Atomic collisional data for neutral beam modeling in fusion plasmas

The injection of energetic neutral particles into the plasma of magnetic confinement fusion reactors is a widely-accepted method for heating such plasmas; various types of neutral beam are also used for diagnostic purposes. Accurate atomic data are required to properly model beam penetration into the plasma and to interpret photoemission spectra from both the beam particles themselves (e.g. beam emission spectroscopy) and from plasma impurities with which they interact (e.g. charge exchange recombination spectroscopy). This paper reviews and compares theoretical methods for calculating ionization, excitation and charge exchange cross sections applied to several important processes relevant to neutral hydrogen beams, including H + Be4+ and H + H+. In particular, a new cross section for the proton-impact ionization of H (1s) is recommended which is significantly larger than that previously accepted at fusion-relevant energies. Coefficients for an empirical fit function to this cross section and to that of the first excited states of H are provided and uncertainties estimated. The propagation of uncertainties in this cross section in modeling codes under JET-like conditions has been studied and the newly-recommended values determined to have a significant effect on the predicted beam attenuation. In addition to accurate calculations of collisional atomic data, the use of these data in codes modeling beam penetration and photoemission for fusion-relevant plasma density and temperature profiles is discussed. In particular, the discrepancies in the modeling of impurities are reported. The present paper originates from a Coordinated Research Project (CRP) on the topic of fundamental atomic data for neutral beam modeling that the International Atomic Energy Agency (IAEA) ran from 2017 to 2022; this project brought together ten research groups in the fields of fusion plasma modeling and collisional cross section calculations. Data calculated during the CRP is summarized in an appendix and is available online in the IAEA’s atomic database, CollisionDB

A História da Alimentação: balizas historiográficas

Os M. pretenderam traçar um quadro da História da Alimentação, não como um novo ramo epistemológico da disciplina, mas como um campo em desenvolvimento de práticas e atividades especializadas, incluindo pesquisa, formação, publicações, associações, encontros acadêmicos, etc. Um breve relato das condições em que tal campo se assentou faz-se preceder de um panorama dos estudos de alimentação e temas correia tos, em geral, segundo cinco abardagens Ia biológica, a econômica, a social, a cultural e a filosófica!, assim como da identificação das contribuições mais relevantes da Antropologia, Arqueologia, Sociologia e Geografia. A fim de comentar a multiforme e volumosa bibliografia histórica, foi ela organizada segundo critérios morfológicos. A seguir, alguns tópicos importantes mereceram tratamento à parte: a fome, o alimento e o domínio religioso, as descobertas européias e a difusão mundial de alimentos, gosto e gastronomia. O artigo se encerra com um rápido balanço crítico da historiografia brasileira sobre o tema

Copula-based inference for bivariate survival data with left truncation and dependent censoring

When pricing life annuity or insurance products issued to multiple lives, actuaries require a model for the survival of coupled lifetimes. For reasons of simplicity these multiple life premiums are often calculated under the assumption of independent lifetimes. In some circumstances this assumption is not realistic, and a number of correction methods based on bivariate survival data have been proposed in the actuarial literature. However, when we only observe the first occurring event time, the applicability of the models suggested for bivariate survival data turns out to be limited. The aim of this paper is to propose a copula-based analysis for bivariate survival data subject to left truncation and dependent censoring when only the first event time is observed. Our method is based on parametric marginals and parametric copulas. For this model, we show that the association between the survival and dependent censoring time is identifiable from the distribution of the observed data. The proposed model is estimated using maximum likelihood, which simultaneously estimates the marginal and dependency parameters. We also develop a goodness-of-fit test approach to examine the validity of the fitted copula model. Finally, our approach is illustrated on data from a large Canadian life insurance company. We hereby price joint and last-survivor annuities from data subject to left-truncation, administrative as well as dependent censoring

Copula-based inference for bivariate survival data with left truncation and dependent censoring

When pricing life annuity or insurance products issued to multiple lives, actuaries require a model for the survival of coupled lifetimes. For reasons of simplicity these multiple life premiums are often calculated under the assumption of independent lifetimes. In some circumstances this assumption is not realistic, and a number of correction methods based on bivariate survival data have been proposed in the actuarial literature. However, when we only observe the first occurring event time, the applicability of the models suggested for bivariate survival data turns out to be limited. The aim of this paper is to propose a copula-based analysis for bivariate survival data subject to left truncation and dependent censoring when only the first event time is observed. Our method is based on parametric marginals and parametric copulas. For this model, we show that the association between the survival and dependent censoring time is identifiable from the distribution of the observed data. The proposed model is estimated using maximum likelihood, which simultaneously estimates the marginal and dependency parameters. We also develop a goodness-of-fit test approach to examine the validity of the fitted copula model. Finally, our approach is illustrated on data from a large Canadian life insurance company. We hereby price joint and last-survivor annuities from data subject to left-truncation, administrative as well as dependent censoring

Variabilidade espacial dos parâmetros hidrodinâmicos de duas parcelas agrícolas no estado da Paraíba Spatial variability of hydrodynamic parameters in two agricultural plots in Paraíba state - Brazil

O conhecimento das curvas de retenção e da condutividade hidráulica da água do solo é indispensável para a modelagem do transporte de água e de poluentes em sistemas agrícolas. Essas propriedades são afetadas por numerosas fontes de variabilidade, geralmente associadas a fatores espacial e temporal, e relacionadas com o manejo agrícola. O objetivo desse trabalho foi analisar a variabilidade espacial dos parâmetros das curvas de retenção da água (van Genuchten) e da condutividade hidráulica (Brooks & Corey) da água do solo, obtidos com o método "Beerkan", que se baseia em ensaios de infiltração simplificados e nas informações texturais do solo. Esses parâmetros são de forma ou texturais (parâmetros de ajuste que dão forma às curvas) e de normalização ou estruturais (umidade volumétrica saturada, condutividade hidráulica saturada do solo e potencial de entrada de ar). Os ensaios de campo foram conduzidos em uma malha regular de 25 x 25 m num Neossolo Flúvico e num Latossolo Amarelo cultivados com feijão (Vigna unguiculata (L.) Walp.). Para ambos os solos, os valores dos parâmetros de forma, da umidade volumétrica saturada, dos logaritmos da condutividade hidráulica saturada e do potencial de entrada de ar apresentaram dependência espacial. Os valores da umidade volumétrica saturada e dos logaritmos do potencial de entrada de ar foram mais sensíveis à variação a pouca distância no Neossolo Flúvico do que do Latossolo Amarelo, com semivariogramas apresentando estruturas de variação com fraca dependência espacial.<br>Knowledge on soil hydraulic properties such as water retention and hydraulic conductivity curves is indispensable for water and pollutant transport modeling of agricultural systems. This soil hydraulic properties are affected by numerous sources of variability, mostly associated with spatial, temporal, and management-related factors. The objective of this study was to analyze the spatial variability of parameters of water retention (van Genuchten) and hydraulic conductivity (Brooks & Corey) curves obtained with the "Beerkan" method based on simple infiltration experiments and soil texture data. These parameters are related to shape or texture (fitting parameters that shape the curves) and normalization or structure (saturated water content, saturated hydraulic conductivity and air entry potential). The field tests were carried out in a 25 x 25 m grid in a Fluvent soil and in an Oxisoil planted with beans (Vigna Unguiculata (L.) Walp.). For both soils, spatial dependence was verified in the values of parameters of shape, saturated water content, logarithms of the saturated hydraulic conductivity and air entry potential. The values of saturated water content and air entry potential were more sensitive to variation at short distances in the Fluvent than in the Oxisoil. The spatial dependence in the variograms was weak