103,736 research outputs found
A B-ISDN-compatible modem/codec
Coded modulation techniques for development of a broadband integrated services digital network (B-ISDN)-compatible modem/codec are investigated. The selected baseband processor system must support transmission of 155.52 Mbit/s of data over an INTELSAT 72-MHz transponder. Performance objectives and fundamental system parameters, including channel symbol rate, code rate, and the modulation scheme are determined. From several candidate codes, a concatenated coding system consisting of a coded octal phase shift keying modulation as the inner code and a high rate Reed-Solomon as the outer code is selected and its bit error rate performance is analyzed by computer simulation. The hardware implementation of the decoder for the selected code is also described
Single crystals of metal solid solutions: A study
Report describes growth of silver-alloy crystals under widely varying conditions of growth rate, temperature gradient, and magnetic field. Role of gravitation and convection on crystal substructure is analyzed, as well as influence of magnetic fields applied during crystallization
Formulation and evaluation of C-Ether fluids as lubricants useful to 260 C
Three base stocks were evaluated in bench and bearing tests to determine their suitability for use at bulk oil temperatures (BOT) from -40 C to +260 C. A polyol ester gave good bearing tests at a bulk temperature of 218 C, but only a partially successful run at 274 C. These results bracket the fluid's maximum operating temperature between these values. An extensive screening program selected lubrication additives for a C-ether (modified polyphenyl ether) base stock. One formulation lubricated a bearing for 111 hours at 274 C (BOT), but this fluid gave many deposit related problems. Other C-ether blends produced cage wear or fatigue failures. Studies of a third fluid, a C-ether/disiloxane blend, consisted of bench oxidation and lubrication tests. These showed that some additives react differently in the blend than in pure C-ethers
Carrier-interference ratios for frequency sharing between frequency-modulated amplitude-modulated-vestigial-sideband television systems
For just perceptible interference, an FM television signal interfering with another FM television signal must have an average signal power that is 26 to 37 db less than the wanted signal power. For an AM-VSB television signal interfering with an FM television signal, the AM-VSB television's sync peak average power must be 18 to 31 db below the FM television signal's average power. Also, when an FM television signal interferes with an AM-VSB signal, the average signal power of the FM signal should be 56 to 59 db below the sync peak average power of the AM-VSB television signal. The range of power ratios occur as a result of different TV scenes used in the tests and different FM-signal frequency deviations used. All tests were performed using 525 line, system M, color-television signals
LHC Signatures of the Constrained Exceptional Supersymmetric Standard Model
We discuss two striking Large Hadron Collider (LHC) signatures of the
constrained version of the exceptional supersymmetric standard model (cE6SSM),
based on a universal high energy soft scalar mass m_0, soft trilinear coupling
A_0 and soft gaugino mass M_{1/2}. The first signature we discuss is that of
light exotic colour triplet charge 1/3 fermions, which we refer to as
D-fermions. We calculate the LHC production cross section of D-fermions, and
discuss their decay patterns. Secondly we discuss the E6 type U(1)_N spin-1 Z'
gauge boson and show how it may decay into exotic states, increasing its width
and modifying the line shape of the dilepton final state. We illustrate these
features using two representative cE6SSM benchmark points, including an "early
LHC discovery" point, giving the Feynman rules and numerical values for the
relevant couplings in order to facilitate further studies.Comment: 30 pages, 5 figures, corrections to figure caption
Identification of nonlinear vibrating structures: Part I -- Formulation
A self-starting multistage, time-domain procedure is presented for the identification of nonlinear, multi-degree-of-freedom systems undergoing free oscillations or subjected to arbitrary direct force excitations and/or nonuniform support motions. Recursive least-squares parameter estimation methods combined with nonparametric identification techniques are used to represent, with sufficient accuracy, the identified system in a form that allows the convenient prediction of its transient response under excitations that differ from the test signals. The utility of this procedure is demonstrated in a companion paper
Identification of nonlinear vibrating structures: Part II -- Applications
A time-domain procedure for the identification of nonlinear vibrating structures, presented in a companion paper, is applied to a "calibration" problem which incorporates realistic test situations and nonlinear structural characteristics widely encountered in the applied mechanics field. The "data" set is analyzed to develop suitable, approximate nonlinear system representations. Subsequently, a "validation" test is conducted to demonstrate the range of validity of the method under discussion. It is shown that the procedure furnishes a convenient means for constructing reduced-order nonlinear nonparametric mathematical models of reasonably high fidelity in regard to reproducing the response of the test article under dynamic loads that differ from the identification test loads
The Highly Oscillatory Behavior of Automorphic Distributions for SL(2)
Automorphic distributions for SL(2) arise as boundary values of modular forms
and, in a more subtle manner, from Maass forms. In the case of modular forms of
weight one or of Maass forms, the automorphic distributions have continuous
first antiderivatives. We recall earlier results of one of us on the Holder
continuity of these continuous functions and relate them to results of other
authors; this involves a generalization of classical theorems on Fourier series
by S. Bernstein and Hardy-Littlewood. We then show that the antiderivatives are
non-differentiable at all irrational points, as well as all, or in certain
cases, some rational points. We include graphs of several of these functions,
which clearly display a high degree of oscillation. Our investigations are
motivated in part by properties of "Riemann's nondifferentiable function", also
known as "Weierstrass' function".Comment: 27 pages, 6 Figures; version 2 corrects misprints and updates
reference
Phenomenological Consequences of the Constrained Exceptional Supersymmetric Standard Model
The Exceptional Supersymmetric Standard Model (ESSM) provides a low
energy alternative to the MSSM, with an extra gauged U(1) symmetry, solving
the -problem of the MSSM. Inspired by the possible embedding into an E
GUT, the matter content fills three generations of E multiplets, thus
predicting exciting exotic matter such as diquarks or leptoquarks. We present
predictions from a constrained version of the model (cESSM), with a
universal scalar mass , trilinear mass and gaugino mass . We
reveal a large volume of the cESSM parameter space where the correct
breakdown of the gauge symmetry is achieved and all experimental constraints
satisfied. We predict a hierarchical particle spectrum with heavy scalars and
light gauginos, while the new exotic matter can be light or heavy depending on
parameters. We present representative cESSM scenarios, demonstrating that
there could be light exotic particles, like leptoquarks and a U(1) Z'
boson, with spectacular signals at the LHC.Comment: Contribution to the proceedings of SUSY 09, Boston, USA, June 2009, 4
page
Transmission Oscillator Ultrasonic Spectrometer (TOUS): A new research instrument
TOUS is capable for measuring very small changes in acoustic attenuation and phase velocity. Its high sensitivity to small changes in ultrasonic absorption results in part from operation under marginal conditions. In spite of high sensitivity, TOUS system is relatively simple, inexpensive, and compact
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