Static process

In the limit of very slow change (quasi-static process) the frictional component is zero and then the work done by the external force equals the free energy change, i.e.. 

Piezoelectric Transducers Certain ciystals produce a potential difference between their surfaces when stressed in appropriate directions. Piezoelectric pressure transducers generate a potential difference proportional to a pressure-generated stress. Because of the extremely high electrical impedance of piezoelectric crystals at low frequency, these transducers are usually not suitable for measurement of static process pressures. 

This phenomena has been attributed to the very high strain rates associated with shock loading and the subsonic restriction on dislocation velocity requiring the generation and storage of a larger dislocation density during the shock process than for quasi-static processes [1], [2], [12],... 

If the grains of sand are small, each step does not represent a very large departure from equilibrium between p and ptxt. This process is an example of a quasi-static process that is, one in which the process is never far from equilibrium during the expansion. 

The number of reports on on-line TLC analysis of extracts is quite limited. Stahl [16,29] described a device for supercritical extraction with deposition of the fluid extract on to a moving TLC plate. On-line SFE-TLC provides rapid and simple insight into the extraction performance. Its strength is that the extract is deposited on a plate, which means that detection is a static process. Limitations of SFE-TLC are that quantification is difficult, and that the stability of components on the support material or in the presence of oxygen may be a problem. For additives in beverages (such as benzoic... 

As has already been mentioned in Chapter 2, ISO 9001, Management Systems - Requirements , is increasingly being adopted by laboratories to cover the aspects of their business that are not laboratory based. This is because this Standard is more about controlling the process and service enhancement rather than technical issues. It requires continuous improvement, demonstrating that quality is not a static process. The requirements for such matters as documentation, document control, purchasing and management responsibilities are much the... 

The flow rates and static processes are approximately the same for all vacuum lines. The velocity profile does show turbulence In both processes. Except for the drilling operation in the IauIs-lana AAP, the dust concentrations at location 10 and 11 were the highest recorded. In location 10, the dust concentration was more concentrated at the bottom, while the top and centerline concentrations were fairly uniform. 

The extent to which ions, etc. adsorb or experience an electrostatic ( coulombic ) attraction with the surface of an electrode is determined by the material from which the electrode is made (the substrate), the chemical nature of the materials adsorbed (the adsorbate) and the potential of the electrode to which they adhere. Adsorption is not a static process, but is dynamic, and so ions etc. stick to the electrode (adsorb) and leave its surface (desorb) all the time. At equilibrium, the rate of adsorption is the same as the rate of desorption, thus ensuring that the fraction of the electrode surface covered with adsorbed material is constant. The double-layer is important because faradaic charge - the useful component of the overall charge - represents the passage of electrons through the double-layer to effect redox changes to the material in solution. 

Any finite expansion that occurs in a finite time is irreversible. A reversible expansion can be approximated as closely as desired, and the values of the thermodynamic changes can be calculated for the limiting case of a reversible process. In the limiting case, the process must be carried out infinitely slowly so that the pressure P is always a well-defined quantity. A reversible process is a succession of states, each of which is an equilibrium state, in which the temperature and pressure have well-defined values such a process is also called a quasi-static process. 

The enhanced catalatic activity could arise from more facile exhaust of products just as easily as from enhanced substrate accessibility. The effect of inhibitors is a largely static process that is complete once the inhibitor has become bound in the active site. The catalatic process, on the other hand, requires a constant influx of substrate peroxide and efflux of product oxygen and water. As a result, the inlet channels for inhibitors and substrate may be different. 

As the mismatches of the state variables of a dynamic system (i.e. instant distillate and reboiler compositions in batch distillation) are dynamic in behaviour, they have to be treated as such and not as static processes. To develop them from first principles would be very difficult due to their non-linear dynamic behaviour and it would also be difficult to quantify them in terms of the original state variables. 

The standard RPA bubble diagram summation prevails for static processes. The result is... 

Adsorption capacity of carbons depends on equilibrium concentration in static conditions. At concentration of 0.2 mg/dm it may be even 3 times greater than in dynamic conditions. When equilibrium concentrations in static conditions decrease, these differences also decrease, and at 99% reduction of SLS quantity, these values are similar. Carbons of plant origin show the opposite dependence. For example, adsorption capacity of Z—3 carbon in dynamic conditions is 6 times greater than in static processes. Lower adsorptivity of carbons in dynamic conditions results from short time of contact and small depth of bed. Because of this, determination of bed depth is important from economic point of view. Studies of time of adsorption have shown, that in order obtain concentration of 0.2 mg/dm of SLS in effluent about 60 hrs are required and to total exhaustion of bed about 300 hrs. These times are longer for molecules of greater size and for lower concentrations and, of course, in semi-technical scale studies, where depth of bed should be similar to depth of adsorptive filter (1 —4 m). Because of this, to shorten the reaction times low depth of bed was proposed for primary evaluation of carbons [39]. Studies should also take into accoimt differences in filtration rates (adsorptive filters 5 — 30 m/h, mechanical—adsorptive filters up to 10 m/h) in technical conditions of water supply system. 

If there are no dissipative effects, that is, friction, viscosity, inelasticity, electrical resistance, and so on, during a quasi-static process, the process is termed reversible. Only an infinitesimal change is required to reverse the process, a concept that leads to the name reversible. Most industrial processes exhibit heat transfer over finite temperature differenees, mixing of dissimilar substances, sudden changes in phase, mass transport under finite concentration differences, free expansion, pipe friction, and other mechanical, chemical, and thermal nonidealities, and consequently are deemed irreversible. An irreversible process always involves a degradation of the potential of the process to do work, that is, will not produce the maximum amount of work that would be possible via a reversible process (if such a process could occur). 

The excess heat AW is the additional work in a non-quasi-static process. It is given as the difference between work in a non-quasi-static process and work in the quasi-static process ... 

We consider the work in a quasi-static (QS) process and define an adiabatic invariant. In the quasi-static process, we assume that the probability density is given as p(x, t) = pme(x, c(tj). Then,... 

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