In this paper we propose a 4-index formulation for the uncapacitated multiple allocation hub location problem tailored for urban transport and liner shipping network design. This formulation is very tight and most of the tractable instances for MIP solvers are optimally solvable at the root node. While the existing state-of-the-art MIP solvers fail to solve even small size instances of problem, our accelerated and efficient primal (Benders) decomposition solves larger ones. In addition, a very efficient greedy heuristic, proven to be capable of obtaining high quality solutions, is proposed. We also introduce fixed cost values for Australian Post (AP) dataset. 相似文献
This paper is concerned with model development for a short-term fleet deployment problem of liner shipping operations. We first present a mixed integer nonlinear programming model in which the optimal vessel speeds for different vessel types on different routes are interpreted as their realistic optimal travel times. We then linearize the proposed nonlinear model and obtain a mixed integer linear programming (MILP) model that can be efficiently solved by a standard mixed integer programming solver such as CPLEX. The MILP model determines the optimal route service frequency pattern and take into account the time window constraints of shipping services. Finally, we report our numerical results and performance of CPLEX on randomly generated instances. 相似文献
The aim of this paper is to propose a comprehensive framework for simultaneously measuring the performance of sustainable service and manufacturing supply chain management. Application of the proposed approach also results in reduced uncertainty of the performance measurement process caused by qualitative criteria evaluation. The proposed approach consists of two main steps. First, the fuzzy decision‐making trial and evaluation laboratory (DEMATEL) method has been used to determine important criteria by avoiding low influences; and then a Mamdani fuzzy inference system model has been adopted and applied for performance evaluation of sustainable supply chain management (SSCM). This model is employed in order to cope with the vagueness that exists in the SSCM performance investigation due to the vagueness intrinsic in the evaluation of criteria. In the proposed model, human reasoning has been modelled with fuzzy inference rules and has been set in the system, which is an advantage compared with those models in which fuzzy set theory and multicriteria decision‐making models are integrated. The proposed approach has been implemented in the pipe and fitting industry in order to highlight its application in real life. Sensitivity analysis has been carried out to determine the influence of service and manufacturing criteria on SSCM performance. The findings reveal that sustainable manufacturing criteria compared with sustainable service criteria have more effect on the performance of SSCM. 相似文献
A mixed integer programming formulation is proposed for hub-and-spoke network design in a competitive environment. It addresses the competition between a newcomer liner service provider and an existing dominating operator, both operating on hub-and-spoke networks. The newcomer company maximizes its market share—which depends on the service time and transportation cost—by locating a predefined number of hubs at candidate ports and designing its network. While general-purpose solvers do not solve instances of even small size, an accelerated Lagrangian method combined with a primal heuristic obtains promising bounds. Our computational experiments on real instances of practical size indicate superiority of our approach. 相似文献
A mixed integer linear programming formulation is proposed for the simultaneous design of network and fleet deployment of a deep-sea liner service provider. The underlying network design problem is based on a 4-index (5-index by considering capacity type) formulation of the hub location problem which are known for their tightness. The demand is elastic in the sense that the service provider can accept any fraction of the origin–destination demand. We then propose a primal decomposition method to solve instances of the problem to optimality. Numerical results confirm superiority of our approach in comparison with a general-purpose mixed integer programming solver. 相似文献
Despite dedicated effort and research in the last two decades, the entrepreneurship field is still limited by little evidence-based knowledge of the impacts of entrepreneurship programs on the entrepreneurial intention of students in pre-university levels of study. Further, gender equity continues to be an issue in the entrepreneurial sector, particularly in STEM-focused entrepreneurship. In this context, this study was designed to explore the effects of a one-day female-focused STEM-based entrepreneurship program (for brevity, we call it the OzGirlsEntrepreneurship program) on the entrepreneurial intention of secondary school female students. The study collected data from two surveys completed by 193 secondary school female students, aged 14–16 years, who participated in the OzGirlsEntrepreneurship program. This program encouraged girls to develop and implement creative computational solutions to socially relevant problems, with an Internet of Things (IoT) component using the micro:bit device. The findings reveal that a key factor in the development of entrepreneurial attitudes in young female students is associated with soft-skills development, particularly in the areas of creative thinking, risk-taking, problem-solving, and leadership development. The importance of meaningful human connections, including positive role modelling and peer to peer learning were also important factors in fostering entrepreneurial intent. With these factors in mind, our findings highlight that the OzGirlsEntrepreneurship program substantially increased the entrepreneurial intention of secondary school female students. In addition, this study offers actionable implications and recommendations to develop and deliver entrepreneurship education programs for secondary school level students.
The application of economic methodology to the problem of terrorism is discussed. Theoretical and empirical results are discussed
with particular focus on the September 11 attack and the retaliatory response by the United States. Economists have relied
on the rational agent model to derive testable hypotheses regarding the behavior of terrorists. The rational agent model postulates
that terrorists respond to incentives, including media publicity, and the model predicts that when the net marginal benefit
from one type of terrorist activity is diminished, terrorists will substitute into alternative modes of terrorism. Empirical
results demonstrating that such substitutions indeed occur are discussed. Therefore, policy designed to reduce a particular
form of terrorism, such as increased airport security to prevent airplane hijackings, may simply result in terrorists choosing
alternative modes of terrorism. Empirical evidence demonstrating that terrorism is cyclical in nature is also discussed. Evidence
on substitution and cycles suggests that following temporary reduction in terrorist activity after retaliation against terrorists
and their infrastructure, terrorists are able to successfully regroup and attack using alternative means. Therefore, the current
US focus on fighting terrorism on all fronts and over the long haul is the correct approach. 相似文献
The extant literature has studied the effects of a firm’s service recovery efforts on the reactions of customers and employees following an individual service failure. However, the impact of recovery efforts on a firm’s performance after a public and large service failure—such as a large-scale information breach—has received scant attention. To address this gap, this current research develops a framework and finds support for the impact of service crisis recoveries on a firm’s performance, as measured by firm-idiosyncratic risk. Using a unique dataset of service crisis recoveries, the authors find that firms offering compensation (i.e., tangible redresses) or process improvement (i.e., improvements in organizational processes) show more stable performance (less idiosyncratic risk), from two quarters to two calendar years after the announcement of their recovery plan. In line with the documented dual effect of apologies, firms that offer apology-based recoveries display more volatile performance (higher idiosyncratic risk). Of note, this volatility increases with the number of affected individuals, and it remains unaffected even when the apology is expressed with high intensity. 相似文献