Analysis of electromagnetically coupled two-layer elliptical microstrip stacked antennas

Theoretical analysis of a coaxially fed, electromagnetically coupled two-layer elliptical microstrip stacked antenna based on circuit theory is presented in which mutual coupling is considered. Consequently, various parameters such as input impedance, VSWR, return loss, bandwidth etc. are investigated as a function of frequency, which shows resonance at 3.0GHz. It is also observed that there exists a critical value of frequency (3.0GHz) below which capacitive coupling is dominant and above which inductive coupling is dominant. The electromagnetic coupling enhances the radiated power which depends directly on the permittivity of the substrate, in spite of the fact that radiated power generally decreases with increasing permittivity of the substrate.     

Experimental modeling and multi-objective optimization of traveling wire electrochemical spark machining (TW-ECSM) process

The present paper attempts to focus an application of a hybrid methodology comprising of Taguchi methodology (TM) coupled with response surface methodology (RSM) for modeling and TM coupled with weighted principal component (WPC) methodology for multiobjective optimization of a self developed traveling wire electro-chemical spark machining (TW-ECSM) process. First optimum level of input parameters is found using TM which is used as the central values in RSM to develop the second-order response model. For multiobjective optimization two quality characteristics surface roughness (R_a) and material removal rate (MRR), which are of opposite nature (R_a is the lower-the-better type, while MRR is the higher-the-better type), have been selected. The WPC is employed for the calculation of weight corresponding to each quality characteristic. The results indicate that the hybrid approaches applied for modeling and optimization of the TW-ECSM process are reasonable.     

Purification and functional characterisation of an α‐l‐rhamnosidase from Penicillium citrinum MTCC‐3565

An extracellular α‐l ‐rhamnosidase from Penicillium citrinum MTCC‐3565 has purified to homogeneity from its culture filtrate using ethanol precipitation and cation‐exchange chromatography on carboxymethyl cellulose. The purified enzyme gave a single protein band corresponding to molecular mass of 45.0 kDa in SDS‐PAGE analysis showing the purity of the enzyme preparation. The native PAGE analysis showed the monomeric nature of the purified enzyme. Using p‐nitrophenyl α‐l ‐rhamnopyranoside as substrate, K_m and V_max values of the enzyme were 0.30 mm and 27.0 μm min mg^?1, respectively. The k_cat value was 20.1 s giving k_cat/K_m value of 67.0 mm s^?1 for the same substrate. The pH and temperature optima of the enzyme were 8.5 and 50 °C, respectively. The activation energy for the thermal denaturation of the enzyme was 29.9 KJ mol^?1. The α‐l ‐rhamnosidase was able to hydrolyse naringin, rutin and hesperidin and liberated l ‐rhamnose, indicating that the purified enzyme can be used for the preparation of α‐l ‐rhamnose and pharmaceutically important compounds by derhamnosylation of natural glycosides containing terminal α‐l ‐rhamnose. The α‐l ‐rhamnosidase was active at the level of ethanol concentration present in wine, indicating that it can be used for improving wine aroma.     

Optical dispersion of homogeneously mixed ZnSMgF2 films

Mixed films of ZnSMgF₂ were prepared by co-evaporation from a single source. The dispersion of the optical constants was obtained from the reflectance and transmittance data of the films for various compositions in the spectral range 2000–7000 Å. The values of the optical constants of the mixed films at any wavelength lie between the values of the optical constants of pure ZnS and MgF₂ films. The refractive index of the mixed films closely obeys the Lorentz-Lorenz relation at wavelengths at which the absorption is small. The fundamental absorption edge of the mixed films shifts from that of MgF₂ to that of ZnS continuously but non-linearly on increasing the concentration of ZnS in MgF₂. Thus it is possible to use these films as variable frequency cut-off filters. The fundamental absorption edge of the mixed films follows the (hv-E_g)² relation, indicating an indirect optical transition, in sharp contrast to the direct optical transition observed in bulk ZnS.     

Parametric Study of Temperature Distribution in Electrodischarge Diamond Grinding

Electrodischarge diamond grinding (EDDG) is a potential process for machining of advance engineering components, but there is no theory to support it. The work reported in this article makes an attempt in this direction. This article reports on determination of temperature distribution in the workpiece due to EDDG using the finite element method. The temperature distribution in the workpiece domain due to EDDG is obtained by superposition of the two temperature distributions for grinding and electrical discharge mechining (EDM) (i.e., 2D for grinding and axisymmetric for EDM). The effects of duty cycle, on-time, current, energy partition, time of machining, and feed velocity while machining are computationally investigated.     

Characteristics of sensitivity derivatives of static responses

Mathematical expressions for linear structures consisting of prismatic elements have been developed, which corroborate well-known facts: (a) nodal displacements depend on many design variables and (b) element stresses depend on fewer numbers of design variables. Even though the above expressions are valid for any type of linear finite element discretization, presently numerical experimentations are performed only for a frame structure.Deceased prior to publication of this paper     

Electrophoretic studies of mixed ligand complexes in solution—copper(II), nickel(II), cobalt(II), uranyl(II) and thorium(IV)—tartarate—nitrilotriacetate

Paper electrophoresis has been used for the study of the equilibria in mixed ligand complex systems in solution. The method is based on the migration of a spot of a metal ion, with the complexants added in the background electrolyte (0.1 M perchloric acid), at a fixed pH. The concentration of one of the complexants [A] is kept constant, while that of second ligand [L] is varied. A graph of—log [L] against mobility is used to obtain information on the formation of the mixed ligand complex, and to calculate the stability constant. Using this technique, the values of overall stability constant of the complex metal—tartarate—nitrilotriacetate have been found to be 10^12.25, 10^5.98, 10^?3.56, and 10^3.74 for Cu(II), Ni(II), Co(II), UO₂(II) and Th(IV) complexes, respectively at μ = 0.1 and temp. = 40°C.     

Hole scattering mechanisms in Hg1−xCdxTe

In this paper, we analyze and discuss the roles of nine different scattering mechanisms—ionized impurity, polar and nonpolar optical, acoustic, dislocation, strain field, alloy disorder, neutral impurity, and piezoelectric—in limiting the hole mobilities in p-type Hg_1−xCd_xTe crystals. The analysis is based on obtaining a good fit between theory and experiment for the light and heavy hole drift mobilities by optimizing certain unknown (or at the most vaguely known) material parameters such as the heavy hole mobility effective mass, degree of compensation, and the dislocation and strain field scattering strengths. For theoretical calculations, we have adopted the relaxation time approach, keeping in view its inadequacy for the polar scattering. The energy dispersive hole relaxation times have been drawn from the published literature that take into account the p-symmetry of valence band wave functions. The temperature dependencies of multiple charge states of impurities and of Debye screening length have been taken into account through a numerical calculation for the Fermi energy. Mobility data for the present analysis have been selected from the HgCdTe literature to represent a wide range of material characteristics (x=0.2–0.4, p=3×10¹⁵–1×10¹⁷ cm⁻³ at 77K, μ_peak≅200-1000cm²V⁻¹s⁻¹). While analyzing the light hole mobility, the acoustic deformation and neutral impurity potentials were also treated as adjustable. We conclude that

Experimental investigation of kerf characteristics through wire electrochemical spark cutting of alumina epoxy nanocomposite

Alumina epoxy nanocomposite (AENC) is an emerging class of composites with a wide range of functionality and applicability; however, managing AENC using a machine is difficult because of its special mixed characteristics. The presence of extremely hard alumina particles in soft epoxy matrix enhances material properties. The present work investigates the kerf characteristics of a straight cut made in AENC through Wire electrochemical spark cutting (WECSC) process. The kerf characteristics, such as kerf deviation and taper, are used to measure the cut quality. The applied voltage, electrolyte concentration, wire velocity, pulse on-time and pulse off-time are varied, and their effects on the kerf characteristics are experimentally investigated in a developed setup. Influencing parameters for straight cutting of AENC are applied voltage, concentration of electrolyte and wire velocity.