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URURAHY, MARCELO FERREIRA PINTO. "THEORETICAL-EXPERIMENTAL THERMAL STRESS ANALYSIS IN VISCOELASTIC CYLINDERS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 1991. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=19375@1.
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COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIORApresenta-se neste trabalho o desenvolvimento de um modelo teórico-numérico baseado na Teoria da Viscoelasticidade Linear capaz de prever as distribuições transientes e residuais das componentes de tensão e de deformação de um cilindro polimérico longo submetido a resfriamento brusco. Descrevem-se, ainda, os procedimentos experimentais adotados como intuito de se determinarem algumas propriedades térmicas e mecânicas do sistema epóxi DER331/XG0103/XB81215. Finalmente, comparam-se os resultados fornecidos pelo modelo teórico-numérico com resultados experimentais obtidos através da utilização de uma técnica extensométrica conhecida como Método de Sachs.
This work presents the development of a theoretical and numerical model based on the Linear Viscoelastic Theory able to predict the transient and residual stress and deformation distributions in a long polymeric cylinder subject to a rapid cooling. The work describes the experimental procedures adopted aiming to determine some thermal and mechanical properties of the epoxy system DER331/XG0103/XB81215. Finally, the results from the theoretical numerical model are compared to the ones obtained experimentally by na extensometric technique known as Sachs’ Method.
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Schepers, Scott Timothy. "Renewal In The Context Of Stress: A Potential Mechanism Of Stress-Induced Reinstatement." ScholarWorks @ UVM, 2017. http://scholarworks.uvm.edu/graddis/780.
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In the animal laboratory, stressors can produce the relapse of drug-seeking behaviors after the behavior has been inhibited by extinction. This type of relapse has been called stress-induced reinstatement, and it models the relapse that is commonly reported in human populations. Interestingly, in the laboratory, stress does not typically reinstate extinguished behaviors that have been reinforced by food. One account of the discrepancy is that drugs of abuse may induce stress; therefore, when organisms learn to respond for drugs, they might learn to make the response in the “context” of stress. If so, then stress-induced reinstatement may be better described as renewal in a stress context. Renewal is the type of relapse that occurs when a behavior is returned to the original training context (or is shifted to a new context) after it has been inhibited or suppressed by extinction. Although renewal has usually been studied with contexts that differ in their exteroceptive cues, interoceptive cues (e.g., mood, food deprivation, and drug states) may also provide contexts. Accordingly, if an interoceptive stress state is present when food-seeking behavior is learned, then extinguished food seeking, like drug seeking, should also renew when the organism is stressed after extinction. In this dissertation, I discuss six experiments that investigated this hypothesis. Experiment 1 found that stressors renew extinguished food-seeking if they are also present during instrumental training. Experiments 2 and 3 then provided preliminary evidence that this effect is not exclusively due to incentive learning. Experiment 4 then suggested that interoceptive stress, and not the particular stressor that produces it, may indeed serve as a general interoceptive context that controls the effect. Experiment 5 found that stressors present for acquisition but not extinction training render behavior susceptible to stress induced relapse. The final experiment found that food-reinforced behavior learned in a context created by a cocaine injection renews after cocaine administration but not after footshock stress. Overall, the results indicate that the presence of interoceptive stress stimuli may play the role of context in a renewal paradigm and promote behavioral relapse when re-encountered after extinction. The implications for relapse that often occur following successful suppression of drug use and overeating behaviors are both discussed.
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Ward, David. "Hydrodynamic effects on soiled surfaces : an experimental study and theoretical analysis." Thesis, Open University, 2000. http://oro.open.ac.uk/58091/.
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Chaparala, Satish Chandra. "Die stress analysis in plastic encapsulated electronic packages an experimental and numerical approach /." Diss., Online access via UMI:, 2006.
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Park, Hyuen Me (Mia) Park. "Numerical and experimental analysis of stress behavior of plasma-sprayed Bioglass on titanium /." Full text open access at:, 1996. http://content.ohsu.edu/u?/etd,587.
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Wei, Ling. "Experimental study of growth and protein dynamics in yeast Hog1 mutants under osmotic stress." HKBU Institutional Repository, 2011. http://repository.hkbu.edu.hk/etd_ra/1282.
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Johnson, Shane Miguel. "Computational modeling, stochastic and experimental analysis with thermoelastic stress analysis for fiber reinforced polymeric composite material systems." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/34668.
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Many studies with Thermoelastic Stress Analysis (TSA) and Infrared Thermography, in Fiber Reinforced Polymeric materials (FRPs), are concerned with surface detection of "hot spots" in order to locate and infer damage. Such experimental analyses usually yield qualitative relations where correlations between stress state and damage severity cannot be obtained. This study introduces quantitative experimental methodologies for TSA and Digital Image Correlation to expand the use of remote sensing technologies for static behavior, static damage initiation detection, and fatigue damage in FRPs. Three major experimental studies are conducted and coupled with nonlinear anisotropic material modeling: static and TSA of hybrid bio-composite material systems, a new stochastic model for fatigue damage of FRPs, and fracture analysis for FRP single-lap joints. Experimental calibration techniques are developed to validate the proposed macromechanical and micromechanical nonlinear anisotropic modeling frameworks under multi-axial states of stress. The High Fidelity Generalized Method of Cells (HFGMC) is a sophisticated micromechanical model developed for analysis of multi-phase composites with nonlinear elastic and elastoplastic constituents is employed in this study to analyze hybrid bio-composites. Macro-mechanical nonlinear anisotropic models and a linear orthotropic model for fracture behavior using the Extended Finite Element method (XFEM) are also considered and compared with the HFGMC method. While micromechanical and FE results provide helpful results for correlating with quasi-static behavior, analyzing damage progression after damage initiation is not straightforward and involves severe energy dissipation, especially with increasing damage progression. This is especially true for fatigue damage evolution, such as that of composite joints as it is associated with uncertainty and randomness. Towards that goal, stochastic Markov Chain fatigue damage models are used to predict cumulative damage with the new damage indices proposed using full-field TSA image analysis algorithms developed for continuously acquired measurements during fatigue loading of S2-Glass/E733FR unidirectional single-lap joints. Static damage initiation is also investigated experimentally with TSA in single-lap joints with thick adherends providing for new design limitations. The computational modeling, stochastic and experimental methods developed in this study have a wide range of applications for static, fracture and fatigue damage of different FRP material and structural systems.
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Javidinejad, Amir. "An experimental stress analysis approach for pure shear testing and analysis of a fiber reinforced plastic composite." Thesis, Georgia Institute of Technology, 1994. http://hdl.handle.net/1853/20706.
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Park, Joon Boo. "Theoretical and Experimental Analysis of Residual Stress Formation after Implant Resistance Welding of Polycarbonate." The Ohio State University, 1992. http://rave.ohiolink.edu/etdc/view?acc_num=osu1392653414.
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鈴木, 賢治, Kenji SUZUKI, 啓介 田中, Keisuke TANAKA, 義明 秋庭, Yoshiaki AKINIWA, 昌志 川村, et al. "放射光高エネルギーX線による遮熱コーティングのはく離応力の評価." 日本機械学会, 2004. http://hdl.handle.net/2237/9140.
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Liu, Zhiqiang. "Modelling and experimental studies of contact and friction of metallic rough surfaces in initial sliding." Thesis, Heriot-Watt University, 2001. http://hdl.handle.net/10399/542.
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Albakri, Mohammad Ismail. "Modeling and Experimental Analysis of Piezoelectric Augmented Systems for Structural Health and Stress Monitoring Applications." Diss., Virginia Tech, 2017. http://hdl.handle.net/10919/84513.
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Detection, characterization and prognosis of damage in civil, aerospace and mechanical structures, known as structural health monitoring (SHM), have been a growing area of research over the last few decades. As several in-service civil, mechanical and aerospace structures are approaching or even exceeding their design life, the implementation of SHM systems is becoming a necessity. SHM is the key for transforming schedule-driven inspection and maintenance into condition-based maintenance, which promises enhanced safety and overall life-cycle cost reduction. While damage detection and characterization can be achieved, among other techniques, by analyzing the dynamic response of the structure under test, damage prognosis requires the additional knowledge of loading patterns acting on the structure. Accurate, nondestructive, and reference-free measurement of the state-of-stress in structural components has been a long standing challenge without a fully-satisfactory outcome.
In light of this, the main goal of this research effort is to advance the current state of the art of structural health and loading monitoring, with focus being cast on impedance-based SHM and acoustoelastic-based stress measurement techniques. While impedance-based SHM has been successfully implemented as a damage detection technique, the utilization of electromechanical impedance measurements for damage characterization imposes several challenges. These challenges are mainly stemming from the high-frequency nature of impedance measurements. Current acoustoelastic-based practices, on the other hand, are hindered by their poor sensitivity and the need for calibration at a known state of stress. Addressing these challenges by developing and integrating theoretical models, numerical algorithms and experimental techniques defines the main objectives of this work.
A key enabler for both health and loading monitoring techniques is the utilization of piezoelectric transducers to excite the structure and measure its response. For this purpose, a new three-layer spectral element for piezoelectric-structure interaction has been developed in this work, where the adhesive bonding layer has been explicitly modeled. Using this model, the dynamic response of piezoelectric-augmented structures has been investigated. A thorough parametric study has been conducted to provide a better understanding of bonding layer impact on the response of the coupled structure. A procedure for piezoelectric material characterization utilizing its free electromechanical impedance signature has been also developed. Furthermore, impedance-based damage characterization has been investigated, where a novel optimization-based damage identification approach has been developed. This approach exploits the capabilities of spectral element method, along with the periodic nature of impedance peaks shifts with respect to damage location, to solve the ill-posed damage identification problem in a computationally efficient manner.
The second part of this work investigates acoustoelastic-based stress measurements, where model-based technique that is capable of analyzing dispersive waves to calculate the state of stress has been developed. A criterion for optimal selection of excitation waveforms has been proposed in this work, taking into consideration the sensitivity to the state of stress, the robustness against material and geometric uncertainties, and the ability to obtain a reflections-free response at desired measurement locations. The impact of material- and geometry-related uncertainties on the performance of the stress measurement algorithm has also been investigated through a comprehensive sensitivity analysis. The developed technique has been experimentally validated, where true reference-free, uncalibrated, acoustoelastic-based stress measurements have been successfully conducted.
Finally, the applicability of the aforementioned health and loading monitoring techniques to railroad track components has been investigated. Extensive in-lab experiments have been carried out to evaluate the performance of these techniques on lab-scale and full-scale rail joints. Furthermore, in-field experiments have been conducted, in collaboration with Norfolk Southern and the Transportation Technology Center Inc., to further investigate the performance of these techniques under real life operating and environmental conditions.Ph. D.
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Ragab, Adham Ezzat. "Sensitivity Analysis of Casting Distortion and Residual Stress Prediction Through Simulation Modeling and Experimental Verification." The Ohio State University, 2003. http://rave.ohiolink.edu/etdc/view?acc_num=osu1052493015.
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Marsh, Richard. "Experimental analysis of oil based cavitation peening in air." Thesis, Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/43602.
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Oil Jet Cavitation Peening in Air (OPA) is capable of inducing compressive residual stress in standard aerospace materials. This paper demonstrates the process capabilities of OPA on Al 2024-T3. Specifically, changes in the workpiece residual stress, microhardness, mass loss and surface roughness are investigated as a function of the control parameters for the system. Additionally, the paper identifies a method to monitor the process in situ through the use of high frequency acoustic emission sensors. The results indicate the OPA process is capable of generating residual stresses comparable to those of standard shot peening, up to 60% of the yield strength of the material, at similar depths, around 300 µm. Finally, the acoustic emission signal may be utilized to monitor the process, specifically in predicting the microhardness and mass loss of the system.
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Dallmeier, Johannes. "Experimental analysis and numerical fatigue modeling for magnesium sheet metals." Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2016. http://nbn-resolving.de/urn:nbn:de:bsz:105-qucosa-209124.
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The desire for energy and resource savings brings magnesium alloys as lightweight materials with high specific strength more and more into the focus. Most structural components are subjected to cyclic loading. In the course of computer aided product development, a numerical prediction of the fatigue life under these conditions must be provided. For this reason, the mechanical properties of the considered material must be examined in detail. Wrought magnesium semifinished products, e.g. magnesium sheet metals, typically reveal strong basal textures and thus, the mechanical behavior considerably differs from that of the well-established magnesium die castings. Magnesium sheet metals reveal a distinct difference in the tensile and compressive yield stress, leading to non-symmetric sigmoidal hysteresis loops within the elasto-plastic load range. These unusual hysteresis shapes are caused by cyclic twinning and detwinning. Furthermore, wrought magnesium alloys reveal pseudoelastic behavior, leading to nonlinear unloading curves. Another interesting effect is the formation of local twin bands during compressive loading. Nevertheless, only little information can be found on the numerical fatigue analysis of wrought magnesium alloys up to now.
The aim of this thesis is the investigation of the mechanical properties of wrought magnesium alloys and the development of an appropriate fatigue model. For this purpose, twin roll cast AM50 as well as AZ31B sheet metals and extruded ME21 sheet metals were used. Mechanical tests were carried out to present a comprehensive overview of the quasi-static and cyclic material behavior. The microstructure was captured on sheet metals before and after loading to evaluate the correlation between the microstructure, the texture, and the mechanical properties. Stress- and strain-controlled loading ratios and strain-controlled experiments with variable amplitudes were performed. Tests were carried out along and transverse to the manufacturing direction to consider the influence of the anisotropy. Special focus was given to sigmoidal hysteresis loops and their influence on the fatigue life. A detailed numerical description of hysteresis loops is necessary for numerical fatigue analyses. For this, a one-dimensional phenomenological model was developed for elasto-plastic strain-controlled constant and variable amplitude loading. This model consists of a three-component equation, which considers elastic, plastic, and pseudoelastic strain components. Considering different magnesium alloys, good correlation is reached between numerically and experimentally determined hysteresis loops by means of different constant and variable amplitude load-time functions.
For a numerical fatigue life analysis, an energy based fatigue parameter has been developed. It is denoted by “combined strain energy density per cycle” and consists of a summation of the plastic strain energy density per cycle and the 25 % weighted tensile elastic strain energy density per cycle. The weighting represents the material specific mean stress sensitivity. Applying the energy based fatigue parameter on modeled hysteresis loops, the fatigue life is predicted adequately for constant and variable amplitude loading including mean strain and mean stress effects. The combined strain energy density per cycle achieves significantly better results in comparison to conventional fatigue models such as the Smith-Watson-Topper model. The developed phenomenological model in combination with the combined strain energy density per cycle is able to carry out numerical fatigue life analyses on magnesium sheet metals.
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Zhang, Chao. "Random delamination of graphite/epoxy laminated composites : stress analysis, failure criteria, experimental characterization and stochastic modeling." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/NQ63992.pdf.
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Almeida, Camila de. "Modelling of the protection mechanisms against methylgyoxal stress in Escherichia coli : dynamical analysis and experimental validation." Thesis, University of Aberdeen, 2009. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=103942.
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The main MG detoxification pathway in Escherichia coli consists of two enzymes, the glyoxalases I and II, and is dependent on glutathione (GSH). MG readily conjugates with GSH in a non-enzymatic manner. Two subsequent enzymatic reactions via the glyoxalases complete a cyclic process that recycles GSH and produces the non-toxic compound, D-lactate. An intermediate compound in the detoxification pathway, S-lactoylglutathione (SLG), activates potassium efflux systems KefB and KefC. This triggers a second mechanism of protection mediated by cytoplasmic acidification, enhancing chances of survival. Therefore, it is important to understand how cells regulate the concentration of this important intermediate compound. A deterministic model was proposed that describes the series of chemical reactions in the MG detoxification pathway, allowing one to predict the flux of all compounds produced during detoxification. Through an iterative process involving model formulation, parameter estimation, data fitting and validation against experimental data, different models were analysed and discriminated in this study. Mathematical simulations predicted that the glyoxalase pathway is not linear because it involves feedforward mechanisms for the control of SLG, the activator of the potassium efflux systems. The activities of the potassium efflux systems were investigated using deterministic models that describe the interactions between protein and ligand. From this model, it was possible to quantify the dependence of the possible binding states on the kinetic parameters of the system. Parameter estimation methods were used for the analysis of experimental data on the gating of the efflux systems, which proved useful for the design of new experimental strategies.
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Olden, Elizabeth Jane. "The application of experimental stress analysis techniques to the study of cracks around cold-expanded holes." Thesis, University of Sheffield, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.286604.
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Jain, Anurag. "Experimental study and numerical analysis of compression molding process for manufacturing precision aspherical glass lenses." Columbus, Ohio : Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1148650470.
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Sutherland, Brandy. "Experimental and analytical analysis of the stress-strain diagram of FRP-confined concrete with different loading rates." Thesis, Manhattan, Kan. : Kansas State University, 2007. http://hdl.handle.net/2097/420.
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Lai, Chun Hon. "Experimental study of stress-dependent soil-water characteristics and their applications on numerical analysis of slope stability /." View abstract or full-text, 2004. http://library.ust.hk/cgi/db/thesis.pl?CIVL%202004%20LAIC.
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SUZUKI, Kenji, Keisuke TANAKA, and Yoshiaki AKINIWA. "Estimation of Spalling Stress in Thermal Barrier Coatings Using Hard Synchrotron X-Rays." The Japan Society of Mechanical Engineers, 2004. http://hdl.handle.net/2237/9176.
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Ozsoy, Serhan. "Vibration Induced Stress And Accelerated Life Analyses Of An Aerospace Structure." Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/2/12606966/index.pdf.
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Fatigue failure of metallic structures operating under dynamic loading is a
common occurrence in engineering applications. It is difficult to estimate the
response of complicated systems analytically, due to structure’
s dynamic characteristics and varying loadings. Therefore, experimental, numerical or a combination of both methods are used for fatigue evaluations. Fatigue failure can occur on systems and platforms as well as components to be mounted on the platform. In this thesis, a helicopter&
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s Missile Warning Sensor - Cowling assembly is analyzed. Analytical, numerical and experimental approaches are used wherever necessary to perform stress and fatigue analyses. Operational flight tests are used for obtaining the loading history at the analyzed location by using sensors. Operational vibration profiles are created by synthesizing the data (LMS Mission Synthesis). Numerical fatigue analysis of the assembly is done for determining the natural modes and the critical locations on the assembly by using a finite element model (MSC Fatigue). In addition, numerical multiaxial PSD analysis is performed for relating the experimental results (Ansys). Residual stresses due to riveting are determined (MSC Marc) and included in experimental analysis as mean stresses. Bolt analysis is performed analytically (Hexagon) for keeping the v assembly stresses in safe levels while mounting the experimental prototype to the test fixture. Fatigue tests for determining the accelerated life parameters are done by an electromagnetic shaker and stress data is collected. Afterwards, fatigue test is performed for determining whether the assembly satisfies the required operational life. Resonance test is performed at the frequency in which the critical location is at resonance, since there was no failure observed after fatigue testing. A failure is obtained during resonance test. At the end of the study, an analytical equation is brought up which relates accelerated life test durations with equivalent alternating stresses. Therefore, optimization of the accelerated life test duration can be done, especially in military applications, by avoiding the maximum stress level to reach or exceed the yield limit.
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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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Adeleke, Bukola. "Experimental and Finite Element Analysis of Wind Induced Displacement of a Dual Axis Photovoltaic Solar Trackers." Thesis, Université d'Ottawa / University of Ottawa, 2016. http://hdl.handle.net/10393/34310.
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Photovoltaic (PV) solar panels and trackers represent one of the most common renewable energy
technology which converts sunlight radiation into electrical energy. The solar trackers specifically
are more complex structures because they involve mechanical devices, a supporting slender
structure, and photovoltaic modules mounted and positioned on top of the supporting structure.
Solar trackers are mounted on mobile supports or racks, in order to enable the rotation and tilt of
the PV which thus maintains their optimum exposure to the incident sunlight. Solar trackers
support structures should be designed for wind resistance during the operation and at stow position
for its life span and this became a concern considering the new tendency of installing the solar
trackers on the rooftop of low-rise or medium-rise buildings. The current research focused on
performing site measurements of the wind-induced displacement for a dual-axis solar tracking
system installed on the roof of the Mann Parking building of the University of Ottawa, for different
azimuth, elevations.
The supporting structure of the solar tracker was instrumented with 16 strain gauges and the strains
developed in the metal truss members were measured during the months February 2015 and March
2015. The tracker was rotated and tilted at different angles through the duration of the experiment
and the strains observed on each structural element were recorded. In order to estimate deflections
of the supporting structure for wind speeds higher than the ones measured, a finite element (FE)
model of the solar tracker was created and static analysis was performed for different inclinations
using the SAP 2000 structural software. The experimental results were in agreement with the FE
simulation results as the stresses obtained ranged between 1.02 × 107 Pa and 7.88 × 107 Pa. Lower
attack angles between 45° and 60° were found to have significant effect on the elements of the
solar tracker irrespective of the wind load magnitude. Operational attack angles between 65° and
75° were found to be safer positions as obtained displacements and stress analysis result showed
that the supporting structure of the solar tracker was stable for wind speeds between 0 m/s and
33m/s in Ottawa region
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鈴木, 賢治, Kenji SUZUKI, 一秀 松本, Kazuhide MATSUMOTO, 貴博 久保, Takahiro KUBO, 修太郎 町屋, et al. "高エネルギー反射光によるEB-PVD遮熱コーティングの残留応力分布の解析." 日本機械学会, 2005. http://hdl.handle.net/2237/9130.
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鈴木, 賢治, Kenji SUZUKI, 修太郎 町屋, Shutaro MACHIYA, 啓介 田中, Keisuke TANAKA, 喜久 坂井田, and Yoshihisa SAKAIDA. "熱遮へいコーティング膜の変形特性のＸ線的研究." 日本機械学会, 2001. http://hdl.handle.net/2237/9163.
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Cantrell, Ashley M. "Understanding Posttraumatic Stress and Academic Achievement: Exploring Attentional Control, Self-Efficacy, and Coping Among College Students." TopSCHOLAR®, 2016. http://digitalcommons.wku.edu/theses/1618.
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The present study examined differences in attentional control, attentional control self-efficacy, and coping as self-regulatory mechanisms among students with varying grade point averages (GPA) who experience posttraumatic stress symptoms (PTSS). Subjects included 58 college students from one large comprehensive university in the Mid-South who met the criteria for diagnosis of PTSS based on the Impact of Event Scale-Revised (IES-R). Three groups were created based on college GPA and graduation requirements at the university (at-risk for graduation, on-track for graduation, and ontrack for graduating with honors). Participants completed a survey that included demographics and measures of PTSS, attentional control, attentional control self-efficacy, and coping. A one-way between groups ANOVA revealed statistically significant differences in attentional control self-efficacy and avoidant coping between the Honors and At-Risk groups. The current study provides additional information and support that success for students with PTSS may be explained by their confidence in their abilities to control their attention and using less avoidant coping strategies. However, as a group, students with PTSS need strategies for increasing their attentional control, self-efficacy beliefs, and adaptive coping.
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Chekkilla, Avinash Goud. "Monitoring and Analysis of CPU Utilization, Disk Throughput and Latency in servers running Cassandra database : An Experimental Investigation." Thesis, Blekinge Tekniska Högskola, Institutionen för tillämpad signalbehandling, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-13706.
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Context Light weight process virtualization has been used in the past e.g., Solaris zones, jails in Free BSD and Linux’s containers (LXC). But only since 2013 is there a kernel support for user namespace and process grouping control that make the use of lightweight virtualization interesting to create virtual environments comparable to virtual machines. Telecom providers have to handle the massive growth of information due to the growing number of customers and devices. Traditional databases are not designed to handle such massive data ballooning. NoSQL databases were developed for this purpose. Cassandra, with its high read and write throughputs, is a popular NoSQL database to handle this kind of data. Running the database using operating system virtualization or containerization would offer a significant performance gain when compared to that of virtual machines and also gives the benefits of migration, fast boot up and shut down times, lower latency and less use of physical resources of the servers. Objectives This thesis aims to investigate the trade-off in performance while loading a Cassandra cluster in bare-metal and containerized environments. A detailed study of the effect of loading the cluster in each individual node in terms of Latency, CPU and Disk throughput will be analyzed. Method We implement the physical model of the Cassandra cluster based on realistic and commonly used scenarios or database analysis for our experiment. We generate different load cases on the cluster for Bare-Metal and Docker and see the values of CPU utilization, Disk throughput and latency using standard tools like sar and iostat. Statistical analysis (Mean value analysis, higher moment analysis and confidence intervals) are done on measurements on specific interfaces in order to show the reliability of the results. Results Experimental results show a quantitative analysis of measurements consisting Latency, CPU and Disk throughput while running a Cassandra cluster in Bare Metal and Container Environments. A statistical analysis summarizing the performance of Cassandra cluster while running single Cassandra is surveyed. Conclusions With the detailed analysis, the resource utilization of the database was similar in both the bare-metal and container scenarios. From the results the CPU utilization for the bare-metal servers is equivalent in the case of mixed, read and write loads. The latency values inside the container are slightly higher for all the cases. The mean value analysis and higher moment analysis helps us in doing a finer analysis of the results. The confidence intervals calculated show that there is a lot of variation in the disk performance which might be due to compactions happening randomly. Further work can be done by configuring the compaction strategies, memory, read and write rates.
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Crammond, G. "Development of optical techniques for the experimental analysis of local stress and strain distributions in adhesively bonded composite joints." Thesis, University of Southampton, 2013. https://eprints.soton.ac.uk/355981/.
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This research seeks to evaluate the local stress and strain distributions formed in adhesively bonded composite joints under quasi static and high strain rate loading. A literature review of current analytical, numerical and experimental studies of adhesively bonded joints is presented and identifies the lack of knowledge in the behaviour of composite bonded joints in the through-thickness direction. Detailed analysis of the stress and strain in the joint, and their impact on the development of damage prior to and during failure have been obtained using Digital Image Correlation (DIC). An experimental methodology is established to perform DIC at the mesoscopic scale using high magnification optics, enabling accurate, high spatial resolution analysis of the strains around the geometric discontinuity between adherends. It is demonstrated that the small through-thickness strains are critical in the development of damage in the joint around the discontinuity between adherends. Errors in the DIC technique are assessed using a robust morphological methodology to evaluate the quality of different speckle patterns based upon the properties of the speckles in the pattern. The strain data is manipulated to evaluate the principal stresses in the joint, which govern failure in the brittle epoxy matrix of the composite, providing a concise evaluation of the transfer of load between the adherends and damage initiation within the joint. The DIC results and methodology are validated against independent infra-red measurements using Thermoelastic Stress Analysis (TSA). Limitations in the TSA analysis approach are identified around joint discontinuity due to the varying principal stress direction. A new TSA analysis methodology is presented to overcome this. The results of the experimental analysis are used to validate a representative 2D finite element model modelling approach for adhesively bonded joints, showing good agreement to the experimental data. Finally the full-field DIC methodology is applied to analyse the response of a single lap joint during high strain rate loading, providing unprecedented full-field measurement of the strain fields up to failure.
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VanDenBosch, Leah M. "Investigating the effect of fluid shear stress on the failure of cancer cell membranes: an experimental and computational analysis." Thesis, University of Iowa, 2018. https://ir.uiowa.edu/etd/6318.
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Cancer metastasis, or the formation of a secondary tumor at a site distant from the primary tumor, is known to be an inefficient process. Historically, it was believed that the shear stresses and forces experienced by cancer cells traveling through the circulatory system are major limiting factors to their metastatic potential and viability. High levels of fluid shear stress are known to be capable of destroying tumor cells. However, more recent research has shown that cancer cells survive migration through the circulatory system and extravasation into distant tissues with a high degree of efficiency, indicating that hemodynamic forces are not primarily responsible for metastatic cancer cell death. A current subject of investigation is the biomechanical effect of fluid shear stress on cancer cells – how do cancer cells react to the fluidic forces and stresses they experience in circulation? This study focused on quantifying the elastic modulus and rupture behavior of prostate cancer and prostate epithelial cells, with and without exposure to fluid shear stress. Micropipette aspiration was the means of inducing deformation and rupture of the cell membrane. Images obtained through micropipette aspiration were analyzed to calculate elastic modulus and to quantify local stresses along the aspirated cell membrane. An axisymmetric stress model of the aspirated cell membrane was solved using MATLAB; the trends for direction and relative magnitude of stresses were confirmed by an Abaqus finite element model.
Results of the micropipette aspiration included statistically significant differences in elastic modulus and rupture pressure between experimental groups. The elastic modulus of epithelial cells exposed to shear stress was significantly higher than that of the cancer cell groups, both exposed and unexposed to shear stress. There was no difference in elastic modulus between cancer cells exposed to shear stress and unexposed to shear stress. This is contrary to the findings of a previous study; prostate cancer cells have been observed to stiffen after exposure to shear stress. It has also been well documented that epithelial cells exhibit higher elastic moduli than cancer cells; however, no difference was observed in this study in the comparison of elastic moduli of cancer and epithelial cells that were unexposed to shear stress. The rupture pressure of the cancer cells unexposed to shear stress was significantly lower than any other group. This suggests a strengthening reaction of the cancer cell membrane in response to shear stress exposure. This effect was observed to be transient; the increase in rupture pressure disappeared by an hour after the shear stress exposure. The epithelial cells did not exhibit any change in rupture pressure after exposure to shear stress. There was no correlation between elastic modulus and rupture pressure; the stiffness of the cells did not indicate how likely they were to rupture.
The MATLAB and Abaqus models agreed well for trends of principal stresses and von Mises stress. The MATLAB model was quite sensitive to the curvature of the spline fitted to the membrane edge, resulting in irregular patterns and some extreme values of stress and making the results difficult to interpret. The maximum stress did tend to increase with increased aspiration pressure. The location of the maximum stress along the membrane did not reliably correspond to the location of rupture during micropipette aspiration. This model may be improved by automating the process of fitting a spline to the edge of the membrane to reduce user error in plotting individual points.
Further studies to characterize the effects of fluid shear stress on cancer cell mechanics will be useful to confirm differences in elastic modulus and rupture pressure and to investigate the effect of time, temperature, cancer cell line, culture medium, and other variables on cancer cell properties.
32
Kelly, Brennan James. "Experimental and Simulated Analysis of Voltage Stress Within a Bar-Wound Synchronous Machine Excited by a Silicon Carbide Inverter." The Ohio State University, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=osu1619111736344023.
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田中, 啓介, Keisuke TANAKA, 賢一 水野, Kenichi MIZUNO, 修太郎 町屋, Shutaro MACHIYA, 義明 秋庭, and Yoshiaki AKINIWA. "シリコン単結晶の重回帰分析を用いたX線応力測定." 日本機械学会, 2006. http://hdl.handle.net/2237/9153.
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Lacerda, Larissa Gomes. "Chronic Mild Stress (CMS): um estudo sobre a interação entre manipulação neonatal e submissão ao protocolo de estressores na vida adulta." Pontifícia Universidade Católica de São Paulo, 2013. https://tede2.pucsp.br/handle/handle/16705.
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Chronic Mild Stress (CMS) an experimental animal model of anhedonia induced by exposing the rats to a protocol of chronic stress for a long period of time. At the Laboratório do Programa de Pós Graduação em Psicologia Experimental: Análise do Comportamento, a research line about CMS and its relation with the operant behavior has been developed since 2001, as in Pereira (2009). Unlike other studies conducted in this laboratory, Pereira (2009) did not observe sucrose intake and preference reducing (anhedonia) along stressors. One pointed hypothesis was the neonatal handling was a responsible variable for that. The goal of this study was to investigate whether the neonatal handling alters the fluid intake and preference on rats that were submitted to the stressors protocol (CMS) during the adult phase. Three groups were divided among experimental conditions: 1) neonatal handling, 2) protocol and 3) neonatal handling and protocol. The used measures were: weight, ration and water intake and weekly tests over intake and fluid preference. Results found show that stressors protocol reduced weight of subjects from the manipulation group (MP) as for the ones from only stressors protocol group (P). Food and water intake also presented similar results for Groups P and MP: all subjects presented water intake enhance and ration intake reducing during protocol. For fluid intake and preference tests, both Group P and MP presented preference oscillation at no stressors period and sucrose intake enhance during protocol submission weeks, that means, they did not produced anhedonia. Results allow to assure that the group submitted to maternal manipulation with 15min mother s separation did not show any difference in comparison to the nohandling group, specially related to preference and intake tests, when submitted to CMS
Chronic Mild Stress (CMS) um modelo animal experimental de anedonia induzida através da exposição de ratos a um protocolo de estressores crônicos por um longo período de tempo. No Laboratório do Programa de Pós Graduação em Psicologia Experimental: Análise do Comportamento, uma linha de pesquisa sobre o CMS e a relação com o comportamento operante tem sido desenvolvida desde 2001, como em Pereira, 2009. Diferente de outros estudos realizados nesse laboratório, Pereira (2009) não observou redução da ingestão e preferência de sacarose (anedonia) durante os estressores. Uma das hipóteses levantadas foi que a manipulação neonatal tenha sido uma variável responsável por isso. O objetivo do presente estudo foi investigar se a manipulação neonatal, altera a ingestão e preferência de líquidos em ratos que passaram pelo protocolo de estressores (CMS) durante a fase adulta. Três grupos foram divididos entre as condições experimentais: 1) manipulação neonatal, 2) protocolo e 3) manipulação neonatal e protocolo. As medidas utilizadas foram: peso, consumo de ração e de água e testes semanais de ingestão e preferência de líquido. Os resultados encontrados mostram que o protocolo de estressores diminuiu o peso dos sujeitos tanto para o grupo que passou pela manipulação (MP) quanto para o que passou apenas pelo protocolo de estressores (P). O consumo de alimento e água também apresentou resultados semelhantes para os Grupos P e MP: todos apresentaram aumento na ingestão de água e diminuição do consumo de ração durante o protocolo. Para os testes de consumo e preferência de líquido, tanto o Grupo P quanto o MP apresentaram oscilação de preferência no período sem estressores e aumento da ingestão de sacarose durante as semanas de submissão ao protocolo, ou seja, não produziram anedonia. Os resultados permitem afirmar que o grupo que passou pelo procedimento de manipulação neonatal separados da mãe por 15min não apresentou diferença em comparação com o grupo que não foi manipulado, principalmente em relação aos testes de ingestão e preferência, quando submetidos ao CMS
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Kreamelmeyer, Fred Dennis. "Teacher burnout : an analysis of the relationship between participation in an experimental undergraduate program and longevity of career." Virtual Press, 1985. http://liblink.bsu.edu/uhtbin/catkey/436969.
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The main problem under investigation was to determine whether or not statistically significant differences exist in the characteristics associated with stress-burnout tendencies and attrition rate of teachers prepared in a traditional elementary teacher education program and an experimental teacher education program.Secondly, the study examined the additional impact of an overseas experience in the experimental teacher education program. Results were analyzed to determine whether or not statistically significant differences existed between the experimental group and subgroup which went overseas.Population in the study consisted of the 1976 elementary education graduates of Ball State University, Muncie, Indiana. Two instruments were sent to the subjects in the study. One was an 18-item questionnaire developed specifically for use in this research, The Class of '76 Follow-up Questionnaire, designed to gather data related to stress, burnout, attrition, and degree of satisfaction with the teaching profession. The second instrument, The Tedium Measure, was developed by Pines and Aronson (1980) and has been used to measure burnout. Questionnaires were mailed to the population sample of 248, with 194 returned (78.2%).The program used for the calculation of group variances and the t-value was the SPSS-X, on the VAX computer. The t-test was employed to determine statistical significance between the responses of the various groups. The .05 level of significance was used as the criterion for significance.Findings Statistical significance of the difference between groups within the elementary education program at Ball State University was found in eight areas of The Class of '76 Follow-up Questionnaire.These findings support a conclusion that graduates who participated in the experimental elementary education (EXEL) program held more positive views of professional teacher education, teaching experiences, and future years in teaching.
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Kulkarni, Kanchan Avinash. "Experimental Characterization and Finite Element Simulation of Laser Shock Peening Induced Surface Residual Stresses using Nanoindentation." University of Cincinnati / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1352489043.
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Xiao, Kewei. "A diffusion-viscous analysis and experimental verification of the drying behavior in nanosilver-enabled low-temperature joining technique." Diss., Virginia Tech, 2014. http://hdl.handle.net/10919/25137.
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The low-temperature joining technique (LTJT) by silver sintering is being implemented by major manufacturers of power electronics devices and modules for bonding power semiconductor chips. A common die-attach material used with LTJT is a silver paste consisting of silver powder (micron- or nano-size particles) mixed in organic solvent and binder formulation. It is believed that the drying of the paste during the bonding process plays a critical role in determining the quality of the sintered bond-line. In this study, a model based on the diffusion of solvent molecules and viscous mechanics of the paste was introduced to determine the stress and strain states of the silver bond-line. A numerical simulation algorithm of the model was developed and coded in the C++ programming language. The numerical simulation allows determination of the time-dependent physical properties of the silver bond-line as the paste is being dried with a heating profile. The properties studied were solvent concentration, weight loss, shrinkage, stress, and strain. The stress is the cause of cracks in the bond-line and bond-line delamination. The simulated results were verified by complementary experiments in which the formation of cracks in bond-line and interface delamination was observed during the pressure-free drying of a die-attach nanosilver paste. Furthermore, the important drying parameters, such as drying pressure, low temperature drying time and temperature ramp rate of nanosilver LTJT process, are experimentally studied and analyzed with the numerical simulation. The simulated results were consistent with the experimental findings that the quality of sintered silver bond-line increases with increasing external drying pressure, with increasing low temperature drying time, and with decreasing temperature ramp rate. The insight offered by this modeling study can be used to optimize the process profile that enable pressure-free, low-temperature sintering of the die-attach material to significantly lower the cost of implementing the LTJT in manufacturing.Ph. D.
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Sahoo, Dipankar. "Experimental analysis of the vorticity and turbulent flow dynamics of a pitching airfoil at realistic flight (helicopter) conditions." Diss., Texas A&M University, 2008. http://hdl.handle.net/1969.1/85893.
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Improved basic understanding, predictability, and controllability of vortex-dominated and unsteady aerodynamic flows are important in enhancement of the performance of next generation helicopters. The primary objective of this research project was improved understanding of the fundamental vorticity and turbulent flow physics for a dynamically stalling airfoil at realistic helicopter flight conditions. An experimental program was performed on a large-scale (C = 0.45 m) dynamically pitching NACA 0012 wing operating in the Texas A&M University large-scale wind tunnel. High-resolution particle image velocimetry data were acquired on the first 10-15% of the wing. Six test cases were examined including the unsteady (k>0) and steady (k=0) conditions. The relevant mechanical, shear and turbulent time-scales were all of comparable magnitude, which indicated that the flow was in a state of mechanical non-equilibrium, and the expected flow separation and reattachment hystersis was observed. Analyses of the databases provided new insights into the leading-edge Reynolds stress structure and the turbulent transport processes. Both of which were previously uncharacterized. During the upstroke motion of the wing, a bubble structure formed in the leading-edge Reynolds shear stress. The size of the bubble increased with increasing angle-of-attack before being diffused into a shear layer at full separation. The turbulent transport analyses indicated that the axial stress production was positive, where the transverse production was negative. This implied that axial turbulent stresses were being produced from the axial component of the mean flow. A significant portion of the energy was transferred to the transverse stress through the pressure-strain redistribution, and then back to the transverse mean flow through the negative transverse production. An opposite trend was observed further downstream of this region.
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Mercimek, Umit. "Shock Failure Analysis Of Military Equipments By Using Strain Energy Density." Master's thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/12612721/index.pdf.
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Failure of metallic structures operating under shock loading is a common
occurrence in engineering applications. It is difficult to estimate the response of
complicated systems analytically, due to structure&rsquos dynamic characteristics and varying loadings. Therefore, experimental, numerical or a combination of both methods are used for evaluations. The experimental analysis of the shocks due to firing is done for 12.7mm Gatling gun and 25mm cannon. During the tests, the Gatling gun and the cannon are located on military Stabilized Machine Gun Platform and Stabilized Cannon Platform respectively. For the firing tests, ICP (integrated circuit piezoelectric) accelerometers are attached to obtain the loading history for corresponding points. Shock Response Spectrum (SRS) analysis (nCode Glypworks) is done to define the equivalent shock profiles created on test pieces and the mount of 25mm cannon by means of the gun and the cannon firing. Transient shock analysis of the test pieces and the mount are done by applying the obtained shock profiles on the parts in a finite element model (ANSYS). Furthermore, experimental stress analysis due to shock loading is performed for two different types of material and different thicknesses of the test pieces. The input data for the analysis is obtained through measurements from strain rosette precisely located at the critical location of the test pieces. As a result of the thesis, a proposal is tried to be introduced where strain energy density theory is applied to predict the shock failure at military structures.
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Charonko, John James. "Studies of Stented Arteries and Left Ventricular Diastolic Dysfunction Using Experimental and Clinical Analysis with Data Augmentation." Diss., Virginia Tech, 2009. http://hdl.handle.net/10919/26875.
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Cardiovascular diseases are among the leading causes of deaths worldwide, but the fluid mechanics of many of these conditions and the devices used to treat them are only partially understood. This goal of this dissertation was to develop new experimental techniques that would enable translational research into two of these conditions. The first set of experiments examined in-vitro the changes in Wall Shear Stress (WSS) and Oscillatory Shear Index (OSI) caused by the implantation of coronary stents into the arteries of the heart using Particle Image Velocimetry. These experiments featured one-to-one scaling, commercial stents, and realistic flow and pressure waveforms, and are believed to be the most physiologically accurate stent experiments to date. This work revealed distinct differences in WSS and OSI between the different stent designs tested, and showed that changes in implantation configuration also affected these hemodynamic parameters. Also, the production of vortices near the stent struts during flow reversal was noted, and an inverse correlation between WSS and OSI was described.
The second set of experiments investigated Left Ventricular Diastolic Dysfunction (LVDD) using phase contrast magnetic resonance imaging (pcMRI). Using this technique, ten patients with and without LVDD were scanned and a 2D portrait of blood flow through their heart was obtained. To augment this data, pressure fields were calculated from the velocity data using an omni-directional pressure integration scheme coupled with a proper-orthogonal decomposition-based smoothing. This technique was selected from a variety of methods from the literature based on an extensive error analysis and comparison. With this coupled information, it was observed that healthy patients exhibited different flow patterns than diseased patients, and had stronger pressure differences during early filling. In particular, the ratio of early filling pressure to late filling pressure was a statistically significant predictor of diastolic dysfunction. Based on these observations, a novel hypothesis was presented that related the motion of the heart walls to the observed flow patterns and pressure gradients, which may explain the differences observed clinically between healthy and diseased patients.Ph. D.
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TANAKA, Keisuke, Yoshiaki AKINIWA, Yoshihisa SAKAIDA, and Hirohisa KIMACHI. "Lattice Strain and Domain Switching Induced in Tetragonal PZT by Poling and Mechanical Loading." The Japan Society of Mechanical Engineers, 2000. http://hdl.handle.net/2237/9183.
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Andraéy, Erik. "Development of verified FE simulation method on crimp joint with gasket : A combined experimental and numerical study." Thesis, Blekinge Tekniska Högskola, Institutionen för maskinteknik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-21924.
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When developing drivetrain cooling modules for commercial vehicles, the top priority is the strength of the products. The reason lays within the structural change that companies are undergoing where the warehouses are minimized and the companies are relying on the transportation of commercial vehicles. If a drivetrain cooling module would fail to maintain a targeted temperature range of the drivetrain, there is not long until the vehicle is forced to a stop. At worst, the downtime of commercial vehicles can cause companies to come to a halt as well. Therefore, developing verified FE simulation methods together with strength verification tests, are some of the core activities to ensure the strength of the cooling modules before implementation in vehicles. One of the methods that have not been sufficiently verified regards how to perform structural FEA on a crimp joint with a gasket. A crimp joint is established through a hemming process, where the aluminium header tabs are crimped over the polyamide tank, creating a watertight seal together with a gasket. The objective of this master’s thesis is to verify the existing simulation methods of the crimp joint and determine the margin of error with respect to strains. The objective of this thesis is also to develop a verified FE simulation method with a lower margin of error compared to the existing methods. The verification of the methods has been conducted through a comparison between numerical results and an experimental stress analysis, where the strain located on the header is measured with strain gauges in a pressure pulsation rig. The average margin of error found on the three existing methods of simulating the crimp joint was 39,7%, 13,4%, and 11,5% located on the outer bottom dimensioning radius of the crimp joint at a pressure of 100 kPa. However, the method used to determine the margin of error was found to be invalid, but the margin of error is only slightly affected by the verification method where the existing methods still are insufficiently representing the crimp joint. The method of determining the margin of error was then corrected for the development of the new method to represent the crimp joint in the FE model. The developed method in this thesis has an average margin of error of 6,9% at 100, 160, 220, and 260 kPa.Vid utveckling av kylarmoduler för drivlinor som appliceras i kommersiella fordon, är högsta prioritet att säkerhetsställa hållfastheten hos produkterna. Anledningen ligger kring den strukturomvandling som företag genomgår där storleken på lagerlokaler minskar och företagen väljer att förlita sig på transporterna som utförs av kommersiella fordon istället. Ifall en kylarmodul inte skulle klara av att bibehålla ett bestämt temperaturintervall hos drivlinan så dröjer det inte länge förens fordonet tvingas att stanna. I värsta fall kan fordonets stillestånd påverka ett företag att tvingas stanna i väntan. Därför är utveckling av FE simuleringsmetoder tillsammans med utmattningstest, några av de kärnaktiviteter som utförs för att säkerhetsställa hållfastheten av kylarmodulerna innan de implementeras i fordon. En av de metoder som ännu inte blivit tillräckligt verifierat gäller hur man utför FEA på ett falsförband med packning. Falsförbandet skapas genom en falsningsprocess där ändplåten av aluminium falsas över polyamidtanken, vilket skapar ett vattentätt förband med hjälp av packningen. Omfattningen av detta examensarbete gäller att verifiera de existerande simuleringsmetoderna av falsförbandet och bestämma felmarginalen med avseende på töjningar. Omfattningen av examensarbetet innefattar även ett utvecklingsarbete av en ny FE simuleringsmetod med en lägre felmarginal jämfört med de existerande metoderna. Verifieringen av metoderna sker genom en jämförelse mellan de numeriska resultaten och en experimentell spänningsanalys där töjningen på ändplåten är uppmätt med hjälp av trådtöjningsgivare i en tryckpulsationsrigg. Den genomsnittliga felmarginalen av de tre existerande metoderna för att simulera falsförbandet var 37,9%, 13,4%, och 11,5% vid den nedre dimensionerande yttre radien på falsförbandet vid ett tryck på 100 kPa. Den använda metoden för att bestämma felmarginalen upptäcktes senare vara felaktig, men det resulterar endast i små förändringar av den bestämda felmarginalen, de existerande simuleringsmetoderna är fortfarande sedda som otillräckliga. Metoden för att bestämma felmarginalen korrigerades sedan inför utvecklandet av den nya FE simuleringsmetoden av falsförbandet. Den utvecklade metoden i detta examensarbete har en genomsnittlig felmarginal på 6,9% vid 100, 160, 220 och 260 kPa.
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Chivante, Maurício Roberto de Pinho. "Avaliação experimental das relações tensão-deformação de um tecido de fibra de vidro recoberto com PTFE." Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/3/3144/tde-18122009-134136/.
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Com o crescente uso de estruturas de membrana tensionada, as relações tensãodeformação do tecido utilizado em sua fabricação devem ser bem entendidas. Deste modo, esta dissertação apresenta um estudo sobre o comportamento mecânico de um tecido arquitetônico PTFE-vidro, ressaltando seu complexo mecanismo de deformação que engloba efeitos de anisotropia, não-linearidade física, troca de ondulações, histerese, remoção do espaçamento entre os fios e variação de temperatura. Diferentes métodos para modelagem do material foram estudados, com ênfase no modelo de material ortótropo representado por um funcional energia de deformação hiperelástico. Além disso, vários protocolos para ensaios de tração em tecidos recobertos foram analisados e uma série de ensaios biaxiais com amostras cruciformes foram realizados no Centro de Pesquisa e Desenvolvimento da Birdair, Inc. Um determinado funcional energia de deformação foi então ajustado aos dados de campo obtidos nestes testes, cujos resultados foram então comparados diretamente aos dados obtidos em campo e a um ajuste direto de uma superfície suave tensão-deformação. A performance do modelo ajustado não se encontra ainda em um patamar de aplicação industrial, entretanto este estudo permite um entendimento global dos mecanismos de deformação do tecido PTFEvidro, fornecendo também uma massa de dados consistentes que podem ser utilizados em situações práticas.Considering the growing use of tensioned membrane structures, the stress-strain relation of the fabric used on its construction must be well understood. This dissertation presents a study of the mechanical behavior of a PTFE coated fiberglass fabric, emphasizing its complex strain mechanism which is influenced by the material anisotropy, physical non-linearity, crimp interchange, hysteresis, removal of yarn spacing and changes in temperature. Different material models were studied, focusing on an orthotropic material model represented by a hyperelastic strain energy function. Also, different test protocols were reviewed and a series of biaxial tests on cruciform samples were performed at the Birdair, Inc.s Research and Development Center. A strain energy function was adjusted to the collected data and than its results compared to the data itself and to another stress-strain function directly adjusted to the data. The performance of the strain-energy function chosen is not on a level of industrial application; however this study gives a global understanding of the PTFE coated fiberglass strain mechanism and also provides a consistent database that may be used on real situations.
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TANAKA, Keisuke, and Yoshiaki AKINIWA. "Diffraction Measurements of Residual Macrostress and Microstress Using X-Rays, Synchrotron and Neutrons." The Japan Society of Mechanical Engineers, 2004. http://hdl.handle.net/2237/9178.
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Azzabou-Kacem, Soundess. "Stress shift in English rhythm rule environments : effects of prosodic boundary strength and stress clash types." Thesis, University of Edinburgh, 2018. http://hdl.handle.net/1842/33200.
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It is well-known that the early assignment of prominence in sequences like THIRteen MEN vs. thirTEEN, (defined as the Rhythm Rule, or post-lexical stress shift), is an optional phenomenon. This dissertation examines some of the factors that encourage the application of stress shift in English and how it is phonetically realised. The aim is to answer two sets of questions related to why and how stress shift occurs in English: 1a) Does prosodic boundary strength influence stress shift? 1b) Does the adjacency of prominences above the level of the segmental string encourage stress shift? 2) How is stress shift realized? a) Is stress shift only a perceptual phenomenon? and b) Which syllables, if any, change acoustically when stress shift is perceived? To answer these questions, four experiments were designed. The first three experiments test whether the strength of the prosodic boundaries before and after the target word (e.g., canteen) influence stress shift. The effect of the strength of the left-edge prosodic boundary was investigated by comparing perceived stress patterns of the target (e.g., canteen) as produced in isolation where it is preceded by an utterance- and a phrase- initial prosodic boundary (the Isolated condition) with its rendition when embedded in a frame sentence (e.g., Say canteen again) where the left prosodic boundary before canteen is weaker (the Embedded condition). Results show a very clear tendency towards late phrasal prominence on the final accentable syllable (e.g., -teen in canteen) in the Embedded condition while in the Isolated condition this pattern appeared in less than half of the targets, showing that the stronger left boundary increased the incidence of stress shift. Two more experiments manipulated the strength of the boundary to the right of the target (#) respectively by changing the syntactic parse of the critical phrase (e.g. canteen cook) in sequences like (1) and by manipulating constituent length as in (2). Results showed that the syntactic manipulation significantly affected the strength of the prosodic boundary between the clashing words which was stronger in (1b) relative to (1a), and affected the incidence of stress shift, which was higher in (1a) relative to (1b). The length manipulation also affected the rate of stress shift, which was significantly higher in the phrase with the shorter word, e.g., soups (2a) relative to phrase with the longer word, e.g., supervisors (2b). (1) Example from the Syntax Experiment a. Who is the canteen (#) cook these days? (Pre-modifier + Noun) b. How do the canteen (#) cook these days? (NP + VP) (2) Example from the Length Experiment a. It should include the canteen (#) soups again. (Shorter constituent) b. It should include the canteen (#) supervisors again. (Longer constituent) Whilst we knew from the literature that the grouping of the clashing words within one Intonational Phrase (IP) encourages stress shift, results from the Syntax and Length experiments indicate that this (i.e., the phrasing of the clashing words within same IP) is not sufficient condition for the occurrence of stress shift, and that fine-grained degrees of boundary strength below the Intonational Phrase can drive changes in prominence pattern. The fact that higher rates of stress shift (and associated significant acoustic changes) were driven by manipulations of constituent length --for sequences with the same syntactic structure-- provides support for the idea that prosodic (rather than syntactic) boundaries directly influence stress shift. The fourth experiment tests the definition of stress clash in English in cases like fourteen candles where the two main lexical prominences are strictly adjacent along the time dimension, in fourteen canoes where the prominences are not adjacent in time, but adjacent at the higher levels of the metrical hierarchy, and in fourteen canteens where the main lexical prominences are not adjacent, and do not clash. This experiment highlighted and resolved an unacknowledged disagreement about what clash status sequences with one weak intervening syllable (e.g., fourTEEN caNOES). The fourTEEN caNOES type were shown to behave like metrically clashing sequences (e.g., fourteen CANdles) in attracting stress shift, and differently from the non-metrically-clashing sequences (e.g., fourteen CANTEENS) in discouraging it. These results provide empirical support for the Standard Metrical Theory (e.g. Selkirk, 1984; Nespor & Vogel, 1989) claim that 1) stress clash matters in triggering stress shift and that 2) stress clash in English is defined at the higher prosodic levels and not restricted to the level of the segmental string as indirectly assumed in a growing body of research (e.g., Vogel, Bunnel & Hoskins, 1995; Tomlinson, Liu & Fox Tree, 2014). Along with the establishment of prosodic boundary strength as one of the predictors influencing stress shift, another important contribution of the thesis is providing empirical evidence that the English Rhythm Rule is not solely a perceptual phenomenon and that it is associated with acoustic correlates. The main correlates of perceived stress shift consistently appearing across experiments is the decrease in the duration of the main lexical prominence of the target (e.g., -teen in canteen) and the increase of fundamental frequency and Sound Pressure Level peaks and on the initial syllable (e.g., canin canteen), when followed by a main clashing phrasal prominence. The acoustic analysis shows that the first accentable syllable also contributes in the perception of stress shift. This latter result does not lend support to the deletion formulation of the Rhythm Rule (Gussenhoven, 1991) which stipulates that the impressions of stress shift are solely associated with changes of prominence in the last accentable syllable of the target (e.g. -teen in canteen). Along with the determination of the acoustic correlates of perceived stress shift in English, the present research 1) indicates that fine-grained gradations of prosodic boundary strength can influence stress shift, 2) shows that while stress clash can increase the incidence of stress shift, stress shift can take place even in environments completely free of stress clash, and 3) provides evidence that stress clash should not be construed simply as the concatenation of two main lexical prominences along the time dimension.
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El-Hajjar, Rani Fayez. "Experimental study and analytical modeling of translayer fracture in pultruded FRP composites." Diss., Available online, Georgia Institute of Technology, 2004:, 2004. http://etd.gatech.edu/theses/available/etd-03152004-230942/unrestricted/elhajjar%5Frani%5Ff%5F200405%5Fphd.pdf.
Full textAbstract:
Thesis (Ph. D.)--Civil and Environmental Engineering, Georgia Institute of Technology, 2004.Dr. Zureick, Abdul-Hamid, Committee Member; Dr. White, Donald, Committee Member; Dr. Saxena, Ashok, Committee Member; Dr. Jacobs, Laurence, Committee Member; Dr. Haj-Ali, Rami, Committee Chair; Dr. Armanios, Erian, Committee Member. Vita. Includes bibliographical references (leaves 164-172).
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Stamatialis, Dimitrios F., Dimitrios N. Soulas, and Merope Sanopouloua. "Mechanisms of non-fickian micromolecular diffusion in glassy polymer films: analysis of experimental sorption and concurrent dilation kinetics in the light of a differential swelling stress model." Diffusion fundamentals 11 (2009) 10, S. 1-2, 2009. https://ul.qucosa.de/id/qucosa%3A13930.
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Job, Sarah. "Identity-Specific Positive Psychology Intervention for Sexual Minorities: A Randomized Control Trial." Digital Commons @ East Tennessee State University, 2021. https://dc.etsu.edu/etd/3891.
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Sexual minorities experience mental and physical health disparities in comparison to heterosexual individuals due to minority stress (Branstrom et al., 2016; Kerridge et al., 2017; Meyer, 2003). Positive psychology interventions have improved mental and physical health (Antoine et al., 2018; Lambert D'raven et al., 2015), and therefore these interventions have potential to address health disparities. The current study tested an identity-specific intervention (n = 30) to a general positive psychology intervention (n = 30) and a control group (n = 30) among sexual minorities. This built on a recent pilot study which tested the efficacy of an identity-specific intervention designed for sexual minorities and showed significant improvements in depressive and anxiety symptoms. Thus, I hypothesized that individuals in intervention conditions would have better mental health, physical health, and substance use outcomes than the control group. Additionally, outcomes of the identity-specific condition were compared to those of the general positive psychology intervention. Participants included 91 sexual minority adults that completed three surveys (baseline, one week after the intervention, one month follow-up) including outcomes measures (depressive symptoms, anxiety symptoms, problematic drinking, problems associated with drug use, well-being, and self-rated health), potential covariates (anticipated stigma, internalized stigma, concealment) and manipulation checks (self-compassion, forgiveness, optimism, coping using humor, social support seeking). Fifty-three participants completed interventions featuring five intervention tasks eliciting self-compassion, optimism, forgiveness, humor, and social support seeking. Analyses included descriptive statistics, bivariate correlations, and multilevel modeling. Compared to the control condition, results showed significantly greater improvements in well-being (b = .40, p = .013), self-rated health (b = -.42, p = .006), and problems associated with drug use (b = -.97, p = .004) among participants in the intervention conditions. No significant differences emerged for depressive symptoms, anxiety symptoms, or problematic drinking. Limitations include lack of power for analyses examining extended follow-up and comparing intervention types, as well as a number of history effects. Despite these limitations, the current study has potential to improve health outcomes and aid clinical practices. More research on positive psychology interventions with sexual minorities is needed.
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Dominguez, John Alexis. "INFLUÊNCIA DA INCORPORAÇÃO DE UM PLASTIFICANTE E UM POLIETILENO DE ALTO PESO MOLECULAR NAS PROPRIEDADES DE UMA RESINA EXPERIMENTAL E DIMINUIÇÃO DO ESTRESSE DE CONTRAÇÃO." UNIVERSIDADE ESTADUAL DE PONTA GROSSA, 2015. http://tede2.uepg.br/jspui/handle/prefix/1722.
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Previous issue date: 2015-08-13The objectives of this study were: 1) to evaluate the degree of conversion, shrinkage stress, flexural and compressive strength of an experimental resin with a lactic polyacid and castor oil; 2) to evaluate the cytotoxicity of an experimental resin with a lactic polyacid, and castor oil; 3) evaluate, degree of conversion, shrinkage stress, flexural and compressive strength an experimental resin with addition of a high molecular weight polyethylene; 4) to assess the cytotoxicity of an experimental resin with addition of a high molecular weight polyethylene. Initially, it was synthesized a poly (lactic acid) (PLA) via a polycondensation process. After 24 hours, the castor oil (OR) was incorporated by an esterification process with N, N-Dicyclonecylcarbodimide and 99% 4-Dimethylamino-Pyridine in 40 mL of tetrahydrofuran. After this, the blend was characterized by X-ray diffraction (XRPD), Raman spectroscopy, scanning electron microscopy (SEM) and shrinkage stress, where was proven the incorporation of PLA + OR in the experimental composite resin. In the third chapter, PLA + OR were manipulated in two concentrations (1.5% and 3%) in an experimental composite: (2,2 bis [4- (2-hydroxy-3-metacrilatoxypropoxy) phenol] (BisGMA) Triethylene glycol dimethacrylate (TEGDMA), camphorquinone (CQ), N, N-dimethylaminoethyl methacrylate (DEMA-EMA), butylated hydroxytoluene (BHT), silanated barium borosilicate glass, and the tests of degree of conversion, compressive and flexural strength and shrinkage stress were made. The cytotoxicity assay was done; a suspension of 3 x 103 cells/mL of culture medium was prepared. For this, the cells were detached from the bottom of the bottle by the addition of trypsin with EDTA, after incubation in 5% CO2 with 3 mL Eagle's medium supplemented culture. After 24 h incubation period, the culture medium was removed and 200 uL of a solution of culture medium and methylltetrazolium salt (MTT). Subsequently, the analysis of mitochondrial activity was performed in a spectrophotometer (Biotek EL 800, Biotek, Winooski, VT, USA) with a 10 wavelength of 570 nm. The data from each test were analyzed by one-way ANOVA. No significant differences were found (p <0.005) in compressive and degree of conversion tests, and significant differences in shrinkage stress where obtained, up to 69% decrease. and flexion, statistically significant . In the fourth chapter, it was incorporated a high molecular weight polyethylene and polypropiylene, in the experimental resin proposed in chapter two, at two concentrations (1.5% and 3%), and tested by degree of conversion, compressive and flexural strength and shrinkage stress. The data from each test were analyzed by one way ANOVA, finding no significant difference (p> 0.005) in degree of conversion, compressive and flexural strength, and the contraction stress showed a significant reduction of up to 40%. Conclusion: PLA + castor oil and the high molecular weight polyethylene decreases the shrinkage stress and properties like flexural and compressive strength and degree of conversion were not influenced.
Os objetivos deste estudo foram: 1) avaliar o grau de conversão, tensão de contração, resistência à flexão e compressão de uma resina experimental com um poliácido lático e óleo de rícino; 2) avaliar a citotoxicidade de uma resina experimental com um poliácido lático e óleo de rícino; 3) avaliar o grau de conversão, tensão de contração, resistência à flexão e compressão de uma resina experimental com adição de um polietileno de alto peso molecular e 4) avaliar a citotoxicidade de uma resina experimental com adição de um polietileno de alto peso molecular. Previamente realizou-se a síntese de um Poli-ácido lático (PLA) por meio de um processo de policondensação. Após 24 horas, foi incorporado o óleo de rícino (OR) por meio de um processo de esterificação junto a N,N-Diciclonecilcarbodimida e 4-Dimetilamino-Piridina a 99% em 40 mL de tetrahidrofeurano. Em seguida, o conjunto foi caracterizado por difração de espectroscopia Raman, microscopia eletrônica de varredura (MEV) e estresse de contração, onde foi comprovada a incorporação do PLA+OR numa resina composta experimental. No terceiro capítulo foi feita a incorporação do PLA+OR em duas concentrações (1,5% e 3%) numa resina composta experimental: (2,2 bis[4-(2-hidroxi-3-metacrilatoxipropoxi)fenol](BisGMA), Trietilglicoldimetacrilato (TEGDMA), canforoquinona (CQ), N,N– dimetilaminoetil metacrilato (DMAEMA), hidroxitolueno butilado (BHT), vidro de borossilicato de bário silanizado e foram realizados os testes de flexão, compressão, grau de conversão e estresse de contração. Foi feito o teste de citotoxicidade, uma suspensão de 3 x 103 células/mL de meio de cultura foi preparada. Para isso, as células foram descoladas do fundo da garrafa por meio da adição de tripsina com EDTA, após incubação em estufa com 5% de CO2 e 3 mL de meio de cultura Eagle suplementado. Após o período de incubação de 24 h, o meio de cultura foi removido e 200 μL de uma solução de meio de cultura e sal metiltetrazólio (MTT).Posteriormente, a análise da atividade mitocondrial foi realizada em espectrofotômetro (Biotek EL 800, Biotek, Winooski, VT, EUA) com comprimento de onda de 570 nm. Os dados obtidos de cada teste foram analisados com ANOVA um fator. Não encontrou-se diferença significativa (p> 0.005) nos testes de compressão e grau de conversão; já para o teste de estresse de contração, houve diminuição estatisticamente significativa de até 69% e no teste de resistência à flexão . No quarto capítulo foi feita a incorporação de um polipropileno (PP) e o polietileno de ultra-alto peso molecular (UTEC) a uma resina experimental com os mesmos materiais manipulados no capítulo dois, em duas concentrações (1,5% e 3%), e realizados os testes de compressão, flexão, grau de conversão e estresse de contração. Os dados de cada teste foram analisados com ANOVA um fator. Não houve diferença significativa (p> 0.005) nos testes de compressão, flexão e grau de conversão; já para o teste de estresse de contração houve diminuição estatisticamente significativa de até 40%. Conclusão: OPLA+óleo de rícino e o polietileno de ultra alto peso molecular em 1,5%, diminuíram o estresse de contração e propriedades como resistência à flexão, compressão e grau de conversão não foram influenciadas.
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Hurley, Caitlin Mae. "Kinetic study of hydrogen-material interactions in nickel base alloy 600 and stainless steel 316L through coupled experimental and numerical analysis." Phd thesis, Toulouse, INPT, 2015. http://oatao.univ-toulouse.fr/14454/1/hurley.pdf.
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In France all of the nuclear power plant facilities in service today are pressurized water reactors (PWR). Some parts of the PWR in contact with the primary circuit medium, such as the steam generator tubes (fabricated in nickel base alloy A600) and some reactor core internal components (fabricated in stainless steel 316L), can fall victim to environmental degradation phenomena such as stress corrosion cracking (SCC). In the late 1950's, H. Coriou observed experimentally and predicted this type of cracking in alloys traditionally renowned for their SCC resistance (A600). Just some 20 to 30 years later his predictions became a reality. Since then, numerous studies have focused on the description and comprehension of the SCC phenomenon in primary water under reactor operating conditions. In view of reactor lifetime extension, it has become both critical and strategic to be capable of simulating SCC phenomenon in order to optimize construction materials, operating conditions, etc. and to understand the critical parameters in order to limit the damage done by SCC. This study focuses on the role hydrogen plays in SCC phenomenon and in particular H-material interactions. Hydrogen, from primary medium in the form of dissolved H gas or H from the water, can be absorbed by the alloy during the oxidation process taking place under reactor operating conditions. Once absorbed, hydrogen may be transported across the material, diffusing in the interstitial sites of the crystallographic structure and interacting with local defects, such as dislocations, precipitates, vacancies, etc. The presence of these [local defect] sites can slow the hydrogen transport and may provoke local H accumulation in the alloy. This accumulation could modify the local mechanical properties of the material and favor premature rupture. It is therefore essential to identify the nature of these H-material interactions, specifically the rate of H diffusion and hydrogen trapping kinetics at these defects. Concerning these H-trap site interactions, literature presents very few complete sets of kinetic data; it is therefore necessary to study and characterize these interactions in-depth. This work is composed of two interdependent parts: (i) the development of a calculation code capable to manage these H-material interactions and (ii) to extract the kinetic constants for trapping and detrapping from experimental results in order to fuel the simulation code and create a solid database. Due to the complexity of industrial materials (A600 and SS316L), \enquote{model materials} were elaborated using a series of thermomechanical treatments allowing for the study of simplified systems and the deconvolution of the different possible trapped and interstitial hydrogen contributions. These \enquote{model} specimens were charged with deuterium (an isotopic hydrogen tracer) by cathodic polarization. After charging, specimens were subjected to thermal desorption mass spectroscopy (TDS) analysis where the deuterium desorption flux is monitored during a temperature ramp or at an isotherm. Interstitial diffusion and kinetic trapping and detrapping constants were extracted from experimental TDS spectra using a numerical fitting routine based upon the numerical resolution of the McNabb and Foster equations. This study allowed for the determination of the hydrogen diffusion coefficient in two alloys, Ni base alloy 600 and stainless steel 316L, and the kinetic trapping and detrapping constants at two trap site types, chromium carbides and dislocations. These constants will be used to construct a kinetic database which will serve as input parameters for a numerical model for the prediction and simulation of SCC in PWRs