Matching utility

The program also has a Matching utility that records the results of two or more searches, stores, and compares them. Matches may be made by material (polymer) or by product model. The Matching utility eliminates test records that do not appear in all of the searches that were made. Matching by product model always eliminates more models as the number of searches increases. Conversely, matching by polymer may increase or decrease the number of models found as the number of searches increases. 

For example, two comprehensive databases, ICSD and CSD, contain crystallographic data and structural information about inorganic, and organic and metal organic compounds, respectively, while NIST database encompasses all types of compounds but provides only crystal data with references. Other databases are dedicated to specific classes of materials, such as metals and alloys, proteins and macromolecules, minerals or zeolites. Search-match utilities are usually provided with databases or they may be obtained separately. 

Value Value matching utilizes domain constraints (e.g., drop lists, check boxes, and radio buttons). It becomes valuable when comparing two attributes that do not exactly match through their names. For example, consider attributes arrivalDate and checklnDay. These two attributes have associated value sets (Select), 1,2,..., 31 and (Day), 1,2,..., 31 respectively, and thus their content-based similarity is = 94%, which improves significantly over their term similarity (11(arr2 1Date)- = 18%). 

Remote actuated valves must be chosen to match process requirements. Design decisions include materials of construction, valve seat material, valve t q)e, actuator type and controls characteristics. The design must match utility supply levels (air pressure, hydraulic pressure, flow capacity) and tolerances with actuator design to provide the correct torque/thrust to the valve. The torque/thrust must be above breakaway requirements and must be below stress limits of the drive train. With some valves, the ratio of these values may limit the available operating safety factor. 

Find a way to overcome the constraint while still maintaining the areas. This is often possible by using indirect heat transfer between the two areas. The simplest option is via the existing utility system. For example, rather than have a direct match between two streams, one can perhaps generate steam to be fed into the steam mains and the other use steam from the same mains. The utility system then acts as a buffer between the two areas. Another possibility might be to use a heat transfer medium such as a hot oil which circulates between the two streams being matched. To maintain operational independence, a standby heater and cooler supplied by utilities is needed in the hot oil circuit such that if either area is not operational, utilities could substitute heat recovery for short periods. 

In this context, the points correspond to process and utility streams and the lines to heat exchange matches between the heat sources and heat sinks. 

Let us now consider a few examples for the use of this simple representation. A grand composite curve is shown in Fig. 14.2. The distillation column reboiler and condenser duties are shown separately and are matched against it. Neither of the distillation columns in Fig. 14.2 fits. The column in Fig. 14.2a is clearly across the pinch. The distillation column in Fig. 14.26 does not fit, despite the fact that both reboiler and condenser temperatures are above the pinch. Strictly speaking, it is not appropriately placed, and yet some energy can be saved. By contrast, the distillation shown in Fig. 14.3a fits. The reboiler duty can be supplied by the hot utility. The condenser duty must be integrated with the rest of the process. Another example is shown in Fig. 14.36. This distillation also fits. The reboiler duty must be supplied by integration with the process. Part of the condenser duty must be integrated, but the remainder of the condenser duty can be rejected to the cold utility. 

Figure 16.4a shows the grid diagram with a CP table for design above the pinch. Cold utility must not be used above the pinch, which means that hot streams must be cooled to pinch temperature by recovery. Hot utility can be used, if necessary, on the cold streams above the pinch. Thus it is essential to match hot streams above the pinch with a cold partner. In addition, if the hot stream is at pinch conditions, the cold stream it is to be matched with must also be at... 

Turning now to the cold-end design, Fig. 16.6a shows the pinch design with the streams ticked off. If there are any cold streams below the pinch for which the duties eu e not satisfied by the pinch matches, additional process-to-process heat recovery must be used, since hot utility must not be used. Figure 16.66 shows an additional match to satisfy the residual heating of the cold streams below the pinch. Again, the duty on the unit is maximized. Finally, below the pinch the residual cooling duty on the hot streams must be satisfied. Since there are no cold streams left below the pinch, cold utility must be used (Fig. 16.6c). 

Before any matches are placed, the target indicates that the number of units needed is equal to the number of streams (including utility streams) minus one. The tick-off heuristic satisfied the heat duty on one stream every time one of the units was used. The stream that has been ticked off is no longer part of the remaining design problem. The tick-off heuristic ensures that having placed a unit (and used up one of our available units), a stream is removed from the problem. Thus Eq. (7.2) is satisfied if eveiy match satisfies the heat duty on a stream or a utility. 

Figure 16.10 shows another threshold problem that requires only hot utility. This problem is different in characteristic from the one in Fig. 16.9. Now the minimum temperature difference is in the middle of the problem, causing a pseudopinch. The best strategy to deal with this type of threshold problem is to treat it as a pinched problem. For the problem in Fig. 16.10, the problem is divided into two parts at the pseudopinch, and the pinch design method is followed. The only complication in applying the pinch design method for such problems is that one-half of the problem (the cold end in Fig. 16.10) will not feature the flexibility offered by matching against utility.

The pinch design method developed earlier followed several rules and guidelines to allow design for minimum utility (or maximum energy recovery) in the minimum number of units. Occasionally, it appears not to be possible to create the appropriate matches because one or other of the design criteria cannot be satisfied. 

Figure 16.9 Even though threshold problems have large driving forces, there are still often essential matches to be made, especially at the no-utility end.

Figure 16.10 Some threshold problems must be treated as pinched problems requiring essential matches at both the no-utility end and the pinch.

The algorithm may calculate Qnmia and Qcmm to be unchanged. In this case, the designer knows that the match will not penalize the design in terms of increased utility usage. 

The algorithm may calculate an increase in Qnmin and Qcmin- This means that the match is transferring heat across the pinch or that there is some feature of the design that will cause cross-pinch heat transfer if the design was completed. If the match is not transferring heat across the pinch directly, then the increase in utility will result from the match being too big as a result of the tick-off heuristic. 

Placing the next match above the pinch as shown in Fig. 16.21c also allows the CP inequality to be obeyed. The area for both matches in Fig. 16.21c is 7856 m , and the target for the remaining problem is 1020 m . Accepting both matches causes the overall area target to be exceeded by 17 m (0.2 percent). This seems to be reasonable, and both matches are accepted. No further process-to-process matches are possible, and it remains to place hot utility. 

The cold-utility target for the problem shown in Fig. 16.22 is 4 MW. If the design is started at the pinch with stream 3, then stream 3 must be split to satisfy the CP inequality (Fig. 16.22a). Matching one of the branches against stream 1 and ticking off stream 1 results in a duty of 8 MW. 

Figure 16.22c shows an additional match placed on the other branch for stream 3 with its duty maximized to 3 MW to tick off stream 3. No further process-to-process matches are possible, and it remains to place cold utility. 

With conventional nonspectroscopic detectors, other methods must be used to identify the solutes. One approach is to spike the sample by adding an aliquot of a suspected analyte and looking for an increase in peak height. Retention times also can be compared with values measured for standards, provided that the operating conditions are identical. Because of the difficulty of exactly matching such conditions, tables of retention times are of limited utility. 

A low temperature of approach for the network reduces utihties but raises heat-transfer area requirements. Research has shown that for most of the pubhshed problems, utility costs are normally more important than annualized capital costs. For this reason, AI is chosen eady in the network design as part of the first tier of the solution. The temperature of approach, AI, for the network is not necessarily the same as the minimum temperature of approach, AT that should be used for individual exchangers. This difference is significant for industrial problems in which multiple shells may be necessary to exchange the heat requited for a given match (5). The economic choice for AT depends on whether the process environment is heater- or refrigeration-dependent and on the shape of the composite curves, ie, whether approximately parallel or severely pinched. In cmde-oil units, the range of AI is usually 10—20°C. By definition, AT A AT. The best relative value of these temperature differences depends on the particular problem under study. 

Shaping. Most metal-shaping operations in ECM utilize the same inherent feature of the process whereby one electrode, generally the cathode tool, is driven toward the other at a constant rate when a fixed voltage is appHed between them. Under these conditions, the gap width between the tool and the workpiece becomes constant. The rate of forward movement between the tool and the workpiece becomes constant. The rate of forward movement of the tool is matched by the rate of recession of the workpiece surface resulting from electrochemical dissolution. 

The thermal expansivity of Ni—Fe alloys vary from ca 0 at ca 36 wt % Ni (Invar [12683-18-OJ) to ca 13 x 10 / C for Ni. Hence, a number of compositions, which are available commercially, match the thermal expansivities of glasses and ceramics for sealing electron tubes, lamps, and bushings. In addition, the thermal expansion characteristic is utilized ia temperature controls, thermostats, measuriag iastmments, and condensers. 

Amine Cross-Linking. Two commercially important, high performance elastomers which are not normally sulfur-cured are the fluoroelastomers (FKM) and the polyacrylates (ACM). Polyacrylates typically contain a small percent of a reactive monomer designed to react with amine curatives such as hexamethylene-diamine carbamate (Diak 1). Because the type and level of reactive monomer varies with ACM type, it is important to match the curative type to the particular ACM ia questioa. Sulfur and sulfur-beating materials can be used as cure retarders they also serve as age resistors (22). Fluoroelastomer cure systems typically utilize amines as the primary cross-linking agent and metal oxides as acid acceptors. 

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