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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.
291

Visualizing reciprocity in an online community to motivate participation

Sankaranarayanan, Kadhambari 13 September 2010 (has links)
Online communities thrive on their members participation and contributions. Continuous encouragement of participation of these members is vital for an online community. Social visualizations are one of the methods to make members explicitly aware of their connections and relationships. There are numerous ways to visually represent information, current-status, power, and acceptance of members in an online community. In this thesis I present a design of a visualization representing the evolving reciprocity of relationships among users based on the comments they give to each others posts. The purpose of the visualization is to emphasize and hopefully trigger a common bond in the community and thereby increase their participation. We developed and deployed the visualization in an online community called WISETales where women in science and engineering share personal stories. We also deployed modified and improved versions of the visualization in two other communities, I-Help class discussion forums and the Vegatopia discussion forum for vegetarians. In this thesis we present the results of the evaluation in these three communities. The results unfortunately, were negative. Even though separate explanations for the lack of motivational effect can be found in each of the experiments, it seems that the chosen motivational approach was too gentle to encourage participation. It seems for reciprocation to take place, the users need to be committed to the community and already have some other underlying motivation to participate actively. The visualization also should provide some new information that they werent aware of previously. This was not the case with the users in the three chosen communities. WISETales was too new and can barely be called a community. I-Help was not a community, but a place for student to post questions for the teacher to answer. Vegatopia, in contrast, is well established, active community, where people know each other, and engage in conversations with each other. The visualization did not provide any new information for them that they didnt know and only served as a brief attraction for a day (novelty effect). We are still optimistic, however, that the visualization may be useful for active and too dynamic communities where people are unaware of their social relationships because they are too many, for example, social network sites like Twitter.
292

Splice tests of plain steel bars in concrete

Hassan, N. (Nazmul) 07 March 2011 (has links)
Fifteen splice specimens reinforced with plain steel bars, including three specimens instrumented with both steel and concrete strain gauges, were tested under monotonically applied four-point loading to develop a database of reliable bond test results and contribute to the development of a reliability based bond provision for plain steel bars to evaluate historical concrete structures. The maximum applied load for the specimens and their observed failure behaviour are reported. In addition to that, a strain compatibility analysis, average bond stress distribution, and flexural section analysis within the lap splice length of the instrumented specimens are also reported.<p> All of the specimens failed in bond within the lap splice length. The load capacity of two specimens reinforced with plain steel bars was 60% of the reported load resistance of specimens with identical geometry and reinforced with deformed bars. The CEB-FIP Model Code provisions for average bond stress of plain steel bars underestimated the maximum applied load recorded for the tested specimens by 16% on average. An empirically derived equation to predict the bond capacity of plain steel bars was determined to be proportional to both the splice length and the nominal bar diameter. <p> Observed cracks in the shear spans remained vertical and suggest the development of arch action within this region. The formation of a large crack at one end of the lap splice length and a review of the load versus deflection behaviour indicated a sudden bond failure of the specimens. Removal of concrete cover at the ends of the lap splice length following testing of the specimens showed evidence of slip of the lapped bars.<p> Instrumented splice specimens provided evidence of bond loss within the lap splice region. As-measured steel strains were higher than those measured for the surrounding concrete due to a loss of strain compatibility. The average bond stress distribution within the lap splice length became more uniform as the applied load approached the maximum applied load. The flexural analysis calculated based on concrete strains above the neutral axis and steel strain provided a reasonable estimate of specimen capacity.
293

Evaluation of contact and non-contact lap splices in concrete block masonry specimens

Ahmed, Kawsar 11 July 2011 (has links)
An experimental program was performed for qualitative and quantitative comparison of the maximum tensile resistance of contact and non-contact lap spliced bars in reinforced concrete block masonry using double pullout and wall splice specimens. A total of 32 specimens were tested, consisting of an equal number of double pullout specimens and full-scale wall splice specimens. Both specimen types had the identical cross-section. Eight replicate specimens for each specimen type were constructed with both contact and non-contact lap splice arrangements. Grade 400 deformed reinforcing bars with a 300 mm lap splice length were provided in all specimens. The double pullout specimens were tested applying direct tension to the lapped reinforcing bars. The splice resistance and displacement were recorded during testing. All double pullout specimens with contact lap splices developed, as a minimum, the yield strength of the reinforcing bars and generally displayed evidence of a yield plateau. In contrast, the double pullout specimens with non-contact lap splices failed when only 46.1% of the theoretical yield strength of the reinforcing bars was recorded as the maximum splice resistance. The difference between the average value of the tensile resistance in the contact and non-contact spliced bars was identified as being statistically significant at the 95% confidence level. Wall splice specimens were tested under a four-point loading arrangement with the lapped bars located in the constant moment region. The applied load and specimen deflection were recorded until failure occurred. A numerical analysis was then performed to calculate the maximum resistance of the spliced bars. The specimens with contact lap splices developed the theoretical yield capacity of the reinforcing bars. In contrast, the wall splice specimens with non-contact lap splices developed an average tensile resistance of 78% of the theoretical yield capacity. The difference between the average tensile resistances of the lapped bars in the two splice arrangements was identified as being statistically significant at the 95% confidence level. On average, the contact and non-contact lap spliced bars in the double pullout specimens developed 8.47% and 41.2% less tensile resistance, respectively, as compared to the wall splice specimens with the identical splice arrangement. Both differences were identified as being statistically significant at the 95% confidence level. Bond loss between the reinforcing bars and the surrounding grout was identified as the failure mode for both the double pullout and wall splice specimens with contact lap splices. In contrast, bond loss at the masonry block/grout interface was observed along the non-contact lapped bars in both specimen types, as identified by visual observations upon removal of the face shell and the surrounding grout. Based on the test results of the wall splice specimens with non-contact lap splices, a correction factor of 1.5 is suggested when calculating the effective splice length for the non-contact splice arrangement as tested.
294

Prebiotic Synthesis of Pyrimidine Nucleosides

Collins, James P. 28 November 2005 (has links)
The problem of forming a glycosidic bond between ribose and the free nucleoside bases to produce beta-nucleosides under plausible prebiotic conditions is commonly referred to in origin of life research as The Nucleoside Problem. The lack of a general solution to this problem currently represents one of the largest stumbling blocks to the RNA world hypothesis and many other theories regarding the origin of life. Over thirty years ago the purine nucleosides were successfully synthesized by drying the fully-formed bases and ribose together in the presence of divalent metal ion salts. However, glycosidic bond formation by the pyrimidine bases has never been achieved under similar reaction conditions. This thesis describes the first plausible prebiotic synthesis of a pyrimidine nucleoside, demonstrated with the pyrimidine base analogue 2-pyrimidinone. Information provided by nucleoside-formation reaction involving 2-pyrimidinone and related pyrimidine bases should provide valuable insights into the possible mechanism by which glycosidic bond formation was accomplished on the prebiotic Earth.
295

Synthesis and Mechanistic Studies on the Reaction of N-phenylpyridin-2-Amine Palladacycle with Aryltrifluoroboratess to 9-(pryidin-2yl)-9H-carbazole

Li, Ya-Ming 09 August 2010 (has links)
An effiecient stoichiometric amount system has been developed for the synthesis of N-phenylpyridin-2-amine Palladacycle, and then reation with aryl trifluoroborate to 9-(pyridine-2-yl)-9H-carbazoles by C-H bond activation/ C-C bond formation and C-N bond formation. The subsitutent effect of the aryl trifluoroborate with N-phenylpyridin-2-amine Palladacycle intermediate was observed. Mechanistic studies of C-H bond cleavaged, including trapping of reaction intermediates and kinetic isotope effect experiments, are also presented.
296

Block Copolymer-Templated Mesoporous Materials obtained by Evaporation-Induced Self Assembly

Lin, Yu-De 26 July 2011 (has links)
A series of immiscible crystalline-crystalline diblock copolymers, poly(ethylene oxide)-b-(£`-caprolactone) (PEO-b-PCL), were synthesized through ring-opening polymerization and then blended with phenolic resin. FT-IR analyses provide that the ether group of PEO is a stronger hydrogen bond acceptor than the carbonyl group of PCL with the hydroxyl group of phenolic. Phenolic after curing with hexamethylenetetramine (HMTA) results in the excluded and confined PCL phase based on differential scanning calorimeter (DSC) analyses. This effect leads to the formation of a variety of composition-dependent nanostructures, including disorder, gyroid and short cylinder. The self-organized mesoporous phenolic resin was only found at 40~60 wt% phenolic content by intriguing balance of the contents of phenolic, PEO, and PCL. In addition, the mesoporous structure was destroyed with the increasing the ratio of PCL to PEO in block copolymers by small angle X-ray scattering (SAXS) and transmission electron microscopy (TEM) analyses. In addition, the large and long-range order of bicontinuous gyroid-type mesoporous carbon was obtained from mesoporous gyroid phenolic resin calcined at 800 ¢XC under nitrogen.
297

Reaction of Dichloromethane with Zinc Thiolate Complexes

Dai, Min-Bin 01 September 2011 (has links)
Dichloromethane is one solvent that is used widely in laboratory. It is so stable that it seldom reacts with other materials. There are only a few reports that involves dichloromehane as a reactant. Previous in our laboratory, we discovered a dichloromethane activation product. To study the details of the methylene insertion prouct, [(SCH2S)PS]2Zn form (Et4N)2 (PS3Zn)2, we used monodentate thiols in different condition as models to understand what condition thiols may react with dichloro methane. We found out thiols can react with dichloromethane under strong base. When there is aromatic ring in a thiol, that thiol will react with dichloromethane easily. Adding zinc salts showed that zinc ion is an inhibitor in thiolate/dichloromethane reactions. We synthesized Tris(3-trimethylsilyl-2-thiophenyl)phosphine [H3SiPS3] and SiPS3Zn complex to study the parallel effect of adding bulky silyl substitaents on PS3 ligand towards reaction with dichloromethane. Most conclusion are similar to that of monodentate thiols. There is one thing that differs from the results of monedentate thiols: the SiPS3Zn complex does react with dichloromethane.
298

Using Dogs in a Home-Based Intervention with Children with Autism Spectrum Disorders

Alison, Courtney E. 2010 August 1900 (has links)
Humans and dogs have lived among each other in mutually beneficial relationships for thousands of years. In recent years, this human-animal bond has emerged as a catalyst for animal-assisted activities and therapies that may benefit those with disabilities, including children with autism spectrum disorders (ASD). ASD are characterized by qualitative impairments in social interaction and communication and restricted repetitive and stereotyped patterns of behavior, interests, and activities. The nonverbal and nonjudgmental nature of dogs may be non-threatening and easier for children with ASD to decode, which may decrease anxiety and facilitate social bonding. Further, with their roles as social lubricants/transitional objects and natural foci of interest, dogs may facilitate social interaction between children with ASD and other people. Using a single case, multiple baseline design across participants, this study investigated whether multiple semi-structured interactions with dogs would increase social and communicative behaviors and decrease restricted repetitive and stereotyped patterns of behavior in children. Although only two had statistically significant results, all three participants showed responses to intervention in the hypothesized directions. This study supports the position that children with ASD may benefit from participating in animal-assisted activities with dogs.
299

Morphed Potential Energy Surfaces from the Spectroscopy of Weakly Bound Complexes

Rivera-Rivera, Luis A. 2011 May 1900 (has links)
In this research the so-called potential morphing method was used to generate reliable interaction potential energy surfaces for weakly bound complexes. The potential morphing method is based on the optimization of modified computed ab initio potential energy surfaces to give predicted spectroscopic data, in agreement with the experimental values. In the standard potential morphing procedure the computed ab initio potential is adjusted by scaling, shifting, and dilating transformations to reproduce the experimental data. In this research, selected systems have been chosen to be studied based on the availability of varied and accurate sets of experimental data. In the present work, accurate interaction potential energy surfaces are obtained for the weakly bound complexes: Ne:HCl, OC:HX (X = F, Cl, Br, I) and HI:CO2. A comprehensive study on the interaction potential of these systems provides fundamental perspectives on the influence of different intermolecular forces. In addition the ground state isotopic isomerization observed in the OC:HI system may suggest a possible structural change of proteins, and other biological macromolecules, in deuterated solvents. In this dissertation, an alternative approach to morphing the potential energy surfaces of non-covalent interactions is also presented. In this approach the morphed potential is generated as a linear combination of ab initio potentials, that are computed at different levels of theory. This new morphing approach is applied to OC:HCl and is found to be of similar accuracy to that of the previous morphing method. In addition, this new method is also extended from four-dimensions to six-dimensions and is applied to the OC:HF system to obtain a vibrationally-complete six-dimensional morphed potential.
300

The Effect of The Financial Holding Company¡¦s Value for Their Issuing European Convertible Bond

Wang, Hui-Wen 28 June 2004 (has links)
Abstract Though there were many international paper on the European Convertible Bond¡]ECB¡^. Most of them focus on the electronic industry. Financial industry was excluded. A financial holding company made the good use of international source by issuing ECB overseas under the pressure of achieving internationalizes. The purpose of this study is to explore the distinctions of the financial holding companies who have announced issuing European Convertible Bond¡]ECB¡^during 2002 to 2003. To identify the financial character and evaluate the influence on the companies¡¦share price followed by the issuance of ECB from the statistic viewpoint of financial analysis and the dynamic viewpoint of the impacts on the company¡¦s value. There are two parts of the thesis. The first part is about the effect of the financial holding company¡¦s value for their issuing ECB by using the event study. Using probit and logic regression analysis to examine the effect of various financial factors in decision-making process of issuing ECB abroad did the second part. The financial character of financial holding companies with ECB issuance have significant differences in compared to those who have not yet issued ECB. Conclusion: 1.With¡¨Event study¡¨the results shown that there is no significant effect in the short term but cumulative average abnormal return is negative in the long term on the announcement data in exiting shareholders stake of issuing ECB. 2.At 5% significance level¡Aempirical results shown that listed financial holding companies with ECB issuance have significant differences in debt ratio, EPS and firm size compared to the companies who have not yet issued ECB.

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