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41.
G. Michałek B.R. Bułka 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,28(1):121-128
The currents and their fluctuations in two capacitively coupled single electron transistors are determined in the limit of
sequential tunnelling. Our considerations are restricted to the case when the islands (dots) of the transistors are atomic-sized,
which means each of them has only one single electronic level available for the tunnelling processes. The Coulomb interactions
of accumulated charges on the both single electron transistors lead to the effect of the negative differential resistance.
An enhancement of the current shot-noise was also found. Spectral decomposition analysis indicated the two main contributions
to the shot-noise: low- and high-frequency fluctuations. It was found that the low frequency fluctuations (polarization noise)
are responsible for a strong enhancement of the current noise.
Received 9 October 2001 / Received in final form 8 March 2002 Published online 9 July 2002 相似文献
42.
On the numerical solution of axisymmetric domain optimization problems by dual finite element method
Shape optimization of an axisymmetric three-dimensional domain with an elliptic boundary value state problem is solved. Since the cost functional is given in terms of the cogradient of the solution, a dual finite element method based on the minimum of complementary energy principle is used. © 1994 John Wiley & Sons, Inc. 相似文献
43.
Adducts of the conjugate addition of benzylamine to enantiopure amides of aroylacrylic acid possess high enantiomeric and diastereomeric purity. A high degree of stereoselectivity has been achieved by means of crystallization-induced asymmetric transformation. A practical synthesis leading to dipeptides containing homophenylalanine is depicted. 相似文献
44.
František Toman Ludvík Beneš 《Journal of inclusion phenomena and macrocyclic chemistry》2007,59(3-4):231-236
Differential molar adsorption enthalpies (DMAE) were determined by gas chromatographic measurements of specific retention
volume of vapors on the surface of two forms of Mg–Al hydrotalcite. A linear dependence of the DMAE on the number of the carbon
atoms in hydrocarbons was observed for both form of hydrotalcite. The dependence of the differential molar adsorption enthalpies
on the number of chlorine atoms in organic molecules is discussed. A linear dependence of DMAE on the molecular weight of
chloroderivatives of methane and ethylene on the basic form in an order monochloromethane < dichloromethane < trichloromethane
or vinylidene chloride < 1,1-dichloroethylene < trichloroethylene was found. 相似文献
45.
Adsorption of the copper ions from aqueous solutions, benzene, and water on the active carbon obtained by chemical activation
from walnut shells was studied. The active carbon was additionally oxidized with hydrogen peroxide and then impregnated with
nitrogen-containing compounds. As a result of impregnation with melamine, a secondary porosity is formed within the oxidized
active carbon, leading to an increase in the specific surface of the sorbent. A modified carbon surface is heterogeneous,
and the carbons themselves exhibit catalytic activity in the oxidation of luminol and decomposition of hydrogen peroxide. 相似文献
46.
R. Strašek 《Acta Mathematica Hungarica》2003,101(1-2):63-68
We consider the class of Euclidean algebras associated to Minkowski light cones and called Lorentz algebras. We prove that in Lorentz algebras the estimate ∥P(a,b) ∥∞≥(√2-1) ∥a∥∞ ∥b∥∞ is valid for the spectral norm and is therefore independent of the dimension of the Lorentz algebra. 相似文献
47.
We prove lower bounds of the form exp(nε d), εd > 0, on the length of proofs of an explicit sequence of tautologies, based on the Pigeonhole Principle, in proof systems using formulas of depth d, for any constant d. This is the largest lower bound for the strongest proof system, for which any superpolynomial lower bounds are known. 相似文献
48.
49.
Jan Kraí
ek 《Mathematical Logic Quarterly》1998,44(4):450-458
We introduce a notion of a real game (a generalisation of the Karchmer-Wigderson game (cf. [3]) and of real communication complexity, and relate this complexity to the size of monotone real formulas and circuits. We give an exponential lower bound for tree-like monotone protocols (defined in [4, Definition 2.2]) of small real communication complexity solving the monotone communication complexity problem associated with the bipartite perfect matching problem. This work is motivated by a research in interpolation theorems for prepositional logic (by a problem posed in [5, Section 8], in particular). Our main objective is to extend the communication complexity approach of [4, 5] to a wider class of proof systems. In this direction we obtain an effective interpolation in a form of a protocol of small real communication complexity. Together with the above mentioned lower bound for tree-like protocols this yields as a corollary a lower bound on the number of steps for particular semantic derivations of Hall's theorem (these include tree-like cutting planes proofs for which an exponential lower bound was demonstrated in [2]). 相似文献
50.
A special two-sided condition for the incremental magnetic reluctivity is introduced which guarantees the unique existence of both the weak and the approximate solutions of the nonlinear stationary magnetic field distributed on a region composed of different media, as well as a certain estimate of the error between the two solutions. The condition, being discussed from the physical as well as the mathematical point of view, can be easily verified and is fulfilled for various magnetic reluctivity models used in electrotechnical practice. 相似文献