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41.
Z. Vít 《Catalysis Letters》1992,13(1-2):131-136
Activity and selectivity of carbon supported Mo catalyst was tested in parallel hydrodenitrogenation (HDN) of pyridine and hydrodesulfurization (HDS) of thiophene in the temperature range 260–350 °C at 2 MPa of hydrogen pressure and compared with that of commercial NiMo-alumina catalyst Shell 324. The main advantages of carbon supported Mo sulfide over commercial NiMo catalyst can be summarized as follows: the markedly higher HDN and better HDS activities normalized to moles of active metals, the lower content of piperidine in the reaction products and the distinctly better selectivity towards HDN reaction. 相似文献
42.
Véronique Gauthier Benoît Cochepin Sylvain Dubois Dominique Vrel 《Journal of the American Ceramic Society》2006,89(9):2899-2907
Ti3 SiC2 is synthesized by self-propagating high-temperature synthesis (SHS) of elemental titanium, silicon, and graphite powders. The reaction paths and structure evolution are studied in situ during the SHS of the 3Ti+Si+2C mixture by time-resolved X-ray diffraction coupled with infrared thermography. The proposed reaction mechanism suggests that Ti3 SiC2 might be formed from Ti–Si liquid phase and solid TiC x . Finally, the effect of the powders starting composition on the Ti3 SiC2 synthesis is studied. For the investigated initial mixtures, TiC x is always formed as a major impurity together with the Ti3 SiC2 phase. 相似文献
43.
Data reconciliation consists in modifying noisy or unreliable data in order to make them consistent with a mathematical model (herein a material flow network). The conventional approach relies on least-squares minimization. Here, we use a fuzzy set-based approach, replacing Gaussian likelihood functions by fuzzy intervals, and a leximin criterion. We show that the setting of fuzzy sets provides a generalized approach to the choice of estimated values, that is more flexible and less dependent on oftentimes debatable probabilistic justifications. It potentially encompasses interval-based formulations and the least squares method, by choosing appropriate membership functions and aggregation operations. This paper also lays bare the fact that data reconciliation under the fuzzy set approach is viewed as an information fusion problem, as opposed to the statistical tradition which solves an estimation problem. 相似文献
44.
The curing behavior of two kinds of commercial powdered resol phenolic resins was studied by differential scanning calorimetry. Liquid‐state 13C‐NMR spectroscopy was used to aid in understanding the curing behavior by detecting the structure of powdered resins. The reaction mechanism was interpreted with the dependency of activation energy on the degree of conversion. The results indicate that there are differences in the curing mechanism between core and face phenolic resins. The curing process of core resin was faster than that of face resin at the same reaction temperature. The water added in the curing system played an important role of plasticizer or diluent according to different curing stages and water content. In the initial curing stage, water mainly diluted the system and retarded the curing reactions. However, at the higher degrees of conversion, water played the role of plasticizer to decrease the effect of diffusion on the curing reactions to make the curing reactions more complete. The excess water added in the curing system played the role of diluent at almost all stages during the curing process. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1371–1378, 2003 相似文献
45.
During the preparation of alumina as a catalyst support from aluminium nitrates by precipitation with a NH4OH base, NO
2
⋅
radicals have been formed in the catalyst after calcination under air in the solid at different temperatures. These radicals
remained stable until a calcination temperature of 800°C. When the calcined catalyst was degassed under vacuum above 300 °C,
the NO
2
⋅
was reduced to give NO⋅ and O- species which were both tightly trapped in the solid. These latter species remained stable until vacuum treatment at 800
°C.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
46.
This paper presents an FPGA implementation of the quartic neuron model. This approach uses digital computation to emulate individual neuron behavior. We implemented the neuron model using fixed-point arithmetic operation. The neuron model’s computations are performed in arithmetic pipelines. It was designed in VHDL language and simulated prior to mapping in the FPGA. We show that the proposed FPGA implementation of the quartic neuron model can emulate the electrophysiological activities in various types of cortical neurons and is capable of producing a variety of different behaviors, with diversity similar to that of neuronal cells. The neuron family of this digital neuron can be modified by appropriately adjusting the neuron model’s parameters. 相似文献
47.
The isotopic exchange has been studied between catalyst radiosulfur and H2S, formed in thiophene hydrodesulfurization (HDS) (named S-displace) on alumina supported molybdena, on CoMoOx, PdMoOx, PtMoOx and on silica–alumina supported NiWOx. S-displace was compared with radiosulfur exchange data between catalyst radiosulfur and gas phase H2S (Sexc) determined previously. The extent of Sexc was higher than that of the S-displace for Mo, CoMo in and NiW, whereas the extent of S-displace from PdMoO and PtMoO was
significantly higher, than that of Sexc. Thiophene HDS product distribution data are discussed in terms of increased C=C hydrogenation and C–C hydrogenolysis activity,
explained by increasing H2S production with longer circulation time of the thiophene/H2 mixture, The C1/C3<1 ratios among C4-hydrogenolysis products indicate some coke formation. The decrease of thiophene HDS activity is presumably a consequence
of increasing site-blocking with the formation of more H2S and coke with longer duration of thiophene treatment. 相似文献
48.
Daniel?ZemanEmail author Ond?ej?Du?ek David?Mare?ek Martin?Popel Loganathan?Ramasamy Jan??těpánek Zdeněk??abokrtsky Jan?Haji? 《Language Resources and Evaluation》2014,48(4):601-637
We present HamleDT—a HArmonized Multi-LanguagE Dependency Treebank. HamleDT is a compilation of existing dependency treebanks (or dependency conversions of other treebanks), transformed so that they all conform to the same annotation style. In the present article, we provide a thorough investigation and discussion of a number of phenomena that are comparable across languages, though their annotation in treebanks often differs. We claim that transformation procedures can be designed to automatically identify most such phenomena and convert them to a unified annotation style. This unification is beneficial both to comparative corpus linguistics and to machine learning of syntactic parsing. 相似文献
49.
Petr Štěpànek Jaromír Jakeš Česmír Koňák Robert Johnsen Wyn Brown 《Polymer Bulletin》1987,18(2):175-182
Summary Measurements of autocorrelation functions extending over a broad time range are reported for a sample of polystyrene in ethyl acetate as a function of temperature between –44°C (-temperature) and 70°C. The corresponding spectra of decay times are obtained by two mathematical methods. The existence of three dynamic processes is shown and their temperature and angular behaviour is studied. 相似文献
50.
Mariem Nafti Chiraz Hannachi Jaber Hsaini Béchir Hamrouni Habib Nouaïgui 《分离科学与技术》2020,55(15):2772-2778
ABSTRACT A new approach of cloud point extraction CPE procedure is optimized for hexavalent chromium determination in airborne dusts. Triton X-114 is used as a surfactant and 1-(2-pyridylazo)-2-naphthol as a specific complexing agent for the trivalent chromium’s removal from the aqueous phase to isolate hexavalent chromium compounds. The parameters influencing the extraction protocol (pH, surfactant concentration, and temperature are optimized. The obtained detection and quantification limits are 0.1 and 0.4 μg/L, respectively. The linearity is verified, with a regression coefficient close to 0.999 and the extraction recovery exceeds 99%. The method was successfully applied to analyze airborne samples collected from workplaces. 相似文献