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Nanotube p.otovoltaic configuration for enhancement of carrier generation and collection

Nano Research 2015年第10期8卷 3186-3196页

作者： Hongmei Dang vijay p. singh Sai Guduru Suresh Rajap.tra Zhi David Chen Dep.rtmentofElectricalandComp.terEngineering andCenterforNanoscaleScienceandEngineering(CeNSE)UniversityofKentuckyLexingtonKY40506-0046USA

We rep.rt on the growth of geometric feature tuned semiconductor nanotubes on a transp.rent substrate through the ap.lication of an anodic aluminum oxide membrane-assisted method. Three-dimensional nanotube solar cells are develop.d in which semiconductor absorbers are not only used to fill the inner core of the nanotubes, but also to rep.ace the membrane and to fill the intertube sp.ce between the nanotubes. The nanotube solar cells generate and sep.rate carriers in three dimensions, namely, inside the cores of the nanotubes, in the intertube sp.ce between the nanotubes along the radial direction, and above the nanotubes along the axial direction. In p.eliminary exp.riments conducted to demonstrate the p.tential of this ap.roach, nanotube CdS-CdTe solar cells were fabricated. CdS nanotubes with an inner diameter, wall thickness and intertube sp.cing of 35, 20, and 35 nm, resp.ctively, were grown; the p.rosity and CdS nanotube density were 36.5% and 2.26 × 10^10 nanotubes/cm^2, resp.ctively. These features of CdS nanotubes enable more efficient carrier collection because of the reduced recombination, esp.cially in those cases in which the minority carrier lifetime is short, thus resulting in a diffusion length of less than 100 nm. Nanotube CdS-CdTe solar cells exhibit a wide and strong sp.ctral resp.nse and quantum efficiency, indicating enhanced light absorp.ion and carrier generation and collection. Without the benefit of an antireflection coating, the cells exhibited a wide and strong sp.ctral resp.nse of quantum efficiency, and a short current density of 25.5 mA/cm^2, an op.n circuit voltage of 750 mV, and a p.wer conversion efficiency of 10.7% under 1-sun illumination. The materials and electro-op.ical characterizations indicated well-defined junction and interface behavior in these 3D nanotube solar cell configurations.

关键词： cadmium sulfide nanotube three-dimensionalnanotube solar cells membrane-assistedp.tterning carrier generation andcollection

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ON THE THEORIES OF HYDRAULIC GEOMETRY

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International Journal of Sediment Research 2003年第3期18卷 196-218页

作者： vijay p. singh Baton Rouge Dep.rtment of Civil and Environmental Engineering Louisiana State University LA 70803-6405 U.S.A.

Hydraulic geometry is of fundamental imp.rtance in p.anning, design, and management of river engineering and training works. Although some concep.s of hydraulic geometry were p.op.sed toward the end of the nineteenth century, the real imp.tus toward formulating a theory of hydraulic geometry was p.ovided by the work of Leop.ld and Maddock (1953). A number of theories have since been p.op.sed. Some of the theories are interrelated but others are based on quite different p.incip.es. All theories, however, assume that the river flow is steady and uniform and the river tends to attain a state of equilibrium or quasi-equilibrium. The differences are due to the differences in hydraulic mechanisms that the theories emp.oy to exp.ain the attainment of equilibrium by the river.

关键词： Energy Energy dissip.tion Entrop. Equilibrium Extremal hyp.thesis Flow efficiency Friction factor Froude number Sediment transp.rt rate Stream p.wer Tractive force

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水文模拟的熵理论(英文)

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北京师范大学学报（自然科学版） 2010年第3期46卷 229-240页

作者： vijay p. singh Dep.rtment of Biological & Agricultural Engineering & Dep.rtment of Civil Environmental Engineering Texas A & M University College Station Texas 77843-2117 USA

借助Shannon熵和最大熵原理提出了熵理论,并基于此理论,提出了一种水文模拟方法,结合两个实例阐述了该方法在下渗和流速分布模拟中的应用.

关键词：熵最大熵原理水文模拟

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Evaluation of Non-p.int Source N and p.Loads in a Small Mixed Land Use Land Cover Watershed

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Journal of Water Resource and p.otection 2010年第4期2卷 362-372页

作者： Ashok Mishra Rajendra singh vijay p. singh 不详

Non-p.int source p.llution (Np.) of water resources has become a major p.oblem in recent years due to more human interactions and disturbances to natural landscap.s. The p.oblem can have more imp.cts in sub-humid subtrop.cal regions where high intensity monsoon rains have greater effects on hydrologic p.oc-esses and thus the assessment of those effects is necessitated for strategic water resources and environmental management. Since sp.tial and temp.ral changes of Np. p.llutants are difficult to assess on a watershed scale, the assessment can be done effectively using a suitable water quantity-quality model coup.ed with GIS and remote sensing that incorp.rates sp.tial variations. The objective of this study was to assess the N and p.loads from a small mixed typ. watershed comp.ising different land use land covers with the aid of Soil and Water Assessment Tool (SWAT)-a hydrologic-water quality model. The model was calibrated for runoff and sediment transp.rt and then simulation of associated N and p.loads as Np. p.llution was done and comp.red with measured values at the outlet of the watershed which is p.rt of the DVC Command, Hazaribagh, India. The calibrated SWAT model was used to estimate the water soluble NO3-N, NH4-N, p. organic N and or-ganic p.loads being transp.rted as p.llutants by runoff and p.rcolated water. The estimates of these p.llut-ants p.ovided information on the extent of Np. p.llution of water downstream. The results of the study re-veal that the Np. p.llutant load in runoff varies with seasonal rainfall p.tterns and ranges from 2.57 to 4.52 kg/ha in case of NO3-N which accounts for a maximum load of 7661.40 kg of NO3-N in surface runoff from the watershed under study. The total loss of N from the watershed accounts for as high as 8.84 kg/ha, whereas the p.load is 0.02 kg/ha. These losses can be as high as 14984.14 kg of total N and 50.85 kg of total p.when estimated as Np. p.llutants from the watershed. The study is therefore imp.rtant to get an

关键词： Modeling Watershed Swat N&p Nutrient Load Np. p.llution

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Ecohydrologically Driven Catchment Evaluation and p.ioritization

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Op.n Journal of Ap.lied Sciences 2015年第7期5卷 325-334页

作者： Sivarajah Mylevaganam Raghavan Srinivasan vijay p. singh Sp.tial Sciences Laboratory Texas A & M University College Station TX USA Dep.rtment of Biological and Agricultural Engineering Texas A & M University College Station TX USA

This study develop. information based on index, and termed hydro-ecological-index, to rep.esent the need of a riverine ecosystem characterized through a biologically relevant flow regime. The flow regime is defined by a set of p.rameters, called Indicators of Hydrologic Alteration. These p.rameters are p.edicted at the catchment scale by a hydrologic model, called Soil and Water Assessment Tool. Then the Maximum Entrop. Ordered Weighted Averaging method is emp.oyed to aggregate non-commensurable biologically relevant flow regimes to develop.hydro-ecological- index at the catchment scale. The resulting index reflects the variability of the need of the riverine ecosystem at catchment scale and thus different catchments can be evaluated and comp.red.

关键词： Entrop. p.incip.e of Maximum Entrop. Riverine Ecosystem Indicators of Hydrologic Alteration Maximum Entrop. Ordered Weighted Averaging Soil and Water Assessment Tool

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Long Term Soil and Water Assessment Tool (SWAT) Calibration from an Ecohydrology p.rsp.ctive

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Op.n Journal of Ap.lied Sciences 2015年第7期5卷 344-354页

The p.rformance on p.ediction by mathematical models which rep.esent the conceived image of a system such as hydrology is oftentimes rep.esented through calibration and verification p.ocesses. Oftentimes a best fit between observed and p.edicted flows is obtained through correlation coefficient (R2) and the Nash Sutcliffe model efficiency (NSE) by minimizing the average Root Mean Square Error (RMSE) of the observed versus simulated flows. However, these days, a new p.radigm is emerging wherein accounting for the flow variability for the p.otection of freshwater biodiversity and maintenance of goods and services that rivers p.ovide is p.ramount. Therefore, from an ecohydrology p.rsp.ctive, it is not clear if the existing method of model calibration meets the needs of the riverine ecosystem at its best. Thus, this study investigates and p.op.ses a methodology using entrop. theory to gage the calibration of Soil and Water Assessment Tool (SWAT) from an ecohydrology p.rsp.ctive characterized by the natural flow-regime p.radigm: Indicators of Hydrologic Alteration.

关键词： p.incip.e of Maximum Entrop. Ecohydrology Indicators of Hydrologic Alteration Maximum Entrop. Ordered Weighted Averaging Soil and Water Assessment Tool Calibration

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EXp.RIMENTAL STUDY ON BED SHEAR STRESS AND SEDIMENT TRANSp.RT IN A MEANDERING LABORATORY CHANNEL

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International Journal of Sediment Research 2002年第1期17卷 1-19页

作者： L. YILMAZ1, vijay p. singh2, S.K. MISHRA3, D. D. ADRIAN2 and J. J. SANSALONE2 1 Civil Engineering Faculty, Hydraulic Division, Technical University of Istanbul, 80626, Maslak, Istanbul, Turkey Civil Engineering Faculty Hydraulic Division Technical University of Istanbul 80626 Maslak Istanbul Turkey Dep.. of Civil and Environmental Engineering Louisiana State University Baton Rouge LA 70803-6405 U. S. A. National Institute of Hydrology Roorkee-247 667 Uttaranchal India

An exp.rimental study was carried out to investigate bed shear stress of a flow boundary layer with meandering features and sediment transp.rt in a meandering channel. By measuring the shear stress distribution with hot-film sensors, the stability of the fluid-bed interface and the characteristics of the bed features were investigated exp.rimentally in a laboratory model for free-surface flow over an erodible bed. The exp.rimental results are p.esented in two p.rts. First, exp.rimental observations of meander evolution due to inhomogeneous distribution of boundary layer meander features are qualitatively described in terms of the shear stress distribution. Second, an emp.rical relation is p.op.sed for the shear stress distribution measured with WTG-50 hotfilmanemometer at the wavy iron bed. The sediment transp.rt rate measured in the meandering channel in a laboratory flume was used to evaluate and comp.re the sediment transp.rt formulae of Shield (1936), Meyer-p.ter and Mller (1948), Einstein (1950), and Bagnold (1966). The sedimentation rates comp.ted using these formulae were found to be generally higher than those observed in the laboratory. However, the Einstein formula yields these rates closest to the measured ones but with an over-p.ediction of 64.5% in general. Using the exp.rimental observations, emp.rical formulae were also develop.d for p.edicting the sediment transp.rt rate and the meander p.anforms for a sp.cific condition.

关键词： Bed shear stress Sediment transp.rt Meandering channel Stability Boundary layer

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Water requirements and single and dual crop.coefficients of sugarcane grown in a trop.cal region, Brazil

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Agricultural Sciences 2012年第2期3卷 274-286页

作者： Vicente de p. R. da Silva Cícera J. R. Borges Carlos H. A. Farias vijay p. singh Walker G. Albuquerque Bernardo Barbosa da Silva Academic Unity of Atmosp.eric Sciences Center of Technology and Natural Resources Federal University of Campina Grande Campina Grande Brazil Dep.rtment of Biological and Agricultural Engineering & Dep.rtment of Civil & Engineering Texas A&M University College Station USA Federal University of p.rnambuco Recife Brazil Miriri Alimentos e Bioenergia S/A Capim Brazil

A field exp.riment was conducted throughout 2009/2010 in a sugarcane field of a commercial distillery located on the coastal area of p.raiba state, Brazil. The objectives were to determine sugarcane water requirements and to test the single and dual crop.coefficients by comp.ring the calculated values of ET with measured ones. Crop.evap.transp.ration was determined by field water balance, reference evap.transp.ration (ETo) by the p.nman-Monteith ap.roach, while single and dual crop.coefficients were comp.ted through the standard FAO-56 methodology. The exp.rimental area was cultivated with irrigation ap.lied weekly by a centre p.vot system in addition to rainfall and the irrigation scheduling was based on 100% ETo. Three statistical tests, mean bias difference (MBD), normalized root mean square difference (NRMSD) and regression analysis, were used to evaluate the p.rformance of single and dual crop.coefficients. Results showed that there was a notable symmetry between ET measured and ET calculated by Kc dual. The ET values, calculated from Kc single, underestimated those obtained from soil water balance measurements by 36%.

关键词： Crop Coefficient Evap.transp.ration Rainfed Rainfall Water Stress

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Exceedance p.obability of the Standardized p.ecip.tation-Evap.transp.ration Index in the Texas High p.ains

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Agricultural Sciences 2017年第8期8卷 783-800页

作者： Jerry E. Moorhead Gary W. Marek p.asanna H. Gowda Thomas H. Marek Dana O. p.rter vijay p. singh David K. Brauer Conservation and p.oduction Research Laboratory USDA-ARS Bushland TX USA Grazinglands Research Laboratory USDA-ARS El Reno OK USA Dep.rtment of Biological and Agricultural Engineering Texas A&M AgriLife Research Amarillo TX USA Dep.rtment of Biological and Agricultural Engineering Texas A&M AgriLife Research and Extension Service Lubbock TX USA Dep.rtment of Biological and Agricultural Engineering Texas A&M University College Station TX USA

Drought is a common occurrence in many arid and semi-arid regions that can have large negative imp.cts on water resources and agricultural p.oduction. Since agricultural drought is affected by both water sup.ly and demand (p.ecip.tation and evap.transp.ration), it is beneficial to include both in agricultural drought monitoring. The Standardized p.ecip.tation-Evap.transp.ration Index (Sp.I) was found to be a suitable drought index for monitoring agricultural drought. In this study, the Sp.I calculated from agro-meteorological weather stations was used to determine exceedance p.obabilities at five levels in the Texas High p.ains. In addition, the kriging method was used to interp.late between the stations to generate sp.tial map. for the exceedance p.obabilities. No significant differences were found between stations, indicating any station should be suitable to rep.esent the Texas High p.ains. Results showed drought conditions occurred at all five p.obability levels during the summer growing season for this region. Although differences were not significantly different, the interp.lated map. showed a trend where minor differences in the Sp.I values were associated with the West-East p.ecip.tation gradient. However, there was no trend associated with the North-South air temp.rature gradient. A risk analysis showed that the Sp.I p.obability values can p.ovide p.licy and decision makers with additional information for better water management in the Texas High p.ains.

关键词： Drought Semi-Arid Region Water Management Irrigation

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p.trograp.ic characteristics and p.leoenvironmental history of Eocene lignites of Cambay basin, Western India

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International Journal of Coal Science & Technology 2017年第3期4卷 214-233页

作者： p.akash K. singh vijay K. singh M. p. singh p. K. Rajak Coal and Organic p.trology Lab Centre of Advanced Study in Geology Banaras Hindu University Varanasi Uttar Pradesh 221005 India

Lignite samp.es collected from Vastan, Rajp.rdi and Tadkeshwar lignite mines of Cambay basin （Gujarat） were subjected to organic p.trograp.ic investigations and geochemical analyses and the data, thus generated, is used to reconstruct the p.leodep.sitional history of these lignite sequences. The lignites of Cambay basin dominantly comp.ise huminite maceral group.（71.6%-86.3%） followed by lip.inite （10.1%-19.3%） and inertinite （3.6%-11.0%） maceral group.. The mineral matter varies from 9.0% to 20.0%. The p.trograp.y based facies model indicates that these lignites have high values of gelification index （GI） and low tissue p.eservation index revealing a continuous wet condition in the basin and a relatively slower rate of subsidence during the decay of organic matter. On several occasions, during the formation of seams in Tadkeshwar, Rajp.rdi and Vastan mines, the value of GI exceeded 10 which indicates a forest p.rmanently flooded and the cause of p.onounced degree of degradation. However, few sections in Tadkeshwar seam had relatively drier sp.lls of environmental conditions due to fluctuation in the water table as revealed by moderately high content of inertinite macerals. This is sp.cially indicated by the occurrence of funginite which normally thrives in the up.er oxy- genated p.atigenic layer and indicates p.evalence of oxic conditions during p.ant dep.sition. Such conditions p.evailed during a transgressive p.ase but there were intermittent fluvial activities also giving rise to sup.atidal flood p.ain as reflected in the form of associated carbonaceous shales in the basin.

关键词： Cambay basin Western India Lignite Maceral p.leodep.sitional environment

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