A high-resolution Fabry-Pérot spectrometer for emission line studies in planetary nebulae and other extended astronomical objects     

D. P. K. Banerjee  B. G. Anandarao  J. N. Desai  N. S. Jog  P. K. Kikani  R. K. Mahadkar  K. S. B. Manian  F. M. Pathan  N. C. Shah  M. Thomas 《Astrophysics and Space Science》1987,139(2):327-335

We describe here a scanning piezo-electric Fabry-Pérot spectrometer operating in the photoncounting mode whose plate spacing and parallelism are maintained by a servo-controlled system, ensuring high accuracy, for the study of emission lines from extended astronomical objects in the spectral range 4500–7000 Å. Details of the optical set-up and the Data Acquisition System (DAS) are described. Its performance at the Cassegrain focus of the 1 m telescope at Kavalur is discussed. Some line profiles on planetary nebulae studied with the above spectrometer are also presented.  相似文献   

Seismic microzonation for Penang using geospatial contour mapping     

Chee Ghuan Tan  Taksiah A. Majid  Kamar Shah Ariffin  Norazura Mohamad Bunnori 《Natural Hazards》2014,73(2):657-670

Shear wave velocity (V _s) and the fundamental site period of the subsurface condition are the primary parameters that affect seismic soil amplification in particular sites. Within the topmost layer of the soil, which measures 30 m, the average shear wave velocity V _s30 is commonly used to build codes for site classification for the design of earthquake-resistant structures and to conduct microzonation studies. In this study, the development of a microzonation map for V _s30 distribution, National Earthquake Hazard Reduction Program V _s30 site classification, and a fundamental site period for Penang are presented. The multichannel analysis of surface wave (MASW) test was conducted for more than 50 sites with available borehole data to develop the microzonation maps. The ten selected V _s profiles measured by MASW show a good correlation with the data obtained using empirical correlations in a previous study. The highest V _s values were identified at the northeastern and southeastern parts of Penang Island, corresponding to the shallow bedrock and the outcrop zone. Conversely, the lowest V _s values were found in the northwestern and southwestern parts of the Penang mainland owing to the thick layer of soft clay and silt deposits. The site period map shows the variation in site periods, with the highest value of 1.03 s at the western part of the Penang mainland and the lowest value of 0.02 s at the eastern part of the Penang Island. The microzonation maps developed in this study are vital to studies on seismic hazard and earthquake mitigation programs in Malaysia.  相似文献   

Holocene vegetation and climate of south Tripura based on palynological analysis     

Amalava Bhattacharyya  Nivedita Mehrotra  Santosh K. Shah 《Journal of the Geological Society of India》2011,77(6):521-526

Palynological analysis of sub surface samples at 1.20 m deep sediment profile from Srinagar, southwest Tripura, provides information on vegetation and climate during 7000–3000 years B.P. During this time span, the area is occupied by moist deciduous forest under warm humid climate with intermittent changes in precipitation regime i.e., comparatively less humid around 6.8 Kyr B.P. and 3.7–3.8 Kyr B.P.  相似文献   

Estimating minimum and maximum air temperature using MODIS data over Indo-Gangetic Plain     

D B Shah  M R Pandya  H J Trivedi  A R Jani 《Journal of Earth System Science》2013,122(6):1593-1605

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Assessment of heavy metals in sediments near Hazira industrial zone at Tapti River estuary, Surat, India   总被引：3，自引：1，他引：2  

Bhavna A. Shah  Ajay V. Shah  Chirag B. Mistry  Alok J. Navik 《Environmental Earth Sciences》2013,69(7):2365-2376

Heavy metal accumulation due to industrial activities has become a very sensitive issue for the survival of the aquatic life. Therefore, distributions of several heavy metals have been studied in the surface sediments of Tapti–Hazira estuary, Surat, to assess the impact of anthropogenic and industrial activities near estuary. Totally 60 sediment samples were collected from four different sites at Tapti–Hazira estuary, Surat from January 2011 to May 2011 and examined for metal contents. The average heavy metal load in the study area are found to be 43.28–77.74 mg/kg for Pb, 48.26–72.40 mg/kg for Cr, 117.47–178.80 mg/kg for Zn, 71.13–107.82 mg/kg for Ni, 123.17–170.52 mg/kg for Cu, 0.74–1.25 mg/kg for Cd, 14.73–21.69 mg/kg for Co. Calculated enrichment factors (EF) reveal that enrichment of Pb and Cd is moderate at all sites, whereas other metals Cr, Ni, Zn, Co, and Cu show significant to very high enrichment. Geo-accumulation index (I _geo) results revealed that the study area is nil to moderately contaminated with respect to Cd, moderately to highly polluted with respect to Pb, Zn, and Cu and high to very highly polluted with respect to Co and Cr.  相似文献   

Astrophysical naturally moderated classical positron beam interaction with nonlinear waves in nonextensive astrophysical plasmas     

Asif Shah  Q. Haque  S. Mahmood 《Astrophysics and Space Science》2013,344(1):119-126

The positron acoustic shock and solitary wave are explored in nonextensive electron-positron-ion plasma. The plasma system under-consideration, consists of a classical positron beam, q distributed electrons and positively charged bulky ions constitute a neutralizing background. The nonlinear Korteweg-de Vries and Burger equations are derived by employing the standard reductive perturbation method. The positron acoustic wave in linear limit is also discussed for dissipative as well as nondissipative cases of nonextensive plasmas. The plasma parameters such as, the concentration of neutralizing ions background, beam velocity, temperature and q parameter of the nonextensive electrons are noticed to significantly affect the positron acoustic shock and solitary waves. Our findings may be helpful in the understanding of laboratory beam plasma interaction experiments as well as the astrophysical nonextensive plasmas interacting with positron beam.  相似文献   

Acoustic evidence of a submarine slide in the deepest part of the Arctic,the Molloy Hole     

Francis Freire  Richard Gyllencreutz  Rooh Ullah Jafri  Martin Jakobsson 《Geo-Marine Letters》2014,34(4):315-325

The western Svalbard continental margin contains thick sediment sequences with areas known to contain gas hydrates. Together with a dynamic tectonic environment, this makes the region prone to submarine slides. This paper presents results from geophysical mapping of the deepest part of the high Arctic environment, the Molloy Hole. The mapping includes multibeam bathymetry, acoustic backscatter and sub-bottom profiling. The geophysical data reveal seabed features indicative of sediment transport and larger-scale mass wasting. The large slide scar is here referred to as the Molloy Slide. It is located adjacent to the prominent Molloy Hole and Ridge system. The slide is estimated to have transported >65 km³ of sediments over the deep axial valley of the Molloy Ridge, and further into the Molloy Hole. A unique feature of this slide is that, although its run-out distance is relatively short (<5 km), it extends over an enormous vertical depth (>2,000 m) as a result of its position in a complex bathymetric setting. The slide was most likely triggered by seismic activity caused by seafloor spreading processes along the adjacent Molloy Ridge. However, gas-hydrate destabilization may also have played a role in the ensuing slide event.  相似文献   

A GIS evaluation of land use dynamics and forest soil fertility in a watershed in Nepal     

Margaret G. Schmidt  Hans E. Schreier  Pravakar B. Shah 《International journal of geographical information science》2013,27(3):317-327

Abstract

A geographical information system (GIS) based study was carried out in a densely-populated watershed in Nepal. An evaluation of land use change between 1972 and 1990 indicated that there has been an increase in forest and agricultural land area and a decrease in shrubland and grassland area. GIS techniques were used to produce single and composite fertility index maps, which can be used for problem identification and planning. These maps indicate that forest soil fertility is generally poor in the watershed. GIS was found to be very beneficial in addressing critical resource issues in small watersheds in developing countries.  相似文献   

Improving the spatial resolution of ground motion variability using earthquake and seismic noise data: the example of Bishkek (Kyrgyzstan)     

S. Ullah  D. Bindi  M. Pittore  M. Pilz  S. Orunbaev  B. Moldobekov  S. Parolai 《Bulletin of Earthquake Engineering》2013,11(2):385-399

Site response analysis plays an important role in seismic hazard and risk assessment, and in defining the optimal engineering design for civil structures. However, due to increasing urbanization, target areas are often too vast to be covered by standard approaches, resulting in large uncertainties in the spatial variability of the expected ground motion. Here, we propose a method to improve the spatial resolution of ground motion variability in terms of Standard Spectral Ratios (SSRs), using earthquakes recorded at a few selected sites for a relatively short amount of time, and seismic noise data collected over a denser grid, taking advantage of clustering and correlation analysis. The method is applied to Bishkek, Kyrgyzstan. Using the K-means clustering algorithm, three clusters of site response types have been identified, based on their similarity of SSRs. The cluster’s site responses were adopted for sites where only single station noise measurements were carried out, based on the results of correlation analysis. The spatial variability of the site response correlates well with the main geological features in the area. In particular, variability is noted from south to north, consistent with both the changes in the thickness of the sedimentary cover over the basin and in the Quaternary material outcropping at the surface. This method has therefore the potential to improve the estimation of site effects at the local scale in the future.  相似文献   

Multi-stage metamorphism by progressive accretion of continental blocks,example from the Western Hindu Kush     

Hezbullah Moiny  Shah Wali Faryad  Renata Čopjaková  Radim Jedlicka 《Journal of Metamorphic Geology》2020,38(7):693-717

Basement rocks from the Western Hindu Kush preserve evidence of multiple metamorphic and magmatic events that occurred along the boundary between the Archean–Proterozoic Afghan Central and Afghan–Tajik Blocks. To verify the different metamorphic stages or events, mineral textures and phase equilibria in metamorphic basement rocks and their age relations to magmatic episodes have been investigated. Quartzofeldspathic gneiss and migmatite with lenses of amphibolite (with assumed Proterozoic age for their metamorphism) are intruded by the Triassic Hindu Kush granitoid batholith and small Cretaceous and Oligocene granite intrusions. The age of thermal overprint (210–170 Ma) by the Triassic batholith is confirmed by new monazite data. Both Triassic and Cretaceous granitoids and surrounding basement rocks underwent subsequent metamorphism up to epidote–amphibolite facies. The degree of this metamorphism increases southward at the contact to the Kabul Block, which under-plates the Western Hindu Kush from the south. An early Miocene age was obtained by Pb–Th analyses in thorite and huttonite, which are close or slightly younger than the Oligocene granite in this area. The Cretaceous meta-granodiorite near the border with the Kabul Block contains xenoliths of granulite facies rocks that could come from the Neoarchean granulite facies basement of the Kabul Block. The multi-stage metamorphic and magmatic evolution classifies the Hindu Kush mountain belt as a long-lived suture zone that was active since the early Palaeozoic. The results of this study support the interpretation about possible relations of the Afghan Central Blocks to the southern margin of Eurasia during the evolution of Para- and Neotethys.  相似文献