Stalk lodging, or failure of the stalk structure, presents a serious problem in the production of maize (Zea mays L.). Lodged stalks negatively impact crop yields by inhibiting further grain growth and often prevent the harvest of the grain. Addressing this problem requires the development of new maize hybrids that exhibit enhanced lodging resistance, which in turn requires an understanding of the parameters that influence lodging resistance. Current methods make use of specimen-specific geometry and material properties, but these methods have limited ability to examine geometric effects and can require excessive time. A parameterized model of the maize stalk has the potential to overcome these limitations. The purpose of this study was to develop a model of the maize stalk cross-section that could accurately predict transverse stiffness. Principal component analysis was utilized to discover underlying geometric patterns that could be used as parameters in a cross-sectional model. Using the resulting principal components, a series of approximated cross-sections was created that represented various levels of fidelity to real cross-section geometry. The real and approximated cross-sections were modeled in transverse compression with a prescribed deformation load, and the predictive accuracy of each approximated model was calculated. A sensitivity study was also performed to quantify the strength of individual parameter effects. The simplest model, an elliptical cross-section, accurately predicted transverse stiffness while minimizing the number of model parameters. This model may later be used as a basis for a three-dimensional parameterized model of the maize stem.

An option is a contract between two parties where the holder has the option to buy or sell some underlying asset after a predefined exercise time. Options where the holder only has the right to buy or sell at the exercise time is said to be of European-style, while options that can be exercised any time before the exercise time is said to be of American-style. Asian options are options where the payoff is determined by some average value of the underlying asset, e.g., the arithmetic or the geometric average. For arithmetic Asian options, there are no closed-form pricing formulas, and one must apply numerical methods. Several methods have been proposed and tested for Asian options. For example, the Monte Carlo method isslowforEuropean-styleAsianoptionsandnotapplicableforAmerican-styleAsian options. In contrast, the finite difference method have successfully been applied to price both European- and American-style Asian options. But from a financial point of view, one is also interested in different measures of sensitivity, called the Greeks, which are hard approximate with the finite difference method. For more accurate approximations of the Greeks, researchers have turned to the finite element method with promising results for European-style Asian options. However, the finite element method has never been applied to American-style Asian options, which still lack accurate approximations of the Greeks. Here we present a study of pricing European- and American-style Asian options using the finite element method. For European-style options, we consider two different pricing PDEs. The first equation we consider is a convection-dominated problem, which we solve by applying the so-called streamline-diffusion method. The second equation comes from modelling Asian options as options on a traded account, which we solve by using the so-called cG(1)cG(1) method. For American-style options, the model based on options on a traded account is not applicable. Therefore, we must consider the first convection-dominated problem. To handle American-style options, we study two different methods, a penalty method and the projected successive over-relaxation method. For European-style Asian options, both approaches give good results, but the model based on options on a traded account show more accurate results. For American-style Asian options, the penalty method give accurate results. Meanwhile, the projected successive over-relaxation method does not converge properly for the tested parameters. Our result is a first step towards an accurate and fast method to calculate the price and the Greeks of both European- and American-style Asian options. Because good estimations of the Greeks are crucial when hedging and trading of options, we anticipate that the ideas presented in this work can lead to new ways of trading with Asian options.

In design of bridges and for estimation of dynamic properties and load carrying capacity Finite Element Method (FEM) is often used as a tool. The physical quantities used in the Finite Element (FE) model are often connected to varying degrees of uncertainty. To deal with these uncertainties conservative parameter estimates and safety factors are used. By calibrating the bridge FE model to better fit with the response of the real structure, less conservative parameter values can be chosen. This method of comparing measured and response with estimates from a FE model and calibrating the model parameters is called Finite Element Model Updating (FEMU). In the present thesis different aspects of FEMU are investigated. The first part comprises a literature review covering all aspects of FEMU with special focus on the choice of updating parameters, objective functions for iterative updating procedures and the automatic pairing of modes. This part is concluded with a flowchart suggesting a systematic approach to a FEMU project. In the second part of the text two bridge case studies are presented. In the first case study a railway bridge in the north of Sweden is studied. A detailed FE bridge model from a previous project is used as a simulation model for extraction of modal data by eigenvalue analysis. Then simplified models are created and attempts to update these models are performed. The updating parameters are chosen based on a simple sensitivity analysis. Tests are performed to investigate the influence of chosen updating parameters and objective function on the computational cost and the quality of the updated model. Case study number two is more comprehensive and focuses on the sensitivity analysis for the choice of updating parameters and on the choice of objective function. A road bridge in the Stockholm area is used and as for case study one a detailed model from a previous project is used as simulation model. Also a new criteria for the automatic pairing of modes is presented and tested. In the end an attempt to verify two of the updated models is performed. / <p>QC 20150825</p>