Switching dynamics of IGBTs in soft-switching converters

Next generation of power semiconductor devices will be designed and optimized to meet the specific application requirements. Mixed-mode simulations are used to study the carrier dynamics in punch-through and nonpunch-through Insulated Gate Bipolar Transistor (IGBT) structures during soft- and hard-switching conditions. The simulation results are shown to qualitatively predict the measured bump in the tail current with varying output dv/dt conditions and excessive forward conduction voltage under varying di/dt conditions. A new physical effect termed “conductivity modulation lag” is shown to occur during turn-on under soft-switching conditions. This mechanism is caused by the fact that minority carrier injection into the base of the bipolar transistor significantly lags behind the rate at which drift region conductivity can be modulated. The proposed phenomenon leads to an inductive effect that results in dynamic voltage saturation during turn-on and causes excessive forward voltage drop     

IP router using optical address recognition with second-harmonic generator

A novel optical header address recognition using a second-harmonic generator cascaded with optical correlator is proposed as a cost-effective way of realising routing in optical networks. The second-harmonic generator is used for minimising optical loss due to wavelength mismatch, while the optical correlator performs address recognition.     

Wavelet filter for improving detection performance of compression-based joint transform correlator

A new method for improving fingerprint detections by a compression-based joint transform correlator (JTC) via wavelet filter is proposed. The simulation results show that the proposed method has advantages over the conventional compression-based JTC in that detection performance can be maximized to be higher than a classical JTC by using a smaller file size for the compressed-reference images.     

Experimental investigation of fructose 1,6-diphosphate production and simultaneous ATP regeneration by conjugated enzymes in an ultrafiltration hollow-fiber reactor

The enzymatic synthesis of fructose 1,6-diphosphate (FDP) from glucose and the enzymatic ATP regeneration were performed simultaneously in an ultrafiltration hollow-fiber reactor using both the purified enzymes and the crude cell extract of Bacillus stearothermophilus. The process consisted of the three-step synthetic reactions catalyzed by glucokinase, phosphoglucose isomerase and phosphofructokinase, and the ATP regeneration reaction catalyzed by acetate kinase. The experimental results of the yield and the recycle number agreed well with the theoretical predictions calculated using a computer program developed in our preceding study. This proved the validity of this computer program for predicting or analyzing the reactor performance.     

Theoretical investigation of fructose 1,6-diphosphate production and simultaneous ATP regeneration by conjugated enzymes in an ultrafiltration hollow-fiber reactor

The performance of an ultrafiltration hollow-fiber reactor, in which enzymatic synthesis of fructose 1,6-diphosphate (FDP) from glucose and enzymatic ATP regeneration are performed simultaneously, was analyzed theoretically. The reaction system consists of three-step synthetic reactions catalyzed by glucokinase (GK), phosphoglucose isomerase and phosphofructokinase, and the ATP regeneration reaction catalyzed by acetate kinase. Based on a simple analytical model developed previously in which the liquid flowing in a tube was assumed to be plug flow and the radial concentration gradients in the tubes and shell side space were both neglected, a computer program was developed to calculate the concentration profiles of all the components along the flow direction in the tubes and shell side space of the reactor. From the FDP concentrations at the reactor outlet calculated under various operational conditions, reactor performances such as the FDP yield and the ATP recycle number were determined. The calculation showed the interesting phenomenon that under some conditions the FDP yield was higher when GK concentration was lower.     

Detection performance of wavelet-based joint transform correlation

The detection performance of a wavelet-based joint transform correlator (JTC) is studied by use of two types of images with different spatial-frequency contents and contrast. The simulation results show that, in comparison with an amplitude-modulated JTC, the performance for intraclass pattern recognition can be optimized by using a single wavelet filter.     

Spectral renormalization for multi-component fourier transform infrared absorbance data: importance to multivariate calibration and quantitative exploratory chemometrics studies

Although infrared spectroscopy is a very common analytical tool in the chemical sciences, quantitative infrared spectroscopic studies of multi-component solutions (particularly on-line or in-line studies) have been hampered by the lack of a concise and robust numerical approach. Using an inert chemical species as internal standard, the usual absorbance ratio analysis is generalized into a mathematical form that converts typical absorbance measurement A into its renormalized absorbance A(renorm), with the latter directly relating to the absolute moles rather than the concentration of the constituents. The renormalized absorbance has a number of very important properties, including (1) insensitivity to path length changes due to variations in temperature or pressure of the Fourier transform infrared (FT-IR) cell and (2) insensitivity to solution volume changes arising from reaction, chemical transport, or thermodynamic conditions. The methodology is first applied to a simple model test system to demonstrate its utility for multivariate calibration, and then re-applied to a real problem: the calibration of the rhodium carbonyl hydride HRh(CO)4, a long-sought species in organometallic chemistry and homogeneous catalysis (Angewandte Chemie Int. Ed., vol. 41, 3786 (2002)). The utility of the developed methodology for multivariate calibration and exploratory chemometric studies is demonstrated. Emphasis is placed on providing a numerical recipe for the practicing analytical chemist.