Die zentralen Fragestellungen der Arbeit sind, wie die Insolvenzwahrscheinlichkeiten von Unternehmen prognostiziert und wie sie durch zielgerichtetes Handeln beeinflusst werden können. Hierzu gibt der Autor zunächst einen ausführlichen Überblick über die derzeit in Wissenschaft und Praxis verwendeten Ansätze zur Prognose von Unternehmensinsolvenzen, Schätzgütemaßen von Insolvenzprognosen sowie Datenquellen, die für die Prognose von Unternehmensinsolvenzen zur Verfügung stehen. Anschließend entwickelt er ein kausales Unternehmensmodell, das er mit stochastischen Simulationsverfahren analysiert. Das Modell wird validiert und mit Benchmarkverfahren verglichen. Abschließend zeigt der Autor, wie das Modell zur Ableitung von Handlungsempfehlungen zur Beeinflussung der individuellen Insolvenzwahrscheinlichkeit von Unternehmen herangezogen werden kann.

This thesis investigates simulation of synchronous machines using a novel Magnetic Equivalent Circuit (MEC) model. The proposed model offers sufficient detail richness for design calculations, while still keeping the simulation time acceptably short. Different modeling methods and circuit alternatives are considered. The selected approach is a combination of several previous methods added with some new features. A detailed description of the new model is given. The flux derivative is chosen as the magnetic flow variable which enables a description with standard circuit elements. The model is implemented in dq-coordinates to reduce complexity and simulation time. A new method to reflect winding harmonics is introduced. Extensive measurements have been made to estimate the traditional dq-model parameters. These in combination with analytical calculations are used to determine the parameters for the new MEC model. The model is implemented using the Dymola simulation program. The results are evaluated by comparison with measurements and FEM simulations. Three different operation cases are investigated; synchronous operation, asynchronous start and inverter fed operation. The agreement with measurements and FEM simulations varies, but it is believed that it can be improved by more work on the parameter determination. The overall conclusion is that the MEC method is a useful approach for detailed simulation of synchronous machines. It enables proper modeling of magnetic saturation, and promises sufficiently detailed results to enable accurate loss calculations. However, the experience is that the complexity of the circuits should be kept at a reasonable low level. It is believed that the practical problems with model structure, parameter determination and the simulation itself will otherwise be difficult to master.

Thermo-elastic errors are one of the main drivers for reduced quality of workpieces in machining. Cooling systems can prevent these errors and improve quality. The paper describes a simulation method that takes into account both the temperature field of a machine tool frame and the fluid cooling system. Such simulations can help to improve the thermal stability of the machine tool frame.

This paper will give an overview about the technological change in Industrial Hydraulics and the impact of the Digital Twin on the related new engineering processes and methods in order to overcome the challenges coming out of that technology change. Simulation models will more and more become a decisive factor for the engineering process. The Digital Twin will be a window of opportunity for innovations and a technology push for the engineering process and the products in the Industrial Hydraulics.

This research is concerned with the modeling and development of algorithmic approaches for solving airport operational problems that arise in Air Traffic Control (ATC) systems within the terminal area at hub airports. Specifically, the problems addressed include the Aircraft Sequencing Problem (ASP) for runway operations, the Network Assignment Problem (NAP) for taxiway operations, and a simulation model for the evaluation of current or proposed ATC system in detail. For the ASP, we develop a mathematical model and apply the Reformulation-Linearization-Technique (RLT) of Sherali and Adams to construct an enhanced tightened version of the proposed model. Since ASP is NP-Hard and in fact, it is a variation of the well-known Traveling Salesman Problem with time-windows, sub-optimal solutions are usually derived to accommodate the real-time constraints of ATC systems. Nevertheless, we exhibit a significant advancement in this challenging class of problem. Also for the purpose of solving relatively large sized problems in practice, we develop and test suitable heuristic procedures. For the NAP, we propose a quasi-dynamic assignment scheme which is based on the incremental assignment technique. This quasi-dynamic assignment method assumes that the current aircraft route is influenced only by the previous aircraft assigned to the network. This simplified assumption obviates the need for iterative rerouting procedures to reach a pure equilibrium state which might not be achievable in practical taxiway operations. To evaluate the overall system, we develop a microscopic simulation model. The simulation model is designed to have the capability for reproducing not only the dynamic behavior of aircraft, but also incorporates communication activities between controllers and pilots. These activities are critical in ATC operations, and in some instances, might limit the capacity of the facility. Finally, using the developed simulation model named Virginia Tech Airport Simulation Model (VTASM) in concert with ASP and NAP, we compare the overall efficiencies of several control strategies, including that of the existing control system as well as of the proposed advanced control system. / Ph. D.

The presented work deals with doctoral thesis named “Electrical drives for critical application”, which is solved in the Institute of Production Machines, Systems and Robotics. The paper tries to subsequently describe the progress during development of electric drive and to introduce the findings reached during project solving. The critical application requirements have been defined at the beginning, especially for the aerospace industry point of view. The work deals with the architecture of the control and power electronic, control software algorithms of the brush and brush-less BLDC motor with respect to the final certification aspects. It is also discussed the effectivness of the new development methods based on the modeling and simulation. The Model Based Design approach have been proved and verified during aircraft onboard equipment development. The findings of these are discussed at the end of this work.

The impact of climate changes on various sectors of human activity and preparation of mitigation and adaptation measures are becoming an important subject of global policy, thus also the policy of the Czech Republic. According to the research results, the impact of climate changes on minimum discharges is very significant and indicates a threat to storage function of water sources, without adequate accumulation for period of drought. One of the ways of preventing or completely avoiding the appearance of these problems is the construction of new reservoirs or the re-evaluation of the size of the storage and protective capacity of existing reservoirs. In relation to climate changes and their impact on the water yield there is a growing need for the participation of operative control progressive methods of reservoir storage function today. The dissertation thesis is aimed at storage function of water management system. Aim of the dissertation work is to create program with graphical user interface, which allows solving the storage function of water management system. Program allows automatically set up optimization and simulation model of any water supply system and solve of optimal control and optimal development of the water supply system. The program was verified on the selected water supply subsystem.

This thesis takes a closer look at the complex maneuver known as gravity assist, a popular method of interplanetary travel. The maneuver is used to gain or lose momentum by flying by planets, which induces a speed and direction change. A simulation model is created using the General Mission Analysis Tool (GMAT), which is intended to be easily reproduced and altered to match any desired gravity assist maneuver. The validity of its results is analyzed, comparing them to available data from real missions. Some parameters, including speed and trajectory, are found to be extremely reliable. The model is then used as a tool to investigate the way that different parameters impact this complex environment, and the advantages of performing thrusting burns at different points during the maneuver are explored. According to theory, thrusting at the point of closest approach to the planet is thought to be the most efficient method for changing speed and direction of flight. However, the results from this study show that thrusting before this point can have some major advantages, depending on the desired outcome. The reason behind this is concluded to be the high sensitivity of the gravity assist maneuver to the altitude and location of the point of closest approach. / Detta examensarbete tittar närmare på den komplexa manöver inom banmekanik som kallas gravitationsassisterad manöver, vilken är vanligt förekommande vid interplanetära rymduppdrag. Manövern används för att öka eller minska farkostens rörelsemängd genom att flyga förbi nära planeter, vilket ger upphov till en förändring i fart och riktning. En simuleringsmodell är skapad i NASAs mjukvara GMAT med syftena att den ska vara reproducerbar samt möjlig att ändra för olika gravitationsassisterade manövrar. Resultaten från simuleringarna är validerade mot tillgängliga data från riktigt rymduppdrag. Vissa parametrar, som fart och position, har en väldigt bra överenstämmelse. Modellen används sedan för att noggrannare undersöka hur olika parametrar påverkar det komplexa beteendet vid en graviationsassisterad manöver, genom att specifikt titta på effekterna av en pålagd dragkraft från motorn under den gravitationsassisterade manövern. Teoretiskt fås mest effekt på fart och riktning om dragkraften från motorn läggs på vid punkten närmast planeten. Resultaten från denna studie visar att beroende på vilken parameter man vill ändra så kan man erhålla mer effekt genom att lägga på dragkraften innan den närmsta punkten. Förklaringen till detta är att den gravitationsassisterade manövern är väldigt icke-linjär, så en tidigare pålagd dragkraft kan kraftigt förändra farkostens bana nära planeten, så att farkosten t.ex. kommer närmare och då påverkas mer.

This degree project was performed in collaboration with the division of nuclear physics at the department of physics, KTH Royal Institute of Technology. A partial goal of the project was to create a simulation model, where the relationship be- tween the multiplication of electrons that occurs in an ionization chamber and the different pressures of air in the detector could be visualized. The main goal was then to use this model in order to examine the behaviour of electron multiplication for different geometries of the simulated ionization chamber. The simulation was performed in Python 3.7 (Python Soft- ware Foundation, DE, United States), and geometry was modified by increasing and decreasing the simulated inner and anode wire radius of the chamber. Results showed that the peak of the multiplication curve occurred at different pressures for different geometries. When the anode wire radius was fixed, the peak occurred at a lower pressure for an increase of the inner radius, whereas, when the inner radius was fixed, the peak occurred at a higher pressure for an increase of the anode wire radius. The number of created electrons are dependent of Townsend’s coefficent, α, which in turn is dependent of the relationship between pressure and electric field strength. The electric field strength within an ionization chamber varies for different geometries, and therefore is the relationship between pressure and electric field that results in the max- imum value of α, and thus the maximum peak of the multiplication factor, consequently given by different pressures for different chamber geometries. If the results from the simulations in this project are to correspond with actual experimental data, the knowledge of this geometry-dependence may be used to include or exclude the multiplication peak in further measurements depending upon preference.

Energy demand forecasting has been more vital in recent years with countries setting goals to become climate neutral by 2050. Indeed, energy demand forecasting allows the understanding of drivers of the energy demand in all sectors of the economy. It also allows the planning of transformation of the future energy system. This study focuses on forecasting energy demand in Europe using a multi-country bottom-up modelling approach. The work explores ways of collecting large quantity of data to feed an energy model and method of completion for missing data series. It also aims at studying attributes that make a model user friendly and easy to use for the modelling of several countries. A model and a database are developed to answer these questions. A case application is conducted on the specific topic of the phase out of internal combustion engines in the EU to validate model dynamics and practical use. It is found that an energy demand forecasting model is easier and more time efficient to use with an included historical database. The case study shows that multi-country modelling can be relevant for policy assessment. Finally, improvements and future developments are proposed for the present work. / Prognoser för energiefterfrågan har blivit allt viktigare under de senaste åren i och med att länder har satt upp mål om att bli klimatneutrala senast 2050. Prognoser för energiefterfrågan gör det möjligt att förstå drivkrafterna bakom energiefterfrågan inom alla ekonomiska sektorer. Det gör det också möjligt att planera omvandlingen av det framtida energisystemet. Denna studie fokuserar på prognoser för energiefterfrågan i Europa med hjälp av en bottom-up-modelleringsmetod för flera länder. I arbetet undersöks olika sätt att samla in stora mängder data för att mata en energimodell och metoder för att komplettera saknade dataserier. Det syftar också till att studera attribut som gör en modell användar vänlig och lätt att använda för modellering av flera länder. En modell och en databas utvecklas för att besvara dessa frågor. För att validera modellens dynamik och praktiska användning genomförs en fallstudie om utfasningen av förbränningsmotorer i EU. Det visar sig att en modell för prognostisering av energiefterfrågan är enklare och mer tidseffektiv att använda med en inkluderad historisk databas. Fallstudien visar att modeller för flera länder kan vara relevanta för policybedömning. Slutligen föreslås förbättringar och framtida utveckling för det aktuella arbetet.