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1.
A static spherically-symmetric model, based on an exact solution of Einstein's equation, gives the permissible matter density 2×1014 g cm–3. If we use the change in the ratio of central density to the radiusr=a (i.e., central density per unit radius (0/a), we call it radius density) minimum, we have estimated the upper limit of the density variation parameter () and minimum mass limit of a superdense star like a neutron star. This limit gives an idea of the domain where the neutron abundance with negligible number of electrons and protons (may be treated as pure neutrons) and equilibrium in neutrons begins. 相似文献
2.
David P. Bacon Nash’at N. Ahmad Thomas J. Dunn Michael C. Monteith Ananthakrishna Sarma 《Natural Hazards》2008,44(3):317-327
By definition, a crisis is a situation that requires assistance to be managed. Hence, response to a crisis involves the merging
of local and non-local emergency response personnel. In this situation, it is critical that each participant: (1) know the
roles and responsibilities of each of the other participants; (2) know the capabilities of each of the participants; and (3)
have a common basis for action. For many types of natural disasters, this entails having a common operational picture of the unfolding events, including detailed information on the weather, both current and forecasted, that may impact on either
the emergency itself or on response activities. The Consequences Assessment Tool Set (CATS) is a comprehensive package of
hazard prediction models and casualty and damage assessment tools that provides a linkage between a modeled or observed effect
and the attendant consequences for populations, infrastructure, and resources, and, hence, provides the common operational
picture for emergency response. The Operational Multiscale Environment model with Grid Adaptivity (OMEGA) is an atmospheric
simulation system that links the latest methods in computational fluid dynamics and high-resolution gridding technologies
with numerical weather prediction to provide specific weather analysis and forecast capability that can be merged into the
geographic information system framework of CATS. This paper documents the problem of emergency response as an end-to-end system
and presents the integrated CATS–OMEGA system as a prototype of such a system that has been used successfully in a number
of different situations. 相似文献
3.
Joel A. Eaton Franco Scaltriti M. Cerruti-Sola M. B. K. Sarma B. D. Ausekar Santo Catalano Marcello Rodono 《Astrophysics and Space Science》1982,82(2):289-306
We present a relatively completeV-band light curve of SZ Psc for 1978 and a partial light curve for 1977. From the 1978 light curve we derive a new time of primary minimum, JD2443823.674±0.001, and a Russell-model solution,i=75°.8±0°.1,r
h
=0.096±0.003,r
c
=0.351±0.001, andL
h
=0.253±0.002. The hotter component of this system is a F5-8 main-sequence star, the cooler component a K3-4 star well above the main sequence. The system is detached with the larger component filling only 82% of its Roche lobe. The distortion wave in this RS CVn-type binary seems not to migrate regularly as do those in many other such systems, but rather seems to change phase and amplitude more erratically. Between 1977 and 1978 its phase stayed practically constant while its amplitude decreased by a factor of three. We discuss the implications of this behavior for the spot model of RS CVn-type activity. We find that the traditional comparison star for SZ Psc, HD 219018, is very likely a constant star contrary to a recent suggestion that it is variable. Its brightness and colors,V=7.705, (B-V)=0.628, and (V-I)
c
=0.688, are those of a G2V star.Visiting Astronomer, Kitt Peak National Observatory, which is operated by AURA, Inc., under contract with the National Science Foundation, and Visiting Astronomer, Prarie Observatory, University of Illinois. 相似文献
4.
M. V. M. S. Rao K. J. Prasanna Lakshmi L. P. Sarma K. B. Chary 《Journal of Earth System Science》2006,115(6):673-683
Compressional and shear wave velocities and attenuation measurements have been carried out in some of the borehole samples
of acidic, basic and intermediate granulites of Mahabalipuram, Tamil Nadu, India. The results have been obtained at ambient
conditions using ‘time-of-flight’ pulse transmission technique at 1.0 MHz frequency. The results show linear relationships
between velocity and density, and velocity and attenuation properties of the rocks. The acidic granulites show lower velocities
and higher attenuation than the intermediate and basic granulites. The average values of the Poisson’s ratio of acidic, intermediate
and basic granulites have been found to be 0.210, 0.241 and 0.279 respectively. The variations in velocities and attenuation
in these low porosity crystalline rocks are found to be strongly influenced by their mineral composition. The laboratory velocity
data (extrapolated to high pressure) of the present study and the published field velocity data from deep seismic sounding
studies indicate that these granulite facies rocks may belong to mid-crustal depths only. 相似文献
5.
Assuming the minimum detectable anomaly to be 10%, depths of detection of a 2D vertical resistive sheet of thickness t are found to be 4.0t, 3.0t, 4.0t and 4.0t with Wenner, two-electrode, three-electrode and dipole-dipole (β-Wenner) arrays, respectively, when the array spread is in-line. On the other hand, the depths of detection obtained with a broadside spread of the arrays right over the sheet are much less and are correspondingly 2.5t, 2.0t, 2.5t and 2.5t. An increase in the depth extent W of the sheet from 10t to 20t does not increase its depth of detection with the arrays. The depths of detection of an infinitely resistive horizontal cylinder of radius R are respectively 1.5R, 1.8R, 2.0R and 2.0R with the above-listed arrays when the array spread is in-line. With broadside spread of any of the arrays, the depth of detection is seen to be 2.5R. In the case of a spherical target of radius R, the detection depths of any of the arrays are found to be small and to vary between 0.8R and 1.1R. Comparatively, the detection depths of resistive targets are much lower than those of conductive targets of the same size and shape, with any electrode array. Among all the arrays studied, the two-electrode array performs worst in the detection of resistive targets while it performs best in detecting conducting targets of limited lateral extent. In the case of a spherical target, either resistive or conductive, there is no distinct change in its detection depth with array. 相似文献
6.
Recycling domestic wastewaters is one way to maximize the utilization of freshwater. Although sewage treatment plants help to remove particulate wastes, organic matter still remains, which can be used to harvest sizeable populations of zooplankton. In an effort to identify cladocerans which could grow on this organic matter, we tested the life table demography of the commonly found cladocerans (Alona rectangula, Ceriodaphnia dubia, Moina macrocopa, and Daphnia pulex) feeding on wastewater at three different stages of purification (tank that receives crude wastes (A), the biological reactor (B), and the penultimate stage of the treatment process (C)) from the Iztacalco water treatment plant in Mexico City. Experiments were conducted using the medium from each of the 3 tanks previously mentioned and a control of Chlorella vulgaris at 1.0 × 106 cells mL?1. We found that the average lifespan ranged from 5…30 days with D. pulex living the longest. The growth rate, which ranged from ?0.57 to +1.5 was highest for M. macrocopa. Our data indicate that Moina macrocopa, which had higher reproductive rates on wastewater than the controls, was most suited for growing in wastewaters. 相似文献
7.
Classification of hyperspectral remote sensing data is more challenging than multispectral remote sensing data because of the enormous amount of information available in the many spectral bands. During the last few decades, significant efforts have been made to investigate the effectiveness of the traditional multispectral classification approaches on hyperspectral data. Formerly extensively established conventional classification methods have been dominated by the advanced classification approaches and many pre‐processing techniques have been developed and incorporated in hyperspectral classification. A perspective survey of hyperspectral remote sensing classification approaches is presented here. It comprehensively highlights the taxonomy of major classification approaches reported during the last two decades and describes an experimental evaluation of a few major classification algorithms. Recent advancements in the development of classification approaches are also emphasized with a set of guidelines for achieving better classification performances. 相似文献
8.
K. Chakraborty P. K. Joshi K. K. Sarma 《Journal of the Indian Society of Remote Sensing》2009,37(1):99-106
Meghalaya is a landlocked state where the progress of industrialization is very slow. Majority of the population (rural) depends
on agriculture. Agriculture in the state is carried on in primitive ways with Jhumming prevailing in many parts. This practice is considered destructive as vast forest areas are cleared and burnt. Such areas
are used for cultivation and left out. After a gap of few years (2–3 years as of now and 15–20 years in past) the area is
revisited for cultivation without allowing to rejuvenate. The present work provides a status and trend of Land use land cover
dynamics in parts (at watershed level) of Meghalaya. The geospatial tools have been used to assess (a) the changes in land
use land cover since 1970s to 2005; (b) patch dynamics for understanding the degree of fragmentation; (c) changes along the
terrain topography. Umngot watershed of Meghalaya is taken as experimental area, which is a representative of mid-altitudinal
watershed particularly in the Jaintia hills district of Meghalaya. 相似文献
9.
It is seen that the apparent chargeability (Ma)L anomaly over a 2D graphite body splits into two distinct (Vs)L anomalies which closely follow the apparent resistivity profile. This suggests that the electric field amplitude is distorted due to a superficial inhomogeneity creating a (Vs)L anomaly, which bears no relation to the polarized body. The target depth obtained by continuation of such a profile is therefore, not acceptable. 相似文献
10.
-- This work extends the results that Apparao et al. (1997a) obtained for a vertical resistive sheet to the case of inclined resistive sheet models for different electrode arrays. It is found that the depth of investigation (DI) remains the same as that for the vertical target. Using this DI, modified pseudo-depth sections have been constructed over sheet models at different inclinations. It is noted that, for the Wenner array, the maximum anomaly contours fall directly over the target cross section. For dipole-dipole and three-electrode arrays, these contours fall on the up-dip side of the dipping target, with the maximum anomaly contour matching the depth level of the top of the target. It is also observed that the target cross section is at a distance of about 0.33L (L/3) from the maximum anomaly value/contour position for the three-electrode array and 0.25L (L/4) for the dipole-dipole system. These features are identifiable in the individual profiles and may help field geophysicists in the recognition and location of dipping target bodies. 相似文献