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61.
62.
The accuracy of extremely low frequency (ELF) magnetic field measurements can be sensitively varied by the meter probe size when the spatial distribution of the magnetic flux density is highly non-uniform, e.g. if the measurement point is close to the field source. The deviation between measured and actual field varies from point to point depending on the probe dimension and on the source configuration, once the other measurement conditions are fixed. The analysis of this effect is developed through a two-dimensional numerical model that enables the evaluation of the actual field value and of the corresponding probe indication. The error distribution, i.e. the deviation between actual and measured value, is computed for magnetic fields generated by industrial three-phase systems under both balanced and unbalanced supply conditions. The analysis shows how, for a given source, the error depends not simply on the distance from the source in relation to the probe size, but on its spatial distribution, which is complex and cannot be a priori predicted without using a computational tool such as the one proposed. 相似文献
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Miklósi áam; Pongrácz Péter; Lakatos Gabriella; Topál József; Csányi Vilmos 《Canadian Metallurgical Quarterly》2005,119(2):179
Dogs' (Canis familiaris) and cats' (Felis catus) interspecific communicative behavior toward humans was investigated. In Experiment 1, the ability of dogs and cats to use human pointing gestures in an object-choice task was compared using 4 types of pointing cues differing in distance between the signaled object and the end of the fingertip and in visibility duration of the given signal. Using these gestures, both dogs and cats were able to find the hidden food; there was no significant difference in their performance. In Experiment 2, the hidden food was made inaccessible to the subjects to determine whether they could indicate the place of the hidden food to a naive owner. Cats lacked some components of attention-getting behavior compared with dogs. The results suggest that individual familiarization with pointing gestures ensures high-level performance in the presence of such gestures; however, species-specific differences could cause differences in signaling toward the human. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
65.
This paper introduces a tabu search heuristic for a production scheduling problem with sequence-dependent and time-dependent
setup times on a single machine. The problem consists in scheduling a set of dependent jobs, where the transition between
two jobs comprises an unrestricted setup that can be performed at any time, and a restricted setup that must be performed
outside of a given time interval which repeats daily in the same position. The setup time between two jobs is thus a function
of the completion time of the first job. The tabu search heuristic relies on shift and swap moves, and a surrogate objective
function is used to speed-up the neighborhood evaluation. Computational experiments show that the proposed heuristic consistently
finds better solutions in less computation time than a recent branch-and-cut algorithm. Furthermore, on instances where the
branch-and-cut algorithm cannot find the optimal solution, the heuristic always identifies a better solution. 相似文献
66.
Laguerre-Gauss and Bessel-Gauss beams in uniaxial crystals 总被引:1,自引:0,他引:1
Cincotti G Ciattoni A Palma C 《Journal of the Optical Society of America. A, Optics, image science, and vision》2002,19(8):1680-1688
A simple correspondence between the paraxial propagation formulas along the optical axis of a uniaxial crystal and inside an isotropic medium is found in the case of beams with linearly polarized circularly symmetric boundary distributions. The electric fields of the ordinary and the extraordinary beams are related to the corresponding expressions in a medium with refractive index n(o) and n(e)2/n(o), where n(o) and n(e) are the ordinary and the extraordinary refractive indexes, respectively. Closed-form expressions for Laguerre-Gauss and Bessel-Gauss beams propagating through an anisotropic crystal are given. 相似文献
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Valentina Di Egidio Nicoletta Sinelli Gabriella Giovanelli Agostina Moles Ernestina Casiraghi 《European Food Research and Technology》2010,230(6):947-955
Fifteen micro-fermentation trials were conducted during the 2008 vintage harvest in the Valtellina (Northern Italy) viticultural
area. During fermentation, the spectra were achieved in the near and mid-infrared region by a FT-NIR spectrometer and a FT-IR
spectrometer, respectively. Samples were also analysed by using chemical methods to evaluate sugars (glucose and fructose),
alcohols (ethanol and glycerol) and phenolic compounds (total phenolics, total anthocyanins and total flavonoids). The pretreated
spectral data were processed using principal component analysis. After feature selection by the algorithm SELECT, linear discriminant
analysis (LDA) was applied to spectral data as a classification technique, to predict the fermentation stage from initial
to final phase. Moreover, partial least square regression was used to predict sugar content, ethanol, glycerol and phenolic
compounds simultaneously. LDA results, characterised by a high percentage of correct classification (87% and 100% as average
value in prediction for NIR and MIR spectroscopy, respectively), showed that samples belonging to a particular fermentation
step could be correctly classified. Good calibration models for the prediction of the main compositional changes during alcoholic
fermentation were obtained with both FT-NIR and FT-IR, suggesting that either instruments could be used to evaluate online
and simultaneously these compounds in red wine. 相似文献
70.
Elena Orban Gabriella Di Lena Maurizio Masci Teresina Nevigato Irene Casini Roberto Caproni Loretta Gambelli Michele Pellizzato 《Journal of the science of food and agriculture》2004,84(14):1929-1938
Quality aspects of oysters (Crassostrea gigas) from a suspended culture in the lagoon of Venice (Valle Dogà) were examined in different seasons over a 1‐year period. Ecophysiological and commercial quality indicators (condition index, content of meat, shell and intervalvar fluid), nutritional quality parameters (proximate and mineral composition, glycogen content, fatty acid profile, cholesterol, plant sterols, fat‐soluble vitamins content) and levels of organic pollutants (polychlorinated biphenyls and organochlorine pesticides) were determined at different times of the year. Seasonal variations were observed in the nutrient content, with particular regard to moisture (ranging from 866.8 g kg?1 in June to 938.8 g kg?1 in September), protein (23.9 g kg?1 in September to 76.6 g kg?1 in June), ash (22.5 g kg?1 in February to 29.5 g kg?1 in July), lipid (3.0 g kg?1 in September to 8.8 g kg?1 in June) and glycogen (0.7 g kg?1 in September to 11.5 g kg?1 in February). In spite of this variability, the nutritional quality of the oysters was generally good, especially just before gamete release when the concentration of nutrients was at its maximum. Low levels of organochlorine chemicals were detected in the edible meat of oysters but, because only a limited number of samples were analysed, no general conclusion can be drawn on the safety of seafood from this area. Copyright © 2004 Society of Chemical Industry 相似文献