Robert de Souza

Discrete Time Model and Algorithms for Container Yard Crane Scheduling

Container terminal (CT) operations are often bottlenecked by slow YC (yard crane) movements. PM (prime mover) queues in front of the YCs are common. Hence, efficient YC scheduling to reduce the PM waiting time is critical in increasing a CTs throughput. We develop an efficient model for YC scheduling by taking into account realistic operational constraints such as inter-crane interference, fixed YC separation distances and simultaneous container storage/retrievals. Among them, only inter-crane interference has ever been considered in the literature. The model requires far fewer integer variables than the literature by using bi-index decision variables. We show how the model can be solved quickly using heuristics and rolling-horizon algorithm, yielding close to optimal solutions in seconds. The solution quality and solution time are both better than the literature even with additional constraints considered. The proposed formulations and algorithms can be extended to other problems with time windows and space constraints.

Development and simulation analysis of real-time yard crane control systems for seaport container transshipment terminals

As more and more container terminals open up all over the world, terminal operators are discovering that they must increase quay crane work rates to remain competitive. In this paper, we develop a real-time yard crane control system and show that a terminal’s long-run average quay crane rate depends on the portion of this system that dispatches yard cranes in the storage area in real time. Several real-time yard crane dispatching systems are evaluated by a fully-integrated, discrete event simulation model of a pure transshipment terminal that is designed to reproduce the multi-objective, stochastic, real-time environment at an RTGC-based, multiple-berth facility. Results indicate that yard cranes should prioritize the retrieval of containers from the stacks, rather than the storage of containers into stacks. Also, the yard crane dispatching system should not only consider the trucks already waiting for service in the yard, but also the trucks that are heading towards the yard. The experiments provide the first direct connection in the literature between real-time yard crane control systems and long-run performance at a seaport container terminal. We also make a qualitative comparison between rule-based and look-ahead yard crane dispatching schemes, and discuss deadlocking issues in detail.

Three-dimensional bin packing problem with variable bin height

This paper studies a variant of the three-dimensional bin packing problem (3D-BPP), where the bin height can be adjusted to the cartons it packs. The bins and cartons to be packed are assumed rectangular in shape. The cartons are allowed to be rotated into any one of the six positions that keep the carton edges parallel to the bin edges. This greatly increases the difficulty of finding a good solution since the search space expands significantly comparing to the 3D-BPP where the cartons have fixed orientations. A mathematical (mixed integer programming) approach is modified based on [Chen, C. S., Lee, S. M., Shen, Q. S., 1995. An analytical model for the container loading problem. European Journal of Operational Research 80 (1), 68-76] and numerical experiments indicate that the mathematical approach is not suitable for the variable bin height 3D-BPP. A special bin packing algorithm based on packing index is designed to utilize the special problem feature and is used as a building block for a genetic algorithm designed for the 3D-BPP. The paper also investigates the situation where more than one type of bin are used and provides a heuristic for packing a batch of cartons using the genetic algorithm. Numerical experiments show that our proposed method yields quick and satisfactory results when benchmarked against the actual packing practice and the MIP model with the latest version of CPLEX.

A global search framework for practical three-dimensional packing with variable carton orientations

This article aims to tackle a practical three-dimensional packing problem, where a number of cartons of diverse sizes are to be packed into a bin with fixed length and width but open height. Each carton is allowed to be packed in any one of the six orientations, and the carton edges are parallel to the bin edges. The allowance of variable carton orientations exponentially increases the solution space and makes the problem very challenging to solve. This study first elaborately devises the packing procedure, which converts an arbitrary sequence of cartons into a compact packing solution and subsequently develops an improved genetic algorithm (IGA) to evolve a set of solutions. Moreover, a novel global search framework (GSF), utilizing the concept of evolutionary gradient, is proposed to further improve the solution quality. Numerical experiments indicate that IGA provides faster and better results and GSF demonstrates its superior performance, especially in solving relative large-size and heterogeneous instances. Applying the proposed algorithms to some benchmarking cases of the three-dimensional strip packing problem also indicates that the algorithms are robust and effective compared to existing methods in the literature.

Collaboration in urban logistics: motivations and barriers

Urban logistics activities, while essential to the development of cities, also contribute to congestion and pollution if poorly managed. Synchronizing the last mile of delivery is critical, but challenging to implement. Collaboration between the stakeholders is thus needed and timely to improve the efficiency of last mile delivery in a growing city while advancing environmental sustainability. This paper is an exploratory study undertaken in Singapore, to identify the motivations and barriers to collaboration in urban logistics, which may influence a stakeholders decision to participate. Our initial results suggest that the expected benefits (motivation) and the competitive intelligence risks (barrier) influence the participation decision.

Lagrangian-Dual Functions and Moreau-Yosida Regularization

In this paper, we consider the Lagrangian-dual problem of a class of convex optimization problems. We first discuss the semismoothness of the Lagrangian-dual function

Return on investment calculator for RFID ecosystem of high tech company

\varphi

Remanufacturing in Asia : location choice and outsourcing

. This property is then used to investigate the second-order properties of the Moreau-Yosida regularization

Learning mechanisms for humanitarian logistics

\eta

Scheduling Multiple Yard Cranes with Crane Interference and Safety Distance Requirement

of the function