1. Logistics Planning and Control Under Uncertainties in Distribution Centers
J. Ashayeri and R.P. Kampstra
This paper represents the challenges of distribution facilities coping with high uncertainties in
demand and supply. Then a case is presented to highlight the uncertain distribution
environment and to introduce an indicator to measure the nature of problems facing distribution
centers. It is shown that there is a need for a “Synchronized Logistics Planning and Control
System” to closely coordinate purchasing, sales and logistics departments’ decision-making
processes. The concept of such a system is presented and the key characteristics of the
developed concept are integrate process approach, robustness and flexibility to handle both
demand and supply uncertainties. The concept enables distributors to move from a buy-holdsell
distribution model to a sell-source-ship model and speed the movement of goods through
the distribution center.
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2. Assembly System Layout Design
Yossi Bukchin, Russell Meller and Qi Liu
This paper addresses the layout design of an assembly system consisting of multiple lines of
different shapes. According to the proposed model (a mixed-integer linear program), the areas
and shapes of the assembly lines constituting the assembly system are given and cannot be
changed due to technological considerations. Still, the physical placement of each line and its
orientation within the facility are decision variables. The objective function of the proposed
model is to minimize the distances traveled by material flow. The mixed-integer programming
formulation for the problem is presented. Computational results give an indication of the
maximal problem size that can be solved in a reasonable amount of time and examine the effect
of the problem parameters on the solution run time.
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3. Choosing The Carrier
David Sourek and Vaclav Cempirek
This paper contains descriptions of methods for choosing carriers. These mathematical
methods require evaluation criteria and the weights of the criteria. Various criteria and
weightings are presented and were implemented in software.
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4.
Single-Command Travel Time Estimation and Optimal Rack Design for a
3-Dimensional Compact AS/RS
M.B.M. de Koster and Tho Le Duc
In this paper, we consider a new type of compact automated storage and retrieval system
(AS/RS). The system consists of an automated crane taking care of movements in the
horizontal and vertical direction. A gravity conveying mechanism takes care of the depth
movement. The aim of the research was to facilitate the problem of optimal design and
performance evaluation of the system. We estimate the crane’s expected travel time for single
command cycles. From the expected travel time, we calculate the optimal ratio between three
dimensions that minimize the travel time for a random storage strategy. Finally, we present an
example where we apply the findings of this study.
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5. Monitoring and Evaluation of Logistics Performance
Alejandro Mendoza, John English and G. Don Taylor
A comprehensive list of performance measures for measuring logistics performance is provided
that builds upon previous documented efforts. The performance measures are grouped into
four groups: financial, quality, cycle time and resource. We document the measured units of
each performance measure and recommend an appropriate multivariate SPC approach for
monitoring underlying processes. Example data sets are then presented that represent the
applications of such techniques.
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6.
A Framework of Stochastic Finite Elements for Models of Material
Handling Systems
Kai Furmans
The aim of this work is to introduce a framework of model elements and associated computation
methods which are well suited to model information flow and physical processes in warehouses
and distribution centers. All elements are based on a discrete representation of time, in order to
render distribution assumptions unnecessary.
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7. Strategic Design of Robust Global Supply Chains Under Uncertainty
Marc Goetschalckx, Shabbir Ahmed, Alexander Shapiro, Tjendera Santosa and Gonzalo
Cordova
We will present a model for the strategic design of the global supply chain of an individual
company. The model presented is a multi-period, two-stage stochastic, multi-country, multiproduct,
multi-echelon formulation based on forecasted exchange rates and with bill of materials
(BOM) flow conservation. The objective is maximization of the expected value of the timediscounted
worldwide after-tax net cash flows NPV (NCF). The uncertainty of the data is
explicitly considered through the inclusion of scenarios in the deterministic equivalent problem
(DEP). However, the problem size of the DEP is so large that convergence of standard
Benders decomposition requires an excessive amount of computer time. We have
implemented several acceleration techniques for Benders decomposition.
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8. Extended Models for Automated Palletizing Systems
Fahrettin Eldemir, Robert Graves and Charles Malmborg
We address the determination of decision parameters in conceptualizing Automated Palletizing
Systems (APS). Conceptualizing is the process of developing an initial system design solution
for a complex real-world material handling problem. Such an initial solution is preliminary in
nature and reflects the interaction between the problem environment (e.g., throughput needs,
cost) and the material handling system environment (e.g., equipment, operating system
practices). The decision parameters for the concept are grouped in two categories,
configuration options and operational strategies. In the system configuration stage, a system
type is chosen among end-of-line, multi-line, and multi-line-with-sortation. The number and
length of the accumulation lines, and the number of palletizers are also determined in this stage.
Operational strategies are listed in regard to assigning the accumulation lanes to the items,
selection of a dispatching rule, and the setting of conveyor speeds. We develop state equation
models for end-of-line and multi-line cases and consider means for determining the steady state
probabilities involved.
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9. A Layout Algorithm for Very High Density Storage Systems
Kevin Gue
A Very High Density Storage systems is characterized by frequently having to move interfering
items in order to gain access to desired items. This characteristic increases the storage
density, which is a good thing, but also increases the expected retrieval time, which is a bad
thing. We describe the nature of this tradeoff in storage systems design and describe a simple
but effective algorithm to fill rectangular storage spaces densely, without making it “too difficult”
to retrieve any individual item.
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10. An Efficient Model for Allocating Products and Designing a Warehouse
Sunderesh Heragu, Jason C.S. Huang, Ronald Mantel and Peter Schuur
The two primary functions of warehouse include (I) temporary storage and protection of goods,
and (ii) providing value added services such as fulfillment of individual customer orders,
packaging of goods, after sales services, repairs, testing, inspection, and assembly. To perform
the above functions, the warehouse is divided into several functional areas such as reserve
storage area, forward (order collation) area, and cross-docking. In this paper, we present a
mathematical model and a heuristic algorithm that jointly determines product allocation to the
functional areas in the warehouse as well as the size of each area using data readily available
to a warehouse manager.
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