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Modal Analysis of General Cyclically Symmetric Systems with Applications to Multi-Stage StructuresDong, Bin 10 October 2019 (has links)
This work investigates the modal properties of general cyclically symmetric systems and the multi-stage systems with cyclically symmetric stages. The work generalizes the modal properties of engineering applications, such as planetary gears, centrifugal pendulum vibration absorber (CPVA) systems, multi-stage planetary gears, etc., and provides methods to improve the computational efficiency to numerically solve the system modes when cyclically symmetric structures exist.
Modal properties of cyclically symmetric systems with vibrating central components as three-dimensional rigid bodies are studied without any assumptions on the system matrix symmetries: asymmetric inertia matrix, damping, gyroscopic, and circulatory terms can be present. In the equation of motion of such a cyclically symmetric system, the matrix operators are proved to have properties related to the cyclic symmetry. These symmetry-related properties are used to prove the modal properties of general cyclically symmetric systems. Only three types of modes can exist: substructure modes, translational-tilting modes, and rotational-axial modes. Each mode type is characterized by specific central component modal deflections and substructure phase relations. Instead of solving the full eigenvalue problem,all vibration modes and natural frequencies can be obtained by solving smaller eigenvalue problems associated with each mode type. This computational advantage is dramatic for systems with many substructures or many degrees of freedom per substructure.
Group theory is applied to further generalize the modal properties of cyclically symmetric systems when both rigid-body and compliant central components exist, such as planetary gears with an elastic continuum ring gear. The group theory for symmetry groups is introduced, and the group-theory-based modal analysis does not rely on any knowledge of the properties of system matrices in system equations of motion. The three types of modes (substructure modes, translational-tilting modes, and rotational-axial modes) are characterized by specific rigid-body central component modal defections, substructure phase relations, and nodal diameter components of compliant central components. The general formulation of reduced eigenvalue problems for each mode type is obtained through group-theory-based method, and it applies to discrete, continuous, or hybrid discrete-continuous cyclically symmetric systems. The group-theory-based modal analysis also applies to systems with other symmetry types.
The group-theory-based modal analysis is generalized to analyze the multi-stage systems that are composed of symmetric stages coupled through the motions of rigid-body central components. The proposed group-theory-based modal analysis applies to multi-stage systems with cyclically symmetric stages, such as multi-stage planetary gears and CPVA systems with multiple groups of absorbers. The method also applies to multi-stage systems with component stages that have different types of symmetry. For a multi-stage system with symmetric stages, a unitary transformation matrix can be built through an algorithmic and computationally inexpensive procedure. The obtained unitary transformation matrix provides the foundation to analyze the modal properties based on the principles of group-theory-based modal analysis. For general multi-stage systems with symmetric component stages, the vibration modes are classified into two general types, single-stage substructure modes and overall modes, according to the non-zero modal deflections in each component stage. Reduced eigenvalue problems for each mode type are formulated to reduce the computational cost for eigensolutions.
Finite element models of multi-stage bladed disk assemblies consist of multiple cyclically symmetric bladed disks that are coupled through the boundary nodes at the inter-stage interface. To improve the computational efficiency of calculating the full system modes, a numerical method is proposed by combination of the multi-stage cyclic symmetry reduction method and the subspace iteration method. Compared to the multi-stage cyclic symmetry reduction method, the proposed method improves the accuracy of obtained eigensolutions through an iterative process that is derived from the subspace iteration method. Based on the cyclic symmetry in each component stage of bladed disk, the proposed iterative method that can be performed using single stage sector models only, instead of using matrix operators for the full multi-stage bladed disks. Parallel computations can be performed in the proposed iterative method, and the computational speed for eigensolutions can be increased significantly. / Doctor of Philosophy / Cyclically symmetric structures exist in many engineering applications such as bladed disks, circular plates, planetary gears, centrifugal pendulum vibration absorbers (CPVA), etc. During steady operation, these cyclically symmetric systems are subjected to traveling wave dynamic loading. Component vibrations result in undesirable effects, including high cycle fatigue (HCF) failure, noise, performance reduction, etc. Knowledge of the modal properties of cyclically symmetric systems is helpful to analyze the system forced response and understand experimental modal testing.
In this work, single stage cyclically symmetric systems are proved to have highly structured modes. The single stage systems considered in this work can have both rigid bodies and elastic continua as components. Group theory is used to study the modal properties, including the system mode types and the characteristics of different mode types. All the vibration modes of single stage cyclically symmetric systems can be solved from reduced eigenvalue problems. The methodology also applies to systems with other types of symmetry. For multi-stage systems with cyclically symmetric substructures, such as multi-stage planetary gears, a group-theory-based method is developed to analyze the modal properties. For industrial applications, such as multi-stage bladed disk assemblies, this work develops an iterative method to facilitate the calculations of system modes. The modal properties and methods for solving system modes apply to mechanical systems, including CPVA systems, the single/multi-stage planetary gears in power transmission systems, bladed disk assemblies in turbines, circular plates, elastic rings, etc.
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Modeling and simulation of the dual stage pressure retarded osmosis systemsSoltani, Roghayeh 31 May 2019 (has links)
Utilization of renewable energy sources, as an approach to reduce greenhouse
gas (GHG) emissions, have been globally popular in the last few decades. Among
renewable energy sources, pressure retarded osmosis (PRO) has been scrutinized by
scientists since the mid 70's. However, even today, the existing river-sea PRO systems
can only marginally meet the generally approved criterion of 5 W/m2 power density,
a threshold for an economically feasible PRO system. As an approach to increase the
performance of PRO systems, multi-staging of PRO modules are investigated.
A mathematical model of the scaled up PRO process is proposed with consideration
for internal and external concentration polarization, reverse salt flux, and spatial
variations along the membrane. A thermodynamic model is also developed with consideration
for entropy generation and losses in the process. It predicts the percentile
of each work loss source compared to the net work in the system. Several confi gurations
of dual stage PRO system are presented and compared to single stage PRO.
The comparison is based on three proposed target functions of power density (PD),
specifi c energy (SE), and work per drawn freshwater (Wdrawn). Applied hydraulic
pressures and flow rates of draw and feed solutions are optimized for maximizing the
target functions. The results indicate that overall performance of the system could
be improved by up to 8 % with a dual stage PRO in the case of SE. The system performance is not improved by depressurizing the draw solution before the second
module in cases of SE and Wdrawn. The thermodynamic analysis demonstrate the
contribution of each work loss and justify the reason of diminishing the net work over
the losses. The effect of membrane area and membrane characteristics on the SE target
function is also investigated. The distribution of membrane area in each module
depends on the selected con figuration and inlet draw solution. In the dual stage systems,
the SE value increases up to 14% by improving the membrane characteristics.
Reducing the salt rejection coefficient (B) is the most e ective membrane characteristic
in our con figurations. Replacing seawater with RO brine in draw solution results
in a signifi cant improvement in SE values. / Graduate
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A two-stage method for system identification from time seriesNadsady, Kenneth Allan January 1998 (has links)
No description available.
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Measuring the efficiency of two stage network processes: a satisficing DEA approachMehdizadeh, S., Amirteimoori, A., Vincent, Charles, Behzadi, M.H., Kordrostami, S. 2020 March 1924 (has links)
No / Regular Network Data Envelopment Analysis (NDEA) models deal with evaluating the performance of a set of decision-making units (DMUs) with a two-stage construction in the context of a deterministic data set. In the real world, however, observations may display a stochastic behavior. To the best of our knowledge, despite the existing research done with different data types, studies on two-stage processes with stochastic data are still very limited. This paper proposes a two-stage network DEA model with stochastic data. The stochastic two-stage network DEA model is formulated based on the satisficing DEA models of chance-constrained programming and the leader-follower concepts. According to the probability distribution properties and under the assumption of the single random factor of the data, the probabilistic form of the model is transformed into its equivalent deterministic linear programming model. In addition, the relationship between the two stages as the leader and the follower, respectively, at different confidence levels and under different aspiration levels, is discussed. The proposed model is further applied to a real case concerning 16 commercial banks in China in order to confirm the applicability of the proposed approach at different confidence levels and under different aspiration levels.
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Estudo clínico-cirúrgico, tomográfico e imuno-histoquímico de cães com neoplasia intranasal tratados com rinotomia e quimioterapia / Clinical, surgical, CT scan and immunohistochemical study in dogs with intranasal neoplasia treated with rhinotomy and chemotherapyFernanda de Assis Bueno Auler 17 December 2015 (has links)
Introdução: Neoplasias malignas nasais e sinonasais em cães são invasivas e de difícil tratamento. Para conclusão diagnóstica indica-se a rinoscopia, estudo histopatológico (HP) da biópsia, e exame tomográfico de cabeça (TCC). São escassos na literatura estudos desta afecção sobre tempo de sobrevida e remissão correlacionando achados clínicos, estadiamento por meio da TCC, HP, tratamento e a influência da expressão de marcadores tumorais. Objetivo: Avaliou-se o tempo de sobrevida e remissão em cães com neoplasias nasais e nasossinusais malignas, correlacionando com a idade, sexo, características clínicas, e graduação da afecção por meio de estadiamento, tratamentos quimioterápicos adjuntoriamente ou não a rinotomia e influência da expressão dos marcadores tumorais COX-2, EGFR, VEGF, p53, Ki-67 e PCNA. Materiais e métodos: Este estudo foi aprovado pela Comissão de Ética com o número 2488/11. Foram inseridos 25 cães com raça, sexo e idade variadas atendidos no Departamento de Cirurgia e provenientes Hospital Veterinário da Faculdade de Medicina Veterinária e Zootecnia da Universidade de São Paulo, com diagnóstico conclusivo de neoplasia nasal, após resultados dos exames de TCC, rinoscopia e HP. O protocolo quimioterápico empregado utilizou a carboplatina 300mg/m2 e a doxorrubicina 30mg/m2 em sessões intercaladas, e rinotomia quando indicado. O tempo de sobrevida foi avaliado após o diagnóstico HP e a remissão a partir da primeira sessão quimioterápica. Dados sobre as manifestações clínicas, tipo tumoral, classificação baseada no estadiamento de Adams et al. (2009), modificado por nós, e expressão dos marcadores, foram correlacionados com a resposta ao tratamento, remissão e tempo de sobrevida. Resultados: Destes animais 56% eram machos (n=14), com idade média de 10,1 anos, sendo 60% neoplasias epiteliais (n=15) e 40% mesenquimais (n=10). Animais com epistaxe obtiveram menor tempo de sobrevida e de remissão (p = 0,015). Pelo estadiamento classificou-se os cães como T3 (7/25), T4 (9/25) e T5(9/25), observando menor tempo de sobrevida global em animais com graduação elevada (p = 0,006). Controle da afecção ocorreu em 80% dos animais (n=20) com tempo médio de sobrevida de 276,8 dias. Animais com remissão (p = 0,001) obtiveram menor risco de mortalidade (98%). Expressões elevadas de COX-2 (p = 0,006) influenciou no menor tempo de sobrevida e de EGFR ao menor tempo de remissão (p= 0,021), a expressão dos demais marcadores não representou significância estatística. Conclusão: Os resultados demonstram presença de expressão dos marcadores nos tumores epiteliais e mesenquimais nasais e nasossinusais, com resultados significativos relacionados a influência do EGFR e da COX-2. A ocorrência de epistaxe pode ser considerada característica de mau prognóstico, assim como a deformidade facial, no menor tempo de remissão. O emprego do estadiamento da TCC colaborou com a avaliação prognóstica desta afecção. Apesar de não curativo e sem resultados estatisticamente significativos, as modalidades terapêuticas utilizadas apresentaram aumento no tempo remissão influenciando no aumento de tempo sobrevida global. Estes resultados foram promissores quanto a expressão dos marcadores tumorais nas neoplasias nasais malignas de cão, assim como o emprego do estadiamento e tratamento em relação ao tempo de sobrevida e de remissão dos animais afetados por esta afecção / Introduction: Nasal malignant neoplasia in dogs are invasive with a difficult treatment. The diagnostic includes rhinoscopy, histopathology (HP), and head tomography (CT). There are few studies in the literature evaluating survival time and remission, with clinical findings, CT staging, HP, treatment and the influence of cellular markers expression. Objective: To evaluate the effects of chemotherapy in conjunction or not with rhinotomy in dogs with malignant nasal and sinonasal neoplasia, and associated age, sex, clinical features, staging system and presence of cell markers COX-2, EGFR, VEGF, p53, Ki-67 and PCNA with survival time and disease control. Methods: the Ethics Committee with the number 2488/11 approved this study. In this study, 25 dogs with different breeds, gender and age evaluated from Department of Surgery and from the Veterinary Hospital of the Veterinary Medicine and Animal Science School of the University of São Paulo, with nasal malignant neoplasia, after rhinoscopy, CT scan and histopathological diagnostic. The chemotherapy protocol used was carboplatin 300 mg/m2 and doxorubicin 30 mg/m2 in intercaled sessions. Rhinotomy was applied when indicated. Survival time was evaluated after the histopathological conclusion and remission was evaluated from the first chemotherapy application. Clinical characters, tumor type, stage based on staging system (ADAMS et al., 2009) modified for this study, treatment and expression of the markers were associated with disease control and survival time. Results: Fifty six per cent were males (n = 14), with mean age 10.1 years, and 60% epithelial neoplasms (n = 15) and 40% mesenchymal (n = 10). Animals with epistaxis had lower survival time and remission time (p = 0.015). In according with staging system twenty-eight per cent was classified inT3 (7/25), and 36% classified in T4 (9/25) and the others 36% in T5 (9/25) the lower overall survival time was associated in animals with more advanced stage (p = 0.006). Control of the disease occurred in 80% of animals (n = 20) with mean survival time of 276.8 days. Animals with remission (p = 0.001) had decreased death (98%). High COX-2 expression (p = 0.006) was associated with shorter survival and EGFR expression with the disease control (p = 0.021). The expression of other markers did not present statistical significance. Conclusion: The results indicated significant about the influence of COX-2 and EGFR expression in malignant nasal neoplasia in dogs. Epistaxis was considered a signal for bad prognosis and facial deformity have influence in remission time. The staging system by CT was applicable and useful prognostic factor. Although the results was not statistically significant about the therapeutic modalities used, but showed an increase remission time and overall survival time. These results were promising as the expression of cellular markers in malignant nasal tumors dog, as well as the use of staging system and treatment in relationship with survival time and remission of animals affected by this disease
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Estudo clínico-cirúrgico, tomográfico e imuno-histoquímico de cães com neoplasia intranasal tratados com rinotomia e quimioterapia / Clinical, surgical, CT scan and immunohistochemical study in dogs with intranasal neoplasia treated with rhinotomy and chemotherapyAuler, Fernanda de Assis Bueno 17 December 2015 (has links)
Introdução: Neoplasias malignas nasais e sinonasais em cães são invasivas e de difícil tratamento. Para conclusão diagnóstica indica-se a rinoscopia, estudo histopatológico (HP) da biópsia, e exame tomográfico de cabeça (TCC). São escassos na literatura estudos desta afecção sobre tempo de sobrevida e remissão correlacionando achados clínicos, estadiamento por meio da TCC, HP, tratamento e a influência da expressão de marcadores tumorais. Objetivo: Avaliou-se o tempo de sobrevida e remissão em cães com neoplasias nasais e nasossinusais malignas, correlacionando com a idade, sexo, características clínicas, e graduação da afecção por meio de estadiamento, tratamentos quimioterápicos adjuntoriamente ou não a rinotomia e influência da expressão dos marcadores tumorais COX-2, EGFR, VEGF, p53, Ki-67 e PCNA. Materiais e métodos: Este estudo foi aprovado pela Comissão de Ética com o número 2488/11. Foram inseridos 25 cães com raça, sexo e idade variadas atendidos no Departamento de Cirurgia e provenientes Hospital Veterinário da Faculdade de Medicina Veterinária e Zootecnia da Universidade de São Paulo, com diagnóstico conclusivo de neoplasia nasal, após resultados dos exames de TCC, rinoscopia e HP. O protocolo quimioterápico empregado utilizou a carboplatina 300mg/m2 e a doxorrubicina 30mg/m2 em sessões intercaladas, e rinotomia quando indicado. O tempo de sobrevida foi avaliado após o diagnóstico HP e a remissão a partir da primeira sessão quimioterápica. Dados sobre as manifestações clínicas, tipo tumoral, classificação baseada no estadiamento de Adams et al. (2009), modificado por nós, e expressão dos marcadores, foram correlacionados com a resposta ao tratamento, remissão e tempo de sobrevida. Resultados: Destes animais 56% eram machos (n=14), com idade média de 10,1 anos, sendo 60% neoplasias epiteliais (n=15) e 40% mesenquimais (n=10). Animais com epistaxe obtiveram menor tempo de sobrevida e de remissão (p = 0,015). Pelo estadiamento classificou-se os cães como T3 (7/25), T4 (9/25) e T5(9/25), observando menor tempo de sobrevida global em animais com graduação elevada (p = 0,006). Controle da afecção ocorreu em 80% dos animais (n=20) com tempo médio de sobrevida de 276,8 dias. Animais com remissão (p = 0,001) obtiveram menor risco de mortalidade (98%). Expressões elevadas de COX-2 (p = 0,006) influenciou no menor tempo de sobrevida e de EGFR ao menor tempo de remissão (p= 0,021), a expressão dos demais marcadores não representou significância estatística. Conclusão: Os resultados demonstram presença de expressão dos marcadores nos tumores epiteliais e mesenquimais nasais e nasossinusais, com resultados significativos relacionados a influência do EGFR e da COX-2. A ocorrência de epistaxe pode ser considerada característica de mau prognóstico, assim como a deformidade facial, no menor tempo de remissão. O emprego do estadiamento da TCC colaborou com a avaliação prognóstica desta afecção. Apesar de não curativo e sem resultados estatisticamente significativos, as modalidades terapêuticas utilizadas apresentaram aumento no tempo remissão influenciando no aumento de tempo sobrevida global. Estes resultados foram promissores quanto a expressão dos marcadores tumorais nas neoplasias nasais malignas de cão, assim como o emprego do estadiamento e tratamento em relação ao tempo de sobrevida e de remissão dos animais afetados por esta afecção / Introduction: Nasal malignant neoplasia in dogs are invasive with a difficult treatment. The diagnostic includes rhinoscopy, histopathology (HP), and head tomography (CT). There are few studies in the literature evaluating survival time and remission, with clinical findings, CT staging, HP, treatment and the influence of cellular markers expression. Objective: To evaluate the effects of chemotherapy in conjunction or not with rhinotomy in dogs with malignant nasal and sinonasal neoplasia, and associated age, sex, clinical features, staging system and presence of cell markers COX-2, EGFR, VEGF, p53, Ki-67 and PCNA with survival time and disease control. Methods: the Ethics Committee with the number 2488/11 approved this study. In this study, 25 dogs with different breeds, gender and age evaluated from Department of Surgery and from the Veterinary Hospital of the Veterinary Medicine and Animal Science School of the University of São Paulo, with nasal malignant neoplasia, after rhinoscopy, CT scan and histopathological diagnostic. The chemotherapy protocol used was carboplatin 300 mg/m2 and doxorubicin 30 mg/m2 in intercaled sessions. Rhinotomy was applied when indicated. Survival time was evaluated after the histopathological conclusion and remission was evaluated from the first chemotherapy application. Clinical characters, tumor type, stage based on staging system (ADAMS et al., 2009) modified for this study, treatment and expression of the markers were associated with disease control and survival time. Results: Fifty six per cent were males (n = 14), with mean age 10.1 years, and 60% epithelial neoplasms (n = 15) and 40% mesenchymal (n = 10). Animals with epistaxis had lower survival time and remission time (p = 0.015). In according with staging system twenty-eight per cent was classified inT3 (7/25), and 36% classified in T4 (9/25) and the others 36% in T5 (9/25) the lower overall survival time was associated in animals with more advanced stage (p = 0.006). Control of the disease occurred in 80% of animals (n = 20) with mean survival time of 276.8 days. Animals with remission (p = 0.001) had decreased death (98%). High COX-2 expression (p = 0.006) was associated with shorter survival and EGFR expression with the disease control (p = 0.021). The expression of other markers did not present statistical significance. Conclusion: The results indicated significant about the influence of COX-2 and EGFR expression in malignant nasal neoplasia in dogs. Epistaxis was considered a signal for bad prognosis and facial deformity have influence in remission time. The staging system by CT was applicable and useful prognostic factor. Although the results was not statistically significant about the therapeutic modalities used, but showed an increase remission time and overall survival time. These results were promising as the expression of cellular markers in malignant nasal tumors dog, as well as the use of staging system and treatment in relationship with survival time and remission of animals affected by this disease
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Amélioration des rendements de traitement des déchets par digestion anaérobie : rôle d'un pré-traitement thermique et d'un traitement en bioréacteur en deux étapes / Enhanced anaerobic digestion of organic solid waste through thermal pretreatment and biofilm based two-stage reactorsYeshanew, Martha Minale 15 December 2016 (has links)
La digestion anaérobie est utilisée depuis près d’un siècle comme un traitement efficace des déchets organiques. L’intérêt de ce traitement en anaérobie est en essor, car il présente des avantages significatifs sur les traitements alternatifs biologiques et d’autres options d’élimination des déchets. Cette étude se focalise sur l’optimisation du processus de digestion anaérobie en utilisant deux stratégies différentes. La première vise à augmenter la biodégradabilité du substrat par un prétraitement thermique. La seconde technique repose sur l’utilisation d’un système de biofilms pour augmenter le taux de production de biogaz et minimiser la taille du réacteur.Les déchets alimentaires sont principalement utilisés comme substrat modèle de par leur composition, leur abondance et leur renouvellement. Dans ces travaux de thèse, l’influence de la température des prétraitements thermiques sur la solubilisation de la matière organique, ainsi que la production de méthane des déchets alimentaires sous différentes conditions ont été étudié. Une amélioration significative de la solubilisation et de la biodégradabilité des déchets alimentaires ont été observés pour tous les prétraitements thermiques sur les déchets alimentaires comparativement aux déchets non traités. La plus importante amélioration (28%) de la biodégradabilité a été observée pour les déchets alimentaires traités à la plus basse température de prétraitements (80°C). Les résultats montrent une corrélation forte entre le type de substrats (carbohydrate, protéines et teneur en lipides), la température de prétraitement thermique et son efficacité dans l’amélioration de la biodégradabilité.Dans une seconde partie, une opération prolongée d’un système intégré à deux étages, incluant une cuve agitée en continu et un réacteur à biofilm anaérobie a été réalisé pour produire du biohytane (biohydrogène et méthane) à partir de déchets alimentaires. Le réacteur à biofilm anaérobie a été utilisé pour remédier au lessivage de la biomasse du réacteur. La formation d’une biomasse mature et équilibrée a amélioré de façon importante la stabilité du processus, ce dernier n’ayant pas été affecté par un raccourcissement du temps de rétention hydraulique (HRT) de 6 à 3,7 jours dans le premier réacteur, et de 20 à 1,5 jours dans le second réacteur. De plus, le système à deux étages, constitué d’un pilote à l’échelle d’un batch pour la fermentation sombre et d’un réacteur à biofilm anaérobie, coproduisant de l’hydrogène et du méthane à partir de la fraction organique des déchets solide ménagers (OFMSW), a été utilisé afin de déterminer la capacité d’un réacteur à biofilm anaérobie à supporter un choc de charge organique. Les résultats montrent une récupération plus rapide du réacteur à biofilm anaérobie après un évènement de charge organique / Anaerobic digestion (AD) has been used over a century for an effective treatment of organic wastes. Interest in anaerobic treatment is continually increasing since it presents significant advantages when compared to alternative biological treatments and waste disposal options. This research study was mainly focused on optimization of the AD process, that was achieved through two different strategies. The first aimed at increasing the substrate biodegradability by a means of thermal pretreatment. The second was focused on the application of a biofilm based system to improve the biogas production rates and minimize the reactor size.Food waste (FW) was mainly used as a model substrate due to its suitable composition, abundance and renewability. In this thesis the influence of thermal pretreatment temperature on organic matter solubilization and methane yield of FW under different operational conditions was investigated. Significant improvement of the FW solubilization and biodegradability were observed for all thermally pretreated FW compared to the untreated FW. The highest biodegradability enhancement, i.e. + 28 %, was observed for FW treated at the lowest thermal pretreatment temperature, i.e. 80 ⁰C. The results showed a strong correlation between the substrate type (e.g. carbohydrate, protein and lipid content), the thermal pretreatment temperature and its effectiveness in promoting the biodegradability.In the second part of the work, a prolonged operation of an integrated two-stage system, including a continuously stirred tank and an anaerobic biofilm reactor, was carried out to produce biohythane (biohydrogen and methane) from the FW. The anaerobic biofilm reactor was employed to overcome the biomass wash-out from the reactor. The formation of a well-matured and balanced AD biomass greatly improved the process stability, which was not affected by shortening the hydraulic retention time (HRT) from 6 to 3.7 days in the first reactor and from 20 to 1.5 days in the second reactor. Moreover a two-stage system, comprised of a pilot scale batch dark fermenter and an anaerobic biofilm reactor co-producing hydrogen and methane from the organic fraction of municipal solid waste (OFMSW), was used to assess the capability of the anaerobic biofilm reactor to face an organic shock loads. The results showed a faster recovery of anaerobic biofilm reactor performance after the shock load events
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La déglaciation du bassin du Lac Saint-Jean (Wisconsinien/Holocène, Québec, Canada) : enregistrement d'une régression forcée glacio-isostatique et de l'hydrodynamique d'un système fermé contrôlé par le vent / The Saint-Jean basin deglaciation (Wisconsinian/Holocene, Quebec, Canada) : record of a glacio-isostatic forced regression and hydrodynamics of an enclosed wind-driven water bodyNutz, Alexis 25 November 2013 (has links)
Dans ce travail de thèse, certaines étendues d’eaux continentales regroupant plusieurs types de système de dépôt comme les lacs, mers intérieures et lagunes ont été regroupées au sein d'un nouveau groupe de système sédimentaire mentionnés sous l'appellation de Wind-driven Water Body (WWB).Afin de caractériser l'évolution et l'enregistrement sédimentaire d'un exemple de WWB, une étude sédimentologique intégrée du bassin quaternaire du Lac Saint-Jean (Québec, Canada) a été menée à partir d'une approche intégrant géologie de terrain et imagerie géophysique très haute résolution (CHIRP 2D). A l'échelle du cortège sédimentaire, le régime glaciaire à paraglaciaire de la sédimentation et le rebond glacio-isostatique ont contrôlé au premier ordre, à la fois la succession lithologique et les architectures grandes échelles du bassin pour générer un Cortège de Régression Forcée (CRF) atypique. Au sein de ce cortège de régression forcée fini-glaciaire, une dynamique de système WWB s'est progressivement affirmée à partir de 8,5 cal. ka BP. Elle s'est exprimée par la mise en place d'une dynamique littorale importante occasionnellement associée à une circulation interne générant des courants de fonds lors d'épisodes de vents forts.Finalement, l'analyse sédimentologique du bassin du Lac Saint-Jean a permis de dégager plusieurs interprétations ayant attrait (1) à l'évolution des systèmes WWB et (2) aux séquences de déglaciation en domaine précédemment englacé. De plus, ce travail représente une contribution à l'échelle régionale pour les modalités de la dernière déglaciation du Sud-Est du Québec. / In this study, a certain number of continental enclosed basins including several depositional systems such as lakes, inland seas or lagoons have been grouped in a new sort of sedimentary system referred to as Wind driven Water Body. To characterize the sedimentary evolution and record of a WWB basin, an integrated sedimentological study has been carried out on the quaternary Saint-Jean basin (Québec, Canada) based on field onshore geology and offshore geophysics (CHIRP 2D).At the system-tract scale, the glacial to paraglacial sedimentation and the glacio-isostatic rebound controlled at first-order the lithofacies succession and large-scale architectures to generate an original Falling Stage System Tract (FSST). Within this FSST, since 8.5 cal. ka BP a WWB related sedimentary evolution overprinted the glacial to paraglacial evolution. This expressed in the form of the emplacement of an important coastal dynamics, occasionally accompanied by a lake-scale hydrodynamics at the origins of bottom currents during strong wind to storm events.Finally, the sedimentological analysis of the Saint-Jean basin brought numerous interpretations related to (1) the sedimentary evolution of WWB systems and (2) deglaciation sequences in previously glaciated domains. In addition, this work supplements the regional quaternary framework concerning the latest deglaciation evolution in southeast Quebec.
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Energy valorization of agro-industrial wastes and sweet sorghum for the production of gaseous biofuels through anaerobic digestion / Ενεργειακή αξιοποίηση αγροτο-βιομηχανικών αποβλήτων και γλυκού σόργου για την παραγωγή αέριων βιοκαυσίμων μέσω αναερόβιας χώνευσηςΔαρειώτη, Μαργαρίτα 09 February 2015 (has links)
It is clear that renewable resources have received great interest from the international community during the last decades and play a crucial role in the current CO2-mitigation policy. In this regard, energy from biomass and waste is seen as one of the most dominant future renewable energy sources. Thus, organic waste i.e. animal wastes, wastewaters, energy crops, agricultural and agro-industrial residues are of specific importance since these sources do not compete with food crops in agricultural land usage. The various technologies that are available for power generation from biomass and waste can be subdivided into thermochemical, biochemical and physicochemical conversion processes. Anaerobic digestion (AD), classified within the biochemical conversion processes, is a robust process and is widely applied. Various types of biomass and waste, can be anaerobically co-digested to generate a homogeneous mixture increasing both process and equipment performance.
This study focused on the valorization of agro-industrial wastes (such as olive mill wastewater (OMW), cheese whey (CW) and liquid cow manure (LCM)) and sweet sorghum stalks. Olive mills, cheese factories and cow farms are agro-industries that represent a considerable share of the worldwide economy with particular interest focused in the Mediterranean region. These industries generate millions of tons of wastewaters and large amounts of by-products, which are in many cases totally unexploited and thus dangerous for the environment. On the other hand, sweet sorghum as a lignocellulosic material represents an interesting substrate for biofuels production due to its structure and composition.
Anaerobic co-digestion experiments using different mixtures of agro-industrial wastes were performed in a two-stage system consisting of two continuously stirred tank reactors (CSTRs) under mesophilic conditions (37°C). Subsequently, more mixtures were studied, where sweet sorghum was added, in order to simulate the operation of a centralized AD plant fed with regional agro-wastes which lacks OMW or/and CW due to seasonal unavailability. Two operational parameters were examined in a two-stage system, including pH and HRT. Batch experiments were performed in order to investigate the impact of controlled pH on the production of bio-hydrogen and volatile fatty acids, whereas continuous experiments (CSTRs) were conducted for the evaluation of HRT effect on hydrogen and methane production.
Moreover, further exploitation of digestate from an anaerobic methanogenic reactor was studied using a combined ultrafiltration/nanofiltration system and further COD reduction was obtained. On the other hand, vermicomposting was conducted in order to evaluate the sludge transformation to compost and as a result, good results in terms of increased N-P-K concentration values were obtained. Furthermore, simulation of mesophilic anaerobic (co)-digestion of different substrates was applied, using the ADM1 modified model, where the results indicated that the modified ADM1 was able to predict reasonably well the steady-state experimental data. / Είναι φανερό ότι οι ανανεώσιμες πηγές ενέργειας έχουν προσελκύσει το ενδιαφέρον της διεθνούς κοινότητας τις τελευταίες δεκαετίες καθώς διαδραματίζουν καθοριστικό ρόλο στην μείωση του CO2. Η ενέργεια από βιομάζα και απόβλητα θεωρείται ως μία από τις πλέον κυρίαρχες ανανεώσιμες πηγές ενέργειας του μέλλοντος. Έτσι, τα οργανικά απόβλητα όπως κτηνοτροφικά, ενεργειακές καλλιέργειες, γεωργικά και βιομηχανικά υπολείμματα κ.ά έχουν ιδιαίτερη σημασία, δεδομένου ότι οι πηγές αυτές δεν ανταγωνίζονται με τις καλλιέργειες τροφίμων της γεωργικής γης και ωστόσο μπορούν να χρησιμοποιηθούν για την παραγωγή ηλεκτρικής ενέργειας, θερμότητας και βιοκαυσίμων. Το αυξημένο ενδιαφέρον για τις διεργασίες που αφορούν στη μετατροπή της βιομάζας σε ανανεώσιμες πηγές ενέργειας, όπως είναι η αναερόβια χώνευση, τόνωσε την έρευνα σε αυτόν τον τομέα με αποτέλεσμα την υλοποίηση ενός σημαντικού αριθμού ερευνητικών έργων για να αξιολογηθούν οι ιδανικές συνθήκες χώνευσης διαφόρων υποστρωμάτων, όπως είναι τα αγροτο-βιομηχανικά απόβλητα και οι ενεργειακές καλλιέργειες.
Στη παρούσα διατριβή πραγματοποιήθηκαν πειράματα αναερόβιας συγχώνευσης χρησιμοποιώντας αγροτο-βιομηχανικά απόβλητα ή/και γλυκό σόργο. Τα αγροτο-βιομηχανικά απόβλητα, όπως είναι τα απόβλητα ελαιοτριβείου, τυροκομείου αλλά και βουστασίου, χαρακτηρίζονται από υψηλό οργανικό φορτίο και συνεπώς θεωρούνται ακατάλληλα για απευθείας διάθεση σε περιβαλλοντικούς αποδέκτες. Συγχώνευση αυτών οδήγησε σε υψηλές αποδόσεις μεθανίου κάτι το οποίο οφείλεται σε συνεργιστικές επιδράσεις όπως η συμβολή επιπλέον αλκαλικότητας, ιχνοστοιχείων, θρεπτικών κτλ. Περαιτέρω μίγματα μελετήθηκαν χρησιμοποιώντας το γλυκό σόργο με σκοπό την προσομοίωση λειτουργίας μιας κεντρικής μονάδας αναερόβιας χώνευσης, η οποία τροφοδοτείται με τοπικά απόβλητα τα οποία θα αντικατασταθούν σε περίοδο μη εποχικής διαθεσιμότητας από το γλυκό σόργο. Τα μίγματα αυτά μελετήθηκαν σε διβάθμιο σύστημα διερευνώντας την επίδραση των δύο σημαντικότερων λειτουργικών παραμέτρων (του pH και του υδραυλικού χρόνου παραμονής, HRT) στην απόδοση του συστήματος. Πιο συγκεκριμένα, πραγματοποιήθηκαν πειράματα διαλείποντος έργου προκειμένου να διερευνηθεί η επίδραση του pH στην παραγωγή υδρογόνου και μεταβολικών προϊόντων, ενώ πειράματα συνεχούς λειτουργίας διεξήχθηκαν για τη μελέτη της επίδρασης του HRT στην παραγωγή υδρογόνου και μεθανίου σε διβάθμιο σύστημα.
Περαιτέρω αξιοποίηση του χωνευμένου υπολείμματος μελετήθηκε με χρήση συνδυασμένου συστήματος υπερδιήθησης/νανοδιήθησης επιτυγχάνοντας επιπρόσθετη μείωση του οργανικού φορτίου στο διήθημα. Η μετατροπή της αναερόβια χωνευμένης ιλύος σε λίπασμα αξιολογήθηκε μέσω κομποστοποίησης με γεωσκώληκες (vermi-composting) επιτυγχάνοντας ικανοποιητικά αποτελέσματα στην αύξηση των συγκεντρώσεων N-P-K. Επιπλέον, αναπτύχθηκε τροποποιημένο μοντέλο της αναερόβιας χώνευσης (ADM1) με στόχο την προσομοίωση της αναερόβιας συγχώνευσης διαφορετικών υποστρωμάτων. Τα αποτελέσματα που προέκυψαν έδειξαν ότι το μοντέλο ήταν σε θέση να προβλέψει σε ικανοποιητικό βαθμό την πορεία των πειραματικών δεδομένων.
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Faciès, architectures stratigraphiques et dynamiques sédimentaires en contexte de régression forcée glacio-isostatique : la réponse pro- à paraglaciaire des complexes deltaïques de la Côte Nord de l'Estuaire et du Golf du Saint-Laurent (Québec, Canada) / Faciès, stratigraphic architecture and sedimentary dynamics in glacio-isostatically forced-regression : the pro- to paraglacial response of the deltaic complexes of the North Shore of the St. Lawrence Estuary and Gulf (Québec, Canada)Dietrich, Pierre 01 December 2015 (has links)
La Côte Nord de l’Estuaire et du Golfe du St. Laurent (Québec, Canada) est caractérisée par une série de complexes deltaïques mis en place en contexte de chute de Niveau Marin Relatif (NMR) forcée par le rebond glacio-isostatique, lors du retrait des marges de l’Inlandsis Laurentidien. L’étude de trois complexes deltaïques montre qu’un motif d’évolution morphostratigraphique contrôlé par le retrait des marges glaciaires prévalait au premier ordre. Le premier stade de sédimentation se caractérise par la mise en place de cônes d’épandage juxtaglaciaires sous-aquatiques. Leur localisation au front de la marge glaciaire fait que la répartition spatiale des corps sédimentaires montre localement un empilement en rétrogradation. Dès l’émergence d’un front glaciaire continental, des deltas proglaciaires se développent en contexte de chute de NMR, formant des lobes dont l’altitude décroît vers le bassin. Ces derniers sont initialement associés à un système fluviatile en tresse alimenté en sédiments glaciogéniques par les marges glaciaires en retrait. Malgré des taux de chute de NMR de plusieurs cm/an, aucune incision fluviatile n’est observée à ce stade et la dynamique de transfert est prédominante du fait des forts taux d’apports sédimentaires. Plus tard, à la suite du retrait des marges glaciaires hors des bassins versants, le remaniement paraglaciaire se développe du fait de la réduction drastique des apports en eaux et sédiments. Le système fluviatile, devenu méandriforme, s’encaisse dans les anciens dépôts deltaïques maintenant inactifs et les bordures de deltas sont remaniées par les processus littoraux (plages soulevées, terrasses marines). Cette étude révèle que la majorité du volume de ces complexes deltaïques (10-20 km3) est mis en place en quelques milliers d’années seulement, immédiatement après la déglaciation ; le remaniement paraglaciaire n’ayant contribué à l’accrétion deltaïque que très marginalement. La modélisation numérique (Dionisos) valide les différents forçages identifiés par l’analyse morphosédimentaire. Une synthèse des complexes deltaïques à l’échelle de toute la Côte Nord du St. Laurent a permis de catégoriser 21 complexes deltaïques en 4 scénarios d’évolution morphosédimentaire, directement liés à la dynamique de retrait de la marge glaciaire. Leur décryptage offre une clef de lecture originale pour l’historique du retrait des marges glaciaires de l’Inlandsis Laurentidien sur la période 12-7.5 ka cal BP. / The North Shore of the St. Lawrence Estuary and Gulf is characterized by the presence of deltaic complexes that were emplaced under falling Relative Sea Level (RSL) forced by the glacio-isostatic rebound, immediately after the retreat of the Laurentide Ice Sheet (LIS) margin. The study of three deltaic complexes reveals that a common morphostratigraphic evolution forced by the retreat of the LIS prevailed for the edification of these structures, reflecting the retreat of the LIS margin. The emplacement of subaqueous outwash fans beyond the retreating or stillstanding glaciomarine margin constitutes the first stage of this evolution. As tied to the ice-margin position, these fans are characterized in places by a backstepping stacking pattern, in spite of the forced regressive setting. From the emergence of a continental ice front, the proglacial deltaic system develops and forms lobes staged accordingly to the RSL fall. These deltaic systems actively prograde at that time because they are fed in glaciogenics by the retreating LIS margin through braided meltwater streams. In spite of the RSL fall reaching several centimeters per years, no fluvial entrenchment occurs mainly owing to the significant amount of sediment supply. Later, when the LIS margin retreats from the drainage basins of feeding rivers, fluvial systems experience a drastic drop in sediment supply that forced the interruption of the deltaic progradation and the onset of paraglacial reworking. The paraglacial reworking consists in the entrenchment of a meandering fluvial system within former deltaic deposits and shows the prevalence of shallow-marine processes (waves, tides) at the delta rim (raised beaches, marine terraces). This study reveals that the bulk of the deltaic volume (c.a. 10-20 km3) for each complex was emplaced in only a few thousands of years following the LIS margin retreat when the latter was still located in the drainage basin. The paraglacial reworking had a minor influence on the deltaic accretion. A forward stratigraphic model (Dionisos) is used to validate the variety of forcing as understood from the sedimentary analysis. A synthesis including 21 deltaic complexes of the St. Lawrence North Shore allowed the establishment of a fourfold categorization. This scheme of deltaic evolution was used in order to refine the position of the LIS margin retreating upland for a period ranging from 12 to 7.5 ka cal BP.
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