Our main objective is to investigate the dynamics of inventory oscillations as a function of delays in supply chains.

Delays in supply chains arise due to

  1. Transportation of products
  2. Outsourcing
  3. Production/lead times
  4. Decision making
  5. Information availability

Presence of delays may lead to undesirable oscillations in inventories. This ultimately reflects to costs, quality of service and demand amplification.

How can we explain inventory oscillations as a function of delays? We combine this problem with our expertise on stability charts, which in essence display which combinations of delays are "friendly", i.e. lead to desirable behavior of the inventories. With these unique tools in hand, we investigate the following open problems:

  1. Presence of multiple delays (delay heterogeneity) and how delay effects cross couple when affecting inventory oscillations
  2. Extraction of high-dimensional stability charts
  3. Utilization of stability charts for better supply chain management, such as for ordering, policy writing and cost optimization
  4. Understanding collaboration across supply chains for improved inventory regulation

We see the impacts of our research in the following areas

  1. Improved supply chain management through "delay management"
  2. Stability charts to assist supply chain managers
  3. Assistance in policy writing and negotiations
  4. Direct impacts to supply chain management for early stage firms
  5. Cost minimization for companies that are prone to large delivery delays due to outsourcing
  6. Reverse supply chains

Students
  1. Ismail Ilker Delice - PhD candidate, Northeastern University

  2. Rodrigue Tchapnga Takoudjou - visitor, Ecole Centrale de Nantes

 

Recently Published Relevant Work

  1. Sipahi, R., Delice, I.I., Stability of Inventory Dynamics in Supply Chains with Three Delays, in print, International Journal of Production Economics.

  2. Sipahi, R., Lammer, S., Niculescu, S.-I., Helbing, D., 2009, Delays due to Transport Phenomenon in Supply Networks and Arising Stability Problems, ASME Journal of Dynamic Systems, Measurement & Control, vol. 131, 021005, 1-9.

  3. Sipahi R., Delice, I.I., Inventory Dynamics Models of Supply Chains with Delays; System-Level Connection & Stability, chapter in Topics in Time-Delay Systems: Analysis, Algorithms and Control in Lecture Notes in Control and Information Sciences, Springer-Verlag, Editors: Loiseau, J.-J., Niculescu, S.-I., Michiels, W., Sipahi, R.

  4. Delice, I.I., Sipahi, R., Identifying Stability vs. Instability of Inventory Dynamics of Supply Chains in Presence of Delays, ASME IMECE, Boston, 2008.

  5. Delice, I.I., Sipahi, R., Marion, T.J. Minimization of Costs in Interconnected Supply Networks with Transportation and Decision-Making Delays, SIAM Conference on Optimization, Boston, 2008.

  6. Sipahi, R., Delice, I.I, Delay Modeling in Supply Network Dynamics; Performance, Synchronization, Stability, 17th IFAC World Congress, Seoul, Korea, 2008.

Recent Presentations

  1. Northeastern University Research Expo Delice (2008), Delice (2009), Rodrigue (2009)

  2. ASME - IMECE 2006, Chicago. Stability of supply networks under presence of transportation delays.

  3. IFAC World Congress, 2008, Seoul. Presentation