69 research outputs found
Combined quay crane assignment and quay crane scheduling with crane inter-vessel movement and non-interference constraints
Integrated models of the quay crane assignment problem (QCAP) and the quay crane scheduling problem (QCSP) exist. However, they have shortcomings in that some do not allow movement of quay cranes between vessels, others do not take into account precedence relationships between tasks, and yet others do not avoid interference between quay cranes. Here, an integrated and comprehensive optimization model that combines the two distinct QCAP and QCSP problems which deals with the issues raised is put forward. The model is of the mixed-integer programming type with the objective being to minimize the difference between tardiness cost and earliness income based on finishing time and requested departure time for a vessel. Because of the extent of the model and the potential for even small problems to lead to large instances, exact methods can be prohibitive in computational time. For this reason an adapted genetic algorithm (GA) is implemented to cope with this computational burden. Experimental results obtained with branch-and-cut as implemented in CPLEX and GA for small to large-scale problem instances are presented. The paper also includes a review of the relevant literature
Adjunctive cenobamate in people with focal onset seizures: Insights from the Italian Expanded Access Program
Objective: This study was undertaken to assess the effectiveness/tolerability of adjunctive cenobamate, variations in the load of concomitant antiseizure medications (ASMs) and predictors of clinical response in people with focal epilepsy. Methods: This was a retrospective study at 21 centers participating in the Italian Expanded Access Program. Effectiveness outcomes included retention and responder rates (>= 50% and 100% reduction in baseline seizure frequency). Tolerability/safety outcomes included the rate of treatment discontinuation due to adverse events (AEs) and their incidence. Total drug load was quantified as the number of concomitant ASMs and total defined daily dose (DDD). Concomitant ASMs were also classified according to their mechanism of action and pharmacokinetic interactions to perform explorative subgroup analyses. Results: A total of 236 subjects with a median age of 38 (Q(1)-Q(3) = 27-49) years were included. At 12 months, cenobamate retention rate was 78.8% and responders were 57.5%. The seizure freedom rates during the preceding 3 months were 9.8%, 12.2%, 16.3%, and 14.0% at 3, 6, 9, and 12 months. A higher percentage of responders was observed among subjects treated with clobazam, although the difference was not statistically significant. A total of 223 AEs were recorded in 133 of 236 participants, leading to cenobamate discontinuation in 8.5% cases. At 12 months, a reduction of one or two concomitant ASMs occurred in 42.6% and 4.3% of the subjects. The median total DDD of all concomitant ASMs decreased from 3.34 (Q(1)-Q(3) = 2.50-4.47) at baseline to 2.50 (Q(1)-Q(3) = 1.67-3.50) at 12 months (p < .001, median percentage reduction = 22.2%). The highest rates of cotreatment withdrawal and reductions in the DDD were observed for sodium channel blockers and gamma-aminobutyric acidergic modulators (above all for those linked to pharmacokinetic interactions), and perampanel. Significance: Adjunctive cenobamate was associated with a reduction in seizure frequency and in the burden of concomitant ASMs in adults with difficult-to-treat focal epilepsy. The type of ASM associated did not influence effectiveness except for a favorable trend with clobazam
An evolutionary approach to a combined mixed integer programming model of seaside operations as arise in container ports
This paper puts forward an integrated optimisation model that combines three distinct problems, namely berth allocation, quay crane assignment, and quay crane scheduling that arise in container ports. Each one of these problems is difficult to solve in its own right. However, solving them individually leads almost surely to sub-optimal solutions. Hence, it is desirable to solve them in a combined form. The model is of the mixed-integer programming type with the objective being to minimize the tardiness of vessels and reduce the cost of berthing. Experimental results show that relatively small instances of the proposed model can be solved exactly using CPLEX. Large scale instances, however, can only be solved in reasonable times using heuristics. Here, an implementation of the genetic algorithm is considered. The effectiveness of this implementation is tested against CPLEX on small to medium size instances of the combined model. Larger size instances were also solved with the genetic algorithm, showing that this approach is capable of finding the optimal or near optimal solutions in realistic times
Business Networks in Clusters and Industrial Districts. The governance of the global Value chain
During the 1980s the Marshallian concept of industrial district (ID) became widely
popular due to the resurgence of interest in the reasons that make the agglomeration
of specialized industries a territorial phenomenon worth being analyzed. The
analysis of clusters and IDs has often been limited, considering only the local
dimension of the created business networks. The external links of these systems
have been systematically under-evaluated.
This book offers a deep insight into the evolution of these systems and the
internal-external mechanism of knowledge circulation and learning. This means
that the access to external knowledge (information or R&D cooperative research)
or to productive networks (global supply chains) is studied in order to describe
how external knowledge is absorbed and how local clusters or districts become
global systems. It provides a unified approach: showing that existing capabilities
expand when locally embedded knowledge is combined with accessible external
knowledge. In this view, external knowledge linkages reduce the danger of cognitive
\u2018lock-in\u2019 and \u2018 over-embeddedness\u2019, which may become important obstacles to
local learning and innovation when technological trajectories and global economic
conditions chang
Evolution and relocation in fashion- led industrial districts: evidence from two case studies
The aim of this paper is to contribute to the debate about how, in advanced countries, industrial
districts specialised in traditional manufacturing industries evolve as a consequence of new
challenges linked to the globalization process. Using a multiple case study design, the study
examines the evolution of two fashion-led Italian districts: the Montebelluna sportswear system
and the Vibrata-Tordino-Vomano clothing district. Our findings reveal that cluster firms\u2019
ability to shift from manufacturing to other activities providing higher returns along the global
value chain is key to understanding the effect of globalization and relocation processes on the
cluster\u2019s long-term competitiveness. As illustrated in this study, weak learning districts are the
most threatened while innovative districts are able to enact a selective process of relocation,
substituting outplaced activities with more valuable ones and attracting inward investments.
Keywords: industrial districts; evolution; relocation; global value chains
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