A unified IMEX Runge-Kutta approach for hyperbolic systems with multiscale relaxation

In this paper we consider the development of Implicit-Explicit (IMEX) Runge-Kutta schemes for hyperbolic systems with multiscale relaxation. In such systems the scaling depends on an additional parameter which modifies the nature of the asymptotic behavior which can be either hyperbolic or parabolic. Because of the multiple scalings, standard IMEX Runge-Kutta methods for hyperbolic systems with relaxation loose their efficiency and a different approach should be adopted to guarantee asymptotic preservation in stiff regimes. We show that the proposed approach is capable to capture the correct asymptotic limit of the system independently of the scaling used. Several numerical examples confirm our theoretical analysis

Implicit-Explicit Runge-Kutta schemes for hyperbolic systems and kinetic equations in the diffusion limit

We consider Implicit-Explicit (IMEX) Runge-Kutta (R-K) schemes for hyperbolic systems with stiff relaxation in the so-called diffusion limit. In such regime the system relaxes towards a convection-diffusion equation. The first objective of the paper is to show that traditional partitioned IMEX R-K schemes will relax to an explicit scheme for the limit equation with no need of modification of the original system. Of course the explicit scheme obtained in the limit suffers from the classical parabolic stability restriction on the time step. The main goal of the paper is to present an approach, based on IMEX R-K schemes, that in the diffusion limit relaxes to an IMEX R-K scheme for the convection-diffusion equation, in which the diffusion is treated implicitly. This is achieved by an original reformulation of the problem, and subsequent application of IMEX R-K schemes to it. An analysis on such schemes to the reformulated problem shows that the schemes reduce to IMEX R-K schemes for the limit equation, under the same conditions derived for hyperbolic relaxation. Several numerical examples including neutron transport equations confirm the theoretical analysis

Semi-Implicit-type order-adaptive CAT2 schemes for systems of balance laws with relaxed source term

In this paper we present two semi-implicit-type second order Compact Approximate Taylor (CAT2) numerical schemes and blend them with a local a posteriori Multi-dimensional Optimal Order Detection (MOOD) paradigm to solve hyperbolic systems of balance laws with relaxed source term. The resulting scheme presents high accuracy when applied to smooth solutions, essentially non-oscillatory behavior for irregular ones, and offers a nearly fail-safe property in terms of ensuring positivity. The numerical results obtained from a variety of test cases, including smooth and non-smooth well-prepared and unprepared initial condition, assessing the appropriate behavior of the semi-implicit-type second order CATMOOD schemes. These results have been compared in accuracy and efficiency with a second order semi-implicit Runge-Kutta (RK) method

Implicit and semi-implicit well-balanced finite-volume methods for systems of balance laws

The aim of this work is to design implicit and semi-implicit high-order well-balanced finite-volume numerical methods for 1D systems of balance laws. The strategy introduced by two of the authors in some previous papers for explicit schemes based on the application of a well-balanced reconstruction operator is applied. The well-balanced property is preserved when quadrature formulas are used to approximate the averages and the integral of the source term in the cells. Concerning the time evolution, this technique is combined with a time discretization method of type RK-IMEX or RK-implicit. The methodology will be applied to several systems of balance laws.This work is partially supported by projects RTI2018-096064-B-C21 funded by MCIN/AEI/10.13039/501100011033 and “ERDF A way of making Europe”, projects P18-RT-3163 of Junta de Andalucía and UMA18-FEDERJA-161 of Junta de Andalucía-FEDER-University of Málaga. G.Russo and S.Boscarino acknowledge partial support from the Italian Ministry of University and Research (MIUR), PRIN Project 2017 (No. 2017KKJP4X) entitled “Innovative numerical methods for evolu-tionary partial differential equations and applications”. I. Gómez-Bueno is also supported by a Grant from “El Ministerio de Ciencia, Innovación y Universidades”, Spain (FPU2019/01541) funded by MCIN/AEI/10.13039/501100011033 and “ESF Invest-ing in your future”. // Funding for open access charge: Universidad de Málaga/CBUA

CWI at TREC 2012, KBA track and Session Track

We participated in two tracks: Knowledge Base Acceleration (KBA) Track and Session Track. In the KBA track, we focused on experi- menting with different approaches as it is the first time the track is launched. We experimented with supervised and unsupervised re- trieval models. Our supervised approach models include language models and a string-learning system. Our unsupervised approaches include using: 1)DBpedia labels and 2) Google-Cross-Lingual Dic- tionary (GCLD). While the approach that uses GCLD targets the central and relvant bins, all the rest target the central bin. The GCLD and the string-learning system have outperformed the oth- ers in their respective targeted bins. The goal of the Session track submission is to evaluate whether and how a logic framework for representing user interactions with an IR system can be used for improving the approximation of the relevant term distribution that another system that is supposed to have access to the session infor- mation will then calculate. the documents in the stream corpora. Three out of the seven runs used a Hadoop cluster provide by Sara.nl to process the stream cor- pora. The other 4 runs used a federated access to the same corpora distributed among 7 workstations

Mental Health in New York City After the September 11 Terrorist Attacks: Results From Two Population Surveys

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/40345/2/Galea_Mental Health in New York city After_2002.pd

EFECTOS DEL ESTRÉS COMBINADO DE ALTA TEMPERATURA Y DEFICIENCIA DE AGUA EN LA FLORACIÓN FEMENINA, MASCULINA Y EL NÚMERO DE GRANOS EN MAÍZ.

Extremely high temperatures and water deficits commonly affect crop productivity worldwide (Prasad et al., 2008; Lobell et al., 2013). The frequency of these events may increase as a result of global warming (Rezaei et al., 2015; IPCC, 2023; Heino et al., 2023) impacting to a greater extent in low latitudes with high probability of heat stress during crop growth and development (Easterling et al., 1997). Feng et al. (2020), in a global analysis, determined that Argentina is among the seven producing countries with the highest probability of occurrence of events with high temperatures and water deficit. Thus, the increase in the frequency and magnitude of heat stress (TS) due to high temperature and water deficit (DH) are among the main abiotic constraints with considerable adverse effects on maize yield (Lobell and Field, 2007; Hatfield et al., 2011). The number of grains (NG) is the component that explains most of the variations in maize yield (Tollenaar et al., 1992). The most critical time for NG determination in maize is around flowering (e.g., Tollenaar et al., 1992; Carrera et al., 2023). In particular, it was shown that the effects of ET on NG reduction were greatest between stigma emission and 15-17 days after stigma emission (Rattalino Edreira and Otegui, 2013; Neiff et al., 2016; Shim et al., 2017), coinciding with the period of maximum susceptibility to DH (Ouattar et al., 1987). Both the occurrence of ET or DH often result in the lag between the anthesis-stigmas interval (Cairns et al., 2013; Trachsel et al., 2016; Wang et al. 2019), leading to NG declines. Episodes of ET often reduce the pollen release period (PLP) and its daily production (Wang, 2019), as well as the % of viable pollen grains (Alam et al., 2017).Las temperaturas extremadamente altas y el déficit hídrico comúnmente afectan la productividad de los cultivos en el mundo (Prasad et al., 2008; Lobell et al., 2013). La frecuencia de estos eventos puede aumentar como resultado del calentamiento global (Rezaei et al., 2015; IPCC, 2023; Heino et al., 2023) impactando en mayor medida en latitudes bajas con alta probabilidad de golpes de calor durante el crecimiento y desarrollo de los cultivos (Easterling et al., 1997). Feng et al. (2020), en un análisis global, determinaron que Argentina se encuentra dentro de los siete países productores que presentan una mayor probabilidad de ocurrencia de eventos con altas temperaturas y déficit hídrico. Así, el aumento de la frecuencia y la magnitud del estrés térmico (ET) por alta temperatura y déficit hídrico (DH) son unas de las principales limitantes abióticas con efectos adversos considerables en el rendimiento de maíz (Lobell y Field, 2007; Hatfield et al., 2011). El número de granos (NG) es el componente que explica en mayor medida las variaciones en rendimiento de maíz (Tollenaar et al., 1992). El momento más crítico para la determinación del NG en maíz es alrededor de su floración (e.g., Tollenaar et al., 1992; Carrera et al., 2023). En particular se demostró que los efectos del ET sobre la reducción en NG fueron mayores entre la emisión de estigmas y 15-17 días posteriores a la misma (Rattalino Edreira y Otegui, 2013; Neiff et al., 2016; Shim et al., 2017), coincidente con el periodo de máxima susceptibilidad al DH (Ouattar et al., 1987). Tanto la ocurrencia de ET o DH a menudo producen el desfase entre el intervalo antesis-estigmas (Cairns et al., 2013; Trachsel et al., 2016; Wang et al. 2019), lo cual conlleva a disminuciones del NG. Episodios de ET a menudo reducen el periodo de liberación de polen (PLP) y su producción diaria (Wang, 2019), como así también el % de granos de polen viables (Alam et al., 2017). Además, se han reportado reducciones del número total de flores pistiladas y disminuciones de estigmas exertos por fuera de las chalas atribuibles a episodios de ET con diferencias genotípicas (Rattalino Edreira et al. 2011; Liu et al., 2020). A menudo, los genotipos con germoplasma tropical han presentado una mayor tolerancia al ET (Rattalino Edreira y Otegui, 2012; Mayer et al., 2016) que los híbridos templados. Sin embargo, gran parte de los híbridos sembrados en el Nordeste Argentino poseen genética de origen templada. Por su parte, el DH durante el PC también produce importantes reducciones en el NG como consecuencia delretraso en la emergencia de los estigmas y el fallo en el cuaje de los granos (i.e., aborto; Westgate y Boyer, 1986; Bassetti y Westgate, 1993). La principal causa de aborto de granos ocurre por la escasez de asimilados hacia los ovarios fecundados (Westgate y Boyer 1986; McLaughlin y Boyer, 2004) que son resultado de las bajas tasas de crecimiento (Andrade et al., 2002; Nagore et al., 2017). Más aún, la aparición y el número total de estigmas y su relación con el porcentaje de cuaje fueron estudiados para estreses individuales por ET (Rattalino et al., 2011), DH (Otegui et al., 1995) y nitrógeno (Rossini et al., 2020), no existiendo estudios a campo que proporcionen información bajo ET*DH y que contrasten genotipos de distinto origen (templado vs. subtropical). La mayoría de los estudios en maíz se han centrado en los efectos del ET y DH como factores de estrés individuales. Sin embargo, varios estudios revelan que los efectos combinados del ET*DH reducen en mayor medida el rendimiento del cultivo maíz respecto a estreses individuales (Neiff et al., 2015; Meseka et al., 2018; Hussain et al., 2019; Nelimor et al., 2019). Además, la tolerancia de híbridos de maíz a estreses individuales no confirió tolerancia al ET*DH combinado (Mittler et al., 2006; Cairns et al., 2013). Por lo tanto, y considerando la escasez de estudios en condiciones de campo que combinen la incidencia de ET*DH y que contrasten genotipos de distinto origen, este trabajo tiene como objetivos: (i) caracterizar la floración masculina (período de liberación, producción y viabilidad de polen) y femenina (número de estigmas totales y exertos), (ii) cuantificar el intervalo antesis-emisión estigmas y (iii)establecer el impacto en el número de granos y su relación con las variables mencionadas

Mental Health Service and Medication Use in New York City After the September 11, 2001, Terrorist Attack

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/40261/2/Boscarino_Mental Health Service and Medication Use_2004.pd

Uncertainty quantification for kinetic models in socio-economic and life sciences

Kinetic equations play a major rule in modeling large systems of interacting particles. Recently the legacy of classical kinetic theory found novel applications in socio-economic and life sciences, where processes characterized by large groups of agents exhibit spontaneous emergence of social structures. Well-known examples are the formation of clusters in opinion dynamics, the appearance of inequalities in wealth distributions, flocking and milling behaviors in swarming models, synchronization phenomena in biological systems and lane formation in pedestrian traffic. The construction of kinetic models describing the above processes, however, has to face the difficulty of the lack of fundamental principles since physical forces are replaced by empirical social forces. These empirical forces are typically constructed with the aim to reproduce qualitatively the observed system behaviors, like the emergence of social structures, and are at best known in terms of statistical information of the modeling parameters. For this reason the presence of random inputs characterizing the parameters uncertainty should be considered as an essential feature in the modeling process. In this survey we introduce several examples of such kinetic models, that are mathematically described by nonlinear Vlasov and Fokker--Planck equations, and present different numerical approaches for uncertainty quantification which preserve the main features of the kinetic solution.Comment: To appear in "Uncertainty Quantification for Hyperbolic and Kinetic Equations