Experimental and numerical investigations on zigzag porous screen breakwater     

J. S. Mani 《Natural Hazards》2009,49(2):401-409

Pile supported porous breakwaters are commonly adopted for shielding small-scale harbors, such as marinas, fishing harbors, and recreational harbors from external waves. To improve efficiency of such breakwaters, attempts have been made to provide a filter screen containing porous material. Possible alternative to the existing pile supported screen breakwaters is the zigzag breakwater. This article details on the numerical and experimental investigations carried out on the performance of zigzag porous screen breakwater. Results related to the wave amplification in front of the structure, wave reflection, and transmission, forces exerted by the waves on the structure are discussed. The studies clearly indicate that the transmission coefficient of the order of 0.5 can be achieved for H _i/gT ² > 0.008 for 50% submergence, whereas the reflection coefficient can be effectively reduced to 0.2. Reduction in wave force is of the order of 50% which is primarily due to reduction in reflection coefficient. Substantial reduction in wave force contributes directly to reduction in the cost of construction of the breakwater, a definite advantage over other similar breakwaters.  相似文献   

Percolation pond as a method of managed aquifer recharge in a coastal saline aquifer: A case study on the criteria for site selection and its impacts     

Raicy Mani Christy  Elango Lakshmanan 《Journal of Earth System Science》2017,126(5):66

Percolation ponds have become very popular methods of managed aquifer recharge due to their low cost, ease of construction and the participation and assistance of community. The objective of this study is to assess the feasibility of a percolation pond in a saline aquifer, north of Chennai, Tamil Nadu, India, to improve the storage and quality of groundwater. Electrical resistivity and ground penetrating radar methods were used to understand the subsurface conditions of the area. From these investigations, a suitable location was chosen and a percolation pond was constructed. The quality and quantity of groundwater of the nearby area has improved due to the recharge from the pond. This study indicated that a simple excavation without providing support for the slope and paving of the bunds helped to improve the groundwater quality. This method can be easily adoptable by farmers who can have a small pond within their farm to collect and store the rainwater. The cost of water recharged from this pond works out to be about 0.225 Re/l. Cleaning the pond by scrapping the accumulated sediments needs to be done once a year. Due to the small dimension and high saline groundwater, considerable improvement in quality at greater depths could not be achieved. However, ponds of larger size with recharge shafts can directly recharge the aquifer and help to improve the quality of water at greater depths.  相似文献   

Problems of standardization of total ozone measurements     

Mani  A. 《Pure and Applied Geophysics》1973,106(1):967-970

Pure and Applied Geophysics -  相似文献   

Erosion study of a part of Majuli River-Island using remote sensing data     

Pankaj Mani  Rakesh Kumar  C Chatterjee 《Journal of the Indian Society of Remote Sensing》2003,31(1):12-18

Majuli, the world’s largest river island, is situated in mid of river Brahmaputra in Assam. River Brahmaputra flows in highly braided channels most of them are transient in nature, being submerged during high monsoon flows and changing drastically their geometry and location. Majuli island, home of about 1.3 million people is endangered because of the erratic behavior of the river. In this study, an attempt has been made to observe the trends of erosion in a small part of Majuli island, the area near Kaniajan village in south Majuli- a stretch of about 11 km, using satellite data of 1991, 1997 and 1998. Image processing of digital data has been done in ILWIS software. Supervised for delineation of river from land and then change detection analysis has been done to find out changes in river course from 1991 to 1997 and further from 1997 to 1998. Erosion and deposition maps of the area have been prepared and the erosion of island is measured at various sections at 1 km interval. Erosion of 1900 ha has been observed during the period of six years from 1991 to 1997 and 845 ha during the period of one year from 1997 to 1998.  相似文献   

Implicit time integration for pseudodynamic tests: Convergence and energy dissipation     

Pui-Shum B. Shing  Mani T. Vannan 《地震工程与结构动力学》1991,20(9):809-819

The convergence and energy-dissipation characteristics of an unconditionally stable implicit time integration scheme that has been adopted for pseudodynamic testing are examined in this paper. A convergence criterion is derived for general multiple-degree-of-freedom softening systems. Furthermore, it is shown that undesired loading and unloading cycles can be avoided in numerical iterations by scaling down the incremental corrections. Finally, it is proved that the total energy dissipation introduced by the residual convergence errors and proposed numerical correction is always positive for any softening structures.  相似文献   

A model for the simulation of turbulent and eddy diffusion processes at heights of 0–65 km     

C. G. Justus  Kurian K. Mani 《Pure and Applied Geophysics》1978,117(3):513-530

A generalized turbulent diffusion model has been developed which evaluates the time rate of growth of a simulated cloud of particles released into a turbulent (i.e. diffusive) atmosphere. The general model, in the form of second-order differential equations, computes the three-dimensional size of the cloud as a function of time. Parameters which influence the cloud growth, and which are accounted for in the model equations, are: (1) length scales and velocity magnitudes of the diffusive field, (2) rate of viscous dissipation , (3) vertical stability as characterized by the relative adiabatic lapse rate (1/T)(g/C _p +T/z), and (4) vertical shear in the mean horizontal winds , and , for a given height and of spatial extent equal to that of the diffusing cloud. Sample results for near ground level and for upper stratospheric heights are given. For the atmospheric boundary layer case, the diffusive field is microscale turbulence. In the upper stratospheric case it is considered to be a field of highly interactive and dispersive gravity waves.  相似文献   

Hydrocarbon source potential of the Proterozoic Sirban Limestone Formation,NW Himalaya,Jammu     

Naveen Hakhoo  Bindra Thusu  Devleena Mani  Ghulam M. Bhat  Jonathan Craig  Juergen Thurow  Mateen Hafiz  Sudeep Kanungo  Sumita Koul  Waquar Ahmed 《Journal of the Geological Society of India》2016,88(6):685-692

The Proterozoic Sirban Limestone Formation (SLFm) crops out as detached allochthons in the northwest Himalaya (Jammu region, India) and has its coeval equivalents laterally disposed in the west in Salt Range, in the northwest in Abbotabad (Pakistan) and in southeast in Himachal Pradesh (India). The oil and gas occurrences have been reported from the Proterozoic successions globally and the hydrocarbon potential of the SLFm cannot be ruled out.The interbedded shales and algal laminated dolostones within the SLFm have yielded microflora comparable to those reported in the North African Neoproterozoic sandstones and the Late Proterozoic carbonates of the giant oil and gas fields of the Siberian Platform. The SLFm contains a rich and diverse biota comprising ~ 10% of the rock volume in thin section. The rich organic assemblage justified a hydrocarbon source potential analysis of the SLFm, tested in this study by Rock Eval (RE) pyrolysis.RE pyrolysis yielded a total organic carbon (TOC) content of 0.02 to 1 wt. % with very low Hydrogen Index (HI) values for the shales and TOC content averaging 0.02 wt. % for the dolostones. The organically lean shales and dolostones exhibit T_max values indicative of immature to post mature stage. But, since these values are for the samples with complex thermal and tectonic history the results may be unreliable. The highly altered organic matter and kerogen present in the SLFm had the potential to generate hydrocarbons and presently indicates no significant source potential. This study is important for understanding the hydrocarbon occurrences in the SLFm particularly in light of the recent oil and gas discoveries from the coeval Proterozoic successions.  相似文献   

Whistler observations of magnetospheric electric field in the night side plasma-sphere at low latitude     

P. N. Khosa  M. M. Ahmad  Lal Mani 《Earth, Moon, and Planets》1982,27(4):453-462

Whistlers recorded at low latitude ground stations of Gulmarg, Nainital and Varanasi were used to infer the east-west component of electric field on the nightside plasmasphere atL=1.2, 1.12, and 1.07 during magnetic storm periods. The method of measuring electric field from the observed cross-L motions of whistler ducts within the plasma-sphere, indicated by changes in nose frequency of whistlers has been outlined. The nose frequencies of the non-nose whistlers under consideration have been deduced from Dowden-Allocock linear Q-technique. The results show eastward electric fields of 0.7 mVm^–1 in the equatorial plane of Gulmarg and 0.3 mVm^–1 in the equatorial plane of Nainital in the premidnight local time sector. Near midnight, there is a sharp transition from eastward field to a westward electric field of 0.2–0.7 mV m^–1 for Gulmarg, 0.3–0.5 mV m^–1 for Nainital and 0.1–0.3 mVm^–1 for Varanasi.  相似文献   

Groundwater resources development in hard rock terrain - an approach using remote sensing and GIS techniques     

Jagannathan Krishnamurthy  Arul Mani  Venkatakrishnan Jayaraman  M Manivel 《International Journal of Applied Earth Observation and Geoinformation》2000,2(3-4)

To demonstrate the capabilities of remote sensing and Geographic Information System (GIS) techniques for groundwater resources development in hard rock terrains, specifically for the demarcation of suitable sites for artificial recharge of groundwater aquifers, a study was carried out in the Kallar Basin, which is located in parts of the Salem and Tiruchirapalli districts, Tamil Nadu, India. Thematic maps defining lithology, lineaments, landforms, landuse, drainage density, thickness of weathered zone, thickness of fractured zone, hydrological soils, and well yield were prepared from data collected by the Indian Remote Sensing Satellite (IRS) -1C and by conventional methods. All the thematic layers were integrated using a GIS-based model developed specifically for this purpose, enabling a map showing artificial recharge zones to be generated. The exact type of artificial recharge structure, eg, check dam, nallabund, gully plugging and percolation pond, suitable for replenishing groundwater was identified by superposing a drainage network map over an artificial recharge zones map. The GIS-based demarcation of artificial zones developed in the study was based on logical conditions and reasoning, so that the same techniques (with appropriate modifications) could be adopted elsewhere, especially in hard rock terrain, where the occurrence of groundwater is restricted and subject to greater complexity.  相似文献   

Depth-wise distribution, mobility and naturally occurring glutathione based phytoaccumulation of cadmium and zinc in sewage-irrigated soil profiles     

D. Mani  B. Sharma  C. Kumar  S. Balak 《International Journal of Environmental Science and Technology》2013,10(6):1167-1180

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