In this thesis, a load path caused by arching action in reinforced concrete slabs is described and validated using a three-dimensional model. Currently, the CHBDC enforces a 4 meter girder spacing requirement in the design of deck slabs. The aim of this thesis is to investigate the load path induced by arching action in deck slabs with a wide range of girder spacing. To do this, a two-dimensional model was developed to examine the path of horizontal stress and was validated using a FEM. A parametric study showed that girder spacing does not affect the development of restraining stress while cantilever width does. As well, cracking of the slab is necessary for arching action to occur. These results help with future development of a rational model to be used by bridge designers.

Le développement régional et l'inspiration puisée dans d'autres disciplines : Les possibilités de l'application des concepts de la biologie évolutionnaire aux sujets sélectionnés du développement régional. - L'application des concepts de la biologie évolutionnaire (BE) à la problématique de la réalité socioéconomique n'est pas un sujet nouveau dans certaines disciplines socioéconomiques, même si cette inspiration pour la problématique de la géographie socioéconomique, ou plutôt du développement régional, est plus récente et en général se fonde sur les applications réalisées notamment en économie. L'objectif principal de cette thèse est d'identifier de nouveaux concepts de la BE et de tenter de les appliquer aux sujets sélectionnés du développement régional dierectement, sans le rôle d'intermédiaire d'autres disciplines. L'attention est dans un premier temps prêtée à la recherche du cadre théorique convenable et d'un aperçu des concepts de la BE déjà appliqués aux sciences sociales. La seconde partie présente certains concepts de la BE pour lesquels les applications potentielles (par l'intermédiaire des analogies et des métaphores) aux thèmes choisis du développement régional ont été identifiées. Les concepts appliqués ont été divisés en quatre ensembles thématiques biologiques plus larges - l'adaptation, la coévolution, la sélection et la spéciation. L'application de la spéciation peut être probablement perçue comme la contribution la plus précieuse de la thèse. Elle s'appuie sur l'hypothèse qu'il est possible d'identifier certains traits analogues entre les concepts socioéconomiques path dependence et lock-in et les concepts de la BE concernant la spéciation et d'identifier et de classifier les mécanismes / structures qui fonctionnent comme des barrières socioéconomiques. Mots-clés : développement régional ; application des concepts de la biologie évolutionnaire ; path dependence

Finding the shortest paths in a graph has been studied for a long time, and there are many main memory based algorithms dealing with this problem. Among these, Dijkstra's shortest path algorithm is one of the most commonly used efficient algorithms to the non-negative graphs. Even more efficient algorithms have been developed recently for graphs with particular properties such as the weights of edges fall into a range of integer. All of the mentioned algorithms require the graph totally reside in the main memory. Howevery, for very large graphs, such as the digital maps managed by Geographic Information Systems (GIS), the requirement cannot be satisfied in most cases, so the algorithms mentioned above are not appropriate. My objective in this thesis is to design and evaluate the performance of external memory (disk-based) shortest path algorithms and data structures to solve the shortest path problem in very large digital maps. In particular the following questions are studied:What have other researchers done on the shortest path queries in very large digital maps?What could be improved on the previous works? How efficient are our new shortest paths algorithms on the digital maps, and what factors affect the efficiency? What can be done based on the algorithm? In this thesis, we give a disk-based Dijkstra's-like algorithm to answer shortest path queries based on pre-processing information. Experiments based on our Java implementation are given to show what factors affect the running time of our algorithms.

It is widely accepted that the LGB (Lesbian, gay and bisexual) population have a higher risk of psychological distress compared to their heterosexual counterparts. Meyer (2003) proposed the minority stress model to explain this increased prevalence. This model proposed that the LGB population are subjected to additional stressors due to their minority status which results in the increased psychological distress observed. The purpose of this study was to investigate some of the risk factors proposed by this model, specifically experiences of sexual prejudice, negative internalised beliefs about homosexuality/bisexuality, coping strategies and how these factors interact to influence the development of psychological distress. This study included 542 LGB individuals who completed measures of sexual prejudice, internalised homophobia, coping strategies and current levels of psychological distress using an online survey. The study found a high prevalence of sexual prejudice within the sample, with 84% of the sample reporting at least one experience of sexual prejudice. 67% reported being verbally abused and 17% reported being physically assaulted. A high number of participants scored above the cut-off for a diagnosis of depression (27%) and anxiety (19%). Regression and path analysis revealed that maladaptive coping had the strongest effect on psychological distress. Sexual prejudice and internalised homophobia, also both had a significant direct impact upon psychological distress, and they were also partially mediated by maladaptive coping. Problem-focused coping was found to be a protective factor with a direct, albeit weak, effect on psychological distress. Problem-focused coping also partially mediated the relationship between sexual prejudice and psychological distress, slightly reducing the negative impact of sexual prejudice. The results suggest that maladaptive coping was the greatest risk factor, out of the ones measured, in the development of psychological distress in the LGB population. The outcomes suggest that clinical psychologists may wish to target their interventions at the development of more adaptive coping strategies, and the reduction of internalised homophobia. They should consider ways to reduce experiences of sexual prejudice by working at a community level to reduce the stigma of homosexuality/bisexuality.

No description available.

In this thesis, a cognitive neural predictive controller system has been designed to guide a nonholonomic wheeled mobile robot during continuous and non-continuous trajectory tracking and to navigate through static obstacles with collision-free and minimum tracking error. The structure of the controller consists of two layers; the first layer is a neural network system that controls the mobile robot actuators in order to track a desired path. The second layer of the controller is cognitive layer that collects information from the environment and plans the optimal path. In addition to this, it detects if there is any obstacle in the path so it can be avoided by re-planning the trajectory using particle swarm optimisation (PSO) technique. Two neural networks models are used: the first model is modified Elman recurrent neural network model that describes the kinematic and dynamic model of the mobile robot and it is trained off-line and on-line stages to guarantee that the outputs of the model will accurately represent the actual outputs of the mobile robot system. The trained neural model acts as the position and orientation identifier. The second model is feedforward multi-layer perceptron neural network that describes a feedforward neural controller and it is trained off-line and its weights are adapted on-line to find the reference torques, which controls the steady-state outputs of the mobile robot system. The feedback neural controller is based on the posture neural identifier and quadratic performance index predictive optimisation algorithm for N step-ahead prediction in order to find the optimal torque action in the transient to stabilise the tracking error of the mobile robot system when the trajectory of the robot is drifted from the desired path during transient state. Three controller methodologies were developed: the first is the feedback neural controller; the second is the nonlinear PID neural feedback controller and the third is nonlinear inverse dynamic neural feedback controller, based on the back-stepping method and Lyapunov criterion. The main advantages of the presented approaches are to plan an optimal path for itself avoiding obstructions by using intelligent (PSO) technique as well as the analytically derived control law, which has significantly high computational accuracy with predictive optimisation technique to obtain the optimal torques control action and lead to minimum tracking error of the mobile robot for different types of trajectories. The proposed control algorithm has been applied to monitor a nonholonomic wheeled mobile robot, has demonstrated the capability of tracking different trajectories with continuous gradients (lemniscates and circular) or non-continuous gradients (square) with bounded external disturbances and static obstacles. Simulations results and experimental work showed the effectiveness of the proposed cognitive neural predictive control algorithm; this is demonstrated by the minimised tracking error to less than (1 cm) and obtained smoothness of the torque control signal less than maximum torque (0.236 N.m), especially when external disturbances are applied and navigating through static obstacles. Results show that the five steps-ahead prediction algorithm has better performance compared to one step-ahead for all the control methodologies because of a more complex control structure and taking into account future values of the desired one, not only the current value, as with one step-ahead method. The mean-square error method is used for each component of the state error vector to compare between each of the performance control methodologies in order to give better control results.

One channel model that characterises multipath fading effect of a wireless channel is called Flat Rayleigh Fading channel model. Given the properties of Flat Rayleigh Fading channel, an equation to find the capacity of a Flat Rayleigh fading channel with hard decision decoding is derived. The difference of power requirement to achieve the Additive White Gaussian Noise (AWGN) capacity over a Flat Rayleigh Fading channel fading is found to increase exponentially with Es /N0 . Upper and lower bounds of error performance of linear block codes over a Flat Rayleigh Fading channel are also studied. With the condition that the excess delay of a channel is known earlier, it is shown that a correlator with shorter length, according to excess delay of the channel, can be constructed for use in wireless channel response measurements. Therefore, a rule of construction of a shorter length correlator is defined, involving concatenation of parts of a Constant Amplitude Zero Auto-Correlation (CAZAC) sequence. Simulation of [136,68,24] Double Circulant Code with Dorsch List Decoding is also done in order to evaluate error performance of the channel coding scheme over one of the IEEE Wireless Metropolitan Area Network (WirelessMAN) channel models, the Stanford University Interim Channel Model No. 5 (SUI-5) channel. Performance of the channel cod- ing was severely degraded over the SUI-5 channel when it is compared to its performance over the AWGN channel. Indoor path losses within three multifloor office buildings were investigated at 433 MHz, 869 MHz and 1249 MHz. The work involved series of extensive received signal strength measurements within the buildings for all of the considered frequencies. Results have shown that indoor path loss is higher within a square footprint building than indoor path loss in a rectangular building. Parameters of Log-Distance Path Loss and Floor Attenuation Factor Path Loss models have been derived from the measurement data. In addition, a new indoor path loss prediction model was derived to cater for path loss pre- diction within multifloor buildings with indoor atriums. The model performs with better prediction accuracy when compared with Log-Distance Path Loss and Floor Attenuation Factor Path Loss models.

Worldwide energy policies are built on three pillars: ‘cost competitiveness’, ‘security of energy supply’, and ‘environmental responsibility.’ This has brought about the integration of renewable energy sources into national systems with the deployment of policy instruments to make renewable energy sources electricity (RES-E) capable of nearly competing on a commercial basis with traditional forms of electricity generation. At the national level within the EU, there has been much experimentation with different policy instruments with varying levels of success. Nevertheless the EU as a whole will not meet its stipulated renewable energy target. This study challenges the theoretical and abstract evaluation presented in the literature about EU wind power delivery systems and has developed an integrative evaluation framework. This evaluation framework is used in this study to present the views of key stakeholders on their experiences with the performance of key policy instruments (feed-in tariff, and renewables obligation) implemented in three EU Member States namely: Germany, The Netherlands, and United Kingdom. It also challenges the EU-wide harmonised renewable energy policy agenda as proposed in Directive 2001/77/EC. The concept of path dependency of the historical institutional approach was adopted in order to explore the diversity of the wind power industry across the three country cases. An indepth semi-structured interview with fifty-five senior wind power policy makers and experts was conducted to explore the historical emergence, the architect, and the outcome of the support and implementation of the policy instruments. Findings showed that the approach to wind power deployment in the three country cases differs significantly and this has affected the pattern of each country’s wind power policy instrument. Also, the role and contribution of the stakeholder groups to the success of the wind power policy instruments differ significantly in each of the country cases. This helps to explain the performance of the different policy instruments adopted. Concerning the harmonisation of EU renewable energy policy instruments which have received much attention in recent times, this study found that harmonisation based on a single policy instrument is not feasible and may ultimately inhibit the growth of the European wind power market. A harmonised system may cause uncertainties amongst willing investors, thereby causing a withdrawal of further investment in the wind power market. If this happens, Europe may also lose its position as the world leader in the wind power market. Furthermore, national histories demonstrates that Member States have different culture, stakeholder groups, political, and business practices that will influence policy instruments and the likelihood of any policy succeeding. Thus, rather than promoting harmonisation and political market for wind power, it is important that Member States adopt and implement, stable, flexible, and transparent policy instruments that enable wind power and other renewable energy sources to emerge, develop, and go through the R&D stage to a point of maturity where they can compete with other energy sources with limited financial support.

No description available.

This study examines the relationship between voluntary associations and the psychological well-being of older people through path analysis. The goals of the study were: (1) to ascertain whether differential research findings are due to measurement artifact, (2) to evaluate the assertions of traditional activity theory versus those of a modified activity theory taking quality into account, and (3) to isolate factors which contribute to and/or mediate the relationship of voluntary-association participation and psychological well-being. Analysis was conducted at two levels. First, a model was developed to study individual participation in voluntary associations, satisfaction with participation, and well-being. Second, a model was developed to examine types of volimtary associations and their effects on satisfaction with participation and on well-being. Subjects were 50 members of voluntary associations who were recruited from target groups in the Durham, North Carolina area. There were 26 males and 24 females. They ranged in age from 61 to 90. The results of the individual path analysis indicate that differential findings due to measurement artifact is likely. After controlling for the effects of health, education, income, and social desirability bias in the model, voluntary-association activity as measured by the Chapin scale was significantly correlated with psychological well-being as measured by the Bradburn scale; however, measurement of volantary-association activity by an average number of meetings measure was not correlated significantly with any measure of well-being. In addition, the Chapin measure did not correlate significantly with the LSI-Z or with the Cantril Ladder. The examination of traditional activity theory versus modified activity theory was somewhat inconclusive, although the results did suggest that mere participation may have effects on psychological well-being that are equal to or greater than the effects of satisfaction with participation. The results of the voluntary association path analysis indicate that their characteristics have consequences both for satisfaction with voluntary associations and for psychological well-being. People who belonged to larger groups were significantly more satisfied with those groups and also were significantly happier. Also, even though people who belonged to age-graded groups were slightly more satisfied with these groups, they were significantly less happy. In addition, people who belonged to church-related groups were slightly more satisfied with these groups, but were significantly less happy. Finally, people who belonged to instrumental groups were slightly less satisfied with these groups than with more expressive groups and were slightly less happy. Discussion focused on possible explanations for the findings. It was suggested that a "happiness" measure seems more sensitive to effects such as those of voluntary-association activity. As for satisfaction with voluntary associations, it was acknowledged that the mere fact that respondents are taking an active part in life may be a key factor to their well-being. As explanations for the findings related to size of voluntary associations, it was suggested that large group activity may be less emotionally demanding and/or may allow contact with more potential friends. For age-graded groups, it was suggested that many older people may maintain a view of themselves as "younger" as the result of non-age-graded activities. For church- related groups, it was suggested that prior findings are due to the relationship between religiosity and well-being rather than characteristics of such groups. Finally, for the instrumental-expressive variable, it was suggested that older people such as in this sample may not value "feeling useful" as much as has been thought. Suggestions for future research included alternative methods of measuring association satisfaction, longitudinal analysis with representative sampling, and further investigation of voluntary-association characteristics. / This thesis was digitized as part of a project begun in 2014 to increase the number of Duke psychology theses available online. The digitization project was spearheaded by Ciara Healy.