102,137 research outputs found
NAND Flash Storage Technology for Mission-critical Space Applications
No full textMass memories in space systems are evolving from simple tape-like data recorders to complex intelligent (sub)systems capable of autonomous operations. This evolution is driven by more complex functional requirements coming from complex multi-payload missions and by the availability of ever higher density memory components. In commercial markets, NAND flash memories are widespread as data storage in consumer electronics (e.g., USB flash drives) because of their high storage density, low power, low cost and high data throughput. However, hi-rel electronics is struggling in keeping the pace with the aggressive scaling down of NAND flash technology. As a consequence, the use of NAND flash in space applications is not as established as in the consumer market and is still under research. Furthermore, the full commercial availability of space qualified memories is not an option due to costs, manufacturer's interest, long lead times or performance reasons. Adoption of Commercial Of The Shelves (COTS) NAND flashes is unavoidable. Upscreening of COTS memory chips has demonstrated that most of those components are not able to successfully operate and survive in the demanding space environment. The few candidates that demonstrate promising robustness request additional design effort to meet reliability requirements for space missions. Furthermore, long term reliability and combination of aging and radiation effects over mission and storage lifetimes of decades has not been studied in sufficient breadth. This paper aims to provide an overview of the design challenges to overcome when applying latest generation of terrestrial memory technologies in to high reliability space system
Implementação e validação de um método cromatográfico para a Detecção e Quantificação de Furano em Feijão Enlatado
No full textO furano tem sido detectado em diversos alimentos em particular nos que são sujeitos a
tratamento térmico durante o processo de preparação industrial. É considerado um
composto potencialmente cancerígeno para seres humanos, pelo que a sua presença nos
alimentos se tornou uma questão de segurança alimentar. Desde 2007 que a Autoridade
Europeia para a Segurança Alimentar tem procurado recolher o maior número de
informação possível, relativa à presença de furano nos alimentos.
Neste trabalho utilizou-se a técnica de Cromatografia Gasosa de Espaço de Cabeça
acoplada a um espectrómetro de massa (HS-GC/MS) para avaliar os teores de furano
em feijões enlatados. Foram analisadas 10 amostras (latas) independentes, seleccionadas
aleatoriamente no mercado, de três marcas comercializadas em Portugal.
A concentração média obtida foi de 3,27 ng/g, numa gama que variou entre 2,61 e 4,45
ng/g. Os limites de detecção calculados foram de 0,80 ng/g para as amostras PD, 1,26
ng/g para as amostras C e de 0,58 ng/g para as amostras F. Os limites de quantificação
foram, respectivamente, de 2,44, 3,82 e 1,77 ng/g. Os coeficientes de variação do
método foram inferiores a 10% e a percentagem de recuperação foi de 95%.
Para estudar o efeito do tratamento térmico doméstico, foram também, analisadas
amostras aquecidas à temperatura de 80°C, tendo-se verificado um aumento
significativo na concentração do furano detectada.
Comparou-se ainda a concentração média do furano obtido nos feijões em lata com a
concentração média para o mesmo tipo de feijão conservado em frascos de vidro, tendose
constatado não existirem diferenças significativas.universidade técnica de Lisboa Faculdade de Medicina Veterinári
Síntese e estudo das propriedades mesogênicas de compostos contendo o heterociclo furano
No full textDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Ciências Físicas e Matemáticas. Programa de Pós-Graduação em Química.A síntese e caracterização de duas séries homólogas de compostos derivados de 4-acriloiloxibenzilideno-4-alcoxianilinas e 4-acriloiloxi-3-metoxibenzilideno-4-alcoxianilinas contendo o heterociclo furano ligado à porção acriloíla da cadeia são apresentadas
Guest Editorial: IEEE Transactions on Emerging Topics in Computing Special Issue on Advanced Command, Control and On-Board Data Processing for Space Avionic Systems
No full textThe papers in this special issue focus on advanced command, control and on-board data processing for space avionic systems. The domain of space avionic systems is changing extremely rapidly, compared to other technical domains in the spacefaring industry, under the pressure of intense competition, the continuous emergence of new markets and players, the need for cost reduction, as well as an increased obsolescence rate of components and processes due to the relative reduction of hi-rel parts market share with respect to booming volumes of consumer electronics. The emergence of "new space" paradigm, with new (mostly private) players taking the risk of compromising with system's dependability in favour of stripped down cost further contributes to this rapidly changing landscape: new opportunities are opening for the space avionic systems
Total ionizing dose effects on DRAM data retention time
No full textDynamic random access memory (DRAM) data retention time degradation induced by radiation exposure is investigated in this paper. We present the experimental setup and the results of total ionizing dose (TID) test on a COTS SDRAM de- vice. We observed a significant retention time reduction related to the absorbed dose and we assume radiation induced interface trap generation as the origin of the retention time reduction. By measuring individual cells retention time before and after radiation exposures, we found out that the reduction is not homogeneous among cells: the amount of leakage current increase depends on the position and the energy level of the generated trap, leading to a wide distribution of retention time reduction. Of particular interest is the fact that device was unbiased during irradiation and that no post-irradiation recovery was observed
Contaminantes alimentares resultantes do processamento térmico: furano e hidroximetilfurfural
No full textDissertação de Mestrado em Biotecnologia e Qualidade AlimentarO furano e o hidroximetilfurfural são dois contaminantes que se formam durante o processamento térmico dos alimentos. O seu potencial efeito nocivo para a saúde humana, em particular do furano que é considerado um composto potencialmente cancerígeno para seres humanos, tem justificado a realização de numerosos trabalhos com o propósito de proporcionarem o maior número de informação possível sobre os teores destes contaminantes em alimentos. O conhecimento destes teores é determinante para se fazer uma estimativa fidedigna sobre a exposição ao furano através da alimentação e do risco associado à presença destes contaminantes nos alimentos. Os dados relativos à presença destes contaminantes em alimentos comercializados em Portugal são muito escassos. No trabalho de dissertação apresentado pretendeu-se contribuir para a avaliação dos teores de furano e de hidroximetilfurfural em alguns alimentos comercializados em Portugal. O trabalho experimental englobou duas partes. Na primeira procedeu-se à otimização e validação de um método de cromatografia gasosa com deteção por espectrometria de massa (GC-MS) para a deteção e quantificação de furano em amostras de feijões enlatados e alimentos infantis. Foi igualmente efetuado um estudo sobre a eficiência de algumas práticas domésticas, usadas na preparação dos alimentos, na perda de furano por volatilização. Na segunda parte realizou-se a otimização e validação de um método de cromatografia líquida de alta eficiência com deteção por fotodiodos (HPLC-DAD) para a deteção e quantificação de hidroximetilfurfural em amostras de sumos, alimentos infantis e compotas. Os resultados obtidos mostram que os teores de furano e de hidroximetilfurfural nos alimentos analisados são da mesma ordem de grandeza dos teores obtidos em alimentos similares e comercializados noutros países.Furan and hydroxymethylfurfural are two contaminants formed during the heat processing of food. The potential harmful effect on human health, particularly furan that is considered a potentially carcinogenic compound to humans, has justified the realization of numerous studies in order to provide as much information as possible about the levels of these contaminants in food. Knowledge of contaminants content is crucial to make a reliable estimate of furan exposure through food and the risk associated with these contaminants in food. Data for these contaminants in foods sold in Portugal are very scarce. This dissertation intended to contribute for the evaluation of furan and hydroxymethylfurfural content in foods available and consumed in Portugal. The experimental work comprised two parts. The first part was focused on the optimization and validation of a headspace gas chromatography - mass spectrometry (CG-MS) method for the identification and quantification of furan in infant foods and canned beans. Additionally, the efficiency of some domestic practices, used in food preparation, in the loss of furan by volatilization was also evaluated. The second part was focused on the optimization and validation of a high performance liquid chromatography with diode array detection (HPLC-DAD) for the identification and quantification of hydroxymethylfurfural in fruit juice, infant foods and jams.
The results obtained show that the amounts of furan and hydroxymethylfurfural in foods analyzed are of the same order of magnitude as the yields obtained in similar foods consumed in other countries
Characterization of data retention faults in DRAM devices
No full textDynamic random access memory (DRAM) is the most widely used type of memory in the consumer market today, and it is still widely used for mass memories for space application. Even though accurate tests are performed by vendors to ensure high reliability, DRAM errors continue to be a common source of failures in the field. Recent large-scale studies reported how most of the errors experienced by DRAM subsystem are due to faults repeating on the same memory address but occurring only under specific condition. As these failures could be related to the memory cell’s ability to retain its stored charge, an empirical characterization of DRAM data retention time was performed within this study. Retention time information was collected from SDRAM devices from two different vendors to evaluate the impact of four different factors (temperature, data background, previous charge level and variable retention time) on DRAM cells retention time. Gathered results can be useful in defining enhanced test procedures for the early detection of data retention faults
An FPGA-based hardware accelerator for CNNs inference on board satellites: Benchmarking with Myriad 2-based solution for the cloudscout case study
No full textIn recent years, research in the space community has shown a growing interest in Artificial Intelligence (AI), mostly driven by systems miniaturization and commercial competition. In particular, the application of Deep Learning (DL) techniques on board Earth Observation (EO) satellites might lead to numerous advantages in terms of mitigation of downlink bandwidth constraints, costs, and increment of the satellite autonomy. In this framework, the CloudScout project, funded by the European Space Agency (ESA), represents the first time in-orbit demonstration of a Convolutional Neural Network (CNN) applied to hyperspectral images for cloud detection. The first instance of this use case has been done with an INTEL Myriad 2 VPU on board a CubeSat optimized for low cost, size, and power efficiency. Nevertheless, this solution introduces multiple drawbacks due to its design not specifically being for the space environment, thus limiting its applicability to short-lifetime Low Earth Orbit (LEO) applications. The current work provides a benchmark between the Myriad 2 and our custom hardware accelerator designed for Field Programmable Gate Arrays (FPGAs). The metrics used for comparison include inference time, power consumption, space qualification, and components. The obtained results show that the FPGA-based solution is characterized by a reduced inference time, and a higher possibility of customization, but at the cost of greater power consumption and a longer Time to Market. As a conclusion, the proposed approach might extend the potential market of DL-based solutions to long-term LEO or interplanetary exploration missions through deployment on space-qualified FPGAs, with a limited cost in energy efficiency
Mosquito Larvicidal Constituents from Lantana Viburnoides SP Viburnoides Var Kisi (A. rich) Verdc (Verbenaceae).
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Lantana viburnoides sp viburnoides var kisi is used in Tanzania ethnobotanically to repel mosquitoes as well as in traditional medicine for stomach ache relief. Bioassay-guided fractionation and subtraction bioassays of the dichloromethane extract of the root barks were carried out in order to identify the bioactive components for controlling Anopheles gambiae s.s. mosquito larvae. Twenty late III or early IV instar larvae of An. gambiae s.s. were exposed to various concentrations of the plant extracts, fractions, blends and pure compounds, and were assayed in the laboratory by using the protocol of WHO 1996. Mean mortalities were compared using Dunnett's test (p < 0.05) and lethal concentration calculated by Lackfit Inversel of the SAS programme. The crude extract (LC50 = 7.70 ppm in 72 h) and fractions exhibited different level of mosquito larvicidal activity with subtraction of some fractions resulting in activity enhancement. The active fractions contained furanonaphthaquinones regio-isomers (LC50 = 5.48-5.70 ppm in 72 h) and the lantadene triterpenoid camaric acid (LC50 = 6.19 ppm in 72 h) as active principles while the lupane triterpenoid betulinic acid (LC50 < 10 ppm in 72 h) was obtained from the least active fraction. Crude extracts and some fractions had higher or comparable larvicidal activity to the pure compounds. These results demonstrate that L. viburnoides sp viburnoides var kisi extracts may serve as larvicides for managing various mosquito habitats even in their semi-purified form. The isolated compounds can be used as distinct markers in the active extracts or plant materials belonging to the genus Lantana
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