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101.
The oxidative erosion of seven types of graphite has been investigated by heating in air at temperatures between 600 and 1000 K. The specimens include pyrolytic graphite, fine-grain graphites, carbon-fibre composites (CFC), and graphites doped with Si and Ti. The weight loss was measured using a microbalance, the surface morphology by scanning electron microscopy, and the composition of the surface layer by MeV ion beam techniques. Pyrolytic graphite is least affected by erosion, while pure and Si-doped CFCs erode particularly fast. Typical erosion rates for specimens with a surface area of ?4 cm2 are below 0.2 μg/m2 s at 600 K for all graphite types, and at 900 K range from 0.34 mg/m2 s for pyrolytic graphite to about 9 mg/m2 s for the strongest eroding types. The temperature dependence of the erosion rate of all types of graphite studied is well described by an activation energy of 1.7 eV. The erosion rates of these graphites are by far lower than the removal rates for deposited amorphous hydrocarbon layers. In contrast to all other types, the Ti-doped graphite absorbs a significant amount of oxygen reaching up to ?5% of its original mass. Once the oxygen uptake is saturated, it erodes with rates similar to those of the strongest eroding types. 相似文献
102.
Jacques Angel Alain Boissier Sylvain Lallemant Franois Leblanc Bertrand Pcout Jacob W. Lin James Tung 《Journal of the Society for Information Display》2003,11(3):533-538
Abstract— As the need for high‐resolution ultra‐low‐power bistable displays grows, it is important to rapidly implement the mass‐production manufacturing of BiNem® LCDs. The cost‐effective approach for BiNem® manufacturing is based on using STN manufacturing process technologies since BiNem® and STN displays have a similar internal structure. The key differences between BiNem® and STN displays from a manufacturing point of view will be discussed. We show that industrial STN manufacturing equipment can be used to produce BiNem® LCDs at competitive costs. Reflective e‐book display modules with VGA resolution are produced in the pilot‐production series. 相似文献
103.
104.
This research builds on prior work on developing near optimal solutions to the product line design problems within the conjoint analysis framework. In this research, we investigate and compare different genetic algorithm operators; in particular, we examine systematically the impact of employing alternative population maintenance strategies and mutation techniques within our problem context. Two alternative population maintenance methods, that we term “Emigration” and “Malthusian” strategies, are deployed to govern how individual product lines in one generation are carried over to the next generation. We also allow for two different types of reproduction methods termed “Equal Opportunity” in which the parents to be paired for mating are selected with equal opportunity and a second based on always choosing the best string in the current generation as one of the parents which is referred to as the “Queen bee”, while the other parent is randomly selected from the set of parent strings. We also look at the impact of integrating the artificial intelligence approach with a traditional optimization approach by seeding the GA with solutions obtained from a Dynamic Programming heuristic proposed by others. A detailed statistical analysis is also carried out to determine the impact of various problem and technique aspects on multiple measures of performance through means of a Monte Carlo simulation study. Our results indicate that such proposed procedures are able to provide multiple “good” solutions. This provides more flexibility for the decision makers as they now have the opportunity to select from a number of very good product lines. The results obtained using our approaches are encouraging, with statistically significant improvements averaging 5% or more, when compared to the traditional benchmark of the heuristic dynamic programming technique. 相似文献
105.
Cubic silicon carbide (3C-SiC) thin films were grown on (100) and (111) Si substrates by CVD technique using hexamethyldisilane
(HMDS) as the source material in a resistance heated furnace. HMDS was used as the single source for both Si and C though
propane was available for the preliminary carbonization. For selective epitaxial growth, patterned Si (100) substrates were
used. The effect of different growth parameters such as substrate orientation, growth temperature, precursor concentration,
etc on growth was examined to improve the film quality. The surface morphology, microstructure and crystallinity of grown
films were studied using optical microscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD) analysis and X-ray
photoelectron spectroscopy (XPS). 相似文献
106.
Addis Michael E.; Hatgis Christina; Krasnow Aaron D.; Jacob Karen; Bourne Leslie; Mansfield Abigail 《Canadian Metallurgical Quarterly》2004,72(4):625
Eighty clients enrolled in a managed care health plan who identified panic disorder as their primary presenting problem were randomly assigned to treatment by a therapist recently trained in a manual-based empirically supported psychotherapy (M. G. Craske, E. Meadows, & D. H. Barlow, 1994) or a therapist conducting treatment as usual (TAU). Participants in both conditions showed significant change from pre- to posttreatment on a number of measures. Those receiving panic control therapy (PCT) showed greater levels of change than those receiving TAU. Among treatment completers, an average of 42.9% of those in PCT and 18.8% in TAU achieved clinically significant change across measures. The results are discussed with reference to the dissemination of PCT and other evidence-based psychotherapies to clinical practice settings. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
107.
Comparison of land surface emissivity and radiometric temperature derived from MODIS and ASTER sensors 总被引:1,自引:0,他引:1
Frédéric Jacob Franc?ois Petitcolin Éric Vermote Kenta Ogawa 《Remote sensing of environment》2004,90(2):137-152
This study compared surface emissivity and radiometric temperature retrievals derived from data collected with the MODerate resolution Imaging Spectroradiometer (MODIS) and Advanced Spaceborne Thermal Emission Reflection Radiometer (ASTER) sensors, onboard the NASA's Earth Observation System (EOS)-TERRA satellite. Two study sites were selected: a semi-arid area located in northern Chihuahuan desert, USA, and a Savannah landscape located in central Africa. Atmospheric corrections were performed using the MODTRAN 4 atmospheric radiative transfer code along with atmospheric profiles generated by the National Center for Environmental Predictions (NCEP). Atmospheric radiative properties were derived from MODTRAN 4 calculations according to the sensor swaths, which yielded different strategies from one sensor to the other. The MODIS estimates were then computed using a designed Temperature-Independent Spectral Indices of Emissivity (TISIE) method. The ASTER estimates were derived using the Temperature Emissivity Separation (TES) algorithm. The MODIS and ASTER radiometric temperature retrievals were in good agreement when the atmospheric corrections were similar, with differences lower than 0.9 K. The emissivity estimates were compared for MODIS/ASTER matching bands at 8.5 and 11 μm. It was shown that the retrievals agreed well, with RMSD ranging from 0.005 to 0.015, and biases ranging from −0.01 to 0.005. At 8.5 μm, the ranges of emissivities from both sensors were very similar. At 11 μm, however, the ranges of MODIS values were broader than those of the ASTER estimates. The larger MODIS values were ascribed to the gray body problem of the TES algorithm, whereas the lower MODIS values were not consistent with field references. Finally, we assessed the combined effects of spatial variability and sensor resolution. It was shown that for the study areas we considered, these effects were not critical. 相似文献
108.
This paper addresses the problem of identification of hybrid dynamical systems, by focusing the attention on hinging hyperplanes and Wiener piecewise affine autoregressive exogenous models, in which the regressor space is partitioned into polyhedra with affine submodels for each polyhedron. In particular, we provide algorithms based on mixed-integer linear or quadratic programming which are guaranteed to converge to a global optimum. For the special case where the estimation data only seldom switches between the different submodels, we also suggest a way of trading off between optimality and complexity by using a change detection approach. 相似文献
109.
Friction and adhesion measurements between surfaces of cross-linked, stiff polymers of varying roughness against smooth, bare
mica surfaces were carried out in dry air as well as in the presence of lubricating oil. The nominal (macroscopic) contact
area varies with the applied load according to the Johnson, Kendall and Roberts (JKR) theory, yet shows significant hysteresis
due to the irreversibility arising from the loading/unloading curves of multiple asperities. Upon introducing the oil between
the surfaces, the critical shear stress is reduced to zero due to the elimination of the adhesion force. However, the effect
is less noticeable on the friction coefficient. Lastly, the effect of increasing the (RMS) roughness was greatest over the
first few nanometers due to the diminution of the adhesion-controlled contribution to the friction, after which a further
increase in roughness had less dramatic effects. A model is presented to account for the observed adhesion hysteresis during
repeated loading/unloading cycles of purely elastically deforming rough surfaces.
Bruno Zappone and Kenneth J. Rosenberg made equal contributions. 相似文献
110.
Berman Alan Steinberg Suzi Campbell Samuel Ulman Avi Israelachvili Jacob 《Tribology Letters》1998,4(1):43-48
The rational control of the friction and wear (damage) of engineering, as opposed to model, surfaces under practical conditions
such as high contact pressures has long been a technological challenge with much fundamental interest. Lubricant fluids and
physisorbed surfactant monolayers (boundary lubricants) are effective friction modifiers but often fail at high loads. We
show that the chemisorption of a suitably designed single-chained phosphonate surfactant onto crystalline α-alumina surfaces
produces robust protective monolayers that significantly reduce the friction forces and wear even at high loads. The mechanisms
are explained, which point to some general principles that offer a basis for scale-up in many different engineering systems.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献