Master of Science / Food Science Institute / Kelly J. K. Getty / In response to recent claims that synthetic antioxidants have the potential to cause toxicological effects and consumers’ increased interest in purchasing natural products, the meat and poultry industry has been seeking sources of natural antioxidants to replace synthetic antioxidants, which are currently being used by the industry. Due to their high phenolic compound content, fruits and other plant materials provide a good alternative to conventional antioxidants. Plum, grape seed extract, cranberry, pomegranate, bearberry, pine bark extract, rosemary, oregano, other spices, irradiated almond skins, and green tea have functionality as antioxidants in meat and poultry products. Pomegranate, pine bark extract, cinnamon, and cloves have exhibited stronger antioxidant properties than some of the synthetic antioxidants currently used by the meat and poultry industry. Of the discussed natural antioxidants, grape seed extract, cranberry, sage extract, thyme extract, basil extract, ginger extract, pine bark extract, and a Chinese 5-spice blend had the highest percent antioxidant activity (% AOA). (The quality of the antioxidant used may also impact its ability to function as an antioxidant). Some of these natural antioxidants have influenced color and sensory properties of finished meat and poultry products. Plum products used in meat and poultry products have increased redness of the finished product. In some products such as pork sausage or uncured meats, an increase in red color may be desired. Grape seed extract, pine bark extract, rosemary, almond skin powder, some spices and green tea extract have been shown to impact the color of finished meat or poultry products. Plum products and many other spices affect the overall sensory properties of meat or poultry products as well. Depending on the finished product, consumers may view these changes as positive or as negative. When selecting a natural antioxidant to use in a meat or poultry product, the sensory and quality impact on the product should be considered in order to achieve a product with the desired traits.

The usage of conventional energy applications generates disproportionate emissions of greenhouse gases and the consumption of part of the energy resources available in the world. It has become an important problem which has serious effects on the climatic change. Therefore, it is crucial to reduce these emissions as much as possible. To be able to achieve this, renewable energy technologies must be used instead of conventional energy applications. Solar Photovoltaic (PV) technologies do not release greenhouse gas emissions directly and can save more than 30 million tonnes of carbon per exajoule of electricity generated relative to a natural gas turbine running at 45% efficiency. Shadowing is one of the most important aspects that affects the performance of PV systems. Consequently, many investigations through this topic are being done in order to develop new technologies which mitigate the impact of shadowing during PV production. In order to minimise the impact of shadowing it is desired to be able to predict the performance of a system with PV-modules during shadowing. In this thesis a simulation program for calculating the IV-curve for series connected PV-modules during partial shadowing has been developed and experimentally validated. PV systems modelling and simulation in LTspice environment has been presented and validated by means of a comparative analysis with the experimental results obtained in a set of tests performed in the laboratory of Gävle University. Experimental measurements were carried out in two groups. The first group corresponds with the experiments done in the string of six modules with bypass diodes while the measurements of the second group have been performed on a single PV module at HIG University. The simulation results of both groups demonstrated a remarkable agreement with the experimental data, which means that the model designed at LTspice supposes a very useful tool that can be used to study the performance of PV systems. This tool contributes to the investigations in this topic and it aims to benefit future installations providing a better knowledge of the shading problem. The master’s thesis shows an in-depth description of the required method to design a PV cell, a PV module and a PV array using LTspice IV and the input parameters as well as the needed tests to adjust the models. Moreover, it has been carried out a pedagogical study describing the effect that different shadow configurations have in the performance of solar cells. This study facilitates the understanding of the performance of PV modules under different shadowing effects. Lastly, it has also been discussed the benefits of installing some newer technologies, like DC-DC optimizers or module inverters, to mitigate the shadowing effects. The main conclusion about this topic has been that although most of the times the output power will be increased with the use of optimizers sometimes the optimizer does not present any benefits.

There is a growing demand for safe and convenient meat products. The effect of natural spice extracts incorporated with other hurdles for controlling pathogenic bacteria and extending the shelf life of RTE doner kebab were investigated. A comprehensive literature review was undertaken to establish the status of microbial risk, use of additives, knowledge on oxidative deterioration and HACCP associated with meat products. The in vitro antioxidant and antibacterial activities of spice extracts were screened and compared. Cinnamon, clove, and sumac alcoholic extracts demonstrated strong antimicrobial effect, however, rosemary proved effective as antioxidant in a lamb fat model. An accelerated shelf life study on a model system indicated that storage temperature was the most critical factor affecting lipid oxidation, which was effectively delayed by vacuum packaging and rosemary extracts. The effects of spice extracts, packaging and storage time on physiochemical, microbiological, and sensory attributes of doner kebab were evaluated. Application of rosemary and cinnamon extracts significantly reduced TVC, inhibited LAB, and retarded lipid oxidation rate. Sensory evaluation by a consumer panel indicated that only taste and spiciness perception was significantly different between treatments. A challenge test against Listeria monocytogenes showed significant differences between control and spice treatments at day 28. Strong inhibitory effects were associated to high levels of cinnamon particularly when applied after cooking. The effect of heat treatment and sumac (Rhus coriaria) on Bacillus cereus and Clostridium perfringens inactivation was evaluated on a doner kebab prototype. Addition of sumac significantly reduced D-values and z-values for both organisms in comparison to the control. The investigation of the effect of spice extracts, and environmental conditions on changes in growth kinetic parameters for L. monocytogenes and Salmonella Typhimurium showed that spice extracts are highly significant. For both microorganisms, Mumax was reduced as salt and spice concentrations increased, and pH levels decreased. This study shows that spice extracts incorporated with other hurdles can help to maintain safe and good quality RTE doner kebab.

This project is an interrogation of three examples from recent popular culture of girlculture, specifically texts that target young female consumers: the Spice Girls, Scream and Buffy the Vampire Slayer. These examples are fundamentally different than texts from earlier female targeted generic models because they not only reflect the influence of the feminist movement, they work on feminism's behalf. The project's methodology grows out of feminist film theories and cultural studies theories. One chapter is dedicated to each text, and each reading works to reappropriate girlculture texts for a counter-hegemonic agenda by highlighting the moments when each text manages to subvert its mass mediated conservative biases.

El objetivo del presente trabajo es analizar y comprobar el comportamiento de los ISFETs respecto a los MOSFETs. Para lograr lo anterior se utilizarán técnicas modernas de simulación y ensayos en laboratorio; de esta forma se podrá observar las similitudes y diferencias de comportamiento, y dependencias entre las variaciones tales como corriente de drenador respecto a variaciones del voltaje umbral. Además, esta comprobación se realizará considerando los valores de los parámetros de fabricación que ha generado el fabricante de los ISFETs y asumiendo valores intrínsecos de este dispositivo y siempre observando lo que sucede con los MOSFETs en situaciones similares. / Tesis

Cette thèse présente l’étude des effets des radiations sur des composants analogique du commerce. Il est mis en place une méthode de caractérisation expérimentale de la sensibilité des composants électroniques par le biais de simulation électrique et de stimulations laser. Grâce à la simulation électrique, nous classons par sensibilité des structures académiques, composant un amplificateur opérationnel, face à la propagation d’un signal transitoires. Le laser impulsionnel a permis d’extraire la sensibilité des composants testés en fonction de leur topologie. La technique d’absorption deux photons est utilisée afin d’extraire en trois dimensions le volume sensible d’un transistor / In space, natural radiation induces dysfunction in electronic device. Particle strikes silicon and generate transient current. We study this single event transient in fast commercial amplifiers. We investigate sensitivity of devices with simulation and laser property. SPICE simulation allows us to investigate the propagation of SET inside classical structure like current mirror or push pull. This work was applied at each stage of the amplification chain of an amplifier. In the other part we use laser bench with non linear property, due to non-linear absorption in silicon, to extract the sensitive volume

<p>Cilj istraživanja doktorske disertacije bio je da se ispita pojedinačni i sinergistički uticaj<br />ekstrakata kima (Carum carvi L.), bosiljka (Ocimum basilicum L.), origana (Origanum<br />vulgare L.) i etarskih ulja crnog (Allium cepa L. kultivar Kupusinski jabučar) i belog luka<br />(Allium sativum L. kultivar Bosut) na rast plesni izolovanih iz prehrambenih proizvoda, kao i<br />njihov uticaj na biosintezu mikotoksina.<br />Ukupan broj plesni u uzorcima salata od povrća spremnih za konzumiranje kretao se od<br />10,0 do 5,5&acute;102 cfu/g, u uzorcima poslastičarskih proizvoda do 6,1&acute;102 cfu/g i u<br />proizvodima od mesa do 60,0 cfu/g. Najveći broj plesni izolovan je na DG18 podlozi<br />(1,53&acute;102 cfu/g), a najmanji na MY50G (42,0 cfu/g). U ukupnoj mikopopulaciji svih ispitivanih<br />uzoraka dominirale su vrste rodova Penicillium (39,07%), Cladosporium (23,40%) i<br />Aspergillus (20,42%). Vrste iz rodova Alternaria, Fusarium i Eurotium su bile zastupljene sa<br />5,85%, 4,97% i 2,76%. Dominantne vrste u ukupnoj mikopopulaciji bile su C.<br />cladosporioides (21,63%), A. niger (16,0%) i P. aurantiogriseum (11,81%).<br />Dominirali su potencijalni producenti ohratoksina A (31,89%), proizvo&ntilde;ači fumonizina<br />(4,74%), moniliformina (1,43%) i sterigmatocistina (1,54%). Izolati A. versicolor su<br />biosintetisali sterigmatocistin u koncentracijama od 56,3 i 109,2 ng/mL. Ostale potencijalne<br />toksin-produkujuće vrste nisu pokazale sposobnost produkcije mikotoksina.</p><p>Mikotoksikolo&scaron;kim ispitivanjem hrane u dva uzorka salata spremnih za konzumiranje<br />(kupus beli rezani i FIT salata) utvr&ntilde;en je sadržaj sterigmatocistina u koncentracijama od 3,5<br />i 5,5 mg/kg.<br />Kao glavna komponenta u ekstraktu kima odre&ntilde;en je karvon (43,98%), u ekstraktu bosiljka<br />estragol (metil kavikol) (86,72%), a u ekstraktu origana karvakrol (34,20%) i karvon (18,05%).<br />Najveći deo etarskog ulja crnog luka činili su: dimetil-trisulfid, metil-propil-trisulfid, dimetiltetrasulfid,<br />dietil-1,2,4-tritiolan, metil-(1-propenil)-trisulfid, metil-(1-propenil)-disulfid. Dialildisulfid,<br />dialil-trisulfid, metil-alil-trisulfid i metil-alil-disulfid su glavne komponente koje su<br />odre&ntilde;ene u etarskom ulju belog luka.<br />Koncentracija od 0,35 mL/100 mL ekstrakta kima je bila fungicidna (MFC) prema C.<br />cladosporioides, dok je 0,70 mL/100 mL potpuno inhibirala rast A. carbonarius, A. wentii, E.<br />nidulans, Eurotium spp., C. cladosporioides, P. glabrum, P. brevicompactum, F.<br />subglutinans i F. verticillioides. Na rast P. chrysogenum i P. aurantiogriseum ista<br />koncentracija bila je inhibitorna (MIC). Najslabije delovanje ovaj ekstrakt ispoljio prema A.<br />niger, A. versicolor, F. oxysporum i F. proliferatum.<br />Primena ekstrakta bosiljka u koncentraciji od 0,70 mL/100 mL pokazala je fungicidno<br />delovanje na C. cladosporioides. Koncentracija od 1,50 mL/100 mL potpuno je inhibirala<br />rast A. wentii, A. versicolor, E. nidulans, E. herbariorum, E. chevalieri, E. rubrum, P.<br />chrysogenum i Fusarim spp. Ekstrakt bosiljka je najslabije delovao prema A. niger, A.<br />carbonarius, P. aurantiogriseum, E. amstelodami, P. glabrum i P. brevicompactum.<br />Ekstrakt origana je pokazao najslabije ihibitorno delovanje na rast ispitivanih plesni.<br />Primena ekstrakta u koncentraciji od 1,50 mL/100 mL je bila fungicidna prema E. rubrum.<br />Koncentracija od 2,50 mL/100 mL je pokazala fungicidno delovanje na E. rubrum, E.<br />herbariorum, A. wentii, C. cladosporioides i P. aurantiogriseum, a inhibitorno prema E.<br />nidulans, E. chevalieri, E. amstelodami, P. glabrum i P. brevicompactum. Ovaj ekstrakt je<br />najslabije delovao na A. niger, A. carbonarius, F. proliferatum, F. subglutinans i P.<br />chrysogenum.<br />Etarsko ulje crnog luka pokazalo je signifikantno jače antifungalno delovanje na ispitivane<br />plesni u odnosu na etarsko ulje belog luka. Koncentracija od 14,0 mL/100 mL ulja belog luka<br />fungicidno je delovala prema E. rubrum, E. chevalieri i C. cladosporioides, dok je ulje crnog<br />luka na ovoj koncentraciji pokazalo fungicidni efekat i na E. herbariorum i E. amstelodami.<br />Za ostale plesni fungicidna koncentracija iznosila je 28,0 mL/100 mL, osim za A. niger i P.<br />aurantiogriseum.<br />Neke od ispitivanih sme&scaron;a bosiljka i kima, bosiljka i origana, origana i kima i etarskih ulja<br />lukova pokazale su sinergističko delovanje na inhibiciju rasta A. wentii, E. herbariorum, F.<br />verticilllioides i P. aurantiogriseum sa FICindex od 0,63 do 0,97.<br />Začinski ekstrakti i etarska ulja lukova su pored ograničavanja rasta kolonija plesni<br />uzrokovali i promene u makro i mikromorfologiji.<br />Potpuna inhibicija biosinteze sterigmatocistina i rasta A. versicolor postignuta je pri<br />koncentraciji od 0,20 mL/100 mL ekstrakta kima i origana u periodu od 21 dana. Na ovoj<br />koncentraciji ekstrakt bosiljka je inhibirao biosintezu sterigmatocistina za 88,73% i rast<br />plesni za 52,56%. Sme&scaron;a koja je sadržavala 75% ekstrakta kima i 25% ekstrakta bosiljka<br />potpuno je inhibirala rast plesni i biosintezu sterigmatocistina u YES bujonu tokom 21 dana<br />inkubiranja.<br />Pojedinačne koncentracije etarskih ulja crnog i belog luka od 5,0 i 10,0 mL/100 mL i u sme&scaron;i<br />sa 1,50 mL/100 mL etarskog ulja crnog luka i 0,50 mL/100 mL etarskog ulja belog luka bile su<br />potrebne za potpunu inhibiciju rasta A. versicolor i biosintezu sterigmatocistina.<br />Dodatak sme&scaron;e ekstrakata kima i bosiljka (0,35 mL/100 mL ekstrakta kima + 0,70 mL/100 mL<br />ekstrakta bosiljka) u svež kupus rezanac uticao je na smanjenje inicijalne kontaminacije<br />plesnima za 93,9%, uz pojavu intenzivnijeg, ali prihvatljivog mirisa i neznatne promene boje.</p><p>Definisani matematički model za komparaciju uticaja ekstrakata i etarskih ulja na rast plesni<br />može se primenjivati u formiranju matrica inhibicije i optimizaciji vremena i koncentracije<br />antifungalnih agenasa.<br />Dobijena saznanja o antifungalnom delovanju ekstrakata začina i etarskih ulja lukova mogu<br />biti značajna u pobolj&scaron;anju antifungalne za&scaron;tite namirnica, smanjenju biosinteze<br />mikotoksina i ukupnim smanjenju &scaron;teta izazvanih delovanjem plesni.</p> / <p>The aim of this PhD thesis was to study the individual and synergistic effects of extracts of<br />caraway (Carum carvi L.), basil (Ocimum basilicum L.), oregano (Origanum vulgare L.) and the<br />essential oils of onion (Allium cepa L. cultivar Kupusinski jabučar) and garlic (Allium sativum<br />L. cultivar Bosut) on the growth of moulds isolated from food products. The study also<br />focused on the impact of extracts and the essential oils on mycotoxins biosynthesis.<br />The total number of moulds detected in samples of vegetable salads &ldquo;ready for use&rdquo; ranged<br />from 10.0 to 5.5&acute;102 cfu/g. In cake and pastries, as well as, meat samples, the number<br />reached 6.1&acute;102 cfu/g and 60.0 cfu/g, respectively. The highest number of mould colonies was<br />isolated in DG18 medium (1.53 &acute; 102cfu/g) and the lowest in MY50G medium (42.0 cfu/g). The<br />species of the genera Penicillium (39.07%), Cladosporium (23.40%) and Aspergillus (20.42%)<br />prevailed in the entire mycopopulation of all tested samples. Species of the genera Alternaria,<br />Fusarium and Eurotium were represented with 5.85%, 4.97% and 2.76%, respectively, while C.<br />cladosporioides (21.63%), A. niger (16.0%) and P. aurantiogriseum (11.81%) were the most<br />dominant species in the entire mycopopulation.<br />Potential producers of ochratoxin A (31.89%) accounted for the largest share of the isolated<br />mycopopulation. The share of producers of fumonisin, moniliformin and sterigmatocystin<br />amounted to 4.74%, 1.43% and 1.54%, respectively. Sterigmatocystin was biosynthesised in</p><p>the concentration of 56.3 ng/mL and 109.2 ng/mL by both isolates of A. versicolor, while other<br />potential toxin producers did not show the ability of mycotoxin production.<br />Mycotoxicological investigation showed the sterigmatocystin content in two samples of<br />vegetable salads &quot;ready for use&quot; (shredded white cabbage and FIT salad - carrot, lettuce and<br />red chicory) in concentrations of 3.5 mg/kg and 5.5 mg/kg, respectively.<br />The major component in the extract of caraway was carvon with a share of 43.98%. The basil<br />extract contained estragol (methyl cavicol) in the highest percentage (86.72%), while<br />carvacrol (34.20%) and carvon (18.05%) were major components of the oregano extract. As for<br />the essential oil of onion, dimethyl trisulphide, methyl propyl trisulphide, dimethyl tetrasulfid,<br />diethyl-1, 2, 4-tritiolan, methyl-(1-propenyl)-trisulphide, and methyl-(1-propenyl) &ndash; disulfide<br />constituted the largest share. The major components isolated in garlic essential oil were<br />diallyl disulfide, diallyl-trisulphide, allyl methyl trisulphide and allyl methyl disulfide.<br />The concentration of the caraway extract of 0.35 mL/100mL exhibited fungicidal effect (MFC)<br />on C. cladosporioides, while the concentration of 0.70 mL/100mL completely inhibited the<br />growth of A. carbonarius, A. wentii, E. nidulans, Eurotium spp., C. cladosporioides, P.<br />glabrum, P. brevicopmactum, F. subglutinans and F. verticillioides. The same concentration<br />showed the inhibitory effect (MIC) on the growth of P. chrysogenum and P. aurantiogriseum.<br />The poorest effect of the caraway extract was expressed on the growth of A. niger, A.<br />versicolor, F. oxysporum and F. proliferatum.<br />The basil extract application in the concentration of 0.70 mL/100mL showed fungicidal effects<br />(MFC) on the growth of C. cladosporioides. The concentration of 1.50 mL/100mL completely<br />inhibited (MFC) the growth of A. wentii, A. versicolor, E. nidulans, E. herbariorum, E.<br />chevalierii, E. rubrum, P. chrysogenum and Fusarim spp. The poorest effect of the basil<br />extract was exhibited on A. niger, A. carbonarius, P. aurantiogriseum, E. amstelodami, P.<br />glabrum and P. brevicompactum.<br />The oregano extract showed the weakest growth inhibition influence on all of the tested<br />moulds. The application of this extract in the concentration of 1.50 mL/100mL was fungicidal<br />(MFC) to E. rubrum. The concentration of 2.50 mL/100mL showed fungicidal effects (MFC) on<br />the growth of E. rubrum, E. herbariorum, A. wentii, C. cladosporioides and P. aurantiogriseum<br />and inhibitory effects (MIC) on E. nidulans, E. chevalieri, E. amstelodami, P. glabrum and P.<br />brevicompactum. The weakest effect of this extract was expressed on the growth of A. niger,<br />A. carbonarius, F. proliferatum, F. subglutinans and P. chrysogenum.<br />Onion essential oil showed a significantly stronger antifungal effect on the tested moulds in<br />comparison to garlic essential oil. While the concentration of 14.0 mL/100mL of garlic oil had a<br />fungicidal effect on E. rubrum, E. chevalieri and C. cladosporioides, the same concentration<br />of onion oil was also fungicidal to E. herbariorum and E. amstelodami. With an exception of A.<br />niger and P. aurantiogriseum, the concentration that showed a fungicidal effect on the<br />remaining moulds equalled 28.0 mL/100mL.<br />Some of the tested mixtures of basil with caraway, basil with oregano, oregano with caraway,<br />and essential oils of onion and garlic, showed a synergistic effect on the growth inhibition of<br />A. wentii, E. herbariorum, F. verticilllioides and P. aurantiogriseum with the FIC index ranging<br />from 0.63 to 0.97.<br />Apart from the inhibitory effect on the mould colony growth, the spices extracts and the<br />essential oils of onion and garlic also caused changes in the macro- and micro- morphology<br />of the moulds.<br />Complete inhibition of the growth of A. versicolor and sterigmatocystin biosynthesis was<br />achieved at a concentration of 0.20 mL/100mL of the extract of caraway and oregano in the<br />period of 21 days. At this concentration the basil extract delayed the sterigmatocystin<br />biosynthesis by 88.73% while the mould growth was inhibited by 52.56%. Mixtures containing</p><p>75% of the caraway extract and 25% of the basil extract completely inhibited the mould<br />growth and sterigmatocystin biosynthesis in YES broth during 21 days of incubation.<br />The concentrations of 5.0 m L/100mL (onion essential oil) and 10.0 m L/100mL (garlic essential<br />oil) applied in a mixture containing 1.50 mL/100mL of onion and 0.50 mL/100mL of garlic<br />essential oil were necessary for a complete inhibition of the growth of A. versicolor and<br />sterigmatocystin biosynthesis.<br />The addition of the mixture of caraway and basil extracts (0.35 mL/100mL of caraway + 0.70<br />mL/100mL of basil) to fresh shredded cabbage influenced the reduction of initial mould<br />contamination by 93.9%. This was accompanied by the occurrence of acceptable more<br />intense flavour and slight discoloration.<br />The defined mathematical model for comparing the effects of extracts and essential oils on<br />the growth of moulds can be applied in establishing inhibition matrices and optimisation of<br />the time and the concentration of antifungal agents.<br />The obtained results on the antifungal effects of the spices extracts and onion and garlic<br />essential oils can be beneficial for improving the antifungal protection of food and reducing<br />the mycotoxin biosynthesis as well as the overall damage caused by the action of moulds.</p>

The performance of SPICE and Network C (NC) circuit simulator when simulating MOS transistor circuits has been investigated and compared. SPICE analog model, NC analog model and NC MOS_PWL model are the three MOS transistor models being used. The comparison between SPICE and NC includes five areas. They are MOS transistor model, circuit analysis and computational methods, limitation on the ability to simulate circuits containing the MOS transistor diode configuration, run time and the ability to build new circuit component models using derived equations.

This study determined antioxidant and sensory effects of cinnamon, cloves, fennel, pepper, and star anise (Chinese 5-spice ingredients) in cooked ground beef. In experiment 1, thiobarbituric acid (TBA) values of cooked samples were measured during refrigerated storage. In experiment 2, trained panelists evaluated cooked samples for rancid, beef, and spice flavor intensity. Total aerobic plate counts were also measured. Mean TBA values were high (3.4) for control samples. In previous studies, TBA values >1.0 were associated with unacceptably rancid cooked meats. At the lowest spice level of 0.1% of meat weight, all spices except pepper had lower TBA values than controls. Thus, the minimum effective level was 0.1% for all spices except pepper. For all spices except cloves, increasing the use level to 0.5% significantly decreased TBA values (dose-response effect). Cloves did not exhibit a dose-response effect, since all clove levels were very effective, and not different, for maintenance of TBA values In experiment 2 (sensory evaluation), there was a high positive correlation (p < 0.01) between TBA values and panel scores for rancid odor and flavor (0.83 and 0. 78, respectively). Hence, TBA values were in good agreement with sensory panel scores as a measure of oxidation during storage. Spice flavor was inversely correlated (p < 0.01) with rancid odor and flavor (-0.57 and -0.61, respectively), suggesting that spices also decreased the perception of rancid flavor in these samples. The 5-spice blends did not inhibit microbial growth of cooked samples during storage, compared to controls, perhaps due to heat inactivation or loss of antimicrobial components from the spices during cooking. In conclusion, all spices and blends had a dual effect, reducing chemical oxidation as measured by TBA values, and also imparting a distinctive flavor to cooked ground beef.

La conception des oscillateurs à quartz a été longtemps basée sur des méthodes empiriques ou des techniques de modélisation approximatives ou inappropriées. Bien que ces méthodes permettent de réaliser des oscillateurs stables, leur procédure de conception reste lourde et fastidieuse et le comportement du circuit oscillateur n'est pas toujours déterminé avec une précision optimale. Le logiciel ADOQ (Analyse Dipolaire des Oscillateurs à Quartz) a été développé pour remédier aux limitations de ces méthodes. Cet outil fondé sur l'analyse dipolaire consiste à modéliser un oscillateur à quartz en tenant compte des non linéarités de la partie amplificateur séparément de celles du résonateur. Grâce à cette séparation, on s'affranchit du temps de calcul prohibitif imposé par le coefficient de qualité très élevé du résonateur. Le comportement non linéaire de l'amplificateur est déterminé en boucle ouverte par une analyse temporelle réalisée à l'aide d'un simulateur électrique de type SPICE. Les résultats fournis par ce simulateur permettent de déterminer avec précision l'impédance non linaire équivalente de l'amplificateur, c'est-à-dire son impédance en fonction de la fréquence et de l'amplitude. L'analyse consiste ensuite à rechercher de manière itérative la solution en boucle fermée à partir d'une série d'analyses dipolaires en boucle ouverte et de définir avec précision les conditions de fonctionnement de l'oscillateur : fréquence, amplitude, puissance d'excitation du résonateur en régime permanent, régime transitoire et spectres de bruit d'amplitude et de phase. ADOQ permet également de déterminer la sensibilité des caractéristiques de l'oscillateur en fonction des variations de la valeur des composants ou d'autres paramètres tels que la tension d'alimentation ou la température. La méthode dipolaire nécessite de calculer l'impédance non linaire de l'amplificateur en fonction de l'amplitude de la source harmonique en régime permanent. Bien que la séparation du résonateur et de l'amplificateur permette un gain de temps appréciable, l'utilisation d'un simulateur temporel tel que SPICE nécessite tout de même d'attendre que le régime permanent soit atteint ce qui reste pénalisant pour la méthode. D'autres méthodes d'analyses utilisées dans certains simulateurs industriels permettent d'obtenir le régime permanent d'un circuit non linaire beaucoup plus rapidement : équilibrage harmonique (harmonic—balance) ou méthode balistique (shooting—method). D'autre part les modèles des composants utilisés par SPICE sont assujettis aux bibliothèques de composants fournies par le concepteur de l'outil ou le fabricant des composants. La plus grande partie du travail effectué dans cette thèse consiste à exploiter les fonctionnalités de l'outil de conception Cadence pour étendre les performances en termes de calculs (SpectreRF) et les possibilités en termes de modèles de composants (Dracula) pour optimiser le logiciel ADOQ. Des tests et des simulations ont été réalisés et les résultats ont permis de mettre en évidence les améliorations acquises ainsi que leurs limites.