Ce travail porte sur la vie psychique des populations sans domicile fixe, des exclus ou des sujets gravement précaires. Malgré les différents profils parsemant ce public, l’errance n’est pas un épiphénomène survenant autour de pathologies psychiatriques mais une maladie psychique profonde, singulière, et non réductible à d’autres entités nosographiques. C’est une configuration psychodynamique qui prend son origine dans une incapacité à se loger dans l’objet primaire, c’est-à-dire à se sentir contenu dans sa préoccupation et dans sa fonction de rêverie, créant un « trou noir » dans lequel l’errant menace sans cesse de tomber. Les mécanismes défensifs associés à cette psychodynamique ont des effets sur l’aménagement de l’extériorité : l’extériorité est un prisme où s’articulent l’espace, le corps, la sensorialité et l’objet. Si d’ordinaire, l’extériorité fonctionne de manière silencieuse, dans l’errance elle se révèle bruyante et symptomatique, si bien que les différents espaces qui constituent l’extériorité se collusionnent. Pour analyser ces emmêlements de l’extériorité, l’investigation clinique s’est effectuée sur les champs de la grande exclusion par la participation à des équipes mobiles psychiatrie-précarité et au Samu Social, mais également par la création de groupes de parole et à médiation au sein d’accueils de jour. La présentation des pratiques cliniques et du travail d’accompagnement social tentant de faire émerger un lien durable et sécurisé, fait partie des préoccupations de cette recherche. Au terme de ce travail, deux concepts sont proposés : celui de Manteau Cloacal, pouvant se définir comme une corruption autocalmante et autostimulante des enveloppes psychiques dans une recherche de contact avec l’objet primaire ; et celui d’Effondrement scénique, tentative pour forcer un « domicile psychique fixe » en l’objet par l’usage des sensations, de la mise en scène et d’une certaine forme de séduction. / This work concerns the psychic life of the populations without fixed residence, excluded or the seriously precarious subjects. In spite of the various profiles strewing this public, the wandering is not an epiphenomenon occurring around psychiatric pathologies but a major, singular psychic disease non-reducible with other nosographic entities. It is a psychodynamic configuration which takes its origin in incapacity to place itself in the primary object, i.e. to feel contained in its concern and its function of daydream, creating a « black hole » into which unceasingly the subject is likely to fall. The defensive mechanisms associated with this psychodynamic have effects on the externality: the externality is a prism where space, the body, the sensoriality and the object are articulated. So usually, the externality functions in a quiet way. But in the psychic wandering it appears noisy and symptomatic so that various spaces which constitute the externality mix. To analyze these mixings up of the externality, the clinical investigation was carried out on the fields of the great exclusion by the participation in psychiatry-precariousness mobile teams and Samu Social, but also by the creation of therapeutic group into social structures. Presentation of the clinical practices and the work of social accompaniment aiming to make emerge a durable and safe bond belonged to the concerns of this research. At the end of this work, two concepts are proposed: the Cloacal Coat, which can be defined as an anesthetic and stimulative psychic envelope in a search for contact with the primary object; and the Scenic Collapse, which attempt to force by the use of the sensoriality and a certain form of seduction, a « psychic residence » in the object.

0 comportamento higroscópico do suco de laranja liofilizado, e aditivado com malto-dextrinas e lactose, e de misturas mecânicas do suco liofilizado com os aditivos secos, foi estudado através da cinética e das isotermas de sorção de água, em diferentes temperaturas. Avaliou-se as características espectrais no visível e ultravioleta, e o teor de vitamina C, de amostras de suco de laranja liofilizado expostas a diferentes umidades relativas e temperaturas. Estudou-se a influência do valor de pH e natureza do tampão sobre a retenção do limoneno emulsionado em soluções de lactose, liofilizadas. A liofilização praticamente não alterou o teor de vitamina C e as características espectrais do suco de laranja, mas aumentou o valor monomolecular da malto-dextrina (dextrose equivalente de 9 a 12%). A lactose liofilizada apresentou-se no estado amorfo. Os teores de umidade de equilíbrio das misturas aditivadas liofilizadas, foram menores que os das misturas mecânicas. Os aditivos reduziram a sorção de umidade em função do tempo. A retenção do limoneno foi influenciada pela sua concentração inicial, sendo que ocorreu a major perda, durante a liofilização na major concentração utilizada. / The higroscopic behavior of freeze-dried orange juice, with added maltodextrins and lactose and mechanical mixtures with this additives was studied through the kinetics and isoterms of water sorption in different temperatures. It was evaluated the spectral characteristics, in the visible and ultraviolet range, and the vitamin C content from samples of freeze-dried orange juice exposed at different relative humidities and temperatures. It was studied the influence of pH and buffer composition, on the limonene retention of freeze-dried emulsions. The spectral characteristics and vitamin C content showed no alterations after liofilization the maltodextrin (9-12 % dextrose equivalent monomolecular value increased. Freezedried lactose was amorphous. The equilibrium humidity content of the samples with additives were reduced when compared with mechanical mixtures. The additives also reduced the rate of water sorption. The limonene retention during freeze-drying was influenced by the initial concentration of the emulsion. The greater concentration studied showed the lower retention value.

Estudo clínico prospectivo, em 11 pacientes com SARA ou LPA, avaliando o comportamento regional da densidade do tecido pulmonar e do colapso alveolar ao longo dos três eixos do espaço. Foram realizadas tomografias seriadas, após manobra de recrutamento inicial e após níveis de PEEP progressivamente decrescentes. Regressão linear múltipla (R2=0.83) mostrou importante gradiente no eixo gravitacional (p<0.001) e não no sentido céfalo-caudal (p<0.001), nem da direita para a esquerda (p<0.05). Isto corrobora o conceito do pulmão líquido, em que a resultante das pressões exercidas pelo diafragma, estruturas mediastinais e derrames seria transmitida uniformemente pelo tecido pulmonar. Cada um destes níveis isogravitacionais tem uma pressão crítica de fechamento (Pclosing), que é maior do que a pressão superimposta calculada. PEEP tem um efeito homogeneizador sobre o parênquima pulmonar. Dentre os parâmetros clínicos estudados, Pflex mostrou a pior correlação com colapso pulmonar documentado enquanto PO2 e a complacência máxima se mostraram equivalentes. / A prospective clinical study performed on 11 patients with ARDS or ALI with the intention of studying the regional behavior of lung tissue density and alveolar collapse along the three spatial axes. An initial recruitment maneuver was followed by multiple semi-complete CT scans at descending levels of PEEP. Multiple linear regression (R2=0.83) showed a gravitational gradient of densities and collapse (p<0.001) and no cephalo-caudal (p<0.001) or right-toleft increase (p<0.05), corroborating the liquid-like behavior of the lung. Pressure exerted by mediastinal structures, chest wall and effusions is transmitted uniformly throughout the lung. PEEP has a homogenizing effect on lung parenchyma. Among commonly used clinical surrogates, Pflex showed the worst correlation with actual lung collapse, while arterial PO2 and compliance were equivalent.

In this study, the effects of the neonicotinoid pesticide, thiamethoxam, are examined through the Proboscis Extension Response (PER) in honey bees (Apis mellifera). PER is a form of classical conditioning applied to honey bees through scent and reward association which quantifies learning rates. Results between groups treated with thiamethoxam did not differ significantly from untreated control groups. Potential reasons for these results are discussed. The method and experimental apparatus for testing the PER assay are also discussed.

La Formation Ayabacas est une unité resédimentée, affectée de déformations spectaculaires, qui affleure irrégulièrement dans les Andes du sud du Pérou. Elle résulte du collapse sous-marin, aux alentours de la limite Turonien-Coniacien (~91-89 Ma), de la quasi-totalité de la plate-forme carbonatée qui s'était mise en place au cours de deux transgressions, entre l'Albien inférieur et l'Albien supérieur (~108,5 - ~102 Ma) pour la première, et entre le Cénomanien supérieur et le Turonien supérieur (~95 - ~90 Ma) pour la seconde. Le collapse a affecté une surface d'au moins 80 000 km2 et les dépôts, parfois absents à l'amont, atteignent plus de 500 m d'épaisseur à l'aval. Il a été déplacé, au cours d'un événement unique à l'échelle des temps géologiques, un volume de matériaux estimé à > 10 000 km3. Ces dimensions, de l'ordre de celles des glissements sous-marins géants récents, font du collapse Ayabacas le plus grand glissement sous-marin fossile actuellement connu.<br />Le collapse s'organise du NE au SW en six zones basées sur les faciès de déformation, en relation avec deux importants systèmes structuraux d'échelle lithosphérique (une septième zone, à l'extrême NE, correspondant aux dépôts non déstabilisés). Dans les parties amont du collapse (zones 1 à 3, au NE), les dépôts forment une méga-brèche, avec des éléments de taille décamétrique à kilométrique (principalement des nappes et des radeaux calcaires, souvent plissés plastiquement ; plus rarement des blocs rigides dérivés de formations crétacées et paléozoïques) flottant dans un mélange de petits clastes carbonatés ou siliciclastiques et de matériaux pélitiques rougeâtres. Ce mélange de matériaux enclins à se liquifier et à se déformer plastiquement a servi de semelle de glissement aux plus gros éléments. Ces zones se caractérisent également par des déformations et des faciès bréchiques quelle que soit l'échelle d'observation. Les parties aval, au SW, sont exclusivement carbonatées, avec un empilement de masses calcaires de tailles croissantes, une disparition de la semelle de glissement très ductile et une organisation croissante des dépôts marquant un amortissement du collapse.<br />Le collapse Ayabacas, qui s'est produit sur une marge qui paraissait a priori stable, est atypique comparé aux autres glissements actuels ou fossiles. Intervenant immédiatement avant la rapide continentalisation du bassin d'arrière-arc sud-péruvien, et donc l'émergence des Andes, le collapse est une des conséquences de changements géodynamiques à l'échelle de la cellule de convection mantellique du Pacifique, qui ont notamment entraîné une brusque modification des conditions de subduction dans le sud du Pérou. Ce bouleversement a provoqué une flexure de la lithosphère de l'arrière-arc et un découpage du substratum ante-Ayabacas en blocs basculés par des failles normales, créant des pentes favorables au collapse de la plate-forme.

<p>This thesis presents a method of measuring the distribution of fiber bonding ability in mechanical pulp furnishes. The method is intended for industrial use, where today only average values are used to describe fiber bonding ability, despite the differences in morphology of the fibers entering the mill. Fiber bonding ability in this paper refers to the mechanical fiber’s flexibility and ability to form large contact areas to other fibers, characteristics required for good paper surfaces and strength.</p><p> </p><p>Five mechanical pulps (Pulps A-E), all produced in different processes from Norway spruce (<em>Picea Abies)</em> were fractionated in hydrocyclones with respect to the fiber bonding ability. Five streams were formed from the hydrocyclone fractionation, Streams 1-5. Each stream plus the feed (Stream 0) was fractionated according to fiber length in a Bauer McNett classifier to compare the fibers at equal fiber lengths (Bauer McNett screens 16, 30, 50, and 100 mesh were used).</p><p> </p><p>Stream 1 was found to have the highest fiber bonding ability, evaluated as tensile strength and apparent density of long fiber laboratory sheets. External fibrillation and collapse resistance index measured in FiberLab^TM, an optical measurement device, also showed this result. Stream 5 was found to have the lowest fiber bonding ability, with a consecutively falling scale between Stream 1 and Stream 5. The results from acoustic emission measurements and cross-sectional scanning electron microscopy analysis concluded the same pattern. The amount of fibers in each hydrocyclone stream was also regarded as a measure of the fibers’ bonding ability in each pulp.</p><p> </p><p>The equation for predicted Bonding Indicator (BIN) was calculated by combining, through linear regression, the collapse resistance index and external fibrillation of the P16/R30 fractions for Pulps A and B. Predicted Bonding Indicator was found to correlate well with measured tensile strength. The BIN-equation was then applied also to the data for Pulps C-E, P16/R30, and Pulp A-E, P30/R50, and predicted Bonding Indicator showed good correlations with tensile strength also for these fibers.</p><p> </p><p>From the fiber raw data measured by the FiberLab^TM instrument, the BIN-equation was used for each individual fiber. This made it possible to calculate a BIN-distribution of the fibers, that is, a distribution of fiber bonding ability.</p><p> </p><p>The thesis also shows how the BIN-distributions of fibers can be derived from FiberLab^TM measurements of the entire pulp without mechanically separating the fibers by length first, for example in a Bauer McNett classifier. This is of great importance, as the method is intended for industrial use, and possibly as an online-method. Hopefully, the BIN-method will become a useful tool for process evaluations and optimizations in the future.</p> / <p>Den här studien presenterar en metod för att mäta fördelning av fiberbindning i mekaniska massor. Metoden hoppas kunna användas industriellt, där i dagsläget enbart medelvärden används för att mäta fiberbindnings-fördelning, trots råvarans (fibrernas) morfologiska skillnader.</p><p> </p><p>Fem mekaniska massor (Massa A-E) från olika massaprocesser men från samma råvara, norsk gran (<em>Picea Abies</em>), har fraktionerats i hydrocykloner med avseende på fiberbindningsförmåga. Från hydrocyklon-fraktioneringen bildades fem strömmar, Ström 1-5. Varje ström plus injektet (Ström 0) fraktionerades också med avseende på fiberlängd i en Bauer McNett för att kunna jämföra fibrerna vid samma fiberlängd (Bauer McNett silplåtarna 16, 30, 50 och 100 mesh användes).</p><p> </p><p>Fiberbindingsförmåga i den här studien härrör till fiberns flexibilitet och förmåga att skapa stora kontaktytor med andra fibrer, vilket bidrar till papprets yt- och styrkeegenskaper.</p><p> </p><p>Ström 1 visade sig ha den högsta fiberbindningsförmågan, utvärderat som dragstyrka och densitet av långfiberark, samt yttre fibrillering och kollaps resistans index mätt i den optiska analysatorn FiberLab^TM. Akustisk emission och tvärsnittsanalyser visade samma resultat. Ström 5 visade sig ha den lägsta fiberbindningsförmågan, med en avtagande skala från Ström 1 till Ström 5. Andelen fibrer från injektet som gick ut med varje hydrocyklon-ström ansågs också vara ett mått på fibrernas bindningsförmåga i varje massa.</p><p> </p><p>Genom att kombinera fiberegenskaperna kollaps resistans och yttre fibrillering från den optiska mätningen på varje fiber genom linjär regression, kunde Bindnings Indikator (BIN) predikteras. Medelvärdet av Bindnings Indikator för varje hydrocyklon-ström korrelerar med dragstyrka för långfiber-labark.</p><p> </p><p>Det visade sig att predikterad Bindnings Indikator inte bara fungerade för Massa A och Massa B P16/R30 fraktionen, som var de fraktioner som användes i den linjära regressionen, utan även för Massa C-E, P16/R30, och Massa A-E P30/R50 som också visade goda korrelationer med långfiber-dragstyrka när de sattes in i BIN-formeln.</p><p> </p><p>BIN-formeln användes sedan för varje enskild fiber, i den rådata som levererats från FiberLab^TM. Detta gjorde det möjligt att få en BIN-distribution av fibrerna, d.v.s. en fördelning av fiberbindningsförmåga.</p><p> </p><p>Den här rapporten visar också hur det går att få BIN-distributioner också från mätningar på hela massan, för valbara fiberlängder, utan att först mekaniskt separera massan efter fiberlängd. Det är viktigt, då metoden är tänkt att användas som en industriell metod, och eventuellt som en online-metod. Förhoppningsvis kommer BIN-metoden att bli ett användbart verktyg för processutveckling- och optimering i framtiden.</p> / FSCN – Fibre Science and Communication Network / Bonding ability distribution of fibers in mechanical pulp furnishes

The collapse of the I-35W Bridge in Minneapolis, MN on August 1, 2007 brought into question the design and inspection of gusset plates in steel truss bridges. The experimental tests performed in this research study the sway-buckling strength and behavior of large-scale steel gusset plates in an isolated truss connection. Parameters studied include plate thickness,combination member loading, initial out-of-plane imperfection, diagonal compression member out-of-plane flexural stiffness, corrosion, and alternative retrofits to increase lateral stiffness. The flexural stiffness of the diagonal compression member and retrofit designs were unique to the testing program. The variables monitored during testing include gusset plate surface stresses and strains, member axial strains, out-of-plane displacement of the gusset plate free edge, and buckling capacity. The results were compared with previously established design models for predicting buckling capacity of gusset plates which include the Whitmore effective width, the Modified-Thornton method, and the FHWA Load Rating Guidelines. A parametric finite element model was developed to determine the lateral stiffness of the gusset plate connection and the additional stiffness provided by the alternative retrofit options. The results showed interaction between the diagonal compression member and gusset plate occurs, which affects sway-buckling capacity. Combination of member loads showed evidence of detrimental effects on sway-buckling capacity. Corrosion of the gusset plates along the top edge of the bottom chord did not lead to significant reduction in sway-buckling capacity. The two retrofit designs showed increases in both lateral stiffness and buckling capacity as well as economic benefits over traditional retrofit methods. Comparison of the results to the current design guidelines showed that the current methods are conservative and do not accurately represent the true behavior of gusset plate connections. The research concludes with two proposed models for future use in design and retrofit of gusset plates. The first is a member-gusset plate interaction model based on a stepped column analogy that takes into account the effects of member flexural stiffness and gusset plate stiffness. The second is a general design guideline developed for retrofit of gusset plate connections dominated by sway-buckling behavior which uses a stiffness based approach to increase the capacity of gusset plate connections. / Graduation date: 2012

This thesis presents a method of measuring the distribution of fiber bonding ability in mechanical pulp furnishes. The method is intended for industrial use, where today only average values are used to describe fiber bonding ability, despite the differences in morphology of the fibers entering the mill. Fiber bonding ability in this paper refers to the mechanical fiber’s flexibility and ability to form large contact areas to other fibers, characteristics required for good paper surfaces and strength.   Five mechanical pulps (Pulps A-E), all produced in different processes from Norway spruce (Picea Abies) were fractionated in hydrocyclones with respect to the fiber bonding ability. Five streams were formed from the hydrocyclone fractionation, Streams 1-5. Each stream plus the feed (Stream 0) was fractionated according to fiber length in a Bauer McNett classifier to compare the fibers at equal fiber lengths (Bauer McNett screens 16, 30, 50, and 100 mesh were used).   Stream 1 was found to have the highest fiber bonding ability, evaluated as tensile strength and apparent density of long fiber laboratory sheets. External fibrillation and collapse resistance index measured in FiberLabTM, an optical measurement device, also showed this result. Stream 5 was found to have the lowest fiber bonding ability, with a consecutively falling scale between Stream 1 and Stream 5. The results from acoustic emission measurements and cross-sectional scanning electron microscopy analysis concluded the same pattern. The amount of fibers in each hydrocyclone stream was also regarded as a measure of the fibers’ bonding ability in each pulp.   The equation for predicted Bonding Indicator (BIN) was calculated by combining, through linear regression, the collapse resistance index and external fibrillation of the P16/R30 fractions for Pulps A and B. Predicted Bonding Indicator was found to correlate well with measured tensile strength. The BIN-equation was then applied also to the data for Pulps C-E, P16/R30, and Pulp A-E, P30/R50, and predicted Bonding Indicator showed good correlations with tensile strength also for these fibers.   From the fiber raw data measured by the FiberLabTM instrument, the BIN-equation was used for each individual fiber. This made it possible to calculate a BIN-distribution of the fibers, that is, a distribution of fiber bonding ability.   The thesis also shows how the BIN-distributions of fibers can be derived from FiberLabTM measurements of the entire pulp without mechanically separating the fibers by length first, for example in a Bauer McNett classifier. This is of great importance, as the method is intended for industrial use, and possibly as an online-method. Hopefully, the BIN-method will become a useful tool for process evaluations and optimizations in the future. / Den här studien presenterar en metod för att mäta fördelning av fiberbindning i mekaniska massor. Metoden hoppas kunna användas industriellt, där i dagsläget enbart medelvärden används för att mäta fiberbindnings-fördelning, trots råvarans (fibrernas) morfologiska skillnader.   Fem mekaniska massor (Massa A-E) från olika massaprocesser men från samma råvara, norsk gran (Picea Abies), har fraktionerats i hydrocykloner med avseende på fiberbindningsförmåga. Från hydrocyklon-fraktioneringen bildades fem strömmar, Ström 1-5. Varje ström plus injektet (Ström 0) fraktionerades också med avseende på fiberlängd i en Bauer McNett för att kunna jämföra fibrerna vid samma fiberlängd (Bauer McNett silplåtarna 16, 30, 50 och 100 mesh användes).   Fiberbindingsförmåga i den här studien härrör till fiberns flexibilitet och förmåga att skapa stora kontaktytor med andra fibrer, vilket bidrar till papprets yt- och styrkeegenskaper.   Ström 1 visade sig ha den högsta fiberbindningsförmågan, utvärderat som dragstyrka och densitet av långfiberark, samt yttre fibrillering och kollaps resistans index mätt i den optiska analysatorn FiberLabTM. Akustisk emission och tvärsnittsanalyser visade samma resultat. Ström 5 visade sig ha den lägsta fiberbindningsförmågan, med en avtagande skala från Ström 1 till Ström 5. Andelen fibrer från injektet som gick ut med varje hydrocyklon-ström ansågs också vara ett mått på fibrernas bindningsförmåga i varje massa.   Genom att kombinera fiberegenskaperna kollaps resistans och yttre fibrillering från den optiska mätningen på varje fiber genom linjär regression, kunde Bindnings Indikator (BIN) predikteras. Medelvärdet av Bindnings Indikator för varje hydrocyklon-ström korrelerar med dragstyrka för långfiber-labark.   Det visade sig att predikterad Bindnings Indikator inte bara fungerade för Massa A och Massa B P16/R30 fraktionen, som var de fraktioner som användes i den linjära regressionen, utan även för Massa C-E, P16/R30, och Massa A-E P30/R50 som också visade goda korrelationer med långfiber-dragstyrka när de sattes in i BIN-formeln.   BIN-formeln användes sedan för varje enskild fiber, i den rådata som levererats från FiberLabTM. Detta gjorde det möjligt att få en BIN-distribution av fibrerna, d.v.s. en fördelning av fiberbindningsförmåga.   Den här rapporten visar också hur det går att få BIN-distributioner också från mätningar på hela massan, för valbara fiberlängder, utan att först mekaniskt separera massan efter fiberlängd. Det är viktigt, då metoden är tänkt att användas som en industriell metod, och eventuellt som en online-metod. Förhoppningsvis kommer BIN-metoden att bli ett användbart verktyg för processutveckling- och optimering i framtiden. / FSCN – Fibre Science and Communication Network / Bonding ability distribution of fibers in mechanical pulp furnishes

Se ha elaborado un modelo general para la consolidación del suelo parcialmente saturado en condiciones unidimensionales. El modelo acopla los cambios de succión con la deformación volumétrica a través del concepto de superficie de estado. Adicionalmente, se ha propuesto una metodología de cálculo para evaluar los cambios de volumen y de presión de aire y de agua en un proceso de carga no drenada. El modelo se ha implementado utilizando la técnica de los elementos finitos y se ha aplicado a diversos casos de interés geotécnico: consolidación en un suelo no saturado, infiltración con hinchamiento o colapso, desarrollo de presión de hinchamiento en condiciones confinadas y construcción capa a capa de obras de tierra. Paralelamente, en el laboratorio se ha desarrollado una célula edométrica para realizar ensayos con succión controlada. Este equipo se ha utilizado para obtener las superficies de estado de un caolín comercial y para comprobar de forma experimental la validez del modelo numérico propuesto. Se ha obtenido un buen ajuste entre las medidas de laboratorio y las predicciones del modelo si se tienen en cuenta las deformaciones debidas a la fluencia del suelo. Este trabajo constituye una aportación en la tarea de desarrollar nuevos métodos de cálculo y técnicas de laboratorio que pueden ser de utilidad en situaciones en las que el flujo acoplado con la deformación en un medio no saturado sea relevante, tal como es el caso de terraplenes, presas de tierra , barreras de residuos, etc.

Determining the maximum power system loadability, as well as preventing the system from being operated close to the stability limits is very important in power systems planning and operation. The application of optimization techniques to power systems security and electricity markets is a rather relevant research area in power engineering. The study of optimization models to determine critical operating conditions of a power system to obtain secure power dispatches in an electricity market has gained particular attention. This thesis studies and develops optimization models and techniques to detect or avoid voltage instability points in a power system in the context of a competitive electricity market. A thorough analysis of an optimization model to determine the maximum power loadability points is first presented, demonstrating that a solution of this model corresponds to either Saddle-node Bifurcation (SNB) or Limit-induced Bifurcation (LIB) points of a power flow model. The analysis consists of showing that the transversality conditions that characterize these bifurcations can be derived from the optimality conditions at the solution of the optimization model. The study also includes a numerical comparison between the optimization and a continuation power flow method to show that these techniques converge to the same maximum loading point. It is shown that the optimization method is a very versatile technique to determine the maximum loading point, since it can be readily implemented and solved. Furthermore, this model is very flexible, as it can be reformulated to optimize different system parameters so that the loading margin is maximized. The Optimal Power Flow (OPF) problem with voltage stability (VS) constraints is a highly nonlinear optimization problem which demands robust and efficient solution techniques. Furthermore, the proper formulation of the VS constraints plays a significant role not only from the practical point of view, but also from the market/system perspective. Thus, a novel and practical OPF-based auction model is proposed that includes a VS constraint based on the singular value decomposition (SVD) of the power flow Jacobian. The newly developed model is tested using realistic systems of up to 1211 buses to demonstrate its practical application. The results show that the proposed model better represents power system security in the OPF and yields better market signals. Furthermore, the corresponding solution technique outperforms previous approaches for the same problem. Other solution techniques for this OPF problem are also investigated. One makes use of a cutting planes (CP) technique to handle the VS constraint using a primal-dual Interior-point Method (IPM) scheme. Another tries to reformulate the OPF and VS constraint as a semidefinite programming (SDP) problem, since SDP has proven to work well for certain power system optimization problems; however, it is demonstrated that this technique cannot be used to solve this particular optimization problem.