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61.
A. I. Gamal el Din I. A. Issa A. M. I. Osman F. Y. Kamal 《Astrophysics and Space Science》1992,190(1):67-88
Results from a detailed isophotometric survey of NGC 5595, NGC 5597, NGC 5605, and NGC 7769 are given. It includes isophotic maps, luminosity profiles and ellipticity curves as well. Scanning of these galaxies was done in theB andV colours. 相似文献
62.
Krishna Raj Choubey 《Astrophysics and Space Science》1984,105(2):301-305
In this paper, the flow of a visco-elastic liquid between two coaxial circular cylinders has been studied when inner cylinder is moving from rest for a certain period with linearly growing speed and then stops suddenly. The Laplace transform technique has been employed to solve the basic differential equations. The expression for the velocity field is obtained. 相似文献
63.
Raj Bali 《Astrophysics and Space Science》1984,107(1):155-165
The object of this paper is to investigate the behaviour of magnetic field in a viscous fluid cosmological model. Various physical and geometrical properties of the model have also been discussed. 相似文献
64.
The populated and expanding city of Chandigarh is located in the foothills of Himalaya, near the potentially active Main Frontal
Thrust (MFT). A hazard assessment for this city is consequently of major importance. Thick sediments underlies the city and
that can potentially amplify the earthquake shaking and contribute to an earthquake disaster in the city. The present study
applies the Horizontal to Vertical Spectral Ratio (HVSR) ambient noise methodology to estimate the resonance frequency of
the soft sediments and to obtain a first order estimate of sediment thickness.
The study indicates that the soil thickness range from 30 to 270 m and that the resonance frequencies vary from 0.236 to 1.479
Hz. A smooth correlation function between soil thickness and resonance frequency is found, indicating relatively homogeneous
soil. 相似文献
65.
Hema J. Siriwardane Raj K. Gondle Duane H. Smith 《International Journal of Coal Geology》2009,77(1-2):188-202
Geologic sequestration in deep unmineable coal seams and enhanced coalbed methane production is a promising choice, economically and environmentally, to reduce anthropogenic gases such as carbon dioxide in the atmosphere. Unmineable coal seams are typically known to adsorb large amounts of carbon dioxide in comparison to the sizeable amounts of sorbed methane, which raises the potential for large scale sequestration projects. During the process of sequestration, carbon dioxide is injected into the coalbed and desorbed methane is produced. The coal matrix is believed to shrink when a gas is desorbed and swell when a gas is sorbed, sometimes causing profound changes in the cleat porosity and permeability of the coal seam. These changes may have significant impact on the reservoir performance. Therefore, it is necessary to understand the combined influence of swelling and shrinkage, and geomechanical properties including elastic modulus, cleat porosity, and permeability of the reservoir.The present paper deals with the influence of swelling and shrinkage on the reservoir performance, and the geomechanical response of the reservoir system during the process of geologic sequestration of carbon dioxide and enhanced coalbed methane production in an actual field project located in northern New Mexico. A three-dimensional swelling and shrinkage model was developed and implemented into an existing reservoir model to understand the influence of geomechanical parameters, as well as swelling and shrinkage properties, on the reservoir performance. Numerical results obtained from the modified simulator were compared to available measured values from that site and previous studies. Results show that swelling and shrinkage, and the combination of geomechanical and operational parameters, have a significant influence on the performance of the reservoir system. 相似文献
66.
The paper consists of some exact solutions for a homogeneous Bianchi type VI0 universe. The material distribution is taken to be a magnetized bulk viscous fluid in presence of massive cosmological string. We assume that current is flowing along x-direction. Therefore, the magnetic field is in yz-plane. For deterministic model of the universe, we assume that shear (σ) is proportional to the expansion (θ) and ζ θ=constant=ξ where ζ the coefficient of bulk viscosity and θ the expansion in the model. The physical and kinematical parameters of the models thus formed are discussed. 相似文献
67.
Kuntal Ganguly Rajiv Kumar K. Mruthyunjaya Reddy P. Jagadeeswara Rao Manoj Raj Saxena G. Ravi Shankar 《国际地球制图》2017,32(7):777-796
This study investigated land use/land cover change (LULCC) dynamics using temporal satellite images and spatial statistical cluster analysis approaches in order to identify potential LULCC hot spots in the Pune region. LULCC hot spot classes defined as new, progressive and non-progressive were derived from Gi* scores. Results indicate that progressive hot spots have experienced high growth in terms of urban built-up areas (20.67% in 1972–1992 and 19.44% in 1992–2012), industrial areas (0.73% in 1972–1992 and 3.46% in 1992–2012) and fallow lands (4.35% in 1972–1992 and ?6.38% in 1992–2012). It was also noticed that about 28.26% of areas near the city were identified as new hot spots after 1992. Hence, non-significant change areas were identified as non-progressive after 1992. The study demonstrated that LULCC hot spot mapping through the integrated spatial statistical approach was an effective approach for analysing the direction, rate, spatial pattern and spatial relationship of LULCC. 相似文献
68.
K. Babu Govindha Raj 《Journal of the Indian Society of Remote Sensing》2017,45(6):1031-1038
The importance of mass wasting in glacier environments and its impacts on glacier dynamics is not fully understood. This is the first occurrence of a debris avalanche event onto a Himalayan glacier through satellite data analysis. The analysis of various factors indicates the slide was a climate-driven hill-slope event activated in 2009 masking the Miyar glacier surface up to ~1.5% including its both lateral moraines and medial moraines. Due to this addition the glacier had neither advance nor retreat from 2009 to 2014. Eventually the debris will contribute to the supraglacial and englacial debris of the glacier. This showcases the way of mass wasting an important contribution to the debris budget of the Himalayan glaciers. 相似文献
69.
Microseismic events enhancement and detection in sensor arrays using autocorrelation‐based filtering 下载免费PDF全文
Entao Liu Lijun Zhu Anupama Govinda Raj James H. McClellan Abdullatif Al‐Shuhail SanLinn I. Kaka Naveed Iqbal 《Geophysical Prospecting》2017,65(6):1496-1509
Passive microseismic data are commonly buried in noise, which presents a significant challenge for signal detection and recovery. For recordings from a surface sensor array where each trace contains a time‐delayed arrival from the event, we propose an autocorrelation‐based stacking method that designs a denoising filter from all the traces, as well as a multi‐channel detection scheme. This approach circumvents the issue of time aligning the traces prior to stacking because every trace's autocorrelation is centred at zero in the lag domain. The effect of white noise is concentrated near zero lag; thus, the filter design requires a predictable adjustment of the zero‐lag value. Truncation of the autocorrelation is employed to smooth the impulse response of the denoising filter. In order to extend the applicability of the algorithm, we also propose a noise prewhitening scheme that addresses cases with coloured noise. The simplicity and robustness of this method are validated with synthetic and real seismic traces. 相似文献
70.
Transport of moderately sorted gravel at low bed shear stresses: The role of fine sediment infiltration 下载免费PDF全文
Emeline Perret Céline Berni Benoît Camenen Albert Herrero Kamal El Kadi Abderrezzak 《地球表面变化过程与地形》2018,43(7):1416-1430
A reliable estimation of sediment transport in gravel‐bed streams is important for various practical engineering and biological studies (e.g., channel stability design, bed degradation/aggradation, restoration of spawning habitat). In the present work, we report original laboratory experiments investigating the transport of gravel particles at low bed shear stresses. The laboratory tests were conducted under unsteady flow conditions inducing low bed shear stresses, with detailed monitoring of the bed topography using a laser scanner. Effects of bed surface arrangements were documented by testing loose and packed bed configurations. Effects of fine sediments were examined by testing beds with sand, artificial fine sand or cohesive silt infiltrated in the gravel matrix. Analysis of the experimental data revealed that the transport of gravel particles depends upon the bed arrangement, the bed material properties (e.g., size and shape, consolidation index, permeability) and the concentration of fine sediments within the surface layer of moving grains. This concentration is directly related to the distribution of fine particles within the gravel matrix (i.e., bottom‐up infiltration or bridging) and their transport mode (i.e., bedload or suspended load). Compared to loose beds, the mobility of gravel is reduced for packed beds and for beds clogged from the bottom up with cohesive fine sediments; in both cases, the bed shear stress for gravel entrainment increases by about 12%. On the other hand, the mobility of gravel increases significantly (bed shear stress for particle motion decreasing up to 40%) for beds clogged at the surface by non‐cohesive sand particles. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献