Classifier Efficiency

Dependence of the FN, FP, TN, and TP on the threshold value is elearly reflected by a Receiver Operator Characteristic (ROC) curve [48] in the TPR-FPR coordinates (tme positive rate versus false positive rate), where TRP=TP/(TP+TN) and FPR=FP/(FP+TN). The laiger the area under the curve (AUC), the higher is the classifier efficiency. 

Fig. 2. Device for the enhancement of classifier efficiency developed by POSTEC.

Scmbbers make use of a combination of the particulate coUection mechanisms Hsted in Table 5. It is difficult to classify scmbbers predominantly by any one mechanism but for some systems, inertial impaction and direct interception predominate. Semrau (153,262,268) proposed a contacting power principle for correlation of dust-scmbber efficiency the efficiency of coUection is proportional to power expended and more energy is required to capture finer particles. This principle is appHcable only when inertial impaction and direct interception are the mechanisms employed. Eurthermore, the correlation is not general because different parameters are obtained for differing emissions coUected by different devices. However, in many wet scmbber situations for constant particle-size distribution, Semrau s power law principle, roughly appHes ... 

Axial fans are classified as propeller, tube-axial, and vane-axial (Fig. 9). The choice of fan requited is determined by the resistance (static pressure) the fan must work against as well as the volume flow requited. PtopeUet fans usually discharge iato a plenum or directly iato the atmosphere. Tube-axial fans are usually mounted ia ducts as ia an air conditioning system. Vane-axial fans are also mounted ia ducts but feature a stationary guide vane on the discharge side that straightens the air flow to improve efficiency. Tube-axial fans can work at static pressures up to 623 Pa (2.5 ia. H2O) vane-axial fans can work up to 2000 Pa (8 ia. H2O). 

Several feed additives for rumiaants are available. All additives iacrease animal growth or efficiency of weight gain, and many provide additional benefits (see Growth regulators). Additives can be classified into groups based on function. 

The products are an oversize (underflow, heavies, sands) and an undersize (overflow, lights, slimes). An intermediate size can also be produced by varying the effective separating force. Separation size maybe defined either as a specific size in the overflow screen analysis, eg, 5% retained on 65 mesh screen or 45% passing 200 mesh screen, or as a d Q, defined as a cut-off or separation size at which 50% of the particles report to the oversize or undersize. The efficiency of a classifier is represented by a performance or partition curve (2,6), similar to that used for screens, which relates the particle size to the percentage of each size in the feed that reports to the underflow. 

Asymmetric synthesis is a method for direct synthesis of optically active amino acids and finding efficient catalysts is a great target for researchers. Many exceUent reviews have been pubHshed (72). Asymmetric syntheses are classified as either enantioselective or diastereoselective reactions. Asymmetric hydrogenation has been appHed for practical manufacturing of l-DOPA and t-phenylalanine, but conventional methods have not been exceeded because of the short life of catalysts. An example of an enantio selective reaction, asymmetric hydrogenation of a-acetamidoacryHc acid derivatives, eg, Z-2-acetamidocinnamic acid [55065-02-6] (6), is shown below and in Table 4 (73). 

In order to operate a process facility in a safe and efficient manner, it is essential to be able to control the process at a desired state or sequence of states. This goal is usually achieved by implementing control strategies on a broad array of hardware and software. The state of a process is characterized by specific values for a relevant set of variables, eg, temperatures, flows, pressures, compositions, etc. Both external and internal conditions, classified as uncontrollable or controllable, affect the state. Controllable conditions may be further classified as controlled, manipulated, or not controlled. Excellent overviews of the basic concepts of process control are available (1 6). 

A recirculation design (Fig. 10) returns the gas to the classifier through the fan after the fine particles are removed from the gas stream. Such an arrangement requires an excellent soHd/gas separator otherwise the classification becomes less efficient. A perfect soHd/gas separator would be a device having a = 1. If the recirculated gas is entered through a secondary coarse stream classification section, then the classification is not less efficient unless the secondary classification is very iaefficient. 

Gives very clean sands and has relatively low hydraulic water requirements (0.5 t/t underflow). One of the most efficient single-stage classifiers available for closed circuit grinding and washing. Relatively expensive. 

Classification efficiency of the hvdroseparator compares with that of the cone classifier and is appreciably lower than that obtained from mechanical or hvdraiilic units. The chief virtue of the hvdroseparator is its ability to receive and slough off great quantities of vv ater at low per-imit-voliirne cost. 

The hberation of a valuable constituent does not necessarily translate direclly into recoveiy in downstream processes. For example, flotation tends to be more efficient in intermediate sizes than at coarse or fine sizes [Mclvor and Finch, Minerals Engineeiing, 4(1), 9-23 (1991)]. For coarser sizes, failure to liberate may be the hmitation finer sizes that are liberated may still be carried through by the water flow. A conclusion is that overgrinding should be avoided by judicious use of size classifiers with recycle grinding. 

Typical separation efficiency curves of an air classifier versus particle size are given in Fig. 20-14. The amount of top size in the fines may be very low, but there is typically 10 to 30 percent fines in the coarse product that is, the low end of the cui ve tends to flatten out at 10 to 30 percent. In addition, the separation at the cut size is typically a gradu cui ve. Data of this sort, which are needed to evaluate closed-circuit mill performance, are seldom available. See subsection on characteristics of size classifiers for a testing method. 

The new gas turbines have fired inlet temperatures as high as 2300° F (1260° C) with efficiencies as high as 42-45 percent. Pressure ratios have increased from 5 1 in the 1950s to as high as 30 1 in some of the new turbines of the 1990s. Gas turbines are classified into two major categories ... 

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