If-then construct

THEOREM 4.16 Every primitive recursive function can be computed by a program (P,I) where P is a STEP scheme not enploying any IF-THEN construction and I is an interpretation over the nonnegative integers assigning to function letters only functions S, Z, and x - 1 and to predicate letters only the inter-... 

In a computational toxicology expert system [313], structure-toxicity relationships recognized and trusted by professional toxicologists are stored as a computer-discernable collection of often largely nested IF-THEN constructs. When challenged to predict the toxicity of a compound, the expert system parses its structure and makes comparisons against the available KB of rules. The rules triggered by the compound s structure are collected and presented to the IE for qualitative deductive assessment of potential toxicity. 

A PROLOG rule is an if-then construction in PROLOG notation this would look like the following ... 

The instructions and subroutines must be performed in sequence and in the same order as they were specified. There are cases, however, in which an algorithm may have to select an execution path from a number of options. The most basic construct for path selection is the if-then construct. The following example illustrates the functioning of the if-then construct. Note how Instruction 2 is executed only if something is true ... 

The method of standard additions can be used to check the validity of an external standardization when matrix matching is not feasible. To do this, a normal calibration curve of Sjtand versus Cs is constructed, and the value of k is determined from its slope. A standard additions calibration curve is then constructed using equation 5.6, plotting the data as shown in Figure 5.7(b). The slope of this standard additions calibration curve gives an independent determination of k. If the two values of k are identical, then any difference between the sample s matrix and that of the external standards can be ignored. When the values of k are different, a proportional determinate error is introduced if the normal calibration curve is used. 

If then we construct a tentative diagram for the proton levels in formic acid solution, the gap between the vacant level of (JICOO)- and the occupied level of HjO will be a little wider than in Fig. 36. This has been shown in Fig. 65. 

This general procedure will only be completely successful, of course, if the correct RICs are examined and it may be that the analyst feels it more appropriate to carry out a manual analysis of the TIC trace. This is not perhaps as daunting as it may at first appear, since although the TIC trace may contain a large amount of information, the ionization techniques employed invariably yield simple spectra and changes in m/z values of the intense ions present are often obvious. The RICs of the ions selected in this way are then constructed for further examination of the spectra involved. 

Rules seemingly have the same format as IF.. THEN.. statements in any other conventional computer language. The major difference is that the latter statements are constructed to be executed sequentially and always in the same order, whereas expert system rules are meant as little independent pieces of knowledge. It is the task of the inference engine to recognize the applicable rules. This may be different in different situations. There is no preset order in which the rules must be executed. Clarity of the rule base is an essential characteristic because it must be possible to control and follow the system on reasoning errors. The structuring of rules into rule sets favours comprehensibility and allows a more efficient consultation of the system. Because of the natural resemblance to real expertise, rule-based expert systems are the most popular. Many of the earlier developed systems are pure rule-based systems. 

If the characteristic polynomial passes the coefficient test, we then construct the Routh array to find the necessary and sufficient conditions for stability. This is one of the few classical techniques that we do not emphasize and the general formula is omitted. The array construction up to a fourth order polynomial is used to illustrate the concept. 

For each n there must be an input from D which causes the computation in P to go around the loop W at least n times otherwise, as far as concerns input from D, we could replace W with n "IF-THEN-ENDIF" constructions. After... 

For a conditional IF-THEN or IF-THEN-ELSE construction we can state the Rules of Conditional Statements ... 

Fortunately, the partial decoupling of the ET and conformational processes afforded by the absence of synchronous events in principle and in practice allows for the identification of an observed decay rate constant. For example, if one constructs a series of systems in which the ET energetics (or electronic coupling) is modified without change in the conformational equilibrium, thus leaving the conformational rates unchanged, then the observed rate constants will be unchanged if the reaction is controlled by a conformational rate, but will vary if this is not so. 

Ternary Phase Diagrams. In a ternary system, it is necessary to specify temperature, pressure, and two composition parameters to completely describe the system. Typically, pressure is fixed, so that there are three independent variables that are needed to fix the system temperature and two compositions. The third composition is, of course, fixed by the first two. We could create a three-dimensional plot with three mutually perpendicular axes, as is usually the case in mathematics however, it is more convenient, and graphically more appealing, to establish two compositional axes 60° apart from each other, with a third, redundant compositional axis, as in the form of an equilateral triangle (see Figure 2.14). The temperatme axis is then constructed perpendicular to the plane of the triangle, if desired. 

Our immediate problem, then, is to combine the four outer orbitals into linear combinations having A2u, BUn and ER symmetry and also to combine the four inner orbitals into linear combinations having these same symmetries. As in the case of the carbocyclic rings, this process can be simplified by using only the corresponding rotation group C4 instead of >4/l, since the former can discriminate between the orbitals. That is, if we construct an orbital of A... 

High performance composites may be laminates wherein veils of carbon fiber are treated with an epoxy resin, stacked up to the desired final product thickness, and then laminated together under heat and pressure (see Composite materials Carbon and graphite fibers). Simply mixing together carbon or glass fibers and polymeric resins to form a reinforced plastic leads to a composite material, but this is not a laminate if not constructed from discrete plies. 

Suppose I observe some people under stress and see that they wave their arms frantically. I also take blood samples and observe that there is an abnormally high amount of adrenalin in their blood. I might then construct a theory that adrenalin is released in response to stress and that the presence of adrenalin in the bloodstream directly affects muscular coordination, with the result that people wave their arms wildly. It sounds plausible. But if the theory is true, where can it lead I might then go on to reason that if this is true, in the absence of a stressful situation, the direct injection of adrenalin into the bloodstream should make people wave their arms wildly. I test this prediction and find that it is not true. 

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