排序方式: 共有26条查询结果,搜索用时 31 毫秒
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T. Kanerva V. Kröger K. Rahkamaa-Tolonen M. Vippola T. Lepistö R. L. Keiski 《Topics in Catalysis》2007,45(1-4):137-142
Laboratory-scale ageing and poisoning procedures were performed on selected diesel catalysts. The results showed that phosphorus
poisoning together with high temperature ageing has a strong effect on the catalytic activity and microstructure of platinum
containing catalysts. Phosphorus poisoning contaminated the catalysts resulting in phosphate formation, e.g. CePO4 and AlPO4. Poisoning and air ageing increased platinum particle-size and washcoat grain-size. 相似文献
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Suvi Santa-aho Minnamari Vippola Aki Sorsa Mari Lindgren Jyrki Latokartano Kauko Leiviskä Toivo Lepistö 《Journal of Materials Processing Technology》2012,212(11):2282-2293
Calibration samples for the Barkhausen noise (BN) method were produced with laser processing. A planet gear wheel used for production quality control was subjected to laser irradiation to verify the BN sensor output. Different samples were found to respond similarly to the laser processing although the laser parameters needed to be adjusted for different surface qualities separately. The surface optimization for laser processing was studied with different surface qualities of samples. The ground surface was compared with a sandblasted and vibratory ground surface. The ground and sandblasted surfaces were both amenable to the laser processing whereas the vibratory grinding process created inhomogeneous surfaces for laser beam absorption. Laser processing was found to produce uniform changes in the residual stress values in two perpendicular measuring directions. The root mean square value of the BN voltage signal exhibited linear correlations with the values of the residual stress and surface hardness. 相似文献
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Aki Sorsa Kauko Leiviskä Suvi Santa-aho Minnamari Vippola Toivo Lepistö 《Journal of Nondestructive Evaluation》2013,32(4):341-349
Residual stress of case-hardened steel samples is predicted in this paper with the linear multivariable regression model. The development of the prediction model is based on the huge set of features calculated from the Barkhausen noise measurement signal among which the most suitable ones are chosen. The selection uses a genetic algorithm with leave-multiple-out cross-validation in the objective function. The original feature set contains collinear features that make the selection task even more complex. Thus a feature elimination procedure based on the successive projections algorithm is studied in this paper. Also the standard genetic algorithm is slightly modified to better serve the feature selection task. The obtained results are good showing that the proposed procedures suit well for residual stress predictions. Also the applied feature elimination procedure is applicable and can be safely used to reduce the dimensionality of the selection problem. 相似文献
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Aki Sorsa Ari Isokangas Suvi Santa-aho Minnamari Vippola Toivo Lepistö Kauko Leiviskä 《Journal of Nondestructive Evaluation》2014,33(1):43-50
Residual stresses are quantitatively predicted based on the Barkhausen noise measurement with a partial least squares regression model. The measurements are taken from two sets of case-hardened samples. The benefits of using certain feature elimination strategies prior model identification are also studied. The elimination methods applied are correlation-based elimination, uninformative variable elimination and successive projections algorithm. The results show that the best predictions are usually obtained when the successive projections algorithm is applied. The prediction accuracy of the best models found shows that partial least squares models can be successfully used for prediction of material properties based on the Barkhausen noise measurement. 相似文献
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By using hybrid structures, attractive and advantageous combinations of material properties can be achieved. In addition to the combination of good mechanical properties and low weight, also dynamical properties can be enhanced by suitable materials selection. However, the hybrid structure properties depend on the properties of the constituent materials as well as on the interfacial properties. 相似文献
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Aki Sorsa Suvi Santa-aho Jukka Wartiainen Lasse Suominen Minnamari Vippola Kauko Leiviskä 《Journal of Nondestructive Evaluation》2018,37(1):10
The production of gear components includes numerous manufacturing operations which are carried out to ensure proper surface characteristics of components to deal with wear and fatigue. Surface shot peening is one way to increase the compressive residual stresses on the surface and thus ensure better wear and fatigue resistance. An experimental plan for shot peening was conducted to produce samples with varying surface characteristics. Residual stress profile and Barkhausen noise measurements were carried out for the samples. The objective of the study was to evaluate the interactions between the shot peening parameters studied, the residual stress profiles and the Barkhausen noise measurements. A multivariable regression analysis was applied for the task. Some remarkable correlations were found between the shot peening parameters, residual stress profile and Barkhausen noise features. The most important finding was that when the shot peening intensity was high enough, over 0.5 mmA, it dominated the shot peening coverage density parameter and thus no correlations could be gained. On the other hand, if the intensity parameter was lower than the limit of 0.5 mmA, the correlation between residual stress and Barkhausen noise measurements was remarkable. This means that the surface Barkhausen noise measurements could be used for the evaluation of the stress gradient in the shot peening process. 相似文献
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Tanja Kolli Mika Huuhtanen Tomi Kanerva Minnamari Vippola Kauko Kallinen Toni Kinnunen Toivo Lepist? Jouko Lahtinen Riitta L. Keiski 《Topics in Catalysis》2011,54(16-18):1185-1189
Sulphur, sulphur-water, and water pretreatments were done to find out the effect of these compounds on a diesel oxidation Pd/??-zeolite catalyst and ??-zeolite washcoat. After pretreatments, the samples were analysed by BET, XRF, TEM-SEM, and XPS. In addition, the activity of fresh and pretreated Pd/??-zeolite catalysts was studied utilizing the by Gasmet FT-IR in production gas analysis. Sulphur compounds (SO2 or ?SO4) were found to have a deactivating effect on the activity of the studied Pd/??-zeolite catalyst. 相似文献