Freight and Goods Movement

This paper examines the stability of decentralized, multistage supply chains under arbitrary demand conditions. It looks for intrinsic properties of the inventory replenishment policies that hold for all customer demand processes and for policies with desirable properties. It is found that the overall conditions experienced by suppliers several stages removed from the final customer, e.g., the variances of the orders they receive and the inventories they keep, depend on the policy much more than on the demand process. A policy-specific but demand-independent upper bound for the order...

This paper analyzes the bullwhip effect in decentralized, linear and time-invariant (LTI) supply chains. It generalizes existing results by broadening the class of policies and customer demand processes under consideration. The supply chain is modeled as a single-input, singleoutput control system driven by arbitrary demands. The paper discusses the appropriateness of various metrics for the bullwhip effect, and derives analytical conditions to predict its presence independently of the demand process. The paper also gives a formula for the variance of the order stream at any stage when the...

This paper shows how to reduce the bullwhip effect by introducing advance demand information (ADI) into the ordering schemes of supply chains. It quantifies the potential costs and benefits of ADI, and demonstrates that they are not evenly distributed across the chain. Therefore, market-based strategies to re-distribute wealth without penalizing any supplier are presented. The paper shows that if a centralized operation can eliminate the bullwhip effect and reduce total cost, then some of this reduction can also be achieved with decentralized negotiation schemes. Their performance is...

This report compares the performance of three double-cycling algorithms used to determine the sequence with which to load and unload containers from a vessel with a quay crane. Double cycling is a technique which can improve the efficiency of a quay crane and container port by unloading and loading containers in the same crane cycle. The three algorithms, the greedy strategy, the proximal strategy, and Johnson’s rule, are introduced and results from applying the three strategies to a set of simulated vessels are compared. While Johnson’s rule provides the minimum number of cycles required...