Fault-tolerant onboard digital information switching and routing for communications satellites

The NASA Lewis Research Center is developing an information-switching processor for future meshed very-small-aperture terminal (VSAT) communications satellites. The information-switching processor will switch and route baseband user data onboard the VSAT satellite to connect thousands of Earth terminals. Fault tolerance is a critical issue in developing information-switching processor circuitry that will provide and maintain reliable communications services. In parallel with the conceptual development of the meshed VSAT satellite network architecture, NASA designed and built a simple test bed for developing and demonstrating baseband switch architectures and fault-tolerance techniques. The meshed VSAT architecture and the switching demonstration test bed are described, and the initial switching architecture and the fault-tolerance techniques that were developed and tested are discussed

Description and Simulation of a Fast Packet Switch Architecture for Communication Satellites

The NASA Lewis Research Center has been developing the architecture for a multichannel communications signal processing satellite (MCSPS) as part of a flexible, low-cost meshed-VSAT (very small aperture terminal) network. The MCSPS architecture is based on a multifrequency, time-division-multiple-access (MF-TDMA) uplink and a time-division multiplex (TDM) downlink. There are eight uplink MF-TDMA beams, and eight downlink TDM beams, with eight downlink dwells per beam. The information-switching processor, which decodes, stores, and transmits each packet of user data to the appropriate downlink dwell onboard the satellite, has been fully described by using VHSIC (Very High Speed Integrated-Circuit) Hardware Description Language (VHDL). This VHDL code, which was developed in-house to simulate the information switching processor, showed that the architecture is both feasible and viable. This paper describes a shared-memory-per-beam architecture, its VHDL implementation, and the simulation efforts

Silicon-Germanium Fast Packet Switch Developed for Communications Satellites

Emerging multimedia applications and future satellite systems will require high-speed switching networks to accommodate high data-rate traffic among thousands of potential users. This will require advanced switching devices to enable communication between satellites. The NASA Lewis Research Center has been working closely with industry to develop a state-of-the-art fast packet switch (FPS) to fulfill this requirement. Recently, the Satellite Industry Task Force identified the need for high-capacity onboard processing switching components as one of the "grand challenges" for the satellite industry in the 21st century. In response to this challenge, future generations of onboard processing satellites will require low power and low mass components to enable transmission of services in the 100 gigabit (1011 bits) per second (Gbps) range

Tiempo de estallidos : La disconformidad social de los pasajeros de trenes urbanos

En el presente documento de trabajo presentamos un avance investigativo sobre las formas de disconformidad social, en particular aquellas que asumen el carácter de acción directa, desarrolladas en el marco del sistema de transporte ferroviario de pasajeros del Área Metropolitana de Buenos Aires, entre octubre de 2002 y junio de 2010. El núcleo de este trabajo lo constituye el análisis comparativo de los episodios de violencia colectiva ocurridos en las estaciones de Haedo (noviembre de 2005), Constitución (mayo de 2007) y Castelar (septiembre de 2008). La hipótesis que postulamos sostiene que la configuración sistémica del servicio produce niveles extraordinarios de disconformidad que no logran ser procesados eficazmente por dicha configuración. El sistema en su interacción con determinadas condiciones de contorno, en este caso la difusión de una cultura de la acción directa, genera perturbaciones cuya muestra más extrema son los estallidos de hostilidad protagonizados por pasajeros del servicio. En la perspectiva de los usuarios, estos adquieren un carácter más expresivo que instrumental, no obstante, y como consecuencia no necesariamente buscada de la acción, los estallidos dinamizan cambios, que -en ocasiones- son favorables a sus intereses

Efecto de la presión de prensado y la adición de lignina kraft en la producción de tableros aglomerados autoenlazados a partir de Gynerium sagittatum pretratada con vapor

El Gynerium sagittatum es una gramínea que presenta gran adaptabilidad ecológica lo cual la hace una fuente lignocelulósica ideal para la fabricación de tableros aglomerados sin aditivos sintéticos. Se evalúa el efecto de la presión de prensado y de la adición de lignina kraft purificada sobre las propiedades fisicomecánicas de tableros de fibras de Gynerium sagittatum de alta densidad. La materia prima es pretratada en un reactor de steam explosion a severidad 4,1 y la temperatura de prensado se fija en 217°C. Se varia la presión de prensado entre 2 y 15 MPa. Se determina que la presión de prensado más apropiada para obtener tableros de buena calidad es 2 MPa obteniendo valores para el módulo de elasticidad de 6000 MPa, módulo de ruptura de 47 MPa, enlace interno de 1,50 MPa, absorción de agua durante 24 horas de 25% e hinchamiento en espesor durante 24 horas del 15%. Partiendo de estas condiciones de operación, se evalúa la inclusión de lignina entre 0 y 30%. Se determina que el aumento de lignina no afecta significativamente el desempeño mecánico de los tableros, pero sí su estabilidad dimensional, dando como resultado una absorción de agua durante 24 horas de 19% e hinchamiento en espesor durante 24 horas del 8,5%, a un valor óptimo de 20% de inclusión de lignina. Gynerium sagittatum is a grass that has great ecological adaptability, which makes it an ideal lignocellulosic source for the manufacture of fiberboards. The effects of pressing pressure and the addition of kraft lignin on the physicomechanical properties of high density fiberboards of Gynerium sagittatum are evaluated. The raw material is pretreated in a steam explosion reactor at severity 4,1. The pressing temperature is set at 217°C. The pressing pressure is varied between 2 and 15 MPa. The most appropriate pressing pressure to obtain a good quality boards is 2 MPa. The values of properties at optimal conditions are: modulus of elasticity 6000 MPa, modulus of rupture 47 MPa, internal bond 1,50 MPa 24 h water absorption 25% and 24 h thickness swelling 15%. Based on these operating conditions, the inclusion of lignin between 0 and 30% is evaluated. The addition of lignin does not significantly affect the mechanical performance of the fiberboards but improve its dimensional stability. The obtained values for 24 h water absorption and 24 h thickness swelling are 19% and 8,5% respectively, at a 20% of lignin addition.   PDF XM

Intellectual disability and ageing: a new challenge for the twenty-first century

[Resumen] OBJETIVO: Mediante el presente trabajo se pretende conocer las características de la población con retraso mental que ha supera- do la edad de 45 años. MÉTODO: Estudio descriptivo de carácter transversal, entre una muestra representativa de 189 personas mayores de 45 años, con certificado de minusvalía que acredite la discapacidad psíquica, seleccionadas aleatoriamente entre las institucionalizadas en los centros de la comunidad autónoma gallega. La herramienta para recoger la información ha sido un cuestionario de elaboración propia, debidamente contrastado. RESULTADOS: El 60% de los entrevistados reside con sus familias, con las que mantienen una relación calificada como buena en el 49,7% de los casos. El 48,7% presenta un coeficiente intelectual con un retraso moderado, y profundo en el 36,5%; no se conoce el origen del retraso mental en el 42,85% de los casos. CONCLUSIONES: Las necesidades detectadas en la calidad asistencial llevan a concluir la urgencia de actuar sobre los recursos, equipamientos y el grado de especialización de los profesionales implicados, sin obviar a las familias, que constituyen el verdadero soporte asistencial.[Abstract] OBJECTIVE: The aim of this study was to determine the characteristics of adults with intellectual disability who survive for more than45 years. METHODS: We performed a cross-sectional, descriptive study of a representative sample of 189 individuals aged more than 45 years with certified intellectual disability. The subjects were randomly selected from individuals attending centres of the Autonomous Community of Galicia in Spain. The instrument used to gather information was a specifically-designed and validated questionnaire. RESULTS: Sixty percent of subjects lived with their families, with whom 49.7% reported a good relationship. The degree of intellectual disability was moderate in 49.7% and severe in 36.5%. Aetiology was unknown in 42.5%. CONCLUSIONS: Shortfalls detected in the quality of care indicate that urgent action should be taken to improve resources and the degree of specialisation among staff, as well as to aid families, who provide the main support to individuals with mental disability

Destination-directed, packet-switched architecture for a geostationary communications satellite network

A major goal of the Digital Systems Technology Branch at the NASA Lewis Research Center is to identify and develop critical digital components and technologies that either enable new commercial missions or significantly enhance the performance, cost efficiency, and/or reliability of existing and planned space communications systems. NASA envisions a need for low-data-rate, interactive, direct-to-the-user communications services for data, voice, facsimile, and video conferencing. The network would provide enhanced very-small-aperture terminal (VSAT) communications services and be capable of handling data rates of 64 kbps through 2.048 Mbps in 64-kbps increments. Efforts have concentrated heavily on the space segment; however, the ground segment has been considered concurrently to ensure cost efficiency and realistic operational constraints. The focus of current space segment developments is a flexible, high-throughput, fault-tolerant onboard information-switching processor (ISP) for a geostationary satellite communications network. The Digital Systems Technology Branch is investigating both circuit and packet architectures for the ISP. Destination-directed, packet-switched architectures for geostationary communications satellites are addressed

Capillary electrophoresis as a tool for genotyping SH3 mediated coffee leaf rust resistance

Coffee is an important agricultural commodity in the world. However, it is susceptible to Hemileia vastatrix (Hv), an obligatory biotrophic fungus that causes coffee leaf rust (CLR). Natural resistance to rust has been identified in the wild species Coffea canephora and Coffea liberica. These species have been used in breeding programs where interspecific resistant hybrids have been generated. The SH3 gene, derived from C. liberica, has been shown to confer extreme and long-lasting resistance to Hv. A total of 167 accessions of the INIA’s Coffee Germplasm Collection of Peru (INIA-CGC) were screened with 4 markers linked to the SH3 gene. As positive controls, EA67 (C. liberica) and the hybrid S.288 (C. arabica x C. liberica) were used. Separation of PCR products was done by capillary electrophoresis, which allow to discriminate the alleles of each marker. For three markers, specific alleles for either C. arabica or C. liberica species were found. In all cases, S.288 exhibited specific alleles for both species; whereas the INIA-CGC accessions had exclusively C. arabica alleles and EA67 had C. liberica alleles. The BA-48-21O-f marker did not produce PCR fragments for any of the positive controls, suggesting that this marker is not as predictive as the other three to determine the presence of SH3. This work reports the existence of multiple alleles for the Sat244 marker; however, the collection does not have the SH3 mediated-resistance gene. Finally, the utility of capillary electrophoresis as a tool to identify alleles linked to SH3 was demonstrated

Análisis comparativo de diferentes estructuras de compensación por carga balasto, aplicadas a generadores de inducción autoexcitados para pequeñas centrales hidroeléctricas

Este artículo presenta el análisis comparativo de diferentes estructuras de compensación, destinadas al control de tensión y frecuencia en generadores de inducción autoexcitados, aplicados a pequeñas centrales hidroeléctricas (PCHs). El análisis es efectuado mediante los resultados obtenidos con la implementación de dos prototipos de control por carga balasto. Ambos prototipos permiten controlar la tensión y frecuencia, midiendo únicamente la tensión generada. Uno de los prototipos utiliza una estructura de compensación fija y el otro posee distintas estructuras, configurables para estudiar las características de control sobre el sistema de generación. El desempeño en régimen transitorio y permanente de estos prototipos fue verificado en un banco de ensayos, constituido por un grupo motor-generador de 1HP. El análisis comparativo de los resultados se efectúa observando la respuesta de la tensión generada para distintos niveles y tipos de carga, lineales como no lineales; utilizando las diferentes estructuras de compensación proporcionadas por los prototipos mencionados.This paper presents a comparative analysis of different compensation structures, for the control of voltage and frequency of self-excited induction generators, applied to small hydropower (SHP). The analysis is carried out by the results obtained with the implementation of two prototype of dummy load control. Both prototypes use only the measure of the generated voltage to control the voltage and frequency. The first prototype uses a fixed compensation structure and the second one has different structures, configurable to study the characteristics of control over the generation system. The transient and steady-state response of these prototypes has been verified in a motor-generator module of 1HP. Comparative analysis of the experimental results was done by observing the response of the voltage generated for different levels and types of loads, linear and nonlinear, using different compensation structures provided by the prototypes mentioned.Asociación Argentina de Energías Renovables y Medio Ambiente (ASADES