Black-box programs

The book explains how to solve coupled systems of ordinary differential equations of the kind that commonly arise in the quantitative description of the evolution of environmental properties. All of the computations that I shall describe can be performed on a personal computer, and all of the programs can be written in such familiar languages as BASIC, PASCAL, or FORTRAN. My goal is to teach the methods of computational simulation of environmental change, and so I do not favor the use of professionally developed black-box programs. 

The discussion of the preceding paragraphs clearly shows that indeed supermolecule method should be applied with great care. So we wish to end this section by saying that even though the supermolecule approach is conceptually very simple it cannot be used by simply running standard black box programs of quantum chemistry. 

At present, black-box programs for solving initial value problems typically maintain fairly rigorous automatic control of the numerical errors. However, for multidimensional reacting-flow simulations (boundary value problems), error control is usually not automated, relying on the user performing the... 

Many expert systems which have been developed are very large software systems. A large system does not lend itself to maintenance or modifications. With the recent improvement of expert system shells, the opportunity to develop smaller, modular expert system, with highly specific knowledge bases has become possible. A small system could be treated as a black box program. Expert systems could be developed and used in the same way as mathematical libraries on computers are today. These small modular expert systems would be easily shareable. Modular expert systems libraries could the be used as building blocks to develop problem-specific expert systems. 

For the computation of the interaction between two closed-shell monomers there are at present two excellent computational methods, both implemented in black box programs. The first is based on SAPT [135] and the second is the supermolecule CCSD method [136,137] with triply excited terms added in a non-iterative fashion. 

Density functional calculations with black-box programs will become... 

The wavefunction, which is used in such an MRDCI approach to compute molecular properties other than energy, includes the zeroth-order reference list plus all selected configurations (generally between 20000 and 100000), The disadvantage of this MRDCI method is that it cannot be handled as a black box program, and that the contribution of the unselected species may become quite large (and different... 

Unfortunately, the supennolecule approach [81, 82] is full of teclmical diflSculties, which stem chiefly from the very small magnitude of the interaction energy relative to the energy of the supennolecule. Even today, a novice would be ill-advised to attempt such a computation using one of the black-box computer programs available for perfonning ab initio calculations. 

This completes the black box estimates portion of the design program. As one can see, some very useful information can be determined by performing these estimates. 

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. 

As computer programs evolve they become easier to use. Modem programs often communicate with the user in terms of a graphical interface, and many methods have become essential black box procedures if you can draw the molecule, you can also do the calculation. This effectively means that you no longer have to be a highly trained theoretician to run even quite sophisticated calculations. 

The SCR catalyst is considerably more complex than, for example, the metal catalysts we discussed earlier. Also, it is very difficult to perform surface science studies on these oxide surfaces. The nature of the active sites in the SCR catalyst has been probed by temperature-programmed desorption of NO and NH3 and by in situ infrared studies. This has led to a set of kinetic parameters (Tab. 10.7) that can describe NO conversion and NH3 slip (Fig. 10.16). The model gives a good fit to the experimental data over a wide range, is based on the physical reality of the SCR catalyst and its interactions with the reacting gases and is, therefore, preferable to a simple power rate law in which catalysis happens in a black box . Nevertheless, several questions remain unanswered, such as what are the elementary steps and what do the active site looks like on the atomic scale ... 

As is the case for standard orthogonal-orbital MCSCF calculations, the optimization of VB wavefimctions can be a complicated task, and a program such as CASVB should therefore not be treated as a black box . This is true, to a greater or lesser extent, for most procedures that involve orbital optimization (and, hence, non-linear optimization problems), but these difficulties are compounded in valence bond theory by the... 

In the second stage the student uses the computational method in a transparent form to explore a more sophisticated chemical question. Because this is a course in computational methods - not computer programming, these programs are supplied, but are not black boxes. The students have the code before them as they use the programs. The chemical or physical problem posed in this stage should lead the student to a more complete understanding of some chemical phenomenon. 

The answer addresses one of the key modern engineering dilemmas, that of providing engineering judgment to evaluate calculations from black-box complex computer codes. Computer programs may provide a number that may not be a good model of physical reality. The simpler methods in this chapter are very valuable, first for intuitive understanding and second to provide both a first estimation and a check of more complex calculations. 

This testing involves running the program under known conditions with defined inputs, and documented outcomes that can be compared to predefined expectations. Functional testing is sometimes called black box testing. 

The operational qualification for standard instruments, microcontrollers, and smart instrumentation consists of a black box test. This type of test is based on the user s firm application requirement and challenges a program s external influences. It views the software as a black box concerned with program inputs and its corresponding outputs. The black box testing must consider not only the expected (normal) inputs, but also unexpected inputs. Black box testing is discussed in Chapter 9. 

---