Twin-range method

Table 7.1 presents us with something of a dilemma. We would obviously desire to explore i much of the phase space as possible but this may be compromised by the need for a sma time step. One possible approach is to use a multiple time step method. The underlyir rationale is that certain interactions evolve more rapidly with rime than other interaction The twin-range method (Section 6.7.1) is a crude type of multiple time step approach, i that interactions involving atoms between the lower and upper cutoff distance remai constant and change only when the neighbour list is updated. However, this approac can lead to an accumulation of numerical errors in calculated properties. A more soph sticated approach is to approximate the forces due to these atoms using a Taylor seri< expansion [Streett et al. 1978] ... 

Both twin studies and quantitative trait loci mapping methods have provided evidence for a significant genetic contribution to the risk of developing a substance dependence disorder. However, both of these lines of research have underscored the importance of environmental factors. A rich body of preclinical work has demonstrated that stress delivered at a wide range of time points in development can modulate proclivity towards drug self-administration. Evidence has suggested... 

For the coarse estimation of extruder size and screw speed, simple mass and energy balances based on a fixed output rate can be used. For the more detailed design of a twin-screw extruder configuration it is necessary to combine implicit experience knowledge with simulation techniques. Theses simulation techniques cover a broad range from specialized programs based on very simple models up to detailed Computational Fluid Dynamics (CFD) driven by Finite Element Analysis (FEA) or Boundary Element Method (BEM). 

Extrusion is a tradititmal process in plastics processing, (Mie that is characterized by a wide range of product types, continuous processes, and a high level of economy. Extrusion of hard PVC is a special case of this method, since processing of this material type usually requires a special extruder constraction, the so-called counterrotating twin-screw extruder. This type of extruder is characterized by a chamberlike conveyance mode and a narrow spectrum of residence times. 

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