Robust fundamentals

The models must be considered to be approximations. Therefore, the goals of robustness and uniqueness are rarely met. The nonlinear nature of the physical model, the interaction between the database and the parameters, the approximation of the unit fundamentals, the equipment boundaries, and the measurement uncertainties all contribute to the limitations in either of these models. 

On a different note, after some 50 years of intensive research on high-pressure shock compression, there are still many outstanding problems that cannot be solved. For example, it is not possible to predict ab initio the time scales of the shock-transition process or the thermophysical and mechanical properties of condensed media under shock compression. For the most part, these properties must presently be evaluated experimentally for incorporation into semiempirical theories. To realize the potential of truly predictive capabilities, it will be necessary to develop first-principles theories that have robust predictive capability. This will require critical examination of the fundamental postulates and assumptions used to interpret shock-compression processes. For example, it is usually assumed that a steady state is achieved immediately after the shock-transition process. However, due to the fact that... 

Inherently safer design is a fundamentally different way of thinking about the design of chemical processes and plants. It focuses on the elimination or reduction of the hazards, rather than on management and control. This approach should result in safer and more robust processes, and it is likely that these inherently safer processes will also be more economical in the long run (Kletz, 1984, 1991b). 

The question is often asked. How often should calibration be carried out Is it sufficient to do it once, or should it be repeated The answer to this question depends on the instrument type. A very simple instrument that is robust and stable may require calibrating only once during its lifetime. Some fundamental meters do not need calibration at all. A Pitot-static tube or a liquid U-tube manometer are examples of such simple instruments. On the other hand, complicated instruments with many components or sensitive components may need calibration at short intervals. Also fouling and wearing are reasons not only for maintenance but also calibration. Thus the proper calibration interval depends on the instrument itself and its use. The manufacturers recommendations as well as past experience are often the only guidelines. 

In industry, the emphasis is mainly on developing an active, selective, stable and mechanically robust catalyst. To accomplish this, tools are needed which identify those structural properties that discriminate efficient from less efficient catalysts. All information that helps to achieve this is welcome. Empirical relationships between those factors that govern catalyst composition (e.g. particle size and shape, and pore dimensions) and those that determine catalytic performance are extremely useful in catalyst development, although they do not always give fundamental insights into how the catalyst operates on the molecular level. 

There is little doubt on the basis of the above review that speleothems are useful in an extremely wide range of applications and the frequency of publications devoted to speleothem-based archives is increasing rapidly. Fundamental to all applications is a robust and high-precision chronology and uranium-series techniques currently set the standard in this regard for speleothems. Reliable ages can be obtained for most samples where material appears to be well-preserved. However, it will become increasingly important to demonstrate reliability as the spatial resolution of analysis improves further. 

One tool for working toward this objective is molecular mechanics. In this approach, the bonds in a molecule are treated as classical objects, with continuous interaction potentials (sometimes called force fields) that can be developed empirically or calculated by quantum theory. This is a powerful method that allows the application of predictive theory to much larger systems if sufficiently accurate and robust force fields can be developed. Predicting the structures of proteins and polymers is an important objective, but at present this often requires prohibitively large calculations. Molecular mechanics with classical interaction potentials has been the principal tool in the development of molecular models of polymer dynamics. The ability to model isolated polymer molecules (in dilute solution) is well developed, but fundamental molecular mechanics models of dense systems of entangled polymers remains an important goal. 

Fig. 12 An example of guanidinium-sulfonate superstructures. The fundamental interaction responsible for both robustness and flexibility is the charge-assisted (+)N-H---0( ) hydrogen bonding between the guanidinium cations and the sulfonate anions, which can be varied in shape and length [44]...

As recently recognized by the Nobel Chemistry award committee, the conceptualization, development, and commercial application of enantioselective, homogeneous hydrogenation of alkenes represents a landmark achievement in modem chemistry. Further elaboration of asymmetric hydrogenation catalysts by Noyori, Burk, and others has created a robust and technologically important set of catalytic asymmetric synthetic techniques. As frequently occurs in science, these new technologies have spawned new areas of fundamental research. Soon after the development of... 

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