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631.
Reviews the book, Vers une logique des significations by Jean Piaget and Rolando Garcia (1987). This volume is a collection of Piaget's works. Each chapter describes one of his logico-mathematical studies on the play activities of children. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
632.
A complex dynamical behaviour called chaos is observed in second-order recurrences with a non-unique inverse (endomorphisms). The chaotic solutions of such second-order point-mappings are located in bounded domains of the phase plane, called chaotic areas. All the attractive limit sets of an endomorphism, such that fixed point, cycle, invariant closed curve or chaotic solution are located in phase plane domains designated by absorptive areas. Two methods for the construction of absorptive areas and chaotic areas are done. Different bifurcations giving rise to a modification of the nature of these areas are described. Various examples whose one is related to a sampled-data control system are done. 相似文献
633.
Yu-Shen Jean-Claude Jun-Hai Pi-Qiang Hui Jia-Guang Karthik 《Computer aided design》2006,38(12):1251-1263
A novel method for projecting points onto a point cloud, possibly with noise, is presented based on the point directed projection (DP) algorithm proposed by Azariadis P., Sapidis N. [Drawing curves onto a cloud of points for point-based modelling. Computer-Aided Design 2005; 37(1): 109–22]. The new method operates directly on the point cloud without any explicit or implicit surface reconstruction procedure. The presented method uses a simple, robust, and efficient algorithm: least-squares projection (LSP), which projects points onto the point cloud in a least-squares sense without any specification of the projection vector. The main contribution of this novel method is the automatic computation of the projection vector. Furthermore, we demonstrate the effectiveness of this approach through a number of application examples including thinning a point cloud, point normal estimation, projecting curves onto a point cloud and others. 相似文献
634.
Trung-Hien Nguyen Pascal Scalart Mathilde Gay Laurent Bramerie Christophe Peucheret Fausto Gomez-Agis Olivier Sentieys Jean-Claude Simon Michel Joindot 《Photonic Network Communications》2018,36(3):326-337
We report on a simple alternative method for the compensation of quadrature imbalance in optical quadrature phase-shift-keying (QPSK) coherent systems. By introducing a new metric, the phase imbalance can be determined and compensated. The proposed method is theoretically and numerically analyzed. In particular, it is shown that the method exhibits a small bias of estimated phase imbalance value. Thanks to its deterministic property, this bias can be simply compensated by incorporating at the receiver a phase rotator (or phase shift) whose value can be determined based on an analytical analysis. Moreover, the algorithm is also experimentally validated through bit-error-rate and error vector magnitude (EVM) measurements. A good agreement on the performance of the proposed method with that of the Gram–Schmidt orthogonalization procedure is shown in a 20-Gbit/s optical QPSK experiment. The robustness of both methods was verified with up to \(30^\circ \) phase imbalance by comparing the signal with and without phase imbalance compensation. A 10% reduction in EVM is achieved with our method for a high phase imbalance of \(30^\circ \), while the implementation complexity can be reduced owing to the suppression of the use of square-root operators. 相似文献
635.
Auger JC Martinez V Stout B 《Journal of the Optical Society of America. A, Optics, image science, and vision》2007,24(11):3508-3516
The purpose of this work is to show that an appropriate multiple T-matrix formalism can be useful in performing qualitative studies of the optical properties of colloidal systems composed of nonspherical objects (despite limitations concerning nonspherical particle packing densities). In this work we have calculated the configuration averages of scattering and absorption cross sections of different clusters of dielectric particles. These clusters are characterized by their refraction index, particle shape, and filling fraction. Computations were performed with the recursive centered T-matrix algorithm (RCTMA), a previously established method for solving the multiple scattering equation of light from finite clusters of isotropic dielectric objects. Comparison of the average optical cross sections between the different systems highlights variations in the scattering and absorption properties due to the electromagnetic interactions, and we demonstrate that the magnitudes of these quantities are clearly modulated by the shape of the primary particles. 相似文献
636.
Mohamed R Richoz-Payot J Gremaud E Mottier P Yilmaz E Tabet JC Guy PA 《Analytical chemistry》2007,79(24):9557-9565
A simple and fast selective extraction of the antibiotic chloramphenicol (CAP) from milk (raw milk, skimmed milk, and milk powder) using a molecularly imprinted polymer (MIP) sorbent is described. The method entails a single centrifugation step prior to loading the supernatant onto the MIP cartridge and subsequent elution with a mixture of solvents. CAP was further analyzed by isotope dilution liquid chromatography electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS) operating in negative ionization acquisition mode. The advantages of the MIP approach were assessed by comparing the data generated from a classical solid-phase and liquid-liquid extractions procedure, previously developed in our laboratory. A better recovery of CAP due to an enhanced selectivity and a faster turnaround time (18 samples processed within 3 h compared to 8 h with the classical approach) were evidenced when using the MIP cleanup. The analysis of CAP in raw milk was further validated according to the 2002/657/EC European Union criteria for the analysis of veterinary drug residues at the minimum required performance limit (MRPL) of 0.3 microg/kg, using CAP-d(5) as internal standard. Non-internal-standard corrected recovery values ranged between 50% and 87% over the range of concentrations considered. The decision limit (CCalpha) and detection capability (CCbeta) were calculated to be 0.06 and 0.10 microg/kg, respectively. 相似文献
637.
Different (3-phenoxypropyl)piperidine derivatives have been coupled to fluorescent moieties (5-dimethylaminonaphthalene-1-sulfonyl, carbazol-9-ylcarbonyl, 2-cyanoisoindol-1-yl, 2-cyanobenzo[f]isoindol-1-yl, 2,4-dinitrobenzen-1-yl, 2,4-diaminophenyl, 7-nitrobenzofurazan-4-yl, 7-aminosulfonylbenzofurazan-4-yl, 4-methylcoumarin-6-yl) as novel histamine H(3) receptor ligands. They have been synthesised starting from piperidine in a few steps. The compounds display good to excellent histamine hH(3) receptor affinities with K(i) values ranging from 13.4 to 0.048 nM. Some of the new compounds belong to the most potent ligands known so far and may act as tools for identification and understanding of the binding site on the histamine H(3) receptor. In vivo screening on selected derivatives of Sanger's reagent showed antagonist potencies with ED(50) values from 7.9 to 0.39 mg kg(-1), p.o. 相似文献
638.
Abstract. Spatial interaction (SI) is the process whereby entities at different points in physical space make contacts, demand/supply decisions or locational choices. The entities can be individuals or firms and the choices can include housing, jobs, production quantities, exports, imports, face-to-face contacts, schools, retail centres and activity centres. The first SI models can be grouped under the generic heading gravity models. Their main characteristic is that they model the behaviour of demand or supply segments, rather than that of individuals and firms. This article traces the development of these models from their inception in the early part of the twentieth century to the present. The key advances include the replacement of the gravity analogy by the more general concepts of entropy or information theory, a statistical framework commonly used in physics. With the arrival of the regional science paradigm over 50 years ago, a key challenge has been to broaden these models compared to those arising in spatial economics, thus arriving at a more inclusive probabilistic framework. These efforts are discussed here, as well as inclusion of geographical advances, embracing activities as generators of travel, time-geography, recognition of spatial interdependencies, and use of neuro-computing principles. 相似文献
639.
The purpose of this study was to validate a new version of the Driver Behavior Questionnaire (DBQ) on a sample of French drivers in order to gain a better understanding of different driver behaviors, by differentiating two types of violations (aggressive and ordinary), three types of errors (dangerous, inattention and inexperience) and by taking positive behaviors into account. 525 drivers (205 men and 320 women), between 18 and 79 years of age, filled in a questionnaire on line including the 41 items in the new version of the DBQ and information relative to their mobility and their accident history. Exploratory factor analysis confirmed a six-factor structure: “dangerous errors”, “inattention errors”, “inexperience errors”, “ordinary violations”, “aggressive violations” and “positive behaviors”. A revised version with 23 items of the new version of the DBQ was produced by selecting the items that loaded most strongly on the six factors. The results also showed the link between demographic variables (age and gender), mobility (kilometers driven weekly), the DBQ scores and the involvement in an accident in the previous five years. This study permitted to validate a more detailed version of the “Driving Behavior Questionnaire” among French drivers of all age and all level of experience. 相似文献
640.
Noureddine Della Mostefa Belkhatir Ahmed Arab Jean Canou Jean-Claude Dupla 《Acta Mechanica》2014,225(7):2043-2057
It is well known that the specimen preparation method and the resulting sand fabric significantly affect sand behavior and sand liquefaction resistance. In many cases, the fabric and behavior of reconstituted sand samples do not represent those of in-situ deposits. Therefore, understanding the influence of specimen preparation and sand fabric on its behavior, particularly at the critical state, is important for relating the behavior of laboratory reconstituted specimens to in-situ soil response. In this study, the effect of sand fabric and specimen preparation method on the shearing behavior of sand is studied using triaxial shear tests. Dry funnel pluviation (DFP) and wet tamping (WT) are used to prepare the specimens. The results from instability lines and stress–strain curves indicate that the liquefaction resistance of specimens prepared with the DFP method is more than specimens reconstituted by the WT method. 相似文献