Hypotheses, engineering

This result is in contradiction to the second law, hence we conclude that the hypothesis entertained is inadmissible, so that [/3] is an impossible engine, which establishes the proposition. 

The experimental evidences that medium engineering might represent an efficient method to modify or improve enzyme selectivity (alternative to protein engineering and to the time-consuming search for new catalysts) were immediately matched by the search for a sound rationale of this phenomenon. The different hypotheses formulated to try to rationalize the effects of the solvent on enzymatic enantioselectivity can be grouped into three different classes. The first hypothesis suggests that... 

In an attempt to identify new, biocompatible diphenols for the synthesis of polyiminocarbonates and polycarbonates, we considered derivatives of tyrosine dipeptide as potential monomers. Our experimental rationale was based on the assumption that a diphenol derived from natural amino acids may be less toxic than many of the industrial diphenols. After protection of the amino and carboxylic acid groups, we expected the dipeptide to be chemically equivalent to conventional diphenols. In preliminary studies (14) this hypothesis was confirmed by the successful preparation of poly(Z-Tyr-Tyr-Et iminocarbonate) from the protected tyrosine dipeptide Z-Tyr-Tyr-Et (Figure 3). Unfortunately, poly (Z-Tyr-Tyr-Et iminocarbonate) was an insoluble, nonprocessible material for which no practical applications could be identified. This result illustrated the difficulty of balancing the requirement for biocompatibility with the need to obtain a material with suitable "engineering" properties. 

The Reynolds-averaged approach is widely used for engineering calculations, and typically includes models such as Spalart-Allmaras, k-e and its variants, k-co, and the Reynolds stress model (RSM). The Boussinesq hypothesis, which assumes pt to be an isotropic scalar quantity, is used in the Spalart-Allmaras model, the k-s models, and the k-co models. The advantage of this approach is the relatively low computational cost associated with the computation of the turbulent viscosity, fit. For the Spalart-Allmaras model, one additional transport equation representing turbulent viscosity is solved. In the case of the k-e and k-co models, two additional transport equations for the turbulence kinetic energy, k, and either the turbulence dissipation rate, s, or the specific dissipation rate, co, are solved, and pt is computed as a function of k and either e or co. Alternatively, in the RSM approach, transport equations can be solved for each of the terms in the Reynolds stress tensor. An additional scale-determining equation (usually for s) is also required. This means that seven additional transport equations must be solved in 3D flows. 

As a result, the limited ability of unit processes to create a viable niche for themselves within chemical engineering must ultimately be understood in terms which also involve unit operations. Although the historical resilience of unit processes turned out to be less than that of unit operations, it was no different in its essential elements. Studying the uneasy and ultimately unsuccessful career of unit processes can therefore be easily justified as a way to shed light on the far more successful career of unit operations. In particular, the career of unit processes raises a hypothesis about the evolution of unit operations. The staying power of unit operations was not so much because of the structural coherence of its conceptual elements as its essential links with social and, more specifically, professional groups. As a theoretical entity, unit operations appears far less stable and, in fact, appears quickly threatened by notions which rest on fewer and more fundamental scientific concepts. Ultimately, this threat came to be realized with the advent of transport phenomena, but this is another story. In effect, unit processes can be interpreted as both the attempt to extend the reach of unit operations and a symptom of their conceptual fragility. 

SpinPro is a typical backward chaining, rule-based expert system. Rule-based systems are systems in which the expert s knowledge is encoded primarily in the form of if-then rules, i.e., if a set of conditions are found to be true then draw a conclusion or perform an action. "Backward chaining" refers to the procedure for finding a solution to a problem. In a backward chaining system, the inference engine works backwards from a hypothesized solution to find facts that support the hypothesis. Alternative hypotheses are tried until one is found that is supported by the facts. 

Results of analysis of formic acid in diesel engine exhaust subjected to various forms of post-combustion control, i.e., catalytic oxidation and water conditioning, indicate both a reduction of formic acid due to oxidation in the catalyst and dissolution in the water scrubber. In-mine analysis of formic acid at increasing distances from a source of diesel exhaust indicates that no significant change in concentration occurs. This finding contradicts a hypothesis that formaldehyde concentration decreases with increasing distance due to gas phase oxidation to formic acid. Surface reactions may, however, be important sinks for formaldehyde. 

K rm n (K3) and Prandtl (P7) indicated analogies between momentum and thermal transport and placed the matter before the engineering profession. Using Karm n s original analysis (Kl) Deissler (D2) indicated that on the basis of the similarity hypothesis the eddy viscosity may be evaluated for steady, uniform flow in the following way ... 

All the data we will report here confirm the potential of the material as a broad-range extraction medium. In order to build interest, however, we will have to provide engineers with more infonnation than our anecdotal studies can provide. The cited studies lend credibility to our hypothesis. As stated, only large field trials will ultimately confirm our hypothesis, but current studies provide sufficient reasons for optimism. 

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