Multi-scale structures

To meet the industrial demand for both large-scale computation and good predictability, the reasonable way out is not to simulate from the beginning of the micro-scale, but to use coarse-grid simulation with meso-scale modeling for the effects of structure. This kind of approach can be termed the "multi-scale CFD." It is entitled "multi-scale," not because the problem it solves is multi-scale, but because its meso-scale model contains multi-scale structure parameters. 

Many polymer blends or block polymer melts separate microscopically into complex meso-scale structures. It is a challenge to predict the multiscale structure of polymer systems including phase diagram, morphology evolution of micro-phase separation, density and composition profiles, and molecular conformations in the interfacial region between different phases. The formation mechanism of micro-phase structures for polymer blends or block copolymers essentially roots in a delicate balance between entropic and enthalpic contributions to the Helmholtz energy. Therefore, it is the key to establish a molecular thermodynamic model of the Helmholtz energy considered for those complex meso-scale structures. In this paper, we introduced a theoretical method based on a lattice model developed in this laboratory to study the multi-scale structure of polymer systems. First, a molecular thermodynamic model for uniform polymer system is presented. This model can... 

Gradually we have come to recognize that understanding of the spatio-temporal multi-scale structures in various chemical processes is essential for upgrading our ability. In fact, as much as we know about macro-scale chemical processing, e.g., radial and axial profiles, and what happens at micro-scales, e.g., chemical reaction and even molecular structures, we really know little about what happens at the meso-scale in between. That is, meso-scale is the key to understanding multi-scale structures. This is the bottleneck ... 

Stimulated by this recognition, multi-scale analysis and simulation have received unprecedented attention in recent years, as shown by the dramatic increase in related publications. However, measurement technology focused on multi-scale structures, particularly, on meso-scale phenomena, has not been sufficiently tackled. Without breakthroughs in this aspect, theories and simulations could not be verified and validated, and upgrading the knowledge base for chemical engineering would be futile. 

We hope the publication of this issue would stimulate the application of these measurement techniques in chemical engineering and further our understanding of multi-scale structures. I thank Prof. Guy B. Marin, the editor-in-chief of this book series, for his advice in selecting the present topic and, Prof. Zhuyou Cao and Dr. Jiayuan Zhang, for their contributions made in editing this issue. Thanks are also extended to reviewers and authors for their efforts and time. 

Chinga-Carrasco, G. Syverud, K. Computer-assisted quantification of the multi-scale structure of films made of nanofibrillated cellulose. J. Nanopart. Res. 2010, 12 (3), 841-851. 

The successes enjoyed by nanosciences in many fields [2-10] have resulted in a need for adequate theory and large-scale numerical simulations in order to understand what the various roles are played by surface effects, edge effects, or bulk effects in nanomaterials. The dynamics of colloidal particle transport calls not only for passive transport, but also for additional processes such as agglomeration/dispersion, driven interfaces, adsorption to pore wall grains, and biofihn interactions [4,11-14]. In many cases, there is a dire need to investigate these multi-scale structures, ranging from nanometers to micrometers in complex geometries, such as in vascular and porous systems [4,15-17]. 

For all of these reasons, the structured multi-scale chemical devices envisioned here offer the perspective of significant innovation through the use of microfabrication in the chemical process industries. To illustrate these possibilities, the following sections demonstrate how multi-scale structuring can provide a new degree of freedom for process intensification/miniaturization and contribute to the satisfaction of criteria for sustainability. In conclusion, a critical comparison of scale-up, numbering-up and multi-scale design is proposed. 

Multi-scale Structuring for Sustainable Intensification/Miniaturization... 

In order to quantify the interest of these multi-scale structures with respect to process intensification, the equation that describes the gain in sustainability of the system must also include both aspects of process intensification ... 

Rigacci A, Ehrburger-Dolle F, Geissler E, ChevaUer B, Sallee H, Achard P, Barbieri O, Berthon S, Bley F, Livet F, Pajonk GM, Pinto N, Rochas C (2001), Investigation of the multi-scale structure of silica aerogels by SAXS. J. Non-Cryst Solids 285 187-193... 

Fig. 6.1 Sketch of typical MFC multi-scale structure at micrometer (left) and nanometer scale right). Processing direction is vertical. SEM can probe polyamide microfibrils dark rods) embedded in a fibriilated HOPE matrix [13,15]. SAXS monitors mainly the semi-crystaUine nanostructure of the HOPE matrix. CrystaUine domains are frequently arranged in processing direction forming nanofibrils (in the conceptual notion of microfibrils [16]). One nanofibril is highlighted in gray...

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