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排序方式: 共有1323条查询结果,搜索用时 15 毫秒
101.
Inverse problems are considered for the linear one-way one-dimensional wave equation or transport equation. In particular the wave speed reconstruction problem for a medium is discussed. Inverse problems for non-stationary, but also non-dispersive, media are examined; this means problems for which the slab medium parameters are both spatially and temporally varying are considered. Both theoretical and numerical results are given for the methods presented. Theoretical results obtained for this equation can be generalised to second order equations. 相似文献
102.
Jonas Eskhult Christian Ulrich Fredrik Björefors Leif Nyholm 《Electrochimica acta》2008,53(5):2188-2197
It is demonstrated that current oscillations can be observed during chronoamperometric and cyclic voltammetric experiments in solutions containing 0.4 M CuSO4 and 1.2 M citrate at pH 11 and 50 °C. The oscillations, which are shown to originate from local variations in the pH, result in the deposition of nanostructured Cu and Cu2O materials. It is concluded that the current oscillations are analogous to the previously described potential oscillations obtained under controlled current conditions in alkaline Cu(II)-lactate, -tartrate and -citrate solutions. Rotating disk electrode results clearly show that the reduction of the Cu(II)-complexes is kinetically controlled and that the rate of the reduction increases with increasing pH and temperature. It is also shown that the presence of a cathodic peak on the anodic scan in the cyclic voltammograms can be used to identify the experimental conditions leading to the spontaneous current (or potential) oscillations. Electrochemical quartz crystal microbalance results indicate that the cathodic peak stems from an increased rate of the reduction of the Cu(II)-citrate complexes due to a rapid increase in the local pH. This causes Cu2O rather than Cu to be deposited which, however, results in a decrease in the local pH and a decreasing current. In situ ellipsometry data confirm that Cu2O deposition replaces that of Cu in the potential region of the cathodic peak. The present findings should facilitate syntheses of nanolayered materials based on spontaneous potential or current oscillations. 相似文献
103.
Ieva Raudoniūtė Jordi Rovira Petras Rimantas Venskutonis Jonas Damašius María Dolores Rivero‐Pérez María Luisa González‐SanJosé 《International Journal of Food Science & Technology》2011,46(5):935-943
The present study characterises garden strawberry leaf extract and reports its effect on shelf life and quality characteristics of fish oil. Radical scavenging capacity of the extract in DPPH? and ABTS?+ assays was equivalent to 1207 and 1579 μmol g?1 of trolox equivalents, respectively, total phenolic content was 257 mg g?1 of gallic acid equivalents. Phenolic and volatile constituents were analysed by liquid chromatography/mass spectrometry (LC/MS) and gas chromatography/mass spectrometry (GC/MS). The extract was added to fish oil and its oxidation was followed during 42 days: peroxide, p‐anisidine values and hexanal concentration were lower in the samples with extract, particularly at the end of storage. The effect of extract on fatty acid composition was not significant, however the changes in the percentages of some individual acids were observed. Fish oil containing 5% of extract had lower levels of lipid oxidation in comparison to other samples. The results indicate that strawberry leaves could be a potential source of natural antioxidants. 相似文献
104.
Rosana de Cassia de Souza Schneider Luciano Roni Silva Lara Marieli Milanesi Ceolin Jonas Alvaro Kaercher Manuella Schneider 《Clean Technologies and Environmental Policy》2013,15(6):977-985
In the vegetable oil chemical industry, hydrogenation is one of the most important processes. An alternative method for vegetable oil hydrogenation is the use of catalytic transfer hydrogenation (CTH), which can utilize organic molecules as hydrogen donors at ambient pressure. These alternative processes should be optimized in relation to the variables required for a good conversion and impacts should also be known to be minimized. An assessment of the environmental impact of laboratory scale chemical processes is an important tool to improve the technological aspects of a process (increased yields, reduced production times, lower costs) and it can also lead to the creation of a cleaner technology. Using the Leopold Matrix, we have succeeded in developing a more efficient and cleaner process for the CTH of castor oil using Raney Ni as a catalyst and cyclohexene or isopropanol as a hydrogen donor solvent. The results of the technical and environmental assessments showed that the extent of conversion for the unsaturation reaction was high (>99 %), and the environmental impact of the process could be significantly reduced to create a cleaner technology. It was found, after process optimization, that the remaining environmental impacts were negative (67.48 %), local (78.95 %), temporary (95.33 %), direct (80.12 %), and reversible (95.32 %). 相似文献
105.
Jonas Poelmans Sergei O. Kuznetsov Dmitry I. Ignatov Guido Dedene 《Expert systems with applications》2013,40(16):6601-6623
This is the first part of a large survey paper in which we analyze recent literature on Formal Concept Analysis (FCA) and some closely related disciplines using FCA. We collected 1072 papers published between 2003 and 2011 mentioning terms related to Formal Concept Analysis in the title, abstract and keywords. We developed a knowledge browsing environment to support our literature analysis process. We use the visualization capabilities of FCA to explore the literature, to discover and conceptually represent the main research topics in the FCA community. In this first part, we zoom in on and give an extensive overview of the papers published between 2003 and 2011 on developing FCA-based methods for knowledge processing. We also give an overview of the literature on FCA extensions such as pattern structures, logical concept analysis, relational concept analysis, power context families, fuzzy FCA, rough FCA, temporal and triadic concept analysis and discuss scalability issues. 相似文献
106.
TALplanner: A temporal logic based forward chaining planner 总被引:1,自引:0,他引:1
Jonas Kvarnström Patrick Doherty 《Annals of Mathematics and Artificial Intelligence》2000,30(1-4):119-169
We present TALplanner, a forward-chaining planner based on the use of domain-dependent search control knowledge represented
as formulas in the Temporal Action Logic (TAL). TAL is a narrative based linear metric time logic used for reasoning about
action and change in incompletely specified dynamic environments. TAL is used as the formal semantic basis for TALplanner,
where a TAL goal narrative with control formulas is input to TALplanner which then generates a TAL narrative that entails
the goal and control formulas. The sequential version of TALplanner is presented. The expressivity of plan operators is then
extended to deal with an interesting class of resource types. An algorithm for generating concurrent plans, where operators
have varying durations and internal state, is also presented. All versions of TALplanner have been implemented. The potential
of these techniques is demonstrated by applying TALplanner to a number of standard planning benchmarks in the literature.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
107.
Implementation of a Lattice Boltzmann kernel using the Compute Unified Device Architecture developed by nVIDIA 总被引:2,自引:0,他引:2
Jonas Tölke 《Computing and Visualization in Science》2010,13(1):29-39
In this article a very efficient implementation of a 2D-Lattice Boltzmann kernel using the Compute Unified Device Architecture (CUDA?) interface developed by nVIDIA® is presented. By exploiting the explicit parallelism exposed in the graphics hardware we obtain more than one order in performance gain compared to standard CPUs. A non-trivial example, the flow through a generic porous medium, shows the performance of the implementation. 相似文献
108.
Daniel R. Scheffler Jonas A. Zukas 《International Journal of Impact Engineering》1990,10(1-4):487-497
The performance of segmented and continuous penetrators impacting semi-infinite and spaced armor is studied using both the EPIC-2 and HULL hydrocodes. First the performance of a segmented rod is studied, striking semi-infinite armor, for various parameters such as striking velocity, segment spacing and number of segments. Then an actual penetrator configuration proposed by A. Charters is analyzed and the use of normalized penetration is discussed. Finally three-dimensional simulations are presented for segmented and continuous penetrators impacting oblique spaced armor varying such parameters as striking velocity, segment spacing, number of segments, and target thickness. 相似文献
109.
Variable Resolution 4-k Meshes: Concepts and Applications 总被引:2,自引:0,他引:2
110.