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111.
112.
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
113.
Juan Morote Anna Celma Jacques Planas José Placer Inés de Torres Mireia Olivan Juan Carles Jaume Reventós Andreas Doll 《International journal of molecular sciences》2014,15(8):13615-13623
The aim of this study was to analyze the relationship between statin use along with serum cholesterol levels and prostate cancer (PCa) detection and aggressiveness. Statin users of three years or more and serum cholesterol levels (SC) were assessed in 2408 men scheduled for prostate biopsy. SC was classified as normal (NSC: <200 mg/dL) or high (HSC: >200 mg/dL). High-grade PCa (HGPCa) was considered if the Gleason score was greater than 7. Statin users comprised 30.9% of those studied. The PCa detection rate was 31.2% of men on statins and 37% of non-statin users (p < 0.006). The PCa detection rate was 26.3% in men with NSC and 40.6% in those with HSC (p < 0.001). In the subset of NSC men, the PCa rate was 26.5% for statin users and 26.2% for non-users (p = 0.939), while in men with HSC, the PCa rate was 36.4% for statin users and 42.0% for non-statin users (p = 0.063). The HGPCa rate was 41.8% for statin users and 32.5% for non-users (p = 0.012). NSC men had a 53.8% rate of HGPCa, while the rate was only 27.6% in HSC men (p < 0.001). NSC men on statins had an HGPCa rate of 70.2%, while non-statin users had a rate of 41.2% (p < 0.001). The HGPCa rate for HSC men on statins was 18.8%, while the rate was 30.0% (p = 0.011) for non-users. Logistic regression analysis suggested that serum cholesterol levels could serve as an independent predictor of PCa risk, OR 1.87 (95% CI 1.56–2.24) and HGPCa risk, OR 0.31 (95% CI 0.23–0.44), while statin usage could not. Statin treatment may prevent PCa detection through serum cholesterol-mediated mechanisms. A disturbing increase in the HGPCa rate was observed in statin users who normalized their serum cholesterol. 相似文献
114.
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
115.
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
116.
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
117.
118.
Numerical modeling and performance evaluation of multi-tubular sodium alanate hydride finned reactor
Maha Bhouri Jacques Goyette Bruce J. Hardy Donald L. Anton 《International Journal of Hydrogen Energy》2012
The optimization of the hydrogen loading process in a multi-tubular sodium alanate hydride reactor equipped with longitudinal fins is investigated numerically. The effect of the number, thickness and tip clearance of the fins on the hydrogen charging rate is assessed, so that the fin optimal geometric properties are determined by the compromise between the hydrogen loading rate and the fin contribution to the weight and the volume of the storage system. Simulation results have shown that the hydrogen loading rate corresponding to this optimized configuration is 41% greater than the case without fins if we suppose a perfect interconnectivity between the fin tips and the internal walls of the hydride tubes. Otherwise, the amount of stored hydrogen decreases drastically. The loading of hydrogen under high charging pressures results in higher hydrogen loading rates and there is an interaction between the geometric and operating parameters leading to the optimized amount of stored hydrogen. 相似文献
119.
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
120.