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81.
82.
83.
Peverini OA Herrmann H Orta R 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2004,51(10):1298-1307
We report on a detailed theoretical and experimental investigation of film-loaded surface acoustic wave (SAW) waveguides in lithium niobate (LiNbO3) for integrated acousto-optical (AO) polarization converters. The numerical analysis is based on both a scalar and a full-vectorial model. Dispersion plots and figures of merit for several structures are given, which lead to design parameters for optimized polarization converters. It is pointed out that very attractive structures are metal/dielectric/LiNbO3 strip waveguides and dielectric/LiNbO3 slot waveguides, in which metal is either gold (Au) or aluminum (Al), and the dielectric film is an optical transparent material such as silicon oxide (SiO2), magnesium oxide (MgO), or aluminium oxide (Al2O3). Polarization converters with the designed acoustical waveguides have been realized and characterized by optical conversion and laser probing measurements. 相似文献
84.
85.
Harald Nottebohm 《化学,工程师,技术》1983,55(5):346-352
Automation in the chemical industry – scope and limitations . Tempestuous developments in semiconductor technology centering upon the microprocessor open up new possibilities of automation in chemical engineering. The traditional appearance of process control rooms is changing drastically. A few video display units with uniform keyboards suffice to monitor and control an extensive chemical plant. In spite of all technical perfection, automation has its limitations wherever unavoidable irregularities require human intervention. This in turn requires that one is in command of both the process and the function of the automatic mechanism. 相似文献
86.
The N-acylethanolamine phospholipids (NAPE) are precursors for N-acylethanolamines (NAE), including anandamide (20∶4-NAE), which is a ligand for the cannabinoid receptors. Previously, NAPE
were believed to be found only in injured tissue, e.g., after neurodegenerative insults. Neuronal injury may occur in response
to seizure activity. Therefore, we investigated the effect of pentylenetetrazol (PTZ)-induced seizures in PTZ-kindled mice
on the level of NAPE in the brain. Male NMRI mice were kindled with PTZ injections 3 times/wk, thereby developing clonic seizures
in response to PTZ. Mice were killed within 30 min after the clonic seizure on the test day (12th injection) and the brains
were collected. Eight species of NAPE were analyzed as the glycerophospho-N-acylethanolamines by high-performance liquid chromatography-coupled electrospray ionization mass spectrometry. No effect
of the PTZ kindling on the NAPE levels in murine brains was observed. Total NAPE in control mice cortex (n=4) was 16.4±3.0 μmol/g wet weight of which 20∶4-NAPE accounted for 3.6 mol%, and the major species was 16∶0-NAPE, accounting
for 52.1 mol%. Determination of the activity of NAPE-hydrolyzing phospholipase D and of N-acyltransferase in brain membrane preparations from adult and 3-d-old mice revealed an enzyme pattern in the adult mice that
was favorable for NAE accumulation as opposed to NAPE accumulation. Thus, there was no difference in NAPE levels; at present,
however, this does not exclude that NAE may accumulate during seizure. 相似文献
87.
Structural Superplasticity at High Strain Rates of Super Duplex Stainless Steel Fe‐25Cr‐7Ni‐3Mo‐0.3N
The fine‐grained super duplex stainless steel Fe‐25Cr‐7Ni‐3Mo‐0.3N consisting of two phases (δ‐ferrite/austenite) exhibits structural super‐plasticity at higher strain rates of ? ≈ 10?2s?1 in the temperature range between 975 and 1100°C. The equiaxed microstructure with an average grain size of was produced by thermomechanical processing. Maximum strain‐rate‐sensitivity exponents of m ≈ 0.5 and elongations to failure of more than 500% were achieved. From thermal activation analysis an activation energy for superplastic flow of Q = 310 ± 20 kJ/mole was derived. The superplastic behaviour at higher strain rates is quantitatively described by a deformation model where grain or interphase boundary sliding is accommodated by sequential steps of dislocation glide and climb. The high strain‐rate‐sensitivity exponent and the observed dislocation density indicate that dislocation climb in the slightly solid solution strengthened austenite is the rate controlling step for superplastic flow. The deformation mechanism reveals that the investigated super duplex stainless steel exhibits superplastic behaviour that is typical for class II solid solution alloys. 相似文献
88.
89.
Harald Hruschka 《OR Spectrum》2007,29(4):579-595
Clusterwise pricing is characterized by prices of each brand of a category being equal in stores belonging to the same cluster.
Expected sales necessary to compute profits are estimated using coefficients of a multilayer perceptron which performs better
than several parametric models. Store-specific coefficients of sales response models are estimated by a MCMC method. Both
assignment of stores to clusters and prices of each cluster are determined by means of improving hit-and-run, a stochastic
optimization method. The objective function to be optimized includes both profits and adherence to the usual price level at
individual stores. Based on empirical data on sales, prices and marginal costs of a retail chain it is demonstrated that for
a moderate level of risk aversion clusterwise pricing leads to higher expected utility than micromarketing pricing with different
prices of each brand across individual stores. Clusterwise pricing attains a high percentage of the profits generated by micromarketing
pricing and entails lower menu costs than micromarketing pricing.
H. Hruschka thanks two anonymous reviewers for their interest and their detailed helpful comments. 相似文献
90.
Erik Benkler Andreas G. Steffan Harald R. Telle 《Photonics Technology Letters, IEEE》2007,19(5):267-269
We demonstrate a novel synchronization scheme for optical sampling which is based on a nonstandard phase-locked loop (PLL). Phase comparison is performed at a 10-GHz optical time-division-multiplexing (OTDM) base rate, thus avoiding ultrafast detectors and electronics. The employed frequency-offset PLL allows synchronous sampling of OTDM signals (or any other signals with bit rates given by integer multiples of the base rate), which would be impossible using a standard PLL. This provides a higher degree of flexibility for problem-specific sweeping than asynchronous sampling 相似文献