<?xml version="1.0" encoding="UTF-8"?><xml><records><record><source-app name="Biblio" version="6.x">Drupal-Biblio</source-app><ref-type>47</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Tewari, Param H.</style></author><author><style face="normal" font="default" size="100%">V. Lofftus</style></author><author><style face="normal" font="default" size="100%">Arlon J. Hunt</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Structure and Chemistry of Sol-Gel Derived Silica Aerogel</style></title><secondary-title><style face="normal" font="default" size="100%">2nd International Conference on Ultrastructure Processing of Ceramics, Glasses, and Composities</style></secondary-title></titles><dates><year><style  face="normal" font="default" size="100%">1985</style></year><pub-dates><date><style  face="normal" font="default" size="100%">03/1985</style></date></pub-dates></dates><urls><related-urls><url><style face="normal" font="default" size="100%">http://eetd.lbl.gov/sites/all/files/publications/18586.pdf</style></url></related-urls></urls><pub-location><style face="normal" font="default" size="100%">Palm Coast, FL</style></pub-location><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">&lt;p&gt;A large set of illuminance and irradiance data has been collected for four years at 15-minute intervals in San Francisco. This data set has been used to investigate the impact ofsatmospheric turbidity on daylight calculations. Existing predictive formulae for Linke turbidity,sTL, provide moderate agreement to measured values of TL when using nominal designsvalues for the Angstrom scattering coefficient, P, and precipitable water vapor, w. When averagesmeasured values for p and w are used, the agreement improves. We suggest the use of ansilluminance turbidity, Til, to calculate direct normal illuminance directly. We derive a simplesapproximate solution, Til = 1 + 21.6 B. Til appears to be a better parameter to describe atmosphericsconditions since, unlike TL, it is insensitive to air mass and thus solar altitude or time ofsday. We present and compare plots of Til and TL vs. solar altitude, time of day, and month.sFinally, we examine and compare several alternative pathways to derive direct normal illuminancesfrom irradiance and luminous efficacy (dependent on P and w), or directly from P.&lt;/p&gt;</style></abstract><call-num><style face="normal" font="default" size="100%">LBL-18586</style></call-num><custom1><style face="normal" font="default" size="100%">&lt;p&gt;Windows and Daylighting Group&lt;/p&gt;</style></custom1><custom2><style face="normal" font="default" size="100%">LBL-18586</style></custom2></record></records></xml>