1,215 research outputs found
Input filter compensation for switching regulators
The problems caused by the interaction between the input filter, output filter, and the control loop are discussed. The input filter design is made more complicated because of the need to avoid performance degradation and also stay within the weight and loss limitations. Conventional input filter design techniques are then dicussed. The concept of pole zero cancellation is reviewed; this concept is the basis for an approach to control the peaking of the output impedance of the input filter and thus mitigate some of the problems caused by the input filter. The proposed approach for control of the peaking of the output impedance of the input filter is to use a feedforward loop working in conjunction with feedback loops, thus forming a total state control scheme. The design of the feedforward loop for a buck regulator is described. A possible implementation of the feedforward loop design is suggested
Possible eta-mesic 3He states within the finite rank approximation
We extend the method of time delay proposed by Eisenbud and Wigner, to search
for unstable states formed by eta mesons and the 3He nucleus. Using few body
equations to describe eta-3He elastic scattering, we predict resonances and
unstable bound states within different models of the eta-N interaction. The
eta-3He states predicted within this novel approach are in agreement with the
recent claim of the evidence of eta-mesic 3He made by the TAPS collaboration.Comment: 10 pages LaTex, 3 figure
Small eta-N scattering lengths favour eta-d and eta-alpha states
Unstable states of the eta meson and the 3He nucleus predicted using the time
delay method were found to be in agreement with a recent claim of eta-mesic 3He
states made by the TAPS collaboration. Here, we extend this method to a
speculative study of the unstable states occurring in the eta-d and eta-4He
elastic scattering. The T-matrix for eta-4He scattering is evaluated within the
Finite Rank Approximation (FRA) of few body equations. For the evaluation of
time delay in the eta-d case, we use a parameterization of an existing Faddeev
calculation and compare the results with those obtained from FRA. With an eta-N
scattering length, fm, we find an eta-d unstable
bound state around -16 MeV, within the Faddeev calculation. A similar state
within the FRA is found for a low value of , namely, fm. The existence of an eta-4He unstable bound state close to
threshold is hinted by fm, but is ruled out by
large scattering lengths.Comment: 21 pages, LaTex, 7 Figure
Venous thromboembolism related to cytomegalovirus infection: A case report and literature review
Silicon carbide as a photoconductive switch material for high power applications
The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file.Title from title screen of research.pdf file (viewed on August 3, 2007)Vita.Thesis (Ph. D.) University of Missouri-Columbia 2006.This research work discusses the effort at the Electrical and computer engineering (ECE) department at the University of Missouri Columbia (UMC) in developing this technology through simulation and experiments with SiC material. Specifically, the rationale for employing extrinsic photoconductivity, the role of compensation mechanisms have been demonstrated, modeled, and analyzed. The device material fabrication methods and package structures developed to date are discussed. The behavior and the response of the two compensated structures have been discussed in terms of recombination time and optical sensitivity. Material characterization showing agreement with the experimental results was based on choosing the right parameters on trap levels and compensation mechanisms. The experimental switching results with both intrinsic and compensated SiC photo switches using sub-band gap photon energy for code calibration and high power PCSS analysis is presented and compared with semiconductor physics models. The methods used to determine the density and recombination cross section of interband dopants is also presented. A method to improve the hold off voltage of the PCSS by many orders of magnitude is proposed. Laser illumination data with the improved design is also presented.Includes bibliographical reference
Input filter compensation for switching regulators
A novel input filter compensation scheme for a buck regulator that eliminates the interaction between the input filter output impedance and the regulator control loop is presented. The scheme is implemented using a feedforward loop that senses the input filter state variables and uses this information to modulate the duty cycle signal. The feedforward design process presented is seen to be straightforward and the feedforward easy to implement. Extensive experimental data supported by analytical results show that significant performance improvement is achieved with the use of feedforward in the following performance categories: loop stability, audiosusceptibility, output impedance and transient response. The use of feedforward results in isolating the switching regulator from its power source thus eliminating all interaction between the regulator and equipment upstream. In addition the use of feedforward removes some of the input filter design constraints and makes the input filter design process simpler thus making it possible to optimize the input filter. The concept of feedforward compensation can also be extended to other types of switching regulators
Nifty Auto Index prediction on the basis of tweets sentiments
In this paper we investigate the complex relationshipbetween tweet sentiments with the Nifty Stock market AutoIndex (esp. stock prices). We will analyze sentiments for nearly 1million tweets from December 2015 to March 2016 for Nifty AutoIndex which includes 15 auto industries stocks. Our results willshow high correlation between stock prices and twittersentiments. A Granger causality analysis and a Neural Networkare then used to investigate the hypothesis that public moodstates are predictive of changes in Nifty Auto Index closingvalues
Surveillance of health care workers for multidrug-resistant organisms in faecal samples in a tertiary care cancer centre
Large deflections of circular isotropic membranes subjected to arbitrary axisymmetric loading
Circular membranes with fixed peripheral edges, subjected to arbitrary axisymmetric loading are analyzed. A single governing differential equation in terms of radial stress is used. This nonlinear governing equation is solved using the finite difference method in conjunction with Newton-Raphson method. Three loading cases, namely (1) uniformly loaded membrane, (2) a membrane with uniform load over an inner portion, and (3) a membrane with ring load, are analyzed. Calculated central displacement and the central and edge radial stresses for uniformly loaded membrane, agree extremely well with the classical solution
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