@article{luo_ahiska_fang_king_warsing_wu_2021, title={An analysis of optimal ordering policies for a two-supplier system with disruption risk}, volume={105}, url={https://doi.org/10.1016/j.omega.2021.102517}, DOI={10.1016/j.omega.2021.102517}, abstractNote={• Optimal policy can be proved for a two-supplier system with an unreliable supplier. • Stable (s,S) policy is robust outside of parameter conditions for optimality. • There is an easily computed condition for exclusive unreliable supplier ordering. • Optimal policies move from exclusive ordering to splitting as key parameters vary. We study a single-product, periodic-review inventory system with the presence of fixed ordering cost. There are two suppliers: One is perfectly reliable while the other offers a cost advantage but is subject to possible supply interruptions. We present a theoretical framework with mathematical proofs for the optimal ordering policy in the finite-horizon setting, which exhibits an ( s , S ) structure, but with multiple, sometimes overlapping, reorder points and order-up-to levels. Then, we analyze the limiting behavior of our ( s , S ) policy and show that both the optimal cost and ordering policy parameters converge over time. This steady-state ( s , S ) policy characterizes the optimal sourcing strategy for the infinite-horizon setting. Through computational studies, we investigate the effects of parameter changes on the optimal policy and demonstrate that our two-supplier ( s , S ) ordering policy is optimal under a wide range of system parameters beyond the conditions required in the optimality proof.}, journal={Omega - The International Journal of Management Science}, publisher={Elsevier BV}, author={Luo, Sha and Ahiska, S. Sebnem and Fang, Shu-Cherng and King, Russell E. and Warsing, Donald P., Jr. and Wu, Shuohao}, year={2021}, month={Dec}, pages={102517} }
 @misc{powers_bieliaieva_wu_nam_2015, title={The Human Factors and Ergonomics of P300-Based Brain-Computer Interfaces}, volume={5}, ISSN={["2076-3425"]}, DOI={10.3390/brainsci5030318}, abstractNote={Individuals with severe neuromuscular impairments face many challenges in communication and manipulation of the environment. Brain-computer interfaces (BCIs) show promise in presenting real-world applications that can provide such individuals with the means to interact with the world using only brain waves. Although there has been a growing body of research in recent years, much relates only to technology, and not to technology in use—i.e., real-world assistive technology employed by users. This review examined the literature to highlight studies that implicate the human factors and ergonomics (HFE) of P300-based BCIs. We assessed 21 studies on three topics to speak directly to improving the HFE of these systems: (1) alternative signal evocation methods within the oddball paradigm; (2) environmental interventions to improve user performance and satisfaction within the constraints of current BCI systems; and (3) measures and methods of measuring user acceptance. We found that HFE is central to the performance of P300-based BCI systems, although researchers do not often make explicit this connection. Incorporation of measures of user acceptance and rigorous usability evaluations, increased engagement of disabled users as test participants, and greater realism in testing will help progress the advancement of P300-based BCI systems in assistive applications.}, number={3}, journal={BRAIN SCIENCES}, author={Powers, J. Clark and Bieliaieva, Kateryna and Wu, Shuohao and Nam, Chang S.}, year={2015}, month={Sep}, pages={318–354} }