172,887 research outputs found
1948 Candela Standard Lamp
No full textThe photometric standard is called the candela. This artifact is a 500 Watt gas-filled incandescent lamp and was used as the lumious intensity standard in the 1970s. The lamp has a luminous intensity of approximately 790 candela, operated at 4.2A and 111, and color temperature 2,854K. From 1948-1979 the candela was defined as the luminous intensity, in the perpendicular direction, of a surface of 1/600,000 square meter of a blackbody and the temperature of freezing platinum under a pressure of 101,325 newtons per square meter.19 x 8 x 9 c
Photodetector for Standard Candela
No full textIn 1979 the candela, the SI unit for luminous intensity, was redefined as ""the luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency 540x10^12 hertz and that has a radiant energy of 1/683 watt per steradian."" The redefinition made it possible to realize the candela using calibrated detectors of optical radiation. The National Institute of Standards and Technology implemented this technique in the early 1990s with this artifact, a silicon diode photodetector which included a filter that spectrally matched the accepted human visual response. This was the first use of a detector device to realize the candela for the United States, and was a fundamental and historical change from all previous measurements of the candela which, since its inception, had relied upon various types of lamps.8 x 19 x 11 c
Calculation process of long cylindrical shells in the work of Felix Candela. The equilibrium approach
No full textThe objective of the present work is to show how from the 50's, Felix Candela got to analyze the roof long cylindrical shells in reinforced concrete. It was done from a structural point of view, with calculations based simply on equilibrium equations, with just an objective: to get a safely and easily calculation method, respecting the assignment of reinforced concrete and, therefore, obviating the considerations of compatibility and deformation that could undergo the structure. And he did it in a moment when Elastic Theory of Shells was practically inapplicable when it involved the resolution of eighth order differential equations. The theory is developed mathematically choosing an example of work of Félix Candela, done by roof long cylindrical shells, and making the necessary structural calculations proposed.El objetivo del presente trabajo consiste en evidenciar como a partir de los años 50 Félix Candela consiguió diseñar y calcular estructuralmente cáscaras cilíndricas largas de cubierta de hormigón armado mediante análisis basados simplemente en ecuaciones de equilibrio, con un claro objetivo: conseguir un método de cálculo sencillo y seguro, respetando la característica de cedencia del hormigón armado y, por tanto, obviando las consideraciones de compatibilidad y deformación que pudiera sufrir la estructura. Y lo hizo en un momento donde la teoría elástica de cáscaras resultaba prácticamente inaplicable al implicar la resolución de ecuaciones diferenciales de octavo orden. Se justifica analíticamente la teoría escogiendo un ejemplo de la obra de Félix Candela, ejecutada por medio de cáscaras cilíndricas largas de cubierta, y elaborando el proceso de cálculo necesario propuesto
Studio comparativo in vitro della resistenza alla trazione applicata a corone proteiche metal-free cementate con due diversi cementi adesivi definitivi
No full textProblemática lingüístico-cognitiva: Abordaje lingüístico-cognitivo de un texto en inglés
No full textFil: Pérez Albizú, Candela. Universidad Nacional de La Plata. Facultad de Humanidades y Ciencias de la Educación; Argentina
An existence result for perturbed (p,q)-quasilinear elliptic problems
No full textWe investigate the existence of solutions of the quasilinear elliptic problem
\left\{\begin{array}{lll}
\displaystyle{ -\Delta_p u -\Delta_q u\ =\ g(x, u) + \varepsilon\, h(x,u)} & & \mbox{ in } \Omega,\\
\displaystyle{u=0} & & \mbox{ on } \partial\Omega,\\
\end{array}\right.
where is an open bounded domain in , 1<+\infty, the nonlinearity behaves at infinity as , and .
In spite of the possible lack of a variational structure of this problem, appropriate procedures and estimates allow us to prove the existence of at least one nontrivial solution for small perturbations
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