Effect of spin-orbit coupling on zero-conductance resonances in asymmetrically coupled one-dimensional rings

The influence of Rashba spin-orbit coupling on zero conductance resonances appearing in one dimensional ring asymmetrically coupled to two leads is investigated. For this purpose, the transmission function of the corresponding one-electron scattering problem is derived analytically and analyzed in the complex energy plane with focus on the zero-pole structure characteristic of transmission (anti)resonances. The lifting of real conductance zeros due to spin-orbit coupling in the asymmetric Aharonov-Casher (AC) ring is related to the breaking of spin reversal symmetry in analogy to the time-reversal symmetry breaking in the asymmetric Aharonov-Bohm (AB) ring.Comment: 10 pages, 11 figure

Robust fitting for generalized additive models for location, scale and shape

The validity of estimation and smoothing parameter selection for the wide class of generalized additive models for location, scale and shape (GAMLSS) relies on the correct specification of a likelihood function. Deviations from such assumption are known to mislead any likelihood-based inference and can hinder penalization schemes meant to ensure some degree of smoothness for nonlinear effects. We propose a general approach to achieve robustness in fitting GAMLSSs by limiting the contribution of observations with low log-likelihood values. Robust selection of the smoothing parameters can be carried out either by minimizing information criteria that naturally arise from the robustified likelihood or via an extended Fellner–Schall method. The latter allows for automatic smoothing parameter selection and is particularly advantageous in applications with multiple smoothing parameters. We also address the challenge of tuning robust estimators for models with nonlinear effects by proposing a novel median downweighting proportion criterion. This enables a fair comparison with existing robust estimators for the special case of generalized additive models, where our estimator competes favorably. The overall good performance of our proposal is illustrated by further simulations in the GAMLSS setting and by an application to functional magnetic resonance brain imaging using bivariate smoothing splines

Robust Fitting for Generalized Additive Models for Location, Scale and Shape

The validity of estimation and smoothing parameter selection for the wide class of generalized additive models for location, scale and shape (GAMLSS) relies on the correct specification of a likelihood function. Deviations from such assumption are known to mislead any likelihood-based inference and can hinder penalization schemes meant to ensure some degree of smoothness for non-linear effects. We propose a general approach to achieve robustness in fitting GAMLSSs by limiting the contribution of observations with low log-likelihood values. Robust selection of the smoothing parameters can be carried out either by minimizing information criteria that naturally arise from the robustified likelihood or via an extended Fellner-Schall method. The latter allows for automatic smoothing parameter selection and is particularly advantageous in applications with multiple smoothing parameters. We also address the challenge of tuning robust estimators for models with non-linear effects by proposing a novel median downweighting proportion criterion. This enables a fair comparison with existing robust estimators for the special case of generalized additive models, where our estimator competes favorably. The overall good performance of our proposal is illustrated by further simulations in the GAMLSS setting and by an application to functional magnetic resonance brain imaging using bivariate smoothing splines

SU(2) symmetry in a Hubbard model with spin-orbit coupling

We study the underlying symmetry in a spin-orbit coupled tight-binding model with Hubbard interaction. It is shown that, in the absence of the on-site interaction, the system possesses the SU(2) symmetry arising from the timereversal symmetry. The influence of the on-site interaction on the symmetry depends on the topology of the networks: The SU(2) symmetry is shown to be the spin rotation symmetry of a simply-connected lattice, so it still holds in the presence of the Hubbard correlation. In contrary, the on-site interaction breaks the SU(2) symmetry of a multi-connected lattice.Comment: 5 pages, 2 figure

Obtención de biogás a partir de heces de canes, un aporte al cuidado del medio ambiente de la ciudad de Buenos Aires

Se informa las primeras experiencias llevadas a cabo en el GIDER (Grupo de Investigación de Energías Renovables) del Dpto. de Termodinámica de la Facultad de Ingeniería de la UNNE sobre el aprovechamiento de las heces de canes de la ciudad de Buenos Aires, en colaboración con la Universidad Tecnológica Nacional, Facultad Regional General Pacheco de la provincia de Buenos Aires. La gran disponibilidad de estos residuos en espacios verdes de dicha ciudad motivó la idea de un aprovechamiento efectivo como la generación de biogas. El biogas generado fue de 40.5768 gr de biogas, con un valor de 223.818 gr de sólidos totales incorporados. También se miden pH de la mezcla, calculo de la masa total de gas generada y estimación del porcentaje de sólidos secos y totales. Se considera viable este aprovechamiento en cuanto a cantidad de biogas generado a partir de un recurso abundante y gratuito, a la vez que contribuye al saneamiento ambiental de la ciudad.It is reported the first experiments carried out in the Gider (Research Group on Renewable Energy) of the Department of Thermodynamics, Faculty of Engineering UNNE on the use of feces of dogs in the city of Buenos Aires, collaboration with the Universidad Tecnológica Nacional, Facultad Regional General Pacheco in the province of Buenos Aires. The availability of these residues in green spaces in the city led to the idea of effective use and generation of biogas. We obtained an acceptable value of total mass of biogas generated from 730 g of dog feces, also measured pH of the mixture and the estimated proportion of total dry solids. This use is considered viable in terms of quantity of biogas generated from a free and abundant resource, while contributing to environmental sanitation in the city.Asociación Argentina de Energías Renovables y Medio Ambiente (ASADES

Diseño y construcción de un calorímetro de junkers para determinación del poder calorífico del biogás

Se presentan los primeros resultados obtenidos a través de un calorímetro de Junkers, diseñado y construido por el grupo G.I.D.E.R. (Grupo de Investigación y Desarrollo en Energías Renovables), utilizado para determinar el poder calorífico de gases. Este dispositivo consiste básicamente en un intercambiador de calor tipo serpentina vertical, de cobre, por la cual fluye agua en forma descendente, ubicada en el interior de un cilindro de acero donde circulan, en sentido contrario, los humos de la combustión. Primeramente se realizaron ensayos con un gas conocido como el butano con el fin de calibrar el aparato. Posteriormente se llevaron a cabo experiencias con metano resultando el poder calorífico del mismo 47341,2 Kj/Kg. Si bien los valores hallados en forma práctica difieren ligeramente de los extraídos de la bibliografía, los mismos se consideran satisfactorios, teniendo en cuenta que son los primeros resultados obtenidos con el prototipo construido.We present the first results obtained from a Junkers calorimeter, designed and built by the group G.I.D.E.R. (Research and Development Group on Renewable Energies), used to determine the calorific power of gases. This device is basically a vertical serpentine heat exchanger, of copper, water which flows downwards, located inside a steel cylinder, which circulate in the opposite direction, the smoke of combustion. First tests were performed with a gas known as butane to calibrate the device. Later experiments were conducted with methane resulting in a calorific power of 47341.2 KJ / KG. Although the values found in practically differ slightly from those from the literature, they are considered satisfactory, bearing in mind they are the first results obtained with the prototype built.Asociación Argentina de Energías Renovables y Medio Ambiente (ASADES

Diseño y construcción de un calorímetro de junkers para determinación del poder calorífico del biogás

Se presentan los primeros resultados obtenidos a través de un calorímetro de Junkers, diseñado y construido por el grupo G.I.D.E.R. (Grupo de Investigación y Desarrollo en Energías Renovables), utilizado para determinar el poder calorífico de gases. Este dispositivo consiste básicamente en un intercambiador de calor tipo serpentina vertical, de cobre, por la cual fluye agua en forma descendente, ubicada en el interior de un cilindro de acero donde circulan, en sentido contrario, los humos de la combustión. Primeramente se realizaron ensayos con un gas conocido como el butano con el fin de calibrar el aparato. Posteriormente se llevaron a cabo experiencias con metano resultando el poder calorífico del mismo 47341,2 Kj/Kg. Si bien los valores hallados en forma práctica difieren ligeramente de los extraídos de la bibliografía, los mismos se consideran satisfactorios, teniendo en cuenta que son los primeros resultados obtenidos con el prototipo construido.We present the first results obtained from a Junkers calorimeter, designed and built by the group G.I.D.E.R. (Research and Development Group on Renewable Energies), used to determine the calorific power of gases. This device is basically a vertical serpentine heat exchanger, of copper, water which flows downwards, located inside a steel cylinder, which circulate in the opposite direction, the smoke of combustion. First tests were performed with a gas known as butane to calibrate the device. Later experiments were conducted with methane resulting in a calorific power of 47341.2 KJ / KG. Although the values found in practically differ slightly from those from the literature, they are considered satisfactory, bearing in mind they are the first results obtained with the prototype built.Asociación Argentina de Energías Renovables y Medio Ambiente (ASADES

Monitoreo y simulaciones de desempeño higrotérmico de vivienda social unifamiliar en la ciudad de Resistencia, en días de verano e invierno

Se presentan los resultados del monitoreo de desempeño higrotérmico de una vivienda social unifamiliar de la ciudad de Resistencia, comparados con los que resultan de la simulación del modelo mediante los programas ECOTECT y QUICK II, con el objeto de detectar posibles problemas de disconfort. El aceptable ajuste y grado de aproximación encontrado entre los resultados monitoreados respecto de los simulados, así como el aporte particular de cada programa, demuestra que los mismos podrían ser usados con buen grado de confiabilidad como herramienta de diseño. Por los resultados obtenidos, y teniendo en cuenta que la vivienda analizada constituye una tipología constructiva representativa de los conjuntos habitacionales sociales regionales, constituye un caso de condiciones higrotémicas deficientes durante días típicos de verano de esta zona cálido-húmeda, y regulares durante días de invierno moderado típicos, que hace imperativo el uso de climatización artificial de los espacios, especialmente en el período cálido.It presents the results of the hygrothermal performance monitoring of a single-family house in Resistencia city, compared with the results from the simulation model using ECOTECT and QUICK II softwares, in order to detect potential discomfort problems. The fit and acceptable degree of accuracy found among the monitored results and the simulated ones and the unique contribution of each software, shows that these could be used with good degree of reliability as a design tool. From the results, taking into account that the monitored house is a representative building typology of the parking - house in the city, it’s a case of poor hygrothermal conditions for typical summer days in a hot and humid area, and regularly for typical mild winter days, which makes it imperative to use artificial cooling of the spaces, especially in the warm season.Asociación Argentina de Energías Renovables y Medio Ambiente (ASADES

Relevamiento del parque habitacional social de Resistencia y Corrientes y su desempeño térmico: monitoreo y simulaciones

Habiendo finalizado un relevamiento que incluye cincuenta tipologías de viviendas sociales implementadas masivamente en las provincias de Corrientes y Chaco, gestionadas por programas habitacionales oficiales en diferentes períodos, se trabajó con el objetivo de elaborar un diagnóstico de desempeño térmico y energético de dichas viviendas, de interés considerando que el panorama provincial y regional se caracteriza por un alto consumo eléctrico para acondicionamiento del aire. Mediante monitoreo experimental en una muestra de estas viviendas, contrastado con simulaciones mediante software específico (Ecotect), se ha verificado que sus espacios interiores presentan problemas en cuanto al confort de sus usuarios en relación al clima cálido-húmedo, fundamentalmente durante el período estival, en parte debido a la baja resistencia térmica de las soluciones constructivas aplicadas a las envolventes y al escaso uso de las aislaciones en muros y techos. Los problemas detectados sirvieron para orientar la propuesta de criterios de optimización.Having completed a data collection and surveys about fifty types of social houses massively applied in the provinces of Corrientes and Chaco, officially managed by programs at different stages, we worked with the objective of developing a diagnosis of thermal performance and energy consumption of these houses, of interest considering that the provincial and regional energy landscape is characterized by high energy consumption for air conditioning. By measurements on a representative sample of these houses, contrasted with simulations using specific software (Ecotect) has verified that its interior spaces have problems regarding the comfort of their users in relation to warm-humid climate, mainly during the summer period partly due to the low thermal resistance of the constructive solutions applied to the surround and low use of insulations in walls and roofs. The identified problems were used to guide the proposal of improvements.Asociación Argentina de Energías Renovables y Medio Ambiente (ASADES

Relevamiento del parque habitacional social de Resistencia y Corrientes y su desempeño térmico: monitoreo y simulaciones

Habiendo finalizado un relevamiento que incluye cincuenta tipologías de viviendas sociales implementadas masivamente en las provincias de Corrientes y Chaco, gestionadas por programas habitacionales oficiales en diferentes períodos, se trabajó con el objetivo de elaborar un diagnóstico de desempeño térmico y energético de dichas viviendas, de interés considerando que el panorama provincial y regional se caracteriza por un alto consumo eléctrico para acondicionamiento del aire. Mediante monitoreo experimental en una muestra de estas viviendas, contrastado con simulaciones mediante software específico (Ecotect), se ha verificado que sus espacios interiores presentan problemas en cuanto al confort de sus usuarios en relación al clima cálido-húmedo, fundamentalmente durante el período estival, en parte debido a la baja resistencia térmica de las soluciones constructivas aplicadas a las envolventes y al escaso uso de las aislaciones en muros y techos. Los problemas detectados sirvieron para orientar la propuesta de criterios de optimización.Having completed a data collection and surveys about fifty types of social houses massively applied in the provinces of Corrientes and Chaco, officially managed by programs at different stages, we worked with the objective of developing a diagnosis of thermal performance and energy consumption of these houses, of interest considering that the provincial and regional energy landscape is characterized by high energy consumption for air conditioning. By measurements on a representative sample of these houses, contrasted with simulations using specific software (Ecotect) has verified that its interior spaces have problems regarding the comfort of their users in relation to warm-humid climate, mainly during the summer period partly due to the low thermal resistance of the constructive solutions applied to the surround and low use of insulations in walls and roofs. The identified problems were used to guide the proposal of improvements.Asociación Argentina de Energías Renovables y Medio Ambiente (ASADES