Open-loop configuration

The CCD detector and the potentiostat were synchronized in an open-loop configuration by starting the experiment with a common trigger. Careful measurements... 

The USP Apparatus 4, also known as the flow-through cell, was introduced and extensively studied by Langenbucher (22). In the open loop configuration, this system offers the advantage of unlimited medium supply, which is of particular interest for the dissolution of poorly soluble drugs. The idea to develop a flow-through cell method dates back more than 45 years. As early as 1957, a flow-through cell method with a... 

Thermal or instrumental drift (e.g., due to scanner creep in open loop configurations) is a problem that leads to elongated features. As drift is a vectorial quantity (shifted length over time in a given direction) its distorting impact on the image... 

The open loop configuration has some advantages in terms of its simplicity, but also has some disadvantages especially when the product is sensitive to heat or shear effects (e.g., intracellular products, some beverages, and enzymes). Furthermore, when higher cross-flow velocities are required (which is typically the case in many applications) the recirculation rates necessary to sustain them may not be achievable in the open loop configuration, especially if it is also desirable to maintain a concentrate to permeate ratio of at least 10. 

Starting from the steady-state conditions, step variations were introduced into the system at time zero the first 6 s of simulation were in open-loop configuration, and thereafter for 24 s, the control loops were closed, with a sampling time of 6 s. Only this highly dynamic regime was chosen since the solvers perform nearly the same when the process is close to steady state, and choosing longer simulation times will not suffice to measiu-e the solvers performances. 

Fig. 11.4 - The operational amplifter (a) the open loop configuration, (b) the principle of negative feedback, (c) the voltage follower as used to measure the voltage, K, of a standard cell.

Based on the number of inputs used and the input terminal where input is applied, there are three different open-loop configurations, such as ... 

The open-loop configuration is not suitable for linear apphcations since the high gain of this configuration drives the output to saturation level, rendering the output to swing... 

Two versions of the ACP have been developed (1) an open-loop configuration in which the dry spent absorbent is simply removed from the system for disposal and fresh alkali is continuously fed to the spray dryer, and (2) a closed-loop process in which the spent absorbent is regenerated and reused. The open-loop system was installed on the 410 MW, Coyote Station at Beulah, North Dakota (Botts et al., 1978). The plant used a spray dryer followed by a fabric filter for simultaneous SO2 and dust removal. As indicated by the flow diagram of Figure 7-32, the process is extremely simple. Because the particulate collected on the fabric filter bags remains on the fobric for a period of time, the gas-solids contact time is extended beyond the particulate residence time in the spray diyo so additional absorption of SO2 by the alkaline material occurs. After this system went conunercial in 1981. no other large soda ash spray dryers were built. About 1990, this scrubber was converted finm soda ash to lime to eliminate solids build-up in the dryer vessel and to use lower cost lime. The... 

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