Chempy\mathit{Chempy}: A flexible chemical evolution model for abundance fitting - Do the Sun's abundances alone constrain chemical evolution models?

Elemental abundances of stars are the result of the complex enrichment history of their galaxy. Interpretation of observed abundances requires flexible modeling tools to explore and quantify the information about Galactic chemical evolution (GCE) stored in such data. Here we present Chempy, a newly developed code for GCE modeling, representing a parametrized open one-zone model within a Bayesian framework. A Chempy model is specified by a set of 5-10 parameters that describe the effective galaxy evolution along with the stellar and star-formation physics: e.g. the star-formation history, the feedback efficiency, the stellar initial mass function (IMF) and the incidence of supernova type Ia (SN Ia). Unlike established approaches, Chempy can sample the posterior probability distribution in the full model parameter space and test data-model matches for different nucleosynthetic yield sets. We extend Chempy to a multi-zone scheme. As an illustrative application, we show that interesting parameter constraints result from only the ages and elemental abundances of Sun, Arcturus and the present-day interstellar medium (ISM). For the first time, we use such information to infer IMF parameter via GCE modeling, where we properly marginalize over nuisance parameters and account for different yield sets. We find that of the IMF $11.6_{-1.6}^{+2.1}$ % explodes as core-collapse SN, compatible with Salpeter 1955. We also constrain the incidence of SN Ia per 10^3 Msun to 0.5-1.4. At the same time, this Chempy application shows persistent discrepancies between predicted and observed abundances for some elements, irrespective of the chosen yield set. These cannot be remedied by any variations of Chempy's parameters and could be an indication for missing nucleosynthetic channels. Chempy should be a powerful tool to confront predictions from stellar nucleosynthesis with far more complex abundance data sets.Comment: 19 pages, 17 figures, accepted for publication in A&A, python code: https://github.com/jan-rybizki/Chemp

The Origin of the Czech and Slovak Pluralist Party Systems

The article analyzes the process of pluralistic party system renewal in Czechoslovakia after the fall of communism in 1989. It shows the initial conditions and major actors, as well as factors that infl uenced party system structure and behaviour in the environment of a post-communist society without a recent democratic tradition. Special attention is devoted to the differences between Czech and Slovak party systems, as both parts of the former united Czechoslovakia demonstrated differences in their respective party systems both before and after 1989. After the introduction of key political parties, the results of 1990 general parliamentary election and its impact on the party system are analyzed

Aerodynamics of axial wind turbines

Tato diplomová práce se zabývá problematikou aerodynamiky větrných turbín. V práci je odvozena základní teorie založená na zákonu zachování hybnosti, která je základním nástrojem pro návrh a výpočet větrné turbíny. Tato teorie je následně doplněna o korekční faktory a posléze použita při návrhu větrné elektrárny pro konkrétní parametry. Výpočet je proveden iteračně s využitím softwaru MATLAB, přičemž samotný kód je uveden v příloze. V práci jsou uvedeny grafy shrnující průběh jednotlivých veličin po délce lopatky. V závěrečné části jsou stručně popsány pokročilejší témata aerodynamiky cílená na determinaci dalších upřesňujících faktorů, jimiž se obor větrné energetiky zabývá v poslední době.This master thesis concerns about problematics of wind turbines. The document summarizes basic theory based on the law of momentum conservation which is essential tool for the design and calculation of wind turbines. The theory is complemented by number of correction factors and then used in the design of wind turbine for specific parameters. The calculation is performed iteratively using Matlab software and the actual code is given in appendix. Graphs summarizing the progress of various units along the blades are presented in the document. The final section briefly describes advanced topics of aerodynamics concerning other important factors that the field of wind energy deal with in recent time.

Small photovoltaic system

Bakalářská práce popisuje dnešní podobu fotovoltaiky. V úvodní časti je popsán samotný zdroj solární energie, základní princip její přeměny na elektrickou a jeho historie. V navazujících oddílech práce shrnuje druhy fotovoltaických článků, jejich členění z hlediska ekonomického, druhu použitého materiálu a stručný popis získaných vlastností. Vlastní práce dále obsahuje konstrukci fotovoltaických panelů a následné uspořádání do celků (systémů) s připojením k distribuční elektrické síti nebo bez něj, shrnuje dostupné technologie vhodné pro zvyšování účinnosti a současné legislativní podmínky pro provoz fotovoltaických elektráren v České republice. Nosná část celé práce je založena na návrhu fotovoltaického systému grid-on pro reálný objekt - rodinný dům. Zahrnuje komplexní studii zabývající se polohou daného objektu, volbou vhodných komponent a výpočtem jejich celkové produkované elektrické energie včetně teoretické kalkulace návratnosti investic. V závěrečné části jsou prezentovány dosažené cíle, výhody a nevýhody investice a samotná realizovatelnost projektu v praxi.This thesis describes the fotovoltaics at the present time. Introduction includes information regarding to resources of solar energy, main principle of transformation solar energy to electrical and history. Next parts summarise types of solar cells in economical term, types of material and description of their properties. Thesis includes the construction of fotovoltaic panel and its configuration to fotovoltaic systems with or without connection to electrical power network, contains convenient technologies for improving efficiency and the czech legislation. Final part focuses on designing grid-on system for real object including komplex study of object location, used components and calculation of whole produced electric energy and pay-back time. The main aims are presented in conclusion as well as advantages and disadvantages of the investment.

ORGANIZATION PERFORMANCE AND ENTERPRISE RISK MANAGEMENT

Enterprise risk management (ERM) is an integrated approach to manage the risks of companies. Despite the wide adoption of ERM into companies' organizational processes, there are neither clear standards for ERM nor ground based theories about the outcome of it. This paper gives an overview of scientific research in the topic of ERM by comparing recent academic papers which focus ERM in the context of performance evaluation or effectiveness by categorizing and evaluating each source against its limitations. The limitations are used to develop a unified view on the question of how ERM influences performance of organizations. This also involves aspects of measuring the current status of ERM within companies and the effects of ERM on the other side. This paper shows that there is diversity in scientific literature of how to measure performance in the ERM-context. The authors identify reasons for that and suggest approaches to solve the problem by identifying best-practice approaches and a generic framework on how to use them to improve ERM-assessment in practice as well as researc

Continuation with Non-invasive Control Schemes: Revealing Unstable States in a Pedestrian Evacuation Scenario

This paper presents a framework to perform bifurcation analysis in laboratory experiments or simulations. We employ control-based continuation to study the dynamics of a macroscopic variable of a microscopically defined model, exploring the potential viability of the underlying feedback control techniques in an experiment. In contrast to previous experimental studies that used iterative root-finding methods on the feedback control targets, we propose a feedback control law that is inherently non-invasive. That is, the control discovers the location of equilibria and stabilizes them simultaneously. We call the proposed control zero-in-equilibrium feedback control and we prove that it is able to stabilize branches of equilibria, except at singularities of codimension n+1, where n is the number of state space dimensions the feedback can depend on. We apply the method to a simulated evacuation scenario were pedestrians have to reach an exit after maneuvering left or right around an obstacle. The scenario shows a hysteresis phenomenon with bistability and tipping between two possible steady pedestrian flows in microscopic simulations. We demonstrate for the evacuation scenario that the proposed control law is able to uniformly discover and stabilize steady flows along the entire branch, including points where other non-invasive approaches to feedback control become singular.Comment: submitted (34 pages 12 figures

MEANING AND USAGE OF A CONCEPTUAL ENTERPRISE RISK MANAGEMENT FRAMEWORK – A CASE STUDY

Enterprise Risk Management (ERM) includes processes and methodologies for organizations to manage companies’ risks. Due to an increase in the environmental complexity, a standardized approach of managing risks and opportunities is not only useful, but absolutely essential for business continuation – the way organizations deal with such risks is the key role for success and can be seen in the company’s overall performance. In a previous paper the authors suggested a model for ERM assessment. In order to proof this model, this paper presents a case study of a production company with a working ERM to evaluate the model, based on a real example. The results demonstrate that a suggested model to assess ERM and its performance is practically useable by organizations and might be further extended in future studies