Assembly processes variability

In addition to material variables, as reviewed in Chapter 6, there are a number of factors in equipment hardware and controls that cause processing variabilities. They include factors such as accuracy of machining component products, method and degree of accuracy during the assembly of component products, temperature and pressure control capability particularly when interrelated with time and heat transfer uniformity in metal components such as those used in molds and dies. 

For the mathematical models based on transport phenomena as well as for the stochastic mathematical models, we can introduce new grouping criteria. When the basic process variables (species conversion, species concentration, temperature, pressure and some non-process parameters) modify their values, with the time and spatial position inside their evolution space, the models that describe the process are recognized as models with distributed parameters. From a mathematical viewpoint, these models are represented by an assembly of relations which contain partial differential equations The models, in which the basic process variables evolve either with time or in one particular spatial direction, are called models with concentrated parameters. 

The process is under study by Othmer and associates at the Brooklyn Polytechnic Institute (29). Few experimental results are available at this time. Process variables have been studied with the aid of a digital computer and two laboratory units have been assembled a small five-stage unit to demonstrate the... 

An important distinction to be made is that instead of being induced by spontaneous evaporation of solvent, the movement of the contact line will be controlled by the motion of the lower substrate, resulting in a programmable stick-slip motion in FESA. Therefore, ordered patterns (e.g., thin films, snipes and spokes) can be readily produced in a controllable manner. Notably, the transition between the different patterns may be observed by gradually tuning each variable individually (e.g., velocity of lower substrate). The influence of each variable on the evaporative self-assembly process can also be scrutinized separately. 

The term macromolecular architecture has been coined to subsume the realm of polymer stmctures that can be obtained using modem synthetic polymer chemistry. In addition to the control over the bulk properties that results from tunability of the various parameters outlined in Figure 1, each aspert also provides for variability in the individual macromolecular shapes and guidance in their multimolecular assembly processes to lead to well-defined discrete objects of nanoscopic dimensions. 

Gaining control of the crystallization of a particular isomer remains challenging at present. Both thermodynamic and kinetic factors play a role (Figure 2), and understanding the full energy profile of a self-assembly process is extremely difficult. Some workers have instead attempted to identify and control pivotal individual variables within... 

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