1,374 research outputs found
TACL - a timeshared hybrid system for control laboratories
A generalized control-system model encompassing a wide variety of systems has been programmed on the analog portion of a hybrid computation system. Five terminals with storage oscilloscopes are con nected to the hybrid computer and are serviced on a round-robin basis. The generalized system can be configured in milliseconds to a specific problem by setting the values of the digital coefficient units and switches of the analog system. A library of specific problems is kept on the system's digital disk. Students use the system by referencing a problem in the library and entering parameter values to define the problem from their terminals. The per-solution time varies with the time scale seZect ed, but averages around a few hundred milliseconds. A user-oriented compiler helps the instructor define new problems to be added. Digital values are assigned by the student to select ed parameters of specific problems, and families of curves representing system performance as a function of control settings may be displayed on the student's terminal. The terminals also display digital data and alphanumerical information.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68305/2/10.1177_003754977502500203.pd
Radiative corrections to deeply virtual Compton scattering
We discuss possibilities of measurement of deeply virtual Compton scattering
amplitudes via different asymmetries in order to access the underlying skewed
parton distributions. Perturbative one-loop coefficient functions and two-loop
evolution kernels, calculated recently by a tentative use of residual conformal
symmetry of QCD, are used for a model dependent numerical estimation of
scattering amplitudes.Comment: 9 pages LaTeX, 3 figures, czjphyse.cls required Talk given by D.
M\"uller at Inter. Workshop ``PRAHA-Spin99'', Prague, Sept. 6-11, 199
Dynamic instability in resonant tunneling
We show that an instability may be present in resonant tunneling through a
quantum well in one, two and three dimensions, when the resonance lies near the
emitter Fermi level. A simple semiclassical model which simulates the resonance
and the projected density of states by a nonlinear conductor, the Coulomb
barrier by a capacitance, and the time evolution by an iterated map, is used.
The model reproduces the observed hysteresis in such devices, and exhibits a
series of bifurcations leading to fast chaotic current fluctuations.Comment: 7 pages, 2 figure
Weak Boson Production Amplitude Zeros; Equalities of the Helicity Amplitudes
We investigate the radiation amplitude zeros exhibited by many Standard Model
amplitudes for triple weak gauge boson production processes. We show that
production amplitudes have especially rich structure in terms of
zeros, these amplitudes have zeros originating from several different sources.
It is also shown that TYPE I current null zone is the special case of the
equality of the specific helicity amplitudes.Comment: 27 pages, 12 figures, 2 table
PMH40 How do Patients Describe Their Depression? - Incorporating the Patient's Voice Into Instrument Development
Letter from CGIAR Chairman Ismail Serageldin to CGIAR heads of delegation, board chairs, center directors and the TAC chairman and secretariat, leading up to ICW94. Serageldin described the work of various ad hoc and standing bodies in preparation for International Centers Week 1994 and the Ministerial-level Meeting being planned for early 1995. He also announced that as a result of additional funding by donors and matching funds from the World Bank, the 1994 core program was fully funded
Top-Quark Pair Production Beyond Next-to-Leading Order
We report on recent calculations of the differential cross section for
top-quark pair production at hadron colliders. The results are differential
with respect to the top-pair invariant mass and to the partonic scattering
angle. In these calculations, which were carried out by employing
soft-collinear effective theory techniques, we resummed threshold logarithms up
to next-to-next-to-leading logarithmic order. Starting from the differential
cross section, it is possible to obtain theoretical predictions for the
invariant-mass distribution and the total cross section. We summarize here our
results for these observables, and we compare them with the results obtained
from different calculational methods.Comment: Talk presented at Loops and Legs in Quantum Field Theory 2010,
Woerlitz, Germany, April 25-30, 2010. 6 page
Big data and other challenges in the quest for orthologs
Given the rapid increase of species with a sequenced genome, the need to identify orthologous genes between them has emerged as a central bioinformatics task. Many different methods exist for orthology detection, which makes it difficult to decide which one to choose for a particular application. Here, we review the latest developments and issues in the orthology field, and summarize the most recent results reported at the third ‘Quest for Orthologs' meeting. We focus on community efforts such as the adoption of reference proteomes, standard file formats and benchmarking. Progress in these areas is good, and they are already beneficial to both orthology consumers and providers. However, a major current issue is that the massive increase in complete proteomes poses computational challenges to many of the ortholog database providers, as most orthology inference algorithms scale at least quadratically with the number of proteomes. The Quest for Orthologs consortium is an open community with a number of working groups that join efforts to enhance various aspects of orthology analysis, such as defining standard formats and datasets, documenting community resources and benchmarking. Availability and implementation: All such materials are available at http://questfororthologs.org. Contact: [email protected] or [email protected]
Determination of nuclear parton distributions
Parametrization of nuclear parton distributions is investigated in the
leading order of alpha_s. The parton distributions are provided at Q^2=1 GeV^2
with a number of parameters, which are determined by a chi^2 analysis of the
data on nuclear structure functions. Quadratic or cubic functional form is
assumed for the initial distributions. Although valence quark distributions in
the medium x region are relatively well determined, the small x distributions
depend slightly on the assumed functional form. It is difficult to determine
the antiquark distributions at medium x and gluon distributions. From the
analysis, we propose parton distributions at Q^2=1 GeV^2 for nuclei from
deuteron to heavy ones with the mass number A~208. They are provided either
analytical expressions or computer subroutines for practical usage. Our studies
should be important for understanding the physics mechanism of the nuclear
modification and also for applications to heavy-ion reactions. This kind of
nuclear parametrization should also affect existing parametrization studies in
the nucleon because "nuclear" data are partially used for obtaining the optimum
distributions in the "nucleon".Comment: 16 pages, REVTeX4b5, revtex4.cls, url.sty, natbib.sty, 10pt.rtx,
aps.rtx, revsymb.sty, 21 eps figures. Submitted for publication. Computer
codes for the nuclear parton distributions could be obtained from
http://www-hs.phys.saga-u.ac.jp Email: [email protected]
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