A method to determine whether two polynomials are relatively prime

In this paper, it is established that a necessary and sufficient condition for two monic polynomialsf(lambda)andg(lambda)to have a common root is thatdet [f(B)] = 0ordet [g(A)] = 0, whereAandBare, respectively, the companion matrices associated withf(lambda)andg(lambda). The simplicity of this method is illustrated by examples.     

Estimation of hole conductivity of AgI through tarnishing studies of silver in iodine vapour at about room temperature

This work reports the hole conductivity data of growing AgI film on silver both for the thicker (5500 to 30 000 Å) and thinner (<6000 Å) ranges at about room temperature. Hole conductivity has been estimated through tarnishing studies of silver in iodine atmosphere and estimation has been based on the fundamental equation of Wagner relating the rate constant and the conductivity of the film. It is revealed that the thinner films show a higher hole conductivity than that of the thicker films under similar temperature and iodine pressure.     

Editorial

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Editorial     

High-frequency, depressing inhibition facilitates synchronization in globally inhibitory networks

Motivated by the study of sharp wave-associated ripples, high-frequency (approximately 200 Hz) extracellular field oscillations observed in the CA1 region of the rat hippocampus during slow-wave sleep and periods of behavioural immobility, we consider a single inhibitory neuron synapsing onto a network of uncoupled, excitatory neurons. The inhibitory synapse is depressing and has a small synaptic delay. Each excitatory cell provides instantaneous, positive feedback to the inhibitory cell. We show that the interneuron can rapidly synchronize the action potentials of the pyramidal cells if the frequency of inhibitory input is increased in a ramp-like manner as occurs during the ripple. We show that the basin of attraction of the synchronous solution is larger when the inhibition frequency is gradually increased as opposed to remaining constant.     

An efficient algorithm for superresolution in medium field imaging

In this paper, we study the problem of reconstruction of a high-resolution (HR) image from several blurred low-resolution (LR) image frames in medium field. The image frames consist of blurred, decimated, and noisy versions of a HR image. The HR image is modeled as a Markov random field (MRF), and a maximum a posteriori (MAP) estimation technique is used for the restoration. We show that with the periodic boundary condition, a HR image can be restored efficiently by using fast Fourier transforms. We also apply the preconditioned conjugate gradient method to restore HR images in the aperiodic boundary condition. Computer simulations are given to illustrate the effectiveness of the proposed approach. This research was conducted with support from the Army Research Office Grant DAAD 19-03-1-0261 and the National Science Foundation Grant CCF-0429481. Research supported in part by RGC Grant Nos. 7130/02P, 7046/03P, 7035/04P and 7035/04P and FRG/04-05/II-51.     

Control and Simulation of a Current-Fed Linear Inductor Machine

A self-controlled, current-fed inverter excited linear inductor machine is described, in which the field current and inverter switching angles are programmed such that the machine operates at constant air-gap flux and unity displacement factor under all operating conditions. The machine can operate in wide speed range and constant predetermined torque is developed during both motoring and regeneration. The control incorporates overlap angle compensation for the inverter and permits modulation of inverter firing angle with resolution of a fraction of a degree. The dynamic d-q axis model of the machine with the power converters and the proposed control strategy has been simulated on a hybrid computer, and static and dynamic performance have been studied in detail. The control circuit has been designed and tested with a 112-kW prototype inductor machine. The experimental results give good agreement with the theory and with simulation.     

Reverse Micelle-Mediated Synthesis and Characterization of Tricalcium Phosphate Nanopowder for Bone Graft Applications

Nanocrystalline β-tricalcium phosphate (β-TCP) powder was synthesized using reverse micelle as a template system. Cyclohexane was used as the oil phase, aqueous solutions of calcium nitrate and phosphoric acid as the aqueous phase, and poly(oxyethylene)₅ nonylphenol ether (NP-5) and/or poly(oxyethylene)₁₂ nonylphenol ether (NP-12) as the surfactants. The powder were synthesized at a fixed Ca/P molar ratio of 1.5 at a pH of 10. The synthesized powder were calcined at 800°C to obtain monophasic β-TCP. Particle size, morphology, and surface area of the synthesized powder were dependent on the chemistry of the surfactant and composition of the microemulsion. The powder were characterized using a BET surface area analyzer, powder X-ray diffraction, dynamic light scattering technique, and transmission electron microscopy. TCP nanoparticles had a particle size between 32 and 135 nm, and a BET-specific average surface area between 57 and 103 m²/g with controlled morphology. The powder were consolidated and sintered at 1250°C in a 3 kW microwave furnace in the form of a compact disk. Human osteoprecursor cells (osteoblastic precursor cell line 1 [OPC1]) were used to assess the biocompatibility of TCP disks after 1, 5, and 11 days in culture using scanning electron microscopy, MTT assay, and alkaline phosphatase expressions. Disk samples were biocompatible and showed excellent OPC1 cell adhesion, growth, and proliferation. Biocompatible β-TCP nanopowder were synthesized with controlled particle size, morphology, and surface area using a reverse micelle-mediated template system.     

A novel trench clustered insulated gate bipolar transistor (TCIGBT)

A new trench clustered insulated gate bipolar transistor (TCIGBT) is reported. In this device, a multitude of UMOS cathode cells is enclosed within a common n-well and p-well. The TCIGBT provides a unique "self-clamping" feature to protect the trenches from high electric fields. The simulation results based on 1.2 kV nonpunchthrough technology indicate an improvement of 25% in on state and 28% in the turn-off losses in comparison to the state-of-the-art trench IGBT. The saturation current levels of the TCIGBT, which can be designed independent of the forward drop, are also lower.