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991.
Pushpa Tuppad Narayanan Kannan Raghavan Srinivasan Colleen G. Rossi Jeffrey G. Arnold 《Water Resources Management》2010,24(12):3115-3144
The Bosque River Watershed in Texas is facing a suite of water quality issues including excess sediment, nutrient, and bacteria.
The sources of the pollutants are improperly managed cropland and grazing land, dairy manure application, and effluent discharge
from wastewater treatment facilities. Several best management practices (BMPs) have been proposed for pollution reduction
and watershed protection. The overall objectives of this study were to demonstrate a modeling approach using Soil and Water
Assessment Tool (SWAT) model to simulate various BMPs and assess their long-term impacts on sediment and nutrient loads at
different spatial levels. The SWAT model was calibrated and validated for long-term annual and monthly flows at Valley Mills
and for monthly sediment, total nitrogen (TN) and total phosphorus (TP) at Hico and Valley Mills monitoring locations. The
BMPs including streambank stabilization, gully plugs, recharge structures, conservation tillage, terraces, contour farming,
manure incorporation, filter strips, and PL-566 reservoirs were simulated in the watershed areas that met the respective practice’s
specific criteria for implementation. These BMPs were represented in the pre- and post-conditions by modifying one or more
channel parameters (channel cover, erodibility, Manning’s n), curve number (CN), support practice factor (P-factor), filter
strip width, and tillage parameters (mixing efficiency, mixing depth). The BMPs were simulated individually and the resulting
Hydrologic Response Units (HRUs), subwatershed, and watershed level impacts were quantified for each BMP. Sensitivity of model
output values to input parameters used to represent the BMPs was also evaluated. Implementing individual BMPs reduced sediment
loads from 3% to 37% and TN loads from 1% to 24% at the watershed outlet; however, the changes in TP loads ranged from 3%
increase to 30% decrease. Higher reductions were simulated at the subwatershed and HRU levels. Among the parameters analyzed
for sensitivity, P-factor and CN were most sensitive followed by Manning’s n. The TN and TP outputs were not sensitive to
channel cover. This study showed that the SWAT modeling approach could be used to simulate and assess the effectiveness of
agricultural best management practices. 相似文献
992.
Arun Narayanan Amarteja Kocherla Kolluru V. L. Subramaniam 《Journal of Nondestructive Evaluation》2017,36(4):64
An embedded PZT (Lead Zirconate Titanate)-based sensor is developed for real-time, continuous, in-situ monitoring of hydrating cementitious materials after casting. The development of a multi-layer protection for a PZT patch, which provides a physical barrier with the surrounding medium while ensuring the sensitivity of measurement is described. Electrical impedance measurements from the sensor embedded inside mortar mixtures of different compositions are shown to sensitively provide an indication of changes in the state and the mechanical impedance of the material during periods associated with setting and early strength gain. An analytical procedure is developed for extracting the mechanical impedance of the surrounding cementitious material from the electromechanical measurements of the embedded PZT sensor. Changes in the mechanical impedance of mortars through periods of setting and early strength gain obtained from the embedded PZT sensor are validated using pin penetration, isothermal calorimetry and vibration-based measurements. Kinetics of hydration reaction obtained from isothermal calorimetry and increase in the penetration resistance during the setting behavior in the material, are accurately reflected in the increase in the mechanical impedance of the surrounding mortar obtained from the embedded PZT sensor. The continued increase in the mechanical impedance of the mortar after setting, up to 28 days, correlates well with the increase in elastic modulus of material obtained from vibration-based measurements. The durability of the sensor protection scheme is verified by evaluating the performance of sensors recovered from inside the mortar after long-term embedment. The embedded PZT sensor offers the potential for monitoring the local property development in a cementitious material from within the bulk of the structure and for use in quality assessment. 相似文献
993.
V. Murugesan P. S. Sreejith Sushant K. Manwatkar S. Sankar Narayan S. V. S. Narayana Murty P. Ramesh Narayanan 《Journal of Failure Analysis and Prevention》2017,17(2):178-188
Hydraulic control actuation systems in launch vehicles use flexible hoses for transmission of forces to actuators at different locations. The hose ends are connected to the interface adapters by AISI 304 stainless steel sleeves. These sleeves are assembled to nipple end fittings of the high-pressure hose by a swaging operation to obtain leak-proof hose assemblies. The swaging operation is carried out at room temperature by a hydraulically operated swaging machine. Performance of the system as a whole requires strict adherence to the quality standards maintaining the critical interface dimensions within specified tolerances and ensuring the compression given to the swaged joint through the sleeve. If the joining forces are less, this can result in loose joints and gross leakage, whereas excessive compression can cause damage to the parts of the system namely the sleeve, stainless steel braid, PTFE or the adapter. The swaged joint is a single-point failure mode, indicating that a failure in the joint can lead to mission failure. It has to withstand harsh environments such as high pressure, low and high temperature extremes, fatigue loading due to pressure cycling as well as vibration. Therefore, as part of design verification, a detailed qualification plan has been prepared and the hoses were tested as per the plan. As per the test plan, these hoses undergo acceptance tests which include pneumatic and hydraulic pressure testing. During acceptance testing of hoses, one of the hose sleeves was found to be cracked. The cracking was observed after carrying out the pneumatic test when the assembly was being prepared for hydraulic pressure set-up. This paper describes the detailed metallurgical investigation carried out to understand the cause of failure and actions taken to avoid similar failures. 相似文献
994.
The potential of the expanded-bed granular activated carbon (GAC) anaerobic reactor in treating a high strength waste containing RCRA volatile organic compounds (VOCs) was studied. A total of six VOCs, methylene chloride, chlorobenzene, carbon tetrachloride, chloroform, toluene and tetrachloroethylene, were fed to the reactor in a high strength matrix of background solvents. Performance was evaluated. The reactor was found to effect excellent removal of all VOCs (97%). Chloroform, while itself removed at levels in excess of 97%, was found to inhibit the degradation of acetate and acetone, two of the background solvents. Without any source of chloroform in the feed, excellent COD removals were obtained in addition to near-complete removal of all the VOCs. 相似文献
995.
Scene-based nonuniformity correction technique that exploits knowledge of the focal-plane array readout architecture 总被引:2,自引:0,他引:2
Spatial fixed-pattern noise is a common and major problem in modern infrared imagers owing to the nonuniform response of the photodiodes in the focal plane array of the imaging system. In addition, the nonuniform response of the readout and digitization electronics, which are involved in multiplexing the signals from the photodiodes, causes further nonuniformity. We describe a novel scene based on a nonuniformity correction algorithm that treats the aggregate nonuniformity in separate stages. First, the nonuniformity from the readout amplifiers is corrected by use of knowledge of the readout architecture of the imaging system. Second, the nonuniformity resulting from the individual detectors is corrected with a nonlinear filter-based method. We demonstrate the performance of the proposed algorithm by applying it to simulated imagery and real infrared data. Quantitative results in terms of the mean absolute error and the signal-to-noise ratio are also presented to demonstrate the efficacy of the proposed algorithm. One advantage of the proposed algorithm is that it requires only a few frames to obtain high-quality corrections. 相似文献
996.
Cellular and subcellular distribution of metals in molluscs 总被引:6,自引:0,他引:6
Marigómez I Soto M Cajaraville MP Angulo E Giamberini L 《Microscopy research and technique》2002,56(5):358-392
The cellular processes involved in metal metabolism in molluscs are reviewed, with emphasis on the contribution of microscopy (AMG, ARG, EPMA, and SIMS) to both basic research of metal cell biology and applied environmental research. In molluscs, metal uptake may occur by facilitated diffusion, active transport, or endocytosis, and can be enhanced by MT synthesis or formation of mineralized granules. In aquatic molluscs, gills constitute a key interface for dissolved metal uptake, where metals are bound to MT, incorporated into lysosomes, and released basally towards the blood plasma and circulating hemocytes. However, particulate metal uptake is mainly achieved via the digestive tract by endocytosis; further metals are transferred first to lysosomes and then to residual bodies, especially in the digestive cells of the digestive gland. Additionally, metals can be accumulated selectively in specific cell types. As ligands pools differ from cell to cell, different metals may be retained in different cell types. Class "a" metals are localized in cells with granules composed of carbonate, oxalate, phosphate, and sulfate (oxygen donors), whereas "b" metals are associated with those cell types rich in sulfur and nitrogen ligands (sulfur donors). In molluscs, oxygen donors occur in connective tissue calcium cells and basophilic cells, whereas sulfur donors are present in digestive cells, podocytes, nephrocytes, and rhogocytes. Hemocytes, which constitute the most relevant system for metal transport between tissues, move around the body and may penetrate tissues and remove metals from the inner medium to be accumulated in lysosomes as nondigested products. Rhogocytes also participate in metal mobilization, accumulation, and release. The assessment of metal levels in target cells of sentinel molluscs by microscopic techniques provides an early-warning measure, with promising applications as an exposure biomarker for environmental monitoring programs. 相似文献
997.
998.
Integer subdivision algorithm for rendering NURBS curves 总被引:1,自引:1,他引:0
A integer version of the well-known subdivision algorithm of NURBS curves is presented here. The algorithm is used to render NURBS curves of any degree on a raster device using a piece-wise linear approximation. The approximation is independent of the parametrization, that is, it is independent of the weights used. The maximum deviation between a precisely sampled curve and that of the subdivisionbased rendering is one pixel — an inherent feature of the subdivision technique. The algorithm works entirely in the screen coordinate system and produces smooth rendering of curves without oversampling. The integer arithmetic allows the rendering of relatively complex curves of 2 to 8 degrees within a fraction of a second on an i80286/386 processor, and is a good candidate for hardware implementation. 相似文献
999.
Vivek Narayanan Bopaya Bidanda
Jacob Rubinovitz
《Computers & Industrial Engineering》1992,23(1-4):15-18The use of off-line programming is an important step in the implementation of effective CAD-CAM integration. This paper first outlines the tasks involved in the CAD-based off-line programming of spray glazing robots. Different interactive path specification methods and glaze spraying strategies are presented. 相似文献
1000.