Compositional,temperature and frequency dependence of dielectric behaviour of zinc substituted copper- ferri-chromates

The comprehensive study on compositional, temperature and frequency dependent dielectric properties of Zn_xCu_1−xFeCrO₄ (x = 0.0, 0.2, 0.4 and 0.6 ) was carried out by means of a. c. resistivity (ρ_ac), dielectric constant (ε′) and loss tangent (tanδ) measurements in the frequency range from 100 Hz to 1 MHz at different temperatures ranging from 40 °C to 500 °C. An abnormal behaviour of ε′ as a function of temperature is explained on the basis of contribution of two types of charge carriers in the polarization process. It is found that magnetic ordering does not have marked influence on the dielectric properties. The probable conduction mechanism in the present system is due to electron transition such as Fe²⁺ Fe³⁺ and Cu²⁺ Cu¹⁺ rather than ionization or polaron hopping mechanism.     

Celecoxib-cyclodextrin systems: characterization and evaluation of in vitro and in vivo advantage

Solid dispersions of Celecoxib were prepared with hydroxypropyl β cyclodextrin by various methods such as physical mixture, cogrinding, kneading, and coevaporation. The dispersions were characterized by differential scanning calorimetry (DSC), X-ray diffraction patterns, infrared spectroscopy, and nuclear magnetic resonance studies. The DSC thermograms of the dispersions indicated potential of heat-induced interaction between Celecoxib and cyclodextrin that could influence in vitro drug dissolution. The dispersions exhibited faster rates of dissolution compared to that of Celecoxib. The kneaded dispersion with the fastest in vitro dissolution rate when compressed into tablets showed a better release profile compared to the tablets of pure Celecoxib. In vivo studies revealed that the kneaded dispersion provided for quicker response and was more effective in inhibiting rat paw edema as compared to Celecoxib alone, thus confirming the advantage of improved pharmacological activity of Celecoxib when administered as a solid dispersion with cyclodextrin.     

Ranking and Reranking with Perceptron

This work is inspired by the so-called reranking tasks in natural language processing. In this paper, we first study the ranking, reranking, and ordinal regression algorithms proposed recently in the context of ranks and margins. Then we propose a general framework for ranking and reranking, and introduce a series of variants of the perceptron algorithm for ranking and reranking in the new framework. Compared to the approach of using pairwise objects as training samples, the new algorithms reduces the data complexity and training time. We apply the new perceptron algorithms to the parse reranking and machine translation reranking tasks, and study the performance of reranking by employing various definitions of the margins.Editors: Dan Roth and Pascale Fung     

Heating rate dependent delamination of metal–polymer interfaces: experiments and modeling

Bimaterial interfaces in microelectronics packages are the most common regions of failure under thermo-mechanical excursions. In this work, we report experimentally observed role of heating rate on the delamination initiation and propagation across a metal-polymer interface in a microelectronic package. We observe that the rate of delamination propagation increases with increasing heating rate. When the heating rate increases, in addition to the higher amount of delamination growth per unit time, experimental results suggests that higher growth will also incur per unit temperature (loading). Correspondingly, the temperature at which complete delamination occur decreases. Using finite element modeling with cohesive interfaces, we provide a plausible explanation to this observed phenomenon. The analyses indicate that the mechanical behavior of the bimaterial interface is sensitive to both temperature and thermal rate.     

Transceiver Design and Performance Analysis of Space Time Coded Fractal Modulation

The filterbank transceiver structure for fractal modulation has been developed. It has been shown that the transceiver complexity is comparable to that of OFDM.The use of orthogonal space time block codes (OSTBC) in conjunction with Fractal Modulation (STFrM) in the presence of frequency selective fading channels has also been considered. An L scale fractal modulation and coherent demodulation effectively converts a frequency selective channel into L flat fading channels per information symbol with random scale gains. The analysis of the proposed scheme in terms of bit error rate has been performed. A diversity order of m _T m _R L can be achieved, where m _T ,m _R are the number of transmitters and receivers, respectively. This increase in diversity order in comparison with that achieved for the OFDM case is at a cost of lower spectral efficiency. However the spectral efficiency of STFrM can be improved R times by the use of multiplicity ‘R’ multiwavelets.