Computer programs Subject

Near top speed, a fan may operate at a speed that is near or above the natural frequency of the wheel and shaft. Under such conditions, the fan can vibrate badly even when the wheel is clean and properly balanced. Whereas manufacturers often do not check the natural frequency of the wheel and shaft ia standard designs, many have suitable computer programs for such calculations. Frequency calculations should be made on large high speed fans. The first critical wheel and shaft speed of a fan that is subject to wheel deposits or out-of-balance wear should be about 25—50% above the normal operating speed. 

To determine the pipeline potentials, the resultant induced field strengths have to be included in the equations in Section 23.3.2. Such calculations can be carried out with computers that allow detailed subdivision of the sections subject to interference. A high degree of accuracy is thus achieved because in the calculation with complex numbers, the phase angle will be exactly allowed for. Such calculations usually lead to lower field strengths than simplified calculations. Computer programs for these calculations are to be found in Ref. 16. 

The relative merits of various MO methods have been discussed in die literature. In general, the ab initio type of calculations will be more reliable, but the semiempirical calculations are faster in terms of computer time. The complexity of calculation also increases rapidly as the number of atoms in the molecule increases. The choice of a method is normally made on the basis of evidence that the method is adequate for the problem at hand and the availability of appropriate computer programs and equipment. Results should be subjected to critical evaluation by comparison widi experimental data or checked by representative calculations using higher-level mediods. Table 1.12 lists some reported deviations from experimental AHf for some small hydrocarbons. The extent of deviation gives an indication of the accuracy of the various types of MO calculations in this application. 

Catalytic crackings operations have been simulated by mathematical models, with the aid of computers. The computer programs are the end result of a very extensive research effort in pilot and bench scale units. Many sets of calculations are carried out to optimize design of new units, operation of existing plants, choice of feedstocks, and other variables subject to control. A background knowledge of the correlations used in the "black box" helps to make such studies more effective. 

When required, combined with the use of computers, the finite element analysis (FEA) method can greatly enhanced the capability of the structural analyst to calculate displacement and stress-strain values in complicated structures subjected to arbitrary loading conditions. In its fundamental form, the FEA technique is limited to static, linear elastic analysis. However, there are advanced FEA computer programs that can treat highly nonlinear dynamic problems efficiently. 

Automated randomization systems have been developed using voice response [44] and telephone touch-tone technology [45,46]. Others have used a preloaded password-protected system with hidden encrypted randomization files into the trial s laptop or desktop computers that are used as distributed data collection devices [47] or have developed centralized computer programs that dynamically randomize subjects [48]. 

Palmar M, Broekhoven M, Garrah A, Tu D. CTASSIST a computer program for subjects randomization and tracking of drug distribution. Clin Trials 2000 21 2S 110S. 

The quote, however, is as true today as it was nearly twenty years ago. We stand on the threshold of exciting new applications for computers both within the field of education and elsewhere. The subject of this paper is a computer program which represents one totally different approach for the use of computers in chemical education. We hope that it is only one new approach out of many that we will see in the future. 

Although the details of computer programming are beyond the scope of this text, the student unfamiliar with the subject is urged to consult one of the many books available (8). Many programs designed to carry out the calculations described in this section are available commercially for use on desktop personal computers. 

This is the fun (and frustration) of chemical reaction engineering. While thermodynamics, mass and heat transfer, and separations can be said to be finished subjects for many engineering apphcations, we have to reexamine every new reaction system from first principles. You can find data and construct process flowsheets for separation units using sophisticated computer programs such as ASPEN, but for the chemical reactors in a process these programs are not much help unless you give the program the kinetics or assume equihhrium yields. 

The mathematical basis of the Mie theory is the subject of this chapter. Expressions for absorption and scattering cross sections and angle-dependent scattering functions are derived reference is then made to the computer program in Appendix A, which provides for numerical calculations of these quantities. This is the point of departure for a host of applications in several fields of applied science, which are covered in more detail in Part 3. The mathematics, divorced from physical phenomena, can be somewhat boring. For this reason, a few illustrative examples are sprinkled throughout the chapter. These are just appetizers to help maintain the reader s interest a fuller meal will be served in Part 3. 

At the outset it may also be advantageous to consider problems of structural identifiability and distinguishability. A model is not identifiable if in principle it is impossible to determine the desired parameters on the basis of proposed data to be obtained even if there is no experimental uncertainty or inadequacy in computer programming. Even when it is theoretically possible to determine the parameters for a given model, it may also be possible to compute those for a competing model from the same data and the models will then be indistinguishable. Resolution of these problems is often not simple. The subject is discussed in an advanced monograph by Walter (49) as well as in papers by Park and Himmelblau (49a) and Walter et al. (49b). 

The similarity judgments are then analyzed by one of a number of specially designed computer programs that have been detailed by Schiffman, Reynolds and Young ( .) Some programs, such as INDSCAL, ALSCAL, and MULTISCALE, not only provide multidimensional arrangements of molecules based on their flavor similarity but provide quantitative measures that delineate the individual differences in response for each subject as well. The... 

Such results may also suggest that, although excellent as an interpolative tool as was intended by ruby s designers (i.e., for explosives with compositions and properties between RDX and TNT, see also Appendix C), the ruby code may be less satisfactory in extrapolative situations. Various ruby users have computed detonation properties of hypothetical explosives at predicted densities as high as 2.1-2.2 g/cc, and have used the results as a basis for extended synthesis programs. It 4s now suggested that predictions of explosive properties based on such computations are subject to serious question. 

The reader is urged to read Initiation of Explosives by Impact in Vol 7,135-R ff of this Encycl, Whereas that article dealt principally with the testing of expls, we shall want to include propints in the discussion. There is probably no subject in hazards analysis which is so actively studied as the role of impact, shock and thermal effects on the safety of expls and proplnts and which is as poorly understood. We have alluded to this incomplete state of theoretical development in the section of this article on Application of Computer Programming... 

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