Final Selection

Most of the publications in the area of supplier selection have focused on final selection. In the final selection step (Figme 6.3), the buyer identifies the suppliers to do business with and allocates order quantities among the chosen supplier(s). In reviewing the literature, there are basically two kinds of supplier selection problem, as stated by Ghodsypour and O Brien (2001)  

A multiple sourcing strategy results in obtaining raw materials and parts from more than one supplier and provides greater flexibility to a company. It introduces competition among the suppliers, which helps to drive the procurement costs down and improve quality of parts (Jayaraman et al., 1999). It also protects the company from major supply disruptions. However, the overhead costs will increase as the company has to deal with multiple suppliers for each part. Bilsel and Ravindran (2011) discuss a hybrid sourcing strategy, wherein the company uses one main supplier but has several back-up suppliers that can be used in case of supply disruption at the main supplier. 

This situation will require the reviewers to weigh additional aspects such as  

The company seeking to toll internationally in this case will benefit from selecting an experienced team of reviewers with international experience. Tollers seeking business from foreign companies would benefit by recognizing these new aspects may present difficulties when their capabilities are being assessed. The candidate tollers could prepare information in advance that helps respond to these potential concerns. 

Differences in each country s regulatory requirements may, in turn, cause differences in operating philosophies. It is important to clearly review expectations with regard to health, safety and environmental matters during initial assessments of foreign tollers. 

In this phase of the toller selection process, we assume the long list became a short list and now one or more candidate tollers from the short list will be given an opportunity to prepare a commercial bid. This by no means indicates the short listed tollers are perfect. There may be deficiencies that need to be corrected in concert with the client. With proper effort, one will be successful and be engaged for the toll. Sometimes it is appropriate to decide on a backup toller, as complications can develop that prevent the primary candidate from executing the project as originally planned, due to an incident in their plant, departure of key personnel, or unexpected production demands on the toller. 

If a standard form was used in the qualification phase, a system should exist to rank the respondents that are being considered. Such a system can be as simple as the reviewers making a written recommendation summarizing the strong points of their selections. Some companies have developed forms that allow the final scores to be quantified. Appendix C, Sample Toller Assessment—Qjiantitative Format contains such an example. With either method, the client should consider having two or more reviewers discuss the candidates and agree on the recommended finalists. 

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Once the quality of the dataset is defined, the next task is to improve it. Again, one has to remove outliers, find out and remove redundant objects (as they deliver no additional information), and finally, select the optimal subset of descriptors. 

The most desirable characteristics of a solvent for recrystalhsation are (a) a high solvent power for the substance to be purified at elevated temperatures and a comparatively low solvent power at the laboratory temperature or below (6) it should dissolve the impurities readily or to only a very small extent (c) it should yield well-formed crystals of the purified compound and (d) it must be capable of easy removal from the crystals of the purified compound, i.e., possess a relatively low boiling point. It is assumed, of course, that the solvent does not react chemically with the substance to be purified. If two or more solvents appear to be equally suitable for the recrystallisation, the final selection will depend upon such factors as ease of manipulation, inflammability and cost. 

Finally, selective hydrogenation of the olefinic bond in mesityl oxide is conducted over a fixed-bed catalyst in either the Hquid or vapor phase. In the hquid phase the reaction takes place at 150°C and 0.69 MPa, in the vapor phase the reaction can be conducted at atmospheric pressure and temperatures of 150—170°C. The reaction is highly exothermic and yields 8.37 kJ/mol (65). To prevent temperature mnaways and obtain high selectivity, the conversion per pass is limited in the Hquid phase, and in the vapor phase inert gases often are used to dilute the reactants. The catalysts employed in both vapor- and Hquid-phase processes include nickel (66—76), palladium (77—79), copper (80,81), and rhodium hydride complexes (82). Complete conversion of mesityl oxide can be obtained at selectivities of 95—98%. 

For many centuries the application of materials for low friction and wear in sliding and rolling contacts primarily involved wood, stone, leather, iron, and copper. Almost all engineering materials have since been employed at one time or another in the continuing search for the best bearing material. Final selection is commonly a judgment based on the most essential material properties, ease of appHcation, and cost. 

Finally, selective separation and dewatering of one suspended substance in a slurry containing different minerals or precipitates is possible by selectively adsorbing a magnetic material (usually hydrophobic) onto a soHd that is also naturally or chemically conditioned to a hydrophobic state. This process (Murex) was used on both sulfide ores and some oxides (145). More recently, hydrocarbon-based ferrofluids were tested and shown to selectively adsorb on coal from slurries of coal and mineral matter, allowing magnetic recovery (147). Copper and zinc sulfides were similarly recoverable as a dewatered product from waste-rock slurries (148). 

Final. selection of diyer From the results of the diying tests and quotations, the final selection of the most suitable dryer can be made. A recent article describing diyer scale-up methodology in the... 

The quick reference Table 19-8 will help by way of rapid elimination of poor possibihties. Following that the brief comments and illustrations will help pinpoint most probable selections. Further study of the more elaborate data in the references and contact with the usual suppliers are recommended, as there are many possible modifications of equipment which can improve operating results from any type of machine finally selected. 

Belt selection depends on power and development of the required tensile strength. Knowing drive-shaft power, belt tension can be calculated and a belt selected. However, since various combinations of width and ply thickness will develop the required strength, final selection is influenced by lump size, troughability of the belt, and abihty of the belt to support the load between idlers. Thus it is necessaiy to use an empirical approach to arrive at a belt selection which meets all requirements. 

The final selection was a tubular reactor with upward concurrent flow, with hquid holdup of 20 to 30 percent, and with residence times of 1.0 s for gas and 3 to 5 min for hquid. 

Site Selection Factors that must be considered in evaluating potential solid-waste-disposal sites are summarized in Table 25-71. Final selection of a disposal site usually is based on the results of a preliminary site survey, results of engineering design and cost studies, and an environmental-impact assessment. 

A confidentiality agreement is frequently required prior to the final selection process. Depending on the process technology, a confidentiality agreement may be required during initial discussions with the toller. Alternately, it may be included in the request for bid or when the final contract is executed. 

It is presumed that the protective distance (distance of the protected equipment from the arrester) is short and within safe limits. It too must be checked before a final selection of the arrester, as explained in Section 18.6.2. The above selection, however, seems to be appropriate for a distance up to 8-10 m as considered in Example 18.4. 

Step 3. The final selection of a specific air blower and turboexpander must be made after fully considerating the results of Steps 1 and 2. The normal operating point must be located on the system operating map (similar to Figure 4-66) so that reasonable latitude is available in operating variables between normal operating point and air blower minimum flow, and between operating point and expander bypass point. 

To be used as guide, pressure drop and system environment govern final selection of pipe size. 

A 5.000 hp break point has been used rather arbitrarily, as larger motors are built, ranging in size to 30,000 hp. Generally as the size increases, the synchronous motor becomes more competitive. However, final selection is not only dictated by the driver economics above, but includes the power system as well. 

Based on technical specifications, acceptable equipment is identified. The final selection is made on the same basis as in Selection of System. The decision tree is shown in Fig. 3.13. 

Finally, select acetone from the molecules on screen. Here, both the LUMO and the LUMO map are available under the Surfaces menu. First, select LUMO and display it as a Solid. It describes a 7U-type antibonding ( i ) orbital concentrated primarily on the earbonyl carbon and oxygen. Next, turn off this surface (select None under the LUMO sub-menu), and then seleet LUMO Map under the Surfaces menu. Display the map as a transpareni solid. Note the blue spot (maximum value of the LUMO) directly over the carbonyl carbon. This reveah the most likely site for nucleophilic attack. 

The efficiency of this type of unit varies, and is a function of the effectiveness of the impingement baffling arrangement. About 70% of separator applications can use the line-type unit the other 30% require the vessel construction. The preference of the designer and problems of the plant operator are important in the final selection of a unit to fit a separation application. 

Read manufacturer s capacity tables or charts to select model and size of pressure relief, reading table to closest capacity, but toward larger size if in between. Consult manufacturer for final selection. 

The curves are necessarily the approximate midrange of a spread or band of the magnitude of the respective influences on the ground area. That is, the information is good for guidance as to the direction certain changes w ill take in the final selection. For example, the data are refer-... 

It is important to note that quite often the actual compression ratios for the individual cylinders of a multistage machine will not be balanced exacdy. This condition arises as a result of the limiting horsepower absorption for certain cylinder sizes and designs of the manufacturer. In final selection these will be adjusted to give compression ratios to use standard designs as much as possible. 

Determine whether any other fan could be used in this application. The next larger or smaller fan size should be examined. Other manufecturers could possibly give a different size that might be more efficient. The final selection should be based on an analysis of several different manufacturers fans. 

Axial or centrifugal fans can be applied in most cases and are significant factors in the final selection and optimization (Figures 34.2 and 34.3). 

The final selection can be made only after consideration of the first cost of the compressor, motor, starter, aftercooler and receiver. The cost of installation, including foundations, piping and wiring as well as the operating power cost must also be considered. In the example. Table 41.3 provides a basic comparison of the three options. 

Even within a generic type of alloy there are significant performance differences. Thus, for example, Al-Zn-In alloys provide a higher driving voltage but a lower current capacity than Al-Zn-Hg alloys. Once a decision to use a generic type of alloy has been made, these apparently small differences in performance become important in the final selection. This subject is also discussed below. 

The choice of compressor type is now a wide one, and at least two alternatives should be considered before making a final selection. 

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