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1
Lim, C. S. "Plastic limit pressures for pressure vessels with defects at openings." Thesis, Cardiff University, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.234339.
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Quin, David John Gilbert. "Bridging the pressure gap : taking surface science to more realistic pressures." Thesis, University of Southampton, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.484956.
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Traditional surface science experiments are conducted under ultra high vacuum conditions, this enables surface cleanliness to be strictly controlled and the use of electron based measurements, to determine surface structure and composition. Unfortunately, lftlV conditions are very different from those in real world catalysis (e.g. car exhaust clean-up) and only limited insight can be obtained from such studies. For example, it has been found that certain catalytic species do not exist under UHV conditions. It is an essential step in the progression of surface science to move to more realistic conditions whilst still retaining the simplicity enabled by a UHV cleaned, ideal surface such as a single crystal. this thesis the development of two new pieces of equipment, which bridge this gap, at the SRS at Daresbury Laboratory are presented. The High Pressure Reaction Cell (HPRC), based on the far-IR beamline 13.3 at Daresbury laboratory, enables samples to be cleaned under lJHV conditions before being exposed to pressures, inside the cell, of up to 200 mbar of a chosen gas, without compromising the external vacuum. Far-IR RAIRS, which is useful for adsorbate investigations, is unaffected by the presence of a partial pressure of gas, enabling in-situ measurements as well as postexperiment UHV measurements. Results are presented for investigations into the high pressure oxidation and reduction copper, these are supported by DFT calculations ofthe phonon modes for common copper oxides. The High Ambient Pressure Photoelectron spectroscopY (H.APPY) system is a peripatetic end station designed to allow sample cleaning in UHV, before performing in-situ photoelectron spectroscopy at pressures up to 10-2 mbar. The commissioning experiments in which a commercial supported catalyst was studied are presented. The future of these two newly developed pieces of equipment is discussed alongside the future offar-IR RAIRS as a whole.
3
Watts, Travis James. "DIRECT MEASUREMENT OF CROSSTIE-BALLAST INTERFACE PRESSURES USING GRANULAR MATERIAL PRESSURE CELLS." UKnowledge, 2018. https://uknowledge.uky.edu/ce_etds/74.
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The magnitudes and relative pressure distributions transmitted to the crosstie-ballast interface of railroad track significantly influences the subsequent behavior and performance of the overall track structure. If the track structure is not properly designed to distribute the heavy-axle loads of freight cars and locomotives, deficiencies and inherent failures of the crossties, ballast, or underlying support layers can occur, requiring substantial and frequent maintenance activities to achieve requisite track geometrical standards. Incorporating an understanding of the pressure distribution at the crosstie-ballast interface, appropriate designs can be applied to adequately provide a high performing and long-lasting railroad track. Although this can be considered a simple concept, the magnitudes and distributions of pressures at the crosstie-ballast interface have historically proven to be difficult to quantifiably measure and assess over the years.
This document describes the development and application of a method to measure average railroad track crosstie-ballast interfacial pressures using timber crossties and pressure cells specifically designed for granular materials. A procedure was specifically developed for recessing the cells in the bottoms of timber crossties. The validity of the test method was initially verified with a series of laboratory tests. These tests used controlled loads applied to sections of trackbed constructed in specifically designed resilient frames. The prototype trackbed section was intended to simulate typical in-track loading conditions and ballast response.
Cells were subsequently installed at a test site on an NS Railway well-maintained mainline just east of Knoxville, TN. Six successive crossties were fitted with pressure cells at the ballast interface below the rail seat. Pressure cells were also installed at the center of two crossties where the ballast is typically not tamped or consolidated. Trackbed pressures at the crosstie-ballast interface were periodically measured for numerous revenue freight trains during a period of twenty-one months. After raising and surfacing the track, the ballast was permitted to further consolidate under normal train traffic before again measuring pressures. Having the ballast tightly and uniformly compacted under crossties is important to ensuring representative and reproducible pressure measurements.
Measured maximum pressures under the rail at the crosstie-ballast interface ranged from 20 to 30 psi (140 to 210 kPa) for locomotives and loaded freight cars with smooth wheels producing negligible wheel/rail impacts. Crosstie-ballast interface pressures were typically 3 psi (20 kPa) maximum for empty freight cars with smooth wheels. Heavily loaded articulated intermodal car pressures for shared trucks tended to reach nearly 40 psi (280 kPa), actually higher than locomotive-produced pressures. The recorded pressures under the center of the ties were normally negligible, less than 1 psi (7 kPa) for locomotives and loaded freight cars.
Wheel-Rail force parameters measured by nearby wheel-impact load detectors (WILD) were compared to crosstie-ballast pressure data for the same trains traversing the test site. Increases in peak WILD forces, either due to heavier wheel loads or increased impacts, were determined to relate favorably to increases in recorded trackbed pressures with a power relationship. The ratios between the peak and nominal wheel forces and trackbed pressures also have strong relationships.
4
Svensson, Stefan. "Micropumps for extreme pressures." Thesis, Uppsala University, Micro Structural Technology, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-110880.
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<p>The objective of this thesis was to improve a paraffin actuated micropump design, to be able to pump against extreme pressures (above 100 bar). This was accomplished by initially studying the membrane activation, using video capturing. The micropump has been improved to withstand pressures high enough, to enable use in an high-performance liquid chromatography (HPLC) system. The micropump has been shown to pump against back pressures up to 150 bar, with a positive net-flow. This should be compared with the previously recorded maximum back pressure of 50 bar. The pumping against high back pressures was possible due to an increased understanding of the sealing of the membranes. This resulted in a new design that was manufactured and characterised. Without clamping the pump was measured to manage back pressures of 10 bar, and then starting to leak in a bond at the flow channel. With supporting clamping, the managed back pressures increased ten folded.</p><p>When measured on the different valves, pressure above 200 bar has been possible to withhold. Although the valves were below their maximum limit, the pressure was not possible to be further increased due to a limitation in the equipment, i.e. risk of damaging the connections. When examined after pressurised at extreme pressures (above 100 bar) several times, no signs of fatigue or damage of the membrane was seen.</p><p>A new behaviour of the valves was discovered. Above certain pressures some designs self sealed, i.e. withholding the pressure after the voltage was turned off. For these valves the pressure had to be released by some other means.</p>
5
Kowal, Daniel Joseph. "Pressures experienced by adolescents." Thesis, University of British Columbia, 1985. http://hdl.handle.net/2429/25432.
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The purpose of this study was to examine the types of pressures adolescents experience. The factors of age and/or gender were also investigated in order to determine any possible effects upon adolescent experienced pressures. The researcher believed that findings from such a study could be useful to high school counsellors in both planning future Guidance programs for adolescents as well as aiding in individual counselling sessions with their adolescent clients.
Using a cluster-sampling technique, 505 adolescents were selected from a Vancouver high school. Subjects were chosen with consideration to the factors of age and gender. The researcher designed an open-form measurement instrument intended to gather adolescent responses to the three greatest pressures they had experienced during the previous four months. Following a pilot of the instrument, which was to aid in determining construct validity, the survey was administered to the sample over an eight day testing period. With the initial help of an assistant, responses were content analyzed and initial categories constructed. All responses were coded and assigned a frequency score to one of eleven mutually exclusive categories. The chi-square "Goodness of Fit" test for significant difference between or among groups was then applied.
Results of the statistical analysis indicated that the factors of age and/or gender are related to certain types of pressures experienced by adolescents. Future Pressure was found to be a significant pressure experienced by older age adolescents. Regardless of gender, age appears to be an important factor related to who will experience Future Pressure. Female adolescents experience greater Family Pressure than do males. Whether within the same age group or within a total female and. a total male population comparison, this result remains consistent. Younger age adolescents also indicate greater gender differences compared with older age adolescents. Younger age female adolescents are more likely to experience greater Family Pressure and Peer Pressure while young male adolescents are more likely to experience greater Situational Pressure.
In conclusion, it appears that significant gender differences found in this study tend to support the notion that differences in the rate of physical growth as well as learned sexual stereotypes are significant factors in determining such differences.<br>Education, Faculty of<br>Educational and Counselling Psychology, and Special Education (ECPS), Department of<br>Graduate
6
Tissot, Héloïse. "Beyond the gap of pressure : XPS studies of interfaces at near ambient pressures." Thesis, Paris 6, 2014. http://www.theses.fr/2014PA066615/document.
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Dans de nombreux procédés technologiques, tels que la fabrication de matériaux pour la microélectronique, l’étude des réactions chimiques à une électrode, ou encore la catalyse… L’interface entre la surface d’un solide ou d’un liquide avec un liquide ou une phase gaz joue un rôle fondamental. De façon analogue, les sciences de l’environnement ainsi que celles du vivant intègrent dans leurs modèles la réactivité aux interfaces solide/ liquide ou liquide/ gaz.L’XPS est une technique parfaitement adaptée à l’étude des interfaces et a été largement utilisée pour l’analyse des surfaces de solides. Le principal avantage de l’XPS est sa grande sensibilité aux surfaces. En effet, en raison du faible libre parcours moyen des électrons dans un solide, uniquement les photoélectrons provenant de l’extrême surface (1 – 10 nm) peuvent échapper à celle-ci. Cependant, l’XPS est traditionnellement utilisée dans des conditions d’ultravide (UHV) et cela pour deux raisons. La première est que les analyseurs d’électrons sont construits pour fonctionner en UHV. La seconde est que les électrons doivent pouvoir atteindre l’analyseur, or leur libre parcours moyen est faible dans un gaz à haute pression. Par exemple, à une pression de 1 mbar, des électrons possédant une énergie de 100 eV vont parcourir 1 mm alors qu’ en UHV ils pourront atteindre jusqu’ à 105 m.Dans le but de rendre possible l’utilisation de l’XPS à des pressions plus élevées, quelques groupes autour du monde, dont le groupe de Berkeley (sous la direction de M. Salmeron at de H. Bluhm) et celui du Fritz Haber Institute à Berlin, ont élaborés un équipement permettant d’atteindre des pressions proche de l’ambiant (5 mbar). La construction d’un analyseur d’électron capable de fonctionner à des pressions de l’ordre du mbar, c’est-à-dire à des pressions 7 ordres de grandeur supérieures à l’UHV, a été une avancée à la fois conceptuelle et technologique. Un système de pompage différentiel permet de maintenir l’échantillon dans des conditions dites environnementales tout en maximisant le libre parcours moyen des électrons de façon à ce qu’ils atteignent l’analyseur. De plus, des tensions sont appliquées à des lentilles électrostatiques dans le but d’accélérer et de focaliser ces électrons.Un système similaire (Near Ambient Pressure XPS, NAP-XPS) a été installé sur la ligne TEMPO du synchrotron Soleil en février 2013, le premier temps de faisceau ayant eu lieu au mois de mai suivant. Durant ma thèse, deux projets différents ont été développés, tous les deux liés à l’étude d’interfaces avec l’utilisation de la NAP-XPS.Le premier projet traite des procédés utilisés en micro-electronique pour déposer de fines couches d’oxydes : le dépôt chimique en phase vapeur (CVD) et la déposition de couches atomiques (ALD). En particulier, des molécules de la famille des silanes sont utilisées pour fonctionnaliser des surfaces d’oxyde de silicium ou comme précurseur, combiné à un agent oxydant comme l’eau pour le dépôt de films mince d’oxyde de silicium. Cependant, les mécanismes réactionnels des silanes sur les surfaces de silicium n’ont jamais été étudiés par des techniques telles que la microscopie a effet tunnel (STM) ou l’XPS et l’on sait peu de choses concernant leur mécanisme de dissociation et l’adsorption des divers fragments sur la surface<br>In many processes or technological objects, such as coating deposition, advanced material processing for electronics, magnetic or optical devices, electrochemical processes at an electrode, sensors and catalysis, etc. the interface between a surface of a solid and a liquid or a gas phase, plays a prominent role. Analogously, environmental sciences and sciences of the Living integrate into their models chemical reactions taking place at solid/liquid or liquid/gas interfaces.XPS is a powerful technique for interface analysis and has been widely use in the case of solid surface. The main advantage of XPS is its sensitivity to the material surface. Indeed, due to the low electron mean free path of electrons in a solid, only the photoelectrons at the extreme outer surface (1-10 nm) can escape the sample. However, XPS has traditionally been conducted under ultra-high vacuum (UHV) conditions. UHV conditions are utilized for two reasons. First, the analyzers are designed to work under UHV conditions. Second, the electrons must reach the detector and their mean free path is short at high pressures. For example at a pressure of 1 mbar, 100 eV electrons will travel 1 mm while under UHV conditions, the mean free path increases to 105 m. UHV chambers (10-10 mbar) help maximize the mean free path so that a high number of electrons will reach the detector/analyzer and the signal/noise ratio will increase making it possible to analyze the spectrum produced. This constraint makes UHV the standard environment of X-ray Photoelectron Spectroscopy (XPS) experiments.In order to make possible the use of XPS on a larger pressure range, a few groups around the world have designed photoemission equipment that can be operated under ambient pressure (up to 5 mbar). The Berkeley group (M. Salmeron LBNL-Materials Sciences Division, H. Bluhm LBNL-Chemical Sciences Division), who pioneered this field, has two such setups installed at the Advanced Light Source. The Fritz Haber Institute has built a high pressure XPS based on the Berkeley prototype, installed at BESSY synchrotron (Berlin), since 2002. The building of Ambient Pressure XPS (APXPS) analyzers of the Berkeley type, able to be operated at pressures in the range of 1 mbar, about 7 orders of magnitude higher than the pressure limit of conventional UHV equipment is both a technological and conceptual breakthrough. Differential pumping stages allow the sample to remain at environmental pressures, while maximizing the mean free path of emitted electrons, so they can reach the detector. Additionally, voltages are applied to electrostatic lenses in the unit to accelerate and focus the electrons onto the focal plane of the electron energy analyzer. A similar system Near-Ambient Pressure XPS, NAP-XPS), described in details in chapter 1, was delivered in December 2012 and installed at TEMPO beamline in February 2013. The first beamtime occurred in May 2013. During my thesis that started in October 2011 two different projects were developed, both related to interface analysis using the NAP-XPS instrument
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Gilmore, Tim. "Evaluation of Various Inspiratory Times and Inflation Pressures During Airway Pressure Release Ventilation." Diss., NSUWorks, 2017. https://nsuworks.nova.edu/hpd_hs_stuetd/5.
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There are few recommendations on how best to apply certain modes of mechanical ventilation. The application of Airway Pressure Release Ventilation (APRV) includes strategic implementation of specific inspiratory times (I-times) and particular mean airway pressures (MAWP) neither of which is standardized. This study utilized a retrospective analysis of archived electronic health record data to evaluate the clinical outcomes of adult patients that had been placed on APRV for at least 8 hours. 68 adult subjects were evaluated as part of a convenient purposive sample. All outcomes of interest (surrogates) for short-term clinical outcomes to include the PaO2/FiO2 (P/F) ratio, Oxygen Index and Oxygen Saturation Index (OI; OSI), and Modified Sequential Organ Failure Assessment (MSOFA) scores showed improvement after at least 8 hours on APRV. Most notably, there was significant improvement in P/F ratio (p = .012) and OSI (p = .000). Results of regression analysis showed P low as a statistically significant negative predictor of pre-APRV P/F ratio with a higher initial P low coinciding with a lower P/F ratio. The regression analysis also showed MAWP as a significant positive predictor of post-APRV OSI and P high and P low as significant negative predictors of post-APRV MSOFA scores. In summary, it was found that settings for P high, Plow, and T low in addition to overall MAWP and Body Mass Index (BMI) had significant correlation to impact at least one of the short-term clinical outcomes measured.
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Kempson, Ruth, and Ronnie Cann. "Dialogue pressures and syntactic change." Universität Potsdam, 2006. http://opus.kobv.de/ubp/volltexte/2006/1046/.
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On the basis of the Dynamic Syntax
framework, this paper argues that the
production pressures in dialogue determining
alignment effects and given versus
new informational effects also drive
the shift from case-rich free word order
systems without clitic pronouns into systems
with clitic pronouns with rigid relative
ordering. <br>The paper introduces assumptions
of Dynamic Syntax, in particular
the building up of interpretation
through structural underspecification and
update, sketches the attendant account
of production with close coordination of
parsing and production strategies, and
shows how what was at the Latin stage a
purely pragmatic, production-driven decision
about linear ordering becomes encoded
in the clitics in theMedieval Spanish
system which then through successive
steps of routinization yield the modern
systems with immediately pre-verbal
fixed clitic templates.
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Evans, Jodi K. "Institutional pressures for sustainable development." Thesis, University of Oxford, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.361738.
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Moore, Stephen Richard. "Earth pressures on spillthrough abutments." Thesis, University of Surrey, 1985. http://epubs.surrey.ac.uk/843896/.
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The earth pressures exerted by cohesionless backfill against spill through abutments have been investigated by instrumenting two full size structures with vibrating wire earth pressure cells which were calibrated in soil under laboratory conditions. The abutment deformations were recorded with inclinometer tubes and precise surveying techniques, and the column bending was measured using vibrating wire strain gauges. The earth pressures were found to be influenced by the concrete expansion during hydration which caused transverse bending of the columns after the capping beam pour, as well as longitudinal backward rotations and bending of the abutments after the deck slab pours. High residual lateral earth pressures were exerted against the rear of the capping beams due to heavy compaction of the backfill at this level, thus causing the abutment to rotate forwards and become effectively propped by the deck slab. Traffic loading and deck slab temperature fluctuations were found to cause seasonal earth pressure variations. The lateral earth pressure profiles as predicted by the existing design methods were found to be totally unrepresentative of the Wisley results, and a modified design approach has been proposed. Model tests were performed in the laboratory to investigate the behaviour of embedded laterally loaded columns within a spill through abutment. At small lateral displacements, the friction of the soil against the column sides was found to contribute significantly to the total soil resistance. Soil deformations were measured using specialised photography and the interaction between columns was found to be negligible. A nuclear density probe was compared with other common methods of measuring the in-situ density of compacted backfill. A modified resin impregnation technique was developed to measure the density variations within a laboratory test specimen of dry sand.
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Feng, Qingfu. "On Pre-image Topological Pressures." Case Western Reserve University School of Graduate Studies / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=case1121100065.
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Wood, John Anderson Carleton University Dissertation Geology. "Internal pressures in freezing soils." Ottawa, 1985.
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Guilhem, Mathieu. "Conception and optimization of a piezo-optic pressure transducer : application to high hydrostatic pressures sensing." Strasbourg, 2010. https://publication-theses.unistra.fr/public/theses_doctorat/2010/GUILHEM_Mathieu_2010.pdf.
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La mesure de pression est un domaine vieux de plusieurs siècles, dont le développement a été motivé par l’importance de ses applications technologiques. Le but de ce travail est de proposer une technique de mesure de fortes pression hydrostatiques par capteur optique à bas coût. De nombreux types de capteurs de pression ont été développés au cours du temps, et la première partie de ce document présente une vue d’ensemble du domaine. Nous nous concentrons ensuite sur les techniques optiques et présentons leurs avantages et inconvénients. Au vu de notre cahier des charges, nous choisissons de développer un capteur de pression basé sur l’effet piezo-optique, c’est à dire l’apparition d’une biréfringence dans un matériau diélectrique soumis à une force extérieure. La Partie II du mémoire présente les différents outils qui seront par la suite utilisés pour modéliser le capteur proposé : tout d’abord nous rappelons les détails de la théorie de la polarisation, son origine physique ainsi que le formalisme de Mueller-Stokes. Nous nous intéressons ensuite aux interactions entre une lumière polarisée et un milieu diélectrique, en présentant l’effet piezo-optique ainsi que les effets polarisant des réflexions à une interface. Les effets présentés sont modélisés par leur matrice de Mueller afin de simplifier l’étude à suivre. Dans la Partie III nous proposons un concept original de capteur de pression, utilisant une approche novatrice par rapport à celle usuellement mise en œuvre. Le capteur proposé est basé sur l’analyse d’une lumière dont la polarisation est modifiée par la traversée d’un milieu diélectrique rendu biréfringent par la pression à mesurer. Certains aspects du capteur sont optimisés, et ses inconvénients discutés. Cette étude aboutit à la proposition d’un capteur dans lequel les éléments polarisant discrets ont été remplacés par des réflexions successives. Ce nouveau concept est modélisé, puis nous présentons les différentes sources potentielles d’erreur de mesure et proposons des solutions pour compenser celles qui prédominent. La Partie IV présente la validation expérimentale des concepts précédents. Nous décrivons la conception, la calibration et la validation d’un polarimètre de Mueller par Transformée de Fourier, conçu dans le but d’étudier la dépendance de l’effet piezo-optique à la température. Ensuite nous présentons la réalisation d’un démonstrateur de capteur piezo-optique de pression. Les essais effectués sont en accord avec les prédictions théoriques et valident donc le principe du capteur développé au cours de ce travail<br>The measurement of pressure is a field that has been studied for centuries due to its important technological implications. Our goal is to propose an original method to measure high hydrostatic pressures using a low cost optical sensor. A number of pressure sensors have been developed over the years, and the first part of this work presents an overview of the main ones. We then focus on optical pressure sensors, discuss the advantages and inconveniences of each method with regards to our constraints, and decide to develop the concept of a sensor based on the piezo-optic effect, i. E. The stress-induced birefringence in a transparent dielectric subjected to a force. We presents the tools that will be used to modelize the piezo-optic pressure sensor: we first review the theory of polarization of light, from its physical origin to the Mueller-Stokes formalism; we then focus on the interaction of polarized light with matter: we discuss the theory of the piezooptic effect and the polarization effects of total and partial reflections at an interface. Both effects are modelized in terms of their Mueller matrices. We then propose an original concept for a pressure sensor, using an approach different from the one usually seen in polarimetric sensors. First the concept of a piezo-optic pressure sensor is presented where polarized light interacts with a dielectric material subjected to a pressure; the resulting state of polarization is analyzed by a second polarizer and a photodetector. Some aspects of the sensor are optimized while its shortcomings are listed. In light of this analysis we propose a revised concept to addresses these issues. The new proposal uses carefully oriented reflections to replace all polarizing elements, enabling simpler and cheaper production. We modelize this device, analyze its optical behavior, and then present the different sources of measurement error. Most of them are negligible, and we present methods to mitigate the influence of these that are not. Part IV focuses on the experimental validation of the concepts presented so far. We describe the conception, calibration and validation of a Fourier Transform Mueller polarimeter that we intend to use to study the temperature dependence of the piezo-optic effect. We build a prototype based on the initial concept of the piezo-optic pressure sensor presented in Part III, and test its response to pressure. Its behaviour is found to be coherent with theoretical predictions, and these measurement serve to validate the concept of the sensor that was developed during this work
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Kombe, Sheila. "The role of innovation and institutional pressures in sustainable packaging." Diss., University of Pretoria, 2021. http://hdl.handle.net/2263/81318.
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There is an under-developed scale of research conducted on sustainable production and consumption of environmentally friendly packaging Tanzania. Using the main concepts from institutional theory along with the diffusion of innovation model, this paper will examine the environmentally friendly packaging innovations in the Tanzanian food and beverage industry. The purpose of this research is to understand the factors that enable adoption. It suggests that mimetic, coercive and normative pressures exist within manufacturing firms that can regulate and coordinate solutions. A level of understanding of perceived fidelity and perceived effort required were established to develop conditions where firms can create strategies for the adoption environmentally sustainable packaging. The research setting is in the manufacturing industry. The data gathered for this study was collected by distributing a survey to respondents using convenience and snow-balling technique. Manufacturing businesses and packaging suppliers of the food and beverage industry participated. The respondents were requested to forward the survey by passing on the google form link to business owners, company CEOs, CFOs, COOs. 29 firm responses from the target population were measured to establish the pressures that they face and their intention to adopt. After applying regression analysis to the data, coercive pressure and intention to adopt with perceived fidelity as a moderator suggested a significant relationship. Similarly, perceived effort required positively moderated the relationship between mimetic pressure and intention to adopt. However, the results showed that no significant relationship from each of the three isomorphic constructs namely normative, mimetic and coercive and intention to adopt. This was contradictory to previous researchers of isomorphic pressures and should be subjected to future research.<br>Mini Dissertation (MBA)--University of Pretoria, 2021.<br>Gordon Institute of Business Science (GIBS)<br>MBA<br>Unrestricted
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Nilsson, Annika. "Bacterial adaptation to novel selection pressures /." Stockholm, 2005. http://diss.kib.ki.se/2005/91-7140-192-X/.
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Wang, Zhou. "Metal vapour condensation at reduced pressures." Thesis, McGill University, 1990. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=59853.
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In the process of extracting silver from lead bullion, zinc is added to the lead bullion to form a zinc crust. The crust is subsequently distilled and metallic zinc is condensed for reuse. In the present work, four aspects of the process were studied: the thermodynamic properties of zinc in zinc crust (the Pb-Ag-Zn ternary system); the heat and mass transfer of zinc vapour in a vertical tube condenser in the presence of a non-condensable gas; the cooler-condenser design for the vapour and gas mixture; and the zinc vapour condensation behaviour.
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Zakaria, Salman. "Gas-polymer interaction at high pressures." Thesis, Imperial College London, 1990. http://hdl.handle.net/10044/1/46628.
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Ventura, Sónia Patrícia Marques. "Gas liquid equilibria at high pressures." Master's thesis, Universidade de Aveiro, 2007. http://hdl.handle.net/10773/4865.
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Mestrado em Medição de Equilíbrios Gás Líquido a Altas Pressões<br>Este trabalho tem como objectivo a medição da solubilidade de gases em
líquidos a altas pressões. Para a realização experimental foi usada uma célula
de altas pressões de volume variável e um método de observação directa para
a detecção das transições de fase. As condições usadas neste trabalho
experimental foram temperaturas entre 276.00 e 373.15 K e pressões ate
100 MPa.
Numa primeira fase foram efectuadas medições de solubilidade de metano em
anilina pura e para uma solução aquosa de composição mássica igual a 5%
em anilina. A anilina é fundamentalmente usada em processos como a
produção de borracha, de poliuretanos, pigmentos e tintas, fármacos,
herbicidas e fungicidas. É usualmente produzida através de processos de
redução do nitrobenzeno por reacção com o HCl. De facto, esta síntese é um
processo químico complexo onde um grande número de processos compete
entre si. Alterações nas condições do processo com a possível formação de
produtos intermediários podem afectar a eficiência do processo. Para a sua
melhoria foi sugerido que o hidrogénio usado fosse simultaneamente
produzido e gasto no reactor principal. Neste caso e para a produção do
mesmo, era necessário adicionar metano e água ao reactor. Tendo por base a
ideia de que as reacções onde o hidrogénio é reagente e produto ocorrem em
simultâneo, torna-se clara a importância do estudo da solubilidade do metano
em anilina pura e em soluções aquosas desta.
Numa segunda fase foi estudada a solubilidade do dióxido de carbono em
soluções aquosas de tri-iso-butil(metil)fosfónio tosilato, com composições
molares são de 4, 8 e 12% em líquido iónico. Este pertencente à família dos
fosfónios. Possui uma viscosidade e densidade elevadas, é térmica e
quimicamente estável e ainda possui uma elevada polaridade. Apresenta uma
miscibilidade completa em água e nos solventes mais usuais, como o
diclorometano e tolueno, não sendo no entanto míscivel em hexano. O tri-isobutil(
metil)fosfónium tosilato é usado como solvente nos processos de
hidroformilação de olefinas e ainda em processos de captura e conversão de
dióxido de carbono.
Neste trabalho experimental, a temperatura e a pressão foram inicialmente
aumentadas até o sistema atingir o equilíbrio. A pressão é diminuída
lentamente até se verificar o aparecimento/desaparecimento da última bolha
de gás. A pressão à qual a última bolha de gás desaparece representa a
pressão de equilíbrio para aquela temperatura. Este procedimento foi
efectuado para vários sistemas e várias temperaturas.<br>The aim of this work is the measurement of the solubilities of different gases in
different liquids systems at high pressures. A variable volume high pressure
cell was used to perform the measurements based on the visual synthetic
method for the detection of phase transitions. The conditions used in this work
were temperatures ranging from 276.00 to 373.15 K and pressures up to 100
MPa.
The first step of this work was the measurement of methane’s solubility in pure
aniline and for one aqueous solution of 5% (w/w) in aniline. The main
applications of aniline are the manufacture of polyurethane, rubber, dyes and
pigments, drugs and agrochemicals (herbicides and fungicides).
This compound is normally produced by reduction of nitrobenzene by reaction
with HCl. In fact, that synthesis is a complex chemical process where a number of
competing processes contribute to the final product. Changes in process conditions with
the possible formation of intermediates can act as catalyst poisons that change the
process’s efficiency. For the improvement of the production process it was
suggested that the hydrogen, used for the reduction of the nitrobenzene, could
be simultaneously generated and used in the main reactor. In this case for the
in situ production of hydrogen it would be necessary the addition of methane
and water in the reactor. Having in mind that these reactions occur
simultaneously, it becomes clear the importance of studying the solubility of
methane in aniline and in its aqueous solutions.
In the second step the solubility of carbon dioxide in aqueous solutions of triiso-
butyl(methyl)phosphonium tosylate with molar compositions of 4, 8 and
12% molar of ionic liquid, was studied. This compound belongs to the
phosphonium - based ionic liquids family. It is characterized by a high viscosity
and density. It is thermal and chemically stable and has a high polarity. This
compound is totally miscible with water as well as with common organic
solvents such as dicloromethane and toluene but is not miscible with hexane.
The main applications of Tri-iso-butyl(methyl)phosphonium tosylate are like
solvents in the hydroformylation of olefins and in processes of capture and
conversion of carbon dioxide.
In this experimental work, temperature and pressure were slowly increased
until the system becomes homogeneous. After that, the pressure is slowly
decreased until the appearance/disappearance of the last bubble of gas. The
pressure at witch the last bubble disappears represents the equilibrium
pressure for that temperature. This procedure was repeated for several
systems and several temperatures.
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Zain, Husni K. "Phase equilibrium studies at moderate pressures." Thesis, Aston University, 1992. http://publications.aston.ac.uk/9743/.
Full textAbstract:
The theory of vapour-liquid equilibria is reviewed, as is the present status or prediction methods in this field. After discussion of the experimental methods available, development of a recirculating equilibrium still based on a previously successful design (the modified Raal, Code and Best still of O'Donnell and Jenkins) is described. This novel still is designed to work at pressures upto 35 bar and for the measurement of both isothermal and isobaric vapour-liquid equilibrium data. The equilibrium still was first commissioned by measuring the saturated vapour pressures of pure ethanol and cyclohexane in the temperature range 77-124oC and 80-142oC respectively. The data obtained were compared with available literature experimental values and with values derived from an extended form of the Antoine equation for which parameters were given in the literature. Commissioning continued with the study of the phase behaviour of mixtures of the two pure components as such mixtures are strongly non-ideal, showing azeotopic behaviour. Existing data did not exist above one atmosphere pressure. Isothermal measurements were made at 83.29oC and 106.54oC, whilst isobaric measurements were made at pressures of 1 bar, 3 bar and 5 bar respectively. The experimental vapour-liquid equilibrium data obtained are assessed by a standard literature method incorporating a themodynamic consistency test that minimises the errors in all the measured variables. This assessment showed that reasonable x-P-T data-sets had been measured, from which y-values could be deduced, but that the experimental y-values indicated the need for improvements in the design of the still.
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Rafaquat, Mohammed. "Phase equilibrium studies at normal pressures." Thesis, Aston University, 1991. http://publications.aston.ac.uk/9734/.
Full textAbstract:
A total pressure apparatus has been developed to measure vapour-liquid equilibrium data on binary mixtures at atmospheric and sub-atmospheric pressures. The method gives isothermal data which can be obtained rapidly. Only measurements of total pressure are made as a direct function of composition of synthetic liquid phase composition, the vapour phase composition being deduced through the Gibbs-Duhem relationship. The need to analyse either of the phases is eliminated. As such the errors introduced by sampling and analysis are removed. The essential requirements are that the pure components be degassed completely since any deficiency in degassing would introduce errors into the measured pressures. A similarly essential requirement was that the central apparatus would have to be absolutely leak-tight as any leakage of air either in or out of the apparatus would introduce erroneous pressure readings. The apparatus was commissioned by measuring the saturated vapour pressures of both degassed water and ethanol as a function of temperature. The pressure-temperature data on degassed water measured were directly compared with data in the literature, with good agreement. Similarly the pressure-temperature data were measured for ethanol, methanol and cyclohexane and where possible a direct comparison made with the literature data. Good agreement between the pure component data of this work and those available in the literature demonstrates firstly that a satisfactory degassing procedure has been achieved and that secondly the measurements of pressure-temperature are consistent for any one component; since this is true for a number of components, the measurements of both temperature and pressure are both self-consistent and of sufficient accuracy, with an observed compatibility between the precision/accuracy of the separate means of measuring pressure and temperature. The liquid mixtures studied were of ethanol-water, methanol-water and ethanol-cyclohexane. The total pressure was measured as the composition inside the equilibrium cell was varied at a set tmperature. This gave P-T-x data sets for each mixture at a range of temperatures. A standard fitting-package from the literature was used to reduce the raw data to yield y-values to complete the x-y-P-T data sets. A consistency test could not be applied to the P-T-x data set as no y-values were obtained during the experimental measurements. In general satisfactory agreement was found between the data of this work and those available in the literature. For some runs discrepancies were observed, and further work recommended to eliminate the problems identified.
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Winardi, Leonard. "Procedures for predicting pressures inside cores." Birmingham, Ala. : University of Alabama at Birmingham, 2007. https://www.mhsl.uab.edu/dt/2009r/winardi..pdf.
Full textAbstract:
Thesis (Ph. D.)--University of Alabama at Birmingham, 2007.<br>Title from PDF of title page (viewed October 13, 2009). Additional advisors: J. Barry Andrews, Gregg M. Janowski, Peter M. Walsh, Srinath Viswanathan, Harry E. Littleton. Includes bibliographical references (p. 207-209).
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Tait, Robert Niall. "Ignition of arc discharges at high pressures." Thesis, University of British Columbia, 1988. http://hdl.handle.net/2429/28523.
Full textAbstract:
This report describes attempts to discover a method for starting a water walled argon arc at high pressure. It is demonstrated that addition of small amounts of acetylene to the argon causes a very small reduction of breakdown voltage at pressures of about 3 atmospheres. Droplets of distilled water and of KC1 solution are shown to effectively increase the breakdown potential of a gas. A calculation of static fields before arc ignition
is presented, and alternative starting circuit tests are done. Parallel starting pulse injection is found inferior to the normally used series injection. An auxiliary discharge is found to aid starting slightly, and a drastic decrease in the breakdown potential due to removal of the water wall is discovered.<br>Science, Faculty of<br>Physics and Astronomy, Department of<br>Graduate
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Kelly, Camilla Theresa. "Gas - elastomer interactions at high pneumatic pressures." Thesis, Imperial College London, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.298253.
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Castle, Saffron Jane. "Sensing bilayer pressures with pyrene-labelled probes." Thesis, Imperial College London, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.281742.
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Jackson, Dickon H. "Microwave-induced bulk pressures for liquid analysis." Thesis, Edinburgh Napier University, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.285236.
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Paquette, Julie Rebecca. "The supply chain response to environmental pressures." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/34530.
Full textAbstract:
Thesis (S.M.)--Massachusetts Institute of Technology, Engineering Systems Division, Technology and Policy Program; and, Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2006.<br>Includes bibliographical references (p. 131-135).<br>Understanding and shaping the relationship between supply chain management and the natural environment is critical not only to human health and the environment, but to the future success of business. While the cumulative environmental impacts of industrial production are best addressed at the supply chain level, little research has connected the overall context of supply chain management, including the characteristics of environmental pressures and market drivers, to a general approach for developing operational supply chain processes that may deliver environmental and economic performance improvements. Findings from a series of semi-structured interviews indicate that there are four sources of environmental pressure currently affecting supply chain management in unique ways. These include regulations, customer demands, resources, and ethical responsibility. Corporations that are better able to identify and understand these impacts will be better positioned to address them strategically. A framework of supply chain environmental excellence is presented to illustrate how corporations may integrate environmental operating models, operational objectives, and new supply chain processes into a comprehensive corporate strategy.<br>(cont.) A case study of the emergence of reverse supply chains within the electronics industry illustrates why supply chain processes should be developed in a context defined by environmental pressures and market drivers. As the electronics industry is faced with environmental pressure from evolving regulatory directives, liability concerns, and social responsibility demands, leading companies are researching and piloting reverse processes to varying extents. Findings from a second series of industry interviews reveal a number of regulatory, behavioral, and economic trends and challenges that collectively shape both strategic considerations for individual corporations and the overall supply chain capabilities of the industry.<br>by Julie Rebecca Paquette.<br>S.M.
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Mahowald, Kyle. "Cognitive and communicative pressures in natural language." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/106435.
Full textAbstract:
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Brain and Cognitive Sciences, 2016.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (pages 189-204).<br>Why do languages have the words they do instead of some other set of words? In the first part of this thesis, I argue that cognitive and communicative demands strongly influence the structure of the lexicons of natural languages. It is known that words in natural language are distributed such that shorter words are more frequent and occur after more predictive contexts. I provide evidence that, at least in part, this pattern is driven by word shortenings (i.e., chimp -+ chimpanzee) and that word shortenings can be predicted by principles of efficient communication. I also show that, using nonce words with no pre-existing semantic meaning, a Zipfian correlation between length and frequency emerges in freely produced text and that this correlation is driven by participants' tendency to reuse short words more readily than longer words. In addition to word length, I investigate phonetic probability in a corpus of 97 languages. Across a wide variety of languages and language families, phonetic forms are optimized for efficient communication. And, using baseline phonetic models, I show that the words in the lexicons of four languages (English, Dutch, German, and French) are more tightly clustered in phonetic space than would be suggested by chance alone. This thesis depends on standard methods in language research. How reliable is the data that we work with as a field? In the second part of this thesis, I tackle that question by examining two dominant methods in modern language research: behavioral experiments (specifically syntactic priming) and linguistic acceptability judgments. I present data, based on large-scale surveys, showing that many of the standard syntactic and semantic judgments in a mainstream linguistic journal are flawed. Using this data, I construct a Bayesian prior over judgments and give recommendations for performing small sample-size experiments in linguistics that will not overly burden researchers. Finally, I present a large-scale meta-analysis of syntactic priming (the largest meta-analysis of a psycholinguistic phenomenon) and find that, while many priming studies are severely underpowered, there is no evidence of intense p-hacking.<br>by Kyle Mahowald.<br>Ph. D.
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Moon, Chanki. "Cultural differences in responses to hierarchical pressures." Thesis, University of Kent, 2016. https://kar.kent.ac.uk/61052/.
Full textAbstract:
Social hierarchy is one of the most fundamental features of human social interaction and has important psychological consequences. How hierarchies function and impact psychological processes, however, varies across cultures. Social interactions in Korea are more hierarchical and collectivistic compared to those in the UK, which are less hierarchical and individualistic. This is reflected in the Power Distance cultural dimension (Hofstede, 1980, 2001), according to which the UK is lower on this dimension than Korea. Social norms enforce hierarchies such as deference, respect, honour and politeness which operate as an invaluable virtue in Korean society. The current research examines consequences of social hierarchy in the UK and Korea and asks the following questions: a) are there any differences between Korea and the UK in terms of how individuals' interactions are governed by the status of the interaction partner; b) how does the impact of rude behaviours exhibited by people occupying different ranks differ in Korea and the UK, focusing on the level of distress caused and individuals' evaluations of the perpetrator; and c) are there any differences between Korea and the UK in terms of how hierarchical relations are embedded in objective organisational prescriptions? Findings from Studies 1 and 2 demonstrated that Korean participants' communication was affected to a greater extent by hierarchical relations showing that Korean participants wrote longer emails to decline a request by a senior colleague compared to a junior colleague; in contrast, the length of the emails written by British participants were not affected by the status of the recipient. Furthermore, across three studies (1-3), findings indicated that Koreans (compared with British) found it less stressful and more acceptable to be exposed to uncivil behaviours (rude and discourteous actions) of a senior colleague compared to a junior colleague. Study 4 confirmed that a similar pattern of hierarchical differentiation can be observed in organisations structured vertically (mirroring Korean culture), but not in organisations structured horizontally (mirroring British culture). Furthermore, in Studies 2, 3 and 4, mediational analyses showed that the observed cultural differences in reported levels of hierarchical relational stress (discomfort) can be explained by group differences in prescriptive norms (acceptability), but not by differences in descriptive norms (likelihood of occurrence). Finally, Study 5 examined how hierarchies are manifested in objective institutional regulations in the form of Code of Ethics adopted by Korean and British organisations. Findings revealed that relative to British organisations, Korean organisations endorsed Code of Ethics that places greater emphasis on hierarchical relations, consistent with prevalent cultural values and beliefs. Together, Studies 2 and 3 have highlighted cross-cultural variations in individuals' subjective mental representations of norms related to the behaviours of high and low ranking individuals and Study 5 demonstrated cross-cultural variations in how hierarchies are embedded in objective organisational prescriptions in Korea and the UK. I discuss the implications of these findings for literatures on social hierarchies/status, social norms, organisational behaviour and culture.
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Zajicek, Petr. "Large rivers’ fish assemblages under multiple pressures." Doctoral thesis, Humboldt-Universität zu Berlin, 2019. http://dx.doi.org/10.18452/19885.
Full textAbstract:
Europäische große Flüsse wurden über Jahrhunderte entscheidend verändert und zu Wasserstraßen für die Schifffahrt ausgebaut. Flussregulierung, Begradigung und Hochwasserschutz tragen zu multiplen Stressoren bei, wobei die Schifffahrt bislang keine Beachtung als potentieller zusätzlicher Einflussfaktor (Stressor) fand. Die zentrale Fragestellung dieser Arbeit befasste sich mit der Rolle der Schifffahrt zwischen multiplen Stressoren und deren Auswirkungen auf die Fischgemeinschaften großer Flüsse. Hierzu wurde die „Large River Fish Database“ (LRDB), ein weltweit einzigartiger Datensatz zusammengestellt, der 2693 Befischungen an 358 Probestellen in 16 europäischen großen Flüssen enthält. Die Probestellen sind durch verschiedene Einflussfaktoren (Stressoren) und Schiffsverkehr beschrieben. Um ein für große Flüsse repräsentatives Abbild der Fischgemeinschaften zu erhalten, wurden zunächst die angewendeten Fischfangmethoden analysiert. Mit der Elektrofischerei wurden die höchsten Fischdichten und die höchste Biodiversität erfasst. Die Elektrofischerei ist daher für eine repräsentative Erfassung der Fischgemeinschaften großer Flüsse geeignet und wurde für weitere Analysen ausgewählt. Die kommerzielle Frachtschifffahrt trat als einer der einflussreichsten Stressoren hervor, zusammen mit erhöhter Fließgeschwindigkeit und dem Verlust von Überschwemmungsflächen. Dichten von insbesondere Habitat-sensitiven Fischen sanken bereits ab acht Frachtschiffen pro Tag signifikant ab. Darüberhinaus hatte auch die Freizeitschifffahrt (Flusskreuzfahrten und motorisierte Sportboote) deutliche und zu Frachtschiffen unterscheidbare ökologische Konsequenzen. Die Wirkungen der Schifffahrt sind ebenso verheerend wie die der hydromorphologischen Degradierung und benötigen eine gesonderte Beachtung im Flussmanagement und der Flussrevitalisierung. Freizeitboote und Flussdampfer wirken der Flussrenaturierung kleinerer Wasserstraßen entgegen und gefährden den ökologischen Erfolg des Blauen Bandes.<br>European large rivers have been tremendously modified over centuries and transformed into waterways for inland navigation. Extensive river modifications such as river regulation, channel straightening and flood protection have resulted in multiple pressures. However, inland navigation has not been considered as a potential pressure yet. This thesis aimed to assess the role of inland navigation among the most prevailing pressures in large rivers under field conditions. A worldwide unique and complementary dataset, the Large River Fish Database (LRDB) was compiled. The LRDB consists of 2693 fish samples assessed at 358 sampling sites in 16 European large rivers. Sites were characterized by various pressure variables and frequencies of ship traffic. To derive representative samples of large rivers fish assemblages, performance of various fishing gears applied was assessed. Electrofishing samples represented highest densities of fish and highest overall biodiversity. Therefore, electrofishing is suitable for fish-based assessments of large rivers and only electrofishing samples were selected to assess multiple pressures and inland navigation. Commercial cargo navigation appeared as the most influential pressures on large rivers fish assemblages among increased velocities and the loss of floodplains. Starting at already eight passing vessels per day, densities of particularly habitat-sensitive spawners significantly declined. Moreover, recreational navigation such as river cruises and motorized sport boats had distinct ecological consequences to those of cargo vessels. Inland navigation is as detrimental as the hydromorphological degradation of the river channel and requires specific attention in river management and rehabilitation. Pleasure boating (river cruises and sport boats) will counteract river rehabilitation also in smaller waterways and delimit ecological success of the Blue Band initiative in Germany.
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Cartwright, Debra K. "Strategic responsiveness to institutional pressures : resistance and internalization strategies in response to conflicting institutional pressures regarding assessment in higher education /." free to MU campus, to others for purchase, 1998. http://wwwlib.umi.com/cr/mo/fullcit?p9901222.
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Waters, Richard. "Equalising the pressures : principals, consultants and ethical dilemmas /." [St. Lucia, Qld], 2004. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe18190.pdf.
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Sapaz, Burak. "Lateral Versus Vertical Swell Pressures In Expansive Soils." Master's thesis, METU, 2004. http://etd.lib.metu.edu/upload/1053040/index.pdf.
Full textAbstract:
Expansive or swelling soils, exist in many part of the world, show excessive volume changes with increasing water content. As a result of this volume increase, expansive soils apply vertical and lateral pressures to the structures located or buried in these regions. Many researchs have been carried out on vertical swelling pressures helping to the engineers to design structures withstanding on these stresses. However, lateral swell behaviour of swelling soils have not been fully understood yet. Structures such as<br>basement walls, water tanks, canals, tunnels, underground conduits and swimming pools which will be built in expansive soils have to be designed to overcome the lateral swelling pressures as well as the other lateral pressures exerted by the soil. For this aim accurate and reliable methods are needed to predict the magnitude of lateral swelling pressures of expansive soils and to understand the lateral swelling behaviour of expansive soils.
In this experimental study, the lateral swelling behaviour of an highly expansive clay is investigated using a modified thin wall oedometer which was developed in the METU Civil Engineering Department Soil Mechanics Laboratory earlier.
Statically compacted samples were used in constant volume swell (CVS) tests to measure the magnitude of the lateral and vertical swelling pressures. To study the relationship between the lateral and vertical sweeling pressures, they were measured simultaneously. The samples having different initial water contents and different initial dry densities were used to study the effects of these variables on the vertical and the lateral swelling pressures.
It is observed that both lateral and vertical pressures increases with increasing initial dry density and they decrease with increasing initial water content. Swell pressure ratio, the ratio of lateral swelling pressure to the vertical one, is increasing with increasing initial water content. Time needed to obtain the magnitude of maximum lateral and vertical pressures decreases with increasing initial water content and increases with increasing initial dry density.
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Johnson, James Stewart. "Secular change pressures in UK corporate bank lending." Thesis, Loughborough University, 1995. https://dspace.lboro.ac.uk/2134/31922.
Full textAbstract:
This thesis examines the question of the existence of banks as financial intermediaries. It is apparent in UK corporate bank lending that there is a long-term secular decline which is reducing the scale and affecting the form of such lending and which is inducing a redefinition of the role of banks in the financial system. In the final analysis banks exist as a response to market imperfections: scale economies; information asymmetries; monitoring reputation; control facilities; and commitment abilities. These provide alternative conditions defining banks, their position in the financial system and their comparative advantages.
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Take, W. Andrew. "Lateral earth pressures behind rigid fascia retaining walls." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0010/MQ38414.pdf.
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Meißner, Thomas. "Exploring Nuclear Magnetic Resonance at the Highest Pressures." Doctoral thesis, Universitätsbibliothek Leipzig, 2013. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-115023.
Full textAbstract:
Die vorliegende Arbeit beschäftigt sich mit der Entwicklung und Anwendung der Kernmagnetresonanz (NMR) unter extremen Drücken bis 101 kbar. Es wird gezeigt, dass die Empfindlichkeit von NMR Experimenten unter hohen Drücken in Diamantstempel- und ähnlichen Hochdruckzellen im Vergleich zu früheren experimentellen Versuchsanordnungen durch Verwendung von Mikrospulen um mehrere Größenordnungen verbessert werden kann. Die neue Versuchsanordnung wird dann zum einen bei der Untersuchung der Druckabhängigkeit elektronischer Eigenschaften von metallischem Aluminium bis 101 kbar verwendet. Zum anderen wird damit der Pseudogap des Hochtemperatursupraleiters YBa2Cu4O8 bei Drücken bis zu 63 kbar untersucht.
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Ahn, B. K. "Modelling unsteady wall pressures beneath turbulent boundary layers." Thesis, University of Cambridge, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.595397.
Full textAbstract:
The objective is to estimate the surface pressure distributions and corresponding spectra induced by fully developed hairpin vortices inclined at an angle of 45 degree to the wall in turbulent boundary layers. On the assumption that fully developed hairpin vortices are governed by inviscid dynamics, we obtain an exact formulation for the stagnation pressure, in terms of a Green function integral along the vortex lines. We then evaluate the surface static pressure by subtracting the dynamic pressure from the results of this formulation applied to our vortex geometry. On the basis of the attached eddy model, which implies that the form of the wave number spectrum can be deduced from the properties of a single eddy, we develop the expressions needed for the surface pressure spectra in terms of eddy number-density. This approach draws on flow visualization evidence, which indicates that the number of eddies observed in both streamwise and spanwise directions of the flow is inversely proportional to their size. The overall wavenumber spectrum consists of contributions from eddies of all sizes, weighted by the number-density. From a parameter study we investigate the influence of varying the largest and smallest eddy scales for different eddy aspect ratios. We then validate our model against existing descriptions and measurements of turbulent boundary layer pressures. We examine the predicted wave number spectra and compare them with those of existing empirical models, available direct numerical simulation and also with the results of flight-test measurements. The present model clearly predicts a theoretically-expected characteristic of the wavenumber spectrum (the -1 slope), whereas this is absent from the empirical models. This discrepancy apart, good quantitative agreement is achieved, particularly for the spanwise (cross-flow) spectrum. The agreement is best for the novel formulation for off-axis correlations proposed by Smol'yakov and Tkachenko (1991), rather than the traditional form (e.g. Corcos). The comparison with flight-test data is made via predicted and measured spatial correlations, and again shows good agreement. The present hairpin vortex model shows that it is capable of predicting the properties of the wall pressure field, and is therefore a promising candidate for use in exploring features less readily obtainable by other methods, e.g. off-axis correlations.
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Chua, H. Y. "Horizontal arching of earth pressures on retaining structures." Thesis, University of Cambridge, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.597676.
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The horizontal arching mechanism transfers horizontal earth pressures acting on a retaining wall panel to neighbouring elements via soil shear stresses. In this research, the horizontal arching mechanism and lateral deformations of fixed cantilever walls are investigated using centrifuge tests. A 300mm high, L-shaped model basement comprising separate but contiguous wall panels of different widths and stiffnesses was built to accommodate this purpose. A re-entrant corner was included as part of the basement geometry, in order that an idealization of the stress distribution at such corners might be made. The model basement retained dry sand poured within an external confining steel tub of 850mm in diameter. Heavy fluid was contained within to generate stress conditions similar to those found in-situ after casting a wall. The fluid was then drained in-flight to simulate an excavation sequence. A series of six tests were carried out at 45g where the panel widths and thicknesses around the model basement were varied, so that the effects of panel geometry and stiffness on horizontal arching could be studied. Displacement distributions at the re-entrant corner were investigated with the help of Particle Image Velocimetry (PIV), a programme that tracks object movements in patches through a series of still digital images. Photogrammetric calibration was then applied to establish the soil and panel movement vectors in object space. Results indicate that the magnitude of horizontal arching reduces with increasing panel width and stiffness. The equivalent earth pressure coefficient, K, was established through the superimposition of predicted and measured panel displacements and bending moments. Data obtained showed that the earth pressure dropped to below active values, represented by a new coefficient K<sub>min</sub>, as the wall rotation exceeded 10<sup>-3</sup> radians.
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Zhao, Jianguang, and 趙建光. "Characteristics of fluctuating pressures on a cantilevered roof." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2001. http://hub.hku.hk/bib/B29753296.
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Goff, Simon E. J. "Organometallic chemistry at high pressures and low temperatures." Thesis, University of Nottingham, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.338521.
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Yu, Shenkai. "Finite element prediction of wall pressures in silos." Thesis, University of Wolverhampton, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.401036.
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Thompson, Pauline. "Behaviour of potassium feldspar at high water pressures." Thesis, University of Edinburgh, 1995. http://hdl.handle.net/1842/11469.
Full textAbstract:
Some natural potassium feldspars have been shown to contain traces of structural "water" which may have been incorporated into the structure at high partial pressures of water. At even higher partial pressures of water potassium feldspar is known to break down to form a hydrated phase (referred to as "sanidine hydrate") which is structurally comparable to cymrite which forms from barium feldspar (celsian) at high pressures. This study investigates the capacity for potassium feldspar and "sanidine hydrate" to act as reservoirs for hydrous fluids in the Earth's crust and upper mantle, and establishes the pressure-temperature range of stability of the hydrate phase. Sanidine and "sanidine hydrate" have been synthesised from gels at a variety of pressures and temperatures in a piston cylinder apparatus and cold seal apparatus. These run products have been used to determine the equilibrium position of the reaction between sanidine and water to form "sanidine hydrate". The reaction was found to lie between four brackets of 2.35 and 2.5 GPa at 450°C, 2.4 and 2.59 GPa at 550°C, 2.67 and 2.74 GPa at 650°C and 2.70 and 2.72 GPa at 680°C. Infrared spectroscopy showed that the dominant water species in "sanidine hydrate" was structural H<SUB>2</SUB>O. The quantity of this structural H<SUB>2</SUB>O, measured by thermogravimetric analysis, was found to vary between 4.42 and 5.85 wt% over the pressure range of 2.7 to 3.2 GPa and the temperature range of 450 to 680°C. Systematic variation in water content over the experimental range studies was not clearly established. The samples may have been contaminated with platinum from the capsule and the resultant thermogravimetric analyses would be too low. The maximum value was below 6.07 wt% which would be equivalent to 1 molecule of H<SUB>2</SUB>O per formula unit. It was possible to remove the water entirely by heating at atmospheric pressure to produce anhydrous hexagonal KAlSi<SUB>3</SUB>O<SUB>8</SUB> ("hexasanidine") implying that the structural "water" content of "sanidine hydrate" is variable, perhaps as a continuous solid solution between the end members where n = 1 and n = 0 in the formula KAlSi<SUB>3</SUB>O<SUB>8</SUB>.nH<SUB>2</SUB>O. The unit cell parameters measured by powder X-ray diffraction, for "sanidine hydrate" were <I>a</I> = 0.5337 nm and <I>c</I> = 0.7714 nm, and those for "hexasanidine" were <I>a</I> = 0.5288 nm and <I>c</I> = 0.7818 nm. This change in the unit cell parameters on dehydration was of a similar magnitude and direction to those for cymrite and hexacelsian, which would also suggest a solid solution in the water content as was found in the barium analogue. The water content data was not of a sufficient quality to calculate the average enthalpy and entropy of the dehydration of "sanidine hydrate". If the structural "water" content of "sanidine hydrate" is presumed constant over the pressure-temperature range of the study the average values for the enthalpy is 18000 (±5000)Jmol<SUP>-1</SUP> and for the entropy is 92.75 (±5.80) JK<SUP>-1</SUP>mol<SUP>-1</SUP>.
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Meier, Thomas. "High Sensitivity Nuclear Magnetic Resonance at Extreme Pressures." Doctoral thesis, Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-203643.
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Moderne Hochdruckforschung entwickelt sich rasant zu einer der vielfältigstens und überraschensten Disziplinen der Festkörperphysik. Unter Benutzung von Diamantstempelzellen können Drücke erreicht werden, die den Bedingungen im Inneren unserer Erde ähneln.
Eine Anwendung von Kernmagnetischen Resonanzexperimenten (NMR) in Diamantstempelzellen galt jedoch fur lange Zeit als unmöglich. In der vorliegenden Arbeit wird ein neuartiger Ansatz weiterentwickelt, der Radiofrequenz-(RF)-Mikrospulen benutzt, die direkt zwischen den Diamantstempeln platziert werden, und somit zu einer
signififikanten Sensitivitatssteigerung führen.
Es ist gelungen, Hochdruckzellen zu entwickeln, die fur die speziellen Anforderungen der NMR zugeschnitten sind. Des Weiteren konnte eine nicht metallische, nicht magnetische Dichtung entwickelt werden, die zudem zu einer signififikanten Stabilisierung des Probenvolumens führt. Eine breit angelegte Analyse der Leistungsfähigkeit dieser
neuartigen NMR-Hochdruckprobenköpfe zeigt deren Leistungsfähigkeit mit sehr hohen Empfifindlichkeiten sowie einer exzellenten RF Anregung und Zeitauflösung.
Drei Anwendungsbeispiele, die das Potenzial dieses Ansatzes in dieser Arbeit
unterstreichen, werden vorgestellt. Bei Drücken von bis zu 4 GPa werden die elektronischen und dynamischen Eigenschaften von elementarem Gallium untersucht. Unter höheren Drücken ist es gelungen, einen druckinduzierten Isolator-Metall-Übergang in dem ternaren Chalkogenid AgInTe2 zu beobachten. Schlussendlich ist es gelungen, die strukturellen und elektronischen Eigenschaften von Rubin bei Drücken von bis zu 30.5
GPa zu untersuchen, was einer Verdreifachung des bisher zugänglichen experimentellen Druckbereiches entspricht und die NMR fur moderne Hochdruckanwendungen möglich macht.
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Sehn, Allen L. "Experimental study of earth pressures on retaining structures." Diss., Virginia Tech, 1990. http://hdl.handle.net/10919/39696.
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Pilemalm, Robert. "TiAlN-based Coatings at High Pressures and Temperatures." Licentiate thesis, Linköpings universitet, Nanostrukturerade material, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-112213.
Full textAbstract:
TiAlN and TiAlN-based coatings that are used of relevance as protection of cutting tool inserts used in metal machining have been studied. All coatings were deposited by reactive cathodic arc evaporation using industrial scale deposition systems. The metal content of the coatings was varied by using different combinations of compound cathodes. The as-deposited coatings were temperature annealed at ambient pressure and in some cases also at high pressure. The resulting microstructure was first evaluated through a combination of x-ray diffraction and transmission electron microscopy. In addition, mechanical properties such as hardness by nanoindentation were also reported. TiAlN coatings with two different compositions were deposited on polycrystalline boron nitride substrates and then high pressure high temperature treated in a BELT press at constant 5.35 GPa and at 1050 and 1300 °C for different times. For high pressure high temperature treated TiAlN it has been shown that the decomposition is slower at higher pressure compared to ambeint pressure and that no chemical interaction takes place between TiAlN and polycrystalline cubic boron nitride during the experiments. It is concluded that this film has the potential to protect a polycrystalline cubic boron nitride substrate during metal machining due to a high chemical integrity. TiZrAlN coatings with different predicted driving forces for spinodal decomposition were furthermore annealed at different temperatures. For this material system it has been shown that for Zr-poor compositions the tendency for phase separation between ZrN and AlN is strong at elevated temperatures and that after spinodal decomposition stable TiZrN is formed.
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Seemiller, Eric S. "Selective pressures influencing color-vision in Neotropical primates." Kent State University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=kent1309883439.
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Burrell, Robert Roe. "Studies of Methane Counterflow Flames at Low Pressures." Thesis, University of Southern California, 2017. http://pqdtopen.proquest.com/#viewpdf?dispub=10271093.
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<p> Methane is the smallest hydrocarbon molecule, the fuel most widely studied in fundamental flame structure studies, and a major component of natural gas. Despite many decades of research into the fundamental chemical kinetics involved in methane oxidation, ongoing advancements in research suggest that more progress can be made. Though practical combustors of industrial and commercial significance operate at high pressures and turbulent flow conditions, fundamental understanding of combustion chemistry in flames is more readily obtained for low pressure and laminar flow conditions. </p><p> Measurements were performed from 1 to 0.1 atmospheres for premixed methane/air and non-premixed methane-nitrogen/oxygen flames in a counterflow. Comparative modeling with quasi-one-dimensional strained flame codes revealed bias-induced errors in measured velocities up to 8% at 0.1 atmospheres due to tracer particle phase velocity slip in the low density gas reacting flow. To address this, a numerically-assisted correction scheme consisting of direct simulation of the particle phase dynamics in counterflow was implemented. Addition of reactions describing the prompt dissociation of formyl radicals to an otherwise unmodified USC Mech II kinetic model was found to enhance computed flame reactivity and substantially improve the predictive capability of computed results for measurements at the lowest pressures studied. Yet, the same modifications lead to overprediction of flame data at 1 atmosphere where results from the unmodified USC Mech II kinetic mechanism agreed well with ambient pressure flame data. The apparent failure of a single kinetic model to capture pressure dependence in methane flames motivates continued skepticism regarding the current understanding of pressure dependence in kinetic models, even for the simplest fuels.</p>
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Gohari, Darabkhani Hamid. "Experimental investigations on sooty flames at elevated pressures." Thesis, University of Manchester, 2010. https://www.research.manchester.ac.uk/portal/en/theses/experimental-investigations-on-sooty-flames-at-elevated-pressures(36655740-7ea3-4a91-a2ce-4357902fd71b).html.
Full textAbstract:
This study addresses the influence of elevated pressures, fuel type, fuel flow rate and co-flow air on the flame structure and flickering behaviour of laminar oscillating diffusion flames. Photomultipliers, high speed photography and schlieren, accompanied with digital image processing techniques have been used to study the flame dynamics. Furthermore, the effects of pressure on the flame geometry and two-dimensional soot temperature distribution in a laminar stable diffusion flame have been investigated, utilising narrow band photography and two-colour pyrometry technique in the near infra-red region. This study provides a broad dataset on the diffusion (sooty) flame properties under pressures from atmospheric to 16 bar for three gaseous hydrocarbon fuels (methane, ethylene and propane) in a co-flow burner facility.It has been observed that the flame properties are very sensitive to the fuel type and flow rate at elevated pressures. The cross-sectional area of the stable flame shows an average inverse dependence on pressure to the power of n, where n was found to be 0.8±0.2 for ethylene flame, 0.5±0.1 for methane flame and 0.6±0.1 for propane flame. The height of a flame increases firstly with pressure and then decreases with further increase of pressure. It is observed that the region of stable combustion was markedly reduced as pressure was increased. An ethylene flame flickers with at least three dominant modes, each with corresponding harmonics at elevated pressures. In contrast, methane flames flicker with one dominant frequency and as many as six harmonic modes at elevated pressures. The increase in fuel flow rate was observed to increase the magnitude of oscillation. The flickering frequency, however, remains almost constant at each pressure. The dominant flickering frequency of a methane diffusion flame shows a power-law dependence on chamber pressure.It has been observed that the flame dynamics and stability are also strongly affected by the co-flow air velocity. When the co-flow velocity reached a certain value, the buoyancy driven flame oscillation was completely suppressed. The schlieren imaging has revealed that the co-flow of air is able to push the initiation point of outer toroidal vortices beyond the visible flame to create a very stable flame. The oscillation frequency was observed to increase linearly with the air co-flow rate. The soot temperature results obtained by applying the two-colour method in the near infra-red region shows that in diffusion flames the overall temperatures decrease with increasing pressure. It is shown that the rate of temperature drop is greater for a pressure increase at lower pressures in comparison with higher pressures.
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Zhao, Jianguang. "Characteristics of fluctuating pressures on a cantilevered roof /." Hong Kong : University of Hong Kong, 2001. http://sunzi.lib.hku.hk/hkuto/record.jsp?B23530194.
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Economou, Emmanuel. "How institutional pressures influence data-driven corporate communications." Thesis, Queensland University of Technology, 2021. https://eprints.qut.edu.au/209153/1/Emmanuel_Economou_Thesis.pdf.
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This study explores the use of data to guide corporate communications, a practice of which empirical research is limited, and is the first to investigate how institutional pressures influence practitioners in their work. In-depth interviews were conducted with 15 participants from a wide range of organisations in Brisbane, Australia. Additionally, the study illustrates the current state of research on big data in corporate communication in a systematic literature review. The study’s findings indicate that institutional pressures influence data-driven corporate communications and are generally consistent with the results of practitioner studies around the world.
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Brehaut, Richard Jeremy. "Groundwater, Pore Pressure and Wall Slope Stability – a model for quantifying pore pressures in current and future mines." Thesis, University of Canterbury. Geological Sciences, 2009. http://hdl.handle.net/10092/4465.
Full textAbstract:
The Hamersley Province, located approximately 1200 km north of Perth, Western Australia forms part of the southern Pilbara craton, an extensive area of Band Iron Formations (BIF). The area has a high economic significance due to several enrichment stages of the country rock (BIF) resulting in several large high-grade iron ore deposits. Mount Whaleback near Newman and Mount Tom Price are the largest deposits, where reserves have been estimated at 1400 Mt and 900 Mt respectively. These ore bodies have been quantified as being high grade resources at approximately 64 % iron, with a high lump to fines ratio, and low impurities. The Mount Tom Price ore body is a hematite-rich ore, associated with a variety of shale and some dolomitic units (MacLeod et al., 1963, MacLeod, 1966, Taylor et al., 2001, Morris, 1980).
The local hydrogeology of the Mount Tom Price area involves two main aquifer systems. The Dales Gorge member of the Brockman Iron Formation with contributions from the upper mineralised section of Footwall zone make up the main semi confined aquifer within the area. The underlying low permeability Mount McRae Shale and Mount Sylvia Shale lithologies separate a secondary aquifer which is located within the Wittenoom Formation. A dewatering program within Mount Tom Price has been ongoing since installation in 1994.
Within the open pit mining industry, pits depths are increasingly being deepened as the easily accessible surface ore has been removed. This involves excavating pit walls below the existing groundwater table, which can lead to instabilities within pit walls. Added to this is the timing and economic considerations which need to be accounted for in a working mine. As dewatering and depressurisation are pivotal to the extraction of ore resources below the groundwater table, there can often be considerable time pressures to maintain planned mine developments (Hall, 2003).
The South East Prongs pit, located within the Mount Tom Price mine, holds some of the most valued low impurity, high grade hematite ore. Structurally the South East Prongs is unique as the deposit lies in the base of a steeply dipping double plunging syncline, intersected by the Southern Batter Fault which runs parallel in strike to the Turner Syncline.
The current pit floor of South East Prongs is located at 600 mRL. The long term development plan for the western end of this pit includes a further 30 m of excavation to a final depth of 570 mRL. This currently poses a number of stability issues that require resolution before any development can be undertaken.
A conceptual understanding of flow dynamics within structurally complex wall rock environment has been generated through the utilisation of finite element numerical modelling. The complex structural setting within the northern wall of the South East Prongs has shown to interact with high conductivity lithologies to promote preferential flow of groundwater from the underling Wittenoom Formation aquifer. Recharge to the semi confined DG aquifer occurs as groundwater travels up shear zones within the South East Prongs Fault Zone before migrating along Brunos Band.
An investigation into alternative methods of depressurisation has been recommended to ensure the ongoing management of pore water pressures within the northern pit wall during planned pit cut backs. Limiting recharge from the WF to the pit through stated preferential flow paths has been identified as a potential issue when the remaining DG aquifer is removed. Maintaining the proposed dewatering buffer will be difficult to achieve using the current system.
The ability to design optimal pit shells for access and ore recovery as well as an effective dewatering and depressurisation system relies heavily on the a sound geological model. Further to this, time allocations to ensure forward planning deadlines are met can be significantly interrupted if adjustments to initial plans are required.