Steady-state mode

Tye [38] explained that separator tortuosity is a key property determining the transient response of a separator (and batteries are used in a non steady-state mode) steady-state electrical measurements do not reflect the influence of tortuosity. He recommended that the distribution of tortuosity in separators be considered some pores may have less tortuous paths than others. He showed mathematically that separators with identical average tortuosities and porosities can be distinguished by their unsteady-state behavior if they have different distributions of tortuosity. 

The Ti02 (001) surface was cleaned and reduced by cycles of ion bombardment as previously described [3]. The distribution of titanium oxidation states was determined from cxirve fitting the Ti(2p3/2) envelope in x-ray photoelectron spectra [3]. After surface preparation, reaction experiments were conducted in either the TPD or steady state mode. TPD experiments have been described [1]. XPS spectra were also obtained following a saturation exposure of the sample using the same procedure as that for the TPD experiments. After pump down, the crystal was placed under the Mg X-ray source and the Ti(2p), 0(ls), and C(ls) regions were scanned. For steady-state experiments a dosing needle was aligned perpendicular to the axis of the mass spectrometer. It was used to direct a steady beam of methylacetylene (Linde, 95%) at the crystal surface when the sample was placed at the aperture of the mass spectrometer. Steady state reaction experiments were... 

In this work we present results obtained with the YSZ reactor operated in the hatch mode with electrochemical oxygen addition, and with the quartz plug flow reactor operated in the continuous-flow steady-state mode. In the case of continuous flow operation, the molecular sieve trap comprised two packed bed units in parallel in a swing-bed arrangement (Fig. 1), that is, one unit was maintained at low temperature (<70°C) to continuously trap the reactor products while the other was heated for -30 min to 300°C to release the products in a slow stream of He. 

Rod bundle heat transfer analysis (Anklam, 1981a) A 64-rod bundle was used with an axially and radially uniform power profile. Bundle dimensions are typical of a 17 X 17 fuel assembly in a PWR. Experiments were carried out in a steady-state mode with the inlet flow equal to the steaming rate. Generally, about 20-30% of the heated bundle was uncovered. Data were taken during periods of time when the two-phase mixture level was stationary and with parameters in the following ranges ... 

In our studies we have demonstrated that the redox mechanism that was used to model dynamic behavior of CO oxidation is consistent with a kinetic model of the selective CO oxidation obtained under steady-state mode of operation [62], We propose the following tentative scheme (Figure 7.15) for the selective CO oxidation over the CuolCe(J902 v catalyst CO and H2 adsorb on the... 

The esterification by-product, water, is removed via a process column in a continuous steady-state mode of operation. The bottom product of the column, being mainly EG, flows back into the esterification reactor. The condensed top product consists mainly of water with small traces of EG. In cases where a reverse-osmosis unit is connected to the distillate flow line, the residual EG can be separated very efficiently from the water [124], The combination of a process column with reverse osmosis saves energy cost and capital investment. The total organic carbon (TOC) value of the permeate is sufficiently low to allow its discharge into a river or the sea without any environmental impact. 

There is no site-site cooperativity in ATP synthase in the physiological steady state mode of operation. 

The molecular basis of site-site cooperativity in ATP synthase still remains unelucidated [46], and the absence of any direct evidence for cooperativity (despite almost three decades of effort) is explained, within the framework of the torsional mechanism, by the fact that site-site cooperativity does not exist in the physiological, steady state mode of functioning. Since, according to the torsional mechanism, no rotation takes place in uni-site or bi-site catalysis... 

In principle, there are two possible ways to measure this effect. First, there is the end-point measurement (steady-state mode), where the difference is calculated between the initial current of the endogenous respiration and the resulting current of the altered respiration, which is influenced by the tested substances. Second, by kinetic measurement the decrease or the acceleration, respectively, of the respiration with time is calculated from the first derivative of the currenttime curve. The first procedure has been most frequently used in microbial sensors. These biosensors with a relatively high concentration of biomass have a longer response time than that of enzyme sensors. Response times of comparable magnitude to those of enzyme sensors are reached only with kinetically controlled sensors. 

As with gamma radiation. X-rays in the steady-state mode have not produced any initiations in any of the expls irradiated. Effects are being directed towards intense, pulsed irradiations in order to simulate nuclear weapons effects. The prospect of higher dose rates in short time frames should produce results not common, to the steady-state irradiation... 

If all cells are recycled back into the fermenter, the cell concentration will increase continuously with time and a steady state will never be reached. Therefore, to operate a CSTF with recycling in a steady-state mode, we need to have a bleeding stream, as shown in Figure 6.19. The material balance for cells in the fermenter with a cell recycling unit is... 

In addition to the steady-state mode, the double-cell device of Fig.7 can be operated in the so-called transient and oscillatory modes of operation(18.). In the transient mode, one measures the slope dVg/dt when the pumping current is changed in a stepwise fashion from zero to a constant value. A simple analysis(18) gives the following differential equations for Vg and Pv,... 

Dynamic optimisation of this type of periodic operation was first attempted and reported in the literature by Mayur et al. (1970), who considered the initial charge to the reboiler as a fresh feed stock mixed with the recycled off-cut material from the previous distillation task. Each batch cycle is then operated in two distillation tasks. During the Task 1, a quantity of overhead distillate meeting the light product specification is collected. The residue is further distilled off in Task 2 until it meets the bottom product specification. The overhead during Task 2 meets neither specifications (but the composition is usually kept close to the that of the initial charge for thermodynamic reasons) and is recycled as part of the charge for the next batch. As the batch cycle is repeated a quasi-steady state mode of operation is attained which is characterised by the identical amount and composition of the recycle (from the previous batch) and the off-cut (from the current batch). Luyben (1988) indicates that the quasi-steady state mode is achieved after three or four such cycles. 

The necessity of the above discussion will now be realised (also see Christensen and Jorgensen, 1987). Figure 8.2 shows a quasi-steady state mode of operation, with off-cut recycle. A fresh charge BO, of composition xB0 is mixed with the off cut (Rl, xRi) from the previous batch to produce a mixed charge to the reboiler (BC, xBc) The main cut (Dl, x D]) is produced over the time // (Task 1), leaving a residue (B1, xbj). At this time the distillate is simply diverted to a second receiver, and further distillation in Task 2 for time t2 produces the off cut and the final bottom product (B2. x B2) where, B2 is the solution of Equations (8.1-8.4) as mentioned before. 

It could be argued, of course, that the differences and similarities cited above stem from the fact that solvent extraction is essentially a steady-state (equilibrium) process while electrophoresis and sedimentation are transient (rate) processes. However, such an argument would overlook the fact (to be explained later) that the different forms of the chemical potential profile determine which systems can be run successfully in the steady-state mode and which in the transient mode. Thus the chemical potential profile and associated flow structure emerge as dominant influences that should be classified at the very beginning of any attempt to organize separation phenomena into a cohesive discipline. 

The four fresh reactant feed streams must be managed in an appropriate way to satisfy overall component balances. Fortunately, composition analyzers are available. Figure 8.2 gives a sketch of the process with nomenclature and the values of flowrates, compositions, temperatures, and pressures at the initial steady state (Mode 1). 

Most continuous processes are simulated only in steady-state mode. Some of the simulation programs allow a steady-state simulation to be converted to run in a dynamic mode. Dynamic simulation is useful for... 

Experiments in the flow-through mode, in which the FMC operates in steady-state mode. Here, first of all, the appropriate amount of IMB in the column to be used is determined. Then, the steady state kinetic data - the dependence of the thermometric signal on substrate concentration - is measured ... 

Once the desired conditions have been reached and the planned process rate established, the system can be operated in a steady-state mode. This may take four or five hours from a cold start or two to three in a run where hot char from the previous days operation is in the convertor. During the steady mode operation, feed is added about every 30 minutes, the char grate opened for a few seconds 30 to 9-0 times each hour and the char drums changed every hour. Two char barrels equipped with quick disconnect hardware are used for rapid replacement of the drums. To prevent burning, the char is stored in sealed barrels while it cools. The oil is periodically gathered from the condenser and demister. Typically, the condenser recovers about three quarters of the total oil while the demister recovers the remainder. 

An example of the training classification is displayed in Figure 7.4 where normal and abnormal situation simulations are also superimposed. The second window shows data progressing at a normal steady-state mode. When a change in the system occurs, the coolant flow rate reacts to compensate... 

The volcano-type behaviour of the rates shown in figure 1 is also manifested in the steady-state mode and it is remarkable that similar promoting-poisoning behaviour of Na has been also observed in the cases of CO [4] and ethylene [9] oxidation and NO reduction by CO [11] under appropriate conditions. 

Curvature of the vapor-liquid interface is reliant on the vapor-liquid pressure drop determined for each steady state mode as the entire hydraulic resistance of LHP or CPL. The value of curvature remains constant within single elementary cell of circumferential channel (Fig. 2, mode 2). 

The most important point is that in the TS mode of operation there is no need to wait for a reaction to reach isothermal steady state. This is a large part of the reason why, using TS methods, kinetic data can be collected so much foster than in the conventional isothermal steady state mode of operation. We must also resign ourselves to the feet that TSR methods often yield primary data that cannot be interpreted by conventional methods of data handling. This is disconcerting, and therefore the question that needs to be examined first is how are valid reaction rates to be calculated from the plentitude of seemingly uninterpretable TS data ... 

Methods based on spatial gradients in the direction of advection These include the small-plot techniques reviewed by Denmead (1994, 1995) and also chambers operated in a continuously ventilated, quasi-steady-state mode. The control region is designed so that all terms except II and IV are small. 

A variety of catalyst substrates, washcoats, and formulations were screened on a Mercedes OM 366 LA direct injection, turbocharged-intercooled engine in order to identify the optimal engine/catalyst combination for US applications. The engine was operated at five steady state modes, and on the US transient and European 13-mode cycles. 

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