Dielectric properties of LiF single crystals

The dielectric constant,, loss, tan, and a.C. Conductivity, , of high quality single crystals of LiF have been measured in the frequency range 10² to 10⁵ Hz and in the temperature range 30 to 400° C. of LiF at 30° C is 8.3 and is frequency independent; tan was below detection level (tan<0.0001). increases slowly with temperature up to about 150° C (frequency independent region) beyond which it rises rapidly, being frequency dependent with larger values at lower frequencies. A similar behaviour is exhibited by tan . The activation energy for conduction in the high temperature region is calculated to be 0.93 eV from log against 1/T graphs. Log () against 1/T plots (where is the difference between the dielectric constant at any temperature and the value at room temperature, 30° C) yields an activation energy value of 1.0 eV in the high temperature region. This activation energy is found to be independent of frequency. This agreement between the two activation energy values, one for the a.c. conductivity and the other for the increase with temperature. This suggests that the same charge carriers are responsible for the two processes in the high temperature region.     

Insulating and Other Physical Properties of CoO‐Doped Zinc Oxyfluoride‐Borate Glass‐Ceramics

Zinc oxy fluoro borate glasses mixed with different concentrations of CoO (ranging from 0 to 2.0 mol%) are synthesized and subsequently crystallized. The scanning electron microscopy pictures have exhibited crystallinity. Differential scanning calorimetric studies have indicated that the prepared samples consist of multiple crystal phases. The X‐ray diffraction patterns have indicated that the glass‐ceramic samples are composed of αZn(BO₂)_2, (Zn)₃(BO₃)_2, CoF₂, CoF₃, Co₃FB₇O₁₃, ZnCo₂O₄, Co₃O₄ crystalline phases. The optical absorption and photoluminescence studies have indicated that there is a gradual increase of tetrahedral cobalt ion concentration with increase of CoO concentration in the glass network. IR spectroscopic studies have pointed out increased degree of polymerization of the zinc oxy fluoro borate glass network with increase of CoO content. The analysis of results of dielectric properties indicated increase of insulating strength of the glass‐ceramics with increase of CoO content. Finally, the dielectric breakdown strength of the samples is measured at room temperature in air medium and it is found to increase from 12.9 to 19.2 kV/cm with increase of CoO from 0.2 to 2.0 mol%. The reasons for such increase of breakdown strength are discussed quantitatively in terms of dielectric parameters with aid of data on spectroscopic properties.     

Multi-objective optimization of feature selection using hybrid cat swarm optimization

With the pervasive generation of information from a wide range of sensors and devices, there always exist a large number of input features in databases, thus complicating machine learning problem formulation. However, certain features are relatively impertinent to specific problems, which may degrade the performances of classifiers in terms of prediction accuracy, sensitivity,specificity, and recall rate. The main goal of a multi-objective optimization problem is to identify the subsets of the given features. To this end, a hybrid cat swarm optimization(HCSO) algorithm is proposed in our paper for performance improvement of the basic cat swarm optimization(CSO) that incorporates guided and competitive inherent characteristics into the original CSO. The performance of HCSO has been tested by finding the optimal feature subset for 15 benchmark datasets. The number of class labels for these datasets varies between 2 and 40. The time complexity analysis of both CSO and HCSO has also been evaluated. Moreover, the performance of the proposed algorithm has been compared with that of simple CSO and other state-ofthe-art techniques. The performances obtained by HCSO have an average 2.68% improvement with a standard deviation of 2.91.The maximum performance improvement is up to 10.09% in prediction accuracy. Tested on the same datasets, CSO has yielded improvements within the range of-7.27% to 8.51% with an average improvement 0.9% and standard deviation 3.96. The statistical tests carried out in the experiments prove that HCSO manifests a moderately better feature selection capacity than that of its counterparts.     

Nimesulide and beta-cyclodextrin inclusion complexes: physicochemical characterization and dissolution rate studies

Complex formation of nimesulide (N) and β-cyclodextrin (βCD) in aqueous solution and in solid state and the possibility of improving the solubility and dissolution rate of nimesulide via complexation with βCD were investigated. Phase solubility studies indicated the formation of a 1:1 complex in solution. The value of the apparent stability constant Kc was 158.98 M^-1. Solid inclusion complexes of N and βCD were prepared by kneading and coevaporation methods. Differential scanning calorimetry (DSC) studies indicated the formation of solid inclusion complexes of N-βCD at a 1:2 molar ratio in both the methods. Solid complexes of N-βD (1:1 and 1:2 M) exhibited higher rates of dissolution and dissolution efficiency values than the corresponding physical mixtures and pure drug. Higher dissolution rates were observed with kneaded complexes than with those prepared by coevaporation. Increases of 25.6- and 38.7-fold in the dissolution rate were observed, respectively, with N-βCD 1:1 and 1:2 kneaded complexes.     

Synthesis of a spatial 3-RPS parallel manipulator based on physical constraints

The range of motion of the moving platform of a spatial 3-RPS parallel manipulator will be greatly influenced by the physical constraints such as limits on the lengths of the limbs and the range of motion of the spherical joints. Therefore, while synthesizing the parallel manipulator, the physical constraints have to be considered. Synthesis of the manipulator involves determination of the architectural parameters of the manipulator so that a point on the moving platform passes through a prescribed set of positions in space. This paper presents a synthesis procedure that determines location and direction of revolute joints and location of spherical joints along with orientation of sockets of spherical joints, considering the physical constraints. The synthesis procedure is demonstrated through a numerical example.     

Biosorption of chromium onto Erythrina Variegata Orientalis leaf powder

The biosorption of chromium from an aqueous solution onto Erythrina Variegata Orientalis leaf powder was investigated in batch operations. The equilibrium agitation time was 180 min. The extent of chromium biosorption increased from 74.2% to 86.4% with decrease in biosorbent size from 150 to 45 μm for a dosage of 30 g/L. The biosorption decreased from 99.1 (0.45 mg/g) to 45.5% (1.64 mg/g) with an increase in chromium initial concentration (C _o ) from 22.5 to 180 mg/L. The extent of biosorption was maximum at pH=3. The experimental data were well explained by Langmuir and Redlich-Peterson isotherm models. The biosorption data followed second-order kinetics with a rate constant of 0.078 g/mg-min for 50 g/L of 45 μm size biosorbent. The biosorption was exothermic and feasible. The biosorption was tending towards irreversibility with increasing temperature.     

Induced crystallization and physical properties of Li2O–CaF2–P2O5:TiO2 glass system: Part I. Characterization, spectroscopic and elastic properties

Li₂O–CaF₂–P₂O₅ glasses mixed with different concentrations of TiO₂ (ranging from 0 to 0.8 mol%) were crystallized at 500 °C. The samples are characterized by X-ray diffraction, scanning electron microscopy and differential thermal analysis techniques. Spectroscopic properties (IR and Raman) and elastic properties (viz., Young's modulus E, shear modulus G and micro-hardness H) at room temperature are studied. The X-ray diffraction and the scanning electron microscopic studies revealed the presence of lithium phosphate, lithium titanium phosphate and titanium phosphate crystal phases. The differential thermal analysis traces of these samples exhibit three crystalline temperatures. The IR and Raman spectra of these samples have exhibited bands due to TiO₄ and TiO₆ structural units in addition to the conventional bands due to various phosphate structural groups. The analysis of these results indicated that the sample crystallized with 0.6 mol% of TiO₂ possesses the highest density, high mechanical strength and more compact network.     

A novel fast medical image segmentation scheme for anatomical scans

Multimedia Tools and Applications - Medical image is the visual representation of anatomy or physiology of internal structures of the body and it is useful for clinical analysis and medical...