Soroush Saghafian

Flowshop-scheduling problems with makespan criterion: a review

This paper is a complete survey of flowshop-scheduling problems and contributions from early works of Johnson of 1954 to recent approaches of metaheuristics of 2004. It mainly considers a flowshop problem with a makespan criterion and it surveys some exact methods (for small size problems), constructive heuristics and developed improving metaheuristic and evolutionary approaches as well as some well-known properties and rules for this problem. Each part has a brief literature review of the contributions and a glimpse of that approach before discussing the implementation for a flowshop problem. Moreover, in the first section, a complete literature review of flowshop-related scheduling problems with different assumptions as well as contributions in solving these other aspects is considered. This paper can be seen as a reference to past contributions (particularly in n/m/p/c max or equivalently F/prmu/c max) for future research needs of improving and developing better approaches to flowshop-related scheduling problems.

Multi-criteria Group Decision Making Using A Modified Fuzzy TOPSIS Procedure

In this paper we propose a modified fuzzy technique for order performance by similarity to ideal solution (modified fuzzy TOPSIS) for the multi-criteria decision making (MCDM) problem when there is a group of decision makers. Regarding the value of the truth that a fuzzy number is greater than or equal to another fuzzy number, a new distance measure is proposed in this paper. This distance measure calculates the distance of each fuzzy number from both fuzzy positive ideal solution (FPIS) and fuzzy negative ideal solution (FNIS). Then, the alternative which is simultaneously closer to FPIS and farther from FNIS would be selected as the best choice. To clarify our proposed procedure, a numerical example is discussed

Patient Streaming as a Mechanism for Improving Responsiveness in Emergency Departments

Crisis-level overcrowding conditions in emergency departments EDs have led hospitals to seek out new patient-flow designs to improve both responsiveness and safety. One approach that has attracted attention and experimentation in the emergency medicine community is a system in which ED beds and care teams are segregated and patients are “streamed” based on predictions of whether they will be discharged or admitted to the hospital. In this paper, we use a combination of analytic and simulation models to determine whether such a streaming policy can improve ED performance, where it is most likely to be effective, and how it should be implemented for maximum performance. Our results suggest that the concept of streaming can indeed improve patient flow, but only in some situations. First, ED resources must be shared across streams rather than physically separated. This leads us to propose a new “virtual-streaming” patient flow design for EDs. Second, this type of streaming is most effective in EDs with 1 a high percentage of admitted patients, 2 longer care times for admitted patients than discharged patients, 3 a high day-to-day variation in the percentage of admitted patients, 4 long patient boarding times e.g., caused by hospital “bed-block”, and 5 high average physician utilization. Finally, to take full advantage of streaming, physicians assigned to admit patients should prioritize upstream new patients, whereas physicians assigned to discharge patients should prioritize downstream old patients.

Complexity-Augmented Triage: A Tool for Improving Patient Safety and Operational Efficiency

Hospital emergency departments (EDs) typically use triage systems that classify and prioritize patients almost exclusively in terms of their need for timely care. Using a combination of analytic and simulation models, we demonstrate that adding an up-front estimate of patient complexity to conventional urgency-based classification can substantially improve both patient safety (by reducing the risk of adverse events) and operational efficiency (by shortening the average length of stay). Moreover, we find that EDs with high resource (physician and/or examination room) utilization, high heterogeneity in the treatment time between simple and complex patients, and a relatively equal number of simple and complex patients benefit most from complexity-augmented triage. Finally, we find that (1) although misclassification of a complex patient as simple is slightly more harmful than vice versa, complexity-augmented triage is relatively robust to misclassification error rates as high as 25p; (2) streaming patients based on complexity information and prioritizing them based on urgency is better than doing the reverse; and (3) separating simple and complex patients via streaming facilitates the application of lean methods that can further amplify the benefit of complexity-augmented triage.

A Hybrid Manufacturing/Remanufacturing System With Random Remanufacturing Yield and Market-Driven Product Acquisition

Remanufacturing has created considerable benefits to both industry and community. This paper generates insights into the acquisition management and production planning of a hybrid manufacturing/remanufacturing system. The acquisition quantity of the used products is stochastic and sensitive to the acquisition price, and the uncertain quality of the acquired used products leads to a random yield in the remanufacturing process. With such a market-driven acquisition channel and a random remanufacturing yield, it is shown how the acquisition pricing, remanufacturing, and manufacturing decisions can be coordinated in order to maximize the total expected profit. Sequential and parallel remanufacturing/manufacturing processes are considered in different cases. In each case, we use a stochastic dynamic programming to formulate and analyze the model, showing that the optimal policy is characterized by several critical values and functions. We derive conditions under which the firm should open/close the acquisition channel and utilize/discard the remanufacturing option. By comparing the two cases, we show that expediting the remanufacturing process will help the firm to better utilize the acquisition channel and the remanufacturing option, as the optimal acquisition price and remanufacturing quantity are both higher in the case of sequential processes.

Joint control of production, remanufacturing, and disposal activities in a hybrid manufacturing–remanufacturing system

To generate insights into how production of new items and remanufacturing and disposal of returned products can be effectively coordinated, we develop a model of a hybrid manufacturing–remanufacturing system. Formulating the model as a Markov decision process, we investigate the structure of the optimal policy that jointly controls production, remanufacturing, and disposal decisions. Considering the average profit maximization criterion, we show that the joint optimal policy can be characterized by three monotone switching curves. Moreover, we show that there exist serviceable (i.e., as-new) and remanufacturing (i.e., returned) inventory thresholds beyond which production cannot be optimal but disposal is always optimal. We also identify conditions under which idling and disposal actions are always optimal when the system is empty. Using numerical comparisons between models with and without remanufacturing and disposal options, we generate insights into the benefit of utilizing these options. To effectively coordinate production, remanufacturing, and disposal activities, we propose a simple, implementable, and yet effective heuristic policy. Our extensive numerical results suggest that the proposed heuristic can greatly help firms to effectively coordinate their production, remanufacturing, and disposal activities and thereby reduce their operational costs.

EMERGENCY DEPARTMENT RAPID MEDICAL ASSESSMENT: OVERALL EFFECT AND MECHANISTIC CONSIDERATIONS

BACKGROUND Although the use of a physician and nurse team at triage has been shown to improve emergency department (ED) throughput, the mechanism(s) by which these improvements occur is less clear. OBJECTIVES 1) To describe the effect of a Rapid Medical Assessment (RMA) team on ED length of stay (LOS) and rate of left without being seen (LWBS); 2) To estimate the effect of RMA on different groups of patients. METHODS For Objective 1, we compared LOS and LWBS on dates when we utilized RMA to comparable dates when we did not. For Objective 2, we utilized patient logs to divide patients into groups and estimated the effects of the RMA on each. RESULTS Objective 1. LOS fell from 297.8 min pre-RMA to 261.7 min during RMA, an improvement of 36.1 (95% confidence interval 21.8-50.4) min; LWBS did not change significantly. Objective 2. Patients seen and dispositioned by the RMA had an estimated decrease in LOS of 117.8 min (estimated decrease in LOS of 45%), but patients seen by the RMA whose care was transitioned to the main ED had an estimated increase in LOS of 25.0 min (estimated increase in LOS of 8%). CONCLUSIONS On a system level, the addition of an RMA shift at a single facility was associated with an improvement in LOS, but not LWBS. On a mechanistic level, it seems that improvements occurred as a result of the rapid disposition component of the RMA rather than placing advanced orders at triage.

The Newsvendor Under Demand Ambiguity: Combining Data with Moment and Tail Information

that accommodates partial distributional information. We prove the proposed approach is (weakly) consistent under some technical regularity conditions and we analytically characterize its rate of convergence. We provide an analytical upper bound for the newsvendor’s cost of ambiguity, i.e., the extra per-period cost incurred due to ambiguity, under SOBME, and show that it approaches zero quite quickly. Numerical experiments demonstrate that SOBME performs very well. We nd that it can be very benecial to incorporate partial distributional information when deciding stocking quantities, and that information in the form of tighter moment bounds is typically more valuable than information in the form of tighter ambiguity sets. Moreover, unlike pure data-driven approaches, SOBME is fairly robust to the newsvendor quantile. Our results also show that SOBME quickly detects and responds to hidden changes in the unknown true distribution. We also extend our analysis to consider ambiguity aversion, and develop theoretical and numerical results for the ambiguity-averse, repeated newsvendor setting.

Emergency Department Rotational Patient Assignment

STUDY OBJECTIVE We compare emergency department (ED) operational metrics obtained in the first year of a rotational patient assignment system (in which patients are assigned to physicians automatically according to an algorithm) with those obtained in the last year of a traditional physician self-assignment system (in which physicians assigned themselves to patients at physician discretion). METHODS This was a pre-post retrospective study of patients at a single ED with no financial incentives for physician productivity. Metrics of interest were length of stay; arrival-to-provider time; rates of left before being seen, left subsequent to being seen, early returns (within 72 hours), and early returns with admission; and complaint ratio. RESULTS We analyzed 23,514 visits in the last year of physician self-assignment and 24,112 visits in the first year of rotational patient assignment. Rotational patient assignment was associated with the following improvements (percentage change): median length of stay 232 to 207 minutes (11%), median arrival to provider time 39 to 22 minutes (44%), left before being seen 0.73% to 0.36% (51%), and complaint ratio 9.0/1,000 to 5.4/1,000 (40%). There were no changes in left subsequent to being seen, early returns, or early returns with admission. CONCLUSION In a single facility, the transition from physician self-assignment to rotational patient assignment was associated with improvement in a broad array of ED operational metrics. Rotational patient assignment may be a useful strategy in ED front-end process redesign.

Can Public Reporting Cure Healthcare? The Role of Quality Transparency in Improving Patient-Provider Alignment

In the past two decades, government and private organizations have ramped up efforts to measure and publicly report clinical outcomes, a practice known as “public reporting.” For example, in 2005 t...