Selected working papers

1. S. Shu#, Z. Xu*, and R. Baldacci, "New Dynamic Discretization Discovery Strategies for Continuous-Time Service Network Design", under review.

2. S. Jia#, Z. Ao, and Z. Xu, "Managing Truck Service to Mitigate Congestion in a Container Terminal", under review.

3. Y. Yang, X. Hao#*, S. Wang, and Z. Xu, "Column Enumeration via Strategic Row Aggregation for Split Delivery Vehicle Routing with Time Windows", under review.

JOURNAL Publications

(* for the corresponding author; # stands for PhD students/Postdoctoral fellows supervised)

1. S. Shu#, Z. Xu*, and J. Qi, 2026, "Robust Service Network Design under Travel Time Uncertainty: Formulations and Exact Solutions", INFORMS Journal on Computing (IJOC), forthcoming.

2. S. Zhou, X. Liu, J. Chen*, L. Wu, Z. Xu, and M. Zhao, 2026, "Truck-drone Collaborative Delivery under Real-time Traffic Congestion: A Novel Variable Neighborhood Search Metaheuristic", Transportation Research Part E (TRE), forthcoming.

3. Y. Zhang, J. Zheng*, Y. Yuan, and Z. Xu, 2026, "Stabilizing Cooperation in E-Waste Recycling with Collective Extended Producer Responsibility: An Inverse Optimization Approach", Transportation Research Part E (TRE), 210:104837.

4. Y. Liu, J. Xia#*, and Z. Xu, 2026, “Drone Scheduling Optimization for Continuous Sea Area Monitoring”, Transportation Research Part E (TRE), 208, 104701.

5. Z. Huang#, Z. Xu, and X. Fu, 2026, "Simulation-Optimization for Resource Allocation at SF Express Hub", INFORMS Journal on Applied Analytics (IJAA), 56(3), 213-309. 

6. J. Feng#, H. Ma*, Z. Xu, 2026, "Optimizing Three-Dimensional Bag Packing", IEEE Transactions on Automation Science and Engineering (T-ASE), 23, 1519-1532.

7. Z. Liang*, S. Li*, Y. Chen, and Z. Xu, 2026, "Complexity and Approximation Algorithms for Fixed Charge Transportation Problems", Journal of Computer and System Sciences (JCSS), 162, 103830.

8. Y Liu#, T. Wang#, H. Ma*, and Z. Xu, 2026 "Integrated Optimization of Multi-period Yard Template Planning and Loading and Unloading Scheduling for Transshipment Vessels", Asia-Pacific Journal of Operational Research (APJOR), forthcoming.

9. M. Wang, F. Li#*, Z. Xu, X. Yang#, and J. Wang, 2025, "Order Selection and Fulfillment Integration with Flexible Products", 2026, Omega, 138, 103429.

10. J. Xia#, Z. Xu*, and R. Baldacci, 2025, "A Simultaneous Column-and-Row Generation Solution Method for Liner Shipping Network Design", Operations Research (OR), 73(4),1825-1848.

11. C. Zhang#, Z. Xu, L. Yang*, Z. Gao, and Y. Gao, 2025, "Robust Train Carriage Planning for Mixed Transportation of Passengers and Uncertain Freights in a High-Speed Railway", Transportation Research Part B (TRB), 196, 103216.

12. L. Xu#, C. Zhang*, Z. Xu, and D. Long, 2025, "A Non-Parametric Robust Optimization Approach for Chance-Constrained Knapsack Problem", SIAM Journal on Optimization (SIOPT), 35(2), 739-766.

13. H. Ma, J. Zhu#, Z. Xu, and Y. Liu#, 2025, "Flight Retiming Problem under Time-Dependent Uncertainty”, IEEE Transactions on Intelligent Transportation Systems (T-ITS), 26(11), 20965-20975.

14. X. Zhang#, M. Li, Z. Xu, and Y. Zhao, 2025, "The Stack Loading Problem with Load-Bearing Limit", IEEE Transactions on Automation Science and Engineering (T-ASE), 22, 1801-1816.

15. Z. Xu, F. Li#*, and Z.-L. Chen*, 2024, "Shipment Consolidation with Multiple Shipping Methods under Nonlinear Cost Structures", Management Science (MS), 70(5), 2823-2841.

16. L. Liu#, X. Qi, and Z. Xu*, 2024, "Stabilizing Grand Cooperation via Cost Adjustment: An Inverse Optimization Approach", INFORMS Journal on Computing (IJOC), 36(2), 635-656.

17. S. Shu#, Z. Xu, and R. Baldacci*, 2024, "Incorporating Holding Costs in Continuous-Time Service Network Design: New Model, Relaxation, and Exact Algorithm", Transportation Science (TS), 58(2), 412-433.

18. X. Yang#, F. Li#*, Z. Liu, and Z. Xu, 2024, "New Exact and Heuristic Algorithms for General Production and Delivery Integration", European Journal of Operational Research (EJOR), 316, 419-442.

19. J.J. Huang#*, C.P. Teo, F. Wang, and Z. Xu, 2023, "Buffer Times Between Scheduled Events in Resource Assignment Problem: A Conflict-Robust Perspective", Manufacturing & Service Operations Management (M&SOM), 25(6), 1999-2370.

20. X. Lai#, L. Xu#*, Z. Xu, and Y. Du, 2023, "An Approximation Algorithm for k-Depot Split Delivery Vehicle Routing Problem", INFORMS Journal on Computing (IJOC), 35(5), 909-1213.

21. N. Zhang, Z. Liu, F. Li#, Z. Xu, and Z. Chen, 2023, "Stable Matching for Crowdsourcing Last-Mile Delivery", IEEE Transactions on Intelligent Transportation Systems (T-ITS), 24(8),  8174-8187.

22. J. Li#, H. Qin, Z. Luo*, R. Baldacci, and Z. Xu, 2023, "A New Exact Algorithm for Single Commodity Vehicle Routing with Split Pickups and Deliveries", INFORMS Journal on Computing (IJOC), 35(1), 31-49.

23. F. Li#, S. Xu#, Z. Xu*, 2023, "New Exact and Approximation Algorithms for Integrated Production and Transportation Scheduling with Committed Delivery Due Dates and Order Acceptance", European Journal of Operational Research (EJOR), 306(1), 127-140.

24. J. Li#, H. Qin, H. Shen*, X. Tong, and Z. Xu, 2022, "Exact Algorithms for the Multiple Depot Vehicle Scheduling Problem with Heterogeneous Vehicles, Split Loads and Toll-by-weight Scheme", Computers & Industrial Engineering (CIE), 108137.

25. T. Wang#, H. Ma*, Z. Xu, and J. Xia#, 2022, "A New Dynamic Shape Adjustment and Placement Algorithm for the 3D Yard Allocation Problem with Time Dimensions", Computers and Operations Research (COR), 138, 105585.

26. X. Yang#, Z. Liu, F. Li#*, and Z. Xu, 2021, "Integrated Production and Transportation Scheduling with Order-dependent Inventory Holding Costs", Computers and Operations Research (COR), 136, 105477.

27. X. Xu#, C.-L. Li*, and Z. Xu, 2021, "Train Timetabling with Stop-Skipping, Passenger Flow, and Platform Choice Considerations", Transportation Research Part B (TRB), 150, 52-74.

28. C.-Y. Lee, S. Shu#*, and Z. Xu, 2021, "Optimal Global Liner Service Procurement by Utilizing Liner Service Schedules", Production and Operations Management (POM), 30 (3), 703-714.

29. S. Jia#, C.-L. Li, and Z. Xu*, 2020, "A Simulation Optimization Method for Deep-Sea Vessel Berth Planning and Feeder Arrival Scheduling at a Container Port", Transportation Research Part B (TRB), 142, 174-196.

30. F. Li#, Z. Xu*, and Z.-L. Chen, 2020, "Production and Transportation Integration for Commit-to-Delivery Mode with General Shipping Costs", INFORMS Journal on Computing (IJOC), 32(4), 1012-1029.

31. S. Zhou, H. Zhang, N. Shi, Z. Xu, and F. Wang, 2020, "A New Convergent Hybrid Learning Algorithm for Two-stage Stochastic Programs", European Journal of Operational Research (EJOR), 283(1), 33-46. 

32. S. Jia#, C.-L. Li, and Z. Xu*, 2019, "Managing Navigation Channel Traffic and Anchorage Area Utilization of a Container Port", Transportation Science (TS), 53(3), 728-745.

33. X. Xu#, C.-L. Li*, and Z. Xu, 2018, "Integrated Train Timetabling and Locomotive Assignment", Transportation Research Part B (TRB), 117A, 573-593.

34. L. Liu#, X. Qi, and Z. Xu, 2018, "Simultaneous Penalization and Subsidization for Stabilizing Grand Cooperation", Operations Research (OR), 66(5), 1189-1456.

35. Z. Xu and C.-Y. Lee, 2018, "New Lower Bound and Exact Method for the Continuous Berth Allocation Problem", Operations Research (OR), 66(3), 778-798.

36. Z. Xu* and B. Rodrigues, 2017, "An Extension of the Christofides Heuristic for the Generalized Multiple Depot Multiple Traveling Salesmen Problem", European Journal of Operational Research (EJOR), 257(3), 735--745.

37. L. Liu#, X. Qi, and Z. Xu, 2016, "Computing Near-Optimal Stable Cost Allocations for Cooperative Games by Lagrangian Relaxation", INFORMS Journal on Computing (IJOC), 28(4), 687--702.

38. L. Zhen*, Z. Xu, K. Wang, and Y. Ding, 2016, "Multi-Period Yard Template Planning in Container Terminals", Transportation Research Part B (TRB), 93B, 700--719.

39. X. Lai# and Z. Xu*, 2016, "Improved Algorithms for Joint Optimization of Facility Locations and Network Connections", European Journal of Operational Research (EJOR), 250(3), 745-753.

40. Z. Xu* and B. Rodrigues, 2015, "A 3/2-Approximation Algorithm the Multiple TSP with a Fixed Number of Depots", INFORMS Journal on Computing (IJOC), 27(4), 636-645.

41. J. Xia#, K. Li, H. Ma*, and Z. Xu, 2015, "Joint Planning of Fleet Deployment, Speed Optimization and Cargo Allocation for Liner Shipping", Transportation Science (TS), 49(4), 922-938.

42. Z. Xu, X. Lai#, F. Wang*, and A. Lim, 2014, "An Improved Approximation Algorithm for the Capacitated TSP with Pickup and Delivery on a Tree", Networks, 63(2), 179--195.

43. Z. Xu*, 2013, "The Knapsack Problem with a Minimum Filling Constraint", Naval Research Logistics (NRL), 60(1), 56-63.

44. L. Xu#, Z. Xu*, and D. Xu, 2013, "Exact and Approximation Algorithms for the Min-max k-Traveling Salesman Problem on a Tree", European Journal of Operational Research (EJOR), 227(2), 284-292.

45. F. Wang and Z. Xu*, 2013, "Metaheuristics for Robust Graph Coloring", Journal of Heuristics (JOH), 19(4), 529-548.

46. Z. Xu*, 2012, "A Strongly Polynomial FPTAS for the Symmetric Quadratic Knapsack Problem", European Journal of Operational Research (EJOR), 218(2), 377-381.

47. Z. Xu*, D. Xu, and W. Zhu, 2012, "Approximation Results for a Min-Max Location-Routing Problem", Discrete Applied Mathematics (DAM), 160(3), 306-320.

48. A. Lim, H. Qin*, and Z. Xu, 2012, "The Freight Allocation Problem with Lane Cost Balancing Constraint", European Journal of Operational Research (EJOR), 217(1), 26-35.

49. Z. Xu, B. Cheang*, A. Lim, and Q. Wen, 2011, "Evaluating OR/MS Journals via PageRank", Interfaces, 41(4), 375-388.

50. Z. Xu*, L. Xu#, and B. Rodrigues, 2011, "An Analysis of the Extended Christofides Heuristic for the k-depot TSP", Operations Research Letters (ORL), 39(3), 218-223.

51. A. Pang, Z. Xu, and C.-L. Li*, 2011, "Ship Routing Problem with Berthing Time Clash Avoidance Constraints", International Journal of Production Economics (IJPE), 131(2), 752-765.

52. Z. Xu*, L. Xu#, and C.-L. Li, 2010, "Approximation Results for Min-max Path Cover Problems in Vehicle Routing", Naval Research Logistics (NRL), 57(8), 728-748.

53. Z. Xu* and Q. Wen, 2010, "Approximation Hardness of Min-max Tree Covers", Operations Research Letters (ORL), 38(3), 169--173.

54. Q. Fu, L. Liu, and Z. Xu*, 2010, "Port Resource Rationalization for Better Container Barge Services in Hong Kong", Maritime Policy and Management (MPM), 37(6), 543-561.

55. A. Lim, H. Ma, Q. Wen, Z. Xu*, and B. Cheang, 2009, "Distinguishing Citation Quality for Journal Impact Assessment", Communications of the ACM (CACM) , 52(8), 111-116.

56. A. Lim, and Z. Xu*, 2009, "Searching Optimal Resequencing and Feature Assignment on an Automated Assembly Line", Journal of Operational Research Society (JORS), 60(3), 361-371.

57. A. Lim, B. Rodrigues, and Z. Xu*, 2008, "Transportation Procurement with Seasonally Varying Shipper Demand and Volume Guarantees", Operations Research (OR), 56(3), 758-771.

58. A. Lim, F. Wang, and Z. Xu*, 2008, "The Bidding Selection and Assignment Problem with Minimum Quantity Commitment", Journal of the Operational Research Society (JORS), 59(5), 693-702.

59. A. Lim, B. Rodrigues, and Z. Xu*, 2007, "A m-Parallel Crane Scheduling Problem With A Non-Crossing Constraint", Naval Research Logistics (NRL), 54(2), 115-127.

60. A. Lim, F. Wang, and Z. Xu*, 2006, "A Transportation Problem with Minimum Quantity Commitment", Transportation Science (TS), 40(1), 117-129.

61. A. Lim and Z. Xu*, 2006, "The Bottleneck Problem with Minimum Quantity Commitments", Naval Research Logistics (NRL), 53(1), 91-100.

62. A. Lim and Z. Xu*, 2006, "A Critical Shaking Neighborhood Search for Yard Allocation", European Journal of Operational Research (EJOR), 174(2), 1247-1259.

63. F. Wang*, A. Lim, and Z. Xu, 2006, "The One-Commodity Pickup and Delivery Traveling Salesman Problem on a Path or a Tree", Networks, 48(1), 24-35.

64. A. Lim, Z. Miao*, B. Rodrigues, and Z. Xu, 2005, "Transshipment through Crossdocks with Inventory and Time Windows", Naval Research Logistics (NRL), 52(8), 724-733.

65. A. Lim, B. Rodrigues, F. Wang, and Z. Xu*, 2005, "K-Center Problems With Minimum Coverage", Theoretical Computer Science (TCS), 332(1-3), 1-17.