One-sided control

The really interesting issues in control of polymerization are not in the control of the operating conditions (flow, temperature, etc.). These loops are controlled in much the same way as would be done in any other chemical process. The real interest is in the control of polymer properties (monomer conversion, MW, particle size, copolymer composition, etc.). The next sections will review a number of control studies, each using a different approach to deal with the control problems specific to polymer property control (lack of sensors, one-sided control, nonlinearities, etc.). This will be followed by a discussion of an alternative approach to polymerization reactor control, statistical process control, and a discussion of the optimization of operating trajectories. 

The one-carbon fragment is ethyl formate. This reaction is important as a method of control since it occurs only on one side of the carbonyl group that is it is regioselective. The reason is that this product can itself enohse in... 

Special attention should be paid to one-sided deviation from the control limits, because systematic errors more often cause deviation in one direction than abnormally wide scatter. Two systematic errors of opposite sign would of course cause scatter, but it is unlikely that both would have entered at the same time. It is not necessary that the control chart be plotted in a time sequence. In any... 

The Z-spray inlet/ionization source sends the ions on a different trajectory that resembles a flattened Z-shape (Figure 10.1b), hence the name Z-spray. The shape of the trajectory is controlled by the presence of a final skimmer set off to one side of the spray instead of being in-line. This configuration facilitates the transport of neutral species to the vacuum pumps, thus greatly reducing the buildup of deposits and blockages. 

Humidification. For wiater operation, or for special process requirements, humidification maybe required (see Simultaneous HEAT and mass transfer). Humidification can be effected by an air washer which employs direct water sprays (see Evaporation). Regulation is maintained by cycling the water sprays or by temperature control of the air or water. Where a large humidification capacity is required, an ejector which direcdy mixes air and water in a no22le may be employed. Steam may be used to power the no22le. Live low pressure steam can also be released directly into the air stream. Capillary-type humidifiers employ wetted porous media to provide extended air and water contact. Pan-type humidifiers are employed where the required capacity is small. A water filled pan is located on one side of the air duct. The water is heated electrically or by steam. The use of steam, however, necessitates additional boiler feed water treatment and may add odors to the air stream. Direct use of steam for humidification also requires careful attention to indoor air quahty. 

Test salons are often used to evaluate hair fixatives. Half-head studies are performed, with the test product appHed to one side of the head and a control product to the other in reaHstic use amounts. Similar properties as desctibed in laboratory tests are measured. Finished products are often sent to testers homes where they have an opportunity to evaluate the products in real use situations for extended pedods. 

Curl Control. Many grades of paper tend to cud, especially as humidity varies, because of the stresses produced duting the dryiag process. This is especially troublesome when only one side of the paper receives a surface treatment. Judicious appHcation of water to the opposite side of the dry sheet followed by redryiag may correct the curling. Water may be appHed by surface appHcation at the size press, water box, or calender stack or it may be sprayed on. Small amounts of water can be appHed to the paper surface as a foam with exceUent results. 

One of the remarkable features of the heart, which is about the size of a fist, is that the pumping action or contractions (- 70 times/min) of atria and ventricles are simultaneous. Deoxygenated blood is pumped out to the lungs from one side of the heart at the same time oxygenated blood is pumped out from the other side to the aorta and onward through the body. The entire process of blood flow between the atria, ventricles, and the principal vessels is in unison, controlled in part by four one-way valves. The atrioventricular valves, tricuspid on the right and mitral on the left, prevent blood from flowing... 

Oxygen Transport. The most widely used methods for measuring oxygen transport are based upon the Ox-Tran instmment (Modem Controls, Inc.). Several models exist, but they all work on the same principle. The most common apphcation is to measure the permeabihty of a film sample. Typically, oxygen is introduced on one side of the film, and nitrogen gas sweeps the other side of the film to a coulometric detector. The detector measures the rate that oxygen comes through the film. The detector response at steady state can easily be converted to At (eq. 1). Simple... 

Scroll compressors are currently used in relatively smaU-sized installations, predominantly for residential air-conditioning (up to 50 kW). They are recognized for low-noise operation. Two scrolls (free-standing, involute spirals bounded on one side by a flat plate) facing each other form a closed volume while one moves in a controlled orbit around a fixed point on the other, fixed scroll. 

Speed of containers sliding down a spiral may be controlled by the pitch of the spiral or by banldug the outer or inner edge of the blade. Banldug tends to throw the container to one side of the blade, thus varying its total travel distance. While usually fabricated of steel, blades may be specified in different materials, as required by specific appheations. 

In metal-enclosed assemblies, the equipment is contained within a grounded metal enclosure. In metal-clad types, separate compartments are provided for the circuit interrupter, the components connected to one side of the interrupter (e.g. the cable box) and those connected to the other side of the interrupter (e.g. the busbar chamber and the control equipment). 

High-pressure cut-outs are fitted to all hut the smallest of systems. The compressor outlet pressure is brought to one side of a bellows or diaphragm, and balanced by an adjustable spring. A scale on the control indicates the pressure setting to commercial accuracy and is checked on commissioning the system. 

Process used provides different control capabilities. As an example closed molding (injection, compression, etc.) provides fine detail on all surfaces. Open molding (blow molding, thermoforming, spray-up, etc.) provides detail only on the one side in contact with the mold, leaving the second side free-formed. Continuous production (extrusion and pultrusion) yields products of continuous length. Hollow (rotational or blow) produces hollow products. These processes can be used creatively to make different types of products. For example, two molded or thermo-formed components can be bonded together to form a hollow product, or they can be blow molded. 

The short wavelength of x-rays naturally makes them difficult to focus. Electrons, on the other hand, can rather easily be controlled to give beams a few square microns in cross section, a fact that made possible the x-ray emission electron-microprobe (9.9). Clearly, such a concentrated electron beam striking one side of a suitable thin target can give rise to an x-ray spot on the other, and this spot can be small enough to be regarded as a point source of x-rays. 

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