An integrated shipment planning and storage capacity decision under uncertainty: a simulation study

Purpose – In transportation and distribution systems, the shipment decisions, fleet capacity, and storage capacity are interrelated in a complex way, especially when the authors take into account uncertainty of the demand rate and shipment lead time. While shipment planning is tactical or operational in nature, increasing storage capacity often requires top management’s authority. The purpose of this paper is to present a new method to integrate both operational and strategic decision parameters, namely shipment planning and storage capacity decision under uncertainty. The ultimate goal is to provide a near optimal solution that leads to a striking balance between the total logistics costs and product availability, critical in maritime logistics of bulk shipment of commodity items. Design/methodology/approach – The authors use simulation as research method. The authors develop a simulation model to investigate the effects of various factors on costs and service levels of a distribution system. The model mimics the transportation and distribution problems of bulk cement in a major cement company in Indonesia consisting of a silo at the port of origin, two silos at two ports of destination, and a number of ships that transport the bulk cement. The authors develop a number of “what-if” scenarios by varying the storage capacity at the port of origin as well as at the ports of destinations, number of ships operated, operating hours of ports, and dispatching rules for the ships. Each scenario is evaluated in terms of costs and service level. A full factorial experiment has been conducted and analysis of variance has been used to analyze the results. Findings – The results suggest that the number of ships deployed, silo capacity, working hours of ports, and the dispatching rules of ships significantly affect both total costs and service level. Interestingly, operating fewer ships enables the company to achieve almost the same service level and gaining substantial cost savings if constraints in other part of the system are alleviated, i.e., storage capacities and working hours of ports are extended. Practical implications – Cost is a competitive factor for bulk items like cement, and thus the proposed scenarios could be implemented by the company to substantially reduce the transportation and distribution costs. Alleviating storage capacity constraint is obviously an idea that needs to be considered when optimizing shipment planning alone could not give significant improvements. Originality/value – Existing research has so far focussed on the optimization of shipment planning/scheduling, and considers shipment planning/scheduling as the objective function while treating the storage capacity as constraints. The simulation model enables “what-if” analyses to be performed and has overcome the difficulties and impracticalities of analytical methods especially when the system incorporates stochastic variables exhibited in the case example. The use of efficient frontier analysis for analyzing the simulation results is a novel idea which has been proven to be effective in screening non-dominated solutions. This has provided the authors with near optimal solutions to trade-off logistics costs and service levels (availability), with minimal experimentation times

Evaluating the Location Efficiency of Arabian and African Seaports Using Data Envelopment Analysis (DEA)

In this paper the efficiency and performance is evaluated for 22 seaports in the region of East Africa and the Middle East. The aim of our study is to compare seaports situated on the maritime trade road between the East and the West. These are considered as middledistance ports at which goods from Europe and Far East/Australia can be exchanged and transhipped to all countries in the Middle East and East Africa. All these seaports are regional coasters, and dhow trade was built on these locations, leading this part of the world to become an important trade centre. Data was collected for 6 years (2000-2005) and a non-parametric linear programming method, DEA (Data Envelopment Analysis) is applied. The ultimate goal of our study is: 1) to estimate the performance levels of the ports under consideration. This will help in proposing solutions for better performance and developing future plans. 2) to select optimum transhipment locations.Middle East and East African Seaports; Data Envelopment Analysis; Seaports Efficiency; Performance measurement of Containers Ports; transshipment.

How to Auction an Essential Facility When Underhand Integration is Possible

There are many industries in which potentially competitive segments require services provided by natural monopoly bottlenecks (essential facilities). Since it is difficult to regulate these facilities, developing countries are using Demsetz auctions, where the facility is awarded to the firm that bids the lowest user fee. In this paper we show that when underhand agreements between the monopoly bottleneck and downstream firms are possible, Demsetz auctions need floors on bids, since otherwise welfare can be lower than with an unregulated monopoly. We model an underhand agreement using a standard hidden information model. The essential facility is an uninformed principal randomly matched to a downstream company, which observes its costs after closing the underhand agreement. When the essential facility prefers the option of vertical separation, there is downstream competition, which implies that only low cost firms survive. We find that a sufficiently high floor on bids promotes vertical separation, yielding higher welfare than either an unregulated or a vertically integrated monopoly. Moreover, prohibiting open vertical integration means this floor can be lower, thus enhancing welfare. The incentive compatibility constraints required by underhand agreements imply rent sharing and production distortions that make vertical integration less attractive.

Sequence-Based Simulation-Optimization Framework With Application to Port Operations at Multimodal Container Terminals

It is evident in previous works that operations research and mathematical algorithms can provide optimal or near-optimal solutions, whereas simulation models can aid in predicting and studying the behavior of systems over time and monitor performance under stochastic and uncertain circumstances. Given the intensive computational effort that simulation optimization methods impose, especially for large and complex systems like container terminals, a favorable approach is to reduce the search space to decrease the amount of computation. A maritime port can consist of multiple terminals with specific functionalities and specialized equipment. A container terminal is one of several facilities in a port that involves numerous resources and entities. It is also where containers are stored and transported, making the container terminal a complex system. Problems such as berth allocation, quay and yard crane scheduling and assignment, storage yard layout configuration, container re-handling, customs and security, and risk analysis become particularly challenging. Discrete-event simulation (DES) models are typically developed for complex and stochastic systems such as container terminals to study their behavior under different scenarios and circumstances. Simulation-optimization methods have emerged as an approach to find optimal values for input variables that maximize certain output metric(s) of the simulation. Various traditional and nontraditional approaches of simulation-optimization continue to be used to aid in decision making. In this dissertation, a novel framework for simulation-optimization is developed, implemented, and validated to study the influence of using a sequence (ordering) of decision variables (resource levels) for simulation-based optimization in resource allocation problems. This approach aims to reduce the computational effort of optimizing large simulations by breaking the simulation-optimization problem into stages. Since container terminals are complex stochastic systems consisting of different areas with detailed and critical functions that may affect the output, a platform that accurately simulates such a system can be of significant analytical benefit. To implement and validate the developed framework, a large-scale complex container terminal discrete-event simulation model was developed and validated based on a real system and then used as a testing platform for various hypothesized algorithms studied in this work

How to Auction an Essential Facility When Underhand Integration Is Possible

Regulating seaports is difficult in general, even more so for the weak regulatory institutions common in developing countries. For this reason some countries have awarded these facilities via Demsetz auctions, to the port operator that bids the lowest cargo-handling fee. A major concern with Demsetz auctions in this context, is that the winning operator may integrate with a shipper and monopolize the shipping market, by worsening the service quality for competing shippers. The standard policy recommendation against service quality discrimination is to ban the seaport from operating in the shipping market. The effectiveness of such prohibitions is suspect, however, because they can be circumvented by an (illegal) underhand agreement between the port operator and the shipper. In this paper we show that a ban on integration increases welfare if it is combined with a (sufficiently high) floor on the cargo-handling fee that operators can bid in the auction. In the absence of such a floor, however, a Demsetz auction is worse than no regulation at all of the bottleneck monopoly. Our results apply beyond the port and shipping markets, to any essential facility that can monopolize a downstream market. The results only require that profits with underhand vertical integration agreements be less than with legal vertical integration.Auctions, ex ante vs. ex post rents, Demsetz auctions, hidden action, monopoly regulation, productive efficiency, vertical integration

How to Auction an Essential Facility When Underhand Integration is Possible

Regulating seaports is difficult in general, even more so for the weak regulatory institutions common in developing countries. For this reason some countries have awarded these facilities via Demsetz auctions, to the port operator that bids the lowest cargo-handling fee. A major concern with Demsetz auctions in this context, is that the winning operator may integrate with a shipper and monopolize the shipping market, by worsening the service quality for competing shippers. The standard policy recommendation against service quality discrimination is to ban the seaport from operating in the shipping market. The effectiveness of such prohibitions is suspect, however, because they can be circumvented by an (illegal) underhand agreement between the port operator and the shipper. In this paper we show that a ban on integration increases welfare if it is combined with a (sufficiently high) floor on the cargo-handling fee that operators can bid in the auction. In the absence of such a floor, however, a Demsetz auction is worse than no regulation at all of the bottleneck monopoly. Our results apply beyond the port and shipping markets, to any essential facility that can monopolize a downstream market. The results only require that profits with underhand vertical integration agreements be less than with legal vertical integration.auctions, ex ante vs. ex post rents, Demsetz auctions, hidden action, monopoly regulation, productive efficiency, vertical integration

Strengthening measurements from the edges: application-level packet loss rate estimation

Network users know much less than ISPs, Internet exchanges and content providers about what happens inside the network. Consequently users cannot either easily detect network neutrality violations or readily exercise their market power by knowledgeably switching ISPs. This paper contributes to the ongoing efforts to empower users by proposing two models to estimate -- via application-level measurements -- a key network indicator, i.e., the packet loss rate (PLR) experienced by FTP-like TCP downloads. Controlled, testbed, and large-scale experiments show that the Inverse Mathis model is simpler and more consistent across the whole PLR range, but less accurate than the more advanced Likely Rexmit model for landline connections and moderate PL

A Simulation-Based Optimization Approach for Integrated Port Resource Allocation Problem

Todays, due to the rapid increase in shipping volumes, the container terminals are faced with the challenge to cope with these increasing demands. To handle this challenge, it is crucial to use flexible and efficient optimization approach in order to decrease operating cost. In this paper, a simulation-based optimization approach is proposed to construct a near-optimal berth allocation plan integrated with a plan for tug assignment and for resolution of the quay crane re-allocation problem. The research challenges involve dealing with the uncertainty in arrival times of vessels as well as tidal variations. The effectiveness of the proposed evolutionary algorithm is tested on RAJAEE Port as a real case. According to the simulation result, it can be concluded that the objective function value is affected significantly by the arrival disruptions. The result also demonstrates the effectiveness of the proposed simulation-based optimization approach. </span