997 resultados para 900


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Review of Memory and Gender in Medieval Europe, 900-1200 by Elizabeth van Houts (Toronto UP, 1999).

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Kela alkoi maksaa takuueläkettä 1.3.2011. Takuueläke korotti Suomessa asuvan vähimmäiseläkkeen 687,74 euroon. Huhtikuussa takuueläkkeen saajia oli 87 900.

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Thermodynamic properties of Li3N dissolved in the molten LiCl salt at 900 K were explored using electrochemical methods. It was difficult to determine precisely the decomposition voltage of Li3N dissolved in the molten salt by cyclic voltammetry. The oxidation wave of N3– ion could not be located with high accuracy. However, the lithium activity of the Pb-Li alloy in equilibrium with the molten salt containing dissolved Li3N under nitrogen atmosphere could be measured electrochemically with high accuracy using the Li/Li + reference electrode. Under the conditions used in this study, the potential of the Li-Pb electrode is equal to the decomposition voltage of Li3N. The activity of Li3N in molten LiCl was determined for anionic fractions of N3– ranging from xN3– = 10–4 to 0.028. The nitride ion concentration in the salt was determined by chemical titration. The activity coefficient of the Li3N at high dilution was found to be very low, around 10–4. The activity coefficient increases sharply with composition and has a value of 0.25 at xN3– = 0.028. ©2001 The Electrochemical Society. All rights reserved.

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This paper presents a fully integrated CMOS analog front end for a passive 900-MHz radio-frequency identification (RFID) transponder. The power supply in this front end is generated from the received RF electromagnetic energy by using an RF-dc voltage rectifier. In order to improve the compatibility with standard CMOS technology, Schottky diodes in conventional RF-dc rectifiers are replaced by diode-connected MOS transistors with zero threshold. Meanwhile, theoretical analyses for the proposed rectifier are provided and verified by both simulation and measurement results. The design considerations of the pulsewidth-modulation (PWM) demodulator and the backscatter modulator in the front end are also discussed for low-power applications. The proposed front end is implemented in a 0.35-mu m 2P4M CMOS technology. The whole chip occupies a die area of 490 x 780 mu m(2) and consumes only 2.1 mu W in reading mode under a self-generated 1.5-V supply voltage. The measurement results show that the proposed rectifier can properly operate with a - 14.7-dBm input RF power at a power conversion efficiency of 13.0%. In the proposed RFID applications, this sensitivity corresponds to 10.88-m communication distance at 4-W equivalent isotropically radiated power from a reader base station.

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UANL

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Proyecto realizado por nueve profesores del IES Pintor Luis Sáez de Burgos, se desarrolla en la comunidad de Castilla Y León (Soria, Burgos y Zamora). Los profesores implicados trabajan en el instituto llevando a cabo actividades académicas y fuera del mismo en las provincias mencionadas realizando trabajos de campo. Nuestros objetivos son: a) Conocer los puntos geográficos donde el Cid realizó sus hazañas. b) Aproximación al Mundo Medieval Británico. c) Práctica matemática desde el juego del ajedrez. d) Evolución de los cambios medioambientales. En todas las áreas la metodología empleada ha sido la siguiente: a) Trabajo en grupos dentro del aula. b) Trabajo de investigación individual en la biblioteca. c) Trabajo de campo. La evaluación de las actividades se ha hecho de forma cionjunta entre profesores y alumnos, siendo valorado positivamente tanto por el alumnado como por el profesorado. Los materiales elaborados son: cuestionarios, cómics y fotografías. Los materiales utilizados han sido: videos, libros, diccionarios específicos, ajedreces, mapas, revistas y cámaras fotográficas de un solo uso. No está publicado..

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What was it like to be a teenager in medieval England? Despite the fact that medieval society often singled young apprentices and workers out for comment, their study has been largely neglected in medieval archaeology. The skeletal remains of 4940 adolescents (6.6-25 years) from 151 sites in medieval England was compiled from a combination of primary data collection and secondary data from published and unpublished skeletal reports and on-line databases. The aim was to explore whether apprentices could be identified in the archaeological record and if so, at what age they started work and what impact occupation had on their health. The data were divided into urban and rural groups, dating from before and after the Black Death of AD 1348-9, and before the Industrial Revolution. A shift in the demographic pattern of urban and rural adolescents was identified after the Black Death, with a greater number of young females residing in the urban contexts after 14 years. The average age of males increased from 12 years to 14 years after the plague years, contrary to what we might expect from the documentary sources. There were higher rates of spinal and joint disease in the urban adolescents and their injuries were more widespread than their rural counterparts. Domestic service was the potential cause of the greater strain on the knees and backs of the urban females, with interpersonal violence evident in the young urban males. Overall, it was the urban females that carried the burden of respiratory and infectious diseases suggesting they may have been the most vulnerable group. This study has demonstrated the value of adolescent skeletal remains in revealing information about their health and working life, before and after the Black Death.