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151.
Manuel Evaristo Tomas Polcar Albano Cavaleiro 《International Journal of Mechanics and Materials in Design》2008,4(2):137-143
W-S-C films were deposited by non-reactive sputtering from a carbon target incrusted with WS2 pellets in the eroded zone. This process allows depositing coatings with a wide range of compositions, with a precise control
of their carbon content. Before the deposition, a Ti interlayer was interposed between the film and the substrate to improve
the final adhesion. The carbon content in W-S-C system was varied from 29 at.% to 70 at.%, which led to an hardness enhancement
from 4 GPa up to 10 GPa where the maximum hardness was reached in films with a carbon content between 40 at.% and 50 at.%.
The tribological behaviour of the coatings was evaluated by pin-on-disk testing, in environments with different humidity levels.
Generally, the tribological performance of W-S-C coatings in environments with moderate to high humidity is better for coatings
with high carbon content. Friction coefficients, as 0.05 or lower could be reached at low humidity ranges (<7%) to all compositions.
However, for higher humidity values, friction coefficient increased up to 0.30 in the W-S-C film with low carbon content whereas
it was kept approximately constant for the others compositions. 相似文献
152.
The extreme high speed of change in the area of information technology creates a new demand for a process of continues learning and relearning in the workplaces but also among the public as a whole. There is need for a deeper crossdisciplinary and interdisciplinary understanding of the effects of this extreme demand for learning and relearning, both on us as individuals, on public and private organization and on the society as a whole. Information technology provides to some extent possible solutions to the problems it creates. Consequently, web based learning is also expanding with an accelerating speed. But this new form of learning is not to the same extent backed up by a fast growing research, in areas like on-the job-learning, workplace pedagogics, 'competence ergonomics', etc. But there are a number of very good exceptions like the Knowledge Media Institute of the Open University, and also a number of newly established facilities like the network university in the north of Sweden, the Mid Sweden University. In this special issue these types of problems are discussed, including those where the emphasis lies in creating rational and effective methods for web-based training and learning. The following was put forward in the invitation to a particular target group for this special issue. 相似文献
153.
This paper describes the deformation and breakage behaviour of granulates in single particle compression test. Three industrial spherical granulates—γ-Al2O3, the synthetic zeolite Köstrolith® and sodium benzoate (C6H5COONa) were used as model materials to study the mechanical behaviour from elastic to plastic range. The elastic compression behaviour of granulates is described by means of force-displacement curves, by application of Hertz-Huber contact theory and continuum mechanics. An elastic-plastic contact model was proposed to describe the deformation behaviour of elastic-plastic granules. The effects of granulate size and stressing velocity on the breakage force and contact stiffness during elastic and elastic-plastic displacement are examined. It is shown that the zeolite granulates with elastic-plastic behaviour have viscous properties as well. Breakage mechanisms of granulates during elastic, elastic-plastic and plastic deformation are also explained. The breakage probability is approximated by Weibull distribution function. The behaviour of the granulate during compression under the repeated loading-unloading conditions was investigated. 相似文献
154.
Lindblom J. Larsson E.G. Jorswieck E.A. 《Wireless Communications, IEEE Transactions on》2010,9(2):500-504
We study the achievable rate region of the multipleinput single-output (MISO) interference channel (IFC), under the assumption that all receivers treat the interference as additive Gaussian noise. We assume the case of two users, and that the channel state information (CSI) is only partially known at the transmitters. Our main result is a characterization of Paretooptimal transmit strategies, for channel matrices that satisfy a certain technical condition. Numerical examples are provided to illustrate the theoretical results. 相似文献
155.
The investigation of breakage probability by compression of single particles was carried out. The spherical glass particles and irregularly shaped particles of NaCl, sugar, basalt and marble were subjected to a breakage test. The breakage test includes the compression up to breakage of 100 particles to obtain the distribution of the breakage probability depending on the breakage force or compression work. The breakage test was conducted for five particle size fractions from each individual material, at two stressing rates. Thus obtained 50 breakage force distributions and corresponding 50 breakage work distributions were fitted with log-normal distribution function.Usually, the breakage probability distribution can be found by means of stress or energy approach. The first one uses the stress to calculate the breakage probability distribution. The second approach uses the mass-related work done to break the particle. We prefer to use the breakage force and energy as essential variables. The correlation between the force and energy at their breakage points is obtained by integrating the characteristic force–displacement curve, i.e. the constitutive function of elastic–plastic mechanical behavior of the particle. The irregularly shaped particle is approximated by comparatively “large” hemispherical asperities. In terms of elastic–plastic deformation of the contacting asperities with the plate, a transition from elastic to inelastic deformation behavior was considered. Thus, one may apply the model of soft contact behavior of comparatively stiff hemispheres. Based on this model a relationship between the breakage force distributions and corresponding energy distributions was analyzed. Every tested material exhibits a linear relationship between average breakage energy and average breakage force calculated for every size fraction.For future consideration both force and energy distributions were normalized by division by average force or energy, consequently. The relationship between the fit parameters of normalized energy distribution and corresponding fit parameters of normalized force distribution was established. The mean value and standard deviation of normalized force distribution can be found from mean value and standard deviation of normalized energy distribution by means of system of two linear equations. The coefficients of those linear equations remain the same for all of the above tested materials; particle size fractions and stressing rates. As a result the simple transformation algorithm of distributions is developed. According to this algorithm the force distribution can be transformed into energy distribution and vice versa. 相似文献
156.
Krizkova S Fabrik I Huska D Adam V Babula P Hrabeta J Eckschlager T Pochop P Darsova D Kukacka J Prusa R Trnkova L Kizek R 《International journal of molecular sciences》2010,11(12):4826-4842
The drugs based on platinum metals represent one of the oldest, but also one of the most effective groups of chemotherapeutic agents. Thanks to many clinical studies it is known that resistance of tumor cells to drugs is a frequent cause of chemotherapy failure. With regard to platinum based drugs, multidrug resistance can also be connected with increased expression of low-molecular weight protein metallothionein (MT). This study aimed at investigating the interactions of MT with cisplatin or carboplatin, using the adsorptive transfer technique coupled with differential pulse voltammetry Brdicka reaction (AdTS DPV Brdicka reaction), and a comparison of in vitro results with results obtained in vivo. The results obtained from the in vitro study show a strong affinity between platinum based drugs and MT. Further, we analyzed extracts of neuroblastoma cell lines treated with cisplatin or carboplatin. It is clear that neuroblastoma UKF-NB-4 cisplatin-resistant and cisplatin-sensitive cell lines unlikely respond to the presence of the platinum-based cytostatics cisplatin and carboplatin. Finally, we determined the level of MT in samples from rabbits treated with carboplatin and patients with retinoblastoma treated with the same drug. 相似文献
157.
Chao Wang Zhaoqing Xu Tomas Tobrman Ei‐ichi Negishi 《Advanced Synthesis \u0026amp; Catalysis》2010,352(4):627-631
The hitherto unprecedented palladium‐catalyzed cross‐coupling of (Z)‐β‐bromo‐β‐arylethenylboranes can be made to proceed satisfactorily through (1) the use of highly catalytically active bis(tri‐tert‐butylphosphine)palladium or dichloro[N,N‐bis‐(2,6‐diisopropylphenyl)imidazol‐2‐yl](m‐chloropyridine)palladium and (2) conversion of the dibromoboryl group to the (pinacol)boryl group. Thus, a wide variety of carbon groups can be used to substitute bromine in ≥98% stereo‐ and regioselectivity, while suppressing the otherwise dominant β‐debromoboration. Together with the alkylethyne‐based protocols, the alkyne bromoboration–Negishi coupling tandem process has emerged as the most widely applicable and highly selective route to trisubstituted alkenes including those that are otherwise difficult to access. 相似文献
158.
159.
Effect of acid deposition on quantity and quality of dissolved organic matter in soil-water 总被引:1,自引:0,他引:1
Ekström SM Kritzberg ES Kleja DB Larsson N Nilsson PA Graneli W Bergkvist B 《Environmental science & technology》2011,45(11):4733-4739
The aim of this study was to explore how acid deposition may affect the concentration and quality of dissolved organic matter (DOM) in soil-water. This was done by a small-scale acidification experiment during two years where 0.5 × 0.5 m(2) plots were artificially irrigated with water with different sulfuric acid content, and soil-water was sampled using zero-tension lysimeters under the O-horizon. The DOM was characterized using absorbance, fluorescence, and size exclusion chromatography analyses. Our results showed lower mobility of DOM in the high acid treatment. At the same time, there was a significant change in the DOM quality. Soil-water in the high acid treatment exhibited DOM that was less colored, less hydrophobic, less aromatic, and of lower molecular weight, compared to the low acid treatment. This supports the hypothesis that reduction in sulfur deposition is an important driver behind the ongoing brownification of surface waters in many regions. 相似文献
160.
ɛ ′) and relative loss factor (ɛ′′) give information on how the microwaves can penetrate into the wood object and of possible thermal gradient effects on
the wood during modification. This investigation shows that microwave energy effectively heats the acetic anhydride used for
modification by acetylation and that the power penetration depth (d
p) of the microwaves is about 10 cm in acetic anhydride impregnated wood. The relative permittivity and the relative loss factor
were found to decrease with increasing temperature, which indicates that the energy absorption will preferably be directed
to less heated parts of the wood object. This will promote a more uniform heat distribution, and, accordingly, a more uniform
acetylation of the wood.
d p) für das getr?nkte Holz etwa 10 cm betr?gt. Dielektrizit?tskonstante und Verlustfaktor nehmen mit steigender Temperatur ab; d.h. die Energieaufnahme wird vorzugsweise zu den weniger erhitzten Teilen des Holzes gelenkt. Das wiederum f?rdert eine gleichf?rmige Acetylierung des Holzes.相似文献