An exploratory study of adolescent's perceptions of the Web

Abstract The purpose of this exploratory study was to investigate the influence of two individual characteristics (Web experience and academic focus) of adolescents on the Web perception, using off-line questionnaires (a Lickert response scale) constituted on the basis of a series of interviews. Questions concerned: perceptions about the nature of information found in the Web; 'strategies' of access to the interesting Internet sites and the reliability of different information resources (libraries, television, Web, etc.). Results lead to the assumption that adolescents with high Web experience became more critical, less confident and less enthusiastic than adolescents with low Web experience and that, in some dimensions, perceptions of literature students are different to those of science students. Even if some interesting results were obtained, further research is needed to explore users' perceptions related to individuals' characteristics and to determine the generalisability of the influences identified in this exploratory study.     

Introduction and Elucidation of the Quality of Sagacity in the Extended Variable Precision Rough Sets Model

This paper introduces the quality of sagacity measure in the extended variable precision rough sets model - VPRS_l,u. The need for this measure is a direct consequence of the use of the associated l and u values. Moreover, different levels of miss-classification are allowed in the classification of objects to a decision class or its compliment. This measure attempts to take this into account, by acknowledging the classification of an object to the compliment of a decision class, as an appropriate (if not optimum) classification of that object. A consequence of the analysis is a discussion of the notion of open and closed worlds in VPRS_l,u.     

On bisymmetric operators on a finite chain

The bisymmetry property is studied for operators defined on a finite chain. In particular, a characterization of all bisymmetric, commutative and smooth binary operators is given. It is deduced from this characterization that bisymmetry and associativity are equivalent for finite chains, under these additional conditions.     

Serial deployment of attention during visual search.

This study examined whether objects are attended in serial or in parallel during a demanding visual search task. A component of the event-related potential waveform, the N2pc wave, was used as a continuous measure of the allocation of attention to possible targets in the search arrays. Experiment 1 demonstrated that the relative allocation of attention shifts rapidly, favoring one item and then another. In Experiment 2, a paradigm was used that made it possible to track the absolute allocation of attention to individual items. This experiment showed that attention was allocated to one object for 100-150 ms before attention began to be allocated to the next object. These findings support models of attention that posit serial processing in demanding visual search tasks. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Determination of shear strength values according to EN 408

This paper presents the results of 382 shear tests carried out according to EN 408. The test pieces consisted of spruce (Picea abies) and varied in density and ring width orientation (radial, tangential and at an angle of 45° to the steel plates). In addition pieces containing pith and knots were tested. The paper discusses problems observed when using this test configuration and shows that the test results do not support the characteristic shear strength values as given in EN 338. Moreover, the test results do not support the relationship between characteristic shear strength and characteristic bending strength as given in EN 384.

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Résumé Cet article présente les résultats de 382 essais de cisaillement menés conformément à EN 408. Les éprouvettes d’essai sont en épicéa (Picea abies) et présentent une variabilité en termes de masse volumique et d’orientation des cernes d’accroissement (radiale, tangentielle, à un angle de 45° par rapport aux plaques métalliques). Des éprouvettes supplémentaires contenant du cœur et des nœuds ont également été testées. L’article évoque les problèmes qui ont été mis en évidence lors de l’utilisation de ce dispositif expérimental et montre que les résultats expérimentaux ne sont pas en accord avec les valeurs caractéristiques de résistance au cisaillement données dans EN 338. De plus, ces résultats ne confirment pas la relation entre résistance caractéristique au cisaillement et résistance caractéristique à la flexion telle que stipulée dans EN 384.

     

Effects of urbanization on the aquatic fauna of the Line Creek watershed, Atlanta—a satellite perspective

Impervious surface area (ISA) was derived for a period from 1979 to 1997 from Landsat MSS and TM data for the Line Creek watershed that lies to the south of the city of Atlanta, GA. The change in ISA is presented as an ecological indicator to examine the cumulative water resource impacts on mussel population in three sub-watersheds of Line Creek—namely, Line, Flat, and Whitewater creeks. The satellite analysis shows that ISA expansion occurred substantially from 1987 to 1997 and is predominantly in industrial, commercial, and shopping center (ICS) complexes but also in smaller lot-size residential development. Evidence of mussel habitat degradation is indicated and loss of species (in the region of 50 to 70%) is present in areas where ISA expansion is observed—specifically in ICS complex development in and around Peachtree City that drains directly into the Line and Flat creeks. This is in marked contrast to Whitewater Creek where overall development of ISA is less and no major loss of mussel species is observed.     

Getting a handle on MATLAB graphics

Among engineers and scientists, MATLAB is one of the most popular computational packages. Part of MATLAB's popularity stems from its simple, yet sophisticated, graphics capabilities. While basic plots are relatively easy to obtain, specialized plots require a little more effort to produce. This article introduces MATLAB's Handle Graphics, which provides a mechanism to fully control and customize graphics objects in MATLAB. With a basic understanding of Handle Graphics, users can produce plots that meet the unique needs and quality standards commonly required by the profession, several examples are presented to illustrate the concepts.     

Reference feedforward in the idle speed control of a direct-injection spark-ignition engine

The direct-injection spark-ignition engine has emerged as a focus of research in improving fuel economy and controlling emissions. This engine can operate in multiple modes, including a stratified charge mode with an air-fuel ratio as large as 50:1. Operating in stratified mode results in improved fuel economy and reduced CO/sub 2/ emissions. The stratified charge mode is employed during low speed and load conditions, such as during engine idle. The idle speed control problem is cast as a two-input-two-output control problem and a baseline feedback controller is developed based on an existing topology from the literature. Significant delays, however, inhibit our ability to improve the transient response via feedback alone. An improved scheme employing reference feedforward is proposed and several potential topologies are presented. A reference feedforward algorithm is derived and nonlinear simulation results are shown in which the system transient responses are improved considerably.