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Jjunju, F. P. M. "In-situ mass spectrometry analysis under ambient conditions." Thesis, University of Liverpool, 2016. http://livrepository.liverpool.ac.uk/3004973/.
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Mass Spectrometry (MS) is an important analytical tool in the identification and quantification of a wide range of samples, primarily because of its speed, sensitivity, selectivity and versatility in analysing, gases, solids and liquids. MS is an interdisciplinary analytical tool, impacting many areas of science from physics, through chemistry, to biology. However MS is mainly limited to laboratory settings due to the high vacuum requirement needed for ion generation and processing. The main theme of this work is the development of ionisation methods that enable ion generation and processing under ambient conditions in the open air outside of the laboratory for in-situ applications. To that end, it is also important that ions are generated and processed with little or no extensive sample preparation steps required. In this work the development of two ambient ionisation methods: desorption atmospheric pressure chemical ionisation (DAPCI) and paper spray (PS) ionisation and their application for in-situ MS analysis is demonstrated. A DAPCI handheld ion source version based on DAPCI was developed to ignite a corona discharge in air and operates for up to 12 h continuously using only 12 V battery. Both DAPCI and PS ambient ionisation methods were implemented for in-situ MS analysis and were used to detect trace amounts (< ng) of different classes of chemical compounds (i.e hydrocarbons, explosives corrosion inhibitors and metaldehyde in waters samples); this was achieved rapidly (i.e. less than 1 minute) with little or no sample preparation in the open air. Both ambient ionisation methods (i.e., DAPCI and PS) were used with either a commercial instrument or with a custom miniature mass spectrometer to identify and characterize traces amounts of petroleum oil hydrocarbons and additives (e.g. quaternary ammonium corrosion inhibitors), and water pollutants (e.g. metaldehyde) with high sensitivity and selectivity. The handheld DAPCI and PS methods were also applied to the in-situ direct analysis of explosives. Good performance was achieved with the miniaturised instrument giving detection limits within an order of magnitude to those achieved using a benchtop commercial instrument. The results reported in this thesis should be of importance to those interested in ambient ionisation mass spectrometry, miniature mass spectrometry, in-situ MS analysis, oilfield chemical analysis, homeland and border security agencies and environmental monitoring.
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Vant, Stewart Charles. "Investigation of fluid properties at non-ambient conditions." Thesis, University of Strathclyde, 2003. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=27056.
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A requirement for thermophysical property data of diesel fuels at conditions removed from ambient was identified. A series of measurements of the pressure-volume-temperature relations of diesel fuels was undertaken using a Micro-PVT apparatus at pressures to 300MPa in the temperature range 25 to 75°C. A new calibration procedure for this instrument was devised to enable measurements of high accuracy to be made. Viscosity measurements of diesel fuels over a range of temperature and pressure were made using the National Engineering Laboratory high pressure viscometer to pressures of 460MPa in the temperature range 25 to 100°C.Corresponding states theory was applied for compressed liquid density prediction. Improvement in density prediction in this region was found through use of iso-octane and heptadecane as reference fluids. Compressibility factors of these were represented by Tait-style equations. An iterative solution technique was developed to allow the corresponding states method to be applied to diesel fuelsusing limited density measurement and a guess value of boiling point as inputs. Densities predicted from this method agreed well with measurements made using the Micro-PVT apparatus. Hard sphere theory was applied as a method for viscosity prediction. Despite the complexity of the diesel fuel mixture, reasonable estimates of viscosity were made with limited measurement input at higher temperatures. At lower temperatures, an additional simple empirical correction term was required. A method of viscosity estimation of complex hydrocarbon mixtures based upon composition is presented. Further development of this would require additional measurements and greater characterisation of the fuel.
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Spicer, Christopher D. "Suzuki biology : palladium mediated reactions under ambient conditions." Thesis, University of Oxford, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.711749.
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Takebayashi, Yoshihiro. "Dipolar hydration structure from ambient to supercritical conditions." 京都大学 (Kyoto University), 2004. http://hdl.handle.net/2433/145456.
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Smith, Philip S. "Systematic studies of crystal structures under non-ambient conditions." Thesis, Durham University, 2004. http://etheses.dur.ac.uk/2996/.
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Variable temperature single crystal X-ray diffraction analysis has been used to study four molecular systems: 4-(p-trlfluoromethyl phenylethynyl) prefluorotoluene (1), 2-methyl-4-(4-trifluoromethyl-phenyl) but-3-yn-2-ol (2), phenylethynyl perfluorotoluene (3) and Zinc Pyromellitate. In the case of the systems (1) - (3), the aim was to analyse the extent of the dynamic disorder in the CF3 groups that are contained in these systems. To this end, segmented rigid body analysis has been employed to estimate forces constants and barriers to rotation of the relevant groups. Complimentary computational methods have been used to obtain further estimates of this barrier to rotation in these systems for both the isolated (gas phase) molecules and for the condensed matter phases for compounds (1) and (3).For Zinc Pyromellitate, variable temperature single crystal X-ray and neutron analysis have been used to probe the behaviour of a proton that sits in a short, strong intramolecular hydrogen bond. The aim here was to discover whether the system exhibits proton migration along the hydrogen bond as a function of temperature and thus gain insights into the energy potential well in which the proton sits. To this end, both computational methods have been used to study the pyromellitate fragment, and variable temperature full crystal structure data so as to gain direct access to information regarding this potential well.
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Vilalai, Sirapong. "Forecasting odor levels for biosolids product based on ambient conditions." College Park, Md. : University of Maryland, 2004. http://hdl.handle.net/1903/128.
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Thesis (M.S.) -- University of Maryland, College Park, 2004.Thesis research directed by: Dept. of Civil and Environmental Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Conere, Thomas James. "The radiobiological effects of gas mixtures under ambient and hyperbaric conditions." Thesis, Queen's University Belfast, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.292290.
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Cardellach, i. Redon Mar. "Study of interfacial water at the nanoscale at ambient conditions with SPM." Doctoral thesis, Universitat Autònoma de Barcelona, 2012. http://hdl.handle.net/10803/107707.
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La tesi que es presenta es veu emmarcada dins l’àrea de ciència de superfícies. Dos dels grans temes desenvolupats en aquesta tesi estan relacionats amb l’estudi de superfícies amb constants de xarxa (distàncies atòmiques que componen la molècula) properes a la del pla basal de la fase hexagonal del gel (Ih) (el gel més comú a l’escorça terrestre). L’objectiu d’aquesta premissa és veure com superfícies que tenen la constant de xarxa propera a la del gel (Ih) provoquen que l’aigua d’origen atmosfèric s’adsorbeixi a sobre en forma d’aigua en estat sòlid (gel) i no en forma d’aigua líquida a temperatures relativament altes. Aquest tipus de superfícies tindrien grans utilitats en processos meteorològics tals com la inducció de pluja, comercialització de productes propulsors de neu artificial o simplement per a conèixer els límits de congelació de l’aigua en sistemes biològics.
En el capítol 3, es presenta el BaF2 com a possible nucleador de gel sobre la seva superfície, ja que la seva constant de xarxa difereix només un 4% de la del gel (Ih). Amb l’ajuda d’un microscopi de forces atòmiques (AFM) s’ha pogut observar com les molècules d’aigua difonen fàcilment sobre la seva superfície, i a més a més aquestes tenen preferència en la seva acomodació. S’ha observat que els esglaons de BaF2 i les zones que tenen un excés de càrrega degut al clivatge, són els defectes ideals per l’aigua, ja que s’hi sent molt més còmode. Aquests esglaons generats durant el clivatge tenen unes direccions cristal·logràfiques concretes i ben definides, i l’aigua no té una preferència aleatòria per ells sinó que, contràriament del que pensàvem, les molècules d’aigua tenen en general més afinitat per aquells esglaons menys energètics, amb menys densitat d’àtoms al descobert. El BaF2 no és un bon nucleador pel que fa al creixement de gel tridimensional, ja que la conformació que adopten les molècules d’aigua paral·lela al pla no afavoreix la formació de gel tridimensional, però gràcies a la seva constant de xarxa i als defectes ocasionats durant el clivatge resulta que és un nucleador bidimensional. S’ha seguit el mateix patró pel CaF2, un compost isoestructural del BaF2, amb la diferència que té una constant de xarxa més petita, que difereix un 14% respecte la cara basal del gel (Ih). Els experiments realitzats mostren com l’aigua s’hi adsorbeix de manera aleatòria i més caòtica, tot i que té certa preferència pels esglaons com en el cas del BaF2. Podem concloure doncs, que la constant de xarxa és un paràmetre molt important, però no és l’únic.
En el capítol 5, es planteja l’opció d’obtenir una superfície de manera artificial, amb les característiques que busquem per tal que l’aigua s’hi adsorbeixi en forma de gel (Ih) fàcilment. La tècnica utilitzada per aquest propòsit és la Langmuir-Blodgett, la qual ens permet fer monocapes en l’interfase líquid-gas, i es poden transferir a una superfície sòlida. Depenent de la superfície, obtindrem monocapes hidrofòbiques o hidrofíliques. Tot i que l’objectiu llunyà és formar una monocapa ideal i observar a través de l’AFM com s’adsorbeix l’aigua a sobre, fins ara s’ha aconseguit formar superfícies hidrofíliques a partir de substrats hidrofòbics (grafit) i també formar superfícies hidrofòbiques a partir de substrats hidrofílics (mica). Les molècules utilitzades per a la formació de les monocapes són alcohols alifàtics de cadena llarga, estudiats a la bibliografia com a possibles bons nucleadores de gel.
En el capítol 4, l’atenció es veu desviada per l’investigació de la càrrega residual que es produeix a sobre de les superfícies. Per les propietats electròniques que té el grafè, es va creure convenient fer-lo servir de superfície model. A través de la punta d’AFM s’ha injectat càrrega a una làmina de grafè sobre òxid de silici, i s’ha vist com la càrrega provocada per la punta es va dissipant cap a l’òxid de silici en funció de la humitat relativa. Amb aquest estudi es va poder analitzar l’efecte de càrrega residual en superfícies i el rol que hi juga l’aigua. En aquest treball també es va fer pal·lesa que les dimensions de la punta determinaven fortament les mesures electroestàtiques en AFM.This thesis is framed into the surface science area. Two main chapters developed in the present work are related to the study of surfaces with lattice constant near to the basal plane of the hexagonal ice (Ih) (the most common ice on Earth). The main goal of this topic is observe how these surfaces induce water adsorption on its surfaces as solid water at high temperatures. These surfaces could be used in meteorological processes such as rain induction, snow making industry or the knowledge of the freezing limits of water in biological systems. In chapter 3, BaF2 is presented as a possible ice nucleation because its lattice constant differs only 4% respect to the basal plane of the hexagonal ice (Ih). With the help of an Atomic Force Microscopy (AFM) it can be observed how water molecules easily spread on the surface and showing adsorption preferences. It was observed that steps and charge excess zones on BaF2 surface are perfect defects to water molecules anchoring, where water molecules feel more comfortable. Steps generated during the cleavage have specific and well defined crystallographic directions, and water molecules have preference and more affinity for the less energetic steps (with less atomic density). Finally, it is concluded that BaF2 is not a good three-dimensional nucleator because the conformation of water molecules onto the plane does not promote the ice formation, but the lattice constant and defects caused during the cleavage make it a good two-dimensional ice nucleator. The same studies were performed on CaF2, an isostructural compound of BaF2 but with a different lattice constant, which differs 14% from basal plane of the hexagonal ice (Ih). The experiments show chaotic and random water adsorption on CaF2 but with a certain preference to the steps. It can be concluded that the lattice constant is an important parameter to consider but is not the only parameter to take account. In chapter 5, the construction of an artificial surface with specific characteristics is proposed. The goal is to create a surface capable to induce water freezing. The technique used for this purpose is the Langmuir-Blodgett trough, which allows a monolayer formation in the liquid-gas interface that can be transferred to a solid substrate. Depending on the surface, hydrophilic or hydrophobic monolayers are obtained. Although water adsorption with AFM was studied yet in this thesis, we were able to form hydrophobic surfaces from hydrophilic substrates (mica) and hydrophilic surfaces from hydrophobic substrates (graphite). The molecules used for this purpose are long chain aliphatic alcohols, studied in the bibliography as probably good ice nucleators. In chapter 4 our attention is diverted to the study of residual charge produced on the surfaces. Due to the electronic properties of graphene, it was thought appropriate to use it as a model surface. Using the AFM tip charge was injected onto a graphene sheet deposited on a silicon oxide wafer, and discharging of the graphene sheet was observed. The charge spreading to the silicon oxide depends on the relative humidity. The role of adsorbed water in the discharge of surfaces was analysed. This work also demonstrated that the probe dimensions have critical influence on the electrostatic measures in AFM.
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Hargreaves, Natasha Jayne. "Crystallisation of nano-quartz and nano-graphite from microemulsions under ambient conditions." Thesis, Durham University, 2016. http://etheses.dur.ac.uk/11725/.
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The principal basis for the following work is to demonstrate the importance of controllable crystallisation and consequential applications for both silica-based significant inorganic materials and carbonaceous materials. Microemulsions have been employed as a vector to explore the possibility of thermodynamically controlling the crystallisation process, utilising the 3D confinement of crystallisable material within nano-scale droplets. This opens a route to circumvent Ostwald’s Rule of Stages, for a multitude of potential applications. We show here that both quartz and nanographite can be synthesised at room temperature and pressure using this methodology. Previous attempts at silica synthesis from within the microemulsion have only presented the amorphous phase, leaving many questions unanswered, whilst failing to reveal the underlying cause. Further, traditional methods of quartz synthesis employs hydrothermal conditions, or temperatures >1100 0C. Microemulsions were adopted to behave as confined mini reactors for the synthesis of α-quartz at room temperature and pressure from a precursor from sodium metasilicate nonahydrate (SMS) which can be used as a precursor of silica, circumnavigating the traditional hydrothermal methodologies. At higher supersaturations, both the metastable amorphous phase and the high temperature polymorph, cristobalite were also observed. Upon the acidification of the microemulsions, the size and morphology of the quartz nanoparticles was found to be dependent upon the pH and the ratio of surfactant:silica units. Conventional wisdom stipulates that graphite can only be produced using high temperatures, with natural graphite arising via progressive metamorphisms of carbonaceous material subjected to temperatures above ~600 K and pressures >2 kbar. Previous attempts to use carbohydrate precursors have resulted in the formation of luminescent carbon dots or required templation, followed by calcination. In these prior investigations, high temperatures or extremely severe reactants are used to drive the precipitation of graphitic forms. Analogous experiments were successful in employing the 3D nano-confinement microemulsions as confined mini reactors for the synthesis of nanographite at room temperature and pressure from a sucrose precursor, through a simple process of acidifying sucrose microemulsions. Crucially, the reaction was conducted in nanometre-sized microemulsion droplets to exert control over the reaction and sheet stacking process, ensuring that only sufficiently pristine graphene nanosheets could stack, thereby producing nanographite in a simple one-step synthesis under ambient conditions. The primary nanographitic particles of size ~3-30 nm stacked to form larger µm-sized nanographitic aggregates. The amount of nanographite produced from the microemulsions is limited as sucrose concentration must be kept very low to slow the reaction kinetics to ensure the mainly graphitic, rather than amorphous, product.
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Erdem, Ayça. "Short-term toxicity of photocatalytic titanium dioxide to bacteria under ambient conditions." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 204 p, 2008. http://proquest.umi.com/pqdweb?did=1679680941&sid=14&Fmt=2&clientId=8331&RQT=309&VName=PQD.
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Arnerlöv, Karin, and Cecilia Bengtsson. "Open-Plan Offices : The Importance of the Ambient Conditions´ Characteristics for Employee Satisfaction." Thesis, Umeå University, Umeå School of Business, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-1245.
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The ambient conditions such as air quality, noise, music, temperature, lighting and colour, in open-plan offices and their impact on employees are important for managements to recognize because open-plan offices are becoming more and more common in Swedish companies' office design today (Aronsson, 2005). For students, who will soon be entering the work force, it is important to understand how the characteristics of the ambient conditions can influence employee behaviour/satisfaction.
To have a working knowledge of what kinds of effects the ambient conditions can have is likely to increase one's chances of becoming a satisfied employee. An employee that is aware of the importance of creating a servicescape (the attributes of the physical surrounding) that meets its needs and desires is likely to enhance its satisfaction in the ambient conditions. A great number of managements may not be aware of the risks of working in an open-plan office where the ambient conditions are not satisfying the employees; ergonomic issues as well as heart diseases are the most serious results (Evans and Johnson, 2000, pp. 780-782). This leads to the problem formulation of this thesis: "How can management improve employee satisfaction in an open-plan office through the characteristics of a servicescape's ambient conditions?”.
Four main theories are included in the Theoretical Framework to provide a deep understanding for the reader about the complexity of problems that comes with working in an open-plan office. The Bitner theory and the research compiled by Sundstrom discuss ambient conditions and their impacts on employees' behaviour/satisfaction. Evans and Johnson’s theory discusses how stress is related to low-intensity noise. The final main theory, Person-Environment Fit, upholds the importance of a servicescape that fits employees’ needs and desires.
The ambient conditions influence employee behaviours in numerous ways (Davis, 1984, pp. 271) and at Sogeti’s open-plan office several ambient conditions are studied through an observation conducted during April 17th 2007 and a questionnaire with 15 closed questions. The outcomes of the observation and the questionnaire are analysed and concrete proposals are created for the Sogeti management to act upon in order to improve the characteristics of their open-plan office’s ambient conditions and thereby improve employee satisfaction.
One of the concrete proposals to how Sogeti may improve the ambient conditions in their open-plan office is to introduce a survey that should be handed out to the employees three or four times a year. The purpose of the survey is to define employees’ perceptions of the different ambient conditions.
Based on the outcomes from the survey, employees’ needs and desires of the servicescape, the ambient conditions’ characteristics, can be improved. Also, some examples of actions geared towards reducing the level of noise in the Sogeti open-plan office are to use ear phones when listening to music and to leave the open-plan office when conducting phone calls. The concrete proposals developed based on the Sogeti employees’ perceptions of the ambient conditions in the open-plan office are outcomes of this thesis that may serve as a tool for the Sogeti management to improve the ambient conditions of their servicescape and thereby increase employee satisfaction.
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Torun, Boray Barış [Verfasser]. "In-situ analysis of particles in contact under ambient conditions / Boray Barış Torun." Paderborn : Universitätsbibliothek, 2016. http://d-nb.info/1099462614/34.
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West, Ryan James. "Effect of Peripheral Cooling on Interval Work Performance in Ambient and Hot Conditions." Thesis, University of California, Davis, 2013. http://pqdtopen.proquest.com/#viewpdf?dispub=1546265.
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The effect of peripheral cooling on interval work performance in ambient and hot conditions was investigated in 4 male varsity rowers ages 18 – 22, with a nude equivalent weight of 78.23 +/- 4.19 kg. Subjects performed 4 trials consisting of 5 rounds of 5 minutes of near maximal work performed on a Concept II rowing ergometer, followed by 5 minutes of active recovery in both a moderate (24°C) and hot (30°C) environment. During rest intervals subjects were either cooled or noncooled via the use of a peripheral cooling device called The Glove ,which applied a -40 mmhg pressure and a 17 C cooling effect to the palmar surface. Subject trial order was randomized. Heart rate, blood lactate, esophageal temperature, 6 site skin temperature, and cumulative and individual work bout meters rowed were measured for all trials. Subjects performed an average of 6,415.37 +/- 1,057.57 total meters per trial. However, adjusting for incomplete trials, due to either subject fatigue or termination criteria being reached yielded a more representative average of 6,787.07 +/- 322.42 total meters per trial. Performing a three way ANOVA with repeated measures analysis of all results indicated that there were no significant differences in work performed in both cumulative and individual work bouts, nor in subjects' heart rate, blood lactate, Tesoph, T-skin, between non-cooled and cooled trials and/or 30 °C and 24 °C environmental test conditions. However, while there were no statistically significant differences it should be noted that due to the small subject number of 4, and incomplete data sets within the subject population, this study's resultant power (.144), is insufficient to definitely claim success or failure of the peripheral cooling devices effectiveness on interval work performance in both warm and hot environments. Further studies with a more controlled work rate are required to conclusively determine the effectiveness of peripheral cooling on interval work performance.
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Tilburey, Graham E. "Understanding molecular interactions in the precipitation and dissolution of silica under ambient conditions." Thesis, Nottingham Trent University, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.478854.
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Akgul, M. Zafer. "Environmentally friendly nanocrystals synthesized and processed in ambient conditions for solution-processed solar cells." Doctoral thesis, Universitat Politècnica de Catalunya, 2021. http://hdl.handle.net/10803/671521.
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Due to the continuously increasing energy demand and the environmental concerns about climate changes raised by international community, alternative energy resources have been put under intense investigation for the past decade. As a consequence, different technologies have been proposed, photovoltaics being a promising one among them. Till now, different structures and methods have been employed to fabricate photovoltaics for energy production. Traditionally, vacuum-based deposition methods have been used to form the stacks required for proper photovoltaic operation. Triggered by the advancements in colloidal synthesis methods, thin films of colloidal semiconductor nanocrystals (CNCs) have gained tremendous attention as cheap substitutes for vacuum-deposited layers. Up to date, various colloidal synthesis methods have been developed to produce semiconductor nanocrystals for applications in photovoltaics. Thanks to the high degree of controllability and high material quality, hot injection methods have been the way-to-go for the past decades. However, the application of CNC films in large-scale photovoltaics has been delayed due to the synthesis constraints originating from hot injection methods itself.
In this work, we demonstrate that it is possible to eliminate the need for air-free techniques by careful selection of the precursors and oxygen-aware design of reaction conditions. We use the semiconducting compound silver bismuth sulfide (AgBiS2) as the prototype material to demonstrate the easiness and efficiency of the method. This semiconducting compound is selected as the prototype material thanks to its attractive optical properties for photovoltaics and the environmentally friendly nature of the constituent elements. Solar cells fabricated using CNCs synthesized at room temperature have yielded a power conversion efficiency of 5.5 %, demonstrating the promising potential of the method. The application of the method in the synthesis of AgBiS2 CNCs results in a cost reduction of at least 60 % compared to the previous studies reporting similar photovoltaics-grade AgBiS2 CNCs. Another important challenge in employing hot injection methods is the scalability. Due to the difficulties in maintaining the thermal fluctuations within the reaction volume low and in the maintenance of inert atmosphere inside the reaction vessel, hot injection methods impose an inherent scale constraint on the synthesis. On the other hand, with the elimination of scale constraint by the use of an ambient condition synthesis method, the requirement for high temperature reaction and chemically inert reaction environment is eliminated, enabling us to achieve large-scale volume production of CNCs. This, in turn, can lower the production cost of CNCs further, hence the cost of photovoltaics that are based on CNCs. In addition, we show that the ambient condition method can be adapted for the synthesis of another metal chalcogenide, namely silver bismuth selenide CNCs (AgBiSe2) with an extended absorption spectrum further into the near infrared down to ~ 0.9 eV. The resulting AgBiSe2 CNC solar cells achieved a preliminary efficiency up to 2.6 %. Also, thanks to the structural similarity of these two compounds, the two methods that are developed for the synthesis of AgBiS2 and AgBiSe2 CNCs are combined and optimized to obtain alloyed quaternary AgBiSSe CNCs as a facile means of bandgap tuning in silver bismuth chalcogenide semiconductor family. The formation of AgBiSSe CNCs are verified through optical and structural characterization methods to show the formation of quaternary phase and also the phase purity of the obtained product. Overall, it is shown that the proposed ambient condition synthesis method is capable of providing photovoltaics-grade RoHS-compliant materials at a lower cost and higher throughput compared to the hot-injection based methods, opening a novel way for low-cost environmentally friendly photovoltaics.Debido al continuo aumento de la demanda de energía y las preocupaciones ambientales sobre el cambio climático planteadas por la comunidad internacional, los recursos energéticos alternativos han sido objeto de una intensa investigación durante la última década. Como consecuencia, se han propuesto diferentes tecnologías, siendo la fotovoltaica una prometedora entre ellas. Hasta ahora, se han empleado diferentes estructuras y métodos para fabricar células solares para la producción de energía. Tradicionalmente, se han utilizado métodos de deposición basados en vacío para formar las capas necesarias para el funcionamiento fotovoltaico adecuado. Debido a los avances en los métodos de síntesis coloidal, las películas finas de nanocristales semiconductores en solución coloidal (CNCs) han ganado una gran atención como sustitutos baratos de las capas depositadas al vacío. Hasta la fecha, se han desarrollado varios métodos de síntesis coloidal para producir nanocristales semiconductores para aplicaciones en energía fotovoltaica. Gracias al alto grado de controlabilidad y la alta calidad del material, los métodos de inyección en caliente han sido el camino a seguir durante las últimas décadas. Sin embargo, la aplicación de películas de CNCs en fotovoltaica a gran escala se ha retrasado debido a las propias limitaciones de estos métodos de síntesis. En este trabajo, demostramos que es posible eliminar la necesidad de técnicas inertes mediante la selección cuidadosa de los precursores y el diseño de las condiciones de reacción conscientes del oxígeno. Usamos el compuesto semiconductor sulfuro de bismuto y plata (AgBiS2) como material prototipo para demostrar la facilidad y eficiencia del método. Este compuesto semiconductor se ha seleccionado como material prototipo gracias a sus atractivas propiedades ópticas para la energía fotovoltaica y la naturaleza ecológica de los elementos constituyentes. Las células solares fabricadas con CNCs sintetizadas a temperatura ambiente han arrojado una eficiencia de conversión de energía del 5,5 %, lo que demuestra el potencial prometedor del método. La aplicación del método en la síntesis de CNCs de AgBiS2 da como resultado una reducción de costes de al menos un 60 % en comparación con los estudios anteriores que reportaron CNCs de AgBiS2 de una calidad fotovoltaica similar. Otro desafío importante al emplear métodos de inyección en caliente es la escalabilidad. Debido a las dificultades para mantener bajas las fluctuaciones térmicas y la atmósfera inerte dentro del recipiente de reacción, los métodos de inyección en caliente imponen una restricción de escala inherente a la síntesis. Por otro lado, con la eliminación de la restricción de escala mediante el uso de un método de síntesis en condiciones ambientales, se elimina también el requisito de reacción a alta temperatura y entorno de reacción químicamente inerte, lo que nos permite lograr una producción en volumen a gran escala de CNCs. Esto, a su vez, puede reducir aún más el coste de producción de los CNCs, y en consecuencía el coste de las células fotovoltaicas que se basan en CNCs. Además, mostramos que el método en condiciones ambientales se puede adaptar para la síntesis de otro calcogenuro metálico, por ejemplo, CNCs de seleniuro de bismuto y plata (AgBiSe2) con un espectro de absorción más extendido en el infrarrojo cercano, hasta ~ 0.9 eV . Las células solares de CNCs de AgBiSe2 alcanzaron una eficiencia preliminar de hasta el 2,6 %. Además, gracias a la similitud estructural de estos dos compuestos, los dos métodos desarrollados para la síntesis de CNCs de AgBiS2 y AgBiSe2 se combinan y optimizan para obtener CNCs de la aleación cuaternaria AgBiSSe como un medio fácil de sintonización de bandgap en familia de semiconductores de calcogenuro de bismuto y plata.La formación de AgBiSSe CNCs se verifica mediante métodos de caracterización óptica y estructural para mostrar la formación de fase cuaternaria y también la pureza de fase del producto obtenido. En general, se demuestra que el método de síntesis de condiciones ambientales propuesto es capaz de proporcionar materiales fotovoltaicos compatibles con RoHS a un costo menor y un mayor rendimiento en comparación con los métodos basados en inyección en caliente, lo que abre un camino novedoso para la energía fotovoltaica ecológica de bajo costo. .
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Wada, Nohara. "Internal moisture movement in hem-fir timbers exposed to ambient conditions following kiln drying." Thesis, University of British Columbia, 2013. http://hdl.handle.net/2429/44050.
Full textAbstract:
This study aimed to investigate the changes of internal moisture content distributions of high-value hem-fir timbers after kiln drying while exposed to two different local outdoors seasonal conditions for a period of time of few weeks.
Hem-fir is the most abundant species in coastal British Columbia, Canada, and high-quality thick hem-fir timbers used as construction material are one of the most important, and profitable products due to international market demand especially in Japan. Presently more-and-more of those houses are pre-fabricated and dimensional stability is paramount. Internal moisture profiles after kiln drying and their behaviour as a function of weather exposure in storage can result in dimensionally unstable products and consequently compromise quality.
Conventional kiln drying of thick timbers is relatively difficult and requires long drying time to reduce final moisture content variation. Fast drying will result in steep moisture content gradients which may result in undesirable dimensional changes when products are used in normal service conditions. Thus, it is important to understand moisture behavior after drying and how that is affected by the environment.
In this study, 90 x 90 mm in cross-section hem-fir timbers were dried to three different target moisture contents. Thereafter, stickered packages were stored under two diverse seasonal coastal environments thus emulating outdoor timber storage in a local sawmill. Moisture contents at 25 mm and 45 mm depths were continuously monitored for a period of three weeks.
The results showed that moisture movement was observed between at 25 mm and at 45 mm depths regardless seasonal conditions while no significant net moisture content reduction took place during the cold-wet season after kiln drying. Also, regardless seasonal condition or target moisture content, moisture movement between at 25 mm and at 45 mm depths slowed down when differential moisture content between them was below 2.5%. In particular, at high target moisture content of 22%, moisture content values both at 25 mm and at 45 mm depths remained constant at moisture content difference value of 2.5% after two weeks regardless seasonal conditions, and no further drying or no further moisture content equalization were observed after that point.
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Chirawatkul, Prae. "Structure of liquid and glassy materials from ambient to extreme conditions : a multiprobe approach." Thesis, University of Bath, 2010. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.537488.
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The structure of molten Au0.81Si0.19, Au0.72Ge0.28 and Ag0.74Ge0.26 alloys with a composition at or near to the eutectic was investigated by using neutron diffraction (ND). The results suggest that the Au-Au distance in the alloys is similar to that of liquid Au, there is a preference for Au-Si bonds and show that there are pre-peaks in the total structure factors for Au0.72Ge0.28 and Ag0.74Ge0.26 at 1.3(2) and 1.6(3) ˚, A−1 respectively. The asymptotic decay of the pair correlation functions was found to agree both with a theoretical prediction based on simple pair potentials and a fractal model for metallic glasses. The structure of glassy (R2O3)0.2(Al2O3)0.2(SiO2)0.6, where R denotes Dy, Ho or a 50:50 mixture of Dy and Ho, was investigated by using the method of isomorphic substitution in ND, x-ray diffraction (XRD) and extended x-ray absorption fine structure (EXAFS) spectroscopy. The network is made from SiO4 tetrahedral units with a distribution of AlO4, AlO5 and AlO6 units giving an average coordination number of 4.5(1). There is a distribution of RO5, RO6, RO7, RO8 and RO9 units with an average coordination number of 7.2(3) and an average R-O distance of 2.33(2) ˚ A. The EXAFS results confirmed that Dy and Ho are isomorphic and were used to refine an RMC model of the structure. R-Al and R-Si nearest neighbour shells with average distances of 3.15(3) and 3.6(1) ˚A were required to fit the EXAFS results. The structure of glassy and liquid ZnCl2 was studied by using ND and XRD. The material has a network structure made from ZnCl4 tetrahedra units which is retained in the liquid at temperatures near to the boiling point. An increase of temperature promotes edge sharing connectivity as inferred from a decrease of the Zn-Zn nearest neighbour distance and average Zn-Cl coordination number. An EXAFS study on crystalline ZnCl2 at room temperature shows that Zn remains 4fold coordinated at pressures less than 1 GPa, is 4+2-fold coordinated at 2-4 GPa, and is 6-fold coordinated above 4 GPa. For liquid ZnCl2, Zn is 4-fold coordinated by Cl at a pressure of about 1 GPa and could be 6-fold coordinated at 2-3 GPa.
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Andreae, Morgan M. (Morgan MacKenzie). "Effect of ambient conditions and fuel properties on homogeneous charge compression ignition engine operation." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/35616.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2006.Includes bibliographical references (p. 197-198).
Practical application of Homogeneous Charge Compression Ignition (HCCI) combustion must demonstrate robust responses to variations in environmental conditions. This work examines the impact of ambient conditions and fuel changes on HCCI engine operation, and evaluates cam phasing as a mechanism to compensate for these changes. Experiments were carried out on a modified 2.3 L 14 production engine, and HCCI operation was achieved by the use of residual trapping by negative valve overlap. The first phase of the project examined the impact of changes in intake air temperature and humidity on HCCI operation. Exhaust cam phasing was used to control load, and intake cam phasing was use to produce a change in combustion phasing. Cam timing control was largely able to compensate for changes in combustion due to changes in air temperature and humidity. Higher intake air temperature advanced combustion phasing and resulted in a 1 bar reduction of the net indicated mean effective pressure (NIMEP) at the high load limit for lower engine speeds. Intake air temperature did have more of an impact during lean operation. Higher intake air humidity delayed combustion phasing.
(cont.) During stoichiometric operation, this delay allowed a small extension (a few tenths of a bar in NIMEP) in the high load limit. During lean operation, the delay in combustion timing resulted in a reduction of the high load limit. The second phase of the project examined the impact of market fuel composition variations on HCCI operation. Twelve test fuels were created to vary the composition of 5 fuel properties: Research Octane Number (RON), Reid Vapor Pressure (RVP), olefin content, aromatic content, and ethanol content. The test fuels were blends of different commercial refinery streams and contained hundreds of different hydrocarbons to be representative market gasolines. Fuel type was found to have only a small impact on the HCCI operating range, and cam phasing was largely able to compensate for changes in fuel composition. The main effect of the different fuel composition appeared to be differences in ignition delay.
by Morgan M. Andreae.
Ph.D.
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Bacela, Ntobeko. "Studies on captive rearing of spotted grunter, pommadasys commersonnii (Pisces : Haemulidae) under ambient conditions." Thesis, Rhodes University, 1999. http://hdl.handle.net/10962/d1005167.
Full textAbstract:
The effects of stocking density, size grading, feeding frequency and ambient temperature on the growth performance and size variation of spotted grunter, Pomadasys commersonnii were investigated. The time that would be required to rear the species to market size was modelled. An area where maximum growth rate could be achieved under ambient temperature conditions, and therefore the location of a commercial farm within the distribution range of spotted grunter along the coast of South Africa, was predicted. The growth performance of spotted grunter was not significantly affected by stocking density. Growth performance seemed to improve with increasing stocking density. Competitive behaviour was absent among fish in the various stocking densities. Growth in terms of fork length and body weight was not significantly different between stocking densities. The highest specific growth rate, best food consumption, food conversion ratio and protein efficiency ratio of the fish were recorded at a density of 6.4 kg/m³, whereas the best condition factor was recorded at a density of 3.8 kg/m³. The lack of significant difference in many of the growth parameters between the various stocking densities suggest that juvenile spotted grunter could be reared at densities higher than 6.4 kg/m³. Further investigations are needed to determine the optimal initial stocking density of juvenile spotted grunter under ambient temperature and photoperiod conditions. Replacing the largest fish with average sized fish did not have a significant effect on the specific growth rate and competitive behaviour based on the relationship between the coefficient of variation and average size. Feeding frequency had a sIgnificant effect on food consumption, food conversion and protein efficiency ratio, and not on size increase, specific growth rate and condition factor. Its effect on competitive behaviour could not be conclusively explained. The best food conversion ratio recorded when feeding once a day showed that although the fish consumed a limited amount of food, they utilised the food that was fed most effectively. It is suggested that the fish be fed three times a day. The survival of juvenile spotted grunter was 95.6 % when feeding three times a day compared to 90 and 90.2 % when feeding once and five times a day, respectively. Fluctuating ambient temperature had a dramatic effect on specific growth rate and food consumption of spotted grunter. Growth modelling showed that the fish could be reared to a market size of 550 g (270 mm FL) in 19 months under ambient temperature conditions (23.2°C) at Richard's Bay. The optimal predicted rearing period of 19 months is approximately seven months less than that calculated for fish in the wild, and can possibly, be reduced further by feeding a balanced diet. The overall food consumption (on a dry weight basis) in the three size classes ranged from 0.15 ± 0.16 to 0.38 ± 0.35 % body weight per day. Food conversion ratio improved with increasing fish size. This relationship was attributed to diet quality and more specifically, the protein : energy ratio. As a result, fish in the large size class had the best overall protein efficiency ratio. Maximum specific growth rates of1.5, 0.84 and 0.74 % body weight per day were recorded from the small, medium and large size classes in the peak of summer with average daily temperature ranging from 21 to 22°C. Positive slopes in the coefficient of variation against fish size in the large size class indicated the presence of competitive behaviour which was attributed to the onset of adolescence. The information from this study can be used for pilot production of spotted grunter. Further research should be undertaken to investigate captive reproduction of the species.
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Milbourne, Suzanne A. "The effect of ambient working conditions on teacher-child interactions and teacher stress and wellness." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 272 p, 2007. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:3247574.
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Ouellette, Diane. "A study of the effect of surround and ambient lighting conditions on CRT screen colors /." Online version of thesis, 1988. http://hdl.handle.net/1850/10424.
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Al-Mahtot, O. B. "An experimental investigation on Archie parameters at ambient and overburden conditions of clean reservoir rocks." Thesis, Robert Gordon University, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.286423.
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PATWARDHAN, SIDDHARTH VIJAY. "SYNTHESIS OF SILICA NANO AND MICROMETER SIZE STRUCTURES AT NEUTRAL pH AND UNDER AMBIENT CONDITIONS." University of Cincinnati / OhioLINK, 2002. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1020192318.
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PARODI, Ilaria. "Structural characterization of zeolitic catalysts in non-ambient conditions by X-ray and neutron diffraction." Doctoral thesis, Università degli studi di Ferrara, 2009. http://hdl.handle.net/11392/2388659.
Full textAbstract:
This PhD thesis strives to give an exhaustive characterization of the behaviour of zeolites in nonambient
conditions. Zeolites presents a lot of peculiar characteristics, such as shape selectivity,
high thermal stability, but the most important is their catalytic activity, which have been
evaluated for many petrochemical reactions, such as gas-oil cracking and hydrocracking,
aromatic alkylation and isomerisation ecc.
The catalytic activity of zeolites is due to their particular structure. These minerals, in fact, are
characterized by large pores and channels. Only molecules with determined dimensions,
consistent with the pores dimensions, can have access to the acid sites located inside these
cavities and can be processed.
The importance of a detailed structural characterization is due to the fact that it is necessary to
explain the efficiency of these materials, their stability as well as the different types of shape
selectivity seen in a wide range of catalytic systems.
The understanding of the zeolite behaviour upon heating is of particular importance since the
sorptive and catalytic properties, molecular sieve effects are enhanced in the dehydrated/calcined
phases. Besides, it is important to study the response to heating because reactions involving
hydrocarbons need high temperature (about 300-500°C), so it is important that zeolites used for
these reactions have a good thermal stability, and it is important to localize acid sites.
The study of the characterization of these materials in non-ambient conditions was carried out
starting from structure analysis of diffraction data collected on powder or single crystals, using Xray
(conventional source or synchrotron radiation) or neutron diffraction.
The main results obtained in this PhD thesis can be summarize as follows: 1) zeolite tschernichite.
It has been evaluated how defects due to the simultaneous presence of two different polytypes
affect the thermal stability of this material; 2) zeolite gmelinite. The most important results is that
it was possible to observe that gmelinite, when heated at T>330°C transform into a new phase
(AFI-type) which is very important for catalysis and has a good thermal stability; 3) zeolite omega.
It was possible to follow in real time the activation of this important catalyst and its acid sites were
localized; 4) zeolite ferrierite and heulandite: protons bonded to framework oxygens were located,
and it is put in evidence the importance of water interaction with these catalysts.
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CORVA, MANUEL. "Experimental modeling of nanostructured and single metal atom supported catalysts at close-to-ambient conditions." Doctoral thesis, Università degli Studi di Trieste, 2019. http://hdl.handle.net/11368/2991050.
Full textAbstract:
This Thesis work deals with the growth and characterization of model nanostructured surface systems in ultra-high vacuum environment (UHV, <10−9 mbar) and with their evolution at near ambient pressure (NAP, 0.1 - 100 mbar) conditions. The investigations are performed with the aid of specific in situ techniques (IR-Vis SFG, NAP-XPS, etc.) in order to probe the structural, electronic, chemical and catalytic properties of the models.
The latter span from ordered lattices of metal nanoparticles to 2D metallorganic crystals, where stabilized mono-metallic centers act as the active cores. These systems, based on single metal atom centers, represent the main topic of this manuscript and they will be referred to as Single Metal Atom Catalysts (SMAC).
The discussion of the scientific findings will first focus on the evolution of graphene supported Pt nanoclusters in CO atmosphere, varying both surface temperature and CO pressure to test the stability of the nanostructures. As degradation of this nanosystem occurs at realistic reaction conditions, the attention was shifted to the design and synthesis of model SMAC systems, where the single metal atom is stabilized in a metallorganic cage, thus preventing structural degradation.
A first, prototype SMAC model system consisted of a single layer of Nickel tetraphenyl porphyrins (Ni-TPPs) deposited on the Cu(100) surface. We proved that, following to NO exposure, a hyponitrite species (N2O2) readily forms at the Ni sites already at UHV conditions and is stable at room temperature. The NO conversion is observed only on the NiTPP monolayer interacting with the underlying copper surface, showing that the substrate plays a major role, governing the properties of the nanostructured system through trans-effects associated with a strong surface-to-molecule charge transfer.
A single Iron Phthalocyanine (FePc) layer was instead considered for a model carbonylation reaction. The metalorganic molecules were deposited both on a single foil of graphene, grown on the Ir(111) surface (FePc/GR), and on an alumina ultra-thin film, grown on the Ni3Al(111) surface (FePc/alumina). In both cases, we exploited CO adsorption to probe the molecular active sites.
On the FePc/GR layer, IR-Vis SFG evidenced unexpected CO stretching modes in 1-10 mbar CO at 300 K. We ascribe the observed vibrational features to the production of long-lived molecular excitons (induced by the visible radiation). The long lifetime of these excitons and their efficient production through singlet-fission mechanisms represent intriguing findings for innovative organic devices for solar energy conversion. We also investigated the interaction of the same system with gas-phase CO2 We found that oxidation of the underlying graphene support yields the control of the charge transfer to the active sites, thus reducing the threshold pressure for CO2 adsorption and activation at 300 K by at least two orders of magnitude.
As CO2 catalytic conversion is hindered by its low reactivity, enhancing its adsorption to metal sites is crucial in the framework of the efficient conversion of this waste gas to valuable chemicals. A practical route to alter the mesoscopic properties of the single metal atom centers has been found, and in parallel we proved a novel graphene oxidation route employing molecular oxygen at near ambient pressure.
Concerning instead the FePc/alumina film, we demonstrated that decoration by Cu nanoclusters
tunes the surface potential energy, inducing a different symmetry in the molecular overlayer lattice, scarcely affecting the reactivity of the metallic sites, as proved by the vibrational modes of adsorbed CO molecules. Thus, we succeeded in tailoring the motif of a self-assembled metallorganic layer while preserving its active sites properties.This Thesis work deals with the growth and characterization of model nanostructured surface systems in ultra-high vacuum environment (UHV, <10−9 mbar) and with their evolution at near ambient pressure (NAP, 0.1 - 100 mbar) conditions. The investigations are performed with the aid of specific in situ techniques (IR-Vis SFG, NAP-XPS, etc.) in order to probe the structural, electronic, chemical and catalytic properties of the models. The latter span from ordered lattices of metal nanoparticles to 2D metallorganic crystals, where stabilized mono-metallic centers act as the active cores. These systems, based on single metal atom centers, represent the main topic of this manuscript and they will be referred to as Single Metal Atom Catalysts (SMAC). The discussion of the scientific findings will first focus on the evolution of graphene supported Pt nanoclusters in CO atmosphere, varying both surface temperature and CO pressure to test the stability of the nanostructures. As degradation of this nanosystem occurs at realistic reaction conditions, the attention was shifted to the design and synthesis of model SMAC systems, where the single metal atom is stabilized in a metallorganic cage, thus preventing structural degradation. A first, prototype SMAC model system consisted of a single layer of Nickel tetraphenyl porphyrins (Ni-TPPs) deposited on the Cu(100) surface. We proved that, following to NO exposure, a hyponitrite species (N2O2) readily forms at the Ni sites already at UHV conditions and is stable at room temperature. The NO conversion is observed only on the NiTPP monolayer interacting with the underlying copper surface, showing that the substrate plays a major role, governing the properties of the nanostructured system through trans-effects associated with a strong surface-to-molecule charge transfer. A single Iron Phthalocyanine (FePc) layer was instead considered for a model carbonylation reaction. The metalorganic molecules were deposited both on a single foil of graphene, grown on the Ir(111) surface (FePc/GR), and on an alumina ultra-thin film, grown on the Ni3Al(111) surface (FePc/alumina). In both cases, we exploited CO adsorption to probe the molecular active sites. On the FePc/GR layer, IR-Vis SFG evidenced unexpected CO stretching modes in 1-10 mbar CO at 300 K. We ascribe the observed vibrational features to the production of long-lived molecular excitons (induced by the visible radiation). The long lifetime of these excitons and their efficient production through singlet-fission mechanisms represent intriguing findings for innovative organic devices for solar energy conversion. We also investigated the interaction of the same system with gas-phase CO2 We found that oxidation of the underlying graphene support yields the control of the charge transfer to the active sites, thus reducing the threshold pressure for CO2 adsorption and activation at 300 K by at least two orders of magnitude. As CO2 catalytic conversion is hindered by its low reactivity, enhancing its adsorption to metal sites is crucial in the framework of the efficient conversion of this waste gas to valuable chemicals. A practical route to alter the mesoscopic properties of the single metal atom centers has been found, and in parallel we proved a novel graphene oxidation route employing molecular oxygen at near ambient pressure. Concerning instead the FePc/alumina film, we demonstrated that decoration by Cu nanoclusters tunes the surface potential energy, inducing a different symmetry in the molecular overlayer lattice, scarcely affecting the reactivity of the metallic sites, as proved by the vibrational modes of adsorbed CO molecules. Thus, we succeeded in tailoring the motif of a self-assembled metallorganic layer while preserving its active sites properties.
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Chen, Chiu. "Studies of oxide growth on some Al, Mg and Mg alloy surfaces under ambient exposure conditions." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/mq21036.pdf.
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Schmid-Lorch, Dominik G. [Verfasser]. "Scanning Probe Magnetometry with Nitrogen Vacancy Centers in Diamond under Ambient Conditions / Dominik G. Schmid-Lorch." München : Verlag Dr. Hut, 2019. http://d-nb.info/1202169155/34.
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Peiris, Gallage Sunari. "Pd and Pd based alloy nanoparticles as visible light photocatalysts for coupling reactions under ambient conditions." Thesis, Queensland University of Technology, 2017. https://eprints.qut.edu.au/113715/1/Gallage%20Sunari_Peiris_Thesis.pdf.
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This PhD thesis presents an investigation on the development of novel metal nanoparticle (NP) photocatalysts including non-plasmonic NPs and their alloy NPs for several important organic synthesis reactions. This study has provided solid information and advances in new materials design, synthesis and application for photocatalysis. The findings of this study demonstrate the use of visible light or sunlight to drive chemical reactions, which is an important aspect in the view of a sustainable and green chemistry.
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Lotti, P. "CANCRINITE-GROUP MINERALS AT NON-AMBIENT CONDITIONS: A MODEL OF THE ELASTIC BEHAVIOR AND STRUCTURE EVOLUTION." Doctoral thesis, Università degli Studi di Milano, 2014. http://hdl.handle.net/2434/231573.
Full textAbstract:
The minerals of the cancrinite group are zeolite-like compounds, sharing the [CAN]-topology of the framework. Their structure shows large 12-ring channels along [0001], bound by columns of cages, the so-called can units. Natural and synthetic compounds exhibit a remarkable chemical variability. Among the natural species, the majority shows an aluminosilicate framework. Two subgroups can be identified according to the extraframework content of the can units: the cancrinite- and the davyne-subgroups, showing Na-H2O and Ca-Cl chains, respectively. The channels are stuffed by cations, anions and molecules. In Nature, cancrinite-group minerals occur in the late/hydrothermal stages of alkaline (SiO2)-undersaturated magmatism and in related effusive or contact rocks. Cancrinite-group compounds have been proposed as stable storage form for alkaline wastes. The characterization of the phase-stability fields, thermo-elastic behavior and structure response to applied (P,T) is needed to evaluate and predict their behavior in natural and industrial processes.
The present study aimed to model the thermo-elastic behavior and the mechanisms of (P,T)-induced structure evolution of cancrinite-group minerals, with a special interest on the role played by the extraframework population. The study was restricted to the following (CO3)-rich and (SO4)-rich end-members: cancrinite {[(Na,Ca)6(CO3)1.2-1.7][Na2(H2O)2][Al6Si6O24]}, vishnevite {[(Na,Ca,K)6(SO4)][Na2(H2O)2][Al6Si6O24]}, balliranoite {[(Na,Ca)6(CO3)1.2-1.7][Ca2Cl2][Al6Si6O24]} and davyne {[(Na,Ca,K)6((SO4),Cl)][Ca2Cl2][Al6Si6O24]}. Their high-P and low-T (T < 293 K) behavior was investigated by means of in situ single crystal X-ray diffraction, using diamond-anvil cells and (N2)-cryosystems, respectively.
Though sharing a similar volume compressibility and thermal expansivity, these minerals have a different thermo-elastic anisotropy, more pronounced in the cancrinite-subgroup compounds. This behavior is governed by different deformation mechanisms, which reflect the different coordination environments of the cage population between the minerals of the two subgroups. The davyne sample studied at high-P showed a displacive phase transition from the P63/m to the P63 space group after the load of pressure [0.0001 ≤ P (GPa) ≤ 0.38(2)]. In vishnevite, a P-induced re-organization of the extraframework population took place at P > 3.5 GPa, coupled with a significant increase in compressibility, suggesting that the channel-constituents can also play an active role at non-ambient conditions.
Besides common features likely ascribable to the [CAN]-topology, the nature of the extraframework population appears to control significantly the (P,T)-induced structure evolution and thermo-elastic behavior of the cancrinite-group compounds.
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Guse, Christa [Verfasser]. "Properties of confined and unconfined water A computer simulation study at ambient and supercooled conditions / Christa Guse." Wuppertal : Universitätsbibliothek Wuppertal, 2011. http://d-nb.info/1018297987/34.
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Downie, Laura E. "Pathways to Recovering Single-Bonded Nitrogen at Ambient Conditions: High Pressure Studies of Molecular and Ionic Azides." Thesis, University of Ottawa (Canada), 2010. http://hdl.handle.net/10393/28849.
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Working towards the goal of recovering single-bonded nitrogen at ambient conditions, the approach taken in this work is to subject nitrogen-rich molecular and ionic azides (specifically, cyanuric triazide and ammonium azide) to high pressures to induce transitions to phases that contain single-bonded nitrogen. The samples were subjected to extreme pressures using a diamond anvil cell and subsequently studied using high-resolution synchrotron powder x-ray diffraction and vibrational Raman spectroscopy. The experimental results indicate that both cyanuric triazide and ammonium azide undergo a pressure-induced first order structural phase transition at 30 and 3.0 GPa, respectively. The analyses and characterizations of these dense energetic materials are discussed in detail, and will be used to explore the possibility of recovering single-bonded nitrogen at ambient conditions.
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Musaev, Omar Wróbel Jerzy. "UV laser assisted processing of InP at different ambient conditions with variable number of pulses and fluences." Diss., UMK access, 2006.
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Thesis (Ph. D.)--Dept. of Physics and School of Computing and Engineering. University of Missouri--Kansas City, 2006."A dissertation in physics and telecommunications networking." Advisor: Jerzy Wrobel. Typescript. Vita. Title from "catalog record" of the print edition Description based on contents viewed Nov. 1, 2007. Includes bibliographical references (leaves 185-190). Online version of the print edition.
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Daniel, Simon James. "Investigations into the nutritional requirements of juvenile dusky kob, Argyrosomus japonicus (Pisces sciaendae), under ambient culture conditions." Thesis, Rhodes University, 2004. http://hdl.handle.net/10962/d1002602.
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The effect of dietary protein, protein and energy ratios, fish meal replacement by Soya bean meal and feeding frequency was investigated on the growth, feed efficiency and body composition, of juvenile dusky kob, Argyrosomus japonicus. The effect of dietary protein levels was investigated by comparing isocaloric diets containing 35, 40, 45 and 55% protein. Dietary protein inclusion level significantly affected specific growth rates, feed efficiency and body composition (in terms of fat deposition) and results show that a minimum of 45% and maximum of 52.3% dietary protein is optimal. The protein and energy requirements were investigated by comparing three protein levels (35,40 and 45%) with three lipid levels (6, 9 and 12%) in a 3x3 factorial design. A diet 45% protein and 9% lipid, with a P: E ratio of29 mglkJ and DE of 15.5 kJ/g resulted in an optimal specific growth rate (1.6± 0.2), feed efficiency (FCR= 1.7±0.44; PER= 1.36) and body composition for A. japonicus. To investigate the effect of partial fish meal replacement by Soya bean meal (SBM) in the diet, 20-50% of the protein from fish meal was substituted by protein from SBM, and were compared with a control diet containing only fish meal. No significant differences in the specific growth rates, feed efficiencies and the body composition were recorded for the fish fed the control diet and for fish fed the 20 and 30% SBM treatments. Results show that up to 30% of the protein from fish meal can be replaced with protein from SBM in the diet of this species. The effect of feeding frequency and gut evacuation time was investigated by comparing four feeding frequencies. Fish were fed to satiation either once, twice, three or four times a day. Feed intake was significantly affected by feeding frequency and fish fed 2, 3 and 4 meals a day ate significantly more food (p< 0.05) than the fish fed one meal a day. No significant differences (p> 0.05) in the specific growth rates, feed efficiencies and body composition were recorded for fish fed 2, 3 and 4 times a day. Feed intake was used to calculate an optimal daily ration and feeding two meals a day resulted in an optimal daily ration of 4% BW/day. A gut evacuation time of 7.25 hours indicates that fish fed twice a day probably had sufficient time to digest their food and evacuate their guts, resulting in the same daily feed intake as fish given 3 and 4 meals a day. Results conclude that under the present experimental conditions, a minimum daily ration of 4% BW/day, fed twice a day (in the morning and evening) is required for optimal growth (SGR= 1.33± 0.1), feed efficiency (FCR= 1.96± 0.4; PER= 1.44± 0.2) and body composition in juvenile dusky kob.
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DAVI', ROCCO. "Reactivity under cover in controlled Near Ambient Pressure conditions: CO on bare and graphene covered NI(111)." Doctoral thesis, Università degli studi di Genova, 2022. http://hdl.handle.net/11567/1073036.
Full textAbstract:
The graphene–metal interface, as an interesting graphene-based system, attracts much attention from both the application and the fundamental science points of view. One of the reasons is that Chemical Vapor Deposition (CVD) on metal surfaces is the most promising method to produce large area graphene sheets with nickel and copper as most frequently used substrates. However, Ni has a severe drawback due to the high solubility of carbon at the temperatures required for CVD (>800 K). Dissolved carbon atoms may segregate to the surface of the substrate while cooling down the system, producing unwanted graphene multilayer structures. Careful preparation protocols have therefore to be followed, which leave carbide traces on the surface which can absorb the segregating carbon atoms by transforming into graphene. Another reason is that the graphene properties may be strongly affected by the interaction with the substrate, thus yielding interesting catalytic properties. My thesis is focused on the interaction of CO with Ni(111) which I studied in operando conditions with Near Ambient Pressure by X-Ray Photoemission Spectroscopy (NAP-XPS) at ~ 3 mbar thus extending the so far explored pressure range by nearly one order of magnitude. Under these conditions I observed the detachment of the strongly interacting graphene and its conversion into weakly interacting graphene caused by CO intercalation under it already at 500 K. Intercalation of gases is important since it restores the Dirac cone and thus the exceptionally large carrier mobility of graphene and because chemical reactions may be favored under cover by the constrained volume. Indeed, above 600 K, formation of physisorbed CO2 is observed under the graphene cover, a process I ascribe to the onset of the Boudouard reaction. The latter leads to the formation of additional carbon atoms which transform the residual carbide, present at the surface, into graphene causing the expansion of the graphene islands. Furthermore, my data confirm that CO does not only intercalate, but adsorbs also above the strongly interacting graphene areas forming a weakly bonded species of possible catalytical relevance. The reaction has been observed also after drilling single and double vacancies into the graphene layer by ion bombardment. CO2 tends then to mend the vacancies forming a bridge over their borders.
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Ali, Hatim F. A. "Assessment of lime-treated clays under different environmental conditions." Thesis, University of Bradford, 2019. http://hdl.handle.net/10454/18313.
Full textAbstract:
Natural soils in work-sites are sometimes detrimental to the construction of engineering projects. Problematic soils such as soft and expansive soils are a real source of concern to the long-term stability of structures if care is not taken. Expansive soils could generate immense distress due to their volume change in response to a slight change in their water content. On the other hand, soft soils are characterised by their low shear strength and poor workability. In earthwork, replacing these soils is sometimes economically and sustainably unjustifiable in particular if they can be stabilised to improve their behaviour. Several techniques have evolved to enable construction on problematic soils such as reinforcement using fibre and planar layers and piled reinforced embankments.
Chemical treatment using, e.g. lime and/or cement is an alternative method to seize the volume change of swelling clays. The use of lime as a binding agent is becoming a popular method due to its abundant availability and cost-effectiveness. When mixed with swelling clays, lime enhances the mechanical properties, workability and reduces sensitivity to absorption and release of water. There is a consensus in the literature about the primary mechanisms, namely cation exchange, flocculation and pozzolanic reaction, which cause the changes in the soil characteristics after adding lime in the presence of water. The dispute is about whether these mechanisms occur in a sequential or synchronous manner. More precisely, the controversy concerns the formation of cementitious compounds in the pozzolanic reaction, whether it starts directly or after the cation exchange and flocculation are completed.
The current study aims to monitor the signs of the formation of such compounds using a geotechnical approach. In this context, the effect of delayed compaction, lime content, mineralogy composition, curing time and environmental temperature on the properties of lime-treated clays were investigated.
The compaction, swelling and permeability, and unconfind compression strength tests were chosen to evaluate such effect. In general, the results of the geotechnical approach have been characterised by their scattering. The sources of this dispersion are numerous and include sampling methods, pulverisation degree, mixing times and delay of compaction process, a pre-test temperature and humidity, differences in dry unit weight values, and testing methods. Therefore, in the current study, several precautions have been set to reduce the scattering in the results of such tests so that they can be used efficiently to monitor the evolution in the properties that are directly related to the formation and development of cementitious compounds. Four clays with different mineralogy compositions, covering a wide range of liquid limits, were chosen. The mechanical and hydraulic behaviour of such clays that had been treated by various concentrations of lime up to 25% at two ambient temperatures of 20 and 40oC were monitored for various curing times.
The results indicated that the timing of the onset of changes in mechanical and hydraulic properties that are related to the formation of cementitious compounds depends on the mineralogy composition of treated clay and ambient temperature. Moreover, at a given temperature, the continuity of such changes in the characteristics of a given lime-treated clay depends on the lime availability.
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Franzoni, Lorenzo. "Mechanical behavior of regularly spaced Cross Laminated Timber panels : Modeling and experimental validation in ambient and fire conditions." Thesis, Paris Est, 2016. http://www.theses.fr/2016PESC1113/document.
Full textAbstract:
Les panneaux en bois lamellé croisé (en anglais CLT - Cross Laminated Timber) sont des éléments de structure composés de couches en bois collées entre eleese et empilées de façon croisée. Chaque couche est composée de planches en bois juxtaposées et généralement non collées sur leur chants. Dans cette thèse, nous étudions l'influence sur le comportement mécanique des espacements entre planches des panneaux avec une approche par modélisation et expérimentation. Les panneaux CLT standard sont considérés comme des panneaux avec des espacements de très faible dimension par opposition aux panneaux avec espacements importants que nous appelons panneaux innovants. Nous modélisons dans un premier temps le comportement en flexion de panneaux standard à l'aide d'un modèle de couche homogène équivalente basée sur des hypothèses simplifiées de la mécanique d'une couche avec chants collés ou non collés. Nous observons un bon accord entre les résultats de notre modélisation et des résultats expérimentaux issus de la littérature. Des études paramétriques sont ensuite réalisés portant sur certaines propriétés des panneaux.Nous avons ensuite réalisé des essais de flexion 4-points sur des panneaux CLT standard et innovants pour quantifier l'influence des espacements sur la réponse mécanique des panneaux. Il se trouve que l'influence des effets de cisaillement transverse sur le comportement élastique et à la rupture augmente avec l'augmentation des vides dans le panneau.Afin de prendre correctement en compte les effets du cisaillement, les CLT espacés sont modélisés comme des plaques épaisses périodiques à l'aide d'un modèle de plaque d'ordre supérieur. Ce modèle a été appliqué à la géométrie des panneaux CLT espacés avec un schéma d'homogénéisation périodique. Des méthodes simplifiées existantes ont également été comparées avec les résultats des essais et le modèle de plaque. De plus, des résultats d'essais de cisaillement dans le plan des panneaux CLT standard issus de la littérature ont été comparés avec nos résultats. La raideur de flexion des CLT espacés peut être prédite avec des méthodes simples existantes, alors que seule la modélisation que nous proposons permet de prédire le comportement en cisaillement transverse et dans le plan. Finalement, des formules analytiques ont été obtenues pour prédire le comportement élastique des CLT espacés. Ces formules donnent une bonne approximation u comportement des CLT espacés et peuvent être utilisées dans le cadre d'une démarche pratique de dimensionnement.Enfin, une étude concernant l'analyse du comportement au feu des panneaux CLT standard est présentée. La comparaison entre des résultats d'essais au feu et une modélisations avancée et simplifiée a permis de proposer une possible amélioration de la méthode de dimensionnement au feu standardCross Laminated Timber (CLT, or crosslam) panels are engineered timber products composed of layers made of wooden lamellas placed side by side, glued on their upperand lower faces and stacked crosswise. In the present thesis, the influence of lateral spaces between lamellas of each layer on the panel’s mechanical response is investigated with modeling and tests. Both configurations of standard panels having short spaces and innovative CLT panels with large spaces are analyzed.As a first approach, the bending behavior of standard crosslam was modeled by means of an equivalent-layer model based on simplified hypotheses on mechanical properties of laterally glued or unglued layers. The good agreement of the predicted behavior with an experiment of the literature finally allowed an investigation on several CLT properties by means of parameter studies.Then, 4-points bending tests on standard and innovative CLT floors were performed in order to quantify the influence of periodic spaces on the panels' mechanical response. It appears that the influence of transverse shear effects on the elastic and failure behavior of spaced CLT increases with the increasing spaces between boards.In order to take into account transverse shear effects, spaced CLT have been modeled as periodic thick plates by means of a higher-order plate theory for laminated plates. This model has been applied to the geometry of spaced CLT with a periodic homogenization scheme. Existing simplified methods for spaced crosslam were compared as well with refined modeling and test results. Moreover, available in-plane shear tests of the literature have been compared to the modeling results. It appears that the bending behavior of spaced CLT can be predicted with simplified existing approaches, while only the more refined modeling can predict the in-plane and transverse shear behavior. Then, closed-form solutions for predicting spaced CLT elastic behavior were derived in order to encourage the application of spaced CLT panels in modern timber construction.One further study within this thesis concerns the analysis of fire-exposed standard CLT floors. The comparison between test results and both advanced and simplified modeling led to a suggestion for a possible improvement the standard fire design model
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Duguay, Louise S. "Bench-scale treatability study of a dilute synthetic dairy wastewater, by combined anaerobic-aerobic systems, at ambient temperature conditions." Thesis, University of Ottawa (Canada), 2003. http://hdl.handle.net/10393/26369.
Full textAbstract:
This research project consisted of studying the feasibility of a combined UASB-activated sludge process configuration for treating a dilute synthetic substrate, simulating a dairy wastewater, at a laboratory temperature averaging 23.5 +/- 0.8°C. The bench-scale experimental work was carried-out in two parallel biotreatment systems fed in series. They consisted of relatively small-scale Upflow Anaerobic Sludge Blanket (UASB) reactors of 3.85 and 3.75 L, respectively, followed by 2 L-activated sludge polishing processes. The feed concentration applied to one of the systems consisted of the minimum influent strength recommended for successful anaerobic treatment (∼1 000 mg CODt/L) while the second system was of the domestic sewage-strength range (∼500 mg CODt/L), achieved by dilution.
The mainly soluble complex feedstock used consisted of tap water and Iron Fortified Enfalac(TM) Infant Formula. It was supplemented chemically to ensure that proper (N and P) nutrient requirements were met as well as to increase its buffering capacity and to adjust pH.
Three experimental runs were carried out by applying increasing UASB influent flow rates of 2, 4 and 8 L/d, in both systems. (Abstract shortened by UMI.)
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Daniil, Dimitra. "Rock Magnetic Studies of Magnetite and Quartzite: Results at Ambient Conditions and From Diamond Anvil Pressure Experiments (~2 GPa)." Thesis, Uppsala universitet, Geofysik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-437026.
Full textAbstract:
Numerous techniques are used to study the magnetic history and properties of rocks, which provides important data on the Earth’s interior. In this study we conducted a series of experiments on two different sample sets, comprising pure magnetite (Set1) and a mixture of magnetite-hemoilmenite-bearing quartzite (Set2), in order to gather information about their magnetic susceptibility and remanent magnetization. A miniature diamond anvil cell (mDAC) constructed from hardened non-magnetic alloy (40HNU) was used for high pressure experiments. With the help of high sensitivity susceptibility bridge (MFK1-FA Kappabridge, AGICO), we measured the susceptibility of three samples and of the mDAC. Consequently, we loaded one of the samples in the mDAC and acquired susceptibility measurements during the compression and decompression of the system. For remanence measurements we used a 2G Enterprises SQUID magnetometer. We measured the natural remanent magnetization (NRM) and performed alternating field (AF) demagnetization on ten samples and on the mDAC. Additionally, isothermal and anhysteretic remanent magnetization (IRM and ARM) acquisition were performed on nine and one samples, respectively and demagnetization on three and one samples, respectively. Results showed that Set1 samples consist of both SD and MD magnetite grains. Regarding Set2 samples, the main magnetic carriers are SD and MD magnetite or titanium bearing magnetite grains, while there are indications that hematite and ferrimagnetic titanohematite might be present as well. The presence of eddy currents, due to the conducting materials of the mDAC, resulted in masking the signal of the sample making it difficult to draw any safe conclusions regarding how the susceptibility of the sample changes with pressure. All in all, there was a satisfactory response of the instruments working with very small amounts of material and an adequate signal stability of both the samples and the mDAC. Our study provided us with an insight into high pressure experiments and showed possible directions for future studies.Många metoder används för att studera magnetiska egenskaper i berg, vilket ger viktig information om Jordens inre. I denna studie genomförde vi en rad experiment på två olika uppsättningar prov, innefattande ren magnetit (Set1) och en blandning av magnetit-hemoilmenit-bärande kvartsit (Set2), för att samla information om deras magnetisk susceptibilitet och magnetiska remanens. En miniatyr diamantstädcell (mDAC) konstruerad av en härdad icke-magnetisk legering (40HNU) användes för högtrycksexperiment. Susceptibilitetet av tre prover och av mDAC mättes en MFK1-FA Kappabridge, AGICO. Följaktligen monterade vi ett av proverna i mDAC och vi genomförde susceptibilitetsmätningar under kompression och dekompression. Vi använde en 2G Enterprises SQUID magnetometer för remanensmätningar. Den naturlig remanentmagnetiseringen (NRM) mättes och vi utförde alternerande fält (AF) demagnetisering på tio prover och på mDAC. Dessutom genomfördes isotermisk och anhysteretisk remanentmagnetisering (IRM och ARM) på nio respektive ett prover, och demagnetisering på tre respektive ett prover. Resultaten visade att Set1-prover består av både enkeldomän (SD) och multidomän (MD) magnetit. SD och MD magnetit- och titanomagnetitkorn är de viktigaste magnetiska mineral av Set2-prover, medan finns det indikationer på att hematit och ferrimagnetisk titanohematit också bidrar till signal. Virvelströmmar, som skapats av mDACs ledande material, maskerade provets magnetiska susceptibilitet och det var svårt att kommentera på hur provets susceptibilitet förändras med tryck. Sammantaget var instrumentens prestanda tillfredsställande, även vid små mängder material. Prov och mDACs signalstabilitet var också adekvat. Vår studie gav oss en inblick i högtrycksexperiment och magnetiska egenskaper och den visade möjliga riktningar för framtida studier.
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Crole, David Alexander. "The direct synthesis of hydrogen peroxide in water at ambient temperature : a study of reaction conditions, catalyst design and implementation." Thesis, Cardiff University, 2017. http://orca.cf.ac.uk/107580/.
Full textAbstract:
The research presented in this thesis focuses on the process of direct synthesis of hydrogen peroxide from molecular hydrogen and oxygen. This reaction potentially offers an approach which is greener and more sustainable when compared to the current industrial indirect auto-oxidation process. The work presented herein examines some of the key factors in determining the viability of the process in a water solvent at ambient temperature, conditions which would represent a very economically and environmentally attractive option, if feasible. The first part of this thesis investigates the ways in which changing reaction conditions affects the fundamental reaction processes of the direct synthesis reaction – synthesis of hydrogen peroxide and its subsequent degradation by decomposition and hydrogenation. It was found that moving to a water solvent and ambient temperature results in significantly lower yields and greater degradation comparative to previously used water/methanol solvents and 2°C reactions. The second part of this thesis explores the design of catalysts which are active for the direct synthesis of hydrogen peroxide while limiting degradation activity, to increase the yield in water at ambient temperature. A series of supported metal catalysts of the nominal formulation 0.5 wt. % Pd - 4.5 wt. % ‘base metal’ were prepared and treated with a cyclic oxidative-reductive-oxidative heat treatment. This produced highly stable catalysts with activity for the synthesis of hydrogen peroxide, but low to no activity for both decomposition and hydrogenation pathways. These catalysts also fulfilled a secondary aim of producing economically attractive catalysts due to the low loadings of precious metals used. The third and final part of this thesis studies the implementation of these highly selective catalysts in both gas and gas/liquid phase flow reactors. The production of hydrogen peroxide in a gas phase flow system is shown to be attainable although most likely not a commercially viable option. The direct synthesis of hydrogen peroxide in a gas/liquid flow system is shown to proceed with selectivities greater than those previously reported for different catalysts under similar conditions. Tests also show that hydrogen peroxide can be produced under ‘real world’ conditions of high flow rates, a hard water solvent and a dilute hydrogen in air gas mix. These studies could be used to inform future work on high throughput water cleaning technologies.
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Gamazo, Rusnac Pablo Andrés. "A code for multiphase reactive transport modeling of concentrated solutions under extreme dry conditions." Doctoral thesis, Universitat Politècnica de Catalunya, 2010. http://hdl.handle.net/10803/6276.
Full textAbstract:
La modelació del transport reactiu multifàsic (TRMF) involucra la simulació del flux de fases fluïdes, el transport de compostos químics i energia, i les reaccions químiques. La majoria dels codis de transport reactiu desacoblen els càlculs de flux de fases del transport reactiu. Aquesta metodologia que s'utilitza per resoldre diversos problemes de TRMF resulta inadequada per adreçá problemes com ara l'evolució de piles de deixalles mineres o la salinització de sòls a on poden trobar-se solucions concentrades o condicions d'extrema sequedat. En aquests casos la quantitat d'aigua líquida pot ser tan petita que tant el vapor com la precipitació mineral poden afectar el seu balanç. Wissmeier i Barry (2008) han desenvolupat un codi que acobla el terme font químic i els càlculs de flux, però solament serveix per a casos on el transport està limitat a la fase líquida. Tot i això, sota aquestes condicions, el transport de gas pot ser important i l'activitat de l'aigua que controla la pressió de vapor es pot veure afectada tan per efectes capil·lars com ara de la salinitat. A més, certes paragènesis (les que produeixen punts invariants) poden fixar l'activitat de l'aigua, produint que la geoquímica controli la pressió de vapor, la qual és una variable clau per simular correctament el flux de gas. Per tant, una solució que acobli el flux de fases i el transport reactiu és necessària.El principal objectiu d'aquesta tesi és desenvolupar un codi de TRMF capaç de representar la influència de la geoquímica sobre els fluxes i el transport en solucions concentrades i condicions d'extrema sequedat. Com objectiu secundari s'estudien alguns casos sota aquestes condicions.
En primer lloc, es discuteix l'acoblament de la salinitat i la pressió de vapor (i per tant l'evaporació), i es presenta un mètode per calcular l'evolució de sistemes altament salins. Es fa especial èmfasi en la valoració de punts invariants, on l'activitat de l'aigua és controlada pel conjunt de minerals precipitats. El mètode és contrastat contra un experiment d'evaporació d'una salmorra natural rica en MgSO4 i amb un model simplificat d'una llacuna salobre perenne. Els resultats obtinguts indiquen que la paragènesis mineral pot tenir una influència considerable sobre l'evolució de sistemes salobres en fixar la composició química durant un interval considerable de temps.
En segon lloc, es discuteix l'evolució d'una solució concentrada en un mitjà porós. En aquestes condicions l'evaporació es veu afectada no solament per efectes de la salinitat sinó també per capil·lars, i per processos de transport. Es presenta una formulació composicional per TRMF que considera els efectes de l'acoblament entre processos geoquímics i hidrodinàmics, i es discuteixen alguns aspectes en relació a la seva solució numèrica. Els avantatges d'aquesta formulació són il·lustrades mitjançant la simulació de l'efecte de la deshidratació mineral en els processos hidrodinàmics en una columna de guix en condicions d'extrema sequedat. Els resultats indiquen que els efectes acoblats poden tenir una influència significativa en l'evolució de sistema.
Finalment, presentem la implementació del codi. Es discuteix la importància de la flexibilitat en el desenvolupament de codis de transport reactiu mitjançant la programació orientada a objectes. Es presenten les principals classes que utilitza el codi i com interaccionen entre elles. El codi s'utilitza per modelar un experiment d'evaporació d'una columna de sorra saturada en una solució de MgSO4. La interacció entre processos hidrodinàmics i geoquímics és analitzada. Els resultats obtinguts mostren que l'aparició de punts invariants en l'extrem superior de la columna té un efecte apreciable en la valoració de la sortida de vapor i en la precipitació de sals en la columna. De fet, els punts invariants expliquen les fluctuacions espacials observades en la precipitació de sals.
Multiphase Reactive Transport (MPRT) modelling involves simulating flow of fluid phases, transport of species and energy, and reactions between species within the same or different phases. Reactive transport codes decouple phase flow calculations from reactive transport. This approach has been successfully applied to a wide range of MPRT problems, but it may be unsuitable for problems like the chemical evolution of unsaturated tailings or the salinization of soils, where concentrated solutions or extremely dry conditions are be reached. The amount of liquid water in these cases can be so small that both vapor and water in hydrated minerals can be significant for the water balance. Wissmeier and Barry (2008) developed a code which couples chemical sink-sources and water flow, but only for cases where transport is limited to unsaturated liquid phase. However, under these extreme conditions gas transport becomes important and water activity, which controls vapor pressure, is affected by capillary and salinity effects. Moreover, certain mineral paragenesis (the ones that produce invariant points) fix water activity, causing the geochemistry to control vapor pressure, which is a key gas flow variable. Thus, a fully coupled solution of phase fluxes and reactive transport is required for these conditions.
The main objective of this thesis is to develop a general MPRT code capable of representing the effect of geochemistry on flow and transport for concentrated solutions under extreme dry conditions. As a secondary objective, the behavior of some cases under such conditions is studied. Different aspects of this code and different cases are discussed through the chapters of this thesis.
First, coupling of salinity and vapor pressure (and thus evaporation rate) is discussed, and a method for computing the evolution of high salinity systems is presented. Special emphasis is placed on the treatment of invariant points, that are sets of minerals that fix water activity. The method is applied to a natural MgSO4-rich brine evaporation experiment and to a simplified model of a perennial saline playa lake. The results indicate that mineral paragenesis can have a considerable influence on the evolution of shallow brine systems by fixing chemical composition for a significant portion of time.
Second, the evolution of concentrated solution in porous media is discussed. In this scenario evaporation is affected not only by salinity but also by capillary effects. Also transport is considered. A generalized compositional formulation for MPRT, which considers coupling effects between geochemical and hydrodynamic process problems, is presented. Some aspects related to its numerical solution are discussed as well. The advantages of the formulation are illustrated by simulating the effect of mineral dehydration on the hydrodynamic processes in a gypsum column that reaches extremely dry conditions. The results indicate this significantly affects the evolution of the system.
Finally, implementation of the code is presented. The importance of flexibility for reactive transport codes and the way how objects oriented programming can facilitate this feature is discussed. The code's main classes and their interactions are presented. The code is used to model a laboratory experiment where a sand column saturated with an MgSO4 solution is subject to evaporation. Extreme dry conditions and high salinity content are reached in this experiment. The interaction between hydrodynamic and geochemical processes on the model is analyzed. Model results shows that the occurrence of invariant points on the top of the domain can have an appreciable effect on the outlet of vapor from the column and on the distribution of salt precipitates along the column. In fact, invariant points explain spatial fluctuation of salt precipitates.
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Ehsan, Abbasi Atibeh. "A Study On The Catalytic Pyrolysis And Combustion Characteristics Of Turkish Lignite And Co-processing Effects With Biomass Under Various Ambient Conditions." Master's thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614512/index.pdf.
Full textAbstract:
In this study the catalytic pyrolysis and combustion characteristics of Turkish coal samples in O2/N2 and O2/CO2 (oxy-fuel conditions) ambient conditions were explored and the evolution of emissions during these tests was investigated using non-isothermal Thermo-gravimetric Analysis (TGA) technique combined with Fourier Transform Infrared (FTIR) spectroscopy. Potassium carbonate (K2CO3), calcium hydroxide (Ca(OH)2), iron (III) oxide (Fe2O3) and iron (III) chloride (FeCl3) were employed as precursors of catalysts to investigate the effects of potassium (K), calcium (Ca) and iron (Fe). Furthermore the effects of these catalysts on calorimetric tests of Turkish coal samples were investigated.
TGA-FTIR pyrolysis tests were carried out in 100 % N2 and 100 % CO2 ambient conditions which are the main diluting gases in air and oxy-fuel conditions. Lignite pyrolysis tests revealed that the major difference between pyrolysis in these two ambient conditions was observed beyond 720
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Kohler, Angela. "Food quality, fasting periods and temperature stress : effects of energy challenges on the feeding patterns of avian nectarivores." Thesis, University of Pretoria, 2009. http://hdl.handle.net/2263/28655.
Full textAbstract:
The small size of nectarivorous birds is associated with high mass-specific metabolic rates and energetic lifestyles. Their energy balance is likely to be strongly influenced by environmental factors. Firstly, nectar varies in sugar concentration between different food plants and birds must adjust their consumption to maintain a constant energy intake. Secondly, unfavourable weather conditions, such as storms and heavy rains, may prevent birds from feeding, and they must increase their energy intake to compensate for the loss in foraging time. Low ambient temperature, as a third energetic challenge, results in higher energy demands for thermoregulation, which leads to increased food intake. However, these compensatory feeding responses may be constrained by physiological limitations to nectar ingestion, digestion and osmoregulatory processes. My research focused on the behavioural and physiological responses of captive sunbirds (Nectariniidae) and honeyeaters (Meliphagidae) to energetic challenges, namely variations in nectar quality and availability and in ambient temperature. For sunbirds, I also investigated on a novel short-term scale how feeding patterns are adjusted in order to compensate for alterations in energy intake or requirements. Feeding events were recorded using a photodetection system, and body mass was monitored continuously by connecting the perches to electronic balances, interfaced to a computer. Whitebellied sunbirds (Cinnyris talatala) were fed various nectar sugar concentrations. Their feeding durations were found to provide an estimate of meal size on all food concentrations. When exposed to a decrease in sugar concentration, birds generally demonstrated an increased feeding frequency and food intake within 10 min. The number and duration of meals increased in the first few minutes after return of a more concentrated diet. When whitebellied sunbirds and brown honeyeaters (Lichmera indistincta) were exposed to a 2 h fasting period during the day, they increased their nectar intake and energy accumulation after the fast. Sunbirds achieved this by increasing meal size but not meal frequency. However, both species weighed less in the evening following the fast than the previous evening, indicating that the compensation for lost foraging time was incomplete. During acute cold exposure, whitebellied sunbirds, amethyst sunbirds (Chalcomitra amethystina) and brown honeyeaters increased their nectar intake, but lost body mass irrespective of nectar sugar concentration. Honeyeaters ingested more food at subsequent cold exposure, suggesting physiological adaptation to high feeding rates. A chemical reactor model of digestive capacity, which assumes sucrose hydrolysis to be the limiting step in nectar digestion, accurately predicted maximal food intake in honeyeaters, but mostly underestimated it in sunbirds. Sugar assimilation efficiency was higher than 99% in whitebellied sunbirds and brown honeyeaters. Lastly, licking frequencies and tongue loads of whitebellied and amethyst sunbirds were investigated. In both species, tongue lick duration increased, and licking frequency and consumption per lick decreased, with increasing nectar concentration. Birds did not adjust their licking behaviour after a fasting period. In conclusion, the response to varied energy challenges is shaped by both compensatory feeding and physiological constraints. Although unrelated, sunbirds and honeyeaters showed convergence in their responses, probably due to their similar nectarfeeding lifestyle.Thesis (PhD)--University of Pretoria, 2009.
Zoology and Entomology
unrestricted
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Lappalainen, N. (Niina). "The responses of ectohydric and endohydric mosses under ambient and enhanced ultraviolet radiation." Doctoral thesis, University of Oulu, 2010. http://urn.fi/urn:isbn:9789514262142.
Full textAbstract:
Abstract
Previous reports on the effects of enhanced UV-B radiation on bryophytes have been equivocal. This study shows that mosses not only respond to enhanced UV-B, but they are affected by changes in ambient radiation. The studies were conducted with two model species common in northern environments; red-stemmed feather moss (Pleurozium schreberi) and juniper haircap moss (Polytrichum juniperinum).
Both species showed high concentrations of methanol-extractable UV-absorbing compounds (UACs) with high spring-time and early-summer UV, whereas in P. juniperinum, the concentration was affected by early-summer drought. The UACs of P. juniperinum increased again towards autumn suggesting a role in winter hardening. The (spring-time) cell wall-bound UV screen was important to both species. The fundamental adaptation of P. juniperinum to open and exposed environments was reflected in relatively higher concentrations of total UACs compared to P. schreberi.
The enhanced UV-B experiments in situ were conducted over two years in Oulu and six years at the FUVIRC site in Sodankylä. Some of the effects of UV-B were seen within the first years of the experiments, or even within hours, while others were observed after several years. Five or six years of enhanced UV-B treatment increased the methanol-extractable UACs of P. schreberi and decreased the green shoot growth of P. juniperinum. The immediate light environment was proposed to have an impact on the varying UAC concentrations. Some mitigating effects of UV-A were observed as well.
Off-site measured, reconstructed and modelled UV radiation data was used for comparisons of light environment in situ, or when performing a reconstructive research with historical samples. The environmental sample banks can provide a useful tool to study past environmental conditions, and even reconstruct past radiation levels.
It was shown in this study that UACs in P. schreberi and P. juniperinum have fundamental roles as UV-B screens in the cell walls, but there is also a variable response with the soluble fraction that reacts and adapts to the changes in UV radiation. The responses to increasing UV-B radiation vary in magnitude and in time. As P. schreberi and P. juniperinum possess circumboreal and cosmopolitan distributions, the effects of UV-B on these species and consequently on ecosystems has a broad application.
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Miyauchi, Teruhisa. "Development of a new analytical method for quantifying benzalkonium chloride in treated wood and evaluation of its leaching characteristics under different ambient conditions." Kyoto University, 2008. http://hdl.handle.net/2433/136698.
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Kyoto University (京都大学)0048
新制・論文博士
博士(農学)
乙第12215号
論農博第2673号
新制||農||959(附属図書館)
学位論文||H20||N4382(農学部図書室)
UT51-2008-C985
北海道大学大学院農学研究科林産学専攻
(主査)教授 今村 祐嗣, 教授 中野 隆人, 教授 梅澤 俊明
学位規則第4条第2項該当
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Roy, K. "Toward bridging the pressure gap between real world catalysis and ideal surface science conditions using ambient pressure photoelectron spectroscopy and molecular beam instrument." Thesis(Ph.D.), CSIR-National Chemical Laboratory, Pune, 2015. http://dspace.ncl.res.in:8080/xmlui/handle/20.500.12252/2007.
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Nyrow, Alexander [Verfasser], Metin [Akademischer Betreuer] Tolan, and Max [Gutachter] Wilke. "Iron containing compounds of the inner earth: X-ray Raman scattering from ambient to extreme conditions / Alexander Nyrow. Betreuer: Metin Tolan. Gutachter: Max Wilke." Dortmund : Universitätsbibliothek Dortmund, 2014. http://d-nb.info/1104947420/34.
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Laubscher, Franciscus Xavierus. "A model to predict the effect of the radiator core and ambient conditions on the performance of the cooling system of a rally car." Pretoria : [s.n.], 2005. http://upetd.up.ac.za/thesis/available/etd-04172007-110452.
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Vicedo, Jover Maria Esmeralda [Verfasser], Burkhard [Akademischer Betreuer] [Gutachter] Rost, and Bertram [Gutachter] Müller-Myhsok. "Comprehensive analysis of intrinsically disordered protein content in organisms exposed to extreme ambient conditions / Maria Esmeralda Vicedo Jover ; Gutachter: Burkhard Rost, Bertram Müller-Myhsok ; Betreuer: Burkhard Rost." München : Universitätsbibliothek der TU München, 2016. http://d-nb.info/1113749156/34.
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Fishman, Benjamin. "Influence of Environmental Parameters on Mold Sampling Results." Scholar Commons, 2017. http://scholarcommons.usf.edu/etd/6838.
Full textAbstract:
Mold is a type of fungus present in nearly all environments. Mold thrives under several environmental parameters such as high humidity and an adequate food source. A professional, such as an industrial hygienist, can measure mold in indoor and outdoor environments. Industrial hygienists commonly use a cascade impactor with a culture plate to capture air within a sampling area. While collecting air samples, environmental parameters such as temperature, humidity, and carbon dioxide are recorded. A laboratory then cultures and analyzes the samples, identifying the types and amounts of viable mold found in the sampling area.
In this study, a data analysis method is used to interpret lab results and compare those results to the environmental parameters measured during collection. The study aims to show the relationship between the environmental parameters (temperature, humidity, carbon dioxide) and the types and amounts of mold that were measured in both indoor built environments and their surrounding outdoor areas.
Among all 170 different sampling locations, the outdoor areas had higher counts and concentrations of mold. In addition, both indoor and outdoor areas saw Penicillium, Aspergillus, and Cladosporium as the most prevalent molds, with Cladosporium having the highest counts. Lower temperatures and humidity had a very small influence on mold growth and thus, yielded the lowest counts. Furthermore, the highest concentrations of mold were found within the same temperature and humidity ranges for both indoor and outdoor environments.
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Vondracek, Hendrik [Verfasser], Martina [Gutachter] Havenith, and Patrick [Gutachter] Nürnberger. "Resolving the interaction of biomolecules and water under ambient and high pressure conditions by THz spectroscopy / Hendrik Vondracek ; Gutachter: Martina Havenith, Patrick Nürnberger ; Fakultät für Physik und Astronomie." Bochum : Ruhr-Universität Bochum, 2018. http://d-nb.info/1167505166/34.
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