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991.
992.
993.
Segregation of reactive metals at the bonding interface has been observed in various ceramic and/or metal joints bonded with
reactive metal-bearing braze alloys. When a d.c. of 20 mAcm−2 is applied to the ceramic/braze/ceramic system at a brazing temperature of, say, 1373 K, the electric field assists the segregation
at the braze-ceramic interface on the cathode side and suppresses the segregation at the interface on the anode side. This
may imply that reactive metal atoms in the braze can migrate as a cation. E.m.f. measurement on the ceramic (AIN or ZrB2)-metal foil systems with increasing temperature shows that a negative e.m.f. to the ceramic pole appears from about 900 K
for AIN and from 500 K for ZrB2, as does the thermally stimulated current in polymers. These temperatures coincide well with those where the electrical conductivity
of AIN and ZrB2, respectively, begins to increase with increasing temperature. Therefore, it is considered that the polarization of the ceramics
may take place and assist the migration, and consequently segregation, of reactive metals in braze alloys to the braze-ceramic
interface during brazing. 相似文献
994.
995.
M. Kangas J. Villegas N. Kumar T. Salmi D.Yu. Murzin F. Sandelin E. Harlin 《Catalysis Today》2005,100(3-4):363-366
An investigation of the effect of reaction conditions on product distribution in the skeletal isomerisation reaction of linear butenes has been carried out. The main reaction routes over ferrierite have been identified. Beside the main product isobutene, major by-product formation occurs. The unwanted reactions include dimerisation of butene to form octenes, hydrogen transfer yielding small amounts of saturated C3 and C4 hydrocarbons and disproportionation producing propene and pentenes. The most abundant by-products were pentene and propene, though these were not formed in equimolar amounts as could be expected. Oligomerisation experiments of propene over ferrierite produced large amounts of butene and pentene, revealing the presence of adsorbed nonene. The cracking of this surface species to hexene and propene is the most likely reaction route for the excess propene formation. This additional path to propene formation operates mainly at temperatures above 623 K. 相似文献
996.
J.H. Kaneko T. Tanaka S. Kawamura Y. Oshiki K. Tsuji M. Katagiri K. Ochiai T. Nishitani F. Fujita A. Homma T. Sawamura T. Iida M. Furusaka 《Diamond and Related Materials》2005,14(11-12):2027
Radiation detector was made of a high-quality CVD polycrystalline diamond composed of frost column like structure diamond grains, and induced charge distribution spectra and drift velocities were measured by using alpha particles. As a result, the CVD polycrystalline achieved maximum induced charge of 83% of HP/HT type IIa diamond. Moreover, the CVD crystal had lower charge loss on electrons compared with the HP/HT type IIa diamond. Drift velocities of electrons and holes were ve = 7.7 × 104 and vh = 7.3 × 104cm/s at an electric field of 20 kV/cm, respectively. In addition, response function measurement for 14 MeV neutrons was carried out. 相似文献
997.
The results of the synthesis of ceramic pigments using coprecipitation of hydroxides and difficultly soluble salts of multivalent
metal ions are described. The specifics of the coprecipitation process and the effect of various factors on the production
of the initial precipitates for subsequent synthesis of ceramic pigments are analyzed. The technology of pigment production
is described.
__________
Translated from Steklo i Keramika, No. 6, pp. 37 – 39, June, 2005. 相似文献
998.
The Metaflow architecture, a unified approach to maximizing the performance of superscalar microprocessors, is introduced. The Metaflow architecture exploits inherent instruction-level parallelism in conventional sequential programs by hardware means, without relying on optimizing compilers. It is based on a unified structure, the DRIS (deferred-scheduling, register-renaming instruction shelf), that manages out-of-order execution and most of the attendant problems. Coupling the DRIS with a speculative-execution mechanism that avoids conditional branch stalls results in performance limited only be inherent instruction-level parallelism and available execution resources. Although presented in the context of superscalar machines, the technique is equally applicable to a superpipelined implementation. Lightning, the first implementation of the Metaflow architecture, which executes the Sparc RISC instruction set is described 相似文献
999.
The strengths of two graphite/epoxy notched laminate systems with a softening strip were investigated. The softening strip was created by replacing the 0°-graphite/epoxy plies by a glass/epoxy composite. Experimental results indicated that the use of softening strips could significantly increase the laminate strength. Analysis was performed with finite elements developed using the classical laminated plate theory and was shown to be adequate. A simple point-stress failure criterion was used to predict the strength of notched laminates with softening strips and the result was found to be satisfactory. 相似文献
1000.
V. Kasyanov 《Theoretical computer science》1991,90(1):37-46
This paper focuses on the problem of program concretization by applying correctness-preserving transformations of annotated programs. According to the approach presented, a general-purpose program can be annotated by known information about a specific context of its applications and correctly transformed into a specialized program which is equivalent to the original one on the context-defined ranges of inputs and outputs and is better than it by quality criteria given by the context. Tools for program concretizations via annotated program transformations are considered. 相似文献