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La rupture des matériaux quasi-fragiles, tels que les céramiques ou les bétons, peut être représentée schématiquement par la succession des étapes de nucléation et de coalescence de micro-fissures. Modéliser ce processus de rupture est un enjeu particulièrement important lorsque l'on s'intéresse à la résistance des structures en béton, en particulier à la prédiction de la perméabilité des structures endommagées. La démarche choisie est une vision multi-échelle où le comportement global est caractérisé par la mécanique de la rupture, et le comportement local représenté par la méthode des éléments discrets. Le modèle représente la fissuration par des grandeurs généralisées, qui seront définies dans le cadre de la mécanique de la rupture. Afin de prendre en compte l’aspect non linéaire de la fissuration dans les matériaux quasi-fragiles, la cinématique usuelle de la mécanique de la rupture est enrichie par l’ajout de degrés de libertés supplémentaires chargés de représenter la part non linéaire du champ de vitesse. L'évolution du comportement est alors condensé par l'évolution de facteurs d'intensité. Le modèle proposé permet de prédire le comportement lors de chargements de mode mixte I+II proportionnel et non-proportionnel. Enfin, une campagne d'essais visant à caractériser le comportement en fissuration du mortier à été réalisée. Les résultats obtenus montrent un rôle important de la fissuration par fatigue. La méthode de changement d'échelle a également été appliquée sur les champs de vitesse en pointe de fissure, confirmant la représentation du comportement en pointe de fissure par une cinématique enrichie. / Fracture in quasi-brittle materials, such as ceramics or concrete, can be represented schematically by series of events of nucleation and coalescence of micro-cracks. Modeling this process is an important challenge for the reliability and life prediction of concrete structures, in particular the prediction of the permeability of damaged structures. A multi-scale approach is proposed. The global behavior is modeled within the fracture mechanics framework and the local behavior is modeled by the discrete element method. An approach was developed to condense the non linear behavior of the mortar. A model reduction technic is used to extract the relevant information from the discrete elements method. To do so, the velocity field is partitioned into mode I, II, linear and non-linear components, each component being characterized by an intensity factor and a fixed spatial distribution. The response of the material is hence condensed in the evolution of the intensity factors, used as non-local variables. A model was also proposed to predict the behavior of the crack for proportional and non-proportional mixed mode I+II loadings. An experimental campaign was finally conducted to characterize the fatigue and fracture behavior of mortar. The results show that fatigue crack growth can be of significant  importance. The experimental velocity field determined, in the crack tip region, by DIC, were analyzed using the same technic as that used for analyzing the fields obtained by the discrete element method showing consistent results.

Any composite material is made up from two or more materials and therefore contains interfaces, which usually represent planes of weakness. Interfacial fractures are effectively constrained to propagate along these interfaces as mixed-mode fractures with all three opening, shearing and tearing actions (i.e. mode I, mode II and mode III), instead of kinking to maintain pure-mode-I conditions at the advancing crack front, as would typically happen in an isotropic material. This is significant because mixed-mode fracture toughness is load-dependent and not a purely intrinsic material property (although clearly the pure mode fracture toughnesses are indeed intrinsic material properties that can be determined experimentally). Therefore, in order to know the fracture toughness under general loading conditions, it is necessary to know both the interface failure criterion (that describes the fracture toughness as a function of the mode mixity), and the mode mixity of the crack under the specified loading conditions. This is a complex problem that has occupied researchers in the fracture mechanics community for decades. Consequently, the literature contains a large number of different mixed-mode partition theories. This work appears to show that, of all the partition theories assessed, Wang and Harvey s (2012a) Euler beam partition theory is able to most accurately predict the fracture toughness of a mixed-mode delamination in a fibre-reinforced polymer composite laminate. This statement is based on the outcomes of three separate studies: The first study uses data reported in the literature from a thorough programme of mixed-mode fracture testing of unidirectional and multi-directional laminates. The Euler beam partition theory is able to accurately predict the fracture toughness in all cases. Furthermore, the Euler beam partition theory, which is completely analytical, closely agrees over a large domain with Davidson et al. s (2000) independently-derived non-singular field partition theory, which was derived with the aid of experimental test results. In general, the singular-field approach based on 2D elasticity and the finite element method give poor predictions. In the second study, an original programme of mixed-mode fracture testing is carried out, which incorporates several novel aspects including new test apparatus and a methodology for testing with a wide range of applied pure bending moments. Eighty five fracture tests are performed on unidirectional glass/epoxy laminates to determine the initiation and propagation fracture toughnesses. Although the second study was inconclusive with respect to the correctness of any particular partition theory, the development of the test apparatus and test methodology are considered to be major contributions that will be useful for both design engineers and academic researchers, not only working with fibre-reinforced polymer composite laminates, but also working with other composite materials containing interfacial cracks. The third study uses digital image correlation to investigate the near-crack tip strain fields of mixed-mode delaminations to try to discover the underlying mechanics that govern the selection of a mixed-mode partition theory. The new testing apparatus is used again, and another novel testing methodology is developed. The work appears to confirm (with some caveats) that two sets of pure modes exist, that is, two pure mode I modes, and two pure mode II modes, with their numerical values roughly corresponding to those from Wang and Harvey s (2012a) Euler beam partition theory. It should be noted that, as far as the author s knowledge is concerned, Euler beam partition theory is the only one in the literature to predict the existence of two sets of pure modes. Although this work set out to conclusively determine which mixed-mode partition theory is able to most accurately predict the fracture toughness of a mixed-mode delamination in a fibre-reinforced polymer composite laminate, and also, to discover why, the outcomes cannot truly be called conclusions . Rather, they only offer strong support for Wang and Harvey s (2012a) Euler beam partition theory for predicting the fracture toughness fibre-reinforced polymer composite laminates against delamination. Despite this, the work makes major contributions that will be useful for both design engineers and academic researchers in the field, as described in the above.

In this work a new current-sweep stress methodology for quantitatively assessing the mixed-mode reliability (simultaneous application of high current and high voltage) of advanced SiGe HBTs is presented. This stress methodology allows one to quickly obtain the complete damage spectrum of a given device from a particular technology platform, enabling better understanding of the complex voltage, current, and temperature interdependence associated with electrical stress and burn-in of advanced transistors. We consistently observed three distinct regions of mixed-mode damage in SiGe HBTs, and find that hot carrier induced damage can be introduced into SiGe HBTs under surprisingly modest mixed-mode stress conditions. For more aggressively scaled silicon-germanium technology generations, a larger percentage of hot carriers generated in the collector-base junction are able to travel to and hence damage the EB spacer, leading to enhanced forward-mode base current leakage under stress. A new self-heating induced mixed-mode annealing effect was observed for the first time under fairly high voltage and current stress conditions, and a new damage mechanism was observed under very high voltage and current conditions. Finally, as an example of the utility of our stress methodology, we quantified the composite mixed-mode damage spectrum of a commercial third-generation (200 GHz) generation SiGe HBT. It is found that if devices are stressed with either voltage or current alone during burn-in, they can easily withstand extreme over-stress conditions. Unfortunately, devices were easily damaged when stressed with a combination of stress voltage and current, and this has significant implications for the device and circuit lifetime prediction under realistic mixed-signal operating conditions.

Differential signaling is suitable for high speed signal transmission due to lower noise induction and higher common-mode noise rejection compared to its single-ended signaling counterpart. However, for a high performance differential transmission-line pair, excellent symmetry and appropriate design for substrate layer stack-up is necessary. Especially for a practical IC package substrate, differential transmission-line pair is inevitable for asymmetry because of considering the locations of IC pads and solderballs. Furthermore, different differential transmission-line pair architectures are also demanded in consideration of limited substrate floorplan space and substrate layer stack-up structures. In this thesis, several differential pairs have been implemented on the conventional 4-layer laminate package substrate. The consequent high frequency performances are measured using vector network analyzer and then compared by converting into mixed-mode S-parameters.

In VLSI circuits, signal delays play an important role in design, timing verification and signal integrity checks. These delays are attributed to the presence of parasitic resistance, capacitance and inductance. With increasing clock speed and reducing feature sizes, these delays will be dominated by parasitic inductance. In the next generation VLSI circuits, with more than millions of components and interconnect segments, fast and accurate inductance estimation becomes a crucial step. A generalized approach for inductance extraction requires the solution of a large, dense, complex linear system that models mutual inductive effects among circuit elements. Iterative methods are used to solve the system without explicit computation of the system matrix itself. Fast hierarchical techniques are used to compute approximate matrix-vector products with the dense system matrix in a matrix-free way. Due to unavailability of system matrix, constructing a preconditioner to accelerate the convergence of the iterative method becomes a challenging task. This work presents a class of parallel algorithms for fast and accurate inductance extraction of VLSI circuits. We use the solenoidal basis approach that converts the linear system into a reduced system. The reduced system of equations is solved by a preconditioned iterative solver that uses fast hierarchical methods to compute products with the dense coefficient matrix. A Green’s function based preconditioner is proposed that achieves near-optimal convergence rates in several cases. By formulating the preconditioner as a dense matrix similar to the coefficient matrix, we are able to use fast hierarchical methods for the preconditioning step as well. Experiments on a number of benchmark problems highlight the efficient preconditioning scheme and its advantages over FastHenry. To further reduce the solution time of the software, we have developed a parallel implementation. The parallel software package is capable of analyzing interconnects con- figurations involving several conductors within reasonable time. A two-tier parallelization scheme enables mixed mode parallelization, which uses both OpenMP and MPI directives. The parallel performance of the software is demonstrated through experiments on the IBM p690 and AMD Linux clusters. These experiments highlight the portability and efficiency of the software on multiprocessors with shared, distributed, and distributed-shared memory architectures.

No description available.

No description available.

Le profilage d’impuretés de candidats médicaments est une préoccupation majeure des industries pharmaceutiques. L’identification et la quantification des impuretés doivent être strictement contrôlées pour assurer l’efficacité et la toxicité limitée du principe actif. Il est donc nécessaire de disposer de méthodes analytiques performantes afin de s’assurer que l’ensemble des impuretés est identifié. L’HPLC phase inverse sur phase C18 reste aujourd’hui la méthode de choix pour cette tâche. Cependant, il arrive que cette méthode échoue, notamment lorsque le principe actif n’est pas suffisamment retenu sur la colonne ou que les impuretés ne sont pas parfaitement séparées du composé principal. Il est alors essentiel de pouvoir se tourner vers des méthodes analytiques alternatives et complémentaires.Ce travail de recherche traite du développement et de l’évaluation de méthodes analytiques alternatives à l’HPLC phase inverse sur phase C18 pour le profilage d’impuretés de principes actifs pharmaceutiques. L’HPLC phase inverse sur d’autres phases stationnaires, l’HPLC mixed-mode ainsi que la SFC ont été explorées et leurs performances chromatographiques comparées. La comparaison et l’étude des différentes méthodes ont permis de proposer une stratégie d’analyse du candidat médicament. / Impurity profiling of drug candidates is a significant concern of pharmaceutical industries. The identification and quantification of impurities must be strictly controlled to ensure the efficacy and limited toxicity of the active ingredient. It is therefore necessary to have efficient analytical methods to ensure that all impurities are identified. Today, reversed-phase HPLC with C18 column remains the method of choice for this task. However, this method sometimes fails, particularly when the active pharmaceutical ingredient is not sufficiently retained on the column or when the impurities are not resolved from the main compound. It is therefore essential to turn to alternative and complementary analytical methods.This work deals with the development and evaluation of alternative analytical methods to reversed-phase HPLC on C18 phase for impurity profiling of pharmaceuticals. Reversed-phase HPLC on other stationary phases, mixed-mode HPLC as well as SFC were explored and their chromatographic performances compared. The comparison and the study of the different methods allowed proposing a strategy of analysis of the drug candidate.

Detta arbete ämnar att beskriva hur arbetsmarknaden för sjökaptensexaminerade från examensåren 2010, 2013 och 2016 ser ut. Här redogörs skillnader och likheter mellan såväl de tre examensåren som svenska lärosäten med sjökaptensutbildning. Genom att kombinera en kvantitativ enkätundersökning med kvalitativa inslag ges en inblick i situationen för den undersökta gruppen. Arbetet är en mixed mode-studie, datainsamlingsmetoder bestående av webb- post- och telefonenkät användes. Resultatet visar att en stor andel av respondenterna arbetar inom sjöfartssektorn, men att sysselsättningsgraden till sjöss har minskat jämfört med tidigare studier. Arbetsbrist har blivit en faktor att ta hänsyn till för sjökaptensexaminerade som är nya på arbetsmarknaden. En högre procentuell andel respondenter från Sjöfartshögskolan i Kalmar är sysselsatta till sjöss medan Chalmers i Göteborg representeras av en högre sysselsättning i land. Arbetets slutsats är att arbetsmarknaden för nyutexaminerade från sjöbefälsskolarna i Sverige genomgår en förändring. / This thesis focuses on study of the employment market for graduates from the Master Mariner degree that graduated in 2010, 2013 and 2016. It is a comparison between the three years of graduation within two Swedish universities that offer the Master Mariner programme. Data collection with combined quantitative and qualitative techniques within a mixed-mode study. Results show a majority occupied within the maritime sector, although vessel-based employment has decreased compared to past studies and redundancy is an emerging element. The percentage occupied within the vessel-based sector is higher in Kalmar Maritime Academy, Linnaeus University, compared to Chalmers University, the results from which show a higher concentration in shore-based occupation. The conclusion of this thesis is that the employment market for graduates from maritime institutions in Sweden is undergoing change.