Category Archives: Research Skills

IIE Transactions Best Paper Honorable Mention

 

ISERC 2016 Repositioning Rental Vehicles Presentation

My co-authors and I received an honorable mention designation in the IIE Transactions Focused Issue on Design and Manufacturing Best Applications Paper Award Competition for 2016. (The award is selected by an examining committee from all papers published from July 1, 2014 through June 30, 2015, issues 46:7 through 47:6).

Roy, Debjit, Jennifer A. Pazour, and René De Koster. “A novel approach for designing rental vehicle repositioning strategies.” IIE Transactions 46.9 (2014): 948-967.

While the paper can be downloaded here  I also had the opportunity to present our research at the Industrial and Systems Engineering Research Conference.  If you weren’t able to attend my talk, here’s the cliff notes version.

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The rental car industry has experienced “the Amazon effect” where customers place requests with little or no warning.

ResearchFocus

An important tactical decision for vehicle rental providers is the design of a repositioning strategy to balance vehicle utilization with customer wait times due to vehicle unavailabilities.

 

RentalOptions

To address this problem, this article analyzes alternative repositioning strategies: a no-repositioning strategy, a customer repositioning strategy, and a vehicle repositioning strategy, using queuing network models that are able to handle stochastic demand and vehicle unavailabilities.

ResearchGoal

Optimization models are formulated to determine the repositioning fractions for alternate strategies that minimize the rental provider’s cost by balancing repositioning costs with customer waiting penalty costs. The nonlinear optimization problems are challenging to solve because the objective functions are non-differentiable and the decision variables (such as effective arrival rates and customer repositioning fractions) are interrelated.

CostFunctions

Therefore, a two-phase sequential solution approach to estimate the repositioning fractions is developed. Phase 1 determines the effective arrival rates by developing an approximate network model, deriving structural results, determining a high-quality solution point, and refining the solution. Phase 2 determines the repositioning fractions by solving a transportation problem.

SolutionApproach

Numerical experiments are used to evaluate the efficacy of the proposed solution approach, to analyze alternate repositioning strategies, and to illustrate how the developed techniques can be adopted to create a better readiness at a depot.

CurrentState

OrlandoExample

Conclusions

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2015 End-of-Year Update

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Art done on my whiteboard by my talented brother-in-law Blake Neubert.

The red ink from grading exams combined with the still-green grass on campus has me in the holiday spirit.  Here’s my blog tradition of an end-of-year update.

The biggest update from 2015 was a change in location.  I made the move to Rensselaer Polytechnic Institute this summer and it has proved to be a Pareto-optimal life solution.  The Industrial and Systems Engineering department at RPI is a nice place to be a junior faculty.  Already, interactions with my colleagues have led to new insights and directions for my research, and mentoring has led to a potential industry project and an award nomination.  We love our new community in Troy, and my husband found a super-charged job as a data analyst for Vicarious Visions.

In 2015, I have been lucky to lead a talented research team that has helped further research on the development of mathematical representations of complex systems and processes to better understand the implications of their design and operation.  My research has focused on three main stems of discovery: military logistics, distribution systems, and peer-to-peer sharing systems.  In 2015, I received my first NSF funding.  The project focuses on peer-to-peer sharing systems, which are systems where a resource owned by an individual is collectively shared with a group of users. The shared resource can be a physical resource (like a power drill) or a human resource (like the ability to perform a task). By focusing on access over ownership, these Systems allow physical assets to be consumed as services and tasks to be completed by independent individuals. Examples include sharing economy companies like Uber, Flexe, Cargomatic, and Instacart.

I’m thankful that I was able to convince Shahab Mofidi to transfer with me from UCF to RPI.  He is working on his Ph.D. research on two-stage multi-product procurement decisions with cost fluctuations.  He did an excellent job presenting his work at ISERC (to 3 generations of his academic family) and INFORMS.  It’s fun to jointly put our heads together during our weekly research meetings.

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Shahab Mofidi presents to three-generations of his academic tree at the 2015 ISERC conference (Mofidi, Pazour, Meller, [Bozer, not pictured], White)

I started working with Uzma Mushtaque this summer, and she has jumped right into her research on developing and using models that incorporate assortment properties into random utility models.  Specifically, she is interested in how to explicitly model no-choice probabilities associated when individual users are recommended an assortment of options to choose from.  Her work has wide application from recommendations in e-commerce and Netflix, as well as facilitating freelancer options in peer-to-peer resource sharing apps.  Shahab and she gained valuable experience attending the Purdue CIBER PhD Consortium on International Operations Management.  Uzma is excited to have her first research abstract accepted to present at ISERC in 2016.  Finally, I am excited to have Yuan (Eric) Meng join my group.  He will research bi-level optimization models for peer-to-peer sharing systems.

As new members joined, a number of students graduated in 2015.  Patrick Reilly defended his Master’s Thesis this spring on “Propagation of Unit Location Uncertainty in Dense Storage Environments”.  With help from Dr. Kellie Schneider, a journal out of his work has been submitted for review.  Mohamed Awwad defended his Ph.D. dissertation this Fall, which focuses on searching in dense storage environments.  We have received constructive reviews back on a submitted paper and are currently working on revisions.  Finally, Faraz Ramtin (who was the first student to jointly work with me) graduated this Spring with his Ph.D. His work on MIAPP AS/RS is ongoing and has led to interesting discussions with other facility logistics researchers who are modeling other aspects of the technology used for distribution.  He has two accepted publications in IIE Transactions and is preparing a third contribution for publication.

 

MohamedDefense

Mohamed Awwad defends his dissertation at UCF, while I attend proudly from NY.

Undergraduate researchers bring a rad perspective to our research.  This semester I had six undergraduates who worked on projects associated with supply chain modeling of ship-from-store fulfillment, sharing economy models for supply chains, and seabased logistics.

On my drive from Florida to New York, I got an awesome tour of Duke’s campus from Catherine Ninah, who was an undergraduate researcher at UCF and conducted research via an REU.  Catherine Ninah and Kristin Elias were involved with ICubed at UCF – their collaborations with art students created some cool art based on our seabased logistics research.

 

In 2015, I finally got to teach a logistics course in the spring, and enjoyed incorporating my research and the material handling and logistics US roadmap into the course.  I just wrapped up a rewarding class on the Design and Analysis of Supply Chains.  One of the introductory assignments was to have students create a “Supply Chain and You” slide to motivate the students to think about the importance and impact of the course topics on the students’ lives, and also allowed me to get to know the students better.   Here’s mine:

Supply Chains and Me

The course ended with a review of the topics helped by students’ memes.  Here is my favorite, which reminds students when calculating the amount of safety stock you need to use the square root of the lead time.

Final Exam Review - Fall 2015

My mission to create more Industrial Engineers has continued in 2015.  I enjoyed participating at CAMP Connect, presenting to the Eureka! Program of Girls Incorporated in the Capital Region, to the RPI student chapter of IIE about “What is Industrial Engineering and Why Does it Rock?” and attending the Women at Rensselaer Mentor Program.

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Attending the Women at Rensselaer Mentor Program.

My 2016 calendar already contains a number of projects that will allow me to learn a lot.  Some I am most excited about include an interdisciplinary academic-industry partnership proposal on smart, secure on-demand authorization systems for logistics and distribution  (with material scientists and computer science researchers from SDSMT), presenting at the Transportation Research-Board workshop on “On-Demand and Sharing Economy for Freight” and leading a panel discussion at the Warehousing Education and Research Council (WERC) on Crowdsourcing and Collaborative Warehousing and Logistics.

Cheers!

Jen

Selfie with the newly hooded Dr. Ali Bozorgi

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It was my honor to hood Dr. Ali Bozorgi today at UCF Commencement. My first graduated Ph.D. Student is off to Clemson University for a post doctoral position starting this summer.  I co-advised Ali with Dima Nazzal at Georgia Tech.

What Supply Chain Means to Me? #SC4ME

SupplyChainDay

April 10th, 2014 is Supply Chain Day.  And to celebrate, Eye for Transport is posting a daily quote on what supply chain means to individuals within the industry.  Given my primary research focus is applying operations research methodologies to logistic challenges, I thought I would offer my opinion on what supply chain means to me.

Supply chain and logistics enables us to experience the things that make us happy and healthy.  Here are three personal, tangible reasons why I think supply chain and logistics play an important role in our day-to-day lives and our economy.

  1. FacebookLogistics
    The picture above is a screen shot of my mother-in-law’s Facebook post around her birthday.  Logistics is THE modern marvel that enables her to enjoy beautiful tulips in frigid Wyoming in February.

  2. PazourFamilyFeedersMy family is in the beef business.  They produce a great product that they believe should be consumed around the world.  Great supply chains and logistics are what enable me to enjoy Pazour Beef in Florida.  On the flipside, logistics is also what enables my Dad to enjoy Lobster in South Dakota.  Without logistics, we would be confined to experiencing only the products that we could produce in front of us.
  3. Given that in the U.S. almost 40 percent of the drugs we take are made somewhere else, logistics plays a vital role in getting the medications that save lives to the patients that need them. 

To understand what supply chains have done for others, follow the twitter hashtag #SC4ME.

Congratulations-your-manuscript-has-been-accepted email

It is always fun to get the Congratulations-your-manuscript-has-been-accepted email, but it is especially rewarding when your coauthor of the accepted paper is your Ph.D. student!    This is an academic first for me — an accepted publication with a student.  Congrats to Faraz Ramtin for his hardwork and dedication to this research.  The idea came from me visiting a grocery distribution center and watching their case fulfillment process in cold temperature distribution centers; however, Faraz, took the idea and made it his own.    

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The paper specifics:

“Analytical Models for an Automated Storage and Retrieval System with Multiple in-the-Aisle Pick Positions”

Faraz Ramtin 1 & Jennifer A. Pazour 1

1 Department of Industrial Engineering and Management Systems, University of Central Florida, Orlando, FL, 32816, USA

E-mail: faraz.ramtin@ucf.edu; jennifer.pazour@ucf.edu

to appear in IIE Transactions.  

An automated storage and retrieval system with multiple in-the-aisle pick positions (MIAPP-AS/RS) is a case-level order-fulfillment technology that enables order picking via multiple pick positions (outputs) located in the aisle. We develop expected travel time models for different operating policies and different physical configurations.  These models can be used to analyze MIAPP-AS/RS throughput performance during peak and non-peak hours. Moreover, closed-form approximations are derived for the case of an infinite number of pick positions, which enable us to derive the optimal shape configuration that minimizes expected travel times.  We compare our expected travel time models with a simulation model of a discrete rack, and the results validate that our models provide good estimates. Finally, we conduct a numerical experiment to illustrate the trade-offs between performance of operating policies and design configurations. We find that MIAPP-AS/RS with a dual picking floor and input point is a robust configuration because a single command operating policy has comparable throughput performance to a dual command operating policy.  

 

Seminar Series at the University of Florida

UF

I presented in the University of Florida’s Industrial and System’s Engineering Seminar Series on Halloween.  I enjoyed my  time among the Gators, especially the time I spent meeting the ISE faculty and learning about the neat research they are working on.  The comments and questions I received from my presentation on “Analytical Modeling of Logistics System Design” sparked some new thoughts and directions for my research.

Here’s my research presentation description:

Logistics is concerned with the efficient flow and storage of goods from point of origin to point of consumption, and plays an important role in our day-to-day lives and our economy.  To illustrate, consider the “journey” of the things we use in our lives.  Think about the succulent strawberries in your lunch that provide nourishment, think about the medical supplies necessary to keeping us healthy, or think about the smart phone that you constantly check.  Logistics has enabled us to enjoy all of these things.  My research focuses on greater understanding of logistic system design through the development of analytical decision-making models.  This presentation will focus on an important problem in distribution center design and in military logistics.

Reshuffling is a warehouse strategy where the storage locations of items are changed during idle time to create a new layout configuration that will improve picking and put-away performance. This study investigates how to optimize reshuffling and quantifies the effect of common assumptions in the reshuffling literature. The contributions of this study include the first mathematical programming formulation for the general reshuffling problem, a lower bound that demonstrates the intrinsic complexity of the problem, several heuristics based on the problem structure, and managerial insights on the performance of reshuffling policies in various environments. Experimental results suggest that the proposed insight-based heuristics statistically improve upon a benchmark heuristic by relaxing how items in cycles are handled and incorporating double-handling.

Seabasing is a strategy implemented by the US Navy 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 eliminate the need for a stockpile of materials on shore.  Vital components of seabasing include selective offloading capabilities, ship-to-objective logistics via aerial delivery, and vessel-to-vessel cargo replenishment. Sea-based logistics operate in a challenging and uncertain environment and have unique mission characteristics; consequently, sea-based logistics require the development of specific logistics models.  We are currently building analytical models to help design and evaluate responsive sea-based logistics delivery systems with imperfect visibility.

Coding — an achievable super power

Who hasn’t wanted to have special powers like superheroes. How cool would it be to have even one of Superman’s powers or to live one day with the powers of a superhero?  It turns out you can.

A great video about the power of coding has been circulating around the internet.  Watch it.  Learn to Code.  It’s good stuff.  Also, check out www.code.org for some inspiring quotes from a wide consortium of people about the power and usefulness of computer coding.

Two of my favorite quotes from http://www.code.org are:

Meg Whitman
President & CEO, Hewlett-Packard
“If you have a daughter, she should go be an engineer.“
John Thune
U.S. Senator, South Dakota
“Whether our children want to become farmers, doctors, teachers, or entrepreneurs, it’ll be easier for them to achieve their dreams in the digital age if they have some background in computer science. We need our children to learn 21st century skills for a 21st century world, and coding teaches them the creativity and problem-solving skills that are necessary for success.“

I really enjoy coding, especially the aspects of breaking a problem down into logical elements.  I do not claim to be a great coder, but view coding as a vital part of illustrating the impacts of my research and something that I truly enjoy.

If I could go back to high school or to undergrad, one of the things I would do differently would be to take a course in computer programming.  I didn’t get exposed to coding until graduate school, where I was blessed to have graduate school friends like Hugh and Steve who helped me obtain skills in object oriented programming.  When I first started, I was extremely intimidated.  However, through a process of learning as I went coding different projects and thanks to taking a course in heuristics, which forced me to code, I gradually learned enough to get by.  I now use computer programming in my research to implement solution approaches.  Coding is an extremely rewarding experience (when your code does what you want it to do).  I like that with coding you get to see directly the fruits of your labor.  It is also pretty cool that with computer programming you can enable, with just a push of a button, some pretty powerful and amazing things.    It is also one of the more valuable skills I believe companies are looking for in employees, and one of the important skills we can instill in our students.