https://scholarworks.bwise.kr/hanyang/handle/2021.sw.hanyang/208 2026-07-03T13:59:04Z 2026-07-03T13:59:04Z Tian, Runcao Bae, Suk Joo Chen, Zhongshu Liu, Yu https://scholarworks.bwise.kr/hanyang/handle/2021.sw.hanyang/212275 2026-04-21T04:30:26Z 2026-08-01T00:00:00Z

Title: Unified stochastic modeling and reliability assessment for coupled degradation mechanisms Authors: Tian, Runcao; Bae, Suk Joo; Chen, Zhongshu; Liu, Yu Abstract: Engineered systems often experience coupling effects with multiple degradation mechanisms during their operation. A well-tuned modeling process of such complex degradation mechanisms is crucial for accurate reliability assessment of engineered systems. This study puts forth a unified stochastic process model for (accelerated) degradation data with coupled mechanisms in a form of weighted mixture. The weighted hybrid degradation process is based mainly on the Tweedie exponential dispersion process (TEDP) as a unified model of traditional stochastic processes for a unique degradation mechanism via a continuously adjustable shape parameter and nonlinear time transformation. By assigning proper weights to quantify the contributions of coupled degradation effects, the weighted mixture model permits flexible modeling of complex degradation mechanisms. Under the proposed degradation modeling framework, we propose a new accelerated degradation test (ADT) model to extrapolate lifetime distribution at normal use condition through the relationship between stress and degradation rate. To derive maximum likelihood estimates (MLEs) of the model parameters, we newly design the expectation-maximization (EM) algorithm and compare the performance of widely adopted numerical optimizers in terms of convergence rate and computational efficiency. A variety of simulation studies and analyses of two real-world cases validate the effectiveness of the proposed degradation modeling and reliability assessment framework.

2026-08-01T00:00:00Z Kim, Hyeon-Il Lee, Dong-Ho https://scholarworks.bwise.kr/hanyang/handle/2021.sw.hanyang/214012 2026-06-22T06:30:27Z 2026-07-01T00:00:00Z

Title: Two-phase optimal and heuristic algorithms for flow shop scheduling with reworks under overlapped queue time limits Authors: Kim, Hyeon-Il; Lee, Dong-Ho Abstract: This study addresses flow shop scheduling in which each job is reworked when one of its overlapped queue time limits is violated. The problem is to determine the start times of jobs at each stage and rework setups/operations if occur. After decomposing the problem into the job process route selection and the resulting flow shop or reentrant flow shop scheduling sub-problems, a two-phase optimal branch and bound (TP-B&B) algorithm is proposed for the three-stage makespan problem. The algorithm consists of generating the job process routes using a two-level tree, and finding the resulting optimal schedules using a B&B algorithm while reducing the search space by a dominance property and the best upper bound obtained by solving the resulting scheduling problems. Moreover, for the multi-stage makespan problem, a basic two-phase variable neighborhood search (TP-VNS) algorithm is proposed that solves the two sub-problems iteratively, where each sub-problem is solved using a shaking and local search improvement method with different neighborhood structures. Then, it is extended to a general TP-VNS algorithm with a variable neighborhood descent method. Computational results show that the TP-B&B algorithm gave 21.5% more optimal solutions than the Gurobi while requiring much less computation times for the small sized test instances. Also, the TP-VNS algorithms outperform the existing one significantly. Specifically, the basic (general) TP-VNS algorithm gave 0.7% (1.2%) improvement in the overall optimality gap for small sized test instances, and 1.2% (2.9%) improvement in the overall relative performance ratio for medium-to-large sized test instances.

2026-07-01T00:00:00Z 이동호 https://scholarworks.bwise.kr/hanyang/handle/2021.sw.hanyang/214149 2026-06-29T12:00:30Z 2026-06-05T00:00:00Z

Title: Dynamic System Configuration Selection Algorithms for Reconfigurable Single-part Flow Lines with Controllable Processing Times Authors: 이동호

2026-06-05T00:00:00Z 이동호 https://scholarworks.bwise.kr/hanyang/handle/2021.sw.hanyang/214148 2026-06-29T12:00:28Z 2026-06-05T00:00:00Z

Title: A Multi-objective Genetic Programming based Variable Neighborhood Search Algorithm for Dynamic Hybrid Flow Shop Scheduling with Machine Availability and Possible Reworks under Overlapped Queue Time Limits Authors: 이동호

2026-06-05T00:00:00Z