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1
Fuchs, Sven. "Well-log based determination of rock thermal conductivity in the North German Basin." Phd thesis, Universität Potsdam, 2013. http://opus.kobv.de/ubp/volltexte/2013/6780/.
Full textAbstract:
In sedimentary basins, rock thermal conductivity can vary both laterally and vertically, thus altering the basin’s thermal structure locally and regionally. Knowledge of the thermal conductivity of geological formations and its spatial variations is essential, not only for quantifying basin evolution and hydrocarbon maturation processes, but also for understanding geothermal conditions in a geological setting. In conjunction with the temperature gradient, thermal conductivity represents the basic input parameter for the determination of the heat-flow density; which, in turn, is applied as a major input parameter in thermal modeling at different scales. Drill-core samples, which are necessary to determine thermal properties by laboratory measurements, are rarely available and often limited to previously explored reservoir formations. Thus, thermal conductivities of Mesozoic rocks in the North German Basin (NGB) are largely unknown. In contrast, geophysical borehole measurements are often available for the entire drilled sequence. Therefore, prediction equations to determine thermal conductivity based on well-log data are desirable. In this study rock thermal conductivity was investigated on different scales by (1) providing thermal-conductivity measurements on Mesozoic rocks, (2) evaluating and improving commonly applied mixing models which were used to estimate matrix and pore-filled rock thermal conductivities, and (3) developing new well-log based equations to predict thermal conductivity in boreholes without core control.
Laboratory measurements are performed on sedimentary rock of major geothermal reservoirs in the Northeast German Basin (NEGB) (Aalenian, Rhaethian-Liassic, Stuttgart Fm., and Middle Buntsandstein). Samples are obtained from eight deep geothermal wells that approach depths of up to 2,500 m. Bulk thermal conductivities of Mesozoic sandstones range between 2.1 and 3.9 W/(m∙K), while matrix thermal conductivity ranges between 3.4 and 7.4 W/(m∙K). Local heat flow for the Stralsund location averages 76 mW/m², which is in good agreement to values reported previously for the NEGB. For the first time, in-situ bulk thermal conductivity is indirectly calculated for entire borehole profiles in the NEGB using the determined surface heat flow and measured temperature data. Average bulk thermal conductivity, derived for geological formations within the Mesozoic section, ranges between 1.5 and 3.1 W/(m∙K).
The measurement of both dry- and water-saturated thermal conductivities allow further evaluation of different two-component mixing models which are often applied in geothermal calculations (e.g., arithmetic mean, geometric mean, harmonic mean, Hashin-Shtrikman mean, and effective-medium theory mean). It is found that the geometric-mean model shows the best correlation between calculated and measured bulk thermal conductivity. However, by applying new model-dependent correction, equations the quality of fit could be significantly improved and the error diffusion of each model reduced. The ‘corrected’ geometric mean provides the most satisfying results and constitutes a universally applicable model for sedimentary rocks. Furthermore, lithotype-specific and model-independent conversion equations are developed permitting a calculation of water-saturated thermal conductivity from dry-measured thermal conductivity and porosity within an error range of 5 to 10%.
The limited availability of core samples and the expensive core-based laboratory measurements make it worthwhile to use petrophysical well logs to determine thermal conductivity for sedimentary rocks. The approach followed in this study is based on the detailed analyses of the relationships between thermal conductivity of rock-forming minerals, which are most abundant in sedimentary rocks, and the properties measured by standard logging tools. By using multivariate statistics separately for clastic, carbonate and evaporite rocks, the findings from these analyses allow the development of prediction equations from large artificial data sets that predict matrix thermal conductivity within an error of 4 to 11%. These equations are validated successfully on a comprehensive subsurface data set from the NGB. In comparison to the application of earlier published approaches formation-dependent developed for certain areas, the new developed equations show a significant error reduction of up to 50%.
These results are used to infer rock thermal conductivity for entire borehole profiles. By inversion of corrected in-situ thermal-conductivity profiles, temperature profiles are calculated and compared to measured high-precision temperature logs. The resulting uncertainty in temperature prediction averages < 5%, which reveals the excellent temperature prediction capabilities using the presented approach.
In conclusion, data and methods are provided to achieve a much more detailed parameterization of thermal models.Die thermische Modellierung des geologischen Untergrundes ist ein wichtiges Werkzeug bei der Erkundung und Bewertung tiefliegender Ressourcen sedimentärer Becken (e.g., Kohlenwasserstoffe, Wärme). Die laterale und vertikale Temperaturverteilung im Untergrund wird, neben der Wärmestromdichte und der radiogenen Wärmeproduktion, hauptsächlich durch die Wärmeleitfähigkeit (WLF) der abgelagerten Gesteinsschichten bestimmt. Diese Parameter stellen die wesentlichen Eingangsgrößen für thermische Modelle dar. Die vorliegende Dissertation befasst sich mit der Bestimmung der Gesteins-WLF auf verschiedenen Skalen. Dies umfasst (1) laborative WLF-Messungen an mesozoischen Bohrkernproben, (2) die Evaluierung und Verbesserung der Prognosefähigkeit von Mischgesetzten zur Berechnung von Matrix- und Gesamt-WLF sedimentärer Gesteine, sowie (3) die Entwicklung neuer Prognosegleichungen unter Nutzung bohrlochgeophysikalischer Messungen und multivariater Analysemethoden im NGB. Im Nordostdeutschen Becken (NEGB) wurden für die wichtigsten geothermischen Reservoire des Mesozoikums (Aalen, Rhät-Lias-Komplex, Stuttgart Formation, Mittlerer Buntsandstein) Bohrkerne geothermischer Tiefbohrungen (bis 2.500 m Tiefe) auf Ihre thermischen und petrophysikalischen Eigenschaften hin untersucht. Die WLF mesozoischer Sandsteine schwankt im Mittel zwischen 2,1 und 3,9 W/(m∙K), die WLF der Gesteinsmatrix hingegen im Mittel zwischen 3,4 und 7,4 W/(m∙K). Neu berechnete Werte zur Oberflächenwärmestromdichte (e.g., 76 mW/m², Stralsund) stehen im Einklang mit den Ergebnissen früherer Studien im NEGB. Erstmals im NDB wurde für das mesozoisch/känozoischen Intervall am Standort Stralsund ein in-situ WLF-Profil berechnet. In-situ Formations-WLF, für als potentielle Modelschichten interessante, stratigraphische Intervalle, variieren im Mittel zwischen 1,5 und 3,1 W/(m∙K) und bilden eine gute Grundlage für kleinskalige (lokale) thermische Modelle. Auf Grund der in aller Regel nur eingeschränkt verfügbaren Bohrkernproben sowie des hohen laborativen Aufwandes zur Bestimmung der WLF waren alternative Methoden gesucht. Die Auswertung petrophysikalischer Bohrlochmessungen mittels mathematischer-statistischer Methoden stellt einen lang genutzten und erprobten Ansatz dar, welcher in seiner Anwendbarkeit jedoch auf die aufgeschlossenen Gesteinsbereiche (Genese, Geologie, Stratigraphie, etc.) beschränkt ist. Daher wurde ein leicht modifizierter Ansatz entwickelt. Die thermophysikalischen Eigenschaften der 15 wichtigsten gesteinsbildenden Minerale (in Sedimentgesteinen) wurden statistisch analysiert und aus variablen Mischungen dieser Basisminerale ein umfangreicher, synthetischer Datensatz generiert. Dieser wurde mittels multivariater Statistik bearbeitet, in dessen Ergebnis Regressionsgleichungen zur Prognose der Matrix-WLF für drei Gesteinsgruppen (klastisch, karbonatisch, evaporitisch) abgeleitet wurden. In einem zweiten Schritt wurden für ein Echtdatenset (laborativ gemessene WLF und Standardbohrlochmessungen) empirische Prognosegleichungen für die Berechnung der Gesamt-WLF entwickelt. Die berechneten WLF zeigen im Vergleich zu gemessenen WLF Fehler zwischen 5% und 11%. Die Anwendung neu entwickelter, sowie in der Literatur publizierter Verfahren auf den NGB-Datensatz zeigt, dass mit den neu aufgestellten Gleichungen stets der geringste Prognosefehler erreicht wird. Die Inversion neu berechneter WLF-Profile erlaubt die Ableitung synthetischer Temperaturprofile, deren Vergleich zu gemessenen Gesteinstemperaturen in einen mittleren Fehler von < 5% resultiert. Im Rahmen geothermischer Berechnungen werden zur Umrechnung zwischen Matrix- und Gesamt-WLF häufig Zwei-Komponenten-Mischmodelle genutzt (Arithmetisches Mittel, Harmonische Mittel, Geometrisches Mittel, Hashin-Shtrikman Mittel, Effektives-Medium Mittel). Ein umfangreicher Datensatz aus trocken- und gesättigt-gemessenen WLF und Porosität erlaubt die Evaluierung dieser Modelle hinsichtlich Ihrer Prognosefähigkeit. Diese variiert für die untersuchten Modelle stark (Fehler: 5 – 53%), wobei das geometrische Mittel die größte, quantitativ aber weiterhin unbefriedigende Übereinstimmungen zeigt. Die Entwicklung und Anwendung mischmodelspezifischer Korrekturgleichungen führt zu deutlich reduzierten Fehlern. Das korrigierte geometrische Mittel zeigt dabei, bei deutlich reduzierter Fehlerstreubreite, erneut die größte Übereinstimmung zwischen berechneten und gemessenen Werten und scheint ein universell anwendbares Mischmodel für sedimentäre Gesteine zu sein. Die Entwicklung modelunabhängiger, gesteinstypbezogener Konvertierungsgleichungen ermöglicht die Abschätzung der wassergesättigten Gesamt-WLF aus trocken-gemessener WLF und Porosität mit einem mittleren Fehler < 9%. Die präsentierten Daten und die neu entwickelten Methoden erlauben künftig eine detailliertere und präzisere Parametrisierung thermischer Modelle sedimentärer Becken.
2
Whisler, Bruce A. "A qualitative and quantitative analysis of the acoustical effect of cryogenic freezing on brass trumpets." Virtual Press, 2002. http://liblink.bsu.edu/uhtbin/catkey/1238742.
Full textAbstract:
The purpose of this study was to determine whether deep-cryogenic freezing produces a change in the timbre or playing characteristics of brass trumpets. The experimental procedure consisted of two parts: quantitative analysis and qualitative analysis. For qualitative analysis a panel of four professional trumpet players evaluated five trumpets: four were frozen and re-evaluated, and one served as the experimental control. Analysis of the harmonic spectra of tones from each instrument provided quantitative data. Since previous studies requiring the analysis of musical instrument tones have suffered from a high degree of variation among tones played by human performers, I constructed a mechanical device that could play tones on the test instruments with greater consistency than is possible with live performers.The changes observed in the qualitative and quantitative analyses are very small, and possibly contradictory. The test panel rated all of the instruments higher after they had been frozen, and any actual improvement in the playing characteristics is suspect because the control instrument received the second highest improvement of the five instruments in the study. In the quantitative analysis, I observed some slight changes in the amplitudes of some of the harmonics in the spectral graphs, but I also observed slight variations in some of the harmonics of the control instrument. Inconsistencies in the performance of the electronic equipment used in the study could account for some of the variation. The instrument that showed the most statistically significant improvements was rated significantly higher in intonation after cryogenic processing, but I was unable to measure any frequency changes in the tones the mechanical embouchure played on the test instruments.Although one may not actually be able to measure differences reported in the qualitative analysis, it is not possible to rule out any acoustical change from cryogenic freezing. In fact, in the quantitative measurements, three of the instruments showed changes greater (some positive and some negative) than the "experimental error" seen in the control instrument's measurements. Additionally, one member of the test panel is convinced that cryogenic freezing has improved his instrument significantly, but the other three trumpeters are ambivalent.School of Music
3
Hsu, Chuan-liang. "Influence of cooling rate on glass transition temperature and starch retrogradation during low temperature storage /." free to MU campus, to others for purchase, 1998. http://wwwlib.umi.com/cr/mo/fullcit?p9924889.
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Jacobi, Christoph, Nadja Samtleben, and Gunter Stober. "Meteor radar observations of mesopause region long-period temperature oscillations." Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-212263.
Full textAbstract:
Meteor radar observations of mesosphere/lower thermosphere (MLT) daily temperatures have been performed at Collm, Germany since August 2004. The data have been analyzed with respect to long-period oscillations at time scales of 2–30 days. The results reveal that oscillations with periods of up to 6 days are more frequently observed during summer, while those with longer periods have larger amplitudes during winter. The oscillations may be considered as the signature of planetary waves. The results are compared with analyses from radar wind measurements. Moreover, the temperature oscillations show considerable year-to-year variability. In particular, amplitudes of the quasi 5-day oscillation have increased during the last decade, and the quasi 10-day oscillations are larger if the equatorial stratospheric winds are eastward.
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Aguilar, Jaramillo Andrea Elizabeth. "Implicación de los genes de la familia RAV en el desarrollo floral." Doctoral thesis, Universitat Autònoma de Barcelona, 2016. http://hdl.handle.net/10803/393982.
Full textAbstract:
La floración es probablemente el proceso más importante en el desarrollo de la
planta, ya que la perpetuación de las especies vegetales depende de ella. En Arabidopsis
thaliana, la inducción floral está controlada por varias rutas genéticas que responden a
estímulos ambientales y endógenos. En nuestro laboratorio se han identificado los genes
TEMPRANILLO (TEM) como represores de la floración tanto en condiciones inductivas
de día largo (LD, 16 horas de luz) como no inductivas de día corto (SD, 8 horas de luz).
Las proteínas TEM pertenecen a una familia de factores de transcripción llamada RAV,
que se caracterizan por contener dos dominios de unión al DNA, que son los dominios
APETALA2 (AP2) y B3. En Arabidopsis esta familia está compuesta por 6 genes. En
LD, la ruta del fotoperiodo induce la floración principalmente a través de la activación
del gen FLOWERING LOCUS T (FT), mientras que en SD la floración depende
principalmente de la acumulación de giberelinas (GAs). TEM1 y TEM2 retrasan la
floración en ambas condiciones al reprimir directamente la expresión de los genes FT,
GA3OXIDASE 1 (GA3OX1) y GA3OX2, siendo los dos últimos genes responsables de la
biosíntesis de la GA bioactiva GA4. Por tanto, TEM1 y TEM2 controlan el tiempo de
floración a través de al menos dos de las rutas genéticas que controlan la inducción
floral: la del fotoperíodo (Castillejo & Pelaz, 2008) y la de las GAs (Osnato et al, 2012).
El objetivo de este trabajo ha sido profundizar en el papel de los genes TEM en
otras rutas genéticas implicadas en el control de la floración y en otros procesos de
desarrollo en Arabidopsis thaliana.
Existe una ruta genética que responde a la edad de la planta y que evita que ésta
florezca en su etapa juvenil. Primero se produce la transición de la etapa vegetativa
juvenil a la adulta y después la inducción floral. Los microRNAs miR156 y miR172
están implicados en la regulación de estas transiciones entre las fases del desarrollo de
la planta (Huijser & Schmid, 2011). miR156 mantiene la fase juvenil y retrasa la
transición floral (Wu & Poeting, 2006; Wu et al, 2009), mientras que los genes diana de
miR156 SQUAMOSA PROMOTER BINDING PROTEIN-LIKE (SPL) y miR172
promueven la transición a la fase adulta y la inducción floral. Nuestros resultados
muestran que los genes TEM están involucrados en varias etapas de la ruta de la edad,
ya que regulan positivamente a miR156 y negativamente a varios genes SPL y miR172,
retrasando así la floración. Por tanto, los genes TEM desempeñan un papel clave en la respuesta a la edad de la planta (Capítulo 1; Aguilar-Jaramillo et al., manuscrito en
preparación).
Por otro lado, cuando las plantas crecen en LD a bajas temperaturas ambientales
de 16ºC, la floración se retrasa respecto a 22°C. Nuestros resultados muestran que los
genes TEM actúan como represores de FT y TWIN SISTER OF FT (TSF) a 16°C. Un
gen que juega un papel clave en la respuesta a las bajas temperaturas ambientales es
SHORT VEGETATIVE PHASE (SVP), cuyos mutantes son insensibles a los cambios de
temperatura y florecen pronto tanto a temperaturas cálidas como frescas. Hemos
descubierto que SVP regula positivamente la expresión de TEM2 a 16ºC en condiciones
de LD y controla la floración a través de TEM2, pero también de manera independiente
mediante la represión directa de FT a bajas temperaturas ambientales (Capítulo 2;
Marín-González et al, 2015).
Además, hemos descubierto la participación de TEM en otro proceso del
desarrollo, la iniciación de los tricomas. Los tricomas son protrusiones epidérmicas que
protegen a la planta de la pérdida de agua, de insectos y de las radiaciones ultravioletas.
Hemos descubierto que los genes TEM controlan la iniciación de los tricomas mediante
la represión directa de los genes epidérmicos que promueven su iniciación y, lo que es
más interesante, a través del control de la acumulación y distribución de las GAs en el
mesófilo. Esta función de los genes TEM desvela el papel clave de una capa celular, el
mesófilo, en la diferenciación celular de los tricomas en la capa exterior adyacente, la
epidermis (Capítulo 3; Matías-Hernández et al, 2016).Flowering is probably the most important process in plant development since the perpetuation of the species depends on it. In Arabidopsis thaliana, floral induction is controlled by several genetic pathways that respond to environmental and endogenous stimuli. In our laboratory we have identified the TEMPRANILLO (TEM) genes as flowering repressors under both inductive long-day (LD, 16 hours of light) and noninductive short-day (SD, 8 hours of light) conditions. The TEM proteins belong to a family of transcription factors called RAV, characterized by the presence of two DNA binding domains, the APETALA2 (AP2) and B3 domains. In Arabidopsis this family is composed of 6 genes. Under LD the photoperiod pathway induces flowering mainly through activation of FLOWERING LOCUS T (FT), while under SD flowering depends mainly on the accumulation of gibberellins (GAs). TEM1 and TEM2 delay flowering under both conditions by directly repressing the expression of the FT, GA 3-OXIDASE 1 (GA3OX1) and GA3OX2 genes, the latter two genes being responsible for the biosynthesis of bioactive GA4. Therefore, TEM1 and TEM2 control flowering time through at least two of the genetic pathways that control floral induction: the photoperiod (Castillejo & Pelaz, 2008) and the GA pathway (Osnato et al, 2012). In this PhD thesis we aimed to deepen the role of TEM genes in other genetic pathways controlling flowering and other developmental processes in Arabidopsis thaliana. There is a genetic pathway that responds to the age of the plant and prevents flowering at the juvenile phase. First there is a transition from the juvenile to the adult vegetative stage and then floral induction occurs. The microRNAs miR156 and miR172 are involved in the regulation of these phase transitions of plant development (Huijser & Schmid, 2011). MiR156 maintains the juvenile phase and delays the floral transition (Wu & Poeting, 2006; Wu et al, 2009), while miR156-target SQUAMOSA PROMOTER BINDING PROTEIN-LIKE (SPL) genes and miR172 promote the transition to adulthood and floral induction. Our results show that TEM genes are involved in regulating various stages of the age-dependent pathway as they positively regulate miR156 and negatively regulate several SPL genes and miR172, thus delaying flowering. Therefore, TEM genes play a key role in responding to the age of the plant (Chapter 1, Aguilar-Jaramillo et al., manuscript in preparation). On the other hand, when Arabidopsis plants grow under LD at low ambient temperatures of 16°C, flowering is delayed relative to 22°C. Our results show that TEM genes act as repressors of FT and TWIN SISTER OF FT (TSF) at 16°C. A gene that plays a key role in the response to low ambient temperatures is SHORT VEGETATIVE PHASE (SVP). svp mutants are insensitive to temperature changes and flower early both under warm and cool temperatures. We have found that SVP positively regulates TEM2 expression at 16 °C under LD conditions, controlling flowering through TEM2 but also independently of TEM2 by directly repressing FT at low temperatures (Chapter 2; Marín-González et al, 2015). In addition, we have discovered the involvement of TEM in another developmental process, the initiation of trichomes. Trichomes are epidermal protrusions that protect the plant from water loss, insects and ultraviolet radiation. We show that TEM genes control the initiation of trichomes by directly repressing the epidermal genes that promote trichome initiation and, more interestingly, by controlling the accumulation and distribution of GAs in the mesophyll. This function of TEM genes reveals a key role of a cell layer, the mesophyll, in trichome differentiation in the outer adjacent cell layer, the epidermis (Chapter 3; Matías-Hernández et al, 2016).
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Fernandez, Juan Manuel Carvajalino. "Tolerância ao congelamento em algumas espécies de anuros de América do Sul: mecanismos e estratégias." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/41/41135/tde-18102017-131508/.
Full textAbstract:
Os limites geográficos que marcam o risco de congelamento são determinantes na biodiversidade de anfíbios. Os mecanismos fisiológicos envolvidos na preparação e reação aos eventos de temperatura extrema são específicos e dependem da previsibilidade e repetitividade destes eventos. Na América do Sul, existem regiões com risco de congelamento para os anfíbios, contudo pouco se conhece da tolerância ao congelamento em espécies endêmicas deste continente. O doutorado foi elaborado em locais com reportes de congelamento na Argentina e o Brasil, usando como modelo as espécies Alsodes gargola, Bokermanohyla gouveai, Dendrosophus minutus, D. microps, Hypsiboas latistriatus, H. polytaenius, Melanophryniscus moreirae, Pleurodema bufoninum, Ologygon brieni, Scinax duartei e S. hayii, avaliando exposição potencial ao congelamento em refúgios termais, sobrevivência a temperatura congelante, mudanças em moléculas com função crioprotetora (colesterol, glicose, proteínas, triglicérides, ureia) e crescimento de gelo corporal. Dentro deste contexto, a minha hipótese geral foi que existem anfíbios que sobrevivem ao congelamento na América do sul e que estas espécies presentam mecanismos de resposta fisiológica que deveriam variar entre espécies em um evento de congelamento controlado. No decorrer do doutorado esta hipótese foi corroborada, encontrando sobrevivência a temperatura congelantes nas especies A. gargola, B. gouveai, D. microps, H. latistriatus, H. polytaenius, M. moreirae, P. bufoninum, S. duartei e S. hayii, sendo que existe uma amplia variedade de estratégias fisiológicas para fazer frente ás baixas temperaturas. Entre as espécies anteriormente reportadas, definiu-se que D. microps, H. polytaenius, P. bufoninum, S. duartei e S. hayii, são tolerantes ao congelamento devido a que apresentarem tanto acumulo de crioprotectores como crescimento de gelo corporal durante a exposição a baixas temperaturas. Por outro lado usando analises filogenéticos, conseguiu-se reforçar a hipóteses que a tolerância ao congelamento é convergente ao longo da historia evolutiva dos anfíbios, acontecendo independentemente em vários clados. As novas descobertas sobre a riqueza fisiologia no nível de adaptações frente ao congelamento em América do Sul são apenas pequenas amostras do que potencialmente pode ser achada pensando na biodiversidade existente neste continente, logo a presente tese, é só um incentivo para futuros trabalho na áreaThe geographical boundaries that mark the risk of freezing are determinants for amphibian biodiversity. The physiological mechanisms involved in the preparation and reaction to extreme temperature events are specific and depend on the predictability and repeatability of these events. In South America, there are regions with freezing risk for amphibians, however little is known about the freezing tolerance in endemic species to this continent. The present doctoral dissertation was prepared in places with freezing reports in Argentina and Brazil, using as biological models the species Alsodes gargola, Bokermanohyla gouveai, Dendrosophus minutus, D. microps, Hypsiboas latistriatus, H. polytaenius, Melanophryniscus moreirae, Pleurodema bufoninum, Ologygon brieni, Scinax duartei and S. hayii, evaluating potential exposure to freezing in thermal refuges, survival to freezing temperature, changes in cryoprotectant molecules (cholesterol, glucose, proteins, triglycerides, urea) and body ice growth. Within this context, my general hypothesis was that there are amphibians that survive freezing in South America and that these species present physiological mechanisms that should vary among species in a controlled freezing event. In the course of my doctorate, this hypothesis was confirmed, finding survival to freezing temperature in the species A. gargola, B. gouveai, D. microps, H. latistriatus, H. polytaenius, M. moreirae, P. bufoninum, S. duartei and S. hayii, being a wide variety of physiological strategies to protect the animals to the low temperatures. Among the previously reported species, D. microps, H. polytaenius, P. bufoninum, S. duartei, S. hayii, were defined as freezing tolerant because they exhibit both accumulation of cryoprotectants and body ice growth during freeze exposure. On the other hand using phylogenetic analyzes, it was possible to reinforce the hypotheses that the freezing tolerance strategy is convergent throughout the evolutionary history of the amphibians, happening independently in several clades. The new findings about physiological richness at the level of adaptations to freezing in South America are only small samples of what can be found within the biodiversity existing on this continent, so the present thesis is only an incentive for future work in the area
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Samtleben, Nadja, and Christoph Jacobi. "Long-period oscillations derived from mesosphere/lower thermosphere meteor radar temperature measurements." Universität Leipzig, 2015. https://ul.qucosa.de/id/qucosa%3A16649.
Full textAbstract:
Using measurements, derived from a meteor radar in Collm (51.3°N, 13°E), the mesopause region is analyzed with respect to the temperature distribution at an altitude of 90 km over a period of 10 years. The analyzed period lasts from 2005 till 2013. Based on these measurements, the typical temperature seasonal cycle of the mesopause region can be observed. The temperature reaches its minimum of about 130 K in summer and its maximum of about 220 K in winter. At this altitude, also strong day-today- fluctuations of up to 35 K exist, which are probably partly induced by planetary waves. Shorter-period oscillations with a period between 2 and 6 days have maximum amplitudes during summer, while longer-period oscillations with a period between 7 and 20 days maximize during winter. During the measurement period the amplitudes of oscillations with periods between 4 and 6 days, which may be attributed to the quasi-5-day-wave, increase with time.Auf der Grundlage von Messungen eines Meteorradars in Collm (51.3°N, 13°E), die in einer Höhe von 90 km erfolgten, was in etwa der Mesopause entspricht, wird die Temperatur hinsichtlich ihres Jahresganges und insbesondere ihrer Variationen in einem Messzeitraum von 10 Jahren analysiert. Der analysierte Zeitraum erstreckt sich von 2005 bis 2013. Anhand der Daten kann man den typischen Jahresgang der Temperatur in der Mesopausenregion erkennen. Die Temperatur erreicht im Sommer das Minimum bei etwa 130 K und im Winter das Maximum bei etwa 220 K. Zudem treten starke Tag-zu-Tag-Fluktuationen auf, die im Maximum 35 K betragen. Diese werden vermutlich durch planetare Wellenaktivität der Atmosphäre hervorgerufen. Hierbei spielen im Sommer die kurzwelligen und im Winter die langwelligen Oszillationen, letztere mit Perioden größer 7 Tage, die wesentliche Rolle. Ferner sind innerhalb des Messzeitraums zunehmende Amplituden von Oszillationen mit Perioden zwischen 4 und 6 Tagen (quasi 5-Tage-Welle) zu erkennen.
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Bonthron, Björn, and Christian Jonsson. "Geogrids in cold climate : Temperature controlled tensile tests & Half-scale installation tests at different temperatures." Thesis, Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-63204.
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Due to the findings of extensive damage on geogrids used in a road embankment in northern Sweden, the Swedish Transport Administration (TRV) started to investigate the reason of these damages. Since the geogrids were installed at low temperature, below 0°C, it was suspected that the damages were connected the low temperature. To analyse whether low temperatures have an influence on the extent of installation damages, both a half-scale setup and temperature controlled tensile tests have been carried out on geogrids. In total five different types of geogrids have been tested; 3 extruded polypropylene geogrids, 1 woven PET geogrid, and 1 welded PET geogrid. All geogrids had an aperture size of approximately 35 mm and specified tensile strength of approximately 40 kN/m. The Half-scale tests was conducted by building a small road embankment inside a freeze container, at the Luleå University of Technology (LTU). The embankment contained crushed aggregate, type 0-70 mm, and geogrids. The purpose of the half-scale test was to simulate installation of geogrids at different temperatures and thereby investigate whether low temperatures have an influence on the rate of installation damages. The half-scale test was done for each type of geogrid at the temperatures: +20°C, -20°C and -30°C. First, the geogrid was covered by 150 mm of crushed aggregate. Then a vibratory plate (160 kg) was used to compact the crushed aggregate. After each installation, the crushed aggregate was removed carefully by vacuum suction. The geogrid was removed and then analysed by visual control and tensile tests conducted according to ISO 10319:2008 (wide width tensile test). Results from the half-scale tests indicate that 2 out of 5 of the tested geogrids were affected by the testing procedure. The results indicate that: - one of the geogrids of polyprophylene (here referred to as G2) was more damaged at lower temperatures compared to installation at +20° C. - the geogrid of woven PET (here referred to as G5) was less damaged at lower temperatures compared to installation at +20° C. Results for the other geogrids are either inconsistent or shows no significant variation of the measured parameters as function of temperature. Hence, these results cannot be interpreted as damage during installation. Temperature controlled tensile tests were done by tensile testing single strands from the geogrids to failure, inside a temperature controlled chamber. The purpose of these tests was to investigate how the strength properties of the geogrids are affected by low temperature. The test was repeated 5 times for each geogrid and temperature (+20°C, 0°C, -10°C and -20°C). Force and strain was measured during the tests. The results from the temperature controlled tensile tests show that the maximum strain decreases with lower temperature for all tested geogrids. The maximum strain decreased by 16% - 49% when the temperature dropped from +20°C to -20°C. The results show that the tensile strength increases with lower temperature for all tested geogrids except for the welded PET geogrid (here referred to as G1). For G1 the tensile strength decreased by approximately 7% at a temperature drop from +20°C to -20°C. For the woven PET geogrid (G5) and the polypropylene geogrids (G2-G3) the tensile strength increased between 13%-45% at a temperature drop from +20°C to -20°C. The E-modulus increased at lower temperature for all tested geogrids. The secant E-modulus at 2% strain increased by 13%-71% at a temperature drop from +20°C to -20°C. Summarized conclusions from the tests: Strength properties changed for all tested geogrids as the temperature decreased. All tested geogrids got stiffer at lower temperatures. The magnitude of the effects is different for different geogrids. The tensile strength increased with lower temperature for all tested geogrids except for the welded PET geogrid, which got lower tensile strength at lower temperature. The half-scale test indicates that the amount of installation damages at geogrids can be dependent of the temperature at installation. However, these indications can only be seen at two out of five tested geogrids. The effect cannot be connected to a specific step in the installation procedure and cannot be explained by the results from the temperature controlled tensile tests. The results from the half-scale test have a statistically low reliability since only one installation for each temperature and geogrid type was done. The compaction equipment used during the test was small, and had low compaction energy compared to a vibratory roller compactor commonly used in construction work. With respect to the discussion above, further studies should be focusing on developing the half-scale test. It is suggested that the test is scaled up to a full-scale test in order to simulate a real installation as close as possible. The test should also be conducted several times for each geogrid at each temperature in order to enable statistical analyses.
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Matthews, Jason E. "Thermoelectric and Heat Flow Phenomena in Mesoscopic Systems." Thesis, University of Oregon, 2011. http://hdl.handle.net/1794/12108.
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xvii, 189 p. ： ill. (some col.)Low-dimensional electronic systems, systems that are restricted to single energy levels in at least one of the three spatial dimensions, have attracted considerable interest in the field of thermoelectric materials. At these scales, the ability to manipulate electronic energy levels offers a great deal of control over a device's thermopower, that is, its ability to generate a voltage due to a thermal gradient. In addition, low-dimensional devices offer increased control over phononic heat flow. Mesoscale geometry can also have a large impact on both electron and phonon dynamics. Effects such as ballistic transport in a two-dimensional electron gas structure can lead to the enhancement or attenuation of electron transmission probabilities in multi-terminal junctions. The first half of this dissertation investigates the transverse thermoelectric properties of a four-terminal ballistic junction containing a central symmetry-breaking scatterer. It is believed that the combined symmetry of the scatterer and junction is the key component to understanding non-linear and thermoelectric transport in these junctions. To this end, experimental investigations on this type of junction were carried out to demonstrate its ability to generate a transverse thermovoltage. To aid in interpreting the results, a multi-terminal scattering-matrix theory was developed that relates the junction's non-linear electronic properties to its thermoelectric properties. The possibility of a transverse thermoelectric device also motivated the first derivation of the transverse thermoelectric efficiency. This second half of this dissertation focuses on heat flow phenomena in InAs/InP heterostructure nanowires. In thermoelectric research, a phononic heat flow between thermal reservoirs is considered parasitic due to its minimal contribution to the electrical output. Recent experiments involving heterostructure nanowires have shown an unexpectedly large heat flow, which is attributed in this dissertation to an interplay between electron-phonon interaction and phononic heat flow. Using finite element modeling, the recent experimental findings have provided a means to probe the electron-phonon interaction in InAs nanowires. In the end, it is found that electron-phonon interaction is an important component in understanding heat flow at the nanoscale. This dissertation includes previously unpublished co-authored material.
Committee in charge: Dr. Richard Taylor， Chair； Dr. Heiner Linke， Advisor； Dr. David Cohen， Member； Dr. John Toner， Member； Dr. David Johnson， Outside Member
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Falquetto, Paula Lyra 1987. "Desenvolvimento de uma bomba de calor doméstica para secagem de hortelã." [s.n.], 2013. http://repositorio.unicamp.br/jspui/handle/REPOSIP/255768.
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Orientador: Vivaldo Silveira JuniorDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos
Made available in DSpace on 2018-08-21T19:48:08Z (GMT). No. of bitstreams: 1 Falquetto_PaulaLyra_M.pdf: 2346097 bytes, checksum: 46b1d8899428de4582aaf03fa022871c (MD5) Previous issue date: 2013
Resumo: Diversos tipos de secagem tem sido utilizados para produtos termossensiveis. O proposito fundamental e a reducao dos custos de transporte, estocagem e o aumento da vida util. Ao mesmo tempo, ha um crescente interesse dos consumidores no uso de ervas e especiarias pelo sabor diferenciado nos alimentos preparados com as mesmas. Em secadores convencionais, o tratamento do ar resulta em temperaturas muito mais altas que a ambiente e umidades absolutas mais baixas, proporcionando maior perda de compostos responsaveis pela cor e sabor, entre outros, durante o processo. Em vista disso, o trabalho teve como objetivos o desenvolvimento e avaliacao de um sistema de tratamento de ar, baseado em uma bomba de calor que produz um ar a baixas temperaturas e pressao de vapor de agua, alimentando um gabinete de bandejas para uso domestico com adaptacao de um refrigerador comercial. Os ensaios foram realizados a pressao atmosferica dentro da cabine. Apos o tratamento do ar (desumidificacao do ar e posterior aquecimento, realizados pela bomba de calor), se obteve uma diferenca das condicoes do ar em comparacao ao ar ambiente de entrada de 22 a 26 oC na temperatura e de 36 a 69% da umidade relativa. O equipamento apresentou bom desempenho na secagem da hortela, produto escolhido para os ensaios, mostrando pouca diferenca na coloracao em relacao a amostra in natura. O tempo de secagem foi de aproximadamente 4 horas, quando se atingiu a umidade do produto desejada, em torno de 6%. O consumo energetico do equipamento no periodo do ensaio ficou em torno de 2 kWh para uma quantidade de 25 g de materia seca
Abstract: Different types of drying are being used for thermosensitive products. The fundamental purpose is the reduction of transportation and storage costs, and increasing of shelf life. At the same time, there is a growing consumer interest in the use of herbs and spices because of the differentiated flavor in distinct foods prepared with them. In conventional dryers air treatment results in higher temperatures that the ambient and lower absolute humidity providing greater loss of compounds responsible for the color and flavor among others during the process. This work had the objective of development and evaluation of an air treatment system, based on a heat pump that operates at low temperatures, feeding a tray cabinet for domestic use with adaptation of a commercial refrigerator. The tests were a source at atmospheric pressure inside the cabin. After treatment of the air (air dehumidification and subsequent heating was done by heat pump), obtaining a difference of air conditions of 22 to 26 °C in temperature and 36 to 69% of moisture with relation to ambient air (input air). The equipment presented good performance in mint drying, the product chosen for the tests, showing differences in coloring low in relation to the fresh sample. The drying time was approximately 4 hours when it has reached the desired product moisture around 6%. The energy consumption of equipment around the time of the test was around 2 kWh for a quantity of 25 g of dry matter
Mestrado
Engenharia de Alimentos
Mestra em Engenharia de Alimentos
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Moen, Kurt Andrew. "Modeling of minority carrier recombination and resistivity in sige bicmos technology for extreme environment applications." Thesis, Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/26642.
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Thesis (M. S.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2009.Committee Chair: Cressler, John; Committee Member: Citrin, David; Committee Member: Shen, Shyh-Chiang. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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Botelho-Almeida, Túlia de Souza. "Avaliação da eficácia e aplicabilidade de processo de esterilização por ozônio." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/9/9139/tde-06122017-101241/.
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A busca contínua por tecnologias de esterilização a baixa temperatura deve-se à necessidade de adequação dos agentes esterilizantes às características físicoquímicas dos produtos, à conveniência de maior rapidez no processamento, além dos apelos ambientais, em comparação, por exemplo, com o método de esterilização por óxido de etileno. Desta forma surgiu interesse pelo ozônio (O3), o qual pode ser considerado o mais potente germicida natural que existe, sendo capaz de eliminar microrganimos (na forma vegetativa e esporulada) com alta eficiência e rapidez, graças a sua atividade altamente oxidante. O presente trabalho teve por objetivo proceder estudos para a determinação de parâmetros para o processo de esterilização empregando ozônio, além de avaliar a eficácia do agente esterilizante em questão. O processo de esterilização foi desafiado com esporos de Geobacillus stearothermophilus ATCC 7953 o qual se caracteriza frente as mesmas com elevada resistência. A eficácia esterilizante do ozônio foi avaliada através de carreadores inoculados com 106 do esporo, introduzidos em seringas de 3 mL e tubos com diferentes comprimentos e diâmetros, simulando produtos médico hospitalares. Tais dispositivos foram submetidos a meio ciclo e ciclo completo do processo de esterilização por ozônio. A validação do processo foi comprovada através dos resultados satisfatórios para meio ciclo, obtidos com os testes efetuados. Desta forma, foi possível constatar a eficácia do processo de esterilização por ozônio. Adicionalmente, foram objeto de investigação materiais termossensíveis distintos obtidos de produtos médico-hospitalares, a fim de estudar a influência do ozônio sobre as características intrínsecas desses materiais. As amostras foram submetidas ao ciclo completo de esterilização e analisadas pelo teste de citotoxicidade in vitro e avaliação da superfície dos materiais por espectrofotometria com transformadas de Fourier com acessório de refletância atenuada (ATR-FTIR) para esclarecer eventuais efeitos do processo sobre a biocompatibilidade das mesmas. Embora os materiais estudados não demonstraram efeito citotóxico após serem submetidos à esterilização por ozônio, a superfície do derivado de polietileno (PE) demonstrou uma banda de oxidação em consequência da ação do agente esterilizante.Ozone (O3) can be considered the most potent natural germicide against microorganisms (in vegetative and spore forms) with high efficiency and speed, because of its highly oxidizing activity. Despite this, there are a few studies describing the application of ozone as a sterilizing agent of medical devices. The aim of this paper was to describe the development and validation of a sterilization cycle applied to medical devices. The sterilization process was challenged with Geobacillus stearothermophilus ATCC 7953 spores, which have shown great resistance. The sterilizing effect of ozone was measured using carriers inoculated with 106 spores, introduced into a 3 mL syringe and lumens of tubes of different sizes and diameters simulating hospital medical products, which have undergone a half-cycle or complete cycle. The validation process was confirmed by the satisfactory results for the half cycle, which indicate an appropriate sterility assurance level. Thus, one can consider the ozone sterilization process effective for medical devices. On the other hand, there was a need to evaluate the safety of ozone sterilization in terms of medical device materials in order to clarify the influence of ozone on the intrinsic characteristics of these materials. The samples were submitted to the complete cycle of sterilization and analysis by the \"in vitro\" cytotoxicity test and evaluation of the surface of the materials using ATR-FTIR spectrometry to clarify eventual of the process on a biocompatibility. Although the materials studied did not demonstrate a cytotoxic effect after being subjected to ozone sterilization, the surface of the polyethylene (PE) derivative demonstrated an oxidation band as a consequence of the action of the sterilizing agent.
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Jelena, Purać. "Molekularne osnove otpornosti polarnih insekata na niske temperature." Phd thesis, Univerzitet u Novom Sadu, Prirodno-matematički fakultet u Novom Sadu, 2009. https://www.cris.uns.ac.rs/record.jsf?recordId=82067&source=NDLTD&language=en.
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Sposobnost insekata da se prilagode različitim ekološkim uslovima je veoma dobrodokumentovana; oni predstavljaju najrasprostranjeniju grupu životinja na planeti, sa vrstama koje naseljavaju različita kopnena i vodena staništa, od tropskih predela do polova. Razumevanje mehanizama koji omogućavaju insektima da prežive ekstremne temperature i zadrže vitalne funkcije tokom dugog perioda dormancije je kao model sistem od interesa za mnoge naučne oblasti. Na osnovu načina na koji preživljavaju temperature ispod 0ºC insekte možemo podeliti u tri grupe: i) insekti koji tolerišu formiranje leda u ekstraćelijskom prostoru,ii) insekti koji ne tolerišu zamrzavanje i moraju da ga izbegnu, a to čine superhlađenjem svojih telesnih tečnosti i iii) insekti koji preživljavaju zahvaljujući gubitku vode kroz permeabilnu kutikulu, što je nazvano krioprotektivna dehidratacija. Zajednička odlika organizama sa različitim mehanizmima adaptacije na niske temperature je setbiohemijskih jedinjenja čija se fiziološka funkcija razlikuje u zavisnosti da li organizam pripada grupi koja toleriše ili ne toleriše zamrzavanje. To su nukleatori kristalizacije leda, krio/anhidroprotektanti i antifriz proteini.Cilj ovih istraživanja je bio ispitivanje molekularne osnove otpornosti na niske temperature dve vrste polarnih kolembola Onychiurus arcticus i Cryptopygus antarcticus kombinujući fiziološki, biohemijski i molekularno biološki pristup. Ispitivane vrste izbegavaju zamrzavanje svojih telesnih tečnosti primenjujući različite strategije preživljavanja. Za antarktičku vrstu C. antarcticus karakteristična je brza promena tačke superhlađenja, kao i njena bimodalna distribucija tokom leta, kada neke jedinke mrznu na višim temperaturama (manje otporne na hladnoću), a druga na nižim (otpornije na hladnoću). Ova bimodalna distribucija tačke superhlađenja je dobro dokumentovana, ali slabo razjašnjena na molekularnom nivou. Druga, arktička vrsta O. arcticus koristi strategiju preživljavanja zimskih temperature koje idu i do -25ºC nazvanu krioprotektivna dehidratacija. Na ovaj način, količina slobodne vode u telu se značajno redukuje, a akumulira se trehaloza koja deluje kao krio/anhidroprotektant. Iako je krioprotektivna dehidratacija opisana i kod drugih vrstainsekata, molekularni mehanizmi koji se nalaze u osnovi ovog fenomena su veoma slabo razjašnjeni.Za karakterizaciju genoma generisano je 16379 EST sekvenci za O. arcticus i 1180 za C. antarcticus. To su ujedno i prvi javno dostupni podaci u bazama podataka o genomima ove dve vrste koji predstavljaju značajnu osnovu za komparativne genomske analize. Činjenica da kod obe analizirane vrste, oko 60% EST sekvenci nije pokazalo statistički značajnu sličnost sa proteinima iz baza podataka ukazuje na specifičan patern genske ekspresije kao adaptivni odgovor ispitivanih vrsta na niske temperature.Sa ciljem da se identifikuju geni uključeni u preživljavanje niskih temperatura konstruisani su mikroereji, za O. arcticus štampanjem 6912 cDNK u duplikatu, a za C. antarcticus štampanjem 672 cDNK u duplikatu.. Analizom sekvenci identifikovanih putem homologije sa dostupnm bazama podataka kod C. antarcticusuočen je jasan trend povećane ekspresije gena koji kodiraju strukturne proteine u grupi koja je otporna na hladnoću. Ove strukturne proteine uglavnom čine kutikularni proteini, što je u skladu sa rezultatima nedavnih istraživanja kod kolembola, da je presvlačenje proces tokom kog se snižava tačka superhlađenja, odnosno da varijacije u tački superhlađenja mogu nastati kao posledica endogenih fizioloških procesa tokom presvlačenja. Kod O. arcticus analizom EST sekvenci i mikroereja identifikovani supotencijalni geni i biohemijski putevi povezani sa krioprotektivnom dehidratacijom, a istakli bi gene uključene u metabolizam ugljenih hidrata, gene za akvaporine, proteine toplotnog stresa, LEA proteine i enzime antioksidativne zaštite.The ability of insects to adapt to diverse ecological conditions iswell documented; they are the most diverse fauna on earth, with different species occupying arange of terrestrial and aquatic habitats from the tropics to the poles. Understanding the mechanisms by which insects survive such extreme temperatures and retain viability for longperiods in the dormant state is of great interest to many scientific fields. Insects have evolved three main strategies to survive sub-zero temperatures: i) freeze tolerance, ii) freeze avoidance and iii) cryoprotective dehydration. The main biochemical compounds involved in surviving sub-zero temperatures are same for different strategies but their physiological role is different. They include: ice nucleating agents (INAs), cryo/ anhydroprotectants, and antifreeze proteins (AFPs). The aim of this study was to determine molecular adaptations to extreme cold environments, combining physiology, biochemistry and molecular biology pproaches, in thePolar Collembola: Cryptopygus antarcticus and Onychiurus arcticus. Both species are freeze avoiding but employ different strategies for surviving low temperatures. The Antarctic springtail C. antarcticusis capable of rapid cold hardening with a bi-modal distribution of super cooling points (SCP) with high (less cold-hardened) and low (more cold-hardened) groups of animals present even during the growing season in summer. This bimodal distribution has been well documented, but is poorly understood. The Arctic springtail O. arcticusemploys the strategy known as cryoprotective dehydration to survive winter temperatures as low as -25ºC. With this technique, the amount ofavailable water in the body is reduced to almost zero and also there is an accumulation of trehalose, which acts as a cryo/anhydroprotectant. Although cryoprotective dehydration has been described in other insects, the molecular mechanisms behind this phenomenon are poorly understood.A total of 16,379 EST clones were generated for O. arcticus and 1180 for C. antarcticus. This represents the first publicly available sequence data for this two species providing useful data for comparative genomic analysis. The fact that around 60% of the clones for both species showed no sequence similarity to annotated genes in the datasets, suggests a specific pattern of gene expression in these species as adaptation to low temperatures.Two microarrays were constructed to identify genes involved in surviving low temperatures, one for C. antarcticus by printing 672 clones in duplicate and the other for O. arcticus by printing 6912 clones in duplicate. An analysis of those where putative function could be inferred via database homology, in C. antarcticus there was aclear pattern of up-regulation of structural proteins being associated with the cold tolerant group. These structural proteins mainly comprised cuticle proteins and provide support for the recenttheory that summer SCP variation within Collembola species could be a consequence of moulting, with moulting population having lowered SCPs. In O. arcticus EST and microarrayanalysis revealed clones and biochemical pathways associated with cryoprotective dehydration with a particular reference to genes involved in carbohydrate metabolism, aquaporin genes, heat shock proteins, LEA proteins and antioxidant enzymes.
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Calder, Beth Louise. "The Use of Polyphosphates to Maintain Yield and Quality of Whole Cooked, Cryogenically Frozen Lobster (Homarus americanus) and the Use of Sorbitol and Tocopherol to Maintain Quality of Whole Cooked, Cryogenically Frozen Crab (Cancer irroratus)." Fogler Library, University of Maine, 2003. http://www.library.umaine.edu/theses/pdf/CalderBL2003.pdf.
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Burger, Marco. "Prediction of the temperature distribution in asphalt pavement samples." Thesis, Stellenbosch : Stellenbosch University, 2005. http://hdl.handle.net/10019.1/50422.
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Thesis (MScEng)--Stellenbosch University, 2005.ENGLISH ABSTRACT: The convection heat transfer coefficient between an infinite, horizontal surface and the natural environment is determined experimentally. It is shown that, during daytime, heat is transferred due to natural and forced convection, while during nighttime heat is transferred due to conduction and forced convection. Equations that correlate the daytime and nighttime convective heat transfer coefficients respectively, are presented. The results are compared with values obtained by other investigators. The equations for the convection heat transfer coefficient are then used to predict the surface temperature and the temperature at depth of asphalt pavement samples using a simulation model. It is found that there is good agreement between the measured and the predicted asphalt pavement sample temperatures.
AFRIKAANSE OPSOMMING: Die konveksie warmteoordrags-koëffisiënt tuseen 'n oneindige, horisontale oppervlak en die natuurlike omgewing is eksperimenteel bepaal. Daar word getoon dat warmte, tydens die dag, oorgedra word deur natuurlike en geforseerde konveksie, terwyl warmte tydens die nag oorgedra word deur geleiding en geforseerde konveksie. Die resultate word vergelyk met die resultate van ander navorsers. Vergelykings wat die konveksie warmteoordrags-koëffisiënt gedurende die dag en nag onderskeidelik korreleer word voorgestel. Die vergelykings vir die konveksie warmteoordrags-koëffisiënt word dan gebruik in 'n simulasiemodel om die oppervlaktemperatuur en die temperatuur onder die oppervlakte van asfalt-padoppervlakmonsters te voorspel.
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Caparroz, Luís Felipe Vicentis. "Efeito da radiação em transistores 3D em baixas temperaturas." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/3/3140/tde-28062017-155642/.
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Nesse trabalho de mestrado estudou-se o comportamento elétrico de transistores verticais de múltiplas portas (3D) sobre isolante (SOI FinFET) sob o efeito da radiação de prótons em baixa temperatura, por meio de métodos experimentais e simulações numéricas. Inicialmente, foram comparados os comportamentos dos transistores antes e depois de serem submetidos à radiação de prótons, em temperatura ambiente. Esta análise foi realizada tanto para dispositivos com canal do tipo p quanto do tipo n, estudando-se tanto como as características analógicas são alteradas após o dispositivo ser irradiado por prótons com uma energia de aproximadamente 60 MeV quanto as características digitais. Estudou-se os efeitos da dose total ionizante (TID) nos dispositivos SOI FinFETs. Estes efeitos se manifestam de formas diferentes, muitas vezes opostas, para transistores nMOS e pMOS. Os efeitos da radiação na inclinação de sublimiar (SS) dos pFinFETs, por exemplo, resultaram em uma melhoria da velocidade de chaveamento, enquanto que os nFinFET sofreram uma degradação. Já a variação negativa da tensão de limiar (VT), uma vez que a maior parte das cargas acumuladas no óxido são positivas, deixa os transistores pMOS mais imunes a corrente parasitária da segunda interface, e novamente degrada as características dos nMOS. Os transistores com aletas mais largas têm uma maior área de óxido enterrado abaixo do filme de silício, o que resulta em um maior acúmulo de cargas. Portanto, a degradação dos parâmetros foi mais acentuada do que em dispositivos com aletas mais estreitas. Transistores com canal curto estão sujeitos aos efeitos de canal curto e se mostraram mais suscetíveis à radiação de próton na região de sublimiar. Além da análise dos parâmetros básicos, realizou-se uma análise de compromisso entre três parâmetros analógicos: a eficiência do transistor (gm/ID), a frequência de ganho unitário (fT) e o ganho intrínseco de tensão (AV). Eles foram estudados em função do coeficiente de inversão (IC), sendo possível verificar o comportamento dos dispositivos em cada regime de inversão e, posteriormente, o melhor compromisso entre os parâmetros, para uma dada aplicação. Em baixas temperaturas foi também observado que enquanto para os parâmetros digitais, os transistores de canal p mostraram um melhor desempenho quando focando os parâmetros digitais (tensão de limiar e inclinação de sublimiar), nFinFETs mostraram-se mais imunes a radiação de prótons em baixa temperatura, quando analisados os parâmetros analógicos como o ganho intrínseco de tensão (resposta mais estável à radiação em baixas temperaturas).This master degree\'s dissertation aims to study the low temperature electrical behavior of tridimensional transistors on insulator (SOI FinFET) under the effects of proton radiation, through experimental methods and numeric simulations. Initially, it was compared the transistors\' behavior before and after they have been subjected to proton radiation, at room temperature. This analysis was performed for both p- and n-channel devices, studying how the analog parameters change after the devices are irradiated by protons with approximately 60 MeV energy. The effects of total ionization dose on SOI FinFET devices were studied. These effects are manifested in different, very often opposing ways for nMOS and pMOS transistors. The radiation effects on the subthreshold slope (SS) in pFinFETs, for example, resulted in a switching speed improvement, while the nFinFETs were degraded. Also, the negative shift in the threshold voltage (VT), as most of the oxide trapped charges are positive, made the pMOS transistors more immune to the parasitic current at the second interface, and, again, the nMOS ones had their characteristics degraded. The wide-fin transistors have a bigger oxide area beneath the silicon film, which results in a greater charge buildup. Hence, the parameter degradation was more substantial than for narrow-fin devices. Short-channel transistors are subject to short-channel effects and showed themselves more susceptible to proton irradiation at the subthreshold region. In addition to the basic parameter analysis, it was done a tradeoff analysis between three analog parameters: the transistor efficiency (gm/ID), the unit gain frequency (fT) and the intrinsic voltage gain (AV). They have been studied as a function of the inversion coefficient (IC), where it was possible to observe the devices\' behavior for each inversion regime and, after, the best tradeoff between the parameters, for a given application. At low temperature, it was also observed that while pFinFETs have a better performance when looking at digital parameters VTH and SS after irradiation, nFinFETs showed more immunity to proton radiation when analyzed from their analog parameter with a more stable response to low temperatures.
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Huang, Chun. "An experimental investigation of low temperature plasma sterilization, treatment, and polymerization processes." Diss., Columbia, Mo. : University of Missouri-Columbia, 2006. http://hdl.handle.net/10355/4434.
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Thesis (Ph.D.)--University of Missouri-Columbia, 2006.The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file viewed on (April 26, 2007). Vita. Includes bibliographical references.
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Haworth, Christopher. "The de Haas-van Alphen effect and the superconducting state." Thesis, University of Bristol, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.294551.
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Wilson, Simon J. "Thermal profiles in oxygen vacuum swing adsorption (VSA) : modelling, observations and optimisation." Monash University, Dept. of Chemical Engineering, 2001. http://arrow.monash.edu.au/hdl/1959.1/7766.
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Matsui, Jeferson Matsuji. "Estudo de degradação a baixa temperatura de cerâmicas Y-TZP/Al2O3 sintetizadas por coprecipitação." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/85/85134/tde-06092017-102722/.
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A zircônia tetragonal estabilizada por ítria (Y-TZP) têm sido utilizada na área odontológica para próteses livres de metais devido à estética associada ao alto desempenho mecânico. Porém, a presença de ambiente úmido pode causar a transformação acelerada da fase tetragonal para monoclínica e consequente falha catastrófica deste material, processo este conhecido como degradação a baixa temperatura ou envelhecimento. A cinética desta transformação é função da composição química da cerâmica e sua microestrutura. Tendo em vista que métodos químicos permitem a síntese de pós cerâmicos à base de zircônia de dimensões nanométricas, cuja microestrutura da cerâmica sinterizada é constituída por grãos submicrométricos quimicamente homogêneos, e que a presença de alumina é indicada para evitar a degradação de fases da zircônia, o objetivo deste estudo foi verificar a degradação a baixa temperatura e ambiente úmido de cerâmicas de zircônia estabilizada com 3 mol% de ítria (Y-TZP) e do compósito Y-TZP/Al2O3, proveniente de pós sintetizados pela rota de coprecipitação. A concentração de alumina na Y-TZP foi estudada na faixa de 0,05 a 20% em massa. A eficiência do processo desenvolvido foi verificada pela avaliação das características físicas dos pós obtidos (granulometria, área de superfície específica, estado de aglomeração e estrutura cristalina). As amostras cerâmicas foram prensadas, sinterizadas e avaliadas quanto à densidade aparente e microestrutura. Após a caracterização inicial das cerâmicas a degradação das amostras foi estudada in vitro em reator hidrotérmico pressurizado a 150°C. As amostras (n=4) foram submetidas à análise de difração de raios X de acordo com o tempo de envelhecimento, acompanhando a curva cinética de transformação de fase. A porcentagem de cada fase cristalina foi determinada pelo Método de Rietveld. A relação entre o tempo de envelhecimento e a concentração de fase monoclínica foi determinada pela equação de Avrami modificada por Kolmogorow (Johnson-Mehl- Avrami-Kolmogorow JMAK). Após envelhecimento a 150°C por 70 horas, todas as amostras contendo alumina apresentaram menor concentração de fase monoclínica, comparativamente à cerâmica Y-TZP, que apresentou 66,5% dessa fase. Menores porcentagens de fase monoclínica após o envelhecimento hidrotérmico foram obtidas com a adição de 10 e 20% em massa de alumina na matriz de zircônia, sendo esses valores 59,1 e 52,9%, respectivamente. Deve-se considerar, no entanto, que a diminuição da degradação total é consequência da menor porcentagem de zircônia na matriz em função da adição de alumina. Neste contexto, o efeito benéfico da adição de alumina ocorre apenas no início do envelhecimento.The yttria tetragonal zirconia polycrystal (Y-TZP) is used in dentistry for metal free prosthesis due to esthetics associated with a high mechanical performance. However, the presence of humid environment can cause an accelerated tetragonal to monoclinic (t-m) phase transformation and consequent catastrophic failure of this material. This process is known as low temperature degradation (LTD) or aging. The kinetics of phase transformation is a function of the chemical composition of the ceramic and its microstructure. Considering that chemical methods allow the synthesis of nanometric zirconium-based ceramic powders, which microstructure of the sintered ceramic consists of submicrometric chemically homogeneous grains, and that the presence of alumina is indicated to delay the tetragonal phase degradation, the aim of this study was to verify the degradation at low temperature in humid environment of 3mol% yttria stabilized zirconia ceramics (Y-TZP) and the Y-TZP/Al2O3 composite prepared from coprecipitated powders. The addition of alumina at Y-TZP was studied in the range of 0.05 to 20wt%. The efficiency of the developed process was verified by the evaluation of the physical characteristics of the obtained powders (granulometry, specific surface area, agglomeration state and crystalline structure). The ceramic samples were pressed, sintered and submitted to apparent density and microstructure evaluation. After the initial characterization of the ceramics, the in vitro degradation of the samples was studied in a hydrothermal pressurized reactor at 150°C. The samples (n = 4) were submitted to X-ray diffraction analysis according to the aging time, followed by the determination of the kinetic curve of phase transformation. The Rietveld Method was employed to determine the percentage of each crystalline phase. The relationship between the aging time and the percentage of monoclinic phase was determined by the Johnson- Mehl-Avrami-Kolmogorow equation (JMAK). After 70 hours aging at 150°C, all the alumina-containing samples presented a lower concentration of monoclinic phase, compared to the Y-TZP ceramics, which monoclinic phase concentration was 66.5%. The lower percentages of monoclinic phase after hydrothermal aging were obtained with the addition of 10%wt and 20 wt% alumina in the zirconia matrix (59.1% and 52.9%, respectively). This behavior is due to the lower concentration of zirconia in the composite containing alumina. In this point of view beneficial effect due to alumina addition occurs in the early stage of aging.
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Schoene, Elizabeth A. 1979. "Cold atom control with an optical one-way barrier." Thesis, University of Oregon, 2010. http://hdl.handle.net/1794/11067.
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xvi, 176 p. : ill. (some col.)The research presented in this dissertation aims to contribute to the field of atom optics via the implementation and demonstration of an all-optical one-way barrier for 87 Rb atoms--a novel tool for controlling atomic motion. This barrier--a type of atomic turnstile--transmits atoms traveling in one direction but hinders their passage in the other direction. We create the barrier with two laser beams, generating its unidirectional behavior by exploiting the two hyperfine ground states of 87 Rb. In particular, we judiciously choose the frequency of one beam to present a potential well to atoms in one ground state (the transmitting state) and a potential barrier to atoms in the other state (the reflecting state). The second beam optically pumps the atoms from the transmitting state to the reflecting state. A significant component of the experimental work presented here involves generating ultra-cold rubidium atoms for demonstrating the one-way barrier. To this end, we have designed and constructed a sophisticated 87 Rb cooling and trapping apparatus. This apparatus comprises an extensive ultra-high vacuum system, four home-built, frequency-stabilized diode laser systems, a high-power Yb:fiber laser, a multitude of supporting optics, and substantial timing and control electronics. This system allows us to cool and trap rubidium atoms at a temperature of about 30 μK. The results presented in this dissertation are summarized as follows. We successfully implemented a one-way barrier for neutral atoms and demonstrated its asymmetric nature. We used this new tool to compress the phase-space volume of an atomic sample and examined its significance as a physical realization of Maxwell's demon. We also demonstrated the robustness of the barrier's functionality to variations in several important experimental parameters. Lastly, we demonstrated the barrier's ability to cool an atomic sample, substantiating its potential application as a new cooling tool. This dissertation includes previously published coauthored material.
Committee in charge: Dr. Hailin Wang, Chair; Dr. Daniel A. Steck, Research Advisor; Dr. Jens U. Nockel; Dr. David M. Strom; Dr. Jeffrey A. Cina
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Thornhill, Lindsey Dorough. "Boundary layers in dense, low-temperature plasmas." Diss., Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/17029.
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Smarra, Devin A. "Low Temperature Co-Fired Ceramic (LTCC) Substrate for High Temperature Microelectronics." University of Dayton / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1493386231571894.
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Fernandes, CÃsar Rodrigues. "Espalhamento Raman dependente da temperatura em cristais de Ãcido DL-aspÃrtico." Universidade Federal do CearÃ, 2010. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=4865.
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Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgicoNesta dissertaÃÃo sÃo apresentados resultados de espalhamento Raman em cristais de Ãcido DL-aspÃrtico sob diversas condiÃÃes de temperatura. O Ãcido DL-aspÃrtico (C4H7NO4) cristaliza-se no grupo espacial C2h6 com oito molÃculas por cÃlula unitÃria, existindo portanto 128 Ãtomos na cÃlula unitÃria que darÃo origem a 384 modos normais de vibraÃÃo. Destes um total de 192 modos sÃo Raman ativos, que poderiam ser observados nos espectros nÃo polarizados, mas que por diversos fatores apenas parte desses modos à observada. Fez-se a identificaÃÃo tentativa de todos os modos normais de vibraÃÃo que aparecem no intervalo espectral entre 50 e 3200cm-1 e um estudo com variaÃÃo de temperatura entre 10 e 433K. O intervalo compreendido entre 0 e 150 cm-1 à de extrema importÃncia para detecÃÃes de transiÃÃes de fase estrutural pois contÃm os modos de vibraÃÃo da rede. No caso do Ãcido DL-aspÃrtico ocorreu uma inversÃo de intensidade para os modos em 82 e 87 cm-1, considerando os extremos do intervalo de temperatura medido. Tal inversÃo foi interpretada como uma pequena mudanÃa conformacional, nada associado a transiÃÃo. Com exceÃÃo desse fato nÃo ocorreram anomalias, nem aparecimento ou surgimento de modos nessa regiÃo, o que apontou para a estabilidade do material. Outro evento ocorreu nessa regiÃo: as bandas em 116 e 132 cm-1, bastante distintas a baixÃssimas temperaturas (< 150 K) tornam-se indistinguÃveis a 200 K. Tal fato nÃo pode ser associado a uma transiÃÃo de fase pois o prÃprio alargamento das linhas, consequÃncia do aumento da temperatura, implica a superposiÃÃo dos modos. Some-se a isso o fato de que nas vibraÃÃes de torÃÃo do NH3 e rocking do CO2â (modos associados Ãs ligaÃÃes de hidrogÃnio) ter-se observado linearidade nas curvas frequÃncia-temperatura. Por fim realizou-se um estudo de calorimetria diferencial de varredura, confirmando-se o que havia sido observado pela espectroscopia Raman â a estabilidade da estrutura em todo o intervalo de temperatura investigado.
This dissertation presents the results of Raman scattering in crystals of DL-aspartic acid under various temperature conditions. The DL-aspartic acid (C4H7NO4) crystallizes in space group C2h6 with eight molecules per unit cell, so there are 128 atoms in the unit cell that give rise to 384 normal modes of vibration. Of these modes a total of 192 modes are Raman active, which could be observed in not polarized spectra, but by various factors only some of these modes are observed. We did an attempt identification of all normal modes of vibration that appears in the spectral range between 50 and 3200cm-1 and a study with variation in temperature between 10 and 433 K. The interval between 0 and 150 cm-1 is extremely important for detection of phase transitions because it contains the structural modes of vibration of the lattice. In the case of DL-aspartic acid there was a reversal of intensity for the modes at 82 and 87 cm-1, in considering the extremes of temperature interval measured. This reversal was interpreted as a small conformational change, not associated with a phase transition. With exception of this reversal there were not anomalies, not appearance or disappearance of modes in this region, which pointed to the stability of the material. Another event occurred in this region: the bands at 116 and 132 cm-1, very different at very low temperatures (< 150 K) become indistinguishable at 200 K. This fact can not be associated with a phase transition because the broadening of bands, arising from increasing temperatures, implies the superposition of modes. Added to this there is the fact that the torsional vibrations of the NH3+ and rocking of CO2- (modes associated with hydrogen bonds) behaved linearly in frequency-temperature curves. Finally we did a study of differential scanning calorimetry, which confirmed what had been observed by Raman spectroscopy - the stability of the structure throughout the temperature range investigated.
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Hay, Duncan C. "Zircon behaviour in low temperature environments." Thesis, Connect to e-thesis. Move to record for print version, 2007. http://theses.gla.ac.uk/70/.
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Thesis (Ph.D.) - University of Glasgow, 2007.Ph.D. thesis submitted to the Faculty of Physical Sciences, Department of Geographical and Earth Sciences , University of Glasgow, 2007. Includes bibliographical references. Print version also available.
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Freeland, Chad Lee. "Low Temperature Drying of Ultrafine Coal." Thesis, Virginia Tech, 2010. http://hdl.handle.net/10919/76750.
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A new dewatering technology, called low temperature drying, has been developed to remove water from ultrafine (minus 325 mesh) coal particles. The process subjects partially dewatered solids to intense mechanical shearing in the presence of unsaturated air. Theoretical analysis of the thermodynamic properties of water indicates residual surface moisture should spontaneously evaporate under these conditions. This is contingent on the large surface area of these fine particles being adequately exposed to an unsaturated stream of air. To demonstrate this process, three dispersion methods were selected for bench-scale testing; the static breaker, air jet conveyor, and centrifugal fan. Each of these devices was chosen for its ability to fully disperse and pneumatically convey the feed cake. The moisture content of the feed cake, and the temperature and relative humidity of the process air were the key parameters that most significantly affected dryer performance. Of the three methods tested, the centrifugal fan produced the best results. The fan was capable of handling feeds as wet as 21.5% and consistently dried the coal fines below 2% moisture. The cost of the air and heat required to provide good drying performance was modeled to explore the practicality of the drying process. Modeling was accomplished by modifying equations developed for thermal dryers. The modeling results indicate, if good exposure of the fine particle surface area is achieved, dryers operating with either heated or unheated (ambient) air can be used for drying ultrafine coal.Master of Science
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Rehn-Molin, Lotta. "Long-term Stability Analysis of Antenna Temperature & Brightness Temperature from ESA's SMOS Satellite." Thesis, KTH, Geoinformatik och Geodesi, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-35299.
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The European Space Agency’s Soil Moisture and Ocean Salinity (SMOS) satellite is designed to accurately detect the energy of the electromagnetic radiation naturally emitted from Earth, from which the level of soil moisture and ocean salinity content can be derived. Studies of these two geophysical parameters will increase the knowledge of the Earth’s water cycle and improve the understanding of the climate. The single payload of the SMOS satellite is the Microwave Imaging Radiometer by Aperture Synthesis (MIRAS). Researchers at Universitat Politècnica de Catalunya in Barcelona have developed the MIRAS Testing Software which basically translates SMOS raw data into useful data. The data is continuously analyzed and it has been discovered that some parameters of the MIRAS instrument are drifting more than expected.The objective of this Master’s thesis project was to create a long-term stability analyzing tool with which the long-term trends of the MIRAS parameters antenna temperature and brightness temperature can be investigated. The long-term stability analyzing tool has been coded in Matlab and the analysis is based on flight data from January to November 2010. The data has been processed in the MIRAS Testing Software with different inversion and calibration options before it has been used as input to the long-term stability analyzing tool. The main goal of this project was to find out which of the options gave the least drifting and most accurate results.The calibration options that have been studied are the 1-point and 4-point calibration, referring to the number of reference points used in each calibration respectively. The long-term stability analysis of the antenna temperature shows that the 1-point calibration gave more stable results than the 4-point calibration. This was expected since the 4-point calibration makes use of the so called NIR (Noise Injection Radiometer) antennas so a drift in the calibration of the NIRs is added to the uncertainty of the 4-point calibration.The inversion options refer to different approaches of inverting the measured visibility to brightness temperature. The two approaches that have been studied differ from each other by a correction term of the visibility that is included in Approach 3 and not in Approach 5. The long-term stability analysis of the brightness temperature shows that the inversion Approach 5 gave more stable results than the inversion Approach 3, which means the correction term causes instability in the results. If the correction was modified though, Approach 3 could possibly give more stable results which might imply a change of this conclusion.This long-term stability analysis aimed to contribute to the assessment of the stability of the MIRAS instrument, and so it has. This Master’s thesis project’s main contribution to the SMOS project is the demonstration of a new kind of systematic long-term stability analysis, which uses the same set of data when comparing things, in this case different inversion and calibration options. As a consequence of this Master’s thesis project, the SMOS calibration community is now discussing the options for finding metrics that can help to establish the SMOS long-term stability.
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施碧紅 and Bihong Shi. "Long-term responses of pseudomonas pseudoalcaligenes to high temperature." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2002. http://hub.hku.hk/bib/B42128729.
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Chen, Tianbing. "Operation of SiGe BiCMOS Technology Under Extreme Environments." Diss., Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/7559.
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Operation of SiGe BiCMOS Technology Under Extreme Environments
Tianbing Chen
96 pages
Directed by Dr. John D. Cressler
"Extreme environment electronics" represents an important niche market and spans the operation of electronic components in surroundings lying outside the domain of conventional commercial, or even military specifications. Such extreme environments would include, for instance, operation to very low temperatures (e.g., to 77 K or even 4.2 K), operation to very high temperatures (e.g., to 200 C or even 300 C), and operation in a radiation-rich environment (e.g., space).
The suitability of SiGe BiCMOS technology for extreme environment electronics applications is assessed in this work. The suitability of SiGe HBTs for use in high-temperature electronics applications is first investigated. SiGe HBTs are shown to exhibit sufficient current gain, frequency response, breakdown voltage, achieve acceptable device reliability, and improved low-frequency noise, at temperatures as high as 200-300 C. A comprehensive investigation of substrate bias effects on device performance, thermal properties, and reliability of vertical SiGe HBTs fabricated on CMOS-compatible, thin-film SOI, is presented. The impact of 63 MeV protons on these vertical SiGe HBTs fabricated on a CMOS-compatible SOI is then investigated. Proton irradiation creates G/R trap centers in SOI SiGe HBTs, creating positive charge at the buried oxide interface, effectively delaying the onset of the Kirk effect at high current density, which increases the frequency response of SOI SiGe HBTs following radiation. The thermodynamic stability of device-relevant epitaxial SiGe strained layers under proton irradiation is also investigated using x-ray diffraction techniques. Irradiation with 63 MeV protons is found to introduce no significant microdefects into the SiGe thin films, regardless of the starting stability condition of the SiGe film, and thus does not appear to be an issue for the use of SiGe HBT technology in emerging space systems. CMOS device reliability for emerging cryogenic space electronics applications is also assessed. CMOS device performance improves with cooling, however, CMOS device reliability becomes worse at decreased temperatures due to aggravated hot-carrier effects. The device lifetime is found to be a strong function of gate length, suggesting that design tradeoffs are inevitable.
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Zhang, Liyuan. "Spin Transport In Aluminum Grains and Single Debye Relaxation In BST nanoparticles." Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/16160.
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This thesis consists of two distinct components: (1) Spin-polarized electron transport through aluminum array nanoparticles, (2) A single electric relaxation process in Barium Strontium Titanate (BST) nanoparticles.
In the first chapter, we summarize our main results and new finding, and we also present our motivation.
For the first component (chapters 2-5), we studied electron spin transport in nanometer scale aluminum grains as embedded in a ferromagnet tunneling junction. We observed tunnelling-magnetoresistance (TMR) and spin valve effects. From the TMR strong asymmetry with bias voltage, we explored spin relaxation effects. Additionally we also obtained the spin-coherence time on the order of nanoseconds by using the Hanle effect.
For the second component (chapters 6-9), we investigated the dielectric response of BST and Barium Titanate (BTA) (high dielectric constant ferroelectrics) nanoparticles. The results were found to be quite unusual when compared with the dielectric response of film or bulk. The dielectric response is Debye relaxation with only a single relaxation time, and the relaxation time exhibits the Arrhenius Law at temperatures below 200 Kelvin.
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Carney, John Paul. "Non linear damping by ballistic quasiparticles in superfluid '3HE-#beta#." Thesis, Lancaster University, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.253496.
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Jackson, Douglas Anthony. "Experiments on a dilute '3He-'4He solution in a large magnetic field gradient." Thesis, Lancaster University, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.384881.
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White, Jeremy Philip. "A PrNiâ†5 refrigerator developed for nuclear orientation below 1mK." Thesis, University of Oxford, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.302870.
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Hornett, Samuel Martyn. "Non-equilibrium phenomena in graphene." Thesis, University of Exeter, 2013. http://hdl.handle.net/10871/13022.
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Graphene has displayed much promise as an electrical conductor and as a optical material. To date there is a large body of literature dedicated to the equilibrium properties of graphene. In this thesis the properties of graphene out of equilibrium are probed. Through combined optical and transport measurements the behaviour of hot electrons are probed at temperatures over five orders of magnitude from 50mK to 2000K. This wide range of temperatures allows access to the behaviour of quantum corrections at the lowest temperatures to the highest energy phonon modes. From ultrafast femtosecond laser pulses to steady state heating from an electric field the cooling of hot electron populations through coupling to various phonon modes in the graphene and the substrate are explored. Additionally the effect of an electric field on the weak localisation correction to the conductivity was separated from heating effects using applied magnetic fields combined with careful modelling of the heat transport properties of the graphene. Finally the desorption dynamics of oxygen bound to the surface are shown using a combination of transport and two pulse correlation technique using an ultrafast laser. Surprisingly the cooling of hot carriers in graphene at low energies shows substrate surface phonons as an important cooling mechanism, highlighting the importance of substrate choice in future graphene devices. In contrast at the very highest energy scales accessed only by photoexcitation the cooling is shown not to be influenced by the presence of a substrate, but out-of-plane phonon modes increase cooling of the hot optical phonons.
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Church, Rosemary Jane. "Properties of '3He-'4He mixtures." Thesis, University of Nottingham, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.329879.
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Sale, Martin William Briddon. "The assessment of the photo response efficiency of the silver halide component in a photo-thermographic material." Thesis, University of Westminster, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.263935.
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Mossavati, Ruzbeh. "Use of '1'9F NMR thermometry in the investigation of magnetic textures in superfluid '3He-A." Thesis, University of Manchester, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.329594.
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Ryder, J. "An experimental investigation into the electrical transport properties of Laâ†2CuOâ†4â†+â†#delta# and Ndâ†2CuOâ†4â†+â†#delta#." Thesis, University of Bristol, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.279724.
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Kent, Anthony Joseph. "An NMR study of adsorbed helium films." Thesis, Royal Holloway, University of London, 1985. http://repository.royalholloway.ac.uk/items/5ad7ff53-aea8-4649-8129-e8ce47a5c292/1/.
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The properties of sub-monolayer Helium-3 films adsorbed on two totally different but planar substrates, Mylar† film and exfoliated graphite have been studied using NMR. The nuclear magnetic relaxation times T1 and T 2 have been measured as functions of fractional monolayer completion, temperature, substrate plane orientation and Larmor frequency using a specially designed and constructed NMR spectrometer system. The results obtained with a Mylar film substrate are consistent3with the formation of patches of solid 3He at regions of preferential adsorption on the substrate. Measurements of T2 m very low coverage 3He films on exfoliated graphite also indicate that the adsorbate forms areas of relatively high density solid, in agreement with the thermodynamic analysis of Elgin and Goodstein. Finally, detailed measurements of T2 as a function of all of the above parameters at low areal densities will help us to characterise the relaxation processes for the fluid phase of 33He on exfoliated graphite. †Mylar is the tradename of poly(ethelene-terephthalate) film, marketed by Du Pont.
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Farrokhpanah, Sonia. "Design of heat integrated low temperature distillation systems." Thesis, University of Manchester, 2009. http://www.manchester.ac.uk/escholar/uk-ac-man-scw:228854.
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This work addresses the challenges in design of heat integrated low-temperature separation processes. A novel, systematic and robust methodology is developed, which contributes to the design practice of heat-integrated separation sequence and the refrigeration system in the context of low-temperature separation processes. Moreover, the methodology exploits the interactions between the separation and refrigeration systems systematically in an integrated design context. The synthesis and optimisation of heat-integrated separation processes is complex due to the large number of design options. In this thesis, task representation is applied to the separation system to accommodate both simple and complex distillation columns. The stream conditioning processes are simulated and their associated costs are included in the overall cost of the process. Important design variables in separation systems, such as the separation sequence, type and operating conditions of the separation units (e.g. the operating pressure, feed quality and condenser type) are optimised. Various refrigeration provision strategies, such as expansion of a process stream, pure and mixed multistage refrigeration systems and cascades of multistage refrigeration cycles, are considered in the present work. A novel approach based on refrigeration system database is proposed, which overcomes the complexities and challenges of synthesis and optimisation of refrigeration systems in the context of low-temperature separation processes. The methodology optimises the key design variables in the refrigeration system, including the refrigerant composition, the number of compression stages, the refrigeration and rejection temperature levels, cascading strategy and the partition temperature in multistage cascaded refrigeration systems. The present approach has selected a matrix based approach for assessing the heat integration potentials of separation and refrigeration systems in the screening procedure. Non-isothermal streams are not considered isothermal and stream splitting and heat exchangers in series are taken into account. Moreover, heat integration of reboiler and condenser of a distillation column through an open loop heat pump system can be considered in this work. This work combines an enhanced simulated annealing algorithm with MILP optimisation method and develops a framework for simultaneously optimising different degrees of freedom in the heat integrated separation and refrigeration processes. Case studies extend the approach to the design of heat integrated separation sequences in above ambient temperature processes. The robustness of the developed framework is further demonstrated when it is utilised to design the LNG and ethylene plant fractionation trains.
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Biasotto, Cleber. "Processos alternativos para micro e nanotecnologia." [s.n.], 2012. http://repositorio.unicamp.br/jspui/handle/REPOSIP/260856.
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Orientador: Jose Alexandre DinizTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação
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Resumo: Atualmente para atender à necessidade de fabricação dos sensores, dispositivos eletrônicos e circuitos integrados com dimensões micro e nanométricas, novos processo de custos e de thermal budgets reduzidos são necessários. Este trabalho apresenta o desenvolvimento de alguns destes novos processos alternativos para aplicação nesta fabricação. O trabalho está dividido em quatro partes: a primeira parte apresenta a obtenção e a caracterização de filmes isolantes de nitreto de silício para aplicação em microsensores, tais como o sensor de pressão. Estes filmes foram obtidos sobre substratos de Si em baixa temperatura (20°C) utilizando-se um reator de plasma do tipo ECRCVD (Electron Cyclotron Resonance - Chemical Vapor Deposition). Normalmente reatores do tipo Low Pressure Chemical Vapor Deposition (LPCVD) ou Plasma Enhanced - CVD (PECVD) em temperaturas maiores que 600ºC e 250ºC, respectivamente, são utilizados para essa aplicação. A caracterização dos plasmas ECR, que foram usados para as deposições dos nitretos, e a fabricação de membranas suspensas com estes filmes são apresentadas. A segunda parte apresenta a fabricação e a caracterização de diodos p+-n fabricados em camada de SiGe crescida por LPCVD sobre substrato de Si. Processo este alternativo em substituição aos executados em reatores epitaxiais de alto custo. Na terceira parte deste trabalho, é apresentado o desenvolvimento de processos em baixa temperatura para aplicação em diodos e tecnologia MOS (Metal-Oxide-Semiconductor). São apresentadas a fabricação e a caracterização elétrica dos capacitores MOS, utilizando as tecnologias ALD (Atomic Layer Deposition) e ICP (Inductively Coupled Plasma) para a obtenção em baixa temperatura dos dielétricos high-k de Al2O3 e SiON de porta MOS, respectivamente. Na quarta parte, são apresentadas também, a fabricação e a caracterização elétrica de diodos n+p utilizando a tecnologia de recozimento a laser. O desenvolvimento de capacitores MOS e diodos possibilitou a fabricação (usando processos em baixa temperatura (?400oC)) de n- e p-MISFETs (Metal- Insulator-Semiconductor Field Effect Transistors), como também a fabricação de um protótipo de transistor MOS de alta velocidade baseado em silício germânio chamado D-DotFET (Disposable Dot Field Effect Transistor). Os processos alternativos desenvolvidos nesta tese apresentam um enorme potencial para aplicação nas próximas gerações de dispositivos CMOS (Complementary Metal Oxide Semiconductor) de dimensões sub-22 nm
Abstract: Nowadays, to attend the needs of the fabrication of sensors, electronic devices and integrated circuits with dimensions of micro and nanometrics, new processes of reduced costs and thermal budgets are needed. This work presents the development of some of these alternative processes for this fabrication. This work is divided in four parts: the first part presents the synthesis and characterization of insulating films of silicon nitride for application in microsensors, such as pressure sensors. These films were deposited on Si substrates at low temperature (20°C) using an ECR-CVD (Electron Cyclotron Resonance - Chemical Vapor Deposition) plasma reactor. Normally, Low Pressure Chemical Vapor Deposition (LPCVD) or Plasma Enhanced CVD - (PECVD) reactors are used for this application with high temperature process higher than 600oC and 250oC, respectively. The characterization of ECR plasmas, which were used to get the silicon nitrides, and the fabrication of suspended membranes based on these nitrides are presented. The second part presents the fabrication and the characterization of p+-n silicon germanium (SiGe) diodes fabricated on SiGe layers, which were grown by LPCVD on Si substrate. The grown of SiGe layers by LPCVD is an alternative process to replace the high cost of epitaxial reactors. In the third part of this work is presented the development of low-temperature processes for application in diodes and MOS (Metal-Oxide-Semiconductor) technology. The fabrication at low temperature and electrical characterization of MOS capacitors, using technologies as: ALD (Atomic Layer Deposition) and ICP (Inductively Coupled Plasma) to get the Al2O3 and SiON high-k gate dielectrics of MOS capacitors are presented, respectively. In the four part, the fabrication and electrical characterization of n+-p diodes using the process of laser annealing are presented as well. The development of MOS capacitors and diodes have become feasible the fabrication (using processes at low temperature (? 400oC)) of n- and p-MISFETs (Metal- Insulator -Semiconductor Field Effect Transistors) and also the fabrication of a high speed MOS transistor prototype based on silicon germanium named D-DotFET (Disposable Dot Field Effect Transistor). In conclusion, the alternative processes developed in this thesis have shown to be a huge potential for application in next generations of CMOS (Complementary Metal Oxide Semiconductor) devices with sub- 22 nm dimensions
Doutorado
Eletrônica, Microeletrônica e Optoeletrônica
Doutor em Engenharia Elétrica
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Santos, Adriana Brombini dos 1979. "Estudo da deposição de lignina em genótipos de cana-de-açúcar sob condição de déficit hídrico e baixa temperatura." [s.n.], 2014. http://repositorio.unicamp.br/jspui/handle/REPOSIP/315465.
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Orientador: Paulo MazzaferaTese (doutorado) - Universidade Estadual de Campinas, Instituto de Biologia
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Resumo: A cana-de-açúcar (Saccharum spp.), uma gramínea C4, representa uma abundante e promissora fonte de biomassa vegetal para a produção de biocombustíveis. O uso da biomassa para a conversão em etanol é limitada pela recalcitrância do material lignocelulósico, principalmente, devido à presença da lignina. O conteúdo e a composição da lignina variam entre diferentes táxons, tipos celulares e podem ser afetados por diversos fatores ambientais. Considerando a demanda mundial por fontes de energia renovável e o alto potencial da biomassa da cana-de-açúcar para a produção de etanol celulósico, o objetivo desse estudo foi avaliar os efeitos do déficit hídrico e da baixa temperatura sobre a deposição de lignina no colmo em diferentes genótipos de cana. Os resultados obtidos para o conteúdo de lignina somados à caracterização anatômica da lignina no caule indicaram que as plantas IACSP94-2094 são mais lignificadas que IACSP95-5000, sob condições normais de crescimento, o que foi principalmente associado aos maiores teores de lignina na região do córtex dos entrenós maduros. O déficit hídrico influenciou negativamente a produção de biomassa nas plantas de cana e o genótipo IACSP94-2094 foi mais fortemente afetado, o que poderia estar relacionado à severidade do estresse ou a maior suscetibilidade desse genótipo durante a fase de alongamento do caule. O déficit hídrico induziu alterações significativas nos níveis de expressão dos genes da biossíntese de lignina, aumentando em cerca de 60 % o conteúdo de lignina na medula jovem, o que foi positivamente relacionado ao acúmulo de transcritos dos genes Sh4CL2 e ShCOMT1 em ambos os genótipos. Paralelamente, este estudo caracterizou alguns aspectos da lignificação do caule em dois outros genótipos de cana-de-açúcar sob condição de baixa temperatura. Verificou-se que as plantas IACSP04-627 apresentaram maior produtividade média por planta (massa fresca do caule) que IACSP04-065 sob condição referência. O frio afetou negativamente o crescimento das plantas e, aparentemente, IACSP04-065 mostrou-se mais sensível às baixas temperaturas que o outro genótipo. O teor de lignina foi significativamente aumentado no córtex jovem do genótipo IACSP04-627 em resposta às baixas temperaturas, o que não pode ser diretamente correlacionado ao perfil de expressão dos genes da biossíntese de monolignóis. O conteúdo de lignina no córtex do entrenó maduro foi reduzido nas plantas IACSP04-065 expostas ao frio, o que poderia estar correlacionado ao baixo nível de expressão dos genes ShCOMT1 e ShCCoAOMT1. A maior expressão de ShF5H ocorreu preferencialmente na medula madura em ambos os genótipos de cana, o que possivelmente estaria relacionado à formação precoce da parede celular secundária induzida pelo frio. Em conclusão, verificou-se que o déficit hídrico parece estar relacionado ao aumento do teor de lignina nos entrenós jovens da cana-de-açúcar em ambos os genótipos; já na condição de baixa temperatura, o nível de expressão gênica não mostrou relação nítida com as alterações nos teores de lignina no caule, que apresentaram um padrão de deposição genótipo-dependente
Abstract: Sugarcane (Saccharum spp.) a C4 grass, is an abundant and promising source of plant biomass for biofuel production. The use of biomass for conversion to ethanol is limited by the recalcitrance of lignocellulosic material mainly due to the presence of lignin. The content and composition of lignin varies between different taxa, cell types and can be affected by various environmental factors. Given the global demand for renewable energy sources and high potential of sugarcane biomass to produce cellulosic ethanol, the aim of this study was to evaluate the effects of drought and low temperature on the deposition of lignin in the stem in different sugarcane genotypes. The results obtained for lignin and the anatomical characterization of lignin in the stem indicated that IACSP94-2094 plants are more lignified than IACSP95-5000 under normal growth conditions, which was mainly associated with higher lignin contents in the rind region of mature internodes. Water deficit negatively affected the biomass production in sugarcane plants and IACSP94-2094 genotype was more strongly affected, what might be related with the severity of stress or increased susceptibility of this genotype during the stem elongation. Drought induced significant changes in expression levels of lignin biosynthesis genes, increasing by about 60% the lignin content in young pith which was positively related to the accumulation of transcripts of Sh4CL2 and ShCOMT1 genes in both genotypes. Simultaneously, this study characterized some aspects of lignification of the stem into two other genotypes of sugarcane under the condition of low temperatures. It was found that the IACSP04-627 plants showed higher average yield per plant (fresh weight of the stem) that IACSP04-065 under reference condition. The cold negatively affected plant growth and apparently IACSP04-065 was more sensitive to low temperatures than the other genotype. The lignin content was significantly increased in young rind of IACSP04-627 genotype in response to low temperature, which can not be directly correlated to the expression profile of monolignols biosynthesis genes. Lignin content in mature rind was reduced in IACSP04-065 plants exposed to cold, which could be correlated to the low level of expression of ShCOMT1 and ShCCoAOMT1 genes. The high expression of ShF5H occurred preferentially in mature pith of both sugarcane genotypes, which possibly is related to the early formation of the secondary cell wall was induced by cold. In conclusion, it was found that water deficit appears to be related to the lignin content increased in young internodes of sugarcane in both genotypes; in the condition of low temperature, the level of gene expression showed no clear correlation with changes in lignin content in the stem, which showed a pattern of deposition genotype-dependent
Doutorado
Biologia Vegetal
Doutora em Biologia Vegetal
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Daine, Robert John. "Temperature Dependence of Current Transport in Metal-SWNT Structures." University of Toledo / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1438958818.
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Alhasan, Ahmad Abdulraheem. "Low Temperature Characterization of Foamed Warm Mix Asphalt." University of Akron / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=akron1374676401.
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Saiedi, Mohammad Reza. "Behaviour of CFRP-Prestressed Concrete Beams under Sustained Loading and High-Cycle Fatigue at Low Temperature." Thesis, Kingston, Ont. : [s.n.], 2009. http://hdl.handle.net/1974/5365.
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Bashiyo-Silva, Cristiane. "Criopreservação de embriões de Astyanax altiparanae influência dos ácidos graxos poli-insaturados na resistência dos embriões ao frio, aos crioprotetores e a vitrificação. /." Botucatu, 2018. http://hdl.handle.net/11449/157336.
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Orientador: Rosicleire Veríssimo SilveiraResumo: O objetivo deste trabalho a incorporação de ácidos graxos essenciais nas membranas dos embriões de Astyanax altiparanae, visando a determinação de protocolos para a crioconservação de embriões desta espécie de peixe neotropical.Para realização do experimento foram selecionados 2400 espécimes deA. altiparanae. Um grupo foi alimentado com ração comum, denominado de Ração Comercial (RC), e outro alimentado com ração comum acrescida de 5% de óleo de peixe marinho, denominado de Ração Comercial com Óleo de peixe marinho (RC+O). No Capítulo I, foi realizado análise de ácidos graxos no fígado, gônada e embrião. E verificado a mobilização destes ácidos graxos e sua influência. No Capítulo IIverificamos a permeabilização do córion nos embriões quando expostos a solução de pronase-E 25mg/mL, por períodos de 10, 20, 30s. Também foi analisado a sensibilidade dos embriões RC e RC+O aos crioprotetores. Os embriões foram expostos a soluções de propileno glicol, metanol, dimetil sulfóxido, dimetil, formamida, dimetil acetamida e glicerol, por 20 minutos. Verificou-se a taxa de eclosão e viabilidade das larvas após a eclosão. No Capítulo III os embriões do grupo RC e RC+O foram vitrificados em solução de propileno glicol 5M, na fase de seis somitos.No capítulo IV buscou-se o resfriamento dos embriões de RC e RC+O a tempeturas de 15°C, 5°C e 0°C, por um período de 12h. Os embriões foram expostos a soluções sem crioprotetor, com propileno glicol 1M e 2M.
Abstract: The objective of this work was the incorporation of essential fatty acids in the membranes of the embryos of Astyanax altiparanae, aiming the determination of protocols for the cryopreservation of embryos of this neotropical fish species. For the experiment, 2400 specimens of A. altiparanae were selected. One group was fed with common ration, called Commercial Ration (CR), and the other was fed with common ration plus 5% of marine fish oil, called Commercial Ration with Marine Fish Oil (CR + O). In Chapter I, analysis of fatty acids in the liver, gonad and embryo was performed. And we verified the mobilization of these fatty acids and their influence. In Chapter II we verified the permeabilization of the chorion in the embryos when exposed to 25mg / mL pronase-E solution, for periods of 10, 20, 30s. The sensitivity of the CR and CR + O embryos to the cryoprotectants was also analyzed. The embryos were exposed to solutions of propylene glycol, methanol, dimethyl sulfoxide, dimethyl, formamide, dimethyl acetamide and glycerol for 20 minutes. The hatch rate and viability of the larvae after hatching were checked. In Chapter III the embryos of the CR and CR + O group were vitrified in 5M propylene glycol solution in the six somites phase. In Chapter IV, the cooling of the CR and CR + O embryos was sought at temperatures of 15 ° C, 5 ° C and 0 ° C for a period of 12 hours. The embryos were exposed to cryoprotectant solutions with 1M and 2M propylene glycol.
Doutor
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Patekar, Kaustubh A. (Kaustubh Ashok) 1974. "Long term degradation of resin for high temperature composites." Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/47674.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1998.Includes bibliographical references (leaves 79-84).
The durability of polymer matrix composites exposed to harsh environments is a major concern. Surface degradation and damage are observed in polyimide composites used in air at 125-300°C. It is believed that diffusion of oxygen into the material and oxidative chemical reactions in the matrix are responsible. Previous work has characterized and modeled diffusion behavior, and thermogravimetric analyses (TGAs) have been carried out in nitrogen, air, and oxygen to provide quantitative information on thermal and oxidative reactions. However, the model developed using these data was not able to capture behavior seen in isothermal tests, especially those of long duration. A test program that focuses on lower temperatures and makes use of isothermal tests was undertaken to achieve a better understanding of the degradation reactions under use conditions. A new, low-cost technique was developed to collect chemical degradation data for isothermal tests lasting over 200 hours in the temperature range 125-300°C. Results indicate complex behavior not captured by the previous TGA tests, including the presence of weight-adding reactions. Weight gain reactions dominated in the 125-225°C temperature range, while weight loss reactions dominated beyond 225°C. The data obtained from isothermal tests was used to develop a new model of the material behavior. This model was able to fully capture the behavior seen in the tests up to 275°C. Correlation of the current model with both isothermal data at 300 °C and high rate TGA test data is mediocre. At 300°C and above, the reaction mechanisms appear to change. Attempts (which failed) to measure non-oxidative degradation indicate that oxidative reactions dominate the degradation at low temperatures. Based on this work, long term isothermal testing in an oxidative atmosphere is recommended for studying the degradation behavior of this class of materials.
by Kaustubh A. Patekar.
S.M.
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Shi, Bihong. "Long-term responses of pseudomonas pseudoalcaligenes to high temperature." Click to view the E-thesis via HKUTO, 2002. http://sunzi.lib.hku.hk/hkuto/record/B42128729.
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Tsagli, Kelvin Xorla. "Temperature Dependence of Photoluminescence Spectra in Polystyrene." University of Akron / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=akron1625744248503334.
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Khandekar, Sameer Sudhakar. "Design and construction of a magnetic force microscope." Thesis, Texas A&M University, 2003. http://hdl.handle.net/1969.1/2435.
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A magnetic force microscope (MFM) is a special type of scanning force microscope which measures the stray field above a ferromagnetic sample with the help of a ferromagnetic cantilever. The aim of this project was to design and build a MFM head and interface it with a commercial scanning probe electronics controller with the help of an appropriate force sensor. The MFM head and the force sensor were to be designed to work at low temperatures (down to 4 K) and in high vacuum. During this work, a magnetic force microscope (MFM) head was designed. Its design is symmetrical and modular. Two dimensional views were prepared to ensure proper geometry and alignment for the various modules. Based on these views, individual parts in the various modules were manufactured and combined for the final assembly of the head. This MFM head has many essential and advanced features which were incorporated during the design process. Our MFM head has an outside diameter of 5 cm and thus has a low thermal mass. The head operates inside a 100 cm long vacuum can which is kept in a cold bath inside a superinsulated dewar. Other features of this MFM head include thermal compensation of the important parts, flexibility to use commercial MFM cantilevers and a large scan range compared to the previous designs. Some of the anticipated system specifications are: 1) room temperature scanning range of 175?? 175 ??m, 2) low temperature scanning range between 35-50 ??m, 3) smallest detectable magnetic force in the range of one pN and 4) smallest detectable magnetic force gradient in the range of 10-3 to 10 -5 N/m. This MFM head was interfaced to a commercial scanning probe electronics apparatus by designing a fiber-optic interferometer as the sensor for the detection of the cantilever deflection. The fiber-optic sensor also has features of its own such as stability, compactness and low susceptibility to noise because of all-fiber construction. With this MFM head, we hope to image many magnetic samples which were previously impossible to image at Texas A&M.