A BETTER DOMINANCE RELATION AND HEURISTICS FOR TWO-MACHINE NO-WAIT FLOWSHOPS WITH MAXIMUM LATENESS PERFORMANCE MEASURE

In this paper, we consider a manufacturing system with two-machine no-wait flowshop scheduling problem where setup times are uncertain. The problem with the performance measure of maximum lateness was addressed in the literature (Computational and Applied Mathematics 37, 67746794) where dominance relations were proposed. We establish a new dominance relation and show that the new dominance relation is, on average, about 90% more efficient than the existing ones. Moreover, since it is highly unlikely to find optimal solutions for problems of reasonable size by utilizing dominance relations and since there exist no heuristic in the literature for the problem, we propose constructive heuristics to solve real life problems. We conduct extensive computational experiments to evaluate the proposed heuristics. Computational experiments indicate that the performance of the worst proposed heuristic is at least 20% better than a benchmark solution. Furthermore, they also indicate that the best proposed heuristic is about 130% better than the worst one. The average CPU time of the heuristics is significantly less than a second

Two-machine flowshop scheduling problem with bounded processing times to minimize total completion time

AbstractWe consider the two-machine flowshop scheduling problem where jobs have random processing times which are bounded within certain intervals. The objective is to minimize total completion time of all jobs. The decision of finding a solution for the problem has to be made based on the lower and upper bounds on job processing times since this is the only information available. The problem is NP-hard since the special case when the lower and upper bounds are equal, i.e., the deterministic case, is known to be NP-hard. Therefore, a reasonable approach is to come up with well performing heuristics. We propose eleven heuristics which utilize the lower and upper bounds on job processing times based on the Shortest Processing Time (SPT) rule. The proposed heuristics are compared through randomly generated data. The computational analysis has shown that the heuristics using the information on the bounds of job processing times on both machines perform much better than those using the information on one of the two machines. It has also shown that one of the proposed heuristics performs as the best for different distributions with an overall average percentage error of less than one

The influence of the approach for blood loss and transfusion in total knee arthroplasty: Medial parapatellar vs. subvastus

The medial parapatellar (MP) and subvastus (SV) approaches are the most common approaches used in total knee arthroplasty (TKA). Blood loss and transfusion requirements during these approaches varies in different studies. This study compared the MP and SV techniques in terms of blood loss and transfusion needs. Sixty-four patients were enrolled for this retrospective, single-centre and single-surgeon study. Patients were allocated into two groups of 32 patients each: TKA utilizing a MP approach (MP group) and TKA utilizing a SV approach (SV group). The calculated blood loss, determined using the Gross method, was the study's primary outcome. Additionally, the amounts of haemoglobin and haematocrit decrease from preoperative to postoperative 3rd day as well as the need for blood transfusions were compared. The mean calculated blood loss was lower in the SV group compared to the MP group (953±362 mL vs. 1245±404 mL, p=0.003). The haematocrit decrease from preoperative to postoperative 3rd day was in favour of the SV group (7.0±2.9 % vs. 9.5±3.0 %, p=0.005). The mean units of packed red cells transfused in the MP and SV groups were 0.28±0.45 and 0.19±0.4, respectively (p>0.05). Although lower blood loss was observed in the SV approach, the postoperative transfusion rates were not affected. When selecting the approach to use in TKA, surgeons should consider that SV approach is efficient in reducing blood loss without any change in transfusion requirement. [Med-Science 2023; 12(1.000): 259-63