11,175 research outputs found
Modal Analysis of Grid Connected Doubly-Fed Induction Generators
This paper presents the modal analysis of a gridconnected doubly fed induction generator (DFIG). The change in modal properties for different system parameters, operating points, and grid strengths are computed and observed. The results offer a better understanding of theDFIG intrinsic dynamics,which can also be useful for control design and model justification. Index Terms—Doubly fed induction generator, eigenvalue analysis, nonlinear dynamic model, small-signal stability.Published versio
Proton Decay and Related Processes in Unified Models with Gauged Baryon Number:
In unification models based on SU(15) or SU(16), baryon number is part of the
gauge symmetry, broken spontaneously. In such models, we discuss various
scenarios of important baryon number violating processes like proton decay and
neutron-antineutron oscillation. Our analysis depends on the effective operator
method, and covers many variations of symmetry breaking, including different
intermediate groups and different Higgs boson content. We discuss processes
mediated by gauge bosons and Higgs bosons parallely. We show how accidental
global or discrete symmetries present in the full gauge invariant Lagrangian
restrict baryon number violating processes in these models. In all cases, we
find that baryon number violating interactions are sufficiently suppressed to
allow grand unification at energies much lower than the usual GeV.Comment: (32 pages LATEX) [DOE-ER\,40757-022, CPP-93-22] {Small changes made
and two references added. This version will appear in Phys. Rev. D
Gravitational decay of the Z-boson
We study the decay process of the Z boson to a photon and a graviton. The
most general form of the on-shell amplitude, subject to the constraints due to
the conservation of the electromagnetic and the energy-momentum tensor, is
determined. The amplitude is expressed in terms of three form factors, two of
which are CP-odd while one is CP-even. The latter, which is the only non-zero
form factor at the one-loop level, is computed in the standard model and the
decay rate is determined.Comment: 30 pages, Latex, uses Axodraw. (Some typographical errors corrected,
and some references added in the new version.
Report on the 68-bus, 16-machine, 5-area system
The present report refers to a small-signal stability study carried over the 68-Bus, 16-Machine, 5-Area System and validated on a widely known software package: MATLAB-Simulink (ver. 2012b). The 68-bus system is a reduced order equivalent of the inter-connected New England test system (NETS) and New York power system (NYPS), with five geographical regions out of which NETS and NYPS are represented by a group of generators whereas, the power import from each of the three other neighboring areas are approximated by equivalent generator models. This report has the objective to show how the simulation of this system must be done using MATLAB in order to get results that are comparable (and exhibit a good match with respect to the electromechanical modes) with the ones obtained using other commercial software packages and presented on the PES Task Force website on Benchmark Systems for Stability Controls
Physical Properties of OSIRIS-REx Target Asteroid (101955) 1999 RQ36 derived from Herschel, ESO-VISIR and Spitzer observations
In September 2011, the Herschel Space Observatory performed an observation
campaign with the PACS photometer observing the asteroid (101955) 1999 RQ36 in
the far infrared. The Herschel observations were analysed, together with ESO
VLT-VISIR and Spitzer-IRS data, by means of a thermophysical model in order to
derive the physical properties of 1999 RQ36. We find the asteroid has an
effective diameter in the range 480 to 511 m, a slightly elongated shape with a
semi-major axis ratio of a/b=1.04, a geometric albedo of 0.045 +0.015/-0.012,
and a retrograde rotation with a spin vector between -70 and -90 deg ecliptic
latitude. The thermal emission at wavelengths below 12 micron -originating in
the hot sub-solar region- shows that there may be large variations in roughness
on the surface along the equatorial zone of 1999 RQ36, but further measurements
are required for final proof. We determine that the asteroid has a
disk-averaged thermal inertia of Gamma = 650 Jm-2s-0.5K-1 with a 3-sigma
confidence range of 350 to 950 Jm-2s-0.5K-1, equivalent to what is observed for
25143 Itokawa and suggestive that 1999 RQ36 has a similar surface texture and
may also be a rubble-pile in nature. The low albedo indicates that 1999 RQ36
very likely contains primitive volatile-rich material, consistent with its
spectral type, and that it is an ideal target for the OSIRIS-REx sample return
mission.Comment: Accepted for publication in Astronomy & Astrophysics, 9 pages, 7
figure
Effect of different spawn rates and substrate supplementation on yield of Indian Oyster mushroom, Pleurotus pulmonarius (Fr.) Quel.
A study was conducted to evaluate the effect of different spawn rates and substrate supplementation on yield of Pleurotus pulmonarius (Fr.) Quel. Among six spawn rates viz., 0.5%, 1%, 2%, 4%, 6% and 8%, respectively tried on wheat straw substrate, the spawn run was fastest (10.50 days) when spawn dose was 8%, followed by 6%, 4%, 2%, 1% and 0.5%, respectively. The pinheads appeared in 12.27 days by using spawn @ 8%, which proved to be the best spawn dose followed by 6%, 4%, 2%, 1% and 0.5%, respectively. Highest yield of 168.7 per 200g dry substrate was achieved @ 8% spawn rate. Lesser yields were recorded when spawn rate was reduced. The results also reveals the significantly highest biological efficiency of 84.33% at 8% spawn rate followed by 6%, 4%, 2%, 1% and 0.5%, respectively. It was concluded that spawn run was rapid at higher spawn rate but there was not much difference in yield when spawn dose was increased from 4 to 8%. Considering spawn cost and performance shown by different doses, 2-4% was found optimum dose for its cultivation.In case of substrate supplementation, wheat straw supplemented with cotton seed meal supported maximum mycelial growth (10.50 days of inoculation) and took mini-mum time for pinheads initiation (13.67 days). Similarly, maximum yield (155.3g) with biological efficiency of 77.65% was recorded on wheat straw supplemented with cotton seed meal followed by supplementation of saw dust, wheat straw (control), calcium ammonium nitrate (CAN), ammonium nitrateand urea, respectively. These studies will help to mushroom growers for selecting the most suitable spawn rate and also opens viable option of supplementation as wheat straw + cotton seed meal for better growth behaviour and optimum yield potential of Pleurotus pulmonarius as well as other oyster mushrooms cultivation
SU(16) grandunification: breaking scales, proton decay and neutrino magnetic moment
We give a detailed renormalization group analysis for the SU(16) grandunified
group with general breaking chains in which quarks and leptons transform
separately at intermediate energies. Our analysis includes the effects of Higgs
bosons. We show that the grandunification scale could be as low as GeV and give examples where new physics could exist at relatively low
energy ( GeV). We consider proton decay in this model and show that
it is consistent with a low grandunification scale. We also discuss the
possible generation of a neutrino magnetic moment in the range of to
with a very small mass by the breaking of the embedded
SU(2) symmetry at a low energy.Comment: (16 pages in REVTEX + 6 figures not included) OITS-49
A Test System Model for Stability Studies of UK Power Grid
The paper presents a test system model to study the effect of variable wind power output on the stability of future power systems. The test system is built upon a future UK transmission system model and it contains different types of generators, HVDC transmission lines, and interconnections. A poorly damped inter-area mode is present in the test system that closely resembles the Scotland-England inter-area mode existing in the UK transmission system. The study system will help to analyze the impact of increased variability in power system operating conditions on the oscillatory mode. © 2013 IEEE
Light Metal Matrix Composites - Present Status & Future Strategies
The unique tailorability of the composites to meet the required properties has made them as advanced engineering materials . The continuous fibre reinforced metal
matrix composites were developed first . The high cost of the fibre as well as fabrication made them very expensive and hence they are used only in selected critical areas
of aerospace and defence . The invention of synthesising discontinuous reinforced metal matrix composites by stir casting initiated in India in the early seventies 1 s a landmark in the history of Metal Matrix Composites (MMC). The initial feasibility studies on making the composites with variety of dispersoids for tailoring new materials possessing special properties with lower cost had kindled interest in many R&D and academic institutions in India in the eighties . Extensive R&D activities were witnessed
during this period . The work carried out during this period can broadly be classified into processing methods . structure property correlation , specific property
evaluation , prototype component development and evaluation , etc. The expected impact of composite as an exciting engineering material did not take place in the nineties.The industries are still not receptive and their response is lukewann . At present,only selective academic and R&D Institutions in India are pursuing MMC activity on
a low profile . Eventhough similar trends in R&D were observed abroad in the developed countries wherein the industrial applications of composites specially in automotive and engineering industries is steadily increasing Indian industries are yet to think of using MMC components . This calls for a renewed concerted and sustaining effort,pooling up the resources and knowledge as well as consortium type approach among Indian R&D and Academic Institutions . The identified areas include generation of data bank on MMC and their properties. pilot plant production facility for demonstration of prototype developments under simulated industrial conditions , bringing down the cost by redesigning the components, etc
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