74 resultados para Series Expansions


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Gaining insight into the mechanisms of chemoreception in aphids is of primary importance for both integrative studies on the evolution of host plant specialization and applied research in pest control management because aphids rely on their sense of smell

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A gain measurement technique, based on Fourier series expansion of periodically extended single fringe of the amplified spontaneous emission spectrum, is proposed for Fabry-Perot semiconductor lasers. The underestimation of gain due to the limited resolution of the measurement system is corrected by a factor related to the system response function. The standard deviations of the gain-reflectivity product under low noise conditions are analyzed for the Fourier series expansion method and compared with those of the Hakki-Paoli method and Cassidy's method. The results show that the Fourier series expansion method is the least sensitive to noise among the three methods. The experiment results obtained by the three methods are also presented and compared.

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An electro-optic variable optical attenuator in silicon-on-insulator is designed and fabricated. A series Structure is used to improve the device efficiency Compared to the attenuator in the single p-i-n diode Structure in the same modulating length, the attenuation range of the device in the series structure improves 2-3 times in the same injecting current density, while the insertion loss is not affected. The maximum dynamic attenuation of the device is greater than 30 dB. The response frequency is obtained to be about 2 MHz.

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Within the Buttiker dephasing model, the backscattering in the dephasing process is eliminated by setting a proper boundary condition. Explicit expression is carried out for the effective total tunneling probability in the presence of multiple pure dephasing scatterers with partial coherence. The derived formula is illustrated analytically by various limiting cases, and numerically for its application in tunneling through multibarrier systems.

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A systematic study of the phase formation, structure and magnetic properties of the R3Fe29-xTx compounds (R=Y, Ce, Nd, Sm, Gd, Tb, and Dy; T=V and Cr) has been performed upon hydrogenation. The lattice constants and the unit cell volume of R3Fe29-xTxHy decrease with increasing R atomic number from Nd to Dy, except for Ce, reflecting the lanthanide contraction. Regular anisotropic expansions mainly along the a- and b-axis rather than along the c-axis are observed for all of the compounds upon hydrogenation. Hydrogenation leads to an increase in the Curie temperature and a corresponding increase in the saturation magnetization at room temperature for each compound. First order magnetization processes (FOMP) occur in the external magnetic fields for Nd3Fe24.5Cr4.5H5.0, Tb3Fe27.0Cr2.0H2.8, and Gd3Fe28.0Cr1.0H4.2 compounds.

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A systematic investigation of crystallographic and intrinsic magnetic properties of the hydrides R3Fe29 - xVxHy (R = Y, Ce, Nd, Sm, Gd, Tb, and Dy) has been performed in this work. The lattice constants a, b, and c and the unit cell volume of R3Fe29 - xVxHy decrease with increasing rare-earth atomic number from Nd to Dy, except for Ce, reflecting the lanthanide contraction. Hydrogenation results in regular anisotropic expansions along the a-, b-, and c-axes in this series of hydrides. Abnormal crystallographic and magnetic properties of Ce3Fe27.5V1.5H6.5, like Ce3Fe27.5V1.5, suggest that the Ce ion is non-triply ionized. Hydrogenation leads to the increase in both Curie temperature for all the compounds and in the saturation magnetization at 4.2 K and RT for R3Fe29 - xVx with R = Y, Ce, Nd, Sm, Gd, and Dy, except for Tb. Hydrogenation also leads to a decrease in the anisotropy field at 4.2 K and RT for R3Fe29 - xVx with R = Y, Ce, Nd, Gd, Tb, and Dy, except for Sm. The Ce3Fe27.5V1.5 and Gd3Fe28.4V0.6 show the larger storage of hydrogen with y = 6.5 and 6.9 in these hydrides. (C) 1998 Elsevier Science B.V. All rights reserved.

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We presented a series of symmetric double crystal X-ray diffraction (DCXD) measurements, (0 0 4), (2 2 0) and (2 - 2 0) diffraction, to investigate the strain relaxation in an InAs film grown on a GaAs(0 0 1) substrate. The strain tensor and rotation tensor were calculated according to the DCXD results. It is found that the misfit strain is relaxed nearly completely and the strain relaxation caused a triclinic deformation in the epilayer. The lattice parameter along the [1 1 0] direction is a little longer than that along the [1 - 1 0] direction. Furthermore, a significant tilt, 0.2 degrees, towards the [1 1 0] direction while a very slight one: 0.002 degrees, towards [1 - 1 0] direction were discussed. This anisotropic strain relaxation is attributed to the asymmetric distribution of misfit dislocations, which is also indicated by the variation of the full-width at half-maximum (FWHM) of (0 0 4) diffraction along four azimuth angles. (C) 1998 Elsevier Science B.V. All rights reserved.

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In modern process industry, it is often difficult to analyze a manufacture process due to its umerous time-series data. Analysts wish to not only interpret the evolution of data over time in a working procedure, but also examine the changes in the whole production process through time. To meet such analytic requirements, we have developed ProcessLine, an interactive visualization tool for a large amount of time-series data in process industry. The data are displayed in a fisheye timeline. ProcessLine provides good overviews for the whole production process and details for the focused working procedure. A preliminary user study using beer industry production data has shown that the tool is effective.

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Ocean acoustic propagation and reverberation in continental shelf regions is often controlled by the seabed and sea surface boundaries. A series of three multi-national and multi-disciplinary experiments was conducted between 2000-2002 to identify and measure key ocean boundary characteristics. The frequency range of interest was nominally 500-5000 Hz with the main focus on the seabed, which is generally considered as the boundary of greatest importance and least understood. Two of the experiments were conducted in the Mediterranean in the Strait of Sicily and one experiment in the North Atlantic with sites on the outer New Jersey Shelf (STRATAFORM area) and on the Scotian Shelf. Measurements included seabed reflection, seabed, surface, and biologic scattering, propagation, reverberation, and ambient noise along with supporting oceanographic, geologic, and geophysical data. This paper is primarily intended to provide an overview of the experiments and the strategies that linked the various measurements together, with detailed experiment results contained in various papers in this volume and other sources

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This paper describes the synthesis and selected reactions of a series of crystalline mono(beta-diiminato) yttrium chlorides 3a, 3b, 4a, 4b, 5a, 5b, 5c and 9. The X-ray structure of each has been determined, as well as of [YCl(L-4)(2)] (6), [Y(L-1)(2)OBut] (7) and [Y{CH(SiMe3)(2)}(thf)(mu-Cl)(2)Li(OEt2)(2)(mu-Cl)](2) (8).