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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.
31

Crack propagation modeling using Peridynamic theory

Hafezi, M. H., Alebrahim, R., Kundu, T. 01 April 2016 (has links)
Crack propagation and branching are modeled using nonlocal peridynamic theory. One major advantage of this nonlocal theory based analysis tool is the unifying approach towards material behavior modeling- irrespective of whether the crack is formed in the material or not. No separate damage law is needed for crack initiation and propagation. This theory overcomes the weaknesses of existing continuum mechanics based numerical tools (e.g. FEM, XFEM etc.) for identifying fracture modes and does not require any simplifying assumptions. Cracks grow autonomously and not necessarily along a prescribed path. However, in some special situations such as in case of ductile fracture, the damage evolution and failure depend on parameters characterizing the local stress state instead of peridynamic damage modeling technique developed for brittle fracture. For brittle fracture modeling the bond is simply broken when the failure criterion is satisfied. This simulation helps us to design more reliable modeling tool for crack propagation and branching in both brittle and ductile materials. Peridynamic analysis has been found to be very demanding computationally, particularly for real-world structures (e.g. vehicles, aircrafts, etc.). It also requires a very expensive visualization process. The goal of this paper is to bring awareness to researchers the impact of this cutting-edge simulation tool for a better understanding of the cracked material response. A computer code has been developed to implement the peridynamic theory based modeling tool for two-dimensional analysis. A good agreement between our predictions and previously published results is observed. Some interesting new results that have not been reported earlier by others are also obtained and presented in this paper. The final objective of this investigation is to increase the mechanics knowledge of self-similar and self-affine cracks.
32

Customization, emotional bonds and identification with the player character : A study into the effects of text-based gameplay

Hackman, Eleonora January 2016 (has links)
The aim of this study is to take a closer look at how customization, or the lack thereof, affectsthe player to character emotional bond and identification in a digital game. Examining previousarticles and studies with similar aim, the lack of study pertaining to a certain game formatsurfaced and sparked a research interest. To gain some clarity into how character customization,and the identification and bond it inspires in players, would be affected by a non-audiovisualbranching stories digital game the researcher created a small game for this study. This paperexplores if previous research results on RPGs can be transferred to the format of a text-basednon-audiovisual branching story game. For this qualitative study, ten people, divided in twogroups, played a version of the game and answered follow-up questions in the form of aquestionnaire. In addition, some observations were carried out of the game play sessions. Theseanswers were studied to give the individuals perspective, as well as allowing for the study of thephenomena by reviewing multiple perspectives to distinguish patterns. The results indicate thatcaring for a character takes longer if the player is not allowed to customize it. It was also indicated that the actual customization was more important than the character created.
33

Spine changes of measure and branching diffusions

Roberts, Matthew January 2010 (has links)
The main object of study in this thesis is branching Brownian motion, in which each particle moves like a Brownian motion and gives birth to new particles at some rate. In particular we are interested in where particles are located in this model at large times T : so, for a function f up to time T , we want to know how many particles have paths that look like f. Additive spine martingales are central to the study, and we also investigate some simple general properties of changes of measure related to such martingales.
34

Distribution of Gene Pair Similarity in Syntenic Regions Within and Between Genomes: A Branching Process Account of the Polyploidization, Speciation and Fractionation Cycle

Zhang, Yue 01 October 2019 (has links)
The evolution of plant genomes is notable for manifesting a cycle of whole genome doubling, fractionation (gradual loss of redundant genes) and speciation. The thesis is based on a branching process model of the doubling and fractionation process, integrated with a standard model of sequence divergence. The immediate application of this work is to account for the distribution of sequence similarity for duplicate gene pairs, both within plant genomes and between two related plant genomes in terms of a cycle of polyploidization, fractionation and speciation. We derive a mixture distribution for duplicate gene pair similarities generated by speciation and/or repeated episodes of polyploidization. We account not only for the timing of these events in terms of local modes or peaks of the component distributions, but also their volume, or amplitude, and variance. We outline how to infer the parameters of the model. We illustrate with analyses of the distribution of homolog similarities in a number of plant families: Brassicaceae, Solanaceae and Malvaceae. To our knowledge, this is the first method to account for the volume of the component normals of a distribution of similarities, preliminary to an evolutionarily meaningful inference procedure. In addition, we solve the problem of identifying the ploidy level of a series of two or three polyploidizations by invoking the observed and predicted gene triple profiles for each model, i.e., by calculating the probability of the four types of triple with origins in one or the other event, or both.
35

Rheology Of Peroxide Modified Recycled High Density Polyethylene

Parmar, Harisinh, h_arzoo@yahoo.com January 2008 (has links)
Consumption of plastics has increased exponentially, in line with the world's population. Not surprisingly this is reflected in enormous growth of the plastic industry especially during the last five decades. Commensurate with this, waste produced from plastics consumption has created a major environmental problem. Many types of waste disposal methods have been used all over the world so far, but all of them have disadvantages. Furthermore, some methods are responsible for the generation of green house gases and further contribution to global warming. Recently, reduction of green house gas emission has become a target of most industries. Plastic recycling and reuse breaks the cycle of endless production of virgin polymer and thus contributes to a net reduction of green house gas emission. Recycling of plastics should produce materials with improved properties to replace virgin plastics for a variety of applications. Improvement in the properties of recycled plastics can be achieved by blending with other plastics, by filler addition and by modification using free radical initiators. Introduction of the free radical initiator (organic peroxide) during reprocessing of the recycled plastics has been found to offer significant property improvements to the recycled materials. Extremely small amounts of a free radical initiator (typically ranging between 0.01 wt% to 0.2 wt%) is capable of enhancing the properties of the recycled plastics to a great extent. This project investigates the use of free radical initiators in the recycling of post consumer recycled high density polyethylene using reactive extrusion. Both molecular and rheological characterisation of recycled and reprocessed materials was carried out and this was followed by tensile testing of the modified materials to satisfy end use applications such as packaging and drainage piping. Post consumer recycled high density polyethylene (R-HDPE) resin and virgin high density polyethylene (V-HDPE) were reactively extruded with low concentrations of dicumyl peroxide (DCP) and 1, 3 1, 4 Bis (tert- butylperoxyisopropyl) Benzene (OP2) respectively in a twin screw extruder in order to produce modified materials with varying composition (0.0 wt%, 0.02 wt%, 0.05 wt%, 0.07 wt%, 0.10 wt% and 0.15 wt%) of both organic peroxides. Morphological characterisation using modulated differential scanning calorimetry (MDSC) demonstrated that there is a decrease in the crystallinity level for all the modified samples. Shear rheological tests were carried out to study the structure of the modified materials within the linear viscoelastic region. Viscoelastic parameters, such as storage modulus (G'), loss modulus (G
36

Towards measurement of the ratio BR(η → 3π<sup>0</sup>) / BR(η → π<sup>+</sup> π<sup>- </sup>π<sup>0</sup>)

Heijkenskjöld, Lena January 2010 (has links)
<p>This diploma thesis presents a preliminary study of the ratio of branching ratio r = BR(η → 3π<sup>0</sup>) / BR(η → π<sup>+</sup> π<sup>- </sup>π<sup>0</sup>). The experimental data used is collected by WASA-at-COSY which is a 4π sr detector optimised to detect light mesons and their decay products and is situated in Jülich, Germany.The focus of the work is to see how different reconstruction methods for the detected particles can alter both the measured values of the  branching ratios and the luminosity dependence of these branching ratios. The results show that for some of the methods, the measured branching ratios have a clear luminosity dependence. Depending on method, the extracted branching ratios vary differently. A few different methods have been studied, so the results provides a qualitative understanding of the behaviour of the measured branching ratios for different luminosities.</p>
37

Towards measurement of the ratio BR(η → 3π0) / BR(η → π+ π- π0)

Heijkenskjöld, Lena January 2010 (has links)
This diploma thesis presents a preliminary study of the ratio of branching ratio r = BR(η → 3π0) / BR(η → π+ π- π0). The experimental data used is collected by WASA-at-COSY which is a 4π sr detector optimised to detect light mesons and their decay products and is situated in Jülich, Germany.The focus of the work is to see how different reconstruction methods for the detected particles can alter both the measured values of the  branching ratios and the luminosity dependence of these branching ratios. The results show that for some of the methods, the measured branching ratios have a clear luminosity dependence. Depending on method, the extracted branching ratios vary differently. A few different methods have been studied, so the results provides a qualitative understanding of the behaviour of the measured branching ratios for different luminosities.
38

Change of benthic communities at Tiaoshi coral reef, southern Taiwan

Wu, Bing-je 27 August 2005 (has links)
Coral community at Tiaoshi in Nanwan Bay, southern Taiwan was originally dominated by branching Acropora corals which formed some monopolized patches. The community had been changed apparently on a local scale (<2 km) since 1994. Several Acropora patches were almost completely replaced by the solitary sea anemone Condylactis sp. after man-made and typhoon disturbances. However, sea anemones were apparently decreased in 2002. To understand the change of the benthic communities, three areas, including Anemone-dominated, Coral-recovery and Acropora-dominated, at depths of 6 to 10 m were selected and monitored by permanent transects from 2003 to 2005. Each site included three replicate patches. At Anemone-dominated area, the mean cover of sea anemone ranged from 24.6 to 15.3% and that of the hard corals was low with 1.4 to 3.9%. At Coral-recovery area, the mean cover of the hard corals was significantly increased from 21.3 to 38.9%, while macroalgae was significantly decreased from 20.7 to 6.1% and sea anemone was low with 1.4 to 3.0%. At Acropora-dominated area, the cover of the hard corals was ranged from 70.0 to 56.6% while macroalgae and anemone was 1.1 - 3.4% and 3.5 - 4.7%, respectively. In general, the results showed that anemone and macroalgae were decreased and corals were recovery. In addition, the diversity index of coral genera at Anemone-dominated area was higher due to coral recruitment in 2004 and 2005. The new recruits were dominated by Montipora stellata.
39

A measurement of the branching fraction of the Ds meson decay into a tau and a neutrino /

He, Lian Harry. January 2000 (has links)
Thesis (Ph. D.)--University of Washington, 2000. / Vita. Includes bibliographical references (p. 120-123).
40

NRAGE in branching morphogenesis of the developing murine kidney /

Nikopoulos, George N., January 2009 (has links)
Thesis (Ph.D.) in Biochemistry and Molecular Biology--University of Maine, 2009. / Includes vita. Includes bibliographical references (leaves 95-107).

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