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971.
研制了一种张应变准体In Ga As半导体放大器光开关.该结构具有显著的带填充效应,从而导致在80 m A的注入电流下,器件的3d B光带宽大于85 nm(1 5 2 0~1 6 0 9nm ) .该带宽几乎同时全部覆盖了C带(1 5 2 5~1 5 6 5 nm )和L带(1 5 70~1 6 1 0 nm ) .最为重要的是,在3d B光带范围内,光开关的偏振灵敏度小于0 .7d B;光纤到光纤无损工作电流在70~90 m A之间;消光比大于5 0 d B.通过降低了载流子寿命,开关速度有所提高.在未来密集波分复用通信系统中,这种宽带偏振不灵敏半导体放大器光开关很有实用前景 相似文献
972.
F. Chantraine M. Viana N. Brielles O. Mondain-Monval C. Pouget P. Branlard G. Rubinstenn D. Chulia 《Journal of surfactants and detergents》2006,9(3):267-277
The aim of this study is to investigate the functional characteristics (mechanical strength and disintegration time) of effervescent
detergent tablets containing chlorine provider in the presence of surfactant. A preliminary study high-lighted that the presence
of 2% of sodium dodecyl sulfate (SDS) was not favorable to the tablet mechanical properties, inducing a lower “bonding ability,”
whereas the disintegration time increased, compared with the reference tablets without surfactant. The linear relationship
between the disintegration time and the end-dissolution time led us to consider just the disintegration time to express the
behavior of the tablets in water. A parametric study has been completed to assess the influence of the mixing method, the
nature, the hydrophilic-lipophilic balance, the granulometry, and the concentration of the surfactant on the tablet properties.
In all cases, surfactant presented adverse effects on the mechanical properties and had a retarding effect on disintegration
time, but neither solubility, hydrophilic-lipophilic balance, interfacial properties, nor ionic character could be clearly
involved to explain surfactant contribution. Furthermore, tablet dissolution could not be correlated to surfactant available
surface, as evidenced by granulometry comparison on one side and concentration impact on the other side (a similar effect
was observed from 1 to 15%). On the contrary, mechanical properties were damaged as much as the area developed by surfactant
particles increased. On the basis of this work, it has been concluded that SDS interacts with the other compounds of the formula
by creating weak interparticle bonds and limiting water uptake responsible for disintegration. 相似文献
973.
Acoustic emission monitoring and numerical modeling
of FRP delamination in RC beams with non-rectangular cross-section 总被引:1,自引:1,他引:0
A case study concerning both numerical modeling and in-situ monitoring of a retrofitted RC beam with non-rectangular cross-section
is presented. Before retrofitting, non-destructive techniques, such as pull-out and impact tests, were used to estimate the
mechanical parameters of concrete. At the same time, a long-term monitoring with the Acoustic Emission (AE) technique was
carried out in order to investigate on creep effects and microcracking phenomena. Then, after a complete removal of the overload
and retrofitting with FRP sheets, an in-situ loading test was performed. At that stage, the AE technique was again profitably
used for the analysis of the cracking progression leading to FRP debonding. A numerical model of the structure is then proposed
in the framework of the FE discretization with mechanical parameters estimated according to an inverse analysis on the monitored
mechanical behavior of the structure before retrofitting. According to this model it is shown that, when the flexural inertia
of the retrofitted beam is considerably higher than that of the unrepaired beam, snap-back instabilities can take place. Finally,
considering the self-similarity between the acoustic emission phenomenon and seismicity, an analogy between the snap-back
instability of the FRP delamination and that occurring during fault growth is proposed.
Résumé Une étude de cas au sujet de modeler numérique et de surveiller in-situ d’un faisceau monté en rattrapage de RC avec la section transversale non-rectangulaire est présentée. Avant l’adaptation d’un faisceau, des techniques non destructives, telles que des essais à dégagement et à choc, ont été employées pour estimer les paramètres mécaniques du béton. En même temps, une surveillance à long terme avec la technique d’émission acoustique (AE) a été effectuée afin d’étudier sur des effets de fluage et des phénomènes de microfissuration. Puis, après un déplacement complet de la surcharge et l’adaptation ultérieure avec des feuilles de FRP, un essai in-situ de chargement a été réalisé. á cette étape, la technique d’AE a été encore profitablement employée pour l’analyse de la progression de fissures menant au décollement du FRP. On propose alors un modèle numérique de la structure dans le cadre de la discrétisation FE avec des paramètres mécaniques estimés selon une analyse inverse sur le comportement mécanique surveillé de la structure avant l’adaptation ultérieure. Selon ce modèle, on le démontre que, quand l’inertie flexural␣du faisceau monté en rattrapage est considérablement plus haute que cela de la structure non réparé, les instabilités de snap-back peuvent avoir lieu. En conclusion, vu l’auto similarité entre le phénomène d’émission et la séismicité acoustiques, on propose une analogie entre l’instabilité de snap-back du décollement de FRP et cela qui se produit pendant la croissance de défaut.相似文献
974.
Danijela A. Skobir Franc Vodopivec Ladislav Kosec Monika Jenko Jelena Vojvodi
‐Tuma 《国际钢铁研究》2004,75(3):196-203
The effect of microstructure on creep resistance of the low carbon chromium steel X20CrMoV121 after 100‐hours of static‐load test at a temperature of 580 °C and constant stress of 170 MPa was investigated. The specimens for the experiments were extracted from steam pipes of a steam power plant and heat treated. The effect of isothermal annealing on the microstructure and hardness as well as the kinetics of the precipitation of the carbide particles were determined. 相似文献
975.
PE管在燃气管网中的应用日趋广泛,目前正在尝试性地应用于定向钻穿越.文章就其允许的曲率半径、穿越长度、防腐及回拖时所受的拉伸应力等进行了讨论与比较. 相似文献
976.
Reduction Annealing for Cast Iron Powder and Its Effect on Sintered Antifriction Material Properties
The effect of reduction annealing for powder obtained from cast iron shavings on powder specimen properties is studied. An approximate mechanism is suggested for the oxidation-reduction process during annealing of cast iron powder. An increase in annealing temperature leads to an increase in carbon gasification rate and change in absolute powder weight. Prior reduction annealing for cast iron powder improves its compactability, and increases the mechanical properties of sintered material. The best mechanical properties were obtained for specimen made from cast iron powder reduced at 1000°C. Alloying an iron-cast iron charge with 3 mass% of nickel-chromium alloy leads to a marked improvement in the mechanical properties of a sintered composite. 相似文献
977.
J.R.F.G. Carvalho 《Chemical engineering science》2006,61(11):3632-3642
A study is presented of the hydrodynamic behaviour of very long gas slugs, rising co-currently with water along a 20 mm i.d. vertical tube. Visual observation (supported by pictures from video and still cameras) and the signals from a set of three fast response differential pressure transducers, were used to elucidate the flow behaviour of individual slugs of argon, with densities in the range 6.6-21.5 kg/m3 (corresponding to operating pressures in the range 0.4-1.3 MPa), as they rose in water that moved up the tube, with constant average velocity in the range 0.17-1.4 m/s. For the lower gas densities and liquid velocities the slugs were stable, but for the higher liquid velocities and/or gas densities, the slugs would become unstable, as a result of flooding in the wetted wall flow around them. The video sequences show clearly that, at the higher pressures, liquid from the film was dragged up by the gas, while the still pictures document the corresponding transition to churn flow in the lower regions of the rising slugs. 相似文献
978.
D'Onofrio Brian M.; Turkheimer Eric; Emery Robert E.; Slutske Wendy S.; Heath Andrew C.; Madden Pamela A.; Martin Nicholas G. 《Canadian Metallurgical Quarterly》2006,42(3):486
Parental divorce is associated with problematic offspring adjustment, but the relation may be due to shared genetic or environmental factors. One way to test for these confounds is to study offspring of twins discordant for divorce. The current analyses used this design to separate the mechanisms responsible for the association between parental divorce, experienced either before or after the age of 16, and offspring well-being. The results were consistent with a causal role of divorce in earlier initiation of sexual intercourse and emotional difficulties, in addition to a greater probability of educational problems, depressed mood, and suicidal ideation. In contrast, the increased risk for cohabitation and earlier initiation of drug use was explained by selection factors, including genetic confounds. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
979.
S. Sarkar A. Chourasia S. Maji S. Sadhukhan S. Kumar B. Adhikari 《Bulletin of Materials Science》2006,29(5):475-484
For tissue engineering purpose two gelatin based polyester urethane scaffolds of different compositions were prepared from
lactic acid, polyethylene glycol 400 (PEG 400) and characterized by FTIR, XRD for their mechanical and morphological properties
using SEM and optical microscopic analyses. Degradation and swelling studies of gelatin based polyester urethane scaffolds
in phosphate buffer saline (PBS) were performed. Human keratinocyte cells were cultured within these scaffolds, which showed
good cell adherence and proliferation. 相似文献
980.
Zhao Han-zhong Department of Mechanics Huazhong University of Science Technology Wuhan China Yeo Khoon Seng Department of Mechanical Production Engineering National University of SingaporeWT”HZ 《水动力学研究与进展(B辑)》2001,(1)
1 . INTRODUCTIONThedesiretoreduceskinfrictionandflownoisehasmotivatedanumberofstudiesonthestabilityoftheboundary layerflowovercompliantwalls .Fluidflowoveracompliantwallinvolvestheinteractionoftwowave bearingmedia .Consequently ,therearemanydifferenttypes… 相似文献