46 research outputs found
Synthesis of new high pressure garnets : Mn3Cr2Si3O12 and Fe3Cr2Si3O12
No full textNew Cr-bearing garnets Mn₃Cr₂Si₃O₁₂ and Fe₃Cr₂Si₃O₁₂ were synthesised in modified-anvil-type high pressure apparatus at 1 000 °C and at pressures above 20 and 60 kbar respectively from their component oxide mixtures. X-ray powder diffraction data obtained from quenched samples correspond to pure garnet phases. Measured values of lattice parameters (a₀), refractive indices (N) and X-ray densities (dx) are as follows : for Mn₃Cr₂Si₃O₁₂ — a₀ = 11.766 (2) Å, N = 1.91 (1), dx = 4.444 g/cm³ ; for Fe₃Cr₂Si₃O₁₂ — a₀ = 11.679 (2) Å, N = 1.95 (1) dx = 4.567 g/cm³. At pressures below stability fields of the garnets the assemblages of spinel (MnCr₂O₄ or FeCr₂O₄) + pyroxenoid (rhodonite MnSiO₃ or ferrosilite FeSiO₃) + SiO₂ (quartz or coesite depending on pressure) were found in run products. Physical properties of the synthesised garnets are in close agreement with various garnet systematics and predictions made previously (e.g. Novack and Gibbs, 1971). Synthesis pressures in the Cr-garnets family are the higher the smaller are the effective ionic radii of [viii]Me²⁺ atoms : Ca-Cr-garnet (uvarovite) — the atmospheric pressure (R[Ca] = 1.12 Å), Mn-Cr-garnet — 20 kbar (R[Mn] = 0.96 Å). Fe-Cr-Garnet — 60 kbar (R[Fe] = 0.92 Å), Mg-Cr-garnet (knorringite) — higher than 110 kbar (R[Mg] = 0.89 Å).Les nouveaux grenats chromifères Mn₃Cr₂Si₃O₁₂ et Fe₃Cr₂Si₃O₁₂ ont été synthétisés à l'aide d'un dispositif haute pression à enclumes, à 1 000 °C et sous des pressions respectivement supérieures à 20 et 60 kbar, à partir de mélanges d'oxydes correspondant à leurs compositions. Les diagrammes de poudre des échantillons trempés ont les caractéristiques des grenats purs. Les valeurs mesurées des paramètres (a₀), des indices de réfraction (N) et les densités calculées sont les suivantes : pour Mn₃Cr₂Si₃O₁₂, a₀ = 11,766 (2) Å, N = 1,91 (1) ; dx = 4,444 g/cm³ ; pour Fe₃Cr₂Si₃O₁₂, a₀ = 11,679 (2) Å, N = 1,95 (1), dx = 4,567 g/cm³. Pour les pressions inférieures à celles du domaine de stabilité de ces grenats, les associations suivantes ont été obtenues : spinelle (MnCr₂O₄ ou FeCr₂O₄) + pyroxénoïde (rhodonite MnSiO₃ ou ferrosilite FeSiO₃) + SiO₂ (quartz ou coésite, suivant la pression). Les propriétés physiques de ces grenats synthétiques sont en bon accord avec les prévisions systématiques antérieures (par ex. Novack et Gibbs, 1971). Dans le groupe des grenats chromifères, les pressions de synthèse s'élèvent lorsque le rayon atomique [viii]Me²⁺ diminue : le grenat Ca-Cr (uvarovite) est synthétisé à pression atmosphérique (R[Ca] = 1,12 Å) ; le grenat Mn-Cr à 20 kbar (R[Mn] = 0,96 Å) ; le grenat Fe-Cr à 60 kbar (R[Fe] = 0,92 Å) ; le grenat Mg-Cr (knorringite) au-dessus de 110 kbar (R[Mg] = 0,89 Å).Fursenko Boris A. Synthesis of new high pressure garnets : Mn3Cr2Si3O12 and Fe3Cr2Si3O12. In: Bulletin de Minéralogie, volume 104, 4, 1981. 12e assemblée générale de l'I.M.A. - Orléans – Juillet 1980. Deuxième partie : inclusions magmatiques / silicates / gemmes / « open session »
Perlite for permanent confinement of cesium
No full textWe present the potential use of expanded perlite, a metastable amorphous hydrated aluminium silicate, as a permanent medium for the long-term confinement of cesium. The method requires simply a loading by mixing an aqueous cesium nitrate solution and expanded perlite at 300 K followed by densification by sintering. The formation of pollucite, CsAlSi2O6, a naturally occurring mineral phase, upon careful heat treatment is demonstrated by X-ray diffraction. Leaching tests on the resulting glass-ceramics reveal a very low Cs departure of 0.5 mg m−2 d−1
Numerical simulations of ignition features of premixtures in three-dimensional vortex flows
No full textCorruption of the Politicized University: Lessons from the Orange Revolution in Ukraine
No full textThis paper argues that corruption is used on a systematic basis as a mechanism of direct and indirect administrative control from the state level down to local authorities and administrations of public and private institutions. Informal approval of corrupt activities in exchange for loyalty and compliance with the regime is commonplace in many countries. This paper explains how corrupt regimes maximize their position in terms of loyalty and compliance by using the example of the 2004 presidential elections in Ukraine. It presents mechanisms by which political bureaucracies politicize universities in order to influence students and channel their electoral power during the Orange Revolution in Ukraine.corruption, elections, politicization, students, university, Ukraine
3D through silicon via profile metrology based on spectroscopic reflectometry for SOI applications
No full textImpact of NI Layer Thickness and Anneal Time on Nickel Silicide Formation by Rapid Thermal Processing
No full textInfluence of corrosion of a metal electrode on the polarization sensitivity of a photodetector based on an Ag-GaAs(InP) Schottky barrier with a corrugated interface
No full textCrystal structure of synthetic Mg3Cr2Si3O12, the high-pressure Cr end-member of the knorringite-pyrope garnet series
No full textKnorringite, the Cr-end-member of the pyrope garnet series (Nixon et al. 1968), often occur in high proportions in kimberlite garnets and is thus used for tracing high-pressure deep-earth conditions favorable to the formation of diamonds, in which knorringite-rich garnet can occur as inclusions. However, although the synthesis of knorringite is reported in the literature (Ringwood 1977; Irifune et al. 1982; Taran et al. 2004), the structure of the pure end-member has not been yet determined from experimental data. In this study, the crystal structure of knorringite, Mg3Cr2(SiO4)3, has been refined from high resolution synchrotron X-ray powder diffraction data recorded under ambient conditions on a polycrystalline sample synthesized at 12 GPa in a multi-anvil apparatus. The structure is cubic, space group Ia-3d, a = 11.5935(1), V = 1558.27(4) Å3, dcalc = 3.97 g.cm-3. The Cr-O distance of 1.957(2) Å is consistent with EXAFS results on the same sample. This short distance indicates a substantial compression of the CrO6 octahedron, compared to ambient pressure Cr3+-minerals such as uvarovite ( = 1.99 Å, Andrut and Wildner 2002). Our experimental results thus confirm early empirical predictions based on series of high-pressure Cr-garnet end-members (Fursenko 1981), showing that the values of the Cr-O distance and the Cr-O-Si angle decrease with the augmentation of pressure and with the diminution of the size of the divalent cation
Badania symulacyjne wpływu opadów gradu na niezawodność konstrukcji ogniw słonecznych
No full textThe mandatory tests of resistance to hail is carried out in order to qualify solar cell modules according to standards (IEC 61215 and IEC 61646). The efficiency of modern photovoltaic systems decreases significantly, when the crystalline structure of solar cells is damaged as a result of climatic factors, such as wind, hail, etc., which are similar to mechanical-dynamic effects. This work presents a conducted research of efficiency and reliability of solar cells, simulating hail effects. A testbed was created specifically for carrying out experimental research. During the research, solar elements were exposed to impact, cyclic dynamic loads, with the frequency of revolutions of the balls simulating hail ranging from 5 to 20 Hz, the amplitude of the impact excitation acceleration of the solar cell - up to 986 m / s2 and the force amplitude - up to 1129 N. Experimental research results revealed the reliability of photovoltaic modules of different sizes during the simulation of hail. The proposed assessment methodology of hail effects can be successfully applied in studies of the influence of mechanical-dynamic effects of solar cells of different structures.Przy kwalifikacji modułów ogniw słonecznych do użytkowania przeprowadza się obowiązkowe badania odporności na gradobicie zgodnie z normami IEC 61215 i IEC 61646. Wydajność nowoczesnych systemów fotowoltaicznych znacznie spada, gdy struktura krystaliczna ogniw słonecznych ulega uszkodzeniu w wyniku czynników klimatycznych, takich jak wiatr, gradobicie itp., które przypominają w swoim działaniu obciążenia mechaniczno-dynamiczne. W pracy przedstawiono wyniki badań symulacyjnych wpływu gradobicia na wydajność i niezawodność ogniw słonecznych. Badania prowadzono na specjalnie do tego celu skonstruowanym stanowisku testowym. Podczas badań, elementy słoneczne były wystawiane na cykliczne obciążenia dynamiczne wywoływane uderzeniami kulek symulujących grad o częstotliwości obrotów od 5 do 20 Hz przy amplitudzie przyspieszenia wzbudzenia uderzeniowego ogniwa słonecznego wynoszącej do 986 m/s2 oraz amplitudzie siły do 1129 N. Wyniki symulacji pozwoliły ocenić niezawodność modułów fotowoltaicznych o różnych rozmiarach. Proponowaną metodologię oceny wpływu opadów gradu można z powodzeniem stosować w badaniach oddziaływania obciążeń mechaniczno-dynamicznych na ogniwa słoneczne o różnych strukturach
Book Reviews
No full textROSE COTTAGE CHRONICLES: CIVIL WAR LETTERS OF THE BRYANT-STEPHENS FAMILIES OF NORTH FLORIDA, edited by Arch Fredric Blakey, Ann Smith Lainhart, and Winston Bryant Stephens Jr., reviewed by Brian R. Rucker; THE SUPREME COURT OF FLORIDA AND ITS PREDECESSOR COURTS, 1821-1917, Walter W. Manley II, editor and co-author; E. Canter Brown Jr., contributing editor and co-author; Eric W. Rise, co-author, reviewed by John J. Guthrie Jr.; GLADESMEN: GATOR HUNTERS, MOONSHINERS, AND SKIFFERS, by Glen Simmons and Laura Ogden, reviewed by John J. Guthrie Jr.; BIOARCHAEOLOGY OF NATIVE AMERICAN ADAPTATION IN THE SPANISH BORDERLANDS, edited by reviewed by Dean J. Saitta, Brenda J. Baker and Lisa Kealhofer; SLAVERY & THE LAW, edited by Paul Finkelman, reviewed by Jonathan Lurie; THE DEVIL’S LANE: SEX AND RACE IN THE EARLY SOUTH, edited by Catherine Clinton and Michele Gillespie, reviewed by Marcia G. Synnott; A HARD FIGHT FOR WE: WOMEN’S TRANSITION FROM SLAVERY TO FREEDOM IN SOUTH CAROLINA, by Leslie A. Schwalm, reviewed by Barbara Krauthamer; COME SHOUTING TO ZION: AFRICAN AMERICAN PROTESTANTISM IN THE AMERICAN SOUTH AND BRITISH CARIBBEAN TO 1830, by Sylvia R. Frey and Betty Wood, reviewed by Cynthia Lynn Lyerly; MASTERED BY THE CLOCK: TIME, SLAVERY, AND FREEDOM IN THE AMERICAN SOUTH, by Mark M. Smith, reviewed by Alexis McCrossen; MANIFEST DESTINY AND EMPIRE: AMERICAN ANTEBELLUM EXPANSIONISM, by Robert W. Johannsen, John M. Belohlavek, Thomas R. Hietala, Samuel W. Haynes, and Robert . May, edited by Sam W. Haynes and Christopher Morris, reviewed by William Earl Weeks; PENITENTIARIES, REFORMATORIES, AND CHAIN GANGS: SOCIAL THEORY AND THE HISTORY OF PUNISHMENT IN NINETEENTH-CENTURY AMERICA, by Mark Colvin, reviewed by Henry Kamerling; “ONE HELL OF A GAMBLE”: KHRUSHCHEV, CASTRO AND KENNEDY, 1958-1964. by Aleksankr Fursenko and Timothy Naftali, reviewed by Frank DeBenedictis; WORKERS’ CONTROL IN LATIN AMERICA, 1930-1979, Edited by Jonathan C. Brown, reviewed by Victor M. Uribe; THE QUIET VOICES: SOUTHERN RABBIS AND BLACK CIVIL RIGHTS, 1880s TO 1990s edited by Mark K. Bauman and Berkley Kalin, reviewed by Mark I. Greenberg; GHOST DANCING ON THE CRACKER CIRCUIT: THE CULTURE OF FESTIVALS IN THE AMERICAN SOUTH, by Rodger Lyle Brown, reviewed by Robert E. Snyder; ALL OVER BUT THE SHOUTIN’, by Rick Bragg, reviewed by William W. Rogers; REGION, RACE, AND CITIES : INTERPRETING THE URBAN SOUTH, by David Goldfield, reviewed by Stan Deato
