1,093 research outputs found
Optimized Control of a Novel DC/3AC Converter Topology with Reduced Component Effort
A previously proposed traction converter topology can reduce component effort and converter volume by decreasing the pulsed voltage across the DC-converter inductance. However, the maximum voltage across the machine phases then becomes a function of the DC source voltage. In this paper, an optimization is presented to ensure a constant maximum phase voltage over a wide source voltage spread
LHC Phenomenology of an Extended Standard Model with a Real Scalar Singlet
Gauge singlet extensions of the Standard Model (SM) scalar sector may help
remedy its theoretical and phenomenological shortcomings while solving
outstanding problems in cosmology. Depending on the symmetries of the scalar
potential, such extensions may provide a viable candidate for the observed
relic density of cold dark matter or a strong first order electroweak phase
transition needed for electroweak baryogenesis. Using the simplest extension of
the SM scalar sector with one real singlet field, we analyze the generic
implications of a singlet-extended scalar sector for Higgs boson phenomenology
at the Large Hadron Collider (LHC). We consider two broad scenarios: one in
which the neutral SM Higgs and singlet mix and the other in which no mixing
occurs and the singlet can be a dark matter particle. For the first scenario,
we analyze constraints from electroweak precision observables and their
implications for LHC Higgs phenomenology. For models in which the singlet is
stable, we determine the conditions under which it can yield the observed relic
density, compute the cross sections for direct detection in recoil experiments,
and discuss the corresponding signatures at the LHC.Comment: 39 pages, 11 figures, 2 table
Dynamical Solutions to the Horizon and Flatness Problems
We discuss in some detail the requirements on an early-Universe model that
solves the horizon and flatness problems during the epoch of classical
cosmology (). We show that a dynamical resolution of
the horizon problem requires superluminal expansion (or very close to it) and
that a truly satisfactory resolution of the flatness problem requires entropy
production. This implies that a proposed class of adiabatic models in which the
Planck mass varies by many orders of magnitude cannot fully resolve the
flatness problem. Furthermore, we show that, subject to minimal assumptions,
such models cannot solve the horizon problem either. Because superluminal
expansion and entropy production are the two generic features of inflationary
models, our results suggest that inflation, or something very similar, may be
the only dynamical solution to the horizon and flatness problems.Comment: 17 page
Ribbons on the CBR Sky: A Powerful Test of a Baryon Symmetric Universe
If the Universe consists of domains of matter and antimatter, annihilations
at domain interfaces leave a distinctive imprint on the Cosmic Background
Radiation (CBR) sky. The signature is anisotropies in the form of long, thin
ribbons of width , separated by angle where L is the characteristic domain size, and
y-distortion parameter . Such a pattern could potentially be
detected by the high-resolution CBR anisotropy experiments planned for the next
decade, and such experiments may finally settle the question of whether or not
our Hubble volume is baryon symmetric.Comment: LaTeX, 10 pages, 4 figures in epsf. Revised version corrects a couple
of relevant mistake
Towards representing human behavior and decision making in Earth system models. An overview of techniques and approaches
Today, humans have a critical impact on the Earth system and vice versa, which can generate complex feedback processes between social and ecological dynamics. Integrating human behavior into formal Earth system models (ESMs), however, requires crucial modeling assumptions about actors and their goals, behavioral options, and decision rules, as well as modeling decisions regarding human social interactions and the aggregation of individuals’ behavior. Here, we review existing modeling approaches and techniques from various disciplines and schools of thought dealing with human behavior at different levels of decision making. We demonstrate modelers’ often vast degrees of freedom but also seek to make modelers aware of the often crucial consequences of seemingly innocent modeling assumptions. After discussing which socioeconomic units are potentially important for ESMs, we compare models of individual decision making that correspond to alternative behavioral theories and that make diverse modeling assumptions about individuals’ preferences, beliefs, decision rules, and foresight. We review approaches to model social interaction, covering game theoretic frameworks, models of social influence, and network models. Finally, we discuss approaches to studying how the behavior of individuals, groups, and organizations can aggregate to complex collective phenomena, discussing agent-based, statistical, and representative-agent modeling and economic macro-dynamics. We illustrate the main ingredients of modeling techniques with examples from land-use dynamics as one of the main drivers of environmental change bridging local to global scales
Freezing of Spinodal Decompostion by Irreversible Chemical Growth Reaction
We present a description of the freezing of spinodal decomposition in
systems, which contain simultaneous irreversible chemical reactions, in the
hydrodynamic limit approximation. From own results we conclude, that the
chemical reaction leads to an onset of spinodal decomposition also in the case
of an initial system which is completely miscible and can lead to an extreme
retardation of the dynamics of the spinodal decomposition, with the probability
of a general freezing of this process, which can be experimetally observed in
simultaneous IPN formation.Comment: 10 page
Measurement of Two-Level Inverter Induced Current Slopes at High Switching Frequencies for Control and Identification Algorithms of Electrical Machines
Several modern control and online identification algorithms for electrical machines are based on fast current slope detection. This paper shows and compares several identification methods for the inverter induced current slopes at high switching frequencies and high bandwidth of the measured signal. Test bench measurements with a SiC-MOSFET-inverter with switching frequencies up to and an RL-load are used to compare the different identification methods. Best results among the investigated methods have been achieved with an easy implementable printed circuit board (PCB) design of a planar Rogowski coil
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