A Relation Between Closure Operators on a Small Category and Its Category of Presheaves

In this paper we show that each factorization structure on a small category , satisfying certain conditions, yields a presheaf on and a morphism of presheaves . We then give connections, and set up one to one correspondences, between subclasses of the following classes: (a) closure operators on (b) subobjects of (c) morphisms from to (d) weak Lawvere–Tierney topologies (e) weak Grothendieck topologies (f) closure operators on .     

Study of polyaniline conducting/electroactive polymer as sensor for some agricultural phosphorus pesticides

Abstract  

Due to their wide applications as insecticides, pesticides, chemical warfare agents, etc., detection of organophosphorus compounds is of great importance. This paper deals with application of polyaniline conducting polymer (PANi) as a sensor material for detection of some agricultural organophosphorus compounds that are commonly used as insecticides and pesticides. The compounds employed in this investigation are dichlorvos, trichlorophon, and chlorpyrifos. The effects of some important parameters such as concentration, thickness of the polymer film, etc., on electrical conductivity and conductivity stability for these compounds have also been investigated. In situ electrical conductivity measurements were performed using a standard direct-current (DC) four-point probe technique. It was found that adsorption and desorption of these compounds on PANi film cause measurable change in the resistance of conducting polymers.     

Selective extraction of Th(IV) over U(VI) and other co-existing ions using eosin B-impregnated Amberlite IRA-410 resin beads

A new chelating polymeric sorbent as an extractant impregnated resin (EIR) has been developed using eosin B and Amberlite IRA-410 resin. The impregnation process was characterized by FT-IR spectroscopy. The eosin B-impregnated resin showed superior binding affinity for Th(IV) over U(VI) and many co-existing ions. The influence of various physicochemical parameters on the recovery of Th(IV) were optimized by both static and dynamic methods. The Langmuir adsorption isotherm gave a satisfactory fit of the equilibrium data. The kinetic studies performed for Th(IV) sorption revealed that <20 min was sufficient for reaching equilibrium metal ion sorption. A preconcentration factor of 100 was found for the column-mode extraction. The accuracy of the developed method in conjunction with Arsenazo III procedure was tested by analyzing geological reference materials and seawater sample, which are prepared, synthetically. Furthermore, the above procedure has been successfully employed for the analysis of natural water samples.     

Analytical solution in transient thermo‐elasticity of functionally graded thick hollow cylinders (Pseudo‐dynamic analysis)

This work studies transient thermal stresses in a thick hollow cylinder made of a functionally graded material (FGM). Material properties are considered to be nonlinear with a power law distribution through the thickness. The cylinder is assumed to be of infinite length, and the plane strain condition is supposed. The displacement and the distribution of stresses are obtained by analytical solution of governing differential equations of the Navier type. The transient dynamic behavior of thermal stresses is determined and discussed for various power law exponents appearing in functions determining mechanical properties of FGMs. Copyright © 2009 John Wiley & Sons, Ltd.     

Experimental and numerical investigation of heat transfer in a miniature heat sink utilizing silica nanofluid

In this paper, heat transfer characteristics of a miniature heat sink cooled by SiO₂–water nanofluids were investigated both experimentally and numerically. The heat sink was fabricated from aluminum and insulated by plexiglass cover plates. The heat sink consisted of an array of 4 mm diameter circular channels with a length of 40 mm. Tests were performed while inserting a 180 W/cm² heat flux to the bottom of heat sink and Reynolds numbers ranged from 400 to 2000. The three-dimensional heat transfer characteristics of the heat sink were analyzed numerically by solving conjugate heat transfer problem of thermally and hydrodynamically developing fluid flow. Experimental results showed that dispersing SiO₂ nanoparticles in water significantly increased the overall heat transfer coefficient while thermal resistance of heat sink was decreased up to 10%. Numerical results revealed that channel diameter, as well as heat sink height and number of channels in a heat sink have significant effects on the maximum temperature of heat sink. Finally, an artificial neural network (ANN) was used to simulate the heat sink performance based on these parameters. It was found that the results of ANN are in excellent agreement with the mathematical simulation and cover a wider range for evaluation of heat sink performance.     

The effect of carbon nanotubes on the corrosion and tribological behavior of electroless Ni-P-CNT composite coating

In this study, Ni-P-CNT composite coating was successfully deposited on the surface of copper by electroless plating. X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM) were used to characterize the coatings. The wear behavior of the coatings was investigated using a pin-on-disk test rig and subsequently friction coefficient data were reported. The corrosion behavior of the Ni-P and Ni-P-CNT coated specimen were evaluated through polarization curves and electrochemical impedance spectroscopy (EIS) in 3.5 wt.% NaCl aqueous solution at the room temperature. The results indicated that the incorporation of carbon nanotubes (CNTs) in the coating improved both tribological behavior and corrosion resistance. These improvements have been attributed to superior mechanical properties, unique topological structure and high chemical stability of nanotubes.     

High-efficiency single and tandem fullerene solar cells with asymmetric monofluorinated diketopyrrolopyrrole-based polymer

Design and synthesis of low bandgap(LBG) polymer donors is inevitably challenging and their processability from a non-halogenated solvent system remains a hurdle to overcome in the area of highperformance polymer solar cells(PSCs).Due to a high aggregation tendency of LBG polymers,especially diketopyrrolopyrrole(DPP)-based polymers coupled with bithiophenes in the polymer backbones,their widespread adoption in non-ha logena ted solvent-processed PSCs has been limited.Herein,a novel LBG DPP-based...     

Effect of ion and negative ion temperatures on KdV and mKdV solitons in a multicomponent plasma

The formation of ion-acoustic solitons (IASs) in an unmagnetized plasma with negative ions has been investigated through the KdV equation in both the situations \(Q^{\prime}\left( { = m_{j} /m_{i} = {\text{negative}}\;{\text{to}}\;{\text{positive}}\;{\text{ion}}\;{\text{mass}}\;{\text{ratio}}} \right)\) less and greater than one and the mKdV equation only for \(Q^{\prime} > 1\). The existence of both KdV and mKdV solitons has been established for \(\alpha \left( { = {\text{ion}}\;{\text{to}}\;{\text{electron}}\;{\text{temperature}}\;{\text{ratio}}} \right)\; > \;\beta \left( { = {\text{negative}}\;{\text{ion}}\;{\text{to}}\;{\text{electron}}\;{\text{temperature}}\;{\text{ratio}}} \right)\) and \(\alpha < \beta\), which is the new outcome of the current investigation. Furthermore, the existence of both compressive and rarefactive solitons for \(Q^{\prime} > 1\) and \(Q^{\prime} < 1\) has been demonstrated.