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排序方式: 共有1092条查询结果,搜索用时 10 毫秒
1.
We have studied the synthesis conditions and crystal structures for one-phase intermetallic alloys Ni5Zr, Ni7Zr2, and NiZr. We used the continuous weighing method to study the oxidation kinetics in air for the alloy Ni7Zr2 in the range 500-1000°C. We have shown that the oxidation process is described mainly by a parabolic law. The kinetic isotherms for the change in mass suggest that over time, the rate constant for parabolic oxidation K p decreases due to improvement in the protective properties of the scale. The temperature dependence of the oxidation rate suggests a change in the oxidation mechanism for T > 800°C, due to changes in the defect structure of the ZrO2 lattice. 相似文献
2.
Valentina I. Simagina Pavel A. Storozhenko Olga V. Netskina Oksana V. Komova Galina V. Odegova Yury V. Larichev Arcady V. Ishchenko Anna M. Ozerova 《Catalysis Today》2008,138(3-4):253
Catalytic hydrolysis of NaBH4 and NH3BH3 has been studied. It was shown that the nature of the support and the active component of the catalyst affect the H2 generation rate. Despite similar sizes of rhodium particles formed on the surface of different supports (γ-Al2O3, TiO2, carbon), their reactivity is different. Rh/TiO2 with low rhodium concentration (1 wt.%) is the most active catalyst both in the hydrolysis of NaBH4 and NH3BH3. The obtained results show that the rhodium chloride interaction with titania determines the reactivity of rhodium particles formed under action of NaBH4 medium. TEM, DRS UV–vis and XPS were used to characterize the catalysts. 相似文献
3.
4.
Emilio Marengo Valentina Longo Elisa Robotti Marco Bobba Fabio Gosetti Orfeo Zerbinati Silvana Di Martino 《应用聚合物科学杂志》2008,109(6):3975-3982
Principal component regression (PCR), partial least squares (PLS), StepWise ordinary least squares regression (OLS), and back‐propagation artificial neural network (BP‐ANN) are applied here for the determination of the propylene concentration of a set of 83 production samples of ethylene–propylene copolymers from their infrared spectra. The set of available samples was split into (a) a training set, for models calculation; (b) a test set, for selecting the correct number of latent variables in PCR and PLS and the end point of the training phase of BP‐ANN; (c) a production set, for evaluating the predictive ability of the models. The predictive ability of the models is thus evaluated by genuine predictions. The model obtained by StepWise OLS turned out to be the best one, both in fitting and prediction. The study of the breakdown number of samples to be included in the training set showed that at least 52 experiments are necessary to build a reliable and predictive calibration model. It can be concluded that FTIR spectroscopy and OLS can be properly employed for monitoring the synthesis or the final product of ethylene–propylene copolymers, by predicting the concentration of propylene directly along the process line. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
5.
Paustovskii Alexander V. Alfintseva Raisa A. Kurinnaya Tatyana V. Pogorelaya Valentina V. Kirilenko Stepan N. 《Powder Metallurgy and Metal Ceramics》2004,43(5-6):251-257
The main parameters of electrospark alloying of steel 45 with anodes made from Ni – Cr – Al – Y alloys have been investigated. The anodes were fabricated by casting and hot pressing. The highest values of the mass transfer coefficient were observed in the case of electrospark alloying with hot-pressed alloys. Microstructure and x-ray phase analyses of electrospark coatings revealed the presence of solid solutions based on nickel, iron, chromium as well as intermetallic compounds. Coatings obtained by electrospark alloying with hot-pressed alloy are more wear-resistant than are coatings obtained by alloying with cast alloys. 相似文献
6.
Monica Bianco Ilenia Viola Miriam Cezza Francesca Pietracaprina Giuseppe Gigli Rosaria Rinaldi Valentina Arima 《Microfluidics and nanofluidics》2012,13(3):399-409
Solid surface/liquid interactions play an important role in microfluidics and particularly in manipulation of films, drops and bubbles, a basic requirement for a number of lab-on-chip applications. The behavior of solvents in coated microchannels is difficult to be predicted considering theories; therefore, experimental methods able to estimate the properties at the interface in real time and during the operational regime are amenable. Here, we propose to use an experimental setup to evaluate the effective dynamics of solvents inside PDMS microchannels. The influence of the solvent properties as well as of the channel wall’s wettability on the fluid movements was evaluated. Modification of the channel properties was achieved by introducing Teflon coatings that allow producing stable hydrophobic microchannel walls. The results were fitted according to Washburn-type power-law and compared with theoretical calculations of the parameter β that expresses the dependence of capillary dynamics on surface tension γ, liquid viscosity η, contact angles θ and the hydraulic radius R H. A comparison between the calculated and the experimental values reveled that parameters other than the contemplated ones influenced the measurements. The main parameter that affects the flow of solvents such as water, methanol ethanol, dimethylformamide, acetonitrile and acetone was found to be the γ/η ratio. Considering these results, the investigation tool described here is believed to be promising to predict the dynamics of common organic solvents inside integrated functional fluidic devices and to accurately control solvent flow, particularly in capillary-driven pumpless systems, a basic requirement for widening the application range of PDMS lab-on-chip devices. 相似文献
7.
Giuseppe Placidi Danilo Avola Marco Ferrari Daniela Iacoviello Andrea Petracca Valentina Quaresima Matteo Spezialetti 《Computer methods and programs in biomedicine》2014
Background and objective
The degeneration of the balance control system in the elderly and in many pathologies requires measuring the equilibrium conditions very often. In clinical practice, equilibrium control is commonly evaluated by using a force platform (stabilometric platform) in a clinical environment.In this paper, we demonstrate how a simple movement analysis system, based on a 3D video camera and a 3D real time model reconstruction of the human body, can be used to collect information usually recorded by a physical stabilometric platform.Methods
The algorithm used to reconstruct the human body model as a set of spheres is described and discussed. Moreover, experimental measurements and comparisons with data collected by a physical stabilometric platform are also reported. The measurements were collected on a set of 6 healthy subjects to whom a change in equilibrium condition was stimulated by performing an equilibrium task.Results
The experimental results showed that more than 95% of data collected by the proposed method were not significantly different from those collected by the classic platform, thus confirming the usefulness of the proposed system.Conclusions
The proposed virtual balance assessment system can be implemented at low cost (about 500$) and, for this reason, can be considered a home use medical device. On the contrary, astabilometric platform has a cost of about 10,000$ and requires periodical calibration. The proposed system does not require periodical calibration, as is necessary for stabilometric force platforms, and it is easy to use. In future, the proposed system with little integration can be used, besides being an emulator of a stabilometric platform, also to recognize and track, in real time, head, legs, arms and trunk, that is to collect information actually obtained by sophisticated optoelectronic systems. 相似文献8.
Open to a Select Few? Matching Partners and Knowledge Content for Open Innovation Performance 下载免费PDF全文
Lars Bengtsson Nicolette Lakemond Valentina Lazzarotti Raffaella Manzini Luisa Pellegrini Fredrik Tell 《Creativity & Innovation Management》2015,24(1):72-86
The purpose of the paper is to illuminate the costs and benefits of crossing firm boundaries in inbound open innovation (OI) by determining the relationships among partner types, knowledge content and performance. The empirical part of the study is based on a survey of OI collaborations answered by R&D managers in 415 Italian, Finnish and Swedish firms. The results show that the depth of collaboration with different partners (academic/consultants, value chain partners, competitors and firms in other industries) is positively related to innovation performance, whereas the number of different partners and size have negative effects. The main result is that the knowledge content of the collaboration moderates the performance outcomes and the negative impact of having too many different kinds of partners. This illustrates how successful firms use selective collaboration strategies characterized by linking explorative and exploitative knowledge content to specific partners, to leverage the benefits and limit the costs of knowledge boundary crossing processes. 相似文献
9.
Giovanni Bellettini Valentina Beorchia Maurizio Paolini 《Journal of Mathematical Imaging and Vision》2008,32(3):265-291
We introduce and study a two-dimensional variational model for the reconstruction of a smooth generic solid shape E, which may handle the self-occlusions and that can be considered as an improvement of the 2.1D sketch of Nitzberg and Mumford
(Proceedings of the Third International Conference on Computer Vision, Osaka, 1990). We characterize from the topological viewpoint the apparent contour of E, namely, we characterize those planar graphs that are apparent contours of some shape E. This is the classical problem of recovering a three-dimensional layered shape from its apparent contour, which is of interest
in theoretical computer vision. We make use of the so-called Huffman labeling (Machine Intelligence, vol. 6, Am. Elsevier,
New York, 1971), see also the papers of Williams (Ph.D. Dissertation, 1994 and Int. J. Comput. Vis. 23:93–108, 1997) and the paper of Karpenko and Hughes (Preprint, 2006) for related results. Moreover, we show that if E and F are two shapes having the same apparent contour, then E and F differ by a global homeomorphism which is strictly increasing on each fiber along the direction of the eye of the observer.
These two topological theorems allow to find the domain of the functional ℱ describing the model. Compactness, semicontinuity
and relaxation properties of ℱ are then studied, as well as connections of our model with the problem of completion of hidden
contours.
相似文献
Maurizio PaoliniEmail: |
10.
Marco Baioletti Alfredo Milani Valentina Poggioni Fabio Rossi 《Annals of Mathematics and Artificial Intelligence》2011,62(3-4):187-217
In this paper the system ACOPlan for planning with non uniform action cost is introduced and analyzed. ACOPlan is a planner based on the ant colony optimization framework, in which a colony of planning ants searches for near optimal solution plans with respect to an overall plan cost metric. This approach is motivated by the strong similarity between the process used by artificial ants to build solutions and the methods used by state?Cbased planners to search solution plans. Planning ants perform a stochastic and heuristic based search by interacting through a pheromone model. The proposed heuristic and pheromone models are presented and compared through systematic experiments on benchmark planning domains. Experiments are also provided to compare the quality of ACOPlan solution plans with respect to state of the art satisficing planners. The analysis of the results confirm the good performance of the Action?CAction pheromone model and points out the promising performance of the novel Fuzzy?CLevel?CAction pheromone model. The analysis also suggests general principles for designing performant pheromone models for planning and further extensions of ACOPlan to other optimization models. 相似文献