Evaluating alternatives chapter

This chapter focused on examples of supply chains and their underl dng supply chain architecture, using a Four C conceptual framework. The Four Cs refer to chain structure and ownership, capacity, coordination, and competitiveness. The supply chain audit permits an understanding of current choices and an approach to evaluate alternate choices for supply chain architecture. The goal of this chapter was to explain the Four C choices made in different successful supply chain contexts. 

Evaluate proposed alternatives—short-list ethical solutions only may be a potential choice between/among two or more totally ethical solutions (In evaluating alternatives, possibly apply some of the evaluation tools discussed in Chapter 7 such as multi voting and SWOT)... 

Model-Based Approach. A dynamic model of the process is first developed that can be helpful in at least three ways (i) it can be used as the basis for model-based controller design methods (Chapters 12 and 14), (ii) the dynamic model can be incorporated directly in the control law (for example, model predictive control), and (iii) the model can be used in a computer simulation to evaluate alternative control strategies and to determine preliminary values of the controller settings. 

In Chapter 8 we explored the steady-state design of the TAME reactive distiUalion system. The reactive column is part of a multiunit process that includes other columns for recovery of the methanol reactant. The recovery is necessary because the presence of methanol/C5 azeotropes unavoidably removes methanol from the reactive column in the distillate stream. The economics of two alternative methanol recovery systems were evaluated in Chapter 8. In this chapter the dynamic control of the process is studied, and an effective plantwide control structure is developed. The process has three distillation columns one reactive column, one extractive distillation column, and one methanol/water separation column from which methanol and water are recycled. 

As explained in Section 2.13, the use of iz,-plots makes it possible to avoid the involvement of either n or when an alternative adsorptive is being used for evaluating the surface areas of a set of related solids. It is then no longer necessary to exclude the use of isotherms having a low value of c, consequently the method is applicable even if the isotherm of the alternative adsorptive is of Type III (cf. Chapter 5). Calibration of one sample by nitrogen or argon adsorption is still required. 

The merits and demerits of the many computer-simulation approaches to grain growth are critically analysed in a book chapter by Humphreys and Hatherly (1995), and the reader is referred to this to gain an appreciation of how alternative modelling strategies can be compared and evaluated. A still more recent and very clear critical comparison of the various modelling approaches is by Miodownik (2001). 

In vitro tools could be used alone or in test batteries with increased potency of the description of cellular events and changes. The chapter provides a brief introduction on the components of an in vitro system, the main differences between models for research and models for testing and a list of validated alternative methods according to the European Centre for the Validation of Alternative Methods (ECVAM) (http // ecvam.jrc.it/, http //ecvam.jrc.ec.europa.eu/) evaluation. 

In this chapter we will introduce and discuss the use of alternative methods to evaluate the carcinogenic potential of some PFCs. In detail, in silico (QSAR) models and BALB/c 3T3 CTA will be used to investigate the issue. 

Among possible alternative, QSARs models and the BALB/c 3T3 in vitro CTA represent a possible solution. An example of the application of these methodologies is reported in this chapter focusing on the evaluation of PFCs. 

Although, as explained in Chapter 9, many optimization problems can be naturally formulated as mixed-integer programming problems, in this chapter we will consider only steady-state nonlinear programming problems in which the variables are continuous. In some cases it may be feasible to use binary variables (on-off) to include or exclude specific stream flows, alternative flowsheet topography, or different parameters. In the economic evaluation of processes, in design, or in control, usually only a few (5-50) variables are decision, or independent, variables amid a multitude of dependent variables (hundreds or thousands). The number of dependent variables in principle (but not necessarily in practice) is equivalent to the number of independent equality constraints plus the active inequality constraints in a process. The number of independent (decision) variables comprises the remaining set of variables whose values are unknown. Introduction into the model of a specification of the value of a variable, such as T = 400°C, is equivalent to the solution of an independent equation and reduces the total number of variables whose values are unknown by one. 

Part I comprises three chapters that motivate the study of optimization by giving examples of different types of problems that may be encountered in chemical engineering. After discussing the three components in the previous list, we describe six steps that must be used in solving an optimization problem. A potential user of optimization must be able to translate a verbal description of the problem into the appropriate mathematical description. He or she should also understand how the problem formulation influences its solvability. We show how problem simplification, sensitivity analysis, and estimating the unknown parameters in models are important steps in model building. Chapter 3 discusses how the objective function should be developed. We focus on economic factors in this chapter and present several alternative methods of evaluating profitability. 

Thus, in Chapter 6, the transport equations for /++ x, t) and the one-point joint velocity, composition PDF /u+V, + x. / ) are derived and discussed in detail. Nevertheless, the computational effort required to solve the PDF transport equations is often considered to be too large for practical applications. Therefore, in Chapter 5, we will look at alternative closures that attempt to replace /++ x, t) in (3.24) by a simplified expression that can be evaluated based on one-point scalar statistics that are easier to compute. 

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