Selectivity tradeoffs

Freeman, B. D. (1999). Basis of permeability/selectivity tradeoff relations in polymeric gas separation membranes, Macromolecules 32(2),... 

B.D. Freeman, Basis of Permeability/Selectivity Tradeoff Relations in Polymeric Gas Separation Membranes, Macromolecules, 32 (1999) 375 -380. 

Freeman, B. D. (1992). Mutual diffusion in polymeric systems. In S. L. Aggarwal and S. Russo (Eds.), Comprehensive Polymer Science First Supplement. Pergamorr, New Yrrrk p. 167. Freeman, B. D. (1999). Basis of permeabihty/selectivity tradeoff relations in polymeric gas separation membranes. Macromolecules 32, 375. 

If k-2 increases faster than kx, operate at low temperature (but beware of capital cost, since low temperature, although increasing selectivity, also increases reactor size). Here there is an economic tradeoff between decreasing byproduct formation and increasing capital cost. 

The Tradeoffs Between Process Changes, Utility Selection, Energy Cost, and Capital Cost... 

Another factor to remember is that for Ot = 1, or for < >= , or for (1/0) = 1 there is no separation at all. Increasing any of the quantities as defined make for a better separation, but the improvement is diminishing in all cases as the value moves higher. An example of the economic tradeoff between permeability and Ot is illustrated in Fig. 22-76 where the economics are clearly improved by sacrificing selectivity for flux. 

Select a transportation mode to minimize risks to the extent practicable. Drums, ISO tanks, tank trucks, rail tank cars, barges, and pipelines offer tradeoffs in inventory, container integrity, size of potential incidents, distance from supplier or customer, and the frequency of incidents. 

Heretofore, the presented MEN/REAMEN synthesis techniques were applicable to the cases where mass-exchange temperatures are known ahead of the synthesis task. Mass-exchange equilibrium relations are dependent upon temperature and the selection of optimal mass-exchange temperatures is an important element of design. In selecting these temperatures, there is a tradeoff between cost of MSAs and cost of heating/cooling utilities. 

As the materials used in drilling processes are produced from depletable mineral resources, there is a continuous upward trend of cost with time. The field engineer must make a detailed cost comparison of materials available within the target cost of the project. The final choice may be a tradeoff between cost and performance. This is because the choice may narrow down to two or more materials with different initial costs and different expected service lives. Transportation costs of selected materials must also be included in the final cost. 

Both smoothness and accuracy are possible for given selection of the basis functions. It is, however, clear that a tradeoff between the two... 

It is difficult to compare separation techniques in any general way. Comparison may be based on the traditional figures of merit, such as resolution Rs (including column efficiency N, selectivity, retention, and peak capacity), chromatographic speed, sample capacity, sensitivity, detection and column impedance, as well as breadth of application. Usually a tradeoff between these attributes is found. Berger [26] has compared GC, pSFC, cSFC, LC and CE on the basis... 

FIGURE 6.1 Tradeoff between throughput and selectivity in evaluating analytical technologies. 

Despite concentrated efforts to innovate polymer type and tailor polymer structure to improve separation properties, current polymeric membrane materials commonly suffer from the inherent drawback of tradeoff effect between permeability and selectivity, which means that membranes more permeable are generally less selective and vice versa. 

The relationship between molecular weight profile and diversity was then explored using the MOGA approach implemented in MoSELECT. The result was a total of 11 different libraries with each library representing a different tradeoff between the objectives, as shown by the crosses in Fig. 3. The most druglike library (the library with the best molecular weight profile) is the least diverse (169 cells occupied), whereas the most diverse library (282 cells occupied) has the least drug-like profile. The SELECT solution found previously is shown by the solid diamond. 

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