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161.
162.
Pressed pellets of polyoxometalate (POM)-based materials are shown to undergo morphogenesis to produce microtubular network architectures without the need for a large single crystal precursor. The compression of the POM material into a pellet lowers the solubility sufficiently to allow tube initiation and growth from POMs that would otherwise be too soluble in their native crystalline state, thus yielding hollow, highly controllable, tubes of diameter 10-100 μm. 相似文献
163.
Augenstein T Oña-Burgos P Nied D Breher F 《Chemical communications (Cambridge, England)》2012,48(54):6803-6805
We report the synthesis and properties of alkynyl-functionalised and -bridged bicyclo[1.1.1]pentane derivatives consisting of the heavier group 14 elements silicon and tin. 相似文献
164.
C Leroy S Lani KG Sabra WS Hodgkiss WA Kuperman P Roux 《The Journal of the Acoustical Society of America》2012,132(2):883-893
Extracting coherent wavefronts between passive receivers using cross-correlations of ambient noise (CAN) provides a means for monitoring the seismoacoustic environment without using active sources. However, using cross-correlations between single receivers can require a long recording time in order to extract stable coherent arrivals from CAN. This becomes an issue if the propagation medium fluctuates significantly during the recording period. To address this issue, this article presents a general spatio-temporal filtering procedure to enhance the emergence rate for coherent wavefronts extracted from time-averaged ambient noise correlations between two spatially separated arrays. The robustness of this array-based CAN technique is investigated using ambient shipping noise recorded over 24?h in the frequency band [250-850 Hz] on two vertical line arrays deployed 143?m apart in shallow water (depth 20?m). Experimental results confirm that the array-based CAN technique can significantly reduce the recording duration (e.g., from 22?h to 30?min) required for extracting coherent wavefronts of sufficient amplitude (e.g., 20?dB over residual temporal fluctations) when compared to conventional CAN implementations between single pairs of hydrophones. These improvements of the CAN technique could benefit the development of noise-based ocean monitoring applications such as passive acoustic tomography. 相似文献
165.
Zero-term rank preservers 总被引:2,自引:0,他引:2
We obtain characterizations of those linear operators that preserve zero-term rank on the m×n matrices over antinegative semirings. That is, a linear operator T preserves zero-term rank if and only if it has the form T(X)=P(B∘X)Q, where P, Q are permutation matrices and B∘X is the Schur product with B whose entries are all nonzero and not zero-divisors. 相似文献
166.
167.
O.N. Ulenikov E.S. Bekhtereva H. Bürger C. Leroy 《Journal of Molecular Spectroscopy》2004,226(1):7-23
The absorption bands ν1+ν2, ν2+ν3, and ν2+ν6 of PH2D have been recorded for the first time using a high-resolution Bruker 120 HR interferometer, and rotationally analyzed. Some transitions belonging to the very weak band ν2+ν5 and enhanced in intensity by strong interactions with the ν1+ν2 band were also assigned. Sets of parameters obtained from the fit reproduce experimental line position of the bands ν1+ν2 and ν2+ν3 with about the experimental accuracy. The residuals of the ro-vibrational energies of the ν2+ν6 band are about 10 times larger. Reasons for the poorer reproduction of the latter data are given. 相似文献
168.
This paper concerns three notions of rank of matrices over semirings; real rank, semiring rank and column rank. These three rank functions are the same over subfields of reals but differ for matrices over subsemirings of nonnegative reals. We investigate the largest values of r for which the real rank and semiring rank, real rank and column rank of all m×n matrices over a given semiring are both r, respectively. We also characterize the linear operators which preserve the column rank of matrices over certain subsemirings of the nonnegative reals. 相似文献
169.
Leroy W. Mc. Cay 《Analytical and bioanalytical chemistry》1887,26(1):635-636
170.
To study local mode XY3 molecules, we use properties of the group chain U(4)⊃U(3)⊃K(3)⊃S(3)≈C3v. For the Hamiltonian, we deduce diagonal terms and coupling terms between bonds. We analyze the stretching modes of the arsine molecule. An algebraic transition operator is built and applied to the same molecular system. 相似文献