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排序方式: 共有780条查询结果,搜索用时 15 毫秒
51.
Jean-Claude Launay Gérard Villeneuve Michel Pouchard 《Materials Research Bulletin》1973,8(8):997-1005
Single crystals of V1?xNbxO2 ternary oxide (0 ? x ? 0,33) are prepared by chemical transport using TeCl4. The compositions are determined by thermogravimétric analysis under oxygen, X-ray diffraction measurements and evaluation of the insulator-metal transition temperature. 相似文献
52.
53.
Foisel Hans-Martin Jaeger Monika Westphal F.-Joachim Ovsthus Knut Bischoff Jean-Claude 《Photonic Network Communications》2001,3(1-2):41-48
The commonly used IP-backbone network architecture of today is IP/ATM/SDH/WDM. This architecture has many redundant functionalities and is not optimized to transport IP traffic. New approaches for simplified network architectures try to eliminate redundant functionalities and to decrease the protocol overhead and thereby transport IP as efficiently as possible over WDM-based optical networks. EURESCOM project P918 Integration of IP-over-optical networks: networking and management investigated scenarios for optimized IP transport in WDM-based backbone networks. In this paper, three architectures, namely Gigabit Ethernet, Packet over Sonet/SDH and Dynamic Packet Transport are investigated and evaluated as an alternative to the IP/ATM/SDH/WDM architecture. 相似文献
54.
采用不同的升温速率,在膨胀计中对脱脂后的氧化铝粉末射成形坯件进行一系列的烧结试验.结果表明,烧结致密化过程主要发生在升温阶段,快速升温有利于致密化的进行和抑止晶粒长大,但由于烧结时间较短和烧结炉最高温度的限制,产品的最终致密化程度不高.在低温时快速升温,高温时缓慢加热,可以获得较好的致密化效果和微观结构.试验和分析结果将为建立非等温烧结模型和烧结工艺参数的优化方法提供依据. 相似文献
55.
Carlo S. Iorio Oleg A. Kabov Jean-Claude Legros 《Microgravity science and technology》2007,19(3-4):27-29
In this paper, some of the preparatory experiments of the ESA sponsored space program CIMEX-1 are presented. A liquid layer of variable thickness is subject to a flow of inert gas. The non-uniform evaporation induced by the gas flow creates a temperature gradient parallel to the interface triggering in that way thermocapillary convection. The combined action of evaporation, thermocapillarity and gravity has been not completely clarified both theoretically and experimentally. The experiment presented in this work concerns a liquid layer of ethanol of 2.2 mm thickness in presence of a mass flow of Nitrogen whose intensity varies in the range of hundreds of milliliter per minute. The experiments were performed at an initial liquid temperature of 21°C. The patterns observed are strongly dependent on the flow rate of inert gas. A change in the instability patterns has been observed for a gas flow of about 1.7 l/min. 相似文献
56.
Carmen Castañeda Nadine Pourthie´ Jean-Claude Souyris 《International journal of remote sensing》2013,34(7):1861-1884
A high density of local natural and human-induced ground deformation structures resulting from the presence of evaporites occur extensively around Zaragoza (NE Spain), posing risks to infrastructure, buildings and agriculture. We studied the potential of a series of interferograms constructed from 29 European Radar Satellite (ERS)-1/2 images to detect different types of ground deformation related to evaporite dissolution, landslides and mining subsidence. We examined the factors involved in the usefulness and quality of interferograms, especially in relation to coherence and atmospheric circumstances. Favourable conditions were found in desert or developed areas, while agricultural practises caused decorrelation in most sinkhole-prone areas. Results are consistent with previous geomorphological data and indicate that different natural and human-induced deformation phenomena can be detected in a time lag less than 5 years in evaporite areas. Advanced interferometric techniques based on time series of SAR images are needed for precise measurement and monitoring purposes. 相似文献
57.
M.A. Auger B. Savoini A. Muñoz T. Leguey M.A. Monge R. Pareja J. Victoria 《Ceramics International》2009
Porous hydroxyapatite and hydroxyapatite/oxide composites, with 10 wt% addition of Y2O3, ZrO2 or TiO2 have been prepared by hot isostatic pressing after pressureless sintering, and their phase composition, mechanical properties and microstructure investigated. The quantitative X-ray diffraction analyses reveal that the addition of Y2O3 inhibits the hydroxyapatite decomposition completely during the consolidation processes as a result of the Y ion dissolution into the hydroxyapatite lattice. On the contrary, it is found that the addition of ZrO2 or TiO2 enhances the decomposition of hydroxyapatite into Ca3(PO4)2, which causes the transformation of the starting oxides. The mechanical characterization of the materials has been accomplished by three-point flexure tests, and nanoindentation and microhardness measurements. Post-sintering hot isostatic pressed pure hydroxyapatite, which resulted in a porous biphasic material with 13.2 wt% β-Ca3(PO4)2, exhibited the best mechanical properties. The failure of hydroxyapatite-10Y2O3 during the flexure tests was no catastrophic in contrast to the catastrophic behaviour found in the other materials. 相似文献
58.
Jean-Claude Bureau Bernard Bonnetot Pierre Claudy Hassan Eddaoudi 《Materials Research Bulletin》1985,20(10):1147-1155
The Raman spectra of lithium tetrahydroaluminate (LiAlH4) and tetradeuteroaluminate (LiAlD4) in their room pressure phases have been investigated at room temperature. Internal vibrational modes as well as lattice modes have been observed. As the cristallographic structure of LiAlH4-α is not fully determined, a partial vibrational analysis has been performed. Using deuteration as a spectroscopic probe, the separation between librational and translational phonon modes has been established. Raman spectra of the new LiAlD4-α′ form have been analysed. They have confirmed the irreversible transformation of LiAlD4-α′ into the well known LiAlD4- α form, at ca.65°C. 相似文献
59.
Bernard Charra Guillaume Jean Jean-Marc Hurot Jean-Claude Terrat Thierry Vanel Cyril VoVan Foued Maazoun Charles Chazot 《Hemodialysis international. International Symposium on Home Hemodialysis》2001,5(1):42-50
While nephrologists wait for the ideal, non invasive, inexpensive, precise, and reproducible tool to evaluate extracellular volume (ECV), they need to exert their clinical acumen in the quest of that holy grail, dry weight (DW). Estimation of DW using a clinical approach based on blood pressure (BP) and ECV is feasible and reliable as shown by successful experiences in various dialysis modes over more than three decades. But a need still exists to resolve difficulties associated with accurate assessment of BP (methods and circumstances of measurement, and the confounding effects of antihypertensive drugs) and ECV (evaluation of weight changes unrelated to ECV, lack of specificity and sensitivity of clinical symptoms, lag time, confusion in terminology). An essential point in clinical assessment of DW is that a normal BP is at the same time the target and the crucial index of DW achievement. For this reason, a trialand‐error “probe” process has to be used at intervals to make sure that the dry weight target point is correctly estimated. The various “non clinical” methods proposed for dry weight assessment increase the complexity and the cost of hemodialysis. They are, in the present state of things, more clinical research than practice tools. They do not replace clinical judgment. 相似文献
60.
Two populations are subdivided into two categories of individuals (hawks and lows). Individuals fight to have access to a resource which is necessary for their survival. Conflicts occur between individuals belonging to the same population and to different populations. We investigate the long term effects of the conflicts on the stability of the community. The model is a set of ODE's with four variables corresponding to hawk and dove individuals of the two populations. Two time scales are considered. A fast time scale is used to describe frequent encounters and fightings between individuals trying to monopolize the resource. A slow time scale is used for the demography and the long term effects of encounters. We use aggregation methods in order to reduce this model into a system of two ODE's only for the total densities of the two populations which is found to be a classical Lotka-Volterra competition model. We study different cases of proportions of hawks and doves in both populations on the global coexistence and the mutual exclusion of the two populations. Pure dove tactics in both populations are unstable. In cases of mixed hawk and dove in both populations, there is coexistence. Pure dove or mixed hawk-dove tactics in one population can coexist with pure hawks in the other one when the costs of fightings between hawks are large enough. 相似文献