Move to Rensselaer

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I made the move this summer to Rensselaer Polytechnic Institute and am excited to be part of the Industrial and Systems Engineering (ISE) Department.

Some initial observations I have had:

  1. I’ve found a nice home in the Industrial and Systems Engineering department, which has research expertise in supply chains, cognitive and social networks, and infrastructure resiliency.  My research in modeling of supply chains and logistics systems is valued, and I am certain I will learn a lot from my colleagues.  It’s also a good sign that a large portion of the faculty’s favorite food is pizza.
  2. I appreciate Rensselaer’s joint emphasis on research and teaching, and connect with the ideas of The New Polytechnic, which “supports promising areas of interdisciplinary research and learning, and which uses the most advanced tools and technologies to unite a diversity of perspectives.”
  3. I just finished the first week of class and have been impressed with the students’ enthusiasm for the subject – Supply Chain Design.   Still left to figure out is how to write on a chalk board without the “squeaky” sound.
  4. Jennifer really is a popular name.  There are two new Jennifer faculty members on campus,  another Jennifer organized our orientation, yet another Jennifer handled my paperwork in HR, and yet another Jennifer helped me submit my first NSF funded proposal.
  5. We are proud to be Troybots.  Luke and I are living in downtown Troy near the Hudson River in a building from the late 1800’s that has been renovated into lofts.  We are loving our new place and community.  Troy is super walkable with lots of independent restaurants and shops and has really cool architecture.  I even get my dream of walking to work – it is just up 20 flights of stairs.Troybots

Please note my new contact information.  My new email: pazouj@rpi.edu is a little weird, not having the last letter in my last name.

Successful Defenses

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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 )