A diagrammatic approach to search for minimum sampling frequency and quantization resolution for digital control of power converters

A diagrammatic approach to find out the minimum sampling frequency and quantization resolution for digital control of power converters is proposed. The proposed solution algorithm combines consideration on both time sampling and quantization resolution axes to search for the minimum required digital controller settings. Experiments results are presented to justify the proposed algorithm. © 2007 IEEE.published_or_final_versio

Least coupling paths model for non-contact EMI base on lump element approach in switch mode converter

A simplified physical model concludes a minimum of six equivalent physical coupling paths, Least Coupling Paths (LCP), using lump elements approach through non-contact EMI coupling mechanism to the terminals of LISN. Simulation shows both inductive and capacitive coupling through each path may produce substantial EMI measured by a LISN. This physical model is good for understanding, diagnosis and emission estimation.published_or_final_versio

Rift Valley fever virus structural proteins: expression, characterization and assembly of recombinant proteins

BACKGROUND: Studies on Rift Valley Fever Virus (RVFV) infection process and morphogenesis have been hampered due to the biosafety conditions required to handle this virus, making alternative systems such as recombinant virus-like particles, that may facilitate understanding of these processes are highly desirable. In this report we present the expression and characterization of RVFV structural proteins N, Gn and Gc and demonstrate the efficient generation of RVFV virus-like particles (VLPs) using a baculovirus expression system. RESULTS: A recombinant baculovirus, expressing nucleocapsid (N) protein of RVFV at high level under the control of the polyhedrin promoter was generated. Gel filtration analysis indicated that expressed N protein could form complex multimers. Further, N protein complex when visualized by electron microscopy (EM) exhibited particulate, nucleocapsid like-particles (NLPs). Subsequently, a single recombinant virus was generated that expressed the RVFV glycoproteins (Gn/Gc) together with the N protein using a dual baculovirus vector. Both the Gn and Gc glycoproteins were detected not only in the cytoplasm but also on the cell surface of infected cells. Moreover, expression of the Gn/Gc in insect cells was able to induce cell-cell fusion after a low pH shift indicating the retention of their functional characteristics. In addition, assembly of these three structural proteins into VLPs was identified by purification of cells' supernatant through potassium tartrate-glycerol gradient centrifugation followed by EM analysis. The purified particles exhibited enveloped structures that were similar to the structures of the wild-type RVFV virion particle. In parallel, a second recombinant virus was constructed that expressed only Gc protein together with N protein. This dual recombinant virus also generated VLPs with clear spiky structures, but appeared to be more pleomorphic than the VLPs with both glycoproteins, suggesting that Gc and probably also Gn interacts with N protein complex independent of each other. CONCLUSION: Our results suggest that baculovirus expression system has enormous potential to produce large amount of VLPs that may be used both for fundamental and applied research of RVFV

Molecular Dynamics Simulation of Iron — A Review

published_or_final_versio

Analysis of the resonance modes of PZT/epoxy 1-3 composite rings

Author name used is this publication: C. P. ChongRefereed conference paper2001-2002 > Academic research: refereed > Refereed conference paperVersion of RecordPublishe

Essential-coupling-path models for non-contact EMI in switching power converters using lumped circuit elements

This paper proposes a simple lumped circuit modeling approach for describing noncontact EMI coupling mechanisms in switching power converters. The resulting model assumes a minimum number of noise sources and contains essential coupling paths that allow easy physical interpretations. Essentially, all capacitive couplings are represented by an equivalent noise voltage source and six coupling impedances, whereas all inductive couplings are represented by an equivalent noise current source and three coupling impedances. The resulting coupled noise appears as currents flowing into the terminals of the Line-Impedance-Stabilization-Network (LISN). The equivalent voltage source can be conveniently approximated as the switching-node-to-zero voltage, which is typically a rectangular pulse of a few hundred volts. The equivalent current source can be modeled as the current flowing around a loop containing the equivalent voltage source and parasitics such as winding capacitance of the power transformer, the snubber capacitance and connection inductances. Also, the coupling impedances can be estimated by making simplifying assumptions about the geometry of the components and tracks, or by direct measurements. Simulations and experiments verify how inductive and capacitive couplings through each path may produce substantial EMI measured by the LISN. Being based on a lumped circuit approach, the proposed model is easy to apply in practice for understanding, diagnosing and approximating EMI behaviors.published_or_final_versio

Current-driven synchronous rectification technique for flyback topology

For low voltage, high current application, synchronous rectification technique can help improve efficiency in a flyback converter. This paper investigates some technical challenges within a synchronous rectification flyback converter. One of the major problems is that the discontinuous current mode (DCM) operation is not achievable with a control-driven or self-driven synchronous rectifier. Continuous current mode operation may introduce excessive RMS current and circulation energy at light load or high line condition. To solve this problem, we propose to use an energy recovery current-driven synchronous rectifier for flyback topology. Analysis and experiments demonstrate the performance of this approach.published_or_final_versio

Analysis of buck-boost converter inductor loss using a simpleonline B-H curve tracer

A simple method to plot online B-H curves and calculate the core loss of the inductor in a conventional buck-boost power converter is developed. In order to obtain a reliable loss data, measurement error and phase shift error are analyzed and then quantified. A new method to minimize measurement error is given. A new core loss model in terms of switching duty cycle is presented. This model predicts variation of core loss of an inductor operating in various conditions in a switching converter. This inductor model can be generalized to inductors in other switching converter topologies.published_or_final_versio

CS 3180/5180: Comparative Languages

This course will introduce fundamental concepts and paradigms underlying the design of modern programming languages. For concreteness, we study the details of an object-oriented language (e.g. Java, C#, C++), a functional language (e.g., Scheme, and get introduced to multiparadigm languages (e.g., Python, Scala). The overall goal is to enable comparison and evaluation of existing languages. The programming assignments will largely be coded in Java and in Scheme, and optionally in Python or Scala

Holographic non-relativistic fermionic fixed point and bulk dipole coupling

Inspired by the recently discovered non-relativistic fermionic fixed points, we investigate how the presence of bulk dipole coupling modifies the spectral function at one of these novel fixed points. As a result, although the infinite flat band is always visible in the presence of the bulk dipole coupling as well as chemical potential, the band is modified in a remarkable way at small momenta up to the order of magnitude of bulk dipole coupling. On the other hand, like a phoenix, a new Fermi surface sprouts from the formed gap when the bulk dipole coupling is pushed up further such as to overshadow the charge parameter, which is obviously different from what is found at the relativistic fixed points.Comment: JHEP style, 1+17 pages, 9 figures, 1 table, typos corrected, references added, version to appear in JHE