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Showing 81 to 87 of 87 (0.029 seconds)Spelling suggestions: "subject:"oor"" "subject:"poor""
| 81 |
[pt] DEGRADAÇÃO MECÂNICA DE SOLUÇÕES POLIMÉRICAS EM FLUXO LAMINAR EXTENSIONAL / [en] MECHANICAL DEGRADATION OF POLYMER SOLUTIONS IN EXTENSIONAL LAMINAR FLOWLUA SELENE DA SILVA ALMEIDA 28 June 2021 (has links)
[pt] Devido ao seu comportamento físico-químico, os polímeros solúveis em
água são utilizados em várias fases de perfuração, completação, e produção de
poços de petróleo. Portanto, é fundamental prever e controlar o comportamento em
meio poroso para entender o desempenho do polímero. Experimentos foram
conduzidos para estudar a degradação de uma solução aquosa semi-diluída de PEO,
usando dois capilares com diâmetros de entrada diferentes (100 micrômetros e 200 micrômetros)
ambos com constrição de 50 micrômetros, criando fluxos transientes rápidos em seu centro.
Diferentes vazões foram impostas a fim de observar diferentes taxas de
cisalhamento e de alongamento no sistema. O efluente do fluxo foi coletado e
reinjetado, e suas propriedades reológicas foram utilizadas como proxies para a
degradação. Observamos que, para a contração mais abrupta, a vazão mínima
necessária para degradar a solução é menor. Este resultado, analisado apenas sob a
perspectiva da taxa de cisalhamento, não é razoável, já que a taxa de cisalhamento
na constrição a que o polímero é submetido é igual em ambos os capilares. Portanto,
inferimos que a brusquidão da contração desempenha um papel na degradação, o
que significa que a taxa de alongamento pode ser responsável pela menor taxa de
fluxo crítico. Também foi observado um padrão de como ocorre a degradação com
as injeções subsequentes. Podemos inferir que injeções subsequentes causam
degradação incremental antes de se aproximar de um patamar de estabilização e
que vazões mais altas geram patamares de degradação mais baixos. / [en] Due to their physical-chemical behavior, water-soluble polymers are used
extensively in various phases of drilling, completion, workover, and production of
oil and gas wells. Therefore, it is fundamental to predict and to control in-situ
porous medium behavior in order to understand polymer performance. Experiments
were conducted to study the degradation of a semi diluted (2000 ppm) aqueous
solution of PEO, using two capillaries with different entrance diameter (100 micrometers
and 200 micrometers) both with 50 micrometers radius constriction, creating Fast-Transient Flows in their center. Different injection rates were imposed in order to observe different
shear and extensional rates in the system. The effluent of the flow was collected,
and reinjected, and rheological properties of the fluids were used as proxies for the
degradation of the solution. We observed that for the more abrupt contraction, the
minimum flow rate needed for degrading the polymer solution is lower. This result,
when analyzed purely under shear rate perspective, is not reasonable, since the
constriction shear rates to which the polymer is subjected are equal at both
capillaries. Therefore, we inferred that the abruptness of the contraction plays a
role in the degradation, which means elongational rate may be responsible for the
lower critical flow rate. It was also observed a pattern for how the degradation
occurs with subsequent injections. We could infer that subsequent injections cause
incremental degradation before approaching a stabilization plateau and that higher
flow rates generated lower degradation plateaus.
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| 82 |
Электронный образовательный ресурс как структурный компонент методического обеспечения образовательного процесса СПО : магистерская диссертация / Electronic educational resource as a structural component of the methodological support of the educational process SPOКопылова, Е. А., Kopylova, E. A. January 2020 (has links)
The conclusions of the first Chapter represent the results of the study of theoretical materials. The second Chapter is devoted to the development of an electronic educational resource. These are called requirements, principles, and conditions. The necessity and structure of the ESM scenario plan are determined. The plan-EOR prospectus for the discipline is shown. / Работа включает анализ информационно-образовательной среды, электронный образовательный ресурс как компонент информационной образовательной среды, типы и классы ЭОР, рассматривается ЭОР как дидактическое средство. Посвящена разработке электронного образовательного ресурса. Называются требования, принципы, условия. Определена необходимость и структура сценарного плана ЭОР. Показан план-проспект ЭОР для учебной дисциплины.
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| 83 |
Towards Understanding Interfacial Phenomena in Polymer-CO<sub>2</sub> SystemsTalreja, Manish 01 September 2010 (has links)
No description available.
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| 84 |
'n Vergelykende studie tussen Pt en Pd vir die elektro-oksidasie van waterige SO₂ asook ander model elektrochemiese reaksies / Adri YoungYoung, Adri January 2014 (has links)
The pressure on clean and sustainable energy supplies is increasing. In this regard energy conversion by electrochemical processes plays a major role, for both fuel cell reactions and electrolysis reactions. The sulphur dioxide oxidation reaction (SOR) is a common reaction found in the Hybrid Sulphur Cycle (HyS) and the HyS is a way to produce large-scale hydrogen (H2). The problem with the use of the HyS and fuel cells is the cost involved as large amounts of Pt are required for effective operation. The aim of the study was to determine whether there was an alternative catalyst which was more efficient and cost-effective than Pt. The oxygen reduction reaction (ORR), the ethanol oxidation reaction (EOR) and SOR were studied by means of different electrochemical techniques (cyclovoltammetry (CV), linear polarization (LP) and rotating disk electrode (RDE)) on polycrystalline platinum (Pt) and palladium (Pd). The SRR and EOR are common reactions occurring at the cathode and anode, respectively, in fuel cells and these reactions have been investigated extensively. The reason for studying the reactions was as a preparation for the SOR.
This study compared polycrystalline Pt and Pd for the different reactions, with the main focus on the SOR as Pd is considerably cheaper than Pt, and for the SOR polycrystalline Pd has by no means been investigated intensively. Polycrystalline Pt and Pd were compared by different electrochemical techniques and analyses. The Koutecky-Levich and Levich analyses were used to (i) calculate the number of e- involved in the relevant reaction, (ii) to determine whether the reaction was mass transfer controlled at high overpotentials and (iii) whether the reaction mechanism changed with potential. Next the kinetic current density ( k) was calculated from Koutecky-Levich analyses, which was further used for Tafel slope analyses. If it was not possible to carry out the analyses, the activation energy (Ea) was used to determine the electrocatalytic activity of the catalyst. The electrocatalytic activity was also determined by comparing onset potentials (Es), peak potentials (Ep) and limited/maximum current density ( b/ p) of each catalyst. This study was only a preliminary study for the SOR and therefore, further studies are certainly required. It seemed Pd shows better electrocatalytic activity than Pt for the SRR in an alkaline electrolyte because of similar Es, but Pd produced a higher cathodic current density. Pt showed a lower Es than Pd for the SRR in an acid electrolyte, but Pd delivered a higher cathodic current density. This, therefore, means that the SRR in an acid electrolyte is kinetically more favourable on Pd than on Pt. For the EOR better electrocatalytic activity was obtained with Pd than with Pt in an alkaline electrolyte due to higher current densities at lower potentials and Pd showed lower Ea values than Pt in the potential range normally used for fuel cells. Pd was inactive for EOR in an acid electrolyte, while a reaction occurred on Pt. A possible reason for this observation may be due to the H2 absorbing strongly on Pd thus blocking the active positions on the electrode surfaces, preventing further reaction. Pd showed higher electrocatalytic activity for the SOR due to lower Es and higher current densities at low potentials.
From the RDE studies it was established that the SRR in an alkaline electrolyte on polycrystalline Pt and Pd was mass transfer controlled at low potentials (high overpotentials), but the SRR in an acid electrolyte was only mass transfer controlled on Pt. The SOR was not mass transfer controlled on polycrystalline Pt and Pd at high potentials (high overpotentials). These assumptions were confirmed by Levich analysis.
Using Koutecky-Levich analysis, it was determined that the reaction mechanism on polycrystalline Pt and Pd changed with potential for SRR in an alkaline electrolyte and the SOR. For the SRR in an acid electrolyte the reaction mechanism remained constant with changes in potential on polycrystalline Pd, but the reaction mechanism on polycrystalline Pt changed with potential. These assumptions were confirmed by the number of e-, calculated using Koutecky-Levich analyses. Levich and Koutecky-Levich analyses were not performed for EOR as an increase in rotation speed did not produce an increase in current density.
Tafel slope analyses were conducted by making use of overpotentials and k, where possible. As in the case of ethanol, it was not possible to execute Koutecky-Levich analyses and, therefore, it was not possible to perform Tafel slope analyses using k. Tafel slope analyses for the EOR was therefore performed with normal current densities at 0 rotations per minute (rpm). The reaction mechanisms on Pt and Pd for the SRR in alkaline and acidic electrolytes differed due to different Tafel slopes. Pt and Pd displayed similar Tafel slopes for the EOR in alkaline electrolyte, thus suggesting that the reaction mechanisms on Pt and Pd were the same. For the SOR it seemed that the reaction mechanism on Pt and Pd were similar because of similar Tafel slopes. This was only a preliminary and comparative study for polycrystalline Pt and Pd, and the reaction mechanism was not further studied by means of spectroscopic techniques. / MSc (Chemistry), North-West University, Potchefstroom Campus, 2014
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| 85 |
'n Vergelykende studie tussen Pt en Pd vir die elektro-oksidasie van waterige SO₂ asook ander model elektrochemiese reaksies / Adri YoungYoung, Adri January 2014 (has links)
The pressure on clean and sustainable energy supplies is increasing. In this regard energy conversion by electrochemical processes plays a major role, for both fuel cell reactions and electrolysis reactions. The sulphur dioxide oxidation reaction (SOR) is a common reaction found in the Hybrid Sulphur Cycle (HyS) and the HyS is a way to produce large-scale hydrogen (H2). The problem with the use of the HyS and fuel cells is the cost involved as large amounts of Pt are required for effective operation. The aim of the study was to determine whether there was an alternative catalyst which was more efficient and cost-effective than Pt. The oxygen reduction reaction (ORR), the ethanol oxidation reaction (EOR) and SOR were studied by means of different electrochemical techniques (cyclovoltammetry (CV), linear polarization (LP) and rotating disk electrode (RDE)) on polycrystalline platinum (Pt) and palladium (Pd). The SRR and EOR are common reactions occurring at the cathode and anode, respectively, in fuel cells and these reactions have been investigated extensively. The reason for studying the reactions was as a preparation for the SOR.
This study compared polycrystalline Pt and Pd for the different reactions, with the main focus on the SOR as Pd is considerably cheaper than Pt, and for the SOR polycrystalline Pd has by no means been investigated intensively. Polycrystalline Pt and Pd were compared by different electrochemical techniques and analyses. The Koutecky-Levich and Levich analyses were used to (i) calculate the number of e- involved in the relevant reaction, (ii) to determine whether the reaction was mass transfer controlled at high overpotentials and (iii) whether the reaction mechanism changed with potential. Next the kinetic current density ( k) was calculated from Koutecky-Levich analyses, which was further used for Tafel slope analyses. If it was not possible to carry out the analyses, the activation energy (Ea) was used to determine the electrocatalytic activity of the catalyst. The electrocatalytic activity was also determined by comparing onset potentials (Es), peak potentials (Ep) and limited/maximum current density ( b/ p) of each catalyst. This study was only a preliminary study for the SOR and therefore, further studies are certainly required. It seemed Pd shows better electrocatalytic activity than Pt for the SRR in an alkaline electrolyte because of similar Es, but Pd produced a higher cathodic current density. Pt showed a lower Es than Pd for the SRR in an acid electrolyte, but Pd delivered a higher cathodic current density. This, therefore, means that the SRR in an acid electrolyte is kinetically more favourable on Pd than on Pt. For the EOR better electrocatalytic activity was obtained with Pd than with Pt in an alkaline electrolyte due to higher current densities at lower potentials and Pd showed lower Ea values than Pt in the potential range normally used for fuel cells. Pd was inactive for EOR in an acid electrolyte, while a reaction occurred on Pt. A possible reason for this observation may be due to the H2 absorbing strongly on Pd thus blocking the active positions on the electrode surfaces, preventing further reaction. Pd showed higher electrocatalytic activity for the SOR due to lower Es and higher current densities at low potentials.
From the RDE studies it was established that the SRR in an alkaline electrolyte on polycrystalline Pt and Pd was mass transfer controlled at low potentials (high overpotentials), but the SRR in an acid electrolyte was only mass transfer controlled on Pt. The SOR was not mass transfer controlled on polycrystalline Pt and Pd at high potentials (high overpotentials). These assumptions were confirmed by Levich analysis.
Using Koutecky-Levich analysis, it was determined that the reaction mechanism on polycrystalline Pt and Pd changed with potential for SRR in an alkaline electrolyte and the SOR. For the SRR in an acid electrolyte the reaction mechanism remained constant with changes in potential on polycrystalline Pd, but the reaction mechanism on polycrystalline Pt changed with potential. These assumptions were confirmed by the number of e-, calculated using Koutecky-Levich analyses. Levich and Koutecky-Levich analyses were not performed for EOR as an increase in rotation speed did not produce an increase in current density.
Tafel slope analyses were conducted by making use of overpotentials and k, where possible. As in the case of ethanol, it was not possible to execute Koutecky-Levich analyses and, therefore, it was not possible to perform Tafel slope analyses using k. Tafel slope analyses for the EOR was therefore performed with normal current densities at 0 rotations per minute (rpm). The reaction mechanisms on Pt and Pd for the SRR in alkaline and acidic electrolytes differed due to different Tafel slopes. Pt and Pd displayed similar Tafel slopes for the EOR in alkaline electrolyte, thus suggesting that the reaction mechanisms on Pt and Pd were the same. For the SOR it seemed that the reaction mechanism on Pt and Pd were similar because of similar Tafel slopes. This was only a preliminary and comparative study for polycrystalline Pt and Pd, and the reaction mechanism was not further studied by means of spectroscopic techniques. / MSc (Chemistry), North-West University, Potchefstroom Campus, 2014
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| 86 |
Kurz- und langfristige Angebotskurven für Rohöl und die Konsequenzen für den MarktSchlothmann, Daniel 20 April 2016 (has links) (PDF)
In dieser Arbeit wurden Angebotskurven für 22 bedeutende Ölförderländer ermittelt und anschließend zu globalen Angebotskurven aggregiert. Gemäß den ermittelten Angebotskurven sind nahezu alle gegenwärtig in der Förderphase befindlichen Ölprojekte in den Untersuchungsländern auch beim aktuellen Ölpreis von 35 bis 40 US-$ je Barrel unter Berücksichtigung der kurzfristigen Grenzkosten rentabel. Sollte der Ölpreis jedoch in den kommenden Jahren auf diesem Niveau verharren, wird es bis zum Jahr 2024 zu einem Angebotsengpass auf dem globalen Ölmarkt kommen, da zur Deckung der zukünftigen Nachfrage die Erschließung kostenintensiver, unkonventioneller Lagerstätten und von Lagerstätten in tiefen und sehr tiefen Gewässern notwendig ist. Damit es bis zum Jahr 2024 nicht zu einem solchen Angebotsengpass kommt, ist gemäß des ermittelten langfristigen Marktgleichgewichts ein Ölpreis von mindestens 80 (2014er) US-$ je Barrel notwendig.
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| 87 |
Kurz- und langfristige Angebotskurven für Rohöl und die Konsequenzen für den MarktSchlothmann, Daniel 08 March 2016 (has links)
In dieser Arbeit wurden Angebotskurven für 22 bedeutende Ölförderländer ermittelt und anschließend zu globalen Angebotskurven aggregiert. Gemäß den ermittelten Angebotskurven sind nahezu alle gegenwärtig in der Förderphase befindlichen Ölprojekte in den Untersuchungsländern auch beim aktuellen Ölpreis von 35 bis 40 US-$ je Barrel unter Berücksichtigung der kurzfristigen Grenzkosten rentabel. Sollte der Ölpreis jedoch in den kommenden Jahren auf diesem Niveau verharren, wird es bis zum Jahr 2024 zu einem Angebotsengpass auf dem globalen Ölmarkt kommen, da zur Deckung der zukünftigen Nachfrage die Erschließung kostenintensiver, unkonventioneller Lagerstätten und von Lagerstätten in tiefen und sehr tiefen Gewässern notwendig ist. Damit es bis zum Jahr 2024 nicht zu einem solchen Angebotsengpass kommt, ist gemäß des ermittelten langfristigen Marktgleichgewichts ein Ölpreis von mindestens 80 (2014er) US-$ je Barrel notwendig.:1. Einleitung
2. Rohöl - Eine naturwissenschaftliche Einführung
3. Charakteristika von Rohölprojekten
4. Historie der Ölindustrie
5. Ökonomik von Rohölprojekten
6. Fallstudien zu den bedeutendsten Förderländern
7. Ermittlung regionaler und globaler Angebotskurven
8. Zusammenfassung
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