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991.
M. Gowri W.J.P. van Enckevort J.J. Schermer J.P. Celis J.J. ter Meulen J.G. Buijnsters 《Diamond and Related Materials》2009,18(12):1450-1458
Diamond coatings were deposited by hot filament chemical vapor deposition on high speed steel substrates. Iron boride diffusion barrier and WC–Co layers were used as interlayers. At high deposition pressure, the quality of the diamond deposits is poor due to the extensive formation of graphitic deposits. At low pressure, diamond films of better quality were obtained, but their adhesion to the substrate was insufficient. A two-step deposition process at low pressure was developed. In a first deposition step performed at high methane percentage, a high nucleation density was achieved. In a second deposition step, the methane percentage was reduced to achieve continuous, dense, and adherent diamond layers on borided or WC–Co coated high speed steel substrates. Adhesion of these diamond layers on the surface modified high speed steel substrates was tested based on reciprocating sliding tests. 相似文献
992.
Ca-doped ThO2, synthesized by solution combustion method was tested for dehydrogenation of ethane with CO2. Doping ThO2 with Ca resulted in the creation of oxide ion vacancies and an increased conversion of ethane compared to pure ThO2. On Th0.75Ca0.25O2 selectivity to ethene was 97 at 46% ethane conversion at 725 °C. Well-known reference catalysts like 5%Cr/TS-1 or OMS-2 showed significantly lower selectivity, but the former was more active under the same conditions. 相似文献
993.
Gwen van Eijk 《Journal of Housing and the Built Environment》2010,25(4):467-480
This paper examines whether and how living in a poor neighbourhood results in “network poverty”. Through a detailed analysis
of the formation of personal networks of people living in a poor neighbourhood and those living in an affluent neighbourhood
in Rotterdam, I examine the role of the neighbourhood in the formation of personal networks. I address three issues. First,
whether resource-poor people who live in a poor neighbourhood form relationships with fellow-residents to compensate for their
otherwise small network. I find that they do not and that their small network is primarily caused by non-participation in
settings such as study, work, leisure and associations. Second, I distinguish locally maintained relationships that have originated
in other settings from locality-based relationships that originated in the neighbourhood. The study shows that high network
localness is more a matter of maintaining relationships in the neighbourhood than forming many new locality-based relationships
with fellow-residents. Third, I examine how the neighbourhood facilitates relationship formation and conclude that this happens
not in “the neighbourhood” but in neighbourhood settings, which attract a particular segment of a neighbourhood population.
I conclude that the problem of network poverty is not in the first place spatial but rather lies in lack of participation
in certain settings. Furthermore, social mixing policies can only be successful if they are accompanied by initiatives to
draw a mixed population to neighbourhood settings and facilitate routine encounters between resource-rich and resource-poor
people. 相似文献
994.
The structure of semi-crystalline polymers is strongly influenced by the conditions applied during processing and is of major importance for the final properties of the product. A method is presented to quantify the effect of thermal and pressure history on the isotropic and quiescent crystallization kinetics of four important structures of polypropylene, i.e. the α-, β-, γ- and mesomorphic phase. The approach is based on nucleation and growth of spherulites during non-isothermal solidification, described by the Schneider rate equations combined with the Komogoroff-Avrami expression for space filling. Using an optimization routine the time-resolved multi-phase structure development is accurately described using crystal phase dependent growth rates and an overall nucleation density, all as function of temperature and pressure. It is shown that the maximum growth rate of the α-, and γ-phase increases with applied pressure, while it decreases for the mesomorphic phase. Addition of β-nucleation agent is interpreted as a secondary nucleation density with a coupled β-phase growth. This complete crystallization kinetics characterization of isotactic polypropylene allows prediction of the multi-phase structure development for a wide range of quiescent processing conditions. 相似文献
995.
Manoko S. Maubane Messai A. Mamo Edward N. Nxumalo Willem A.L. van Otterlo Neil J. Coville 《Synthetic Metals》2012
A simple methodology to produce tubular nitrogen-doped carbon nanotube/polythiophene covalently linked composites is described. Nitrogen doped carbon nanotubes (N-CNTs) were made by the floating catalyst CVD method using toluene, ferrocene and tetramethylethylenediamine (TMEDA) as reagents. Functionalization of the N-CNTs was achieved using 3-thiophenecarboxaldehyde and N-methylglycine in 1,2-dichlorobenzene (Prato reaction). Elemental analysis showed nitrogen incorporation of N into the N-CNTs (1.8%) and also the N-methylglycine functionalized N-CNTs (f-N-CNTs; 6.2%). A series of f-N-CNT/thiophene monomer mixtures (weight ratios 1:3, 1:10 and 1:20) were used to make f-N-CNT/polythiophene tubular composites. As the amount of thiophene monomer was increased, the overall diameter of the polymer layer attached onto the N-CNTs increased. Polymer thickness also varied with reaction time (1 h, 12 h and 24 h). The combination of acid functionalization and N–doping gives the best coverage of the CNTs by polythiophene, in which the polythiophene preferentially binds to the f-N-CNTs to give tubular structures. 相似文献
996.
J.M.M. Rovers M. Stöck J.W. Jansen C.M.M. van Lierop E.A. Lomonova Y. Perriard 《Mechatronics》2013,23(2):240-246
A transient thermal model used to monitor the temperature distribution in real-time in a long-stroke moving-magnet planar actuator is presented. The temperature distribution in the stator coils of the planar actuator depends on the trajectory of the levitated magnet plate as the set of active coils changes with the position of the translator. Using the presented real-time model, the transient thermal behavior can be investigated. Using this thermal model, the commutation algorithm of the planar actuator is adjusted to actively limit the temperature of the coils, and better spread the temperature over the stator coils. 相似文献
997.
Barry Haseltine Tor‐Ulf Weck Lars Meyer Rob van der Pluijm Oliver Dupont Christoph Alfes Wolfram Jaeger John Roberts Jonathan Silver Dirk Martens O. Pfeffermann Bastian Drewes Erhard Gunkler Jan Kubica Nebojsa Mojsilovic Erhard Gunkler Johann Marx Armin Ohler Hipolito Sousa Rui Sousa Romeu S. Vicente J. R. Mendes Silva Roberto Capozucca 《Mauerwerk》2011,15(6):348-361
998.
999.
S.J. Melles G.B.M. HeuvelinkC.J.W. Twenhöfel A. van DijkP.H. Hiemstra O. BaumeU. Stöhlker 《Computers & Geosciences》2011,37(3):280-288
This study presents a method to optimize the sampling design of environmental monitoring networks in a multi-objective setting. We optimize the permanent network of radiation monitoring stations in the Netherlands and parts of Germany as an example. The optimization method proposed combines minimization of prediction error under routine conditions with maximizing calamity detection capability in emergency cases. To calculate calamity detection capability, an atmospheric dispersion model was used to simulate potentially harmful radioactive releases. For each candidate monitoring network, we determined if the releases were detected within one, two and three hours. Four types of accidents were simulated: small and large nuclear power plant accidents, deliberate radioactive releases using explosive devices, and accidents involving the transport of radioactive materials. Spatial simulated annealing (SSA) was used to search for the optimal monitoring design. SSA was implemented by iteratively moving stations around and accepting all designs that improved a weighted sum of average spatial prediction error and calamity detection capability. Designs that worsened the multi-objective criterion were accepted with a certain probability, which decreased to zero as iterations proceeded. Results were promising and the method should prove useful for assessing the efficacy of environmental monitoring networks designed to monitor both routine and emergency conditions in other applications as well. 相似文献
1000.
C.T. Jayasundara R.Y. Yang B.Y. Guo A.B. Yu I. Govender A. Mainza A. van der Westhuizen J. Rubenstein 《Minerals Engineering》2011,24(3-4):181-187
The IsaMill? is a high speed stirred mill with a horizontal configuration that offers advantages such as energy efficiency and an inert grinding environment. A combined computational fluid dynamics (CFD) and discrete element method (DEM) approach was developed to investigate the particle and fluid flows inside a simplified IsaMill?. The configuration of the mill was simpler than that of an actual IsaMill? and no feed flow or rotor was considered. The CFD–DEM model is a progression from earlier DEM only models of “dry” systems which did not account for the fluid phase. The properties of flows at a macroscopically steady state, such as velocity field, distributions of particle velocity and acceleration in the radial direction and power draw, were analysed. Detailed comparisons were carried out between the simulation results and Positron Emission Particle Tracking (PEPT) measurements under similar conditions. The comparisons showed reasonable agreements, confirming that both techniques can capture the key features of the flow. The discrepancies between simulated and measured results were discussed. The findings indicated that the proposed model can be used to generate microdynamic information that is useful in leading to a better understanding of the underpinning physics of flow inside mills. 相似文献