Search results for "Parametrization"
showing 10 items of 99 documents
First-forbidden transitions in reactor antineutrino spectra
2019
© 2019 American Physical Society. We study the dominant forbidden transitions in the antineutrino spectra of the fission actinides from 4 MeV onward using the nuclear shell model. Through explicit calculation of the shape factor, we show the expected changes in cumulative electron and antineutrino spectra. Relative to the allowed approximation this results in a minor decrease of electron spectra above 4 MeV, whereas an increase of several percent is observed in antineutrino spectra. We show that forbidden transitions dominate the spectral flux for most of the experimentally accessible range. Based on the shell model calculations we attempt a parametrization of forbidden transitions and prop…
Multivariate GARCH estimation via a Bregman-proximal trust-region method
2011
The estimation of multivariate GARCH time series models is a difficult task mainly due to the significant overparameterization exhibited by the problem and usually referred to as the "curse of dimensionality". For example, in the case of the VEC family, the number of parameters involved in the model grows as a polynomial of order four on the dimensionality of the problem. Moreover, these parameters are subjected to convoluted nonlinear constraints necessary to ensure, for instance, the existence of stationary solutions and the positive semidefinite character of the conditional covariance matrices used in the model design. So far, this problem has been addressed in the literature only in low…
Design and analysis of a one-dimensional sea surface simulator using the sum-of-sinusoids principle
2015
Simulators for sea surface waves are useful for many practical applications, such as the construction of offshore structures and ocean surface animations. This paper studies three methods for the design of one-dimensional sea surface waves simulators with given wave spectra using the sum-of-sinusoids (SOS) principle. The wave spectrum provides insight into important statistical properties of the sea surface waves, such as the autocorrelation function (ACF) of the sea surface waves, significant wave height, and the moments of the spectrum. The sea surface simulator is designed by applying the concept of deterministic channel modelling on two main classical wave spectra, namely the Pierson-Mo…
2018
We show that the measured intrinsic octupole moments of $^{220}\mathrm{Rn}$, $^{224}\mathrm{Ra}$, and $^{226}\mathrm{Ra}$ constrain the intrinsic Schiff moments of $^{225}\mathrm{Ra}$, $^{221}\mathrm{Rn}$, $^{223}\mathrm{Rn}$, $^{223}\mathrm{Fr}$, $^{225}\mathrm{Ra}$, and $^{229}\mathrm{Pa}$. The result is a dramatically reduced uncertainty in intrinsic Schiff moments. Direct measurements of octupole moments in odd nuclei will reduce the uncertainty even more. The only significant source of nuclear-physics error in the laboratory Schiff moments will then be the intrinsic matrix elements of the time-reversal noninvariant interaction produced by $CP$-violating fundamental physics. Those matri…
One loop integrals revisited
1992
We present a new calculation of the well-known one-loop two-point scalar and tensor functions. We also present a systematic reduction to a certain class of functions which minimizes the effort for calculating tensor integrals drastically. We avoid standard techniques such as Feynman parametrization and Wick rotation.
Probing nucleons with photons at the quark level
2014
The description of electromagnetic interactions with hadrons from the quark level requires knowledge of the underlying quark-gluon ingredients. I discuss some properties of the quark-photon vertex and quark Compton vertex, along with the role of electromagnetic gauge invariance and vector-meson dominance. A simple parametrization for the quark-photon vertex is given.
Applying Numerical Weather Prediction Models to the Production of New European Wind Atlas : Sensitivity studies of the wind climate to the planetary …
2018
Reliable and precise information about the wind speed climate is crucial for the development of wind energy. Meteorological processes in the mesoscale (2 – 200 km) can be represented using Numerical Weather Prediction (NWP) models such as the Weather Research and Forecast model (WRF), but before their application for creating wind energy atlases, their results and sensitivity to modelling parameters should be investigated. Here the WRF model wind speed results for the year 2015 for the Baltic Sea region are investigated, and the effect of the planetary boundary layer parametrization scheme is analyzed.
Capability of a high resolution hydroclimatic modelling chain to simulate soil water deficit indices for Douglas-fir and common Beeches over Burgundy.
2016
During the 2003 drought and heat wave event, douglas-fir and common beech stands in Burgundy have been heavily affected, and presented symptoms of dieback and mortality. This event seems to be the first occurrence of expected climatic changes in the near future and questions their sustainability in Burgundy since their climate vulnerability is mainly due to the amplitude and accumulated water constraints exercised during their growing cycle. In the context of climate change and in order to provide information to forest managers who partly rely on a mapping of the climatic constraints until the end of this century, this work explores the ability of a high resolution hydroclimatic modelling c…
Capacity of a high resolution hydroclimatic modelling chair to simulate soil water deficit indexes for Douglas-fir and common Beeches over Burgundy
2016
During the 2003 drought and heat wave event, douglas-fir and common beech stands in Burgundy have been heavily affected, and presented symptoms of dieback and mortality. This event seems to be the first occurrence of expected climatic changes in the near future and questions their sustainability in Burgundy since their climate vulnerability is mainly due to the amplitude and accumulated water constraints exercised during their growing cycle. In the context of climate change and in order to provide information to forest managers who partly rely on a mapping of the climatic constraints until the end of this century, this work explores the ability of a high resolution hydroclimatic modelling c…
The effect of disorder on optical spectra of conjugated polymers
1993
Abstract Using the semi-empirical parametrization of the Pariser-Parr-Pople model we determine the excitonic states in conjugated polymers. The employed parameters correspond to a moderate strength of the long-range Coulomb interaction. In order to take the disorder into account, the nearest-neighbour transfer matrix elements are chosen according to a random distribution. Averaging the results over a large number of chains of 100 sites, which are known to be sufficiently long so that finite-size effects become negligible, we obtain the linear and third-order nonlinear optical susceptibilities. With increasing disorder the linear absorption, the two-photon absorption and the third-harmonic g…