Compaction simulator applications

Yang, L. Venkatesh, G. Fassihi, R. Characterization of compactibility and compressibility of poly(ethylene oxide) polymers for modified release application by compaction simulator. J. Pharm. Sci. 1985, 85, 1085-1090. 

Asgharnejad, M. Storey, D. Application of a compaction simulator to the design of a high-dose tablet formulation. Part I. Drug Dev. Ind. Pharm. 1996, 22 (9 10), 967-975. 

This chapter will provide an overview of compaction simulator theory, construction, experimental design, and applications for the practicing pharmaceutical scientist. 

It must be concluded that the quantitative determination of micropore size is still an ambiguous problem new theories, models, mechanisms and simulations are still under study [56-58]. Therefore isotherm interpretations must be used carefully and can be considered as useful mainly for qualitative studies. No reliable method has been developed for the determination of the micropore size distribution. At present the most promising approach appears to be that of pre-adsorption linked with the use of various probe molecules of known size and shape [59-61]. For example, this approach has been applied successfully for silica compacts characterisation in [61] using spherical symmetrical inert molecules, such as neopentane and trimethylsiloxysilane [(CH3)3SiO]4Si with diameters of 6.5 and 11.5 A respectively. In general the limited availability of volatile probe molecules with diameters extending above 10 A puts a restriction on the applicability of this method. Furthermore effective pore sizes determined by this technique depend on the kinetic and thermodynamic properties of the... 

The multiple-stream heat exchanger unit, often called LNG, is used to simulate heat transfer between multiple hot or cold streams (Fig. 3.11-left). Typical applications are the simulation of compact heat exchangers as the plate-type heat exchanger used extensively in gas processing. The simulation of this unit includes the automatic generation of multiple interconnected heaters, as illustrated in Fig. 3.11-right. 

The applicability of continuum theories, such as the Poisson-Boltzmann model, in nanoscale is the most concerned issue in this field yet. Numerous conflicting results were reported in literature. We have done careful MD simulations of EOF and compared the ion distributions with the PB predictions rigorously to clarify the applicability of the continuum theory. To compare the descriptions from two different scales, above all, the observers have to be stand on the same base to avoid definition gaps. First, when presenting the MD results, the bin size should not be smaller than the solvent molecular diameter in comparison with the continuum theory otherwise, the MD results are not the macroscopic properties at the same level of the continuum. A second gap which departs the MD results from the PB predictions is the effect of the Stem layer. As well known, the PB equation describes only the ion distribution in diffusion (outer) layer of the electric double layer (EDL) [1]. In the continuum theory, the compact (iimer) layer of EDL is too thin (molecular scale) to be considered, and therefore, the PB equation almost governs the ion distribution in the whole domain. However, in nanofluidics the iimer layer which is also termed as Stem layer is comparable to the channel in size. The PB equation is not able to govern the ion behavior in the Stem layer in theory. Therefore, if one compares the MD... 

Die compaction of agglomerates has been simulated in a computer sphere model by Thornton et When the particles are in a liquid paste, the liquid is usually expelled through pores in the mold, and the partieles form a filter cake. The mechanism by which this occurs has been modeled by Woodcock et The application of forces to powder beds, sometimes immersed in liquids, is the subject of soil mechanics. " This considers particles to interact via Coulomb s law, Equation (11.16), but also takes into account the hydrodynamic forces acting on the individual particles. Unfortunately, as we have seen. Coulomb s law is not correct for particles which experience molecular adhesion, so the friction coefficients found in soil mechanics theories seem to vary. Friction seems to increase as the particles get smaller because smaller particles adhere more strongly. Soil mechanics is therefore a difficult science. 

---