Trial-and-error methodology

In this review I hope to emphasise the importance of such studies in the development of working sensors. It is possible to construct sensors in an empirical fashion ie. by trial and error methodology, selecting different electrode materials, membranes, electrolytes etc. This approach has been described as haphazard and inadequate [5]. In particular it does not give information about possible routes to improving stability, response range and response time of the device. As will be shown this kind of investigation may lead to analytical methods that would not be likely to arise from empirical studies. 

For a binary system, all of the above problems reduce to two equations that must be solved for two unknowns. However, the nonlinear character of the equations and the discontinuous character of the isotherms require a trial-and-error methodology. We outline below an iterative method for the solution of the bubble P problem. The calculation is streamlined by introducing the K -factors defined in Chapter 8. 

Fig. 4.6). The standard way of improving a potential is to make the fitting to a set of ab initio points or perhaps to data such as vibrational frequencies, which are easily calculated from the potential. Then this quess is used in a dynamical calculation and, for instance, the barrier is modified to bring agreement with experimental data on sticking probabilities. However, the direct dynamical fitting may be feasible instead of this trial-and-error methodology. Certainly this would be the case if the dissociative sticking probability was calculated by transition state theory or any other simple dynamical method which would allow a fast and reliable calculation of it.

Procedures used vary from trial-and-error methods to more sophisticated approaches including the window diagram, the simplex method, the PRISMA method, chemometric method, or computer-assisted methods. Many of these procedures were originally developed for HPLC and were apphed to TLC with appropriate changes in methodology. In the majority of the procedures, a set of solvents is selected as components of the mobile phase and one of the mentioned procedures is then used to optimize their relative proportions. Chemometric methods make possible to choose the minimum number of chromatographic systems needed to perform the best separation. 

Consider that the odor perception by human nose is correlated with the odor value, OVj, in the headspace above the liquid. If a specific OVt distribution values is wanted, the perfume composition can be determined with the help of Equation (2). This methodology can facilitate the optimization of perfume compositions, reducing in this way some trial and error time and chemical wastes. Clearly, the problem is determined by structural decisions because the perfume composition depends on the interaction of the different perfume components. 

Several methods have been proposed to guide the solvent replacement process for the many applications described in the chemical literature. These efforts attempt to build an organized framework for this process and provide a substantial improvement over previously ad hoc or trial-and-error approaches to solvent replacement. Joback outlines a methodology for the selection of replacement solvents for various processes such as extraction or cleaning (Joback, 1994). There are basically four steps to this process identify constraints on important solvent properties, compile data for all properties, rank solvents satisfying the target constraints, and evaluate top solvent candidates using simulation. 

The other source on which our work draws is the heuristic research methodology. Heuristic programming involves trial and error procedures rather than algorithms, and has become more practical with the advent ot real-time interaction. The only condition for the practice... 

Nowadays, most experimentation on tablet formulation development is still performed by changing the levels of each variable (factor) at a time, in an unsystematic way, keeping all other variables constant in order to study the effects of that specific variable on the selected response or to find the optimal conditions of a complete system. This methodology (trial and error) is based on a large number of experiments and often relies merely on the analyst s experience [31]. 

It could be argued that drug discovery strategies of the past were analogous to fishing with a line and hook. A systematic series of trial and error experiments such as quantitative structure-activity relationship (QSAR) methodologies, for example, were commonplace. The process was iterative and labor intensive. A chemist or biologist had relatively few restrictions, particularly with time, to explore ideas and test hypotheses. The overall endeavor was more craft than process. 

The selection of solvents and solvent blends for use in coatings and inks is based upon solubility/viscosity characteristics and application/performance properties. Published solubility parameters and hydrogen bonding indexes are used to construct two-dimensional solubility maps. Methodology is described, and illustrations are shown. Data are provided on evaporation times of neat solvents, viscosities and dry times of polymer solutions, electrostatic characteristics of solvents, and on selected solvent blend recommendations for several polymers. Unpublished test methods for flow testing and for substrate testing are provided. Combination of the results from these areas provides a viable method for practical solvent blend selection this approach is faster than random trial-and-error and can result in superior, formulated solvent blends. 

Direct methods replaced trial and error and other methods of deducing model structures in the middle of the 20th century. In these techniques, statistical relationships between the amplitudes and phases of the strong reflections were established, and the mathematical methodology between these quantities was worked out, particularly by Hauptmann and Karle, in the 1940 s and 1950 s. (The Nobel Prize was awarded to these scientists in 1985 for these studies.) A number of algorithms, which exploited the growing power of electronic computers, used this mathematical framework to derive structures directly from the experimental data set of position, intensity and hkl index. The use of these programs allows the structures of molecular compounds with up to 100 or so atoms to be... 

A definite methodology to find the Attainable Region for given fundamental processes is not available. A trial and error procedure is necessary. However, the AR technique is supported by a powerful test procedure. The candidate region must respect the following necessary conditions, as demonstrated by the works of Glasser, Hildebrand (1997) ... 

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