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2.
Kazuhiko Honda Eiji ૿ sawa Zdenek Slanina Takatoshi Matsumoto 《Fullerenes, Nanotubes and Carbon Nanostructures》1996,4(5):819-834
As a continuation of the studies on thermal transformation of the [2+2] C60 dimer (1), the consequence of the pyracylene-rearrangement-like valence isomerization of the fulvalene partial structure at the bridge of the ring-opened product from 1, namely 2, was searched by dynamic reaction coordinate /AM1 semiempirical MO calculations. It is predicted that the fulvalene bridge of 2 rearranges into naphthalene partial structure by the concerted 'in-plane' mechanism to give a wide-bridged C120 intermediate having twenty five-membered rings and two ten-membered rings (3). The computed energy of activation (145 kcal/mol) is 40 kcal/mol lower than those computed for pyracylene rearrangements. In contrast, the recently reported analogous rearrangement of indigo (13) to dibenzonaphthyridindione (14) is computed to occur by the stepwise 'sp3' mechanism. 相似文献
3.
Jeremy P. Wu Rees D. Rawlings Aldo R. Boccaccini Ivo Dlouhy Zdenek Chlup 《Journal of the American Ceramic Society》2006,89(8):2426-2433
A novel glass–ceramic material was developed from the melt of a TiO2 -containing iron-making slag with additional waste glass. The high percentage (∼20 wt% TiO2 ) of this network-modifying oxide has promoted a crystallization of the parent glass, resulting in a fine-grained, homogeneous polycrystalline material with high mechanical properties ( E =120 GPa, flexural strength=∼180 MPa, and Vickers hardness=7 GPa) after a heat treatment at 1100°C for 2 h. The room temperature and elevated temperature fracture toughness were also studied. The main crystalline phases of the glass–ceramic material were of the pyroxene series until heat-treatment temperature reached 1000°C, at which titanium-rich perovskite and armalcolite crystals became the dominant phases. The end material is high-strength, aesthetically acceptable (metallic gray or opaque brown colored), and suitable for structural and architectural applications. 相似文献
4.
The study of hydration of expansive cement prepared from 64% portland cement clinker, 23% metakaolinite and 13% CaSO4.2H2O is described. It was found that in the course of a 10-day hydration period, all the gypsum entered the reaction with the formation of ettringite. In 7–10 days, after the termination of the expansion processes, typical stalk-like crystals were transformed into leaf-shaped or other formations. Ettringite was identified even after 4 months of hydration. Monosulphate (3CaO.Al2O3.CaSO4.12H2O) was found in none of the investigated high-expansion cement paste samples. 相似文献
5.
Zdenek Vasicek Michal Bidlo Lukas Sekanina 《Soft Computing - A Fusion of Foundations, Methodologies and Applications》2013,17(11):2163-2180
Image processing represents a research field in which high-quality solutions have been obtained using various soft computing techniques. Evolutionary algorithms constitute a class of stochastic search methods that are applicable in both optimization and design tasks. In the area of circuit design Cartesian Genetic Programming has often been utilized in combination with an algorithm of Evolutionary Strategy. Digital image filters represent a specific class of circuits whose design can be performed by means of this approach. Switching filters are advanced non-linear filtering techniques in which the main idea is to detect and filter the noise pixels while keeping the uncorrupted pixels unchanged in order to increase the quality of the resulting image. The aim of this article is to present a robust design technique based on Cartesian Genetic Programming for the automatic synthesis of switching image filters intended for real-time processing applications. The robustness of the proposed evolutionary approach is evaluated using four design problems including the removal of salt and pepper noise, random shot noise, impulse burst noise and impulse burst noise combined with random shot noise. An extensive evaluation is performed in order to compare the properties of the evolved switching filters with the best conventional solutions. The evaluation has shown that the evolved switching filters exhibit a very good trade off between the quality of filtering and the implementation cost in field programmable gate arrays. 相似文献
6.
Paul Mulholland Zdenek Zdrahal John John Domingue Marek Hatala 《Behaviour & Information Technology》2000,19(3):171-180
Integrating working and learning is seen as a desirable alternative to traditional training regimes. An integrated approach to working and learning is more gradual, contextual, problem oriented and cost effective. Knowledge technology aims to catalyze workplace learning, but requires the right organisational culture and brings additional costs regarding the articulation, representation and transmission of knowledge. Our approach reduces these costs by making articulation a natural part of collaborative working, designing for both informal and formal knowledge, and facilitating the transition of socially situated knowledge through enriched documents. To be successful, our approach has certain prequesites concerning organisational culture, and the nature of shared documents, organisational knowledge and work activities. 相似文献
7.
Martina Halasova Zdenek Chlup Adam Strachota Martin Cerny Ivo Dlouhy 《Journal of the European Ceramic Society》2012,32(16):4489-4495
The presented work describes mechanical properties of materials prepared by the pyrolysis of polysiloxane resins. The polymeric precursors have different chemical composition. Materials under investigation are predetermined for high temperature resistant applications usually in composite form, i.e. accompanied by some reinforcement. Instrumented hardness tests were employed for material characterisation. The Vickers hardness, Martens hardness and indentation elastic modulus were the key parameters, determined either from the standard optical technique or load–indentation depth curves. The influence of mechanical properties on the monomers ratio was established. The exposition to the temperature between 1200 °C and 1500 °C in air was applied to observe damage caused by these severe conditions. 相似文献
8.
This paper presents a new method and results from measurement of internal parameters of programmable nanoscale circuits, namely Xilinx FPGA devices and especially Zynq SoC devices designed on 28 nm TSMC’s technology and older 45 nm Spartan 6 device as well as Xilinx Virtex product lines. The method utilizes a new undersampling approach for frequency measurement and an easy way of processing BRAM data streams. The proposed flexible circuits have been used in various measurements of timing parameters and delays in FPGAs, including measurements or detection of the aging issues. The paper presents results of measurements under various core voltage values as performed on selected Xilinx FPGA platforms, including key results about limited usability of the latest 28 nm devices under accelerated conditions and possibility of studying or mitigating aging effects in FPGAs. The paper presents rare results of experiments, real measurements and data available from current as well as previous technology nodes and it attempts to uncover new facts and areas of the latest high-end technologies, including the area of aging and degradation processes in general. The new methodology, presented approach and results can also be used in various dependable systems, including selected aerospace, medical, automotive or transportation ones. It is also directly and easily applicable to modern processor and multicore systems. 相似文献
9.
ABSTRACTThe application of eye drops from flexible dropper bottles fitted with different types of dropper tips is associated with the high variability of eye drop weights. The aim of this report was to investigate the simultaneous effect of three factors influencing the mean weight of drops dispensing from two plastic dropper tips. Using a designed experiment (Box-Behnken), the effect of the concentration of benzalkonium chloride solutions (BAC) in the range of 0–0.02%, the dispensing angle from 90° to 30° from horizontal, and the residual volume of liquid in the dropper bottle from 4 to 10 mL on the mean drop weights were examined. The significant effect of the increase in BAC concentration resulted in a linear decrease in drop weights for both of the dropper tips investigated. The significant effect of the dispensing angle was influenced by the dropper tip design. For the dropper tip A, the effect of the dropper tip tilt was described by the quadratic equation with a minimum, which corresponded to the dispensing angle equal to that of 48° from horizontal. Below this angle, the increase in drop weights occurred due to the drop formation from the wetted external surface of the tip orifice. The linear decrease in drop weights in response to the decrease in dispensing angle was detected for the dropper tip B. The regression equations and the contour line plots obtained allowed the drop weights to be estimated for the actual combinations of both the BAC concentration and the dispensing angle. The effect of the residual volume was found to be non-significant. Based on the formula of Tate's law, the direct proportion between surface tension of a solution and the radius of the effective perimeter of a dropper tip can be used to estimate the theoretical maximal weight of drops at the dispensing angle of 90°. Using the stalagmometric values of surface tension of the BAC solutions, the maximal drop weights were estimated for both of the dropper tips investigated. A comparison between the theoretical and the experimentally measured drop weights enabled the dropper tips behavior to be discussed by using Harkins and Brown correction factor F. The F-value of 0.74 noted for the dropper tip A differed from that of stalagmometer F-value (0.61) indicating a deviation from the simple drop formation process in answer to more complicated design of the dropper tip A. On the other hand, the F-value of 0.6 observed for the dropper tip B demonstrated the better consistency with stalagmometry. As a result, the dropper tip B with the linear decrease of drop weights in response to the increased concentration of BAC and the decreased dispensing angle without the adverse external drop formation could be recommended in real drop dispensing. 相似文献
10.
Daniel Drdlik Dominik Zeman Pavel Tofel Zdenek Chlup Hynek Hadraba Katarina Drdlikova 《Ceramics International》2021,47(2):2034-2042
The development and optimisation of piezoceramics are targeted usually to enhance their piezoelectric properties evaluated by both the direct or indirect measurement methods. The presented work aims to elaborate on the correlation of one direct (Berlincourt) and two indirect (convert and field-dependent) piezoelectric measurement methods on various material states. The role of the ceramic powder treatment by ball milling and electrophoretic deposition (EPD) technique on the determined electric properties as well as basic physical and mechanical properties of (Ba0.85Ca0.15) (Zr0.1Ti0.9)O3 ceramics (BCZT) was investigated. It was found that the EPD technologically supported by milling allows obtaining thick and dense deposits (>2 mm). After sintering, the BCZT ceramics with a relative density of >95%, hardness in the range of 2.3–2.9 GPa and piezoelectric coefficients of d33* = 940 pm/V, d33(E=0) = 427 pm/V and d33 = 364 pC/N can be achieved. Reported results also suggest that indirect (field-dependent) and direct (Berlincourt) measurements of the piezoelectric coefficients can be comparable at optimal poling conditions. 相似文献