Helical inversions and phase separations in binary mixtures of cholesteric liquid crystalline molecules

A mean field theory is introduced to describe a helical inversion in nematic-cholesteric mixtures and binary cholesteric mixtures. Taking into account a chiral coupling between unlike molecules, the helical pitch is derived as a function of orientational order parameters and concentration. We find the conditions of helical inversions for the mixtures and derive the concentration of the helical inversions, depending on the chiral interaction. The numerical results are in agreement with the experimental results. We also examine phase separations on the temperature-concentration plane, including the helical inversions. A large variety of phase separations, such as the two-phase coexistence between a right-handed rich and a left-handed rich phase, etc., are predicted

Helical inversions and phase separations in binary mixtures of cholesteric liquid crystalline molecules

A mean field theory is introduced to describe a helical inversion in nematic-cholesteric mixtures and binary cholesteric mixtures. Taking into account a chiral coupling between unlike molecules, the helical pitch is derived as a function of orientational order parameters and concentration. We find the conditions of helical inversions for the mixtures and derive the concentration of the helical inversions, depending on the chiral interaction. The numerical results are in agreement with the experimental results. We also examine phase separations on the temperature-concentration plane, including the helical inversions. A large variety of phase separations, such as the two-phase coexistence between a right-handed rich and a left-handed rich phase, etc., are predicted

Estudio de alternativas de cúpula geodésica en madera de fácil realización y montaje

[ES] El presente trabajo final de grado pretende estudiar y analizar la potencialidad técnica y constructiva de cúpulas geodésicas en madera como alternativa estructural en intervenciones de fácil instalación y ejecución. Las cúpulas geodésicas son construcciones sencillas y ligeras que presentan grandes prestaciones estructurales tanto de resistencia como de eficiencia. La implantación de este tipo de edificaciones supondrá una serie de ventajas tanto ecológicas como económicas, ya que debido a su entramado ligero y al uso de la madera como material, se contribuye a reducir la huella de carbono en un sector muy relevante como el de la construcción. A partir de unas necesidades funcionales concretas fruto de las prácticas de empresa realizadas en SIDO MADERA (Julio-Septiembre 2016) se realiza un revisión crítica del estado del conocimiento de esta tipología singular. De este modo, se establecen los antecedentes de este tipo de estructuras y la adecuación de las diferentes geometrías y propuestas a unos niveles adecuados de estabilidad y seguridad en consonancia con las exigencias a satisfacer según las prescripciones facilitadas por la empresa colaboradora. Así, el trabajo se fundamenta en el diseño geométrico y estructural de 4 modelos de cúpula geodésica con herramientas avanzadas de sistemas CAD y a su vez, de cálculo estructural. Para dichos modelos, se estudian en profundidad todas aquellas variables que inciden en la calidad funcional, resistente y tecnológica puesto que el objetivo principal a satisfacer con este trabajo es la proposición de tipologías de cúpula geodésica en madera de fácil realización y montaje. La evaluación de los resultados obtenidos permite caracterizar las prestaciones estructurales, funcionales y económicas de cada uno de los diseños. El análisis comparativo entre los diferentes sistemas permite establecer las ventajas y desventajas tecnológicas de cada uno de ellos que estarán íntimamente relacionadas con el ámbito de funcionamiento a proponer.[EN] The present Final Grade research tries to study and analyze the technical and constructive potential of the geodesic domes in wood as a structural alternative in easily installed and executed interventions. The geodesic domes are both simple and light constructions which offer great structural benefits in both resistance and efficacy. The implementation of this type of buildings will entail a series of ecological and economic advantages, since due to its light weave as well as the use of wood as material contribute to reduce carbon footprint in a very relevant sector such as construction. On the basis of specific functional needs resulting from the company practices carried out in SIDO MADERA (July- September 2016), it is carried out a critical revision from the knowledge of this singular typology. In this way it is established these types of structures background as well as the suitability of both the different geometry and proposals background up to the appropriate levels of stability and security along with the demands of satisfying according to the prescriptions provided by the collaborating company. In this sense, the work is based on both the geometrical and structural design of four geodetic domes models with advanced system tools along with structural calculation. For such models, it is studied deeply all those variables that affect the functional resistant and technological quality so that the main goal that this research pursues is to satisfy the typology proposals of the geodesic dome in wood of easy realization and assembly. The evaluation of the results obtained enables us distinguishing the structural, functional and economic benefits of the designs performed. The comparative analysis among the different systems allows us to establish the technological advantages and disadvantages of all the designs, which will be closely related to the scope of the work proposed.Peñalver Oltra, M. (2017). Estudio de alternativas de cúpula geodésica en madera de fácil realización y montaje. http://hdl.handle.net/10251/87750.TFG