9,229 research outputs found
Reduction of cogging torque in interior-magnet brushless machines
An investigation into the cogging torque in a four-pole interior-magnet brushless machines having either a six-slot stator and a short-pitched nonoverlapping winding or a 12-slot stator and a full-pitched overlapping winding is described. It is shown by finite-element analyses and measurements that, by appropriately defining the pole-arc to pole-pitch ratio, the optimal pole-arc to pole-pitch ratio for minimum cogging torque, which has been derived for surface-mounted magnet machines, is equally applicable to interior-magnet machines
The cohomology of superspace, pure spinors and invariant integrals
The superform construction of supersymmetric invariants, which consists of
integrating the top component of a closed superform over spacetime, is
reviewed. The cohomological methods necessary for the analysis of closed
superforms are discussed and some further theoretical developments presented.
The method is applied to higher-order corrections in heterotic string theory up
to \a'^3. Some partial results on and are also given.Comment: 24 pages. Minor changes; added reference
The Schwinger SU(3) construction - I: Multiplicity problem and relation to induced representations
The Schwinger oscillator operator representation of SU(3) is analysed with
particular reference to the problem of multiplicity of irreducible
representations. It is shown that with the use of an unitary
representation commuting with the SU(3) representation, the infinity of
occurrences of each SU(3) irreducible representation can be handled in complete
detail. A natural `generating representation' for SU(3), containing each
irreducible representation exactly once, is identified within a subspace of the
Schwinger construction; and this is shown to be equivalent to an induced
representation of SU(3).Comment: Latex, 25 page
The Threebrane Soliton of the M-Fivebrane
We discuss the supersymmetry algebra of the M theory fivebrane and obtain a
new threebrane soliton preserving half of the six-dimensional supersymmetry.
This solution is dimensionally reduced to various D-p-branes.Comment: 10 pages, phyzz
A New Massive Type IIA Supergravity From Compactification
We consider the most general form for eleven dimensional supersymmetry
compatible with on-shell superfields. This allows for the introduction of a
conformal Spin(1,10) connection. In eleven dimensional Minkowski space this
modification is trivial and can be removed by a field redefinition, however,
upon compactification on S^1 it is possible to introduce a non-trivial `Wilson
line'. The resulting ten dimensional supergravity has massive 1-form and 3-form
potentials and a cosmological constant. This theory does not possess a
supersymmetric eightbrane soliton but it does admit a supersymmetric non-static
cosmological solution.Comment: 13 pages, phyzzx. The introduction is clarifed and a reference adde
The coronavirus outbreak: the central role of primary care in emergency preparedness and response
On the last day of 2019, a cluster of cases of a pneumonia with unknown cause were reported by the Chinese authorities to the World Health Organization (WHO), believed to be connected to a seafood market in Wuhan, China. This market was closed the following day. On 7 January 2020, a novel coronavirus was isolated, and known pathogens were ruled out.1 Coronaviruses usually cause respiratory illness ranging from the common cold to severe acute respiratory syndrome (SARS). Clinical symptoms and signs of the Wuhan coronavirus include fever, with some sufferers experiencing difficulty breathing and bilateral pulmonary infiltrates seen on chest X-ray. WHO are referring to it as ‘2019-nCov’. At the time of writing, there have been over 4,500 confirmed cases and 106 deaths, including among healthcare workers. Over 98% of these cases are within mainland China, but cases have also been confirmed in tens of other countries
Amplitude and frequency control of a vibratory pile driver
Abstract—This paper describes the digital control of a vibratory pile driver in which the vibration is generated via two tandem pairs of electrically driven, geared, contra-rotating eccentrics. Experimental results are included to show the controller-induced system dynamics for a variety of load condtions, and to highlight the fact that, if the relative phase of the eccentric pairs is not controlled, the
natural tendency at high excitation frequency is for the pile driver to operate with a low vibration amplitude. An analytical technique for identifying the system parameters is presented, and analytical performance predictions are compared with experimental results. Analysis of the power flow in the system shows that, although significant
power transfer occurs between the two electrical drives,
the net power dissipation during pile driving is relatively low
Kappa-symmetry for coincident D-branes
A kappa-symmetric action for coincident D-branes is presented. It is valid in
the approximation that the additional fermionic variables, used to incorporate
the non-abelian degrees of freedom, are treated classically. The action is
written as a Bernstein-Leites integral on the supermanifold obtained from the
bosonic worldvolume by adjoining the extra fermions. The integrand is a very
simple extension of the usual Green-Schwarz action for a single brane; all
symmetries, except for kappa, are manifest, and the proof of kappa-symmetry is
very similar to the abelian case.Comment: 18 pages. References adde
D=3, N=8 conformal supergravity and the Dragon window
We give a superspace description of D=3, N=8 supergravity. The formulation is
off-shell in the sense that the equations of motion are not implied by the
superspace constraints (but an action principle is not given). The multiplet
structure is unconventional, which we connect to the existence of a "Dragon
window", that is modules occurring in the supercurvature but not in the
supertorsion. According to Dragon's theorem this cannot happen above three
dimensions. We clarify the relevance of this window for going on the conformal
shell, and discuss some aspects of coupling to conformal matter.Comment: plain tex, 24 pp v2: minor change
Design of robust current tracking control for active power filters
The paper describes a design methodology for robust current-tracking control of active power filters using quantitative feedback theory (QFT). The design aim is to address system issues of power quality and power factor correction in a double-sided converter (rectifierhverter combination) subject to parametric uncertainty, non-linear dynamic behavior and exogenous disturbances. The paper includes simulation results to demonstrate the dynamic performance attributes afforded to the resulting closed-loop control system, and to verify the design procedure
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