Дисертації з теми "Equilibrium pressure"

The objective of this work has been to study equilibrium and non equilibrium situations during high pressure gas processing operations with emphasis on utilization of the high reservoir pressure. The well stream pressures of some of the condensate and gas fields in the North Sea are well above 200 bar. Currently the gas is expanded to a specified processing condition, typically 40-70 bar, before it is recompressed to the transportation conditions. It would be a considerable environmental and economic advantage to be able to process the natural gas at the well stream pressure. Knowledge of thermodynamic- and kinetic properties of natural gas systems at high pressures is needed to be able to design new high pressure process equipment.

Nowadays, reactive absorption into a methyldiethanolamine (MDEA)solution in a packed bed is a frequently used method to perform acid gas treating. The carbon dioxide removal process on the Sleipner field in the North Sea uses an aqueous MDEA solution and the operation pressure is about 100 bar. The planed carbon dioxide removal process for the Snøhvit field in the Barents Sea is the use of an activated MDEA solution.

The aim of this work has been to study high-pressure effects related to the removal of carbon dioxide from natural gas. Both modelling and experimental work on high-pressure non-equilibrium situations in gas processing operations have been done.

Few experimental measurements of mass transfer in high pressure fluid systems have been published. In this work a wetted wall column that can operate at pressures up to 200 bar was designed and constructed. The wetted wall column is a pipe made of stainless steel where the liquid is distributed as a thin liquid film on the inner pipewall while the gas flows co- or concurrent in the centre of the pipe. The experiments can be carried out with a well-defined interphase area and with relatively simple fluid mechanics. In this way we are able to isolate the effects we want to study in a simple and effective way.

Experiments where carbon dioxide was absorbed into water and MDEA solutions were performed at pressures up to 150 bar and at temperatures 25 and 40°C. Nitrogen was used as an inert gas in all experiments.

A general non-equilibrium simulation program (NeqSim) has been developed. The simulation program was implemented in the object-oriented programming language Java. Effort was taken to find an optimal object-oriented design. Despite the increasing popularity of object-oriented programming languages such as Java and C++, few publications have discussed how to implement thermodynamic and fluid mechanic models. A design for implementation of thermodynamic, mass transfer and fluid mechanic calculations in an object-oriented framework is presented in this work.

NeqSim is based on rigorous thermodynamic and fluid mechanic models. Parameter fitting routines are implemented in the simulation tool and thermodynamic-, mass transfer- and fluid mechanic models were fitted to public available experimental data. Two electrolyte equations of state were developed and implemented in the computer code. The electrolyte equations of state were used to model the thermodynamic properties of the fluid systems considered in this work (non-electrolyte, electrolyte and weak-electrolyte systems).

The first electrolyte equation of state (electrolyte ScRK-EOS) was based on a model previously developed by Furst and Renon (1993). The molecular part of the equation was based on a cubic equation of state (Scwarzentruber et.al. (1989)’s modification of the Redlich-Kwong EOS) with the Huron-Vidal mixing rule. Three ionic terms were added to this equation – a short-range ionic term, a long-range ionic term (MSA) and a Born term. The thermodynamic model has the advantage that it reduces to a standard cubic equation of state if no ions are present in the solution, and that public available interaction parameters used in the Huron-Vidal mixing rule could be utilized. The originality of this electrolyte equation of state is the use of the Huron-Vidal mixing rule and the addition of a Born term. Compared to electrolyte models based on equations for the gibbs excess energy, the electrolyte equation of state has the advantage that the extrapolation to higher pressures and solubility calculations of supercritical components is less cumbersome. The electrolyte equation of state was able to correlate and predict equilibrium properties of CO₂-MDEA-water solutions with a good precision. It was also able to correlate high pressure data of systems of methane-CO₂-MDEA and water.

The second thermodynamic model (electrolyte CPA-EOS) evaluated in this work is a model where the molecular interactions are modelled with the CPA (cubic plus association) equation of state (Kontogeorgios et.al., 1999) with a classical one-parameter Van der Walls mixing rule. This model has the advantage that few binary interaction parameters have to be used (even for non-ideal solutions), and that its extrapolation capability to higher pressures is expected to be good. In the CPA model the same ionic terms are used as in the electrolyte ScRK-EOS.

A general non-equilibrium two-fluid model was implemented in the simulation program developed in this work. The heat- and mass-transfer calculations were done using an advanced multicomponent mass transfer model based on non-equilibrium thermodynamics. The mass transfer model is flexible and able to simulate many types of non-equilibrium processes we find in the petroleum industry. A model for reactive mass transfer using enhancement factors was implemented for the calculation of mass transfer of CO₂ into amine solutions. The mass transfer model was fitted to the available mass transfer data found in the open literature.

The simulation program was used to analyse and perform parameter fitting to the high pressure experimental data obtained during this work. The mathematical models used in NeqSim were capable of representing the experimental data of this work with a good precision. From the experimental and modelling work done, we could conclude that the mass transfer model regressed to pure low-pressure data also was able to represent the high-pressure mass transfer data with an acceptable precision. Thus the extrapolation capability of the model to high pressures was good.

For a given partial pressure of CO₂ in the natural gas, calculations show a decreased CO₂ capturing capacity of aqueous MDEA solutions at increased natural gas system pressure. A reduction up to 40% (at 200 bar) compared to low pressure capacity is estimated. The pressure effects can be modelled correctly by using suitable thermodynamic models for the liquid and gas. In a practical situation, the partial pressure of CO₂ in the natural gas will be proportional to the total pressure. In these situations, it is shown that the CO₂ capturing capacity of the MDEA solution will be increased at rising total pressures up to 200 bar. However, the increased capacity is not as large as we would expect from the higher CO₂ partial pressure in the gas.

The reaction kinetics of CO₂ with MDEA is shown to be relatively unaffected by the total pressure when nitrogen is used as inert gas. It is however important that the effects of thermodynamic and kinetic non- ideality in the gas and liquid phase are modelled in a consistent way. Using the simulation program NeqSim – some selected high-pressure non-equilibrium processes (e.g. absorption, pipe flow) have been studied. It is demonstrated that the model is capable of simulating equilibrium- and non-equilibrium processes important to the process- and petroleum industry.

This thesis presents experimental studies of various non-thermal atmospheric pressure gas discharges generated using short pulsed excitation as an alternative to widely used sinusoidal excitation. Several pulse generators are detailed that provide high voltage pulses ranging from hundreds of microseconds to less than ten nanoseconds in duration. A key enabler to the generation of a stable discharge is a suitably high repetition rate; this prerequisite precludes many conventional pulsed power technologies. Fortunately, recent advances in semiconductor technology have made it possible to construct solid state switches capable of producing high voltage pulses with repetition rates of many kilohertz. Pulsed excitation introduces many opportunities to tailor the applied voltage and consequently enhance the discharge which are not possible with sinusoidal excitation sources. Through detailed electrical and optical analysis it is shown that pulsed excitation is not only more energy efficient than a comparable sinusoidal source but produces a higher flux of excited species that are essential in many applications. When pulse widths are reduced to a sub-microsecond timescale a novel barrier-free mode of operation is observed. It is shown that diffuse large area plasmas are easily produced at kilohertz repetition rates without the usually indispensable dielectric barriers. Experimental results show that a short pulse width prevents the onset of the undesirable glow-to-arc transition thus introducing an added degree of stability. A further benefit of pulsed excitation is the ability to produce gas discharges with a high instantaneous peak power yet low average power consumption, resulting in a high density plasma that exhibits roomtemperature characteristics. Finally, as an acid test to highlight the many benefits of pulsed excitation several real-world applications are considered. It is shown that in all cases pulsed gas discharges provide real benefits compared to their sinusoidal counterparts.

This dissertation will be focused on the characterization of an atmospheric pressure plasma jet source with an application oriented diagnostic approach and the description of processes supported by this plasma source. The plasma source investigated is a single electrode plasma jet. Schlieren images, optical emission spectra, temperature and heat flux profiles are analyzed to deeply investigate the fluid dynamic, the chemical composition and the thermal output of the plasma generated with a nanosecond-pulsed high voltage generator. The maximum temperature measured is about 45 °C and values close to the room temperature are reached 10 mm down the source outlet, ensuring the possibility to use the plasma jet for the treatment of thermosensitive materials, such as, for example, biological substrate or polymers. Electrospinning of polymeric solution allows the production of nanofibrous non-woven mats and the plasma pre-treatment of the solutions leads to the realization of defect free nanofibers. The use of the plasma jet allows the electrospinnability of a non-spinnable poly(L-lactic acid) (PLLA) solution, suitable for the production of biological scaffold for the wound dressing.

Thesis (MScEng)--University of Stellenbosch, 2000.
ENGLISH ABSTRACT: Supercritical extraction is being investigated as a possible alternative to the processes currently used in the fractionation of paraffinic waxes. By removing the lighter carbon fractions from the wax, the wax hardness will be improved and its melting temperature range reduced, hence improving the performance of the wax product in certain applications. In order to evaluate and operate such an extraction process optimally, it is necessary to have a thermodynamic model that accurately represents the process system. There are, however, currently no predictive models available for these systems. In order to fit present models to the systems, accurate phase equilibrium data of the supercritical solvent - n-alkane systems are needed. Unfortunately, the amount of reliable published data on these systems in the required operating range is very limited. A view cell was designed and developed with which these high pressure equilibria could be studied. The binary phase equilibria of supercritical CO2 with n-CI2, n-CI6, n-C20, n-C24, n-C28 and n-C36 and of supercritical ethane with n-CI6, n-C24 and n-C28 were measured in the temperature range 313 - 367 K. It was found that the systems with these two solvents have very different types of phase behaviour. The n-alkane solubility is much higher in ethane, but supercritical CO2 will provide a much better degree of control over the selectivity achieved in an extraction process. Of the various equations of state investigated, it was found that the Patel Teja equation of state provided the best fit of the CO2 - n-alkane systems and that the Soave-Redlich- Kwong equation fitted the ethane - n-alkane systems the best. The interaction parameters of both these equations of state display a functional relationship with temperature and nalkane acentric factor, making it possible to determine parameter values for application at other operating temperatures and with other n-alkane systems. It was found that the current equations of state were not able to represent the phase equilibria accurately over the entire range of operating conditions. The poor performance of the equations of state can be attributed to inherent flaws in the existing equations of state.
AFRIKAANSE OPSOMMING: Superkritiese ekstraksie word tans ondersoek as 'n moontlike altematief vir die prosesse wat huidiglik gebruik word om paraffiese wasse te fraksioneer. Die Iigter koolstofwasse word verwyder om die washardheid te verhoog en die temperatuurgebied waaroor die was smelt te verklein. Dit verbeter dan die was se kwaliteit en werkverrigting. Modelle wat die superkritiese ekstraksie proses akkuraat kan voorstel word egter benodig om die ekstraksie proses te kan evalueer en optimaal te bedryf. Daar is tans geen modelle beskikbaar wat die proses direk kan voorstel nie. Akkurate fase-ewewigsdata word benodig om bestaande modelle aan te pas vir gebruik in hierdie sisteme. Daar is egter baie min betroubare faseewewigsdata vir die superkritiese oplosmiddel - n-alkaan sisteme beskikbaar in die literatuur. 'n Sig-sel, waarrnee hierdie hoe druk data gemeet kan word, is ontwerp en ontwikkel. Die volgende binere fase ewewigte is in die temperatuur gebied 313 - 367 K gemeet: superkritiese CO2 met n-CI2, n-CI6, n-C20, n-C24, n-C28 en n-C36, en superkritiese Etaan met n-CI6, n-C24 en n-C28. Daar is gevind dat hierdie twee superkritiese oplosmiddelsisteme verskillende tipes fase-ewewigsgedragte openbaar. Die n-alkane het 'n baie boer oplosbaarheid in Etaan, maar deur superkritiese C02 in 'n ekstraksie kolom te gebruik, sal tot beheer oor die selektiwiteit van die ekstraksieproses lei. Uit die verskillende toestandsvergelykings wat ondersoek is, is daar gevind dat die Patel- Teja vergelyking die CO2 sisteme die beste kon beskryf en dat die Soave-Redlich-Kwong vergelyking die beste vergelyking was om die Etaan sisteme mee te modelleer. Beide die toestandsvergelykings se interaksie parameters het 'n funksionele verband met temperatuur en die n-alkaan asentrise faktor getoon. Dit is dus moontlik om waardes vir die parameters vir sisteme by ander temperature en met ander n-alkaan tipes te bepaal. Daar was gevind dat die bestaande toestandsvergelykings nie die die fase-ewewigte oor die hele eksperimenele gebied akkuraat kon voorstel nie. Dit kan toegeskryf word aan foute wat inherent is aan die vergelykings.

Previous studies have shown that favorable pressure gradients reduce the turbulence levels and length scales in supersonic flow. Wall roughness has been shown to reduce the large-scales in wall bounded flow. Based on these previous observations new questions have been raised. The fundamental questions this dissertation addressed are: (1) What are the effects of wall topology with sharp versus blunt leading edges? and (2) Is it possible that a further reduction of turbulent scales can occur if surface roughness and favorable pressure gradients are combined? To answer these questions and to enhance the current experimental database, an experimental analysis was performed to provide high fidelity documentation of the mean and turbulent flow properties along with surface and flow visualizations of a high-speed ( 2.86 M = ), high Reynolds number (Re 60,000 q » ) supersonic turbulent boundary layer distorted by curvature-induced favorable pressure gradients and large-scale ( 300 s k + » ) uniform surface roughness. Nine models were tested at three separate locations. Three pressure gradient models strengths (a nominally zero, a weak, and a strong favorable pressure gradient) and three roughness topologies (aerodynamically smooth, square, and diamond shaped roughness elements) were used. Highly resolved planar measurements of mean and fluctuating velocity components were accomplished using particle image velocimetry. Stagnation pressure profiles were acquired with a traversing Pitot probe. Surface pressure distributions were characterized using pressure sensitive paint. Finally flow visualization was accomplished using schlieren photographs. Roughness topology had a significant effect on the boundary layer mean and turbulent properties due to shock boundary layer interactions. Favorable pressure gradients had the expected stabilizing effect on turbulent properties, but the improvements were less significant for models with surface roughness near the wall due to increased tendency towards flow separation. It was documented that proper roughness selection coupled with a sufficiently strong favorable pressure gradient produced regions of “negative” production in the transport of turbulent stress. This led to localized areas of significant turbulence stress reduction. With proper roughness selection and sufficient favorable pressure gradient strength, it is believed that localized relaminarization of the boundary layer is possible.

The detection of trace explosives in the subsurface is an active area of research for landmine detection. Understanding the air-water flow and heat transport phenomena in the subsurface plays an important role in improving chemical vapor detection. Implementing a finite element method that accurately captures water vapor transport in the vadose zone is still an open question. A non-equilibrium, pressure-pressure formulation has been implemented based on Smits, et al [22]. This implementation consists of four equations: a wetting phase (water) mass balance equation, a non-wetting phase (air) mass balance equation, a water vapor transport equation, and a heat transport equation. This work will compare two implementations, a fully coupled approach and an operator splitting approach for the water vapor and heat transport equations. The formulation of the methods will be presented and the methods will be tested using collected data from physical experiments.

The volumetric system is a commonly used experimental method for gas adsorption measurements. Starting from the conventional volumetric system (single-branched), the development of differential (double-branched) apparatus has been proposed to overcome some criticalities connected to the original design. The following study is focused on the assessment of the high-pressure differential volumetric apparatus (HP-ADVA) built at the University of Edinburgh in order to discover and characterise system peculiarities at different experimental conditions, in terms of temperature and pressure. To do this, an integrated approach is proposed: an initial experimental campaign has been performed to take confidentiality with the apparatus, then, the experimental results were the starting point for the development of a sensitivity and error analysis aimed at describing the effect of each operating parameter into the final result. In this regard, a different analytical approach, compared to the ones commonly proposed in literature, has been proposed to closely reproduce the real system. Beyond having obtained promising results, some criticalities, matching what originally hypothesized from the experimental campaign, have been noted: valve volume effect and temperature control and measurements have been discovered being crucial aspects, and, supposedly, source of errors leading to explain the unexpected results obtained by the experimental campaign. Moreover, the importance of symmetry maintenance among the branches has been repeatedly confirmed in the analysis. Some recommendations aimed at improving the system set-up have been moved regarding the installation of a temperature control system and more accurate temperature measurement devices. Additionally, an accurate assessment and characterisation of pneumatically-actuated valves, as well as of the differential pressure transducer used for pressure measurement, before the installation, could be useful to reduce inaccuracies.

Vapour-liquid equilibrium data for the ethanol-water system were obtained at 70, 80, 90, 100, 150, 300 and 500 mm Hg absolute pressure. No azeotrope was detected at 70 and 80 mm Hg. Azeotropic data were estimated at other experimental pressures. The VLE data were obtained using a modified Othmer still. A computerised and automatic pressure control system was integrated into the still. An effective Cottrell pump and a new vacuum sampling technique were also incorporated. The data were successfully tested for thermodynamic consistency and thereafter correlated with the NRTL, the Wilson and expansions of the Margules and van Laar equations. The two-parameter Margules and the Wilson equations gave poor correlations. The two-parameter van Laar equation gave relatively good performance. The NRTL and the four-parameter Margules equations gave performances comparable with those of the van Laar equations. After observing the failure of the above equations to predict the correct azeotropic composition, two azeotrope-embedded equations based on the four-parameter Margules and van Laar equations were proposed and tried. Vapour pressure data for ethanol and for water containing between 0 and 0.113 mole fraction potassium acetate were obtained and correlated with the Antoine equation. The effect of potassium acetate on the VLE of the ethanol-water system was studied. Data at 0.053, 0.072, 0.097 and 0.113 mole fraction potassium acetate were obtained. These salt concentrations broke the azeotrope and significantly enhanced the VLE. Minima were observed in the temperature-composition data above 0.8 mole fraction ethanol. The experimental vapour pressure data were used in the correlation of the ternary VLE data using the special binary approach. The correlation was good at low ethanol and salt concentrations but deteriorated at high ethanol concentrations.

Widely employed for a steadily increasing number of industrial processes and experimental studies, plasma can be considered as one of the most pervasive and promising technology of our time. Differently from thermal plasmas, the potentialities offered by non-equilibrium plasmas, especially if working at atmospheric pressure, are still far away to be totally understood, since the surprising and sometimes unpredictable results, coming from studies carried out all over the world, bring out the growing versatility of this technology and its suitability for many applications intersecting our daily lives. The present dissertation, organized in two parts, is focused to present and discuss the results obtained from the Ph.D research activities carried out in the wide field of plasma and materials. The first part of the work is mainly aimed at investigating the potentialities of cold atmospheric plasmas (CAP) for the modification of materials, coating deposition and crosslinking of polymers. In the first two chapters, the conventional techniques and the CAP approaches most employed to carry out the processes will be briefly summarized. In the other chapters, organized by topic, the results achieved during the Ph.D research activities in the fields of surface material modification, coating deposition and crosslinking of polymers will be presented and discussed. The second part of the dissertation is linked to the investigation of the potentialities of plasma-induced chemistry in a liquid environment for the synthesis of nanostructures. Similarly to the first one, the second part of the dissertation will present an overview on the conventional and CAP assisted methods for nanostructures synthesis; moreover, in the second part of the last chapter, the Ph.D experimental activities aimed at synthesising CuO quantum dots in a liquid environment will be illustrated.

The research described in this doctoral thesis work was mainly focused towards the low pressure inductively excited PECVD of organic precursors for biomaterials. An open air atmospheric pressure DBD plasma jet was also studied for the antifouling applications. Systematic studies were carried out in order to optimize the deposition of plasma polymerized (PP) coatings which were deposited at different process parameters for biomedical applications. The optimized amphiphilic PFDA-DEGVE coatings, presented no adhesion with respect to BSA as well as Lysozyme proteins. The plasma processing parameters were optimized using DoE methodology. By adjusting the process parameters, the chemical compositions of the PCL- PEG coatings were tailored to be cell adherent, convenient for biomedical implants such as artificial skin substrates, or cell repellent which could be used for antibiofouling surfaces for urethral catheters, stents etc. Multilayer biodegradable coatings based on PCL- PEG polymers were successfully used for controlled delivery of anticancer drug and tested in vitro. PP Poly (2-ethyl 2-oxazoline), having a peptidomimetic structure was deposited by LP. Such polymers are considered to be a prime candidate for an alternative of PEG like surfaces for antibiofouling applications. The last chapter was devoted to open air AP argon plasma jet. The deposited PEG coatings had 56. 3% of ether functions and were cell repellent as compared to a positive control (PS). This study has shown the capability of plasma processes for the deposition of (co-) polymer coatings with tailorable surface chemical compositions, with considerable promises for the variety of biomedical applications
Les recherches effectuées dans cette thèse se concentrent essentiellement sur la PECVD par plasma basse pression à partir de précurseurs organiques pour la synthèse de biomatériaux. Un procédé à jet de plasma hors équilibre à couplage DBD a aussi été développé pour élaborer des surfaces anti-bioadhésives. Les conditions opératoires ont été optimisées afin de pouvoir répondre à plusieurs applications biomédicales. Des copolymères amphiphiles à base de PFDA-PEG, élaborés et optimisés par des plans d’expériences, n’ont montré aucune adhésion vis à vis des protéines BSA et Lysozyme. Les polymères PCL-PEG ont aussi été étudiés, et les différentes compositions ont permis d’obtenir soit de bonnes propriétés d’adhésion cellulaire, permettant ainsi d’envisager des applications en ingénierie tissulaire, soit des surfaces anti-bioadhésives, intéressantes pour élaborer des cathéters ou des stents. Les copolymères PCL-PEG déposés en multicouches ont permis de contrôler les cinétiques de relargage de médicaments et de réaliser des tests in vitro. Nous avons aussi travaillé sur le remplacement des PEG en déposant un polymère mimant la structure des peptides ; le polyoxazoline. Les résultats obtenus ont donné de bonnes propriétés anti-fouling. Enfin, des surfaces anti-bioadhésives ont été élaborées par PECVD à pression atmosphérique. Les résultats obtenus ont montré une rétention des fonctions éthers de 56. 3% et les surfaces correspondantes repoussent les cellules. En conclusion, les travaux menés au cours de cette thèse ont montré que les procédés plasma permettent de déposer des (co)polymères permettant de répondre à une large palette d’applications dans le domaine biomédical

The objectives of this work are to measure phase equilibria in the carbon dioxide + pyrrole system and to correlate and predict the phase behavior of this system with a thermodynamic model. This binary system is of interest due to the growing applications of supercritical carbon dioxide as a solvent or reaction medium for pyrrole. Polypyrrole is an electrically conducting polymer of interest in a number of applications such as anti-static coatings. Pyrrole has also been used as a reactant in enzymatic reaction. Knowledge of the phase behavior of carbon dioxide + pyrrole system is therefore necessary for evaluating optimal conditions and feasibility of such applications. Phase equilibria in the carbon dioxide + pyrrole system were measured at 313 K, 323 K, and 333 K using a synthetic method. Liquid-vapor (LV) phase behavior and liquid-liquid (LL) phase behavior were observed. The pressure in the experiments ranged from 84 to 151.1 bar. The Patel-Teja equation of state and the Mathias-Klotz-Prausnitz mixing rule with two temperature independent parameters was able to correlate the phase equilibrium data satisfactorily and was used to predict the phase behavior at other temperatures. A pressure-temperature diagram was then constructed from these calculations and suggests that the carbon dioxide + pyrrole system exhibit type IV phase behavior in the classification of Scott and van Konynenburg.

This paper deals with the determination of the capillary pore-size distribution (CPSD) and equilibrium moisture content (EMC) of untreated and thermally modified (TM) Norway spruce [Picea abies (L.) Karst.] by means of the pressure plate technique (PPT). Desorption experiments were conducted at very high values of relative humidity (RH) in the range between 99.2% and 100%. The thermal modification of spruce results in an alteration of the CPSD, owing to the formation of intercellular cracks in the middle lamella, as a result of cell-wall compression. The desorption curves for both untreated and TM spruce show an extremely upward bend at 99.97% RH. This step reflects an EMC of 38.1% for untreated spruce and 33.8% for TM spruce. None of the samples shrunk during the PPT measurements. Following desorption experiments at 97.4% RH, all samples shrunk. This step reflects an EMC of 27.9% for untreated spruce and 21.7% for TM spruce.

The aim of this thesis is to investigate the properties of a Radio Frequency capacitive discharge at atmospheric pressure in argon. In these conditions where the pressure x distance product is around 150 Torr.cm, the discharge usually consists of several locally hot filaments. By pulsing the RF generator with an appropriate width and period, it was found possible to control the filament to glow transition in order to obtain a diffused and stable plasma.¶ The 2 mm gap between the electrodes is open to the ambient air and fed with argon via one hundred submillimetric holes regularly spread on the surface of the top electrode. This configuration allows “on-line” surface treatment of polymer films without having to turn the discharge off between successive samples. An important and lasting improvement of the polymer wettability is quickly obtained without risk of damage. The plasma diagnostic methods are emission spectroscopy and electric measurements. The Stark broadening of the Balmer β transition line of atomic hydrogen is measured to determine a plasma density of 10^15/cm3 in the filamentary mode. The glow mode density estimation was based on power balance yielding a density of 5×10^11/cm3. Emission line ratios between neutrals and Ar+ ions are used in the Saha equation to calculate the electron temperature. It results in an approximation of 1.3 eV for the glow mode and 1.7 eV for the filaments.¶ A unidimensional self-consistent fluid model is developed to gain insight into the homogeneous discharge behaviour. Poisson’s equation for the electric field is coupled to the first moments of the Boltzmann equation (continuity equation, drift-diffusion equation and energy equation). Transport and reaction coefficients are obtained from the mean energy of the electrons.¶ The model is applied to a reduced argon kinetic with the main ionization and excitation processes. Simulation results are in agreement with experimental measurements. The atmospheric pressure RF discharge is similar to a lower pressure RF discharge for which the ionization occurs mainly inside the oscillating sheaths where electrons are the most energetic

Orientador: Antonia Dalla Pria Bankoff
Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Educação Fisica
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Resumo: As corridas de longa distância, sejam de caráter competitivo ou de promoção da saúde, geram cargas compressivas consideráveis no sistema locomotor. Essas cargas, se não adequadamente distribuídas, predispõem os praticantes a lesões crônicas e agudas. Nesse sentido, o objetivo desta pesquisa foi estudar a distribuição da pressão plantar e do equilíbrio corporal em corredores de longa distância. Participaram do estudo 17 corredores de longa distância do sexo masculino com idade X = 28,5 :t 9,5 anos, peso X = 63,6 :t 6,9 Kg e altura X = 173,5 :t 7,0 cm. A seleção dos sujeitos foi feita segundo critérios de acessibilidade. Para o estudo da distribuição da pressão plantar e do equiHbrio corporal, foi utilizado um baropodômetro eletrônico para realizar uma análise estática, dinâmica (andando e correndo) e uma análise estabilométrica. Os três testes foram realizados com os corredores inicialmente descalços e posteriormente utilizando seu tênis de corrida. Além da análise baropodométrica, os sujeitos responderam um questionário contendo 23 perguntas sobre sua rotina de treino, índice de lesões sofridas, distância percorrida semanalmente, dentre outras. Na análise estatística utilizou-se o teste paramétrico t-Student para grupos independentes. Os resultados da análise baropodométrica estática dos corredores demonstraram distribuição assimétrica da carga entre os membros inferiores, com maior carga direcionada para a parte anterior do pé direito. A distribuição da pressão plantar revelou maior carga na parte anterior do pé esquerdo nos testes dinâmicos com os corredores descalços, enquanto que nos testes com o calçado esportivo não foram detectadas diferenças significantes. Foi constatado que os corredores avaliados realizam o contato pé-solo predominantemente com a parte anterior do pé. O uso do calçado esportivo não apresentou nenhuma interferência específica nos testes realizados. A oscilação do centro de pressão foi maior nos testes monopodálicos. O estudo do equilíbrio corporal demonstrou significativa dependência do sistema visual e tendência de maior oscilação do centro de pressão no eixo X
Abstract: Long distance running as a competitive way or even to promote health produces considerable compressive load on the locomotor system. If this load is not properly distributed, it makes practitioners prone to chronic and acute injuries. Therefore, the purpose of this research was to study the plantar pressure distribution and body balance in long distance runners. In total 17 male long distance runners were considered for this study with age X = 28.5 :t 9.5, weight X = 63.6 :t 6.9 kg and height X = 173.5 :t 7.0 cm. The selection of individuaIs was done by following accessibility criteria. To perform the study ofthe plantar pressure distribution and body balance an electronic baropodometer was used. The baropodometric tests comprised a static, a dynamic (walking and running) and a stabilometric analysis. All tests were performed initially barefoot and afterwards with the runners wearing their running shoes. The individuaIs also responded to a 23 question survey about their practice routine, injury incidence, distance performed during the week and so forth. A parametric t-Student test for independent groups was used for the statistic analysis. The results of the static baropodometric analysis showed asymmetric pressure distribution between the lower extremities, with greater pressure directed to the right forefoot. The plantar pressure distribution reveled grater load directed to the left forefoot in the dynamic tests performed with the sport running shoes, meanwhile no significant differences were detected in the barefoot tests. The results also demonstrated that the runners evaluated in this study were predominantly forefoot strikers. The running shoes did not show any specific influence on the tests results. Oscillation of the center of pressure was greater in the unilateral tests. The body balance study revealed significant visual system dependence and a tendency of greater oscillations ofthe center ofpressure on the X-axis
Doutorado
Ciencia do Desporto
Doutor em Educação Física

Thesis (Ph.D.)--Aerospace Engineering, Georgia Institute of Technology, 2008.
Committee Chair: Seitzman, Jerry; Committee Member: Jagoda, Jechiel; Committee Member: Lieuwen, Tim; Committee Member: Menon, Suresh; Committee Member: Tan, David.

The thermophysical properties of supercritical CO₂ and H₂O-CO₂ mixtures are reviewed and their computation and prediction improved through theory and experiment. A resolution is attempted among inconsistencies between and within data sets, including P-V-T measurements, phase equilibrium experiments and equations of state. Pure carbon dioxide: Equations of state for CO₂ (Kerrick & Jacobs, 1981; Bottinga & Richet, 1981; Holloway, 1977) are based solely on P-V-T data up to 8 kbar and lead to deviations from phase equilibrium data at pressures greater than 10-20 kbar. Mathematical programming analysis has been applied to the fitting of parameters for an equation of state using simultaneously constraints from phase equilibrium and P-V-T data. Phase equilibrium data up to 42 kbar are used to define a feasible region for the adjustable parameters in free energy space. Each half-bracket places an inequality constraint on the fugacity of CO₂ provided the thermophysical properties of the solid phases are known. Except for magnesite thermophysical data from the mineral data base of Berman (1988) were used. A least squares objective function served to optimize parameters to P-V-T data. The enthalpy of formation of magnesite was revised on the basis of recent low pressure phase equilibrium experiments by Philipp (1988) to —1112.505 kj/mole. Piston-cylinder experiments were performed to constrain the equilibrium magnesite ⇌ periclase + CO₂ at high pressure. The equilibrium boundary is located at 12.1(±1) kbar, 1173-1183 °C (±10), and at 21.5(±1) kbar, 1375-1435 °C (±10). A van der Waals type equation of state with five adjustable parameters has been developed for CO₂. The function is smooth and continous above the critical region, behaves well in the high and low pressure limits, and the calculation of ʃ VdP for free energy does not require numerical integration. Computed free energies are consistent with all phase equilibrium data at high pressure, and computed volumes agree reasonably with P-V-T measurements. The proposed equation is: [ Equation omitted ] with B₁ = 28.0647, B₂ = 1.7287.10⁻⁴, B3 = 83653, A₁ = 1.0948.10⁹, A₂ = 3.3 7 47.10⁹, and R = 83.147, in units of Kelvin, bar and cm³/mole. The equation is recommended up to 50 kbar and above 400 K with reasonable extrapolation capabilities. A FORTRAN source code to evaluate the volume and fugacity is provided. Thermophysical properties for the calcium carbonate polymorphs calcite-I, IV, V, and aragonite were derived that are consistent with phase equilibrium experiments. Data required for further improvement include high pressure phase equilibria involving CO₂, constraints on the thermal expansion of magnesite, and P-V-T data to resolve inconsistencies among existing measurements. Water-carbon dioxide mixtures: The two widely used equations of state for H₂O-CO₂ mixtures are those proposed by Kerrick & Jacobs (1981) and by Holloway (1977)-Flowers (1979). Evaluation of existing equations and data is difficult due to inconsistencies among experimental studies. P-V-T-X data by Franck ＆ Todheide (1959) are inconsistent with data by Greenwood (1973) and Gehrig (1980), and cannot be reconciled with measured phase equilibria in H₂O-CO₂ fluid mixtures. Data by Greenwood and Gehrig are in loose agreement but extend only to 600 bar and do not constrain activities at higher pressures. A procedure is developed for using experimental phase equilibrium constraints to put limits on the fugacities of components of the fluid mixture. Inconsistencies among phase equilibrium studies are discussed. It is concluded that the data base available is not yet adequate to derive a reliable equation of state for H₂O-CO₂ mixtures. Future work must include P-V-T-X measurements to 8 kbar and phase equilibrium studies to resolve inconsistencies. These can constrain deviations from ideal mixing in the fluid phase, and constrain specific volumes at high pressures where P-V-T-X data connot be obtained.
Science, Faculty of
Earth, Ocean and Atmospheric Sciences, Department of
Graduate

Neste trabalho aplicou-se a metodologia diferencial para o cálculo do equilíbrio osmótico dentro da abordagem de Lewis-Randall para sistemas multisolventes. Nessa abordagem, são obtidas equações diferenciais que relacionam pressão e composição do sistema na condição de potencial químico constante dos solventes: o estado de equilíbrio osmótico é calculado integrando-se as equações, obtendo-se a curva de pressão osmótica em função da concentração do soluto. Essas equações não têm solução analítica, mas foram numericamente integradas para sistemas cuja não idealidade seja descrita pelo modelo UNIQUAC. A metodologia foi aplicada na análise de sistemas em que ocorre equilíbrio de fases líquido-líquido, o que em princípio corresponde ao teste mais severo a que pode ser submetida. A comprovação da eficácia da metodologia foi feita por meio da verificação das relações de equilíbrio nos passos intermediários e pela equação de Gibbs-Duhem. Os resultados mostraram que a abordagem é bastante confiável, e que o equilíbrio é corretamente calculado para uma variedade de situações. Foi possível discernir os casos em que é admissível utilizar um pseudo-solvente na descrição do equilíbrio osmótico (sistemas cujos solventes apresentam estruturas semelhantes, sem interação preferencial), e situações em que o cálculo pode não levar a resultados adequados (sistemas em que os solventes apresentem miscibilidade parcial). Os programas desenvolvidos são genéricos e, portanto, podem ser usados para o cálculo do equilíbrio osmótico em qualquer sistema descrito pela equação UNIQUAC.
A differential approach to the calculation of osmotic equilibrium of multisolvent systems within the Lewis-Randall framework is presented in this work. Differential equations relating pressure and composition at constant solvent chemical potential are developed, through whose integration the osmotic equilibrium is calculated. The curves of osmotic pressure as functions of the solute concentration cannot be analytically calculated, and were obtained through numerical integration. The methodology was used to calculate osmotic equilibrium for systems described by the UNIQUAC equation presenting liquid-phase split, which presumably corresponds to the most severe test. The approach was verified by checking the equilibrium conditions at intermediate points and also by checking the Gibbs-Duhem equation. The results show that the methodology is reliable and that the osmotic equilibrium can be correctly calculated for many situations. It was possible to identify the circumstances wherein a pseudo-solvent can be defined (systems whose solvents show similar structures, without presenting preferential interactions), and wherein the calculation may lead to unreliable results (systems wherein the solvents present partial miscibility). The computer programs developed are not specific, and can therefore be used to calculate osmotic equilibrium for any systems described by the UNIQUAC equation.

A new method of in situ extraction of alcohols from fermentation broth was investigated. The extraction method exploited the latent advantages of the non-equilibrium phase interaction of the fluid system in the flash tank to effectively recover the alcohol. Carbon dioxide gas ranging from 4.2L/min to 12.6L/min was used to continuously strip 2 and 12% (v/v) ethanol solution in a fermentor with a recycle. Ethanol and water in the stripped gas was recovered by compressing and then flashing into a flash tank that was maintained at 5 to 70bar and 5 to 55oC where two immiscible phases comprising CO2-rich phase (top layer) and H2O-rich phase (bottom layer) were formed. The H2O-rich bottom layer was collected as the Bottoms. The CO2-rich phase was continuously throttled producing a condensate (Tops) as a result of the Joule-Thompson cooling effect. The total ethanol recovered from the extraction scheme was 46.0 to 80% for the fermentor containing 2% (v/v) ethanol and 57 to 89% for the fermentor containing 12% (v/v) ethanol. The concentration of ethanol in the Bottoms ranged from 8.0 to 14.9 %(v/v) for the extraction from the 2 %(v/v) ethanol solution and 40.0 to 53.8 %(v/v) for the 12% (v/v) fermentor ethanol extraction. The Bottoms concentration showed a fourfold increase compared to the feed. The ethanol concentration of the Tops were much higher with the highest at approx. 90% (v/v) ethanol, however the yields were extremely low. Compression work required ranged from 6.4 to 20.1 MJ/kg ethanol recovered from the gas stream in the case of 12% (v/v) ethanol in fermentor. The energy requirement for the 2% (v/v) extraction was 84MJ/kg recovered ethanol. The measured Joule-Thompson cooling effect for the extraction scheme was in the range of 10 to 20% the work of compressing the gas. The lowest measured throttle valve temperature was -47oC at the flash tank conditions of 70bar and 25oC. Optimization of the extraction scheme showed that increasing the temperature of the flash tank reduced the amount of ethanol recovered. Increasing the pressure of the flash tank increased the total ethanol recovered but beyond 45bar it appeared to reduce the yield. The 12.6L/min carbon dioxide flow rate favored the high pressure(70bar) extraction whiles 4.2L/min appeared to favor the low pressure(40bar) extraction. The studies showed that the extraction method could potentially be used to recover ethanol and other fermentation products.
Master of Science

The complete consumption of the oceanic domain of a tectonic plate by subduction into the upper mantle results in continent subduction, although continental crust is typically of lower density than the upper mantle. Thus, the sites of former oceanic domains (named suture zones) are generally decorated with stratigraphic sequences deposited along continental passive margins that were metamorphosed under low-grade, high-pressure conditions, i.e., low temperature/depth ratios (< 15°C/km) with respect to geothermal gradients in tectonically stable regions. Throughout the Mesozoic and Cenozoic (i.e., since ca. 250 Ma), the Mediterranean realm was shaped by the closure of the Tethyan Ocean, which likely consisted in numerous oceanic domains and microcontinents. However, the exact number and position of Tethyan oceans and continents (i.e., the Tethyan palaeogeography) remains debated. This is particularly the case of Western and Central Anatolia, where a continental fragment was accreted to the southern composite margin of the Eurasia sometime between the Late Cretaceous and the early Cenozoic. The most frontal part of this microcontinent experienced subduction-related metamorphism around 85-80 Ma, and collision-related metamorphism affected more external parts around 35 Ma. This unsually-long period between subduction- and collision-related metamorphisms (ca. 50 Ma) in units ascribed to the same continental edge constitutes a crucial issue to address in order to unravel how Anatolia was assembled. The Afyon Zone is a tectono-sedimentary unit exposed south and structurally below the front high-pressure belt. It is composed of a Mesozoic sedimentary sequence deposited on top of a Precambrian to Palaeozoic continental substratum, which can be traced from Northwestern to southern Central Anatolia, along a possible Tethyan suture. Whereas the Afyon Zone was defined as a low-pressure metamorphic unit, high-pressure minerals (mainly Fe-Mg-carpholite in metasediments) were recently reported from its central part. These findings shattered previous conceptions on the tectono-metamorphic evolution of the Afyon Zone in particular, and of the entire region in general, and shed light on the necessity to revise the regional extent of subduction-related metamorphism by re-inspecting the petrology of poorly-studied metasediments. In this purpose, I re-evaluated the metamorphic evolution of the entire Afyon Zone starting from field observations. Low-grade, high-pressure mineral assemblages (Fe-Mg-carpholite and glaucophane) are reported throughout the unit. Well-preserved carpholite-chloritoid assemblages are useful to improve our understanding of mineral relations and transitions in the FeO-MgO-Al2O3-SiO2-H2O system during rocks’ travel down to depth (prograde metamorphism). Inspection of petrographic textures, minute variations in mineral composition and Mg-Fe distribution among carpholite-chloritoid assemblages documents multistage mineral growth, accompanied by a progressive enrichment in Mg, and strong element partitioning. Using an updated database of mineral thermodynamic properties, I modelled the pressure and temperature conditions that are consistent with textural and chemical observations. Carpholite-bearing assemblages in the Afyon Zone account for a temperature increase from 280 to 380°C between 0.9 and 1.1 GPa (equivalent to a depth of 30-35 km). In order to further constrain regional geodynamics, first radiometric ages were determined in close association with pressure-temperature estimates for the Afyon Zone, as well as two other tectono-sedimentary units from the same continental passive margin (the Ören and Kurudere-Nebiler Units from SW Anatolia). For age determination, I employed 40Ar-39Ar geochronology on white mica in carpholite-bearing rocks. For thermobarometry, a multi-equilibrium approach was used based on quartz-chlorite-mica and quartz-chlorite-chloritoid associations formed at the expense of carpholite-bearing assemblages, i.e., during the exhumation from the subduction zone. This combination allows deciphering the significance of the calculated radiometric ages in terms of metamorphic conditions. Results show that the Afyon Zone and the Ören Unit represent a latest Cretaceous high-pressure metamorphic belt, and the Kurudere-Nebiler Unit was affected by subduction-related metamorphism around 45 Ma and cooled down after collision-related metamorphism around 26 Ma. The results provided in the present thesis and from the literature allow better understanding continental amalgamation in Western Anatolia. It is shown that at least two distinct oceanic branches, whereas only one was previously considered, have closed during continuous north-dipping subduction between 92 and 45 Ma. Between 85-80 and 70-65 Ma, a narrow continental domain (including the Afyon Zone) was buried into a subduction zone within the northern oceanic strand. Parts of the subducted continent crust were exhumed while the upper oceanic plate was transported southwards. Subduction of underlying lithosphere persisted, leading to the closure of the southern oceanic branch and to subduct the front of a second continental domain (including the Kurudere-Nebiler Unit). This followed by a continental collisional stage characterized by the cease of subduction, crustal thicknening and the detachment of the subducting oceanic slab from the accreted continent lithosphere. The present study supports that in the late Mesozoic the East Mediterranean realm had a complex tectonic configuration similar to present Southeast Asia or the Caribbean, with multiple, coexisting oceanic basins, microcontinents and subduction zones.
Kontinentale Subduktion resultiert aus dem Abtauchen des ozenanischen Gebiets einer tektonischen Platte in den Oberen Erdmantel. Dies geschieht obwohl die kontinentale Erdkruste normalerweise eine geringere Dichte besitzt als der Obere Erdmantel. Die Lage ehemaliger ozeanischer Gebiete (auch als Suturzonen bezeichnet) ist dementsprechend durch stratigraphische, sedimentäre Gesteinsabfolgen gekennzeichnet, die entlang des passiven Kontinentalrandes abgelagert wurden. Anschließend wurden diese Gesteine unter niedrigen Temperaturen und hohem Druck umgewandelt, auch niedrig-gradige Hochdruckmetamorphose genannt. Während der gesamten Zeitspanne des Mesozoikums und Känozoikums (seit etwa 250 Millionen Jahren bis heute) wurde der mediterrane Raum durch die kontinuierliche Schließung des Tethyschen Ozeans (dem heutigen Mittelmeer) geprägt, der vermutlich in zahlreichen kleineren Ozeanen und Mikrokontinenten aufgeteilt war. Dennoch bleiben die genaue Anzahl und Lage der tethyschen Ozeane und Kontinente (die Paläogeographie der Tethys) bis heute umstritten. Das ist insbesondere der Fall in West- und Zentral-Anatolien, wo im Zeitraum zwischen der Oberen Kreide (vor 98 bis 65 Mio. J.) und dem unteren Känozoikum (vor 65 bis 40 Mio. J.) ein kontinentales Fragment am südlichen Kontinentalrand der Eurasischen Platte angelagert wurde (auch als Akkretion bezeichnet). Der vorderste Bereich von diesem Fragment erfuhr vor etwa 85-80 Millionen Jahren eine metamorphe Umwandlung, die mit den Prozessen der fortschreitenden Subduktion assoziiert werden können. Hingegen wurden die hinteren Bereiche erst später vor ca. 40-30 Mio. J. durch die Kollison der zwei Platten metamorph überprägt. Die ungewöhnlich lange Zeitspanne von etwa 40-50 Mio. J. zwischen den metamorphen Prozessen der Subduktion und der Kollision, stellt eine entscheidende Frage zum Verständnis der Entstehung von Anatolien dar. Die Afyon Zone repräsentiert hierbei eine tektonisch-beanspruchte sedimentäre Gesteinseinheit, die in einer strukturell tieferen Position bezüglich des frontalen metamorphen Hochdruckgürtels liegt und südlich von ihm anzutreffen ist. Die Afyon Zone besteht aus mesozoischen sedimentären Einheiten (250 bis 65 Mio. J. alt), die auf präkambrischem (älter als 545 Mio. J.) bis paläozoischem Untergrund (bis vor 250 Mio J.) abgelagert wurden, und vom nordwestlichen bis zentralen Anatolien, entlang der vermutlichen Tethys-Suturzone, verfolgt werden können. Obwohl die Afyon-Zone als eine niedrig-temperierte metamorphe Gesteinseinheit bezeichnet wird, wurde in letzter Zeit von Vorkommen von Hochdruckmineralen (v.a. Eisen(Fe)-Magnesium(Mg)-Karpholith in metamorphen Sedimenten) im zentralen Bereich berichtet. Diese neuen Erkenntnisse stellen die bisherigen Interpretationen zur tektonisch-metamorphen Entstehung der gesamten Region in Frage, insbesondere der der Afyon-Zone. Deshalb war eine erneute gründliche Überarbeitung und Untersuchung der wenig studierten metamorph-überprägten Sedimentgesteine in diesem Gebiet notwendig. Deshalb, überarbeitete ich die metamorphe Entwicklung der gesamten Afyon Zone, beginnend mit intensiver Geländearbeit und -beobachtungen. Mineralvergesellschaftungen aus Karpholith und Glaukophan, die unter niedrigen Temperaturen und hohem Druck entstanden sind, wurden in der gesamten Gesteinseinheit gefunden. Guterhaltene Mineralvergesellschaftungen aus Karpholith und Chloritoid sind nützlich für das Verständnis unter welchen Temperatur- und Druck-Bedingungen die Gesteine in die Tiefe gelangen (prograde Metamorphose). Durch die Untersuchungen von Gesteinsgefügen und der Eisen-Magnesium-Verteilung zwischen den Mineralien Karpholith und Chloritoid lassen sich Aussagen zu der Bildungstemperatur und dem Druck dieser Minerale machen. Dafür benutzte ich eine verbesserte Datenbank mit Mineraleigenschaften, die mir die Modellierung von Temperatur und Druck erlaubte und im Einklang mit den chemischen und mikroskopischen Beobachtungen steht. Es ergab sich, dass die Karpholith-haltigen Gesteine in der Afyon-Zone einen Temperaturanstieg von 280 zu 380°C (bei einer Tiefe von 30-35 km) erfahren haben. Um noch bessere Aussagen über die Entstehung zu treffen, wurden auch radiometrische Datierungen an Proben aus der Afyon-Zone, sowie an zwei weiteren Sedimentgesteinseinheiten (Ören- und Kurudere-Nebiler-Einheit aus SW Anatolien) gemacht. Für die Altersbestimmung benutzte ich die weitverbreitete 40Ar-39Ar Datierungsmethode an Hellglimmer-Mineralien in den Karpholith-haltigen Gesteinen. Temperatur und Druck können auch bestimmt werden, wenn man den Übergang von einer Mineralvergesellschaftung zu einer anderen Vergesellschaftung beobachtet. Dies gilt zum Beispiel für den Übergang von einer Karpholith-haltigen Zusammensetzung zu einer Quartz-Chlorit-Glimmer und Quartz-Chlorit-Chloritoid Mineralvergesellschaftung wenn tief subduzierte Gesteine wieder nach oben gelangen (Exhumation). Damit lassen sich die radiometrischen Alter den metamorphen Prozessen zu bestimmten Temperaturen und Drücken zuordnen. Mit diesen Erkenntnissen lassen sich die Afyon-Zone und die Ören-Einheit einem Hochdruck-Gebirgsgürtel in der späten Kreidezeit zuordnen, während die Kurudere-Nebiler Einheit durch die mit der Subduktion in Verbindung stehende Metamorphose vor ca. 45 Mio. J. beeinflusst wurde. Später wurde diese Einheit durch die Metamorphose, resultierend aus der Kollision vor 26 Mio. J., abgekühlt. Die Ergebnisse dieser und anderer Arbeiten erlauben es die Anlagerung von Kontinenten in West-Anatolien besser zu verstehen. Es wird gezeigt, dass mindestens zwei (im Gegensatz zu vorher einem) voneinander unabhängige Ozeanarme während der Subduktion von 92 bis 45 Millionen Jahren geschlossen wurden. Zwischen 85-80 und 70-65 Millionen Jahren, wurde ein schmales kontinentales Gebiet (welches die Afyon-Zone beinhaltet) in die Subduktionszone hineingzogen. Teile der subduzierten kontientalen Kruste kamen wieder an die Oberfläche (Exhumation), während die obere ozeanische Platte südwärts transportiert wurde. Die anhaltende Subduktion im oberen Bereich des Erdmantels (Lithosphäre) führte zu der Schließung des südlichen Ozeanarms und zu der Subduktion des zweiten kontinentalen Gebietes (welches die Kurudere-Nebiler-Einheit beinhaltete). Darauf folgte die kontinentale Kollisionsphase unter dem Ausklingen der Prozesse der Subduktion, der Krustenverdickung und der Abtrennung der subduzierten ozeanischen Platte von der akkretionierten kontientalen Lithosphäre (auch als Delamination bezeichnet). Die hier präsentierte Arbeit unterstüzt die Annahme das während der Oberen Kreidezeit das Ost-Mediterrane Gebiet tektonsich komplex angeordnet war, vergleichbar mit dem heutigen Südost-Asien oder der Karibik, mit ihren vielen gleichzeitig existierenden ozeanischen Becken, Mikrokontinenten und Subduktionszonen.

Orientador: Maria Alvina Krähenbühl
Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química
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Resumo: O biodiesel e um combustível biodegradável, renovável e com menor emissão de gases poluentes do que o petrodiesel. Ele e composto por ésteres alquilícos de ácidos graxos obtidos pela transesterificação de óleos ou gorduras com um álcool de cadeia curta como o metanol ou o etanol. Os ésteres etílicos resultantes da transesterificação com o etanol ainda são pouco caracterizados. Dados de suas propriedades termofísicas e de equilíbrio de fases; que são muito importantes para o projeto, modelagem, simulação e otimização do processo de produção do biodiesel, são escassos na literatura. Neste trabalho determinaram-se dados de pressão de vapor dos ésteres laurato de etila, miristato de etila, palmitato de etila, estearato de etila, oleato de etila e linoleato de etila, e dados de equilíbrio líquido-vapor dos sistemas palmitato de etila + estearato de etila a 40 mmHg, palmitato de etila + oleato de etila a 40 e 70 mmHg e palmitato de etila + linoleato de etila a 70 mmHg. Para a determinação experimental propôs-se a utilização de uma técnica não convencional: a calorimetria exploratória diferencial ("Differential Scanning Calorimetry" - DSC). Nas analises foram utilizadas de 2-5 mg de amostra a uma taxa de aquecimento de 25 oC/min. As amostras foram colocadas em cadinhos herméticos de alumínio com um pequeno orifício na tampa ("pinhole") de 0,25 mm de diâmetro, para garantir a pressão interna constante. Para a determinação de dados de pressão de vapor, o DSC revelou-se ser uma técnica adequada e suas principais vantagens em relação as técnicas convencionais são: utilização de pequena quantidade de amostra e menor tempo de analise. Os dados de equilíbrio líquido-vapor medidos pelo DSC foram satisfatórios. Esta técnica mostrou-se restrita, não sendo adequada para a determinação do equilíbrio liquidovapor de sistemas cujos componentes apresentam grande diferença de volatilidade
Abstract: Biodiesel is a biodegradable, renewable fuel with lower greenhouse gas emissions. It consists of the alkyl esters of fatty acids, obtained by the transesterification of fats and oils with a short chain alcohol such as methanol or ethanol. Ethyl esters resulting from transesterification with ethanol are poorly characterized. The thermophysical properties and phase equilibrium data involving the fatty acid ethyl esters are very important in the design, modeling, simulation, and the optimization of the production of biodiesel, are scarce in the literature. In this work was determined vapor pressure data of the esters ethyl laurate, ethyl myristate, ethyl palmitate, ethyl stearate, ethyl oleate and ethyl linoleate; and vapor-liquid equilibrium data of systems ethyl pamitate + ethyl stearate at 40 mmHg, ethyl palmitate + ethyl oleate at 40 and 70 mmHg and ethyl palmitate + ethyl linoleate ant 70 mmHg. For the experimental determination proposed the use of a non-conventional technique: differential scanning calorimetry (DSC). Samples of 2 to 5 mg were used in the analysis, with heating rate of 25 ?C/min. The samples were placed in hermetic aluminum crucibles with a small hole in the lid ("pinhole") of 0.25 mm diameter, which maintain a constant internal pressure. The technique of differential scanning calorimetry was shown to be appropriate to determining the vapor pressure of ethyl esters. This technique showed advantages over conventional techniques: the use of a small sample size and shorter analysis time. The vapor-liquid equilibrium data measured by DSC were satisfactory. This technique proved to be restricted and it is not suitable for determining the vapor-liquid equilibrium data of systems whose components have large difference in volatility
Doutorado
Desenvolvimento de Processos Químicos
Doutor em Engenharia Química

The two-phase MD technique employed in this work determines the liquid and vapor phase densities from a histogram of molecular densities within phase clusters in the simulation cell using a new Monte Carlo (MC) sampling method. These equilibrium densities are then fitted in conjunction with known critical-point scaling laws to obtain the critical temperature, and the critical density. This MC post-processing method was found to be more easily implemented in code, and it is efficient and easily applied to complex, structured molecules. This method has been successfully applied and benchmarked for a simple Lennard-Jones (LJ) fluid and a structured molecule, propane. Various degrees of internal flexibility in the propane models showed little effect on the coexisting densities far from critical point, but internal flexibility (angle bending and bond vibrations) seemed to affect the saturated liquid densities in the near-critical region, changing the critical temperature by approximately 20 K. Shorter cutoffs were also found to affect the phase dome and the location of the critical point. The developed MD+MC method was then used to test the efficacy of two all-atom, site-site pair potential models (with and without point charges) developed solely from the energy landscape obtained from high-level ab initio pair interactions for the first time. Both models produced equivalent phase domes and critical loci. The model's critical temperature for methanol is 77 K too high while that for 1-propanol is 80 K too low, but the critical densities are in good agreement. These differences are likely attributable to the lack of multi-body interactions in the true pair potential models used here. Lastly, the transferability of the ab initio potential model was evaluated by applying it to 1-pentanol. An attempt has been made to separate the errors due to transferability of the potential model from errors due to the use of a true-pair potential. The results suggested a good level of transferability for the site-site model. The lack of multi-body effects appears to be dominant weakness in using the generalized ab initio potential model for determination of the phase dome and critical properties of larger alcohols.

Optimal interaction between vision and other somatosensory systems guaranties the control of human body segment stability and change in position. The lack of visual information causes changes in equilibrium, regulation of body segment position and in response to surrounding stimuli. The objective of the study: to carry out the research on the influence of the degree of visual impairment on equilibrium and simple and psychomotor reactions, and to establish the possible manifestation of compensatory reactions of vestibular and proprioception sensory systems when vision disorders are being faced. To investigate the influence of the degree of visual impairment on equilibrium and simple and psychomotor reactions, the sighted subjects, legally blind and totally blind subjects voluntarily participated in the study. A static posturography (or stabilography) method has been used for the equilibrium testing. A force plate and computerized equipment for analysis of the signals was applied for posturography. Centre of pressure coordinates have been started to be registered since the moment when the subject in bare feet stands on the force plate in the position required. Posturogram registration in every position of standing lasted 60 s. To investigate a simple reaction, we have employed an electromyoreflexometer, which consists of the equipment emitting light or sound signals, a response device and a unit for the data registration. The testing has been conducted during two parts when a... [to full text]

The aim of the present work is the development of a non-equilibrium atmospheric pressure plasma multijet device for the treatment of liquids. The interest in plasma multijet device is due to the potentiality for scaling up of plasma jet applications, since such device allows for treatment of higher volume of liquid than single-jet system. The multijet device has been developed in the laboratories of GREMI (Groupe de Recherches sur l’Energétique des Milieux Ionisés) at Orléans, and afterward tested for liquid decontamination in the “Tesla Plasma Research lab” laboratories of the group for Industrial Applications of Plasmas at the Alma Mater Studiorum - Università di Bologna. A versatile multijet device, able to work both in ambient air with jets impinging on a liquid target or in underliquid condition, with plasma discharge formation in bubbles flushed inside the liquid has been realized. Different liquids have been exposed to the plasma investigating the change in pH value, conductivity, temperature and reactive species concentration induced in liquid after plasma treatment. Afterward, electrical characterization has been performed by means of voltage and current probes in order to evaluate the power consumption. Finally, decontamination activity of the plasma treatment has been investigated using a liquid solution inoculated with Escherichia coli revealing antibacterial efficacy.

Resumo O conhecimento dos parâmetros macroscópicos do plasma, tais como a densidade e temperatura, bem como sua evolução e dependência espacial são fundamentais para a compreensão e controle do plasma. Esses parâmetros são essenciais para descrição dos eventos associados a fenômenos de transporte, atividade MHD, estudos de regime de confinamento melhorado (modo H), entre outros. O perfil de temperatura e densidade de íons e elétrons caracteriza um parâmetro extremamente importante em plasmas termonucleares que é o perfil de pressão. Para obter esses perfis foram utilizados os principais diagnósticos disponíveis no tokamak TCABR: espalhamento Thomson, interferometria, reflectometria, ECE e diagnósticos espectroscópicos. O espalhamento Thomson é capaz de determinar o perfil de temperatura e densidade eletrônica durante o disparo; já o diagnóstico ECE é capaz de medir a temperatura eletrônica sob certas condições de descargas. Já os diagnósticos de interferometria e reflectometria medem a densidade eletrônica integrada e a densidade eletrônica local, respectivamente. Por fim, o perfil de temperatura iônica pode ser estimado através do alargamento Doppler das linhas de emissão de impurezas. Tais dados são usados para reconstrução do perfil de pressão, em diferentes tipos de descargas no tokamak, bem como possibilitar a reconstrução do equilíbrio. Não obstante, esses diagnósticos podem fornecer informações como estimativa do Z efetivo do plasma, da velocidade de rotação, e das condições que promovem disrupção no TCABR
The knowledge of the plasma macroscopic parameters such as density and temperature as well as their temporal and spatial evolution are fundamental to the understanding and control of the plasma. These parameters are essential for description of events associated with transport phenomena, magnetohydrodynamics (MHD) activity, improved confinement studies (H mode), among others. The temperature and density profiles of electrons and ions define an extremely important parameter in thermonuclear plasmas that is the pressure profile. To measure these profiles we used all the main diagnostics available in the TCABR tokamak: Thomson scattering, interferometry, reflectometry, ECE and spectroscopic diagnostics. The Thomson scattering is able to determine the local electron temperature and density in the plasma discharge; ECE diagnostic is also able to measure the local electron temperature under certain plasma discharge conditions. And the interferometric and reflectometric diagnostics measure the line-integrated electronic density and the local electronic density, respectively. Finally, the ion temperature profile can be estimated by the Doppler broadening of the impurity line emissions. These data are used to reconstruct the pressure profile in different types of discharges in tokamak, and to enable the MHD equilibrium reconstruction. Nevertheless, these analyzes can provide information to estimate the plasma Z effective, plasma rotation velocity, and the conditions that promote the disruption in the TCABR.

Orientador: Martin Aznar
Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica
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Resumo: Durante a presente década, vários resultados experimentais sobre fenômenos críticos no equilíbrio de fases, tais como efeito de co-solvência, janelas de miscibilidade e regiões de duas fases LV em superfícies de três fases LLV em sistemas ternários foram obtidos experimentalmente por vários grupos de pesquisa. Estes fenômenos são de grande influência em aplicações industriais de tecnologia supercrítica ou quase crítica, já que eles são observados dentro do intervalo de pressão, temperatura e concentração onde acontecem estes processos tecnológicos. O presente trabalho de tese visou modelar computacionalmente o equilíbrio multifásico (ELL, ELV, ELLV) e predizer esses fenômenos, que acontecem perto da região crítica, em sistemas simples (CO2 + n-alcano + n-alcanol, CO2 + 2-nitrofenol + n-alcanol) e complexos, tais como polímero + CO2 + cosolvente [polipropileno (iPP) + CO2 + n-pentano; poliestireno (PS) + CO2 + ciclohexano e poli(D,L-lactida) + CO2 + dimetileter)], fazendo uso de equações de estado (EDE) não cúbicas, que possuem algum embasamento teórico, como modelos termodinâmicos. Esses modelos foram a equação da Teoria Estatística do Fluido Associado de Cadeia Perturbada (Perturbed Chain ¿ Statistical Associating Fluid Theory, PC-SAFT) e de Sanchez- Lacombe (SL). Os resultados obtidos na modelagem do equilíbrio de fases a altas pressões desses sistemas foram comparados com os obtidos pela tradicional EDE de Peng-Robinson (PR). Estes modelos termodinâmicos também foram usados na modelagem do ELV e ELL de sistemas binários compostos de copolímeros comuns e biodegradáveis com solventes a baixas e altas pressões. Cada modelo termodinâmico possui parâmetros de componente puro e um parâmetro de interação (na sua regra de cruzamento) para cada sistema binário. Em todos os modelos termodinâmicos foi usada uma regra de cruzamento convencional e uma regra de mistura de primeira ordem de van der Waals. Os parâmetros de componente puro foram obtidos ajustando por regressão os dados de pressão de vapor e do volume molar do líquido saturado para o componente simples e dados de densidade, pressão e temperatura para o polímero na fase líquida. A modelagem de cada sistema binário foi feita a partir de dados de ELL, ELV e ELLV obtendo um parâmetro de interação binária (que leva em conta as interações entre duas moléculas). A predição do comportamento de fases do sistema ternário foi feita usando os parâmetros de interação binária dos três sistemas binários envolvidos e os resultados foram comparados com os dados experimentais. A otimização foi feita usando o método modificado de Máxima Verossimilhança para determinar o ótimo global dos dois tipos de parâmetros. Em todas as modelagens do comportamento do equilíbrio multifásico dos sistemas apresentados acima, a EDE PC-SAFT teve a melhor performance em termos dos desvios relativos na pressão quando comparada à performance das EDEs SL e PR
Abstract: During the present decade, several experimental results on critical phenomena in phase equilibria, such as co-solvency effect, miscibility windows and two-phases LV regions in three phases LLV surfaces in ternary systems were obtained experimentally by several research groups. These phenomena are of great influence in industrial applications of near-critical and supercritical technology, since they are observed within the pressure, temperature and concentration intervals where these technological processes happen. The present thesis aimed for modeling computationally the phase equilibria (LLE, VLE, VLLE) and predict those phenomena that happen near to critical region in simple systems (CO2 + n-alkane + n-alkanol, CO2 + 2-nitrophenol + n-alkanol) and complex systems, such as polymer + CO2 + co-solvent [polypropylene (iPP) + CO2 + n-pentane; polystyrene (PS) + CO2 + cyclohexane and poly(D,L-lactide) + CO2 + dimethyl ether)] using non-cubic equations of state (EoS), with some theoretical base, as thermodynamic models. Those models were the Perturbed Chain - Statistical Associating Fluid Theory (PC-SAFT) and the Sanchez - Lacombe (SL) EoS. The results obtained in modeling of high-pressure phase equilibria of those systems were compared with those obtained by the traditional Peng- Robinson (PR) EoS. These thermodynamic models were also used in modeling the VLE and LLE of binary systems composed of common and biodegradable copolymers with solvents at low and high pressures. Each thermodynamic model has pure component parameters and one interaction parameter (in its combining rule) for each binary system. Conventional combining and van der Waals one-fluid mixing rules were used in all thermodynamic models. Pure component parameters were obtained by regression of liquid saturated vapor pressure and volume molar data for each simple component, and liquid density, pressure and temperature data for each polymer. The modeling of each binary system was made from LLE, VLE and VLLE data, obtaining one binary interaction parameter (which takes into account the interactions between two molecules). The prediction of phase behavior of ternary system was made using the binary interaction parameters of its three binary systems and the results were compared with experimental data. Optimization was made using the modified likelihood maximum method to determine the global optimum of the two types of parameters. In all the modeling of the multiphase equilibria behavior of the systems presented above, the PC-SAFT EoS had the best performance in terms of relative deviations in pressure when compared to performance of SL and PR EoS
Doutorado
Desenvolvimento de Processos Químicos
Doutor em Engenharia Química

Orientador: Antonio Jose de Almeida Meirelles
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos
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Resumo: Os álcoois superiores são provenientes, em sua maior parte, de transformações de aminoácidos durante o processo de fermentação. São álcoois com números de átomos de carbono entre três e cinco, como o álcool propílico, álcool amílico e seus isômeros, responsáveis pelo odor de algumas bebidas alcoólicas. Eles estão presentes na composição do óleo fúsel, que é a fração alcoólica menos volátil obtida durante a destilação do etanol. Embora o óleo fúsel seja um dos principais subprodutos da destilação do álcool, não é devidamente aproveitado pelas indústrias. Devido à presença desses álcoois superiores no processo de destilação do etanol, este trabalho tem como objetivo estudar o equilíbrio líquido vapor (ELV) desses componentes. O estudo foi feito com sistemas isobáricos a pressões de 760 e 560 mmHg, formados pelos álcoois superiores 2-propanol, 2-metil-1-propanol e 3-metil-1-butanol. O equipamento empregado na obtenção dos dados de equilíbrio (_ 9 _ 9 _ 9 _: foi um ebuliômetro FISCHER ® e a composição das fases em equilíbrio (líquida e vapor condensado) foi determinada utilizando cromatografia gasosa. Os sistemas estudados foram os binários 3-metil-1-butanol + 2-metil-1-propanol a 760 mmHg, 2-propanol + 3-metil-1-butanol a 760 mmHg e 560 mmHg e o ternário 2-propanol + 3-metil-1-butanol + 2-metil-1-propanol a 760 mmHg e 560 mmHg, procurando cobrir toda a faixa de composição, incluindo os compostos puros. Os dados de ELV obtidos experimentalmente foram submetidos ao teste de consistência termodinâmica. Outra contribuição consistiu na obtenção dos parâmetros de interação binária de modelos de coeficientes de atividade da fase líquida como as equações de Wilson, UNIQUAC e NRTL. Estas equações são comumente usados em simuladores de processos. Para o ajuste de parâmetros e o teste de consistência foi utilizado o simulador Aspen Plus ®. Os testes de consistência termodinâmica confirmaram a boa qualidade dos dados obtidos pelo ebuliômetro FISCHER ® para os sistemas binários estudados. Os modelos de Wilson, NRTL e UNIQUAC mostraram-se adequados na representação do ELV de todos os sistemas estudados, binários e ternários, obtendo-se desvios de temperatura e de composição da fase vapor muito próximos para todos os modelos utilizados
Abstract: The higher alcohols are derived, mainly, from the amino acids changes during the fermentation process. These are alcohols with carbon numbers between three and five, such as propyl alcohol, amyl alcohol and their isomers, responsible for the odor of most alcoholic beverages. They are present in the composition of fusel oil, which is the least volatile alcoholic fraction obtained during the ethanol distillation. Although the fusel oil is one of the main by-products of alcohol distillation, it is not properly harnessed by industry. Due to the presence of higher alcohols in the ethanol distillation process, this work aims at studying the vapor-liquid equilibrium (VLE) of these components. The study was developed with isobaric systems at pressures of 760 and 560 mmHg, formed by higher alcohols 2-propanol, 2-methyl- 1-butanol and 3-methyl-1-butanol. The equipment used in obtaining the equilibrium data (P ¿ T ¿ x ¿ y) was an ebuliometer FISCHER and the composition of the equilibrium phases (liquid and condensed steam) was determined using gas chromatography. The studied systems were the binary 3-methyl-1-butanol + 2- methyl-1-propanol at 760 mmHg, 2-propanol + 3-methyl-1-butanol at 760 mmHg and 560 mmHg and the ternary 2-propanol + 3 - methyl-1-butanol + 2-methyl-1- propanol at 760 mmHg and 560 mmHg, always trying to cover the entire composition range including the pure compounds. The VLE data obtained were experimentally tested for thermodynamic consistency. Another contribution was the binary interaction parameters obtained by adjusting the activity coefficient models of the liquid phase (Wilson, NRTL and UNIQUAC) to the experimental data. These equations are commonly used in process simulators. The Aspen Plus simulator was used to adjust the parameters and to test the consistency of the experimental data. The thermodynamic consistency tests confirmed the good data quality obtained by the FISCHER ebuliometer for the binary systems studied. The models Wilson, NRTL and UNIQUAC proved to be adequate for representing the VLE of all studied systems, binary and ternary ones, and the temperature and vapor composition deviations between experimental and calculated data were low for all the models used
Mestrado
Engenharia de Alimentos
Mestre em Engenharia de Alimentos

Durant la dernière décennie, un nouveau type de décharge hors équilibre thermodynamique à pression atmosphérique a suscité un engouement croissant compte tenu de sa capacité de produire un plasma s'étendant dans l'air ambiant à une température proche de l'ambiante. Ces jets de plasma, souvent basés sur un réacteur de type décharge à barrière diélectrique, sont intéressants du point de vue de leurs propriétés physico-chimiques. De plus, ces jets de plasmas ont l'avantage de permettre des applications des matériaux thermosensibles, ouvrant ainsi un nouveau domaine de recherche, Plasma Médecine. Au GREMI le Plasma Gun, a été développé tant pour l'étude de la physique des jets de plasma que pour les applications biomédicales notamment dans le domaine de la cancérologie. Dans une première étape, des traitements par Plasma Gun in vitro et in vivo, dans le cadre d'un modèle murin du carcinome pancréatique, ont été effectués. L'action anti-tumorale du plasma a été démontrée ainsi que la combinaison bénéfique avec un traitement chimiothérapique. Fondée sur ces résultats encourageants, l'objectif principal de cette étude porte sur l'influence drastique de la cible de l'application sur les propriétés du plasma (propagation et production des espèces réactives) ainsi que l'interaction du gaz et du plasma. Des diagnostiques tels que l'imagerie rapide et filtrée en longueur d'onde, la spectroscopie d'émission optique, l'imagerie Schlieren ainsi que la spectroscopie infrarouge à transformée de Fourier ont été utilisés pour caractériser le jet de plasma. Une étude quantitative de la distribution spatiale et temporelle du radical hydroxyle (densité comprise entre 5.1011 et 1.1014 cm-3) a été réalisée par fluorescence induite par laser. L'étude de l'OH en combinaison avec un modèle numérique a permis une meilleure compréhension de la pénétration de l'air dans le jet de gaz et de l'interaction avec les surfaces humides. L'interaction complexe entre le comportement du gaz, du plasma et la nature de la cible est mise en avant en vue d'optimiser les applications biomédicales
Over the past decade, a new type of non-equilibrium discharge at atmospheric pressure has attracted growing interest, given the ability to produce a plasma extending in ambient air close to room temperatures. These plasma jets, often based on a dielectric barrier discharge type of reactor, are interesting on their physicochemical property perspectives. In addition, these cold plasma jets have the advantage of allowing applications to heat sensitive materials, creating a new field of research, Plasma Medicine. At GREMI the Plasma Gun, has been developed for both the study of the physics of plasma jets and for biomedical applications particularly in the field of cancerology. In a first step, in vitro and in vivo were performed, within a rodent model of pancreatic carcinoma. The anti-tumor action of the plasma has been demonstrated as well as its benefic combination with a chemotherapeutic treatment. Based on these encouraging biomedical results, the main focus of this study is to report on the drastic influence of the application target on the plasma properties (propagation and production of reactive species) and on the strong coupling between gas jet and plasma discharge. Diagnostics such as fast, wavelength-filtered and Schlieren imaging, optical emission spectroscopy as well as Fourier transform infrared spectroscopy were used to characterize the plasma. A quantitative study on spatial and temporal distribution of hydroxyl radicals (OH density ranging between 5.1011 and 1.1014 cm-3) was performed by laser-induced fluorescence. The study of the OH in combination with a numerical model allowed a better understanding of the moist air penetration into the gas jet and the interaction with wet surfaces. This PhD work enlightened the complex interaction between the gas flow, the plasma and the nature of the target which has to be taken into account for further optimization of biomedical applications

A total pressure apparatus has been developed to measure vapour-liquid equilibrium data on binary mixtures at atmospheric and sub-atmospheric pressures. The method gives isothermal data which can be obtained rapidly. Only measurements of total pressure are made as a direct function of composition of synthetic liquid phase composition, the vapour phase composition being deduced through the Gibbs-Duhem relationship. The need to analyse either of the phases is eliminated. As such the errors introduced by sampling and analysis are removed. The essential requirements are that the pure components be degassed completely since any deficiency in degassing would introduce errors into the measured pressures. A similarly essential requirement was that the central apparatus would have to be absolutely leak-tight as any leakage of air either in or out of the apparatus would introduce erroneous pressure readings. The apparatus was commissioned by measuring the saturated vapour pressures of both degassed water and ethanol as a function of temperature. The pressure-temperature data on degassed water measured were directly compared with data in the literature, with good agreement. Similarly the pressure-temperature data were measured for ethanol, methanol and cyclohexane and where possible a direct comparison made with the literature data. Good agreement between the pure component data of this work and those available in the literature demonstrates firstly that a satisfactory degassing procedure has been achieved and that secondly the measurements of pressure-temperature are consistent for any one component; since this is true for a number of components, the measurements of both temperature and pressure are both self-consistent and of sufficient accuracy, with an observed compatibility between the precision/accuracy of the separate means of measuring pressure and temperature. The liquid mixtures studied were of ethanol-water, methanol-water and ethanol-cyclohexane. The total pressure was measured as the composition inside the equilibrium cell was varied at a set tmperature. This gave P-T-x data sets for each mixture at a range of temperatures. A standard fitting-package from the literature was used to reduce the raw data to yield y-values to complete the x-y-P-T data sets. A consistency test could not be applied to the P-T-x data set as no y-values were obtained during the experimental measurements. In general satisfactory agreement was found between the data of this work and those available in the literature. For some runs discrepancies were observed, and further work recommended to eliminate the problems identified.

The theory of vapour-liquid equilibria is reviewed, as is the present status or prediction methods in this field. After discussion of the experimental methods available, development of a recirculating equilibrium still based on a previously successful design (the modified Raal, Code and Best still of O'Donnell and Jenkins) is described. This novel still is designed to work at pressures upto 35 bar and for the measurement of both isothermal and isobaric vapour-liquid equilibrium data. The equilibrium still was first commissioned by measuring the saturated vapour pressures of pure ethanol and cyclohexane in the temperature range 77-124oC and 80-142oC respectively. The data obtained were compared with available literature experimental values and with values derived from an extended form of the Antoine equation for which parameters were given in the literature. Commissioning continued with the study of the phase behaviour of mixtures of the two pure components as such mixtures are strongly non-ideal, showing azeotopic behaviour. Existing data did not exist above one atmosphere pressure. Isothermal measurements were made at 83.29oC and 106.54oC, whilst isobaric measurements were made at pressures of 1 bar, 3 bar and 5 bar respectively. The experimental vapour-liquid equilibrium data obtained are assessed by a standard literature method incorporating a themodynamic consistency test that minimises the errors in all the measured variables. This assessment showed that reasonable x-P-T data-sets had been measured, from which y-values could be deduced, but that the experimental y-values indicated the need for improvements in the design of the still.

Приведены результаты разработки эмпирических уравнений для расчета параметров равновесия газ-жидкость в системе NH₃–CO₂–H₂O при давлениях ниже атмосферного и концентрациях NH₃ и CO₂ в жидкости в диапазоне их растворимости в воде. В частности, получены формулы для расчета равновесного давления аммиака, диоксида углерода и водяного пара, а также температуры кипения раствора под атмосферным давлением.
The article presents the results of development of empirical equations for calculation of the gas-liquid equilibria parameters of the system NH₃–CO₂–H₂O at a pressure below atmospheric and NH₃ and CO₂ concentrations in the liquid in the range of their solubility in water. The formulas for calculating of ammonia, carbon dioxide and water vapour equilibrium pressure, and their solution boiling point at atmospheric pressure were obtained.

In several types of coating processes a solid substrate is removed at a controlled velocity U from a liquid bath. The shape of the liquid meniscus and the thickness of the coating layer depend on U. These dependencies have to be understood in detail for non-volatile liquids to control the deposition of such a liquid and to lay the basis for the control in more complicated cases (volatile pure liquid, solution with volatile solvent). We study the case of non-volatile liquids employing a precursor film model that describes partial wettability with a Derjaguin (or disjoining) pressure. In particular, we focus on the relation of the deposition of (i) an ultrathin precursor film at small velocities and (ii) a macroscopic film of thickness h ∝ U^(2/3) (corresponding to the classical Landau Levich film). Depending on the plate inclination, four regimes are found for the change from case (i) to (ii). The different regimes and the transitions between them are analysed employing numerical continuation of steady states and saddle-node bifurcations and simulations in time. We discuss the relation of our results to results obtained with a slip model. In connection with evaporative processes, we will study the pinning of a droplet due to a sharp corner. The approach employs an evolution equation for the height profile of an evaporating thin film (small contact angle droplet) on a substrate with a rounded edge, and enables one to predict the dependence of the apparent contact angle on the position of the contact line. The calculations confirm experimental observations, namely that there exists a dynamically produced critical angle for depinning that increases with the evaporation rate. This suggests that one may introduce a simple modification of the Gibbs criterion for pinning that accounts for the non-equilibrium effect of evaporation.

Les procédés plasma utilisant des décharges à barrières diélectriques (DBD) à pression atmosphérique sont une bonne alternative aux plasmas froids à basse pression pour de nombreuses applications comme le traitement de surface, le dépôt de couches minces, la stérilisation etc. En effet, ils permettent de s'affranchir des systèmes de pompage et donc de réaliser des traitements sur de grandes surfaces directement implantables sur des lignes de production. Cependant, les DBD sont généralement filamentaires, ce qui conduit à des dépôts non homogènes. Dans certaines conditions expérimentales (géométrie, nature du gaz, excitation etc.), on peut néanmoins obtenir une décharge homogène conduisant à un traitement homogène des surfaces. Néanmoins, les caractéristiques des DBD homogènes ne sont pas identiques en tout point de l'espace, notamment en raison du flux de gaz, mais aussi dans le cas de matériaux diélectriques avec un gradient de propriétés ou dans le cas de décharges auto-organisées. Afin de mieux caractériser la distribution spatiale de la décharge, un outil de mesure de densités locales de courant a été développé au cours de cette thèse. En effet, les mesures électriques sont un bon outil de caractérisation de la décharge donnant accès à de nombreux paramètres (courant de décharge, tension gaz, puissance dissipée etc.). Néanmoins, le courant mesuré est intégré sur toute la surface des électrodes. Pour pouvoir mesurer les courants localement, l'électrode de masse de la cellule de décharge de dimension 3×3 cm2 a été divisée en 64 segments, et un système d'acquisition a été développé afin de pouvoir acquérir les 64 courants mesurés simultanément avec une fréquence d'échantillonnage suffisante pour le traitement des données. Ce nouvel outil de diagnostics électriques peut être corrélé temporellement et spatialement à des mesures optiques par caméra intensifiée iCCD couplée à différents filtres optiques, donnant des informations sur les densités de certaines espèces dans le plasma. L'objectif de cette thèse est de mieux comprendre la dissipation de puissance locale et de caractériser plus finement les espèces mises en jeu et les différents régimes de décharge, notamment l'obtention d'un régime homogène. Les DBD homogènes sont initiées par un claquage de type Townsend. Pour cela, une source de production d'électrons est nécessaire entre deux décharges, quand le champ électrique est inférieur au champ de claquage. Ce claquage est lié à un effet mémoire d'une décharge à l'autre, visible sur les mesures électriques, avec un saut du courant de décharge. Les hypothèses sur l'origine de cet effet mémoire peuvent être séparées en deux catégories.[...]
Plasma processes at atmospheric pressure using Dielectric Barrier Discharges (DBD) are a good alternative to low pressure non-thermal plasma processes for various applications such as surface treatment, thin-film coating, sterilization etc. Indeed, they can be operated without complex vacuum facilities and allow the treatment of large surfaces that can be implemented directly into assembly lines. However, DBDs are usually filamentary, leading to non-homogeneous depositions on the treated surfaces. In certain condition depending on the experimental parameters (geometry, gas nature, power supply, etc.), a homogeneous discharge can be obtained leading to a uniform surface treatment. Nevertheless, even in the homogeneous mode, the DBDs properties are not necessarily the same at any point on the discharge surface, because of the gas flow circulation in particular, but also in case of materials with a properties gradient, or in case of self-organization phenomena. In order to better characterize the spatial distribution of the discharge, a new local electrical diagnostic tool to measure the local current densities has been developed during this thesis. Indeed, electrical measurements are widely used to characterize the DBDs as they give access to various parameters such as the gas voltage, discharge current, dissipated power etc. However, the measured current is integrated on all the surface of the electrodes. To be able to measure the local currents, the 3×3 cm2 ground electrode from the discharge cell has been divided into 64 segments, and a data acquisition system has been developed in order to simultaneously acquire the 64 measured currents with a high enough sampling rate for the data processing. This new electrical diagnostic tool can be correlated in time and space with optical measurements with an intensified iCCD camera, coupled with optical filters, to obtain information on the densities of some species in the plasma. The aim of this thesis is to better understand to local power dissipation, and to refine the characterization of the involved species in the different discharge regimes, especially to obtain a homogeneous regime. Homogeneous DBDs are ignited by a Townsend breakdown. For a Townsend breakdown to occur, a production source of seed electrons is necessary between two discharges, when the electric field is lower than the breakdown voltage. This breakdown is related to a memory effect from one discharge to the following one, that is visible on the electrical measurements with a discharge current jump. The hypotheses on the memory effect origin can be separated into two categories.[...]

A study of vapour-liquid equilibria is presented together with current developments. The theory of vapour-liquid equilibria is discussed. Both experimental and prediction methods for obtaining vapour-liquid equilibria data are critically reviewed. The development of a new family of equilibrium stills to measure experimental VLE data from sub-atmosphere to 35 bar pressure is described. Existing experimental techniques are reviewed, to highlight the needs for these new apparati and their major attributes. Details are provided of how apparatus may be further improved and how computer control may be implemented. To provide a rigorous test of the apparatus the stills have been commissioned using acetic acid-water mixture at one atmosphere pressure. A Barker-type consistency test computer program, which allows for association in both phases has been applied to the data generated and clearly shows that the stills produce data of a very high quality. Two high quality data sets, for the mixture acetone-chloroform, have been generated at one atmosphere and 64.3oC. These data are used to investigate the ability of the new novel technique, based on molecular parameters, to predict VLE data for highly polar mixtures. Eight, vapour-liquid equilibrium data sets have been produced for the cyclohexane-ethanol mixture at one atmosphere, 2, 4, 6, 8 and 11 bar, 90.9oC and 132.8oC. These data sets have been tested for thermodynamic consistency using a Barker-type fitting package and shown to be of high quality. The data have been used to investigate the dependence of UNIQUAC parameters with temperature. The data have in addition been used to compare directly the performance of the predictive methods - Original UNIFAC, a modified version of UNIFAC, and the new novel technique, based on molecular parameters developed from generalised London's potential (GLP) theory.

Mestrado em Medição de Equilíbrios Gás Líquido a Altas Pressões
Este trabalho tem como objectivo a medição da solubilidade de gases em líquidos a altas pressões. Para a realização experimental foi usada uma célula de altas pressões de volume variável e um método de observação directa para a detecção das transições de fase. As condições usadas neste trabalho experimental foram temperaturas entre 276.00 e 373.15 K e pressões ate 100 MPa. Numa primeira fase foram efectuadas medições de solubilidade de metano em anilina pura e para uma solução aquosa de composição mássica igual a 5% em anilina. A anilina é fundamentalmente usada em processos como a produção de borracha, de poliuretanos, pigmentos e tintas, fármacos, herbicidas e fungicidas. É usualmente produzida através de processos de redução do nitrobenzeno por reacção com o HCl. De facto, esta síntese é um processo químico complexo onde um grande número de processos compete entre si. Alterações nas condições do processo com a possível formação de produtos intermediários podem afectar a eficiência do processo. Para a sua melhoria foi sugerido que o hidrogénio usado fosse simultaneamente produzido e gasto no reactor principal. Neste caso e para a produção do mesmo, era necessário adicionar metano e água ao reactor. Tendo por base a ideia de que as reacções onde o hidrogénio é reagente e produto ocorrem em simultâneo, torna-se clara a importância do estudo da solubilidade do metano em anilina pura e em soluções aquosas desta. Numa segunda fase foi estudada a solubilidade do dióxido de carbono em soluções aquosas de tri-iso-butil(metil)fosfónio tosilato, com composições molares são de 4, 8 e 12% em líquido iónico. Este pertencente à família dos fosfónios. Possui uma viscosidade e densidade elevadas, é térmica e quimicamente estável e ainda possui uma elevada polaridade. Apresenta uma miscibilidade completa em água e nos solventes mais usuais, como o diclorometano e tolueno, não sendo no entanto míscivel em hexano. O tri-isobutil( metil)fosfónium tosilato é usado como solvente nos processos de hidroformilação de olefinas e ainda em processos de captura e conversão de dióxido de carbono. Neste trabalho experimental, a temperatura e a pressão foram inicialmente aumentadas até o sistema atingir o equilíbrio. A pressão é diminuída lentamente até se verificar o aparecimento/desaparecimento da última bolha de gás. A pressão à qual a última bolha de gás desaparece representa a pressão de equilíbrio para aquela temperatura. Este procedimento foi efectuado para vários sistemas e várias temperaturas.
The aim of this work is the measurement of the solubilities of different gases in different liquids systems at high pressures. A variable volume high pressure cell was used to perform the measurements based on the visual synthetic method for the detection of phase transitions. The conditions used in this work were temperatures ranging from 276.00 to 373.15 K and pressures up to 100 MPa. The first step of this work was the measurement of methane’s solubility in pure aniline and for one aqueous solution of 5% (w/w) in aniline. The main applications of aniline are the manufacture of polyurethane, rubber, dyes and pigments, drugs and agrochemicals (herbicides and fungicides). This compound is normally produced by reduction of nitrobenzene by reaction with HCl. In fact, that synthesis is a complex chemical process where a number of competing processes contribute to the final product. Changes in process conditions with the possible formation of intermediates can act as catalyst poisons that change the process’s efficiency. For the improvement of the production process it was suggested that the hydrogen, used for the reduction of the nitrobenzene, could be simultaneously generated and used in the main reactor. In this case for the in situ production of hydrogen it would be necessary the addition of methane and water in the reactor. Having in mind that these reactions occur simultaneously, it becomes clear the importance of studying the solubility of methane in aniline and in its aqueous solutions. In the second step the solubility of carbon dioxide in aqueous solutions of triiso- butyl(methyl)phosphonium tosylate with molar compositions of 4, 8 and 12% molar of ionic liquid, was studied. This compound belongs to the phosphonium - based ionic liquids family. It is characterized by a high viscosity and density. It is thermal and chemically stable and has a high polarity. This compound is totally miscible with water as well as with common organic solvents such as dicloromethane and toluene but is not miscible with hexane. The main applications of Tri-iso-butyl(methyl)phosphonium tosylate are like solvents in the hydroformylation of olefins and in processes of capture and conversion of carbon dioxide. In this experimental work, temperature and pressure were slowly increased until the system becomes homogeneous. After that, the pressure is slowly decreased until the appearance/disappearance of the last bubble of gas. The pressure at witch the last bubble disappears represents the equilibrium pressure for that temperature. This procedure was repeated for several systems and several temperatures.

This thesis describes the investigation of phase behaviour of binary and ternary mixtures at high pressure. The particular applications chosen to be explored in this phase behaviour investigation were supercritical fluid electrodeposition (SCFED) and carbon capture and storage (CCS). Chapter 1 introduces the phase behaviour of mixtures. Chapter 2 describes the equipment and analytical techniques used throughout this thesis including the high-pressure variable-volume view cell, electrical conductivity cell, high pressure FTIR cell, and high-pressure optical fiber phase analyser. Chapter 3 details the solubility and conductivity investigation of several supporting electrolytes in difluoromethane (CH2F2), which provided an electrochemical bath with sufficient conductivity for electrodeposition in supercritical fluids. The most effective supporting electrolyte amongst the eight ionic compounds tested was [N(nC4H9)4][Al(OC(CF3)3)4] which was found to give a moderate solubility and the highest conductivity (222 Scm2mol-1) in CH2F2. [N(nC4H9)4][Al(OC(CF3)3)4] was followed by [N(nC4H9)4][FAP] and [N(nCH3)4][FAP], , making all of them to be satisfactory potential supporting electrolytes for SCFED. Chapter 4 describes the investigation of water solubility in CO2/N2 mixtures relevant to the CCS process. The scope of the investigation covers a wide pressure range and two levels of N2 (xN2= 0.05 and xN2= 0.10). This experimental study was conducted by using the FTIR technique as described in further detail in Chapter 2. It was found that the presence of N2 in CO2 lowered the solubility of H2O in supercritical CO2 with N2 compared to pure CO2. The solubility of water also decreases significantly when the concentration of N2 is increased from 5% to 10%. Chapter 5 further explores the role of phase behaviour in the application of CCS with the investigation of the phase envelope of the ternary mixtures of CO2 and permanent gases (Ar, N2, and H2). Three ternary mixtures were measured (90% CO2 + 5% N2 + 5% Ar, 98% CO2 + 1% N2 + 1% Ar, and 95% CO2 + 3% H2 + 2% Ar) by using the fiber optic reflectometer, as described in further detail in Chapter 2. The experimental data presented in this part also have been used to validate the equation of state for the CCS applications. It was found that the phase envelope of CO2 shifted to a higher pressure and the two-phase region become broader with the presence of permanent gases. Overall, both GERG-2004 and gSAFT provide a good agreement between the predicted and experimental data for all the ternary mixtures investigated, with the exception of the bubble-point line for the 3%H2 + 2%Ar + 95% CO2 mixture. Finally, Chapter 6 summarises the research that was conducted in this thesis. It also evaluates the progress made towards achieving the aims initially set-up in Chapter 1.

Les comportements thermiques d'une suspension granulaire en deux dimensions maintenue dans un état stationnaire hors équilibre ont été étudiés expérimentalement. L'analyse de la distribution spatiale des particules a montré qu’il existe une équation d’état reliant la densité de particules et deux autres quantités mesurables que nous interprétons comme une température et une pression granulaire. Cette équation d’état révèle l’existence d’interactions interactions attractives entre les particules. De plus, la dépendance de cette température aux différentes quantités physiques du problème montre qu'il existe deux régimes de fluctuations, que nous interprétons comme des régimes inertiels et visqueux. Dans ce dernier régime, la suspension se comporte de manière additive : il n'existe pas de corrélations à longue portée sur les fluctuations de densité, ce qui est étonnant dans une suspension où les corrélations de vitesses sont connues pour être à longue portée. Deuxièmement, le système exhibe une transition de phase ordre/désordre caractérisée par de grandes fluctuations et des hétérogénéités qui émergent proche du point critique. Ces hétérogénéités sont constituées d'amas de particules localement cristallisées dans une phase fluide désordonnée. L'analyse de la morphologie de ces structures révèlent une invariance d'échelle et a permis d'extraire plusieurs exposants critiques à l'aide d'outils de la théorie de la percolation. Troisièmement, la puissance injectée pour maintenir le système dans un état stationnaire hors équilibre peut être relié simplement à certaines quantités physiques de la suspension, et montre que l'injection de l'énergie se fait de la même manière quelque soit la phase ou le régime de fluctuations de la suspension
The thermal-like behavior of a two-dimensional granular suspension maintained in an out-of equilibrium steady state is experimentally studied. We uncovered a state equation relating the density of particles and two measureable quantities that we interpret as a pressure and a temperature. The comparison of the equation of state to the hard disks one shows that there is attractive interaction between particles. The dependency of the temperature to the physical quantities of our suspension shows two regimes of fluctuations that we interpret as a viscous and an inertial regime. In the viscous regime, the system is additive: there is no long range correlation on fluctuations of density, which is surprising in a suspension where velocity correlations are usually known to be long ranged. Second, the system is subjected to liquid-to-crystal phase transition characterized by large fluctuations and heterogeneities that rise near the critical point. Heterogeneities are made of many locally crystallized patches of particles surrounded by a disordered fluid phase. The analysis of their morphologies shows scale invariance and allowed to extract several critical exponents using tools of percolation theory. Third, the energy flux which goes through the suspension in order to keep the system in a out of equilibrium steady state can be expressed simply with respect to physical quantities of the system, and shows that the way we inject energy is independent from the phase or the fluctuations regime of the system

Cette thèse est financée par Total et par l’agence nationale de la recherche (ANR), elle s’inscrit dans le cadre du projet SIGARRR (simulation de l’impact des gaz annexes injectés avec le CO2 pendant le stockage géologique sur la réactivité des roches réservoirs). L’objectif de la thèse est d’acquérir expérimentalement des points de solubilité du CO2 dans des solutions aqueuses salées de chlorure de sodium et de chlorure de calcium dans des conditions de hautes températures (323K < T < 423K) et hautes pressions (5 MPa < P < 20 MPa) à des salinités élevées (1 à 6 mol/kg).Suite à une synthèse bibliographique sur les techniques expérimentales utilisées pour la détermination de la solubilité du dioxyde de carbone dans les solutions aqueuses, trois méthodes de caractérisation ont été expérimentées :  Analyse de la phase aqueuse par chromatographie ionique (analyse en ligne) Estimation de la solubilité à l’aide des bilans matière, des quantités de corps pures injectés initialement dans l’autoclave et des paramètres expérimentaux (masse volumique de la phase liquide, volume molaire de la phase gaz à l’équilibre, volume total de l’autoclave…). Piégeage d’un échantillon liquide dans la soude puis dosage. Une étude de sensibilité a été réalisée sur la méthode d’estimation de solubilité par bilan matière. Cette étude a permis d’identifier le niveau de précision de la mesure du volume de l’autoclave afin d’obtenir des estimations de solubilité fiables et précises à haute pression. Pour la dernière méthode expérimentée (piégeage dans la soude puis dosage), un protocole d’échantillonnage, et deux protocoles d’analyses (titrations) ont été développés ; les échantillons des systèmes CO2-H2O et CO2-H2O-NaCl ont été analysés par dosage pH-métrique et les échantillons des systèmes CO2-H2O-CaCl2 ont été analysés par dosage conductimétrique. 84 points de solubilité ont été obtenus au cours de ce travail dont 45 points complétement originaux. Les données expérimentales obtenues ont été comparées avec les résultats de simulations réalisées par le logiciel PHREEQC avec une base de données Pitzer.dat. Le ‘’salting out effect’’ observé a été évalué pour chaque système dans toutes les conditions de températures et pressions étudiées
This work was supported by Total and ‘’Agence National de la recherche’’ as a part of SIGARRR project (Simulation of the impact of annex gases co-injected with CO2 during its geological storage on the Reservoir-Rocks Reactivity. The aim of the thesis was to obtain experimental CO2 solubility data in salty aqueous solutions of sodium chloride and calcium chloride at different molalities (1, 3 and 6 mol/kg) under high temperature (323K < T < 423K) and high pressure (5 MPa < P < 20 MPa).Following a bibliographical study on experimental methods used for the carbon dioxide solubility determination, three characterization methods were tested: Aqueous phase analysis by ion chromatography Solubility estimation from mass balance, amounts of CO2 and liquid initially loaded into the cell and experimental parameters (density of liquid phase, molar volume of gas phase, and total volume of the equilibrium cell…). A liquid sample trapping in sodium hydroxide solution followed by a titrationA sensitivity study was carried out on the Solubility estimation method from mass balance. This study identified the level of accuracy of autoclave volume measurement to obtain reliable and accurate solubility data high-pressure.A sampling protocol was developed to withdraw aqueous samples and trap them into soda solution at high pressure. Two titration procedures were set up; liquid samples of CO2-H2O and CO2-H2O-NaCl systems were analyzed by potentiometric titration and samples of CO2-H2O-CaCl2 system were analyzed by conductimetric titration. 84 solubility data were obtained during this study, which include 45 new experimental data. Experimental measurement were compared to the results of simulation performed with PHREEQC software using a ‘’Pitzer.dat’’ database.The salting out effect observed was evaluated for each system under all temperature and pressure conditions

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1986.
MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE
Bibliography: v.2, leaves 200-208.
by Athanassios Z. Panagiotopoulos.
Ph.D.

In this thesis we discuss the theory of symmetric MHD equilibria with anisotropic pressure. More specifically, we focus on gyrotropic pressures, where the pressure tensor can be split into components along and across the magnetic field. We first explore 2D solutions, which can be found using total field type formalisms. These formalisms rely on treating quantities as functions of both the magnetic flux function and the magnetic field strength, and reduce the equilibrium equations to a single Grad-Shafranov equation that can be solved to find the magnetic flux function. However, these formalisms are not appropriate when one includes a shear field component of magnetic flux, since they lead to a set of equations which are implicitly coupled. Therefore, in order to solve the equilibrium problem with a magnetic shear field component, we introduce the poloidal formalism. This new formalism considers quantities as functions of the poloidal magnetic field strength (instead of the total magnetic field strength), and yields a set of two equations which are not coupled, and can be solved to find the magnetic flux function and the shear field. There are some situations where the poloidal formalism is difficult to use, however, such as in rotationally symmetric systems. Thus we require a further formalism, which we call the combined approach, which allows a more general use of the poloidal formalism. One finds that the combined formalism leads to multi-valued functions, which must be dealt with appropriately. Finally, we present some numerical examples of MHD equilibria, which have been found using each of the three formalisms mentioned above.

A Tian-Calvet type microcalorimeter has been constructed and used to measure the adsorption isotherms and the isosteric heat of adsorption of pure methane, ethane and CO₂, and the binary mixtures of the above-mentioned three adsorptives in three pure-silica MCM-41 samples with different pore diameters at room temperature and at pressures up to 1 bar. Ideal Adsorption Solution Theory (IAST) was applied to predict the binary adsorption isotherms and isosteric heats for individual components in the mixture. It is found that all the three binary mixtures behave ideally in MCM-41 at room temperature and at low pressures. The adsorption isotherms of binary ethane/CO₂ mixtures in the three MCM-41 samples was measured using a high-pressure volumetric apparatus at 264.6 K and at pressures up to 30 bar. IAST was used to study the adsorption system, and it gives quite accurate predictions of multicomponent adsorption equilibrium at low pressures and shows some deviations at moderate and high pressures, presumably due to the chemical dissimilarity of the two adsorptives. Grand canonical Monte Carlo simulations have been carried out to study the same adsorption system. The simulations were carried out using three different models for MCM-41 with different degrees of surface heterogeneity. The model that has an amorphous structure, generated by an energy-minimization procedure, gives the best predictions for ethane adsorption, especially at low pressures, suggesting that this model incorporates a good representation of the heterogeneity of the real MCM-41 material. Excellent predictions of the adsorption of pure CO₂ and binary mixtures of ethane and CO₂ in MCM-41 are obtained with the model, further confirming the realism of this model Long-ranged electrostatic interactions are included for the simulation of CO₂, these interactions, which play an important role, are treated by a simple one-dimension summation method, which gives an accurate calculation of the potential.