Passive control

The substrates for most enzymes are usually present at a concentration close to K. This facilitates passive control of the rates of product formation response to changes in levels of metabolic intermediates. 

Design procedures for passive control of sulfide problems — procedures used in the design phase that aim at reducing the effect of sulfide but not necessarily the formation. 

DESIGN PROCEDURES FOR PASSIVE CONTROL OF SULFIDE PROBLEMS... 

Passive controls minimize the hazard by use of process and equipment design features. They reduce either the frequency or consequence of the hazard without the active functioning of any device. Examples include dikes, firewalls, orifice plates or narrow bore piping to control flow, and the... 

Passive controls, process controls, 97-98 Paterson, New Jersey incident, 160-161 Peroxide formers, screening methods, 46-48 Physical processing chemical reactivity hazard, 8-10,11 screening methods, 36, 41—42 worked examples, 128,129 Polymerizing compounds, screening methods, 55... 

Procedural controls, process controls, 98-99 Process controls, 96-100 active controls, 98 inherently safer approach, 97 mitigation techniques, 99 passive controls, 97-98 procedural controls, 98-99 safe operating limits, 99-100 Process definition, documentation, 102-104 Process design, documentation, 105 Process hazard analysis (PHA) risk assessment, 92-93 screening methods, 63 Process risk management decisions, documentation, 105-106... 

A. Turhan, K. Heller, J. S. Brenizer, and M. M. Mench. Passive control of liquid water storage and distribution in a PEFC through flow field design. Journal of Power Sources 180 (2008) 773-7 3. 

Yu, K. H., E. Gutmark, and K. C. Schadow. 1993. Passive control of coherent vortices in compressible mixing layers. AlAA Paper No. 93-3262. 

For some purposes, passive control of molecular evolution can be more important than active control one such case occurs when we wish to prevent transfer of population or energy. The phase angle relations are... 

Examination of the passive control conditions in Eqs. (5.26)-(5.29) shows that there are two values of the sum of phase angles for which zero transfer occurs. In principle, then, one can simultaneously block the transfer of, say, the energy and select the direction of the transfer of the population. One particularly interesting case is the definition of the phase angles for zero total power absorption. Since no energy is absorbed or emitted from the field these conditions define laser catalysis [44]. 

The various transfer equations for the control of molecular dynamics can be worked out as before, leading to the following phase angle conditions for active and passive control ... 

Passive control One can overdesign the process equipment, but this can become exceedingly expensive In this case one would select a piping or pressure vessel rating which is far beyond the normal process pressures. Cases are known where this initially happened, but later, for economical reasons during revamps process, pressures were increased to reach the rating limits, which eliminates the initial intention. 

Despite the problems mentioned, the passive control of protein adsorption is excellently suited for short-term applications and many situations in a controlled environment ex vivo. 

The oxygen level in the milkfat may be limited by either active or passive actions. For passive control, processing procedures and plant design are established to minimize air exposure. Deaeration devices (74), vacreation (60), the use of antioxidants (72), effective destmction of lipases (75), and nitrogen spanning of container headspace are examples of active control of product quality. 

Despite these difficulties, several passive control strategies have been developed and tested. As presented in this chapter, these strategies are effective and yield very promising results. 

In a first realization, Jahne et al. (1989) forced a periodical heat flux density onto the water surface using a chopped heat source above the water surface. The temperature response at the water surface was detected with point measuring radiometer. In a further implementation of this technique, HauBcckcr (1996) developed the so-called passive controlled flux method that estimates the skin-bulk temperature difference under natural heat flux conditions assuming a surface renewal model. The naturally occurring heat fluxes at the ocean surface (latent, sensible and long wave radiative heat flux) cause the surface temperature to decrease or increase depending on the direction of these fluxes. The net heat flux forces a skin-bulk temperature difference AT across the thermal sublayer, commonly referred to as the cool skin of the ocean (compare Fig. 2). 

Fig. 8. Gas exchange rates in the Heidelberg wind wave facility rates obtained from the passive controlled flux method compared with previous measurements...

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