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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.
61

The safety of common steel beam/column connections in fire

Wang, Y.C., Davison, J.B., Burgess, I.W., Plank, R.J., Yu, H.X., Dai, Xianghe January 2010 (has links)
No / This paper summarises recent experimental research on structural steel I-section beam/column connections for fire safety, based on a programme of research on robustness of different types of steel beam/column connections, carried out in collaboration between the Universities of Sheffield and Manchester. In this research project, two series of connection tests were conducted, one on isolated connections under different combinations of axial load, shear and moment at different elevated temperatures, and one on steel beam-to-column assemblies in fire, in which the resulting connection forces were varied during the fire exposure. This paper summarises the results and the main findings of these tests, focusing on connection failure modes, tying resistance, the rotation capacity of different types of connection and their potential influences on fire resistance of the connected members. The principal objective of this paper is to discuss the implications of this research project on integrating fire resistance into the design of steel-framed structures, firstly to highlight connection characteristics which contribute most to overall robustness, and to suggest how connection detailing might change to enable connections to possess such desirable characteristics.
62

The load deformation response of single bolt connections

Karsu, Burak 24 January 2009 (has links)
Sophisticated design techniques such as partially restrained connections need detail information on the load-deformation response of bolted connections. The behavior of single bolt, single shear connections are studied. Seventy tests with different configurations were conducted to evaluate their failure mechanisms and load-deformation characteristics. Comparisons to previous study were made. A new analytical model for the determination of load-deformation response of bolted connections was presented as well as a new Unified Design Curves approach for design purposes. It has been proven that this generalized method can be used efficiently. / Master of Science
63

Identifying The Structure Of Genomic Islands In Prokaryotes

Aldaihani, Reem A. A. H. S. 03 August 2022 (has links)
Prokaryotic genomes evolve via horizontal gene transfer (HGT), mutations, and rearrangements. HGT is a mechanism that plays a significant role in prokaryotic evolution and leads to biodiversity in nature. One of the important components of HGT is the genomic island (GI) which is a subsequence of the genome created by HGT. This research aims to identify the structures of the prokaryotic GIs that have a fundamental role in the adoption of prokaryotes and the impact of the species on the environment. Previous computational biology research has focused on developing tools that detect GIs in prokaryotic genomes, while there is little research investigating GI structure. This research introduces a novel idea that has not yet been addressed intensively, which is identifying additional structures of the GIs in prokaryotes. There are two main directions in this research used to study the prokaryotic GIs structure from each different perspective. In the first direction, the aim is to investigate GI patterns and the existence of biological connections across bacterial phyla in terms of GIs on a large scale. This direction mainly aims to pursue the novel idea of connecting GIs across prokaryotic and phage genomes via patterns of protein families across many species. A pattern is a sequence of protein families that is found to frequently occur in the genomes of a number of species. Here the large data set available from the IslandViewer4 database and protein families from the Pfam database have been combined. Furthermore, implementing a comprehensive strategy to identify patterns that makes use of HMMER, BLAST, and MUSCLE; also implement Python programs that link the analysis into a single pipeline. Research results demonstrate that related GIs often exist in multiple species that are not evolutionarily related and indeed may be from multiple bacterial phyla. Analysis of the discovered patterns led to the identification of biological connections among prokaryotes and phages through their GIs. A connection is an HGT relation represented as a pattern that exists in a phage and a number of prokaryotic species. These discovered connections suggest quite broad HGT connections across the bacterial kingdom and its associated phages. In addition, these connections provide the basis for additional analysis of the breadth of HGT and the identification of individual HGT events that span bacterial phyla. Moreover, these patterns can suggest the basis for discovering the specific patterns in pathogenic GIs that could play a crucial role in antibiotic resistance. The second direction aims to identify the structure of the GIs in terms of their location within the genome. Prokaryotic GIs have been analyzed according to the genome structure that they are located in, whether it be a circular or a linear genome. The analysis is performed to study the GIs' location in relation to the oriC, investigating the nature of the distances between the GIs, and determining the distribution of GIs in the genome. The analysis has been performed on all of the GIs in the data set. Moreover, the GIs in one genome from each species and the GIs of the most frequent species are in the data set, in order to avoid bias. Overall, the results showed that there are preferable sites for the GIs in the genome. In the linear genomes, they are usually located in the origin of replication area and terminus, and in the circular genomes they are located in the terminus. / Doctor of Philosophy / Prokaryotes are one of the most abundant species on earth that play an essential role in naturally shaping the planet and its life. This research aims to identify the structure of a component in these species that has a fundamental role in the adoption of prokaryotes and the impact of the species on the environment. This component is a part of the genome named the genomic island (GI). This dissertation aims to identify the structure of the GIs in two different ways that have not yet been addressed extensively. The first direction aims to discover patterns in the GIs and then use them to bring to light biological connections between prokaryotic and bacteriophages. In this direction, a comprehensive strategy has been utilized to identify patterns and connections. This strategy uses several tools such as BLAST, HMMER, and MUSCLE. Furthermore, Python programs that link the analysis into a single pipeline have been implemented. In the second direction, an investigation has been performed to understand the nature of the GIs' locations within the genome. This direction addresses three different analysis techniques to achieve its target. The three analyses are studying the GIs' location in relation to the origin of replication, investigating the nature of the distances between the GIs, and discovering the location distribution of GIs in the genome. The analysis is performed on linear genomes and circular genomes separately. In each group of GIs, the data set has been utilized to see the results from different perspectives. The overall analysis in both directions relived several findings. In the first direction, the discovered patterns merit deep investigation based on the possibility that they are related to diseases. In addition, in prokaryotic genomes, there are specific sites where the GIs can be frequently seen that need further search to understand the relation between the GIs' location and the content of the GI in terms of proteins.
64

Capacity Resistance and Performance of Single-Shear Bolted and Nailed Connections: An Experimental Investigation

Smart, Jason Vincent 16 January 2003 (has links)
The experimental study reported upon in this thesis focused on the development of physical data characterizing the behavior of single-shear, laterally-loaded connections when loaded up to and beyond capacity (i.e., maximum resistance). Specimens included a wide array of connection configurations common in wood construction. All connections were tested monotonically in tension under displacement-controlled loading, parallel to the grain. Results of these tests are presented and discussed. Test variables of nailed connections included nail diameter, side member material type, and side member thickness. Test variables of bolted connections included bolt diameter, commercial species grouping of the main and side members, and main member thickness. Conclusions drawn from this research include mechanics-based explanations of numerous connection response trends observed with respect to test variables. Additionally, observed factors of safety and over-strengths of current design values are quantified on a capacity-basis. / Master of Science
65

Evaluation of the Inelastic Rotation Capability of Flush End-Plate Moment Connections

Boorse, Mark Richard 02 April 1999 (has links)
An experimental investigation was conducted to study the inelastic rotation capability of flush end-plate moment connections. Seven specimens representing two-bolt and four-bolt flush end-plate configurations were tested under cyclic loading. "Quasi-static" or "slow-cyclic" loading histories suggested by SAC and the Applied Technology Council were used to load the specimens. Experimental results for maximum moment resisted by the connections were compared with analytical predictions. Moment strengths of the connections were calculated using yield-line theory to predict end-plate yielding and maximum bolt force calculations including prying action. Experimental results were also compared to previous research with regards to strength and stiffness. The inelastic rotation of connections was calculated and conclusions were drawn on the compliance of these connections with current AISC specifications. / Master of Science
66

"Supervaluationism, Penumbral Connections, and the Nature of Higher-Order Vagueness"

Sayball, Matt 09 June 2009 (has links)
In this paper, I analyze Kit Fine's account of the logic and semantics of vagueness. The overall aim of Fine's project is to develop an account of the logic and semantics of vague language which accommodates distinctive characteristics of vagueness including penumbral connections and higher-order vagueness. I begin Chapter 1 with a discussion of what vagueness is and is not. Next, I trace the development of supervaluationism, and summarize Kit Fine's supervaluationism and specification space approach to vagueness. I also discuss the more salient features of vagueness and I discuss them in relation to specification space models. I close with a look at the logic of vagueness and the logic of higher-order vagueness. Chapter 2 deals with penumbrae and penumbral connections. I analyze Fine's account of penumbral connections before arguing that his characterization of penumbral connections is too broad. Fine mistakenly identifies logically valid formulae and their instances as though they exhibited penumbral connections. After arguing that Fine's misidentification of penumbral connections results in an analysis of penumbral connections which is built for too wide a notion of penumbral connections, I suggest a more refined characterization of penumbral connections. I take up higher-order vagueness in Chapter 3. I begin with an overview of some characterizations of higher-order vagueness. Next, I revisit Fine's accounts of the D operator and higher-order vagueness. Lastly, I argue that higher-order vagueness is not a distinct feature of the vagueness of natural language, but, rather, it is an artifact resulting from the analysis of the vagueness of natural language. / Master of Arts
67

Stiffener Design for Beam-to-Column Connections

Holland, Michelle Leigh 13 October 1999 (has links)
Stiffeners are used as a means of providing additional support to columns at beam connection locations. They are added when the strength of the column is exceeded but full moment strength of the beam section is desired. In determining the design of column stiffeners, there are no specifications for determining the distribution of load between the column web and stiffeners. The AISC Load and Resistance Factor Design Specifications provides guidelines for determining the stiffener area but no specifications are given. The actual loads taken by the stiffener and web are therefore not truly known. In this study, experiments were done to determine the load supported by the stiffeners and web when tensile forces are applied to the specimen. The initial stiffener design for the test specimens was based on LRFD guidelines. The actual load distribution between the column web and stiffeners is determined from strain data obtained during testing. This distribution is compared with the assumed loads obtained from the initial LRFD calculations. Finite element analysis is also utilized to confirm the consistency of the results obtained from the experiments. Using this information, a new method is developed which better predicts the distribution of load between the column web and the stiffener. / Master of Science
68

The development of Jewish ideas of angels : Egyptian and Hellenistic connections, ca. 600 BCE to ca. 200 CE

Evans, Annette Henrietta Margaretha 03 1900 (has links)
Thesis (PhD (Ancient Studies))--University of Stellenbosch, 2007. / This dissertation sets out to test the hypothesis that Egyptian and Hellenistic connections to Jewish beliefs about the functioning of angels facilitated the reception of Christianity. The method of investigation involved a close reading, combined with a History of Religions methodology, of certain texts with marked angelological content. The presence of certain motifs, especially “throne” and “sun/fire”, which were identified as characteristic of angelic functioning, were compared across the entire spectrum of texts. In this way the diachronic development of major angelological motifs became apparent, and the synchronic connections between the respective cultural contexts became noticeable. The course the research followed is reflected in the list of Contents. Ancient Egyptian myth and ritual associated with solar worship, together with Divine Council imagery, provides a pattern of mediation between heaven and earth via two crucial religious concepts which underly Jewish beliefs about the functioning of angels: 1) the concept of a supreme God as the king of the Gods as reflected in Divine Council imagery, and 2) the unique Egyptian institution of the king as the divine son of god (also related to the supremacy of the sun god). The blending of these two concepts can be seen in Ezekiel 1 and 10, where the throne of God is the source of angelic mediation between heaven and earth. An important stimulus to change was the vexed issue of theodicy, which in the traumatic history of the Israelites / Jews, forced new ways of thinking about angels, who in some contexts were implicated in evil and suffering on earth. In the hellenistic period, attainment to the throne of God in heaven becomes the goal of heavenly ascent, reflected in various ways in all three cultural contexts, and specifically by means of merkabah mysticism in the Jewish context; the basic concern is deification of human beings. It was this seminal cultural mixture which mediated Christianity as an outcome of Jewish angelology. The characteristic ambiguity of Jewish descriptions of angelic appearances, as reflected in the Hebrew Bible and in the Book of Revelation, functioned purposefully in this regard. Analysis of the distribution of angelological motifs amongst the Christian texts reflects Jewish angelological traditions, both in terms of merkabah mysticism in the Letter to the Hebrews, and in angelomorphic appearances of Jesus in the Book of Revelation.
69

Stomstabilisering hos prefabricerade betongkonstruktioner i 3D-beräkningsprogram

Rydberg, Carolin, Reiderstedt, Kasper January 2016 (has links)
This thesis has been executed in cooperation with Abetong which is a leading company in the prefabrication of concrete structures. For a prefabricated concrete building the design engineer must take into consideration the connections between the concrete elements in order to make sure that the building will possess a sufficient structural stability. Therefore the structural engineer might have to re-calculate the original structure that often has been designed as an on site-built building. The purpose of this thesis is to examine the forces between elements related to different models to see if the structural engineer has to make a re-design. To get results for this study we have used FEM-design 3D Structure. The results of forces from the program were compared with Abetongs standard forces of point connections and recess lists and showed that the structural engineer can use the original calculation up to around five stories when a prefabricated shall be erected.
70

Three essays on empirical corporate finance

Khatami, Seyed Hossein January 2016 (has links)
This thesis investigates three topics in empirical corporate finance. In the first essay, the focus is on the role of financial constraints in the market for corporate control. In the second and third essays, we explore the effect of personal connections at board and executive levels on corporate credit rating and initial public offering (IPO) underpricing respectively. In the first essay, using a large sample of US acquisitions made between 1985 and 2013, we study the effect of financial constraints on acquisition gains and acquisition likelihood. Our findings show that financial constraints of target companies significantly increase acquisition premiums and abnormal returns for both parties. Our results further show that the presence of financial constraints in the target is one of the most important determinants of a takeover bid. This supports the idea that acquisitions may improve the ability of financially constrained companies to access capital through a better reallocation of resources within segments of the same company (e.g., internal capital market) or through better access to external markets. This would eventually benefit bidders too, as new capital would be invested in valuable growth opportunities that otherwise would expire unexercised. In the second essay, using a large sample of US public debt issues we show that personal connections between directors of issuing companies and rating agencies result in higher credit ratings. We estimate the average effect to be about one notch. The results are robust to several alternative tests including additional controls for managerial traits, placebo tests and propensity score matching. Moreover, our tests on default rates and bond yields do not appear to reflect a favourable treatment by the rating agency. Rather, they suggest that personal connections act as a mechanism to reduce asymmetric information between the rating agency and the issuer. In the final essay, using a large sample of IPOs in the U.S. we show that interpersonal connections between directors and top executives in issuers and underwriting banks result in significantly lower levels of IPO underpricing. We also examine the issuers' long-term stock returns following their IPOs. Our results indicate that the connected companies' long-term returns are not significantly different from the non-connected companies. This suggests that underwriters set lower levels of underpricing for the connected companies not to treat them favourably, but due to better flow of and stronger reliance on soft information and lower risk exposure.

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