Of course, the main research challenges and difficulties in materials selection stem from the requirement of reversibility and efficiency in both discharge and charge processes.
Bulk particulate solids subjected to compression and shearing may experience attrition and segregation of the debris which can cause amongst others dust hazards, difficulty in material handling and 'off-specification' products.
The difficulties lie in material conversion efficiency, module design, and thermal system management.
This is mainly due to difficulties in identifying material properties and vehicle characteristics.
As a result of various difficulties in accessing material for the period prior to 1995, more cases were selected during the 1980 1994 period.
Despite the fundamental role MPs play in vivo, their structural and functional characterization is hampered by their insolubility in aqueous solution, aggregation propensity, and difficulties in obtaining material in adequate quantities and of sufficient purity for analysis.
A nonderivative statistical genetic algorithm is developed which can handle difficulties in designing materials with random particulate microstructure due to objective function nonconvexity and lack of objective function regularity.
This seems to be related to difficulties in accessing materials, finances and insufficient high school preparation.
Shortages of cement, and tin-sheet, and difficulties in getting materials through military check-points, have held back construction.
However, due to the broad variability in field productivity and the difficulty in predicting material demands by field activities, it is more challenging to achieve efficiency in supply chain management in the construction industry than in the manufacturing industry (Dubois and Gadde 2002; Tommelein et al. 2003).
