In this paper, we study various examples of dynamical systems found in nature and extract the necessary concepts to build upon. Then, we develop and propose a new deterministic model for COVID-19 propagation. Our model should serve two purposes. First, we will approximate the infected and deceased individuals after a given time during the pandemic. Then, using a linearized subsystem describing infectious compartments about the disease- free equilibrium (DFE), we will determine the basic reproductive number (R0) by the next-generation matrix method.

Gillespie's Stochastic Simulation Algorithm (SSA) provides an elegant simulation approach for simulating models composed of coupled chemical reactions. Although this approach can be used to describe a wide variety biological, chemical, and ecological systems, often systems have external behaviors that are difficult or impossible to characterize using chemical reactions alone. This work extends the applicability of the SSA by adding mechanisms for the inclusion of external events and external triggers. We define events as changes that occur in the system at a specified time while triggers are defined as changes that occur to the system when a particular condition is fulfilled. We further extend the SSA with the efficient implementation of these model parameters. This work allows numerous systems that would have previously been impossible or impractical to model using the SSA to take advantage of this powerful simulation technique.

Economic events of this era reflect the fact that the value of information and technology has surpassed the value of physical production. This motivates countries to focus on increasing the education levels of citizens. However, policy making about education system and its returns requires dynamical analyses in order to be sustainable. The study aims to investigate the dynamic characteristics of a country-wide education system, in particular, that of Turkey. System Dynamics modeling, which is one of the most commonly referred tools for understanding the complex social structures, is used. Our model introduces dynamic relationships among different classes of labor forces with varying education levels, university admissions, research quality, and the investments made in education, research and other sectors. Model experimentation provides new insights into the investment and capacity-related aspects of the education system environment.

Šiame darbe analizuojama mobilaus ryšio sistema. Yra tariama, jog tinkle egzistuoja dviejų tipų įrenginiai: mobilūs ir fiksuoti. Fiksuoti įrenginiai yra visados įjungti ir prijungti prie tinklo. Fiksuoti įrenginiai, tai mobiliosios palaikymo stotys (MPS) ir duomenų bazė. Mobilūs įrenginiai (mobilūs kompiuteriai) gauna duomenis iš duomenų bazės, tarpininkaujant palaikymo stotims. Mobilūs kompiuteriai prisijungia ir persijungia prie skirtingų MPS, priklausomai nuo jų skleidžiamo signalo stiprumo. Visi veiksmai atliekami nuosekliai, nepertraukiant galutinio vartotojo darbo. Kuriant tokių sistemų programinius modelius pirmiausia reikia jas išanalizuoti ir suformalizuoti. Viena iš formalizavimo kalbų – PLA, neseniai buvo išplėsta, kad gal���tų aprašyti dinamines sistemas. Šiame darbe supažindinama su naujai išplėsta formalizavimo kalba (dynPLA). Ji naudojama mobilaus ryšio sistemos specifikavimui bei tikrinama ar formalizavimo kalbos išplėtimų užtenka aprašyti minėtąją sistemą. Pasiūlyti dynPLA formalizavimo kalbos patobulinimai bei pateiktas sistemos modelio specifikacijos pavyzdys. / The mobile computing system will be analyzed in this work. It is assumed that network consists of two types of devices: mobile and fixed. Fixed devices are always on and always connected to the network. These devices include, but are not limited to database servers and mobile support stations (MSS). Mobile devices access data from database. They connect and reconnect to different MSS depending on the signal strength. All of this is done seamlessly to the end user and the data transfer is not disturbed. When planning to implement such system in programming language, the first step is analyzing and formalizing it. One of the formalization languages – PLA, was recently extended for the sole purpose of formalization of dynamic systems. This work, “The Usage of dynPLA Formalism for Modeling of Mobile Computing System” covers the usage of new extended formalization language (dynPLA) for mobile computing system, analyzing if dynPLA extensions are sufficient for formalizing the said system. Also some improvements for the dynPLA formalization language will be suggested and the example of the mobile computing system will be given.

Dynamic complexity occurs in every social structure. Film industry, as a type of creative industries, constitutes a dynamic environment where uncertainty is at high levels. This complexity of the environment renders the more traditional operations research models somewhat ineffective, and thus, requires a dynamic analysis. In this study, a model showing the dynamics of film exhibition is given. The interactions within and between the theatrical and the DVD sales channels are implemented by the model. Later on, the possible effects of piracy to the model are discussed, using the inferences obtained by the created model. The model is examined with scenario and sensitivity analysis. All the modeling studies are done with a commercial dynamic systems modeling software. The model also can be extended for the whole film industry, or for some other creative industries like the publishing industry.

This thesis aims to propose multiple methods for performing a hardware-in-the-loop simulation, providing the hardware and software tools necessary for design and execution. For this purpose, methods of modeling commonly encountered dynamical system components are explored and techniques suitable for calculating the states of the modeled system are presented. Modules and subsystems that enable the realization of a hardware-in-the-loop simulation application and its interfacing with external controller hardware are explained. The thesis also presents three different simulation scenarios. Solutions suitable for these scenarios are provided along with their implementations. The details and specifications of the developed software packages and hardware platforms are given. The provided results illustrate the advantages and disadvantages of the approaches used in these solutions.

Dažnai realių stochastinių sistemų dinamikos negalime aprašyti Markovo procesu, nes operacijų trukmės paprastai nėra pasiskirstę pagal eksponentinį dėsnį. Darbe buvo išnagrinėtas tokių atsitiktinių dydžių aproksimavimas dviejų eksponentinių atsitiktinių dydžių mišiniu. Paprasčiausioms sistemoms kartais galima gauti analizines formules sistemos būsenų stacionarioms tikimybėms suskaičiuoti, tačiau daugeliui sistemų to padaryti negalima. Būtent tokių sistemų tyrimui, panaudojus aproksimavimo algoritmus, buvo sukurta programinė įranga, kuri leidžia modeliuoti daugelį stochastinių sistemų. Magistro darbo užduotis: Sukurti stochastinių sistemų modelių aproksimavimo Markovo modeliais algoritmus ir programinę įrangą. Buvo iškelti tokie tikslai: Ištirti pasiskirstymo funkcijų aproksimavimo eksponentinių skirstinių mišiniu galimybes; Sukurti universalią programinę priemonę, kuri pagal pateiktą sistemos aprašymą, skaičiuotų jos stacionariąsias tikimybes bei funkcionavimo charakteristikas; Sukurtos programinės priemonės pagalba, sudaryti ir ištirti aptarnavimo sistemų ir vertybinių popierių įkainojimo modelius. Sukurta programinė įranga pasižymi universalumu ir paprastumu vartotojui. Sistemos funkcionavimą galima aprašyti turint minimalias C++ Builder programavimo kalbos žinias. Magistro darbe sukurta programinė įranga buvo pritaikyta aptarnavimo sistemoms modeliuoti, akcijų kainų dinamikai aprašyti bei opcionams įkainoti. / Application of numerical methods with approximation allows to extend a class of systems represented by Markovian processes under investigation compared with analytical methods. So a goal was stated to create algorithms for modeling stochastic systems approximating them by Markovian models. To reach this goal the following tasks were solved: Analyze possibilities to approximate stochastic systems’ models by Markovian models; Create a multipurpose software that would calculate stationary probabilities for given system described in an event-based language; Apply created software for models of service systems and stock valuation. Created software is universal and easy-to-use for anyone that has at least basic knowledge in C++ language. This software was applied for modeling of service systems, for description of share price variability as Markovian process and for option pricing.

The area of business process management in general and and especially business process design has only recently discovered potential applications of social software to facilitate and support collaboration [Scheer and Klueckmann, 2009]. This development is also fueled by the practical insight that organizations have experienced top-down approaches in the design and implementation of business processes to be not effective. In fact, many process management initiatives failed due to a lack of acceptance of chosen methods and tools. As a consequence in many organizations so called [Klückmann and Scheer, 2009] "Guerilla approaches" have been followed where individual organizational units introduced their own business process management philosophy and as well techniques and tools that fit their specific needs. However, Klückmann and Scheer [2009] stress the fact that although distributed business process management initiatives should generally not be hindered, it is important to channel and integrate these initiatives towards a more consistent and efficient process management in the large. Business process modeling in this context serves several purposes in the process management cycle. One purpose is the analysis of business processes to uncover potential performance weaknesses and provide a basis for improvements. Another purpose is the unambiguous documentation of business processes as a resource for knowledge transfer, organizational learning and governance. An increasingly important purpose is the use of process models to support the design and engineering of respective enterprise information systems [Davies et al., 2006]. Hence, the complex and abstract nature of process models and the closedness of process modeling environments has prevented them to be broadly accepted and used by non-experts [Nolte et al., 2011] viz the process community in a wider sense. Consequently, process documentation and models in organizations frequently is outdated, incomplete and inconsistent. This model-reality divide in turn leads to even more reluctance towards the adoption of process modeling environments and use of process models. Bridging this model-reality divide by fostering open and fluent col- laboration through adequate features inspired by social software has gained growing attention by academia and industry [Mathiesen et al., 2012]. Although both industry and academia have addressed the need for collaboration support in process modeling only limited insight exists regarding the specific requirements for software-support in collaborative process modeling. This work refers to existing research (e.g. [Mendling et al., 2012; Riemer et al., 2011]) on requirements for software-support in collaborative process modeling and wiki-based process modeling (e.g. [Ghidini et al., 2010; Dengler and Vrandecic, 2011]). and pursues the following goals: (1) gain an understanding of the nature and requirements of collaborative process modeling in practice, (2) investigate how these requirements can be addressed through the design of a wiki-based collaborative process modeling environment, and (3) gain insight how a wiki-based collaborative process modeling environment supports process design activities in practice. To address these goals a design science approach has been followed. Through a systematic literature review and qualitative expert interviews a preliminary understanding of the problem domain and specification of requirements has been achieved. Through the extension and adaption of a well-proven collaboration platform (a wiki engine) for process modeling support several of the previously identified design issues have been addressed. In particular, issues regarding the flexible integration of a visual process modeling interface component into a collaboration environment and issues regarding concurrent scenarios in process modeling have been discussed in detail and realized partly on a technical level. Two major software components have been developed for the support of collaborative process modeling. First, a light-weight and easily integratable user-interface component for process model creation has been developed and integrated into the collaboration environment (a wiki engine). Second, the identification and handling of concurrent situations when multiple modelers access and modify a process model page has been implemented on an element level which allows for the interactive resolution and semi-automatic merging of conflicting revisions of a process model. Case-studies in an industrial and an academic setting provided valuable insights in the practice of collaborative process modeling and gave feedback on the applicability of a wiki-based approach. The first case-study of a process re-design in the recruiting department of an office supply manufacturing company in Hungary describes the insights gained during a long-term collaboration within a small group. Findings were especially valuable for further enhancements of the software and an understanding of practical requirements in iterative model creation and validation. The second case-study in the context of two bachelor and master courses in information system design has lead to insights regarding the requirements in highly dynamic collaboration scenarios in small groups and large groups but as well regarding the efficiency and effectiveness of wiki-based process modeling in collaborative learning processes. (author's abstract)

Made available in DSpace on 2014-12-17T14:56:07Z (GMT). No. of bitstreams: 1 DanielGVF_DISSERT.pdf: 2881772 bytes, checksum: 5236953fb6bb70560393eeeaa01f96f9 (MD5) Previous issue date: 2012-08-31 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / The control, automation and optimization areas help to improve the processes used by industry. They contribute to a fast production line, improving the products quality and reducing the manufacturing costs. Didatic plants are good tools for research in these areas, providing a direct contact with some industrial equipaments. Given these capabilities, the main goal of this work is to model and control a didactic plant, which is a level and flow process control system with an industrial instrumentation. With a model it is possible to build a simulator for the plant that allows studies about its behaviour, without any of the real processes operational costs, like experiments with controllers. They can be tested several times before its application in a real process. Among the several types of controllers, it was used adaptive controllers, mainly the Direct Self-Tuning Regulators (DSTR) with Integral Action and the Gain Scheduling (GS). The DSTR was based on Pole-Placement design and use the Recursive Least Square to calculate the controller parameters. The characteristics of an adaptive system was very worth to guarantee a good performance when the controller was applied to the plant / As ?reas de controle, automa??o e otimiza??o contribuem para a melhoria dos processos utilizados pelas ind?strias, permitindo uma linha de produ??o r?pida, aprimorando a qualidade do produto final e reduzindo os custos de produ??o. Boas ferramentas para o desenvolvimento de pesquisas nestas ?reas s?o as plantas did?ticas, pois proporcionam um contato direto com equipamentos semelhantes ou at? mesmo usados no setor industrial. Em vista dessas capacidades, o objetivo deste trabalho ? modelar e controlar uma planta did?tica que consiste de um sistema de controle de processo para vaz?o e n?vel com instrumenta??o industrial. Com o modelo ? poss?vel construir um simulador capaz de permitir estudos a respeito do funcionamento do sistema, sem os gastos com a opera??o do processo real. ? o caso de experimentos com controladores, que podem ser testados diversas vezes antes de serem efetivamente utilizados no processo real. Dentre os diversos tipos de controladores existentes, foi dado foco aos de tipo adaptativo, principalmente ao auto-sintoniz?vel direto (Direct Self-Tuning Regulator DSTR) com a??o integral e ao controlador com Escalonamento de Ganho (Gain Scheduling GS). O controlador DSTR foi projetado com base no m?todo de posicionamento de p?los e teve seus par?metros calculados atrav?s da t?cnica dos m?nimos quadrados recursivos. As caracter?sticas dos sistemas adaptativos foram de grande valia para garantir um desempenho satisfat?rio dos controladores, quando aplicados ? planta

The aim of this thesis was to develop stable-isotope steady-state metabolic flux analysis (MFA) based on ¹³C labeling to quantify intracellular fluxes of central carbon metabolism in plants. The experiments focus on the analysis of a heterotrophic cell suspension culture of Arabidopsis thaliana (L) Heynh. (ecotype Landsberg erecta). The first objective was to develop a robust methodology based on combining high quality steady-state stable labeling data, metabolic modeling and computational analysis. A comprehensive analysis of the factors that influence the outcome of MFA was undertaken and best practice established. This allowed a critical analysis of the subcellular compartmentation of carbohydrate oxidation in the cell culture. The second objective was to apply the methodology to nutritional perturbations of the cell suspension. A comparison of growth on different nitrogen sources revealed that transfer to an ammonium-free medium: (i) increased flux through the oxidative pentose phosphate pathway (oxPPP) by 10% relative to glucose utilisation; (ii) caused a substantial decrease in entry of carbon into the tricarboxylic acid cycle (TCA); and (iii) increased the carbon conversion efficiency from 55% to 69%. Although growth on nitrate alone might be expected to increase the demand for reductant, the cells responded by decreasing the assimilation of inorganic N. Cells were also grown in media containing different levels of inorganic phosphate (Pi). Comparison of the flux maps showed that decreasing Pi availability: (i) decreased flux through the oxPPP; (ii) increased the proportion of substrate fully oxidised by the TCA cycle; and (iii) decreased carbon conversion efficiency. These changes are consistent with redirection of metabolism away from biosynthesis towards cell maintenance as Pi is depleted. Although published genome-wide transcriptomic and metabolomic studies suggest that Pi starvation leads to the restructuring of carbon and nitrogen metabolism, the current analysis suggests that the impact on metabolic organisation is much less extreme.