Trial-and-error approach

Some of the inherent advantages of the feedback control strategy are as follows regardless of the source or nature of the disturbance, the manipulated variable(s) adjusts to correct for the deviation from the setpoint when the deviation is detected the proper values of the manipulated variables are continually sought to balance the system by a trial-and-error approach no mathematical model of the process is required and the most often used feedback control algorithm (some form of proportional—integral—derivative control) is both robust and versatile. 

There is more emphasis on a systematic rather than a trial-and-error approach, particularly on systematic methods of identifying hazards and of estimating the probabihty that they will occur, and their consequences. 

X, is determined from Eq. (26-70) using a trial-and-error approach. The effective distance downwind for subsequent calculations using Eq. (26-63) is determined from x + x,J. 

If utilities are supplied to the new project from some other source, the cost and amount must be determined. If purchased from a second party, the cost will be determined by contract and can be estimated by discussions with the vendor. If utilities are transferred from an affiliated source, the cost must include a profit to the supplying entity. Some estimators use a lower return on utility plants than on a new hydrocarbon processing unit, since the utility can be used for some alternate plant if the new one shuts down for any reason. However, the preferred analysis allows a high enough utility transfer price to provide the same return on the utilities as the new unit being studied. This can require a trial and error approach, especially if the utilities are a significant part of the selling price of the product. 

The foregoing design questions are highly combinatorial so any exhaustive enumeration tedmique would be hopelessly complicated. A hit-and-miss or trial-and-error approach to conjecturing the solution is likely to fail because it cannot consider the overwhelming number of decisions to be made. Hence, the designer... 

These relations do not hold closely for large impeller cuts, as the head and capacity drop a litde faster than the relations indicate. Allowance should be made by a trial-and-error approach when actually reducing an impeller size. Efficiency will remain nearly constant during all of the changes discussed. 

The prediction of burning-rate characteristics, on the other hand, has not been possible. This has caused rocket designers to adopt a trial-and-error approach to the development of specific propellants to meet specific mission requirements. In an effort to reduce the large development effort required for each new propulsion system, considerable basic research effort has been directed toward the definition and quantitative characterization of propellant combustion mechanisms. The ultimate objective of this effort is to provide methods for predicting the burning-rate characteristics of particular propellant formulations. 

However, mostly because of the intuitive, trial-and-error approach of thin-layer chromatographers, long ago the technique split into two subtechniques, one bene-fiting from the hnear range of the adsorption isotherm and the other udlizing the... 

It is the main aim of semiempirical chromatographic models to couple the empirical parameters of retention with the established thermodynamic quantities generally used in physical chemistry. The validity of a model for chromatographic practice can hardly be overestimated, because it often and successfully helps to overcome the old trial-and-error approach to running the analyses, especially when incorporated in the separation selectivity oriented optimization strategy. 

Even listing all above problems and requirements leading to their solution indicates that development of the method of semiconductor chemical sensors opens a wide research domain. In order to resolve this problems and implement all capabilities of the method of semiconductor sensors there are two ways now the old trial and error approach and approach related to further studies of physical and chemical properties of surface phenomena, reactions and processes underlying this method. It is quite clear that the second approach is more promising in order to obtain semiconductor sensors designed for the use in accurate scientific studies and for practical gas analysis. 

The trial and error approach to optinizing a separation using serially connected columns can be Very time consuming. 

An important difference between the statistical mixture design techniques popular in HPLC and the PRISMA model is that the former yields a computed optimum solvent composition id>ile the latter relies on a structured trial and error approach, which is readily adaptable to TLC. Solvent changes and re-equilibration in HPLC can be quite time consuming, so that it becomes attractive to ainimize the number of experiments, while for TLC, experiments can be performed in parallel and time constraints are less significant. Changes in solvent strength are also more rapidly adjusted empirically within the PRISMA model when theoretical considerations are found inadequate or require modification due to differences in the experimental approach. 

The task of embarking on method development for a new polymer/additive sample can be intimidating due to the number of parameters that can be varied during an extraction. Because cook-book methods are unavailable for most analyte-matrix pairs, analysts may feel they are condemned to use a trial-and-error approach to optimise extraction-collection conditions for SFE. However, a flow sheet considering the most important parameters in the SFE process is available [3]. There are several approaches to... 

In actual practice, it is common to keep the transformation factors constant throughout the analysts. Engineering judgment is used to select the appropriate factors, depending on the predominant response mode anticipated. A trial and error approach may be used to evaluate the response mode behavior. An average of the clastic and plastic transformation factors is sometimes used. 

Unlike most static design procedures, dynamic design requires a trial and error approach. Only in the verification of shear capacities and in the design of support connections can member proportions be directly determined. For the dynamic analysis, the needed nonlinear response properties are determined from a trial section. The analysis results then indicate the adequacy of the trial section. Experience on the part of the designer will help in reducing the number of iterations. The use of simple computer based design approaches help to reduce the time required for each analysis iteration. 

Experiment-based trial and error - This approach is used when mathematical models for the estimation of the desired (target) properties are not available. A large number of consumer products are developed through experiment-based trial and error approaches. In this case, the desired properties need to be measured and consequently, not many candidate molecules can be considered. A list of candidate molecules may however be supplied by an expert or generated from past knowledge and/or experience. A database of chemicals may also be used to generate a list of candidates. 

The different adsorption and desorption events are controlled via the flow rates adjusted by the means of 3 or 5 external pumps and the column switch times, Fig. 3. The key element for success is the proper selection of the respective flow rates, which must be chosen in such a way that the extract front between zones I and II and the raffinate front between zones III and IV are stabilized, while the separation between zones II and III is assured. A simple trial-and-error approach to such an optimization of the system parameters is unlikely to be successful. Instead, the chromatographic behavior of all compounds has to be modeled and simulated. 

More than 100 CSPs are commercially available nowadays, which should make the separation of any pair of enantiomers feasible. However, the enantiorecognition mechanisms involved in the chiral recognition between the analytes and the CSPs are complex and therefore the selection of the appropriate CSPs, depending on the structure of the analyte, is a difficult task. A common approach to develop a new enantioseparation is the stepwise trial-and-error approach based on detailed consideration of the enantiorecognition mechanisms between the chiral selector and the analyte, or on the analyst s experience, or on the consultation of literature or databases. However, this approach is time-consuming and often unsuccessful owing to the fact that achieving enantioresolution is often purely empirical... 

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