Investigation of consumer over‐indebtedness within the German mail‐order industry using the Theory of Planned Behaviour

This research applied Ajzen´s theory of planned behaviour (TPB) to investigate the payment behaviour of over-indebted consumers within the German mailorder industry. Both imprisoned (N=41) and not-imprisoned (N=97) consumers´ attitudes, social norms, perceived behavioural control (PBC), its correspondent beliefs, and payment intention were analysed using structural equation modelling with the partial least squares approach. Although the sample size was small, the fit of the models were statistically valid and no statistical difference between imprisoned and not-imprisoned consumers was ascertained. The main predictor variables were analysed regarding gender specification and were enriched with moral norms and past behaviour. Subjective norm was the strongest predictor of payment behaviour of the not-imprisoned sample. Gender had a statistically relevant impact on payment intention. In sum, the main constructs of the TPB explained 35.8% of the variance in intention (R²) to pay further mail-order invoices on time. PBC increased the accuracy and the model was therefore superior to the theory of reasoned action (R² = 28.5%). The extension of the TPB with moral norms led to an increase of R² to 47.0%, with past behaviour to 39.5%, and with both to 49.0%. Therefore, this supports the extension of the basic model of the TPB in order to strengthen the explanation of the behaviour under consideration. In general, the outcome of this study identifies further related factors concerning payment behaviour, beyond those previously present within research and practice. From a practical perspective this study adds significant value to the understanding of over-indebtedness in Germany and its implication for the mailorder industry. It demonstrates the alarming debt situation of individuals over the last several years and the ambivalence regarding the normality of having debts in Germany. It emphasizes the complexity of payment behaviour and its personal influences. Payment of a mail-order invoice on time has no single specific causation, but typically is caused by more factors than previously thought

Investigation of consumer over‐indebtedness\ud within the German mail‐order industry using\ud the Theory of Planned Behaviour

This research applied Ajzen´s theory of planned behaviour (TPB) to investigate\ud the payment behaviour of over-indebted consumers within the German mailorder\ud industry. Both imprisoned (N=41) and not-imprisoned (N=97) consumers´\ud attitudes, social norms, perceived behavioural control (PBC), its correspondent\ud beliefs, and payment intention were analysed using structural equation\ud modelling with the partial least squares approach. Although the sample size\ud was small, the fit of the models were statistically valid and no statistical\ud difference between imprisoned and not-imprisoned consumers was ascertained.\ud The main predictor variables were analysed regarding gender specification and\ud were enriched with moral norms and past behaviour. Subjective norm was the\ud strongest predictor of payment behaviour of the not-imprisoned sample. Gender\ud had a statistically relevant impact on payment intention.\ud In sum, the main constructs of the TPB explained 35.8% of the variance in\ud intention (R²) to pay further mail-order invoices on time. PBC increased the\ud accuracy and the model was therefore superior to the theory of reasoned action\ud (R² = 28.5%). The extension of the TPB with moral norms led to an increase of\ud R² to 47.0%, with past behaviour to 39.5%, and with both to 49.0%. Therefore,\ud this supports the extension of the basic model of the TPB in order to strengthen\ud the explanation of the behaviour under consideration.\ud In general, the outcome of this study identifies further related factors concerning\ud payment behaviour, beyond those previously present within research and\ud practice. From a practical perspective this study adds significant value to the\ud understanding of over-indebtedness in Germany and its implication for the mailorder\ud industry. It demonstrates the alarming debt situation of individuals over\ud the last several years and the ambivalence regarding the normality of having\ud debts in Germany. It emphasizes the complexity of payment behaviour and its\ud personal influences. Payment of a mail-order invoice on time has no single\ud specific causation, but typically is caused by more factors than previously\ud thought

A conceptual design of a propulsion system for an autonomous underwater vehicle

The need for developing propulsion systems to support missions of increased endurance for autonomous underwater vehicles is investigated and a conceptual system is proposed, based on currently available technology and desired system characteristics. The investigation evaluates and ranks alternative energy sources and proposes the use of a closed Brayton cycle gas turbine power plant using a chemical energy heat source with a metallic fuel. A thruster system using electric propulsion motors and screw propellers is selected. Evaluation factors include reliability, depth independent operation, weight, endurance, quietness and efficiency. Reliability of the proposed system is analyzed and the design modified to meet proposed reliability requirements. A knowledge-based system is developed to manage the operation of the propulsion plant in an autonomous manner. A simulation system is developed using Common Lisp and the operation of the propulsion plant and its knowledge-based management system are evaluated using the simulator

Stochastic System Design and Applications to Stochastically Robust Structural Control

The knowledge about a planned system in engineering design applications is never complete. Often, a probabilistic quantification of the uncertainty arising from this missing information is warranted in order to efficiently incorporate our partial knowledge about the system and its environment into their respective models. In this framework, the design objective is typically related to the expected value of a system performance measure, such as reliability or expected life-cycle cost. This system design process is called stochastic system design and the associated design optimization problem stochastic optimization. In this thesis general stochastic system design problems are discussed. Application of this design approach to the specific field of structural control is considered for developing a robust-to-uncertainties nonlinear controller synthesis methodology. Initially problems that involve relatively simple models are discussed. Analytical approximations, motivated by the simplicity of the models adopted, are discussed for evaluating the system performance and efficiently performing the stochastic optimization. Special focus is given in this setting on the design of control laws for linear structural systems with probabilistic model uncertainty, under stationary stochastic excitation. The analysis then shifts to complex systems, involving nonlinear models with high-dimensional uncertainties. To address this complexity in the model description stochastic simulation is suggested for evaluating the performance objectives. This simulation-based approach addresses adequately all important characteristics of the system but makes the associated design optimization challenging. A novel algorithm, called Stochastic Subset Optimization (SSO), is developed for efficiently exploring the sensitivity of the objective function to the design variables and iteratively identifying a subset of the original design space that has v i high plausibility of containing the optimal design variables. An efficient two-stage framework for the stochastic optimization is then discussed combining SSO with some other stochastic search algorithm. Topics related to the combination of the two different stages for overall enhanced efficiency of the optimization process are discussed. Applications to general structural design problems as well as structural control problems are finally considered. The design objectives in these problems are the reliability of the system and the life-cycle cost. For the latter case, instead of approximating the damages from future earthquakes in terms of the reliability of the structure, as typically performed in past research efforts, an accurate methodology is presented for estimating this cost; this methodology uses the nonlinear response of the structure under a given excitation to estimate the damages in a detailed, component level

Reliability-based optimization design of geosynthetic reinforced embankment slopes

This study examines the optimization design of geosynthetic reinforced embankment slopes (GRES) considering both economic benefits and technical safety requirements. In engineering design, cost is always a big concern. To minimize the cost, engineers tend to seek an optimal combination of design parameters among the considered alternatives while ensuring the optimal solution is safe. Reliability-based optimization (RBO) is such a technique that provides engineers the optimal design with the minimum cost while all technical design requirements are satisfied. The research goal of this study is to implement a mathematical formulation algorithm of the RBO technique in GRES design. To achieve this goal, slope stability is studied using the limit equilibrium method (LEM). Considering geotechnical uncertainties, the first-order reliability method (FORM) is adopted to perform probabilistic slope stability analysis, address the critical slip surfaces, and assess the reliability of the slope system. The slope stability and reliability are then used as the crucial constraints in the following RBO procedure, wherein the constrained optimization problem will be solved by adopting a genetic algorithm (GA). Sensitivity analysis is carried out on the basis of the probabilistic slope stability analysis to highlight the influence of each involved random variable on the probabilistic performance of the slope system; and thereby, infer the corresponding impact on the optimization design. A framework of how to implement the RBO in GRES design is proposed. An engineering case history is accordingly studied to demonstrate the practical application of the proposed design framework. Compared to the conventional (manual) process, the proposed design framework is more systematic and effective, especially with the large number of design variables involved in geosynthetic reinforced slopes. --Abstract, page iii

The Usefulness of Truth : An Enquiry Concerning Economic Modelling

This thesis attempts to justify a normative role for methodology by sketching a pragmatic way out of the dichotomy between two major strands in economic methodology: empiricism and postmodernism. I discuss several methodological approaches and assess their aptness for theory appraisal in economics. I begin with the most common views on methodology (i.e. empiricism and postmodernism) and argue why they are each ill-suited for giving methodological prescriptions to economics. Then, I consider positions that avoid the errors of empiricism and postmodernism. I specifically examine why the two major strands of methodological criticism fail to give helpful methodological advice to economists and sketch out a pragmatic approach that can do this

Reliability Analysis and Reliability-Based Optimisation Design of SWATH Ships

The primary objective of the current research presented in this thesis was to develop a rationally-based structural design procedure for SWATH type vessels by applying reliability analysis and reliability-based optimisation techniques. Firstly, the primary loads for PATRIA, a built SWATH ship, were calculated by a theoretical method developed by Chan (1990,1991). The response amplitude operators of loads in regular waves were calculated by a three-dimensional oscillating source distribution method in association with linearised potential theory. A program, SPEC, was developed to carry out spectral analysis and to calculate extreme design values as well as instantaneous pressure distribution in the submerged parts of the vessel. Furthermore several factors, such as load combination and longitudinal side force distribution, which are important in structural analysis, were discussed. Having determined the primary loads acting on PATRIA, a series of finite element analyses was carried out aimed at increasing the understanding of the structural behaviour of the ship, and establishing a simplified model for system reliability analysis and multiple criteria optimisation. At the component level the existing ultimate strength formulations for plate panels and stiffened plates were discussed and calibrated by using a considerable amount of experimental and numerical data. A new algorithm for stiffened plates was proposed. The reliability of plating and stiffened plates was then evaluated by using AFOSM, SORM and Monte Carlo simulation methods to investigate the accuracy of these methods for these types of limit states equations. It is found that Guedes Soares' formulae and Faulkner's method are the best for plate panels and stiffened plates respectively. The results for failure probability from SORM are much better than those from AFOSM. In these cases the AFOSM always underestimates the failure probability. The largest relative errors of failure probability and reliability index reach -45.1% and 7.4% respectively. Considering the nominal nature of reliability index the difference between the two methods is so small that the values obtained from AFOSM are acceptable in practice. At the system level the conventional beta-unzipping method was extended by introducing a discarding process in searching for significant failure modes of the structural system. The extension could save computational time when the combined load effects are considered in the analysis. The method was then used to analyse a typical frame in PATRJA. In the analysis the combined load effect including buckling was considered. It is found that the most critical part is in the haunch area, and all the critical sections in the identified significant failure modes are in the haunch area. Hence it may be said that more attention should be paid to the haunch area. The buckling has a moderate effect on system reliability in this particular case, and should be considered in the analysis. Finally, the reliability-based optimisation techniques were used to achieve an efficient design. Various reliability-based optimisation formulations and their associated problems were first discussed. An algoritlim, in which the component and system reliability indices could be balanced, was proposed. The proposed strategy was then applied to optimise the one-dimensional model for the transverse cross-deck frame in PATRIA. It is found that: The algorithm works very well. Computational time in the analysis is not a problem because the system reliability calculation is only applied to the optimum structure. The original design is quite close to the optimal one, so the margin for optimisation is small. It is of interest to note that the system reliability index for the original structure is only 3.756, while it is 4.712 for the optimum structure, at the same time the optimum one is 13% lighter than the original one. The haunch area is confirmed as the critical part. From the values of design variables of the optimum structure, it is observed that increasing the thickness of the side shell is the most efficient way to improve the safety in this area