3,254 research outputs found
An on-line harmonics elimination PWM scheme for three-phase voltage source inverters
An on-line harmonic elimination PWM (HEPWM) scheme for three-phase voltage source inverters is proposed. It is based on curve fitting method derived from the trajectories of the exact (off-line) HEPWM angles. The
main advantage of the technique is its fast and efficient
realization using a microprocessor. An outline to obtain the switching angles is presented. The method is proven by
experimental result
Estimates of Radiation by Superluminal Neutrinos
We show that the more energetic superluminal neutrinos with quadratically
dispersed superluminalities \delta=\beta^2-1, for \beta=v/c where v is the
neutrino velocity, also lose significant energy to radiation to the \nu+e^-+e^+
final state in travelling from CERN to Gran Sasso as has been shown to occur
for those with constant superluminality by Cohen and Glashow if indeed \delta
\simeq 5\times 10^{-5}. In addition, we clarify the dependence of such
radiative processes on the size of the superluminality.Comment: 6 pages, no figures; text re-arranged for journal purposes; improved
references; published version(title changed by Editors
AC voltage regulation of a bidirectional high-frequency link converter using a deadbeat controller
This paper presents a digital controller for AC voltage regulation of a bidirectional high-frequency link (BHFL) inverter using Deadbeat control. The proposed controller consists of inner current loop, outer voltage loop and a feed-forward controller, which imposes a gain scheduling effect according to the reference signal to compensate the steady-state error of the system. The main property of the proposed controller is that the current- and the voltage-loop controllers have the same structure, and use the same sampling period. This simplifies the design and implementation processes. To improve the overall performance of the system, additional disturbance decoupling networks are employed. This takes into account
the model discretization effect. Therefore, accurate
disturbance decoupling can be achieved, and the system
robustness towards load variations is increased. To avoid
transformer saturation due to low frequency voltage envelopes, an equalized pulse width modulation (PWM)
technique has been introduced. The proposed controller
has been realized using the DS1104 digital signal processor
(DSP) from dSPACE. Its performances have been tested on
a one kVA prototype inverter. Experimental results showed
that the proposed controller has very fast dynamic and good
steady-state responses even under highly nonlinear loads
BFKL at next-to-leading order
This is a summary of the contributions on the next-to-leading order
corrections to the BFKL equation which were presented to the `Small-x and
Diffraction' working group at the 1998 Durham Workshop on HERA Physics.Comment: 6 pages, 2 figure
SEIRD Model for Qatar Covid-19 Outbreak: A Case Study
The Covid-19 outbreak of 2020 has required many governments to develop
mathematical-statistical models of the outbreak for policy and planning
purposes. This work provides a tutorial on building a compartmental model using
Susceptibles, Exposed, Infected, Recovered and Deaths status through time. A
Bayesian Framework is utilized to perform both parameter estimation and
predictions. This model uses interventions to quantify the impact of various
government attempts to slow the spread of the virus. Predictions are also made
to determine when the peak Active Infections will occur
The spread of the gluon k_t-distribution and the determination of the saturation scale at hadron colliders in resummed NLL BFKL
The transverse momentum distribution of soft hadrons and jets that accompany
central hard-scattering production at hadron colliders is of great importance,
since it has a direct bearing on the ability to separate new physics signals
from Standard Model backgrounds. We compare the predictions for the gluonic
k_t-distribution using two different approaches: resummed NLL BFKL and DGLAP
evolution. We find that as long as the initial and final virtualities (k_t)
along the emission chain are not too close to each other, the NLL resummed BFKL
results do not differ significantly from those obtained using standard DGLAP
evolution. The saturation momentum Q_s(x), calculated within the resummed BFKL
approach, grows with 1/x even slower than in the leading-order DGLAP case.Comment: 24 pages, 8 figures, An improved, slightly more precise NLL
resummation is used and the figures are updated accordingly. The conclusions
are unchange
Static and dynamic modifications to photon absorption:The effects of surrounding chromophores
This Letter investigates the influence, on the molecular absorption of light, of surrounding chromophores. Two novel rate contributions are identified - one vanishing for a medium with no static dipole moment. The other, dynamic term is used to model a system of primary absorbers and secondary chromophores distributed in a host medium. Further modification provides a basis for modelling a case where the medium is, itself, marginally absorptive, thus accounting for optical losses as the input propagates through the surrounding host. The results facilitate tailoring of secondary chromophore and host effects in the pursuit of materials with specific absorption features
Dynamics of the dispersion interaction in an energy transfer system
On the propagation of resonant radiation through an optically dense system, photon capture is commonly followed by one or more near-field transfers of the resulting optical excitation. The process invokes secondary changes to the local electronic environment, shifting the electromagnetic interactions between participant chromophores and producing modified intermolecular forces. From the theory it emerges that energy transfer, when it occurs between chromophores with electronically dissimilar properties, can itself generate significant changes in the intermolecular potentials. This report highlights specific effects that can be anticipated when laser light propagates across an interface between differentially absorbing components in a model energy transfer system
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