Costing method, choosing

We also described the different analytical techniques used to characterize powders both in terms of their size and composition. To determine particle size it is necessary to choose a method that has sufficient sensitivity. Sieving is a low-cost method and is reliable when the particle size is greater than about 60 pm. But if the particles are smaller than this, as is often the case, then the use of light scattering or X-ray diffraction should be considered. In determining both particle size and chemical composition it is essential that the specimen we choose for analysis is representative of the entire powder sample. 

Note that using this method, we have determined the equivalent annual worth of all cash flow, and because alternative B has a lower annual cost, we choose alternadve B. 

It may be possible to reduce manufacturing costs by choosing an adhesive as the method of joining. In assessing the relative expense of alternative joining techniques it is important to consider all aspects of the manufacturing process and not just to compare the cost of the adhesive... 

The requirements of the analysis determine the best method. In choosing a method, consideration is given to some or all the following design criteria accuracy, precision, sensitivity, selectivity, robustness, ruggedness, scale of operation, analysis time, availability of equipment, and cost. Each of these criteria is considered in more detail in the following sections. 

Chemical agents that increase the rate of grinding are an attractive prospect since their cost is low. However, despite a voluminous literature on the subject, there is no accepted scientific method to choose such aids there is not even agreement on the mechanisms by which they work. The subject has been recently reviewed [Fuerstenau, KONA Powder and Paiticle, 13,5-17 (1995)]. 

Choosing a model chemistry almost always involves a trade-off between accuracy and computational cost. More accurate methods and larger basis sets make jobs run longer. We ll provide some specific examples of these effects throughout the chapters in this part of the book. 

Previous chapters have outlined the methods of estimating loads, choosing methods to achieve the required conditions, and howto select and balance plant for correct operation. Theyhave also mentioned the factors which will give economy in running costs. 

These requirements have special implications with regard to immunoassay methods. Eirst, the lack of commercial availability of reagents precludes preparing antibody-coated tubes or plates on-site, which may require knowledge of special skills. Commercial availability also ensures the analyst access to a reproducibly manufactured product. Therefore, the method must be based on an immunoassay that is a commercial product. Method developers may choose to introduce an in-house assay to the marketplace by partnering with a manufacturer, although this approach is costly and time-consuming. 

Once values have been assigned for the costs and benefits of each proposed risk-reduction modification, a variety of economic evaluation techniques may be used to choose the most attractive option. These techniques include net present value, discounted cash flow rate of return and cost-benefit ratio analyses. Most companies have a preferred method for evaluating project economics, which can be used with little or no modification. Chapter 8 of... 

For the spectroscopist today it is very important to choose the right method, after a cost-benefit analysis, to match the demands of the customer or serve the purpose of his research as effectively as possible. For the characterization of heterogeneous polymers a broad range of methods and instruments is available. We have tried to list the most important of them, and to emphasize their pros and cons when used for polymer imaging. 

In choosing the most appropriate method for the methylation of a particular compound account has to be taken of several factors, namely, the presence of groups in the molecule which are susceptible to attack by one or more of the methylating reagents, the solubility of the compound in the different methylation media, the ease of isolation of the product, the relative efficiency of the reactions, and the relative costs of the various processes. 

HRP substrates (Sred) can be selected to give products that can be monitored easily by colorimetric, fiuorometric or chemiluminescent methods. A popular choice in colorimetric assays is 3,3, 5,5 -tetrameth-ylbenzidine (TMB), a colorless substance that gives a blue product (Sox) on oxidation. Important considerations when choosing suitable substrates are cost, safety, sensitivity, solubility, and stability. It is sometimes necessary to use a substrate that gives an insoluble colored product, for example, in histochemical staining or membrane-bound immunoassays. 

Quantum chemical calculations have become a valuable tool in the research of reactive intermediates. Unfortunately, there is no unique computational method that can be uniformly applied in all cases and give an accurate answer at a practical cost. A variety of computational methods are available, each with its own weaknesses and advantages. The species that are of interest in this chapter and which often have unpaired electrons, pose specific problems in calculating their properties, and some care in choosing appropriate methods is necessary for obtaining meaningful results. In this respect, an excellent guide for calculations on open-shell molecules has been recently published [51]. 

---