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91.
Masayoshi Ohashi Kazuo Nakamura Kiyoshi Hirao Shuzo Kanzaki Stuart Hampshire 《Journal of the American Ceramic Society》1995,78(1):71-76
Homogeneous Y-Si-O-N glasses containing 15 or 20 eq% nitrogen (N) were prepared from compositions with Y/Si ratios in the vicinity of that of the lowest eutectic point on the Y2 O3 –SiO2 phase diagram. The liquidus on the phase diagram shifted toward lower temperatures by incorporation of N. The density, the elastic moduli, and the glass transition temperature of the Y-Si-O-N glasses increased with incorporation of N. This is due to the closer packing of atoms in the glasses by the substitution of N, which is in three-fold coordination with Si, for O which is in two-fold coordination, and the stronger covalent nature of the Si–N bond compared with the Si–O bond. The coefficient of thermal expansion of the Y-Si-O-N glasses increased with increasing Y content, because the discontinuity of the glass network developed with increasing nonbridging anions by the introduction of Y. In contrast, the glass transition temperature and the elastic moduli increased with Y content due to the high coordination of Y for O, and the relatively high cationic field strength of Y. Furthermore, the effect of cationic field strength on properties of Ln-Si-O-N glasses (Ln = lanthanides or Y) is discussed. 相似文献
92.
In laboratory experiments conducted to compare the kairomonal activity forMicroplitis croceipes (Cresson) of frass fromHeliothis zea (Boddie) larvae fed on different host plants,M. croceipes females responded to extracts of frass from larvae reared on cotton or soybeans but not on corn. The lack of response to frass from larvae reared on corn was shown to be a result of a lack of some appropriate chemical(s) in the corn.Lepidoptera: Noctuidae.Hymenoptera: Braconidae.In cooperation with the University of Georgia College of Agriculture Experiment Stations, Coastal Plain Station, Tifton, Georgia 31793. Accepted for publication February 9, 1981.Mention of a proprietary product in this paper does not constitute an endorsement by this product by the USDA. 相似文献
93.
94.
Jeevan S. Abichandani Yatish T. Shah Donald C. Cronauer Raffaele G. Ruberto 《Fuel》1982,61(3):276-282
A model is presented for the kinetic study of the thermal liquefaction of Belle Ayr subbituminous and Burning Star bituminous coals with anthracene oil, hydrogenated anthracene oil and hydrogenated phenanthrene. All experiments were performed in a continuous-feed, stirred tank reactor, at a temperature of 450 °C and a space time of approximately 5 to 55 min. A kinetic model which includes a reaction: coal + oil→more reactive coal, correlates the data reasonably well. This reaction explains the net consumption of anthracene oil during the initial stages of liquefaction. Such a reaction may account for a portion of the swelling of coal at low space times and the sizable increase of viscosity of reaction slurry during these initial stages of liquefaction. It is also observed that the yield of oil increases when solvents of increasing hydrogen donor capacity are used. 相似文献
95.
Pure carbon dioxide was absorbed into distilled water and sodium hydroxide solution, in cocurrent two phase annular flow in helically coiled tubes in order to measure physical and chemical mass transfer coefficients and interfacial areas. (k*La) was correlated by the pressure drop in the test sections and interfacial areas were found to vary with the liquid phase energy dissipation. According to a new theory, (k*L) has been shown to be a function of the root mean square vorticity near the interface. The root mean square vorticity has been related to the pressure drop, gas density, liquid flow rate and liquid velocity. The physical mass transfer coefficients theoretically predicted are in good agreement with experimental results. 相似文献
96.
Apparatus and procedure for measuring release rates from formulations of lepidopteran semiochemicals
John H. Cross James H. Tumlinson Robert E. Heath Donald E. Burnett 《Journal of chemical ecology》1980,6(4):759-770
An apparatus was developed wherein a vacuum source was used to pull air across a controlled-release-formulation dispenser or a planchet containing a known quantity of a semiochemical and into a collector filled with a polymeric adsorbent. After a set time, the semiochemical was eluted with solvent and was quantified by gas-liquid chromatography (GLC). High percentages of known quantities of the lepidopteran semiochemicals (Z)-7-dodecen-l -ol acetate (Z7DDA), boiling point (bp) 275 ° C/1 atm, (Z)-9-tetradecen-1-ol formate (Z9TDF), bp 289 °C/1 atm, and (Z,Z)-3,13-octadecadien-1-ol acetate (ZZODDA), bp 490 °C/1 atm, were recovered. The semiochemicals did not oxidize and were recovered quantitatively from the adsorbent. The release rates of Z9TDF from a controlled-release dispenser were found to be directly proportional to the airflow rates. Release rate measurements on the Z9TDF dispensers were made for the purpose of estimating the method's precision. The method was shown to give internally consistent results by measurements on another Z9TDF formulation. The accuracy of the method is discussed.Mention of a commercial or proprietary product in this paper does not constitute an endorsement by the USDA. 相似文献
97.
Biaoan Shan Li Cai Donald E. Hatfield Shuqin Tang 《Information Technology and Management》2014,15(2):99-108
Despite the fact that the resource-based view has drawn a great deal of attention in studying new ventures, our understanding on resource management in the emerging economies is limited and there are many unsolved issues. In this paper, theoretical reasoning approach is applied to analyze the relationship between the entrepreneurial resources and the organizational capabilities (including operating and dynamic capabilities) for new ventures. An empirical study in the context of emerging economy in China is conducted to verify the theoretical reasoning. As information technology becomes a key element for new ventures, the enterprise resources relevant to the network technology and e-commerce are especially focused, as well as the impact of information acquisition on the resource combination. The results from the theoretical and empirical study have shown that resource combination mediates the relationship of entrepreneurial resources and organizational capability. It is also found that the information acquisition affects the organizational capabilities significantly; however, there is an inverted U-shape relationship between the information acquisition and the resource combination in emerging economies . 相似文献
98.
Processing of Silicon Carbide-Mullite-Alumina Nanocomposites 总被引:2,自引:0,他引:2
Yoshio Sakka Donald D. Bidinger Ilhan A. Aksay 《Journal of the American Ceramic Society》1995,78(2):479-486
Nanocomposite materials in the form of nanometer-sized second-phase particles dispersed in a ceramic matrix have been shown to display enhanced mechanical properties. In spite of this potential, processing methodologies to produce these nanocomposites are not well established. In this paper, we describe a new method for processing SiC-mullite-Al2 O3 nanocomposites by the reaction sintering of green compacts prepared by colloidal consolidation of a mixture of SiC and Al2 O3 powders. In this method, the surface of the SiC particles was first oxidized to produce silicon oxide and to reduce the core of the SiC particles to nanometer size. Next, the surface silicon oxide was reacted with alumina to produce mullite. This process results in particles with two kinds of morphologies: nanometer-sized SiC particles that are distributed in the mullite phase and mullite whiskers in the SiC phase. Both particle types are immersed in an Al2 O3 matrix. 相似文献
99.
Lynnette S. Walsh Hentges Donald C. Beitz Norman L. Jacobson A. Dare McGilliard Jeffrey J. Veenhuizen 《Lipids》1985,20(11):735-742
In a 2×2 factorial arrangement, miniature pigs were fed four diets containing vegetable protein/fat (soybean) and animal protein
(egg white)/fat (beef tallow) to demonstrate the effects of protein and fat source on total plasma cholesterol, lipoprotein
distribution, low density lipoprotein (LDL) composition, and plasma clearance of LDL-cholesterol and protein. Beef tallow
consumption resulted in greater plasma cholesterol concentration, decreased LDL-cholesterol concentration, and a lower LDL-cholesterol
to LDL-protein ratio than did consumption of soybean oil. High density lipoprotein (HDL)-cholesterol concentration was increased
by beef tallow consumption. Cholesterol percentage by weight in LDL was significantly greater in pigs consuming soybean oil
than those consuming beef tallow. Percentages by weight of protein, triglyceride and phospholipid in LDL were not significantly
different in any group. Dietary protein source had no significant effect on total plasma cholesterol concentration, lipoprotein
concentration or LDL composition. Egg white consumption decreased fractional catabolic rate and irreversible loss of LDL-cholesterol
and LDL-protein when compared with consumption of soy protein. Dietary fat source had no consistent effect on LDL clearance
from plasma. Dietary fat and protein seemed to influence lipoprotein metabolism by different mechanisms. Fat source altered
lipoprotein concentration and LDL composition, whereas protein source affected the removal rate of LDL from plasma.
Data taken from a dissertation submitted to Iowa State University by L. S. Walsh Hentges as partial fulfillment of the requirements
for the Ph.D. degree. A preliminary paper, was presented at the meeting of the American Oil Chemists' Society in Dallas, Texas,
May, 1984. 相似文献
100.
Nianxue Song Zhengqian Xuan Jonathan K. Bartley Stuart H. Taylor David Chadwick Graham J. Hutchings 《Catalysis Letters》2006,106(3-4):127-131
The use of a periodic flow reactor is described for the oxidation of butane to maleic anhydride to compare the catalytic performance
of vanadium phosphate catalysts operating under aerobic and anaerobic conditions. It is found that for the catalyst prepared
via a standard VPO method, operation in the absence of oxygen leads to a very small enhancement in selectivity when butane
concentrations in the range 0.9–2.9% are used. Operation in the absence of oxygen leads to very small differences in conversion
such that the overall yield is enhanced and this effect is maximised for reactor feeds containing 1.5% butane. However, the
enhancement is negligible when the catalyst is operated at high conversion required for commercial operation, indicating that
reactors operating with continuous flow with aerobic conditions are preferred. Similar experiments are conducted for a catalyst
prepared by the VPD method and, in contrast, this catalyst gives lower butane conversion and maleic anhydride selectivity
when operated in the absence of oxygen. 相似文献