Impact of chemical treatment on the surface, structure, optical and electrical properties of SnS thin films

The impact of chemical treatment on the surface morphology and other physical properties of tin monosulphide (SnS) thin films have been investigated. The SnS films treated with selected organic solvents exhibited strong improvement in their crystalline-quality and considerable decrease in electrical resistivity. Particularly, the films treated with chloroform showed very low electrical resistivity of similar to 5 Omega cm and a low optical band gap of 1.81 eV as compared to untreated and treated SnS films with other chemicals. From these studies we realized that the chemical treatment of SnS films has strong impact on their surface morphology and also on other physical properties. (C) 2012 Elsevier B.V. All rights reserved.

Bearing capacity of piles in soft clay underlaid by cohesive frictional soil

By using the axisymmetric quasi-lower bound finite-element limit analysis, the bearing capacity factors N-c(p) and N-gamma q(p) have been computed for axially loaded piles, with the shaft embedded in a fully cohesive soil medium and the tip placed over cohesive frictional soil strata. The results were obtained for various combinations of L/D, phi(l), and c(l)/c(u); the subscripts l and u refer to lower and upper soil strata, respectively. The factors N-c(p) and N-gamma q(p) increase continuously with increases in L/D and phi(l); the rate of increase of N-c(p) and N-gamma q(p) with L/D, however, decreases with an increase in L/D. For c(l)/c(u) > 100, the factor N-c(p) hardly depends on L/D.

Urban water supply and management

Population growth and rapid urbanization lead to considerable stress on already depleting water resources. A great challenge for water authorities of urban cities is to supply adequate and reliable safe water to all consumers. In most of the developing countries water scarcity and high demands have led the water authorities to resort to intermittent supplies. Surface and groundwater are the major sources of supply in urban cities. The direct consequences of intermittent supplies and poor sanitation practices are several incidences of water borne diseases posing public health risk. In order to minimize the supply-demand gap and to assure good quality of water, new techniques or models can be helpful to manage the water distribution systems (WDS) in a better way. In the present paper, a review is carried out on the existing urban water supply management methodologies with a way forward for the proper management of the water supply systems.

Physiological and subjective thermal response from Indians

A controlled laboratory experiment was carried out on forty Indian male college students for evaluating the effect of indoor thermal environment on occupants' response and thermal comfort. During experiment, indoor temperature varied from 21 degrees C to 33 degrees C, and the variables like relative humidity, airflow, air temperature and radiant temperature were recorded along with skin (T-sk) and oral temperature (T-core) from the subjects. From T-sk and T-c, body temperature (T-b) was evaluated. Subjective Thermal Sensation Vote (TSV) was recorded using ASHRAE 7-point scale. In PMV model, Fanger's T-sk equation was used to accommodate adaptive response. Stepwise regression analysis result showed T-b was better predictor of TSV than T-sk and T-core. Regional skin temperature response, lower sweat threshold temperature with no dipping sweat and higher cutaneous sweating threshold temperature were observed as thermal adaptive responses. Using PMV model, thermal comfort zone was evaluated as (22.46-25.41) degrees C with neutral temperature of 23.91 degrees C, whereas using TSV response, wider comfort zone was estimated as (23.25-2632) degrees C with neutral temperature at 24.83 degrees C. It was observed that PMV-model overestimated the actual thermal response. Interestingly, these subjects were found to be less sensitive to hot but more sensitive to cold. A new TSV-PPD relation (PPDnew) was obtained with an asymmetric distribution of hot-cold thermal sensation response in Indians. (C) 2013 Elsevier Ltd. All rights reserved.

Temperature dependent electrical behaviour of Cu2SnS3 films

The temperature dependent electrical properties of the dropcasted Cu2SnS3 films have been measured in the temperature range 140 K to 317 K. The log I versus root V plot shows two regions. The region at lower bias is due to electrode limited Schottky emission and the higher bias region is due to bulk limited Poole Frenkel emission. The ideality factor is calculated from the ln I versus V plot for different temperatures fitted with the thermionic emission model and is found to vary from 6.05 eV to 12.23 eV. This large value is attributed to the presence of defects or amorphous layer at the Ag / Cu2SnS3 interface. From the Richardson's plot the Richardson's constant and the barrier height were calculated. Owing to the inhomogeneity in the barrier heights, the Richardson's constant and the barrier height were also calculated from the modified Richardson's plot. The I-V-T curves were also fitted using the thermionic field emission model. The barrier heights were found to be higher than those calculated using thermionic emission model. From the fit of the I-V-T curves to the field emission model, field emission was seen to dominate in the low temperature range of 140 K to 177 K. The temperature dependent current graphs show two regions of different mechanisms. The log I versus 1000/T plot gives activation energies E-a1 = 0.367095 - 0.257682 eV and E-a2 = 0.038416 - 0.042452 eV. The log ( I/T-2) versus 1000/T graph gives trap depths Phi(o1) = 0.314159 - 0.204752 eV and Phi(o2) = 0.007425- 0.011163 eV. With increasing voltage the activation energy E-a1 and the trap depth Phi(o1) decrease. From the ln (IT1/ 2) versus 1/T-1/ 4 graph, the low temperature region is due to variable range hopping mechanism and the high temperature region is due to thermionic emission. (C) 2014 Author(s).

Enhancing the photocatalytic efficiency of sprayed ZnO thin films through double doping (Sn plus F) and annealing under different ambiences

Doubly (Sn + F) doped zinc oxide (ZnO:Sn:F) thin films were deposited onto glass substrates using a simplified spray pyrolysis technique. The deposited films were annealed at 400 degrees C under two different ambiences (air and vacuum) for 2 h. The photocatalytic activity of these films was assessed through photocatalytic decolorization kinetics of Methylene Blue (MB) dye and the decolorization efficiency of the annealed films was compared with that of their as-deposited counterpart. The photocatalytic studies reveal that the ZnO:Sn:F films annealed under vacuum environment exhibits better photocatalytic efficiency when compared with both air annealed and as-deposited films. The SEM and TEM images depict that the surface of each of the films has an overlayer comprising of nanobars formed on a bottom layer, having spherical grains. The studies show that the diameter of the nanobars plays crucial role in enhancing the photocatalytic activity of the ZnO:Sn:F films. The structural, optical and electrical studies substantiate the discussions on the photocatalytic ability of the deposited films. (C) 2014 Elsevier B.V. All rights reserved.

Precipitation response of the magnesium alloy WE43 in strained and unstrained conditions

The precipitation behavior of the magnesium alloy WE43 (Mg-4%Y-2.3%Nd-0.5%Zr) has been studied in strained and unstrained conditions using Transmission Electron Microscopy (TEM). Ageing treatments were carried out at three temperatures, namely 210 degrees C, 230 degrees C and 260 degrees C. The precipitation sequence during static aging of solution treated (ST) samples has been identified as ST —> beta'' —> beta' followed by the formation of beta(1) and equilibrium beta precipitates form after very long ageing periods. Dynamic precipitation was observed during high temperature deformation, leading to the formation of beta' and intermediate beta(1) precipitates. The strained samples, when further heat treated, resulted in the transformation of beta(1) into beta equilibrium precipitates. The sequence of dynamic precipitation is ST —> beta(1) —> beta and ST —> beta'. (C) 2014 Elsevier B.V. All rights reserved.

Luminescence enhancement in monoclinic CaAl2O4:Eu2+, Cr3+ nanophosphor by fuel-blend combustion synthesis

Eu2+ ion doped into a suitable host results in an efficient luminophore with engineering relevance; however stabilizing this ion in a host is known to be a challenge. Here we report a novel approach for the synthesis of efficient CaAl2O4 phosphor containing Eu2+ luminophore and Cr3+ activator. CaAl2O4:Eu2+, Cr3+ is prepared by a solution combustion (SCS) method using (i) urea, (ii) oxalyl dihydrazide (ODH) and (iii) fuel-blend (in which overall fuel to oxidizer ratio (F/O) = 1). A Multi-channel thermocouple setup is used to measure the flame temperatures to study the nature of combustion of various fuel mixtures. The variation of adiabatic flame temperature is calculated theoretically for different urea/ODH mixture ratios according to thermodynamic concept and correlated with the observed flame temperatures. Blue emission of the CaAl2O4:Eu2+ phosphor is enhanced similar to 20 times using the fuel-blend approach. Using the observed reaction kinetics, and the known chemistry of smoldering type combustion, a mechanism is proposed for the observed stabilization of Eu2+ ion in the fuel-blend case. This also explains the observed improvement in blue light emission. We show that the right choice of the fuel ratio is essential for enhancing photoluminescence (PL) emission. The PL intensity is highest for ODH lean and urea rich combination (i.e. when the ratio of ODH:urea is 1:5); measured color purity is comparable to commercial blue phosphor, BAM:Eu2+. (C) 2015 Elsevier B.V. All rights reserved.

A dendrimer facilitates resonance energy transfer between hydrophobic aromatic guest molecules in water

A water soluble third generation poly(alkyl aryl ether) dendrimer was examined for its ability to solubilize hydrophobic polyaromatic molecules in water and facilitate non-radiative resonance energy transfer between them. One to two orders of magnitude higher aqueous solubilities of pyrene (PY), perylene (PE), acridine yellow (AY) and acridine orange (AO) were observed in presence of a defined concentration of the dendrimer. A reduction in the quantum yield of the donor PY* emission and a partial decrease in lifetime of the donor excited state revealed the occurrence of energy transfer from dendrimer solubilized excited PY to ground state PE molecules, both present within a dendrimer. The energy transfer efficiency was estimated to be similar to 61%. A cascade resonance energy transfer in a three component system, PY*-to-PE-to-AY and PY*-to-PE-to-AO, was demonstrated through incorporation of AY or AO in the two component PY-PE system. In the three-component system, excitation of PY resulted in emission from AY or AO via a cascade energy transfer process. Careful choice of dye molecules with good spectral overlap and the employment of dendrimer as the medium enabled us to expand absorption-emission wavelengths, from similar to 330 nm to similar to 600 nm in aqueous solution. (C) 2015 Elsevier B.V. All rights reserved.

Sound radiation from a perforated panel set in a baffle with a different perforation ratio

A finite flexible perforated panel set in a differently perforated rigid baffle is considered. The radiation efficiency from such a panel is derived using a 2-D wavenumber domain formulation. This generalization is later used to represent a more practical case of a perforated panel fixed in an unperforated baffle. The perforations are in the form of an array of uniformly distributed circular holes. A complex impedance model for the holes available in the literature is used. An averaged fluid particle velocity is derived using the continuity equation and the surface pressure is derived using an appropriate momentum equation. The discontinuity in the perforate impedance (due to different hole dimensions or perforation ratio) at the panel-baffle interface is carefully taken into account. It is found that there exists a `coupling' of different wavenumbers of the spatially mean fluid particle velocity field. The change in the resonance frequencies and the modeshapes of the panel due to the perforations is taken into account using the Receptance method. Analytical expressions for the radiated power and radiation efficiency are derived in an integral form and numerical results are presented. Several comparisons are made to understand the radiation efficiency curves. Since both the resistive and reactive components of the hole impedance are taken into account, the model is directly applicable to micro-perforated panels also. (C) 2016 Elsevier Ltd. All rights reserved.

Estudio epidemiológico de la prevalencia de tórsalo (Dermatobia hominis) en bovinos en San Pedro de Lóvago, Chontales, Nicaragua

El presente estudio se realizó con el objetivo de determinar la prevalencia del tórsalo (Dermatobia hominis) en fincas de las diferentes comarcas ubicadas en el Municipio de San Pedro de Lóvago, departamento de Chontales. El municipio se localiza entre las coordenadas 12º 07 ́ latitud norte y 85º07 ́ latitud oeste. La altitud promedio es de 340msnm. El clima es semi húmedo conocido como de sabana tropical. La temperatura promedio anual oscila entre los 25 y 26ºC; su precipitación pluvial varía entre los 1 200 y 1 400mm, caracterizándose por una buena distribución de las lluvias durante todo el año. En el trabajo de muestreo se utilizó un estudio observacional de tipo transversal, utilizándose un muestreo sin reemplazo. Para determinar el tamaño de la muestra se utilizó la formula de Martin et al. (1987) y Trusfield, (1995) donde plantean que N = 1,962* p *q / L 2,donde p es la prevalencia, q = 1 – p y L especifica el límite deseado de error de la prevalencia. Se espera que la prevalencia (p) de 50% sea usada en combinación con él límite deseado de error de 14%, si la prevalencia en la población entera es desconocida. Y cuando la población de bovinos está comprendida entre los rangos de 2 807 a 7 480 individuos de la población. El tamaño requerido de la muestra de este trabajo fue de 52 fincas en producción de toda la zona en estudio. Los resultados obtenidos en el municipio de San Pedro de Lóvago en relación a la Prevalencia de tórsalo en bovinos, de un total de 52 fincas estudiadas, de los cuales se examinaron un total 1 317 animales, de los cuales 1 068 resultaron positivos representando el 81% de prevalencia y 249 animales negativos para un 19%. Al realizar el análisis estadístico se encontró diferencia significativa (p <0.05) entre las regiones anatómicas, siendo las regiones Laterales Toráxico-abdominal derecha, la más afectada. Al relacionar la intensidad de invasión del tórsalo de acuerdo al color de la piel, se observó que existe mayor presentación del mismo en los animales de color Negro, seguido del color Osca, Blanco y color Pardo.

Caracterización y evaluación preliminar de treinta accesiones de frijol común (Phaseolus vulgaris L.)

El presente trabajo se realizó en época de postrera (octubre 1990 en la Estación Experimental La Compañía, situada en el departamento de Carazo en la IV región, con el objetivo de caracterizar y evaluar preliminarmente 30 accesiones de frijol común ( Phaseolus vulgaris L.). El germoplasma fue colectado por el Programa de Recursos Genéticos Nicaragüenses en diferentes localidades del país. En las condiciones ecológicas en las que se desarrolló el ensayo, el material evaluado presentó variación en la mayoría de los caracteres estudiados, tanto entre y dentro de las accesiones. Las accesiones 2947 y 1726 presentaron rendimiento relativo inferior al testigo Rev. 79-A Los menores grados de severidad de la enfermedad mancha angular lo presentaron los materiales 255, 519 ,2939, 317 y 330 Se presenta un catálogo de 30 cultivares estudiados conteniendo el valor máximo, medio y mínimo, desviación estándar y coeficiente de variación para los caracteres cuantitativos y la moda para los caracteres cualitativos.

Thermal transport in high porosity cellular metal foams

The heat dissipation capability of highly porous cellular metal foams with open cells subject to forced air convection is studied using a combined experimental and analytical approach. The cellular morphologies of six FeCrAlY (an iron-based alloy) foams and six copper alloy foams with a range of pore sizes and porosities are quantified with the scanning electronic microscope and image analysis. Experimental measurements on pressure drop and heat transfer for copper foams are carried out. A numerical model for forced convection across open-celled metal foams is subsequently developed, and the predictions are compared with those measured. Reasonably good agreement with test data is obtained, given the complexity of the cellular foam morphology and the associated momentum/energy transport. The results show that cell size has a more significant effect on the overall heat transfer than porosity. An optimal porosity is obtained based on the balance between pressure drop and overall heat transfer, which decreases as the Reynolds number is increased.