Risk Attitudes and Measures of Value for Risky Lotteries.

The topic of this thesis is decision-making under risk. I focus my analysis on expected utility theory by von Neumann and Morgenstern. I am especially interested in modeling risk attitudes represented by Bernoulli utility functions that belong to the following classes: Constant Absolute Risk Aversion, Decreasing Absolute Risk Aversion (understood as strictly decreasing) and in particular a subset thereof - Constant Relative Risk Aversion. I build a theory of buying and selling price for a lottery, the concepts defined by Raiffa, since such theory proves useful in analyzing a number of interesting issues pertaining to risk attitudes' characteristics within expected utility model. In particular, I analyze the following: - Chapter 2 - expected utility without consequentialism, buying/selling price gap, preference reversal, Rabin paradox - Chapter 3 - characterization results for CARA, DARA, CRRA, simple strategies and an extension of Pratt result on comparative risk aversion - Chapter 4 - riskiness measure and its intuition, extended riskiness measure and its existence, uniqueness and propertiesdecision-making under risk; lottery; gamble; expected utility theory; risk attitudes; CARA; DARA; CRRA; buying and selling price for a lottery; D81; D03; C91;Decision making; Strategic planning; Risk-taking (Psychology);

Is Cumulative Prospect Theory a Serious Alternative for the Expected Utility Paradigm?

The purpose of this paper is to demonstrate that Cumulative Prospect Theory is a serious alternative for Expected Utility Theory. It does not contradict Expected Utility, but includes it as a special example. A very useful example, because simple and yet very flexible, Expected Utility proved indispensable in many areas of economic analysis. Though a special example, because it does not capture some important effects observed in real choice behavior

Mechanisms of high pressure hydrogen environment embrittlement in austenitic stainless steels under tensile and fatigue loading

Hydrogen is known to degrade the mechanical performance of many engineering materials. The effects of its entry into metal matrices from manufacturing processes and service environments has been reported previously to result in loss of ductility and fracture toughness as well as increased fatigue crack propagation rates. One of these damage mechanisms, hydrogen environment embrittlement, was explored in stainless steels in order to provide better understanding of the role of the composition and microstructure in susceptibility to the effects of high-pressure hydrogen atmosphere on tensile and fatigue performance.Current knowledge in the field has been extended by investigating the influence of a high pressure hydrogen environment on monotonic tensile failure and fatigue crack propagation processes in the austenitic stainless steels, 304L and 316L, and to explore the effects of secondary variables on damage severity (temperature, pressure, frequency). Assessment of the role of microstructure and composition on susceptibility to damage was completed by comparison of alloys’ relative performance and their fracture characteristics by conducting tensile and fatigue testing in high pressure hydrogen environment at pressures ranging from 200 to 1000 bar and temperatures between -50 and +50?C. Fatigue testing work at high pressure (above 450 bar) and in the low temperature regime was completed using equipment designed as a part of the EngD project.Testing under high pressure hydrogen environment resulted in pronounced loss in ductility and increase in fatigue crack propagation rates in both materials, 304L steel was more adversely affected in all testing conditions than 316L. The degree of damage was observed to increase with increasing hydrogen pressure and reducing temperature in both load regimes. Increased testing temperature resulted in partial recovery of global ductility measurements in tensile tests while fatigue crack propagation rates were still significantly increased.The embrittlement mechanisms differed between 304L and 316L steels due to the different phase stability and deformation mechanisms characterising these alloys. In 304L, hydrogen was seen to facilitate crack propagation along microstructural features such as slip bands, phase and twin boundaries, with some indication of the effects of localised plasticity. While some of these mechanisms were observed to be operative in 316L, it was difficult to attribute the fracture of this steel to a particular mechanism. It appears that martensite formation and planar slip processes were not the only necessary conditions for hydrogen embrittlement. Features of interfacial fracture were noted in this steel, particularly at ferrite stringers and austenite matrix, possibly indicating fracture due to local accumulation of hydrogen and consequent ferrite embrittlement and localised fracture

Is Cumulative Prospect Theory a Serious Alternative for the Expected Utility Paradigm?

The purpose of this paper is to demonstrate that Cumulative Prospect Theory is a serious alternative for Expected Utility Theory. It does not contradict Expected Utility, but includes it as a special example. A very useful example, because simple and yet very flexible, Expected Utility proved indispensable in many areas of economic analysis. Though a special example, because it does not capture some important effects observed in real choice behavior

Ammonia in Dual-Fueled Internal Combustion Engines: Impact on NOx, N2O, and Soot Formation

The combustion of ammonia in internal combustion engines (ICE) releases nitrogen-related exhaust emissions. Numerous studies have shown that the increased formation of nitrous oxide (N2O) may offset ammonia’s carbon-free advantages, leading to a higher greenhouse gas potential than fossil fuels. Moreover, nitrogen contained in ammonia further promotes an increase in NOx formation. This study aims to expand the understanding of emission formation in dual-fuel ICEs when using ammonia as a fuel. By constant-pressure reactor simulations coupled with detailed reaction kinetics, the concept of equivalence ratio–temperature diagrams was employed to characterize conditions featuring high NOx, N2O, and soot concentrations. The diagrams were obtained for pure ammonia, pure n-heptane, and three blends with ammonia energy shares (AES) of 20, 50, and 80%. Our findings strengthen the perception that high concentrations of N2O in ICEs are related to incomplete combustion. A higher AES leads to increased N2O concentration during the ignition, going from single-digit ppm levels for pure n-heptane to conditions featuring levels 3 orders of magnitude higher for pure ammonia. In fully burned mixtures, N2O emissions feature a low fuel dependency and single-digit concentration levels only at low equivalence ratios and high temperatures. Further, varying contributions from the fuel NO, prompt NO, and thermal De-NOx mechanisms were observed with fuel composition; however, the thermal NO contribution led to a fuel-independent behavior for NOx emissions at temperatures above 2600 K. The soot concentration decreases as the carbon content in the fuel decreases. In our configuration, the lowest equivalence ratio at which the 0.1% soot yield limit was observed was 2.20 for pure n-heptane, 2.65 for AES of 20%, 5.05 for 50% AES, and not attained for higher AES. Ultimately, it was found that in fuel-rich regimes and at fully burned conditions, low concentrations of NOx and N2O emissions are observed.publishedVersio