Vapor-phase fabrication and properties of continuous-filament ceramic composites     

Besmann TM  Sheldon BW  Lowden RA  Stinton DP 《Science (New York, N.Y.)》1991,253(5024):1104-1109

The continuous-filament ceramic composite is becoming recognized as necessary for new, high-temperature structural applications. Yet because of the susceptibility of the filaments to damage from traditional methods for the preparation of ceramics, vapor-phase infiltration has become the fabrication method of choice. The chemical vapor infiltration methods for producing these composites are now being studied in earnest, with the complexity of filament weaves and deposition chemistry being merged with standard heat and mass-transport relationships. Two of the most influential effects on the mechanical properties of these materials are the adhesion and frictional force between the fibers and the matrix, which can be controlled by a tailored interface coating. A variety of materials are available for producing these composites including carbide, nitride, boride, and oxide filaments and matrices. Silicon carbide-based materials are by far the most advanced and are already being used in aerospace applications.  相似文献   

Academy of Natural Sciences: Job Cuts     

Lapolla JS  Sheldon FH  Remsen JV  Brumfield RT  Baker DJ 《Science (New York, N.Y.)》2005,307(5715):1560

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Long creep-recovery behavior of bamboo-based products     

Xinxin Ma  Sheldon Q. Shi  Ge Wang  Benhua Fei  Zehui Jiang 《Journal of Wood Science》2018,64(2):119-125

This paper describes the bending creep behavior of two types of bamboo-based products, bamboo-laminated veneer lumber (BLVL), and glued-laminated bamboo (GLB, also called Bamboo Glulam) at different stress levels for half a year and recovery for the same time. It was found that the stress level of BLVL was more sensitive on creep property than that of GLB; the creep resistance of GLB was worse than that of BLVL in the stress levels of 30–50%; the instantaneous recovery ratio (elastic recovery to elastic creep) decreased with an increase of the stress levels, while the residual ratio (residual deformation corresponded to the total creep deflections) increased with an increase of stress levels for all specimens; Burgers model fit creep data very well for both bamboo-based products, while the recovery Weibull equation does not fit recovery data well for GLB.  相似文献   

Season-specific survival rates and densities of coastal cutthroat trout across stream sizes in southwestern British Columbia     

Kim A. Sheldon  John S. Richardson 《Ecology of Freshwater Fish》2022,31(1):102-117

Variation in seasonal survival rates, densities and growth rates of coastal cutthroat trout (Oncorhynchus clarkii clarkii) were assessed across a size gradient of small, forested streams in the Pacific Northwest. We used a robust, mark-recapture study, stratified seasonally to estimate monthly survival rates of trout in coastal British Columbia (not including young-of-the-year). Survival estimates showed that the summer season had the lowest monthly survival rates (0.907) across all streams in our study (0.927 remainder of year). Within the size range of the seven small streams studied, low-flow habitat availability (defined by residual pool depth in summer) was the best predictor of mean monthly survival rates, supporting the hypothesis that trout survival increases with the quantity of aquatic habitat, particularly depths of residual pools. In addition, there was an asymptotic relation between water depth and survival rates, where beyond ~20 cm of residual pool depth, greater depth did not confer greater rates of trout survival. Growth rates in all but the largest stream were also lowest during summer. While densities tended to be higher in streams with greater residual depth, this was not significant. Body mass in a given season was a good predictor of survival to the next sampling period. The distribution and success of resident cutthroat trout populations in small streams appear to be constrained by summer low-flow periods and specific geomorphologies that support deeper pools.  相似文献