Black-box approach

Therefore we increasingly take the view that rather than fully simulating the business context, which may seem like a black box approach, it is better to have decision makers interact with more selective simulations. These help develop their intuitions and hone their judgment and reasoning ability in focused areas, especially in the area of probability, applied statistics, and decision theory, which is nonintuitive without such practice. 

In spite of all the simplifications Bakker and Van den Akker applied and given the black box approach for the impeller swept domain, their simulations resulted in values for the bubble size just below the liquid surface, overall holdup, and average kfl values which are in good agreement with their experimental data (see Table II). The major step forward they made was the acquisition of the different spatial distributions of average bubble size (see Fig. 13), bubble holdup and kfl as effected by three common impeller types. As a matter of fact, their approach may be restricted to low values of the gas hold-up. 

Black-and-white photography, fixation in, 19 213 Blackbody color of, 7 327 emittance from, 19 131-132 spectral radiance of, 24 453 Blackbody radiation law, 24 452 Blackbody responsivity, 19 132 Blackbody temperature sensor, 11 149-150 Black-box approach, to reliability modeling, 26 987-988, 990 Black copper, 16 144 Black crappie, common and scientific names, 3 187t... 

A black box approach as the endpoint of the analysis raw materials and products, overall process-relevant data (e.g., yields, reactor conditions), and boundary conditions are given, leading to a first evaluation of the overall process economics are based on raw materials and products. 

The scales involved in such a reactor should be defined in a relative manner. For a chemist, the molecule is at the start and catalyst (particle) at the end of the scales. To reveal the reaction mechanism over a catalyst particle, a sequence of network of elementary reactions" will be needed. Accordingly, on the basis of, for example, the molecular collision theory (Turns, 2000), the "global reaction" can be derived in terms of global rate coefficient and reaction order. Here, the resultant reaction mechanism is termed "global" by chemists, because the use of it for a specific problem is normally a "black box" approach, without knowing exactly the underlying networks or structures of chemical routes from reactants to products. On the other hand, for a chemical reaction engineer, the catalyst (particle) is often the start and the reactor is the end. The reaction free of inner-particle and outer-particle diffusions, that is,... 

Stochastic modeling is used when a measurable output is available but the inputs or causes are unknown or cannot be described in a simple fashion. The black-box approach is used. The model is determined from past input and output data. An example is the description of incomplete mixing in a stirred tank reactor, which is done in terms of contributions of dead zones and short circuiting. In these cases, a sequence of output called a time series is known, but the inputs or causes are numerous and not known in addition, they may be unobservable. Though the causes for the response of the system are unknown, the development of a model is important to gain understanding of the process, which may be used for future planning. 

In many cases, the black box approach to anchoring of catalysts has been followed A support and a metal compound are simply brought together, and it is hoped that the association between metal and support is persistent even under drastic oxidation conditions. However, this approach frequently leads to failure. It is preferable first to have a clear idea of all the chemical states of the catalyst that must be retained by the support. Thus, knowledge of the full catalytic cycle and of all metal species in the system is needed. Only then can a mechanism for catalyst immobilization be proposed. Although this is a demanding approach, it may often be the only one that is rewarding. 

Maintaining a balance between theory and practice is difficult. We have avoided the arcane areas of electrons and quantum mechanics, but the alternative black-box approach is not acceptable. We avoided these extremes with a pictorial, non-mathematical approach presented in some detail. Diagrams abound and excellent spectra are presented at every opportunity since interpretations remain the goal. 

Quite frequently, and especially in research problems arising in chemistry and chemistry-related areas, an important type of factor variables is encountered, and these are called mixture variables. Apart from the usual properties that are common to all factors considered in the black box approach (see Figure 8.1), mixture... 

Procedure B has been developed and proposed by Fraunhofer IW (Franz et al. 1994) without incorporating model contaminants. It is a black-box approach which monitors inherently present recycling-related substances and is applicable to a ready-to-use food contact article. In this way, the procedure meets not only the R D and quality assurance requirements of the manufacturer but also offers a test possibility for enforcement labs. Essentially, procedure B consists of two experimental key steps ... 

Most of the published results on photammonification were obtained via a black box approach, i.e. without detailed inquiry of underlying mechanisms. The few exceptions are papers by Wang et al. (2000) and Tarr et al. (2001). These authors proposed chemical reactions behind photoammonification (Fig. 10.3), which include a ketone as a photosensitizer. 

It is apparent that the mapping of chambers is necessary to obtain repeatable results. Calibration of the sample area to be used is a good approach once one can be assured that, the radiation reaching that area is of the right qualitative and quantitative requirements. The use of the "black box" approach, which only dwells on numbers, should be avoided if one wishes to adopt the scientific approach. 

Fig. ]. Black Box Approach to project operational evaluation and risk assessment...

Flow in baffled stirred reactors has been modeled by employing several different approaches which can be classified into four types, and are shown schematically in Fig. 10.3. Most flow simulations of stirred vessels published before 1995 were based on steady-state analyses (reviewed by Ranade, 1995) using the black box approach. This approach requires boundary conditions (mean velocity and turbulence characteristics) on the impeller swept surface, which need to be determined experimentally. Although this approach is reasonably successful in predicting the flow characteristics in the bulk of the vessel, its usefulness is inherently limited by the availability of data. Extension of such an approach to multiphase flows and to industrial-scale reactors is not feasible because it is virtually impossible to obtain (from experiments) accurate... 

FIGURE 10.3 Approaches to modeling flow in stirred reactors, (a) Black box approach, (b) sliding mesh approach, (c) multiple reference frame or inner-outer approach, (d) snapshot approach. 

Another example of a seal with an often unpredictable continuity is one formed by diagenetic alteration of fault rocks. Should an area be characterized by such unpredictable processes, it must be risked high, and one can only resort to an empirical black box approach to fault seal analysis. 

There are several alternatives for the mapping of predefined partial workflow processes into dynamic task nets. On the one hand, the whole workflow process can be represented as a single task in the dynamic task net. Its activation reflects the start of the workflow instance within the workflow management system, while the termination of this task reflects the termination of the work-flow instance. In this case, the fine-grained activity structure of the workflow process is hidden black-box approach). This simple form of integration is sufficient in many situations, but because of the encapsulation it is impossible to monitor the progress of the activities in the workflow process within AHEAD. 

There are two distinct classes of analytic approximation that comprise the second and third approaches that were just mentioned. The first is based on the use of so-called macroscopic balances. In this approach, we do not attempt to obtain detailed information about the velocity and pressure fields everywhere in the domain, but only to obtain results that are consistent with the Navier Stokes equations in an overall (or macroscopic) sense. For example, we might seek results for the volumetric flow rates in and out of a flow system that are consistent with an overall mass or momentum conservation balance but not attempt to determine the detailed form of the velocity profiles. The macroscopic balance approach is described in detail in many undergraduate textbooks.2 It is often extremely useful for derivation of quantitative relationships among the average inflows, outflows, and forces (or rates of working) within a flow system but is something of a black-box approach that provides no detailed information on the velocity, pressure, and stress distributions within the flow domain. 

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