Tribo-electrostatic behaviour of high ash non-coking Indian thermal coal     

R.K. Dwari  K. Hanumantha Rao 《International Journal of Mineral Processing》2006

The tribo-electrostatic method was applied to beneficiate non-coking Indian thermal coal from Ramagundam coal mines containing nearly 45% ash content. The microscopic studies revealed that quartz and kaolinite are the dominant minerals whereas illite, goethite, siderite and pyrite are the minor inclusions in the coal. Contact electrification of ash-forming minerals and coal matter was carried out using different tribo-charger materials of Al, Cu, brass, perspex and teflon. The Cu tribo-charger was found to be optimum to acquire differential charge between ash-forming inorganics and coal matter. The temperature effect on the magnitude of contact charge acquisition was found to be significant. Tests on a laboratory in-house built tribo-electrostatic free-fall separator with minus 300 μm coal showed that the ash content was reduced from 45% to about 18%, and a clean coal product as judged by the washability studies can be obtained. The results illustrate that the non-coking coals can be beneficiated using the scientific knowledge on the response and behaviour of coal and non-coal matters to electric charges.  相似文献   

Beneficiation of sillimanite by column flotation—a pilot scale study     

S. Prabhakar  G. Bhaskar RajuS. Subba Rao 《International Journal of Mineral Processing》2006

A fully automated semi-commercial flotation column incorporating state of the art instruments was designed to study the amenability of flotation column for the beneficiation of different minerals. In the present study, beneficiation of sillimanite was investigated by installing the flotation column in the flotation circuit of Orissa Sands Complex, Indian Rare Earths Limited, Chatrapur, Orissa. The effect of process parameters on sillimanite grade and recovery was investigated. At optimum conditions, the flotation column was operated continuously with a feed rate of one ton per hour and demonstrated the efficiency of the technology for the beneficiation of sillimanite. The results show that a concentrate assaying 96% sillimanite at 90% recovery can be obtained in a single column flotation stage.  相似文献   

基于随机分布的断裂破碎带GPR剖面特征分析     

胡绕  吴健生  赵永辉 《物探与化探》2006,30(6):551-553,561

为了验证探地雷达在查找基岩中断裂破碎带的有效性、以及进一步认识破碎带在探地雷达反射剖面上的表现特征,结合概率论和数理统计知识,通过设置断裂破碎带中介质的介电常数在一定空间范围内随机分布,建立了更为贴合实际的断裂破碎带模型,使用时域有限差分方法正演模拟其二维GPR反射剖面,较好地揭示了断裂破碎带的GPR剖面特征。通过对不同破碎程度和基岩具有不同介电常数的破碎带模型进行正演模拟,分析其正演GPR剖面的图像差异,较为深入地认识了断裂破碎带在GPR剖面上反映出的特征。最后,进一步引入工程实例,发现通过正演模拟揭示的断裂破碎带GPR 剖面特征在断裂破碎带的实际探测剖面上也是存在的,说明通过正演模拟来指导实际资料的解释是现实可靠的。  相似文献   

GPS satellite and receiver instrumental biases estimation using least squares method for accurate ionosphere modelling   总被引：1，自引：0，他引：1  

G. Sasibhushana Rao 《Journal of Earth System Science》2007,116(5):407-411

The positional accuracy of the Global Positioning System (GPS) is limited due to several error sources. The major error is ionosphere. By augmenting the GPS, the Category I (CAT I) Precision Approach (PA) requirements can be achieved. The Space-Based Augmentation System (SBAS) in India is known as GPS Aided Geo Augmented Navigation (GAGAN). One of the prominent errors in GAGAN that limits the positional accuracy is instrumental biases. Calibration of these biases is particularly important in achieving the CAT I PA landings. In this paper, a new algorithm is proposed to estimate the instrumental biases by modelling the TEC using 4th order polynomial. The algorithm uses values corresponding to a single station for one month period and the results confirm the validity of the algorithm. The experimental results indicate that the estimation precision of the satellite-plus-receiver instrumental bias is of the order of ±0.17 nsec. The observed mean bias error is of the order −3.638 nsec and −4.71 nsec for satellite 1 and 31 respectively. It is found that results are consistent over the period.  相似文献   

Origin of Cretaceous phosphorites from the onshore of Tamil Nadu,India     

V. Purnachandra Rao  Pratima M. Kessarkar  R. Nagendra  E. V. S. S. K. Babu 《Journal of Earth System Science》2007,116(6):525-536

Cretaceous phosphorites from the onshore of Tamil Nadu have been investigated for their origin and compared with those in the offshore. Cretaceous phosphorites occur as light brown to yellowish brown or white nodules in Karai Shale of the Uttatur Group in the onshore Cauvery basin. Nodules exhibit phosphatic nucleus encrusted by a chalky shell of carbonate. The nucleus of the nodules consists of light and dark coloured laminae, phosphate peloids/coated grains and detrital particles interspersed between the laminae. Scanning electron microscope (SEM) studies reveal trapping and binding activity of microbial filaments. A mat structure with linearly arranged microbial filaments and hollow, cell-based coccoid cyanobacterial mat are present. Nodules contain abundant carbonate fluorapatite, followed by minor calcite, quartz and feldspar. The P₂O₅ content of the phosphorites ranges from 18 to 26%. The CaO/P₂O₅, Sr and F contents are higher than that of pure carbonate fluorapatite. Concentrations of Si, Al, K, Fe, and Ti are low. We suggest that the nuclei of the nodules represent phosphate clasts related to phosphate stromatolites formed at intertidal conditions. At high energy levels the microbial mats were disintegrated into phosphate clasts, coated with carbonate and then reworked into Karai Shale. On the other hand, Quaternary phosphorites occur as irregular to rounded, grey coloured phosphate clasts at water depths between 180 and 320m on the continental shelf of Tamil Nadu. They exhibit grain-supported texture. Despite Quaternary in age, they also resemble phosphate stromatolites of intertidal origin and reworked as phosphate clasts onto the shelf margin depressions. Benthic microbial mats probably supplied high phosphorus to the sediments. Availability of excess phosphorus seems to be a pre-requisite for the formation of phosphate stromatolites.  相似文献   

On selection of kernel parametes in relevance vector machines for hydrologic applications     

Shivam Tripathi  Rao S. Govindaraju 《Stochastic Environmental Research and Risk Assessment (SERRA)》2007,21(6):747-764

Recent advances in statistical learning theory have yielded tools that are improving our capabilities for analyzing large and complex datasets. Among such tools, relevance vector machines (RVMs) are finding increasing applications in hydrology because of (1) their excellent generalization properties, and (2) the probabilistic interpretation associated with this technique that yields prediction uncertainty. RVMs combine the strengths of kernel-based methods and Bayesian theory to establish relationships between a set of input vectors and a desired output. However, a bias–variance analysis of RVM estimates revealed that a careful selection of kernel parameters is of paramount importance for achieving good performance from RVMs. In this study, several analytic methods are presented for selection of kernel parameters. These methods rely on structural properties of the data rather than expensive re-sampling approaches commonly used in RVM applications. An analytical expression for prediction risk in leave-one-out cross validation is derived. For brevity, the effectiveness of the proposed methods is assessed first by data generated from the benchmark sinc function, followed by an example involving estimation of hydraulic conductivity values over a field based on observations. It is shown that a straightforward maximization of likelihood function can lead to misleading results. The proposed methods are found to yield robust estimates of parameters for kernel functions.  相似文献   

Respiration and denitrification in permeable continental shelf deposits on the South Atlantic Bight: Rates of carbon and nitrogen cycling from sediment column experiments     

Alexandra M.F. Rao  Mark J. McCarthy  Wayne S. Gardner  Richard A. Jahnke 《Continental Shelf Research》2007

Nitrogen (N) cycling and respiration rates were measured in sediment columns packed with southeastern United States continental shelf sands, with high permeability (4.66×10⁻¹¹ m²) and low organic carbon (0.05%) and nitrogen (0.008%). To simulate porewater advection, natural shelf seawater was pumped through columns of different lengths to achieve fluid residence times of approximately 3, 6, and 12 h. Experiments were conducted seasonally at in situ temperature. Fluid flow was uniform in nearly all columns, with minimal dead zones and channeling. Significant respiration (O₂ consumption and ∑CO₂ production) occurred in all columns, with highest respiration rates in summer. Most (78–100%) remineralized N was released as N₂ in the majority of cases, including columns with oxic porewater throughout, with only a small fraction released as NO₃⁻ from some oxic columns. A rate of 0.84–4.83×10¹⁰ mol N yr⁻¹, equivalent to 1.06–6.09×10⁻⁶ mmol N cm⁻² h⁻¹, was calculated for benthic N₂ production in the South Atlantic Bight, which can account for a large fraction of new N inputs to this shelf region. Metal and sulfate reduction occurred in long residence time columns with anoxic outflow in summer and fall, when respiration rates were highest. Because permeable sediments dominate continental shelves, N₂ production in high permeability coastal sediments may play an important role in the global N cycle.  相似文献   

Modulation of Geomagnetic Lunar Daily Variation in H at Alibag with Lunar Distance     

B. R. Arora  D. R. K. Rao 《Geophysical Journal International》1975,43(2):627-633

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Spherical radiation-driven shock waves in a non-uniform atmosphere     

G. Narasimhulu Naidu  M. P. Ranga Rao 《Astrophysics and Space Science》1983,95(2):383-391

Similarity solutions are obtained for spherical radiation-driven shock waves propagating in a non-uniform atmosphere at rest obeying a density power law. Approximate analytical solutions are also obtained and found to be in good agreement with the numerical solutions. The effect of the parameter characterizing the initial density distribution of the gas on solutions of the flow field is studied in detail. It is also shown analytically that the shock wave propagates as an overdriven detonation.  相似文献   

Collinear equilibria and their characteristic exponents in the restricted three-body problem when the primaries are oblate spheroids     

Sharma  Ram Krishan  Rao  P. V. Subba 《Celestial Mechanics and Dynamical Astronomy》1975,12(2):189-201

Celestial Mechanics and Dynamical Astronomy - In this paper location of the collinear libration points is investigated numerically, by taking the oblateness of the primaries into consideration, for...  相似文献