Concurrent operations

Product quality specification Contractual agreements Capacity and availability Concurrent operations Monitoring and control Testing metering Standardisation Flaring and venting Waste disposal Utilities systems... 

In planning a control system, a flow diagram is needed to indicate what may influence each item of plant. In many diagrams it will be seen that complexity arises and two items work in conflict. A typical instance is the cooling and dehumidifying of air, to a room condition lower than design, with concurrent operation of a humidifier. 

In the case of some dreams, their "realism" may persist into the waking state. Thus, realness and sensation are not a unity, but the concurrent operation of two separate functions. Realness (the quality of reality) and reality testing (the judgment of what is external versus what is imaginary) likewise appear to be two different functions, although they usually operate in synchrony. 

The hydrodynamics control the mass transfer rate from gas to liquid and the same from liquid to the solid, often catalytic, particles. In concurrently operated columns not only the gas-continuous flow regime is used for operation as with countercurrent flow, but also the pulsing flow regime and the dispersed bubble flow regime (2). Many chemical reactors perform at the border be-... 

Additional evidence against a simple hedonic function of the NAc DA transmission in food reward is provided by the observation that the behavioral effects of impairment of DA transmission on a concurrent operant and approach response for food are different... 

First it should be very easy, so as not to require any great physical labour whereby a violent corporeal force is applied to the subject. Secondly, it should be simple, or not compounded of various concurrent operations nor require a variety of instruments. Thirdly, the change it makes should not be very remote from the nature of the subject. Fourthly, the effect produced should rather consist in a separation of the parts, such as they were originally, than be changed by the operation. 

Both artifacts may have been concurrently operative. 

The results are in accord with the concept that learning needs only the concurrent operation of functionally different groups of cortical neurons under proper conditions. As the circumstances for the cortical neurons were the same from the beginning until the end in the saline-, and tetrabenazine-treated groups of rats, the modification of behavior was also the same. 

With Organotins. In recent years the ability of organotins and metal soaps (see below) to prevent the appearance of color in degrading PVC has been ascribed most frequently to chemical reactions leading to the deactivation of defect sites. Very strong evidence for the operation of such a mechanism, at least in the case of the organotins, has been provided now by the chemical stabilization effects whose discovery (22,23, 24,25) was noted above. However, these effects do not rule out the concurrent operation of other mechanisms in technological situations (22,23). 

The DOMAR pubhsh-subscribe protocol, implemented in a set of SCORE forms, plays a central role in several important aspects of model building. Within the human performance models themselves, it is used to coordinate the concurrent operation of related procedures. It is frequently employed in the modeling of person-to-person communication, and it is the basis for the distributed execution, in real time or fast time, that DOMAR supports. Very large agent-based simulations may be developed in a distributed computing environment. 

This problem suggests that there are three concurrent operations for the settler, Le. filling with efifiuent, settling and disdiarging to the filters. Considering a 24 h cycle leads to an 8 h time for each operation with the tank divided into three conqtartments. A series of calculations must be made to see if this arrangement can be made to work. 

Fig. 1 Flow regimes in concurrently operated packed bed reactors...

Fig. 7 Stagnant holdup of dispersed phase in concurrently operated trickle-bed and packed bubble reactors...

SCALE-UP PROCEDURES FOR CONCURRENTLY OPERATED MULTIPHASE PACKED BED REACTORS... 

Even then it can be solved only numerically, but for this appropriate integration procedures and even standard routine programs are available. The model as well as its solutions can be applied to downward as well as upward concurrent operation by using the appropriate parameter values. In case of a solid catalyzed reaction, however, an additional effect of the feed concentration must be taken into account, mainly at small Damkohler numbers, since the physico-chemical equilibrium of reactants in liquid phase is not necessarily attained at the inlet. 

This review on concurrently operated multiphase packed bed reactors shows that much information on the behavior of these reactor types has been accumulated in the past, but we are still far from a complete elucidation. The difficulty still exists that not enough information is available on systems different from air/water nonporous packings to safely scale-up multiphase reactors using a sophisticated mathematical model. The fact that fluid-dynamics and thermal effects may be different in laboratory units from those in technical reactors restricts the usefulness of simplified, i.e. lumped, models in reactor scale-up. On the contrary, the different mechanisms acting in multiphase catalytic reactions have to be kept separated to a certain extent, thus enabling the correct inclusion of their probably changing amount of influence during scale-up. 

Of the four different types of processing, concurrent sequential processing requires the most complex system controls to coordinate the concurrent operations. Additionally, if the duration of the concurrent... 

The experimental values of k a are generally obtained either from the increase in oxygen liquid phase concentration after starting the aeration of an oxygen-free solution (dynamic method) or by fitting the axial dispersion model to the steady state axial concentration profile (oxygen concentration) in the liquid phase in a concurrently operated column (steady state method). Occasionally, the mass transfer... 

For packed beds used in gas and liquid contacting, the liquid can flow in the opposite direction to the gas (countercurrent operation), or it can flow in the same direction as the gas (concurrent operation), or the gas flow can be transverse to the liquid flow (crossflow operation). The theory of pressure drop in irrigated packed beds is not as well developed as that for single-phase flow. 

Packed columns that operate with concurrent gas and liquid flows are not widely used. Countercurrent operation provides the greatest efficiency because mass transfer driving forces are at a maximum. However, in those operations where only a single mass transfer stage is required, concurrent operation may offer advantages. 

---