Knife-edge type

The thermobalance was of standard analytical, knife-edge type, but rebuilt for continuous electronic recording. The output from the balance could be monitored on a chart recorder or a computer. The loading capacity of the balance was 160 g with a sensitivity better than 0.2 mg. 

Today a wide range of modem water treatment processes and programs are available that have been developed and perfected to suit the many different types and applications of boilers now operating. These include the many high-pressure (HP) units around the world, which tend to be operated within extremely strict (often knife edge ) control parameters. 

Water treatment monitoring and control is often a knife-edge operation and must be tailored to the overall operation of the boiler because waterside and gas-side problems usually are interlinked. Consequently (and as with other types of WT boiler), not only should the utility boiler FW be essentially free of dissolved oxygen to prevent waterside pitting corrosion of the economizer and other boiler components, but also the temperature must be high enough to prevent dewpoint condensation and subsequent acid attack on the gas side of the economizer tubes. 

Although this chapter looks primarily at relatively common forms of corrosion, we also explore a number of often complex and esoteric boiler section corrosion mechanisms. Many of these types of corrosion will only ever seriously develop in larger high-temperature or high-pressure boilers, especially those requiring knife-edge control and operating under difficult thermal stress conditions. 

The detectors oommonly used in laser ultrasonics include various types of interferometers, which are sensitive to the displacement or velocity of the surface, and of knife-edge e.g. photoelectromotive force reoeivers) detectors, which are sensitive to the tilt of the sample surface [27]. 

Figure 7.1. Example of Monod-type uptake (or growth) functions a /j(S) dominates/jlS) for all values of S, and competitive exclusion holds b /,(S) and fi S) cross exactly at the value of D, producing coexistence, the knife-edge phenomenon c / (S) and fi(S) cross, and competitive exclusion holds.

Parts of these problems are circumvented by using the classical knife-edge surface viscometer developed by Brown et al, 1958 ) and variations of it as the double knife-edge surface viscometer and the blunt knife-edge viscometer. For each of these it is crucial that the knife just touches the monolayer, but does not break it. Therefore the knife-edge has to be non-wetting. However, placing the knife precisely in the surface remains a cumbersome manipulation. Theoretical expressions for the torque upon the torsion wire have been derived for the various types. 

One way to knock your opponent unconscious is to deliver a sharp blow with the knife edge of your hand to the side of the neck, below and slightly to the front of the ear (fig. IS). You can deliver it in two ways A backhand delivery with the palm down or a forward slash with the palm up. This type blow causes unconsciousness by shocking the jugular vein, the carotid artery, and the vagus nerve. It is not particularly dangerous. 

We have seen that there are several types of balances, and the operation of these will differ according to the manufacturer. The specific operation of your particular balance will be explained by your instructor. The main objectives are to (1) protect the knife edges, (2) protect all parts from dust and corrosion, (3) avoid contamination or change in load (of sample or container), and (4) avoid draft (air convection) errors. Some general rules you should familiarize yourself with before weighing with any type of analytical balance are ... 

A typical batch sulfonation kettle is illustrated in Fig. 7-3. Two common types of agitators are shown on the same shaft propeller and turbine. These are used for reaction mixtures of low or moderate viscosity. For more viscous products, a close-fitting anchor agitator equipped with supplemental vertical arms is suitable, especially if the blades have knife edges on the leading sides. 

Figure 8.12 shows the principal types of test. In the Charpy test a beam of the polymer is held at each end and is struck at its centre by a hammer with one or two knife edges, giving a three- or four-point impulsive bending stress, respectively. Figure 8.13 shows a diagram of a standard Charpy impact tester. In the Izod test the specimen is held at one end and struck at the other. For either test a notch is cut in the sample at the point where it is to break and the sample is placed in the tester with the notch pointing away... 

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