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排序方式: 共有1933条查询结果,搜索用时 15 毫秒
981.
Bjorlin E.S. Riou B. Keating A. Abraham P. Chiu Y.-J. Piprek J. Bowers J.E. 《Photonics Technology Letters, IEEE》2000,12(8):951-953
We demonstrate the first 1.3-μm vertical-cavity optical amplifier. The amplifier was optically pumped and operated in reflection mode. Optimization of the top mirror reflectivity resulted in a 9.4-dB continuous wave fiber-to-fiber gain, a gain-bandwidth product of 220 GHz, and a saturation output power of -6.1 dBm, all at room temperature. By modulating the pump source, an extinction ratio of 27 dB in the output signal power was obtained 相似文献
982.
Abraham Berman 《Linear algebra and its applications》2006,419(1):1-7
The purpose of this note is to address the computational question of determining whether or not a square nonnegative matrix (over the reals) is completely positive and finding its CP-rank when it is. We show that these questions can be resolved by finite algorithms and we provide (non-polynomial) complexity bounds on the number of arithmetic/Boolean operations that these algorithms require. We state several open questions including the existence of polynomial algorithms to resolve the above problems and availability of algorithms for addressing complete positivity over the rationals and over {0, 1} matrices. 相似文献
983.
U. German A. Abraham M. Weinstein Z. B. Alfassi 《Journal of Radioanalytical and Nuclear Chemistry》2007,273(3):729-732
Second readouts of TLD 100 crystals exposed to radiation are used to reassess high doses. When the second readout is performed
by a regular readout cycle of 13.3 s, the accuracy of the estimations is too low to be practical for low doses in the 10–100
mSv range. A simple and efficient method was studied, which consists of expanding the heating time to 30 s. The efficiency
relative to a 13.3 readout time is about three timesbetter, and also the background is lower, thus the reassessment efficiency
is significantly improved. 相似文献
984.
Aydiner A.A. Wen Cho Chew Tie Jun Cui Wright D.L. Smith D.V. Abraham J.D. 《Geoscience and Remote Sensing, IEEE Transactions on》2001,39(6):1307-1315
A simple and efficient method for large scale three-dimensional (3D) subsurface imaging of inhomogeneous background is presented. One-dimensional (1D) multifrequency distorted Born iterative method (DBIM) is employed in the inversion. Simulation results utilizing synthetic scattering data are given. Calibration of the very early time electromagnetic (VETEM) experimental waveforms is detailed along with major problems encountered in practice and their solutions. This discussion is followed by the results of a large scale application of the method to the experimental data provided by the VETEM system of the U.S. Geological Survey. The method is shown to have a computational complexity that is promising for on-site inversion 相似文献
985.
Shakouri A. Bin Liu Boo-Gyoun Kim Abraham P. Jackson A.W. Gossard A.C. 《Lightwave Technology, Journal of》1998,16(12):2236-2242
Wafer fusion technique for realization of compact waveguide switches and three-dimensional (3-D) photonic integrated circuits is investigated theoretically and experimentally. Calculations based on beam propagation method show that very short vertical directional couplers with coupling lengths from 40 to 220 μm and high extinction ratios from 20 to 32 dB can be realized. These extinction ratios can be further improved using a slight asymmetry in waveguide structure. The optical loss at the fused interface is investigated. Comparison of the transmission loss in InGaAsP-based ridge-loaded waveguide structures with and without a fused layer near the core region, reveals an excess loss of 1.1 dB/cm at 1.55 μm wavelength. Fused straight vertical directional couplers have been fabricated and characterized. Waveguides separated by 0.6 μm gap layer exhibit a coupling length of 62 μm and a switching voltage of about 2.2 V. Implications for GaAs-based fused couplers for 850 nm applications will also be discussed 相似文献
986.
H. Durchschlag C. Fochler K. Abraham B. Kulawik 《Radiation Physics and Chemistry》1999,55(5-6):691-697
The most important water-soluble components of the vertebrate eye (lens proteins, aqueous humor, vitreous, hyaluronic acid, ascorbic acid) have been investigated in aqueous solution, after preceding X- or UV-irradiation. Spectroscopic, chromatographic, electrophoretic, hydrodynamic and analytic techniques have been applied, to monitor several radiation damages such as destruction of aromatic and sulfur-containing amino acids, aggregation, crosslinking, dissociation, fragmentation, and partial unfolding. Various substances were found which were able to protect eye components effectively against radiation, some of them being also of medical relevance. 相似文献
987.
Abraham Chemtob Valrie Hroguez Yves Gnanou 《Journal of polymer science. Part A, Polymer chemistry》2004,42(5):1154-1163
Latex particles based on 1,4‐polybutadiene were synthesized via dispersion ring‐opening metathesis copolymerization of 1,5‐cyclooctadiene with a α‐norbornenyl poly(ethylene oxide) macromonomer. Stable but polydisperse colloidal dispersions in the 50 nm to 10 μm size range were obtained. In this work, particular attention was paid to the effects of the kinetics of copolymerization on the structure of the graft copolymers formed and on the onset of turbidity. Strategies to prepare monodisperse polybutadiene particles were also designed through the growth of a polybutadiene shell from a well‐defined polynorbornene seed. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1154–1163, 2004 相似文献
988.
Abraham F. Jalbout Kostyantyn Y. Pichugin Ludwik Adamowicz 《Theoretical chemistry accounts》2004,111(2-6):358-362
A very diffuse, but spatially confined, electron trapped in a dipole–bound state of a polar molecule provides an excellent target for testing the interaction of a localized electron positioned outside the molecular frame of its host molecule with other atomic or molecular systems. In this work we use ab initio calculations to investigate systems where a dipole–bound electron attached to a uracil molecule is interacting with an N2 molecule and an Ar atom. Neither of the two systems forms a stable anion and in the aducts they form with the dipole–bound electron the electron becomes suspended between the uracil molecule and Ar or N2. Calculations are performed to determine the vertical electron detachment energies of these anions and to determine the molecular rearrangements occurring when the excess electron is removed from them.Contribution to the Jacopo Tomasi Honorary Issue 相似文献
989.
We introduce the lexicographic balanced optimization problem (LBaOP) and show that it can be solved efficiently if an associated lexicographic bottleneck problem can be solved efficiently. For special cases of cuts in a graph and base system of a matroid, improved algorithms are proposed. A generalization of LBaOP is also discussed. 相似文献
990.
S. Ezrahi Ido Nir Abraham Aserin Nick Kozlovich Yuri Feldman Nissim Garti 《Journal of Dispersion Science and Technology》2013,34(1-3):351-378
The hydration behavior of the system polyoxyethylene (10) oleylalcohol [C18:1 (EO)10 or Brij 97]/water/dodecane/butanol (model system B) was investigated along a dilution line for which the respective weight ratio of dodecane:butanol:Brij 97 is 3:3:4. Two experimental methods were applied: time domain dielectric spectroscopy (TDDS) and sub-zero temperature differential scanning calorimetry (SZT-DSC). Two types of bound water (with melting peaks at -25 and -11°C) were detected by SZT-DSC (using the endothermic mode), whereas TDDS revealed only one such type. Nevertheless, roughly the same total amount of bound water was estimated from these two techniques. The average number of bound water molecules per ethylene oxide (EO) group, NW/EO is 2.3 (TDDS data) or 2.5 (SZT-DSC data) in good agreement with the observation that 1–2 water layers are formed in the hydration of ethoxylated surfactants. We have also shown that butanol is involved in the formation of the bound water that melts at -25°C. We suggest that butanol molecules occupy binding sites within the second hydration shell, thereby reducing the expected total bound water content. 相似文献