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Search Results: 1 - 10 of 140312 matches for " Manish K. Tiwari "
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High-Resolution Monsoon Records Since Last Glacial Maximum: A Comparison of Marine and Terrestrial Paleoarchives from South Asia
Manish Tiwari,Ashutosh K. Singh,Rengaswamy Ramesh
Journal of Geological Research , 2011, DOI: 10.1155/2011/765248
Abstract: Agricultural production and the availability of fresh water in Indian subcontinent critically depend on the monsoon rains. Therefore it is vital to understand the causal mechanisms underlying the observed changes in the Indian monsoon in the past. Paleomonsoon reconstructions show that the water discharge from the Ganges-Brahmaputra River system to the Bay of Bengal was maximum in the early to mid-Holocene; data from the Western Arabian Sea and Omanian speleothems indicate declining monsoon winds during the Holocene, whereas records from the South West Monsoon (SWM) precipitation dominated eastern Arabian Sea show higher runoff from the Western Ghats indicating gradually increasing monsoon precipitation during the Holocene. Thus there exists considerable spatial variability in the monsoon in addition to the temporal variability that needs to be assessed systematically. Here we discuss the available high resolution marine and terrestrial paleomonsoon records such as speleothems and pollen records of the SWM from important climatic regimes such as Western Arabian Sea, Eastern Arabian Sea, Bay of Bengal to assess what we have learnt from the past and what can be said about the future of water resources of the subcontinent in the context of the observed changes. 1. Introduction The Indian economy is based on agriculture, which mostly depends on the monsoon rain and to some extent on river flow and ground water resources. In the absence of monsoon that brings adequate rain, crop yield is reduced and due to recurrent droughts there may even be severe shortage of drinking water. The water resources of India comprise rivers, lakes, and ground water aquifers and the amount of water they hold is linked to the rainfall on the one hand and human exploitation on the other. Thus it is important to have a correct long-term forecast of the monsoon that can help in the proper management of our water resources [1]. Monsoon prediction is seriously hampered by the nonavailability of past data, which is limited to about hundred years [2]. It is very difficult to predict the monsoon without understanding its full variability. Generating quantitative paleomonsoon data using available, dateable, natural archives, such as deep sea and lake sediments, varved sediments, and speleothems is a starting point towards this end [3–6]. Monsoon is a term derived from an Arabic word “Mausim” meaning weather. It is technically applied to the seasonal reversal of winds in the Indian subcontinent and Africa, especially in the Arabian Sea, due to land-sea thermal and pressure contrast. It is
Quantum dynamics of proton migration in H2O dications: formation of H2+ on ultrafast timescales
Manish Garg,Ashwani K. Tiwari,Deepak Mathur
Physics , 2012, DOI: 10.1063/1.3676086
Abstract: Irradiation of isolated water molecules by few-cycle pulses of intense infrared laser light can give rise to ultrafast rearrangement resulting in formation of the H2+ ion. Such unimolecular reactions occur on the potential energy surface of the H2O2+ dication that is accessed when peak laser intensities in the 1015 W cm-2 range and pulse durations as short as 9-10 fs are used; ion yields of ~1.5% are measured. We also study such reactions by means of time-dependent wavepacket dynamics on an ab initio potential energy surface of the dication and show that a proton, generated from O-H bond rupture, migrates towards the H-atom, and forms vibrationally-excited H2+ in a well-defined spatial zone.
Electrostatic Potential as a Descriptor of Anti-Bacterial Activities of Some Anacardic Acid Derivatives: A Study Using Density Functional Theory
Manish K. Tiwari,P. C. Mishra
Physics , 2015,
Abstract: Structures and minimum molecular electrostatic potential (MEP) distributions in anacardic acid and some of its derivatives have been studied by full geometry optimization at the M06-2X/6-31G(d,p), WB97XD/6-31G(d,p) and B3LYP/6-31G(d,p) levels of density functional theory (DFT) in gas phase as well as in DMSO and aqueous solutions. Solvent effect was treated employing the integral equation formalism of the polarizable continuum model. Effects of modifications of the C1-side chain on the minimum MEP values in various regions were studied. Minimum MEP values near the oxygen atoms of the C2-OH group, oxygen or sulfur atoms of the C1-attached urea or thiourea groups and above or below the ring plane considered to be involved in interaction with the receptor were used to perform multiple linear regression. Experimentally observed anti-bacterial activities of these molecules against S. aureus are thus shown to be related to minimum MEP values in the above mentioned regions. Among the three DFT functionals used in the study, the M06-2X functional is found to yield most reliable results. Anti-bacterial activities have been predicted for certain molecules of the class which need to be verified experimentally.
A Survey on the Stability of 2-D Discrete Systems Described by Fornasini-Marchesini Second Model  [PDF]
Manish Tiwari, Amit Dhawan
Circuits and Systems (CS) , 2012, DOI: 10.4236/cs.2012.31003
Abstract: A key issue of practical importance in the two-dimensional (2-D) discrete system is stability analysis. Linear state-space models describing 2-D discrete systems have been proposed by several researchers. A popular model, called Forna- sini-Marchesini (FM) second model was proposed by Fornasini and Marchesini in 1978. The aim of this paper is to present a survey of the existing literature on the stability of FM second model.
Robust Suboptimal Guaranteed Cost Control for 2-D Discrete Systems Described by Fornasini-Marchesini First Model  [PDF]
Manish Tiwari, Amit Dhawan
Journal of Signal and Information Processing (JSIP) , 2012, DOI: 10.4236/jsip.2012.32034
Abstract: This paper considers the guaranteed cost control problem for a class of two-dimensional (2-D) uncertain discrete systems described by the Fornasini-Marchesini (FM) first model with norm-bounded uncertainties. New linear matrix inequality (LMI) based characterizations are presented for the existence of static-state feedback guaranteed cost controller which guarantees not only the asymptotic stability of closed loop systems, but also an adequate performance bound over all the admissible parameter uncertainties. Moreover, a convex optimization problem is formulated to select the suboptimal guaranteed cost controller which minimizes the upper bound of the closed-loop cost function.
Mapping and evaluation of urban sprawl using an integrated approach of Remote Sensing and GIS Technique (Review)
Manish K Tiwari,Dr. Aruna Saxena,Dr. Vivek Katare
International Journal of Advanced Technology & Engineering Research , 2012,
Abstract: Rapid urban development and increasing land use changes due to population and economic growth in selected landscapes is being witnessed of late in India and other developing countries the cities are expanding in all directions resulting in large-scale urban sprawl and changes in urban land use. The spatial pattern of such changes is clearly noticed on the urban fringes or city peripheral rural areas, than in the city centre. In fact, this is reflected in changing urban land use patterns. There is an urgent need to accurately describe land use changes for planning and sustainable management. In the recent times, Remote Sensing and GIS is gaining importance as vital tool in the analysis and integration of spatio-temporal data s.
Dr. Jyoti sarup,Manish K. Tiwari,Vardichand Khatediya
International Journal of Advanced Technology & Engineering Research , 2011,
Abstract: Present study was carried out to delineate groundwater prospect zones and identification of artificial recharge sites using Indian remote sensing satellite (IRS) 1D PAN geocoded data on 1:12,500 scale and Survey of India (SOI) topographical sheets. The information based on lithology, geomorphology, soil, land-use/ land-cover, structures/lineament, slope, drainage and hydrology were generated and integrated to prepare groundwater prospect and artificial recharge site map of the study area.Geographical Information System (GIS) was used to prepare database in the above layers, analysis of relationship and integrated map preparation. On the bases of hydrology and geomorphic characteristics, five categories on groundwater prospect zones are identified: Excellent, good, moderate poor and very poor. The analysis reveals that the river terraces and water bodies with alluvium has excellent (about 15% area), buried pediplain with black cotton soil have good potential (about 24% areas). These unite has highly favorable for ground water exploration and development. Deeply buried pediment with black cotton soil are marked under moderate ground water prospect zones (about 26% area), shallow buried pediment with Deccan basalt and dykes are grouped under poor ground water prospect zones (about 24% area), except along the fractures/lineaments. Residual hills, dykes, linear ridges and plateau, are group have very poor groundwater prospects (about 11% area). Four-artificial recharge sites ware identify out of witch the moderate and poor categories occupy more than 42% area and these are mainly plateau, ridges and buried pediment shallow. The most suitable artificial recharge sites occupy less area about 19% and mainly confined to buried pediplain and river terraces. The residual hill and linear ridge with steep slope (covering about 39% areas) have not suitable for artificial recharge sites. This vital information could be used effectively for identification of suitable location for groundwater potential and artificial recharged sites. The good interrelationship was found among the geological units, hydromorphological units and lineament density. The field data have further helped in quantifying various lithological and hydromorphological units with reference to their potential for groundwater occurrence.
Manish K Tiwari,Dr. Aruna Saxena,Dr. Vivek Katare,Dr. Satish Chakravarty
International Journal of Advanced Technology & Engineering Research , 2012,
Abstract: The Geospatial techniques and its scope of applications have undergone an order of magnitude change since its advent and now it has been universally accepted as a most important and modern tool for mapping and monitoring of various natural resources as well as amenities and infrastructure. The huge and voluminous spatial database generated from various Remote Sensing platforms needs proper management like storage, retrieval, manipulation and analysis to extract desired information, which is beyond the capability of human brain. This is where the computer aided GIS technology came into existence. A GIS with major input from Remote Sensing satellites for the natural resource management applications must be able to handle the spatiotemporal data, supporting spatiotemporal quarries and other spatial operations. Software and the computer-based tools are designed to make things easier to the user and to improve the efficiency and quality of information processing tasks. The natural resources are a common heritage, which we have shared with the past generations, and our future generation will be inheriting these resources from us. Our greed for resource and our tremendous technological capacity to exploit them at a much larger scale has created a situation where we have started withdrawing from the future stocks.Bina petrochemical region had attracted the attention of the planners from the beginning of the five-year plan strategy for Industrial development. However, a number of projects were carried out in the individual Districts (Sagar, Vidisha, Guna and Ashoknagar) which also gave fruitful results, but no serious efforts have been made to involve the entire region. No use of latest Geospatial technique (Remote Sensing, GIS, GPS) to prepare a well structured computerized data base without which it is very different to retrieve, analyze and compare the data for monitoring as well as for planning the developmental activities in future.
What am I? Supercooled droplet or ice?
Carlo Antonini,Adrian Mularczyk,Tanmoy Maitra,Manish K. Tiwari,Dimos Poulikakos
Physics , 2013,
Abstract: In this fluid dynamics video we show the trick played by a supercooled liquid water drop against a superhydrophobic surface. The water drop shows a double personality, impacting onto the surface the first time while still in the liquid state, and then re-impacting as a frozen ice crystal.
Non-Darcy Mixed Convection between Differentially Heated Vertical Walls Filled with a Porous Material: Application of New Modified Adomian Decomposition Method  [PDF]
A. K. Tiwari, Premlata Singh
Open Journal of Fluid Dynamics (OJFD) , 2015, DOI: 10.4236/ojfd.2015.54037
Abstract: This paper presents non-Darcy mixed convective flow of an incompressible and viscous fluid in a differentially heated vertical channel filled with a porous material in the presence of a temperature dependent source/sink. The analytical solution of fourth order non-linear ordinary differential equation for temperature field, which is formed by eliminating velocity field from system of governing equations in non-dimensional form, is obtained by using new modified Adomian decomposition method (NMADM) in terms of various parameters. In order to illustrate the interactive influences of governing parameters on the temperature and velocity fields, a numerical study of the analytical solution is performed with respect to three categories of transport processes i) when forced convection is dominated, ii) when forced and natural convection are equal and iii) when natural convection is dominated. Analysis of all categories has revealed that the temperature and velocity profiles are increasing function of modified Darcy number while decreasing function of Forchheimer number.
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