Successful Defenses

FarazDefense

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Congrats to Dr. Faraz Ramtin, who successfully defended his Ph.D. dissertation thesis entitled, “Modeling and Analysis of Automated Storage and Retrieval Systems with Multiple in-the-aisle Pick Positions,” and to Patrick Reilly, who successfully defended his M.S. thesis entitle, “Propagation of Unit Location Uncertainty in Dense Storage Environments.”

I am super proud of both students, who are excellent researchers and human beings.

 

 

Faraz’s dissertation consists of three contributions all focusing on a special type of case-level order fulfillment technology – an “Automated Storage and Retrieval System with Multiple in-the-aisle pick positions.” These semi-automated systems are common in temperature-controlled warehouses.  Our first contribution includes the first study to analyze AS/RS with multiple in-the-aisle outputs. We develop expected travel time models for random storage policies and provide design insights into these systems.  In our second contribution, we considered the use of MIAPP-AS/RS to fulfill orders for non-identical items’ demand, which relaxed some of the assumptions we made in the first contribution. Specifically, we focused on an important practical design decision, the optimal SKU assignment problem. We studied the impact of different pick position assignments on system throughput, as well as system design trade-offs that occur when the system is running under different operating policies and different demand profiles. We developed optimization models to find the optimal assignment that minimizes the expected travel time.  Finally, we developed optimization models for the SKU-to-pick position assignment problem for dedicated and class-based storage policy for MIAPP-AS/RS.  By exploiting the structure of these optimization models, we decomposes the problem using Benders decomposition.

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The first two contributions of Faraz’s dissertation work has been accepted for publication:

  • Ramtin F., Pazour J. A. “Analytical Models for an Automated Storage and Retrieval System with Multiple in-the-Aisle Pick Positions”. IIE Transactions, 46(9), 968-986.
  • Ramtin F., Pazour J. A. “Product Allocation Problem for an AS/RS with Multiple in-the-Aisle Pick Positions”. IIE Transactions, Accepted Manuscript.

He is working on the manuscript of his third contribution, which explores a dedicated storage policy in these systems.

Patrick’s work focuses on dense storage environments and adds an additional dimension to the warehousing literature in that area, specifically item location uncertainty.  Effective space utilization is an important consideration in logistics systems and is especially important in dense storage environments. Dense storage systems provide high-space utilization; however, because not all items are immediately accessible, storage and retrieval operations often require shifting of other stored items in order to access the desired item, which results in item location uncertainty when asset tracking is insufficient. Given an initial certainty in item location, we use Markovian principles to quantify the growth of uncertainty as a function of retrieval requests and discover that the steady state probability distribution for any communicating class of storage locations approaches uniform. Using this result, an expected search time model is developed and applied to the systems analyzed. We also develop metrics that quantify and characterize uncertainty in item location to aid in understanding the nature of that uncertainty. By incorporating uncertainty into our logistics model and conducting numerical experiments, we gain valuable insights into the uncertainty problem such as the benefit of multiple item copies in reducing expected search time and the varied response to different retrieval policies in otherwise identical systems.IMG_1745

Material Handling Education Foundation Scholarships

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I’m honored to be featured in the Where are they now? article in the MHI Solutions Magazine.  [PDF] You have to read through to the bottom to find my favorite quote from the article, which is

“I find the work extremely rewarding,” Pazour said.  “One of the aspects that I really like about my job is that I get paid to learn.  I’m both creating knowledge and disseminating knowledge to my students, and that’s very rewarding.”

I’m even more excited to announce that two of the students in my research group are recipients of a 2015/2016 Material Handling Education Foundation Scholarship.  The Material Handling Education Foundation provides scholarships and educational opportunities to students studying in the field of material handling, logistics and supply chain.

  •  Shahab Mofidi was awarded the Lee Wood Scholarship for the 2015/2016 academic year from the Material Handling Education Foundation, Inc.
  • Catherine Ninah was awarded the Crane Manufacturers Association of America Honor Scholarship for the 2015/2016 academic year from the Material Handling Education Foundation, Inc.

Shahab Mofidi is a Ph.D. student in the IEMS department, and his research focuses on logistical decision making in environments that exhibit item location uncertainty.  Some examples include sea-based logistics, as well as ship-from-store fulfillment operations for e-commerce orders.  Catherine Ninah is an undergraduate student in the IEMS department, who has conducted research on sea-based logistics and healthcare logistics.  In addition, Catherine will participate in an REU (research experience for undergraduates) this summer at Duke University.  She’ll be working with The Center for the Environmental Implications of NanoTechnology (CEINT) on Risk Assessment and Modeling.

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Catherine Research Poster

2014 in Review

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To keep up with my blogging traditions, below you will find my list of highlights from this past calendar year.

  1.  My academic family grew. Ali Bozorgi, who was co-advised by Dima Nazzal and myself, become the first branch on my academic tree. Ali is currently a postdoctoral fellow at Clemson University and Greenville Health System.  My academic family tree should add two more branches in May when Faraz Ramtin will defend his Ph.D. dissertation and Patrick Reilly will defend his master’s thesis.
  2. Modeling is powerful stuff. My team and I spent lots of time and brain power developing models to quantify and evaluate sea-based logistics system design in the face of imperfect visibility.  We got great feedback when we presented this work to the Marines and the Navy in May, as well as hosted our Office of Naval Research managers in our lab in November.  I am proud of this work as it is illustrative of how mathematical models can be extremely powerful tools in understanding complex problems, and testing possible solutions.  I find research that builds mathematical models and uses them as a playground to test hypothesis and to gain understanding and insights into complex problems is rewarding and has impact.
  3. School is cool.  Education and learning continue to be cool and rewarding experiences for me.  I greatly enjoy my time in the classroom, having taught a graduate production and inventory control course, a graduate operations research course, and an undergraduate industrial engineering in the service sector course this past year.
  4. Conferences are good for my soul. I always look forward to professional conferences, but this year in particular I found conferences to be extremely valuable.  They allowed me to see my research from the forest rather than the trees, and I got to spend time in fun places with new and old friends.
  5. Fruitful and fun collaborations.  Such collaborations with colleagues and students resulted in a number of publications being accepted this year.
    1. Bozorgi, Ali, Pazour, Jennifer A., and Nazzal, Dima, 2014, “A New Inventory Model for Cold Items that Considers Costs and Emissions,” International Journal of Production Economics, 155, 114–125. (Special Issue: Celebrating a Century of the Economic Order Quantity Model).
    2. Carrano, Andres, Pazour, Jennifer A., Roy, Debjit, and Thorn, Brian, (to appear) “Selection of Pallet Management Strategies based on Carbon Emissions Impact,” International Journal of Production Economics. (Special Issue: Carbon-efficient Production, Supply Chains and Logistics).
    3. Pazour, Jennifer A., and Carlo, Hector J. (to appear) “Warehouse Reshuffling: Insights and Optimization,” Transportation Research Part E.
    4. Pazour, Jennifer A. and Roy, Debjit, (to appear) “Analyzing Rental Vehicle Threshold Policies that Consider Expected Waiting Times for Two Customer Classes,”‘ Computers & Industrial Engineering.

All in all, life was pretty great in 2014.  I’m looking forward to what’s in store in 2015!

Mathematical Modeling as Poetry

Mountain 1 by John Murray

Mountain 1 by John Murray

This semester I have been involved in an initiative called ICubed, which is a NSF-funded project that partners with several units at UCF to ensure broaden impact of  NSF funded projects through coordination and integration of education and research activities.  Undergraduate researcher, Krisin Elias, and I have been paired up with the Advanced Printmaking class for the STEAM component of the project.  The idea is to add “art” to “science, technology, engineering, and mathematics” by having art and design students create science-inspired art based on our explanation of science and engineering concepts.

Our initial presentation, where Kristin and I present our research to the printmaking class, is coming up.  To get a feel for how the presentations go, Kristin attended another such presentation and she reported back that many of the questions that were asked were about the researchers’ passion and feelings for their work.  So, as I pondered my research passion on my drive home from work, I heard a great NPR interview on Here and Now with Gregory Orr, who is an American poet.  Towards the end of the interview, Gregory Orr talks about the power and beauty of poetry.  As someone who has never really got poetry, I was surprised to find myself relating so much to his description of poetry.  I just needed to replace the word “poetry” with “math modeling” and it totally resonated with me.  How’s that for an artist and engineer communicating?

Below is my translation of Gregory Orr’s comments about poetry turned into my thoughts about math modeling.

Mathematical modeling is a way of expressing what is in this world, and trying to make sense of it.  Modeling is all about affirming meaning out of a complex situation.  What is beautiful about mathematical modeling is that it asks you to turn the world into numbers and expressions.  It is a way of ordering the complex world, it is a way of organizing, it is a way of expressing, and of capturing the trade-offs of complex phenomena.  It is a way of expressing our world.  It is a way to make sense of it.

Sea-Based Logistics Research Update

Pazour, ONR Fact Sheet September 2014PDF version: Pazour, ONR Fact Sheet September 2014

Above is an “at a glance” update on the research my team of students and myself are working on for the Office of Naval Research.

Seabasing is a United States Navy strategy that allows Joint Forces to be supported from the sea.  From a logistics perspective, seabasing will transform a set of vessels into floating distribution centers that are responsible for fulfilling supply orders from troops on shore.  Vital components of seabasing include selective offloading capabilities in high-space-utilization environments, ship-to-objective logistics via aerial delivery, and vessel-to-vessel cargo replenishment. In addition, sea-based logistics operate in a challenging and uncertain environment.  Thus, our research is interested in developing models to quantify and evaluate sea-based logistic system design in the face of imperfect visibility.  We focus on two important sea-based logistics decisions: selective offloading in dense storage environments and prestaging decisions in vessel-to-vessel cargo transfer.

Dense storage systems provide high-space utilization; however, because not all items are immediately accessible storage and retrieval operations often require shifting of other stored items in order to access the desired item. This shifting creates the propagation of uncertainty in item locations over time.    As a result of location uncertainty, before an item can be retrieved, the item needs to be identified, which requires searching.  We develop models that describe the propagation of uncertainty over time, as well as search plan optimization and expected search time models.

Underway Replenishment is a method for transferring cargo from one ship to another while the two ships are moving at sea.  To reduce the amount of idle time and improve the utilization of the transfer process, the concept of prestaging cargo on the flight deck is used. Prestaging involves retrieving and storing cargo on the flight deck of the supply ship in anticipation of requested demand.  The primary research question we are interested in is determining which items, and in what quantity, to prestage that balances the costs with the rewards of prestaging.  A secondary objective is to quantify the impact that uncertainty has on the logistics process of transferring cargo between ships.

 

Piece Level Order-Fulfillment Technology Selection

IMHRC2014 Pazour and Meller - Piece Level Order Fulfillment Technology Selection

 

I attended the 2014 International Material Handling Research Colloquium in Mason, Ohio in June.  We had great hosts, Intelligated , which is a company that provides intelligent automated material handling solutions.  This colloquium occurs every 2 years and is one of my favorite venues to present and learn about new research.  The mechanisms used to disseminate research are a Book Chapter and a poster session.  I enjoy the two-way dialog that occurs in a poster session format.

One of my favorite things about Austria is their great public transportation.  I got around Graz with a tram ticket and a bicycle.  It was great.

One of my favorite things about Austria is their great public transportation. I got around Graz with a tram ticket and a bicycle. It was great.

The research I presented was on piece-level order-fulfillment technology selection and conducted with my Ph.D. adviser, Russ Meller, and collaborators at SSI Schaefer and the Technical University of Graz.  The work was sponsored by the National Science Foundation through a Doctoral Dissertation Enhancement Project, which enabled me to live 4 months in Graz, Austria.  Not only did I get to work with engineers who design distribution centers for a living, I got to experience living in another country that has amazing public transportation, fresh bread on every corner, and is the place of musicians like Mozart and Beethoven.

Our research focused on the selection of piece-level order-fulfillment technologies.  To design an effective piece-level order-fulfillment strategy that meets customer requirements while minimizing costs, high-demanded SKUs may be fulfilled differently than low-demanded SKUs.  Consequently, more than one order-fulfillment technology may be required due to the variability in SKU profile.  For example, the Figure below provides an example solution to the Piece-Level Order-Fulfillment Technology Problem.

DemandCurveExampleFor this distribution center and technology characteristics, the top 1800 SKUs are fulfilled using an automated technology (like an A-Frame system) and the bottom 6200 SKUs are fulfilled using a Goods-to-Man technology. The remaining in-between SKUs are fulfilled using manual man-to-goods system.

The goals of our research were two-fold.

  1. First, we were interested in developing a tool that can aid in decision making associated with which  technologies to select and the assignment of SKUs to these technologies.
  2. Second, we wanted to understand what key factors resulted in implementing manual versus automated order-fulfillment technologies and to provide insights into the use of different order-fulfillment technology strategies.

To accomplish these two goals, we developed an Integer Linear Program formulation, validated the methodology with data from industry implementations, and conducted a set of numerical experiments and statistical analysis.

The insight that I found most interesting was that if automation was used for piece-level order-fulfillment it was used for:

  • The few, very fast-moving SKUs
  • The many, slow-moving SKUs.

Implementing automation for your fast-moving SKUs makes sense as the investment cost in automated technologies is justified by the high velocity of these products.  Not so obvious is the reason for automation to pick slow moving SKUS.  The reason occurs due to the large number of slow-moving SKUs and the need for quick order-fulfillment times.

Given that slow moving SKUs make up a large number of the total SKUs (e.g., in e-commerce over 90% of a retailer’s catalog can be comprised of slow-moving SKUs ), a large amount of space is consumed by slow-moving SKUs and if they are picked in a manual system, the order picker will have to travel large distances to retrieve these items.  When customers put demands on delivery times, the order-fulfillment process must be completed quickly.  This means that ALL items must be fulfilled within the allotted time (not just fast-moving items).  Therefore, goods-to-man systems provide cost efficiency and reduced order-fulfillment lead times for slow-moving SKUs by eliminating the significant travel costs in manual systems.

Just to be clear, our analysis found that there are many cases when a manual process is best.  For example, when labor rates or the number of order lines are low, a manual piece-level fulfillment process is often recommended.  If you are interested in details, a pdf version of our book chapter can be downloaded here:

Pazour, Jennifer A. and Meller, Russell D., 2014, “A Framework and Analysis to Inform the Selection of Piece-Level Order-Fulfillment Technologies,” Progress in Material Handling Research: 2014, Material Handling Institute, Charlotte, NC. (Download the PDF )

Awesome students win a bunch of awards

Based on their intellectual curiosity and mad modeling skills, I knew I had some pretty great students working in my research lab.  As validation, they also received a bunch of external recognition in the form of awards, scholarships, and career opportunities.

Graduate Student Researchers

Faraz Ramtin and I

Faraz Ramtin received a Graduate Fellowship and is interning at Hertz Rental Company’s OR department.

Faraz Ramtin was awarded a Graduate Research Excellence Fellowship for the 2014-2015 academic year.  He is also gaining great experiences as an Operations Research Intern at Hertz Rental Company this summer.  Faraz, who proposed his dissertation on analytic models for  a case-level order fulfillment technology, will graduate Spring 2014.  He and I arrived at UCF at the same time and was the first student involved in my research team.  It has been fun to watch him grow in his ability for independent research and analysis.

Ali's Ph.D. Graduation

Ali’s Ph.D. Graduation

Ali Bozorgi graduated this May with his Ph.D.  His dissertation on inventory problems in the cold supply chain was co-advised by Dima Nazzal at Georgia tech and myself.  Ali is off to Clemson as a Post Doctoral Fellow, where I’m looking forward to hearing about his many future successes.

 

 

 

Mohamed did a great job presenting at ISERC

Mohamed did a great job presenting at ISERC

Mohamed Awwad presented his research at the Institute of Industrial Engineers Annual Conference in Montreal to a full house.  It was his first presentation at a research conference and he did a great job describing his work on search and retrieval operations in dense storage systems.  I enjoyed chairing the “family session” that also included other branches of my academic tree: Russ Meller, Tish Pohl, and Pratik Parikh.

Kaveh's send off party watching the Netherlands versus Argentina World Cup Match

Kaveh’s send off party watching the Netherlands versus Argentina World Cup Match. (from left to right: Patrick, Kaveh, Jen, Shahab, and Ali).

Kaveh Azadeh has been awarded an assistantship to pursue his Ph.D. under Rene de Koster in the Department of Technology and Operations Management, Rotterdam School of Management, Erasmus University.  Kaveh and I have worked together on research since we both arrived in Orlando in 2011 and he will definitely be missed in our group, especially for his statistics knowledge and movie recommendations.  As an impromptu send off party, our lab got together to watch the Netherlands vs Argentina game in the World Cup.    Although Kaveh was rooting for his soon-to-be new home country, Messi and Argentina were victorious.

Shahab Mofidi is the newest graduate student addition to our team.  He has been a great asset in solidifying and expanding ideas for my CAREER proposal due next week.  In addition to implementing an optimization and simulation model and getting interesting results with short deadlines, I knew he was a perfect fit for my team when he commented that the font for a figure was different than the main text.  This eye for detail is a must after Russ ruined my ability to look at a document and not see formatting and typo errors :).

 Undergraduate Researchers

I’ve enjoyed exposing undergraduate students to the joys and (maybe some perils) of research.  They have done a great job contributing to our research lab, which isn’t surprising given the awards they’ve racked up.

Huber CSCMP Central Florida Roundtable Scholarship 2014

Chris awarded a scholarship from the CSCMP Central Florida Round Table

Whitney awarded a scholarship from the CSCMP Central Florida Round Table

 

 

 

 

 

 

 

  • Patrick Reilly was awarded the Outstanding Graduating Senior award from UCF’s Industrial Engineering Department.  As an undergraduate researcher, Patrick did a great job modeling Operations Research problems found in sea-based logistics.  I am very happy that he will stay on as my graduate student and continue working on research that describes mathematically the propagation of uncertainty in dense storage environments.
  • Brandon Finley has been awarded the Institute of Caster & Wheel Manufacturers Honor Scholarship for the 2014/2015 academic term from the Material Handling Education Foundation, Inc.  Brandon and I are working on research on modeling reshuffling policies in warehouses with multiple operators.
  • Whitney Anderson and Chris Huber were both awarded scholarships from the  Council of Supply Chain Management Professionals Central Florida Round Table for the 2014/2015 academic term.  Through the Undergraduate Research Experience provided via EXCEL, both students conducted research in my lab in Spring 2014.  Whitney participated in research on selecting piece-level order-fulfillment technology and Chris participated in analyzing data for sea-based logistics policies.
  • Margot Tejera was awarded the 2014/2015 UPS Scholarship for Minority Students, which is a National IIE Scholarship awarded to one undergraduate IE student each year.  Margot was a former undergraduate researcher in my lab and she is the current student president of the IIE student chapter.
  • I have been fortunate to have Mohmoud Sbeih and Kristin Elias’s help in writing my CAREER proposal this summer.  Both undergraduate students have provided valuable insights to the research and educational objectives of the proposal.  I’m excited that both will continue research in my lab and are currently in the process of defining a project that they can individually take the lead on.