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991.
A strong and permanent ultraviolet photosensitivity enhancement was locked into standard optical fiber pre-treated with above-bandgap 157-nm F/sub 2/-laser radiation. Below-bandgap 248-nm irradiation of the pre-treated fiber yielded fiber Bragg gratings (FBGs) with an index contrast of 6.5 /spl times/ 10/sup -4/, a value four-fold larger than that available in 16% Ge-doped photosensitive fiber. The F/sub 2/-laser photosensitivity locking was 300 times more effective than with KrF-laser pre-treatment in terms of the accumulated fluence required to lock in a similar refractive index change. Accelerated FBG aging tests equivalent to 25 years at 70/spl deg/C revealed a less than 2% reflectivity decay in both 157- and 248-nm pre-treated fibers, which is sufficient to eliminate the postannealing step typically required in hydrogen-loaded fibers. The large photosensitization and the superior thermal stability of both 248- and 157-nm pre-treated fibers are associated with a new Si-H bond absorption feature at 1387 nm, which appears only during the FBG formation step. 相似文献
992.
Leopoldo P.R. de Oliveira Karl Janssens Peter Gajdatsy Herman Van der Auweraer Paulo S. Varoto Paul Sas Wim Desmet 《Mechanical Systems and Signal Processing》2009,23(2):476-488
Active control solutions appear to be a feasible approach to cope with the steadily increasing requirements for noise reduction in the transportation industry. Active controllers tend to be designed with a target on the sound pressure level reduction. However, the perceived control efficiency for the occupants can be more accurately assessed if psychoacoustic metrics can be taken into account. Therefore, this paper aims to evaluate, numerically and experimentally, the effect of a feedback controller on the sound quality of a vehicle mockup excited with engine noise. The proposed simulation scheme is described and experimentally validated. The engine excitation is provided by a sound quality equivalent engine simulator, running on a real-time platform that delivers harmonic excitation in function of the driving condition. The controller performance is evaluated in terms of specific loudness and roughness. It is shown that the use of a quite simple control strategy, such as a velocity feedback, can result in satisfactory loudness reduction with slightly spread roughness, improving the overall perception of the engine sound. 相似文献
993.
994.
Confocal microscopy of the mitochondrial permeability transition in necrotic cell killing, apoptosis and autophagy 总被引:1,自引:0,他引:1
JJ Lemasters T Qian SP Elmore LC Trost Y Nishimura B Herman CA Bradham DA Brenner AL Nieminen 《Canadian Metallurgical Quarterly》1998,8(3-4):283-285
Onset of the cyclosporin-A-sensitive mitochondrial permeability transition (MPT) in individual mitochondria within living cells can be visualized by laser scanning confocal microscopy. The MPT is a causative event in many types of necrotic and apoptotic cell death, including oxidative stress, ischemia/reperfusion injury, Ca2+ ionophore toxicity and tumor necrosis factor alpha (TNF alpha) induced apoptosis, and may contribute to Reye's-related drug toxicity. Pyridine nucleotide oxidation, mitochondrial generation of reactive oxygen species, and increased mitochondrial Ca2+ and pH can each promote onset of the MPT in situ. The MPT can also be directly visualized during TNF alpha-induced apoptosis to hepatocytes. Mitochondria spontaneously depolarize in situ after nutrient deprivation before entering an acidic lysosomal compartment, suggesting that the MPT precedes the normal process of mitochondrial autophagy. We propose a model in which onset of the MPT to increasing numbers of mitochondria leads progressively to autophagy, apoptosis and necrotic cell death. 相似文献
995.
Restrained and unrestrained eaters were weighed 5 lb (2.27 kg) heavier or 5 lb lighter than their actual weight or were not weighed at all. Unrestrained eaters and restrained eaters who were told they weighed 5 lb less were not affected by the false weight feedback. However, restrained eaters who were informed that they weighed S lb more reported lower self-esteem, less positive moods, and more negative moods than did restrained eaters in the other 2 conditions. Furthermore, restrained eaters who were led to believe that they weighed heavier ate significantly more food during a subsequent "taste test" than did each of the other groups. Restrained eaters who believed that they were heavier experienced lowered self-worth and a worsening of mood that led them to relinquish their dietary restraint and overindulge in available food. lmplications for patients with eating disorders are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
996.
Research into the effects of color on grip strength has produced inconsistent results, but studies show methodological problems, for example, the non-standardised reporting of stimulus colours, differing intertrial rests, and the neglect of warm-up effects. The present study was designed to replicate the 1989 work by Hasson, et al. and also to examine potential brightness effects of stimuli on grip strength. Analysis indicated brightness effects might confound potential to produce Type I errors. 相似文献
997.
PREMO is an emerging international standard for the presentations of multimedia objects including computer graphics. Open Inventor™ is a commercially available "de facto" standard for interactive computer graphics packaged as a library of objects. In this paper, we consider whether the concepts and objects of PREMO are sufficient to represent a professional quality system, such as Open Inventor.
By comparing PREMO with Open Inventor, we hope to show that PREMO's computer graphics environment model and event model can properly describe Open Inventor's rendering action and event model. The scene graph is very important in Open Inventor. Most Open Inventor functions rely on various operations over scene graphs. The construction, edition and traversal of the scene graphs are implemented as a set of newly defined PREMO objects. Graphics rendering, event handling and scene graphs constitute the fundamental parts of Open Inventor, other Open Inventor functionalities can be constructed from these. We conclude that since these three fundamental parts of Open Inventor can be properly modelled and implemented by means of PREMO, that the concepts and objects of PREMO are sufficient to represent Open Inventor. 相似文献
By comparing PREMO with Open Inventor, we hope to show that PREMO's computer graphics environment model and event model can properly describe Open Inventor's rendering action and event model. The scene graph is very important in Open Inventor. Most Open Inventor functions rely on various operations over scene graphs. The construction, edition and traversal of the scene graphs are implemented as a set of newly defined PREMO objects. Graphics rendering, event handling and scene graphs constitute the fundamental parts of Open Inventor, other Open Inventor functionalities can be constructed from these. We conclude that since these three fundamental parts of Open Inventor can be properly modelled and implemented by means of PREMO, that the concepts and objects of PREMO are sufficient to represent Open Inventor. 相似文献
998.
Tommy J. George M. -H. Herman Shen Steven M. Huybrechts Troy E. Meink Peter M. Wegner 《Composite Structures》2001,52(3-4):277-286
An optimization procedure has been developed to uniquely and efficiently determine the “best” local geometry design of a new composite ChamberCore structure. This procedure is based on minimization of the total mass of a single composite ChamberCore subject to a set of design and stress constraints. The stress constraints are obtained in closed form based on the composite box-beam model for various composite lamination designs and loading conditions. The optimization problem statement is constructed and then solved using the VMCON optimization program, which is an iterative sequential quadratic programming (SQP) technique based on Powell's algorithm. The sensitivity of the solution of the optimal geometry to the values of parameters that characterize the structural durability and the failure mechanism is discussed. 相似文献
999.
The control of the amount of solute carbon in ultra low carbon Ti IF steels during ferrite rolling and subsequent recrystallization is of prime importance for the development of an appropriate recrystallization texture and for the production of thin deep drawable hot strips. In the present work, the effect of the solute carbon content and the rolling conditions on the recrystallization texture after ferrite rolling and on the corresponding Lankford value was quantified. Therefore, ultra low carbon Ti IF steels with different sulphur and titanium contents were rolled in the ferrite region, in order to obtain a variation in solute carbon content (from 0 to about 10 ppm) at the ferritic rolling temperatures. It was shown that a deep drawing grade (rmean> 1.4) can be obtained if the chemical composition of the steel guarantees a complete stabilisation of the solute carbon in the austenitic temperature region and if sufficient strain (85%) is given in the finishing train at temperatures lower than about 800°C. It can be concluded that the sulphur and titanium contents have to be chosen slightly higher in comparison to the conventional Ti IF steel grades used for cold rolling and annealing. 相似文献
1000.
Comments on the results used by U. Neisser et al (see record 83-26553) in the American Psychological Association (APA) task force study on intelligence, which cited the Carolina Abecedarian Project (C. T. Ramey and F. A. Campbell, 1987) as an example of a successful early intervention program that produced larger and more lasting effects on intelligence scores than did Head Start programs. The author claims that Neisser et al "shortchange" the Carolina project by mentioning results occurring only at or after age 2, although startling test score differences were apparent in Ss by age 18 mo. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献