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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
381

Development of non-destructive test methods for assessment of in-use fire fighter's protective clothing

Thorpe, Peter A 31 May 2004 (has links)
The very nature of the fire fighting environment makes thermal degradation of turnout gear inevitable. Standards that are currently in place to ensure that new gear performs adequately for the protection of the fire fighter do not provide a quantitative measure for assessing this gear once it is in service. When the performance of the gear is compromised due to degradation, it could put the fire fighter wearing the gear at unnecessary risk. A non-destructive test that indicates the end of the useable service of the garment would be a benefit to the fire service. Full scale fire tests were conducted to suggest a range of heat fluxes that turnout gear specimens should be subjected to in order to simulate degradation caused by in-field use of the gear. A series of destructive tests were conducted on exposed specimens. A number of non-destructive tests were performed on the same specimens. The results of destructive and non-destructive tests were compared. This research explored some options for non-destructive tests of turnout gear. Digital image analysis and colorimetry were both offered as possibilities for a diagnostic test of this gear. Correlations between destructive performance tests and the colour changes of the outer shell fabric could be used to develop non-destructive tests to evaluate every garment owned by a department. More work is required to improve these test methods, but the door has been opened to better testing for in-use gear, and ultimately to provide better protection for the fire fighters who use this clothing.
382

Investigating The Effect Of Deformation And Annealing Texture On Magnetic Anisotropy In Low-c Steel Sheets By Magnetic Barkhausen Noise Method

Akcaoglu, Fehmi Umit 01 February 2013 (has links) (PDF)
Deformation and annealing texture in the cold rolled low carbon steels is important for sheet metal forming operations and service performance. The aim of this study is to non-destructively investigate the effect of texture on magnetic anisotropy. Various samples having different textures and residual stress states, due to different % reduction in thickness, annealing and stress relieving treatment, were prepared. Texture maps were obtained by Magnetic Barkhausen noise measurements performed with 100 steps between the ranges of 00-3600 on the surface. Microstructure investigation by optical &amp / scanning electron microscopy / hardness and tension tests were performed / and texture was determined by X-Ray diffraction method. The results were compared, evaluated and discussed to establish relationship between texture and magnetic Barkhausen Noise emission.
383

Inline Coherent Imaging

WEBSTER, PAUL J L 05 November 2012 (has links)
In laser materials processing, the direct measurement and characterization of material and process depth is traditionally a diffcult task. This is particularly difficult when such information needs to be obtained in real-time for feedback and dynamic analysis applications. This thesis outlines a novel method and apparatus for real-time depth measurement during laser processes such as welding, drilling, cutting and ablation called inline coherent imaging (ICI). The approach borrows the coherent imaging ideas from the primarily medical field of optical coherence tomography and adapts them to the new application. Without requirements for flawless image quality and limitations on sample exposure the design is free to emphasize speed in acquisition and processing. Furthermore, the imaging optics are specialized for compatibility with off-the-shelf beam delivery systems. Several generations of the imaging technique and relevant design equations are described and shown and realized. Also described is the design and construction of two laser processing stations used for testing ICI in macro- and micro-processing applications. A variety of applications for ICI in the understanding of percussion drilling and welding of metals and other industrial materials are discussed. The imaging technique is further extended to provide manual and fully automatic closed-loop control of drilling and ablation processes in industrial materials. Finally, some important applications of ICI in the processing of bone in both open and closed-loop configurations are demonstrated. / Thesis (Ph.D, Physics, Engineering Physics and Astronomy) -- Queen's University, 2012-11-04 15:34:14.379
384

Induktiv provning av ferritiskt rostfritt stå / Eddy current testing on ferritic stainless steel

Westin, Tommy January 2011 (has links)
The report examines the factors which may be a contributing cause to the problems that are present when ferritic stainless steel are eddy current tested in a warm condition. The work is carried out at Fagersta Stainless AB in Fagersta which manufactures stainless steel wire. In the rolling mill there is an eddy current equipment for detection of surface defects on the wire. The ferritic stainless steels cause a noise when testing and this noise complicates the detection of defects.Because of this, a study was made of how the noise related to factors such as steel grade, temperature, size and velocity. By observing the signal and with the possibilities to change the equipment settings the capability to let a signal filter reduce the noise level were evaluated. Theories about the material's physical properties have also been included, mainly the magnetic properties, electrical conductivity and the material's tendency to oxidize.Results from the tests show that a number of factors do not affect the inductive test significantly and to use a filter to reduce the noise level does not seem to be a viable option. The level of noise does not relate to the presence of superficial particles in form of oxides.The ferritic stainless steels showed some difference in noise level. Which noise level there was did match well with the steels probability for a precipitation of a second phase, and precipitation of austenite may in this case contribute to noise when using an eddy current instrument.The noise is probably due to some physical material property that varies within the thread.
385

"Wrist-cutters" : En explorativ studie över socionomstudenters bild av en person med självskadebeteende och den följande problematiken

Johansson, Malin January 2012 (has links)
The purpose of this study is to analyse and describe social work students’ view on a person with self-injurious behaviour and the following issues. The aim and focus is on the general depiction. The theoretical perspectives have been intersectionality and its focus on social constructivism, and gender perspectives. The method was semi-structured interviews with eight social work students at Linnaeus University Kalmar. The collected data was the social work students’ opinions and it was contrasted with the previous research and was analysed from the above perspectives. The main conclusion is that social work students’ view on a person with self-injurious behaviour generally not consistent with the previous research. Previous research says that a person with self-injurious behaviour generally is a young, blonde, normal female. The majority of the social work students say that a person with self-injurious behaviour is a depressed, young female with dark hair and dark clothes. The social work students focus more on why a person goes to such extremes and hurts themselves.
386

Cement-based Materials' Characterization using Ultrasonic Attenuation

Punurai, Wonsiri 05 April 2006 (has links)
The quantitative nondestructive evaluation (NDE) of cement-based materials is a critical area of research that is leading to advances in the health monitoring and condition assessment of the civil infrastructure. Ultrasonic NDE has been implemented with varying levels of success to characterize cement-based materials with complex microstructure and damage. A major issue with the application of ultrasonic techniques to characterize cement-based materials is their inherent inhomogeneity at multiple length scales. Ultrasonic waves propagating in these materials exhibit a high degree of attenuation losses, making quantitative interpretations difficult. Physically, these attenuation losses are a combination of internal friction in a viscoelastic material (ultrasonic absorption), and the scattering losses due to the material heterogeneity. The objective of this research is to use ultrasonic attenuation to characterize the microstructure of heterogeneous cement-based materials. The study considers a real, but simplified cement-based material, cement paste - a common bonding matrix of all cement-based composites. Cement paste consists of Portland cement and water but does not include aggregates. First, this research presents the findings of a theoretical study that uses a set of existing acoustics models to quantify the scattered ultrasonic wavefield from a known distribution of entrained air voids. These attenuation results are then coupled with experimental measurements to develop an inversion procedure that directly predicts the size and volume fraction of entrained air voids in a cement paste specimen. Optical studies verify the accuracy of the proposed inversion scheme. These results demonstrate the effectiveness of using attenuation to measure the average size, volume fraction of entrained air voids and the existence of additional larger entrapped air voids in hardened cement paste. Finally, coherent and diffuse ultrasonic waves are used to develop a direct relationship between attenuation and water to cement (w/c) ratio. A phenomenological model based on the existence of fluid-filled capillary voids is used to help explain the experimentally observed behavior. Overall this research shows the potential of using ultrasonic attenuation to quantitatively characterize cement paste. The absorption and scattering losses can be related to the individual microstructural elements of hardened cement paste. By taking a fundamental, mechanics-based approach, it should be possible to add additional components such as scattering by aggregates or even microcracks in a systematic fashion and eventually build a realistic model for ultrasonic wave propagation study for concrete.
387

An Investigation On The Water Supply And Drainage Systems Of Historical Turkish Baths

Disli, Gulsen 01 February 2008 (has links) (PDF)
Historical Turkish baths still keeping their functional systems represent their original architectural and building technologies. Studies on the functional systems of historical baths are therefore needed to discover such technologies and to maintain them in working order. This study was conducted on a 15th century historical Turkish bath, Seng&uuml / l Hamami, in Ankara for assessment of its water supply and drainage systems. These systems comprised of hot and cold-water supply, wastewater and rainwater drainage, were examined in terms of their adequacy, capacity and faults. Comparisons were made with certain other historical Turkish baths to determine their original water storage and consumption capacities. The investigations were made by using non-destructive methods. Among them, the calculation methods used for discharge capacity assessment of drainage systems in Seng&uuml / l Hamami and consumption capacities of its water supply system were adapted and developed from the calculation methods used for contemporary buildings. Serious dampness problems arising from certain roof drainage faults were identified in the building. The wastewater collection and discharge system was found to have serious problems due to improper grading and inadequate flow dimensions of drains and wastewater channels. The ideal situation for the improvement of discharge systems was discussed together with some suggestions on the urgent remedial interventions, preventive measures and future improvements. The methods developed in this study were considered useful for the calculation of adequacy and capacity of wastewater and roof drainage systems and of water storage and consumption capacities of water supply system for the other historical baths.
388

Structural Identification, Damage Detection By Non-destructive Tests And Determining Axial Loads In Cables

Yucel, Mustafa Can 01 December 2009 (has links) (PDF)
Damage and condition identi&amp / #64257 / cation of existing structures using non-destructive tests is a common challenge that has been worked on for a long time. In this study, two di&amp / #64256 / erent methods were developed to &amp / #64257 / nd existing force on cables as well as determine bending characteristics (EI coe&amp / #64259 / cients) of beam like structures (such as bridges). Comparing forces in symmetrically placed cables or against values obtained from design drawings would indicate structural imbalance as well as &amp / #64257 / nding EI coe&amp / #64259 / cients at a number of segments on a bridge girder might indicate weak regions that might possibly have undergone structural damage, having weak connections, lost composite action etc. With the help of the proposed algorithm, the sti&amp / #64256 / ness parameters of bridges can be assessed and the location of any damage that is in the magnitude which can a&amp / #64256 / ect displacement behavior of system can be located. The developed methods are demonstrated using the values analytically obtained from the created models and the e&amp / #64256 / ectiveness of the algorithm is criticized. Furthermore, several damage scenarios on a scaled lab beam was used to test the application using real experimental data / including tests on undamaged beam (for identi&amp / #64257 / cation) and tests on the damaged beam. Additional experiments were conducted on a cable stretched in the laboratory instrumented using a load cell to measure instantaneous axial load on the cable and compare these values against the values obtained from the developed tension measurement device. The results are compared and conclusions are derived.
389

Comprehensive Path-sensitive Data-flow Analysis

Thakur, Aditya 07 1900 (has links)
Data-flow analysis is an integral part of any aggressive optimizing compiler. We propose a framework for improving the precision of data-flow analysis in the presence of complex control-flow. We initially perform data-flow analysis to determine those control-flow merges which cause the loss in data-flow analysis precision. The control-flow graph of the program is then restructured such that performing data-flow analysis on the resulting restructured graph gives more precise results. The proposed framework is both simple, involving the familiar notion of product automata, and also general, since it is applicable to any forward or backward data-flow analysis. Apart from proving that our restructuring process is correct, we also show that restructuring is effective in that it necessarily leads to more optimization opportunities. Furthermore, the framework handles the trade-off between the increase in data-flow precision and the code size increase inherent in the restructuring. We show that determining an optimal restructuring is NP-hard, and propose and evaluate a greedy heuristic. The framework has been implemented in the Scale research compiler, and instantiated for the specific problems of Constant Propagation and Liveness analysis. On the SPECINT 2000 benchmark suite we observe an average speedup of 4% in the running times over Wegman-Zadeck conditional constant propagation algorithm and 2% over a purely path profile guided approach for Constant Propagation. For the problem of Liveness analysis, we see an average speedup of 0.8% in the running times over the baseline implementation.
390

Air and Water Tightness in Building Envelopes - Evaluation of Methods for Quality Assurance

Gränne, Fredrik January 2001 (has links)
<p>The purpose of this work is to contribute to a process formaking buildings with good function and to avoid prematurefaults.</p><p>The design, construction and installation of low-slopedroofs are important parts of creating a durable building. Mostof the leakages in low-sloped roofs occur where materials withdifferent thermomechanical properties are joined together. Withbetter knowledge about these joints, the expected service lifecould better be estimated. Common roofing materials onlow-sloped roofs are roof membranes.</p><p>To avoid damages and to minimise energy consumption thedetection of air and water leaks is essential. It can bedifficult to localise a leak in e.g. a roof since water canflow far within the construction. Leakage detection can beapplied both as a quality assurance method after installationof low-sloped roofs and as field inspection methods. Theleakage detection can also be extended to terrace slabs and thewhole building envelope.</p><p>To investigate the strength of jointsbetween sheet metaland roofing membranes, several small-scale tests and somelarge-scale tests were performed. The test methods weredeveloped to match the loads that can be expected on this kindof joints.</p><p>A number of water leak-detection methods were evaluatedthrough application on test roofs. Some of the methods todetect leaks on low-sloped roofs can also be used to detect airleakage in other parts of the building envelope. To develop andevaluate air leak-detection procedures, selected methods wereused in two case studies.</p><p>The circumstances regarding welding of the material jointswere found to have great impact on the strength. The roofshould be designed so no long-term strain will appear since acomparatively low stress may damage the joint over time.</p><p>The performance of the leak-detection methods depends on theroofing material. All methods tested were an improvementcompared to visual inspections. Different recommendedapproaches for leakage detection and quality control is given.The case studies show that air leakage detection could beperformed with good accuracy. The potential difference methodcould without doubt be a tool for leakage localisation inwaterproofing layers both on roofs and in terrace slabs.</p><p><b>Keywords:</b>Roofing, roof membrane, durability,waterproofing, leakage, wind-load, non-destructive testing,NDT, BSL4, BSL3, air leakage, building envelope</p>

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