Flux concentrators

The state-of-the-art solar concentrators can provide solar flux concentrations in the following ranges, depending on the type of the concentrator [26] ... 

Figure 5a. Flux-concentration curve for suspension when n = 2.3...

Jacinthe PA, Lai R. Effects of soil cover and land-use on the relations flux-concentrations of trace gases. Soil Sci. 2004 169 243-259. 

Figure 14.16 (a) Circular Dual-Dee induction coil used in early work on the continuous dieless forming process, (b) Addition of ferrite flux concentrator to Dual-Dee coil, (c) Temperature patterns generated in a Gr/PEEK laminate by the circular Dual-Dee coil with ferrite flux concentrator. The coil end was located at various distances from the laminate edge. No one position produced a uniform temperature profile... 

The dependency of the pairs, advection/diffusion and flux/concentration change, on the concentration profile C(x) can be represented in a two-dimensional scheme which helps to remember these relationships (Table 22.1). Note that in this scheme every move to the right (from flux to concentration change) or downward (from advection to diffusion) involves a sign change as well as an additional differentiation of C with respect to x. 

The results by Hetrick et al.32 support the use of NO-release coatings for developing more tissue-compatible sensors. However, the impact of NO on the biocompatibility at a NO-releasing implant is a multifaceted question that is still not fully understood. Further study into the mechanisms by which NO decreases tissue encapsulation and chronic immune response while increasing angiogenesis will aid in optimization of the NO release properties (e.g., flux, concentration, and duration) of an implant coating for sensor applications. 

Evaluating the performance of a gas-solid transport system usually requires a means of macroscopic field description of the distribution of basic flow properties such as pressure, mass fluxes, concentrations, velocities, and temperatures of phases in the system. To conduct such an evaluation, the Eulerian continuum or multifluid approach is usually the best choice among the available approaches. 

In the line of probabilistic approaches, Wilson and Liu [69] solved the transport equation using stochastic differential equations backwards in time. Like in the method developed by Bagtzoglou and co-workers, Wilson and Liu kept the dispersion part positive and reversed the advection part. They provided two types of maps, namely travel time probability and location probability. The travel time probability map was obtained from the normalized flux concentration, given by... 

Concerning the technological point, the development of solar collectors to higher UV flux concentrations, the combination of photocatalytic and thermal effect in the same collector, and the study of series manufacturing techniques incorporating new materials are investigated by some groups. 

Mathematical optimization deals with determining values for a set of unknown variables x, X2, , x , which best satisfy (optimize) some mathematical objective quantified by a scalar function of the unknown variables, F(xi, X2, , xn). The function F is termed the objective function bounds on the variables, along with mathematical dependencies between them, are termed constraints. Constraint-based analysis of metabolic systems requires definition of the constraints acting on biochemical variables (fluxes, concentrations, enzyme activities) and determining appropriate objective functions useful in determining the behavior of metabolic systems. 

Figure 18 Flux concentration distribution of a 90° rim angle parabolic trough solar concentrator. Adapted from Arancibia-Bulnes and Cuevas (2004), with permission from Elsevier.

Typically, large-scale solar concentrators utilize parabolic reflectors in the form of trough, tower, or dish systems. These solar concentrators are characterized in terms of their mean flux concentration ratio Cr over an area Sa at the receiving focal plane as follows ... 

Where qs (WW) refers to the solar flux intercepted by unit area of the receiver at the focal plane and I (WW) is the incident normal beam insolation. Cr is often expressed in units of suns when normalized to 1 = 1000 W/m [13]. The solar flux concentration ratio typically obtained is at the level of 100, 1000, and 10,000 suns for trough, tower, and dish systems, respectively. The most suitable concentrators for applications involving solar thermochemical water splitting cycles are tower and dish systems. 

Figure 5 depicts, the optimum temperatures and maximum achievable efficiencies for the oxygen production step of a sulfur family solar TCWSC as a function of the mean flux concentration ratio at X= 520 nm. Figure 5 also shows the variation of Toptimum vs. X at constant mean flux concentration ratios in the... 

A mathematical model to be solved numerically has been developed and used to predict the separation effects caused by nonstationary conditions for a liquid membrane transport. Numerical calculations were made to compute pertraction characteristics such as input and output membrane selectivity (ratio of respective fluxes), concentration profiles for cations bound by a carrier in a liquid membrane phase, and the overall separation factors. These quantities are discussed as dependent... 

J is the flux (concentration change per unit time) A is the membrane area V is the volume of receiving compartment Cd is the donor compartment concentration Cr is the receiving compartment concentration... 

De Vries DJ, Kroot MPJM. SOM-3, a simple model for estimating fluxes, concentrations and adaptation times of micropollutants in aquatic systems User s manual, T0632. Delft, Delft Hydraulics, Holland, 1989. 

The magnitudes of chemical kinetic and macroscopic transport processes, evaluated as their linear rates [linear rate=(mass flux)/(concentration or density) = F/p], indicate that great differences exist between the mineral dissolution rates, as reported from laboratory measurements, and the rates derived from river-water composition and volume flow. These differences point to an important role of the physical structure of the weathering zone and water residence time within it that control mineral dissolution fluxes and transport of the reaction products. An additional factor responsible for the faster rates of chemical weathering could be bacterial, activity which may be expected to vary from lower levels in the cold regions to the higher levels in the tropics, in parallel with the rates of net primary productivity. 

In addition to the ion-clustered gel morphology and microcrystallinity, other structural features includes pore-size distribution, void type, compaction and hydrolysis resistance, capacity and charge density. The functional parameters of interest in this instance include permeability, diffusion coefficients, temperature-time, pressure, phase boundary solute concentrations, cell resistance, ionic fluxes, concentration profiles, membrane potentials, transference numbers, electroosmotic volume transfer and finally current efficiency. 

Concentration Polarization. The concentration of the species retained on the membrane surface or within its porous structure is one of the most important operating variables limiting flux. Concentration effects in MF/UF can be estimated by using the following most commonly used correlation,... 

It is realized today that in order for a LSC device to be efficient, one of the major requirements is that a great part of the solar spectrum (Fig. 1) should be absorbed, and that a large Stokes shift is needed between the absorption and the emission in order to prevent appreciable self-absorption of the luminescence. Another requirement involves a thermodynamical limitation of flux concentration which may be expressed31 by the inequality... 

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