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91.
Jacques G. Noudem Sophie Meslin Daniel Horvath Christelle Harnois Daniel Chateigner Bachir Ouladdiaf Sophie Eve Mousta Gomina Xavier Chaud Masato Murakami 《Journal of the American Ceramic Society》2007,90(9):2784-2790
The recently reported hole-patterned YBa2 Cu3 O y (Y123) bulks with improved superconducting properties are highly interesting from material quality and application variety points of view. It is well known that the core of plain bulk superconductors needs to be fully oxygenated and some defects like cracks, pores, and voids must be suppressed in order that the material can trap a high magnetic field or carry a high current density. To minimize the above defects, we have used a combination of standard superconducting ceramic processing and an infiltration technique to prepare regularly perforated YBa2 Cu3 O y (Y123) bulk superconductors. This process leads to negligible shrinkage upon annealing and a uniform distribution of Y211 inclusions. Texture was evidenced by neutron pole figure measurements. Flux mapping was used to verify the superconducting homogeneity of the samples and to investigate the field-trapping ability. In addition, the textured drilled samples were reinforced using resin or metal impregnation and the influence of the different processing steps on the hardness of the materials has been investigated. 相似文献
92.
This paper analyses motorcycle educational content in a number of French motorcycle schools on the basis of a naturalistic study of riders’ and trainers’ behaviour. The aim is to specify the situations delivered in motorcycle schools and to study the rider's activity in these situations. The methodology includes ethnographic observation within the motorcycle schools and the longitudinal monitoring of 14 trainee motorcyclists during their initial training. The training situations were described by the combination of audio–visual recordings and interviews data (i.e. concomitant or interruptive verbalization, and self-confrontation data). The results permit to (1) compare the “real” and “official” durations of track and on-road training, (2) characterize the real training situations, (3) describe the preferred forms of instruction, and (4) conduct an in-depth analysis of the situations used during training in traffic. The discussion show, in first, the poverty of the training situations which are based on the repetition of the exercises in the test, and, in second, disparities between the riding situations encountered during training and the demands made by riding in natural traffic. The usefulness and the applications of this type of approach – based on the integration of the rider's point of view notably by self-confrontation interview – for understanding real riding behaviours and how such approaches could supplement vehicle-based data are discussed in a large conclusion. 相似文献
93.
Jacques Désautels 《Canadian Journal of Science, Mathematics, & Technology Education》2013,13(2):189-195
Résumé La métaphore du changement de guide proposée par Fensham (2002a) constitue un véritable faux‐fuyant. Cette solution aux présumés problèmes d'une alphabétisation technoscientifique pour tous et toutes fait l'impasse sur une interrogation plus générale à propos de la socialite des technosciences. Ainsi, l'auteur reconduit la séculaire séparation entre le monde de la science et celui de la société, qui justifie que seuls des ? experts ?, scientifiques ou sociétaux, puissent servir de médiateurs entre ces univers incommensurables. Il élimine donc d'emblée, en évoquant la complexité des problèmes, la possibilité pour les citoyens et les citoyennes ordinaires de s'engager dans les controverses sociotechniques qui traversent inévitablement nos sociétés. En conséquence, il se rabat sur une forme d'alphabétisation technoscientifique à deux vitesses ; l'une pour la populace, l'autre pour une élite qui, à terme, aura le privilège de pénétrer dans l'univers mystérieux et ésotérique de la science. Autrement dit, les contenus des curriculums pourront varier sans que la hiérarchie sociale des savoirs, de même que les pouvoirs forcément politiques des experts, soient menacés. 相似文献
94.
Effects of Speeds,Materials, and Tool Rake Angles on Metallic Particle Emission During Orthogonal Cutting 总被引:1,自引:0,他引:1
Riad Khettabi Victor Songmene Jacques Masounave 《Journal of Materials Engineering and Performance》2010,19(6):767-775
Dry high speed machining has been proposed as a viable and cost-effective process in metal cutting industries. However, it
produces fine and ultra-fine metallic particles, also referred to as dust, which can be harmful to the machine-tool operator.
The risk associated with exposure to metallic particles increases as the particle size decreases. For machining processes,
little data exist on the size and distribution of dust generated during the shaping of materials. In order to reduce or eliminate
the generation of these particles, it is necessary to understand how and under which conditions they are formed, as well as
to be able to make predictions. In this study, the effects exerted by tool geometry, material, and machining parameters on
dust emission were studied experimentally in order to understand the mechanisms of dust generation and to develop a predictive
model. The particle sizes studied include the PM2.5 (particles with aerodynamique diameter below 2.5 μm) and a distribution
of nanoparticles varying in size from 10 nm to 10 μm. Using dry machining and reducing the amount of dust generated should
improve the air quality in machine shops in addition to helping protect the environment. 相似文献
95.
Modeling of Particle Emission During Dry Orthogonal Cutting 总被引:2,自引:0,他引:2
Riad Khettabi Victor Songmene Imed Zaghbani Jacques Masounave 《Journal of Materials Engineering and Performance》2010,19(6):776-789
Because of the risks associated with exposure to metallic particles, efforts are being put into controlling and reducing them
during the metal working process. Recent studies by the authors involved in this project have presented the effects of cutting
speeds, workpiece material, and tool geometry on particle emission during dry machining; the authors have also proposed a
new parameter, named the dust unit (D
u), for use in evaluating the quantity of particle emissions relative to the quantity of chips produced during a machining
operation. In this study, a model for predicting the particle emission (dust unit) during orthogonal turning is proposed.
This model, which is based on the energy approach combined with the microfriction and the plastic deformation of the material,
takes into account the tool geometry, the properties of the worked material, the cutting conditions, and the chip segmentation.
The model is validated using experimental results obtained during the orthogonal turning of 6061-T6 aluminum alloy, AISI 1018,
AISI 4140 steels, and grey cast iron. A good agreement was found with experimental results. This model can help in designing
strategies for reducing particle emission during machining processes, at the source. 相似文献
96.
Professional psychology has increasingly moved toward evidence-based practice. However, instruments used to assess psychologists seeking licensure, such as the Examination for Professional Practice in Psychology (EPPP), have received relatively little empirical scrutiny. Therefore, the authors evaluated the available evidence in support of the EPPP’s validity and current use as a core component of professional licensure. Although the EPPP has in many ways been extensively evaluated, there is a paucity of criterion, predictive, and incremental validity evidence available. Further, several aspects of the content validation studies were examined, and the authors question whether the EPPP, as currently constructed, can meet its stated goals. Given that the EPPP is a high-stakes examination and given the authors’ best estimate (based on a sample of 16 states) that 35% of applicants fail the examination, it is recommended that the EPPP be more extensively evaluated. An outline of major decision points in this proposed evaluation process is provided, several suggestions for further research are proposed, and the field is encouraged to discuss these issues further. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
97.
This paper deals with the scheduling of operations on a multiprocessor machine in the context of shoe manufacturing. Multiprocessor machines are composed of several parallel processors. Unlike parallel machines, the entire machine needs to be stopped whenever a single processor needs a setup. Our industrial partner, one of the major winter-shoe manufacturers in Canada, offers a relatively large variety of models. For each of these models, all the sizes proposed by this manufacturer must be produced in various quantities. Our objective is to schedule the production of the required sizes on the machine's different processors in order to minimize the global makespan, which includes both the production time and the set up time. We first present a mathematical formulation of the problem. Then, we introduce a decomposition procedure based on the mathematical model, and we demonstrate that this procedure is very efficient for small- and medium-size instances. We also propose two construction heuristics and two improvement heuristics for larger problems, and we report the results of our extensive computational experiments to demonstrate the quality of the proposed heuristics in terms of reducing production time and computational effort. 相似文献
98.
Jacques Dauphin 《The International journal of environmental studies》2013,70(1-4):109-115
This paper is intended to be a short survey of the materials problems associated with spacecraft design and manufacture. The space environment is first described and compared with the “Spacecraft Environment”, which is dependent upon the characteristic features of each individual vehicle. Some areas of spacecraft technology, where materials properties are critical, are briefly described; the problems which can arise are then underlined. They are divided between “Classical” problems, not different from those which appear in a number of Earth technologies, and “Specific to Space” problems which are mainly created by vacuum exposure, radiation fluxes and thermal stresses. The conclusions clearly indicate the necessity for proper methods of materials and processes selection for space applications and show that close cooperation between design engineers and materials specialists is absolutely essential. 相似文献
99.
100.
Roger H. Charlier Philippe Morand Jacques Mazé 《The International journal of environmental studies》2013,70(2-3):143-160
Seaweed has proved to be both a potential resource and a problem for coastal areas. In the framework of the European Communities, a scientific commission was created some 8 years ago, in order to address the matter of seaweed bioconversion in Europe. A book, recently published, represents a fair review and survey of seaweed as a resource in Europe. The matter of seaweed problems and expanded use is now under study in a new programme. This paper traces back the development and growth of this inter‐European effort and also provides an overview of achievements. 相似文献