Klonovi nedeterminističkih operacija

This thesis is a survey of some well-known and several new results concerning lattices of total, partial, incompletely specified clones and hyper-clones. We assign to every partial, incompletely specified and hyperoperation a suitable total operation and investigate thereby induced embeddings of the three lattices into corresponding lattices of total clones. Next we modify the famous Galois connection (Pol,Inv) between relations and operations for partial operations, IS operations and hyperoperations and describe classes of clones of IS operations and hyperoperations which strongly and weakly preserve given relations. We also state some known results concerning the four lattices on a two-element set. Finally, we present completeness criteria for the lattices of total and partial clones, and in the case of hyperclones and IS clones we describe four classes of coatoms, determined by four classes of Rosenberg’s relations.Ова теза представља преглед неких познатих и неколико нових резултата везаних за мреже тоталних, парцијалних, непотпуно специфицираних клонова и хиперклонова. Свакој парцијалној, непотпуно специфицираној и хипероперацији придружијемо одговарајућу тоталну операцију, и испитујемо тиме индукована потапања три мреже у одговарајуће мреже тоталних клонова. Потом познату Галоаову везу (Pol,Inv) између релација и операција модификујемо за парцијалне операције, НС опера-ције и хипероперације и описујемо класе клонова непотпуно специфици-раних и хипероперација које јако и слабо чувају дате релације. Такође наводимо неке познате резултате о мрежама на двоелементном скупу. Коначно, наводимо критеријуме комплетности за мреже тоталних и парцијалних клонова, а у случају хиперклонова и НС клонова описујемо четири класе коатома, одређених са четири класе Розенбергових релација.Ova teza predstavlja pregled nekih poznatih i nekoliko novih rezultata vezanih za mreže totalnih, parcijalnih, nepotpuno specificiranih klonova i hiperklonova. Svakoj parcijalnoj, nepotpuno specificiranoj i hiperoperaciji pridružijemo odgovarajuću totalnu operaciju, i ispitujemo time indukovana potapanja tri mreže u odgovarajuće mreže totalnih klonova. Potom poznatu Galoaovu vezu (Pol,Inv) između relacija i operacija modifikujemo za parcijalne operacije, NS opera-cije i hiperoperacije i opisujemo klase klonova nepotpuno specifici-ranih i hiperoperacija koje jako i slabo čuvaju date relacije. Takođe navodimo neke poznate rezultate o mrežama na dvoelementnom skupu. Konačno, navodimo kriterijume kompletnosti za mreže totalnih i parcijalnih klonova, a u slučaju hiperklonova i NS klonova opisujemo četiri klase koatoma, određenih sa četiri klase Rozenbergovih relacija

Techniques for the realization of ultra- reliable spaceborne computer Final report

Bibliography and new techniques for use of error correction and redundancy to improve reliability of spaceborne computer

Theories of Informetrics and Scholarly Communication

Scientometrics have become an essential element in the practice and evaluation of science and research, including both the evaluation of individuals and national assessment exercises. Yet, researchers and practitioners in this field have lacked clear theories to guide their work. As early as 1981, then doctoral student Blaise Cronin published "The need for a theory of citing" —a call to arms for the fledgling scientometric community to produce foundational theories upon which the work of the field could be based. More than three decades later, the time has come to reach out the field again and ask how they have responded to this call. This book compiles the foundational theories that guide informetrics and scholarly communication research. It is a much needed compilation by leading scholars in the field that gathers together the theories that guide our understanding of authorship, citing, and impact

Theories of Informetrics and Scholarly Communication

Scientometrics have become an essential element in the practice and evaluation of science and research, including both the evaluation of individuals and national assessment exercises. Yet, researchers and practitioners in this field have lacked clear theories to guide their work. As early as 1981, then doctoral student Blaise Cronin published The need for a theory of citing - a call to arms for the fledgling scientometric community to produce foundational theories upon which the work of the field could be based. More than three decades later, the time has come to reach out the field again and ask how they have responded to this call. This book compiles the foundational theories that guide informetrics and scholarly communication research. It is a much needed compilation by leading scholars in the field that gathers together the theories that guide our understanding of authorship, citing, and impact

Magnetic Skyrmions and Topological Domain Walls

Whether in the compass in the early ages of mankind or in the hard disk drives that provide the vast quantities of memory that nowadays information technology demands: magnetism is a ubiquitous phenomenon with numerous applications in our everyday life. The comparatively young skyrmion, in turn, adds with its topologically non-trivial structure a new flavor to this extensively studied field. This cumulative dissertation explores the diverse phenomena that occur in magnets, where non-collinear magnetization-textures are stabilized as a consequence of broken mirror or inversion symmetries of the material. These textures include long-ranged spirals, lattices of skyrmions, and polarized structures

Skyrmions and Monopoles in Chiral Magnets & Correlated Heterostructures

The first part of this thesis is called "Skyrmions and Monopoles in Chiral Magnets" and concerned with topological spin textures in chiral magnets. The second part, "Correlated Heterostructures", studies layered, strongly correlated devices within the framework of dynamical mean-field theory. In magnets without inversion symmetry, so called chiral magnets, weak spin-orbit coupling leads to the formation of smooth twisted magnetic structures with a long period. Recently, a new magnetic phase of a lattice of topologically stable whirl-lines was discovered. In the first chapter we introduce the concept of a such a whirling texture and briefly mention its occurrence in other areas of physics. In chapters 2 we review the Ginzburg-Landau theory for chiral magnetic structures describing their equilibrium properties followed by a description of a numerical minimisation technique to explore the mean-field configuration of the free energy functional. In chapter 3 we review the Langevin description for a system at finite temperature and concentrate on especially on the description of magnetic systems. The describe how a numerical integration of the equations of motion, a stochastically differential equation, can be achieved to compute ensemble-averaged quantities. Chapter 4 we present the discovery of emergent magnetic monopoles as the driving mechanism behind topological phase transitions from the Skyrmion lattice into topologically trivial phases. We describe how a Skyrmion lattice unwinds due to the motion of magnetic monopoles in the system as seen both in experiment and numerical simulations. We investigate how the energetics of and forces between monopoles and antimonopoles influence their creation rate and dynamics. In chapter 5 we turn to the dynamical properties of single Skyrmions in ferromagnetic backgrounds. In a first approach we study analytically the fluctuations around the mean-field configuration and determine the spectrum of the bound states, the scattering solutions and their phase shifts and coupling mechanism to the collective Skyrmion coordinate. By integrating out the fluctuations we discover a strongly frequency-dependent effective mass for the collective Skyrmion coordinate. We approach the same question from a different angle in the second part of the chapter. Here we start from numerical simulations of the stochastic Landau-Lifshitz-Gilbert equation and determine the coefficients of the effective equations of motion from a statistical analysis of the collective coordinate fluctuations. We find a strongly frequency-dependent effective mass and a new peculiar damping mechanism proportional to the acceleration of the Skyrmion that we call 'gyro-damping'. The second part of this thesis explores the interface effects in strongly correlated heterostructures. Multilayered heterostructures in the nano sized realm (also known as multilayered nanostructures) are the most common electronic devices. A classic multilayered nanostructure is a tunnel junction consisting of two metallic leads connected by a ``weak link'', often a conventional band insulator. The connection between the two leads is thus governed by inherently quantum mechanical effects. We begin with an introduction to model Hamiltonians, in particular the Hubbard and the single impurity Anderson model. The second chapter describes the static mean-field treatment of anti-ferromagnetic order in the Hubbard model. Chapter 3 introduces the reader to the dynamical mean-field theory (DMFT) and describes extensions of the DMFT to system with antiferromagnetic order. The DMFT maps the lattice problem onto an effective impurity problem. In chapter 4 we review how the single impurity Anderson model can be solved using the numerical renormalisation group (NRG). The generalisation of DMFT to inhomogenous, layered systems is given in chapter 5 including the effects of long-range Coulomb interactions on the Hartree level. Here we also outline our generalisation of the inhomogenous DMFT to systems with antiferromagnetic order. In chapter 6 we derive expressions for the layer-resolved optical conductivity and the Hall conductivity. We apply the former to the Mott-Band-Mott heterostructure where we study the transport properties of the two-dimensional metallic state at the interface where we find a rich temperature dependence. In chapter 7 we turn to the question how the transmission amplitude through a Mott insulator in a linear potential depends on temperature