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Prase, Björn. "Characteristics of hydrodynamic plain bearings with bonded coating." Technische Universität Chemnitz, 2018. https://monarch.qucosa.de/id/qucosa%3A21228.
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Increasing ecological and economic pressures, as well as increased technical requirements, have given rise to the need for research into alternative wear layers for hydrodynamic plain bearings. Previous investigations have tested and researched the bonded coating GL92. It has been possible to demonstrate that the bonded coating (plastic base) is a viable alternative to a conventional white metal alloy.
However, this coating was not able to address all the issues experienced by industrial users, for example the behaviour of the system (changes to operating properties) during penetration of particles, or behaviour in a mixed friction area. The literature has not – or not sufficiently – answered the questions relating to damage patterns and damage tolerance. Therefore, regardless of the proven benefits, industrial use of this coating is currently not possible or is connected with significant risks.
In the study, tests were carried out in the mixed friction area (start-stop testing, emergency testing without oil, insufficient lubrication tests) as well as in the hydrodynamic area. The comparative tests were performed on different wear layer materials. This paper demonstrates and discusses the results for both a conventional white metal alloy bearing and for the bearing with bonded coating (GL92).
Depending on the operating point, the bearing systems exhibit significant differences at the maximum bearing load, lubricating film pressure distribution and maximum bearing temperature. The investigation has proven that GL92 is a technically useful alternative to conventional wear layers.
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Chandran, Davannendran. "Experimental investigation into the physico-chemical properties changes of palm biodiesel under common rail diesel engine operation for the elucidation of metal corrosion and elastomer degradation in fuel delivery system." Thesis, University of Nottingham, 2017. http://eprints.nottingham.ac.uk/35228/.
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Compatibility of fuel delivery materials (FDM) with biodiesel fuel in the fuel delivery system (FDS) under real-life common rail diesel engine (CRDE) operation poses a challenge to researchers and engine manufacturers alike. Although standard methods such as ASTM G31 and ASTM D471 for metals and elastomers, respectively, are deemed suitable for evaluating the effects of water content, total acid number (TAN) and oxidation products in biodiesel on FDM degradation, they do not resemble the actual engine operation conditions such as varying fuel pressure/temperature as well as the presence of a wide range of materials in the FDS of a diesel engine. Hence, the current allowable maximum 20 vol% of biodiesel with 80 vol% of diesel (B20) for use in diesel engines to date is debatable. Additionally, biodiesel utilization beyond B20 is essential to combat declining air quality and to reduce the dependence on fuel imports. This thesis aims to elucidate the actual compatibility present between FDM and biodiesel in the FDS under real-life CRDE operation. This was achieved through multi-faceted experimentations which commenced with analyses on the deteriorated palm biodiesel samples collected during and after CRDE operation. Next, the fuel properties which should be emphasized based on the deteriorated fuel were determined. This was then followed by ascertaining the effects of the emphasized fuel properties towards FDM degradation. Ultimately, the actual compatibility of FDM with biodiesel under engine operation through modified immersion investigations was determined. FDM degradation acceleration factors such as oxidized biodiesel, TAN and water content were eliminated since these factors were not affected based on the analysed fuel samples collected after engine operation. No oxidation products such as aldehydes, ketones and carboxylic acids were detected while the TAN and water content were within 0.446% and 0.625% of their initial values, respectively. Instead, the biodiesel’s dissolved oxygen (DO) concentration and conductivity value were not only found to have changed during and after engine operation by -93% and 293%, respectively, but were also found to have influenced biodiesel deterioration under engine operation. These two properties were subsequently discovered to have adversely affected FDM degradation independently. The copper corrosion rate and nitrile rubber (NBR) volume change increased by 9% and 13%, respectively, due to 22% increase in the conductivity value. In contrast, the copper corrosion rate and NBR volume swelling reduced by 91% and 27%, respectively, due to 96% reduction in the DO concentration. Ultimately, copper corrosion and NBR degradation were determined to be lowered by up to 92% and 73%, respectively, under modified immersion as compared to typical immersion condition. These outcomes distinctly show that acceptable to good compatibility is present between FDM and biodiesel under CRDE operation. The good compatibility is strongly supported since only a maximum lifespan reduction of 1.5 years is predicted for metal exposed to biodiesel as compared to diesel for a typical component lifespan of 15 years. For the elastomers, acceptable compatibility is found present between elastomer and biodiesel based on the determined 11% volume change which conforms to the tolerance level of elastomer degradation as stated by the elastomer manufacturers. These are especially true for the evaluated metals and elastomers investigated under the modified laboratory immersion which replicates similar conditions to a real-life CRDE. Overall, this work has contributed to the advancement of knowledge and application of biodiesel use in diesel engines.
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Park, Han-Up. "Changes in Operating Margins During a Sales Decline and Abnormal Returns." Diss., Temple University Libraries, 2017. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/464964.
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Business Administration/AccountingPh.D.
I examine the implications of changes in operating profit margins during a sales decline for future earnings and abnormal stock returns. When sales decrease, managers decide whether to cut slack resources. Managers who are optimistic about their future operations often retain slack resources in anticipation of resurging sales, thereby decreasing concurrent profitability. Conversely, managers who are pessimistic about their future operations typically reduce slack resources to gain efficiency, thereby increasing concurrent profitability. I find that analysts and investors persistently underestimate the future profitability of firms that exhibit a large decrease in current profitability. I also find that subsequent quarterly earnings announcements gradually reveal future profitability, resulting in concentrated positive abnormal returns in short pre-announcement windows for about a year after a sales decline. These results suggest that analysts and investors have difficulties evaluating managers’ resource adjustment decisions when a large decrease in concurrent profitability can indicate managers’ optimistic expectations.
Temple University--Theses
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Leimalm, Ulrika. "Pellet reduction properties under different blast furnace operating conditions." Licentiate thesis, Luleå : Luleå tekniska universitet/Tillämpad kemi och geovetenskapProcessmetallurgi, 2006. http://epubl.ltu.se/1402-1757/2006/67/LTU-LIC-0667-SE.pdf.
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Chan, Chee-Wan. "Effects of powered harrow operating parameters on soil physical properties." Connect to resource, 1992. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1200585211.
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Boström, Patrik. "Revisiting Observed Changes in Cloud Properties over Europe." Thesis, Uppsala universitet, Luft-, vatten och landskapslära, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-179997.
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The Earth’s atmosphere is a vulnerable system which is easily changed by micro- and macrophysical variations. Big decreases in pollution levels of sulfur dioxide over Central Europe from 1980s to 2000s led to decreased mass concentration of atmospheric solid and liquid particles. This gives the opportunity to investigate how these particles influence the atmosphere. Newly released satellite climatology data was used to analyze statistics of cloud properties during four years in the high polluted atmosphere (1985-88) and four years in the less polluted atmosphere (2004-07). These two periods were investigated in collaboration with Atmospheric Remote Sensing Unit of the research department of the Swedish Meteorological and Hydrological Institute (SMHI). Cloud top temperature of liquid clouds over polluted regions during the earlier period was colder by more than 2 K and more than 5 K for only optical thin liquid clouds. The changes in mass concentrations of atmospheric particles derived by the sulfur dioxide emissions are shown to be a highly possible factor to the observed cloud changes.Jordens atmosfär är ett känsligt system som lätt förändras av mikro- samt makrofysikaliska variationer. Stora minskningar i föroreningsnivåer av svaveldioxid över centrala Europa från 1980 till 2000-talet ledde till minskade masskoncentrationer av fasta och flytande atmosfäriska partiklar. Detta ger en möjlighet att undersöka hur dessa partiklar påverkar atmosfären. Nyligen utvecklad klimatologisk satellitdata användes för att analysera statistik av molnegenskaper under fyra år i en högt förorenad atmosfär (1985-88) och fyra år i en mindre förorenad atmosfär (2004-07). De två perioderna undersöktes i samarbete med Enheten för atmosfärisk fjärranalys av forskningsavdelningen till Sveriges meteorologiska och hydrologiska institut (SMHI). Molntopptemperaturen för moln i vätskefas över förorenande områden under den tidigare perioden var mer än 2 K kallare och mer än 5 K kallare för endast optiskt tunna moln i vätskefas. Förändringarna i masskoncentrationer för atmosfäriska partiklar och droppar med svaveldioxidusläpp som ursprung visas vara högst möjliga att ligga bakom de observerade molnförändringarna.
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Owe-Larsson, Björn. "Changes in neuronal properties induced by neurotropic infections /." Stockholm, 2000. http://diss.kib.ki.se/2000/91-628-4300-1/.
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Kilborn, Michael John. "Postnatal changes in electrophysiological properties of rat cardiomyocytes." Thesis, University of Oxford, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.292673.
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Belova, Olesya, Fatima Jamil, and Chiara Troncatti. "POST ENTRY CHANGES: A case study of large Italian MNCs operating in BRIC markets." Thesis, Uppsala University, Department of Business Studies, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-126772.
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In this paper we aim to identify the most important factors that influence the decisions made by large Western MNCs concerning post entry changes (PEC) in the BRIC markets. Thiss tudy attempts to explain processes and reasons why these changes take place. In addition we make a comparison between strategies followed and the differences between them for each of the BRIC markets.Most academic literature focuses on entry mode theories, however little has been written onPEC. PEC today is a hot topic in the current international business environment. This isevident in the market as many Western MNCs that invested in emerging markets throughJoint Ventures (JV) during the late 1980s and 1990s are now restructuring their strategies in order to further their growth (Luo, 2007).The paper uses a qualitative study to explain and explore PEC strategies in each of the four BRIC markets, using case studies of three Italian large MNCs: Artsana, De Longhi and Luxottica.The study finds that firstly BRIC markets should not be seen as a whole, as academic literature has a tendency to suggest. Secondly, the study finds that country-specific conditions directly affect PEC choices and decisions differently in each market. We have identified a number of variables which influence PEC, of these economic conditions and institutional context pressures were found to be the most important determinants for PEC within the MNCs studied. This study will help management to better choose appropriate PEC and set the most suitable operational mode for each specific environment.
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Holland, Jonathan Eddison. "Changes in soil physical properties under raised bed cropping /." Connect to thesis, 2006. http://eprints.unimelb.edu.au/archive/00002537.
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Schleifenbaum, Stefan, Torsten Prietzel, Gabriela Aust, Andreas Boldt, Sebastian Fritsch, Isabel Keil, Holger Koch, et al. "Acellularization-induced changes in tensile properties are organ specific." Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-204096.
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Introduction: Though xenogeneic acellular scaffolds are frequently used for surgical reconstruction, knowledge of their mechanical properties is lacking. This study compared the mechanical, histological and ultrastructural properties of various native and acellular specimens. Materials and methods: Porcine esophagi, ureters and skin were tested mechanically in a native or acellular condition, focusing on the elastic modulus, ultimate tensile stress and maximum strain. The testing protocol for soft tissues was standardized, including the adaption of the tissue’s water content and partial plastination to minimize material slippage as well as templates for normed sample dimensions and precise cross-section measurements. The native and acellular tissues were compared at the microscopic and ultrastructural level with a focus on type I collagens. Results: Increased elastic modulus and ultimate tensile stress values were quantified in acellular esophagi and ureters compared to the native condition. In contrast, these values were strongly decreased in the skin after acellularization. Acellularization-related decreases in maximum strain were found in all tissues. Type I collagens were well-preserved in these samples; however, clotting and a loss of cross-linking type I collagens was observed ultrastructurally. Elastins and fibronectins were preserved in the esophagi and ureters. A
loss of the epidermal layer and decreased fibronectin content was present in the skin. Discussion: Acellularization induces changes in the tensile properties of soft tissues. Some of these changes appear to be organ specific. Loss of cross-linking type I collagen may indicate increased mechanical strength due to decreasing transverse forces acting upon the scaffolds, whereas fibronectin loss may be related to decreased load-bearing capacity. Potentially, the alterations in tissue mechanics are linked to organ function and to the interplay of cells and the extracellular matrix, which is different in hollow organs when compared to skin.
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Mendez, Casal M. J. "Changes in rock mechanics properties due to formation damage." Thesis, Heriot-Watt University, 2004. http://hdl.handle.net/10399/357.
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Makarem, Maisam. "Developmental changes in the properties of mouse mammary stem cells." Thesis, University of British Columbia, 2013. http://hdl.handle.net/2429/44592.
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Recent findings have suggested that the normal breast is a hierarchically organized tissue in which differentiated cells incapable of further division are continuously produced from a common, self-sustaining stem cell population. However, little is known about the origin, timing or properties of mammary stem cells during development. In some tissues, cells with tissue-specific stem cell properties are known to develop after the first recognizable tissue elements are in place, and these early stem cells also have qualitatively different properties than their adult counterparts. I hypothesized that this would also be true of the mammary gland. I therefore designed a series of experiments to identify, isolate and characterize mammary stem cells when they first appear during development. I also established robust in vitro and in vivo systems to enable their growth and regenerative potential to be compared with that of similarly assessed adult mammary stem cells. I found that a reproducibly detectable mammary stem cell population with transplantable regenerative activity is first detected late in gestation after the early mammary bud is formed. This population then expands in parallel with a more prevalent population detectable as cells with clonogenic activity in vitro. I also discovered that single EpCAM⁺ fetal mammary epithelial cells in semi-solid Matrigel cultures supplemented with added irradiated fibroblasts have a direct and inducible but highly variable growth and regenerative potential that is, nevertheless greater on average than that of their adult counterparts. Analysis of the 4-week regenerative activity of fetal as compared to adult mammary epithelial cells in vivo also indicated an increased output of total cells and clonogenic progenitors from the fetal cells, again with marked variation in this assay. Analysis of published gene expression profiles of fetal and adult mammary enriched stem cell subsets have suggested a number of changes in the external cues that govern their responses as well as the intrinsic molecular network they use to execute these responses. Further elucidation of developmentally-determined changes in the properties of mammary stem cells are likely to be important in understanding perturbations of adult mammary cells that endow them with malignant properties.
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Lau, King Cheung. "Crystallization of amorphous alloy and the associated changes of properties." access abstract and table of contents access full-text, 2005. http://libweb.cityu.edu.hk/cgi-bin/ezdb/dissert.pl?msc-ap-b21174453a.pdf.
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Thesis (M.Sc.)--City University of Hong Kong, 2005.At head of title: City University of Hong Kong, Department of Physics and Materials Science, Master of Science in materials engineering & nanotechnology dissertation. Title from title screen (viewed on Sept. 1, 2006) Includes bibliographical references.
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Rowland, Joanne. "Assessing changes in the surface properties of a crystalline material." Thesis, University of London, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.533545.
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Ramos, Jorgelina. "Mechanisms underlying the age-related changes in muscle contractile properties." Thesis, Manchester Metropolitan University, 2016. http://e-space.mmu.ac.uk/617184/.
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Changes in isometric fore and power output in old age have been extensively studied for but less attention has been paid to eccentric contractions where, paradoxically, there are suggestions that eccentric strength is maintained with ageing. Decreased isometric force and relatively increased eccentric strength are feature of permeabilised single fibres developed in the presence of high inorganic phosphate (Pi) and it is possible that there may be a connection between the changes in contractile function seen with ageing and the actions of Pi. The work described in this thesis involved mouse soleus fibres and had two major aims. The first was to understand more about the nature of the response to stretch and the role of Pi, especially concerning the rate of stress relaxation which may provide information about cross bridge kinetics. The second aim was to study to what extent changes in cross bridge function account for the age related changes in contractile characteristics. In the first study, three features of the force response to stretch, peak force at the end of the ramp stretch, the stress relaxation and the residual force enhancement were observed in young mouse single fibres at different velocities of stretch. Stress relaxation was analysed as a double exponential decay with a constant component, force enhancement (FE). The speed of the fast exponential component increased with speed of stretch and the proportions of the fast component (A2) relative to the slow component (A1) also increased with speed of stretch. FE was independent of speed. Addition of Pi slowed stress relaxation and increased the proportion of the slow component. One explanation is that the slow component represents the detachment of attached cross bridge states that generate little or no force while the fast component is due to detachment of cross bridges in a high force state. FE is probably due to stretching of a series compliance such as titin. The response to stretch varied with age in complex ways. In mice aged 3, 10 and 18-month-old there were small but non-significant increases in the force sustained during stretch relative to the isometric force together with a similar stress relaxation. However, with 32-month-old fibres the stress relaxation was faster than seen with young fibres consistent with an increase in the proportion of the fast A2 cross bridge intermediate state. Adding Pi to the oldest fibres changed the proportions of A1 and A2 to those seen in young fibres in the absence of Pi. The results largely contradict previous reports of the relative preservation of eccentric force with age, which may be due to simple change in fibre type composition of whole muscles, but do indicate possible changes in cross bridge kinetics affecting the transition from low to high force states.
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Baard, Roelof Stephanus. "An empirical analysis of the relationship between operating cash flows and dividend changes in South Africa." Thesis, Stellenbosch : Stellenbosch University, 2008. http://hdl.handle.net/10019.1/18154.
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Thesis (MBA)--Stellenbosch University, 2008.ENGLISH ABSTRACT: The purpose of this study was to investigate the relationship between dividend changes and operating cash flows in South Africa. Previous studies on the relationship in developed markets established that the main determinants of dividend changes are current year earnings and preceding dividend levels. The dividend changes-operating cash flows relationship was successfully studied in the developing market of Nigeria. The procedures and arguments used in this study were largely based on studies undertaken by Charitou and Vafeas (1998) and Adelegan (2003). The relationship was studied by selecting 60 companies that have been listed on the Johannesburg Stock Exchange from 1990 to 2005. A multiple regression model was used in this study to investigate the relationship between dividend changes and operating cash flows. The multiple regression results revealed that there is a significant positive relationship between dividend changes and operating cash flows. The results also revealed that there is a significant positive relationship between dividend changes and profits after tax and a significant negative relationship between dividend changes and the previous year's dividend yield. Relative to profit after tax and operating cash flows, the previous year's dividend yield has the strongest relationship with dividend changes. The strength of the variables in explaining dividend changes has changed over time. In the study, the multiple regression equation was estimated for three different periods, 1990 to 1993, 1994 to 1999 and 2000 to 2005. In the period 1994 to 2005, operating cash flows showed a significant positive relationship with dividend changes. In all three periods, the previous year's dividend yield showed a significant negative relationship with dividend changes and was also relative to profit after tax and operating cash flows, the strongest determinant of dividend changes in all three periods. In the period 1990 to 1999, profits after tax had a significant positive relationship with dividend changes. The results showed that operating cash flows, over time explain more of dividend changes than profits after tax. The study also investigated factors that have the potential to influence the relationship between dividend changes and operating cash flows. The multiple regression results revealed that growth prospects, levels of leverage and the size of a company did not significantly influence the dividend changes-operating cash flows relationship.
AFRIKAANSE OPSOMMING: Die doel van hierdie studie was om die verwantskap tussen dividendveranderinge en kontant uit bedryfsaktiwiteite te ondersoek. Vorige studies oor die verwantskap wat met betrekking tot ontwikkelende markte onderneem is, het bevind dat die hoof determinante van dividendveranderinge die huidge jaar se verdienste en die voorafgaande jaar se dividendopbrengste is. Die dividendveranderinge-kontant uit bedryfsaldiwiteite verwantskap is suksesvol bestudeer in die ontwikkelende mark van Nigerië. Die prosedures en argumente wat gebruik is in hierdie studie is hoofsaaklik op die studies van Charitou en Vafeas (1998) en Adelegan (2003) gebaseer. Die verwantskap is bestudeer deur 60 maatskappye te selekteer wat vanaf 1990 tot 2005 op die Johannesburg se Effektebeurs genoteerd was. 'n Meervoudige regressie model is in die studie gebruik om die verwantskap tussen dividendveranderinge en kontant uit bedryfsaktiwiteite te ondersoek. Die meervoudige regressieresultate het gewys dat daar 'n positiewe betekenisvolle verwantskap tussen dividend veranderinge en kontant uit bedryfsaktiwiteite is. Die resultate het ook gewys dat daar 'n positiewe betekenisvolle verwantskap is tussen dividendveranderinge en wins na belasting asook, 'n negatiewe betekenisvolle verwantskap tussen dividendveranderinge en die voorafgaande jaar se dividendopbrengs. Relatief tot wins na belasting en kontant uit bedryfsaktiwiteite, het die voorafgaande jaar se dividendopbrengste 'n sterker verwantskap met dividendveranderinge gehad. Die sterkte van die veranderlikes in die verduideliking van dividendveranderinge het met verloop van tyd verander. Die meervoudige regressie vergelyking is in die studie vir drie verskillende periodes geraam, naamlik vir 1990 tot 1993, 1994 tot 1999 en 2000 tot 2005. In die periode 1994 tot 2005 was daar 'n positiewe betekenisvolle verwantskap tussen dividendveranderinge en kontant uit bedryfaktiwiteite. Al drie periodes het 'n negatiewe betekenisvolle verwantskap tussen dividendveranderinge en die voorafgaande jaar se dividendopbrengs getoon. Die voorafgaande jaar se dividendopbrengs was ook relatief tot wins na belasting en kontant uit bedryfsaktiwiteite die sterkste determinant van dividendveranderinge in al drie periodes. Daar was 'n positiewe betekenisvolle verwantskap tussen dividendveranderinge en wins na belasting in die periode van 1990 to 1999. Die resultate toon dat kontant uit bedryfsaktiwiteite met verloop van tyd meer verklaar van dividendverandringe as wins na belasting. Die studie het ook faktore wat die verwantskap tussen dividendveranderinge en kontant uit bedryfsaktiwiteite potensieël kan beïnvloed, ondersoek. Die meervoudige regressieresultate het getoon dat groeimoontlikhede, hefboomfinansiering en die grootte van 'n maatskappy nie die verwantskap tussen dividendveranderinge en kontant uit bedryfsaktiwiteite betekenisvol beïnvloed nie.
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Rhodes, Darren P. "The sensitivity of noise in the community to changes in aircraft design parameters and operating practices." Thesis, Loughborough University, 1998. https://dspace.lboro.ac.uk/2134/27110.
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Environmental factors, such as noise and emissions have begun to play a significant role in the design of new aircraft. Although advances in propulsion technology have reduced source noise levels significantly over the past few decades, it is becoming increasingly difficult to project similar advances for the next few decades. It is likely however that some noise benefits may come from improvements in aircraft performance and from changes in operational procedures. In order for such developments to be analysed at the conceptual design stage, an integrated conceptual aircraft design and aircraft noise model is required that enables the designer to rapidly assess the effect of key design parameters on reference noise levels and noise contour area.
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BORGSTROM, MARK CRAIG. "ESTIMATION OF RECEIVER OPERATING CHARACTERISTIC (ROC) CURVE PARAMETERS: SMALL SAMPLE PROPERTIES OF ESTIMATORS." Diss., The University of Arizona, 1987. http://hdl.handle.net/10150/184127.
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When studying detection systems, parameters associated with the Receiver Operating Characteristic (ROC) curve are often estimated to assess system performance. In some applied settings it is often not possible to test the detection system with large numbers of stimuli. The resulting small sample statistics many have undesirable properties. The characteristics of these small sample ROC estimators were examined in a Monte Carlo simulation. Three popular ROC parameters were chosen for study. One of the parameters was a single parameter index of system performance, Area under the ROC curve. The other parameters, ROC intercept and slope, were considered as a pair. ROC intercept and slope were varied along with sample size and points on the certainty rating scale to form a four way factorial design. Several types of estimators were examined. For the parameter, Area under the curve, Maximum Likelihood (ML), three types of Least Squares (LS), and Distribution Free (DF) estimators were considered. Except for the DF estimator, the same estimators were considered for the parameters, intercept and slope. These estimators were compared with respect to three characteristics: bias, efficiency, and consistency. For Area under the curve, the ML estimator was the least biased. The DF estimator was the most efficient, and all the estimators except the DF estimator appeared to be consistent. For intercept and slope the LS estimator that minimized vertical error of the points from the ROC curve (line) was the least biased for both estimators. This LS estimator was also the most efficient. This estimator along with the ML estimator also appeared to be the most consistent. The other two estimators had no significant trend toward consistency. These results along with other findings, illustrate that different estimators may be "best" for different sample sizes and for different parameters. Therefore, researchers should carefully consider the characteristics of ROC estimators before using them as indices of system performance.
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Davies, William Huw. "Estimating aerosol properties using CHRIS/PROBA." Thesis, Swansea University, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.678572.
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Scanlan, Craig Anthony. "Processes and effects of root-induced changes to soil hydraulic properties." University of Western Australia. School of Earth and Environment, 2009. http://theses.library.uwa.edu.au/adt-WU2009.0188.
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[Truncated abstract] Root-induced changes to soil hydraulic properties (SHP) are an essential component in understanding the hydrology of an ecosystem, and the resilience of these to climate change. However, at present our capacity to predict how roots will modify SHP and the consequences of this is limited because our knowledge of the processes and effects are highly fragmented. Also, current models used to investigate the relationship between plants and root-induced changes to SHP are based on empirical relationships which have limited applicability to the various and often contrasting ecosystems that occur. This thesis focuses specifically on the quantifying the processes by which roots modify SHP and developing models that can predict changes to these and the water balance. Both increase and decreases in saturated hydraulic conductivity have been attributed to the presence of roots. In general, decreases occur when the root system is relatively young, and increases occur when the roots senesce and begin to decay, creating voids for water flow. The evidence available suggests that the change in pore geometry created by roots is the dominant process by which roots modify SHP because they are more permanent and of a greater magnitude than changes to fluid properties or soil structure. We first quantified the effects of wheat roots on SHP of a coarse sand with a laboratory experiment where we measured changes in both SHP and the root system at 3, 5, 7 and 9 weeks after sowing (weeks). ... The main message that can be drawn from this thesis is that root-induced changes to SHP are dynamic, and dependent upon the combination of soil texture, connectivity of root-modified pores and the ratio of root radius to pore radius. Consequently, root-induced changes to the water balance have the same dependencies. The work in this thesis provides a significant first step towards improving our capacity to predict how roots modify soil hydraulic properties. By defining the range for the parameters used to predict how the soil is modified by roots, we are able to make quantitative assessments of how a property such as hydraulic conductivity will change for a realistic circumstance. Also , for the first time we have measured changes in soil hydraulic properties and roots and have been able to establish why a rapid change from a root-induced decrease to increase in Ks occurred. The link between physiological stage of the root system, and the changes that are likely to occur has implications for understanding how roots modify SHP: it may provide an effective tool for predicting when the switch from a decrease to increase occurs. Further work is required to test the validity of the assumptions we have made in our models that predict changes to SHP. While we have endeavoured to define the parameter space for those parameters that we have introduced, there is still some uncertainty about the connectivity of root-modified pores. Also, the parameterisation of the soil domain with roots is based upon work that measures 'fine' roots only which may not provide a true representation of the effect trees and perennial shrubs have on SHP. It is inevitable that root-induced changes to SHP will affect the fate of solutes in the soil, and temporal dynamics of root-induced changes to these may be particularly important for the timing of nutrient and pesticide leaching.
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Pencer, Jeremy Samuel. "Light scattering characterization of extruded vesicles, shape changes and mechanical properties." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/NQ61984.pdf.
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Walden, Steven J. "Progressive changes in the properties of bone during soft tissue decomposition." Thesis, Cardiff University, 2017. http://orca.cf.ac.uk/105027/.
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Changes in bone characteristics during soft tissue putrefaction were investigated over 140 days, equating to between 638 and 1450 cumulative cooling degree days (CCDD) depending on ambient temperature using a porcine experimental model in surface and burial depositions. The hypothesis that changes observed in bone characteristics during soft tissue putrefaction could be utilised for possible forensic applications was proved. Human bones were tested for comparison. The techniques used were colorimetric analysis of staining, measurement of micro-crack lengths (in the order of 0.1 to 1.0 mm) on fractured bone surfaces under scanning electron microscopy, inductively coupled plasma optical emission spectroscopy elemental profiling, thermogravimetric analysis (TGA), zoological mass spectrometry profiling non-collagenous peptide content, and Vickers hardness testing. The findings pertaining to the experimental porcine bone samples were as follows. Stain colour did not equalise between periosteal and fractured cortical bone surfaces. The fracture is widely considered perimortem if said surfaces are homogeneous in colour and postmortem if different. Observed inconsistences in colour change limit the potential of this technique as a potential forensic test of postmortem interval (PMI). After 28 CCDD, shorter intersecting micro-cracks changed to longer linear micro-cracks tracking lamellae. A longitudinal to tangential Vickers hardness (HV) ratio of 1.5 to 1 associated with minimal decomposition indicated 250 CCDD or less elapsed. The same ratio associated with marked decomposition indicated 1450 CCDD or more elapsed. A ratio of less than 1:1 indicated 250 to 1450 CCDD. Decreases in iron, sodium and potassium concentrations associated with tissue fluids can determine if bone is in the early stages of decomposition. TGA correlation of water loss between 22 and 100˚C with observed changes in micro-crack lengths, HV, and elemental profiles suggested progressive dehydration as the underlying common factor. These techniques demonstrated some potential to be developed as forensic tests of PMI. As no correlation with PMI was evident with proteomic profiling of non-collagenous peptides, no such potential was demonstrated.
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Englehart, Amy N. 1972. "Changes in a gel's electrical properties due to exposure to air." Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/87178.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2002.Includes bibliographical references (p. 61-62).
by Amy Nicole Englehart.
S.M.
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Pandey, Rohit. "Changes in properties of coal as a result of continued bioconversion." OpenSIUC, 2015. https://opensiuc.lib.siu.edu/theses/1745.
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Microbial actions on coal have long been identified as a source of methane in coalbeds. Andrew Scott (1995) was the first to propose imitating the natural process of biogenic gasification, possibly leading to recharging coalbed methane (CBM) reservoirs, or setting up natural gas reservoirs in non-producing coalbeds. This study was aimed at identifying the changes in coal properties that affect gas deliverability in coal-gas reservoirs, when treated with microbial consortia to generate/enhance gas production. The experimental work tested the sorption and diffusion properties for the coal treated and, more importantly, the variation in the relevant parameters with continued bio-conversion since these are the first two phenomena in CBM production. During the first phase, single component sorption-diffusion experiments were carried out using pure methane and CO2 on virgin/baseline coals, retrieved from the Illinois basin. Coals were then treated with nutrient amended microbial consortia for different periods. Gas production was monitored at the end of thirty and sixty days of treatment, after which, sorption-diffusion experiments were repeated on treated coals, thus establishing a trend over the sixty-day period. The sorption data was characterized using Langmuir pressure and volume constants, obtained by fitting it over the Langmuir isotherm. The diffusion coefficient, D, was estimated by establishing the variation trend as a function of pore pressure. The pressure parameter was considered critical since, with continued production of methane, the produced gas diffuses into the coal matrix, where it gets adsorbed with increasing pressure. During production, the pressure decreases and the process is reversed, gas diffusing out of the coal matrix and arriving at the cleat system. The results indicated an increase in the sorption capacity of coal as a result of bioconversion. This was attributed to increased pore surface areas as a result of microbial actions. However, significant hysteresis was observed during desorption of methane and was attributed to preferential desorption from sorption sites in the pathways leading to pore cavities. This is corroborated by the increased rates of diffusion, especially for methane, which exhibited rates higher than that for CO2. This contradicted the results for untreated/baseline coal, which were in agreement with previous studies. Effort was made to explain this anomaly by the non-monotonic dependence of effective diffusion coefficient on the size of the diffusing particles, where in coalbed environments, CO2 has smaller kinetic diameter than methane.
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Goodrich, Thomas William. "Thermophysical Properties and Microstructural Changes of Composite Materials at Elevated Temperature." Thesis, Virginia Tech, 2009. http://hdl.handle.net/10919/35900.
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Experimental methods were developed and used to quantify the behavior of composite materials during heating to support development of heat and mass transfer pyrolysis models. Methods were developed to measure specific heat capacity, kinetic parameters, microstructure changes, porosity, and permeability. Specific heat and gravimetric data for kinetic parameters were measured with a simultaneous differential scanning calorimeter (DSC) / thermogravimetric analyzer (TGA). Experimental techniques were developed for quantitative specific heat measurement based on ASTM standards with modifications for accurate measurements of decomposing materials. An environmental scanning electron microscope (ESEM) was used in conjunction with a heating platform to record real-time video of microstructural changes of materials during decomposition and cooling following decomposition. A gas infusion technique was devised to measure porosity, in which nitrogen was infused into the pores of permeable material samples and used to determine the open-pore porosity of the material. Permeability was measured using a standard pressure differential gas flow technique with improvements over past sealing techniques and modifications to allow for potential high temperature use.
Experimental techniques were used to measure the properties of composite construction materials commonly used in naval applications: E-glass vinyl ester laminates and end-grain balsa wood core. The simultaneous DSC/TGA was used to measure the apparent specific heat required to heat the decomposing sample. ESEM experiments captured microstructural changes during decomposition for both E-glass vinyl ester laminate and balsa wood samples. Permeability and porosity changes during decomposition appeared to depend on microstructural changes in addition to mass fraction.Master of Science
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Moughrabiah, Wajeeh O. "Effect of operating parameters and particle properties on electrostatics in gas-solid fluidized beds." Thesis, University of British Columbia, 2009. http://hdl.handle.net/2429/12867.
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The influences of operating pressure, temperature and gas velocity on electrostatics in a fluidized bed of glass beads and different grades of polyethylene resin were investigated in a fluidization column of 150 mm inner diameter and 2.0 m height. Eight collision probes at different levels and radial positions measured the electrostatics in the bed. The electrostatics increased as pressure increased, probably due to an increase in bubble rise velocity, frequency and volume fraction. As the pressure increased, particle-particle and particle-wall collisions near the distributor and wall contributed heavily to charge generation. Temperature also played a role. At higher temperatures (up to 90°C), the polarity of net cumulative charge in the bed reversed. As the superficial gas velocity increased, the electrostatics increased. However, at higher gas velocities, the polarity in the freeboard was opposite to that in the bed, indicating that fines entrained from the column carried charges, resulting in a net charge of opposite polarity to that inside the bed.
For Geldart group B particles the degree of electrification in the bed slightly increased with decreasing particle size. Charging for group A particles was significantly greater than for group B particles. For binary mixtures of group A and B particles the electrostatics increased as the proportion of small particles increased.
As the relative humidity (RH) of fluidizing air increased, the electrostatics decreased. For the RH range (5-30%) explored, the sensitivity of the charging to RH varied significantly depending on the location of the probes.
As the proportion of fine glass beads (<30 µm) increased to 2.0 wt% in a fluidized bed of large glass beads (574 µm), the electrostatics in the bed decreased, likely because the fines acted as spacers between larger particles.
The electrostatics decreased as the proportion of an antistatic agent (Larostat) increased from 0.0 to 0.5 wt%, because Larostat tends to adsorb moisture and attach to the surface of the glass beads, consequently enhancing their surface conductivity. However, the degree of electrification increased when the wt% of Larostat exceeded 1.0%, likely due to the tendency of Larostat particles to adsorb water and to agglomerate.
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Lai, Chee-Hoong. "Physical ageing and dimensional changes of acrylate polymers /." Title page, table of contents and summary only, 1992. http://web4.library.adelaide.edu.au/theses/09PH/09phl185.pdf.
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Choy, Suk-fong, and 蔡淑芳. "Quaternary environmental changes and engineering properties of offshore soils in Hong Kong." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2004. http://hub.hku.hk/bib/B31245250.
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Zhang, Yan. "Changes in microstructure and mechanical properties of P91 weld metal during creep." Thesis, University of Nottingham, 2009. http://eprints.nottingham.ac.uk/11419/.
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Creep failure of the weld structure in P91 steel components in high temperature power plant applications is often a key factor limiting the lifetime of the components. Whilst creep failure in weld heat-affected zone (HAZ) regions has been studied widely, the creep properties of the weld metal itself have been less well documented. In this work, the creep response of P91 weld metal in isolation was investigated in terms of microstructural evolution and mechanical properties. The microstructural examination of P91 multi-pass weld metal revealed a typical weld metal structure including columnar regions and refined regions. The columnar region exhibited high hardness whilst the refined region exhibited lower hardness. The anisotropic creep behaviour of P91 weld metal was observed in creep tests of both longitudinal and transverse specimens at 650ºC and various stress levels. This behaviour can be correlated with the microstructural anisotropy observed, where longitudinal specimens with banded columnar regions and refined regions parallel to the stress axis had longer creep life than transverse specimens with overlapped typical-shape beads. Longitudinal weld specimens showed higher strain to failure than transverse specimens. The microstructural investigation of creep tested P91 weld metal revealed two primary modes of creep fractures. In addition to creep fractures along columnar grain boundaries (typical of weld metal creep failure), creep fractures were also found along creep-weak white-bands which had formed at the inter-bead boundaries. The white-band regions consisted of material where the M23C6 carbides had dissolved during creep testing; the loss of carbides had allowed recrystallisation of the martensitic structure to ferrite and consequently this material was much softer than the bulk weld metal. The element mapping over the weld metal by laser-induced breakdown spectroscopy (LIBS) demonstrated that there was significant inhomogeneity in the distribution of certain elements, most significantly, chromium, manganese and molybdenum. This inhomogeneity resulted in strong activity gradients in carbon (even though the carbon concentration was homogeneous following welding) resulting in carbon loss from the alloy-depleted regions, the associated dissolution of carbides and the recrystallisation that accompanied this, and thus the poor mechanical properties which resulted in creep failure. The inhomogeneity in the distribution of certain alloying elements can be partially attributed to the solute partition of alloying elements during weld solidification which has been confirmed with examination of simulation P91 TIG welds. However, the homogeneity of weld metal in this case required mixing of a base steel (the core rod in the weld consumable) and particles of various ferro-alloys (delivered into the weld pool from the flux). It is argued that poor mixing in the stagnant layer (unmixed zone) at the solid-liquid interface during weld solidification also makes a significant contribution to the formation of alloy-depleted regions. The formation of white-bands has been modelled using Thermo-Calc based on the understanding of the formation mechanism involving solute partition and subsequent carbon diffusion out of the alloy-depleted region. A good correlation to experimental results has been shown in the prediction of limiting carbon concentration and M23C6 carbide content in white-bands. In addition, it was also suggested that depletion of carbides and carbon are strongly linked and that depletion of alloying elements only above a critical value will result in total carbide loss and thus recrystallisation into a white-band.
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Faroqy, Anna. "Investigating the changes in the geophysical and geotechnical properties of fine-grained soils when exposed to changes in vertically applied loads." Thesis, University of Birmingham, 2018. http://etheses.bham.ac.uk//id/eprint/8811/.
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Fine-grained soils, containing clay minerals, are known to experience potentially considerable changes in geotechnical properties when exposed to external loads. These could lead to loss of mechanical performance or catastrophic failure. Therefore, this research focuses on simple geophysical sensing techniques which could contribute to a warning system based on correlations between geotechnical and geophysical parameters. Fine-grained soils of differing plasticity were exposed to changes in vertical loading in bespoke experimental chambers. The geophysical properties investigated were apparent permittivity (AP) and bulk electric conductivity (BEC) in a kHz frequency range, measured with time domain reflectometry (TDR) and bulk electrical conductivity (EC) in a Hz frequency range, measured with electrical resistivity (ER). For what is believed to be the first time, TDR measurements were carried out continuously and in both the vertical and horizontal direction during the volumetric change of the soil, induced by changes in the loading conditions. In parallel, EC was measured, utilising the bespoke test chambers and custom-built acquisition system. Based on the results, it is envisaged that monitoring the relative change in AP and BEC over time, in conjunction with spatially distributed ER arrays, could provide temporal indication of the soil response to load under near-saturated conditions.
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Lobo, Alonzo Porfirio Jose. "Changes in soil carbon and nitrogen associated with switchgrass production." Thesis, Texas A&M University, 2004. http://hdl.handle.net/1969.1/1258.
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Greater knowledge of the short- and long-term effects of biomass production practices on soil biological and chemical properties is needed to determine influences on sustainable land management. Soil samples under switchgrass (Panicum virgatum L.), other forage grasses, cultivated crops, and forest were collected seasonally at six locations. Soil organic C (SOC), total N, soil microbial biomass C (SMBC) and N (SMBN), soil mineralizable C and N, and basal soil respiration (BSR) were in general greatest under long-term coastal bermudagrass [Cynodon dactylon (L.) Pers.] pasture (>40 years), second highest under Alamo switchgrass and kleingrass (Panicum coloratum L.) planted in 1992 and forest, followed by Alamo switchgrass planted in 1997, and was lowest under the cultivated soils. Soil organic C at 0-5 cm was 42-220% greater in soils under Alamo switchgrass planted in 1992 than cultivated soils, except at College Station where SOC values under Alamo planted in 1992 and the cultivated rotation were not significantly different. Although the rotation treatment is cultivated at this location, two high residue crops are used, wheat (Triticum aestivum L.) and sorghum [Sorghum bicolor (L.) Moench.]. Similar trends were noted for total N, SMBC, SMBN, mineralizable C and N, BSR, and the ratio of SMBC/SOC. Insufficient information was collected in this study to determine whether the parameters evaluated for forest and switchgrass were different. In addition to its high yield potential, adaptation to marginal sites and tolerance to water and nutrient limitations, switchgrass appeared to be a competitive crop in terms of land sustainability, resulting in enhanced soil quality characteristics compared to long-term cultivated soils.
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Liu, Hua. "ASYMPTOTIC PROPERTIES OF PARTIAL AREAS UNDER THE RECEIVER OPERATING CHARACTERISTIC CURVE WITH APPLICATIONS IN MICROARRAY EXPERIMENTS." UKnowledge, 2006. http://uknowledge.uky.edu/gradschool_diss/463.
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Receiver operating characteristic (ROC) curves are widely used in medical decision making. It was recognized in the last decade that only a specific region of the ROC curve is of clinical interest, which can be summarized by the partial area under the ROC curve (partial AUC). Early statistical methods for evaluating partial AUC assume that the data are from a specified underlying distribution. Nonparametric estimators of the partial AUC emerged recently, but there are theoretical issues to be addressed. In this dissertation, we propose two new nonparametric statistics, partially integrated ROC and partially integrated weighted ROC, for estimating partial AUC. We show that our partially integrated ROC statistic is a consistent estimator of the partial AUC, and derive its asymptotic distribution which is distribution free under the null hypothesis. In the partially integrated ROC statistic, when the ROC curve crosses the Uniform distribution function (CDF) and if the partial area evaluated contains the crossing point, or when there are multiple crossing, the partially integrated ROC statistic might not perform well. To address this issue, we propose the partially integrated weighted ROC statistic. This statistic evaluates the partially weighted AUC, where larger weight is given when the ROC curve is above the Uniform CDF and smaller weight is given when the ROC curve is below the Uniform CDF. We show that our partially integrated weighted ROC statistic is a consistent estimator of the partially weighted AUC. We derive its asymptotic distribution which is distribution free under the null hypothesis. We propose to apply our two nonparametric statistics to functional category analysis in microarray experiments. We define the functional category analysis to be the statistical identification of over-represented functional gene categories in a microarray experiment based on differential gene expression. We compare our statistics with existing methods for the functional category analysis both via simulation study and application to a real microarray data, and demonstrate that our two statistics are effective for identifying over-represented functional gene categories. We also emphasize the essential role of the empirical distribution function plots and the ROC curves in the functional category analysis.
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Al-Smari, Turki A. "Effect of operating conditions and particle properties on electrostatics and entrainment in gas-solid fluidized beds." Thesis, University of British Columbia, 2014. http://hdl.handle.net/2429/47075.
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The effects of superfical gas velocity, pressure, and temperature on entrainment and electrostatic charge with glass beads and polyethylene as bed particles were investigated in a fluidization column of 0.15 m inner diameter and 2.0 m height. Four collision probes at different levels, a freeboard sampler, and a current detection pipe measured the electrostatics in the bed, freeboard, and column exit. The entrainment and electrostatic charge inside the bed and freeboard region increased as the superficial gas velocity or pressure increased. Temperature had negligible effect on the entrainment over the limited range studied. However, electrostatic charges decreased and the charge polarity reversed as the bed temperature increased from 20 to 75 °C.
The calculated electrostatic forces resulting from fine-fine and fine-coarse particle interactions are comparable to the gravitational force on fine particles in the fluidized bed. Entrainment empirical correlations developed in this work showed much better performance after the effect of electrostatic forces was taken into account, with the entrainment flux deceasing as electrostatic forces increase. The Choi et al. (1999) entrainment correlation shows better prediction of the entrainment flux in our system after the effect of the electrostatic force is considered.
The electrostatic charges in the bed decreased with increasing air relative humidity. The charge density of fines decreased and entrainment increased as the air relative humidity increased. The relative humdity had no effect on the charge density or entrainment of polyethylene particles, which can also probably be attributed to the hydrophobic nature of polyethylene.
The magnitude of electrostatic charges generated inside the fluidized bed increased slightly as the size of the coarse particles decreased. The entrainment decreased as the coarse particle size decreased. The electrostatic charges increased and entrainment decreased as the coarse particle density increased.
The magnitude of electrostatic charges generated inside the fluidized bed increased and entrainment decreased as the fine particle density increased. The electrostatic charges and entrainment also increased as the fine concentration increased. The fines concentration had little or no effect on fines charge densities. Bipolar charging was observed in all experiments with fine particles charged positively, whereas large particles were charged negatively.
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Tamai, Goro. "Experimental study of engine oil film thickness dependence on liner location, oil properties and operating conditions." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/31066.
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Müller, Georg Alexander. "Ion-beam induced changes of magnetic and structural properties in thin Fe films." [S.l.] : [s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=971021570.
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Khamsuk, Sunisa. "Changes in Microstructure and Mechanical Properties of Aluminum Alloys Heavily Deformed by Torsion." 京都大学 (Kyoto University), 2013. http://hdl.handle.net/2433/180617.
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Bivins, Jason Lee. "Changes in Dewatering Properties Between the Thermophilic and Mesophilic Stages in TPAD Systems." Thesis, Virginia Tech, 2000. http://hdl.handle.net/10919/36254.
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Temperature-phased anaerobic digestion (TPAD) has become increasingly appealing in recent years due to the pathogen destruction capabilities of the system. However, there has also been concern about the dewatering properties of the sludges created by these systems. A laboratory study was conducted at Virginia Tech to determine the effect of thermophilic solids retention time (SRT) on sludge dewatering properties, to characterize system parameters associated with dewatering, and to understand the mechanisms causing changes in dewatering properties between the thermophilic and mesophilic phases. The study showed that while anaerobic digestion caused dewatering properties to deteriorate, sludges varied little with thermophilic SRT. Acidogenesis was essentially complete after 1.5 days. Subsequent mesophilic digestion resulted in little change to dewatering properties and modest reductions in conditioning doses, but substantial reductions in biopolymer (protein + polysaccharides) occurred. It appears that thermophilic anaerobic digestion creates or releases colloidal materials that cause dewatering to be poor and subsequent mesophilic digestion for 15 days does little to improve sludge properties of TPAD systems.Master of Science
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Kang, Inkyung. "CHANGES IN THE BIOMECHANICAL PROPERTIES OF ENDOTHELIAL CELLS DURING NEUTROPHIL ADHESION AND MIGRATION." Case Western Reserve University School of Graduate Studies / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=case1149881623.
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Miyamoto, Naokazu. "Estimation of changes in muscle contractile properties at various joint angles by mechanomyography." Kyoto University, 2005. http://hdl.handle.net/2433/144976.
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Kyoto University (京都大学)0048
新制・課程博士
博士(人間・環境学)
甲第11677号
人博第283号
新制||人||71(附属図書館)
16||174(吉田南総合図書館)
23320
UT51-2005-D426
京都大学大学院人間･環境学研究科人間･環境学専攻
(主査)教授 森谷 敏夫, 教授 田口 貞善, 助教授 小田 伸午, 助教授 阪上 雅昭
学位規則第4条第1項該当
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Campbell, Anna Jane Patricia. "Changes in soil properties under experimental tree plots on the Isle of Rum." Thesis, University of Central Lancashire, 2000. http://clok.uclan.ac.uk/19053/.
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The ecological importance of native woodland in the Scottish Highlands and Islands is widely acknowledged and many calls for its expansion have been made. Much research into the effects of such an expansion on the above-ground ecosystem has been undertaken, but little is known about the impact it has on the underlying soils. Experimental tree plots, containing species native to western Scotland, were established on the Isle of Rum National Nature Reserve during the 1960's. This thesis seeks to assess the effects of 35 years of birch (Betula spp.), oak (Quercus spp.) and Scots pine (Pinus sylvestris) growth on the relatively fertile, mineral soils at Harris and the less fertile, organic soils at Kilmory Fank. Significant changes in soil characteristics were identified beneath all three species growing on both soil types. These changes were complex in nature. The effects of oak and birch growth could not uniformly be said to constitute soil improvement, however, the soils beneath Scots pine were significantly improved. The role of antecedent conditions in influencing the direction and type of soil change was demonstrably more important than theinfluence of the species type. The direction and nature of change was similar under oak and birch growing on the same soils, rates of organic matter decomposition were elevated but some nutrients, particularly potassium, were depleted by up to 50 kghi. This depletion appeared to represent a nutrient redistribution from soil to trees and litter, rather than a loss to the system as a whole. No clear evidence was found to suggest that one species was a more or less effective soil improver than the other Under Scots pine, plant nutrients had accumulated in the soil, particularly calcium which had increased by more than 90 kgha'. At Harris, the acidity had declined by 0.3 pH units. The net nutrient input appears to derive from marine aerosols trapped by the pine canopy and a subsequent translocation of them to the underlying soil via throughfall and stemfiow. The results are of value to forest managers who perceive the establishment of new native woodlands as a route to soil restoration. They show that many of the commonly held perceptions regarding the influence of tree growth on soils must be treated with caution. This is because the changes that occur appear to be highly site dependent, thus planting of native tree species can have widely varying effects consequent upon the original soil characteristics and prevailing environmental conditions.
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Gardner, P. J. "The effect of operating parameters and matrix properties on the productivity of an expanded bed adsorption column." Thesis, University College London (University of London), 2005. http://discovery.ucl.ac.uk/1444709/.
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Expanded bed adsorption (EBA) combines clarification, concentration and purification into a single processing step reducing processing time and increasing productivity. Much work has been conducted on model proteins but little attention has been paid to the emerging issues of tailoring the operational variables of matrix size, operating flowrate and ligand type so as to maximise process outputs. The aims of this study were to investigate the effects of matrix properties and operating parameters on breakthrough behaviour and productivity. Second generation matrices designed to operate at high flowrates were also examined. Operating at low velocities, beds formed from smaller particles had a shallower breakthrough than beds formed from large particles but the latter were more productive. At the higher velocities typically utilised in EBA, the behaviour of beds formed from either small or large particles was comparable in terms of breakthrough with the beds made up of small particles being slightly more productive than those containing large particles. A prototype 2nd generation EBA matrix consisting of a multi-modal ligand that could operate at high conductivity levels typical of fermentation broths was also examined. It was found that the productivity could be increased 5-fold as compared with commercially available matrices, with no loss of yield or purity. Conventional breakthrough curve analysis is not applicable in situations of variable particle size and operating velocity. Results using a novel dimensionless group to facilitate comparison between unlike systems is presented. The thesis presents an analysis of the relative productivity of a range of systems and highlights the gains in terms of productivity to be achieved with the development of 2nd generation EBA multi-modal adsorbents. The thesis concludes with an analysis of the commercial and regulatory aspects of EBA.
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Valle, Randulf. "The Effect of Strain Path Changes on the Subsequent Recrystallisation Properties of Aluminium Alloys." Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for materialteknologi, 2004. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-188.
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A study of strain path related effects on recrystallisation in aluminium has been carried out. The recrystallisation process has been studied after deformation in torsion and one pass hot rolling. For both deformation models, the work has been a combination of experimental studies of the deformation microstructure and recrystallisation process, as well as use of models for prediction of the deformation- and recrystallisation process. For deformation in torsion AA1050 and AA3103 has been studied. Cyclic deformation to zero net strain resulted in restoration of the initial grain structure, while monotonic deformation yielded an increasingly more elongated grain structure. Studies by EBSD revealed no difference in subgrain size as function of strain path, but the subgrain misorientation was larger after monotonic deformation. Similarly, the distance between high angle boundaries was smaller after monotonic deformation. The recrystallised grain size was larger after cyclic deformation, compared to monotonic deformation to the same cumulative strain. In AA1050 the difference in recrystallised grain size was mainly sees as an effect of difference in grain boundary area, leading to fewer nuclei after cyclic deformation. A small difference in driving pressure also contributed to the difference in recrystallised grain size. In AA3110 an additional effect of weakening of deformation zones surrounding particles was purposed, resulting in lower density of PSN-nuclei after cyclic deformation and accordingly larger grain size. The experimental study of the hot rolling pass was performed on an AA3103 alloy. A slight increase in Vickers hardness was seen from center to surface of the rolling slab after deformation. The microstructure after rolling was predicted by a combination of FEM-simulations and a microstructure model. This approach resulted in a larger predicted gradient in flow stress through thickness than calculated from the hardness measurements. The recrystallisation kinetics were monitored and were found to be fastest in the surface areas. The experimentally measured gradient in recrystallisation kinetics from center to surface was much larger than what was modeled. This was seen as an effect of the models limited coverage of changes in the density of nuclei as a result of other mechanisms than a difference in the driving pressure.
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Lazega, David. "Opioid binding properties after environmental, pharmacological and genetical changes of the endogenous opioid system /." Zürich, 1987. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=8365.
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Shaqour, Fathi M. "Effects of groundwater level changes on the engineering properties of desert sands in Kuwait." Thesis, University of Leeds, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.236916.
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PIMENTA, JOSE MARIA PAOLUCCI. "CHANGES IN THE MECHANICAL PROPERTIES AND FRACTURE RESISTANCE OF THE GRADE R4 STRUCTURAL STEEL." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2007. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=11335@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRONeste trabalho foram estudadas as modificações na resistência à fratura do aço grau R4, largamente adotado na fabricação de componentes estruturais para sistemas de ancoragem de unidades offshore, através de variações microestruturais. Após a fabricação industrial de elos de amarras, corpos de prova para ensaios de tração e CTOD foram usinados do material. A primeira etapa do procedimento experimental consistiu em tratamentos térmicos de têmpera e revenido, com diferentes temperaturas de austenitização (860, 880, 900, 920 e 940(graus)C) e mantendo-se fixa a temperatura de revenido (680(graus)C). Com base nos resultados de CTOD de carga máxima apresentados pelo material, passou-se para a segunda etapa experimental, na qual foi adotada a temperatura de austenitização admitida como ótima na primeira etapa (900(graus)C) e variando-se as temperaturas de revenido (650, 660, 670, 680, 690 e 700(graus)C). Na primeira etapa, os resultados demonstraram que, com o aumento da temperatura de austenitização (860, 880 e 900(graus)C), houve um aumento da resistência à fratura do material. No entanto, os valores praticamente não variaram a partir das temperaturas mais altas (920 e 940(graus)C). Na segunda etapa, os valores do CTOD aumentaram com o aumento da temperatura de revenido, atingindo um valor máximo a 680 (graus)C. Para temperaturas superiores (690 e 700(graus)C) a tenacidade do material sofreu uma pequena redução. As variações da tenacidade do aço grau R4, em ambas as etapas experimentais, foram associadas com as microestruturas obtidas nos respectivos tratamentos térmicos.
A study has been made concerning changes in the fracture resistance of the grade R4 steel, largely used for manufacturing offshore mooring structural components, due to microstrutural variations. After the industrial manufacturing of chain links, specimens for tensile and CTOD tests were machined from the material. The first part of the experimental procedure was related to quenching and tempering heat treatments making use of different austenizing temperatures (860, 880, 900, 920 and 940(Degrees)C) and tempering at a given temperature (680(Degrees)C). On the basis of the CTOD at the maximum load presented by the material, the second experimental part was started, in which the optimal austenitizing temperature obtained in the first part (900(Degrees)C) was adopted and different tempering temperatures (650, 660, 670, 680, 690 and 700(Degrees)C) were selected. According to the CTOD testing carried out during the first experimental part, the fracture resistance of the material has increased when increasing the austenitizing temperature (860, 880 and 900(Degrees)C). However, the material`s toughness did not change significantly when quenching from the highest temperatures (920 and 940(Degrees)C). In the second experimental part, the CTOD values increased when increasing the tempering temperature, reaching a maximum value for 680(Degrees)C. Concerning the highest temperatures (690 and 700(Degrees) C) the fracture resistance of the material presented a slight reduction. The changes in the fracture resistance of the grade R4 steel, in both experimental parts, were associated with the microstrutural characteristics of the heat treatments.
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McIntosh, Nicholas Joseph. "Measurement of the changes to the liquid transport properties of wood due to compression." Thesis, University of British Columbia, 2016. http://hdl.handle.net/2429/60148.
Full textAbstract:
Compression of wood chips coupled with chemical treatment in a liquid bath has been
shown to be an effective method to reduce the energy required to mechanically produce wood pulp. Though the utility of such compression/chip impregnation processes has become well known through implementation at pilot and mill scales, a fundamental understanding of the operational mechanism of these processes remains to be obtained. Towards this end, an experimental and statistical study has been conducted. In this work, better understanding the mechanism of action and measuring the effectiveness of a given compression/impregnation process has come about via developing two complementary methods to characterize arbitrarily compressed wood
chips. The first method, applied to chips compressed at mill and pilot-scale, involves
extracting a pore size distribution from a wood sample by use of a combination of
microscope imaging, digital image analysis, and model fitting to the data obtained from
image analysis. The second method, applied to wooden blocks compressed at lab-scale, involves directly measuring liquid uptake of a wooden block from a reservoir.
Results from image analysis suggest that compression changes the structure of
wood in a way which hinders liquid uptake. This observation, taken with existing
heuristic relationships between compression and liquid uptake ability of wood chips,
implies that the effectiveness of a wood chip compression/impregnation process relies
on the alteration of chip properties on a length scale larger than that captured by the
image analysis (i.e., that of individual fibres). Direct measurement of liquid uptake
of compressed wood blocks at lab-scale resulted in the emergence of a stochastic
relationship between compression conditions (compression rate and total strain applied
to a block) and the changes imparted to wood’s micro-structure. Taken in combination, the results of the experimental program conducted suggest that the effectiveness of wood chip compression/impregnation processes lies within the ability of compression to modify the structure of an aggregate of wood chips rather than individual wood chips on a fibre scale.Applied Science, Faculty of
Graduate
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Laucks, Mary Lisa. "Quantifying the uncertainties in measurements of aerosol optical properties relevant to the direct shortwave forcing of climate /." Thesis, Connect to this title online; UW restricted, 1996. http://hdl.handle.net/1773/10314.
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Yang, Chung-Kai, and 楊中凱. "The Determinants of Operating Performance Changes Surrounding Initial Public Offerings." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/a9u3x7.
Full textAbstract:
碩士國立中正大學
會計學研究所
92
Operating performance of listed companies have been focuses of public investors, top management of firms, and government regulatory agencies. The purpose of IPO should be improving the operating performance, but one of the phenomenon in the Taiwan capital market is that firms’ reported operating performance decline following IPO. The purpose of this study is to find out the determinants of operating performance changes surrounding IPO. Besides, this study uses the firms’ actual operating data surrounding IPO to calculate performance angle, and uses it to measure the performance changes surrounding IPO. The IPOs sample of 144 firms is obtained from listed stock on Taiwan stock change from 1989 to 1998, and the empirical results show that: 1、 Managing the accruals in the periods prior to IPO will increase the range of operating performance change. 2、 The monitoring mechanisms of prestigious underwriter will decrease the range of operating performance change. 3、 The ROE angle has a significant correlation with the changes of holding ratio of directors and blockholders. The explanation for the empirical results may be that directors and blockholders pay much attention to ROE, if the company can’t make profit for them, they will take the information advantages and then sell their holdings before company’s performance starts declining.
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楊秀茹. "The Relation between Operating Changes of Central Daily News and Social Changes¬─from 1949 to 2006." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/97049403853228603363.
Full textAbstract:
碩士國立臺灣師範大學
圖文傳播學系
101
Central Daily News played an important role in the development of Taiwan. This study revealed the relation between operating changes of Central Daily News and social changes from 1949 to 2006 by history study and document analysis, also providing some suggestions to successive researchers and journal or media operators as a reference to research or operate. This study revealed that social changes is an important cause of operating changes of Central Daily News. The operation changed as the society changed. The elimination of restriction on newspapers and the party alternation were two major keys. The following are the reasons of Central Daily News, which was the most popular newspaper after government move to Taiwan, ceased publication temporarily in 1st June, 2006: 1. Burden of party operation, 2. Development of electronic media, 3. Serious competition in journal business, 4. Party alternation. The suggestions provided to journal or media operators are: 1. Understanding the desire of readers, 2. Providing staff in-service education, 3. Knowing the role of the newspaper, 4. Diversifying business.