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   

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

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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   

Seismic response of the superstructure and attached equipment in a base-isolated building     

Hsiang-Chuan Tsai  James M. Kelly 《地震工程与结构动力学》1989,18(4):551-564

Base isolation can be used both to protect the structure and simultaneously to reduce the response of internal equipment. The seismic response of a base-isolated structure has been studied through the shaking table test or numerical calculation before. The object of this paper is to analyse a base-isolated structure by a different analytical approach—perturbation analysis. Recognizing that the horizontal stiffness of an isolation system is much smaller than that of the superstructure, the mathematical expressions of the modal properties of base-isolated structures are derived by the perturbation method in terms of the modal properties of the superstructure and used to study the dynamic response of superstructure and attached equipment in the base-isolated building. This study shows that the first base-isolated mode not only controls the superstructural response but also dominates the response of high-frequency attachment. The contribution of higher modes to the response of base-isolated structures, which is proportional to the horizontal stiffness of isolation system, is very small.  相似文献   

Aseismic base isolation: review and bibliography   总被引：19，自引：0，他引：19  

James M. Kelly 《Soil Dynamics and Earthquake Engineering》1986,5(4):202-216

The idea that a building can be uncoupled from the damaging effects of the ground movement produced by a strong earthquake has appealed to inventors and engineers for more than a century. Many ingenious devices have been proposed to achieve this result, but very few have been tried and the concept now generally referred to as base isolation or seismic isolation has yet to become acceptable to the engineering profession as a whole. Although most of the proposed systems are unacceptably complicated, in recent years a few practical systems have emerged and have been implemented. While some of these systems have been tested on large-scale shaking tables, none has to date been tested as built by a strong earth tremor. The shake testing and related static testing of full-scale components such as isolation bearings, however, has led to a certain degree of acceptance by the profession and it is possible that the number of practical implementations of base isolation will increase quite dramatically in the next few years.

This review summarizes much of the literature on theoretical aspects of seismic isolation, describes testing programmes and enumerates those isolation systems which have been used in buildings completed or under construction. It describes the characteristics of the various implemented systems with an indication of their range of applicability and some assessment of their development as backed by research. A bibliography of all papers published on the topic from 1900 to 1984 is included. The bibliography is as complete as possible, but, due to the rapid increase in research interest in the topic in the past few years, there may be a substantial degree of omission in the later years.  相似文献   

Pollutant transport in a shallow unconfined aquifer in Perry,Ohio     

J. Mark Inglis  Gerald Matisoff  Walton Ross Kelly 《Environmental Geology》1986,8(4):237-245

The groundwater system in northern Perry Township in Lake County, Ohio, is a shallow, unconfined aquifer consisting of periglacial lake beach deposits and less permeable lacustrine plain deposits. Groundwater flow is generally toward Lake Erie from south to north and is controlled by the top of the Ashtabula Till, but strong, local variations are caused by northward flowing streams During the study period, water levels in most wells exhibited a seasonal fluctuation of less than 0 3 m from their mean values. The areal distributions of chloride and nitrate concentrations indicate that road salt runoff easily infiltrates the aquifer and that nitrate may be sourced from fertilizer application. Ground-water flow and solute transport models indicate that in excess of 27 years are required to obtain chemical steady-state under hydrologic steady-state conditions. The simulations also demonstrate that nitrate loading must occur in more than one cultivated field in order to obtain the observed wide-spread nitrate distribution.  相似文献   

Sulphur contents of conifer needles in Great Britain     

John L. Innes Dr.  Roger C. Boswell 《GeoJournal》1989,19(1):63-66

There is currently a lack of convincing evidence linking air pollution and tree health in Great Britain. Field surveys have not revealed a clear association between the spatial distribution of crown thinning and air pollution; the crown condition of some species is apparently better in more polluted areas. This has been attributed to the confounding effects of climate, which is known to have a marked effect on crown condition. In this study, analysis of total sulphur contents of needles ofPicea sitchensis ((Bong.) Carr.),P. abies ((L.) Karst.) andPinus sylvestris (L.) reveals marked patterns that are correlated with modelled atmospheric concentrations of sulphur dioxide. Correlations with other indices of sulphur pollution, including wet and dry deposition and sulphate aerosol concentrations, are less consistent. However, no association has been found between the sulphur contents of needles and the crown densities of trees in Britain.  相似文献