Factors Governing the Performance and Stability of Solid Oxide Fuel Cell Cathodes Prepared by Infiltration

Infiltration method, developed at the University of Pennsylvania, is a unique analytical platform for investigating the effect of material properties and electrode microstructure on the performance of solid oxide fuel cell (SOFC) electrodes. During cell fabrication by infiltration, the ion-conducting electrolyte phase is sintered first, followed by the addition of the catalytically active perovskite phase into the pores of the electrolyte. The use of separate sintering steps for the electrolyte and the active phase gives one a high degree of control over the microstructure of both phases, unattainable with traditional fabrication methods. In this thesis, the infiltration approach has been used to conduct a systematic investigation into the factors that govern the performance and stability of solid oxide fuel cell cathodes. As a result, a number of microstructural and material properties, crucial for obtaining high electrode activity, were identified. In particular, the effect of varying the ionic conductivity of the porous electrolyte, the specific surface area of the perovskite as well as the specific surface area of the porous electrolyte, and the effect of solid-state reactions between the two phases were studied and were found to significantly affect performance. The experimental findings agreed well with the predictions of a mathematical model that was developed to describe the electrochemical characteristics of SOFC composite cathodes. Both theoretical and experimental evidence suggests the performance of SOFC cathodes prepared by infiltration is limited by slow oxygen adsorption on the perovskite surface. The chemical composition of the perovskite surface therefore plays an important role in determining the overall performance of the electrode. The last chapter of this thesis introduces a novel method that may allow one to characterize the active sites on the perovskite surface under SOFC cathode operating conditions (600-700°C, ambient air atmosphere, polarization), unattainable with traditional surface characterization techniques

lt- ja sti-liiteliste adverbide kasutuse muutumine eesti kirjakeeles

Artiklis võetakse vaatluse alla mõningate lt-liiteliste adverbide tarvitamine ning nende funktsioonide muutumine eesti kirjakeeles. Antakse ülevaade lt-adverbiliite esinemisest vanas kirjakeeles ning tuuakse välja ka sufiksi tänapäevane kasutamine. Vana kirjakeele korpuse põhjal analüüsitakse eri autorite lt-liiteliste adverbide ja modaaladverbide kasutamist, keskendudes 17. sajandi autorite Georg Mülleri ja Heinrich Stahli tekstidele. Nendes tekstides on paralleelselt vaatluse all lt- ja sti-adverbiliited, kuna läbi kirjakeele ajaloo on neil sufiksitel olnud sarnane funktsioon. Sellest on tingitud ka nende liidete variatiivsus. Mõlema autori tekstides on valdavad sti-liitelised (modaal)adverbid. Tänapäeva kirjakeeles sagedamate lt-liiteliste adverbide ja modaaladverbide jälgimine vanas kirjakeeles loob tausta nende sõnade uurimiseks tänapäeval, mil lt- ja sti-liiteliste adverbide vahekord keeles on vastupidine. Artikli koostamisel on silmas peetud, et lt-liitega sõnad on tänapäeva eesti keeles üksused, millel on peale täistähendusliku ka pragmaatiline kasutus.The change of the use of lt- and sti-suffixed adverbs in Literary Estonian. This paper investigates the use of some of the lt-suffixed adverbs and the change of their functions in Literary Estonian. -lt as an adverbial suffix will be examined on the basis of corpora data both in older and newer Literary Estonian. The article also focuses on the 17th century texts by Georg Müller and Heinrich Stahl and the authors’ use of adverbs and modal adverbs. In these texts, the parallel usage of lt- and sti-suffixes will be demonstrated, since the functions of these suffixes have been similar in the historical development of the Estonian language. This has caused the variability of -lt and -sti. In the texts of both authors, the sti-suffixed (modal) adverbs are dominant, while in present day Estonian, -lt is more frequent. Thus, it is necessary to investigate the change of lt-suffixed adverbs and modal adverbs in older Estonian in order to provide insights into their functions in the present day. In the process of writing this paper, it is implied that the lt-suffixed words in contemporary Estonian may function both as full content adverbs as well as pragmatic markers

Sisseelamisprogrammi loomine uue töötaja kohanemiseks organisatsiooni Mainegrupp OÜ näitel

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Survival and height growth of coniferous planting stock in RMK Tartu nursery

Bakalaureusetöö Metsamajanduse õppekavalAntud bakalaureusetöö uurimisteemaks on RMK Tartu Puukoolis toodetav kinnisjuurne istutusmaterjal. Uurimustöö käigus mõõdeti hariliku kuuse (Picea abies) ja hariliku männi (Pinus sylvestris) konteinertaimede kõrguskasv ning selgitati välja külvide väljatulek. Andmete võrdlemisel kasutati varasemate aastate andmeid – Kullenga taimla 1.aasta okaspuu kinnisjuursete taimede kõrgusi (2006, 2007) ja Marana taimla 1.aasta okaspuu kinnisjuursete taimede kõrgusi (2006, 2007). Andmete analüüsil kasutati MS Excelit. Kinnisjuurne istutusmaterjal on muutumas üha kasutatavamaks, sest see läheb paremini kasvama kui avamaataim ja ka esialgne kasv on kõrgem. Samuti on töös käsitletud metsataimekasvatuse hetkeseisu Eestis ning metsataimede kvaliteedile kehtestatud nõudeid. Erametsanduses on suurenenud metsauuendamise maht, mis omakorda on tekitanud kohaliku kultiveerimismaterjali puudujäägi. Seepärast võiks metsaistutusel eelistada konteinertaimi, sest nende eeliseks on lühike kasvatusaeg, mis võimaldab tootjal paindlikult reageerida turu nõudlusele.The topic of this thesis is RMK Tartu nursery producible planting. The average height growth of Norway spruce and Scots pine container plants was measured and the yield of seeding was determined. The data was compared with the data of previous years – Kullenga nursery 1st year conifer containerized plants height (2006, 2007) and Marana nursery 1st year conifer containerized plants height (2006, 2007). MS Excel was used to analyse the data. Containerized planting stock has become more and more used because the initial growth is higher and the initial growing is better compared to bare-root plants. The situation of forest growing and the quality standards of forest planting stock in Estonia has been discussed. The rate of reforestation has increased in private forests, which has created the deficit of local planting stock. For this reason using container plants can be advised, because they have a short growing period which helps the producers to react for market need flexibl

Application of flow cytometry to measure genome and spore sizes of selected Basidiomycota groups

Voolutsütomeetriat kasutatakse valdavalt meditsiinis haigustekitajate ja rakutsükli uurimiseks. Seene eoste ja genoomi suuruse mõõtmiseks on varem kasutatud valgusmikroskoopiat. Eose suurus on oluline tunnus seente süstemaatikas, mida kasutatakse nii liikide piiritlemisel kui liikide määramisel (Parmasto E. ja Parmasto I. 1987). Genoomi suurus, tuuma DNA sisaldus ja polüploidsus on olulised parameetrid seente elurikkuse uurimisel. Uuringu eesmärk oli rakendada voolutsütomeetriat taelikute (Phellinus) ja servikute (Pleurotus) liikidel eose ja genoomi suuruse määramisel. Töötati välja uus metoodika ellipsoidsete seeneeoste mõõtmiseks. Eostest genoomis suuruse määramiseks lahendati mitmeid probleeme. Töötati välja uus metoodika eostest tuumade väljutamiseks sest selgus, et genoomi suurust eoste tugeva autofluoresentsi tõttu paksukestaliste eoste tuumadest mõõta ei saa. Seevastu selgus, et eoseid ja tuumi on lihtne grupeerida tänu autofluorestentsi olemasolule nende suuruse mõõtmiseks. Eose autofluoresentsi intensiivsus ise aga uue tunnusena võimaldab koos eose suurusega kasutades eritada gruppe, mis ainult eose pikkuse ja laiuse järgi ei eritu. Töö käigus eraldati intaktsed tuumad liikidel austerservik (Pleurotus ostreatus) ja kopsservik (P. pulmonarius). Uuringu käigus mõõdeti 136 seene eoste suurused ning 16 seene genoomi suurus. Tuuma suuruse ja DNA-sisalduse vahel on seos korrelatsioonikordajaga 0,75. Intaktsete tuumade mõõtmine väldib eoste autofluorestsentsist ja eosproovis mingi osa mitmiktuumadega eoste olemasolust tekkida võivat tegelikust suurema genoomi saamist. Genoomi suuruste suhteliseks määramiseks kasutati referentorganismi austerservik (Pleorotus ostreatus) TAAM126992 (genoomi suurusega 32 Mbp) kasutades selleks rakutsükli faasis G1 olevaid tuumi. Uuringu käigus välja töötatud läbivoolutsütomeetria metoodeid on võimalik kasutada seente süstemaatika jaoks eoste ja genoomi suuruse järgi liikide grupeerimiseks, liikide piiritlemiseks ja määramiseks. Voolutsütomeetria võimaldab kiiresti saada täpseid andmeid eosproovis olevate eoste mitmete parameetrite varieeruvuse kohta. Kasutades etalone saab suhtelistesed mõõdud konverteerida absoluutseteks ja teiste meetoditega saadud andmetega koos kasutadaFlow cytometry is mainly used in medicine to study pathogens and cell cycles. Fungal spore size is one of the most important characteristics in fungal taxonomy when studying species delimitation or determining species (Parmasto E. and Parmasto I. 1987). Previously, fungal spore and genome sizes were usually measured using light microscopy. Genome size, nuclear DNA content, and polyploidy are important if exploring fungal diversity. The aim of this study was to implement flow cytometry to measure spore and genome sizes of selected fungal groups of genus Phellinus and Pleurotus. A new methods for measuring elliptical spore sizes was developed for this. Due to strong autofluorescence of spores genome size was hard to measure for thick-walled spores and a new way to excrete nuclei of spores was therefore developed. In contrast, autofluorescence allowed for an easier way select groups of spore for further measuring. Using spore sizes and intensity of autofluorescence measured by flow cytometry allows for grouping specimen where differentiation based on spore length and width is difficult. Intact nuclei were isolated from Pleurotus ostreatus and P. pulmonarius spores. During this study, spores of 136 fungi and genome sizes of 16 fungi were measured. Correlation coefficient between DNA content and volume of the nucleus was 0,75. Measuring only intact single nucleus of spore excludes possibility to make mistakes by measuring two nuclei as one. To determine genome size reference organism (Pleorotus ostreatus) TAAM126992 (genome size 32 Mbp) cell cycle G1 phase spores were used. The study provides new methods for flow cytometry to measure spores size of elliptical spores and obtain intact nuclei for measure their DNA content. Using flow cytometry, large amounts of spores could be measured in minutes and using random sampling. Using two parameter analysis of spore sizes and intensity of autofluorescence reveal groups for fungal taxonomy to identify and delimit species

The development and functions of pragmatic markers in the Estonian language: The case of lt-words

Väitekirja elektrooniline versioon ei sisalda publikatsioone.Millised oleksid tulemused, kui paluda keelekasutajal defineerida sõnu, nagu näiteks põhimõtteliselt, tegelikult, loomulikult, täpselt, ilmselt, lihtsalt? Siinne keeleteaduslik doktoritöö uuribki nende sõnade näitel ühe eesti keeles esineva sõnagrupi kujunemist ja kasutamist, näidates, kuidas on sama kirjapildiga lt-lõpulisi sõnu võimalik pruukida eri funktsioonides. Need keelendid (lt-sõnad) on sõnaraamatutes esitatud ennekõike konkreetse tähendusega määrsõnadena. Paralleelselt on need aga tarvitusel ka sõnadena, mis omandavad oma täpse funktsiooni alles kindlas keelelises ümbruses. Sellisel juhul kasutatakse neid sekkumisel, parandamisel, öeldu pehmendamisel, kommenteerimisel, rõhutamisel, kinnitamisel, sidumisel jne. Kõrvutades lauseid „Ta tunneb oma tööd nii teoreetiliselt kui ka praktiliselt“ ning „Praktiliselt kõik saalisviibijatest on mehed“, võib märgata, kuidas sõna praktiliselt funktsioneerib kahes lauses eri moel. Esimeses lauses on tegemist määrsõnaga, mis kannab tähendust ’tegelikkuses, praktikas’. Teises lauses on aga sõna praktiliselt kasutusel umbmäärases funktsioonis („Peaaegu kõik saalisviibijatest on mehed“) ning ilmselt ei tõlgendaks keelekasutaja lauset kui „Tegelikkuses on kõik saalisviibijad meessoost“. Siinne uurimus põhineb peamiselt viimase sadakonna aasta eesti kirjakeelel ning sellesse kuuluvad artiklid käsitlevad mitmefunktsiooniliste lt-sõnade arengut, kirjeldades nende kujunemist ja kasutamist nii kvalitatiivselt kui ka kvantitatiivselt. Nendel keelenditel on senise täistähendusliku tarvituse kõrval järjest sagedasemaks muutunud pragmaatiline kasutus. Doktoriväitekiri esitab ühelt poolt lt-sõnade arengumudeli, võttes oluliste faktoritena arvesse esilekerkivat varieerumist ning sõnade funktsioone. Teisalt panustab töö keele muutumise uurimisvaldkonda üldiselt, luues käsitletavast nähtusest tervikpildi.What would be the result if a language user would have to define words like tegelikult ‘actually; in fact’, praktiliselt ‘virtually; practically’, põhimõtteliselt ‘basically; in principle’, täpselt ‘exactly; precisely’, loomulikult ‘of course; naturally’, ilmselt ‘visibly; apparently’, lihtsalt ‘just; simply’ etc.? This dissertation in linguistics investigates the use and development of a group of words in Estonian. Using the words above as examples, it is shown how the items with the same written form can be used in different functions. These so-called lt-words are primarily seen as full content adverbs. Yet at the same time they are also used as items that acquire their precise function in a specific context. In case of the latter, they are used to interfere, to repair, to hedge, to intensify, to comment etc. Consider the following illustrative sentences involving the word praktiliselt ‘practically; in practice, in reality’ in two distinctly different functions: ”Ta tunneb oma tööd nii teoreetiliselt kui ka praktiliselt ‘He knows his work both theoretically as well as practically’“ and „Praktiliselt kõik kohalviibijatest on mehed ‘Practically all of those present are men’. In the first sentence, praktiliselt functions as an adverb that carries a meaning ‘in reality, in practice’. In the second sentence it is a downtoner meaning that almost all of the people present are men. The language user would most likely not interpret the sentence as in reality all of the people present are men. This thesis is mainly based on data from the corpora of written Estonian, analyzing the use and development of the multifunctional items both qualitatively as well as quantitatively. In this dissertation, the evolutionary path for the lt-words is proposed. The thesis also contributes to a better understanding of language change in general

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Regional developments in the labor market and factors affecting it in Estonian counties during 2005-2018

Magistritöö Majandusarvestuse ja finantsjuhtimise õppekavalMagistritöö eesmärgiks on välja selgitada tööturu regionaalsed arengud ja seda mõjutavad tegurid Eesti maakondades 2005-2018. Töö koostamisel on autor kasutanud Eesti Statistikaameti andmebaasist saadud arvnäitajaid ning erinevaid kirjandusallikaid. Andmete analüüsimisel on kasutatud kvantitatiivset meetodit. Lisaks on töö autor kasutanud korrelatsioon- ja regressioonanalüüsi andmete omavaheliste seoste leidmiseks ning arvutanud ka variatsioonikordaja nägemaks kui palju tööhõive määr antud perioodil on varieerunud. Töö koostamisel selgus, et Eesti tööhõive määra mõjutavad mitmed tegurid, kuid töös uuriti rahvastikutihedust, ettevõtluse sünnimäära, palgatöötaja brutotulu, kõrgharidusega inimeste osakaalu maakonna tööjõus, tööjõus osalust vanemaealiste hulgas ja maakondliku SKP võrdlusena kogu Eesti SKP-st. Kõige suurem seos tööhõive määraga on tööhõives osalusel vanemaealiste hulgas ja palgatöötaja brutotulul, mida kinnitasid nii korrelatsioon- kui ka regressioonanalüüs. Autor jõudis järgnevate järeldusteni: mida aktiivsemad on vanemaealised tööturul, seda kõrgem on tööhõive ning mida suurem on keskmine brutotulu osakaal Eesti keskmisest brutotulust, seda suurem on tööhõive määr. Variatsioonikordaja alusel järeldas autor, et piirkonnad, kus varieeruvus on suurem on tööturg ja hõive ebastabiilsem ning tundlikum majandustsüklitele.The aim of this master’s thesis is to find out the regional developments of the labor market and the factors affecting it in Estonian countries during 2005-2018. In writing this thesis the author has used figures collected from Statistics Estonia and varios literature sources. Quantative method was used to analyze the data. In addition, the author used correlation and regression analysis to confirm the relation between different data and also calculated coefficient of variation to see how much the employment rate has varied over the period. In the writing of this thesis it became apparent that there are several factors that affect employment rate. But the main factors that were researched in that theses were the population density, enterprise birth rates, average gross income of employees, people with higher education in the country’s labor force, labour force particiation rate among eldery and GDP from total GDP of Estonia. The largest tie to employment rate was the labor force participation among eldery and average gross income of employees, this was confirmed by both correlation and regression analysis. The author made the conclusion: the more active eldery people in the labor force the labor force increases the employment rate and the higher share of average gross income in Estonian average gross income, the higher is employment rate. The author made also the conclusion that regions with higer variability, the labor market and employment rate are more unstable and sensitive to economic cycles

Effect of the Ionic Conductivity of the Electrolyte in Composite SOFC Cathodes

Solid oxide fuel cell (SOFC) cathodes were prepared by infiltration of 35 wt % La0.8Sr0.2FeO3 (LSF) into porous scaffolds of three, zirconia-based electrolytes in order to determine the effect of the ionic conductivity of the electrolyte material on cathode impedances. The electrolyte scaffolds were 10 mol % Sc2O3-stabilized zirconia (ScSZ), 8 mol % Y2O3-stabilized zirconia (YSZ), and 3 mol % Y2O3- 20 mol % Al2O3-doped zirconia (YAZ), prepared by tape casting with graphite pore formers. Each electrolyte scaffold was 65% porous, with identical pore structures as determined by scanning electron microscopy (SEM). Both symmetric cells and fuel cells were prepared and tested between 873 and 1073 K, using LSF composites that had been calcined to 1123 or 1373 K. Literature values for the electrolyte conductivities were confirmed using the ohmic losses from the impedance spectra. The electrode impedances decreased with increasing electrolyte conductivity, with the dependence being between to the power of 0.5 and 1.0, depending on the operating temperature and LSF calcination temperature

Systematic Studies of the Cathode-Electrolyte Interface in SOFC Cathodes Prepared by Infiltration

In this study, the effect of the morphology and ionic conductivity of the electrolyte material in SOFC composite cathodes is systematically studied. The specific surface area of prous yttria-stabilized zirconia (YSZ) scaffolds was varied by almost two orders of magnitude using different pore formers and surface treatment with hydrofluoric acid (HF). The effect of ionic conductivity on the performance of SOFC cathodes was studied for electrodes prepared by infiltration of 35 wt % LSF into 65% porous scandia-stabilized zirconia (ScSZ), YSZ, or yttria-alumina co-stabilized zirconia (YAZ) scaffolds of identical microstructure cathodes