Freight and Goods Movement

Impact of Parallel Processing on Job Sequences in Flexible Assembly Systems

Udomkesmalee, Narumol
Daganzo, Carlos F.
2025

Parallel processing offers several advantages. However, when processing times are allowed to vary, it can result in unpredictable job sequences. This issue must be addressed in assembly systems where it is necessary to match specific jobs with specific materials downstream. This research analyses job sequences after parallel processing and provides strategies for dealing with jobs getting out of sequence. One strategy involves re-sequencing materials using material buffers and another involves re-sequencing jobs using job buffers. A simple analysis determines the size of material buffers....

The Crane Scheduling Problem

Daganzo, Carlos F.
1989

This paper examines crane scheduling for ports. It starts with a simple static case and uses it as a building block to develop a better understanding of the dynamic problem with berth length limitations. The paper assumes that ships are divided into holds and that (usually) only one crane can work on a hold at a time. Cranes can be moved freely from hold to hold, and ships cannot depart until all their holds have been handled. In the most general case, ships arrive at different times and must queue for berthing space if the berths are full. The objective is to turn around (serve) all the...

Approximate Expressions for Queueing Systems with Scheduled Arrivals and Established Service Order

Sabria, Federico
Daganzo, Carlos F.
1989

This paper studies single server queueing systems where customers arrive according to a schedule, but not punctually, and where service might be provided in the scheduled order; thus, customers may leave the system in a sequence different to that of their arrivals. The situation arises in connection with maritime container terminals. The steady state solution to the problem follows an integral equation that may be solved numerically. When congestion is light (as is usual in well managed ports) approximate analytic solutions to the integral equation can be found. As an illustration,...

A Branch and Bound Solution Method for the Crane Scheduling Problem

Peterkofsky, Roy I.
Daganzo, Carlos F.
1990

Typical cargo ships spend 60% of their time in port, costing their owners about $1000 per hour. In this paper, we attack such costs with a method to speed loading and unloading. We model the need for container handling as generic “work,” which cranes can do at a constant rate. Each hold of each ship has a given amount of this work and cranes can interrupt their work on individual holds without any loss of efficiency. In the parlance of scheduling theory, this constitutes an “open shop” with parallel, identical machines, where jobs consist of independent, single-stage, preemptable tasks....

The Productivity of Multipurpose Seaport Terminals

Daganzo, Carlos F.
1990

This paper studies the peculiar queueing problem that arises at multipurpose port terminals serving two traffic types. Primary (liner ship) traffic obeys a schedule and has absolute priority on the use of the multipurpose facilities. Secondary (tramp) traffic, which arrives at random, can also be served elsewhere in the port. Secondary traffic is routed to the multipurpose berths only if doing so does not delay any primary ship. (The port knows a fair amount ahead of time the arrival times of these ships and the likely service times of both liners and tramps). The goal is to obtain simple...

Optimal Pricing Policies for Temporary Storage at Ports

de Castilho, Bernardo
Daganzo, Carlos F.
1991

Synchronizing Production and Transportation Schedules

Blumenfeld, Dennis E.
Burns, Lawrence D.
Daganzo, Carlos F.
1991

This paper examines whether it is cost-effective to synchronize production and transportation schedules on a production network. The network considered consists of one origin and many destinations. The origin produces parts that are shipped directly to each destination. Trade-offs between production set-up, freight transportation, and inventory costs on the network are analyzed, and total costs are compared for synchronized and independent schedules. The paper focuses on a simple production system, which can be modeled analytically and which allows the basic issues in synchronizing...

Storage Space vs Handling Work in Container Terminals

Taleb-Ibrahimi, Mounira
de Castilho, Bernardo
Daganzo, Carlos F.
1993

This paper describes handling and storage strategies for export containers at marine terminals and quantifies their performance according to the amount of space and number of handling moves they require. Identifying a “best” strategy is complicated because the optimization problem is combinatorial in nature—strategies are characterized, among other things, by the order in which future ship arrivals claim preferential space in the storage area. Given a certain traffic, the paper first examines the minimal storage space needed to implement the recommended strategies. This analysis may be of...

Handling Strategies for Import Containers at Marine Terminals

de Castillo, Bernardo
Daganzo, Carlos F.
1993

Many types of storage systems require goods to be stacked in a storage area. The amount of handling effort required to retrieve individual items from the stacks depends on stack heights and on the adopted storage strategy. The paper focuses on container import operations at marine terminals. It presents methods for measuring the amount of handling effort required when two basic strategies are adopted, one that tries to keep all stacks the same size and another than segregates containers according to arrival time. The strategies are compared in an idealized situation. The methods should be...

Handling Operations and the Lot Size Trade-off

Daganzo, Carlos F.
Newell, Gordon F.
1993

This paper presents a handling cost model for a warehouse that supplies one or more stores with a large number of items and examines operating strategies whose objective is to minimize the sum of handling, transportation and inventory costs. Decisions must be made regarding the frequency of shipments to the store(s) (i.e. the transportation schedule) and the specific items and lot sizes included in each shipment. The paper shows that, conditional on a transportation schedule, lot sizes for the different items (i.e. their delivery frequency consistent with the transportation schedule) can...