critical state are analysed for pre‐, post‐peak softening and residual stages. It is found that the empirical correlation such as Mohr–Coulomb failure criterion based on triaxial compression test results does not necessarily reflect the intrinsic properties of the test materials. Testing conditions are embedded in the empirical correlation. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
356.
The analysis of measured stress waves for the prediction of static pile capacity is described. The usual method of using the measured velocity record as the input boundary condition in a wave equation analysis with a finite element model, if not properly implemented, can lead to significant numerical errors. An alternative scheme using an accurate prescribed displacement procedure with the measured displacement record (obtained from the integration of the velocity) is proposed, and is shown to be very efficient. These aspects of the numerical modelling procedure are illustrated by a case study. 相似文献
357.
Chris Kennedy Hans Ericsson P. L. R. Wong 《Stochastic Environmental Research and Risk Assessment (SERRA)》2006,20(1-2):119-125
A technique for modeling contaminant transport based on Markov process theory is developed. Transport is quantified by summing
the first two moments of independent random displacements and applying the central limit theorem (CLT) to obtain solute distributions
of a Gaussian nature. For non-uniform flow fields the CLT is applied in a streamfunction/equi-travel time space and transforms
are used to give concentrations in Cartesian coordinates. Simulations in uniform, radially converging and circular flow fields
show the method to be two to three orders of magnitude faster than modeling with the advection-dispersion equation, using
a control volume technique. 相似文献
358.
This paper develops approximations for the settlement interaction factors between two dissimilar piles. Via an extensive parametric study using the computer program GEPAN, approximations are developed for interaction factors for piles having dissimilar diameters but equal lengths, piles having dissimilar lengths, and for piles having dissimilar ground conditions at the pile tips. Correction factors are then given to allow for the effects of piles stiffness and length-to-diameter ratio. The approximations may be employed in analyses for group settlements to allow for the case where not all piles in the group are identical. 相似文献
359.
Kylie C.Y. Mak H. Yu M.C. Choi Xiaoyun Shen Michael H.W. Lam M. Martin Rudolf S.S. Wu Patsy S. Wong Bruce J. Richardson Paul K.S. Lam 《Marine pollution bulletin》2005,51(8-12):1010
Green-lipped mussels (Perna viridis) were collected from seven fish culture zones (FCZs) in Hong Kong and analyzed for okadaic acid (OA). A conventional HPLC method was modified by incorporating a proteinase K digestion step. Results suggest that a higher recovery (2.5 times higher) of OA was obtained from spiked samples after the addition of 1.08 mg proteinase K in comparison with samples incubated without the proteolytic enzyme. For the hepatopancreas (HP) of individual field-collected mussels, the additional digestion step can enhance OA extraction by 3.1 times. Spatial and temporal variations in OA concentrations in the mussels from various FCZs were investigated. The highest concentration of OA in mussel HP samples was 1164.9 ng/g HP wet wt. With respect to OA concentrations in whole mussel tissues from seven sites and four seasonal samplings, the concentrations were between 70.0 and 131.0 ng/g wet wt., which did not exceed the generally recognized international regulatory criteria (>200 ng/g) for OA. 相似文献
360.
Spatial interpolation is an important feature of a Geographic Information System, which is the procedure used to estimate values at unknown locations within the area covered by existing observations. In this paper, we describe a conservative spatial interpolation technique that incorporates the advantages of local interpolation, Euclidean interpolation, and conservative fuzzy reasoning, and a dynamic fuzzy–reasoning–based function estimator with parameters optimised by a genetic algorithm. The main objective of this paper is to formulate a computationally efficient spatial interpolation technique similar to the IDWA technique that can be used in real time application. The main feature of our spatial interpolation technique is a capability for spatial interpolation and extrapolation in a higher–dimensional space. Examples from a rainfall spatial interpolation problem are used to illustrate the applicability of the proposed technique. 相似文献