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Івченко, Олександр Володимирович, Александр Владимирович Ивченко, Oleksandr Volodymyrovych Ivchenko та В. М. Хярм. "Дослідження підходів щодо визначення якості та ефективності управлінських рішень в органах виконавчої влади". Thesis, Вид-во СумДУ, 2010. http://essuir.sumdu.edu.ua/handle/123456789/5586.
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Diène, Oumy. "La délégation de pouvoirs dans les sociétés commerciales de droit OHADA." Thesis, Bordeaux, 2018. http://www.theses.fr/2018BORD0131/document.
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C’est avec une ambition modeste que la délégation de pouvoirs est admise dans les sociétés commerciales de droit OHADA. La société anonyme en est la structure d’accueil. Les u travailorganes sociaux en sont les acteurs. Elle est mise en œuvre pour faire face une urgence due à l’empêchement du président ou pour asseoir la rapidité d’une action relative à une opération financière. Or, étant aujourd’hui reconnue comme technique de bonne gouvernance, la délégation de pouvoirs pour remplir une telle fonction en droit OHADA, est à généraliser. Tout dirigeant social doit avoir la liberté d’y recourir et les salariés, plus proches des réalités du terrain, doivent y être associés. Une telle appréhension de la délégation de pouvoirs appelle la conception d’un régime juridique précis qui garantit son jeu loyal<br>It is with the modest ambition that the delegation of power is admitted in the trading companies of OHADA law. The limited company is the reception center and social organs are the actors. It is implemented to face an urgency due to the hindrance of the president or to establish the speed of a financial transaction. Yet, being now acknowledged as a good governance practice, the delegation of power should be generalized to satisfy such a function in OHADA law. Every social leader has to have the freedom to use it and employees, closer to realities of the ground, must be associated there. Such an apprehension of the delegation of power calls the conception of a precise legal regime which guarantees its loyal play
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Boltyanskiy, Boris. "Operation of the heat and power complex Alatyr to power Russian oil and gas facilities." Thesis, KTH, Skolan för industriell teknik och management (ITM), 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-264245.
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B. Boltyansky Operation of the heat and power complex Alatyr to power Russian oil and gas facilities, Master's Dissertation, 2017 - 102 pages, 26 tables, 30 figures Supervisor Prof. V. G. Kucherov, Doctor of Sciences, Department of Energy Technology. The work includes the following. A calculation of the main thermodynamic cycle of the heat and power complex Alatyr heat and power complex. A consideration of various schemes of using the Rankine organic cycle WERE integrated in the Alatyr heat and power complex with the aim of increasing energy efficiency. Conclusions about the feasibility of using the heat and power complex Alatyr. Conclusions about the feasibility of integration of the organic Rankine cycle. Economic comparison of the heat and power complex Alatyr with similar facilities on the distributed power generation market. Economic analysis of the comparison of energy blocks of HPC Alatyr with similar designs from other countries.<br>B. Boltyansky Drift av värme- och kraftkomplexet Alatyr till makten Ryska olje- och gasanläggningar, Masters uppläggning, 2017 - 102 sidor, 26 tabeller, 30 figurer Handledare Prof. VG Kucherov, doktorsexamen, kandidatexamen för teknisk vetenskap, institutionen för termodynamik och termisk motorer. Arbetet innehåller följande. En beräkning av värmekraftkomplexets värmeoch kraftkomplex Alatyrs värmekomplex. En övervägning av olika system för användning av Rankine organiska cykeln var integrerad i Alatyr värme- och kraftkomplexet i syfte att öka energieffektiviteten. Slutsatser om möjligheten att använda värme- och kraftkomplexet Alatyr. Slutsatser om möjligheten att integrera den organiska Rankine-cykeln. Ekonomisk jämförelse av värme- och kraftkomplexet Alatyr med liknande anläggningar på den distribuerade kraftproduktionsmarknaden. Ekonomisk analys av jämförelsen av energiblock av HPC Alatyr med liknande konstruktioner från andra länder.
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Jradi, Fadi M. "Organic light-harvesting materials for power generation." Diss., Georgia Institute of Technology, 2016. http://hdl.handle.net/1853/54976.
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This dissertation focuses on the design, synthesis, and characterization of a variety of organic dyes, semiconducting materials, and surface redox-active modifiers of potential interest to organic-based emerging photovoltaics. A discussion of the materials’ optoelectronic properties, their ability to modify and promote electron transfer through an organic/transparent conducting-oxide interface, and finally their effect on the photovoltaic properties of devices utilizing them as light-harvesters is provided where relevant. The first two research chapters discuss mono-chromophoric asymmetric squaraine-based sensitizers and covalently linked, dual-chromophoric, porphyrin-squaraine sensitizers as light absorbers in dye-sensitized solar cells (DSSCs), in an attempt to address two problems often encountered with DSSCs utilizing this class of near infra-red sensitizers; The lack of panchromatic absorption and aggregation on the surface. Also, this dissertation discusses the design and synthesis of asymmetric perylene diimide phosphonic acid (PDI-PA) redox-active surface modifiers, and reports on the electron-transfer rates and efficiencies across the interface of an ITO electrode (widely used in organic-electronic devices) modified with these perylene diimides. Finally two series of hole-transport materials based on oligothiophenes and benzodithiophenes are reported: optoelectronic properties and preliminary performance of organic photovoltaic (OPV) devices fabricated with them is discussed.
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Stwayi, MB. "Identification and quantification of organ species in power station feedwater." Thesis, Cape Peninsula University of Technology, 2013. http://hdl.handle.net/20.500.11838/735.
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Carlsson, Marcus. "Synthesis and optical characterization of optical power limiting platinum(II) acetylides." Doctoral thesis, Umeå : Chemistry Kemi, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-1130.
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Rohan, James Francis. "A fundamental investigation of the lithium/organic solvent interface." Thesis, University of Southampton, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239679.
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Arslan, Omer. "Modelling emissions of VOCs in modern power plants." Thesis, Imperial College London, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.289852.
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Chow, Philip Chi Yung. "Time-resolved optical studies of excited states in organic photovoltaic diodes." Thesis, University of Cambridge, 2014. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.708343.
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Murugan, V. A. "Synthesis and characterization of organo-inorganic conducting polymer based nanocomposites for electrochemical power sources." Thesis(Ph.D.), CSIR-National Chemical Laboratory, Pune, 2004. http://dspace.ncl.res.in:8080/xmlui/handle/20.500.12252/2422.
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Höchemer, Ralf H. Hoffmann Michael R. "Degradation of organic compounds by acoustic cavitation and pulsed-power discharges /." Diss., Pasadena, Calif. : California Institute of Technology, 1996. http://resolver.caltech.edu/CaltechETD:etd-06262006-111213.
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Joyner, Valencia M. (Valencia Margie) 1976. "A low power display architecture for organic light emitting diode microdisplays." Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/9460.
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Thesis (M.Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1999.<br>Includes bibliographical references (p. 75-78).<br>Organic light-emitting diode (OLED) devices offer a very promising alternative to existing flat panel display technologies, such as liquid crystal displays (LCD) that currently dominate the market. OLED displays offer very attractive characteristics, including higher luminous, larger viewing angle, and low-power consumption, over the established LCD technology. The ability to integrate OLED devices on a silicon microchip is one of the most favorable characteristics of this new technology. The primary goal of this research project is to implement a low-power display driver circuit for an OLED microdisplay. The implementation will be chosen based on the outcome of a feasibility study aimed at investigating the various options available for addressing the display and the design requirements imposed by the operation of the OLED. There are three primary design options to be considered: 1 ). Passive Matrix Addressing with sequentially addressed rows/columns, 2). Active Matrix Addressing with sequentially addressed rows/columns and dynamic storage at each pixel, and 3). Active Matrix Addressing with sequentially addressed rows/columns and static storage at each pixel. Each implementation is compared in terms of the overall power consumed in driving the high capacitance row and column lines in the display matrix.<br>by Valencia M. Joyner.<br>M.Eng.
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Bhandari, Yashpal. "Star-shaped molecules for organic photovoltaics synthesis and structure-property relationships /." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 188 p, 2007. http://proquest.umi.com/pqdweb?did=1313923651&sid=2&Fmt=2&clientId=8331&RQT=309&VName=PQD.
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Bomfim, Betty Anubia Azevedo. "Clima organizacional e gespública: um estudo em um órgão público da cidade de Manaus." Universidade Federal da Paraíba, 2008. http://tede.biblioteca.ufpb.br:8080/handle/tede/6875.
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Previous issue date: 2008-08-29<br>Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES<br>To present research treats of the organizational climate in a public Organ of the
Judiciary Power of the city of Manaus. The interest for the proposed theme lives in
the perception concerning the dizzy change in the world of the organizations,
phenomenon that reached the public sphere. For an appropriate approach of the
theme it is vital presentation of some linked topics to the theme, like this being, this
work is composed by two chapters. The first chapter contemplates the concepts and
theoretical approaches on organizational climate, besides the characterization of the
place of the research. The second chapter treats of the methods and techniques
used in the research, as well as the description of the population, instruments and
procedures adopted for what intends the present study. The objective of this study
was to analyze the organizational climate of a Public Organ of the Judiciary Power in
Manaus / Am, starting from the comparison between the first and the second
instance of the referred Organ. The main hypothesis that orientated the research was
the one that difference exists among the organizational climate noticed by the
servants of the 1st and 2nd instances in the researched Public organ. Starting from
this work, he hopes to produce knowledge for the understanding of the operation of
the organization in the public service.<br>A presente pesquisa trata do clima organizacional em um Órgão público do Poder
Judiciário da cidade de Manaus. O interesse pelo tema proposto reside na
percepção acerca da vertiginosa mudança no mundo das organizações, fen6omeno
que alcançou a esfera pública. Para uma adequada abordagem do tema é vital
apresentação de alguns tópicos ligados ao tema, assim sendo, este trabalho é
composto por dois capítulos. O primeiro capítulo contempla os conceitos e
abordagens teóricas sobre clima organizacional, além da caracterização do local da
pesquisa. O segundo capítulo trata dos métodos e técnicas utilizadas na pesquisa,
assim como a descrição da população, instrumentos e procedimentos adotados para
o que se propõe o presente estudo. O objetivo deste estudo foi Analisar o clima
organizacional de um Órgão Público do Poder Judiciário em Manaus/Am, a partir da
comparação entre a primeira e a segunda instância do referido Órgão. A hipótese
principal que norteou a pesquisa foi a de que existe diferença entre o clima
organizacional percebido pelo servidores da 1ª e 2ª instâncias no Órgão Público
pesquisado. A partir deste trabalho, espera-se produzir conhecimento para a
compreensão do funcionamento da organização no serviço público
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Morris, Christopher. "Synchrotron powder diffraction studies of metal-organic frameworks." Thesis, University of Nottingham, 2017. http://eprints.nottingham.ac.uk/41941/.
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This thesis describes a variety of high resolution synchrotron powder diffraction studies of guest-loaded metal-organic frameworks (MOFs). These studies have been used to provide insight into the binding mechanisms of the guest molecules. Chapter 1 contains an introduction to MOFs, highlighting some potential applications that were investigated in this work. A description of the powder diffraction analysis techniques is also included. Chapter 2 describes the design and implementation of a remote control gas dosing system for use on the powder diffraction beamline (I11) at Diamond Light Source. To assess the precision of this system, and to gain an insight into the high CO2/N2 selectivity of the V(III) MOF, MFM-300(V), an in situ powder diffraction experiment was performed, firstly using pure CO2 and then with an equimolar mixture of CO2/N2. Two CO2 sites were found in all cases, with CO2-A forming a dipole-dipole interaction with the framework’s hydroxyl group, and CO2-B interacting with CO2-A via further dipole-dipole interaction. In the presence of N2, particularly at low loadings, the positions of the CO2 molecules vary quite significantly due to the presence of disordered N2 within the pore. Further to this investigation, the long term SO2 adsorption stability of the Al(III) MOF, MFM-300(Al), was studied by powder diffraction. The SO2-loaded MOF was found to remain stable over a period of 37 weeks. In Chapter 3, an investigation into the C8 hydrocarbon vapour adsorption and liquid phase separation properties of MFM-300(M) (M=Al, V, In) is described, with supporting structural information obtained from high resolution powder diffraction. In the vapour phase, MFM-300(Al) was the only MOF of the three studied to show any discrimination between the 4 isomers, whereas in the liquid phase, it showed no significant separation. Conversely, MFM-300(In) showed the highest degree of separation of m-xylene from ethylbenzene and o-, and p-xylene, however this was accompanied by poor separation of ethylbenzene and o-xylene. MFM-300(V) showed a lesser degree of separation of m-xylene from ethylbenzene and o-, and pxylene, but with a much better separation of ethylbenzene and o-xylene. The structural studies revealed π-π stacking interactions between the C8 hydrocarbons and the phenyl ring of the framework, and in the case of MFM-300(In)(p-xylene), tetragonal I4122 → orthorhombic I212121 phase change was observed. To further investigate the apparent flexible nature of MFM-300(In), high pressure powder diffraction was used, and a similar phase change was observed at 0.584 GPa. Chapter 4 describes the synthesis and characterisation of a Zr(IV) MOF, MFM-450. The CO2 and N2 adsorption properties of this MOF were investigated, and it was found to adsorb 2.32 mmol/g CO2 at 273 K, followed by 1.97 mmol/g CO2 at 283 K, and 1.48 mmol/g CO2 at 298 K. The N2 adsorption at these temperatures was negligible, resulting in high selectivities. To investigate the nature of CO2 binding in MFM-450, in situ powder diffraction was used. Two CO2 adsorption sites were found. The site in cage A was found to interact with the phenyl ring of the framework via π-π interactions, and the site in cage B interacts with the carboxylate group of the phenyl ring via a dipole-dipole interaction.
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Lambert, Damien Jean Henri. "Growth and characterization of group III-nitride power transistors, power rectifiers and solar-blind detectors by metalorganic chemical vapor deposition /." Full text (PDF) from UMI/Dissertation Abstracts International, 2000. http://wwwlib.umi.com/cr/utexas/fullcit?p3004311.
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Gilfillan, Andrew James. "Structure and reactivity of coal fractions related to characterisation using total reflectance histograms." Thesis, University of Nottingham, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.301662.
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Schilinsky, Pavel. "Loss analysis of the power conversion efficiency of organic bulk heterojunction solar cells." [S.l.] : [s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=975187546.
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Kozanoglu, Duygu. "Power Conversion Efficiency Enhancement Of Organic Solar Cells By Addition Of Gold Nanoparticles." Master's thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614702/index.pdf.
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In the first part of the study, power conversion efficiency enhancement of organic solar cells by addition of gold nanorods and gold nanostars into PEDOT: PSS (Poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate)) layer was investigated. Efficiency of each sample set has been characterized by measuring current density-voltage characteristics. The best efficiencies obtained during this study are 2.88 % and 2.54 % by addition of gold nanostars and nanorods, respectively. The increase in PCEs is notable when these values are compared with the ones (1.67 %) obtained with a reference device which is prepared without adding any gold nanoparticles under the same conditions.
In the second part of the study, branched gold nanoparticles were succesfully grown directly on different types of surfaces such as glass, silicon wafer, and indium-tin-oxide (ITO) coated glass with a simple solution-based method in order to utilize them for further applications.
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McBride, Lorraine. "Determination of organic crystal structures by X ray powder diffraction." Thesis, University of Strathclyde, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.248694.
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Jiang, Chen. "All-inkjet-printed low-voltage organic thin-film transistors." Thesis, University of Cambridge, 2019. https://www.repository.cam.ac.uk/handle/1810/285012.
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This thesis presents the development of all-inkjet-printed low-voltage organic thin-film transistors. Organic thin-film transistors (OTFTs), taking advantage of low-temperature printability, mechanical flexibility, and multi-functionality, are promising for a wide range of emerging applications such as wearable electronics. Printed OTFTs provide great benefits in fabrication cost reduction, but they need a very high operating voltage and exhibit severe instability during storage and operation in ambient environment. In this study, all-inkjet-printed OTFTs with a low operating voltage of less than 3 V are demonstrated through reducing trap density in the fabricated devices. The transistors use 6,13-bis(triisopropylsilylethynyl)pentacene as the semiconductor, poly(4-vinylphenol) as the dielectric, silver as the electrodes, and CYTOP as the encapsulation. Several aspects of physical and chemical properties of polymer dielectrics are studied to achieve this goal, including cross-linking, wetting, and moisture affinity. Through the careful selection of device architecture and control of the inkjet-printing processes, the semiconductor-dielectric interface trap density of the fabricated OTFTs is significantly reduced. The applicability of this approach to different materials is also investigated and confirmed, including polyvinyl cinnamate as the dielectric, 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene as the semiconductor, and anisole as the solvent for semiconductor inks. Based on the investigation of different materials, the characteristics and parameters of all-inkjet-printed OTFTs are optimised, demonstrating an ultra-steep subthreshold of 60.2 mV/decade approaching the theoretical limit and a low operating voltage of 1 V. In order to explore their feasibility in real-world applications, the stability of all-inkjet-printed OTFTs is investigated and the factors of instability are analysed. Based on these findings, the stability of the fabricated device is improved, such that the threshold voltage shift is less than 0.1 V in ambient environment storage for 3 months and operation for 1 hour. The electrical characteristics of OTFTs in the subthreshold regime are studied for analogue circuit design. Based on the developed low-voltage stable transistors, an ultra-low-power (< 1 nW) high-gain (> 200 V/V) amplifier is presented and utilised to detect electrophysiological signals from the human body.
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Li, Liang. "Experimental and theoretical investigation of CO2 trans-critical power cycles and R245fa organic Rankine cycles for low-grade heat to power energy conversion." Thesis, Brunel University, 2017. http://bura.brunel.ac.uk/handle/2438/14766.
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Globally, there are vast amounts of low-grade heat sources from industrial waste and renewables that can be converted into electricity through advanced thermodynamic power cycles and appropriate working fluids. In this thesis, experimental research was conducted to investigate the performance of a small-scale Organic Rankine Cycle (ORC) system under different operating conditions. The experimental setup consisted of typical ORC system components, such as a turboexpander with a high speed generator, a scroll expander, a finned-tube condenser, an ORC pump, a plate evaporator and a shell and tube evaporator. R245fa was selected as the working fluid, on account of its appropriate thermophysical properties for the ORC system and its low ozone depletion potential (ODP). The test rig was fully instrumented and extensive experiments carried out to examine the influences of several important parameters, including heat source temperature, ORC pump speed, heat sink flow velocity, different evaporators and with or without a recuperator on overall R245fa ORC performances. In addition, in terms of the working fluid’s environmental impact, temperature match of the cycle heat processes and system compactness, CO2 transcritical power cycles (T-CO2) were deemed more applicable for converting low-grade heat to power. However, the system thermal efficiency of T-CO2 requires further improvement. Subsequently, a test rig of a small-scale power generation system with T-CO2 power cycles was developed with essential components connected; these included a plate CO2 supercritical heater, a CO2 transcritical turbine, a plate recuperator, an air-cooled finned-tube CO2 condenser and a CO2 liquid pump. Various preliminary test results from the system measurements are demonstrated in this thesis. At the end, a theoretical study was conducted to investigate and compare the performance of T-CO2 and R245fa ORCs using low-grade thermal energy to produce useful shaft or electrical power. The thermodynamic models of both cycles were developed and applied to calculate and compare the cycle thermal and exergy efficiencies at different operating conditions and control strategies. In this thesis, the main results showed that the thermal efficiency of the tested ORC system could be improved with an increased heat source temperature in the system with or without recuperator. When the heat source temperature increased from 145 oC to 155 oC for the system without recuperator, the percentage increase rates of turbine power output and system thermal efficiency were 13.6% and 14% respectively while when the temperature increased from 154 oC to 166 oC for the system with recuperator, the percentage increase rates were 31.2% and 61.97% respectively. In addition, the ORC with recuperator required a relative higher heat source temperature, which is comparable to a system without recuperator. On the other hand, at constant heat source temperatures, the working fluid pump speed could be optimised to maximise system thermal efficiency for ORC both with and without recuperator. The pressure ratio is a key factor impacting the efficiencies and power generation of the turbine and scroll expander. Maximum electrical power outputs of 1556.24W and 750W of the scroll expander and turbine were observed at pressure ratio points of 3.3 and 2.57 respectively. For the T-CO2 system, the main results showing that the CO2 mass flow rate could be directly controlled by varying the CO2 liquid pump speeds. The CO2 pressures at the turbine inlet and outlet and turbine power generation all increased with higher CO2 mass flow rates. When CO2 mass flow rate increased from 0.2 kg/s to 0.26kg/s, the maximum percentage increase rates of measured turbine power generation was 116.9%. However, the heat source flow rate was found to have almost negligible impact on system performance. When the thermal oil flow rate increased from 0.364kg/s to 0.463kg/s, the maximum percentage increase rate of measured turbine power generation was only 14.8%. For the thermodynamic analysis, with the same operating conditions and heat transfer assumptions, the thermal and exergy efficiencies of R245fa ORCs are both slightly higher than those of T-CO2. However, the efficiencies of both cycles can be enhanced by installing a recuperator at under specific operating conditions. The experiment and simulation results can thus inform further design and operation optimisations of both the systems and their components.
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Yan, Jack Z. "Organic view of power, a study in the context of organizational analysis and management." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ39898.pdf.
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Conner, Kayleigh. "Revolutionary Destruction in Charlotte Dacre’s Oeuvre Women Finding Power through Fragmentation, Performance, and Orgasm." VCU Scholars Compass, 2019. https://scholarscompass.vcu.edu/etd/5815.
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This thesis attends to the examination of the history-obscured oeuvre of Charlotte Dacre (1771/2-1825), a British woman of Portuguese-Jewish descent and an author of Gothic works in the early nineteenth century. Although her second novel, Zofloya (1806), made a splash in criticism, both during her lifetime and continuing into current scholarship, most of her other works––three novels and two volumes of poetry––are almost completely unstudied. Therefore, the main goal of this thesis is to explore and shed light on the deeply rich implications concerning subjects such as gender, class, race, and sexuality existent in Dacre’s lesser-known works. Although most of Dacre’s oeuvre has not been studied in depth, another goal of this thesis is to argue the importance of the implementation of further research on this body of works, especially for scholarly fields such as gender studies, women’s studies, and queer studies.
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OYEKALE, JOSEPH OYETOLA. "Modelling, thermoeconomic analysis and optimization of hybrid solar-biomass organic Rankine cycle power plants." Doctoral thesis, Università degli Studi di Cagliari, 2020. http://hdl.handle.net/11584/284453.
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The need for modern energy systems to embrace the requirements of energy security, sustainability and affordability in their designs has placed emphatic importance on exploitation of renewable resources, such as solar and wind energy, etc. However, these resources often lead to reduced reliability and dispatchability of energy systems; less-efficient conversion processes; high cost of power production; etc. One promising way to ameliorate these challenges is through hybridization of renewable energy resources, and by using organic Rankine cycle (ORC) for power generation. Thus, this PhD research project is aimed at conceptual design and techno-economic optimization of hybrid solar-biomass ORC power plants.
The methodologies adopted are in four distinct phases:
- First, novel hybrid concentrated solar power (CSP)-biomass scheme was conceived that could function as retrofit to existing CSP-ORC plants as well as in new hybrid plant designs. Thermodynamic models were developed for each plant sub-unit, and yearly techno-economic performance was assessed for the entire system. Specifically, the ORC was modelled based on characteristics of an existing CSP-ORC plant, which currently operates at Ottana, Italy. Off-design models of ORC components were integrated, and their performance was validated using experimental data obtained from the aforementioned real plant.
- Second, detailed exergy and exergoeconomic analyses were performed on the proposed hybrid plant, in order to examine the system components with remarkable optimization potentials. The evaluation on optimization potentials considered intrinsic irreversibilities in the respective components, which are imposed by assumptions of systemic and economic constraints. This has been termed enhanced exergy and enhanced exergoeconomic analyses here.
- Third, the techno-economic implications of using siloxane mixtures as ORC working fluid were investigated, with the aim of improving heat transfer processes in the ORC plant. The studied fluid pairs were actively selected to satisfy classical thermodynamic requirements, based on established criteria.
- Fourth, the biomass retrofit system was optimized multi-objectively, to minimize biomass consumption rate (maximize exergetic efficiency) and to minimize exergy cost rate. Non-dominated Sorting Genetic Algorithm (NSGA-II) was adopted for multi-objective optimization.
The conceptual scheme involves parallel hybridization of CSP and biomass systems, such that each is capable of feeding the ORC directly. Results showed that the proposed biomass hybridization concept would increase both thermodynamic efficiency and economic performance of CSP-ORC plants, thereby improving their market competitiveness. Total exergy destroyed and exergy efficiency were quantified for each component, and for the whole system. Overall system exergetic efficiency of about 7 % was obtained. Similarly, exergoeconomic factor was obtained for each system component, and their implications were analysed to identify system components with high potentials for optimization. Furthermore, it was observed that thermodynamic performance of the hybrid plant would be optimized by using siloxane mixtures as ORC working fluid. However, this would result in larger heat exchange surface area, with its attendant cost implications. Lastly, biomass combustion and furnace parameters were obtained, which would simultaneously optimize exergetic efficiency and exergy cost rate for the hybrid plant.
In sum, a novel scheme has been developed for hybridizing solar and biomass energy for ORC plants, with huge potentials to improve techno-economic competitiveness of solar-ORC systems.
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BALASUBRAMANIAN, GANESH. "EVALUATING THE EFFECT OF SELECTED PROCESS PARAMETERS ON THE PHOTOCATALYTIC DEGRADATION OF ORGANIC POLLUTANTS." University of Cincinnati / OhioLINK, 2002. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1012410668.
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Gilpin, Dawn R. "Organically Grown: Emergent Power and Influence in Complex Issue Networks." Diss., Temple University Libraries, 2008. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/14633.
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Mass Media and Communication<br>Ph.D.<br>While issues management is an important area of research and practice in organizational communication and public relations, the literature focuses primarily on instrumental applications. Conceiving of issue networks--loose configurations of institutional actors, interest groups, organizations, technical specialists, and concerned citizens--as complex systems of interconnected agents offers a fresh perspective on the ways power and influence are exercised and negotiated among organizations, the media, and policymaking bodies. Combined use of social and semantic network analysis makes it possible to examine complex, dynamic linkages between social relationships and conceptual positions. This paper reports on a study of the organic foods issue network in the United States, based on the minutes of National Organics Standards Board meetings and media coverage of the issue. The use of textual as well as relational data allows for more sophisticated computations of patterns, providing insight on power structures as well as organizational and issue identities. This study is intended as a first step toward understanding the mechanisms of issue emergence and development as an aid for scholars and practitioners of media communication, organizational issues management, cultural economy, and policy studies.<br>Temple University--Theses
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Fernandes, Philippe. "Advanced strategies for determining organic crystal structures from powder diffraction data." Thesis, University of Strathclyde, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.438466.
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Chandrasekaran, Vetrivel. "Virtual Modeling and Optimization of an Organic Rankine Cycle." The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1408456065.
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Schemme, Thomas [Verfasser], and Cornelia [Akademischer Betreuer] Denz. "Light control and solar power conversion by organic optoelectronic assemblies / Thomas Schemme ; Betreuer: Cornelia Denz." Münster : Universitäts- und Landesbibliothek Münster, 2019. http://d-nb.info/1201729556/34.
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Al-Jasser, Abdulaziz Omer. "Effects of power level, organic loading and temperature on the performance of facultative aerated lagoons." Thesis, University of Newcastle Upon Tyne, 1995. http://hdl.handle.net/10443/1668.
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Facultative aerated lagoons are aerated lagoons operated at low power levels and are wastewater stabilization ponds with artificial aeration. These lagoons are used more commonly than aerobic aerated lagoons because a satisfactory effluent can be produced with a lower power input. The power level applied to facultative aerated lagoons is sufficient only to satisfy the oxygen demand but not adequate to keep all the solids in suspension and settled solids will decompose aerobically and anaerobically. In the study reported, laboratory-model facultative aerated lagoons of 81 litres volume, aerated with diffused air, were used to study the performance of such lagoons in the treatment of municipal wastewater. Different combinations of four power levels, 0.25,0.5,1 and 2.0 W/m3, three different organic loadings, 20,33 and 62 g BOD5/m3d. , and two temperature levels, 20°C and 30°C, were applied in twenty four experimental runs. Influent and effluent were sampled on a regular basis and their characteristics were determined. The effluent from the model facultative aerated lagoons was always of reasonable quality, with respect to BOD5, COD and suspended solids. This was achieved with no provision for effluent settling or additional treatment. Removals of 91 percent BOD5 and 67 percent COD could be achieved for unfiltered samples. Effluent BOD5 of 13 mg/l in the filtered samples and 31 mg/l in the unfiltered samples was attainable in these lagoons. Effluent suspended solids levels as low as 41 mg/i were also obtained. Thus facultative aerated lagoons will provide both biological and physical treatment operations in a single earthen tank. Because suspended solids in the effluent from facultative aerated lagoons are low, no sludge disposal or processing is needed on a continuous basis. Other performance criteria; nitrogen, phosphorus, iii chlorophyll "a", Escherichia. coli and faecal streptococci, are reported on in the thesis. It was observed that the level of power introduced into the facultative aerated lagoon had positive and significant effects on some performance parameters, including BOD5 and COD filtered removal rate coefficients, removal efficiencies for BOD5 and COD (except for COD removal in facultative aerated lagoons operated at high temperature, 30°C) and effluent suspended solids and negative and significant effects for others, such as suspended solids removal efficiency. The effect of power was insignificant for other parameters, especially BOD5 and COD unfiltered removal rate coefficients. The effect of power level on filtered removal efficiencies was higher than on unfiltered ones. BOD5 and COD removal efficiencies were negatively affected by organic loading (or positively by retention time) and the effect was found to be significant. The organic loading effect was significant and positive on filtered BOD5 and both filtered and unfiltered COD removal rate coefficients whereas it was negative on unfiltered BOD5 removal rate coefficients. Temperature had significant and positive effects on some parameters, including removal rate coefficients both filtered BOD5 and COD as well as unfiltered BOD5 and BOD5 and COD removal efficiencies, and insignificant effects on others, such as unfiltered COD removal rate coefficient. The effect of temperature on the removal rate coefficients, except the unfiltered COD removal rate coefficient, was higher at higher organic loadings (shorter retention times) whereas its effect on BOD5 and COD removals efficiencies was higher at lower power levels. The temperature correction coefficient for BOD5 at low power levels was higher than at higher levels of power. iv The effect of power level on the temperature correction coefficient was significant whereas the organic loading (or retention time) effect was insignificant. Relationships between the individual operating parameters and performance parameters are presented in the form of empirical equations and the combined effects of these operating parameters and performance parameters were also modelled. High organic loading (short retention time) in facultative aerated lagoons operated at low power levels proved to remove more organic material per day per unit of power introduced into the lagoon. Therefore, the optimum conditions of organic loading and power level at which a single facultative aerated lagoon used as a sole treatment process for treating settled sewage should be operated are 0.25 W/m3 for power level and 62 g BOD5 /m3. d for organic loading (3 to 4 days retentiom time). The effect of mixing, represented by the parameters in a simulation model, on performance was also modelled in the form of empirical equations. Nitrogen, phosphorus, Escherichia coli and faecal streptococci removals were considerable. Variations of their removal performance as well as algal concentration variations with the operating parameters were also studied and discussed. A mathematical equation was developed for the determination of the mean solids retention time (SRT) in facultative aerated lagoons. The relationship between SRT and power level and organic loading was determined and represented by an empirical equation. A power level of around 0.5 W/m3 was the threshold for settleable solids suspension below which no significant decrease in effluent or mixed liquor suspended solids concentration would take place.
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Thiers, Paul Robert. "Green food : the political economy of organic agriculture in China /." view abstract or download file of text, 1999. http://wwwlib.umi.com/cr/uoregon/fullcit?p9948031.
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Thesis (Ph. D.)--University of Oregon, 1999.<br>Typescript. Includes vita and abstract. Includes bibliographical references (leaves 303-318). Also available for download via the World Wide Web; free to University of Oregon users. Address: http://wwwlib.umi.com/cr/uoregon/fullcit?p9948031.
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Daka, Fridah Malindima. "Are the current Zambian constitutional provisions sufficient in preventing abuse of power by the executive organ of government?" Master's thesis, University of Cape Town, 2015. http://hdl.handle.net/11427/15210.
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This paper discusses reasons why democratic governance cannot be attained by the Zambian government without deliberate commitment to the maintenance of values and principles of democracy, good governance and the rule of law. Zambia prides itself to be a democratic and peaceful country. However, accountability, openness and responsiveness to the needs of citizens has been a challenge despite this great record, which has come as a result of free, fair and peaceful elections recorded consecutively since Zambia became a multi-party democracy. The partial fusion of the Executive and Legislative organs of government ably qualified by provisions of the current Constitution, makes it difficult to hold government accountable by the governed. Consequently, presidential appointment of Cabinet Ministers from Parliament equally weakens legislative ability of checking and balancing powers of the Executive. Moreover, appointment of judges by the President is another factor that punches holes in judicial independence and injures the last line of defence. It is as such imperative that the colossal presidential powers are reduced to allow a flourishing democratic society. In the view that the current Constitution does not have adequate provisions to prevent abuse of power by the Executive; this thesis has made recommendations for the Constitution to be amended to provide effective ways of balancing power between the three arms of government. This will inevitably create an environment of mutual accountability in government and construct a platform where the electorate could question irregular administrative actions.
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Venkatraman, Vishak. "Optical and Power Source Integrated Paper Microfluidic Devices for Point of Care Systems." University of Cincinnati / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1505206620429159.
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Pruinelli, Lisiane. "Mídia e doação de órgãos : a produção de sujeitos doadores." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2008. http://hdl.handle.net/10183/60575.
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Esta dissertação discute os discursos produzidos pela mídia que se ocupam da possibilidade de que pessoas doem seus órgãos ou os de seus familiares. Tem como objetivo estudar os discursos veiculados pela mídia, como eles se dirigem aos sujeitos e analisar o modo pelo qual eles atravessam e os instituem como doadores. O corpus de análise é o jornal Folha de São Paulo, considerado o mais influente do país. Entendo que as matérias do jornal são artefatos da cultura que produzem verdades e governam sujeitos. O estudo se filia aos Estudos Culturais em sua vertente pós-estruturalista, utilizando nas análises as seguintes ferramentas propostas por Michael Foucault: discurso, governamento e biopoder. As matérias do jornal põem em funcionamento discursos que foram analisados e reunidos em três grupos: pautando o jornal, sustentando o discurso e interpelando sujeitos para que sejam doadores de órgãos. Os discursos são vistos como estratégia biopolítica que utiliza um emaranhado de táticas para conduzir a população, girando em torno das possibilidades da doação de órgãos.<br>This paper dicusses the speeches produced by media that takes up possibility of people to donate their organs or their family members' organs. The goal of this paper is to study the speeches linked by media, how they point to subjects, and to analyse the way they go through and how they are considered as donors. The corpus analysis is the newspaper Folha de São Paulo, considered the most influential of the country. I think that newspaper subjects are culture devices wich produce truth and rule subjetcs. The study join to the Culture Studies and its post-structuralist source, using in the analysis the following tools proposed by Michael Foucault: speech, government and biopower. The newspaper subjects work with speeches wich were analyzed and gathered into three groups: newspaper guidelines, supporting the speech and interpellating subjetcs so that they are organs donors. The speeches are seen as biopolitic strategy that uses a tangle of tactics to lead the population, revolving around the possibilities of organs donation.<br>Esta disertación discute los discursos producidos por los medios de comunicación que se ocupan de la posibilidad de que personas donen sus órganos o los de sus familiares. Tiene como objetivo estudiar los discursos propagados por los medios de comunicación, como ellos se dirgen a los sujetos y analizar el modo por el cual atraviesan y los instituyen como donadores. El objeto de análisis es el periódico “Folha de São Paulo”, considerado el más influyente del país. Entiendo que las materias de los periódicos son artefactos de cultura que producen verdades y gobiernan sujetos. El estudio se une a los estudios culturales en su vertiente pós-estructuralista, utilizando en los análisis las siguientes herramientas propuestas por Michel Foucault: discurso, gobierno y biopoder. Las materias del periódico ponen en funcionamiento discursos que fueron analizados y reunidos en tres grupos: pautando el periódico, sustentando el discurso e interpelando sujetos para que sean donadores de órganos. Los discursos son vistos como estrategia biopolítica que utiliza un enmarañado de tácticas para conducir a la población, girando em torno de las posibilidades de la donación de órganos.
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Ho, Kai Wai. "Evaluation and characterization of efficient organic optoelectronic materials and devices." HKBU Institutional Repository, 2020. https://repository.hkbu.edu.hk/etd_oa/816.
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With the progression towards lighter but larger-display self-sustainable mobile devices, device efficiency becomes increasingly important, owing to the higher power display consumption but at the same time more limitation on the size and volume of energy storage. In this thesis, selected aspects regarding to efficiency of three types of optoelectronic devices, indoor photovoltaics (IPVs), perovskite thin-film transistors (TFTs) and organic light-emitting diodes (OLEDs) have been investigated. IPVs can make off-grid devices self-sustainable by harvesting ambient light energy. Its weak irradiance necessitates high-efficiency IPVs to generate sufficient power. Our work addresses the need of knowing the limit of the device parameters for correct evaluation and understanding the efficiency loss for developing clinical tactics. We delivered a general scheme for evaluating the limiting efficiency and the corresponding device parameters of IPVs under various lights, illuminance and material bandgap. In contrast to the AM1.5G conditions, a maximum power conversion efficiency (PCE) of 51-57 % can be achieved under the optimal bandgap of 1.82-1.96 eV. We also propose using the second thickness peak of interference instead of the first as a better optimal absorber thickness after identifying the finite absorption as the major source of efficiency loss. The work provides insights for device evaluation and material design for efficient IPV devices. The novel hybrid organic-inorganic perovskites have gained enormous research interest for its various excellent optoelectronic properties such as high mobility. TFT as an alternative application to the majorly focused photovoltaics is realized in this work. There are few reports on perovskite TFTs due to wetting issues. By employing polymethacrylates with ester groups and aromatic substituents which provide polar and cation-π interactions with the Pb2+ ions, quality films could be fabricated with large crystals and high electron mobility in TFTs. We further improved the performance by resolving interfacial mixing between the perovskite and the polymer using the crosslinkable SU-8, achieving the highest mobility of 1.05 cm2 V−1 s−1. Subsequently, we cured the grain boundaries using methylamine solvent vapor annealing, suppressing the TFT subthreshold swing. The work provides a map for the improvement of perovskite TFTs. It has been revealed that molecular orientations of the emitters in OLEDs with the transition dipole moment lying in plane enhances light outcoupling efficiency. Multiple experimental techniques are needed to provide complementary orientation information and their physical origin. Here, we propose using TFT to probe the orientation of the phosphorescent emitters. Homoleptic fac-Ir(ppy)3 and heteroleptic trans-Ir(ppy)2(acac) and trans-Ir(ppy)2(tmd) were deposited on polystyrene (PS) and SiO2 substrates. Compared to the PS surface inducing isotropic orientation as the control, trans-Ir(ppy)2(acac) and trans-Ir(ppy)2(tmd) possessed decreased carrier mobilities on SiO2. With the study of initial film growth, we infer that preferred orientation induced by the polar SiO2 surface led to an increase in energetic disorder in the well-stacked trans-Ir(ppy)2(acac) and hopping distance in the amorphous trans-Ir(ppy)2(tmd). The highly symmetric fac-Ir(ppy)3 remained its isotropic orientation despite the dipolar interaction. Surprisingly, the TFT technique gives much higher sensitivity to surface-induced orientation, and thus may potentially serve as a unique electrical probe for molecular orientation.
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Ho, Ka Wai. "Evaluation and characterization of efficient organic optoelectronic materials and devices." HKBU Institutional Repository, 2020. https://repository.hkbu.edu.hk/etd_oa/873.
Full textAbstract:
With the progression towards lighter but larger-display self-sustainable mobile devices, device efficiency becomes increasingly important, owing to the higher power display consumption but at the same time more limitation on the size and volume of energy storage. In this thesis, selected aspects regarding to efficiency of three types of optoelectronic devices, indoor photovoltaics (IPVs), perovskite thin-film transistors (TFTs) and organic light-emitting diodes (OLEDs) have been investigated. IPVs can make off-grid devices self-sustainable by harvesting ambient light energy. Its weak irradiance necessitates high-efficiency IPVs to generate sufficient power. Our work addresses the need of knowing the limit of the device parameters for correct evaluation and understanding the efficiency loss for developing clinical tactics. We delivered a general scheme for evaluating the limiting efficiency and the corresponding device parameters of IPVs under various lights, illuminance and material bandgap. In contrast to the AM1.5G conditions, a maximum power conversion efficiency (PCE) of 51-57 % can be achieved under the optimal bandgap of 1.82-1.96 eV. We also propose using the second thickness peak of interference instead of the first as a better optimal absorber thickness after identifying the finite absorption as the major source of efficiency loss. The work provides insights for device evaluation and material design for efficient IPV devices. The novel hybrid organic-inorganic perovskites have gained enormous research interest for its various excellent optoelectronic properties such as high mobility. TFT as an alternative application to the majorly focused photovoltaics is realized in this work. There are few reports on perovskite TFTs due to wetting issues. By employing polymethacrylates with ester groups and aromatic substituents which provide polar and cation-π interactions with the Pb2+ ions, quality films could be fabricated with large crystals and high electron mobility in TFTs. We further improved the performance by resolving interfacial mixing between the perovskite and the polymer using the crosslinkable SU-8, achieving the highest mobility of 1.05 cm2 V−1 s−1. Subsequently, we cured the grain boundaries using methylamine solvent vapor annealing, suppressing the TFT subthreshold swing. The work provides a map for the improvement of perovskite TFTs. It has been revealed that molecular orientations of the emitters in OLEDs with the transition dipole moment lying in plane enhances light outcoupling efficiency. Multiple experimental techniques are needed to provide complementary orientation information and their physical origin. Here, we propose using TFT to probe the orientation of the phosphorescent emitters. Homoleptic fac-Ir(ppy)3 and heteroleptic trans-Ir(ppy)2(acac) and trans-Ir(ppy)2(tmd) were deposited on polystyrene (PS) and SiO2 substrates. Compared to the PS surface inducing isotropic orientation as the control, trans-Ir(ppy)2(acac) and trans-Ir(ppy)2(tmd) possessed decreased carrier mobilities on SiO2. With the study of initial film growth, we infer that preferred orientation induced by the polar SiO2 surface led to an increase in energetic disorder in the well-stacked trans-Ir(ppy)2(acac) and hopping distance in the amorphous trans-Ir(ppy)2(tmd). The highly symmetric fac-Ir(ppy)3 remained its isotropic orientation despite the dipolar interaction. Surprisingly, the TFT technique gives much higher sensitivity to surface-induced orientation, and thus may potentially serve as a unique electrical probe for molecular orientation.
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Kalua, Tisaye Bertram. "Analysis of factors affecting performance of a low-temperature Organic Rankine Cycle heat engine." Thesis, Nelson Mandela Metropolitan University, 2017. http://hdl.handle.net/10948/17844.
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Organic Rankine Cycle (ORC) heat engines convert low-grade heat to other forms of energy such as electrical and mechanical energy. They achieve this by vaporizing and expanding the organic fluid at high pressure, turning the turbine which can be employed to run an alternator or any other mechanism as desired. Conventional Rankine Cycles operate with steam at temperatures above 400 ℃. The broad aspect of the research focussed on the generation of electricity to cater for household needs. Solar energy would be used to heat air which would in turn heat rocks in an insulated vessel. This would act as an energy storage in form of heat from which a heat transfer fluid would collect heat to supply the ORC heat engine for the generation of electricity. The objective of the research was to optimize power output of the ORC heat engine operating at temperatures between 25℃ at the condenser and 90 to 150℃ at the heat source. This was achieved by analysis of thermal energy, mechanical power, electrical power and physical parameters in connection with flow rate of working fluid and heat transfer fluids.
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Sham, Devin Krishna. "Analysis of exhaust waste heat recovery techniques from stationary power generation engines using organic rankine cycles." Master's thesis, Mississippi State : Mississippi State University, 2008. http://library.msstate.edu/etd/show.asp?etd=etd-11072008-123311.
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Marshall, Ariel S. "Nonlinear optical characterization of organic polymers and small molecules and their application towards optical power limiting." Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/52334.
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This thesis is concerned with the photophysical and nonlinear optical responses, and applications of a set of conjugated polymers and small molecules in the visible and near-IR spectral regions.
Poly(phenylene ethynylene) PPE polymers were substituted with conjugated side-arms in a cruciform fashion to determine the impacts of electronic coupling on the one-photon (1PA), two-photon (2PA), and excited state absorption (ESA) properties of the co-polymer system. The cruciform-like PPEs showed significant changes in their nonlinear and phophysical behavior relative to their linear models, including shifts and splittings of the 1PA bands due to moderate mixing of the lowest singlet excited states, an increase in the 2PA cross section (δ) values, and an increase in the yield of triplet excited-state species. The cruciform-like PPE polymers exhibited effective optical pulse suppression of femtosecond and nanosecond laser pulses over a broad spectral range of ~200 nm in the visible and near-IR. The suppression capability of the cruciform-like PPEs exceeded the best reported value for alkyl-substituted PPE polymers.
The spectroscopic effects due to conjugation length, structural configuration, and intramolecular charge transfer (ICT) are discussed for a family of bent donor-acceptor-donor (D-A-D) -type conjugated oligomers, which incorporate electron-rich triarylamine donors and electron-deficient triarylborane acceptor units into its conjugated structure. These organoborane oligomers are highly fluorescent and exhibit strong 2PA in the visible region with δ values as large as 1410 GM, as well as overlapping ESA bands attributed to singlet-singlet and triplet-triplet absorption. Saturation of the molar absorptivity, ε, and δ was observed at less than two repeat monomer units due to conformational disorder in the oligomer with increasing length. Positive solvatochromism of fluorescence with solvent shifts as large as ~70 nm was observed as a result of ICT from the arylamine donors to boryl-centered acceptor sites. The excited-state dynamics also show sensitivity to the solvent environment. Experimental findings suggest that these organoborane oligomers may have potential use as nonlinear material for optical power limiting (OPL) and two-photon sensing applications.
The spectral properties of two bis-donor chromophores, (bis(diarylamino)biphenyl (TPD) and distyrylthiophene (DST), were investigated with and without the presence of AgNPs in order to better understand the local-field enhancement and subsequent effects on the photophysics and nonlinear behavior of 2PA dyes. While little changes were observed in the excited-state dynamics, measurements of nanoparticle aggregate-dye composite solutions with TPD revealed a 1.6-enhancement in the two-photon excited fluorescence signal. OPL measurements of nanosecond laser pulses at 532 nm revealed a reduction in threshold energy by a factor of 2 in solutions containing TPD and AgNP aggregates, relative to solutions of TPD alone. DST shows exceptional solubility (>1 M) in several organic solvents and exhibits a 2PA spectrum that overlaps well with its singlet-singlet and triplet-triplet ESA bands. Consequently, DST exhibits effective optical limiting of nanosecond laser pulses through two-photon induced excited-state absorption over a broad spectral range of approximately 200 nm in the red and near-IR.
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Wolf, Stefan [Verfasser]. "Silicon-organic hybrid (SOH) electro-optic modulators for high-speed and power-efficient communications / Stefan Wolf." Karlsruhe : KIT Scientific Publishing, 2018. http://www.ksp.kit.edu.
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Öhman, Henrik. "Low temperature difference power systems and implications of multi-phase screw expanders in Organic Rankine Cycles." Doctoral thesis, KTH, Tillämpad termodynamik och kylteknik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-188015.
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New and old data on screw expanders operating with 2-phase mixtures in the admission line has been combined to enable the first public correlation of adiabatic expansion efficiency as a function of entry vapour fraction. Although not yet perfected, these findings have enabled an entirely new approach to the design and optimisation of Organic Rankine Cycles, ORCs. By allowing a continuous variation of vapour fraction at expander entry optima for thermal efficiency, second law efficiency and cost efficiency can be found. Consequently one can also find maxima for power output in the same dimension. This research describes a means of adapting cycle characteristics to various heat sources by varying expander inlet conditions from pure liquid expansion, through mixed fluid and saturated gas expansion, to superheated gas. Thermodynamic analysis and comparison of the above optimisations were a challenge. As most terms of merit for power cycles have been developed for high temperature applications they are often simplified by assuming infinite heat sinks. In many cases they also require specific assumptions on e.g. pinch temperatures, saturation conditions, critical temperatures etc, making accurate systematic comparison between cycles difficult. As low temperature power cycles are more sensitive to the ‘finiteness’ of source and sink than those operating with high temperatures, a substantial need arises for an investigation on which term of merit to use. Along with an investigation on terms of merit, the definition of high level reversible reference also needed revision. Second law efficiency, in the form of exergy efficiency, turned out to be impractical and of little use. A numerical approach, based on a combination of first and second law, was developed. A theory and method for the above is described. Eventually low temperature power cycle test data was compiled systematically. Despite differences in fluid, cycle, temperature levels and power levels the data correlated well enough to allow for a generalised, rough correlation on which thermal efficiency to expect as a function of utilization of source and sink availability. The correlation on thermal efficiency was used to create a graphical method to pre-estimate key economic factors for low temperature site potential in a very simple manner. A major consequence from the findings of this thesis is the reduced dependency on unique choices of process fluid to match heat source characteristics. This development significantly simplifies industrial standardisation, and thereby potentially improves cost efficiency of commercial ORC power generators.
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Wu, Zhenghui. "Impact of metal oxide/bulk-heterojunction interface on performance of organic solar cells." HKBU Institutional Repository, 2015. https://repository.hkbu.edu.hk/etd_oa/159.
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Organic photovoltaics have shown much promise as an alternative photovoltaic technology for application in low-cost, large-scale and flexible solar cells. The application of metal oxides in organic solar cells (OSCs) and the impact of the properties of metal oxide/organic hetero-interfaces on cell performance have attracted a lot of attention. The metal oxide/organic interfaces have a crucial impact on interfacial charge transfer, charge collection and the overall device performance. This thesis is aimed at clarifying the principal interfacial phenomena occurring at the metal oxide/organic hetero-interfaces as well as effective engineering of those interfacial properties in OSCs. Photo-generated electrons and holes undergo different recombination processes, e.g., bimolecular recombination and trap-assisted recombination, before being collected by the electrodes in OSCs. Light intensity-dependent current densityvoltage (JV) characteristics of OSCs were analyzed to study the effect of recombination on charge collection efficiency. Effect of metal oxide/organic hetero-interfaces on charge transfers at organic/electrode interface was analyzed using transient photocurrent (TPC) measurements. Light intensity-dependent JV characteristics and TPC characteristics were applied to explore the charge recombination dynamics in OSCs with a metal oxide interlayer. This project concentrated on an in-depth investigation of the physics and the interface phenomena such as interfacial exciton dissociation, charge recombination processes, charge collection and interface engineering for high performing OSCs. The fundamentals about light intensity-dependent J-V characteristics for OSCs were summarized. The relationship between the charge recombination dynamics and light intensity-dependent J-V characteristics in OSCs were developed. Light intensity-dependent JSC, VOC and FF in OSCs made with different bulk-heterojunction (BHJ) systems of PTB7:PC70BM, PTB7-Th:PC70BM and PNB4:PC70BM were investigated. It is found that bimolecular recombination is the most prominent factor limiting the performance of OSCs. For freshly made OSCs fabricated based on the commercial polymers, e.g. PTB7 & PTB7-Th, and the new polymer PNB4 synthesized in-house, the trap-assisted charge recombination process in the BHJ active layer plays a relatively small role. This suggests that reducing the bimolecular recombination in OSCs through selecting proper materials and device structures is crucial for enhancing the power conversion efficiency (PCE) of OCSs. In this work, device structures which enable reducing bimolecular recombination in OSCs were investigated. The effect of ZnO interlayer at the interface between BHJ and Al cathode on the performance of PTB7:PC71BM based OSCs was studied by a combination of theoretical simulation and experimental characterization techniques, e.g., using light intensity-dependent JV characteristic and TPC measurements etc. It shows that ZnO interlayer has a profound effect on the performance of the PTB7:PC70BM-based OSCs, although it does not have a significant influence on the maximum absorptance in the active layer. The origin of the improvement in the cell performance is associated with the efficient charge collection due to the favorable exciton dissociation at the electrode/active layer interface. It is shown that the presence of the ZnO interlayer allows using a thinner active layer without moderating the absorption in the optically optimized control OSCs without the ZnO interlayer. OSCs with a ~10 nm thick ZnO interlayer are found to be favorable for the efficient charge collection, and thereby improving the cell performance. The TPC measurements also reveal that the dissociation of excitons at the metal/organic interface of regular OSCs hinders the electron collection. The unfavorable interfacial exciton dissociation can be removed by interposing a ZnO interlayer at the Al/organic interface, thus bimolecular recombination at the electrode/active layer interface can be reduced for improving the charge collection efficiency. PCE of the OSCs using ZnO interlayer was 6.5%, which is about 20% higher than a control cell (5.4%), having an identical device configuration without a ZnO interlayer. Solution-processed anode interlayer, a mixture of solution-processed MoOX and PEDOT:PSS, was adopted for application in inverted PTB7:PC71BM-based OSCs. The ratio of MoOX to PEDOT:PSS in the mixed solution was optimized for achieving the best cell performance. A PCE of 7.4% was obtained for OSCs with an optimal MoOX-PEDOT:PSS based interlayer, interposed between the BHJ active layer and Ag anode, which means 10% enhancement over the PCE of control cell made with an evaporated MoOX interlayer. Light intensity-dependent JV characteristics implied that the bimolecular recombination in OSCs with a MoOX-PEDOT:PSS interlayer was reduced. TPC measurements showed that the favorable exciton dissociation occurs at the organic/MoOX interface for the inverted OSCs. The favorable interfacial exciton dissociation generates an electrical field within a very small space near the interface, contributing significant additional photocurrent when the effective bias across the active layer in the OSCs is low, and thereby assisting in an efficient charge collection at the organic/electrode interface. In addition to the improvement in the cell performance, the solution-processed MoOX-PEDOT:PSS interlayer does not require a post-annealing treatment, which is beneficial for application in solution-processed tandem and flexible OSCs.
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Potscavage, William J. Jr. "Physics and engineering of organic solar cells." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/39634.
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Organic solar cells have the potential to be portable power sources that are light-weight, flexible, and inexpensive. However, the highest power conversion efficiency for organic solar cells to date is ~8%, and most high-efficiency solar cells have an area of less than 1 cm². This thesis advances the field of organic solar cells by studying the physics and engineering of the devices to understand the reverse saturation current, which is related to efficiency, and the effects of area scaling.
The most commonly accepted models to describe the physics of organic photovoltaic devices are reviewed and applied to planar heterojunction solar cells based on pentacene / C60 as a model system. The equivalent circuit model developed for inorganic solar cells is shown to work well to describe the behavior of organic devices and parameterize their current-voltage characteristics with five parameters. Changes in the parameters with different material combinations or device structures are analyzed to better understand the operation of the presented organic solar cells. A one-dimensional diffusion model for the behavior of excitons and treatment of the organic layers as planes is demonstrated to adequately model the external quantum efficiency and photocurrent in pentacene / C60 solar cells.
The origin of the open-circuit voltage is studied using cells with different electrodes and different donor materials. While changing the electrodes does not affect open-circuit voltage, it is greatly modified by changes in the donor. Tests with additional semiconductors show the change in open-circuit voltage is not consistent from donor to donor as the acceptor is varied, suggesting a more complex relation than just the difference in energy levels. Study of the temperature dependence of the equivalent circuit parameters shows that the reverse saturation current, which has a significant role in determining the open-circuit voltage, has a thermally activated behavior. From this behavior, the reverse saturation current is related back to charge transfer at the donor / acceptor heterojunction to suggest that both the effective energy barrier presented by the energy levels and the electronic coupling are important in determining the reverse saturation current and open-circuit voltage. This marks a shift from just considering a built-in voltage or the energy levels to also considering the electronic coupling of the donor and acceptor materials. Temperature-dependent performance characteristics are also used to show key differences between organic and inorganic devices.
Finally, the effect of area scaling is explored with pentacene / C60 solar cells having areas of 0.11, 7, and 36.4 cm². Analysis with the equivalent circuit model shows that performance decreases as area increases because of an increasing series resistance presented by the transparent electrode. A metal grid, to provide low resistance pathways for current, fabricated on top of the transparent electrode is proposed to reduce the effective resistance. The grid is unique in that it is placed between the electrode and the semiconductor layer and must be passivated to prevent shorts through the thin semiconductor to the back metal electrode. Analysis of the grid predicts greatly reduced series resistance, and experimental results show reduced resistance and improved performance for the 7 cm² and 36.4 cm² devices when including the grid.
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Dahlqvist, Johan. "Impulse Turbine Efficiency Calculation Methods with Organic Rankine Cycle." Thesis, KTH, Kraft- och värmeteknologi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-104174.
Full textAbstract:
A turbine was investigated by various methods of calculating its efficiency. The project was based on an existing impulse turbine, a one-stage turbine set in an organic Rankine cycle with the working fluid being R245fa. Various methods of loss calculation were explored in the search for a method sufficiently accurate to make valid assumptions regarding the turbine performance, while simple enough to be time efficient for use in industrial research and development. The calculations were primarily made in an isentropic manner, only taking into account losses due to the residual velocity present in the exit flow. Later, an incidence loss was incorporated in the isentropic calculations, resulting in additional losses at off-design conditions. Leaving the isentropic calculations, the work by Tournier, “Axial flow, multi-stage turbine and compressor models” was used. The work presents a method of calculating turbine losses separated into four components: profile, trailing edge, tip clearance and secondary losses. The losses applicable to the case were implemented into the model. Since the flow conditions of the present turbine are extreme, the results were not expected to coincide with the results of Tournier. In order to remedy this problem, the results were compared to results obtained through computational fluid dynamics (CFD) of the turbine. The equations purposed by Tournier were correlated in order to better match the present case. Despite that the equations by Tournier were correlated in order to adjust to the current conditions, the results of the losses calculated through the equations did not obtain results comparable to the ones of the available CFD simulations. More research within the subject is necessary, preferably using other software tools.
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Shaheen, Murtadha A. "POWER MAXIMIZATION FOR PYROELECTRIC, PIEZOELECTRIC, AND HYBRID ENERGY HARVESTING." VCU Scholars Compass, 2016. http://scholarscompass.vcu.edu/etd/4462.
Full textAbstract:
The goal of this dissertation consists of improving the efficiency of energy harvesting using pyroelectric and piezoelectric materials in a system by the proper characterization of electrical parameters, widening frequency, and coupling of both effects with the appropriate parameters.
A new simple stand-alone method of characterizing the impedance of a pyroelectric cell has been demonstrated. This method utilizes a Pyroelectric single pole low pass filter technique, PSLPF. Utilizing the properties of a PSLPF, where a known input voltage is applied and capacitance Cp and resistance Rp can be calculated at a frequency of 1 mHz to 1 Hz. This method demonstrates that for pyroelectric materials the impedance depends on two major factors: average working temperature, and the heating rate.
Design and implementation of a hybrid approach using multiple piezoelectric cantilevers is presented. This is done to achieve mechanical and electrical tuning, along with bandwidth widening. In addition, a hybrid tuning technique with an improved adjusting capacitor method was applied. An toroid inductor of 700 mH is shunted in to the load resistance and shunt capacitance. Results show an extended frequency range up to 12 resonance frequencies (300% improvement) with improved power up to 197%.
Finally, a hybrid piezoelectric and pyroelectric system is designed and tested. Using a voltage doubler, circuit for rectifying and collecting pyroelectric and piezoelectric voltages individually is proposed. The investigation showed that the hybrid energy is possible using the voltage doubler circuit from two independent sources for pyroelectrictity and piezoelectricity due to marked differences of optimal performance.
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Pandey, Laxman. "Theoretical studies of the structure-property relationships of hole- and electron-transport materials for organic photovoltaic applications." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/48964.
Full textAbstract:
Donor-acceptor and thiophene based π-conjugated molecules and polymers, along with fullerene derivatives, are extensively used active components in the photoactive layer of organic photovoltaic devices. In this dissertation, we make use of several computational methodologies to investigate structure-property relationships of these organic systems in their molecular forms. We begin with an overview of the field of organic photovoltaics and some of the important problems in organic solar cells that are currently being investigated. This is then followed by a brief review of the electronic-structure methods (e.g. Hartree-Fock theory, Density Functional Theory, and Time-dependent Density Functional Theory) that are employed.
We then present the main results of the dissertation. Chapter 3 provides a broad overview on how changes to the donor-acceptor copolymer chemical structure impacts its intrinsic geometric, electronic, and optical properties. Chapter 4 focuses on the characterization of the lowest excited-states and optical absorption spectra in donor-acceptor copolymers. In Chapter 5, we investigate the effects of alkyl side-chain placements in the π-conjugated backbone of oligothiophenes and how that impacts their intramolecular properties as well as the oligomer:fullerene interfacial interactions. Chapter 6 presents our investigation on the role of oligomer:fullerene configuration and reorganization energy on exciton-dissociation and charge-recombination processes. Finally, a synopsis of the work and further considerations are presented in Chapter 7.
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Sutcu, Sinan Mahmut. "The effects of ITO surface modification on lifetime in organic photovoltaic devices and a test setup for measuring lifetime." Thesis, Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/34685.
Full textAbstract:
Though relatively young, the field of organic electronics is a rapidly growing market and considerable research is being done in creating a whole range of devices from organic molecules from organic field effect transistors to LEDs to photovoltaic devices. The field of organic photovoltaic in particular has become important in recent years with the push for newer, renewable sources of energy to end the dependence on fossil fuels. While the efficiencies of organic photovoltaic devices continue to rise, one barrier to their commercial adoption has been the limited lifetimes of these devices. While certain degradation methods of organic photovoltaics, such as photo-oxidation, have been extensively studied and solutions to these problems, such as encapsulation, are being researched, certain other degradation mechanisms are less understood and studied. The focus of this thesis is on one such degradation mechanism, UV degradation, specific to the ITO-pentacene interface in pentacene/C60 organic photovoltaic devices. Attempts were made to increase the lifetime of the devices by using phosphonic acids or oxygen plasma to modify the surface of the ITO. While conducting these experiments, the lack of a system to test the lifetime of multiple devices for long periods of time became apparent. As such as system was a requirement for future research into the lifetimes of organic photovoltaic devices a system was designed and built. The system would operate the photovoltaic device in a way comparable to its end-use and would allow over 100 devices to be tested simultaneously for durations exceeding 10,000 hours if necessary. This system would allow for statistically significant lifetime testing to be carried out in the future.
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Woods, Kurt Wade. "Solar Energy Conversion and Control Using Organic Photovoltaic Cells." TopSCHOLAR®, 2013. http://digitalcommons.wku.edu/theses/1315.
Full textAbstract:
Organic photovoltaic (OPV) cells are advanced, newly emerging technologies that are lightweight, mechanically flexible devices with highthroughput processes from low cost material in a variety of colors. Rathnayake et al. of Western Kentucky University have developed a nanostructure-based OPV cell. Presented in this thesis is a model and simulation of a generalized PV powered system that can predict the performance of solar arrays in various environmental conditions. The simulation has been carried out in Matlab/Simulink, and upon entering the cell’s parameters, it provides key electrical characteristics such as the cell’s I-V curve and efficiency information. The total system that is simulated consists of three elements: a universal two-cell solar array that can account for partial shading and manufacturing variation, a current-controlled power converter, and an energy storage device with charging and discharging capabilities.
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Kaller, Kayden. "Aspects of Photovoltaic Systems: Study and Simulation of Silicon Phthalocyanine Bulk Heterojunction Solar Cells and Monochromatic Photonic Power Converters." Thesis, Université d'Ottawa / University of Ottawa, 2021. http://hdl.handle.net/10393/42626.
Full textAbstract:
This thesis discusses two different photovoltaic systems, organic solar cells, and photonic power
converters. The open-source software package Solcore was used to simulate and analyze optoelectronic
properties of both systems.
It is widely accepted that the transition from a fossil-fuel driven economy is necessary in the coming
future. Organic solar cells are an alternative energy generation method with potential for fast energetic
and economic payback periods. Bulk heterojunction organic solar cells are a common design, as they
have particularly low manufacturing costs due to a simple device architecture. In this work, two bulk
heterojunction blends are experimentally assessed using the acceptor molecule silicon phthalocyanine
(bis(tri-n-butyl silyl oxide) silicon phthalocyanine ((3BS)2-SiPc) as a potential low-cost non-fullerene
alternative to the typical acceptor [6,6]-phenyl-C61-butyric acid methyl ester (PC₆₁BM). These acceptors
are compared within blends with the typical donor compound poly(3-hexylthiophene) (P3HT), and also
poly[(2,6-(4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)-benzo [1,2-b:4,5-b’]dithiophene))-alt-(5,5-(1′,3′-di-2-
thienyl-5′,7′-bis(2-ethylhexyl)benzo[1′,2′-c:4′,5′-c’]dithiophene-4,8-dione)] (PBDB-T). Device
performance was assessed under standard conditions, increased angles of incidence, and reduced light
intensities. Devices with the P3HT:(3BS)2-SiPc blend achieved a power conversion efficiency (PCE) of
3.6%, which outperformed P3HT:PC₆₁BM devices with a PCE of 3.0% due to a higher open-circuit voltage
(VOC) of 0.76 V as opposed to 0.53 V. The PBDB-T:(3BS)2-SiPc achieved a high VOC of 1.09 V, but had a
lower PCE of 3.4% in relation to the PBDB-T:PC₆₁BM device with a PCE of 6.4% and a VOC of 0.78 V.
Photonic power converters are devices in optical networks that allow for optical power transmission
rather than the conventional method of electrical power transmission. This provides benefits such as
electrical isolation and resistance to electromagnetic interference, along with the ability to propagate
along the same cable as data. These power converters are used to convert optical power to electrical
power, and operate similarly to a solar cell with a narrow bandwidth. Multijunction designs are often
used for increased operating voltage and efficiency. In such designs employing a vertical architecture,
the bottom-most junction has the largest thickness along with the lowest efficiency due to increased
recombination losses. To improve this lower efficiency, light trapping techniques can be employed to
decrease the junction thickness while retaining the optical thickness. In this work, a current-matched 5-
junction GaAs photonic power converter was simulated with both metallic and distributed Bragg
reflectors at the rear of the device. These reflectors allowed for the thinning of the bottommost
junction, which resulted in an increase in efficiency and overall power output of the power converter.