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排序方式: 共有205条查询结果,搜索用时 15 毫秒
1.
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
2.
Jeannette Aumo Johanna Lilja Päivi Mäki-Arvela Tapio Salmi Mats Sundell Hanna Vainio Dmitry Yu. Murzin 《Catalysis Letters》2002,84(3-4):219-224
A polymer-supported Pd catalyst was investigated in hydrogenation of citral (3,7-dimethyl-2,6-octadienal), which is a stereoisomer with an isolated and a conjugated double bond as well as a carbonyl group. The catalyst was a fibrous polymer-supported catalyst modified with functional groups and immobilized metals. A comparison of the polymer-supported catalyst with conventional catalysts was made. 相似文献
3.
Detailed Real-Time Urban 3D Reconstruction from Video 总被引:2,自引:0,他引:2
M. Pollefeys D. Nistér J.-M. Frahm A. Akbarzadeh P. Mordohai B. Clipp C. Engels D. Gallup S.-J. Kim P. Merrell C. Salmi S. Sinha B. Talton L. Wang Q. Yang H. Stewénius R. Yang G. Welch H. Towles 《International Journal of Computer Vision》2008,78(2-3):143-167
The paper presents a system for automatic, geo-registered, real-time 3D reconstruction from video of urban scenes. The system
collects video streams, as well as GPS and inertia measurements in order to place the reconstructed models in geo-registered
coordinates. It is designed using current state of the art real-time modules for all processing steps. It employs commodity
graphics hardware and standard CPU’s to achieve real-time performance. We present the main considerations in designing the
system and the steps of the processing pipeline. Our system extends existing algorithms to meet the robustness and variability
necessary to operate out of the lab. To account for the large dynamic range of outdoor videos the processing pipeline estimates
global camera gain changes in the feature tracking stage and efficiently compensates for these in stereo estimation without
impacting the real-time performance. The required accuracy for many applications is achieved with a two-step stereo reconstruction
process exploiting the redundancy across frames. We show results on real video sequences comprising hundreds of thousands
of frames. 相似文献
4.
I Ilveskoski UM Saarinen M Perkki? TT Salmi M Lanning A M?kipernaa R Sankila H Pihko 《Canadian Metallurgical Quarterly》1996,13(1):69-80
We evaluated the outcome of 68 children with malignant brain tumors treated with the "8 in 1" chemotherapy protocol in Finland from 1986 to 1993, comparing 5-year survival rates with those for a historical control group (from 1975 to 1985). For all malignant brain tumors, overall survival was 43% (vs 28% in the control group; P <0.05), and progression-free survival (PFS) was 43% (vs 23%; P <0.05). For medulloblastoma and primitive neuroectodermal tumor, survival was 63% (vs 35%; P <0.05), and the corresponding PFS was 59% (vs 35%; P = 0.15). For high-grade glioma, both the survival rate and the PFS were 27% (vs 17%; P = NS). Thus the outcome was significantly better for our "8 in 1" -treated patients than for the historical controls, especially among the children with primitive neuroectodermal tumor and medulloblastoma. In contrast, those with high-grade gliomas and brain stem tumors seem to have received little benefit; different, more effective treatments are needed for these patients. 相似文献
5.
Kinetic modeling of hemicellulose hydrolysis in the presence of homogeneous and heterogeneous catalysts
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Tapio Salmi Dmitry Yu. Murzin Päivi Mäki‐Arvela Bright Kusema Bjarne Holmbom Stefan Willför Johan Wärnå 《American Institute of Chemical Engineers》2014,60(3):1066-1077
Kinetic models were developed for the hydrolysis of O‐acetyl‐galactoglucomannan (GGM), a hemicellulose appearing in coniferous trees. Homogeneous and heterogeneous acid catalysts hydrolyze GGM at about 90°C to the monomeric sugars galactose, glucose, and mannose. In the presence of homogeneous catalysts, such as HCl, H2SO4, oxalic acid, and trifluoroacetic acid, the hydrolysis process shows a regular kinetic behavior, while a prominent autocatalytic effect was observed in the presence of heterogeneous cation‐exchange catalysts, Amberlyst 15 and Smopex 101. The kinetic models proposed were based on the reactivities of the nonhydrolyzed sugar units and the increase of the rate constant (for heterogeneous catalysts) as the reaction progresses and the degree of polymerization decreases. General kinetic models were derived and special cases of them were considered in detail, by deriving analytical solutions for product distributions. The kinetic parameters, describing the autocatalytic effect were determined by nonlinear regression analysis. The kinetic model described very well the overall kinetics, as well as the product distribution in the hydrolysis of water soluble GGM by homogeneous and heterogeneous catalysts. The modelling principles developed in the work can be in principle applied to hydrolysis of similar hemicelluloses as well as starch and cellulose. © 2014 American Institute of Chemical Engineers AIChE J, 60: 1066–1077, 2014 相似文献
6.
T.-K. Rantakyl S. Toppinen T. Salmi J. Aittamaa 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1996,67(3):265-275
The liquid–phase hydrogenation kinetics of toluene, cumene and mesitylene was studied over an alumina-supported nickel catalyst in a laboratory scale trickle-bed reactor operating isothermally at temperature of 75–115°C and at hydrogen pressures of 20–40 bar. The experiments performed in the absence of intraparticular diffusion resistance showed that the catalyst deactivated rapidly at the initial stage of the experiment, after which a virtually stable level of the catalyst activity was attained. The systematic kinetic experiments carried out with a stable aged catalyst revealed that cumene and mesitylene at high concentrations retarded the hydrogenation rate, whereas such an effect was not observable for toluene. The results of the kinetic experiments were interpreted quantitatively with a reaction mechanism involving sequential addition of hydrogen to absorbed aromatic molecules. 相似文献
7.
X-Ray Photoelectron Spectroscopy Investigation of Pd-Beta Zeolite Catalysts with Different Acidities
D. Chichova P. Mäki-Arvela T. Heikkilä N. Kumar J. Väyrynen T. Salmi D. Yu. Murzin 《Topics in Catalysis》2009,52(4):359-379
Three different H-Beta zeolites with SiO2/Al2O3 molar ratios of 300, 150 and 25 were loaded with palladium by evaporation–impregnation method using Pd(NO3)2 as a precursor. Dependence between the electronic states of Pd as a function of the acidity of Beta zeolite was studied by
XPS for calcined and reduced samples. The dependence of the electronic states of Pd on the support was detected to have a
complicated character and to be influenced by various factors such as metal loading, density of the imperfections in the zeolitic
framework and proton localization. In calcined zeolites mainly agglomerated PdO and AlPd
x
O crystallites were detected referring to interaction of palladium with the support. Reduction of PdO led to formation of
metallic Pdn clusters, which further reduced to [Pdn–Hm]m+ complexes and AlPd
x
O complexes. The increase of the reduction temperature seems to enhance interactions of Pdn clusters with imperfect [AlO
x
−] components instead of protons, especially in less acidic samples due to enhanced agglomeration of palladium particles outside
the pores of the zeolite. The fraction, size and shape of the formed species were detected to be sensitive to the acidity
of the support. 相似文献
8.
In this paper, the problem of code acquisition for spread-spectrum systems is investigated in the presence of frequency errors. The classic approach of noncoherent post detection integration (NCPDI) is contrasted with differential post detection integration (DPDI), presented in two different versions, namely DPDI-Real and DPDI-Abs, respectively, suited for fine and large frequency offsets. The differential schemes are characterized thoroughly introducing a novel analytical treatment that is validated by simulations. In order to fairly quantify the potential gains introduced by the differential solutions, specific detector parameter optimization is performed for each scheme. The interesting result is that the DPDI significantly outperforms the classic NCPDI approach for large frequency errors, and behaves close to it for small offsets. DPDI can, thus, be considered as a very robust PDI solution with moderate complexity. 相似文献
9.
Tapio Salmi Henrik GrénmanJohan Wärnå Dmitry Yu. Murzin 《Chemical Engineering Research and Design》2013
Typical features of liquid–solid reactions were reviewed: reaction kinetics, mass transfer effects and particle morphology. It was concluded that classical liquid–solid models based on ideal, non-porous geometries (sphere, infinite cylinder, slab) cannot satisfactorily describe real reactive solid particles with various surface defects, such as cracks, craters and limited porosity. Typically a too low reaction order for the reactive solid is predicted by the classical models. The surface morphology can be revealed by electron microscopy, which gives inspiration to develop new mathematical models for reactive solids. 相似文献
10.
É. Sarkadi-Pribóczki N. Kumar T. Salmi D. Yu. Murzin Z. Kovács 《Topics in Catalysis》2007,45(1-4):169-173
11C-labelled methanol was introduced for study of co-reaction of methanol with ethanol over alumina, H-ZSM-5 and Cu-ZSM-5 between
200 and 320 °C. The radio-method was applied to distinguish the radio-labelled methanol derivatives and co-products from unlabelled
ethanol derivatives during analysis by radio-GC. The co-reaction was compared to 11C-single methanol transformations from the previous work. Besides 11C-dimethyl ether, 11C-methyl ethyl ether as a co-product was formed between 200–240 °C and completely transformed further between 240 and 320
°C over H-ZSM-5 and alumina and partly over Cu-ZSM-5. In view of our results the appearance of 11C-methyl ethyl ether intermediate is related to higher selectivities to form 11C-traced C3 and C4–C5 paraffins compared to the single 11C-methanol transformation over H-ZSM-5 catalyst. These results suggest a modified methanol transformation pathway in the presence
of ethanol over H-ZSM-5. 相似文献