Global Climate Change — the Latest Assessment: Does Global Warming Warrant a Health Warning?     

RT Watson  AJ McMichael 《Global Change & Human Health》2001,2(1):64-75

Global climate change is a qualitatively distinct, and very significant, addition to the spectrum of environmental health hazards encountered by humankind. Historically, environmental health concerns have focused on toxicological or microbiological risks to health from local exposures. However, the scale of environmental health hazards is today increasing; indeed, the burgeoning human impact on the environment has begun to alter global biophysical systems (such as the climate system). As a consequence, a range of larger-scale environmental hazards to human population health has emerged. This includes the health risks posed by climate change, stratospheric ozone depletion, loss of biodiversity, stresses on terrestrial and ocean food-producing systems, changes in hydrological systems and the supplies of freshwater, and the global spread of persistent organic pollutants. Appreciation of this scale and type of influence on human health entails an ecological perspective — a perspective that recognises that the foundations of long-term good health in populations reside in the continued stability and functioning of the biosphere's "life-supporting" ecological and physical systems. This revised version was published online in September 2006 with corrections to the Cover Date.  相似文献   

The Existence and Stability of Equilibrium Points in the Robe’s Restricted Three-Body Problem     

P. P. Hallan  Neelam Rana 《Celestial Mechanics and Dynamical Astronomy》2001,79(2):145-155

The existence of all the equilibrium points, their location and stability in the Robe's (1977) restricted three—body problem have been studied. It is seen that the center of the first primary is always an equilibrium point, whatever be the values of the density parameter K, eccentricity parameter eand mass parameter . The other equilibrium points exist only when K 0 and e = 0 that is when the second primary, a mass point, moves around the first, a spherical shell filled with fluid, in a circular orbit. When K > 1, there is one additional equilibrium point lying on the line joining the center of the first primary and the second primary. When K + = 1, there are infinite number of equilibrium points in the x—yplane lying on a circle of radius one and center as the second primary, provided the points are inside the spherical shell. When K < 0 and K + > 0, there are two more equilibrium points lying in the x—z plane forming triangles with the center of the shell and the second primary. Results of the stability of the equilibrium point (–,0,0), center of the first primary are the same as those given by Robe (1977). Circular points and triangular points are always unstable. The equilibrium point collinear with the center of the shell and the second primary is stable provided and Ksatisfy the inequality .Thus, Robe's elliptic restricted three-body problem has only one equilibrium point for all values of the parameters Kand and Robes circular restricted three-body problem can have two, three or infinite number of equilibrium points depending upon the values of Kand . This is contrary to the classical-restricted problem where there are five equilibrium points, which are finite in number. Further, only the points collinear with the center of the shell and the second primary are stable in the Robe's problem where as in the classcial problem collinear points are unstable and triangular points are stable.This revised version was published online in October 2005 with corrections to the Cover Date.  相似文献   

Pressure distribution phenomena over a wedge and sphere surface in uniform flow     

M. Sohel Rana B.Sc.  A. T. M. Rafiqul Hoque M. Sc.  S. M. Asadul Hossain B.Sc. 《International Journal of Environmental Science and Technology》2007,4(3):395-400

In this paper, experimentally the pressure distribution over wedge and sphere surface in uniform flow has been investigated. Fluid flow over a smooth wedge surface was investigated experimentally to determine the pressure distribution at different values of Reynolds numbers and wedge angles as well as pressure distributions around the sphere of different size are reported for different Reynolds numbers. The variation of static pressures is larger near the wedge vertex and gradually decreases along the length of the wedge surface. At the forward stagnation point the pressure distribution depends on the size of spheres. Separation of flow takes place at an angle of 78° from forward stagnation point for all sizes of spheres. At the rear stagnation point of the sphere the pressure distribution predicts negative pressures. Experimental results provide useful information of interest to potential industrial application. It helps in determining the shape of various wedge and sphere surfaces used in industries for cooling or heating of different wedge surfaces. In the present experiment, it has been found that the pressure near vertex lower as the included angle of the wedge decreases and at lower values of Reynolds number.  相似文献   

An Empirical Comparison of Kriging Methods for Nonlinear Spatial Point Prediction     

Rana A. Moyeed  Andreas Papritz 《Mathematical Geology》2002,34(4):365-386

Spatial prediction is a problem common to many disciplines. A simple application is the mapping of an attribute recorded at a set of points. Frequently a nonlinear functional of the observed variable is of interest, and this calls for nonlinear approaches to prediction. Nonlinear kriging methods, developed in recent years, endeavour to do so and additionally provide estimates of the distribution of the target quantity conditional on the observations. There are few empirical studies that validate the various forms of nonlinear kriging. This study compares linear and nonlinear kriging methods with respect to precision and their success in modelling prediction uncertainty. The methods were applied to a data set giving measurements of the topsoil concentrations of cobalt and copper at more than 3000 locations in the Border Region of Scotland. The data stem from a survey undertaken to identify places where these trace elements are deficient for livestock. The comparison was carried out by dividing the data set into calibration and validation sets. No clear differences between the precision of ordinary, lognormal, disjunctive, indicator, and model-based kriging were found, neither for linear nor for nonlinear target quantities. Linear kriging, supplemented with the assumption of normally distributed prediction errors, failed to model the conditional distribution of the marginally skewed data, whereas the nonlinear methods modelled the conditional distributions almost equally well. In our study the plug-in methods did not fare any worse than model-based kriging, which takes parameter uncertainty into account.  相似文献   

A model for predicting actual evapotranspiration under soil water stress in a Mediterranean region   总被引：1，自引：0，他引：1  

G. Rana  N. Katerji  M. Mastrorilli  M. El Moujabber 《Theoretical and Applied Climatology》1997,56(1-2):45-55

Summary In this paper a model for estimating actual evapotranspiration is developed and tested for field crops (grain sorghum and sunflower) maintained under water stress conditions. The model is based on the Penman-Monteith formulation of ET in which canopy resistance (r _c) is modeled with respect to the crop water status and local climatological conditions. The model was previously tested on reference grass; in this last case no reference was made to soil water conditions andr _c was modeled only as a function of climatological parameters. Herer _c is expressed as a function of available energy, vapour pressure deficit, aerodynamic resistance and crop water status by means of predawn leaf water potential. Results, obtained with various crop water stress intensities, show that, on a daily scale, calculated ET is 98% and 95% of the measured ET for sorghum and sunflower respectively. The correlation between daily calculated and measured ET is very high (r ² = 0.95 for sorghum andr ² = 0.98 for sunflower). On an hourly scale, the model works very well when the crops were not stressed and during the senescence stage. In case of weak and strong stress the model has to be used with some precautions.With 9 Figures  相似文献   

A Measurement Based Sensitivity Analysis of the Penman-Monteith Actual Evapotranspiration Model for Crops of Different Height and in Contrasting Water Status   总被引：4，自引：0，他引：4  

G. Rana  N. Katerji 《Theoretical and Applied Climatology》1998,60(1-4):141-149

Summary This paper presents a study of the sensibility of the Penman-Monteith evapotranspiration model to climatic (available energy and vapour pressure deficit) and parametric (aerodynamic and canopy resistances, r _a and r _c respectively) factors in a semi-arid climate, for crops in contrasting water status (well irrigated and under water stress) and of different heights. Three experiments were carried out in southern Italy on reference grass (≈ 0.1 m), grain sorghum (≈ 1 m) and sweet sorghum (≈ 3 m). For this analysis the sensitivity coefficients, taken as hourly means, were evaluated during the growth season when the crops completely covered the soil. The relative errors on evapotranspiration were also evaluated for r _a and r _c . The results showed that, for reference grass, available energy and aerodynamic resistance play a major role. For crops under water stress the most important term to evaluate is canopy resistance. For a tall crop, as sweet sorghum, the role of the vapour pressure deficit is fundamental, both when the crop is in good water status and under water stress. Received July 14, 1997 Revised February 5, 1998  相似文献   

Influence of strong motion characteristics on permanent displacement of slopes   总被引：1，自引：0，他引：1  

Rana Roy  Debasis Ghosh  Gautam Bhattacharya 《Landslides》2016,13(2):279-292

Landslides triggered by moderate to major earthquakes are a recognized seismic hazard. Arias Intensity (I _a) is a key intensity measure of the ground motion, but significant duration is widely used to define strong motion duration. We calculate Newmark’s displacements using earthquake records bracketing a broad range of Arias Intensity and significant duration employing Newmark’s rigid block method and a number of yield accelerations. Total landslide displacement increases with the increase in the energy content of the ground motion (I _a) above a threshold. Such threshold may be expressed as a function of yield acceleration of the slope regardless of the ground motion characteristics. Newmark displacement decreases with increasing duration for earthquakes with similar energy content. The wide scatter in the results converges when using formal dimensional analysis. Self-similar symmetry may facilitate the assessment of the performance of slopes during earthquakes. The mathematical framework for probabilistic determination of landslides displacement may be a useful aid to estimate the likelihood of landslide hazards provided that the geotechnical properties of the slopes are known.  相似文献   

Growth of medium sized towns in India     

P. Rana  G. Krishan 《GeoJournal》1981,5(1):33-39

The growth of medium sized towns (with a population ranging from 20,000 to less than 100,000) in India was subjected to a detailed analysis. The basic premise was that growth behaviour of this group of towns, rather of cities or small towns, was a sensitive index to decentralisation of the urban process as well as to a balanced development of a region.It was discovered that growth rate of these towns was not just moderate; it was moderate to rapid. This signified that medium sized towns were more akin to cities than to small towns in respect of growth pattern.Among the various factors affecting growth, location of these towns in a particular region was discerned as more critical than their functions or relative size. Their growth was distinctly fast in areas with comparatively low population density, wide spacing of towns and new developmental activities. Here these towns were generally the biggest in their subregional context. The growth behaviour of medium sized towns did confirm dispersal of urbanisation but lack of any consistent relationship between their growth rate and development level of different areas was not in conformity with the hypothesis.  相似文献   

Nature and cosmic integrity a search in Hindu geographical thought     

Rana P. B. Singh Prof. Dr. 《GeoJournal》1992,26(2):139-147

The roots of Hindu geographic thought can be traced to the remote past, going back at least to c. 3500 BC. Formerly the unity of Nature and Man was expressed in the context of religious activities. The idea of nature and human integrity in Hindu thought depends upon ways in which people see and experience themselves, their sense of attachment to nature, and their ways of maintaining this. It is through symbolism, the main expression of mythological understanding, that one can gain insight into the relationships of humanity to Nature. Creation and incarnation myths describe the origin of organic life and of its five basic elements. The integrity of dwelling in space is expressed through the notion of home. Religion plays a vital role in the Hindu quest for harmony between nature and humanity.Mystics understand the roots of the Tao but not its branches; scientists understand its branches but not its roots. Science does not need mysticism and mysticism does not need science; but man needs both (Capra 1976, p. 297).  相似文献   

Plastic ingestion by estuarine mullet Mugil cephalus (Mugilidae) in an urban harbour,KwaZulu-Natal,South Africa     

T Naidoo  AJ Smit  D Glassom 《African Journal of Marine Science》2016,38(1):145-149

Coastal urban environments have high plastic pollution levels, and hence interactions between plastic debris and marine life are frequent. We report on plastic ingestion by mullet Mugil cephalus in Durban Harbour, KwaZulu-Natal, South Africa. Of 70 mullet (13.0–19.5?cm total length), 73% had plastic particles in their guts, with a mean of 3.8 particles per fish (SD 4.7). Plastic ingestion showed no relation to digestive tract content or fish length. White and clear plastic fibres were ingested most commonly. This urban population of M. cephalus had a higher incidence of plastic ingestion than has been reported in studies on fish from other coastal areas or the oceanic environment.  相似文献