Scale effects

Since there may well be chemical or biological reactions happening on or in the solid phase, depending upon the size of the process participants, macro- or micro-scale effects may or may not be appropriate to consider. 

As Fig. 20.7 shows, if DS eutectics ( DSEs ) prove successful, they will allow the metal temperature to be increased by =100°C above conventional DS nickel alloys, and the inlet temperature by =200°C (because of a temperature scaling effect caused by the blade cooling). Further improvements in alloy design are under way in which existing nickel alloys and DS eutectics are being blended to give a fibre-reinforced structure with precipitates in the matrix. 

Air pollutants reach receptors by being transported and perhaps transformed in the atmosphere (Fig. 18-1). The location of receptors relative to sources and atmospheric influences affect pollutant concentrations, and the sensitivity of receptors to these concentrations determines the effects. The location, height, and duration of release, as well as the amount of pollutant released, are also of importance. Some of the influences of the atmosphere on the behavior of pollutants, primarily the large-scale effects, are discussed here, as well as several effects of pollutants on the atmosphere. 

The wear rate of plastics is governed by several mechanisms. The primary one is adhesive wear which is characterised by fine particles of polymer being removed from the surface. This is a small-scale effect and is a common occurrence in bearings which are performing satisfactorily. However, the other mechanism is more serious and occurs when the plastic becomes overheated to the extent where large troughs of melted plastic are removed. Table 1.7... 

Etheridge, D. W. 1977. Crack flow equations and. scale effect. Build. Environ, vol. 12. de Gids, W. E 1978. Calculation method for the natural ventilation of buildings. Verwarming Vent, no. 7, pp. 552-564. 

Turbulent eddies larger than the cloud size, as such, tend to move the cloud as a whole and do not influence the internal concentration distribution. The mean concentration distribution is largely determined by turbulent motion of a scale comparable to the cloud size. These eddies tend to break up the cloud into smaller and smaller parts, so as to render turbulent motion on smaller and smaller scales effective in generating fluctuations of ever smaller scales, and so on. On the small-scale side of the spectrum, concentration fluctuations are homogenized by molecular diffusion. 

Fang, Ken-Shou, How Accurate are Predictions of Required NPSH Wren Based on Speed-Scale Effect , Power, V. 123, No. 2, 1979. 

Nixon, R. A. and Cairney, W. D., Scale effects in centrifugal cooling water pumps for thermal power stations, NEL Report 505(1972). 

In our analysis, we discuss experimental results of heat transfer obtained by previous investigators and related to incompressible fluid flow in micro-channels of different geometry. The basic characteristics of experimental conditions are given in Table 4.1. The studies considered herein were selected to reveal the physical basis of scale effect on convective heat transfer and are confined mainly to consideration of laminar flows that are important for comparison with conventional theory. 

Celata GP, Cumo M, Marcom V, McPhail SJ, Zummo Z (2005) Micro-tube heat transfer scaling effects an experimental validation. In Proceedings of ECI International Conference on Heat Transfer and Fluid Flow in Microchannels, Caste/Vecchio PascoU, Italy, 25-30 September 2005... 

Gao P, Le Person S, Favre-Marinet M (2002) Scale effects on hydrodynamics and heat transfer in two-dimensional mini and micro-channels. Int J Themial Sci 41 1017-1027 Garimella SV, Sobhan CB (2003) Transport in micro-channels - a critical review. Ann Rev Heat Transfer 13 1-50... 

Tullis JP, Govindrajan R (1973) Cavitation and size scale effect for orifices. J Hydraul Div HY13 417 130... 

One of the most popular applications of molecular rotors is the quantitative determination of solvent viscosity (for some examples, see references [18, 23-27] and Sect. 5). Viscosity refers to a bulk property, but molecular rotors change their behavior under the influence of the solvent on the molecular scale. Most commonly, the diffusivity of a fluorophore is related to bulk viscosity through the Debye-Stokes-Einstein relationship where the diffusion constant D is inversely proportional to bulk viscosity rj. Established techniques such as fluorescent recovery after photobleaching (FRAP) and fluorescence anisotropy build on the diffusivity of a fluorophore. However, the relationship between diffusivity on a molecular scale and bulk viscosity is always an approximation, because it does not consider molecular-scale effects such as size differences between fluorophore and solvent, electrostatic interactions, hydrogen bond formation, or a possible anisotropy of the environment. Nonetheless, approaches exist to resolve this conflict between bulk viscosity and apparent microviscosity at the molecular scale. Forster and Hoffmann examined some triphenylamine dyes with TICT characteristics. These dyes are characterized by radiationless relaxation from the TICT state. Forster and Hoffmann found a power-law relationship between quantum yield and solvent viscosity both analytically and experimentally [28]. For a quantitative derivation of the power-law relationship, Forster and Hoffmann define the solvent s microfriction k by applying the Debye-Stokes-Einstein diffusion model (2)... 

Working within a similar scheme, DeBecker and West introduced a treatment of feature scale effects on the overall current distribution which they call the hierarchical model [138]. Rather than represent the features as a smoothly varying density of active area, they retain the features, but simplify their representation in the global model. An integral current for each feature is assigned to the geometric center of the feature to provide a simplified boundary condition for the secondary current distribution. This boundary condition captures a part of the ohmic penalty paid when current lines converge onto features. It thus contains more information than the active area approximation but still less than a fully matched current distribution on the two levels. 

Tewarson, A., and Newman, J.S., "Scale Effects on Fire Properties of Materials," Fire Safety Science, Proceedings of the First International Symposium, 1986, Hemisphere Publishing Corp., Washington, DC, p. 451. 

Steel EA, Lange IA (2007) Using wavelet analysis to detect changes in water temperature regimes at multiple scales effects of multi-purpose dams in the Willamette River basin. River Res Appl 23 351-359... 

In addition to the frequency considerations attendant to the examination of polymorphisms or haplotypes, one must also consider the impact of possible differences in the magnitude of effects of any putative loci. The magnitude of any effects is denoted as "scale" effects based on the notion from quantitative genetics that there will be a displacement from the overall population mean for a trait that is dependent on genotype. To illustrate the effects of scale and frequency, consider two well-known examples of genetic effects. These are the effect of the apolipoprotein E (apo E) polymorphism on cholesterol levels and the impact of the familial hypercholesterolemia polymorphism on cholesterol levels. 

Scaling effects after 6-h exposure at 0.5 ppm C 1 xl=k based on concentrations and exposure durations for the end points of mild and severe headache in the key study... 

Through such chemisorption studies, the values of >, have been determined not only by geometric accessibility, but also by the chemical heterogeneity of the surface. This can result in abnormal values of D, and demonstrates the scale effect on the kinetics and selectivity of catalytic reactions. For such studies, Farin and Anvir [213] derived the equations that can be applied for characterization of supported catalysts ... 

The SR model introduced in Section 4.6 describes length-scale effects and contains an explicit dependence on Sc. In this section, we extend the SR model to describe differential diffusion (Fox 1999). The key extension is the inclusion of a model for the scalar covariance (4> aft p) and the joint scalar dissipation rate. In homogeneous turbulence, the covari-... 

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