Optimization of N, N, N-trimethylchitosan synthesis by factorial design

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Factorial design analysis was applied to optimize the synthesis, via a new route, of N, N, N-trimethylchitosan, based on dimethylsulfate as a methylating agent. The responses analyzed were weight yield, solubility and average degree of quaternization. Temperature was verified as the most important variable, as it caused the most variation in the response. X(T) = -54.52,-9.50 and -7.25, respectively, for weight yield, solubility and degree of quaternization. A sharp decrease in the viscosimetric and gel permeation chromatography parameters proved that severe depolymerization took place at high reaction temperatures. Contact angle measurements showed a decrease in the hydrophilic character of over-methylated samples. (C) 2011 Society of Chemical Industry606SI910915EMBRAPAFundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Dynamic Vehicle Routing and Dispatching

: Dynamic vehicle routing and dispatching refers to a wide range of problems where information on the problem is revealed to the decision maker concurrently with the determination of the solution. These problems have recently emerged as an active area of research due to recent technological advances that allow real-time information to be quickly obtained and processed. There are probably as many variants of these problems as there are real-world applications. After a brief overview of this broad domain, the paper will then focus on problems motivated by courier services and demand responsive transportation systems. These systems typically evolve within a local service area over a relatively short period of time (typically, a few hours), thus putting stringent response time requirements on the decision maker. They are also characterized by a strong routing component: many tasks can be allocated at once to the same vehicle and these tasks must be appropriately sequenced. The ..