328 research outputs found
Investigation of the influence of the zeta-potential on the filtration rate in the presence of collectors
The value of the zeta-potential does not have an explicit effect, which is expressed by a simple math correlation, on filtration rate when a solution of the tested collector is filtered through a cake prepared under standard conditions from the examined particulate material. The zeta-potential measurements and filtration tests were carried out on silica and galena with solutions contg. a cationic container ANP and Et xanthane, resp. at PH = 6.5, varying concentration of the agent (0-2500 g/ton), and under a vacuum of 100 to 600 mm Hg
Cathodoluminescence of Recent biogenic carbonates: environmental and ontogenetic fingerprint
Cathodoluminescence (CL) examination of Recent biogenic carbonates shows that they are often luminescent regardless of their mineralogical composition (calcite v. aragonite), habitat (marine v. fresh water), way of life (sessile v. vagile) or environment (hyper- v. hyposaline water). Thus, the presence of luminescence in biogenic particles is not a reliable indicator of diagenetic alteration as some authors have suggested. In addition, CL can reveal variations in the mineralogy of shell material (e.g. regenerated calcitic v. primary aragonitic) and can highlight growth-related structures. Manganese (Mn2+) is the most likely activator of this luminescence, and its content in the shells of benthic organisms seems to be linked to growth rate, ontogeny, open sea conditions, bathymetry and salinity. In neritic environments the Mn2+ content and the CL of molluscs and foraminifera appear to increase with decreasing salinity. This study indicates that CL may be an important tool for the determination of environmental and ontogenetic parameters in biogenic carbonates in addition to its current use indiagenetic studie
1867, lâannĂ©e de tous les Rapports. Les lettres et les sciences Ă la fin du Second Empire
En juillet 1865, le ministre de lâInstruction publique Victor Duruy propose, au Conseil des ministres, « de faire lâhistoire des progrĂšs de toutes les sciences depuis vingt ans », dans le cadre de la prĂ©paration de lâExposition universelle de 1867. Vers la fin octobre, il adresse Ă NapolĂ©on III un rapport dans lequel il demande Ă lâempereur dâ« autoriser le ministĂšre de lâInstruction publique Ă ĂȘtre exposant » lors de la prochaine Exposition universelle Ă Paris. Une fois ce rapport approuvĂ© par NapolĂ©on III, il informe, en dĂ©cembre, le commissaire gĂ©nĂ©ral de la future Exposition universelle, le conseiller dâĂtat FrĂ©dĂ©ric Le Play, que son ministĂšre dĂ©posera une sĂ©rie de Rapports « sur les principales Ćuvres produites par lâesprit français ».
De cette initiative sortiront 29 Rapports, plus ou moins importants en volume, Ă©crits par des auteurs plus ou moins connus aujourdâhui. Ce corpus considĂ©rable a Ă©tĂ© sorti de lâoubli et Ă©tudiĂ© pendant trois ans par un groupe interdisciplinaire composĂ© dâune quinzaine de chercheurs (historiens, historiens des sciences, de la philosophie et de la littĂ©rature). Il fournit un excellent Ă©tat des prĂ©occupations concernant les sciences et les lettres Ă la veille de la guerre de 1870. Les rĂ©sultats de lâenquĂȘte permettent au lecteur dâaujourdâhui dâĂ©valuer le patrimoine dâun XIXe siĂšcle dont nous sommes les hĂ©ritiers, aussi bien en ce qui concerne les conceptions relatives aux lettres, aux sciences et aux techniques, que pour les relations entre la recherche, lâuniversitĂ© et la sociĂ©tĂ©
Effect of the anisotropy of monocrystalline silicon mechanical properties on the dynamic characteristics of a micromechanical gyroscope
The aim of the research was to determine the effect of temperature on mechanical properties of a micromechanical gyroscope with the sensing element mounted on a silicon wafer, with the crystallographic orientation of (100) (110) (111). The research is of current relevancy since the metrological characteristics that depend on the eigenfrequencies over the full temperature range are to be controlled. The temperature-modal analysis of the micromechanical gyroscope model was performed with ANSYS program. The temperature dependence for eigenfrequencies was obtained. The dependence of the scale factor on temperature for the most temperature-independent variant of sensor positioning on the wafer was determined. The developed mathematical model was used to find the forms of the output oscillations of the gyroscope
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