WebEn électronique, un quartz est un composant électronique qui possède comme propriété utile d'osciller à une fréquence stable lorsqu'il est stimulé électriquement. Les propriétés piézoélectriques remarquables du minéral de quartz permettent d'obtenir des fréquences d'oscillation très précises, qui en font un élément important en électronique numérique …

WebLe quartz fumé (anciennement (XVIII e siècle) enfumé) est une variété de quartz qui doit sa teinte à une irradiation naturelle (ou artificielle) d'impuretés d'aluminium (sous formes d'aluminosilicates [4]) par des minéraux radioactifs (uranium, thorium), phénomène qui s'exagère dans le quartz morion [5].La couleur du quartz fumé peut varier du brun au …

WebLe quartz est une espèce minérale du groupe des silicates [c], sous-groupe des tectosilicates, composé de dioxyde de silicium, ou silice, de formule chimique SiO 2, avec des traces de différents éléments tels que Al, Li, B, Fe, Mg, Ca, Ti, Rb, Na, OH. Il se présente sous la forme ou bien de grands cristaux incolores, colorés ou fumés, ou bien …

WebGlasses, also known as eyeglasses or spectacles, are vision eyewear, with lenses (clear or tinted) mounted in a frame that holds them in front of a person's eyes, typically utilizing a bridge over the nose and hinged arms (known as temples or temple pieces) that rest over the ears.. Glasses are typically used for vision correction, such as with reading glasses …

WebQuartz (silicon dioxide, SiO 2) is a common mineral, a trigonal chemical compound of silicon and oxygen. Nowadays, quartz plates or quartz control plates of different thickness serve as standards to calibrate polarimeters and saccharimeters. In order to ensure reliable and comparable results, quartz plates can be calibrated and certified by metrology institutes. …

WebFused quartz, fused silica or quartz glass is a glass consisting of almost pure silica (silicon dioxide, SiO 2) in amorphous (non-crystalline) form.This differs from all other commercial glasses in which other ingredients are added which change the glasses' optical and physical properties, such as lowering the melt temperature. Fused quartz, therefore, has high …

WebThe cron command-line utility is a job scheduler on Unix-like operating systems.Users who set up and maintain software environments use cron to schedule jobs (commands or shell scripts), also known as cron jobs, to run periodically at fixed times, dates, or intervals. It typically automates system maintenance or administration—though its general-purpose …

WebStone Mountain is a quartz monzonite dome monadnock and the site of Stone Mountain Park, 16 miles (26 km) east of Atlanta, Georgia.Outside the park is the small city of Stone Mountain, Georgia.The park is the most visited tourist site in the state of Georgia. The park is owned by the state of Georgia and is currently managed by Herschend Family …

WebThe first report of the hydrothermal growth of crystals was by German geologist Karl Emil von Schafhäutl (1803–1890) in 1845: he grew microscopic quartz crystals in a pressure cooker. In 1848, Robert Bunsen reported growing crystals of barium and strontium carbonate at 200 °C and at pressures of 15 atmospheres, using sealed glass tubes and …

WebWithin surface science, a quartz crystal microbalance with dissipation monitoring (QCM-D) is a type of quartz crystal microbalance (QCM) based on the ring-down technique. It is used in interfacial acoustic sensing. Its most common application is the determination of a film thickness in a liquid environment (such as the thickness of an adsorbed protein …