Blackbody sources with nearly unity emittance that are in equilibrium with a pure freezing metal such as gold, silver, or copper are used as primary standard sources in the International Temperature Scale of 1990 (ITS-90). Recently, a facility using radio-frequency induction heating for melting and filling the blackbody crucible with the freeze metal under vacuum conditions was developed at the National Institute of Standards and Technology (NIST). The blackbody development under a vacuum environment eliminated the possibility of contamination of the freeze metal during the process. The induction heating, compared to a resistively heated convection oven, provided faster heating of crucible and resulted in shorter turn-around time of about 7 h to manufacture a blackbody. This paper describes the new facility and its application to the development of fixed-point blackbodies.
La reaparición de la ballena azul en el sur de Chile constituye undesafío para las políticas de conservación e invita a repensar la historia del mar austral y, en particular, de la costa aysenina. El paisaje social de este litoral corresponde a un ecosistema de tránsito y marginalizado entre dos regiones conocidas: Chiloé y Patagonia austral. Es un ambiente extremo en el que diversas poblaciones humanas han desplegado variadas estrategias adaptativas asociadas al bosque y a los sistemas marinos, documentadas en registros arqueológicos, históricos y etnográficos, lo que se procura sintetizarpara la reconstrucción de una historia ambiental de la región. Los antecedentes arqueo-históricos dan cuenta de poblaciones canoeras cuya relación con la naturaleza, fundada en un uso extensivo de los recursos, facilitó su integración a los paisajes locales, caracterizados por formaciones archipielágicas. Este patrón se modifica con los procesos históricos desencadenados a partir de la anexión del territorio a los espacios económicos nacionales, situación asociada a sucesivas oleadas poblacionales que se asientan en el litoral de Aysén, modificando las estrategias adaptativas tradicionales. Conla llegada de estas poblaciones se instaura un modelo intensivo y depredador en un paisaje intrínsecamente lábil y, por tanto, agotable. La posibilidad de constituir esta historia en un referente para un adecuado resguardo del área, y, en especial de la ballena azul, especie emblemática cuya presencia se detecta a partir de 2003, es el desafío a que aquí se alude.
The National Institute of Standards and Technology (NIST) candela is maintained via standard photometers which have shown long-term stability of better than 0.1 % per year. The detector-based method has allowed us to reduce the uncertainties of calibrations and to expand the range of calibration capabilities. There have been several new developments in photometry at the NIST. A high-illuminance calibration facility has been developed. Four temperature-controlled standard photometers, tested for linearity and thermal effects at high illuminances, are used with a high-pressure xenon arc source to provide the illuminance scale at levels up to 100 klx. A flashing-light photometric unit (lx s) has been realized using four standard photometers equipped with current integrators, and using two independent methods. Calibration services for illuminance meters at high illuminance levels and flashing-light photometers are now available at the NIST. Ongoing new projects include the development of a detector-based luminous-flux calibration facility using a 2.5 m integrating sphere, realization of the total spectral radiant-flux scale, and the development of a reference spectroradiometer for colorimetry of displays. Calibration services are planned in these areas of photometry and colorimetry in the near future.
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