930 research outputs found
Submicron gate InP power MISFET's with improved output power density at 18 and 20 GHz
The microwave characteristics are presented at 18 and 20 GHz of submicron gate indium phosphide (InP) metal-insulator-semiconductor field-effect transistors (MISFET's) for high output power density applications. InP power MISFET's were fabricated and the output power density was investigated as a function of drain-source spacing. The best output power density and gain were obtained for drain-source spacing of 3 microns. The output power density is 2.7 times greater than was previously measured for InP MISFET's at 18 and 20 GHz, and the power-added efficiency also increased
Electron beam induced damage in PECVD Si3N4 and SiO2 films on InP
Phosphorus rich plasma enhanced chemical vapor deposition (PECVD) of silicon nitride and silicon dioxide films on n-type indium phosphide (InP) substrates were exposed to electron beam irradiation in the 5 to 40 keV range for the purpose of characterizing the damage induced in the dielectic. The electron beam exposure was on the range of 10(exp -7) to 10(exp -3) C/sq cm. The damage to the devices was characterized by capacitance-voltage (C-V) measurements of the metal insulator semiconductor (MIS) capacitors. These results were compared to results obtained for radiation damage of thermal silicon dioxide on silicon (Si) MOS capacitors with similar exposures. The radiation induced damage in the PECVD silicon nitride films on InP was successfully annealed out in an hydrogen/nitrogen (H2/N2) ambient at 400 C for 15 min. The PECVD silicon dioxide films on InP had the least radiation damage, while the thermal silicon dioxide films on Si had the most radiation damage
The Electric Choremaster: Development and Performance of an Agricultural Electric Tractor
The National Rural Electric Cooperative partially funded a project at South Dakota State for development of an electric tractor in 1983. Association University The goals of this project were to build, demonstrate and evaluate a battery-powered farmstead chore tractor which would lead to a commercially produced and widely accepted vehicle. Three major results were expected from the work: 1) test results and analyses to verify the. feasibility of farmstead electric vehicles and to indicate some of the problems and limitations encountered during actual use, 2) a vehicle to demonstrate the concept of electric vehicles to farmers and to farm equipment manufacturers, and 3) design information for an electric vehicle prototype which could be used to aid the commercial development of electric farm vehicles. Design of this tractor, the Electric Choremaster, was a team endeavor. As a member of the design group, this author\u27s responsibilities were to: contribute to the vehicle design criteria; review and evaluate power train components; size, select, and supervise the installation of motors and drive train components; and perform the first phase of testing. and evaluating the completed prototype. This thesis reports on the development of the Electric Choremaster and can serve as a guide for future developments of agricultural electric vehicles. Specific objectives of the research reported in this thesis were to: 1) describe the design process used for development of the Electric Choremaster, 2) detail the power train design for the Electric Choremaster, 3) evaluate the performance of the Electric Choremaster as compared to a conventional diesel tractor, and 4) investigate the effects of battery temperature and state of battery charge on vehicle performance
Online Pattern Recognition for the ALICE High Level Trigger
The ALICE High Level Trigger has to process data online, in order to select
interesting (sub)events, or to compress data efficiently by modeling
techniques.Focusing on the main data source, the Time Projection Chamber (TPC),
we present two pattern recognition methods under investigation: a sequential
approach "cluster finder" and "track follower") and an iterative approach
("track candidate finder" and "cluster deconvoluter"). We show, that the former
is suited for pp and low multiplicity PbPb collisions, whereas the latter might
be applicable for high multiplicity PbPb collisions, if it turns out, that more
than 8000 charged particles would have to be reconstructed inside the TPC.
Based on the developed tracking schemes we show, that using modeling techniques
a compression factor of around 10 might be achievableComment: Realtime Conference 2003, Montreal, Canada to be published in IEEE
Transactions on Nuclear Science (TNS), 6 pages, 8 figure
Self-averaging in the random 2D Ising ferromagnet
We study sample-to-sample fluctuations in a critical two-dimensional Ising
model with quenched random ferromagnetic couplings. Using replica calculations
in the renormalization group framework we derive explicit expressions for the
probability distribution function of the critical internal energy and for the
specific heat fluctuations. It is shown that the disorder distribution of
internal energies is Gaussian, and the typical sample-to-sample fluctuations as
well as the average value scale with the system size like . In contrast, the specific heat is shown to be self-averaging with a
distribution function that tends to a -peak in the thermodynamic limit
. While previously a lack of self-averaging was found for the
free energy, we here obtain results for quantities that are directly measurable
in simulations, and implications for measurements in the actual lattice system
are discussed.Comment: 12 pages, accepted versio
Scaling Analysis of the Site-Diluted Ising Model in Two Dimensions
A combination of recent numerical and theoretical advances are applied to
analyze the scaling behaviour of the site-diluted Ising model in two
dimensions, paying special attention to the implications for multiplicative
logarithmic corrections. The analysis focuses primarily on the odd sector of
the model (i.e., that associated with magnetic exponents), and in particular on
its Lee-Yang zeros, which are determined to high accuracy. Scaling relations
are used to connect to the even (thermal) sector, and a first analysis of the
density of zeros yields information on the specific heat and its corrections.
The analysis is fully supportive of the strong scaling hypothesis and of the
scaling relations for logarithmic corrections.Comment: 15 pages, 3 figures. Published versio
Scaling Relations for Logarithmic Corrections
Multiplicative logarithmic corrections to scaling are frequently encountered
in the critical behavior of certain statistical-mechanical systems. Here, a
Lee-Yang zero approach is used to systematically analyse the exponents of such
logarithms and to propose scaling relations between them. These proposed
relations are then confronted with a variety of results from the literature.Comment: 4 page
Symmetry relation for multifractal spectra at random critical points
Random critical points are generically characterized by multifractal
properties. In the field of Anderson localization, Mirlin, Fyodorov,
Mildenberger and Evers [Phys. Rev. Lett 97, 046803 (2006)] have proposed that
the singularity spectrum of eigenfunctions satisfies the exact
symmetry at any Anderson transition. In the
present paper, we analyse the physical origin of this symmetry in relation with
the Gallavotti-Cohen fluctuation relations of large deviation functions that
are well-known in the field of non-equilibrium dynamics: the multifractal
spectrum of the disordered model corresponds to the large deviation function of
the rescaling exponent along a renormalization trajectory
in the effective time . We conclude that the symmetry discovered on
the specific example of Anderson transitions should actually be satisfied at
many other random critical points after an appropriate translation. For
many-body random phase transitions, where the critical properties are usually
analyzed in terms of the multifractal spectrum and of the moments
exponents X(N) of two-point correlation function [A. Ludwig, Nucl. Phys. B330,
639 (1990)], the symmetry becomes , or equivalently
for the anomalous parts .
We present numerical tests in favor of this symmetry for the 2D random
state Potts model with various .Comment: 15 pages, 3 figures, v2=final versio
CI Aql: a Type Ia supernova progenitor?
If recurrent novae are progenitors of Type Ia supernovae, their white dwarfs must have masses close to the Chandrasekhar limit. The most reliable means of determining white dwarf masses in recurrent novae is dynamically, via radial-velocity and rotational-broadening measurements of the companion star. Such measurements require the system to be both eclipsing and to show absorption features from the secondary star. Prior to the work reported here, the only dynamical mass estimate of a recurrent nova was for U Sco, which has a white dwarf mass of 1.55 ± 0.24M⊙. We present new time-resolved, intermediate-resolution spectroscopy of the eclipsing recurrent nova CI Aquilae (CI Aql) during quiescence. We find the mass of the white dwarf to be 1.00 ± 0.14M⊙ and the mass of the secondary star to be 2.32 ± 0.19M⊙. We estimate the radius of the secondary to be 2.07±0.06 R⊙, implying that it is a slightly evolved early A-type star. The high mass ratio of q = 2.35 ± 0.24 and the high secondary-star mass implies that the mass transfer occurs on a thermal time-scale. We suggest that CI Aql is rapidly evolving into a supersoft X-ray source, and ultimately may explode as a Type Ia supernova within 10 Myr
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