89 research outputs found
The turbulent dissipation rate from PIV measurements
No full textThe result of a particle-image velocimetry (PIV) measurement is a velocity field averaged over interrogation windows. This severely affects the measurement of small-scale turbulence quantities when the interrogation window size is much larger than the smallest length scale in turbulence. A direct measurement of the dissipation rate demands the measurement of gradients of the velocity field, which are now underestimated because the small-scale motion is not resolved. A popular procedure is to relate the statistical properties of the measured, but underresolved gradients to those of the true ones, invoking a large-eddy argument [3]. We show that the used proportionality constant, the Smagorinsky constant, should depend on the window overlap, on the used elements of the strain tensor, and on the way in which derivatives are approximate
How the dispersion of a droplet cloud depends on its initial size
No full textA cloud of droplets evolves under the influence of strong turbulence. The droplets are made from a phosphorescent fluid. From this cloud we select at t = 0 a narrow line by exciting the droplets with a UV laser, which causes them to glow for a few milliseconds. The dispersion of this line is followed in time using a fast intensified camera. A large range of droplet sizes (Stokes number St) was measured. It appears that lines with St \approx 1 disperse faster than a line of fluid tracers. Lines of droplets which are narrowest initially, spread fastest
Pin to pin neutron flux reconstruction in a PWR reactor using support vector regression (SVR) technique
No full textCoarse mesh nodal methods are widely used in the analysis of nuclear reactors. However, these methods provide only average values of the neutron fluxes. From a safety point of view, it is important to have an accurate analysis of the pin to pin flux distribution that nodal methods are not able to provide. Many articles have been published that make use of mathematical techniques to determine flux distributions. Most of these techniques use expansion functions to estimate these distributions. The expansion coefficients of these works are determined by conditions that take into account the average values of certain fluxes supplied by the nodal methods. There are also methods that employ analytical solutions of the neutron diffusion equation. This article presents a different approach for calculating the pin to pin neutron flux distribution for a PWR reactor. The developed method uses support vector regression (SVR) technique to determine this pin to pin neutron flux. The SVR technique uses average data computed with the Nodal Expansion Method (NEM) for learning purposes. A total of 70% of the computed data were used for training and 30% for validation, using multifold-cross-validation. Two fuel elements were removed from the training and validation sets, to test the method. Less than 2% errors were found when compared to the values obtained by the nodal expansion method (NEM), using a fine-mesh spatial discretization. We concluded that use of SVR to reconstruct pin to pin fluxes is another option, which will be of great value in fuel reload calculations, since the same parameters will be applied to all cycles, thus expediting calculations when compared to standard procedure calculations
Authoring multimedia in the CMIF environment
No full textWe present the user interface to the CMIF authoring
environment for constructing and playing multimedia
presentations. Within the environment an author constructs
a presentation in terms of its structure and additional
synchronization constraints, from which the actual timing
information is derived.
The CMIF authoring environment presents three main
views of a multimedia presentation: a hierarchy view for
manipulating and viewing a presentation’s hierarchical
structure; a channel view for managing logical resources
and specifying and viewing precise timing constraints; and a
player for playing the presentation
Productiviteitstrends in de sector verpleging, verzorging en thuiszorg: Een empirisch onderzoek naar het effect van regulering op productiviteit 1972-2010
No full textIn its 2011 letter on the subject of the labour market, the Ministry of Health, Welfare and Sports has indicated that it intends to actualize an increase of productivity in the health care sector in order to contribute to a solution for future problems in the labour market. Developing new policy requires insight into policy measures already in place and the effect that they have had on productivity.Innovation SystemsTechnology, Policy and Managemen
Effects of heavy metals on microbial diversity and bacterial resistance in marine sediments
No full textIn North-Western Europe alone more than 200 million cubic meters of contaminated sludge is dredged on an annual basis. Deposition of dredged harbour sediments in relatively undisturbed ecosystems is often considered a viable option, under the assumption that metals are not released into the environment. This research initially focused on the effects of heavy metals on biodiversity: which types of bacteria disappear and which proliferate? Additionally, this research aimed to develop a new method to analyse effects of heavy metals. Conventional chemical analyses only provide information about the total amount of heavy metals. This is not always relevant, as clay particles, for instance, adsorb heavy metals and therewith lower metal toxicity. In this research a biological essay was developed which does not determine the amount of metal but the toxicity of a metal.Applied Science
Productiviteitstrends in de sector verpleging, verzorging en thuiszorg
No full textDe productiviteit in de VVT-sector is in de periode 1972-1996 gedaald met gemiddeld 0,6 procent per jaar. Vanaf 1997 is de productiviteitsdaling gemiddeld 2 procent per jaar. De daling van de productiviteit valt in de periode waarin veel veranderingen van de AWBZ hebben plaatsgevonden en waarin ook meer en meer kwaliteitsbeleid is gevoerd. Tegelijk is de zorgzwaarte toegenomen. Zorgelijk is de autonome toename van de inzet van personeel in de hele periode en (geringe) afname van gebruik van materiaal en kapitaal. De aard van de dienstverlening leent zich misschien niet voor substitutie van personeel voor materiaal en kapitaal. Dieper inzicht in de oorzaken van de productiviteitsdaling kan verkregen worden door systematische bedrijfsvergelijkingen van alle VVT-instellingen op prestatie-indicatoren, waaronder de productie, ingezette middelen, prijzen en productiviteitsontwikkeling, maar ook technologie en innovatiebeleid, inkoopbeleid, personeelsbeleid, governance en managementstructuur. Dergelijke bedrijfsvergelijking kan de basis vormen voor nieuw beleid
Fabriekschema voor de Productie van Furfural
No full textDocument(en) uit de collectie Chemische ProcestechnologieDelftChemTechApplied Science
Rapid and reversible impairment of episodic memory by a high-fat diet in mice
No full textThe datasets generated during and/or analysed during the current study are available from the corresponding author on reasonable request. This work was supported by an EASTBIO BBSRC PhD studentship to F.H.M., L.M.W., C.G., A.C.M., G.W.H. and F.M.C. are supported by Scottish Government’s Rural and Environment Science and Analytical Services Division (RESAS).Peer reviewe
Life Cycle Assessment of Wire + Arc Additive Manufacturing compared to green sand casting and CNC milling in stainless steel
No full textWire and Arc Additive Manufacturing (WAAM) is a metal 3D printing technique based on robotic welding. This technique yields potential in decreasing material consumption due to its high material efficiency and freedom of shape. Empirical measurements of WAAM, using a deposition rate of 1 kg/h, were performed on site of MX3D. The measured power consumption per kg stainless steel is 2.72 kW, of which 1.74 is consumed by the welder, 0.44 by the robotic arm, and 0.54 by the ventilation. The material loss was 1.1%. A 98% argon 2% CO2 welding gas was used with a flow of 12 l/min.A cradle-to-gate Life Cycle Assessment (LCA) was performed. To give this assessment context, green sand casting and CNC milling were additionally assessed, through literature and databases. The purpose of this study is to develop insight into the environmental impact of WAAM. Results indicate that, in terms of total ReCiPe endpoints, the environmental impact of producing a kg of stainless steel 308 l product using WAAM is comparable to green sand casting. It equals CNC milling with a material utilization fraction of 0.75. Stainless steel is the main cause of environmental damage in all three techniques, emphasizing the importance of WAAM's mass reduction potential. When environmentally comparing the three techniques for fulfilling a certain function, optimized designs should be introduced for each manufacturing technique. Results can vary significantly based on product shape, function, materials, and process settings.Accepted author manuscriptMaterials and Manufacturin
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