We define events so as to reduce the number of events and decision variables needed for modeling batch-scheduling problems such as described in [15]. We propose a new MILP formulation based on this concept, defining non-uniform time periods as needed and decision variables that are not time-indexed. It can handle complicated multi-product/multi-stage machine processes, with production lines merging and diverging, and with minimum and maximum batch sizes. We compare it with earlier models and show that it can solve problems with small to medium demands relative to batch sizes in reasonable computer times. 相似文献
Rapid global industrialization has worsened the heavy metal contamination of aquatic ecosystems globally. In this study, green, ultrafine cellulose-based porous nanofibrous membranes for efficient heavy metal removal were obtained by incorporating chitosan (CS) and using conventional and core–shell electrospinning ways. The relationship between the parameters of the electrospinning solution, the micro-morphology and porosity, the chemically active sites, the thermal stability, and the adsorption performance of the biocomposite nanofibrous membranes were analyzed. The adsorption effects of the copper ions, including the initial concentration, solution pH, and interaction time, were investigated. The results show that the average diameters of the conventional and core–shell ultrafine nanofibers with 50% and 30% CS loading are 56.22 nm and 37.28 nm, respectively. The core–shell cellulose acetate (CA)/CS biocomposite nanofibrous membranes showed the weaker thermal stability with a 48.2 °C lower maximum thermal decomposition temperature and induced the surface aggregation of more copper ions compared to the conventional one. A more uniform distribution of the chemical adsorption sites is obtained by conventional single-nozzle electrospinning than by core–shell electrospinning, which effectively promotes the adsorption performance of copper ions and decreases the surface shrinkage of the nanofibrous membranes during adsorption. The 30% CS conventional nanofibrous membranes at an aqueous solution pH of 5 showed the optimum adsorption capacity of copper ions (86.4 mg/g). The smart combination of renewable biomass with effective chemical adsorption sites, electrospinning technology that produces an interwoven porous structure, and an adsorption method with low cost and facile operation shows a promising prospect for water treatment.
A number of theorems of alternant hydrocarbons presented by Dewar are proved to be wrong. A statement of the related theorem instead of Dewar's is presented. 相似文献
Natural fibers in micro and nano scales may be a potential alternative for man-made fibers because of the comparable mechanical
properties to those of glass, carbon, and aramid fibers. Cellulose fibril and fibril aggregate are generally prepared by physical
treatments, e.g., high-pressure homogenizer, or chemical treatments, e.g., acid hydrolysis. In this study, fibril aggregates
were generated from a regenerated cellulose fiber by a novel mechanical treatment. The geometrical characteristics of the
fibers and the fibril aggregates were investigated using scanning electron microscopy (SEM) and polarized light microscopy
(PLM), and its crystallinity was investigated by wide angle X-ray diffraction (WAXD). The degree of fibrillation of the fibers
was indirectly evaluated by water retention value (WRV). Nano-biocomposites reinforced with fibril aggregates were prepared
by film casting and compression molding and evaluated by tensile test. The morphological characteristics of the nanocomposites
were investigated with SEM and PLM. As reference, commercial microfibrillated cellulose was also used to reinforce biodegradable
polymer. 相似文献