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排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Animesh Chakravorty 《Israel journal of chemistry》1985,25(2):99-105
Model complexes of nickel(III) and nickel(IV) are furnished by hexadentate and tridentate oxime-imine-amine ligands derived by the condensation of biacetyl monoxime with amines. The synthesis, characterisation, structure, redox equilibria and reactivity of these complexes are critically reviewed. Correlations and generalisations pertaining to oxidation state stability, electroprotic equilibria and reaction mechanisms are examined. The possible significance of the present complexes in the context of the nickel-containing methanogenic enzymes is noted. 相似文献
992.
R. W. Warfield 《应用聚合物科学杂志》1985,30(3):1321-1322
993.
L. J. SCHREINER J. C. MACTAVISH L. MILJKOVI M.M. PINTAR R. BLINC G. LAHAJNAR D. LASIC L. W. REEVES 《Journal of the American Ceramic Society》1985,68(1):10-16
The proton free induction decay of a portland cement paste in an advanced stage of hydration can be roughly divided into three main components: (1) a component with a very short spin-spin relaxation time, T2 , representing the protons of the solid OH groups and the water of crystallization, (2) a component with an intermediate T, representing the bonded water in the gel phase, and (3) a third component with a relatively long T2 representing the water in the micropores and layers. The dependences of the intensities, T2 's, and spin-lattice relaxation times (T1 's) of these three components on the cement hardening time have been determined. The proton spin-lattice relaxation time of the "solid" component increases with hardening time whereas T1 decreases for the other two components. The observed time dependence of the diffusion coefficient, D, of water in a tricalcium silicate paste supports the findings of the above correlation study. 相似文献
994.
Mahmoud M. Abou el Leil Frank A. Camaratta Rocco R. DiGenova 《Journal of the American Ceramic Society》1985,68(1):18-C-
In-service fracture of helicopter windshields was studied. Simulated catastrophic fracture tests were conducted by firing alumina and steel spheres onto stationary tempered and as-received glass panels. The results were studied by Hertzian analysis and modified Auerbach's relations. Thermally tempered glass shows much higher impact resistance than that estimated from superposition of residual stresses. Subcritical impact sites exhibit slow crack growth in tempered plates, eventually leading to fracture of the entire plate. 相似文献
995.
J. T. DICKINSON L. C. JENSEN W. DAVID WILLIAMS 《Journal of the American Ceramic Society》1985,68(5):235-240
We present measurements of the electron, positive ion, and photon emission accompanying the fracture in vacuum of poly-crystalline 95/5 lead zirconate-titanate. The intensities of the charged-particle components of this fractoemission are shown to depend strongly on the direction (relative to the direction of fracture) and magnitude of polarization. The most intense emission is observed when the fracture surfaces are perpendicular to the polarization direction. The emission intensity increases monotonically with polarization. These results are interpreted in terms of a model involving charge separation on the fracture surfaces leading to a microdischarge during fracture. Implications to the interpretation of triboluminesence effects are discussed. 相似文献
996.
D. A. Morgan D. B. Shaw M. J. Sidebottom T. C. Soon R. S. Taylor 《Journal of the American Oil Chemists' Society》1985,62(2):292-299
The results presented in the literature, which attempt to elucidate the mechanisms by which triglyceride oils are bleached
by earths, are reviewed. The impact of this work and how the mechanistic proposals affect changes in oil properties are considered,
with particular emphasis on the needs of the palm oil processor. Important properties include color, metals and phosphorus
content and oxidative stability of the oil.
Investigations made in our own laboratories have been aimed at elucidating the effect of varying physical and chemical properties
of the bleaching earth on the quality of bleached and deodorized oils. Techniques used in this work are pore-size distribution,
surface area, scanning and transmission electron microscopy and a variety of chemical and X-ray analysis methods.
The ability to vary such parameters in montmorillonite clays by alteration of process conditions to give materials with specific
performance characteristics is demonstrated.
Comparisons are made between acid-activated montmorillonites and other clay types. 相似文献
997.
998.
Faulkner D.W. Payne D.B. Stern J.R. Ballance J.W. 《Lightwave Technology, Journal of》1989,7(11):1741-1751
Some of the options for optical technology within the local loop environment are examined. In particular, passive shared access networks have been considered in some detail. These networks show great promise for delivering existing telephone services to small to medium business customers (4-30 lines) economically by the early 1990s. Extending fiber to the home will also be possible by virtue of a similar passive network infrastructure for customers requiring new broadband services beyond the single telephone line. For one-line plain old telephone service (POTS) customers, an intermediate approach of terminating the fiber network at the final network distribution point, with copper retained for the final leg, may be used prior to the provision of broadband services. A key feature of the passive optical network architecture is the use of wavelength-division multiplexing (WDM) as an upgrade strategy, allowing graceful upgrading from telephone services to multichannel high-definition television (HDTV) on gigabit/second bearers and full two-way switched broadband services employing wavelength routing across the network 相似文献
999.
1000.