Black Box Analyses

The time that a molecule spends in a reactive system will affect its probability of reacting and the measurement, interpretation, and modeling of residence time distributions are important aspects of chemical reaction engineering. Part of the inspiration for residence time theory came from the black box analysis techniques used by electrical engineers to study circuits. These are stimulus-response or input-output methods where a system is disturbed and its response to the disturbance is measured. The measured response, when properly interpreted, is used to predict the response of the system to other inputs. For residence time measurements, an inert tracer is injected at the inlet to the reactor, and the tracer concentration is measured at the outlet. The injection is carried out in a standardized way to allow easy interpretation of the results, which can then be used to make predictions. Predictions include the dynamic response of the system to arbitrary tracer inputs. More important, however, are the predictions of the steady-state yield of reactions in continuous-flow systems. All this can be done without opening the black box. 

Such relationship can be obtained using the approaches of rigorous modeling, order-of-magnitude analysis, or black box analysis as suggested by Wibowo and Ng [5], Examples of how SA relates to OV are given in Table 12. Note that due to the complex phenomena involved in these unit operations, shortcut empirical models that have some physical basis are often the most practical to describe the relationship. Unfortunately, such models are rarely available, making it difficult to quantify the relationship. For this reason, this part of the procedure is not emphasized in this article. 

For the five mixtures, the cumulative mesoporous volume, Feds, and mesoporous surface area, S edB, and are both linear decreasing functions of the micropore content y (Figure 2b). The cumulative specific surface area SedB is definitely a better estimator of the mesoporous surface than the specific surface S xt computed Ifom the t-plot. The lUPAC classification states that mesopores are pores whose width is larger that 2 nm. In the case of the cylindrical pore model retained for the pore size distribution, this is equivalent to radii larger than 1 nm. It should however be stressed that the calculation of the cumulative surface and volume of the mesopores must not be continued at lower pressures than the closing of the hysteresis loop (gray zones of Figures 3a and 3b). If a black box analysis tool is used and if the calculation is systematically continued down to 1 nm, severe overestimation of the mesopores surface and volume may occur. 

In this book, all the problems you ll solve will be "black-box" problems. This means that we take a look at a unit operation from the outside, looking at what goes into the system and what leaves, and extrapolating data about the properties of the entrance and exit streams from this. This type of analysis is important because it does not depend on the specific type of unit operation that is performed. When doing a black-box analysis, we don t care about how the unit operation is designed, only what the net result is. Let s look at an example ... 

Increased trust in pattern recognition The active user involvement in the data mining process can lead to a deeper understanding of the data and increases the trust in the resulting patterns. In contrast, "black box" systems often lead to a higher uncertainty, because the user usually does not know, in detail, what happened during the data analysis process. This may lead to a more difficult data interpretation and/or model prediction. 

Any formal models of the conduct of research work and success are often soft or fuzzy in nature, and so may be distrusted by those used to hard evidence. There is a particular distrust of opaque, black box solutions, and numerate managers rightly demand to see the detailed assumptions made in any decision analysis. The most controversial assumptions tend to be those about project future costs, chance of success, and potential value within drug... 

As we intend to apply discontinuous automatic analysis as a sensor in process regulation, we must now first consider the manufacturing process as a "black box also, and next discuss how the analytical sensor functions. 

While many aspects of data analysis are introduced, starting from very basic facts, the book is not primarily written for the beginner. Its main audience is expected to come from post-graduate students, research and industrial chemists with sufficient interest in data analysis to warrant the development of their own software rather than relying on other people s packages that all too often are rather black boxes. 

Errors in trace analyses are usually hidden to all except those intimately involved in the sample collection and, later, in the bench analysis. In chromatography, especially, it is too easy to hide behind uncertain work because published research does not concern itself with exactly how the chromatographer makes his quantitative decisions. Today, with the advent of the microprocessor and with the use of black box instruments, the chromatographer knows even less about his calibration graph or line, or the error associated with it. In these instruments, a single point and the origin may determine the calibration graph. Similar problems exist in other modern instrumental analysis techniques. 

Thorough analysis and evaluation of membrane morphology is mandatory for the understanding of transport phenomena in membranes, and es pecially for those with rather complex structures, as described in the present manuscript. Each single membrane can be viewed perhaps as a "black box" when operating in a certain well-defined system. Yet, any deduction on transport mechanism that is based solely on transport data is highly speculative. For example, the presence of a double skin, macrovoids, the densifica-tion of the nodular layer, and other items described herein cannot be predicted by the analysis of transport data. But they can be identified, and can be very supportive to "whoever dares to look into the black box."... 

The identification of putative mammalian clock genes by both homology and mutagenesis screening is described elsewhere in this volume. It represents an enormous achievement, and already it is possible to speak of the new circadian biology in which molecular genetics can be used to understand and re-interpret more classical, black-box descriptions of mammalian circadian behaviour. A key component of this analysis is to understand the behaviour of the clock genes, and... 

The importance of trace elements is manifold and. unfortunately, previously hampered by relatively insensitive analytical methods. Good methods for determining concentrations of I ppm or less have been available for relatively few dements yet these may be the optimum concentrations for a particular trace element. When the responses of living organisms are more sensitive than the laboratory black boxes," the chemist naturally develops an inferiority complex. Fortunately, the recent development of analytical techniques capable of determining parts per billion has opened new vistas for the study of these problems. Some of these techniques are atomic absorption, atomic fluorescence, activation analysis, and X-ray fluorescence. 

Factors may have associated values called levels of variations. Each state of a black box has a definite combination of factor levels. The more different states of the black box that exist, the more complex is the research subject. Formalization of preliminary information includes analysis of reference data, expert opinions and use of direct data, which enables correct selection of response, factors and null point or center of experiment. Factor limitations are also defined at this stage. If the research is linked with several following responses, then response limitations also have to be analyzed. The next phase refers to defining the research problem. When defining this problem one must keep in mind the research-subject model, and in a general case it is Eq. (2.1) that defines the link between the inlet and outlet of the black box. Defining the research problem is possible only now when its aim has been determined, the criteria established, the factors, limitations and null point defined. The problem is a simple one when only one response or optimization criterion is in... 

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