The Engineering Approach

The engineering approach. The design engineer requires the ability to predict behaviour exactly for a proposed situation in terms of as few initial experiments as possible. Empirical relations that describe the performance are adequate, and these need not have any physical significance. 

There is a limited coverage of this field by textbooks. A theoretical survey, using sophisticated mathematical methods, is given in the text by Lockett [1], and the contrasting approach of the practical engineer is typified in the work of Turner [2]. Ferry s textbook [3] covers both theoretical and practical aspects of polymer viscoelasticity. The more recent work of Lakes [4] covers some aspects of non-linearity. 

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The design of a control system is a job of considerable magnitude and a general understanding of the engineering approach is necessary to prevent underestimation of the work to be done. 

This book is intended primarily for students in the various fields of engineering but it is felt that students in other disciplines will welcome and benefit from the engineering approach. Since the book has been written as a general introduction to the quantitative aspects of the properties and processing of plastics, the depth of coverage is not as great as may be found in other texts on the physics, chemistry and stress analysis of viscoelastic materials, this has been done deliberately because it is felt that once the material described here has been studied and understood the reader will be in a better position to decide if he requires the more detailed viscoelastic analysis provided by the advanced texts. 

There are nine rules of thumb tluit represent tlie basic design elements of a pollution control system. The engineering approach suggests tliat each clement be evaluated independently and as part of the whole control system. 

This paper deals mainly with the condensation of trace concentrations of radioactive vapor onto spherical particles of a substrate. For this situation the relation between the engineering approach, the molecular approach, and the fluid-dynamic approach are illustrated for several different cases of rate limitation. From these considerations criteria are derived for the use of basic physical and chemical parameters to predict the rate-controlling step or steps. Finally, the effect of changing temperature is considered and the groundwork is thereby laid for a kinetic approach to predicting fallout formation. The relation of these approaches to the escape of fission products from reactor fuel and to the deposition of radon and thoron daughters on dust particles in a uranium mine is indicated. 

There are central embracing characteristics for the engineering approach deployed during the development of the following basic plant concepts. Examples are presented of plants with a uniform appearance, standardized pitch dimensions, interfaces, etc., either as closed systems or as open systems with interfaces to other suppliers. This strategy is completely different from the hybrid plant concepts. 

MIT President Richard C. MacLaurin could not resolve the dispute between Noyes and Walker with a compromise finally, forced to choose between the two, the Institute backed Walker s concept of stressing the engineering approach based on a systematic analysis of real industrial problems. Noyes resigned in 1919, later founding the modern California Institute of Technology with George Hale and Robert Millikan, both eminent scientists. As the only trustee of both institutions, I can still discern today the influence of these divergent views. 

The engineering approach to the mass-transfer suggests full analogy between heat and mass-transfer when making use of dimensionless hydrodynamic and transport criteria. For our problems, and with the numerical subscripts to indicate the appropriate standard components of our chemical systems, we have ... 

Here km is the mass transfer coefficient and D stays either for D p or /) n. Notice that the engineering approach does not propose individual formulae for different geometric cross sections of the channels. Instead, the non-cylindrical channels are characterized by an effective diameter. For rectangular channels it is 2hi-lbw/(hh + bw), which approaches 2bh for wide channels of small height. 

Below, we shall be interested in the formulae for penetration of channels and for deposition profiles in the case of laminar and turbulent steady flow regimes, and at various initial situations at the inlet of the channel — whether the flow is diffusion-ally and/or hydrodynamically developed. The engineering approach is not rigorous various authors proposed different formulae which, nevertheless, yield reasonably consistent results. The author made a deliberate choice from the alternate formulae. 

Fig. 3.6 Top Density profile of an irreversibly adsorbed species deposited from laminar flow in circular tubes. The reduced distance is z = tf/°z = Jt Dz/Q Analytical solution for hydrody-namically developed flow is given by Eqs. 2.47 (near inlet) and 2.44 - corresponding parts of the curve are divided by the thick mark the engineering approach is Eq. 2.59 with Sh from Eq. 2.54. In the case of hydrodynamicafly developing flow, i// taken from Eq. 2.61 was substituted into Eq. 2.59.

If you reread the above, keeping in mind what was said about the architectural and engineering approaches in the section on detail design, you will realize that the negatives of the general contractor approach are minimized if the project lends itself to the architectural approach, and are maximized on a project that needs the engineering approach. 

The engineers approach is more obviously appropriate in the case of accidental releases (especially if they are major releases), the biologists relates better to incidental continuing or frequent exposure(s). 

The engineering approach is different. Engineers generally try to conceptualize first and fit facts within this established framework. Engineering is thus deductive. 

With the practical approach, most plastics are required to withstand only short-term static mechanical loads—that is, no dynamic loads. Thus, conventional short-term static tests generally suffice. The engineering approach recognizes that many plastic products have been used since their inception to take long-term dynamic or static loads. Thus, they consider fatigue, torsion, creep, and other data that include plastic s viscoelastic properties. See kiss plastic processing. 

Despite present predictions for the number of diesel-powered cars in Europe to increase markedly, discussions on the engineering approach to the control of automobiel emissions have centered on the gasoline motor. Cylinder wall temperature, air-fuel ratios, exhaust gas catalysts, and lead traps were presented and discussed as remedies. Blended fuel, for instance gasohol or synthetic fuels, were not considered because they are used on a local basis or during transient, difficult conditions. The contribution of lubricating oil in PAH emissions exists but was not considered an important issue, and was not discussed in the meeting. 

Selection of licensing basis events (LBEs) is based on the probabilistic risk assessment (PRA) performed as part of the Integrated Approach and constitutes the process which establishes the bridge between the engineering approach and the licensing basis for the Standard MHTGR. The use of the PRA for LBE selection provides a basis for judging, in a quantitative manner, the frequency of the entire event sequence and, therefore, the appropriate dose or risk criteria to be applied. 

Figure 2 Examples of microalgae cultivation systems. Each system has been designed for a specific purpose and was scaled using on the engineering approach described in the text.

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