Electrodeposited Co<Subscript>1-x</Subscript>Mo<Subscript>x</Subscript>S thin films as highly efficient electrocatalysts for hydrogen evolution reaction in acid medium

Efficient and cost-effective electrocatalysts for hydrogen evolution reaction (HER) are significant for the advancement of effective water splitting reaction. Herein, we describe the growth of cobalt molybdenum sulfide (CoMoS) at different composites of tightly packed nanocrystals, prepared by one step process of simple electrodeposition method on fluorine-doped tin oxide (FTO) substrate as highly active and low-cost HER electrocatalyst. The prepared electrocatalysts were characterized via various analytical techniques. The HER activity was evaluated through electrochemical methods such as cyclic voltammetry technique and impedance analysis. Exhaustive electrochemical examinations show that the Co_0.95Mo_0.05S achieved higher cathodic current density value of 14.3 mA/cm² at η?=?250 mV with a lowest Tafel slope value towards HER. Furthermore, the active surface area of the as-deposited composite materials has been calculated by cyclic voltammetry analysis. Hence, the present work illustrates that the Co_0.95Mo_0.05S composite can serve as an encouraging cost-effective substitute to platinum-based electrocatalyst for HER.     

A graph theoretical approach for the yield enhancement of reconfigurable VLSI/WSI arrays

In this paper, we consider the yield enhancement of programmable structures by logical restructuring of the circuit placement. In this approach, an initial placement of a circuit on the array is first obtained by simulated annealing on a defect-free array. To implement the circuit on a defective array, the initial placement is reconfigured so that only the defect-free portion of the array is used. Customizing a given initial placement for each defective chip by logical restructuring, if done very fast, would be a cost effective method for yield enhancement. We describe a formulation of the circuit reconfiguration problem in terms of graphs and pebbles, wherein each processing element (PE) of the array is represented by a vertex which is classified as either defective or nondefective, depending upon whether the PE that it represents is defective or nondefective. Vertices representing PEs that are physically adjacent are connected by an edge, whose length is a measure of the proximity of the PEs. The logic elements of a circuit are represented by weighted pebbles. The initial placement of the circuit on the array corresponds to an initial placement of the pebbles on the vertices of the graph, with at most one pebble per vertex. The problem is to successively shift these pebbles along paths in the graph, such that after reconfiguration no pebble is located on a defective vertex, and an associated cost function is minimized. We describe four cost measures using weighted displacement and weighted shift of the pebbles. After presenting exact algorithms for some special cases of the problem, we prove the NP-completeness of the general cases of the corresponding decision problems.     

The ternary rings of Desarguesian and Pappian planes — A simple proof using perspectivities

The aim of this paper is to give a direct, simple proof of the well-known theorems — that the Hall ternary ring (R, T) of a Pappian projective plane is a linear ternary ring over a field, and that of a Desarguesian plane is a linear one over a skew field — by making repeated application of the perspectivity theorem in a Pappian plane and the characterization of Desarguesian planes in terms of perspectivities.This is a revised version of the paper The Ternary Ring of a Pappian Plane — A Simple Proof presented at the 49th Conference of the Indian Mathematical Society, held at Madras, December 27–29, 1983.     

A numerical investigation of the resonance of gas-filled microbubbles: resonance dependence on acoustic pressure amplitude

The general Keller-Herring equation for free gas bubbles is augmented by specific terms to describe the elasticity, viscosity and thickness of the encapsulating shell in ultrasound contrast agent microbubbles. A numerical investigation that analyses the acoustic backscatter from bubbles is employed to identify resonance frequencies that can be compared, for increasing driving pressure amplitude, with linear approximations obtained via analytical considerations. Calculations for bubbles of the size employed in diagnostic ultrasound, between 2 and 6 mum diameter, that are immersed in water and blood and exposed to monochromatic insonation, causing the bubbles to undergo stable cavitation, reveal that the resonance frequency diverges from the linear approximation as the pressure amplitude is increased. The shift in resonance, to lower frequency values, is found to be more pronounced for larger bubbles with the calculated value differing by up to 40% from the linear approximation. The results of this simulation might be potentially useful in preparation of formulations of ultrasound contrast agents with the specifically desired features, such as for instance resonance frequency.     

A Mössbauer study of FeC2O4·2D2O below the néel temperature

From low-temperature Mössbauer measurement on FeC₂O₄·2D₂O the reported difference in quadrupole splitting from the simple dihydrate is inferred to be due to lattice effects. The Zeeman split spectrum has been analyzed taking into account the ambiguity problem and the hyperfine parameters were determined to be I.S.=1.22 mm/sec; Q.S.=1.93 mm/sec; =0.65 to 0.72; =90 to 83.1^o and =0 to 11.8^o. The principal electric field gradient axis lies along the crystal a-axis with V_YY and lying along the crystal b-axis. The crystal field parameters 10Dq, Ds and Dt have been determined to be 10500, 185 and 211 cm^–1, respectively.     

A trial phase function method for a class of λ-ω reaction-diffusion systems: Reduction to a Schrödinger type problem in an eigen sub-domain

The perturbed central force problem $\text{γ}{}_{\mathrm{xx}}\text{? ?}{}^2\text{γ}\text{a}\text{?}{}^2\text{+ γλ(γ) = 0, γ}\text{a}\text{?}{}_{\mathrm{x}}\text{+ 2}\text{a}\text{?}\text{γ}{}_{\mathrm{x}}\text{+ γ[}\text{}\text{?}\text{gw(γ}{}^1\text{) ?}\text{}\text{?}\text{gw(γ)] = 0}$ arising from the λ-ω system

$\text{α}\text{αt}\text{C}{}_1\text{C}{}_2\text{=}\text{λ}\text{?ω}\text{ω}\text{λ}\text{C}{}_1\text{C}{}_2\text{+}\text{α}\text{αt}\text{C}{}_1\text{C}{}_2$

where $\text{c}{}_1\text{=}\text{γ}\text{(x)cosθ(x,t), c}{}_2\text{=}\text{γ}\text{(x)sinθ(x,t), θ = σt ? ?∝}{}^{\mathrm{x}}\text{a}\text{?}\text{(x′)dx′}\text{and}\text{ω = ?}\text{}\text{?}\text{gw(}\text{γ}\text{)}$ is considered for the class $\text{λ}\text{=}\text{}\text{?}\text{gw}\text{= 1 ? g(}\text{γ}\text{)}$. The resulting linear equation in $\text{γ(x), γ}{}_{\mathrm{xx}}\text{+ 2}\text{a}\text{?}\text{γ}{}_{\mathrm{x}}\text{+}\text{γ[α}{}^2\text{+}\text{a}\text{?}{}_{\mathrm{x}}\text{?}\text{?}{}^2\text{a}\text{?}{}^2\text{] = 0}$ is solved with the aid of a class of trial phase functions $\text{a}\text{?}{}_{\mathrm{T}}\text{(x)}$ generated by the unperturbed central force problem for the case g(γ) = γ². An application of the Liouville-Green approximation procedure reduces the system to a Schrödinger type boundary value problem in an eigen sub-domain. The analytical estimates for α are in reasonable agreement with the results of numerical integration of the nonlinear system. The eigenfunctions γ(x) display expected oscillatory behaviour inside an eigen sub-domain. The higher modes and the span of the most extended centre structure are estimated and interpreted in the context of WKBJ connection formula.     

A Mössbauer study of amorphous Fe40Ni40B20

Amorphous Fe₄₀Ni₄₀B₂₀ (VITROVAC 0040) alloy has been investigated using ⁵⁷Fe Mössbauer Spectroscopy. The Curie temperature T_c is found to be well defined and is 695 ± 1 K. The quadrupole splitting just above T_c is 0.64 mm sec^?1. The crystallization temperature is 698 ± 2 K, close to but definitely above T_c. The average hyperfine field H_eff(T) of the glassy state shows a temperature dependence of $\text{H}{}_{\mathrm{<mtext>eff</mtext>}}\text{(0)[1 ? B}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}\text{(T/T}{}_{\mathrm{c}}\text{)}{}^{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}\text{? C}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}\text{(T/T}{}_{\mathrm{c}}\text{)}{}^{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}\text{? …]}$ indicative of the existence of spin wave excitations. The values of $\text{B}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$ and $\text{C}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}$ are found to be 0.40 and 0.06, respectively, for T/T_c ? 0.72. At temperatures close to T_c, H_eff(T) varies as (1 ? T/T_c)^β where β is one of the critical exponents and its value is found to be 0.29 ± 0.02.     

Quasiperiodic Heisenberg antiferromagnets in two dimensions

We describe some of the properties of 2d quantum quasiperiodic antiferromagnets as reported in studies that have been carried out in the last decade. Many results have been obtained for perfectly ordered as well as for disordered two dimensional bipartite quasiperiodic tilings. The theoretical methods used include spin wave theory, and renormalization group along with Quantum Monte Carlo simulations. These methods all show that the ground state of these unfrustrated antiferromagnets have Néel type order but with a highly complex spatial distribution of local staggered magnetization. The ground state properties, excitation energies and spatial dependence, structure factor, and local susceptibilities are presented and discussed. The effects of introducing geometrical disorder on the magnetic properties are discussed.