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81.
82.
Keiichiro Adachi Gilroy Harrison John Lamb Alastair M. North Richard A. Pethrick 《Polymer》1981,22(8):1026-1031
The effects of annealing on ultrasound propagation in drawn samples of polypropylene are reported. Below 373K the attenuation is dominated by scattering associated with voids generated during the drawing process. Above 383K the void content changes significantly with an associated decrease in the ultrasonic attenuation. Shrinkage, changes in optical clarity and changes in density of the drawn samples are discussed in terms of possible modification of the polymer structure. 相似文献
83.
The attenuation and velocity of ultrasonic longitudinal waves of frequencies 5–35 MHz in poly (methyl methacrylate), poly(ethyl methacrylate), poly (n-butyl methacylate) and poly(isobutyl methacrylate) between 233 and 363K are reported. The methyl and ethyl polymers showed evidence of a single relaxation process (associated with cooperative main chain and ester group motions), but the butyl polymers showed also a second relaxation at about 200–230K. This is associated with conformational rearrangement of the alkyl group, and the acoustic energetics are in line with theoretical predications for this process.The velocity data show the expected decreases due to the main glass transition (and cooperative processes) and to reduction of the intermolecular interaction force constant with increasing size of the alkyl group. Attempts to calculate an acoustic low temperature specific heat yielded values lower than expected from calorimetric observations, showing that the acoustic modes are capable of greater energy storage than is involved in the longitudinal perturbation, and/or that calculation based on a Debye T3 law are invalid for these glassy polymers. 相似文献
84.
85.
The paper summarises recent progress on materials modelling and numerical simulation of soft body impact damage in fibre reinforced
composite aircraft structures. The work is based on the application of finite element (FE) analysis codes to simulate damage
in composite shell structures under impact loads. Composites ply damage models and interply delamination models have been
developed and implemented in commercial explicit FE codes. Models are discussed for predicting impact loads on aircraft structures
arising from deformable soft bodies such as gelatine (synthetic bird) and ice (hailstone). The composites failure models and
code developments are briefly summarised and applied in the paper to numerical simulation of synthetic bird impact on idealised
composite aircraft structures. 相似文献
86.
Tremblay Sébastien; Parmentier Fabrice B. R.; Guérard Katherine; Nicholls Alastair P.; Jones Dylan M. 《Canadian Metallurgical Quarterly》2006,32(5):1208
In 2 experiments, the authors tested whether the classical modality effect--that is, the stronger recency effect for auditory items relative to visual items--can be extended to the spatial domain. An order reconstruction task was undertaken with four types of material: visual-spatial, auditory-spatial, visual-verbal, and auditory-verbal. Similar serial position curves were obtained regardless of the nature of the to-be-remembered sequences, with the exception that a modality effect was found with spatial as well as with verbal materials. The results are discussed with regard to a number of models of short-term memory. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
87.
This paper investigates fundamental properties of marker-based vision (MBV) systems. We present a theoretical analysis of the performance of basic tag designs which is extended through simulation to investigate the effects of different processing algorithms. Real-world data are processed and related to the simulated results. Image processing is performed using Cantag, an open-source software toolkit for building marker-based vision (MBV) systems that can identify and accurately locate printed markers in three dimensions. Cantag supports multiple fiducial shapes, payload types, data sizes and image processing algorithms in one framework. This paper explores the design space of tags within the Cantag system, and describes the design parameters and performance characteristics which an application writer can use to select the best tag system for any given scenario. 相似文献
88.
89.
JA Stoute KE Kester U Krzych BT Wellde T Hall K White G Glenn CF Ockenhouse N Garcon R Schwenk DE Lanar P Sun P Momin RA Wirtz C Golenda M Slaoui G Wortmann C Holland M Dowler J Cohen WR Ballou 《Canadian Metallurgical Quarterly》1998,178(4):1139-1144
The malaria sporozoite vaccine candidate RTS,S, formulated with an oil-in-water emulsion plus the immunostimulants monophosphoryl lipid A and the saponin derivative QS21 (vaccine 3), recently showed superior efficacy over two other experimental formulations. Immunized volunteers were followed to determine the duration of protective immune responses. Antibody levels decreased to between one-third and one-half of peak values 6 months after the last dose of vaccine. T cell proliferation and interferon-gamma production in vitro were observed in response to RTS,S or hepatitis B surface antigen. Seven previously protected volunteers received sporozoite challenge, and 2 remained protected (1/1 for vaccine 1, 0/1 for vaccine 2, and 1/5 for vaccine 3). The prepatent period was 10.8 days for the control group and 13.2 days for the vaccinees (P < .01). Immune responses did not correlate with protection. Further optimization in vaccine composition and/or immunization schedule will be required to induce longer-lasting protective immunity. 相似文献
90.
The bacterial chemotactic peptide, formyl-methionyl-leucyl-phenylalanine (fMLP), induces the generation of platelet-activating
factor (PAF), the mobilization of arachidonic acid and generation of superoxide anion (O2
−) in rabbit polymorphonuclear leukocytes (PMNs). The PAF receptor antagonists, WEB 2086 (10–100 μM) and CV 6209 (1–10 μM),
reduced the mobilization of arachidonic acid and the O2
− generation in response to fMLP but not that in response to A23187. Pretreatment of PMNs with the phospholipase A2 inhibitor, chloroquine, or the serine protease inhibitor, tosyl-phenylalanine chloromethyl ketone, reduced the fMLP-stimulated
generation of PAF and also reduced the generation of O2
−. The respiratory burst induced by a submaximal concentration of phorbol myristate acetate was not affected by these compounds.
These data are consistent with the suggestion that endogenous PAF may contribute to the signal transduction cascade initiated
by fMLP.
Based on a paper presented at the Third International Conference on Platelet-Activating Factor and Structurally Related Alkyl
Ether Lipids, Tokyo, Japan, May, 1989. 相似文献