A Heuristic Approach for Determining Lot Sizes and Schedules Using Power-of-Two Policy

We consider the problem of determining realistic and easy-to-schedule lot sizes in a multiproduct, multistage manufacturing environment. We concentrate on a specific type of production, namely, flow shop type production. The model developed consists of two parts, lot sizing problem and scheduling problem. In lot sizing problem, we employ binary integer programming and determine reorder intervals for each product using power-of-two policy. In the second part, using the results obtained of the lot sizing problem, we employ mixed integer programming to determine schedules for a multiproduct, multistage case with multiple machines in each stage. Finally, we provide a numerical example and compare the results with similar methods found in practice

An improved metric for measuring multi-item multi-level schedule instability under rolling schedules

Disruptions in material plans due to unrealistic schedules and frequent plan revisions are common symptoms of a phenomenon generally referred to as nervousness or schedule instability in literature. A number of instability measures had been proposed so far. However, none of theta deals with instability measurement comprehensively. An appropriate measurement should be able to reflect the degree of changes under rolling schedules, as well as a tool for analyzing the performance of planning systems and nervousness dampening procedures

An application of a circular economy approach to design an energy-efficient heat recovery system

This paper aims to develop an optimal real-life energy-efficient design for a production plant within the concept of the circular economy. The problem is to install a Heat Recovery System (HRS) that utilizes the hot oil used by the compressors to heat the water for the central heating system. To achieve the desired level of energy efficiency this design problem must be formulated from both the optimization and sustainability points of view. Additionally, this design problem must also consider the investment cost. In line with this purpose, this paper formulates this design problem as an optimization problem employing a mathematical programming approach as a single objective, and as a multi-objective optimization problem through a goal programming approach. Besides, this paper uses the return on investment as a key performance indicator, since it deals with a real-life design problem with an investment cost. The related design problem is solved with the single objective and multiobjective versions of the developed mathematical programming model via a commercial solver to identify different design alternatives and hence giving the decision-maker to make a selection option. Finally, the capability of the developed mathematical programming model is tested on a set of randomly generated problems. The obtained results indicate that the developed mathematical programming model is a successful decision support system since its single and multi-objective versions are capable of identifying energy-efficient production designs within the context of the real-life problem on hand and the circular economy

Simultaneous balancing and scheduling of flexible mixed model assembly lines with sequence-dependent setup times

We consider Simultaneous Balancing and Scheduling of Flexible Mixed Model Assembly Lines with Sequence-Dependent Setup Times (SBSFMMAL-SDST). We propose alternate Mixed Integer Programming (MIP) and Constraint Programming (CP) formulations. Our experiments show that while the MIP models could not solve relatively small instances, the CP approach seems more promising. © 2010

Treatment delays and in-hospital outcomes in acute myocardial infarction during the COVID-19 pandemic: A nationwide study

Objective: Delayed admission of myocardial infarction (MI) patients is an important prognostic factor. In the present nationwide registry (TURKMI-2), we evaluated the treatment delays and outcomes of patients with acute MI during the Covid-19 pandemic and compaired with a recent pre-pandemic registry (TURKMI-1). Methods: The pandemic and pre-pandemic studies were conducted prospectively as 15-day snapshot registries in the same 48 centers. The inclusion criteria for both registries were aged ≥18 years and a final diagnosis of acute MI (AMI) with positive troponin levels. The only difference between the 2 registries was that the pre-pandemic (TURKMI-1) registry (n=1872) included only patients presenting within the first 48 hours after symptom-onset. TURKMI-2 enrolled all consecutive patients (n=1113) presenting with AMI during the pandemic period. Results: A comparison of the patients with acute MI presenting within the 48-hour of symptom-onset in the pre-pandemic and pandemic registries revealed an overall 47.1% decrease in acute MI admissions during the pandemic. Median time from symptom-onset to hospital-arrival increased from 150 min to 185 min in patients with ST elevation MI (STEMI) and 295 min to 419 min in patients presenting with non-STEMI (NSTEMI) (p-values <0.001). Door-to-balloon time was similar in the two periods (37 vs. 40 min, p=0.448). In the pandemic period, percutaneous coronary intervention (PCI) decreased, especially in the NSTEMI group (60.3% vs. 47.4% in NSTEMI, p<0.001; 94.8% vs. 91.1% in STEMI, p=0.013) but the decrease was not significant in STEMI patients admitted within 12 hours of symptom-onset (94.9% vs. 92.1%; p=0.075). In-hospital major adverse cardiac events (MACE) were significantly increased during the pandemic period [4.8% vs. 8.9%; p<0.001; age- and sex-adjusted Odds ratio (95% CI) 1.96 (1.20-3.22) for NSTEMI, p=0.007; and 2.08 (1.38-3.13) for STEMI, p<0.001]. Conclusion: The present comparison of 2 nationwide registries showed a significant delay in treatment of patients presenting with acute MI during the COVID-19 pandemic. Although PCI was performed in a timely fashion, an increase in treatment delay might be responsible for the increased risk of MACE. Public education and establishing COVID-free hospitals are necessary to overcome patients' fear of using healthcare services and mitigate the potential complications of AMI during the pandemic. © 2020 by Turkish Society of Cardiology

Baseline clinical characteristics and patient profile of the TURKMI registry: Results of a nation-wide acute myocardial infarction registry in Turkey

Objective: The TURKMI registry is designed to provide insight into the characteristics, management from symptom onset to hospital discharge, and outcome of patients with acute myocardial infarction (MI) in Turkey. We report the baseline and clinical characteristics of the TURKMI population. Methods: The TURKMI study is a nation-wide registry that was conducted in 50 centers capable of percutaneous coronary intervention selected from each EuroStat NUTS region in Turkey according to population sampling weight, prioritized by the number of hospitals in each region. All consecutive patients with acute MI admitted to coronary care units within 48 hours of symptom onset were prospectively enrolled during a predefined 2-week period between November 1, 2018 and November 16, 2018. Results: A total of 1930 consecutive patients (mean age, 62.0±13.2 years; 26.1% female) with a diagnosis of acute MI were prospectively enrolled. More than half of the patients were diagnosed with non-ST elevation MI (61.9%), and 38.1% were diagnosed with ST elevation MI. Coronary angiography was performed in 93.7% and, percutaneous coronary intervention was performed in 73.2% of the study population. Fibrinolytic therapy was administered to 13 patients (0.018%). Aspirin was prescribed in 99.3% of the patients, and 94% were on dual antiplatelet therapy at the time of discharge. Beta blockers were prescribed in 85.0%, anti-lipid drugs in 96.3%, angiotensin converting enzyme inhibitors in 58.4%, and angiotensin receptor blockers in 7.9%. Comparison with European countries revealed that TURKMI patients experienced MI at younger ages compared with patients in France, Switzerland, and the United Kingdom. The most prevalent risk factors in the TURKMI population were hypercholesterolemia (60.2%), hypertension (49.5%), smoking (48.8%), and diabetes (37.9%). Conclusion: The nation-wide TURKMI registry revealed that hypercholesterolemia, hypertension, and smoking were the most prevalent risk factors. TURKMI patients were younger compared with patients in European Countries. The TURKMI registry also confirmed that current treatment guidelines are largely adopted into clinical cardiology practice in Turkey in terms of antiplatelet, anti-ischemic, and anti-lipid therapy. ©Copyright 2020 by Turkish Society of Cardiolog