Concepts Comparison

Which organization supports more efficient retrieval in terms of number of concept comparisons No absolute conclusion can be... 

Metal deposition in hydrotreating of heavy oils is one of the most important phenomenon causing catalyst deactivation. Present work focuses on the modeling of hydrodemetallisation catalyst deactivation by model compound vanadyl-tetraphenylporphyrin. Intrinsic reaction kinetics, restrictive diffusion and the changing catalyst porous texture are the relevant phenomena to describe this deactivation process. The changing catalyst porous texture during metal depositon can be described successfully by percolation concepts. Comparison of simulated and experimental metal deposition profiles in catalyst pellets show qualitative agreement. 

The Spirit is the viewing, cognizant and the judging principle. Its activity consists of the formation of concepts, comparisons and conclusions. It is the principle of the consciousness, the reflection and the apperception, as well as the recollection. 

Established consistent performance criteria and assumptions (e.g., material properties) for concept comparisons... 

Recommended Concept Description Alternate Concepts Comparison Criteria... 

Core Energy 15 full power years is a simplifying assumption used for initial concept comparisons. It approximates to 10 years total thrust (full power) time and 10 years reduced power < 50% power) fora 20 year mission. Based on JPL Document 982-00115, Revision 2, Prometheus Project Multi-mission Project Derived Requirements , dated July 15.2005. 

There are certain limitations to the usefulness of nitration in aqueous sulphuric acid. Because of the behaviour of the rate profile for benzene, comparisons should strictly be made below 68% sulphuric acid ( 2.5 fig. 2.5) rates relative to benzene vary in the range 68-80% sulphuric acid, and at the higher end of this range are not entirely measures of relative reactivity. For deactivated compounds this limitation is not very important, but for activated compounds it is linked with a fundamental limit to the significance of the concept of aromatic reactivity as already discussed ( 2.5), nitration in sulphuric acid cannot differentiate amongst compounds not less than about 38 times more reactive than benzene. At this point differentiation disappears because reactions occur at the encounter rate. 

HyperChem quantum mechanical calculations are ab initio and semi-empirical. Ab initio calculations use parameters (contracted basis functions) associated with shells, such as an s shell, sp shell, etc., or atomic numbers (atoms). Semi-empirical calculations use parameters associated with specific atomic numbers. The concept of atom types is not used in the conventional quantum mechanics methods. Semi-empirical quantum mechanics methods use a rigorous quantum mechanical formulation combined with the use of empirical parameters obtained from comparison with experiment. If parameters are available for the atoms of a given molecule, the ab initio and semi-empirical calculations have an a priori aspect when compared with a molecular mechanics calculation, letting... 

Another concept sometimes used as a basis for comparison and correlation of mass transfer data in columns is the Clulton-Colbum analogy (35). This semi-empirical relationship was developed for correlating mass- and heat-transfer data in pipes and is based on the turbulent boundary layer model... 

Styrene manufacture by dehydrogenation of ethylbenzene is simple ia concept and has the virtue of beiag a siagle-product technology, an important consideration for a product of such enormous volume. This route is used for nearly 90% of the worldwide styrene production. The rest is obtained from the coproduction of propylene oxide (PO) and styrene (SM). The PO—SM route is complex and capital-iatensive ia comparison to dehydrogenation of ethylbenzene, but it stiU can be very attractive. However, its use is limited by the mismatch between the demands for styrene and propylene oxides (qv). 

The symmetry of the preceding example is not always found in practice. For example, there may be six tire types under comparison and fifteen available automobiles. Tires are then assigned to automobiles to obtain the most precise comparison among tire types, using a so-called incomplete block design. Similar concepts apply if there are two or more primary variables, rather than tire type alone. 

An acceptable reconciliation of inherent flaw and fracture energy concepts has not been achieved and provides an area of current study. The two theoretical concepts will be discussed, and several applications in fragment-size prediction will be described. We will make comparisons between the two fragmentation approaches and attempt to identify some conditions which determine when one or the other method applies. 

Comparison of Inherent Flaws and Energy Concepts in Dynamic Fragmentation... 

Having made the comparison with experiment one may then make an assessment as to whether the simulation agrees sufficiently well to be useful in interpreting the experiment in detail. In cases where the agreement is not good, the detennination of the cause of the discrepancy is often instructive. The errors may arise from the simulation model or from the assumptions used in the experimental data reduction or both. In cases where the quantities examined agree, the simulation can be decomposed so as to isolate the principal components responsible for the observed intensities. Sometimes, then, the dynamics involved can be described by a simplified concept derived from the simulation. 

This entire book is about the emergence, nature and cultivation of a new discipline, materials science and engineering. To draw together the strings of this story, it helps to be clear about what a scientific discipline actually is that, in turn, becomes clearer if one looks at the emergence of some earlier disciplines which have had more time to reach a condition of maturity. Comparisons can help in definition we can narrow a vague concept by examining what apparently diverse examples have in common. 

The significance of the concept incorporated in Hammond s postulate is that, in appropriate cases, it permits discussion of transition-state structure in terms of the reactants, inteimediates, or products in a multistep reaction sequence. The postulate indicates that the cases in which such comparison is appropriate are those in which the transition state is close in energy to the reactant, intermediate, or product. Chemists sometimes speak of early or late transition states. An early transition state is reactant-like whereas a late transition state is product-like. 

Common types of membrane materials used are listed in Table 3. This gets us into the concept of geometry. There are three types of modules generally used, namely Tubular, Spiral wound, and Hollow fiber. A comparison of the various geometries is given in Table 4. 

The contiguity factor, Cj is actually a so-called fudge factor used to make sense out of the comparison of experimental dataTwitlirtheore-tical predictions. This correlation factor is useful only when the data fall between the theoretical bounds. The concept of a contiguity factor, i.e.. 

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