Lagrangian potential flow methods are a promising alternative to mainstream wind turbine aerodynamics tools such as blade element momentum methods and grid-based computation fluid dynamics approaches. Potential flow methods are relatively easy to setup and robust with respect to geometry. With the advent of numerical techniques such as the fast multipole method, potential flow methods can be made computationally fast. Viscous core modelling has led to improvements in accuracy and numerical robustness. A C++ programming library employing Prandtl-Weissinger lifting line wing models and tailorable potential flow wake models has been developed under the name LibAero. The library offers steady-state, periodic, and unsteady flow simulators that can be used interchangeably with wake models. (Periodic and unsteady simulation are still under development and validation.) Wake models are constructed from potential flow elements such as vortex particles, laments, and sheets. Fast multipole method, symmetry modelling, multigrid method, and relaxation iteration are utilized to accelerate the computation of element-by-element interactions. The computational performance is assessed and the numerical results are validated against wind tunnel experimental data from the MEXICO Project and the Tj reborg wind turbine. The results of steady-state simulations with respect to a variety of numerical options and rotor blade designs are presented and conclusions are drawn. / Graduate

In this thesis, we investigate methods of finding a local minimum for unconstrained problems of non-convex functions with n variables, by following the solution curve of a system of ordinary differential equations. The motivation for this was the fact that existing methods (e.g. those based on Newton methods with line search) sometimes terminate at a non-stationary point when applied to functions f(x) that do not a have positive-definite Hessian (i.e. ∇²f → 0) for all x. Even when methods terminate at a stationary point it could be a saddle or maximum rather than a minimum. The only method which makes intuitive sense in non-convex region is the trust region approach where we seek a step which minimises a quadratic model subject to a restriction on the two-norm of the step size. This gives a well-defined search direction but at the expense of a costly evaluation. The algorithms derived in this thesis are gradient based methods which require systems of equations to be solved at each step but which do not use a line search in the usual sense. Progress along the Continuous Steepest Descent Path (CSDP) is governed both by the decrease in the function value and measures of accuracy of a local quadratic model. Numerical results on specially constructed test problems and a number of standard test problems from CUTEr [38] show that the approaches we have considered are more promising when compared with routines in the optimization tool box of MATLAB [46], namely the trust region method and the quasi-Newton method. In particular, they perform well in comparison with the, superficially similar, gradient-flow method proposed by Behrman [7].

Subject of research: evaluation of economic efficiency of investment projects. Objective of research: to develop a model for the evaluation of economic efficiency of investment projects based on the discounted cash flow methods and adapted to the Lithuanian business environment. The modern science of economics offers quite a wide range of methods for evaluating the economic efficiency of investments, however, most of them are highly time-consuming and involve complicated calculations. Whereas investors usually require a measure of investment projects‘ efficiency which is readily calculated, objective and easily understandable and which reveals the attractiveness of business ideas. Therefore, in the author‘s view, the current technique of evaluating investment projects based on cash flows can fully meet the investors‘ needs provided that specific features of the technique‘s application are taken into account. Based on the examinations involving the theoretical and application aspects of the analysis and evaluation of investment projects, i. e. the investment project‘s life cycle model, the cash flow calculation and the discount rate setting methods, as well as the main and auxiliary methods for evaluating investment projects‘ efficiency, a model for the evaluation of investment projects which enables the analysis and selection of alternative investment projects has been developed. / Mokslinių tyrimo objektas – investicinių projektų ekonominio efektyvumo vertinimas. Tyrimų tikslas – sukurti investicinių projektų ekonominio efektyvumo vertinimo modelį, pagrįstą diskontuotų pinigų srautų metodais ir pritaikytą Lietuvos verslo sąlygoms. Šiuolaikinis ekonomikos mokslas siūlo pakankamai platų investicijų efektyvumo rodiklių spektrą, tačiau daugeliu atvejų siūlomi metodai pasižymi daug išteklių reikalaujančiais ir gana sudėtingais skaičiavimais, o investuotojui reikalingas lengvai ir pakankamai greitai skaičiuojamas, objektyvus ir visiems suprantamas investicijų efektyvumo vertinimo matas, parodantis tam tikros verslo idėjos patrauklumą. Įvertinus šias aplinkybes, autoriaus nuomone, esama pinigų srautais grindžiama investicinių projektų vertinimo metodologija gali visiškai patenkinti investuotojų poreikius, su sąlyga, kad bus atsižvelgta į įvairius aspektus, susijusius su jos taikymo ypatumais. Remiantis atliktais tyrimais, kurių metu išnagrinėti teoriniai ir taikomieji investicinio projekto analizės ir vertinimo aspektai – investicinio projekto gyvavimo ciklo modelis, pinigų srautų skaičiavimo ir diskonto normos nustatymo metodai, investicinio projekto vertinimo pagrindiniai ir pagalbiniai metodai, buvo parengtas investicinių projektų ekonominio efektyvumo vertinimo modelis, leidžiantis atlikti alternatyvių projektų analizę ir atranką. Raktiniai žodžiai: investicinių projektų vertinimas, pinigų srautai, projekto gyvavimo ciklas, diskontuotų pinigų srautų... [toliau žr. visą tekstą]

Mokslinių tyrimo objektas – investicinių projektų ekonominio efektyvumo vertinimas. Tyrimų tikslas – sukurti investicinių projektų ekonominio efektyvumo vertinimo modelį, pagrįstą diskontuotų pinigų srautų metodais ir pritaikytą Lietuvos verslo sąlygoms. Šiuolaikinis ekonomikos mokslas siūlo pakankamai platų investicijų efektyvumo rodiklių spektrą, tačiau daugeliu atvejų siūlomi metodai pasižymi daug išteklių reikalaujančiais ir gana sudėtingais skaičiavimais, o investuotojui reikalingas lengvai ir pakankamai greitai skaičiuojamas, objektyvus ir visiems suprantamas investicijų efektyvumo vertinimo matas, parodantis tam tikros verslo idėjos patrauklumą. Įvertinus šias aplinkybes, autoriaus nuomone, esama pinigų srautais grindžiama investicinių projektų vertinimo metodologija gali visiškai patenkinti investuotojų poreikius, su sąlyga, kad bus atsižvelgta į įvairius aspektus, susijusius su jos taikymo ypatumais. Remiantis atliktais tyrimais, kurių metu išnagrinėti teoriniai ir taikomieji investicinio projekto analizės ir vertinimo aspektai – investicinio projekto gyvavimo ciklo modelis, pinigų srautų skaičiavimo ir diskonto normos nustatymo metodai, investicinio projekto vertinimo pagrindiniai ir pagalbiniai metodai, buvo parengtas investicinių projektų ekonominio efektyvumo vertinimo modelis, leidžiantis atlikti alternatyvių projektų analizę ir atranką. / Subject of research: evaluation of economic efficiency of investment projects. Objective of research: to develop a model for the evaluation of economic efficiency of investment projects based on the discounted cash flow methods and adapted to the Lithuanian business environment. The modern science of economics offers quite a wide range of methods for evaluating the economic efficiency of investments, however, most of them are highly time-consuming and involve complicated calculations. Whereas investors usually require a measure of investment projects‘ efficiency which is readily calculated, objective and easily understandable and which reveals the attractiveness of business ideas. Therefore, in the author‘s view, the current technique of evaluating investment projects based on cash flows can fully meet the investors‘ needs provided that specific features of the technique‘s application are taken into account. Based on the examinations involving the theoretical and application aspects of the analysis and evaluation of investment projects, i. e. the investment project‘s life cycle model, the cash flow calculation and the discount rate setting methods, as well as the main and auxiliary methods for evaluating investment projects‘ efficiency, a model for the evaluation of investment projects which enables the analysis and selection of alternative investment projects has been developed.

Mit zunehmender wirtschaftlicher Bedeutung der Emerging Markets steigt der Bedarf an Unternehmensbewertungen im Kontext dieser Länder. Ihre besonderen Charakteristika erschweren jedoch eine Anwendung der in Industrieländern standardmäßig verwendeten Methoden. Ausgehend von idealisierenden Bedingungen wird in einer integrativen Betrachtung der Frage nachgegangen, wie die vorherrschenden Bedingungen (insbesondere Länderrisiken und Investmentbarrieren) in einem grenzüberschreitenden Bewertungskalkül berücksichtigt werden können.

Mit zunehmender wirtschaftlicher Bedeutung der Emerging Markets steigt der Bedarf an Unternehmensbewertungen im Kontext dieser Länder. Ihre besonderen Charakteristika erschweren jedoch eine Anwendung der in Industrieländern standardmäßig verwendeten Methoden. Ausgehend von idealisierenden Bedingungen wird in einer integrativen Betrachtung der Frage nachgegangen, wie die vorherrschenden Bedingungen (insbesondere Länderrisiken und Investmentbarrieren) in einem grenzüberschreitenden Bewertungskalkül berücksichtigt werden können.