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排序方式: 共有128条查询结果,搜索用时 31 毫秒
1.
Antti Voss Niko Hänninen Mohammad Pour-Ghaz Marko Vauhkonen Aku Seppänen 《Materials and Structures》2018,51(3):68
The development of visualizing tools to monitor unsaturated moisture flow in cement-based materials is of great importance, as most degradation processes in cement-based materials are connected to and take place in the presence moisture. This paper investigates the ability of electrical capacitance tomography (ECT) to image two-dimensional (2D) unsaturated moisture flow in cement-based materials. In ECT, the electrical permittivity distribution within an object is reconstructed based on measured capacitances between electrodes attached on the object’s surface. In a series of experiments, mortar specimens with and without discrete cracks were imaged with ECT during a 2D moisture ingress. The results show that ECT is able to monitor the evolution of the moisture flow, and to approximate the shape and position of the moisture front. These findings indicate that ECT is a viable method for monitoring and visualizing 2D unsaturated moisture flow in cement-based materials in the presence and absence of discrete cracks. 相似文献
2.
It is shown that the compressed word problem for an HNN-extension ??H,t?Ot ?1 at=?(a) (a??A)?? with A finite is polynomial time Turing-reducible to the compressed word problem for the base group H. An analogous result for amalgamated free products is shown as well. 相似文献
3.
Primates are very good at recognizing objects independent of viewing angle or retinal position, and they outperform existing computer vision systems by far. But invariant object recognition is only one prerequisite for successful interaction with the environment. An animal also needs to assess an object's position and relative rotational angle. We propose here a model that is able to extract object identity, position, and rotation angles. We demonstrate the model behavior on complex three-dimensional objects under translation and rotation in depth on a homogeneous background. A similar model has previously been shown to extract hippocampal spatial codes from quasi-natural videos. The framework for mathematical analysis of this earlier application carries over to the scenario of invariant object recognition. Thus, the simulation results can be explained analytically even for the complex high-dimensional data we employed. 相似文献
4.
5.
Niko Radulovi? Marija Deni? Zorica Stojanovi?-Radi? Danielle Skropeta 《Journal of the American Oil Chemists' Society》2012,89(12):2165-2185
The detailed analyses of the volatile essential oil and lipid profiles of the aerial parts from the blooming and fruit-forming stages of both ripe and unripe fruit of Lycopus europaeus (Lamiaceae) are presented. Both of these profiles are distinguished by components with a restricted occurrence in the Plant Kingdom. These rare compounds include (E)-hotrienol in the volatiles, numerous unusual fatty acids (such as very long chain, odd-numbered and branched-chain) in the bound lipids and a high amount of iso- and anteiso-alkanes in the epicuticular waxes. Furthermore, a Gaussian-like distribution of the relative amounts of the epicuticular wax alkanes was observed. These normal distributions could be interpreted as the end result of the work of elongase enzyme systems where the Gaussian parameter μ should match the length of the “ideal” fatty acid biosynthesised and σ would represent the error of this enzyme system. These curve parameters were shown to have a close relationship with ACL and CPI values usually utilised to describe the natural distribution of wax alkanes. The screening of L. europaeus essential oil for its in vitro antimicrobial activity showed that this oil possesses selectivity towards two gram-negative strains, E. coli and K. pneumoniae. 相似文献
6.
The effect of adding 0.04% additional boron to 6.5% V-5% W high speed steel was investigated. The microstructure characterization, phase identification, and carbide identification of the materials were performed using SEM/EDS and XRD. The cell size and carbide volume fraction were examined using image analysis software. The boron distribution was observed by PTA Boron Tracking. The addition of 0.04% more boron to a HSS alloy exerted a cell refining effect on the sample. The cell refinement of dendritic structures in the alloy containing boron may be attributed to the constitutional supercooling effect associated with the fairly small distribution coefficient for boron in iron. The addition of boron increases the bending strength of the material by more than 10%, as well as increasing its hardness. 相似文献
7.
Joseph Hamuyuni Niko Hellstén Guven Akdogan Pekka Taskinen 《Journal of the American Ceramic Society》2015,98(1):320-323
We present experimental results for the liquidus of the pseudo binary system Cu2O–CaO at metallic copper saturation up to 1698 K in steps of 25 K. In this study, we quantified the liquidus (on the CaO side of the binary) by the equilibration, quench, and analysis technique, with Cu2O, CaO, and Cu as the only primary crystalline phases. Experiments were conducted in an atmosphere of pure argon up to the critical temperature (1618 K) in the Cu–O system. Above this temperature, experiments were performed at a fixed oxygen pressure of (PO2 = 1.01 kPa). Equilibrated specimens were quenched in ice‐cold water. We then quantified the liquid chemical compositions by means of energy‐dispersive X‐ray spectroscopy and electron probe micro‐analyzer. Results from this study reveal that below the critical point, some previous studies have overestimated CaO solubility amounts in the molten phase of the system, by up to 4.35 wt% CaO. Thermodynamic modeling of systems containing this binary should therefore also account for this variance. 相似文献
8.
The bandwidth of the ball-screw drive is limited by the first natural frequency of the mechanical structure. As opposed to conventional drives where the axial bearing stiffness is kept high to obtain higher natural frequencies, this paper proposes to use lower axial bearing stiffness accompanied by a strong damper in parallel with the ball-screw structure. The proposed method, which is experimentally demonstrated, increases the bandwidth of the drive considerably provided that a cost effective and practical damper is available. 相似文献
9.
Torhildur Fjola Kristjansdottir Niko Heeren Inger Andresen Helge Brattebø 《Building Research & Information》2018,46(4):367-382
Different designs and concepts of low-energy and zero-emission buildings (ZEBs) are being introduced into the Norwegian market. This study analyses and compares the life cycle emissions of CO2 equivalents (CO2e) from eight different single-family houses in the Oslo climate. Included are four ZEBs: one active house, two passive houses, and a reference house (Norwegian building code of 2010). Monthly differences in CO2e emissions are calculated for the seasonally sensitive Norwegian context for electricity generation and consumption. This is used to supplant the previous applied symmetric weighting approach for CO2e/kWh factors for import and export of electricity for the ZEB cases. All the ZEBs have lower use-stage emissions compared with the other buildings or the reference case. Embodied impacts are found to be 60–75% for the analysed ZEB cases, confirming the importance of embodied impacts in Norwegian ZEBs. The lowest total emissions were from the smallest ZEB, emphasizing area efficiency. The highest emissions were from the reference case. By abandoning the symmetric approach, a new perspective was developed for assessing the performance of ZEBs within the Norwegian context. One of four ZEB cases managed to balance out its annual energy-related emissions. 相似文献
10.
K. David Wegner Stina Lindén Zongwen Jin Travis L. Jennings Rachid el Khoulati Paul M. P. van Bergen en Henegouwen Niko Hildebrandt 《Small (Weinheim an der Bergstrasse, Germany)》2014,10(4):734-740
Semiconductor quantum dot nanocrystals (QDs) for optical biosensing applications often contain thick polyethylene glycol (PEG)‐based coatings in order to retain the advantageous QD properties in biological media such as blood, serum or plasma. On the other hand, the application of QDs in Förster resonance energy transfer (FRET) immunoassays, one of the most sensitive and most common fluorescence‐based techniques for non‐competitive homogeneous biomarker diagnostics, is limited by such thick coatings due to the increased donor‐acceptor distance. In particular, the combination with large IgG antibodies usually leads to distances well beyond the common FRET range of approximately 1 to 10 nm. Herein, time‐gated detection of Tb‐to‐QD FRET for background suppression and an increased FRET range is combined with single domain antibodies (or nanobodies) for a reduced distance in order to realize highly sensitive QD‐based FRET immunoassays. The “(nano)2” immunoassay (combination of nanocrystals and nanobodies) is performed on a commercial clinical fluorescence plate reader and provides sub‐nanomolar (few ng/mL) detection limits of soluble epidermal growth factor receptor (EGFR) in 50 μL buffer or serum samples. Apart from the first demonstration of using nanobodies for FRET‐based immunoassays, the extremely low and clinically relevant detection limits of EGFR demonstrate the direct applicability of the (nano)2‐ assay to fast and sensitive biomarker detection in clinical diagnostics. 相似文献