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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
401

Engineered Fibre-reinforced Concrete Systems for Bridge Deck Link Slab Applications

Cameron, James January 2014 (has links)
Rehabilitation and maintenance of the aging transportation infrastructure are of major concern in the Province of Ontario. A large portion of this work is related to the durability of highway bridges around the province. One of the weakest points in a bridge structure from a durability aspect is the expansion joints that can allow harmful elements, such as road salts and contaminants to leak down from the road surface and attack the supporting structure of the bridge. Although expansion joints can be eliminated in the design of a new bridge, such as in an integral abutment bridge, this requires major changes to the supports and structure of the bridge, making it impractical for retrofitting existing bridges. One effective alternative is the replacement of a traditional expansion joint with a link slab. A link slab is a concrete slab used in place of an expansion joint to make the bridge deck continuous while keeping the supporting girders simply supported [1]. Link slabs must be able to resist large force effects both in bending and direct tension while minimizing cracking [2], one solution is to use the high tensile and flexural strength properties of an ultra-high performance fibre-reinforced concrete (UHPFRC) [3]. The UHPFRC mixtures are often proprietary and expensive. The purpose of this research was to evaluate the potential of using common fibre types with standard concrete ingredients in a fibre-reinforced concrete (FRC) as an alternative to UHPFRC in a link slab. Using a selection of macro fibres commonly used in slab on grade applications for crack control, an optimized FRC mixture was developed following the principals established by Rossi and Harrouche [4]. This mixture was then used with a variety of fibre types to evaluate the structural and durability properties of the FRC. Testing was conducted for fresh mixture properties, compressive, tensile and flexural strength as well as freezing and thawing resistance, linear shrinkage, environmental and salt exposure along with other durability tests. Results showed that the concrete mixture used for an FRC link slab should consist of; an equal ratio of fine and coarse aggregate by weight and a higher than normal percentage of cement paste, for optimal workability and a dosage of 1.5% by volume of macro steel fibres. Hooked-end steel fibres resulted in the best performance increase to the FRC of the six fibre types tested. Results also showed that reinforcing cage for an FRC link slab should be designed to ensure that fibres can evenly reach all areas of the link slab form to give homogeneous fibre distribution. Although the FRCs created did not perform to the high level of a UHPFRC, these results show a consistent and effective FRC can be created, for use in a link slab with common fibres and standard concrete materials to provide a less expensive and more widely available FRC link slab than UHPFRC.
402

Reconfigurable Feedback Shift Register Cipher Design and Secure Link Layer Protocol for Wireless Sensor Network

Zeng, Guang 11 June 2014 (has links)
Secure wireless communications among sensor nodes is critical to the deployment of wireless sensor networks. However, resource limited sensor nodes cannot afford complex cryptographic algorithms. In this thesis, we propose a low complexity and energy efficient reconfigurable feedback shift register (RFSR) stream cipher, link layer encryption framework RSec and authentication protocol RAuth. RFSR adds one new dimension, reconfigurable cipher structure, to the existing stream ciphers. The proposed RFSR is implemented on a field programmable gate array platform. Simulation results show that much lower power consumption, delay and transmission overhead are achieved compared to the existing microprocessor based cipher implementations. The RSec framework utilizes RFSR ciphers to guarantee message confidentiality. By comparing with other encryption frameworks in terms of energy efficiency, RSec achieves the best benchmark. The RAuth protocol is designed on top of RFSR and RSec. It provides excellent authentication speed and security level by comparing with other authentication protocols. / Graduate / 0544 / 0984 / zggyzz@gmail.com
403

Reconfigurable Feedback Shift Register Cipher Design and Secure Link Layer Protocol for Wireless Sensor Network

Zeng, Guang 11 June 2014 (has links)
Secure wireless communications among sensor nodes is critical to the deployment of wireless sensor networks. However, resource limited sensor nodes cannot afford complex cryptographic algorithms. In this thesis, we propose a low complexity and energy efficient reconfigurable feedback shift register (RFSR) stream cipher, link layer encryption framework RSec and authentication protocol RAuth. RFSR adds one new dimension, reconfigurable cipher structure, to the existing stream ciphers. The proposed RFSR is implemented on a field programmable gate array platform. Simulation results show that much lower power consumption, delay and transmission overhead are achieved compared to the existing microprocessor based cipher implementations. The RSec framework utilizes RFSR ciphers to guarantee message confidentiality. By comparing with other encryption frameworks in terms of energy efficiency, RSec achieves the best benchmark. The RAuth protocol is designed on top of RFSR and RSec. It provides excellent authentication speed and security level by comparing with other authentication protocols. / Graduate / 0544 / 0984 / zggyzz@gmail.com
404

Reconfigurable Feedback Shift Register Cipher Design and Secure Link Layer Protocol for Wireless Sensor Network

Zeng, Guang 11 June 2014 (has links)
Secure wireless communications among sensor nodes is critical to the deployment of wireless sensor networks. However, resource limited sensor nodes cannot afford complex cryptographic algorithms. In this thesis, we propose a low complexity and energy efficient reconfigurable feedback shift register (RFSR) stream cipher, link layer encryption framework RSec and authentication protocol RAuth. RFSR adds one new dimension, reconfigurable cipher structure, to the existing stream ciphers. The proposed RFSR is implemented on a field programmable gate array platform. Simulation results show that much lower power consumption, delay and transmission overhead are achieved compared to the existing microprocessor based cipher implementations. The RSec framework utilizes RFSR ciphers to guarantee message confidentiality. By comparing with other encryption frameworks in terms of energy efficiency, RSec achieves the best benchmark. The RAuth protocol is designed on top of RFSR and RSec. It provides excellent authentication speed and security level by comparing with other authentication protocols. / Graduate / 0544 / 0984 / zggyzz@gmail.com
405

A longitudinal study of academic web links : identifying and explaining change

Payne, Nigel January 2007 (has links)
A problem common to all current web link analyses is that, as the web is continuously evolving, any web-based study may be out of date by the time it is published in academic literature. It is therefore important to know how web link analyses results vary over time, with a low rate of variation lengthening the amount of time corresponding to a tolerable loss in quality. Moreover, given the lack of research on how academic web spaces change over time, from an information science perspective it would interesting to see what patterns and trends could be identified by longitudinal research and the study of university web links seems to provide a convenient means by which to do so. The aim of this research is to identify and track changes in three academic webs (UK, Australia and New Zealand) over time, tracking various aspects of academic webs including site size and overall linking characteristics, and to provide theoretical explanations of the changes found. This should therefore provide some insight into the stability of previous and future webometric analyses. Alternative Document Models (ADMs), created with the purpose of reducing the extent to which anomalies occur in counts of web links at the page level, have been used extensively within webometrics as an alternative to using the web page as the basic unit of analysis. This research carries out a longitudinal study of ADMs in an attempt to ascertain which model gives the most consistent results when applied to the UK, Australia and New Zealand academic web spaces over the last six years. The results show that the domain ADM gives the most consistent results with the directory ADM also giving more reliable results than are evident when using the standard page model. Aggregating at the site (or university) level appears to provide less consistent results than using the page as the standard unit of measure, and this finding holds true over all three academic webs and for each time period examined over the last six years. The question of whether university web sites publish the same kind of information and use the same kind of hyperlinks year on year is important from the perspective of interpreting the results of academic link analyses, because changes in link types over time would also force interpretations of link analyses to change over time. This research uses a link classification exercise to identify temporal changes in the distribution of different types of academic web links, using three academic web spaces in the years 2000 and 2006. Significant increases in ‘research oriented’, ‘social/leisure’ and ‘superficial’ links were identified as well as notable decreases in the ‘technical’ and ‘personal’ links. Some of these changes identified may be explained by general changes in the management of university web sites and some by more wide-spread Internet trends, e.g., dynamic pages, blogs and social networking. The increase in the proportion of research-oriented links is particularly hopeful for future link analysis research. Identifying quantitative trends in the UK, Australian and New Zealand academic webs from 2000 to 2005 revealed that the number of static pages and links in each of the three academic webs appears to have stabilised as far back as 2001. This stabilisation may be partly due to an increase in dynamic pages which are normally excluded from webometric analyses. In response to the problem for webometricians due to the constantly changing nature of the Internet, the results presented here are encouraging evidence that webometrics for academic spaces may have a longer-term validity than would have been previously assumed. The relationship between university inlinks and research activity indicators over time was examined, as well as the reasons for individual universities experiencing significant increases and decreases in inlinks over the last six years. The findings indicate that between 66% and 70% of outlinks remain the same year on year for all three academic web spaces, although this stability conceals large individual differences. Moreover, there is evidence of a level of stability over time for university site inlinks when measured against research. Surprisingly however, inlink counts can vary significantly from year to year for individual universities, for reasons unrelated to research, underlining that webometric results should be interpreted cautiously at the level of individual universities. Therefore, on average since 2001 the university web sites of the UK, Australia and New Zealand have been relatively stable in terms of size and linking patterns, although this hides a constant renewing of old pages and areas of the sites. In addition, the proportion of research-related links seems to be slightly increasing. Whilst the former suggests that webometric results are likely to have a surprisingly long shelf-life, perhaps closer to five years than one year, the latter suggests that webometrics is going to be increasingly useful as a tool to track research online. While there have already been many studies involving academic webs spaces, and much work has been carried out on the web from a longitudinal perspective, this thesis concentrates on filling a critical gap in current webometric research by combining the two and undertaking a longitudinal study of academic webs. In comparison with previous web-related longitudinal studies this thesis makes a number of novel contributions. Some of these stem from extending established webometric results, either by introducing a longitudinal aspect (looking at how various academic web metrics such as research activity indicators, site size or inlinks change over time) or by their application to other countries. Other contributions are made by combining traditional webometric methods (e.g. combining topical link classification exercises with longitudinal study) or by identifying and examining new areas for research (for example, dynamic pages and non-HTML documents). No previous web-based longitudinal studies have focused on academic links and so the main findings that (for UK, Australian and New Zealand academic webs between 2000 and 2006) certain academic link types exhibit changing patterns over time, approximately two-thirds of outlinks remain the same year on year and the number of static pages and links appears to have stabilised are both significant and novel.
406

Record Linkage for Web Data

Hassanzadeh, Oktie 15 August 2013 (has links)
Record linkage refers to the task of finding and linking records (in a single database or in a set of data sources) that refer to the same entity. Automating the record linkage process is a challenging problem, and has been the topic of extensive research for many years. However, the changing nature of the linkage process and the growing size of data sources create new challenges for this task. This thesis studies the record linkage problem for Web data sources. Our hypothesis is that a generic and extensible set of linkage algorithms combined within an easy-to-use framework that integrates and allows tailoring and combining of these algorithms can be used to effectively link large collections of Web data from different domains. To this end, we first present a framework for record linkage over relational data, motivated by the fact that many Web data sources are powered by relational database engines. This framework is based on declarative specification of the linkage requirements by the user and allows linking records in many real-world scenarios. We present algorithms for translation of these requirements to queries that can run over a relational data source, potentially using a semantic knowledge base to enhance the accuracy of link discovery. Effective specification of requirements for linking records across multiple data sources requires understanding the schema of each source, identifying attributes that can be used for linkage, and their corresponding attributes in other sources. Schema or attribute matching is often done with the goal of aligning schemas, so attributes are matched if they play semantically related roles in their schemas. In contrast, we seek to find attributes that can be used to link records between data sources, which we refer to as linkage points. In this thesis, we define the notion of linkage points and present the first linkage point discovery algorithms. We then address the novel problem of how to publish Web data in a way that facilitates record linkage. We hypothesize that careful use of existing, curated Web sources (their data and structure) can guide the creation of conceptual models for semi-structured Web data that in turn facilitate record linkage with these curated sources. Our solution is an end-to-end framework for data transformation and publication, which includes novel algorithms for identification of entity types and their relationships out of semi-structured Web data. A highlight of this thesis is showcasing the application of the proposed algorithms and frameworks in real applications and publishing the results as high-quality data sources on the Web.
407

Record Linkage for Web Data

Hassanzadeh, Oktie 15 August 2013 (has links)
Record linkage refers to the task of finding and linking records (in a single database or in a set of data sources) that refer to the same entity. Automating the record linkage process is a challenging problem, and has been the topic of extensive research for many years. However, the changing nature of the linkage process and the growing size of data sources create new challenges for this task. This thesis studies the record linkage problem for Web data sources. Our hypothesis is that a generic and extensible set of linkage algorithms combined within an easy-to-use framework that integrates and allows tailoring and combining of these algorithms can be used to effectively link large collections of Web data from different domains. To this end, we first present a framework for record linkage over relational data, motivated by the fact that many Web data sources are powered by relational database engines. This framework is based on declarative specification of the linkage requirements by the user and allows linking records in many real-world scenarios. We present algorithms for translation of these requirements to queries that can run over a relational data source, potentially using a semantic knowledge base to enhance the accuracy of link discovery. Effective specification of requirements for linking records across multiple data sources requires understanding the schema of each source, identifying attributes that can be used for linkage, and their corresponding attributes in other sources. Schema or attribute matching is often done with the goal of aligning schemas, so attributes are matched if they play semantically related roles in their schemas. In contrast, we seek to find attributes that can be used to link records between data sources, which we refer to as linkage points. In this thesis, we define the notion of linkage points and present the first linkage point discovery algorithms. We then address the novel problem of how to publish Web data in a way that facilitates record linkage. We hypothesize that careful use of existing, curated Web sources (their data and structure) can guide the creation of conceptual models for semi-structured Web data that in turn facilitate record linkage with these curated sources. Our solution is an end-to-end framework for data transformation and publication, which includes novel algorithms for identification of entity types and their relationships out of semi-structured Web data. A highlight of this thesis is showcasing the application of the proposed algorithms and frameworks in real applications and publishing the results as high-quality data sources on the Web.
408

Evaluation of performance and maximum length of continuous decks in simple-span bridges

Snedeker, Katherine O. 08 April 2009 (has links)
The purpose of this research was to evaluate the performance history of continuous bridge decks in the State of Georgia, to determine why the current design detail works, to recommend a new design detail if necessary, and to recommend the maximum and/or optimum lengths of continuous bridge decks. The continuous bridge decks have continuous reinforcement over the junction of two edge beams with a construction joint for crack control. The current technical literature and current practices and design procedures were synthesized and summarized. GDOT maintenance reports were reviewed, and field evaluations were conducted to determine the performance of the continuous deck detail. The effects of bridge movement due to thermal strains, shrinkage, and live loads were considered in the analytical studies to better understand the demands placed on the GDOT continuous deck detail. A summary of the design and length recommendations was provided upon completion of the research.
409

Effective web service discovery using a combination of a semantic model and a data mining technique

Bose, Aishwarya January 2008 (has links)
With the advent of Service Oriented Architecture, Web Services have gained tremendous popularity. Due to the availability of a large number of Web services, finding an appropriate Web service according to the requirement of the user is a challenge. This warrants the need to establish an effective and reliable process of Web service discovery. A considerable body of research has emerged to develop methods to improve the accuracy of Web service discovery to match the best service. The process of Web service discovery results in suggesting many individual services that partially fulfil the user’s interest. By considering the semantic relationships of words used in describing the services as well as the use of input and output parameters can lead to accurate Web service discovery. Appropriate linking of individual matched services should fully satisfy the requirements which the user is looking for. This research proposes to integrate a semantic model and a data mining technique to enhance the accuracy of Web service discovery. A novel three-phase Web service discovery methodology has been proposed. The first phase performs match-making to find semantically similar Web services for a user query. In order to perform semantic analysis on the content present in the Web service description language document, the support-based latent semantic kernel is constructed using an innovative concept of binning and merging on the large quantity of text documents covering diverse areas of domain of knowledge. The use of a generic latent semantic kernel constructed with a large number of terms helps to find the hidden meaning of the query terms which otherwise could not be found. Sometimes a single Web service is unable to fully satisfy the requirement of the user. In such cases, a composition of multiple inter-related Web services is presented to the user. The task of checking the possibility of linking multiple Web services is done in the second phase. Once the feasibility of linking Web services is checked, the objective is to provide the user with the best composition of Web services. In the link analysis phase, the Web services are modelled as nodes of a graph and an allpair shortest-path algorithm is applied to find the optimum path at the minimum cost for traversal. The third phase which is the system integration, integrates the results from the preceding two phases by using an original fusion algorithm in the fusion engine. Finally, the recommendation engine which is an integral part of the system integration phase makes the final recommendations including individual and composite Web services to the user. In order to evaluate the performance of the proposed method, extensive experimentation has been performed. Results of the proposed support-based semantic kernel method of Web service discovery are compared with the results of the standard keyword-based information-retrieval method and a clustering-based machine-learning method of Web service discovery. The proposed method outperforms both information-retrieval and machine-learning based methods. Experimental results and statistical analysis also show that the best Web services compositions are obtained by considering 10 to 15 Web services that are found in phase-I for linking. Empirical results also ascertain that the fusion engine boosts the accuracy of Web service discovery by combining the inputs from both the semantic analysis (phase-I) and the link analysis (phase-II) in a systematic fashion. Overall, the accuracy of Web service discovery with the proposed method shows a significant improvement over traditional discovery methods.
410

The Personality-Disease Link: An Evaluation of a Predictive Personality Measure, the Mediating Mechanisms of the Personality-Disease Link and a Preventative Intervention.

Gatt, Justine Megan January 2005 (has links)
Doctor of Philosophy / Grossarth-Maticek and Eysenck (1988) demonstrated that personality type as measured by the 70-item Grossarth-Maticek Personality Stress Inventory (GMPSI), predicts mortality and its cause with remarkable accuracy. Further, various forms of autonomy training, such as bibliotherapy and short individual treatment that were designed to reduce the toxic personality features (such as emotional dependence) effectively improved long-term health outcomes. However, several aspects of their theory and research were either insufficiently explicated or require further investigation. For example, the researchers did not thoroughly investigate the psychometric properties of the inventory, and they did not sufficiently examine the mechanisms that may mediate the personality-health relationship. Further, the autonomy training was inadequately described, and perhaps could have been briefer and had the same impact. Three studies were run to investigate these issues further. Study 1 (Chapter 2) investigated the internal consistency, test-retest reliability and convergent, discriminant and concurrent validity of the GMPSI in 312 first-year students, using a variety of statistical techniques (e.g., structural equation modeling, confirmatory factor analysis, and simple correlations). In addition, the psychometric properties of this scale were compared to those of three revised versions of the scale, which were theorised to be psychometric improvements of the original version from basic principles. The revised versions contained reverse-worded items (of different types) to monitor and disrupt acquiescence response sets, and/or an extended response scale to improve internal consistency and stability. Psychometric effects of reverse-wording and the extended response scale on scale reliability were examined via the analysis of construct reliability estimates, personality subscale model fit of congeneric measurement models (a form of structural equation modeling), and test-retest reliability estimates. The original version of the scale appeared to be the most reliable and valid scale of the four versions. This improved reliability of the original version was not an artifact of an acquiescence response set, because this form of responding was not prevalent in the reverse-worded versions. In contrast, it appeared that the incorporation of reverse-wording degraded the internal consistency of the scale as participants appeared to respond to the positive and negative-worded items as if they were measurements of independent constructs, rather than measurements of constructs on opposite ends of a particular dimension. Predicted correlations between the GMPSI and concurrent validity measures offered support for Grossarth-Maticek's theory, and suggest that the GMPSI is an effective and reliable tool for the measurement of these personality types. However, experimental evidence supporting the link between personality, mediating mechanisms and disease is required to further substantiate these findings. The second and third studies (Chapters 3 and 4, respectively) were investigations of the utility of an information pamphlet discussing stress, assertiveness and relaxation, in improving GMPSI personality type stress responses in a student and a community sample (Studies 2 and 3 respectively), and provided an opportunity to investigate the mechanisms mediating the personality-health relationship via experimental manipulation. Specifically, Study 2 investigated the effectiveness of the pamphlet in improving personality scores, mood, coping strategies, health behaviours, and salivary cortisol levels (measured at pre-treatment, 1-month post-treatment and 5-months post-treatment) in 200 first-year university students. Further, two modes of administration of the pamphlet were compared: pure selfadministration versus instruction accompanied by self-administration. Group differences in mood and cortisol reactivity to a visualisation stress task were also assessed. Very few significant differences were found between the two pamphlet administration forms. Both pamphlet forms were effective in improving mood states, some lifestyle habits (e.g., exercise), and salivary cortisol responses to the acute stress task compared to the control group. The strength of these effects ranged from small to medium, and all significant differences were between pre-treatment and the 1-month post-treatment session. The failure to observe differences at the 5-months post-treatment session may have been due to inadequacies of the treatment, or low statistical power for detecting effects from the final session due to the large attrition rate that had occurred by this session. Overall, while large treatment effect sizes were not found, the results could be construed as "clinically" significant when taking into account the low costs of implementing an information pamphlet in the larger community, and the potential benefits on individuals' stress responses and health behaviours. Study 3 aimed to investigate the treatment effects of the same self-administered pamphlet in 77 participants from the general community, who varied largely in age (19 - 77 years). Treatment and control groups were compared in terms of treatment compliance, cortisol levels, health behaviours, personality scores, perceived stress, mood, and coping styles (measured at pre-treatment, 2 weeks posttreatment, 3 months post-treatment, and 6 months post-treatment). In addition, group differences in cortisol reactivity to an acute cognitive stress task were examined. Home visits were arranged for each session to reduce sample attrition. Further, an intervention evaluation form was administered at each post-treatment session to verify and maintain treatment involvement. Several significant treatment effects were observed, including changes in personality scores and non-productive coping strategies, and the strength of these effects ranged from medium to very large. Most participants reported that they found the information pamphlet very appealing and helpful. In addition to the examination of intervention effects in the second and third studies, a path model that aimed to identify direct and mediating relationships between personality and concurrently measured disease was examined for the two samples (Chapter 5). This path model was based on a new integrative theory of personality-disease, which was developed. Eysenck's (1991) proposed personality-disease model formed the foundation of this new theory, and elements of several other generic personality-disease models were also incorporated. This theory was empirically tested using path analysis on the student and community data separately. Common pathways in the two models were then tested for invariance. Overall, most paths proposed by the integrative model were identified in one or both samples; thus, the model was generally supported. All common direct paths were statistically invariant (i.e., equivalent) in the two samples. While personality did not appear to directly predict illness, several significant indirect pathways were identified by which personality appears to affect disease incidence, such as via perceived stress, mood, coping styles, and physical risk factors. These findings appear to support Grossarth-Maticek's theory that personality affects disease incidence via stress responses, as well as other generic approaches (i.e., the personality-induced hyperreactivity model and the stress moderator model) that emphasise the stress-moderating effects of personality on health. However, support for the dangerous behaviours model was not found, which posits that certain personality dispositions seek risky behaviours (e.g., poor health behaviours such as smoking and alcohol consumption) that fit their personality. The final Chapter 6 directly compares the results of these three studies, and discusses their practical and theoretical significance in terms of Grossarth-Maticek's theory and research, views of critics, and other personality-health perspectives and research. In summary, the current studies appear to suggest that the GMPSI is a reliable and valid scale for the measurement of particular personality traits. Further, there appears to be evidence to suggest that personality traits can be changed by an intervention pamphlet. This information pamphlet also appears to be effective in significantly improving responses to stress, and these effects are more prominent in high-risk groups (i.e., subjects with extreme personality trait scores). Moreover, there is some evidence to suggest that personality may have direct effects on several mechanisms involved in the development of disease. Overall, this thesis demonstrates the importance of recognising the role of personality and stress in disease prevention and prediction by providing independent evidence for the benefits of treatment and mechanisms by which benefits may occur.

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