Overall resistance

To achieve the best overall resist performance, the optimum PAG for a given resist system, whether ionic or nonionic, must balance the functional properties Hsted eadier in this section. The development of new photoacid generators, and the characterization of their functional properties, ate considered key to the design of resists with increased levels of performance. 

Because a length of metal associated with the connector contact is ordinarily in the path between the contact end to which a wire is terminated and the contact interface, its resistance (bulk resistance) must be added to contact resistance when considering the connector as a circuit element. This overall resistance is sometimes erroneously called contact resistance. 

It is not practical to determine the contact resistance in power connectors. The resistance of the connection of a specified length of conductor on each side of the connector is measured and is called the overall resistance or the connection resistance. One industry specification (32) defines the included lengths and requites the stabiUty of the connection resistance to be within 5% of its average value throughout the heat-cycle test. 

The factors and Xbm cannot be justified on the basis of mass-transfer theory since they are based on overall resistances. These factors therefore are included in the equations by analogy with the corresponding film equations. 

Overall Resistance With a linear isotherm (R = 1), the overall mass transfer resistance is the sum of intraparticle and extraparticle resistances. Thus, the overall LDF coefficient for use with a particle-side driving force (column 2 in Table 16-12) is ... 

Assume fouling resistances for shell side and tube side. Calculate the overall resistance, less shell-side film resistance ... 

The liquid phase resistance, h] , is considered low when compared to the overall resistance therefore, the should give a reasonable approximation to the overall resistance for the system, because l/U = l/hg + l/h] . 

B = overall resistance to heat transfer less shell-side resistance (for finned tube calculations), 1/Btu (hr) (ft ) (°F). 

HARRIOTT 25 suggested that, as a result of the effects of interfaeial tension, the layers of fluid in the immediate vicinity of the interface would frequently be unaffected by the mixing process postulated in the penetration theory. There would then be a thin laminar layer unaffected by the mixing process and offering a constant resistance to mass transfer. The overall resistance may be calculated in a manner similar to that used in the previous section where the total resistance to transfer was made up of two components—a Him resistance in one phase and a penetration model resistance in the other. It is necessary in equation 10.132 to put the Henry s law constant equal to unity and the diffusivity Df in the film equal to that in the remainder of the fluid D. The driving force is then CAi — CAo in place of C Ao — JPCAo, and the mass transfer rate at time t is given for a film thickness L by ... 

The output from the semibatch model GASPP permits a detailed look at the way in which polymerization resistances increase during the course of a run. Figure 3 shows how these resistances increase with yield for a run using the intermediate activity catalyst (kg = 0.00638 cm/sec), with 50 mg TiCil3 loading. Overall resistance, is the sum of the individual resistances in... 

When Kh is a function of composition, the concept of overall mass transfer coefficient stops being useful. Instead, the overall resistance to mass transfer is divided between two him resistances, one for each phase. This is done by assuming that equilibrium is achieved at the interface. The equilibrium values are related by a function having the form of Henry s law ... 

It was also found [8] that the sintering conditions have significant effects on the resistivity of the Smo.iCeo.gOi.g material. As shown in Fig. 4, the overall resistivity decreases with lower sintering temperature and attains a minimum at the sintering temperature of 1100-1200 °C, which is about 31 ohm-cm at 700 °C measurement. This makes the Smo.2Ceo.801,9 material capable of working as SOFC s electrolyte at temperatures lower than 700 C to avoid possible reduction of cerium (4+) and thus suitable for intermediate-temperature SOFC. 

Using this quantity, one can abandon specific models of separator pore stmctnre and calculate the overall resistance from the separator s overall geometry. 

Afterload The force against which a ventricle contracts that is contributed to by the vascular resistance, especially of the arteries, and by the physical characteristics (mass and viscosity) of the blood. Afterload is the overall resistance to blood flow leaving the heart. 

The overall coefficient is the reciprocal of the overall resistance to heat transfer, which is the sum of several individual resistances. For heat exchange across a typical heat-exchanger tube the relationship between the overall coefficient and the individual coefficients, which are the reciprocals of the individual resistances, is given by ... 

Each of these last two equations represents the additive contribution of gas- and liquid-film resistances (on the right) to the overall resistance (on the left). (Each mass transfer coefficient is a conductance and its reciprocal is a resistance")... 

Apart from the nature of the bulk flow, the hydrodynamic scenario close to the surfaces of drug particles has to be considered. The nature of the hydrodynamic boundary layer generated at a particle s surface may be laminar or turbulent regardless of the bulk flow characteristics. The turbulent boundary layer is considered to be thicker than the laminar layer. Nevertheless, mass transfer rates are usually increased with turbulence due to the presence of the viscous turbulent sub-layer. This is the part of the (total) turbulent boundary layer that constitutes the main resistance to the overall mass transfer in the case of turbulence. The development of a viscous turbulent sub-layer reduces the overall resistance to mass transfer since this viscous sub-layer is much narrower than the (total) laminar boundary layer. Thus, mass transfer from turbulent boundary layers is greater than would be calculated according to the total boundary layer thickness. 

It has been established that in analogy to Ohm s law the overall resistance to diffusion of a multilayer laminate is given simply by the sum of the separate resistances of the layers (Figure 20.2). For example, the total resistance of skin being composed of stratum corneum, viable epidermis, and dermis may be expressed as... 

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