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991.
Motivated by Gauss's first proof of the Fundamental Theorem of Algebra, we study the topology of harmonic algebraic curves.
By the maximum principle, a harmonic curve has no bounded components; its topology is determined by the combinatorial data
of a noncrossing matching. Similarly, every complex polynomial gives rise to a related combinatorial object that we call a
basketball, consisting of a pair of noncrossing matchings satisfying one additional constraint. We prove that every noncrossing
matching arises from some harmonic curve, and deduce from this that every basketball arises from some polynomial. 相似文献
992.
The paper presents a theoretical-numerical hybrid method for determining the stresses distribution in composite laminates
containing a circular hole and subjected to uniaxial tensile loading. The method is based upon an appropriate corrective function
allowing a simple and rapid evaluation of stress distributions in a generic plate of finite width with a hole based on the
theoretical stresses distribution in an infinite plate with the same hole geometry and material. In order to verify the accuracy
of the method proposed, various numerical and experimental tests have been performed by considering different laminate lay-ups;
in particular, the experimental results have shown that a combined use of the method proposed and the well-know point-stress
criterion leads to reliable strength predictions for GFRP or CFRP laminates with a circular hole.
Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 43, No. 4, pp. 531–570, July–August, 2007. 相似文献
993.
A. Subramanian T.-Y. Choi L.X. Dong J. Tharian U. Sennhauser D. Poulikakos B.J. Nelson 《Applied Physics A: Materials Science & Processing》2007,89(1):133-139
We report on a novel method for local control of shell engineering in multiwalled carbon nanotubes (MWNTs) using Joule-heating
induced electric breakdown. By modulating the heat dissipation along a nanotube, we can confine its thinning and shell breakdown
to occur within localized regions of peak temperatures, which are distributed over one-half of the NT length. The modulation
is achieved by using suitably designed nanomachined heat sinks with different degrees of thermal coupling at different parts
of a current-carrying nanotube. The location of electric breakdown occurs precisely at the regions of high temperatures predicted
by the classical finite-element model of Joule heating in the MWNT. The experiments herein provide new insight into the electric
breakdown mechanism and prove unambiguously that shell removal occurs due to thermal stress, underpinning the diffusive nature
of MWNTs. The method demonstrated here has the potential to be a powerful tool in realizing MWNT bearings with complex architectures
for use in integrated nanoelectromechanical systems (NEMS). In addition, the breakdown current and power in the nanotubes
are significantly higher than those observed in nanotubes without heat removal via additional heat sinks. This indicates future
avenues for enhancing the performance of MWNTs in electrical interconnect and nanoelectronic applications.
PACS 73.63.Fg; 65.80.+n 相似文献
994.
Y. Zhao W.C. Zhai W.L. Seah K.Y. Lim F.C. Cheong C.H. Sow 《Applied physics. B, Lasers and optics》2007,87(2):243-247
A study of the variation of the spectral shape and the harmonic distribution of the high-order harmonics generated from silver
plasma on the frequency chirp of the driving laser radiation (793 nm 48 fs) is reported. The results of the systematic study
of the harmonic generation from the 21st order up to the 61st order (λ=13 nm) are presented. A tuning of the harmonic wavelength
up to 0.8 nm can be accomplished by variation of the laser chirp.
PACS 42.65.Ky; 42.79.Nv; 52.38.Mf 相似文献
995.
The solution of the problem of magnetic field penetration into a conducting unclosed ellipsoidal sheath in the presence of a conducting thick-walled spherical sheath is reduced to the solution of the integral Fredholm equation of the second kind. The effect of the apex angle of the unclosed ellipsoidal sheath, geometric parameters of the screens, and electrophysical properties of the spherical sheath material on the field attenuation coefficient inside the ellipsoidal sheath is studied numerically. 相似文献
996.
It is suggested to take as pH of the precipitation onset of metal hydroxides the pH at which 10% of the initial amount of metal ions has precipitated. An equation for calculating this quantity is presented. 相似文献
997.
The paper studies the Painlevé VIe equations from the point of view of Hamiltonian nonintegrability. For certain infinite number of points in the parameter
space we prove that the equations are not integrable. Our approach uses recent advance in Hamiltonian integrability reducing
the problem to higher differential Galois groups as well as the monodromy of dilogarithic functions.
相似文献
998.
We prove the vanishing of the Koszul homology group H
μ(Kos(M)μ), where μ is the minimal number of generators of M. We give a counterexample that the Koszul complex of a module is not always
acyclic and show its relationship with the homology of commutative rings. 相似文献
999.
F. F. Dedus L. I. Kulikova S. A. Makhortykh N. N. Nazipova A. N. Pankratov R. K. Tetuev 《Moscow University Computational Mathematics and Cybernetics》2007,31(2):49-53
The analysis problem for genetic sequences is formulated from the viewpoint of modern mathematical and information approaches. Statistical, correlative, entropic, and spectral approaches are considered. A brief introduction into the background of the problem is given. Genesis of a new interdisciplinary subject area, bioinformatics, a science considering application of computer methods in biological studies, is analyzed. New approaches to studying macromolecular systems on the basis of combined spectral-analytic technologies are proposed. Estimates of the algorithmic complexity of implementation of the proposed approaches are presented. 相似文献
1000.