... Other work on the optimal con-trol of failure-prone manufacturing systems has been carried ou... more ... Other work on the optimal con-trol of failure-prone manufacturing systems has been carried out by Gershwin (1994), Sethi and Zhang (1994), Boukas and Yang (1996), Perkins and Srikant (1998) and the references therein. ...
In this note, we consider the empty vehicle redistribution problem in a two-depot service system ... more In this note, we consider the empty vehicle redistribution problem in a two-depot service system with random demands and uncertain transportation times. It is shown that the optimal stationary policy is of threshold control-type when the long-run average cost is to be minimized. The explicit form of the average cost under threshold controls is presented, which can be used to calculate the optimal threshold values. The sufficient and necessary conditions for the existence of the steady-state are provided. The results are then used to construct suboptimal policies for a more realistic model.
Transportation Research Part B: Methodological, 2015
ABSTRACT Service capacity planning is a key tactic decision in container shipping, which has a si... more ABSTRACT Service capacity planning is a key tactic decision in container shipping, which has a significant impact on daily operations of shipping company. On the other hand, operational decisions such as demand fulfilment and shipment routing will impact on service capacity requirements and utilisation, particularly in the presence of demand uncertainty. This article proposes a two stage stochastic programming model with recourse to deal with the problem of joint service capacity planning and dynamic container routing in liner shipping. The first stage of the model concerns how to determine the optimal service capacity, and the second focuses on the optimal routing of shipments in stochastic and dynamic environments under a given service capacity plan. Initially, SAA (Sample Average Approximation) is employed to solve the model. Noting the computational complexity of the problem, Progressive Hedging Algorithm (PHA) is employed to decompose the SAA model into a number of scenario-based models so that reasonably large scale problems can be solved. To handle larger scale problems, we develop a new solution procedure termed as APHA (Adapted Progressive Hedging Algorithm) that further decomposes the scenario-based model into job (customer order) based models with measurable error bounds. Numerical experiments are conducted to illustrate the effectiveness of the proposed APHA in solving the problems under consideration.
Container shipping companies face various risks from different sources. This paper aims to identi... more Container shipping companies face various risks from different sources. This paper aims to identify the appropriate mitigation strategies and evaluate the relative importance of these strategies. Through literature review and multiple interviews, a set of mitigation strategies are identified and confirmed. A questionnaire survey is conducted to obtain the rank of different risk mitigation strategies in terms of their overall effectiveness. A group of most effective mitigation strategies are then selected. To further evaluate the relative importance of the selected mitigation strategies with respect to different criteria, another round of questionnaire survey is conducted and the collected data are analysed using analytical hierarchy process (AHP) method. The AHP consists of three levels. The first level is the research goal, i.e. mitigating risks in shipping supply chain; the second level includes three criteria, i.e. reducing financial loss, reducing reputational loss, and reducing...
Safety and security has been an increasing concern in the maritime industry over the past few dec... more Safety and security has been an increasing concern in the maritime industry over the past few decades. With regard to container shipping, the relevant risk and management issues are further complicated by the international characteristics of the supply chain. In this paper, three major risk categories, namely, information risk, physical risk, and payment risk are categorised and analysed. The paper uses Taiwan as a case study aiming to provide some insight into the management of safety and security in a wider maritime contest. Both qualitative and quantitative research methods are employed in this paper. An interview survey is undertaken to explore and identify the risk factors in container shipping, and a questionnaire survey is then conducted to collect the relevant data. In order to conduct a comprehensive risk analysis, risk scale is calculated to rank the risk factors; and risk map is used as the main analytical method to identify the level of risks. It is found that with regar...
... Other work on the optimal con-trol of failure-prone manufacturing systems has been carried ou... more ... Other work on the optimal con-trol of failure-prone manufacturing systems has been carried out by Gershwin (1994), Sethi and Zhang (1994), Boukas and Yang (1996), Perkins and Srikant (1998) and the references therein. ...
In this note, we consider the empty vehicle redistribution problem in a two-depot service system ... more In this note, we consider the empty vehicle redistribution problem in a two-depot service system with random demands and uncertain transportation times. It is shown that the optimal stationary policy is of threshold control-type when the long-run average cost is to be minimized. The explicit form of the average cost under threshold controls is presented, which can be used to calculate the optimal threshold values. The sufficient and necessary conditions for the existence of the steady-state are provided. The results are then used to construct suboptimal policies for a more realistic model.
Transportation Research Part B: Methodological, 2015
ABSTRACT Service capacity planning is a key tactic decision in container shipping, which has a si... more ABSTRACT Service capacity planning is a key tactic decision in container shipping, which has a significant impact on daily operations of shipping company. On the other hand, operational decisions such as demand fulfilment and shipment routing will impact on service capacity requirements and utilisation, particularly in the presence of demand uncertainty. This article proposes a two stage stochastic programming model with recourse to deal with the problem of joint service capacity planning and dynamic container routing in liner shipping. The first stage of the model concerns how to determine the optimal service capacity, and the second focuses on the optimal routing of shipments in stochastic and dynamic environments under a given service capacity plan. Initially, SAA (Sample Average Approximation) is employed to solve the model. Noting the computational complexity of the problem, Progressive Hedging Algorithm (PHA) is employed to decompose the SAA model into a number of scenario-based models so that reasonably large scale problems can be solved. To handle larger scale problems, we develop a new solution procedure termed as APHA (Adapted Progressive Hedging Algorithm) that further decomposes the scenario-based model into job (customer order) based models with measurable error bounds. Numerical experiments are conducted to illustrate the effectiveness of the proposed APHA in solving the problems under consideration.
Container shipping companies face various risks from different sources. This paper aims to identi... more Container shipping companies face various risks from different sources. This paper aims to identify the appropriate mitigation strategies and evaluate the relative importance of these strategies. Through literature review and multiple interviews, a set of mitigation strategies are identified and confirmed. A questionnaire survey is conducted to obtain the rank of different risk mitigation strategies in terms of their overall effectiveness. A group of most effective mitigation strategies are then selected. To further evaluate the relative importance of the selected mitigation strategies with respect to different criteria, another round of questionnaire survey is conducted and the collected data are analysed using analytical hierarchy process (AHP) method. The AHP consists of three levels. The first level is the research goal, i.e. mitigating risks in shipping supply chain; the second level includes three criteria, i.e. reducing financial loss, reducing reputational loss, and reducing...
Safety and security has been an increasing concern in the maritime industry over the past few dec... more Safety and security has been an increasing concern in the maritime industry over the past few decades. With regard to container shipping, the relevant risk and management issues are further complicated by the international characteristics of the supply chain. In this paper, three major risk categories, namely, information risk, physical risk, and payment risk are categorised and analysed. The paper uses Taiwan as a case study aiming to provide some insight into the management of safety and security in a wider maritime contest. Both qualitative and quantitative research methods are employed in this paper. An interview survey is undertaken to explore and identify the risk factors in container shipping, and a questionnaire survey is then conducted to collect the relevant data. In order to conduct a comprehensive risk analysis, risk scale is calculated to rank the risk factors; and risk map is used as the main analytical method to identify the level of risks. It is found that with regar...
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Papers by Dong-Ping Song