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101.
Joseph Eng Jr. Bernd Frühberger Jingguang G. Chen Brian E. Bent 《Catalysis Letters》1998,54(3):133-140
The thermal decomposition pathways of isobutene and 1-butene on both Mo(110) and 4 × 4-C/Mo(110) surfaces have been studied using high-resolution electron energy loss spectroscopy (HREELS) in order to highlight the substantially different activities of these two surfaces towards the cleavage of C–H and C–C bonds. On clean Mo(110), the CH2 group of isobutene decomposes upon heating to 150 K, producing either a /-bonded isobutenylidene [(CH3)2CCH] species or a 1,1-di-/-bonded isobutenyl [(CH3)2CC] species. Upon further heating, extensive C–H bond scission occurs to form hydrocarbon fragments which do not contain CH3 or CH2 groups, but appear to have largely intact carbon skeletons. By contrast, isobutene is molecularly adsorbed on the carbide-modified surface at 150 K. Further heating produces isobutylidyne [(CH3)2HCC] by 300 K, which subsequently decomposes via C–C bond scission to generate surface methyl groups. The different activation sequence of the C–H and C–C bonds of isobutene on clean and carbide-modified Mo(110) surfaces is also qualitatively confirmed by comparative studies of 1-butene on the two surfaces. 相似文献
102.
Identifying the presence of anti-nuclear antibody (ANA) in human epithelial type 2 (HEp-2) cells via the indirect immunofluorescence (IIF) protocol is commonly used to diagnose various connective tissue diseases in clinical pathology tests. As it is a labour and time intensive diagnostic process, several computer aided diagnostic (CAD) systems have been proposed. However, the existing CAD systems suffer from numerous shortcomings due to the selection of features, which is commonly based on expert experience. Such a choice of features may not work well when the CAD systems are retasked to another dataset. To address this, in our previous work, we proposed a novel approach that learns a set of filters from HEp-2 cell images. It is inspired by the receptive fields in the mammalian's vision system, since the receptive fields can be thought as a set of filters for similar shapes. We obtain robust filters for HEp-2 cell classification by employing the independent component analysis (ICA) framework. Although, this approach may be held back due to one particular problem; ICA learning requires a sufficiently large volume of training data which is not always available. In this paper, we demonstrate a biologically inspired solution to address this issue via the use of spontaneous activity patterns (SAP). The spontaneous activity patterns, which are related to the spontaneous neural activities initialised by the chemical release in the brain, are found as the typical stimuli for the visual cell development of newborn animals. In the classification system for HEp-2 cells, we propose to model SAP as a set of small image patches containing randomly positioned Gaussian spots. The SAP image patches are generated and mixed with the training images in order to learn filters via the ICA framework. The obtained filters are adopted to extract the set of responses from a HEp-2 cell image. We then employ regions from this set of responses and stack them into “cubic regions”, and apply a classification based on the correlation information of the features. We show that applying the additional SAP leads to a better classification performance on HEp-2 cell images compared to using only the existing patterns for training ICA filters. The improvement on classification is particularly significant when there are not enough specimen images available in the training set, as SAP adds more variations to the existing data that makes the learned ICA model more robust. We show that the proposed approach consistently outperforms three recently proposed CAD systems on two publicly available datasets: ICPR HEp-2 contest and SNPHEp-2. 相似文献
103.
Ba Nghiep Nguyen Brian J Koeppel Said Ahzi Mohammad A Khaleel Prabhakar Singh 《Journal of the American Ceramic Society》2006,89(4):1358-1368
This paper addresses the damage and fracture issues of glass and ceramic materials used in solid oxide fuel cells. Analyses of an internal crack and of an interface crack between dissimilar materials were conducted using a modified boundary layer modeling approach. In this approach, fracture is allowed to occur in a small process window situated at an initial crack tip. Elastic displacement crack-tip fields are prescribed as remote boundary conditions. Crack propagation was first modeled discretely. Next, a continuum damage mechanics (CDM) model for brittle materials was developed to capture damage and crack growth in the process window. In particular, the damage model was applied to a glass-ceramic material that had been developed in-house for sealing purposes. Discrete and continuum damage solutions were then compared. Finally, the CDM model was used to determine the crack propagation direction as a function of a mode mixity measure. 相似文献
104.
Towards an Environmentally Acceptable Heterogeneous Catalytic Method of Producing Adipic Acid by the Oxidation of Hydrocarbons in Air 总被引:1,自引:0,他引:1
Raja Robert Lee Sang-Ok Sanchez-Sanchez Manuel Sankar Gopinathan Harris Kenneth D.M. Johnson Brian F.G. Thomas John Meurig 《Topics in Catalysis》2002,20(1-4):85-88
A survey is given of the catalytic methods potentially available for the production of adipic acid by the oxidation of readily available hydrocarbon precursors under environmentally benign conditions. Encouraging results are reported using H2O2 as oxidant and microporous FeAlPO-5 as catalyst at moderate temperatures. 相似文献
105.
The disproportionation ofn-butane (and of isobutane) was catalyzed by sulfated zirconium oxide containing 1.5 wt% Fe, 0.5 wt% Mn, and 4.0 wt% sulfate at 2.0 atm and temperatures in the range of 30–60C. The reaction accompanies isomerization, which under some conditions is as much as one or two orders of magnitude faster than disproportionation. The conversion to each of the products increased with time on stream in a flow reactor, and then declined. The time on stream for maximum conversion was the same for each product. The results suggest that the disproportionation and isomerization reactions proceed through a common C8 intermediate. Rates of the disproportionation reaction were determined at the time on stream corresponding to the maximum conversion at each temperature; for example, the rate of conversion ofn-butane into isopentane at 60C with ann-butane partial pressure of 0.58 atm was about 1×10–7 mol/(g of catalyst s). 相似文献
106.
Jeremy Gustin Brian Freeman James Stone Mohammad Mahinfalah Amin Salehi‐Khojin 《应用聚合物科学杂志》2005,96(6):2309-2315
Nanocomposites are more widely studied today because of higher stiffness, decreased permeability, thermal stability, and many other properties superior to those of regular polymers. However, manufacturers are concerned about implementing nanocomposites because of their lower impact properties with respect to the base polymer. This study focused on low‐velocity impact tests of a thermoplastic olefin by itself and with 5 wt % nanoclay. The impact tests were conducted at ?40, 23.9, and 65.6°C until the polymer and nanocomposite plates experienced complete striker penetration. The force–time and force–deflection responses obtained from the impact testing provided a means of comparing the impact performances of the two materials. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 2309–2315, 2005 相似文献
107.
Nutthakan Pongrakananon Nathaporn Somrang Worakanya Visitsart Pitt Supaphol Manit Nithitanakul Brian P. Grady 《应用聚合物科学杂志》2004,91(4):2216-2222
The effect of methyl acrylate content in ethylene–methyl acrylate–acrylic acid (E–MA–AA) terpolymers and acrylic acid content in ethylene–acrylic acid (E–AA) copolymers was investigated in blends of these two materials. The E–MA–AA terpolymer with 8 mol % methyl acrylate was not miscible with any E–AA material no matter what the AA content, whereas the terpolymer with only about 2 mol % methyl acrylate was miscible, at least to some extent, with the E–AA copolymer at high acrylic acid contents. Evidence supporting this conclusion derived from gloss, differential scanning calorimetry testing, and dynamic mechanical measurements. For the E–AA polymer material with the highest acid content, there was a synergistic effect for some properties at low added amounts of E–MA–AA copolymer; the tensile strength and hardness were 10% higher than values for the E–AA copolymer, even though the E–AA copolymer was much stiffer. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 2216–2222, 2004 相似文献
108.
Mono-carboxylic, straight-chain fatty acids are present in extracts of lignite and subbituminous coal (0.4–1.0 wt%, daf basis), but not in those of a bituminous coal. They are removed with nearly equal ease by both solvent and supercritical gas (SCG) extraction. Octacosanoic acid is the major constituent, and values of the carbon preference index (even over odd) lie between 2 and 6. Solvent extraction of the coals also removes small quantities (< 0.08 wt%) of straight-chain alkanes which are closely related in composition to the straight-chain fatty acids and are probably derived from them during maturation. However, previous SCG extraction of the coals yielded much larger quantities of straight-chain alkanes (0.3–0.7 wt%). Pyrolysis experiments with a lignite fatty acid fraction and with tetracosanoic acid show that these acids largely survive SCG extraction and, therefore, are not the main source of the relatively large quantity of straight-chain alkanes in these extracts. 相似文献
109.
Brian Coulter Srini Krishnamoorthy 《International Transactions in Operational Research》2014,21(2):263-274
This paper examines the effect of reference prices on companies operating within competitive industries. We confirm that even with competition, firms optimally price high in the short term to generate a high reference price and then decrease this price over time. Competitors' prices converge toward each other over time, emphasizing the short‐term nature of reference prices. We then show that pricing optimally to take advantage of reference prices generates a positive externality for other firms in an industry, such that competitors may generate higher profit. The longer the focus of a given firm, the more profit the firm generates, but less relative to its competitors. This arises because the externalities created through pricing high to increase reference prices outweigh the benefits of the higher reference prices themselves. If pricing managers are compensated relative to their competition, this suggests that short‐termism may be implicitly encouraged to the detriment of profit. 相似文献
110.
A solid oxide fuel cell (SOFC) structure is proposed in which a composite thin film cathode substrate supports a dense thin film electrolyte with a thickness of less than 1 μm. The cathode substrate has a graded porosity achieved through the partial sintering of a spin-coated CeO2 colloidal suspension. The resulting surface has a pore size and surface roughness which allowed a fully dense ZrO2 :16%Y (YSZ) electrolyte to be spin-coated directly from a polymeric precursor without capillary forces removing the precursor from the surface of the porous substrate. Using this process, fuel cell structures were constructed with temperatures not exceeding 800°C. The porous CeO2 interlayer should allow for decreased ohmic losses, as well as decreased reactions between the YSZ and the cathode substrate. In addition, the nanocrystalline grain sizes should allow for increased catalytic activity on the cathode. Calculated ohmic losses indicated the resistance of the CeO2 interlayer limited the power of the structure, which was minimized by impregnating the porous layer with a mixed-conducting perovskite. The final structure shows significantly reduced ohmic losses as calculated at 400°C. 相似文献