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1.
Stylianos S. Stamatakis 《Journal of Geometry》1992,44(1-2):177-183
In this paper we study some vectorfields arising in the theory of rectilinear congruences in the real Euclidean space E3. We also derive some integral formulae concerning the vectorfields above. 相似文献
2.
We investigate some relations concerning the first and the second Beltrami operators corresponding to the fundamental forms I, II, III of a surface in the Euclidean space E3 and we study surfaces which are of finite type in the sense of B.-Y. Chen with respect to the fundamental forms II and III. 相似文献
3.
Elena V. Frolova M. Ivanovskaya V. Sadykov G. Alikina A. Lukashevich S. Neophytides 《Progress in Solid State Chemistry》2005,33(2-4):317-325
Structural peculiarities of Ce–Zr–La–O and Ce–Zr–La–O/Ru samples in mean of catalytic properties are compared. The samples (Ce:Zr = 1:1, La = 10÷30 mol.%, Ru = 1.5 wt.%) were obtained by sol–gel method (X-samples) and co-precipitation (P-samples). It is shown that Ce0.45Zr0.45La0.1O2−δ/Ru X-samples are characterized by high thermal stability and the highest catalytic activity in partial methane oxidation reaction. According to XRD, BET, FTIR, EPR and XPS data it is concluded that the difference in the samples catalytic activity is caused by various disposition of Ru-containing phase on the support surface. The distinction in the dimension of Ru-containing particles (3D or 2D) is conditioned by structural peculiarities of Ce0.45Zr0.45La0.1O2−δ and Ce0.35Zr0.35La0.3O2−δ P- and X-samples. 相似文献
4.
Stylianos Stamatakis 《manuscripta mathematica》1991,71(1):29-33
Let ℱ: x=x(u1, u2) be a C3-surface in the euclidean space E3, n the unit normal vector of ℱ and let
. We consider the vector
of ℝ6 and we denote with μ the rank of the matrix (a, a1, a2, a1, 1, a1, 2, a2, 2). We then prove the Theorem: ℱ is a W-surface if and only if μ≦5. Further, μ is 4 resp. 3 if and only if the surface ℱ is
part of a cylinder of revolution resp. part of a sphere or a plane.
相似文献
5.
6.
Dr. Peter Thumbs M. Sc. Timm T. Ensfelder M. Sc. Markus Hillmeier Dr. Mirko Wagner M. Sc. Matthias Heiss M. Sc. Constanze Scheel M. Sc. Alexander Schön Dr. Markus Müller Prof. Dr. Stylianos Michalakis Dr. Stefanie Kellner Prof. Dr. Thomas Carell 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(30):12451-12455
7.
A time-domain nonlinear system identification method based on multiscale dynamic partitions 总被引:1,自引:0,他引:1
Young S. Lee Stylianos Tsakirtzis Alexander F. Vakakis Lawrence A. Bergman D. Michael McFarland 《Meccanica》2011,46(4):625-649
Based on a theoretical foundation for empirical mode decomposition, which dictates the correspondence between the analytical
and empirical slow-flow analyses, we develop a time-domain nonlinear system identification (NSI) technique. This NSI method
is based on multiscale dynamic partitions and direct analysis of measured time series, and makes no presumptions regarding
the type and strength of the system nonlinearity. Hence, the method is expected to be applicable to broad classes of applications
involving time-variant/time-invariant, linear/nonlinear, and smooth/non-smooth dynamical systems. The method leads to nonparametric
reduced order models of simple form; i.e., in the form of coupled or uncoupled oscillators with time-varying or time-invariant coefficients forced by nonhomogeneous
terms representing nonlinear modal interactions. Key to our method is a slow/fast partition of transient dynamics which leads
to the identification of the basic fast frequencies of the dynamics, and the subsequent development of slow-flow models governing
the essential dynamics of the system. We provide examples of application of the NSI method by analyzing strongly nonlinear
modal interactions in two dynamical systems with essentially nonlinear attachments. 相似文献
8.
Controlled variation in catalyst-electrode potential of metals interfaced with solid electrolytes leads to the effect of Non-faradaic
Modification of Catalytic Activity (NEMCA) which causes dramatic changes in the catalytic activity and selectivity. Its origin
was shown to lie in the controlled variation of the work function upon polarization of the catalyst-solid electrolyte interface
which is due to ion spillover over the entire gas exposed catalyst surface. In the present work the effect of induced work
function changes on the kinetics and energetics of the interaction of oxygen with polycrystalline Pt, interfaced with an yttria
stabilized zirconia solid electrolyte, were studied, by means of the temperature programmed desorption technique. It was found
that by increasing catalyst potential and work function the O2 desorption peak shifts towards lower temperatures, showing that the binding strength of chemisorbed oxygen species weakens
by increasing catalyst work function. The activation energy of desorption of adsorbed O species was measured by the “temperature
rate variation technique” and was found to decrease linearly with slope -1 with increasing catalyst work function. This straightforward
experimental correlation between catalyst work function and the binding energy of chemisorbed O species is in absolute agreement
with previous NEMCA studies which show that the apparent activation energy of all reactions studied, depends linearly on catalyst
potential and work function.
Paper presented at the 1st Euroconference on Solid State Ionics, Zakynthos, Greece, 11 – 18 Spt. 1994 相似文献
9.
The Thermal Desorption or Temperature Programmed Desorption (TPD) technique has been used for the study of oxygen adsorption
on Pt, Ag and Au catalyst films deposited on YSZ. The catalyst film was deposited on the one side of the YSZ specimen while
on the other side gold counter and reference electrodes were deposited, constructing a three-electrode electrochemical cell
similar to those used in Electrochemical Promotion studies. Oxygen adsorption has been carried out either by exposing the
samples to gaseous oxygen (gas phase adsorption) or by the application of a constant current between the catalyst/working
electrode and the counter electrode (electrochemical adsorption) or by mixed gas phase and electrochemical adsorption. Oxygen
adsorption was carried out at temperatures between 200 and 480 °C. After exposure to gaseous oxygen, normal adsorbed atomic
oxygen species have been observed on Pt and Ag surfaces while there was no detectable amount of adsorbed oxygen on Au. Electrochemical
O2− pumping to Pt, Ag and Au catalyst films creates strongly bonded “backspillover” anionic oxygen, along with the more weakly
bonded atomic oxygen. Electrochemical O2− pumping to Pt, Ag and Au catalyst films in presence of preadsorbed oxygen creates strongly bonded “backspillover” anionic
oxygen, with a concomitant pronounced lowering of the Tp of the more weakly bound preadsorbed atomic oxygen. The two oxygen species co-exist on the surface. The activation energy
for oxygen desorption or, equivalently, the binding strength of adsorbed oxygen was found to decrease linearly with increasing
catalyst potential, for all three metal electrodes.
Paper presented at the 4th Euroconference on Solid State Ionics, Renvyle, Galway, Ireland Sept. 13–19, 1997 相似文献
10.
A. C. Kaloyannis C. A. Pliangos D. T. Tsiplakides I. V. Yentekakis S. G. Neophytides S. Bebelis C. G. Vayenas 《Ionics》1995,1(5-6):414-420
The effect of non-Faradaic electrochemical modification of catalytic activity (NEMCA) or electrochemical promotion (EP) was
investigated on Pt films deposited on Y2O3-stabilized-ZrO2 (YSZ), an O2− conductor, TiO2, a mixed conductor, and Nafion 117 solid polymer electrolyte (SPE), a H+ conductor and also on Pd films deposited on YSZ and β″-Al2O3 a Na+ conductor. Four catalytic systems were investigated, i.e. C2H6 oxidation on Pt/YSZ, C2H4 oxidation on Pd/YSZ and Pd/β″-Al2O3, C2H4 oxidation on Pt/TiO2 and H2 oxidation on Pt/Nafion 117 in contact with 0.1 M aqueous KOH solution.
In all cases pronounced and reversible non-Faradaic electrochemical modification of catalytic rates was observed with catalytic
rate enhancement up to 2000% and Faradaic efficiency values up to 5000.
All reactions investigated exhibit a pronounced electrophobic behaviour which is due to the weakening of chemisorptive oxygen
bond at high catalyst potentials. Ethane oxidation, however, also exhibits electrophilic behaviour at low potentials due to
weakened binding of carbonaceous species on the surface.
The general features of the phenomenon are similar for all four cases presented here showing that the NEMCA effect is a general,
electrochemically induced, promoting catalytic phenomenon not depending on the reaction and the type of supporting electrolyte.
Paper presented at the 2nd Euroconference on Solid State Ionics, Funchal, Madeira, Portugal, Sept. 10–16, 1995 相似文献