83,733 research outputs found
Design of Prototype Dynamic Ac Power Machine with Equivalent Circuit Modeling (Torque Speed Curve of Induction Motor 1,1, Kw)
Squirrel cage induction motors are widely used in electric motor drives due to their satisfactory mechanical characteristics (torque, current, overloading) and small dimensions, as well as their low price. When starting an induction motor, a large current is required for magnetizing its core, which results in a low power factor, rotor power losses and a temperature rise in the windings. None of these parameters should reach values beyond certain limits until the motor reaches nominal speed. The speed of an induction motor 1,1kW is affected very little by fluctuations of voltage. The greater the supply voltage of the motor, the induction motor's speed will increase. The torque values (Tstart, TSmax and Tmax) are affected by the value of the motor supply voltage: (Vp-nl : 132.8, Tstart1 : 7.4, T S-max1 : 0.4, Tmax1 : 9.9) V, (Vp-nl : 127.0, Tstart2 : 4.8, T S-max1 : 0.3, Tmax1 : 8.4) V and (Vp-nl : 121.3, Tstart3 : 3.3, T S-max3 : 0.2, Tmax3 : 7.1) V. Stator current (IL-nl ; 2.5, 2.2, 1.9 ) Amp rises gradually on account of the increase in magnetising current (Im : 2.5, 2.2, 1.9) Amp. The magnetising current required to produce the stator flux. The component of the stator current which provides the ampere-turns balancing the rotor ampere-turns will steadily diminish as the rotor current (IL-nl) decrease with the increase in rotor speed (nr). 
Symmetry of Endomorphism Algebras
Motivated by recent problems regarding the symmetry of Hecke algebras, we
investigate the symmetry of the endomorphism algebra for a
-group and a -module with a field of characteristic . We
provide a complete analysis for cyclic -groups and the dihedral 2-groups.
For the dihedral 2-groups, this requires the classification of the
indecomposable modules in terms of string modules and band modules. We
generalize our techniques to consider for a Nakayama
algebra, a local algebra, or even an arbitrary algebra.Comment: Submitted to journal for publicatio
Forward-backward multiplicity correlations in the wounded nucleon model
The forward-backward multiplicity correlation strength is calculated for
arbitrary nucleus-nucleus collision in the framework of the wounded nucleon
model. Discussion of our results in the context of the recent STAR data in
Au+Au collisions at sqrt{s}=200 GeV is presented. It is suggested that the
observed (i) growth of the correlation coefficient with centrality and (ii)
approximately flat pseudorapidity dependence of the correlation strength for
central collisions are due to the fluctuations of the number of wounded
nucleons at a given centrality bin.Comment: 15 pages, 4 figures, accepted for publication in Phys. Rev. C.
Changed content: STAR data included, extended discussion, added reference
Selling packaged software: an ethical analysis
Within the IS literature there is little discussion on selling software products in general and especially
from the ethical point of view. Similarly, within computer ethics, although there is much interest in
professionalism and professional codes, in terms of accountability and responsibility, the spotlight
tends to play on safety-critical or life-critical systems, rather than on software oriented towards the
more mundane aspects of work organisation and society. With this research gap in mind, we offer a
preliminary ethical investigation of packaged software selling. Through an analysis of the features of
competition in the market, the global nature of the packaged software market and the nature of
product development we conclude that professionalism, as usually conceived in computer ethics, does
not apply particularly well to software vendors. Thus, we call for a broader definition of
professionalism to include software vendors, not just software developers. Moreover, we acknowledge
that with intermediaries, such as implementation consultants, involved in software selling, and the
packaged software industry more generally, there are even more “hands” involved. Therefore, we
contend that this is an area worthy of further study, which is likely to yield more on the question of
accountability
Magnetoconductance of the Corbino disk in graphene
Electron transport through the Corbino disk in graphene is studied in the
presence of uniform magnetic fields. At the Dirac point, we observe conductance
oscillations with the flux piercing the disk area , characterized by
the period , where () is the outer
(inner) disk radius. The oscillations magnitude increase with the radii ratio
and exceed 10% of the average conductance for in the case
of the normal Corbino setup, or for in the case of the
Andreev-Corbino setup. At a finite but weak doping, the oscillations still
appear in a limited range of , away from which
the conductance is strongly suppressed. At large dopings and weak fields we
identify the crossover to a normal ballistic transport regime.Comment: RevTeX, 5 pages, 3 figures. New version with minor revisions and
references added; to be published in Phys. Rev.
Topological energy bounds in generalized Skyrme models
The Skyrme model has a natural generalization amenable to a standard
hamiltonian treatment, consisting of the standard sigma model and the Skyrme
terms, a potential, and a certain term sextic in first derivatives. Here we
demonstrate that, in this theory, each pair of terms in the static energy
functional which may support topological solitons according to the Derrick
criterion (i.e., each pair of terms with opposite Derrick scaling) separately
posesses a topological energy bound. As a consequence, there exists a
four-parameter family of topological bounds for the full generalized Skyrme
model. The optimal bounds, i.e., the optimal values of the parameters, depend
both on the form of the potential and on the relative strength of the different
terms. It also follows that various submodels of the generalized Skyrme model
have one-parameter families of topological energy bounds. We also consider the
case of topological bounds for the generalized Skyrme model on a compact base
space as well as generalizations to higher dimensions.Comment: Latex, 26 pages, version accepted for publication in PRD,
presentation and motivation slightly changed, references added, results
unchange
Gauged BPS baby Skyrmions with quantised magnetic flux
A new type of gauged BPS baby Skyrme model is presented, where the derivative
term is just the Schroers current (i.e., gauge invariant and conserved version
of the topological current) squared. This class of models has a topological
bound saturated for solutions of the pertinent Bogomolnyi equations
supplemented by a so-called superpotential equation. In contrast to the gauged
BPS baby Skyrme models considered previously, the superpotential equation is
linear and, hence, completely solvable. Furthermore, the magnetic flux is
quantized in units of , which allows, in principle, to define this theory
on a compact manifold without boundary, unlike all gauged baby Skyrme models
considered so far.Comment: Latex, 17 page
Investigation of the Nicole model
We study soliton solutions of the Nicole model - a non-linear
four-dimensional field theory consisting of the CP^1 Lagrangian density to the
non-integer power 3/2 - using an ansatz within toroidal coordinates, which is
indicated by the conformal symmetry of the static equations of motion. We
calculate the soliton energies numerically and find that they grow linearly
with the topological charge (Hopf index). Further we prove this behaviour to
hold exactly for the ansatz. On the other hand, for the full three-dimensional
system without symmetry reduction we prove a sub-linear upper bound,
analogously to the case of the Faddeev-Niemi model. It follows that symmetric
solitons cannot be true minimizers of the energy for sufficiently large Hopf
index, again in analogy to the Faddeev-Niemi model.Comment: Latex, 35 pages, 1 figur
Theory of anharmonically modified Coriolis coupling in the S1 state of benzene and relation to experiment
Avoided crossings between quasidegenerate rovibrational states in the Doppler-free two-photon excitation of the 141 mode in the S1 excited state of benzene are treated theoretically. Two sets of avoided crossings in plots of spectral line frequency vs J at a given K and DeltaK have been reported experimentally between an initially prepared "light" state (141 in zeroth order) and dark states, namely, one which in zeroth order is a 51101161 state, the other being in zeroth order a 62111 and/or possibly a 31161 state, implicated earlier by Neusser et al. The identification of these states makes the phenomenon an excellent candidate for treatment of the avoided crossing via a Van Vleck transformation, no other basis set states being needed for the diagonalization in order to extract the important features. Two successive transformations are used for handling direct coupling and coupling via virtual states. The dominant calculated contribution to the coupling is, jointly, Coriolis plus cubic–cubic anharmonic interactions between vibrational modes.Playing less of a role are Coriolis terms in which the inverse moment of inertia tensor is expanded up to quadratic terms in the coordinates. There results a 5×5 (for coupling to 51101161 ) and a 3×3 (for coupling to 62111 or 31161 ) matrix of the transformed Hamiltonian, each of which can also be described, if desired, to a very good approximation by a 2×2 matrix. The coupling element V0 and the difference of the rotational constants for the light and dark states (DeltaB) are obtained from the plots of line position vs J(J+1) obtained. For the 141 to 51101161 and for the 141 to 62111 couplings the theoretical results are in reasonable agreement with the experimental results, no adjustable parameters being employed. For a coupling of 141 to 31161 the calculated V0 would be much too high compared with experiment (a factor of 10), the coupling involving the exchange of only three instead of four vibrational quanta. A situation in which the 141 state is coupled to the 62111 state to yield an avoided crossing and off-resonantly coupled to the 31161 state would be consistent with some experimental results and not affect the reasonable agreement of the slope difference and splitting for the avoided crossing plots
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