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991.
The tone sense multiaccess with partial collision detection (TSMA/PCD) protocol is particularly suitable for a packet satellite system serving an area with a dense population of earth stations. By incorporating a narrowband ground radio channel for broadcasting busy ones, the earth stations are able to avoid packet collisions by sensing for the absence of busy tones before transmitting packets. Partial collision detection capability can also be achieved. Single-tone TSMA/PCD gives 97% of the carrier-sense multiaccess with collision detection (CSMA/CD) throughput when N =10 tones are used, while for multitone and slot-by-slot announcement TSMA/PCD protocols only N =8 and N =2, respectively, are sufficient to drive the system to the CSMA/CD performance 相似文献
992.
Ferrite is a potential sorbent for flue gases such as CO2, H2S and SO2. This paper discusses the adsorption and decomposition of CO2 into carbon by hydrogen-activated waste ferrites prepared from Berkeley Pit acid mine water (Butte, MT). The decomposition effectiveness of these waste ferrites was studied at 300 °C and compared with the synthetic magnetite obtained from ferrous sulfate solution in our laboratory. The decomposition was measured by two methods: indirectly by measuring the adsorption rate of CO2 and directly by analysing the carbon deposited on the samples. The results indicated that the mixed waste ferrite had good affinity for the adsorption and decomposition. The CO2 decomposition data of both sorbents fitted the first-order reaction kinetics. Even though the surface area of the magnetite was higher than that of waste ferrite, the CO2 decomposition rate of the waste ferrite was estimated to be 2.5 times higher than that of magnetite under identical conditions. The carbon analysis deposited on the sample indicated that the CO2 was 100% decomposed into carbon and other carbon/hydrogen compounds by the waste ferrite, whereas the conversion was 43% by the magnetite. In terms of specific adsorption of carbon, ferrite was three to five times more efficient than magnetite. 相似文献
993.
A. E. Bohe J. J. Andrade Gamboa E. M. Lopasso D. M. Pasquevich 《Journal of Materials Science》1996,31(13):3469-3474
A chlorination process for recovering Zr from zircaloy scrap has been studied. Zircaloy chlorination was possible at temperatures as low as 220 °C. The scale microstructure and its effect on the zircaloy reactivity was analysed using Thermogravimetric analysis (TGA), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDXS) and scanning electron microscopy (SEM) techniques. A solid-solid phase transformation took place into the oxide scale during the zircaloy chlorination. Zirconium, as ZrCl4(g), was separated from the oxide scale and chlorides of Cr and Fe. The effect of the reaction temperature was also analysed. 相似文献
994.
Relationships among health care costs, social support, and occupational stress are investigated. Health care cost data were collected over two years for 260 working individuals. Multiple regression analyses were used to control for initial health care costs, age, and gender in predicting later costs; independent variables were stress, strain, social support, and their interactions. Main effects and interactions each accounted for significant proportions of the variance in various health care costs. 相似文献
995.
The effect of particle distribution on damage formation in particulate reinforced metal matrix composites deformed in compression 总被引:1,自引:0,他引:1
P.B. Prangnell S.J. Barnes S.M. Roberts P.J. Withers 《Materials Science and Engineering: A》1996,220(1-2):41-56
Image analysis results are reported on the generation of damage in particulate reinforced metal matrix composites during compressive deformation. The technique allows the automated collection of data on the incidence of particle fracture and void formation in the matrix as a function of important microstructural parameters such as local particle volume fraction and particle size. There is a strong relationship between damage and the local volume fraction of the reinforcement proving that damage formation is accentuated in regions of particle clustering. With the SiC reinforced materials examined, there was observed to be a change in dominance of damage mechanism from particle fracture at low local volume fractions to void formation in the matrix within strongly clustered regions. The results are compared with finite element (FE) modelling of the compressive deformation of clustered particles using a simple cluster of equi-spaced particles. The FE results suggest that plastic flow is generally inhibited in clustered regions. In certain highly clustered configurations shielding is such that flow does not occur in the heart of the cluster even at high levels of average plastic strain. The modelling suggests that the change in dominance of damage mechanism is related to the dramatic increase in tensile hydrostatic stresses in the matrix with higher levels of particle clustering. 相似文献
996.
997.
R.M. Scanlan W.A. Barletta D. Dell'Orco A.D. McInturff A. Asner E.W. Collings P.F. Dahl H. Desportes A. Devred R. Garre E. Gregory W. Hassenzahl M. Lamm D. Larbalestier D. Leroy P. McIntyre J. Miller T. Shintomi H. ten Kate S. Wipf 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》1996,380(3):544-554
998.
999.
Three roller/blade tachometric chamber transducers, with capacities of 2, 10, and 20 cm3/rev, have been designed for measuring low flow rates.
Translated from Izmeritel'naya Tekhnika, No. 5, pp. 37–41, May, 1996. 相似文献
1000.
Experiments conducted at ground stations of the Quasar satellite communication network using both a null base as well as a
base of around 2000 km is described. In experiments with a null base, the time scale transmission error was 1 nsec. Comparison
of the results of collocation with data cbtained by the GLONASS system in the course of experiments using a 2100-km base demonstrated
a divergence of the results of from 5 to 25 nsec.
Translated from Izmeritel'naya Tekhnika, No. 4, pp. 35–38, April, 1996. 相似文献