Dyadic-based factorizations for regular paraunitary filterbanks and M-band orthogonal wavelets with structural vanishing moments

Paraunitary filterbanks (PUFBs) can be designed and implemented using either degree-one or order-one dyadic-based factorization. This work discusses how regularity of a desired degree is structurally imposed on such factorizations for any number of channels M /spl ges/ 2, without necessarily constraining the phase responses. The regular linear-phase PUFBs become a special case under the proposed framework. We show that the regularity conditions are conveniently expressed in terms of recently reported M-channel lifting structures, which allow for fast, reversible, and possibly multiplierless implementations in addition to improved design efficiency, as suggested by numerical experience. M-band orthonormal wavelets with structural vanishing moments are obtained by iterating the resulting regular PUFBs on the lowpass channel. Design examples are presented and evaluated using a transform-based image coder, and they are found to outperform previously reported designs.     

New CMOS compatible junction-isolated lateral base resistancecontrolled thyristor

A new 550 V lateral base resistance controlled thyristor structure is proposed and its operation is rigorously characterised by two-dimensional numerical simulation in the off-state, on-state, and turn-off transient mode. Simulations indicate a 40% lower forward voltage drop over a comparable LIGBT, and a superior switching property over other competing lateral thyristor structures     

Advanced SPICE modeling of large power IGBT modules

An enhanced insulated gate bipolar transistor (IGBT) model based on the Kraus model with new derivations based on an extra parameter accounting for p-i-n injection was developed to allow simulation of both trench and DMOS IGBT structures. Temperature dependence was also implemented in the model. The model was validated against steady-state and transient measurements done on an 800-A 1.7-kV Dynex IGBT module at 25/spl deg/C and 125/spl deg/C. The Spice model has also shown excellent agreement with mixed mode MEDICI simulations. The Spice model also takes into account for the first time the parasitic thyristor effect allowing the dc and dynamic temperature-dependent latchup modeling of power modules as well as their temperature-dependent safe operating area.     

Analytic Solution to the Photovoltaic Maximum Power Point Problem

Photovoltaic (PV) power has been successfully used for over five decades. Whether in dc or ac form, photovoltaic cells provide power for systems in many applications on earth and space. Its principles of operation are therefore well understood, and circuit equivalents have been developed that accurately model the nonlinear relationship between the current and voltage of a photovoltaic cell. With the improved efficiencies of power electronics converters, it is now possible to operate photovoltaic system about its maximum power point (MPP) in order to improve the overall system efficiency. Hitherto, this problem has been tackled using tracking (MPPT) algorithms that iteratively find the point of maximum power and respond to changes in solar irradiance accordingly. A mathematical manipulation that uses the mean value theorem is presented here that provides the analytic solution of a point in a close neighborhood of the MPP. It is thoroughly proved that this point is enclosed in a ball of small radius that also contains the MPP and therefore can practically be considered as the MPP. Since the solution is analytic, no iterative schemes are necessary, and only a periodic measurement is required to adjust to changes in solar irradiance. A circuit is implemented that shows the validity of the theory and the accuracy of the solution.     

Analysis and design of the dual-gate inversion layer emitter transistor

The dual-gate inversion layer emitter transistor (DGILET) is a device in which the injection of minority carriers takes place from an inversion layer formed under a MOS gate. Therefore, the device can be switched between MOS and bipolar modes using the gate giving the means to achieve a superior combination of low conduction losses and low switching losses. The structure of the device and operation in both the unipolar and bipolar modes are described in detail. Devices have been fabricated on bulk silicon wafers using junction isolation and experimental results confirm the expected superior performance. In particular, the results confirm predictions that if the inversion layer injector is properly designed, the voltage snapback that occurs during the transition between unipolar and bipolar modes can be completely suppressed. This can be achieved with a compact structure in contrast to the extended structures required in anode-shorted lateral insulated gate bipolar transistor (LIGBTs). An equivalent circuit for the DGILET is presented and the control of the minority carrier injection is also analyzed. Experimental results show that the DGILET can switch at speeds approaching those characteristic of MOSFETs with operating current densities comparable to LIGBTs. The results show that the DGILET offers lower overall losses than an LIGBT at switching frequencies above about 10 kHz.     

Tuning the peak position of subwavelength silica nanosphere broadband antireflection coatings

Subwavelength nanostructures are considered as promising building blocks for antireflection and light trapping applications. In this study, we demonstrate excellent broadband antireflection effect from thin films of monolayer silica nanospheres with a diameter of 100 nm prepared by Langmuir-Blodgett method on glass substrates. With a single layer of compact silica nanosphere thin film coated on both sides of a glass, we achieved maximum transmittance of 99% at 560 nm. Furthermore, the optical transmission peak of the nanosphere thin films can be tuned over the UV-visible range by changing processing parameters during Langmuir-Blodgett deposition. The tunable optical transmission peaks of the Langmuir-Blodgett films were correlated with deposition parameters such as surface pressure, surfactant concentration, ageing of suspensions and annealing effect. Such peak-tunable broadband antireflection coating has wide applications in diversified industries such as solar cells, windows, displays and lenses.     

Step-down trend tests for identifying the minimum effective dose

This article discusses the role of empirically supported treatments (ESTs) in the training of clinical psychologists. Training in ESTs can be integrated in ways that vary depending on the level of training and setting. Predoctoral programs, internships, postdoctoral programs, and continuing education are discussed in regard to special challenges and sequencing of training. A preliminary set of guidelines for training in ESTs is suggested.     

Kinetic mechanism for the sequential binding of two single-stranded oligodeoxynucleotides to the Escherichia coli Rep helicase dimer

Escherichia coli Rep helicase is a DNA motor protein that unwinds duplex DNA as a dimeric enzyme. Using fluorescence probes positioned asymmetrically within a series of single-stranded (ss) oligodeoxynucleotides, we show that ss-DNA binds with a defined polarity to Rep monomers and to individual subunits of the Rep dimer. Using fluorescence resonance energy transfer and stopped-flow techniques, we have examined the mechanism of ss-oligodeoxynucleotide binding to preformed Rep dimers in which one binding site is occupied by a single-stranded oligodeoxynucleotide, while the other site is free (P2S dimer). We show that ss-DNA binding to the P2S Rep dimer to form the doubly ligated P2S2 dimer occurs by a multistep process with the initial binding step occurring relatively rapidly with a bimolecular rate constant of k1 = approximately 2 x 10(6) M-1 s-1 [20 mM Tris (pH 7.5), 6 mM NaCl, 5 mM MgCl2, 5 mM 2-mercaptoethanol, and 10% (v/v) glycerol, 4 degrees C]. A minimal kinetic mechanism is proposed which suggests that the two strands of ss-DNA bound to the Rep homodimer are kinetically distinct even within the P2S2 Rep dimer, indicating that this dimer is functionally asymmetric. The implications of these results for the mechanisms of DNA unwinding and translocation by the functional Rep dimer are discussed.     

The MOS inversion layer as a minority carrier injector

In this paper we report the first experimental demonstration of the concept of MOS inversion layer injection (ILI). The new physical concept is based on the use of a MOS inversion layer as a minority carrier injector as part of a dynamic junction. The carrier injection of such a junction is entirely controlled by the MOS gate. Moreover, when the gate potential is reduced under the MOS threshold voltage, the junction collapses ensuring a very efficient turn-off mechanism. Based on this concept we propose two novel lateral three-terminal structures termed inversion layer diode (ILD) and inversion layer bipolar transistor (ILBT). The concept of inversion layer injection can be applied in power devices where effective MOS gate control of the active junctions is important     

Introduction to wavelets in engineering

The aim of this paper is to provide an introduction to the subject of wavelet analysis for engineering applications. The paper selects from the recent mathematical literature on wavelets the results necessary to develop wavelet-based numerical algorithms. In particular, we provide extensive details of the derivation of Mallat's transform and Daubechies' wavelet coefficients, since these are fundamental to gaining an insight into the properties of wavelets. The potential benefits of using wavelets are highlighted by presenting results of our research in one- and two-dimensional data analysis and in wavelet solutions of partial differential equations.