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  • 1
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 970-972 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The influence of biaxial stress on the optical properties of thin GaN films is studied by x-ray diffraction and Raman and photoluminescence spectroscopy. The stress is caused by differences in the thermal expansion coefficient and lattice mismatch between the film and c-plane sapphire substrates. In particular, the influence of various thicknesses of AlN buffer layers on the strain in GaN films is studied. GaN/AlN films were deposited by low pressure metal organic chemical vapor deposition using triethylgallium and tritertbutylaluminum and ammonia. We observe a pronounced reduction of strain in the GaN films with increasing buffer thickness: An AlN buffer layer thicker than 200 nm eliminates the stress completely. Estimates of the linear coefficient for the near band gap luminescence shift due to biaxial compressive strain yield a value of 24 meV/GPa. © 1996 American Institute of Physics.
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  • 2
    Electronic Resource
    Electronic Resource
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 22 (1967), S. 919-922 
    ISSN: 0001-5520
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences
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  • 3
    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: A boundary element method in terms of the field variables is applied to three-dimensional electromagnetic scattering problems. Especially, the influence of a dipole excited field on low conducting materials situated very close to the antenna will be discussed. We use higher order edge elements of quadilateral shape for the field approximation on curved surfaces. The tangential components of the unknown field variables are interpolated by vector element functions. The Galerkin method is implemented to obtain a set of linear equations. The applicability of the proposed edge element is investigated by the comparison of different BEM-formulations and FEM-results.
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  • 4
    Electronic Resource
    Electronic Resource
    Bradford : Emerald
    Compel 18 (1999), S. 372-384 
    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: This paper deals with the inverse scattering problem of reconstructing the material properties of perfectly conducting or dielectric cylindrical objects. The material properties are reconstructed from measured far-field scattering data provided by the Electromagnetics Technology Division, AFRL/SNH, 31 Grenier Street, Hanscom AFB, MA 01731-3010. The measured data have to be calibrated for use in our reconstruction algorithm. The inverse scattering problem formulated as unconstrained nonlinear optimization problem is numerically solved using an iterative scheme with a variable calibration factor which will be determined during the optimization process. Numerical examples show the successful application of the method to the measured data.
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  • 5
    Electronic Resource
    Electronic Resource
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 24 (1968), S. 456-458 
    ISSN: 1600-5740
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Monatshefte für Chemie 95 (1964), S. 1417-1423 
    ISSN: 1434-4475
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Zusammenfassung Legierungen in den Dreistoffen Ti(Zr, Hf)−B−Al werden durch Heißpressen und Homogenisieren, teilweise durch Reaktion der kaltgepreßten Ansätze bei 1200°C hergestellt. Der Aufbau bei etwa dieser Temperatur ist im wesentlichen durch die Gleichgewichte zwischen den Diboriden der Übergangsmetalle und AlB2, Aluminium sowie den Aluminiden gekennzeichnet. Es wird keinerlei Löslichkeit in den binären Phasen beobachtet, doch treten in den Systemen Zr−B−Al und Hf−B−Al die Bor-stabilisierten Phasen Zr5Al3B x und Hf5Al3B x mit teilweise aufgefülltem Mn5Si3-Typ sowie eine μ-Phase Hf0,45Al0,50B0,05 auf.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Monatshefte für Chemie 96 (1965), S. 232-241 
    ISSN: 1434-4475
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Abstract Alloys within the ternary systems: {Zr, Hf, V, Nb, Ta}-{Ni, Cu, Ag, Au}-{Zn, Al, Ga, Sn, Pb} have been prepared mainly in the domain of 50–60 a/oT, 10–30 a/o 8a- and 1b-metal and 15–40 a/o 2b–4b-metal. The phases Zr3Cu2Zn, Zr3Ag2Zn, Zr3Au2Al, Hf3Cu2Zn, Hf3Au2Al are found to be isostructural with the Ti2Ni-type. Hf5Sn4 crystallizes with Ti5Ga4-type, while homogenous samples having almost the same crystal structure such as Zr5Pb3Cu, Hf5Sn3Ni, Hf5Sn3Cu and Hf5Pb3Cu can also be considered as a filled Mn5Si3-structure. The small Ni- and Cu-atoms do play the same role as non metal atoms. V3(Au, Ga)2Nx, Nb3(Au, Ga)2Nx and Ta3(Au, Ga)2Nx possess a partially ordered parent lattice of the β-manganese-type. It appears however that for stabilization of Nb3Au2 non metals, such as oxygen, nitrogen or carbon have to be present. The phase of formula Nb55Au45 having β-Mn-structure reported in the literature cannot be observed in purely binary Nb-Au-alloys.
    Notes: Zusammenfassung Legierungen in den Systemen: {Zr, Hf, V, Nb, Ta}-{Ni, Cu, Ag, Au}-{Zn, Al, Ga, Sn, Pb} werden aus den Komponenten vorzugsweise im Verhältnis 50–60 At%T-, 10–30 At% 8a-und 1b-Metall und 15–40 At% 2b–4b-Metall hergestellt. Die Phasen Zr3Cu2Zn, Zr3Ag2Zn, Zr3Au2Al, Hf3Cu2Zn, Hf3Au2Al kristallisieren im Ti2Ni-Typ bzw. in einer Variante desselben. Hf5Sn4 ist mit Ti5Ga4 isotyp, dagegen lassen sich homogene Legierungen mit fast gleicher Struktur wie Zr5Pb3Cu, Hf5Sn3Ni, Hf5Sn3Cu und Hf5Pb3Cu ebensogut zum aufgefüllten Mn5Si3-Typ zählen. Die kleinen Ni- und Cu-Atome übernehmen dabei die Rolle von Nichtmetallen. V3(Au,Ga)2Nx, Nb3(Au,Ga)2Nx und Ta3(Au,Ga)2Nx besitzen ein metallisches Wirtgitter vom β-Mangan-Typ; bei Nb3Au2 scheint die Anwesenheit von Stickstoff (Sauerstoff) zur Stabilisierung des β-Mn-Carbid-Typs erforderlich. Die in der Literatur1 angegebene Phase Nb55Au45 mit β-Mn-Typ konnte in stickstoff-freien (binären) Legierungen nicht erhalten werden.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Monatshefte für Chemie 97 (1966), S. 221-229 
    ISSN: 1434-4475
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Abstract X-ray studies were carried out within the ternary system Ce−Th(U)−Si using sintered specimens. A preliminary phase diagram of the binary system cerium-silicon has been established on the basis of additional metallographic findings and melting point measurements. Besides the already described phases Ce3Si2, CeSi, CeSi〈2 and CeSi2 two new compounds Ce∼2Si and Ce∼1,2Si have been detected. The crystal structure of Ce3Si2 has been confirmed, the lattice parameter being determined. The ternary system Ce−Th−Si is characterized by the presence of three continuous solid solution series (Ce,Th)3Si2, (Ce,Th)Si and (Ce,Th)Si2. By contrast the mutual solubility of the Ce- and U-silicides in the system Ce−U−Si is low.
    Notes: Zusammenfassung Die Dreistoffe Ce−Th(U)−Si werden mittels gesinterter Proben röntgenographisch untersucht. Aus Schmelzpunktsmessungen und Gefügebeobachtung wird ein vorläufiges Zustandsschaubild von Cer-Silicium aufgestellt. Neben den bereits bekannten Phasen Ce3Si2, CeSi, CeSi〈2 und CeSi2 werden zwei neue Verbindungen gefunden: Ce∼2Si und Ce∼1,2Si. Der U3Si2-Typ für Ce3Si2 wird bestätigt, die Gitterparameter werden ermittelt. Der Dreistoff Ce−Th−Si ist durch das Auftreten der lückenlosen Mischreihen (Ce,Th)3Si2, (Ce,Th)Si und (Ce,Th)Si2 gekennzeichnet. Im Gegensatz dazu sind im System Ce−U−Si die gegenseitigen Löslichkeiten der Ce- bzw. U-Silicide gering.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Monatshefte für Chemie 95 (1964), S. 552-557 
    ISSN: 1434-4475
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Zusammenfassung Die Phasen Nb3Ga2, Ta5Ga3 und Ta5Al3Bx werden aus den Komponenten hergestellt. Nb3Ga2 kristallisiert im U3Si2-Typ, Ta5Ga3 hat Cr5Br3-Struktur (T 2) und Ta5Al3Bx ist mit Mn5Si3 (teilweise aufgefüllt) isotyp.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Monatshefte für Chemie 95 (1964), S. 1497-1501 
    ISSN: 1434-4475
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Abstract Hot-pressed W-B alloys in the range of about 50 Atomic % boron, annealed at 1200 and 1400°C and quenched, consist of a monoboride phase having a transposition structure. The crystal structure can be derived from an intermediate arrangement of the both δ-MoB- and CrB-types, the shift vector found to be: a/2+b/2.
    Notes: Zusammenfassung In heißgepreßten W-B-Legierungen, bei 1200 und 1400°C geglüht und rasch abgekühlt, tritt im Bereich des Monocarbids bei Bor-defekt eine Transpositionsstruktur auf, die zwischen dem δ-MoB- und dem CrB-Typ vermittelt. Der Transpositionsvektor ist: a/2+b/2.
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