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1
Janezic, Sandra, Valerija Zidaric, Bart Pardon, Alexander Indra, Branko Kokotovic, Jose Blanco, Christian Seyboldt, et al. "International Clostridium difficile animal strain collection and large diversity of animal associated strains." BioMed Central, 2014. http://hdl.handle.net/10150/610058.
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BACKGROUND:Clostridium difficile is an important cause of intestinal infections in some animal species and animals might be a reservoir for community associated human infections. Here we describe a collection of animal associated C. difficile strains from 12 countries based on inclusion criteria of one strain (PCR ribotype) per animal species per laboratory.RESULTS:Altogether 112 isolates were collected and distributed into 38 PCR ribotypes with agarose based approach and 50 PCR ribotypes with sequencer based approach. Four PCR ribotypes were most prevalent in terms of number of isolates as well as in terms of number of different host species: 078 (14.3% of isolates4 hosts), 014/020 (11.6%
8 hosts)
002 (5.4%
4 hosts) and 012 (5.4%
5 hosts). Two animal hosts were best represented
cattle with 31 isolates (20 PCR ribotypes
7 countries) and pigs with 31 isolates (16 PCR ribotypes
10 countries).CONCLUSIONS:This results show that although PCR ribotype 078 is often reported as the major animal C. difficile type, especially in pigs, the variability of strains in pigs and other animal hosts is substantial. Most common human PCR ribotypes (014/020 and 002) are also among most prevalent animal associated C. difficile strains worldwide. The widespread dissemination of toxigenic C. difficile and the considerable overlap in strain distribution between species furthers concerns about interspecies, including zoonotic, transmission of this critically important pathogen.
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Putz-Perrier, Martin W. "Distribution and scaling of extensional strain in sedimentary rocks." Thesis, Imperial College London, 2008. http://hdl.handle.net/10044/1/1293.
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For this study, spatial and size distributions of normal faults and associated tensile fractures were directly measured in deformed sedimentary rocks in three extensional regions: Kimmeridge Bay and Kilve in the UK and the Maltese Islands. The collected data allow i) quantifcation of regional extension at different scales, ii) determination of the relative importance of large and small structures, iii) quan- tifcation of the spatial heterogeneity of brittle extension, iv) comparison of scaling laws for veins and faults belonging to the same extension event, and v) analysis of the evolution of brittle damage in space and time. Multiple scan-lines of different length and resolution were collected in each study area to record the entire extension-related deformation. In order to quantify the heterogeneity of fracture and strain distributions, a new method of spatial analysis has been developed. The method is based on a non-parametric comparison of the cumulative frequency and extension with that for a uniform distribution and pro- vides a measure of heterogeneity based on both the position and the displacement of individual fractures sampled along a linear traverse. Seismically observable extension is found to scale with total extension in the three study areas, obeying a power-law relationship. The proportion of the total extension that is resolved in seismic refl ection data systematically increases with increasing strain. This means that seismic data signifcantly underestimate the total extension at low strains but record most of the total extension in higher strain regions. Heterogeneity analysis carried out for the three study areas shows that i) hetero- geneities of the distributions of fractures and strain in an area can differ signifcantly, ii) heterogeneities are strongly dependent on lithology and mechanical heterogeneity, and iii) heterogeneities evolve with increasing strain. At Kimmeridge Bay, both veins and faults display power-law scaling, but do not form part of the same distribution. Veins and faults along the Kilve-Lilstock section conform to a single power-law distribution. At the Maltese Islands fault-frequencies conform to power-law scaling, but yield a higher scaling exponent in lower-strain zones than in higher-strain (damage) zones. The platform carbonates at the Maltese Islands take up early extension by randomly distributed small-scale faulting. The layered and mudstone-rich rocks around Kim- meridge Bay respond to low strain by distributed ("ductile") deformation in the shales and by randomly distributed or anti-clustered veining in the stiffer carbonate beds. In inter-bedded carbonates and shales along the Kilve-Lilstock section, early extension is highly localised in narrow zones of faults and associated damage, pre- serving large portions of virtually unfractured rock in between. A tensor method has been developed which permits three-dimensional strain analy- sis from line-data. The results of this analysis show that one-dimensional estimates of extension generally are good approximations of the maximum principal strain and that deformation in most sampled sections conforms to pure-shear, plane-strain conditions. Fold-structures associated with normal faults are explained as due to superimposed "normal drag" within the process zone and slip-related "reverse drag" within the damage zone of a (propagating) normal fault.
3
Kang, Wei-Ping. "Application of numerical analysis to neutron strain scanning." Thesis, University of Salford, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.360449.
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Chai, Lauren (Lauren Amy). "Twist error response of periodic lattices to strain energy distribution." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/101331.
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Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2015.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 79-80).
Periodic lattices, when used as assembly scaffolds, can augment pre-existing 2D manufacturing techniques to fabricate 3D structures with heterogeneous materials, components and architecture such as human organs for transplant patients, and micro batteries. Periodic lattices are first preformed and then folded using externally actuating walls that properly constrain the lattice edges. Angular errors of the actuation walls cause the lattice to distort, misaligning components on the lattice panels. Research into the response of a lattice to geometric errors imposed on the lattice edges does not account for how much strain energy is put into the lattice during folding and its impact on the lattice distortion response and magnitude. This thesis shows how design parameters of the lattice can change the magnitude and shape of the twist response of the lattice when external geometric errors are applied to the lattice during folding. A Buckingham Pi analysis was used to show how the twist response of the lattice due to an external angular wall error depends on the torsional stiffnesses of the panels, the initial fold angle of the preformed accordion unit in the lattice and the angular wall error. A FEA simulation study quantified the Buckingham Pi results by varying the torsional stiffness ratio of the panels, the initial fold angle and the final lattice length after folding. The results showed that increasing the ratio of the torsional stiffnesses by two orders of magnitude decreases the magnitude of the response by as much as an order of magnitude and increases the asymmetry by 0.5 to 1.5 orders of magnitude. Increasing the initial fold angle by 50% increases the magnitude of the result by as much as 250% and decreases asymmetry by 26%.
by Lauren Amy Chai.
S.M.
5
Imamoglu, Baris. "Case history strain and force distribution in HDPE reinforced wall /." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 149 p, 2009. http://proquest.umi.com/pqdweb?did=1889078531&sid=8&Fmt=2&clientId=8331&RQT=309&VName=PQD.
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Thesis (M.C.E.)--University of Delaware, 2009.Principal faculty advisors: Dov Leshchinsky and Christopher L. Meehan, Dept. of Civil & Environmental Engineering. Includes bibliographical references.
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Sinha, Arijit. "Strain distribution in OSB and GWB in wood frame shear walls /." Connect to this title online, 2007. http://hdl.handle.net/1957/4655.
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Castillo, Luis E. Hernandez. "Determination of micro-scale strain distribution in hot-worked steel microstructures." Thesis, University of Sheffield, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.425603.
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Kabeer, Saqib. "Application of image analysis techniques to determine strain distribution in leather." Thesis, University of Northampton, 2006. http://nectar.northampton.ac.uk/2672/.
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The optimum cutting of various parts of a shoe, prior to shoe manufacture requires knowledge of the topographical variation of what are termed “lines of tightness”. Currently the cutting operation for shoe parts is guided by a general assumption about the pattern of the lines of tightness. There is a need to have available a system which can determine, in a non-destructive way, the lines of tightness in an indvidual piece of leather. Initially an image analysis system was developed to investigate the uni-axial deformation behaviour of leather. This technique provided more information about the stress-strain behaviour of a leather sample along the gauge length than a conventional mechanical test and it was possible to accurately measure the strain distribution along the gauge length. A system was developed which could determine the relative displacement of marked spots along the gauge length of the sample using images captured during a uni-axial, bi-axial or multi-axial tensile test. The separation of the marked spots along the direction of applied stroke allowed the determination of longitudinal strain while contraction across the width was also measured in some cases, which was useful in calculating the Poisson’s ratio of leather for which a great variation was observed between different locations (Butt, Belly, Neck etc). Various approaches were investigated to determine the lines of tightness. Firstly, the local Poisson’s ratio was observed since a higher value of this parameter was associated with these lines of tightness. Secondly, biaxial stretching of leather by a series of actuators for each axis indicated the lines of tightness along the actuator with lower strain values. Thirdly, the strain was measured when the leather was stretched along number of known axes. This latter technique appeared to be the best approach and mathematical modeling was investigated to provide further refinement. A mechatronics-based device by industrial application of the third approach was also proposed. The software was written using a graphical programming system (LabVJ EW)
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Williams, Kevin Vaughan Carleton University Dissertation Engineering Mechanical. "The numerical prediction of strain distribution in sheet metal forming operations." Ottawa, 1993.
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Fujisawa, Hiromi. "Inheritance and Strain Distribution of a Persistent Hyaloid Vascular System in Mice." Kyoto University, 1997. http://hdl.handle.net/2433/202172.
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Moore, Josephine. "Strain-Driven Elemental Re-Distribution during Hydration of the Mid-Lower Crust." Thesis, Curtin University, 2020. http://hdl.handle.net/20.500.11937/79105.
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Fluids are vital for the transport of mass and energy through the Earth’s crust and also for its thermodynamic re-equilibration in response to changes in pressure and temperature. Presented here are observations for the coupling between deformation and reaction, mass transport, and variations in trace-element composition and isotope ratios. Overall, this thesis communicates the importance of mid- to lower crustal deformation for mass transfer and in the attainment of equilibria in the presence of fluid.
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Christian, Lee Conner. "Thru-thickness bending stress distribution at elevated temperatures." Texas A&M University, 2005. http://hdl.handle.net/1969.1/2315.
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During the bending of flange plate used for dapped girders some highway bridge
fabricators are experiencing cracking of the flange plate particularly when heat is used in
assisting the bending process. Due to the extreme strains experienced during the
fabrication process, investigating this problem requires the use of a finite element
analysis. The fabrication process was broken down into two parts, first the heating of
the plate through the use of either a furnace or an acetylene torch (thermal), and the
second was the bending process (structural). The five different temperatures collected
during the thermal analysis were a uniform temperature of 75oF, a 1100oF uniform
temperature as a result of furnace heating, both five and ten minutes of air-cooling after
the plate had reached a uniform temperature of 1100oF, and the temperature gradient
after heating the flange plate to a surface temperature of 1200oF though the use of an
acetylene torch. After the thermal analysis was completed, the resulting temperatures
were imported into the structural model. The plate thicknesses analyzed were one, one
and a half, and two inches, assuming both 50 and 70 ksi yield strengths. To achieve a 90
degree six-inch radius bend the plate was bent in five separate locations. The result of
this analysis showed that with the introduction of temperature gradients into thefabrication process, the strains along the plate??s extreme fibers increased. The model
further showed that for both a one and a half and two-inch thick plate the extreme fiber
strains exceeded ten percent, which further adds to the increased risk of the flange plate
cracking during fabrication. The highest residual stresses through the plate??s thickness
occurred during cold bending. The residual stresses through the plate??s thickness
decreased when the fabrication process was carried out at elevated temperatures. When
steel exceeds a strain of 10 to 16 percent during the fabrication process, the plate
becomes susceptible to cracking. This strain limit was exceeded for plate thicknesses of
one and a half and two inches.
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Hy, Henrik, and Viktor Hällqvist. "Safety Analysis of Longtan High Dam Considering the Construction Process." Thesis, Umeå universitet, Institutionen för tillämpad fysik och elektronik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-123289.
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To manage China’s growing demands of electricity, more and larger dams could be a part of the solution. It is important to evaluate and perform safety analysis for existing dams, in order to improve our understanding and knowledge about future dams. In this master thesis, a safety research of Longtan Dam on the Hongshui River in China was analysed. The main objectives in this research were to construct a 3D model and determine the critical points of large stress, strain and yield area in the dam for different cases.The factor of safety for sliding when primary loads were acting on the dam was calculated to be 0.50 for the non-overflow section of the dam and 0.48 for the overflow section. A safety factor against overturning was also calculated for the non-overflow and overflow section to 2.24 and 1.96 respectively. The results showed that the dam was safe from both sliding and overturning. The numerical results for distribution of stress, strain and yield area were simulated in 3D models by using ANSYS, a finite element program. Several cases for non-overflow and overflow sections of Longtan Dam were analysed for different heights and load combinations. For the first three cases where only self-weight was applied on the dam, high impacts of stress and strain were located at the dam heel, toe and at the largest maintenance tunnel of the dam. Appearance of plastic strain was also found around these areas. However, when primary loads were applied to the dam sections, the values of stress and strain became larger, especially in the toe area. In the last case when the dam was subjected to seismic activity, the distribution of stress and strain along the z-direction (along the dam) showed an uneven distribution, hence showing the importance of simulation in 3D.
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Bouhamed, Ayda. "Investigation of Stress Distribution and Adhesion Effects of Strain Sensitive Epoxy/MWCNT Nanocomposite Films." Universitätsverlag Chemnitz, 2018. https://monarch.qucosa.de/id/qucosa%3A32781.
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Carbon nanotubes (CNTs) have attracted a significant attention in a wide variety of applications due to their excellent physical and chemical properties. Specifically, CNTs reinforced polymer nanocomposites have considerable potential for the realization of highly sensitive, flexible, stable and durable strain sensors. However, the performance of polymer/CNTs strain sensors is influenced by many factors. Especially, the homogeneity of the CNTs distribution within the polymer matrix and the adhesion of nanocomposite film to the polymer substrate play a decisive role. Additionally, the electrical and piezoresistive responses of polymer/CNTs nanocomposites, as well as their response under variable environmental conditions need to be considered.
The main aim of this thesis is to develop polymer/CNTs nanocomposites for strain sensing applications. Thereby, the focus is on the development of suitable, cost-effective and simple preparation methods of polymer/CNTs-based strain sensitive nanocomposites and on the selection of suitable flexible substrate.
However, during deposition, residual stress can be formed at the interface between the film and the substrate, which leads to thin film failures. Therefore, an analytical model is developed to predict the stress distribution in the film aiming to define the suitable processing conditions for low residual stress formations. Furthermore, specific surface treatments are proposed in order to enhance the adhesion between the substrate and the thin film, which are investigated by contact angle measurement (CAM), X-rays spectroscopy (XPS)and atomic force microscopy (AFM).
Nanocomposites with up to 1 wt.% multi-walled carbon nanotubes (MWCNTs) were prepared using a simple direct mixing method. The process parameters, such as sonication time and curing time, have been determined based on several characterization techniques. Dispersions qualities were examined using morphological and topography characterizations including scanning electron microscopy (SEM) and AFM. Additionally, DC measurements were performed on the polymer/CNTs nanocomposites in order to optimize the process parameters depending on the electrical conductivity and piezoresistivity of the nanocomposite. The impact of surface treatment on the strain sensing behavior was evaluated. Furthermore, electrical and piezoresistive responses
under humidity and temperature effects were investigated.
Analytical investigations show that the residual stresses can be minimized by using low deposition temperatures and by increasing the film thickness. Comparison of surface treatment techniques demonstrates that oxygen plasma cleaning improves adhesion at the interface by enlarging the surface area and enhancing the surface wettability and the surface polarity due to the introduction of functional groups. Morphological characterizations show the good homogeneity of MWCNTs and depict the importance of optimization of sonication time for the uniform filler distribution. Furthermore, AFM analysis show that the surface roughness is reduced as sonication time is increased due to the debundling of CNTs agglomeration. However, excessive sonication time can
lead to higher roughness caused by breaking of CNTs, which get thereby the tendency to re-agglomerate.
A low percolation threshold was achieved at a CNTs concentration of 0.3 wt.% which is significantly lower than the CNT concentrations reported in literature and demonstrating the quality of dispersion process adopted. Higher sensitivity is achieved at this CNTs concentration with approximately linear piezoresistive behavior of around R 2 = 0.9904. The novel strain sensitive nanocomposites show good stability at ambient conditions and good durability under mechanical cyclic test. In addition, it is found that the sensing behavior depends greatly on the surface roughness. A high stability and linearity with good sensitivity were observed for the sensor having low surface roughness. The temperature and humidity dependency of the composite is affected by
the environmental changes. Therefore, an encapsulation of the film is required to minimize moisture absorption in addition to get better sensor recovery under mechanical load comparing to non-encapsulated film.Kohlenstoff-Nanoröhrchen (CNTs) genießen aufgrund ihrer hervorragenden physikalischen und chemischen Eigenschaften in einer Vielzahl von Anwendungen eine große Aufmerksamkeit. Insbesondere CNT-verstärkte polymere Nanokomposite haben ein erhebliches Potenzial für die Realisierung hochempfindlicher, flexibler, stabiler und langlebiger Dehnungssensoren. Die Eigenschaften von Polymer/CNT-Dehnungssensoren werden von vielen Faktoren beeinflusst. Insbesondere die Homogenität der CNT-Verteilung innerhalb der Polymermatrix und die Haftung des Nanokompositfilms auf dem Polymersubstrat spielen eine entscheidende Rolle. Darüber hinaus müssen die elektrischen und piezoresistiven Eigenschaften von Polymer/CNTs-Nanokompositen sowie deren Reaktion auf variable Umgebungsbedingungen berücksichtigt werden. Das Hauptziel dieser Arbeit ist die Entwicklung von Polymer/CNT-Nanokompositen für die Anwendung als Dehnungsmessstreifen. Der Fokus liegt auf der Entwicklung geeigneter, kostengünstiger und einfacher Präparationsmethoden von Polymer/CNT-basierten dehnungsempfindlichen Nanokompositen und deren Realisierung auf geeigneten flexiblen Substraten. Während der Abscheidung kann an der Grenzfläche zwischen Film und Substrat Eigenspannung entstehen, die zu Dünnschichtfehlern führt. Daher wird ein analytisches Modell zur Vorhersage der Spannungsverteilung im Film entwickelt, um die geeigneten Verarbeitungsbedingungen für geringe Eigenspannungsformationen zu definieren. Darüber hinaus werden spezifische Oberflächenbehandlungen vorgeschlagen, um die Haftung zwischen dem Substrat und dem Dünnfilm zu verbessern, die durch Kontaktwinkelmessung (CAM), Röntgenspektroskopie und Rasterkraftmikroskopie (AFM) untersucht werden. Nanokompositen mit bis zu 1 wt.% mehrwandigen Kohlenstoff-Nanoröhren (MWCNTs) wurden mit einem einfachen Direktmischverfahren hergestellt. Die Prozessparameter, wie Ultraschallzeit und Aushärtezeit, wurden auf der Grundlage verschiedener Charakterisierungstechniken bestimmt. Die Dispersionsqualitäten wurden mittels morphologischer und topographischer Charakterisierungen einschließlich Rasterelektronenmikroskopie (REM) und AFM untersucht. Zusätzlich wurden DC-Messungen an den Polymer/CNT-Nanokompositen durchgeführt, um die Prozessparameter in Abhängigkeit von der elektrischen Leitfähigkeit und der Piezoresistivität des Nanokomposits zu optimieren. Der Einfluss der Oberflächenbehandlung auf das Verhalten des Dehnungssensors wurde bewertet. Darüber hinaus wurden elektrische und piezoresistive Reaktionen unter Feuchtigkeits- und Temperatureinflüssen untersucht. Analytische Untersuchungen zeigen, dass die Eigenspannungen durch niedrige Depositionstemperaturen und eine Erhöhung der Schichtdicke minimiert werden können. Der Vergleich von Oberflächenbehandlungstechniken zeigt, dass die Sauerstoff-Plasma-Reinigung die Haftung an der Grenzfläche verbessert, in dem sie die Oberfläche vergrößert und die Benetzbarkeit der Oberfläche sowie die Oberflächenpolarität durch die Einführung von Funktionsgruppen verbessert. Morphologische Charakterisierungen zeigen die gute Homogenität vom Epoxid /MWCNTs Nanokompositen und die Bedeutung der Optimierung der Ultraschallzeit für die gleichmäßige Füllstoffverteilung. Darüber hinaus zeigt die AFM Analyse, dass die Oberflächenrauhigkeit durch die Entbündelung der CNT-Agglomerate für eine längere Ultraschallzeit reduziert wird. Eine übermäßige Ultraschallzeit kann jedoch zu einer höheren Rauigkeit durch Brüche von CNTs führen, die dadurch zu einer erhöhten Reagglomerationsneigung führen. Ein niedriger Perkolationsschwellenwert wurde bei einer CNT-Konzentration von 0.3 wt.% erreicht, welches deutlich niedriger als die in der Literatur berichteten CNT-Konzentrationen ist. Dies belegt die hohe Qualität des vorgeschlagenen Dispersionsprozesses. Eine höhere Empfindlichkeit wird bei dieser CNT-Konzentration mit einem annähernd linearen piezoresistiven Verhalten von etwa R 2 = 0.9904 erreicht. Die neuartigen spannungsempfindlichen Nanokompositen weisen eine gute Stabilität der Umgebungsbedingungen und eine gute Haltbarkeit im mechanischen Zyklustest auf. Darüber hinaus wird festgestellt, dass das Abtastverhalten stark von der Oberflächenrauheit abhängt. Eine hohe Stabilität und Linearität bei guter Empfindlichkeit wurde für den Sensor mit geringer Oberflächenrauigkeit beobachtet. Das Verhalten des Sensors wird durch Umweltveränderungen aufgrund von Temperatur und Luftfeuchtigkeit beeinflusst. Daher ist eine Verkapselung des Films erforderlich, um die Feuchtigkeitsaufnahme zu minimieren. Die realisierte Verkapselung hat zusätzliche Vorteile in Bezug auf die Sensor Rückgewinnung unter mechanischer Belastung im Vergleich zu nicht gekapseltem Film gezeigt.
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Lapadat, Ioan Alexandru. "Control of fault geometry, interaction and mechanical stratigraphy on strain distribution in normal fault zones." Thesis, Durham University, 2017. http://etheses.dur.ac.uk/12926/.
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It is known that the development and distribution of strain associated with normal faulting is influenced by the process of fault growth within mechanically layered and heterogeneous sedimentary rocks. Fault displacement is often partitioned between discontinuous throw on slip surfaces and zones of distributed strain, which in some cases can be the result of folding associated with normal faulting. The amount of ductile deformation can vary significantly along the strike of a normal fault array as a result of various processes, such as fault-tip propagation and fault interaction and linkage. In this study we investigate the influence of mechanical stratigraphy, fault geometry and fault mechanical interaction on the variability and distribution of ductile strain in the rock volume surrounding normal faults. We show that mechanical competence contrasts can control the manner in which strain is accommodated and, hence the overall patterns of secondary fault and fracture systems within normal fault-related folds. This can have consequences on the way in which disruption of an associated shale smear occurs, impacting the sealing properties of the fault zones. Also, we show that folding can be generated by different mechanisms that vary in importance in time and space along a normal fault array. Mechanical properties of the host rocks, together with the spatial configuration of the faults control the mechanical interaction between faults, exerting an influence on the variability of ductile strain within the volume of deformation surrounding normal faults. Specifically, conjugate normal faults that intersect within layers with low compressibility have geomechanical characteristics favorable for migration of stress concentrations near the upper fault tips which generate higher propagation/slip ratios and the development of lower amplitude folds, or no folding. The host rock lithology and the overlapping normal fault configuration at the time of interaction controls the three-dimensional relay ramp geometries and associated strains within relay ramps. Normal faults within mechanically competent rocks tend to develop relay ramps with tabular geometries, that have larger aspect ratios and smaller fault-parallel shear strains compared to those developed in mechanically incompetent rocks. Fault-normal shear strain within ramps can be the result of the development of asymmetric displacement gradients on the overlapping faults as a result of mechanical interaction between surface-breaking normal faults. The probability of a relay ramp bounded by surface-breaking normal faults to be completely breached depends not only on the accumulated ramp shear strains and the ratio between throw and separation of the bounding faults, but also on how the throw is partitioned between the interacting faults. Also, we argue that the style of breaching, dominantly through the upper part of the relay ramps, is influenced by the stress interaction between the overlapping faults and the Earth's free surface.
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Srour, Mohammed R. "X-ray Scattering Study of the Strain In Annealed Silica." Ohio University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1398343409.
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Gonzalez, Javier Knauss Wolfgang Gustav. "Full field study of strain distribution near the crack tip in the fracture of solid propellants via large strain digital image correlation and optical microscopy /." Diss., Pasadena, Calif. : California Institute of Technology, 1997. http://resolver.caltech.edu/CaltechETD:etd-12212004-164817.
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Moorhouse, Alexander James. "Population structure of Candida species : spatio-temporal distribution of strain types and association with ancient Hominins." Thesis, University of Aberdeen, 2016. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=229378.
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Lu, Tonghua. "Characterization and strain distribution of multicopy allelic variants of the M. fermentans membrane lipoprotein gene, p57." free to MU campus, to others for purchase, 1998. http://wwwlib.umi.com/cr/mo/fullcit?p9901259.
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Sabuncuoglu, Baris. "Development of parametric finite element modelling methods for nonwoven materials including rate dependent material behaviour." Thesis, Loughborough University, 2012. https://dspace.lboro.ac.uk/2134/10016.
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Thermally bonded nonwovens are low-price substitutes for traditional textiles. They are used in many areas including filtration, automotive and aerospace industries. Hence, understanding deformation behaviours of these materials is required to design new products tailored for specific applications in different areas. Because of their complex and random structure, numerical simulations of nonwoven materials have been a challenging task for many years. The main aim of the thesis is to develop a computational modelling tool to simulate the effect of design parameters on structural behaviour of low-density nonwoven materials by using a finite element method. The modelling procedure is carried out with a parametric modelling technique, which allows a designer to run a series of analyses with different design parameters and observe the effects of these parameters on the mechanical behaviour of nonwoven materials. The thesis also presents the study of rate dependent behaviour of nonwoven fibres. Novel test and data-interpretation procedures are proposed to determine the creep behaviour of fibres in the nonwoven structure. Some case studies are presented to demonstrate the effectiveness of the model. The developed computational tool allows macro and micro-scale structural investigation of nonwoven materials. Two additional studies are presented, performed with the developed tool. In the first study, the effect of design parameters on tensile stiffness of nonwovens was determined by performing numerical analyses with various nonwoven models. In the second one, strain distribution in fibres is studied thoroughly together with factors affecting the distribution. The models, developed in the thesis can also be employed in further studies of nonwovens, such as investigation of their damage and fracture behaviour.
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Farukh, Farukh. "Experimental and numerical analysis of deformation and damage in thermally bonded nonwoven material." Thesis, Loughborough University, 2013. https://dspace.lboro.ac.uk/2134/12812.
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Ssemakula, Hamzah. "Minimization of stock weight during close-die forging of a spindle." Högskolan Dalarna, Materialteknik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:du-12555.
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In this paper, Finite Element method and full-scale experiments have been used to study a hot forging method for fabri-cation of a spindle using reduced initial stock size. The forging sequence is carried out in two stages. In the first stage, the hot rolled cylindrical billet is pre-formed and pierced in a closed die using a spherical nosed punch to within 20 mm of its base. This process of piercing or impact extrusion leads to high strains within the work piece but requires high press loads. In the second stage, the resulting cylinder is placed in a die with a flange chamber and upset forged to form a flange. The stock mass is optimized for complete die filling. Process parameters such as effective strain distribution, material flow and forging load in different stages of the process are analyzed. It is concluded from the simulations that minor modifications of piercing punch geometry to reduce contact between the punch and emerging vertical walls of the cylinder appreciably reduces the piercing load. In the flange chamber, a die surfaces angle of 52° instead of 45° is pro-posed to ensure effective material flow and exert sufficient tool pressure to achieve complete cavity filling. In order to achieve better compression, it is also proposed to shorten both the length of the inserted punch and the die “tongues” by a few mm.
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Schöfisch, Thorben. "Quantifying strain in analogue models simulating fold-and-thrust belts using magnetic fabric analysis." Licentiate thesis, Uppsala universitet, Mineralogi, petrologi och tektonik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-451977.
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Applying the anisotropy of magnetic susceptibility to analogue models provides detailed insights into the strain distribution and quantification of deformation within contractional tectonic settings like fold-and-thrust belts (FTBs). Shortening in FTBs is accommodated by layer-parallel shortening, folding, and thrusting. The models in this research reflect the different deformation processes and the resulting magnetic fabric can be attributed to thrusting, folding and layer-parallel shortening. Thrusting develops a magnetic foliation parallel to the thrust surface, whereas folding and penetrative strain develop a magnetic lineation perpendicular to the shorting direction but parallel to the bedding. These fabric types can be observed in the first model of this study, which simulated a FTB shortened above two adjacent décollements with different frictional properties. The different friction coefficients along the décollements have not only an effect on the geometric and kinematic evolution of a FTB, but also on the strain distribution and magnitude of strain within the belt. The second series of models performed in this study show the development of a thrust imbricate and the strain distribution across a single imbricate in more detail. Three models, with similar setup but different magnitudes of bulk shortening, show strain gradients by gradual changes in principal axes orientations and decrease in degree of anisotropy with decreasing distance to thrusts and kinkzones. These models show that at the beginning of shortening, strain is accommodated mainly by penetrative strain. With further shortening, formation of thrusts and kinkzones overprint the magnetic fabric locally and the degree of anisotropy is decreasing within the deformation zones. At thrusts, an overprint of the magnetic fabric prior deformation towards a magnetic foliation parallel to the thrust surfaces can be observed. A rather complex interplay between thrusting and folding can be analysed in the kinkzones. In general, this thesis outlines the characteristics of magnetic fabric observed in FTBs, relates different types of magnetic fabric to different processes of deformation and provides insights into the strain distribution of FTBs.
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Ozturk, Sevki. "Distribution Of Bending Moments In Laterally Loaded Passive Pile Groups A Model Study." Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/2/12610378/index.pdf.
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In this study, bending moment distributions developed in laterally loaded passive pile and passive pile groups in cohesionless soil were investigated in laboratory conditions through model pile experiments. Different from the active pile loading, the lateral load was given directly to the piles using a movable large direct shear box. In these experiments strain gauges fastened to the piles and a computer based data reading system were used. The strain values were measured at five levels on the piles. The behavior of a single pile and a pile group having five piles were investigated through strain measurements in order to observe bending moment distribution on the piles.
After evaluating the test results, the behavior of passive single pile was found to be similar to the results obtained in early studies. Negative bending moments were observed at the specified depths above the shear plane and positive bending moments were measured at the level of the shear plane and below the shear plane. Maximum bending moments were obtained at 0.7L (L: Length of Pile) for single piles and piles in the group. Above the shear plane, maximum bending moments within the pile
group were found to be developed on the piles nearest to the loading. On the shear plane maximum bending moments were developed on the piles farthest from the loading just like active piles. Below the shear plane, maximum bending moments were developed mainly on the piles nearest to the loading.
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Styles, Millicent, and milli styles@anu edu au. "Characterisation of the flexural behaviour of Aluminium Foam Sandwich Structures." The Australian National University. Faculty of Engineering and Information Technology, 2008. http://thesis.anu.edu.au./public/adt-ANU20080813.170807.
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Aluminium foam has a range of properties that are desirable in many applications. These properties include good stiffness and strength to weight ratios, impact energy absorption, sound damping, thermal insulation and non combustibility. Many of these characteristics are particularly attractive for core materials within sandwich structures. The combination of aluminium foam cores with thermoplastic composite skins is easily manufactured and has good potential as a multifunctional sandwich structure useful in a range of applications. This thesis has investigated the flexural behaviour of such structures using a combination of experimental and modelling techniques. The development of these structures towards commercial use requires a thorough understanding of the deformation and strain mechanisms of the structure, and this will, in turn, allow predictions of their structural behaviour in a variety of loading conditions.
¶
The experimental research involved the use of an advanced 3D optical measuring technique that produces realtime, full-field strain evolution during loading. This experimental characterisation of strain evolution in this class of sandwich structure under flexural loading is the first of its kind in the world. The experimental work studied the sandwich structure undergoing four-point bend testing. Initial studies compared the behaviour of the aluminium foam structure with a more traditional polymer foam sandwich structure. The aluminium foam structure was found to have equivalent or improved mechanical properties including more ductile deformation and an enhanced energy absorption. An investigation was conducted on the effect of core and skin thickness on the metal structure and a range of flexural behaviours were observed. Analysis of the strain distribution showed a complex development including localised effects from the non-uniform cellular structure of the material. An understanding of the variation with size is important in establishing design methods for utilising these structures. In particular, it is desirable that finite element simulations can be used to predict behaviour of these structures in a diverse range of loading conditions. This aspect was considered in the second half of this study. An existing constitutive model for aluminium foam, developed for use in compression energy absorption studies, was used to investigate finite element simulations of the flexural behaviour of the sandwich structure. The FE model was able to predict the general deformation behaviour of the thinner skinned structures although the magnitude of the load-displacement response was underestimated. It is suggested this may be related to the size effect on the input parameter characterisation. The strain distribution corresponded well with the experimental strain measurements. It was found a simple increase in the material model input parameters was able to more closely match the magnitude of the load-displacement response while maintaining the appropriate strain distribution. The general deformation shape of the model with the thicker skin corresponded reasonably well with the experimental observations. However, further work is necessary on the element failure criterion to capture the shear cracking observed. The strain distributions of the model predicted this failure with high strain concentrations matching those of the experimental contours. The last part of the thesis describes a parametric study on the effect of the foam material model input parameters on the flexural behaviour of the sandwich structure model. An important conclusion of this work is that this material model for aluminium foam can, with some development, be utilized to provide a viable method for simulating aluminium foam composite sandwich structures in flexural loading situations.
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Lavinsky, D. V. "Structural analysis of the technological systems under electromagnetic field action." Thesis, Center of educational literature, 2016. http://repository.kpi.kharkov.ua/handle/KhPI-Press/22372.
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Zhang, Jianhua. "Diversity of aster yellows phytoplasmas in lettuce." The Ohio State University, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=osu1054584888.
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Serra, Michele. "Influence of Metastases' Location and Size on the Strain Field Distribution in Metastatically Involved Human Vertebrae: An In Vitro Study." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2019. http://amslaurea.unibo.it/19365/.
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Con l’aumento della speranza di vita per pazienti afflitti da metastasi, l’attuale pratica clinica tende ad orientarsi verso terapie che ne possano aumentare la qualità della vita.
Per fare ciò è necessario esplorare la meccanica del tessuto metastatico.
Con questo lavoro abbiamo deciso di concentrarci sullo studio del comportamento meccanico di vertebre metastatiche.
Abbiamo rivolto la nostra attenzione alla posizione e alla dimensione della lesione all’interno del corpo vertebrale; un argomento di dibattito per il quale non è disponibile nessuno studio conclusivo.
Otto segmenti di varia lunghezza sono stati ottenuti da cinque colonne vertebrali, con metastasi di differente tipo (i.e. osteolitico e osteoblastico).
I segmenti sono stati testati con una combinazione compressione e flessione anteriore, la distribuzione del campo di deformazione registrata per mezzo di DIC.
La distribuzione del campo di deformazione è stata analizzata sia quantitativamente che qualitativamente.
Le lesioni localizzate anteriormente risultavano influenzare fortemente la distribuzione del campo di deformazione, a prescindere dalla loro dimensione. L’influenza di lesioni posizionate posteriormente era trascurabile.
Le vertebre con metastasi litiche e blastiche mostravano campi omogenei con deformazioni di bassa intensità, anche se sottoposte a carichi significativi (i.e. 1.5 BW).
In aggiunta, è stato progettato uno “strumento” per la localizzazione delle lesioni nel corpo vertebrale a partire dagli scan CT. Questo “strumento” era composto di maschere personalizzabili e di un semplice modello geometrico per studiare la dimensione delle lesioni,
Abbiamo concluso che la distribuzione del campo di deformazione è principalmente influenzata dal tipo di metastasis.
Nel caso di metastasi litiche, l’influenza della posizione sulle deformazioni è più significativa di quella della dimensione.
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Heaton-Adegbile, Philip. "In-vitro assessment of load transfer and strain distribution across the cement-bone and bone-implant interfaces in artificially replaced acetabulum." Thesis, University of Portsmouth, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.424079.
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Shin, Jae-Kyoung. "Mechanical Behavior and Its Relation to Superconducting Property of High Temperature Composite Superconductors." 京都大学 (Kyoto University), 2008. http://hdl.handle.net/2433/66211.
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Kyoto University (京都大学)0048
新制・課程博士
博士(工学)
甲第14163号
工博第2997号
新制||工||1445(附属図書館)
26469
UT51-2008-N480
京都大学大学院工学研究科材料工学専攻
(主査)教授 落合 庄治郎, 教授 河合 潤, 准教授 奥田 浩司
学位規則第4条第1項該当
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Oliinyk, O. V., V. A. Tatarenko, Y. B. Park, and P. O. Selyshchev. "Influence of Fluctuations of the Point-Defects’ Generation Rate and Inhomogeneity of Irradiated F.C.C. Crystal on the Temperature Dependence of the Dissipative-Structure Period in a Spatial Distribution of Radiation Vacancies." Thesis, Sumy State University, 2012. http://essuir.sumdu.edu.ua/handle/123456789/35438.
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A kinetic model for the influence of external noise, such as fluctuations of the point-defects’ production
rate and inhomogeneity of irradiated f.c.c. crystal, on the formation of modulated defect-distribution structure
is considered. Defect-production rate and density of sinks for point defects are simulated as independent
uniform and stationary stochastic fields with certain parameters. The interaction between vacancies is
taken into account. Such stochastic fields can induce a spatial point-defects’ distribution, which is a stationary
uniform stochastic field. Its mean value and correlation functions are estimated, and restricting
conditions are determined when this stochastic field becomes unstable because of interaction between defect-
density fluctuations and a stochastic field with a spatially-periodic mean value is formed. A formula
for evaluating its spatial period is analysed. This geometrical parameter of such a dissipative structure is
determined also by kinetic characteristics.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35438
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Hudson, Lyndsey Olivia. "Methicillin-resistant Staphylococcus aureus : a novel approach to molecular detection and a US countywide study of strain diversity and distribution among healthcare facilities." Thesis, Imperial College London, 2012. http://hdl.handle.net/10044/1/11646.
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Methicillin-resistant Staphylococcus aureus (MRSA) is a global public health problem and is a major cause of morbidity and mortality worldwide, imposing serious economic costs on patients and hospitals. Prior to the mid-1990s, MRSA was largely a healthcare-associated pathogen, causing infection predominantly in people with frequent or recent contact with healthcare facilities (HA-MRSA). Since then, community-associated MRSA (CA-MRSA), which often causes infection among healthy children and young adults with no exposure to the healthcare setting, has become increasingly prevalent. Worryingly, there is evidence that CA-MRSA is penetrating the healthcare MRSA reservoir, and even replacing traditional HA-MRSA strains. This highlights the need to keep abreast of the changing epidemiology of MRSA in order to implement effective infection control strategies. To investigate the composition of the healthcare MRSA reservoir and ascertain the extent to which CAMRSA has penetrated this reservoir, a countywide, population-based cohort study of MRSA in hospital inpatients and nursing home residents was conducted in Orange County (OC), California, covering a total of 46 facilities. CA-MRSA was found to be fully mixed with HA-MRSA in the hospital setting. The predominant CA-MRSA clone in the US, USA300, was the most commonly isolated MRSA clone in OC hospitals. In OC nursing homes, HA-MRSA (specifically a variant of USA100 that is also very common in OC hospitals but has not been reported elsewhere) predominates, but USA300 made up just over a quarter of the isolates and was the second most frequently isolated clone. Both OC hospitals and nursing homes were dominated by the same three strains: USA300, USA100 and a variant of USA100. Not only are community-based infection control strategies needed to stem the influx of community associated strains, in particular USA300, into the hospital setting, but also strategies tailored to the complex problem of MRSA transmission and infection in nursing homes, to minimise the impact of the unique nursing home MRSA reservoir on overall regional MRSA burden. A key component of effective infection control strategies is prompt isolation of MRSA carriers, facilitated by rapid diagnostics. PCR-based methods of MRSA detection offer a much faster alternative to traditional culture techniques, but are expensive and often complex to operate. A novel nucleic acid amplification technique developed by my industrial sponsor, TwistDx Ltd, called recombinase polymerase amplification (RPA), has been incorporated into a probe based detection system called TwistAmp MRSA, and offers a simple and cheap alternative to current commercial PCR-based assays, amplifying MRSA to detectable levels within 20 minutes. I tested the assay with diverse collections of MRSA and discovered that 4% of isolates from a UK MRSA collection could not be detected by the assay. I subsequently developed RPA primers for their detection. Nonetheless, TwistAmp MRSA was able to detect most MRSA strains, and was comparable to current commercial assays in this respect. Despite a very high analytical sensitivity of approximately 20 CFU/swab, the clinical sensitivity of TwistAmp MRSA was lower than expected with respect to the current market leader, Xpert MRSA. I investigated lysis and filtration methods to improve the assay's clinical sensitivity, but found that such methods did not currently warrant inclusion in the TwistAmp MRSA protocol. While TwistAmp MRSA performance is in line with current assays, and is a faster, cheaper and simpler assay, a problem faced by all molecular methods of MRSA detection is the constant emergence of undetectable MRSA strains, necessitating continual assay evaluation and improvement where possible.
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Peres, Fabiano Moreno. "Métodos de mecânica da fratura aplicados a polietileno de média densidade destinado à extrusão de tubos." Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/3/3133/tde-15092009-161933/.
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O polietileno de média densidade (PEMD) é um polímero termoplástico parcialmente cristalino, cujo uso tem crescido bastante em aplicações de engenharia, como em tubos plásticos para sistemas de distribuição de água e de gás. Sob carga constante, entretanto, este material pode eventualmente apresentar fratura por fluência, por meio de um mecanismo de crescimento lento de trincas, provocando acentuadas perdas por vazamento nos sistemas. Os métodos atuais empregados pela indústria para estimar a durabilidade dos tubos são caros, demorados, pouco práticos e imprecisos. Busca-se o desenvolvimento de técnicas mais eficientes, sendo que os métodos da mecânica da fratura são promissores no sentido de descrever a etapa de propagação da trinca. Ensaios de mecânica da fratura, entretanto, requerem a introdução de pré-trincas nos corpos de prova. Sabe-se que as técnicas artificiais de introdução de pré-trincas causam algum tipo de dano na matriz polimérica, que pode ou não afetar os resultados dos ensaios, dependendo dos eventos que ocorrerem após o carregamento inicial. A principal propriedade requerida de um método de introdução de pré-trinca, portanto, é reprodutibilidade. Neste estudo foram aplicados três importantes métodos de mecânica da fratura ao PEMD e investigados os efeitos de diferentes técnicas de introdução de pré-trincas sobre os resultados dos ensaios e sobre as estruturas de deformação na matriz do material na ponta da trinca. Os ensaios de tenacidade à fratura no estado plano de deformação - KIc - foram realizados em condições criogênicas, em vista do comportamento dúctil do material à temperatura ambiente, sendo que a estratégia mostrou-se satisfatória. Os resultados dos ensaios de Integral-J sugerem que o método pode não ser aplicável ao PEMD, devido ao peculiar mecanismo de fratura do material. O método do trabalho essencial de fratura - EWF - se aplica bem ao PEMD. Os resultados dos ensaios de KIc e EWF demonstraram que diferentes técnicas de introdução de pré-trincas provocam diferentes estruturas de deformação no material na ponta da trinca e afetam os resultados de ensaios de fratura no PEMD. Os resultados de EWF demonstraram ainda que o processamento também afeta as propriedades de fratura do material. É proposta uma nova técnica para a introdução de pré-trincas, com características mais naturais, a qual requer estudos complementares para seu aperfeiçoamento.Medium density polyethylene (MDPE) is a semicrystalline thermoplastic polymer that has been increasingly used in engineering applications, as plastic pipes for water and gas distribution systems. Under constant load, however, this material may occasionally present creep failure, by means of a mechanism of slow crack growth, leading to leakage losses in the systems. Current methods used by industry to estimate durability of pipes are expensive, time consuming, non practical and inaccurate. The development of more efficient methods is a common target and fracture mechanics methods are promising in describing the crack propagation stage. Fracture mechanics testing methods, however, require the introduction of pre-cracks into the specimens. It is known that artificial methods of introducing pre-cracks produce some damage on the polymeric matrix, which may or not affect the results of tests, depending on the events that occur after the initial loading. Main propriety required of a pre-crack introducing method, therefore, is reproducibility. In this study three important fracture mechanics methods were applied to MDPE and the effects of different methods of pre-cracking over test results and over deformation structures of material matrix at the crack tip were investigated. Plane-strain fracture toughness - KIc tests were performed under cryogenic conditions, in view of the ductile behavior of material at room temperature and this strategy was well succeed. Results of Integral-J tests suggest that this method may not be applicable to MDPE, due to the peculiar fracture mechanism of the material. The essential work of fracture method EWF is well suited to study MDPE. The results of KIc and EWF tests showed that different pre-cracking methods cause different deformation structures in the material at the crack tip and affect the fracture tests with MDPE. EWF results showed also that the processing affect the fracture properties of materials too. It is proposed a new method for introducing pre-cracks, with more natural characteristics that requires complementary studies for its improving.
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Bouhamed, Ayda [Verfasser], Olfa [Akademischer Betreuer] Kanoun, Olfa [Gutachter] Kanoun, Madhukar [Gutachter] Chandra, and Chokri [Gutachter] Bouraoui. "Investigation of Stress Distribution and Adhesion Effects of Strain Sensitive Epoxy/MWCNT Nanocomposite Films / Ayda Bouhamed ; Gutachter: Olfa Kanoun, Madhukar Chandra, Chokri Bouraoui ; Betreuer: Olfa Kanoun." Chemnitz : Universitätsverlag Chemnitz, 2019. http://d-nb.info/1215909233/34.
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De, Donno Giulia. "Three dimensional strain analysis of vertebrae with artificial metastases through digital volume correlation." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2020. http://amslaurea.unibo.it/19911/.
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Bone is a common site for metastases and spine represent the most frequent site. Lytic lesions are associated with the loss of bone tissue, which can compromise the mechanical competence of the vertebra, leading to spine instability. Rigid stabilization is a solution, but it is a complex surgery, that can be very critical for oncologic patients; on the other hand, an untreated metastasis can lead to mechanical failure of the bone, leading to pain, immobilization and in the worst case, paralysis.
In this study, a protocol to analyse the strain with simulated lytic metastasis under compressive loading has been developed and optimized using a porcine vertebra. The strain distribution has been measured experimentally using micro-computed tomography (micro-CT) and Digital Volume Correlation (DVC), which provided three-dimensional displacements and strains maps inside the specimen. The ideal parameters for the DVC have been found by analysing two repeated scans in constant strain condition and setting a target of 200 microstrain for the errors (one order of magnitude lower than typical strains in bone subjected to physiological loading conditions). An ideal nodal spacing of 50 voxels (approximately 2 mm) has been chosen and a voxel detection algorithm has been applied to all data to remove regions outside the bone. In order to understand how the presence of the defect could alter the strain distribution, the porcine vertebra has also been subjected to non-destructive compressive load before and after the preparation of a mechanically induced lytic metastasis in the vertebral body. An increase of the 40% of the compressive principal strain after the defect has been found in proximity of the lesion.
This protocol will be used in future studies to analyse the effect of size and position of artificially metastatic lesions in the vertebral body of human spines.
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Montanari, Sara. "The effect of intervertebral disc simulated damage on the human spine biomechanics." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2020. http://amslaurea.unibo.it/19926/.
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More than 50% of intervertebral discs in the third and fourth decade of life exhibit annular tears and fissures with different orientations and extents. On the other hand, in vitro biomechanical investigations of the disc surgery treatment, sometimes requires collaterals lesions, such as incision or disc material removal to recreate biological injuries, as in discoplastly. These lesions could have a mechanical impact on the spine flexibility and in the surrounding tissue and could alter the final outcomes of in vitro studies.
The influence of the presence of lesions on the biomechanics of the segment is still a debated research question.
Thus, this in vitro study aims to evaluate changes in spine biomechanics, in terms of stiffness, range of motion and disc height, induced by an increasing damage of human disc. In order to assess the impact of the annulus damage on the surrounding tissues, principal strain distributions were investigated in the lateral side opposite than the damaged region.
Eight fresh cadaver thoraco-lumbar FSUs were used in this study. The specimens were tested sequentially in flexion and extension in five different configurations: a) with the intact disc; b) with two vertical cuts; c) with four cuts, forming a square, without removing any part of the annulus; d) after having removed the cut part of the AF; e) after having removed the nucleus pulposus. Image analysis and surface strain distribution were performed on the lateral disc by means of the Digital Image Correlation.
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Prueter, Phillip Edward. "A Study of the Mechanical Design and Gear Tooth Root Strains in Flexible Pin, Multi-Stage, Planetary Wind Turbine Gear Trains Using Three Dimensional Finite Element/Contact Mechanics Models and Experiments." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1313372765.
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Murphy, Robert T. "Developing, Demonstrating, and Validating a Vehicle Test Bed to Extend the Capabilities of a Chassis Dynamometer Test System." Ohio University / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1226630699.
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McLean, Alastair J. "The effect of modular stems and cement fixation techniques on the initial stability of the tibial prosthesis and the strain distribution within the proximal tibia in primary and revision total knee arthroplasty." Thesis, University of Edinburgh, 2007. http://hdl.handle.net/1842/15352.
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AIMS: The primary aim of this thesis was to determine what effect modular intramedullary stems of differing lengths have on the initial stability experienced by the tidial tray and the strain magnitude experienced within the proximal tibia due to the differing modular stems in a primary and revision TKA. NULL HYPOTHESIS: Increasing the length of the implant stem has no affect on the micromotion of the tibial tray relative to the bone surface. Adding a modular stem does not affect the strain distribution within the proximal tibia. CONCLUSIONS: A 40mm or 80mm press-fit modular stem does not enhance initial fixation with hybrid or cementless implantation in either primary or T2A revision TKA. The addition of a modular stem when implanting an uncemented tibial tray may well increase the instability of the construct. Cemented implants with no modular stem have better initial fixation compared to all uncemented implants tested. In a primary and revision T2A TKA scenario the addition of a press-fit or fully cemented 80mm modular stem offers no added translational or rotational stability. In the bone impaction grafting group a fully cemented tibial tray with an 80mm modular stem significantly increased the migrational and inducible displacement stability. The use of cemented modular stems in primary TKA and simple revision TKA reduces the strains experienced in the proximal tibia and causes excessive strains within the distal cancellous bone at the stem tip. Press-fit stems do not cause significant stress shielding but do cause localised areas of high strain at the stem tip, (which may be linked to patient pain and discomfort). A cemented long modular stem provided the best strain distribution within the proximal graft in the T1 models.
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Oyekanmi, B. O. "The determination of strain distributions in forgings." Thesis, University of Leeds, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.383928.
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Fischer, Jiří. "Analýza vlivu směrové distribuce kolagenních vláken ve stěně tepny na její mechanické vlastnosti." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2020. http://www.nusl.cz/ntk/nusl-418206.
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The aim of this thesis is to analyse literature with focusing on literature about directional distribution of collagen fibres. This knowledge is very important for computational modelling and FEM analysis of arterial wall. Comparison of suitability of different models of directional distribution of collagen fibres is made by fitting of different types of probability density functions. Impact assessment of different collagen fibres distribution on mechanical properties of the arterial wall and impact assessment of wall anisotropy is solved with finite element method. FEM analysis is done on three loading types – uniaxial tension, equibiaxial tension and inflation of artery by internal pressure. Output of this thesis is evaluation of results for various types of collagen fibres arrangement in arterial wall.
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Bazzi, Ali, and Andreas Angelou. "Simulation of the anisotropic material properties in polymers obtained in thermal forming process." Thesis, Tekniska Högskolan, Högskolan i Jönköping, JTH, Produktutveckling, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-40792.
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In an attempt to improve the quality in finite element analysis of thermoformed components, a method for predicting the thickness distribution is presented. The strain induced anisotropic material behaviour in the amorphous polymers of concern is also taken into account in the method. The method comprises of obtaining raw material data from experiments, followed by a simulation of the vacuum thermoforming process where hyperelastic material behaviour is assumed. The theory of hyperelasticity that was applied was based on the Ogden model and implemented in the FE-software LS-DYNA. Material behaviour from thermoformed prototypes is examined by experiments and implemented together with the mapped results from the thermoforming simulation in a succeeding FE-model. For the latter, the three-parameter Barlat model was suggested, giving the possibility to account for anisotropic material behaviour based on an initial plastic strain.
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Shakur, Shahabi Hamed. "Study of deformation-induced structures in a Zr-based bulk metallic glass via high energy x-ray diffraction." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-198272.
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This PhD thesis employed high energy synchrotron x-ray radiation to reveal atomic scale structural features occurring in plastically deformed Zr52.5Ti5Cu18Ni14.5Al10 (Vit105) bulk metallic glass (BMG). The study is divided into three parts: Strain evolution during in-situ compression, strain distribution maps in mechanically-imprinted BMG, and residual strain around a single shear band. 1. Strain evolution during in-situ compression The structural rearrangements occurring during compressive deformation of a plastically deformable BMG showed that the elastic and plastic deformation of the BMG is correlated to the structural changes at short- (SRO) and medium range order (MRO). In the elastic regime, the atomic distances at SRO vary linearly with macroscopic stress. Analysis of the area under radial distribution function indicates that a small fraction of bonds in the first shell is broken in the loading direction whereas some new bonds are formed in the transverse direction. Atomic bonds at SRO appeared significantly stiffer than the MRO shells. Compared to the macroscopic values of the elastic strain, Young’s modulus and Poisson's ratio, both SRO and MRO appeared significantly stiffer, implying that the elastic behavior of the BMG is not only ruled by simple compression of the atoms/clusters but also is aided by rearrangement of atoms/clusters. The deviation of MRO atomic strain-stress correlation from linearity at the onset of plastic deformation was attributed to the activation of irreversible shear transformation zones. It was demonstrated by a strong shear strain value at the onset of yielding. This value is in good agreement with the reported value of the critical shear strain needed for activation of an irreversible STZ. The length scale of 12.5 Å indicated the largest shear strain and is probably the most effective length scale in the formation of STZs. The atomic pairs at SRO with smallest shear strain have the least contribution to the STZs. It was also indicated that the typical fracture angle of this BMG can be explained by the orientation of maximum shear strain at the onset of catastrophic shear band formation. 2. Strain distribution map in mechanically-imprinted BMG In mechanical imprinting, the BMG plate is loaded between two tools with a regular array of linear teeth and, as a result, a regular pattern of linear imprints is created on the surface of the plate. Mechanically imprinting results in considerable tensile plasticity of brittle Vit105 BMG plate. The distribution of hardness and Young’s modulus values at the transverse cross section of imprinted plate probed via nanoindentation revealed oscillating soft and hard regions beneath the surface. Spatially-resolved strain maps obtained via high-energy nano-size beam X-ray diffraction exhibited that the plastic deformation during imprinting creates a spatially heterogeneous atomic arrangement, consisting of strong compressive and tensile strain fields as well as significant shear strain fields in the cross section. It was shown that the heat treatment diminishes the heterogeneous structure resulting in brittle behavior in tension. The analysis of strain tensor components based on changes in the first diffraction maximum of the structure function, q1, revealed that Ɛx, the strain perpendicular to the loading direction, changes from the compressive at near to the surface to the tensile mode at the center of the imprinted plate. In contrast, the strain component along the loading direction, Ɛy, changes from tensile near the surface to the compressive at the center. Beneath the surface, Ɛx reaches to values about 1.5% under the imprints where there is a negligible Ɛy. The distribution map of principal strains, Ɛ1 and Ɛ2, indicated that large regions with compressive Ɛ1 and Ɛ2 exist under the imprints which can result in blocking of the propagating shear bands in agreement with microstructural observations of shear banding after uniaxial tension. Moreover, the region beneath the border of the imprinted and un-imprinted parts has the highest residual shear strain. Microstructural observations indicated that such regions can nucleate new shear bands upon tensile loading of imprinted BMG plate. 3. Residual strain around a single shear band In order to probe structural changes in the shear-induced zone around a single shear band, the distribution of residual strains at short- and medium-range order around a single shear band was determined in cold-rolled BMG plate using the nano-focused high energy x-ray diffraction. Plastic deformation results in significant residual normal and shear strains at distances of more than 15 μm around the shear band. The residual normal strains exhibit an asymmetric distribution whereas the residual shear strain is distributed symmetrically around the shear band. The large amount of residual atomic shear strain magnitude at the vicinity of the shear band triggers the nucleation of the new shear bands. The coincidence of the direction of the nucleating secondary shear bands from the main shear band with the orientation of the residual shear strain at the vicinity of the mature shear band highlight the dominant role of the shear strain in determining further plastic deformation at regions near the shear bandIm Rahmen dieser Arbeit wird hochenergetische Synchrotron Röntgenstrahlung zum Aufzeigen der strukturellen Veränderungen in plastisch verformtem Zr52.5Ti5Cu18Ni14.5Al10 metallischen Glas verwendet. Die Arbeit gliedert sich in drei Teile: Dehnungsentwicklung während in-situ Druckversuch, Dehnungsverteilung eines mechanisch geprägten massiven metallischen Glases, und Restdehnungen in der Umgebung eines einzenen Scherbandes. 1. Dehnungsentwicklung während in-situ Druckversuch Die während der Verformung auftretende strukturelle Neuordnung eines plastisch verformbaren metallischen Glases zeigt die Korrelation der elastischen und plastischen Verformung mit den strukturellen Änderungen in den Größenordnungen der Nah- (SRO) und mittelreichweitigen Ordnung (MRO). Im elastischen Bereich verändern sich die Atomabstände in der SRO linear mit der makroskopisch anliegenden Spannung. Die Untersuchung der Fläche unter der Radialen Verteilungsfunktion (RDF) deutet auf ein Aufbrechen eines geringen Anteils der Bindungen der ersten Schale in Druckspannungsrichtung und deren Neubildung quer dazu. Die atomaren Bindungen in der SRO erscheinen wesentlich steifer als in den MRO Schalen. Vergleicht man die Werte von elastischer Dehnung, E-Modul und Querkontraktionszahl mit ihren makroskopischen Gegenstücken erscheinen beide, SRO und MRO, wesentlich steifer. Dies zeigt, dass die elastische Verformung von metallischen Gläsern nicht nur von der einfachen Stauchung der Atome bzw. Atomgruppen bestimmt, sondern auch durch deren Neuanordnung unterstützt wird. Das Abweichen der Dehnungs-Spannungs-Korrelation vom linearen Verhalten in der MRO am Beginn der plastischen Verformung wird der irreversiblen Bildung von Schertransformations-zonen (STZ) zugeschrieben. Dies zeigt sich zudem in den erhöhten Scherdehnungswerten am Beginn der Dehngrenze, welche mit den in der Literatur berichteten Werten für die kritische Scherdehnung zum Bilden einer STZ übereinstimmen. Bei einem Atomabstand von 12,5 Å tritt der höchste Wert der Scherdehnung auf und markiert den effektivsten Längenbereich der STZ Bildung. Andererseits haben die atomaren Paare in der SRO mit der geringsten Scherdehnung den geringsten Beitrag an der STZ. Es zeigt sich außerdem, dass der typische Bruchwinkel dieses metallischen Glases über die Orientierung der maximalen Scherdehnung am Beginn der kritischen Scherbandbildung erklärt werden kann. 2. Dehnungsverteilung eines mechanisch geprägten massiven metallischen Glases Eine Prägung besteht darin, eine Platte metallischen Glases mit zwei Stempel, auf denen eine regelmäßige Anordnung von geradlinigen Kerben angebracht ist, zu belasten. Dadurch wird eine ebenso regelmäßige Anordnung von geradlinigen Kerben auf der Oberfläche des metallischen Glases erzeugt. Die plastische Verformbarkeit der Vit105 Platte im Zugversuch wird durch Prägung im Vergleich zur gegossenen Probe eindeutig verbessert. Die Untersuchung der Härte und des E-Moduls über den Querschnitt der geprägten Probe zeigt die Einbringung von Abwechselnd weichen und harten Regionen an der Oberfläche. Es wurden räumlich aufgelöste Dehnungskarten des geprägten metallischen Glases durch Beugung eines hochenergetischen nanometergroßen Röntgenstrahles erzeugt. Die Ergebnisse offenbaren, dass die durch Prägung eingebrachte plastische Verformung eine räumlich heterogene Atomanordnung erzeugt, welche aus starken Druck- und Zugdehnungsfeldern besteht. Zusätzlich wird eine signifikante Scherdehnung in die Probe eingebracht. Die Wärmebehandlung beseitigt diese heterogene Struktur und führt sie fast auf den Ausgangszustand zurück. Die Analyse der Dehnungstensorkomponenten basierend auf Änderungen im erstem Maximum des Strukturfaktors, q1, zeigt, dass sich Ɛx von der Oberfläche zur Mitte der Platte hin von einer Stauchung in eine Dehnung umwandelt. Im Gegensatz dazu wandelt sich die Komponente Ɛy von der Oberfläche zur Mitte der Platte hin von einer Dehnung in eine Stauchung um. An der Oberfläche unter den Eindrücken, wo Ɛy vernachlässigbar ist, erreicht Ɛx Werte von ca. 1.5 %. Die Verteilungskarten der Hauptdehnungen zeigt, dass beide e1 und e2 unterhalb der Kerben als Stauchungen vorhanden sind. Daraus resultiert das Blockieren und Ablenken der sich ausbreitenden Scherbänder, was an Zugproben im REM beobachtet werden kann. Weiterhin hat der Bereich an der Grenze der geprägten und nicht geprägten Regionen die höchste Restscherdehnung. Mikrostrukturelle Beobachtungen deuten darauf hin, dass solche Bereiche unter Zuglast Keimstellen für neue Scherbänder sind. 3. Restdehnungen in der Umgebung eines einzenen Scherbandes Es wurde ein einzelnes Scherband einer kaltgewalzte Platte mittels Beugung eines hochenergetischen nanometergroßen Röntgenstrahles untersucht. Die strukturellen Unterschiede in der scherinduzierten Zone um ein einzelnes Scherband werden durch die Verteilung der Restdehnungen in SRO und MRO bestimmt. Plastische Verformung führt zu signifikanten Restnormal- und Restscherdehnungen in Entfernungen von mehr als 15 µm um das Scherband. Die Restnormaldehnungen zeigen eine asymmetrische Verteilung, wohingegen die Restscherdehnungen auf beiden Seiten des Scherbandes symmetrisch verteilt sind. Der große Betrag der atomaren Restscherdehnung in der Nähe des Scherbandes führt zur Bildung von neuen Scherbändern. Das Zusammenfallen der Richtung des sich bildenden sekundären Scherbandes und der Orientierung der Restscherdehnung, in der Nähe des primären Scherbandes, demonstriert die dominierende Rolle der Scherdehnung bei weiterer plastischer Verformung in der Nähe des Scherbandes
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Vondra, Róbert. "Deformačně napěťová analýza zubové spojky." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2020. http://www.nusl.cz/ntk/nusl-432792.
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This thesis deals with the contact analysis study of crown gear couplings during the simulation of its working conditions. The toothed coupling transmits high torque, even when the input and output shafts are misaligned due to outside tooth shape. For this reason, it is necessary to design the gear shape correctly. The inherent use of toothed couplings results in a wide range of working speeds and load transfers. This can cause several problems, if the parameters are selected incorrectly. Among the most significant of these is the generation of vibrations during gear engagement, accompanied by noise and the excessive loading of components, such as shafts and bearings. It is not possible to completely reduce uneven running, even with knowledge of the latest trends in the field of gear development. For this reason, it is necessary to eliminate the paths where the vibrations can propagate during the design itself. Inefficient and costly experiments are often used to determine the correct shape of gear teeth. For this purpose, a computational approach to describe a contact pressure on the teeth of couplings at different misalignment and loads is proposed. The model helps to understand the composition of the contact pressure during the working mode of misalignment and its behaviour within the rotation of the gear coupling. The introductory part of thesis presents the current state of knowledge of gear couplings and a description of load distribution issues, regarding the angular misalignment, torque and friction. In the following chapter, three possible approaches to the problem are described - analytical, experimental and computational. The following work offers the introduction and creation of two different computational models, varying in different tooth shape on the hub and the sleeve. Each geometry was subjected to a different load moment, a misalignment of the hub, or the rotation of the gear coupling as a whole. The main monitored parameter was the course of contact pressure in each step, when changing the degree of misalignment or the rotation of the model. Finally, three main sets of contact pressure on the teeth are presented, in connection with the reduced pressure plotted on the toothed rings. There is derivation of results and mutual comparison of each load case. The computation approach in FEM program Ansys Workbench was used to solve the problem.
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Mustard, Alexander T. "The relationship between zooplankton and their physico-chemical environment at the mesoscale." Thesis, University of Southampton, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.342853.
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Kandur, Aaron S. "The distribution of Mytilus californianus in the Strait of Juan de Fuca." Thesis, The University of Chicago, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=3668260.
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I investigated the determinants of distributional patterns in the mussel Mytilus californianus in the Strait of Juan de Fuca in Washington State. A three pronged approach including evolutionary, geomorphological, and population ecology research methods elucidated processes determining the density and distribution of the species as well as forces impacting its future trajectory. Primary conclusions include: 1. Changes in aerial temperatures in Washington State in the near future are unlikely to dramatically influence the abundance and distribution of Mytilus californianus. 2. The interaction of sea level rise with the geomorphological features of rocky coasts has the potential to dramatically change the distribution and abundance of shallow water depth restricted species like Mytilus californianus. 3. Distributional patterns of Mytilus californianus occurring at multiple spatial scales are a result of the integration of population vital rates as determined by environmental gradients, and variation in vital rates are sometimes scale dependent (growth and recruitment rates) and sometimes not (survival rates). 4. Mussel populations were most sensitive to variation in growth rates, least sensitive to variation in recruitment rates, and intermediately sensitive to variation in survival. 5. Mytilus californianus density is unlikely to be primarily controlled by variation in growth rate or recruitment rate.
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Nsengiyumva, Schadrack. "The mutual influence of strain fields and point defect distributions in krypton implanted polycrystalline titanium." Doctoral thesis, University of Cape Town, 2008. http://hdl.handle.net/11427/11812.
Full textAbstract:
Includes abstract.Includes bibliographical references (leaves 155-182).
Stress migration of point and open-volume defects in materials is an important problem in a wide variety of applications, such as degradation of metallic interconnects in semiconductor devices, metal fatigue, and radiation damage profiles in ion implantation and surface modification. From a fundamental research view point, this study aims to contribute to a better understanding of the basic processes underlying the effect of stress assisted diffusion of foreign interstitial atoms under stress fields, using the Rutherford backscattering to obtain depth profiles, and synchroton radiation diffraction for the determination of stress fields. This has been achieved by creating a well designed model system of krypton implanted polycrystalline titanium.
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Dong, Xudong. "Stress distribution and failure mode of dental ceramic structures under Hertzian indentation." Hong Kong : University of Hong Kong, 2001. http://sunzi.lib.hku.hk/hkuto/record.jsp?B22989560.
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Doniol-Valcroze, Thomas. "Spatial distribution of rorqual whales in the Strait of Jacques Cartier, Gulf of St. Lawrence, Quebec, Canada." Thesis, McGill University, 2001. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=33749.
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The spatial distribution of four species of rorqual whales was studied along the north shore of the Gulf of St. Lawrence during the months of June to October from 1989 to 2000. A research effort of 6511 hours at sea yielded 849 sightings of blue whales (Balaenoptera musculus), 5291 of finback whales (Balaenoptera physalus), 3822 of humpback whales (Megaptera novaeangliae) and 6489 of minke whales (Balaenoptera acutorostrata). Spatial and behavioural data were collected at sea using inflatable boats, and Global Positioning Systems (GPS) were used to obtain accurate positions. These data were plotted and analysed using a Geographic Information System (GIS) to test the hypotheses that patterns of distribution were not random, were associated with bathymetry and reflected specific differences in habitat use. The resulting maps illustrated the clustered distribution of rorqual whales linked to sea-bottom topography, probably associated with areas of local upwelling and increased productivity. Blue and fin whales shared almost the same distribution, humpback whales were found in slightly deeper, offshore waters whereas minke whales were more abundant in shallower waters. Little attention has been given until now to local patterns of distribution in the area and such information can be useful for practical management considerations. The results emphasise the importance of scale in ecological studies of marine mammals and the need for further research using additional oceanographic parameters, in order to better understand habitat selection.
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Lerner, Justin David. "Swordfish Vertical Distribution and Recreational Fishery in the Florida Straits." Scholarly Repository, 2009. http://scholarlyrepository.miami.edu/oa_theses/46.
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This thesis is composed of two studies: (1) an assessment of the vertical habitat use of swordfish Xiphias gladius in the Florida Straits; and (2) a systematic description of the southeast Florida recreational swordfish fishery. First, the vertical distribution of swordfish (Xiphias gladius) was assessed in relation to diel cycles and lunar phase from data gathered utilizing popup satellite archival tags (PSATs). Seven tags were deployed in the Florida Straits during this study from recreational and commercial fishing vessels; two fish died shortly after deployment, and the remaining five were included in the analysis. Tags were deployed for periods ranging from 120 to 151 days and recorded data on temperature, depth, and light level every ten seconds. Transmitted data was summarized into one hour histograms. Swordfish vertical distribution in response to diel cycles was characterized by typically spending daytime hours below 500 m and nighttime hours in waters less than 75 m. Swordfish distribution differed significantly in response to lunar phase, with animals occupying successively deeper depths in response to increasing lunar illumination. This study is consistent with the widely accepted hypothesis that the swordfish vertical distribution is a function of ambient light levels. However, in contradiction to this hypothesis was the observation of a number of daytime surfacing events recorded by the tags. This less pronounced but frequent behavior is hypothesized as a mechanism to warm the fish?s body after extended daytime feeding dives to great depths. A recreational fishery targeting swordfish in southeast Florida has gained popularity in recent years. However, little data is currently available on the fishery and its participants. A survey was distributed to recreational swordfish anglers at local swordfish fishing club meetings and a swordfish fishing tournament to describe the fishery and its participants. Questions were organized into four sections: demographics, fishing habits, cost, and views on regulations. A total of 38 surveys were completed by anglers and included in the study. Recreational swordfish fishermen in southeast Florida were mainly Caucasian, with the largest group by percentage ranging from 41-50 years of age. Most fishers surveyed had over 20 years recreational fishing experience, with less than 10 years experience targeting swordfish. Anglers typically fished out of center console boats ranging from 21-35 feet, and usually made less than 50 trips per year. Costs associated with the fishery typically exceed those associated with general recreational saltwater fisheries by thousands of dollars (USFWS, 2006). Fishers were divided in their views on the current recreational swordfish regulations. Forty percent of anglers surveyed were unsatisfied, 37% were satisfied, and 23% remained neutral.