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Wyszukujesz frazę "Phillips, O. A." wg kryterium: Autor


Wyświetlanie 1-4 z 4
Tytuł:
The geochemical composition of sediment as a proxy of provenance and weathering intensity: a case study of Southwest Nigeria’s Coastal Creeks
Autorzy:
Phillips, O. A.
Falana, A. O.
Adebayo, A. J.
Powiązania:
https://bibliotekanauki.pl/articles/184285.pdf
Data publikacji:
2017
Wydawca:
Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
Tematy:
Badagry Creek
Yewa Creek
elemental ratios
provenance
weathering
Opis:
The study of the geochemical composition of sediments was undertaken to evaluate the degree of weathering and appraise the relative proportion of mafic and felsic rock materials being transported from source to sink. Thirty-three surface sediment samples collected from the creeks were used for particle size and chemical analyses. An inductively coupled plasma-Mass Spectrometer was used to determine the elemental composition of the sediments. The clay dominated Yewa and western Badagry creeks gave evidence of higher average concentrations of Ni, Sr, Y, Nb, Sc, Co, V, and Th than the eastern end of segment of Badagry Creek. The data generated from elemental ratios such as Al 2 O 3 /TiO 2, TiO 2 /Zr and binary plots of Th/Sc-Cr/Sc, Th-Sc, Y/Ni-Cr/V, TiO 2 -Zr and ICV-CIA (index of compositional variability against chemical index of alteration) showed that source sediments are composed of upper and lower crustal compositions. Also, the creeks were marked by their variation in terms of the proportion of felsic and mafic components. For instance, Yewa and western Badagry creeks are more enriched in mafic constituents, whereas the enrichment of felsic materials is significant at the eastern end of Badagry Creek. Inferring from the chemical index of alteration and plagioclase index of alteration (PIA), the Yewa and western Badagry creeks have been moderately to intensely weathered and incipient weathering was identified in the eastern end of Badagry Creek.
Źródło:
Geology, Geophysics and Environment; 2017, 43, 3; 229-248
2299-8004
2353-0790
Pojawia się w:
Geology, Geophysics and Environment
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Piezoelectric Effect in Coherently Strained B-Doped (001)SiGe/Si Heterostructures
Autorzy:
Knizhny, V. I.
Mironov, O. A.
Makarovskii, O. A.
Braithwaite, G.
Mattey, N. L.
Parker, E. H. C.
Phillips, P. J.
Powiązania:
https://bibliotekanauki.pl/articles/1933806.pdf
Data publikacji:
1995-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.50.Rb
73.61.Cw
73.50.Μx
Opis:
We report on two methods which illustrate piezoelectric effects in the strained Si (100)Si $\text{}_{1-x}$/Ge$\text{}_{x}$ system. The non-contact sound excitation technique has been used to reveal the conversion of a high-frequency electric field E into acoustic waves at 77 K which can also be modulated by a dc applied bias voltage (±30 V). The sample was an MBE grown modulation doped Si $\text{}_{0.88}$Ge$\text{}_{0.12}$/(001)Si structure with a carrier sheet density 2.0 × 10 $\text{}^{11}$ cm$\text{}^{-2}$ and a 4.2 K mobility 10500 cm$\text{}^{2}$ V$\text{}^{-1}$ s$\text{}^{-1}$. We deduce that the observed high-frequency electric field acoustic wave conversion is associated with a piezoelectric-like effect possibly due to ordering in the strained SiGe alloy or symmetry breaking effect near Si/SiGe interface. Further evidence is provided by the existence of a piezoelectric phonon interaction in the hot hole energy relaxation mechanism determined from high electric field Shubnikov de Haas He$\text{}^{3}$ low temperature measurements.
Źródło:
Acta Physica Polonica A; 1995, 88, 4; 779-782
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Optical Study of MBE Grown Undoped Si-Si$\text{}_{1-x}$Ge$\text{}_{x}$/Si Superlattices
Autorzy:
Gnezdilov, V. P.
Mironov, M.
Yshakov, V.
Mironov, O. A.
Phillips, P. J.
Parker, E. H. C.
Powiązania:
https://bibliotekanauki.pl/articles/1952678.pdf
Data publikacji:
1996-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.30.-j
78.66.-w
78.66.Db
Opis:
Raman spectroscopy and spectroscopic ellipsometry have been used to characterize Si/Si$\text{}_{0.78}$Ge$\text{}_{0.22}$ superlattices grown by molecular beam epitaxy on (001)Si at different substrate temperatures. The results are interpreted to give information on material and interface quality, layer thicknesses, and state of strain. The observed frequencies of zone-folded longitudinal acoustic phonons in a high quality sample agree well with those calculated using Rytov's theory of acoustic vibrations in layered media.
Źródło:
Acta Physica Polonica A; 1996, 90, 5; 1045-1049
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Study of Two-Dimensional Hole Gas at Si/SiGe/Si Inverted Interface
Autorzy:
Sadeghzadeh, M. A.
Mironov, O. A.
Emeleus, C. J.
Parry, C. P.
Phillips, P. J.
Parker, E. H. C.
Whall, T. A.
Powiązania:
https://bibliotekanauki.pl/articles/1992074.pdf
Data publikacji:
1998-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.20.Fz
Opis:
We have studied the transport properties of a two-dimensional hole gas (2DHG) at the inverted interface of a strained Si$\text{}_{0.8}$Ge$\text{}_{0.2}$ quantum well. By application of a bias voltage to a Schottky gate on top of this inverted heterostructure the 2DHG density n$\text{}_{s}$ can be controlled, in the range of (1.5-5.2)×10$\text{}^{11}$ cm$\text{}^{-2}$. At a temperature T=0.33 K, the Hall mobility is 4650 cm$\text{}^{2}$ V$\text{}^{-1}$ s$\text{}^{-1}$ at the maximum carrier density. For lower sheet densities (n$\text{}_{s}$<2×10$\text{}^{11}$ cm$\text{}^{-2}$) the system undergoes a transition from a weak to strongly localised phase of significantly reduced mobility. From low temperature Shubnikov-de Haas oscillation measurements we have extracted the hole effective masses m*=(0.25 → 0.28)m$\text{}_{0}$ and the ratio of transport to quantum lifetimes α=(0.92 → 0.85) for the corresponding carrier density change of n$\text{}_{s}$=(5.2 → 2.5)×10$\text{}^{11}$ cm$\text{}^{-2}$. These results can be explained in terms of the abnormal movement of the hole wave function towards the interface with decreasing n$\text{}_{s}$, short range interface charge and interface roughness scattering.
Źródło:
Acta Physica Polonica A; 1998, 94, 3; 503-508
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-4 z 4

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