Fundamentals of 3-D Neutron Kinetics and Current Status

This lecture includes the following topics: 1) A summary of the cell and lattice calculations used to generate the neutron reaction data for neutron kinetics, including the spectral and burn up calculations of LWR cells and fuel assembly lattices, and the main nodal kinetics parameters: mean neutron generation time and delayed neutron fraction; 2) the features of the advanced nodal methods for 3-D LWR core physics, including the treatment of partially inserted control rods, fuel assembly grids, fuel burn up and xenon and samarium transients, and ex core detector responses, that are essential for core surveillance, axial offset control and operating transient analysis; 3) the advanced nodal methods for 3-D LWR core neutron kinetics (best estimate safety analysis, real time simulation); and 4) example applications to 3-D neutron kinetics problems in transient analysis of PWR cores, including model, benchmark and operational transients without, or with simple, thermal-hydraulics feedback

Nuevas perspectivas de la política y del derecho audiovisual

Cuando constatamos, en tiempos de presente y futuro, la realidad y perspectivas del sector audiovisual en el marco de la UE podemos advertir la importancia e influencia de este sector en la construcción europea. Basta, para ello, apelar a tres tipos de razones: el gran auge y crecimiento que está experimentando este sector, tanto en inversión como en creación de empleos, en estos momentos y que todavía será mayor en el siglo XXI -con todo lo que implica en el aumento del peso específico de este sector en el conjunto de la economía comunitaria-; la gran transformación que está experimentando este sector con el tránsito de la tecnología analógica hacia la tecnología digital y que va a suponer una gran revolución en los modos y maneras de entender y actuar de estos medios, en los que se multiplicarán el número de frecuencias disponibles, se posibilitará la interactividad y las auto-programaciones de los espectadores, se ampliarán los servicios existentes y se crearán otro conjunto nuevo de servicios, se aumentará la demanda de contenidos audiovisuales, modificándose los hábitos de consumo que ya en la actualidad superan las tres horas por cada europeo medio, y los hábitos de utilización de los medios audiovisuales por los usuarios, al mismo tiempo que favorecerá la aparición de sinergias y alianzas empresariales, mono y multimedia, para competir con más garantías y ventajas en los nuevos mercados; y, por último, la incidencia que los medios de comunicación y especialmente los audiovisuales, tienen sobre la sociedad y la cultura europea. Para la mayor parte de ciudadanos europeos estos medios constituyen no solo la fuente de información de lo que está ocurriendo en su ciudad o en el mundo, sino que también se convierten en punto de referencia para la adquisición de determinados valores sociales o culturales, y en un complemento del proceso educacional y formativo; por lo que la proyección de contenidos que realicen estos medios va a influir en la propia identidad de la sociedad europea. Apuntadas estas razones y la reciente, pero numerosa, actividad regulatoria de la UE, se evidencia la conveniencia de abordar el análisis de las nuevas perspectivas de la política y regulación audiovisual comunitaria, como un sector fundamental en la construcción del futuro de la Unión Europea. Son muchas las preguntas que podemos plantearnos, entre ellas: ¿cómo pueden las autoridades europeas y nacionales ayudar a la industria audiovisual europea a enfrentarse a los nuevos desafíos industriales, culturales y sociales? ¿cuál debe ser el papel del servicio público de radiodifusión en el nuevo panorama audiovisual? ¿cómo puede la industria europea de programas (películas, televisión, multimedia) aprovechar al máximo los cambios previstos? ¿cómo puede preservarse la pluralidad lingüística y cultural europea? ¿cómo hay que entender el interés general, especialmente en términos éticos, a fin de salvaguardar el modelo europeo de sociedad?... Con este artículo se abordan estas preguntas, analizando la normativa por la que surge y por la que se desarrolla una nueva política audiovisual en el seno de la Unión Europea, estudiando los siguientes ámbitos: 1.- La televisión sin fronteras como objetivo comunitario. 2.- Pluralismo, libre competencia y concentración de medios de comunicación. 3.- La armonización de las emisiones de radiodifusión televisiva. 4.- El apoyo al sector cinematográfico y la industria de producción audiovisual europea. 5.- La protección de los derechos de autor en el ámbito audiovisual comunitario. 6.- La armonización de normas técnicas y la convergencia de las nuevas tecnologías. En base a todo esta investigación se plantean las líneas fundamentales sobre las que se apoya dicha política y su regulación, al tiempo que se apuntan y concretan en los cauces como debe discurrir en el futuro

Basis for Coupled 3-D Neutronics-Thermal-Hydraulics

The purpose of this seminar is first to discuss the basis of the coupling between 3-D Neutron- Kinetics and Thermal-Hydraulics codes, including the control and 3-D variables to interchange, the transform of the 3-D NK and TH core nodalizations, and the schemes for temporal coupling and time-step control. As representative examples of the NK-TH core coupling, we discuss first the integration of a 3-D NK nodal code with a TH subchannel code, for detailed transient core analysis; and second the coupling of 3-D NK nodal codes with TH system codes, for general transient and safety analysis. In chapter 2, we analyze several prototype model transients in PWR, where large 3-D core asymmetries are found and the NK-TH coupling is quite significant, including loss-of-flow and symmetric and asymmetric core cooling, considering the effects on the responses of the excore detectors. In chapter 3, we discuss the analysis of an increase-of-flow transient actually occurred in an operating PWR and the comparison with the measured data. In chapter 4, we summarize the phenomena and results of the calculations of the NEA/NSC Benchmark on the main steam line break (MSLB) transient in a PWR. Finally, we will discuss the state-of-the-art issues in LWR coupled NK-TH 3-D transient analysis and ongoing and planned computational developments

Operators on wighted spaces of holomorphic functions

The Ph.D. Thesis ¿Operators on weighted spaces of holomorphic functions¿ presented here treats different areas of functional analysis such as spaces of holomorphic functions, infinite dimensional holomorphy and dynamics of operators. After a first chapter that introduces the notation, definitions and the basic results we will use throughout the thesis, the text is divided into two parts. A first one, consisting of Chapters 1 and 2, focused on a study of weighted (LB)-spaces of entire functions on Banach spaces, and a second one, corresponding to Chapters 3 and 4, where we consider differentiation and integration operators acting on different classes of weighted spaces of entire functions to study its dynamical behaviour. In what follows, we give a brief description of the different chapters: In Chapter 1, given a decreasing sequence of continuous radial weights on a Banach space X, we consider the weighted inductive limits of spaces of entire functions VH(X) and VH0(X). Weighted spaces of holomorphic functions appear naturally in the study of growth conditions of holomorphic functions and have been investigated by many authors since the work of Williams in 1967, Rubel and Shields in 1970 and Shields and Williams in 1971. We determine conditions on the family of weights to ensure that the corresponding weighted space is an algebra or has polynomial Schauder decompositions. We study Hörmander algebras of entire functions defined on a Banach space and we give a description of them in terms of sequence spaces. We also focus on algebra homomorphisms between these spaces and obtain a Banach-Stone type theorem for a particular decreasing family of weights. Finally, we study the spectra of these weighted algebras, endowing them with an analytic structure, and we prove that each function f ¿ VH(X) extends naturally to an analytic function defined on the spectrum. Given an algebra homomorphism, we also investigate how the mapping induced between the spectra acts on the corresponding analytic structures and we show how in this setting composition operators have a different behavior from that for holomorphic functions of bounded type. This research is related to recent work by Carando, García, Maestre and Sevilla-Peris. The results included in this chapter are published by Beltrán in [14]. Chapter 2 is devoted to study the predual of VH(X) in order to linearize this space of entire functions. We apply Mujica¿s completeness theorem for (LB)-spaces to find a predual and to prove that VH(X) is regular and complete. We also study conditions to ensure that the equality VH0(X) = VH(X) holds. At this point, we will see some differences between the finite and the infinite dimensional cases. Finally, we give conditions which ensure that a function f defined in a subset A of X, with values in another Banach space E, and admitting certain weak extensions in a space of holomorphic functions can be holomorphically extended in the corresponding space of vector-valued functions. Most of the results obtained have been published by the author in [13]. The rest of the thesis is devoted to study the dynamical behaviour of the following three operators on weighted spaces of entire functions: the differentiation operator Df(z) = f (z), the integration operator Jf(z) = z 0 f(¿)d¿ and the Hardy operator Hf(z) = 1 z z 0 f(¿)d¿, z ¿ C. In Chapter 3 we focus on the dynamics of these operators on a wide class of weighted Banach spaces of entire functions defined by means of integrals and supremum norms: the weighted spaces of entire functions Bp,q(v), 1 ¿ p ¿ ¿, and 1 ¿ q ¿ ¿. For q = ¿ they are known as generalized weighted Bergman spaces of entire functions, denoted by Hv(C) and H0 v (C) if, in addition, p = ¿. We analyze when they are hypercyclic, chaotic, power bounded, mean ergodic or uniformly mean ergodic; thus complementing also work by Bonet and Ricker about mean ergodic multiplication operators. Moreover, for weights satisfying some conditions, we estimate the norm of the operators and study their spectrum. Special emphasis is made on exponential weights. The content of this chapter is published in [17] and [15]. For differential operators ¿(D) : Bp,q(v) ¿ Bp,q(v), whenever D : Bp,q(v) ¿ Bp,q(v) is continuous and ¿ is an entire function, we study hypercyclicity and chaos. The chapter ends with an example provided by A. Peris of a hypercyclic and uniformly mean ergodic operator. To our knowledge, this is the first example of an operator with these two properties. We thank him for giving us permission to include it in our thesis. The last chapter is devoted to the study of the dynamics of the differentiation and the integration operators on weighted inductive and projective limits of spaces of entire functions. We give sufficient conditions so that D and J are continuous on these spaces and we characterize when the differentiation operator is hypercyclic, topologically mixing or chaotic on projective limits. Finally, the dynamics of these operators is investigated in the Hörmander algebras Ap(C) and A0 p(C). The results concerning this topic are included by Bonet, Fernández and the author in [16].Beltrán Meneu, MJ. (2014). Operators on wighted spaces of holomorphic functions [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/36578TESISPremiad

The structure of finite groups with three class sizes

Let G be a finite group and suppose that the set of conjugacy class sizes of G is f1; m; mng, where m; n > 1 are coprime. We prove that m 1⁄4 p for some prime p dividing n 1. We also show that G has an abelian normal p-complement and that if P is a Sylow p-subgroup of G, then jP0j 1⁄4 p and jP=ZðGÞpj 1⁄4 p2. We obtain other properties and deter- mine completely the structure of G

Nilpotency of p-complements and p-regular conjugacy class sizes

AbstractLet G be a finite p-solvable group. We prove that if the set of conjugacy class sizes of all p′-elements of G is {1,m,pa,mpa}, where m is a positive integer not divisible by p, then the p-complements of G are nilpotent and m is a prime power. This result partially extends a theorem for ordinary classes which asserts that if the set of conjugacy class sizes of a finite group G is exactly {1,m,n,mn} and (m,n)=1, then G is nilpotent

Development of an Analytic Nodal Diffusion Solver in Multigroups for 3D Reactor Cores with Rectangular or Hexagonal Assemblies.

More accurate modelling of physical phenomena involved in present and future nuclear reactors requires a multi-scale and multi-physics approach. This challenge can be accomplished by the coupling of best-estimate core-physics, thermal-hydraulics and multi-physics solvers. In order to make viable that coupling, the current trends in reactor simulations are along the development of a new generation of tools based on user-friendly, modular, easily linkable, faster and more accurate codes to be integrated in common platforms. These premises are in the origin of the NURESIM Integrated Project within the 6th European Framework Program, which is envisaged to provide the initial step towards a Common European Standard Software Platform for nuclear reactors simulations. In the frame of this project and to reach the above-mentioned goals, a 3-D multigroup nodal solver for neutron diffusion calculations called ANDES (Analytic Nodal Diffusion Equation Solver) has been developed and tested in-depth in this Thesis. ANDES solves the steady-state and time-dependent neutron diffusion equation in threedimensions and any number of energy groups, utilizing the Analytic Coarse-Mesh Finite-Difference (ACMFD) scheme to yield the nodal coupling equations. It can be applied to both Cartesian and triangular-Z geometries, so that simulations of LWR as well as VVER, HTR and fast reactors can be performed. The solver has been implemented in a fully encapsulated way, enabling it as a module to be readily integrated in other codes and platforms. In fact, it can be used either as a stand-alone nodal code or as a solver to accelerate the convergence of whole core pin-by-pin code systems. Verification of performance has shown that ANDES is a code with high order definition for whole core realistic nodal simulations. In this paper, the methodology developed and involved in ANDES is presented

Normal subgroups and class sizes of elements of prime power order

[EN] If G is a finite group and N is a normal subgroup of G with two C-conjugacy class sizes of elements of prime power order, then we show that N is nilpotent.We would like to thank the referee for some simplifications in the original proofs. This research was supported by the Spanish Government, Proyecto MTM2010-19938-C03-02, and by the Valencian Government, Proyecto PROMETEO/2011/30. The first author was also supported by grant Fundacio Caixa-Castello P11B2010-47.Beltrán, A.; Felipe Román, MJ. (2012). Normal subgroups and class sizes of elements of prime power order. Proceedings of the American Mathematical Society. 140(12):4105-4109. https://doi.org/10.1090/S0002-9939-2012-11276-6S410541091401

Dynamics of Weighted Composition Operators on Spaces of Entire Functions of Exponential and Infraexponential Type

[EN] Given an affine symbol phi and a multiplier w, we focus on the weighted composition operator C-w,C-phi acting on the spaces Exp and Exp(0) of entire functions of exponential and of infraexponential type, respectively. We characterize the continuity of the operator and, for w the product of a polynomial by an exponential function, we completely characterize power boundedness and (uniform) mean ergodicity. In the case of multiples of composition operators, we also obtain the spectrum and characterize hypercyclicity.The research of the first author was supported by the research project MTM2016-76647-P. The research of the second author was partially supported by MTM2016-76647-P and PID2020-119457GB-I00Beltrán Meneu, MJ.; Jorda Mora, E. (2021). Dynamics of Weighted Composition Operators on Spaces of Entire Functions of Exponential and Infraexponential Type. Mediterranean Journal of Mathematics. 18(5):1-18. https://doi.org/10.1007/s00009-021-01850-1S11818