Stability Analysis of the Continuous-Conduction-Mode Buck Converter Via Filippov's Method

To study the stability of a nominal cyclic steady state in power electronic converters, it is necessary to obtain a linearization around the periodic orbit. In many past studies, this was achieved by explicitly deriving the Poincare map that describes the evolution of the state from one clock instant to the next and then locally linearizing the map at the fixed point. However, in many converters, the map cannot be derived in closed form, and therefore this approach cannot directly be applied. Alternatively, the orbital stability can be worked out by studying the evolution of perturbations about a nominal periodic orbit, and some studies along this line have also been reported. In this paper, we show that Filippov's method - which has commonly been applied to mechanical switching systems - can be used fruitfully in power electronic circuits to achieve the same end by describing the behavior of the system during the switchings. By combining this and the Floquet theory, it is possible to describe the stability of power electronic converters. We demonstrate the method using the example of a voltage-mode-controlled buck converter operating in continuous conduction mode. We find that the stability of a converter is strongly dependent upon the so-called saltation matrix - the state transition matrix relating the state just after the switching to that just before. We show that the Filippov approach, especially the structure of the saltation matrix, offers some additional insights on issues related to the stability of the orbit, like the recent observation that coupling with spurious signals coming from the environment causes intermittent subharmonic windows. Based on this approach, we also propose a new controller that can significantly extend the parameter range for nominal period-1 operation.     

Construction of turbo code interleaves from 3-regular Hamiltonian graphs

In this letter, we present a new construction of interleavers for turbo codes from 3-regular Hamiltonian graphs. The interleavers can be generated using a few parameters, which can be selected in such a way that the girth of the interleaver graph (IG) becomes large, inducing a high summary distance. The size of the search space for these parameters is derived. The proposed interleavers themselves work as their de-interleavers.     

Lowering of thickness of boron-doped microcrystalline hydrogenated silicon film by seeding technique

By using a seeding technique it has been possible to reduce the thickness of p-μc-Si:H film to 230 Å, with an improved electrical conductivity (0.93 S cm⁻¹) and lower optical absorption compared to those of conventional p-μc-Si:H layers without a seed layer, for use at the tunnel junction and as the top layer of a double junction n–i–p structured a-Si solar cell. Undoped-μc-Si:H has been used as the seed layer. The layers were prepared by the radio frequency plasma-enhanced chemical vapour deposition (RF-PECVD) method (13.56 MHz) at 40 mW/cm² rf power density and low substrate temperature (200 °C). The ultrathin seed layer (30 Å) enhances the growth of microcrystallinity of the p-type μc-Si:H film as confirmed by the results of transmission electron microscopy (TEM) analysis and Raman spectroscopy.     

A two‐warehouse inventory model for items with three‐parameter Weibull distribution deterioration,shortages and linear trend in demand

Depending on the type of goods and storage facilities available, perishable goods decay in different manners in terms of the initial point and rate of deterioration. The three‐parameter Weibull distribution is an excellent generalization of exponential decay, with the flexibility of modeling various types of deteriorations. Since inventory management of perishable goods involves expensive storage facilities, the retailer with small storage may have to rent a warehouse. In this paper, we discuss a two‐warehouse inventory model where deteriorations in the two warehouses follow independent three‐parameter Weibull distributions. Transfer of units is from the rented warehouse to the own warehouse, and incurs a positive cost per unit. Demand is a non‐decreasing linear function of time, shortages are backlogged and replenishment is instantaneous. A solution procedure for obtaining optimal values of initial inventory level and cycle time is presented. Sensitivity analysis is carried out. The effect of using other related deterioration distributions is illustrated.     

Effect of Ternary Additions on the Stability of Ordered Phases in Ni-Mo Alloys—Transmission Electron Microscopy Results and First Principles Calculations

The ordering behavior of a Ni-Mo alloy in the presence of ternary additives X (X = Al, Cr, Mn, V) has been studied using transmission electron microscopy (TEM) as well as first-principles calculations using the tight-binding–linear muffin tin orbital (TB-LMTO) method. The sequence of ordering transformations in binary Ni-Mo alloys has been shown earlier to be controlled by a competition between several fcc-based superlattices, viz. Ni₂Mo (Pt₂Mo type), Ni₃Mo (D0₂₂), Ni₄Mo (D1_a), and the so-called short-range ordered (SRO) structure characterized by the presence of {1½0} reflections. These ternary additives have been observed to stabilize the Ni₃Mo (D0₂₂) phase compared to the Ni₂Mo + Ni₄Mo phase mixture, leading to a sequence of transformation different from that obtained in binary alloys. The calculated energies of formation were observed to conform to the experimentally observed stability hierarchy in these binary intermetallics and their ternary analogues. The third element stabilizes the D0₂₂ structure by contributing to the covalent component of bonding in these compounds.     

Chromatin modification of imprinted H19 gene in mammalian spermatozoa

To date, most functional analysis studies have focused on the effects of treatment contingencies on specific targeted aberrant and alternative responses. In the current investigation, the main and collateral effects of the assessment and treatment of attention-maintained self-injury were assessed. Specifically, we evaluated the effects of noncontingent and contingent social attention on four categories of behavior: self-injury, a novel mand, preexisting prosocial responses (e.g., babbling and reaching out), and other aberrant responses (i.e., aggression and destruction). Results suggested that self-injury, prosocial responses, and other aberrant behaviors were within the same functional response class. Possible impact of these results when selecting mands for functional communication training is discussed.     

Algorithms for Integrated Routing and Scheduling for Aggregating Data from Distributed Resources on a Lambda Grid

In many e-science applications, there exists an important need to aggregate information from data repositories distributed around the world. In an effort to better link these resources in a unified manner, many lambda-grid networks, which provide end-to-end dedicated optical-circuit-switched connections, have been investigated. In this context, we consider the problem of aggregating files from distributed databases at a (grid) computing node over a lambda grid. The challenge is (1) to identify routes (that is, circuits) in the lambda-grid network, along which files should be transmitted, and (2) to schedule the transfers of these files over their respective circuits. To address this challenge, we propose a hybrid approach that combines offline and online scheduling. We define the Time-Path Scheduling Problem (TPSP) for offline scheduling. We prove that TPSP is NP-complete, develop a Mixed Integer Linear Program (MILP) formulation for TPSP, and then propose a greedy approach to solve TPSP because the MILP does not scale well. We compare the performance of the greedy approach on a few representative lambda-grid network topologies. One key input to the offline schedule is the file transfer time. Due to dynamics at the receiving end host, which is hard to model precisely, the actual file transfer time may vary. We first propose a model for estimating the file transfer time. Then, we propose online reconfiguration algorithms so that as files are transferred, the offline schedule may be modified online, depending on the amount of time that it actually took to transfer the file. This helps in reducing the total time to transfer all the files, which is an important metric. To demonstrate the effectiveness of our approach, we present results on an emulated lambda-grid network testbed.     

Models for electron and hole mobilities in MOS accumulation layers

We present new physically based effective mobility models for both electrons and holes in MOS accumulation layers. These models take into account carrier-carrier scattering, in addition to surface roughness scattering, phonon and fixed interface charge scattering, and screened Coulomb scattering. The newly developed effective mobility models show excellent agreement with experimental data over the range 1×10¹⁶-4×10¹⁷ cm^-3 for which experimental data are available. Local-field dependent mobility models have also been developed for both electrons and holes, and they have been implemented in the two-dimensional (2-D) device simulators, PISCES and MINIMOS, thus providing for more accurate prediction of the terminal characteristics in deep submicron CMOS devices. In addition, transition region mobility models have been developed to account for the transition in the mobility in going from the accumulation layer in the gate-to-source overlap region to the inversion layer region in the channel     

Rigorous coupled wave analysis of induced photorefractive gratings

The usefulness of rigorous coupled wave theory in the analysis of induced transmission and reflection grating formation, wave mixing, and higher order generation is demonstrated. No approximations air made, exact photorefractive material equations are used, and optical and electrical anisotropies are included. Several new effects, such as time oscillation, higher order generation, etc., are predicted