Analysis of long-term ozone trend over Delhi and its meteorological adjustment   总被引：1，自引：0，他引：1  

S. Kumari  G. Jayaraman  C. Ghosh 《International Journal of Environmental Science and Technology》2013,10(6):1325-1336

Present study deals with the statistical analysis of long-term ground level ozone (O₃) trend and the influence of meteorological variables on its variation over Delhi, India. Daily mean and maximum of O₃ and meteorological data, obtained from India Meteorological Department, were arranged for the period of 9 years (1998–2006). Based on the preliminary correlation study of all the data with O₃, six variables viz. daily maximum temperature, daily average relative humidity, dew point, wind speed, visibility, and total sunshine were selected. Classical additive time series decomposition technique was used to obtain seasonally adjusted long-term trend. To analyze the masking effect of meteorology, adjustment was made using Kolmogorov–Zurbenko filters followed by stepwise regression analysis to the smoothed series of O₃ maximum and meteorological variables, which showed that long-term trend was independent of sunshine duration. Results indicate a significant increasing trend with annual increase of 1.13 % for O₃ mean and 3 % for O₃ maximum. Annual deseasonalized trend for seasonal cycle shows bimodal oscillations. About 43 % of O₃ variation was explained by the selected meteorological factors and rest of variation attributed to factors like emission of precursor gases, pollutant transport, policy changes, etc. Among the three tested regression models, performance of Model 2 with variable temperature, wind speed, and visibility was found to be best that resulted in lowering of O₃ trend. Large variability (23 %) was explained by the variable visibility depicted that the emission of primary pollutants not only provides the precursor gases but also control the local photochemical reactions.  相似文献   

Estimation of hysteretic energy demand using concepts of modal pushover analysis   总被引：1，自引：0，他引：1  

Tholen Prasanth  Siddhartha Ghosh  Kevin R. Collins 《地震工程与结构动力学》2008,37(6):975-990

Hysteretic energy dissipation in a structure during an earthquake is the key factor, besides maximum displacement, related to the amount of damage in it. This energy demand can be accurately computed only through a nonlinear time‐history analysis of the structure subjected to a specific earthquake ground acceleration. However, for multi‐story structures, which are usually modeled as multi‐degree of freedom (MDOF) systems, this analysis becomes computation intensive and time consuming and is not suitable for adopting in seismic design guidelines. An alternative method of estimating hysteretic energy demand on MDOF systems is presented here. The proposed method uses multiple ‘generalized’ or ‘equivalent’ single degree of freedom (ESDOF) systems to estimate hysteretic energy demand on an MDOF system within the context of a ‘modal pushover analysis’. This is a modified version of a previous procedure using a single ESDOF system. Efficiency of the proposed procedure is tested by comparing energy demands based on this method with results from nonlinear dynamic analyses of MDOF systems, as well as estimates based on the previous method, for several ground motion scenarios. Three steel moment frame structures, of 3‐, 9‐, and 20‐story configurations, are selected for this comparison. Bias statistics that show the effectiveness of the proposed method are presented. In addition to being less demanding on the computation time and complexity, the proposed method is also suitable for adopting in design guidelines, as it can use response spectra for hysteretic energy demand estimation. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

The structure of black hole magnetospheres I. Schwarzschild black holes     

Pranab Ghosh 《Monthly notices of the Royal Astronomical Society》2000,315(1):89-97

We introduce a multipolar scheme for describing the structure of stationary, axisymmetric, force-free black hole magnetospheres in the '3+1' formalism. We focus here on Schwarzschild spacetime, giving a complete classification of the separable solutions of the stream equation. We show a transparent term-by-term analogy of our solutions with the familiar multipoles of flat-space electrodynamics. We discuss electrodynamic processes around disc-fed black holes in which our solutions find natural applications: (i) 'interior' solutions in studies of the BlandfordZnajek process of extracting the rotational energy of holes, and of the formation of relativistic jets in active galactic nuclei and 'microquasars'; (ii) 'exterior' solutions in studies of accretion disc dynamos, disc-driven winds and jets. On the strength of existing numerical studies, we argue that the poloidal field structures found here are also expected to hold with good accuracy for rotating black holes, except for the cases of the maximum possible rotation rates. We show that the closed-loop exterior solutions found here are not in contradiction with the MacdonaldThorne theorem, as these solutions, which diverge logarithmically on the horizon of the hole , only apply to those regions that exclude .  相似文献   

Spatio‐temporal prediction of land surface temperature using semantic kriging     

Shrutilipi Bhattacharjee  Jia Chen  Soumya K. Ghosh 《Transactions in GIS》2020,24(1):189-212

Spatio‐temporal prediction and forecasting of land surface temperature (LST) are relevant. However, several factors limit their usage, such as missing pixels, line drops, and cloud cover in satellite images. Being measured close to the Earth's surface, LST is mainly influenced by the land use/land cover (LULC) distribution of the terrain. This article presents a spatio‐temporal interpolation method which semantically models LULC information for the analysis of LST. The proposed spatio‐temporal semantic kriging (ST‐SemK) approach is presented in two variants: non‐separable ST‐SemK (ST‐SemK_NSep) and separable ST‐SemK (ST‐SemK_Sep). Empirical studies have been carried out with derived Landsat 7 ETM+ satellite images of LST for two spatial regions: Kolkata, India and Dallas, Texas, U.S. It has been observed that semantically enhanced spatio‐temporal modeling by ST‐SemK yields more accurate prediction results than spatio‐temporal ordinary kriging and other existing methods.  相似文献   

On the possible origin of troilite‐metal nodules in the Katol chondrite (L6‐7)          下载免费PDF全文

Dwijesh Ray  S. Ghosh  S.V.S. Murty 《Meteoritics & planetary science》2017,52(1):72-88

Microtextural study of a single troilite‐metal nodule (TMN) from the Katol L6‐7 chondrite, a recent fall (May, 2012) in India suggests that the TMN is primarily an aggregate of submicron‐scale intergrowth of troilite and kamacite (mean Ni: 6.18 wt%) juxtaposed with intensely fractured silicates, mainly olivine (Fa: 25 mole%), low‐Ca pyroxene (Fs: 21.2 mole%), and a large volume of maskelynite. Evidence of shock textures in the TMN indicates a high degree of shock metamorphism that involves plagioclase‐maskelynite and olivine‐wadsleyite/ringwoodite transformations and formation of quenched metal‐sulfide melt textures due to localized shear‐induced frictional melting. It is inferred that the TMN formation is an independent, localized event by a high energy impact and its subsequent incorporation in the ejected chondritic fragment of the parent body. Katol chondrite has been calibrated with a peak shock pressure of S5 (~45 GPa) after Stöffler et al. (1991), whereas peak shock pressure within the TMN exceeds the shock facies S6 (>45 GPa) following Bennett and McSween (1996) and Stöffler et al. (1991). Overall, the shock‐thermal history of the Katol TMN is dissimilar as compared to the host chondrite.  相似文献   

New insights on petrography and geochemistry of impactites from the Lonar crater,India          下载免费PDF全文

Dwijesh Ray  Dewashish Upadhyay  Saumitra Misra  Horton E. Newsom  Sambhunath Ghosh 《Meteoritics & planetary science》2017,52(8):1577-1599

The Lonar impact crater, India, is one of the few known terrestrial impact craters excavated in continental basaltic target rocks (Deccan Traps, ~65 Ma). The impactites reported from the crater to date mainly include centimeter‐ to decimeter‐sized impact‐melt bombs, and aerodynamically shaped millimeter‐ and submillimeter‐sized impact spherules. They occur in situ within the ejecta around the crater rim and show schlieren structure. In contrast, non–in situ glassy objects, loosely strewn around the crater lake and in the ejecta around the crater rim do not show any schlieren structure. These non–in situ fragments appear to be similar to ancient bricks from the Daityasudan temple in the Lonar village. Synthesis of existing and new major and trace element data on the Lonar impact spherules show that (1) the target Lonar basalts incorporated into the spherules had undergone minimal preimpact alteration. Also, the paleosol layer as preserved between the top‐most target basalt flow and the ejecta blanket, even after the impact, was not a source component for the Lonar impactites, (2) the Archean basement below the Deccan traps were unlikely to have contributed material to the impactite parental melts, and (3) the impactor asteroid components (Cr, Co, Ni) were concentrated only within the submillimeter‐sized spherules. Two component mixing calculations using major oxides and Cr, Co, and Ni suggest that the Lonar impactor was a EH‐type chondrite with the submillimeter‐sized spherules containing ~6 wt% impactor components.  相似文献   

Classification of glacial lakes using integrated approach of DFPS technique and gradient analysis using Sentinel 2A data     

Prateek Verma  Sanjay Kumar Ghosh 《国际地球制图》2019,34(10):1075-1088

It is important to identify and locate glacial lakes for assessing any potential hazard. This study presents a combination of semi-automatic method Double-Window Flexible Pace Search (DFPS) and edge detection technique to identify glacial lakes using Sentinel 2A satellite data. Initially, Normalized Difference Water Index (NDWI) has been used to identify water and non-water areas, while DFPS and Edge detection technique has been used to identify an optimum threshold value to distinguish between water and shadow areas. The optimal threshold from DFPS process is 0.21, while threshold value of gradient magnitude using edge detection process is 0.318. The number of glacial lakes identified using the above algorithm is in close agreement with previously published results on glacial lakes in Gangotri glacier using different techniques. Thus, a combination of DFPS and edge detection process has successfully segregated glacial lakes from other features present in Gangotri glacier.  相似文献   

Effective medium modeling to assess gas hydrate and free-gas evident from the velocity structure in the Makran accretionary prism, offshore Pakistan     

Ranjana Ghosh  Kalachand Sain 《Marine Geophysical Researches》2008,29(4):267-274

Seismic properties of sediments are strongly influenced by pore fluids. Stiffness of unconsolidated marine sediment increases with the presence of gas hydrate and decreases with the presence of gas. A strong bottom-simulating reflector (BSR) observed on a seismic profile in the Makran accretionary prism, offshore Pakistan, indicates the presence of gas hydrate and free-gas across the BSR. Elastic properties of gas depend largely on pressure and temperature. We, therefore, first determine the elastic modulus of gas at pressure and temperature calculated at the BSR depth in the study region. The interval velocities derived from the seismic data are interpreted by the effective medium theory, which is a combination of self-consistent approximation and differential effective medium theories, together with a smoothing approximation, for assessment of gas hydrate and free-gas. The results show the saturations of gas hydrate and free-gas as 22 and 2.4% of pore space, respectively, across the BSR.  相似文献   

Neutral fermions as the missing mass matter in galactic halos     

B. Datta  C. Sivaram  S. K. Ghosh 《Astrophysics and Space Science》1985,111(2):413-417

We point out that several independent considerations rule out the hypothesis that the missing mass in galactic halos is dominated by massive neutral fermions such as neutrinos, gravitinos or photinos.  相似文献   

Diffusion of the galactic cosmic rays in the vicinity of the solar system     

L. I. Dorman  A. Ghosh  V. S. Ptuskin 《Astrophysics and Space Science》1985,109(1):87-97

Cosmic-ray propagation in the vicinity of 1 kpc from the Sun is considered. The data on the 10¹²–10¹⁵ eV particle anisotropy, on 10¹² eV electron spectrum, and on temporal cosmic-ray variations are analyzed. The diffusion coefficientD(10¹²–10¹³ eV)=10²⁹–10³⁰ cm²s^–1 inferred from the analysis coincides with its standard value in the large-halo model withh=15 kpc. The total power of cosmic-ray generation, about 3×10⁴⁹ erg per SN in the proton component and about 10⁴⁸ erg per SN in the electron component, typical of the galactic diffusion model is in agreement with the obtained parameters of local sources.  相似文献