Kevin Gue

Fortna · Research & Development

Intelligent autonomous vehicles bring the potential to achieve very high parking density by blocking other cars. In such dense parking lots, vehicles can be parked in many ways, most of which result in very long retrieval time. We propose a Simulated Annealing algorithm combined with a reinforcement learning method to construct parking designs that...

Even though order picking is the most costly operation in a warehouse, current design practices have used the same principles (straight rows with parallel pick aisles and perpendicular cross aisles) to reduce travel distances between pick locations for more than sixty years. We present an open-source computational software system for facilitating t...

In a common parking lot, much of the space is devoted not to parking but to lanes in which cars travel to and from parking spaces. Lanes must not be blocked for one simple reason: a blocked car might need to leave before the car that blocks it. Self-parking and intelligent communication capabilities of autonomous vehicles introduces an opportunity...

We introduce the visibility graph as an alternative way to estimate the length of a route traveled by order pickers in a warehouse. Heretofore it has been assumed that workers travel along a network of travel paths corresponding to centers of aisles, including along the right angles formed where picking aisles join cross aisles. A visibility graph...

We propose a new type of automated goods‐to‐person system based on a grid of unit‐sized conveyors. The system uses a negotiation‐based decentralized control algorithm to route required totes or cartons to one or more picking positions on the perimeter of the grid. We describe the algorithms to accomplish a “puzzle‐like” movement of totes on the gri...

We describe a method to generate layouts for unit-load warehouses that use multiple slot heights as a way to maximize warehouse space utilization. The problem has two parts: slots must be arranged into rack-bays, and rack-bays must be arranged into a layout. We describe two methods for the first subproblem, depending on whether the warehouse has di...

Storing pallets of products on top of one another on the floor of a warehouse is called block stacking. The arrangement of lanes, aisles, and cross-aisles in this storage system affects both utilization of the storage space and material handling costs; however, the existing literature focuses exclusively on lane depths and their impact on space uti...

The Kentucky Humane Society (KHS) is a private, nonprofit organization dedicated to saving every healthy, behaviorally sound animal that they take in. They are also the largest no-kill animal shelter in Kentucky, USA. Due to limited resources, the KHS has a great need for an optimized methodology for allocating available animals to their adoption f...

In block stacking warehouses, pallets of stock keeping units (SKUs) are stacked on top of one another in lanes on the warehouse floor. A conventional layout consists of multiple bays of lanes separated by aisles. The depths of the bays and the number of aisles determine the storage space utilization. Using an analytical model, we show that the trad...

Using data from 88 journals over an 8 year period, we investigate the relationships among researchers in material handling. We apply social network analysis to measure many attributes of the network, including papers published each year, papers published per author, number of collaborators per author, strength of collaboration between authors, and...

Storage racks in a unit-load warehouse typically have slots of equal height, whereas the unit-loads themselves have heights that vary significantly. The result of this mismatch is unused vertical space and storage spaces larger than they otherwise could be. We propose the use of storage racks with multiple slot heights to better match the distribut...

The physical layout of a retail store is known to influence the attitude and behavior of shoppers and affect store performance. An important role of the store's layout is to expose shoppers to merchandise in order to facilitate consideration and ultimately purchasing of exposed products. This work focuses on determining which rack layouts maximize...

A retail store's layout affects a shopper's visual experience and correspondingly the time spent in the store, navigation through the aisles, and allocation of attention and money across departments and categories. We show that alternate rack layouts allow for more of a rack's facing to appear in the shopper's visual field. To this end, we introduc...

In this paper, we describe and compare serial, parallel, and distributed solver implementations for large batches of Traveling Salesman Problems using the Lin-Kernighan Heuristic (LKH) and the Concorde exact TSP Solver. Parallel and distributed solver implementations are useful when many medium to large size TSP instances must be solved simultaneou...

Storing pallets of Stock Keeping Units (SKUs) on top of one another in lanes on a warehouse floor is known as block stacking. This storage system is widely used in manufacturing systems and distribution centers. The arrangement of lanes in the layout of this system significantly impacts utilization of the storage space and transportation costs. Exi...

Block stacking storage is an inexpensive storage system widely used in manufacturing systems where pallets of stock keeping units (SKUs) are stored in a warehouse at the finite production rates. However, determining the optimal lane depth that maximises space utilisation under a finite production rate constraint has not been adequately addressed in...

Service performance of an order fulfillment system is mainly determined by how quickly and accurately it fills customer orders. A higher service level can be o�ffered with a later cutoff� time, before which customers are assured of receiving their orders. However, the desire to o�er a later cutoff� time must be tempered by the need to provide servi...

Purpose – Puzzle-based storage is a novel approach enabling very dense storage. Previous analytical studies have focussed on retrieval time when one or more usable escort locations (empty slots) are located near the system input/output location, and on simulation results for more complex situations. The purpose of this paper is to extend analytical...

We develop an approximation model for the sojourn time distribution of customers or jobs arriving to an acyclic multi-server queueing network. The model accepts general interarrival times and general service times, and is based on the characteristics of phase-type distributions. The model produces excellent results for multi-server networks with a...

We develop a network-based warehouse model of individual pallet locations and their interactions with appropriate cross aisles in order to evaluate the expected travel distance of a given design. The model is constructive in that it uses Particle Swarm Optimization to determine the best angles of cross aisles and picking aisles for multiple, pre-de...

Purpose The literature on organizational change has increasingly recognized that characteristics of change recipients influence their reactions to workplace change. Yet little is known about the influence of employees’ adaptability and change-related uncertainty on their interpretation of organizational actions. We examined these antecedents and th...

Randomly presented physical items can be temporarily stored in a grid-based material handling system, e.g., before they are handled by a robot. The grid-based material handling system arranges the randomly presented physical items within the grid, so that they exit the grid in an ordered sequence, e.g., for pickup by the robot. Programmable modules...

We describe a high-density storage system for physical goods in which identical conveyor modules can be plugged together to store and retrieve unit-loads or small containers. Material movement conforms to the “puzzle architecture” found in popular board games such as the 15-puzzle and Rush Hour. Control of the system is decentralized, meaning that...

Full text at: http://calhoun.nps.edu/bitstream/handle/10945/39399/doerrguepoms1375.pdf?sequence=1 A performance metric and goal-setting procedure is defined for an order fulfillment operation. In this operation, order requests arrive continuously, and filled orders are shipped at a specific time each day. The metric links the continuous operation...

Submission Deadline: April 30, 2013

To meet the requirement of flexibility in intralogistics systems, the GridFlow 2D storage system has been developed which is able react to fluctuating processing volumes and layout changes. It consists of multiple autonomous conveyor modules, FlexConveyors, each equipped with a controller. The decentralized control can be described with a set of ru...

We develop an approximation model for the state-dependent sojourn time distribution of customers or orders in a multi-stage, multi-server queueing system, when interarrival and service times can take on general distributions. The model can be used to make probabilistic statements about the departure time of a customer or order, given the number and...

We show how to configure a cross aisle in a unit-load warehouse to facilitate travel between storage locations and multiple pickup and deposit points on one side. We use our models to investigate designs having two types of cross aisles—those that form a “Flying-V” and those that form an “Inverted-V.” Our numerical results suggest that there is a b...

We present a continuous space model for travel in a unit-load warehouse that allows cross aisles and picking aisles to take on any angle. The model produces optimal designs for one, two and three cross aisle warehouses, which we call the Chevron, Leaf and Butterfly. We then use a more accurate discrete model to show which designs are best for a wid...

We present a new semi-automated system for carton and piece picking op-erations in the distribution centers. The system features decentralized control based on a message-passing protocol in which cells communicate with their neighbors to determine action in each step. The result is a dynamically chang-ing pick face that provides high sku density an...

We develop discrete time models for the throughput time distribution of orders arriving to a one-block warehouse. The models accommodate single- or multi-line orders, and we show how to use them to determine the optimal batch size, given a desired probability of on-time order fulfillment. Experiments suggest that the optimal batch size is slightly...

Four biorefinery technologies were studied for feedstock allocation, optimum facility location, economic feasibility, and their economic impacts on Alabama. The studied technologies are: (1) circulated fluidized bed gasification of woody biomass for Fischer-Tropsch (F-T) fuels and power production; (2) simultaneous saccharification and fermentation...

This article investigates the effect of assigning the most-active items to the best locations in unit-load warehouses with non-traditional aisles. Specifically, the performance of flying-V and fishbone designs are investigated when products exhibit different velocity profiles. Both single- and dual-command operations are considered for a warehouse...

We introduce and model a new type of physical goods storage system in which items move among square cells in a rectangular grid. A relatively simple, decentralized algorithm controls the formation and collapse of short aisle segments in front of moving items in order to extract and replenish multiple items simultaneously. Thus, the system offers at...

This paper investigates a new aisle design for unit-load warehouses that interleave storage and retrieval operations to form dual-command cycles. We refer to this design as "fishbone triangle" because it is a fishbone design with an extra cross aisle inserted in the upper region to facilitate travel between storage locations. We compare its perform...

Unit-load warehouses store and retrieve unit-loads, typically pallets. When storage and retrieval operations are not coordinated, travel is from a pickup and deposit (P&D) point to a pallet location and back again. In some facilities, workers interleave storage and retrieval operations to form a dual-command cycle. Two new aisle designs proposed by...

In a warehouse that uses dual-command operations, workers travel loaded from the pickup and deposit (P&D) point first to a location to store a pallet, then to a second location from which they pick a pallet and return to the P&D point. We develop expected travel distance expressions for such operations and use them to analyze three common warehouse...

Unit-load warehouses are used to store items—typically pallets—that can be stowed or retrieved in a single trip. In the traditional, ubiquitous design, storage racks are arranged to create parallel picking aisles, which force workers to travel rectilinear distances to picking locations. We consider the problem of arranging aisles in new ways to red...

We have recently developed methods for approximating the sojourn time distribution for customers or jobs entering a multi-server queueing network with general interarrival and processing times. Here we propose to continue the development of such models, and use them to allocate workers dynamically in an order fulfillment system to improve its servi...

Operations in unit-load warehouses include single-command cycles and dual-command cycles, where storage and retrieval operations are interleaved. We model dual-command travel in two warehouse layouts that occur commonly in industry, and compare the efficiency of the two designs. General guidelines for optimizing the two aisle layouts are provided.

In storage environments in which space is highly constrained and high-density storage is required, puzzle-based storage systems offer a viable alternative. This paper makes use of the 15-puzzle, a children's game in which 15 tiles slide in 2 dimensions, as a platform for a high-density storage system. We use simulation to examine the effects of den...

We introduce and develop models for a physical goods storage system based on the 15-puzzle, a classic children's game in which 15 numbered tiles slide within a 4 × 4 grid. The objective of the game is to arrange the tiles in numerical sequence, starting from a random arrangement. For our purposes, the tiles represent totes, pallets, or even contain...

Crossdocking is widely seen as a way to reduce inventory costs and ensure more efficient deliveries. It can do this, and a lot more. But it is not a panacea. Crossdocking only fits certain retail conditions. Then there is the implementation.

Unit-load warehouses store and retrieve one pallet at a time, which typically requires a worker to travel from a pickup/deposit (P/D) point to a pallet location and back again. In some facilities workers store a pallet, retrieve another pallet at a different location, and then return to the P/D point. This is called a dual-command cycle. Two innova...

The cost and service performance of an order fulfillment center are determined partly by how workers are organized into an order picking system. One common approach is batch picking, in which workers circumnavigate a picking area with other workers, gathering items on a pick list. In some systems with high space utilization, narrow aisles prohibit...

We introduce and develop models for very high density physical goods storage systems, which are characterized by sometimes having to move interfering items in order to gain access to desired items. We describe a simple but effective algorithm to densely fill rectangular storage spaces, subject to a constraint on the number of interfering items. We...

Within both retail distribution and less-than-truckload transportation networks crossdocks vary greatly in shape. Docks in the shape of an I, L, or T are most common, but unusual ones may be found, including those in the shape of a U, H, or E. Is there a best shape? We show that the answer depends on the size of the facility and on the pattern of f...

New warfighting concepts for the US Marine Corps emphasize small, highly mobile forces supported from the sea, rather than from large, land-based supply points. The goal of logistics planners is to support these forces with as little inventory on land as possible. We develop a multi-period, facility location and material flow model, and show how to...

In most physical queueing applications, customers join a queue and move forward after each service, leaving room for others to join behind them. Some queues found in material handling and transportation systems do not operate like this because the queued entities (pallets or unoccupied cars, for example) are incapable of moving forward autonomously...

In most physical queueing applications, customers join a queue and move forward after each service, leaving room for others to join behind them. Some queues found in material handling and transportation systems do not operate like this because the queued entities (pallets or unoccupied cars, for example) are incapable of moving forward autonomously...

Handling freight in a crossdocking terminal is labor intensive and therefore costly because workers must unload, sort, and transfer a wide variety of freight from incoming to outgoing trailers. The efficiency of workers depends in large part on how trailers are assigned to doors around the dock; that is, on its layout. A good layout reduces travel...

The Department of Defense and the Joint Recruiting Facilities Committee oversee the operation and maintenance of recruiting facilities for the Service recruiting commands. DOD is concerned with identifying the most cost-effective geographic locations for the Services recruiting offices. This report provides an overview of the Recruiting Station Loc...

We describe a methodology for developing repair parts inventories for deploying Marine Corps units, including data collection and sparing models. Deployed units provide an excellent opportunity to make local corrections to systemic data collection and maintenance problems. We show how to use that data to establish spares levels for Class IX repair...

Evolving doctrine in the U. S. Marine Corps emphasizes small, highly-mobile forces, supported from the sea rather than from large, land-based supply points. Weintroduce some emerging problems in seabased logistics, and showhow simulation might be used to address them. We describe a simulation model of the o#oad of supplies to support a Marine Air-G...

We present a large scale production scheduling problem where each order is unique and the processing time for an operation can be close to the size of a time period. Because modeling the problem as a multiprocessor #owshop results in a computationally intractable formulation, we cast the problem in production planning terms and extract a production...

We describe two simulation models for repair processes of aircraft in the Navy, and suggest ways to reduce cycle time and improve readiness. The models illustrate the e#ects of material availability and process redesign on repair cycle time and work-in-process inventory levels for critical components. Our results indicate that the Navy could signi#...

We describe two simulation models for repair processes of aircraft in the Navy, and suggest ways to reduce cycle time and improve readiness. The models illustrate the effects of material availability and process redesign on repair cycle time and work-in-process inventory levels for critical components. Our results indicate that the Navy could signi...

ahead into the queue of incoming trailers and assign them to doors to minimize worker travel. We develop a model of the resulting material flows and use it to construct layouts that exploit this type of scheduling policy. Based on data from a test site, our results suggest that look-ahead scheduling alone can reduce labor costs due to travel by 15-...

We showhow to minimize labor costs in a less-than-truckload #LTL# freight terminal by properly assigning incoming and outgoing trailers to doors. Our models are based on the geometry of the terminal, the material handling systems within, and the mix of freight passing through. We report on the application of our models at di#erent terminals, includ...

We describe two simulation models for repair processes of aircraft in the Navy, and suggest ways to reduce cycle time and improve readiness. The models illustrate the effects of material availability and process redesign on repair cycle time and work-in-process inventory levels for critical components. Our results indicate that the Navy could signi...

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We describe two simulation models for repair processesof aircraft in the Navy, and suggest ways toreduce cycle time and improve readiness. The modelsillustrate the e#ects of material availability and processredesign on repair cycle time and work-in-processinventory levels for critical components. Our resultsindicate that the Navy could signi#cantly...

Thesis (Ph. D.)--School of Industrial and Systems Engineering, Georgia Institute of Technology 1996. Directed by John J. Bartholdi, III. Includes bibliographical references (leaves 109-110). Vita.

One disadvantage of automated material handling systems is their relative inflexibility: once racks are installed and conveyors are laid, making even mi-nor changes to a system can be cumbersome and expensive. However, recent progress in the capabilities and cost of basic system components, such as con-trollers, drives, and sensors, has made possib...

We develop economic models of freight terminals for the less-than-truckload (LTL) motor carrier industry. Our models capture important detailed aspects of terminal operations, such as worker travel time, waiting time due to congestion, multiple material handling systems, and information about incoming freight flows. We use our models to improve the...