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We applied a three-dimensional panel data model of individual match attendance, while controlling for all nuisance variables affecting the home team, visiting team, and season, to the panel dataset...

To investigate the surgical outcomes of vitrectomy for macular hole-induced retinal detachment(MHRD), with respect to the surgical adjunctive method used.We performed retrospective multicenter study of patients who underwent vitrectomy for MHRD. The visual/anatomical outcomes after vitrectomy were analyzed. We also analyzed these outcomes according to surgical method and the presence of persistent macular hole after the vitrectomy.Thirty-four patients (34 eyes) from 6 hospitals were included in this study. The mean age of the patients was 64.56 ± 12.23 years; 31 patients (91.2%) were female. The mean LogMAR best-corrected visual acuity (BCVA) significantly improved 6 months after vitrectomy (The surgeries to treat MHRD differed in terms of the procedure depending on the surgeons, but the visual outcomes did not differ depending on the surgical adjunctive method employed. There were no differences in the visual prognoses, regardless of whether there was a persistent macular hole; however, recurrence was significantly higher in eyes with persistent macular holes. Therefore, further surgical treatment might be considered for eyes with persistent macular holes after MHRD surgery.

We extend the literature on unbiased estimators of sports league outcomes to include outcome uncertainty. While competitive balance and outcome uncertainty are related, generally, they are not the ...

Asian countries have emerged as an important player in international sport business. In particular, China, Japan, and Korea are frequent hosts of the Olympics, FIFA World Cup, and other int...

Rottenberg’s uncertainty of outcome hypothesis is about preferences that can vary across fans and sports. We provide the first evidence of the empirical power of the hypothesis in the Korean Professional Baseball League (KPBL). In a panel data set, team-level aggregation over years shows that fans of this league attend in ways consistent with the hypothesis at the level of game uncertainty and consecutive season uncertainty, but only the first is statistically significant. KPBL fans appear to just be looking for a good game. This is consistent with the nearly complete concentration of post-season participation among a very few teams outside of the major population centre in Seoul and a lack of local team identification among KPBL fans. Our work adds to the diversity of league structures in the competitive balance literature since talent levels in KPBL are the result of parent company advertising choices rather than geographic identification. There are research questions and a policy implication.

In this paper, the problem of minimising maximum completion time on a single batch processing machine is studied. A batch processing is performed on a machine which can simultaneously process several jobs as a batch. The processing time of a batch is determined by the longest processing time of jobs in the batch. The batch processing machine problem is encountered in many manufacturing systems such as burn-in operations in the semiconductor industry and heat treatment operations in the metalworking industries. Heuristics are developed by iterative decomposition of a mixed integer programming model, modified from the successive knapsack problem by Ghazvini and Dupont (1998, Minimising mean flow times criteria on a single batch processing machine with non-identical jobs sizes. International Journal of Production Economics 55: 273–280) and the waste of batch clustering algorithm by Chen, Du, and Huang (2011, Scheduling a batch processing machine with non-identical job sizes: a clustering perspective. Interna...

This paper first formulates a binary integer programming (BIP) model that minimises C max for a multi-stage flexible job shop floor with machine compatibility. Due to a computational limitation, the exact optimal model is then relaxed as a linear programming model. The output from the relaxation model then turns into the objective of the BIP-based real-time scheduling (RTS) heuristic model. The RTS heuristic requires an iteration to calculate the final C max. At each iteration, the RTS heuristic assigns just one job to the earliest available machines. Since the set of jobs and machines included in the RTS model is relatively small, RTS can be solved in a very short computational time. We evaluate an overall effectiveness (in terms of solution quality and run time) of the RTS heuristic by way of computer experiments.

On-time delivery is one of the performance measurements in the make-to-order semiconductor industry. Many control policies, such as input dispatching rules, CONWIP and optimization-based rules, have been implemented based on the managing objectives of the fabrication line. These models focus, however, mainly on the high throughput, short cycle time and high equipment utilization which are proper for the mass production in the semiconductor industry. In this paper, three due date-based production control models are suggested: the target control model, the movement control model and the WIP control model. Mathematical formulations using linear programming are given, and the effectiveness of the proposed models is evaluated by computational experiment. It is shown that suggested models outperform models in the literature with respect to the throughput and on-time delivery.

This paper applies a stochastic frontier production model to the data from Penn World Table’s 49 countries over the period 1965-1990, to decompose total factor productivity growth into technical change and technical efficiency change. Empirical results show East Asian countries led the whole world in productivity growth, mainly because their technical efficiency gain was so much faster than that of other countries. East Asian countries also registered rapid technical change, which was comparable to that of the G6 countries after the late 1980s. The results provide evidence that negate the hypothesis that East Asian growth was mostly input-driven and unsustainable.

In semiconductor manufacturing, wafer fabrication is the most complicated and important process, and is composed of several hundred process steps and involves several hundred machines. The productivity of the manufacturing process depends mainly on controlling the balance of WIP (work-inprogress) flow to achieve maximum throughput under short manufacturing cycle times. This paper discusses how to determine the proper WIP level for operations, against which balance status can be measured. Balance measurement can be applied in mathematical modelling for bottleneck scheduling and operations management of the fabrication line. Performances are evaluated through computational experiments to show that balance driven management leads to 15-33% more production in 21% shorter manufacturing cycle time than production driven management.

Semiconductor products are manufactured through the process of wafer fabrication, probe or electrical die sorting, assembly and final test. In particular, in this study we deal with the wafer probe process which requires several types of equipment with different capacities. As a connecting procedure of the fabrication and the assembly, the probe process may determine the capacity of whole semiconductor manufacturing. The throughput needs to be maximized as for most manufacturing lines. Because of unexpected machine failure and planned preventive maintenance, the utilization of machines has to be kept at a certain range for stabilizing the process. Hence, the production progress for each device and the utilization of machines are objectives to be maximized simultaneously, while both tend to work in opposite directions because of changeover time loss.

Cheju island is occupied by very permeable and productive basaltic aquifers with the highest rainfall in South Korea. Moreover, the aquifers, whose DRASTIC index ranges from 101 to 187 are most vulnerable to potential and existing contaminant sources. Since 1980, more than 3300 water wells were drilled all over the island without any institutional pollution controls. This has created serious groundwater contamination problems, by nitrate, viruses, and E‐coli especially in the down‐gradient area. A study for establishing regional and local groundwater protection strategies was conducted to set up the rational use of groundwater from sole source aquifer and to protect it from potential contaminants. Those strategies are based on the best management practices(BMP) of the groundwater resources. Three protection zones for regional protection and local protection programs including, buffer, recharge and aquifer protection areas, are set up to regulate the potential contaminant sources in the areas. Reg...

We propose a three-phase heuristic for the problem of minimizing the total weighted tardiness on a single machine in the presence of sequence-dependent setup times. In the first phase a number of parameters characterizing the problem instance at hand are calculated. In the second phase we develop a schedule by using a new priority rule whose parameters are calculated based on the results of the first phase. Computational experiments show that this rule significantly outperforms the only other rule so far developed in the literature. The third phase consists of a local improvement procedure to improve the schedule obtained in the second phase. The procedure we suggest has been successfully implemented in an industrial scheduling system.

A hybrid approach to solve job sequencing problems using heuristic rules and artificial neural networks is proposed. The problem is to find a job sequence for a single machine that minimizes the to...