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991.
Asymmetric scaling of a square matrixA 0 is a matrix of the formXAX
–1 whereX is a nonnegative, nonsingular, diagonal matrix having the same dimension ofA. Anasymmetric scaling of a rectangular matrixB 0 is a matrix of the formXBY
–1 whereX andY are nonnegative, nonsingular, diagonal matrices having appropriate dimensions. We consider two objectives in selecting a symmetric scaling of a given matrix. The first is to select a scalingA of a given matrixA such that the maximal absolute value of the elements ofA is lesser or equal that of any other corresponding scaling ofA. The second is to select a scalingB of a given matrixB such that the maximal absolute value of ratios of nonzero elements ofB is lesser or equal that of any other corresponding scaling ofB. We also consider the problem of finding an optimal asymmetric scaling under the maximal ratio criterion (the maximal element criterion is, of course, trivial in this case). We show that these problems can be converted to parametric network problems which can be solved by corresponding algorithms.This research was supported by NSF Grant ECS-83-10213. 相似文献
992.
Magnetic metal and metal oxide nanoparticles capped with alkylamines have been synthesized and characterized by transmission
electron microscopy. X-ray diffraction, energy dispersive X-ray analysis and magnetization measurements. Core-shell Pd-Ni
particles with composition, Pd561Ni3000, (diameter ∼3.3 nm) are superparamagnetic at 5 K and organize themselves into two-dimensional crystalline arrays. Similar
arrays are obtained with Pd561Ni3000Pd1500 nanoparticles containing an additional Pd shell. Magnetic spinel particles of γ-Fe2O3, Fe3O4 and CoFe2O4 of average diameters in the 4–6 nm range coated with octylamine are all supermagnetic at room temperature and yield close-packed
disordered arrays. Relatively regular arrays are formed by dodecylaminecapped Fe3O4 nanoparticles (∼8.6 nm diameter) while well-ordered hexagonal arrays were obtained with octylamine-covered Co3O4 nanoparticles (∼4.2 nm diameter). 相似文献
993.
讨论了一维奇异P-Laplace方程{φp(u′))′ f(t,u)=0,t∈(0,1);u(0=u(1)=0存在C^1[0,1]或C[0,1]正解的一个充分必要条件.用到的方法主要有上下解方法和Schaude,不动点定理. 相似文献
994.
995.
V Werner D Belic P von Brentano C Fransen A Gade H von Garrel J Jolie U Kneissl C Kohstall A Linnemann A.F Lisetskiy N Pietralla H.H Pitz M Scheck K.-H Speidel F Stedile S.W Yates 《Physics letters. [Part B]》2002,550(3-4):140-146
Following the successful identification of mixed-symmetric one- and two-phonon states in the N=52 nuclei 94Mo and 96Ru, we have performed a photon scattering experiment on the N=52 isotone 92Zr. Experimental data and shell model calculations show that both, single particle and collective degrees of freedom are present in the low-lying levels of 92Zr. The second excited quadrupole state shows the signatures of the one-phonon mixed-symmetric 2+ state, while calculations and data indicate an almost pure neutron configuration for the 2+1 state, in contradiction with the F-spin symmetric limit. Furthermore, two strong dipole excitations, which are candidates for the two-phonon quadrupole–octupole coupled E1 excitation and for the mixed-symmetric 1+ two-phonon state, were observed. 相似文献
996.
U. Kulshreshtha D. S. Kulshreshtha 《International Journal of Theoretical Physics》2002,41(10):1941-1956
The nonlinear sigma model in one-space one-time dimension is considered on the light-front. The front-form theory is seen to possess a set of three first-class constraints and consequently it possesses a local vector gauge symmetry. This is in contrast to the usual instant-form theory, which is well known to be a gauge noninvariant theory possessing a set of four second-class constraints. The front-form Hamiltonian, path integral, and BRST formulations of this theory are investigated under some specific gauge choices. 相似文献
997.
The validity of the local-potential approximation, which was proposed previously for the singlet-pairing problem in semi-infinite nuclear matter, is investigated in the Bethe-Goldstone equation for the Brueckner G matrix. For this purpose, use is made of the method developed earlier for solving this equation for a planar slab of nuclear matter in the case of a separable form of NN interaction. The 1 S 0 singlet and the 3 S 1+3 D 1 triplet channel are considered. The complete two-particle Hilbert space is split into a model and the complementary subspace that are separated by an energy E 0. The two-particle propagator is calculated precisely in the first subspace, and the local-potential approximation is used in the second subspace. With an eye to subsequently employing the G matrix to calculate the Landau-Migdal amplitude, the total two-particle energy is fixed at E=2μ, where μ is the chemical potential of the system under consideration. Specific numerical calculations are performed at μ=?8 MeV. The applicability of the local-potential approximation is investigated versus the cutoff energy E 0. It is shown that, in either channel being considered, the accuracy of the local-potential approximation is rather high for E 0≥10 MeV. 相似文献
998.
C. Fabre U. Andersen H. Bachor B. Buchler S. Gigan P. K. Lam A. Maître N. Treps 《Superlattices and Microstructures》2002,32(4-6)
Optical images can be used to transport, store and process information in a parallel way. We discuss different results obtained in the domain of ‘quantum imaging’, aiming at exploiting at the same time the quantum properties of optical images and their intrinsic parallelism. We define the notion of standard quantum limit (SQL) in optical resolution, set by the quantum noise of usual coherent light, and show that it can be much lower than the diffraction limit. We also prove that this limit can be circumvented by especially designed nonclassical and multimode light. We present an experiment showing that OPOs oscillating inside an exactly confocal cavity actually produce such transverse multimode nonclassical light. We finally describe another experiment which has surpassed the SQL in the case of beam positioning, both in the 1D and 2D cases. 相似文献
999.
Herrmann J Griebner U Zhavoronkov N Husakou A Nickel D Knight JC Wadsworth WJ Russell PS Korn G 《Physical review letters》2002,88(17):173901
We report on an experimental study of supercontinuum generation in photonic crystal fibers with low-intensity femtosecond pulses, which provides evidence for a novel spectral broadening mechanism. The observed results agree with our theoretical calculations carried out without making the slowly varying envelope approximation. Peculiarities of the measured spectra and their theoretical explanation demonstrate that the reason for the white-light generation in photonic crystal fibers is fission of higher-order solitons into redshifted fundamental solitons and blueshifted nonsolitonic radiation. 相似文献
1000.
We relate the semiclassical asymptotics of the 6j symbols for the quantized enveloping algebra
at q a root of unity (resp. q real positive) to the geometry of spherical (resp. hyperbolic) tetrahedra. 相似文献