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排序方式: 共有159条查询结果,搜索用时 78 毫秒
81.
Alexandr Gorski Vitaliy YurkivDzmitry Starukhin Hans-Robert Volpp 《Journal of power sources》2011,196(17):7188-7194
The mechanism of H2O dissociation as well as the adsorption and oxidation reaction of H2 on yttria-stabilized zirconia (YSZ), commonly used as part of solid oxide fuel cell (SOFC) anodes, was investigated employing temperature-programmed desorption (TPD) spectroscopy and density functional theory (DFT). In agreement with theory the experimental results show that interaction of gaseous H2O with YSZ results in dissociative adsorption leading to strongly bound OH surface species. In the interaction of gaseous H2 with an oxygen-enriched YSZ surface (YSZ + O) similar OH surface species are formed as reaction intermediates in the H2 oxidation. Our experiments showed that in both the H2O/YSZ and the H2/YSZ + O heterogeneous reaction systems noticeable amounts of H2O are “dissolved” in the bulk as interstitial hydrogen and hydroxyl species. The experimental H2O desorption data is used to access the accuracy of the H2/H2O/YSZ adsorption/desorption and surface reaction kinetics data, employed in previous modeling studies of the electrochemical H2 oxidation on Ni-pattern/YSZ model anodes by Vogler et al. [J. Electrochem. Soc., 156 (2009) B663] and Goodwin et al. [J. Electrochem. Soc., 156 (2009) B1004]. Finally a refined experimentally validated H2/H2O/YSZ adsorption/desorption and surface reaction kinetics data set is presented. 相似文献
82.
Lead-lithium alloys are of great interest for practice as the advanced materials to be used in new technique, nuclear energetics, and so forth. Terefore, study on the physico-chemical properties of the latter is of major significance. An analysis of the available literature shows that there are a few works, devoted to study of Pb-Li alloys densities. However, temperature dependence of the density ρ(T), and its temperature coefficientK=dρ/dT for eutectic alloy were obtained by either extrapolation of the density data up to the eutectic alloy''s composition, or calculation method. There is a certain discrepancy amounting to as high as 4,, while the allowable error in the density measurements is less than 0.5,. The discrepancy between the results for the temperature coefficients of density amounts to 80,.In this work we present the experimental data on the temperature dependence of Ph0.83 Li0.17 eutectic alloy''s density in the temperature range 520K to 643 K. The alloys were prepared using Pb and Li with 99. 999, and 99.8, contents of the basic elements, respectively. We use the improved device, which permits to get the results with error less than 0. 15,. The results of 115 measurements of density in 520K to 643K temperature range were processed by the least-square method. Density polytherm of Pb0.83 Li0. 17 eutectic alloy is described by linear equation ρ(T) =9507.89-0. 79813(T-508) , kg/m3 ,where T is the absolute temperature by K. Mearsurement error was 0. 12, at 95, reliability.Discrepancy in the temperature coefficient data was 1.08,.Thus, the temperature dependence of the Pb-Li eutectic alloy density was studied by the precise two-capillary method. The obtained results may be recommended as the most reliable reference data. 相似文献
83.
Dobrynskiy Alexandr V. Dobrynskiy Vladimir A. 《Open Systems & Information Dynamics》2000,7(4):391-400
Conditions and regimes of population stable coexistence which are present in a discrete mathematical model "host and parasite" that describes interaction of two insect species are studied by analytical tools. It is shown the model possesses of two kind stable regimes at least. Species population numbers of the first one are always equal to certain constants for all times and those of the second one vary with during time chaotically, i.e. complete unpredictable manner. Parameter value domains such that a future asymptotical stable regime of population coexistence depends essentially on not only parameter values but else on initial numbers of both population are found too. 相似文献
84.
A review of ferromagnetism in C60 polymeric materials synthesized by high pressure high temperature (HPHT) treatment is presented. Analysis of published data proves that the reported ferromagnetism cannot be assigned to polymeric structure in either perfect or defect states. Most recent experimental studies have not confirmed previously reported levels of magnetization in polymeric samples while it appears that ferromagnetism of "magnetic carbon" is preserved above the depolymerization point of any C60 polymer. Identical ferromagnetic properties in some samples of fullerene polymer and graphite like hard carbon phase also show that the effect is most likely not connected to fullerenes at all. Most of the data published previously as an evidence of ferromagnetism in C60 polymers synthesized at HPHT conditions can be explained by contamination with magnetic impurities. Formation of iron carbide (Fe3C) due to reaction of metallic iron with fullerene molecules allows to explain observed Curie temperature of approximately 500 K and levels of magnetization reported for "magnetic carbon". 相似文献
85.
Viktor V. Zakharov Nikita V. Chukanov Nadezdha N. Dremova Alexandr D. Chervonnyi Gennadiy V. Shilov Boris L. Korsounskii Anatoliy I. Kazakov Nina N. Volkova 《Propellants, Explosives, Pyrotechnics》2016,41(6):1006-1012
Stuctural transformations of 1,1‐diamino‐2,2‐dinitroethene (FOX‐7) were investigated in the temperature range 298–513 K by means of DSC, TG, isothermal calorimetry, PXRD, IR spectroscopy, and electron microscopy. The data obtained confirm the existence of the high‐temperature δ‐FOX‐7 polymorph stable above 480 K. The heat effect of the γ→δ transformation is − 4.6 J g−1 (−680 J mol−1). Metastable γ‐phase formed in the reverse process δ→γ has a perfect crystal structure and is stable towards thermal decomposition. Possible mechanisms of sharp deceleration of thermal decomposition of FOX‐7 at the 40 % conversion are discussed. 相似文献
86.
Alchagirov Boris B. Mozgovoi Alexandr G. Taova Tamara M. 《材料研究与应用》2005,(3):192-195
Lead-lithium alloys are of great interest for practice as the advanced materials to be used in new technique, nuclear energetics, and so forth. Terefore, study on the physico-chemical properties of the latter is of major significance. An analysis of the available literature shows that there are a few works, devoted to study of Pb-Li alloys densities. However, temperature dependence of the density ρ(T), and its temperature coefficientK=dρ/dT for eutectic alloy were obtained by either extrapolation of the density data up to the eutectic alloy‘s composition, or calculation method. There is a certain discrepancy amounting to as high as 4%, while the allowable error in the density measurements is less than 0.5%. The discrepancy between the results for the temperature coefficients of density amounts to 80%.In this work we present the experimental data on the temperature dependence of Ph0.83 Li0.17 eutectic alloy‘s density in the temperature range 520K to 643 K. The alloys were prepared using Pb and Li with 99. 999% and 99.8% contents of the basic elements, respectively. We use the improved device, which permits to get the results with error less than 0. 15%. The results of 115 measurements of density in 520K to 643K temperature range were processed by the least-square method. Density polytherm of Pb0.83 Li0. 17 eutectic alloy is described by linear equation ρ(T) =9507.89-0. 79813(T-508) , kg/m3 ,where T is the absolute temperature by K. Mearsurement error was 0. 12% at 95% reliability.Discrepancy in the temperature coefficient data was 1.08%.Thus, the temperature dependence of the Pb-Li eutectic alloy density was studied by the precise two-capillary method. The obtained results may be recommended as the most reliable reference data. 相似文献
87.
Effect of scatter on reconstructed image quality in cone beam computed tomography: evaluation of a scatter-reduction optimisation function 总被引:2,自引:0,他引:2
The effect of scatter on reconstructed image quality in cone beam computed tomography was investigated and a function which can be used in scatter-reduction optimisation tasks was tested. Projections were calculated using the Monte Carlo method in an axially symmetric cone beam geometry consisting of a point source, water phantom and a single row of detector elements. Image reconstruction was performed using the filtered backprojection method. Image quality was assessed by the L2-norm-based difference relative to a reference image derived from (1) weighted linear attenuation coefficients and (2) projections by primary photons. It was found that the former function was strongly affected by the beam hardening artefact and did not properly reflect the amount of scatter but the latter function increased with increasing beam width, was higher for the larger phantom and exhibited properties which made it a good candidate for scatter-reduction optimisation tasks using polyenergetic beams. 相似文献
88.
89.
Zeeshan Rashid Umut Can Coşkun Yağız Morova Berna Morova Asuman Aşıkoğlu Bozkurt Ahmet Erten Alexandr Jonáš Selçuk Aktürk Alper Kiraz 《Microfluidics and nanofluidics》2017,21(10):160
We demonstrate controlled guiding of nanoliter emulsion droplets of polar liquids suspended in oil along shallow hydrophilic tracks fabricated at the base of microchannels located within microfluidic chips. The tracks for droplet guiding are generated by exposing the glass surface of polydimethylsiloxane (PDMS)-coated microscope slides via femtosecond laser ablation. The difference in wettability of glass and PDMS surfaces together with the shallow step-like transverse topographical profile of the ablated tracks allows polar droplets wetting preferentially the glass surface to follow the track. In this study, we investigate guiding of droplets of two different polar liquids (water/ethylene glycol) with and without surfactant suspended in an oil medium along surface tracks of different depths of 1, 1.5, and 2 \(\upmu\)m. The results of experiments are also verified with computational fluid dynamics simulations. Guiding of droplets along the tracks as a function of the droplet composition and size and the surface profile depth is evaluated by analyzing the trajectories of moving droplets with respect to the track central axis, and conditions for stable guiding are identified. The experiments and numerical simulations indicate that while the track topography plays a role in droplet guiding using 1.5- and 2-\(\upmu\)m deep tracks, for the case of the smallest track depth of 1 \(\upmu\)m, droplet guiding is mainly caused by surface energy modification along the track rather than the presence of a topographical step on the surface. Our results can be exploited to sort passively different microdroplets mixed in the same microfluidic chip, based on their inherent wetting properties, and they can also pave the way for guiding of droplets along reconfigurable tracks defined by surface energy modifications obtained using other external control mechanisms such as electric field or light. 相似文献
90.
In this study, we have investigated different methods for preparation of thin films of C60 and C70-sulfur compounds. Films of good quality were obtained by reaction of amorphous C60 and C70 films with a saturated sulfur solution in toluene at 40°C or with saturated sulfur vapour at a temperature of 140°C for several hours. The quality of the fullerene-sulfur films were strongly dependent on the microstructure of the initially deposited fullerene film and the synthesis temperature. X-ray diffraction analyses showed that both methods lead to the formation of films consisting of C60S16 and C70S48 (space groups C 2/c and Amm2, respectively). C60S16 films synthesised on Al2O3(012) and Si(100) substrates were texture-free while C70S48 films typically exhibited a preferential (100) orientation. The films were also characterised by Raman and IR- spectroscopy, which confirmed that the interactions between the fullerene molecules and the S8 rings are weak. The fullerene-sulfur compounds were found to be unstable at high vacuum conditions. Both materials C60S16 and C70S48 are non-conductive at room temperature with conductivities less then 10−5 (Ω/cm). 相似文献