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91.
PAUL PREDECKI J. HAAS JOHN FABER Jr. R. L. HITTERMAN 《Journal of the American Ceramic Society》1987,70(3):175-182
The mechanism of lattice thermal expansion in pure hexagonal cordierite prepared by glass devitrification was investigated by time-of-flight neutron powder diffraction at temperatures from 22° to 750°C under vacuum. Full matrix least-squares refinement of the diffraction spectra was carried out in space group P6/mcc using the Rietveld method. The structural data from the refinements were resolved into components parallel and normal to the c axis. The negative c axis expansion results from two effects: (1) increasing distortion of the T2 tetrahedral (ring tetrahedra) with temperature, primarily due to displacement of the T2 cations toward the c-axis channels in the structure; (2) decreasing distortion of the T1 /M tetrahedra/ octahedra with increasing temperature, due to octahedral I (M-O1 ) bond expansion and an associated decrease in torsional distortion of the T1 tetrahedra. 相似文献
92.
Processing and Properties of Particulate Composites from Coated Powders 总被引:13,自引:0,他引:13
Tyrone D. Mitchell Jr. Lutgard C. De Jonghe 《Journal of the American Ceramic Society》1995,78(1):199-204
A method is described for sintering of highly loaded (≤20 vol%) alumina matrix/silicon carbide whisker or platelet composites to closed porosity. The method uses controlled heterogeneous precipitation in a suspension of whiskers or platelets. The suspension-coated particles are calcined to produce a free-flowing composite powder which can be hot-pressed or free-sintered to high density. The results of consolidation and mechanical property testing are reported. 相似文献
93.
Eicosa-5,8,11,14-tetraynoic acid or arachidonic acid or no supplement (controls) was given orally to rats maintained on a
fat free diet and the fatty acid composition of total lipids of several organs determined. No changes were noted in the total
fatty acid concentrations of the organs examined in the various groups. A decrease in the amount of arachidonic acid, 22∶4ω6
and 22∶5ω6 (as percent of total fatty acids), and an increase in the amount of 20∶3ω6 and linoleate were observed in total
lipids of several organs. In the group receiving the arachidonate supplement, there was less linoleate and 20∶3ω6 and more
arachidonate than in the controls. Both eicosa-5,8,11,14-tetraynoic acid and arachidonate supplements resulted in a decrease
in 20∶3ω9 in most organs studied. Generally, the most marked changes were seen in liver but, of the other organs examined
(heart, kidney, testis, brain, and adrenals), only the adrenals failed to show any significant differences between the controls
and each of the two supplemented groups. Although the experimental conditions preclude conclusive interpretation of the changes
observed, it is suggested that eicosa-5,8,11,14-tetraynoic acid was effective in inhibiting the conversion of linoleate to
arachidonate and the conversion of arachidonate to 22∶4 and 22∶5. 相似文献
94.
Thomas J. Brumm C. R. Hurburgh Jr. 《Journal of the American Oil Chemists' Society》1990,67(11):747-749
Drought stress created shriveled and wrinkled (S/W) soybeans in the 1988 soybean crop. Seven lots of 1988 soybeans were examined
to validate the Federal Grain Inspection Service (FGIS) definition of S/W. Lots were subdivided into sized fractions with
both slotted and round-hole screens. Shriveled and wrinkled soybeans were found in all size fractions, whether those fractions
were determined by a slotted or a round-hole screen. None of the size fractions adequately isolated or characterized S/W soybeans.
The FGIS definition of shriveled and wrinkled does not sonsider larger wrinkled soybeans, but only shriveled soybeans passing
through a 10/64″ by 3/4″ slotted screen. The most accurate determination of S/W soybeans can be made by examining the entire
soybean sample, not a sized fraction. 相似文献
95.
Desulphurization of fifteen US coals of rank ranging from anthracite to sub-bituminous B and five high-temperature chars by carbon monoxide and other gases and gas mixtures between 400 and 600 °C has been studied. The sulphur content of the parent coals ranged between 3.0 and 7.3% and that of the chars between 1.3 and 3.8% by weight. A comparison between air, nitrogen, carbon monoxide, and steam-carbon monoxide mixtures as desulphurizing gases shows the order of desulphurizing ability as . 相似文献
96.
Evandro Eduardo Broday Antonio Augusto de Paula XavierReginaldo de Oliveira 《International Journal of Industrial Ergonomics》2014
The incorrect determination of metabolic rate can be linked to discrepancies between the model of the PMV (Predicted Mean Vote) and real thermal sensation collected in field studies. Aiming to improve the correlation of the PMV model and the real thermal sensation, this work established new values for the metabolic rate: one way being called “calculated” using Newton's Method and the other called "measured" using a metabolic analyzer. Welder's activities were evaluated, through the measurements of environmental and personal variables. New values of metabolic rate were determined for this activity. The values found for the calculated form and the measured one were, respectively, 178.63 and 145.46 W/m2, different from the range provided by the table of ISO 8996 (2004) for this activity (75–125 W/m2). In order to verify which of the values of the metabolic rate was closer to the real thermal sensation of PMV, a linear regression was made between the PMV and the real thermal sensation in three ways: S × PMVtabulated (R2 = 0.1749), S × PMVcalculated (R ² = 0.7481) and S × PMVmeasured (R2 = 0.7854). It was found that the values measured by the instrument gave a higher coefficient of determination which was chosen for the correction of the table. The correction of the table provides a value of Mpredicted, that is a value of metabolic rate that corrects the values provided by the tables of ISO 8996 (2004), by means of a correction coefficient. For the welder's activities in a metal-mechanics industry, tabulated values can be multiplied by the correction coefficient 1.4648 in order to minimize inaccuracies. The PMVpredicted, obtained through the Mpredicted, when related to the actual thermal sensation, provides a coefficient of determination of 0.7511, thereby improving the model of the PMV. 相似文献
97.
R. J. Hron Sr. S. P. Koltun A. V. Graci Jr. 《Journal of the American Oil Chemists' Society》1982,59(5):233-237
The 1976 and 1977 crops of glanded cottonseed from oil mills located in 7 major U.S. cottonbelt growing areas were evaluated
as to their suitability for processing into edible, high-protein flours. Both the physical and chemical characteristics of
fuzzy seed samples were studied. Ginned seed samples were hulled, dried, comminuted, slurried with hexane and liquid classified
by both a laboratory differential settling test (DST) and pilot plant liquid cyclone process (LCP). Liquid cyclone operating
data and extensive analytical data of the kernels, flour and meals produced are shown. A free gossypol level of 1.10% or less
in full fat kernels was the determining factor for producing edible flours from glanded seed by the LCP. The Lower Rio Grande
Valley area was the only area from which liquid classified cottonseed flour consistently exceeded the current maximal free
gossypol standard of 450 ppm. Ca. 94% of the total U.S. cottonseed production is suitable for producing edible, high-protein
flours by liquid classification. 相似文献
98.
J. Mustafa M. S. Ahmad Jr. A. Rauf S. M. Osman 《Journal of the American Oil Chemists' Society》1990,67(12):937-939
Branched-chain thioethers have been prepared from methyl 4-oxo-trans-2-hexadecenoate and 9,12-dioxo-trans-10-octadecenoic acid. The reagents involved in these preparations were mercaptoacetic and mercaptopropionic acids. The yields
of these thioethers are almost quantitative. 相似文献
99.
Phenolic acids and related compounds were separated by gas chromatography using three separate columns. One of these columns was coupled to a Fourier transform infrared spectrometer. The trimethylsilyl derivatives could be separated and identified by comparing the relative retention times of the three different columns. However, where there was overlap, the accompanying infrared data clearly distinguished between the questionable derivatives, thus enabling characterization of all derivatives.The use of trade, firm, or corporation names in this article is for the information and convenience of the reader. Such use does not constitute an official endorsement or approval by the U.S. Department of Agriculture or the Forest Service of any product or service to the exclusion of others that may be suitable. 相似文献
100.
G. SCOTT GLAESEMANN JOHN E. RITTER Jr. KARL JAKUS 《Journal of the American Ceramic Society》1987,70(9):630-636
Mixed-mode failure of soda-lime glass under inert and fatigue test conditions was studied using Knoop indentation flaws. For annealed cracks (residual stress-free) crack extension (catastrophic or subcritical) is by an abrupt transition from the initial crack plane to a noncoplanar crack plane followed by a reorientation of the crack normal to the applied stress. Although fatigue strength of these inclined flaws increased linearly with respect to orientation of the flaws to the applied stress up to an angle of 60°, this increase was considerably less than what was predicted by existing theories. It is believed that subcritical crack growth causes the crack to be realigned perpendicular to the applied stress before failure for all orientations; hence, fatigue strength does not show the dramatic increase at orientation angles as predicted by theory. For as-indented cracks the contact residual stress causes the crack extension to be less inclined to the initial crack plane than for annealed cracks, but in this case also, the crack realigns itself perpendicular to the applied stress. Again, fatigue strength is relatively insensitive to the orientation angle as predicted by theory and subcritical crack growth is believed to play a primary role in determining this strength dependency. 相似文献