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151.
Kevin Mitchell 《Architectural Design》2015,85(1):38-45
Despite a distinguished heritage of learning in the Middle East, the expansion of provision for higher education is currently at an unprecedented scale. The Gulf States, in particular, are seeking to keep up with accelerated population growth and a demographic ‘youth bulge’. Guest-Editor Kevin Mitchell describes the architectural approaches employed in the design of institutions in the region from the first universities in Saudi Arabia to Foster + Partners's ground-breaking sustainable design for the Masdar Institute in Abu Dhabi and future projects. 相似文献
152.
J. H. Mitchell 《The International journal of environmental studies》2013,70(2-3):99-100
Three examples are given of views considered by the author to be misconceptions. 相似文献
153.
154.
New Zealand flower thrips, Thrips obscuratus (Thysanoptera: Thripidae), are attracted to ripening fruits, especially peaches. Volatiles from unripe and ripe peach fruits were collected and analyzed by gas chromatography/mass spectrometry. Six lactones were found only in ripe peach volatiles: γ-heptalactone, γ-octalactone, γ-nonalactone, 6-pentyl-2H-pyran-2-one, γ-decalactone, and δ-decalactone. When these compounds were tested individually in field-trapping experiments, three of them (γ-octalactone, γ-nonalactone, and 6-pentyl-2H-pyran-2-one) attracted New Zealand flower thrips. In another field-trapping experiment, aimed at testing various combinations of the three active compounds, no synergistic effects were found among all combinations tested; no combination caught more thrips than 6-pentyl-2H-pyran-2-one, alone. A further field-trapping experiment was conducted to determine the dose (10, 100, and 500 mg) of 6-pentyl-2H-pyran-2-one that gave the greatest catch of T. obscuratus, while also comparing it against another attractant, ethyl nicotinate, for T. obscuratus. The greatest catches in traps baited with either attractant were at loadings of 500 mg. At both 10 and 500 mg, traps baited with 6-pentyl-2H-pyran-2-one caught more T. obscuratus than those baited with the same amounts of ethyl nicotinate. 6-Pentyl-2H-pyran-2-one is a potent attractant for New Zealand flower thrips and, therefore, could be used for monitoring and control of New Zealand flower thrips. Work is underway developing monitoring and control options utilizing 6-pentyl-2H-pyran-2-one for this important pest. 相似文献
155.
156.
Philip F. Pagoria Alexander R. Mitchell Edward S. Jessop 《Propellants, Explosives, Pyrotechnics》1996,21(1):14-18
We report the synthesis and characterization of several bicyclic mono- and dinitrourea compounds as energetic materials and discuss their use as precursors to other energetic compounds. The new nitrolyzing reagent, trifluoromethanesulfonic acid anhydride/20% N2O5/nitric acid, will also be described. 相似文献
157.
Mitchell R. Armstrong Bohan Shan Joseph Winarta Bin Mu 《American Institute of Chemical Engineers》2020,66(2):e16816
A new class of core–shell adsorbents has been created by electrospun metal–organic framework (MOF) particles embedded in polymer nanofibers, which have provided many unique properties compared to the existing MOF coating technologies. For the first time, we demonstrate the improved adsorption selectivity of CO2 over N2 using electrospun polymer/ZIF-8 adsorbents in experiments. Furthermore, an analytical model based on the assumption that the diffusivity in core is 10 times higher than that in shell is developed to describe the theory of improved selectivity for core–shell adsorbents that is validated against a more accurate finite element model developed in COMSOL. Our model shows three regimes including exclusive shell uptake, linear core uptake, and asymptotic core uptake. These regimes are related to material properties and uptake times, which could be used as design criteria to balance core stability, maximum selectivity, and maximum uptake. An advanced HAADF STEM tomography (Movie S1 ) shows that the shell thickness in the case of polymer/ZIF-8 is on the order of 10 nm, allowing the regime of maximum selectivity to be realized. Kinetically limited adsorption tests at 45°C demonstrate that these composite fibers can perform in a regime of selectivity and uptake for the separation of CO2 and N2 that is unobtainable by either the MOF or fiber independently, showing a great potential for postcombustion CO2 capture. 相似文献
158.
Scott J. Robertson Marina B. Ruggles-Wrenn Randall S. Hay Theodore Shillig Ronald Mitchell Brian Kroeger Logan Gumucio 《Journal of the American Ceramic Society》2020,103(2):1358-1371
A facility for testing SiC fiber tows in static fatigue and creep at elevated temperatures in air and steam was developed. Static fatigue of Hi-Nicalon™-S fibers was investigated at 800°C-1100°C at applied stresses between 115 and 1250 MPa in air, in Si(OH)4(g)-saturated steam, and in unsaturated steam. Fibers tested in Si(OH)4(g)-saturated steam and in air had silica scales throughout the test sections, but those tested in unsaturated steam did not develop scales near the steam injection point. Fiber lifetimes in static fatigue were shortest in unsaturated steam, intermediate in Si(OH)4(g)-saturated steam, and longest in air. Failure strains did not exceed 0.3%. Steady-state strain rates and static fatigue lifetimes are modelled empirically by the Monkman-Grant relationship. Failure mechanisms are discussed. 相似文献
159.
Alexandra L. Mitchell Charlene M. Smith 《Journal of the American Ceramic Society》2020,103(9):4925-4938
Ion-exchangeable, transparent spinel glass-ceramics are presented and discussed here for the first time. To retain transparency with increasing crystallinity, spinel glass-ceramics must have uniform crystallization of small (~9 nm) crystallites, not large spherulitic structures comprised of small crystallites. To obtain such a uniform microstructure, the amount of total nucleating agents (ZrO2 + TiO2) in the precursor glass composition must be greater than 5 mol%. With small changes in composition and significant differences in microstructure, the demarcation between transparent and opaque glass-ceramics is distinct as is the decrease in K diffusivity during ion-exchange from the transparent (14.7 microns2/h) to the opaque (11.2 microns2/h) compositions. Understanding how to retain transparency during ceramming and increase diffusivity during chemical strengthening is critical in designing materials for many real-world applications. Ion-exchangeable, transparent spinel glass-ceramics are presented and discussed here for the first time. To retain transparency with increasing crystallinity, spinel glass-ceramics must have uniform crystallization of small (~9 nm) crystallites, not large spherulitic structures comprised of small crystallites. To obtain such a uniform microstructure, the amount of total nucleating agents (ZrO2 + TiO2) in the precursor glass composition must be greater than 5 mol%. With small changes in composition and significant differences in microstructure, the demarcation between transparent and opaque glass-ceramics is distinct as is the decrease in K diffusivity during ion-exchange from the transparent (14.7 microns2/h) to the opaque (11.2 microns2/h) compositions. Understanding how to retain transparency during ceramming and increase diffusivity during chemical strengthening is critical in designing materials for many real-world applications. 相似文献
160.
G.R Mitchell 《Polymer》1984,25(11):1562-1572
Molecular orientation parameters have been measured for the non-crystalline component of crosslinked natural rubber samples deformed in uniaxial tension as a function of the extension ratio and of temperature. The orientation parapeters 〈P2(cosα)〉 and 〈P4(cosα)〉 were obtained by an analysis of the anisotropy of the wide-angle X-ray scattering functions. For the measurements made at high temperatures the level of crystallinity detected was negligible and the orientation-strain behaviour could be compared directly with the predictions of molecular models of rubber elasticity. The molecular orientation behaviour with strain was found to be at variance with the estimates of the affine model particularly at low and moderate strains. Extension of the crosslinked rubber at room temperature led to strain-crystallization and measurements of both the molecular orientation of the non-crystalline chains and the degree of crystallinity during extension and relaxation enabled the role of the crystallites in the deformation process to be considered in detail. The intrinsic birefringence of the non-crystalline component was estimated, through the use of the 〈P2(cosα)〉 values obtained from X-ray scattering measurements, to be 0.20±0.02. 相似文献