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991.
992.
993.
V. Pichot M. Comet E. Fousson C. Baras A. Senger F. Le Normand D. Spitzer 《Diamond and Related Materials》2008,17(1):13-22
This article reports the purification process of detonation soot to obtain pure nanodiamond powder. Nanodiamonds are synthesized by detonation using a high explosive mixture composed of trinitrotoluene and hexogen. The detonation of the charge leads to a powder containing nanodiamonds as well as metallic impurities and sp2 carbon species. Further, to remove metallic particles, an unusual acidic treatment (hydrofluoric/nitric acids; i.e. fluorinated aqua regia) was set up. To eliminate sp2 carbon species such as graphite and amorphous carbon, a thermal oxidation treatment was performed at 420 °C under air in a furnace during several hours. Transmission Electronic Microscopy, Raman spectroscopy, X-ray diffraction and Thermo-Gravimetric Analysis showed that this purification process is very efficient. From TGA measurements, a model of the carbon grain combustion was developed by considering graphitic shells surrounding the nanodiamond particles, and was used to demonstrate that the selective oxidation of graphite was experimentally realistic. Moreover, another model was set up from specific area measurements to evaluate the thickness of the functional groups surrounding the nanodiamonds after the oxidation of sp2 carbonaceous species. The treatment described herein was achieved on several tens of grams of product and could be easily adapted to the industrial scale. 相似文献
994.
Calculation and experimental methods showed that the use of lithium metaphosphate for making up batches of Li2O-Li2SO4-P2O5 multilithium glass systems reduces the founding temperature-time parameters while simultaneously increasing the homogeneity of the melts. 相似文献
995.
I. A. Studenikin V. V. Grachev 《International Journal of Self-Propagating High-Temperature Synthesis》2008,17(4):237-241
Silicon oxynitride Si2N2 O was synthesized from a mixture of Si, SiO2, and Si3N4 by infiltrationmediated combustion in nitrogen gas. The chemical/phase composition of product and process parameters (temperature
and burning velocity) were studied upon variation in charge composition and initial pressure of gas reagent. Parameters of
the reaction yielding single-phase Si2N2O have been optimized.
相似文献
996.
S. Thió-Henestrosa J.J. Egozcue V. Pawlowsky-Glahn L.Ó. Kovács G.P. Kovács 《Computers & Geosciences》2008,34(12):1682-1696
A statistical analysis of compositional data based on the Aitchison geometry of the simplex requires an appropriate basis for representing the data. A simple and intuitive way of building such a basis employs a sequential binary partition of the compositional vector. The partition, together with some statistical summaries of the coordinates, or balances, can be represented in a dendrogram-type graph. In this paper we introduce an implementation of this methodology inside CoDaPack, which is freeware. An example with real data illustrates the use of the Balance-Dendrogram routine. 相似文献
997.
Computational results are presented for the neutron characteristics of BIR and BIGR fast pulse reactors, specifically, cylindrical systems with a core consisting of an alloy of 90% or 36% enrichment uranium with 10 mass% molybdenum or a composite uranium–graphite material. The purpose of the calculations is to determine the possibility of increasing the size of the interior cavities in reactors without appreciably degrading the time parameters of the pulses.Reactor models with a metal core, which are best for further consideration, are systems with a disk core which have a cavity with a diameter up to 30 cm along the axis and a thickness-limited iron reflector. For reactors with uranium–graphite core, it is best to develop a new pulse reactor with an axial cavity which has a larger volume and is more accessible for sample placement than BIGR.An important problem of the calculations was to determine screen variants for a cavity which would prevent fuel overheating and at the same time be free of autocatalysis manifestations. 相似文献
998.
Matrix metalloproteinases are thought to be key players in the remodelling activity of cells associated with both physiological and pathological processes. They share a relatively conserved structure with a number of identifiable modules linked to their specific functions. The structure of the individual domains of a number of matrix metalloproteinases have now been elucidated. Here we review these data in the light of complementary studies on the behaviour of these enzymes in biological systems. In particular we focus on the C-terminal hemopexin-like domain which has intriguingly specific roles in individual matrix metalloproteinases. 相似文献
999.
1000.
N. N. Novikov O. V. Korovin Yu. V. Astapenko D. V. Overchenko 《Measurement Techniques》1996,39(6):607-612
This article considers the influence of changes in monitorability indicators on the operational characteristics of communications
equipment. For indicators of monitorability we take the depth of defect search, failure localizability, overhead, and others.
Among the operational characteristics, those considered include time to repair, probability of undetected failure, probability
of failure-free operation, etc. The results obtained make it possible to estimate, during the design phase, the influence
of changes in monitorability factors on the operational characteristics of equipment and to make selections that meet given
requirements.
Translated from Izmeritel'naya Tekhnika, No. 6, pp. 23–26, June, 1996. 相似文献