Propagation of Rayleigh waves on cylindrical surfaces of transversely isotropic material and of varying density in a magnetic field     

Surya Narain  B. G. Verma 《Pure and Applied Geophysics》1972,98(1):13-25

Summary Three dimensional magneto-elastic equations pertaining to the problem of propagation of axial Rayleigh waves on the surface of elastic cylinder of isotropic material have been solved. Two cases have been considered — first, when the density varies linearly and second, when it varies inversely as the radius vector and frequency equations for both the cases have been obtained.  相似文献   

Propagation of a spherical magnetogasdynamic shock in a self gravitating system     

B. G. Verma 《Pure and Applied Geophysics》1970,83(1):21-30

Summary This paper considers a spherical shock, in a conducting gas, produced on account of explosion into an inhomogeneous self gravitating system. Similarity principles have been used to reduce the equations governing the flow to ordinary differential equations under the assumption that the density varies as an inverse-power of distance from the explosion centre.  相似文献   

Comparison of Linear Regression Models for Quantitative Geochemical Analysis: An Example Using X-Ray Fluorescence Spectrometry   总被引：1，自引：0，他引：1  

Mirna Guevara  Surendra P. Verma  Fernando Velasco-Tapia  Rufino Lozano-Santa Cruz  Patricia Girón 《Geostandards and Geoanalytical Research》2005,29(3):271-284

This paper presents statistical aspects related to the calibration process and a comparison of different regression approaches of relevance to almost all analytical techniques. The models for ordinary least-squares (OLS), weighted least-squares (WLS), and maximum likelihood fitting (MLF) were evaluated and, as a case study, X-ray fluorescence (XRF) calibration curves for major elements in geochemical reference materials were used. The results showed that WLS and MLF models were statistically more consistent in comparison with the usually applied OLS approach. The use of uncertainty on independent and dependent variables during the calibration process and the calculation of final uncertainty on individual results using error propagation equations are the novel aspects of our work.  相似文献   

A comparative study of ANN and Neuro-fuzzy for the prediction of dynamic constant of rockmass   总被引：1，自引：0，他引：1  

T. N. Singh  R. Kanchan  A. K. Verma  K. Saigal 《Journal of Earth System Science》2005,114(1):75-86

Physico-mechanical properties of rocks have great significance in all operational parts in mining activities, from exploration to final dispatch of material. Compressional wave velocity (p-wave velocity) and anisotropic behaviour of rocks are two such properties which help to understand the rock response under varying stress conditions. They also influence the breakage mechanism of rock. There are different methods to determine thep-wave velocity and anisotropyin situ and in the laboratory. These methods are cumbersome and time consuming. Fuzzy set theory, Fuzzy logic and Neural Networks techniques seem very well suited for typical geotechnical problems. In conjunction with statistics and conventional mathematical methods, hybrid methods can be developed that may prove to be a step forward in modeling geotechnical problems. Here, we have developed and compared two different models, Neuro-fuzzy systems (combination of fuzzy and artificial neural network systems) and Artificial neural network systems, for the prediction of compressional wave velocity.  相似文献   

Integrated resource study for conservation and management of Ropar wetland ecosystem, Punjab     

V K Verma  Rajiv Chopra  P K Sharma  Charanjit Singh 《Journal of the Indian Society of Remote Sensing》1998,26(4):185-195

Integrated resource study in Ropar wetland ecosystem was undertaken to analyse physiography, drainage, landuse and vegetation status. Various thematic maps have been prepared using black and white aerial photographs on 1:20,000 scale and IRS 1A LISS-II (FCC) on 1:50,000 scale. The Ropar wetland ecosystem is comprised of six major landforms i.e. Siwalik hills, Valley, Piedmont plain, Alluvial plain, River terraces and River courses. The study area show high drainage density with sub dendritic and sub parallel drainage. The area has poor vegetative cover which results in extensive erosion and sedimentation of Ropar lake. The water spread and. qualitative turbidity level in the notified wetland area was also monitored. Anthropogenic pressure, industrial pollution, sedimentation, eutrophication, illegal fishing and flooding have been identified as major threats to the wetland. Keeping in view the threats to Ropar wetland, the conservation measures have been suggested.  相似文献   

Extreme enrichment of Sb, Tl and other trace elements in altered MORB   总被引：2，自引：0，他引：2  

K. P. Jochum  S. P. Verma 《Chemical Geology》1996,130(3-4):289-299

We have analyzed 25 trace elements (e.g., Sb, Tl, Sn, rare earth elements (REE), Th, U, Nb, Pb, Zr, Hf, and Y) in altered mid-ocean ridge basalts (MORB) from locations near the mouth of the Gulf of California. Our results imply that the heavy REE and Y are not seriously affected by seawater alteration, in agreement with previous studies. The elements Zr, Hf, Nb, light REE and Sr are enriched up to a factor of 2 in some extremely altered samples. However, element ratios between Zr, Hf, and Nb (e.g., Zr/Hf, and Zr/Nb) are not greatly affected, presumably due to the chemical similarity of these elements during any exchange process. The enrichment of Th and Sn is even higher. Antimony, Tl, Cs, Rb, Rb, and Ba are most easily altered by water-rock interaction and are therefore the best indicators for seawater alteration. The enrichment factor of the most mobile element Sb is up to 2000.

There is a weak correlation between the concentration in seawater and the enrichment factors. On the other hand, the worldwide pelagic clay pattern matches the enrichment pattern much more closely, and the limited data available for local oceanic sediments give an even better correlation. A plausible model to explain the enrichment pattern may be an elemental exchange between basalt and seawater that had interacted earlier with overlying sediments.  相似文献   

Tissue enzymes as biomonitors of PCP intoxication in Notopterus notopterus     

S. R. Verma  P. K. Tyagi  D. Dutt  R. Chand  A. K. Sharma 《洁净——土壤、空气、水》1988,16(6):633-641

In this paper, toxicity effects of pentachlorophenol have been studied using enzymes, phosphatases, transaminases and hydrogenases as indicators for toxicity. The sublethal concentrations used were 0.019, 0.0063 and 0.0038 mg/l (1/5th, 1/15th and 1/25th fractions of LC₅₀) and the experimental fishes were exposed for the periods of 15, 30, 45 and 60 days. Most of the significant alterations in enzymes were observed at 1/5th and 1/10th fractions except at few places in the liver where a significant alteration in the enzyme acid phosphatase occurs at 1/15th fraction. Glutamic pyruvic transaminase (GPT) and glutamic oxaloacetic transaminase (GOT) and lactic dehydrogenase (LDH) showed a significant increase in different tissues in all the fractions of treatment.  相似文献   

Carbon dioxide,water vapor and sensible heat exchanges of a grain sorghum canopy   总被引：3，自引：0，他引：3  

Dean E. Anderson  Shashi B. Verma 《Boundary-Layer Meteorology》1986,34(4):317-331

With the aid of eddy correlation instrumentation, the components of the energy budget and CO₂ flux were measured over grain sorghum grown at Mead, Nebraska. Diurnal patterns of sensible heat, latent heat, CO₂ and momentum flux are examined for typical days. On a mostly clear day when the crop leaf area index was 3.7, net radiation reached a mid-day peak of 560 W m^-2, while sensible and latent heat fluxes peaked at 50 and 460 W m^-2, respectively. The peak CO₂ flux occurring just prior to solar noon was 1.5 mg m^-2(ground area) s^-1. CO₂ flux (respiration from plants, soil and roots) in the early evening was about -0.28 mg m^-2 (ground area) s^-1.A relationship between CO₂ flux and photosynthetically active radiation (PAR) was developed. Except during the late stage of growth (growth stage 8.5, toward the initiation of senescence), the crop showed no evidence of saturation up to PAR 1800 Ei m^-2s^-1. The light compensation point was found to be about 211 Ei m^-2s^-1. Examination of CO₂ flux-PAR relationships for selected days through the season indicated an aging effect in terms of a decrease in photosynthetic activity of the sorghum canopy. Measurements made on two consecutive days demonstrate the effects of weather conditions on CO₂ flux and carbon-water flux ratio (a measure of water use efficiency of the crop). The occurrence of regional sensible heat advection with concommitant high vapor pressure deficit and air temperature-limited CO₂ exchange reduced the carbon-water flux ratio.Published as Paper No. 7717, Journal Series, Nebraska Agricultural Research Division. The work was conducted under Regional Research Project 11-33 and Nebraska Agricultural Research Division Project 27-003.Formerly Post Doctoral Research Associate (now at the University of Connecticut Department of Renewable Natural Resources Storrs CT)  相似文献   

Interannual and long-term variability of the summer monsoon and its possible link with northern hemispheric surface air temperature     

R. K. Verma  K. Subramaniam  S. S. Dugam 《Journal of Earth System Science》1985,94(3):187-198

Some statistical properties of the summer monsoon seasonal rainfall for India during the last 100 years (1881–1980) are presented. The most recent decade of 1971–1980 shows the lowest value of standard-decadal average monsoon rainfall (86.40 cm) and is also characterised by the second highest value of coefficient of variation in monsoon rainfall (12.4 %). The combined last two standard-decadal period of 1961–1980 was the period of the largest coefficient of variation and the lowest average monsoon rainfall for India. The possible influence of global climatic variability on the performance of the monsoon is also examined. Analyses of correlation coefficient show that a statistically significant positive relationship with a time-lag of about six months exists between monsoon rainfall and northern hemispheric surface air temperature. A cooler northern hemisphere during January/February leads to a poor monsoon. All the major drought years during the last 3 decades had much cooler January/February periods over the northern hemisphere—1972 having the coldest January/February with a temperature departure of −0.94°C and the most disastrous monsoon failure.  相似文献   

Biomonitoring of the Contamination of Water by a Sublethal Concentration of Pesticides — A System Analysis Approach     

S. R. Verma  I. P. Tonk 《洁净——土壤、空气、水》1984,12(4):399-409

Heteropneustes (Saccobranchus) fossilis (Pisces; Clariidae) is exposed to the biocides Chlordane, Aldrin, Metasystox, Dichlorvos, Carbofuran and Sevin for 30 d at a concentration of the 1/15 fraction of LC_50;96h with daily exchange of the medium. At intervals of 5 d the respiration rate was determined for 1 h. In addition, after the end of tests 13 haematological parameters as well as the activities of the adenosine triphosphatases and the acetylcholinesterase were determined in the liver, the kidney and the gills. During all exposures to biocides the respiration rate decreases significantly with the test time. At all exposures the blood concentrations of glucose, sodium- and chloride-ions show a significant increase, whereas the cholesterin content and the clotting time decrease significantly. The ATPase activity is significantly reduced only by Aldrin and Chlordane. A significant reduction of the acetylcholinesterase activity occurs in each of the three investigated tissues only for Metasystox and Dichlorvos and in the liver in addition also for Chlordane, Aldrin and Carbofuran. Therefore, the respiration rate and haematological criteria permit a general stress indication, enzymatic activities constitute a specific indication of individual groups of biocides, so that a systematic analysis of these three indication groups will probably provide a specific resultant statement in a biomonitoring system due to the specific inhibition pattern.  相似文献