Chemical fractionations in meteorites—VIII. Iron meteorites and the cosmochemical history of the metal phase     

William R. Kelly  John W. Larimer 《Geochimica et cosmochimica acta》1977,41(1):93-111

The composition of the metal phase is traced through an idealized, traditional history from condensation, oxidation and accretion in the nebula to melting, segregation and freezing in a parent body. Fifteen elements are considered: Au, Co, Cu, Fe, Ga, Ge, Ir, Mo, Ni, Os, Pd, Pt, Re, Rh and Ru. All are strongly siderophile but differ in volatility and melting-freezing behavior. This simplifies the problem yet provides a means to resolve chemical trends which evolve at different stages in the metal's history.The parent bodies of 5 (IC, IIAB, IIC, IID and IIIAB) of the 12 iron meteorite groups resolved by Scott and Wasson (1975) seem to have had a traditional history. That is condensation, oxidation to various levels, accretion, melting, segregation and fractional crystallization during freezing, presumably in cores. The others seem to have had more unusual histories. The composition of the metal in group IVB matches that predicted for the metal condensate at 1270°K (at$\text{P}{}_{\mathrm{T}}\text{= 10}{}^{\mathrm{?5}}\text{atm}$). This implies accretion at high temperatures; no other combination of the processes can produce this composition. It does not rule out secondary processing, however. The metal in group IVA, whose members have different cooling rates (7–200°/myr), has a composition indicative of aggregates in a body undergoing progressive stages of partial melting. This is consistent with a model in which molten metal collects into pods or raisins at various depths. The composition of the metal in group IAB is indicative of a partial melt which refroze during the initial stages of segregation, before it had managed to aggregate into a single mass. The physical setting implied is consistent with observed inhomogeneities in the metal and abundant inclusions.Three of the 12 groups are deficient in volatiles (IIIF, IVA and IVB) implying a high accretion temperature. In all three cases, cooling rates are comparatively rapid, indicating small bodies or low radioactive element contents. Conceivably all three were deficient in K.  相似文献   

Seismic response of torsionally coupled base isolated structures     

Tso-Chien Pan  James M. Kelly 《地震工程与结构动力学》1983,11(6):749-770

An analytical study of the seismic response of typical base isolated structures mounted on rubber bearings is presented. Isolated buildings are liable to have closely spaced lower modes of vibration with small eccentricity between centres of mass and rigidity. The isolated structure is modelled as a rigid deck with lumped masses supported on axially inextensible elastomeric rubber bearings. This simplified system has three degrees of freedom (dof), two translations and one rotation in the horizontal plane. The Green's functions for the displacement response of the 3 dof system are derived for both undamped and damped cases with small and large eccentricities. The small eccentricity case is taken from a specific isolated building, while the large eccentricity case arises from the 5 per cent accidental eccentricity which is required by various seismic codes. An interaction equation for normalized displacements is established for an idealized flat velocity spectrum or hyperbolic acceleration spectrum. An isolated building on rubber bearings would have its fundamental period fall into this range of a design spectrum. Numerical results for the specific building subjected to the El Centro earthquake of 1940 are presented. Both the time history and the response spectrum modal superposition analysis were performed. In the response spectrum analysis, the Complete Quadratic Combination (CQC) showed superiority over the Square Root of the Sum of Squares (SRSS) in estimating maximum responses. It is concluded that the effect of torsional coupling on the transient response of base isolated structures is insignificant, due to the combined effect of the time lag between the maximum translational and torsional responses and the influence of damping in the isolation system which for elastomeric bearings can be as high as 8 to 10 per cent.  相似文献   

Bailing and Construction Considerations for Deep Aquifer Monitoring Wells on Western Oil Shale Leases     

K. E. Kelly 《Ground water》1982,20(2):179-185

  相似文献   

Characterization of the effects of high multipath phase rates in GPS     

Joseph?M.?Kelly  Michael?S.?BraaschEmail author  Michael?F.?DiBenedetto 《GPS Solutions》2003,7(1):5-15

GPS multipath has been studied since the early 1970s. Prior to the investigation described in this paper, however, the effects due to the relative Doppler shift between the direct and multipath signal components have received scant attention. The single previous study that did address the issue indicated coherent receivers had significant performance advantages over noncoherent receivers. Specifically, it was stated that under the condition of fast-fading multipath, noncoherent receivers would yield a bias error, whereas coherent receivers would not. After reviewing the background theory, this paper describes a revised model of the phenomenon and shows the results of hardware simulations which validate the existence of the bias in both receiver types and offer support for the new model. A case study of a specific commercial receiver is presented. Electronic Publication  相似文献   

The loss of the chemical tanker Ievoli Sun in the English Channel,October 2000     

Law RJ  Kelly C  Matthiessen P  Aldridge J 《Marine pollution bulletin》2003,46(2):254-257

A chemical product tanker, The Ievoli Sun, was abandoned and later sank approximately 11 miles NW of Alderney in the English Channel in October 2000. The vessel carried a mixed cargo comprising 4000 tonnes of styrene, and 1000 tonnes each of methyl ethyl ketone and isopropyl alcohol. These chemicals are of low to moderate toxicity to aquatic life, are not persistent and have a low potential for bio-accumulation. Both of the solvents are miscible in water, whilst styrene is practically insoluble and, following release, it will rise to the sea surface and rapidly evaporate. More than 1000 tonnes of styrene are believed to have been lost to sea during the incident, resulting in an aerial plume of vapour which crossed Alderney and episodic contamination of air and water in the immediate vicinity of the wreck site. Analysis of edible tissues using coupled gas chromatography/mass spectrometry demonstrated low-level styrene contamination of crabs recovered from pots laid very close to the wreck site prior to the incident. These concentrations posed no risks to human consumers, and no fishery controls were implemented. The remainder of the styrene and the ship's main bunker fuel were recovered from the wreck on the seabed, whilst the two chemical solvents were released to the water column in a slow, controlled manner.  相似文献   

Flow Adjustments Across Sea-Surface Temperature Changes     

L. Smahrt  Dean Vickers  Erin Moore 《Boundary-Layer Meteorology》2004,111(3):553-564

The adjustment of airflow across sea-surface temperature changes is examinedusing aircraft eddy-correlation data. Major features of the observed flow adjustmentare not included in the theory of internal boundary layers. However, the data samplesize and coverage are not sufficient to accurately quantify the additional influences.With flow from warm water over cooler water, substantial turbulence intermittentlydevelops above the newly formed surface inversion layer. The corresponding,spatially-averaged, downward momentum flux is stronger than that close to the surface.With stably stratified flow over modest increases of sea-surface temperature, areduction of stratification can trigger episodic shear generation of turbulence. Inthese cases, the primary role of increasing surface temperature in the downwinddirection is to induce shear generation of turbulence. With larger increases ofsurface temperature, upward heat flux generates turbulence, warms the air and generates a significant horizontal gradient of hydrostatic pressure. This contributionto the pressure field appears to strongly modify the flow. Major inadequacies inexisting data and future needs are noted.  相似文献   

Recent climatic change,greenhouse gas emissions and future climate: The implications for India     

P. Govinda Rao  P. M. Kelly  M. Hulme 《Theoretical and Applied Climatology》1996,55(1-4):41-64

Summary In this paper, we discuss past climatic trends over India, greenhouse gas emissions due to energy consumption, forest and land-use changes, climate change scenarios for the year 2050, potential consequences for agriculture and cyclone activity and the possibility that India might limit the increasing trend in its emissions.India's mean surface air temperature has increased significantly by about 0.4°C over the past ccntury. Neither monsoon nor annual rainfall shows any significant trend. On average, there has been a rise in sea levels around India over recent decades, though considerable uncertainties exist in the accuracy and interpretation of the available data.Carbon emissions from the energy sector amount to 71 MT a year, equivalent to all other sectors combined. From land-use data, a marginal net sequestration of 5.25 million tonnes of carbon occurred during 1986. Following the IPCC guidelines, methane emissions from rice and livestock are estimated at 17.4 and 12.8 Tg/year, respectively.According to recent climate model projections, India may experience a further rise in temperature of 1 °C by the year 2050, about four times the rate of warming experienced over the past 100 years. A modest increase in precipitation amounts might occur. Cereals production is estimated to decrease and the nutrition security of the population-rich but land-hungry region of India might be hampered. An increase in local tropical cyclone activity may occur over thc next century, posing added problems as large areas in the coastal regions have a dense population.About 70% of the electricity generation in India is from coal-based power stations. Altering this dependence significantly to reduce emissions would imply a substantial change in the present energy policy of India. There is great potential for improving energy efficiency and conservation. The adoption of cleaner coal-technologies should be considered, as must the development of renewable, non-conventional energy sources. In all cases, serious institulional barriers and resource limitations need to be addressed. The scope for carbon sequestration is limiled by land availabilily and other factors. It is argued that any response to global warming must be located firmly in the framework of sustainable development.With 5 Figures  相似文献   

Persistent patterns in the geomagnetic field during the last 2.5 Myr     

Peter Kelly  David Gubbins 《Surveys in Geophysics》1996,17(2):173-176

  相似文献   

THE IDENTIFICATION OF THE VOLCANIC SIGNAL IN GLOBAL SURFACE TEMPERATURE RECORDS   总被引：1，自引：0，他引：1  

Jia Pengqun  P. M. Kelly 《Acta Meteorologica Sinica》1996,10(2):222-232

In an attempt to clearly separate the volcanic signal,we use a mixture of principal componentanalysis(PCA)and superposed epoch analysis to identify volcanic signal in the global surface tem-perature field.In this way,the spatial and temporal pattern of volcanic signals is identified in theglobal surface temperature records.Our results show that the strongest ENSO and volcanic signalsare related with the first and the third principal components respectively.Both ENSO and volcanicsignals have responses in the second principal component.  相似文献   

Non-classical damping in dynamic analysis of base-isolated structures with internal equipment     

Hsiang-Chuan Tsai  James M. Kelly 《地震工程与结构动力学》1988,16(1):29-43

It has been shown that the use of base isolation not only attenuates the response of a primary structural system but also reduces the response of a secondary system mounted on or within the main structure. The isolation system, superstructure and equipment may be made of different materials with significantly different energy dissipation characteristics such that the damping matrix for the combined system is non-classical and can only be approximately expressed by modal damping ratios if the classical mode method is used for analysis. The object of this paper is to evaluate the accuracy of this procedure in approximating the responses of base-isolated structures and internal equipment. The complex mode method can provide exact solutions to problems with non-classical damping and is used here to find the exact response of the isolation-superstructure-equipment system. The entire system is assumed to be linear elastic with viscous damping and the superstructure is assumed to be proportionally damped so that the deformation of the superstructure can be expressed in terms of its classical modes. Recognizing that the ratio of the equipment mass to the structural mass and the ratio of the stiffness of the isolation system to the superstructural stiffness are both small, perturbation methods are used to find the response. This study shows that the response of base-isolated structures can be determined by the classical mode method to some degree of accuracy, but the higher frequency content is distorted. The equipment response derived by the classical mode method is much smaller than the exact solution so that the complex mode method should be applied to find equipment response.  相似文献