排序方式: 共有16条查询结果,搜索用时 15 毫秒
1.
Lenka Kvetková Annamária Duszová Monika Kašiarová Františka Dorčáková Ján Dusza Csaba Balázsi 《Journal of the European Ceramic Society》2013,33(12):2299-2304
Silicon nitride + 1 wt% graphene platelet composites were prepared using various graphene platelets (GPL) and two processing routes; hot isostatic pressing (HIP) and gas pressure sintering (GPS). The influence of the processing route and graphene platelets’ addition on the fracture toughness has been investigated. The matrix of the composites prepared by GPS consists of Si3N4 grains with smaller diameter in comparison to the composites prepared by HIP. The indentation fracture toughness of the composites was in the range 6.1–9.9 MPa m0.5, which is significantly higher compared to the monolithic silicon nitride 6.5 and 6.3 MPa m0.5. The highest value of KIC was 9.9 MPa m0.5 in the case of composite reinforced by the smallest multilayer graphene nanosheets, prepared by HIP. The composites prepared by GPS exhibit lower fracture toughness, from 6.1 to 8.5 MPa m0.5. The toughening mechanisms were similar in all composites in the form of crack deflection, crack branching and crack bridging. 相似文献
2.
Annamária Kovács 《Algorithmica》2010,57(2):413-433
We provide new bounds for the worst case approximation ratio of the classic Longest Processing Time (Lpt) heuristic for related machine scheduling (Q||C max?). For different machine speeds, Lpt was first considered by Gonzalez et al. (SIAM J. Comput. 6(1):155–166, 1977). The best previously known bounds originate from more than 20 years back: Dobson (SIAM J. Comput. 13(4):705–716, 1984), and independently Friesen (SIAM J. Comput. 16(3):554–560, 1987) showed that the worst case ratio of Lpt is in the interval (1.512,1.583), and in (1.52,1.67), respectively. We tighten the upper bound to $1+\sqrt{3}/3\approx1.5773We provide new bounds for the worst case approximation ratio of the classic Longest Processing Time (Lpt) heuristic for related machine scheduling (Q||C
max ). For different machine speeds, Lpt was first considered by Gonzalez et al. (SIAM J. Comput. 6(1):155–166, 1977). The best previously known bounds originate from more than 20 years back: Dobson (SIAM J. Comput. 13(4):705–716, 1984), and independently Friesen (SIAM J. Comput. 16(3):554–560, 1987) showed that the worst case ratio of Lpt is in the interval (1.512,1.583), and in (1.52,1.67), respectively. We tighten the upper bound to
1+?3/3 ? 1.57731+\sqrt{3}/3\approx1.5773
, and the lower bound to 1.54. Although this improvement might seem minor, we consider the structure of potential lower bound
instances more systematically than former works. We present a scheme for a job-exchanging process, which, repeated any number
of times, gradually increases the lower bound. For the new upper bound, this systematic method together with a new idea of
introducing fractional jobs, facilitated a proof that is surprisingly simple, relative to the result. We present the upper-bound proof in parameterized
terms, which leaves room for further improvements. 相似文献
3.
Based on location information, users’ mobility profile building is the main task for making different useful systems such as early warning system, next destination and route prediction, tourist guide, mobile users’ behavior-aware applications, and potential friend recommendation. For mobility profile building, frequent trajectory patterns are required. The trajectory building is based on significant location extraction and the user’s actual movement prediction. Previous works have focused on significant places extraction without considering the change in GSM (global system for mobile communication) network and is based on complete data analysis. Since network operators change the GSM network periodically, there are possibilities of missing values and outliers. These missing values and outliers must be addressed to ensure actual mobility and for the efficient extraction of significant places, which are the basis for users’ trajectory building. In this paper, we propose a methodology to convert geo-coordinates into semantic tags and we also purposed a clustering methodology for recovering missing values and outlier detection. Experimental results prove the efficiency and effectiveness of the proposed scheme. 相似文献
4.
Annamária Mockovčiaková Marek Matik Zuzana Orolínová Pavol Hudec Erika Kmecová 《Journal of Porous Materials》2008,15(5):559-564
Natural zeolite of Slovak provenience has been modified with magnetic nanoparticles at selected temperatures of 20, 50 and
85 °C with the aim to enhance its sorption properties. The pore, surface and structural properties of zeolite/iron oxide composite
were characterized using nitrogen adsorption measurements, electron probe microanalysis and powder X-ray diffraction. The
crystallinity of the host zeolite was strongly influenced by the temperature of iron oxide particles precipitation, but it
was still retained. It followed from the nitrogen adsorption measurements that the surface area and the pore volume of zeolite
composites have increased in relation to the precipitation temperature, the best sorption properties were revealed at the
composite prepared at 85 °C. As followed also from the SEM images, the iron oxide nanoparticles being of size 30 nm are forming
mesoporous aggregates adsorbed on the zeolite surface. Fractal analysis used to describe the modified geometry of zeolite
composites has given the values of surface fractal dimension between 2.36 and 2.51. 相似文献
5.
Daniela Kladeková Renáta Orináková Annamária Krajníková Miriam Kupková Margita Kabátová Kveta Markuová 《材料科学技术学报》2010,26(5):454-460
The poly(methyl methacrylate)(PMMA) coatings onto surface of iron particles were electrochemically prepared and the effect on both surface structure and internal structure of the resulted material after compaction was carried out.The electrochemical polymerization treatment was performed in a fluidized bed electrolyzer using sulphuric acid solution containing potassium persulphate and methyl methacrylate(MMA).The surface topography and the microstructure of the samples were observed by scanning electron mic... 相似文献
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7.
Bujna Erika Farkas Nikoletta Annamária Tran Anh Mai Dam Mai Sao Nguyen Quang Duc 《Food science and biotechnology》2018,27(2):547-554
Food Science and Biotechnology - Apricot is a popular fruit in the world with rich in carbohydrates, vitamins and elements as well as has high antioxidant capacity. In this study, fermentation of... 相似文献
8.
Mesároš Peter Behúnová Annamária Mandičák Tomáš Behún Marcel Krajníková Katarína 《Wireless Networks》2021,27(3):1641-1648
Wireless Networks - Business results and enterprise performance depends on various factors. First of all, there are primarily human resources and their knowledge, skills and competencies.... 相似文献
9.
A novel approach for analyzing underivatized very long chain fatty acids (C16-C26) and other apolar compounds such as triacylglycerols is described. It is based on reversed-phase HPLC separation followed by mass spectrometric detection. Partly miscible solvents are used for stepwise gradient elution starting with a methanol/water and ending with a methanol/n-hexane binary mixture. The developed technique does not need derivatization, and analysis is fast (fatty acids were separated in 2-min-long chromatograms) and robust. The developed method is also very sensitive; a quantitation limit in the low-picogram range was achieved for fatty acids. The separation mechanism and advantages of the suggested technique are discussed and illustrated in the case of blood analysis and plant oil characterization. 相似文献
10.
Ján Dusza Jerzy Morgiel Annamária Duszová Lenka Kvetková Martin Nosko Péter Kun Csaba Balázsi 《Journal of the European Ceramic Society》2012,32(12):3389-3397
Silicon nitride + 1 wt% graphene platelet composites were prepared using various graphene platelets (GPLs) as filler. The influence of the addition of GPLs on the microstructure development and on the fracture toughness of Si3N4 + GPLs composites was investigated. The GPLs with thickness from 5 nm to 50 nm are relatively homogeneously distributed in the matrix of all composites, however overlapping/bundle formation of GPLs was found, containing 2–4 platelets as well. The single GPLs and overlapped GPLs are located at the boundaries of Si3N4, and hinder the grain growth and change the shape of the grains. The fracture toughness was significantly higher for all composites in comparison to the monolithic Si3N4 with the highest value of 9.9 MPa m0.5 for the composite containing the GPLs with smallest dimension. The main toughening mechanisms originated from the presence of graphene platelets, and responsible for the increase in the fracture toughness values are crack deflection, crack branching and crack bridging. 相似文献