Continuous measurements

An actual problem of a paper mill was the continuous measurement of the wall thickness of a heated roll which dries the paper in order to avoid severe crashes due to wearing. On one side the roll shall be used as long as possible because of economic aspects and on the other side the roll has to be replaced in time to avoid a severe crash. 

In both cases special probes were designed and manufactured For the first ease a special probe which fits geometrically exactly to the contour of the turbine blade and in the other case a combined transducer system was developed which enables a continuous measurement of... 

Continuous mea.sui ements. An example of a continuous measurement is a level measurement device that determines the liquid level in a tank (in meters). 

In continuous processes, most process control applications rely on continuous measurements. In batch processes, many of the process control applications will utihze discrete as well as continuous measurements. In both types of processes, the safety interlocks and process interlocks rely largely on discrete measurements. 

Continuous Measurements In most apphcations, continuous measurements are considerably more ambitious than discrete measurements. Basically, discrete measurements involve a yes/no decision, whereas continuous measurements may entail considerable signal processing. 

The components of a typical continuous measurement device are as follows ... 

Another technique for organics measurement that overcomes the long period required for the BOD test is the use of continuous respirometry. Here the waste (full-strength rather than diluted as in the standard BOD test) is contacted with biomass in an apparatus that continuously measures the dissolved oxygen consumption. This test determines the ultimate BOD in a few hours if a high level of biomass is used. The test can also yield information on toxicity, the need to... 

The classical problem of obtaining a best estimate of a signal by combining two noisy continuous measurements of the same signal was first solved by Weiner (1949). 

Demand-controlled ventilation (DCV) is one approach to reduce energy consumption due to ventilation, that is gaining popularity in both industrial and nonindustrial applications. It is used in cases where ventilation requirements vary with time, regularly or irregularly. The control is based on a specified level of indoor air quality by means of continuous measurement of the parameters, that are expected to primarily determine the lAQ, such as the concentration of the main contaminant liberated from the production process. The principle is thus similar to the one in some better-known nonindustrial applications, e.g., CO2 levels in rooms with dense human occupancy (theaters, classrooms, etc.) or nicotine concentration in smoking rooms. See also Section 9.6. 

TTie system can be used for continuous measurement of the mass concentration at a single point for up to 12 hours, for traverse measurements of stack particulate mass concentrations using sample probe extensions, with the mass transducer up to 6 m in the stack, or for intermittendy measuring particulate mass concentrations of emission gases for long-term readings (e.g.. 30-sec samples every 60 minutes. ... 

Optical devices or optical systems have provided most of the available strong shock data and were the primary tools used in the early shock-compression investigations. They are still the most widely used systems in fundamental studies of high explosives. The earliest systems, the flash gap and mirror systems on samples, provided discrete or continuous measurements of displacement versus time. 

Garside, J. and Mullin, J.W., 1966. Continuous measurement of solution concentration in a crystallizer. Chemistry and Industry, November 26, pp. 2007-2008. 

The primary process variables affecting the economics of sulfuric acid alkylation are the reaction temperature, isobutane recycle rate, reactor space velocity, and spent acid strength. To control fresh acid makeup, spent acid could be monitored by continuously measuring its density, the flow rate, and its temperature. This can reduce the acid usage in alkyla-tion units. 

Special products include transparent vitreosil springs, which are ideal for continuous measurement in corrosive atmospheres, and quick-immersion thermocouple protection sheaths for rapid temperature measurement. 

Infrared spectroscopy. Due to experimental difficulties, infrared spectroscopy is used infrequently in these kinetic studies. However, continuous measurements have been carried out by Schumann28 in the study of the poly(ethylene terepthalate) synthesis. 

As the vapor leaves the tube, the compounds in the sample are detected by a device such as a thermal conductivity detector. This instrument continuously measures the thermal conductivity (the ability to conduct heat) of the carrier gas, which changes when a solute is present. The detection techniques are very sensitive, allowing tiny amounts of solutes to be detected. Many environmental monitoring and forensic applications have been developed. 

It should be stressed that such models are valid only when the medium is continuous. Measurements by Ye et al. (2004) showed that bubble nucleation in water may be considered as continuous when rc > 10 nm. 

Basis. The rotational mobility of a small ligand is relatively unrestricted in solution (anisotropy approaches 0). The mobility is restricted when the ligand binds to a large immobilized molecule such as the receptor. In a T-format fluorometer, the parallel and perpendicular components of the emission can be examined simultaneously. While precautions must be exercised in working with turbid suspensions, it is nonetheless practical to make continuous measurements of binding and dissociation. 

CO concentration at the outlet of each zone was continuously measured using a CO analyzer (Shimadzu CGT-7000). To evaluate the performance of the reactors, the conversion of CO for the PBR (Xco) with 4g of catalyst and the time-average conversion of CO for the SCMBR (Tea) with 2g of catalyst in each zone were calculated and compared. It should be noted that the CO concentration wave used for Eq. (1) was obtained whrai the system is at cyclic steady state (after 30 min of operation). 

The nature of the performance metric, y, is determined by the characteristics of the specific process under analysis. Since we are particularly interested in analyzing situations where y is related to product or process quality, it is quite common to find systems where a categorical variable y is chosen to classify and evaluate their performance. This may happen due to the intrinsic nature of y (e.g., it can only be measured and assume qualitative values, such as good, high, and low ), or because y is derived from a quantization of the values of a surrogate continuous measure of performance (e.g., y = good if some characteristic z of the product has value within the range of its specifications, and y= bad, otherwise). 

Thermal solid-state reactions were carried out by keeping a mixture of powdered reactant and reagent at room temperature or elevated temperature, or by mixing with pestle and mortar. In some cases, the solid-state reactions proceed much more efficiently in a water suspension medium or in the presence of a small amount of solvent. Sometimes, a mixture of solid reactant and reagent turns to liquid as the reaction proceeds. All these reactions are called solid-state reactions in this chapter. Solid-state reactions were found to be useful in the study of reaction mechanisms, since it is easy to monitor the reaction by continuous measurement of IR spectra. 

Since solid-state reactions can easily be monitored by continuous measurement of spectra, it is easy to study the mechanism of the reactions. For this purpose, IR spectroscopy is the most useful, because IR spectra can be measured simply as Nujol mulls or directly for any mixture of solid-solid, solid-liquid, or liquid-liquid by using the ATP (attenuated total reflection) method. Some such examples of the mechanistic study are described. 

Microcosms are laboratory systems generally consisting of tanks such as fish aquaria containing natural sediment and water or soil. In those that have been most extensively evaluated for aquatic systems, continuous flow systems are used. In all of them, continuous measurement of evolved... 

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