Design and optimization of a self-deploying single axis tracking PV array

This study was performed in order to design a tracking photovoltaic (PV) array and optimize the design for maximum specific power. The design considerations were minimal deployment time, high reliability, and small stowage volume. The array design was self-deployable, from a compact stowage configuration, using a passive pressurized gas deployment mechanism. The array structural components consist of a combination of beams, columns, and cables used to deploy and orient a flexible PV blanket. Each structural component of the design was analyzed to determine the size necessary to withstand the various forces to which it would be subjected. An optimization was performed to determine the array dimensions and blanket geometry which produce the maximum specific power. The optimization was performed for both lunar and Martian environments with 4 types of PV blankets (silicon, GaAs/Ge, GaAs CLEFT, and amorphous silicon). For the lunar environment, the amorphous silicon array produced the highest specific power, whereas, for Mars the GaAs CLEFT array produced the highest specific power. A comparison was made to a fixed PV tent array of similar design. The tracking array produced a higher specific power with all types of the PV blankets examined except amorphous silicon at both locations

Conductance anomalies in quantum wires

We study the conductance threshold of clean nearly straight quantum wires in the magnetic field. As a quantitative example we solve exactly the scattering problem for two-electrons in a wire with planar geometry and a weak bulge. From the scattering matrix we determine conductance via the Landauer-Buettiker formalism. The conductance anomalies found near 0.25(2e^2/h) and 0.75(2e^2/h) are related to a singlet resonance and a triplet resonance, respectively, and survive to temperatures of a few degrees. With increasing in-plane magnetic field the conductance exhibits a plateau at e^2/h, consistent with recent experiments.Comment: Quantum wire with planar geometry; in-plane magnetic fiel

Self-deploying photovoltaic power system

A lightweight flexible photovoltaic (PV) blanket is attached to a support structure of initially stowed telescoping members. The deployment mechanism comprises a series of extendable and rotatable columns. As these columns are extended the PV blanket is deployed to its proper configuration

Hydrogen Generation Through Renewable Energy Sources at the NASA Glenn Research Center

An evaluation of the potential for generating high pressure, high purity hydrogen at the NASA Glenn Research Center (GRC) was performed. This evaluation was based on producing hydrogen utilizing a prototype Hamilton Standard electrolyzer that is capable of producing hydrogen at 3000 psi. The present state of the electrolyzer system was determined to identify the refurbishment requirements. The power for operating the electrolyzer would be produced through renewable power sources. Both wind and solar were considered in the analysis. The solar power production capability was based on the existing solar array field located at NASA GRC. The refurbishment and upgrade potential of the array field was determined and the array output was analyzed with various levels of upgrades throughout the year. The total available monthly and yearly energy from the array was determined. A wind turbine was also sized for operation. This sizing evaluated the wind potential at the site and produced an operational design point for the wind turbine. Commercially available wind turbines were evaluated to determine their applicability to this site. The system installation and power integration were also addressed. This included items such as housing the electrolyzer, power management, water supply, gas storage, cooling and hydrogen dispensing

Degeneration and Regeneration in the Vertebrate Retina

International audienceThe human retina is a complex, layered tissue responsible for the perception of the visual stimuli coming from the external environment. Since the visual inputs account for about 30% of our sensory stimulations, it is not surprising that partial or complete blindness results in a strong decrease of life quality. Several diseases affect the retina, often leading to degeneration of one or several cell types. The damage induced by these diseases is often irreversible, thus leading to a permanent loss of the visual ability. Over the last decades significant progress has been made to elucidate the molecular basis of retinal degenerative diseases. This knowledge is necessary in order to design valid approaches for the treatment of retinopathies

Avaliação, diagnóstico e tratamento da surdez: conhecimento e conduta de médicos com atuação em neonatologia e/ou pediatria de um hospital-escola terciário

CONTEXT AND OBJECTIVE: Infant hearing deficiency is a human disorder with devastating effects and serious implications for the development of speech and language. Early diagnosis of hearing loss should be the objective of a multidisciplinary team, and early-intervention programs should immediately follow this. The aim of this study was to investigate the knowledge and conduct of pediatricians and pediatric residents in a tertiary teaching hospital regarding deafness. DESIGN AND SETTING: Cross-sectional study in a tertiary hospital in the state of São Paulo, Brazil. METHODS: Eighty-eight questionnaires were randomly distributed to pediatricians and pediatric residents. RESULTS: Thirty-six questionnaires were analyzed. Most respondents (61.1%) were residents in pediatrics and/or neonatology. Eighty-three percent of them performed special procedures on babies presenting a high risk of deafness, and 55% reported that they had no knowledge of techniques for screening hearing. Most of them were unaware of the classifications of level and type of hearing loss. According to 47.2% of them, infants could begin to use a hearing aid at six months of age. Most of them reported that infants could undergo hearing rehabilitation during the first six months of life, and all respondents stated 's responsibilities. CONCLUSIONS: Even though most of the participants followed special procedures with babies presenting a high risk of deafness, they did not routinely investigate hearing. All respondents believed that it is a doctor's responsibility to be concerned about child communication.CONTEXTO E OBJETIVO: A deficiência auditiva na criança é uma das desordens humanas cujo impacto tem efeito devastador produzindo sérias conseqüências no desenvolvimento da fala e linguagem. O diagnóstico precoce da perda auditiva deve ser objetivo de uma equipe interdisciplinar e ser seguido imediatamente por programas de intervenção precoce. O objetivo foi investigar o conhecimento e condutas de pediatras e residentes em pediatria de um hospital-escola terciário em relação à surdez. TIPO DE ESTUDO E LOCAL: Estudo transversal, hospital terciário do Estado de São Paulo. MÉTODOS: Oitenta e oito questionários distribuídos para pediatras e residentes em pediatria. RESULTADOS: Analisados 36 questionários. A maioria dos entrevistados (61,1%) foi de residentes em pediatria e/ou neonatologia. Oitenta e três por cento realizavam alguma conduta especial com bebês de alto risco para surdez, e 55% referiram não ter conhecimento sobre técnicas de triagem auditiva. A maioria desconhecia as classificações de grau e tipo de perda auditiva. Para 47,2%, a criança poderia utilizar o aparelho auditivo a partir de seis meses. A maioria referiu que a criança poderia realizar reabilitação auditiva nos primeiros seis meses de vida e todos os entrevistados responderam que é função do médico ter preocupação com a comunicação da criança. CONCLUSÕES: Mesmo a maioria adotando condutas especiais com bebês de alto risco para surdez, não se investigava rotineiramente a audição. Todos os entrevistados julgaram ser função do médico se preocupar com a comunicação da criança