• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권7호
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• pp.2952-2971
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• 2016

Outsourcing jobs to a public cloud is a cost-effective way to address the problem of satisfying the peak resource demand when the local cloud has insufficient resources. In this paper, we studied the management of deadline-constrained bag-of-tasks jobs on hybrid clouds. We presented a binary nonlinear programming (BNP) problem to model the hybrid cloud management which minimizes rent cost from the public cloud while completes the jobs within their respective deadlines. To solve this BNP problem in polynomial time, we proposed a heuristic algorithm. The main idea is assigning the task closest to its deadline to current core until the core cannot finish any task within its deadline. When there is no available core, the algorithm adds an available physical machine (PM) with most capacity or rents a new virtual machine (VM) with highest cost-performance ratio. As there may be a workload imbalance between/among cores on a PM/VM after task assigning, we propose a task reassigning algorithm to balance them. Extensive experimental results show that our heuristic algorithm saves 16.2%-76% rent cost and improves 47.3%-182.8% resource utilizations satisfying deadline constraints, compared with first fit decreasing algorithm, and that our task reassigning algorithm improves the makespan of tasks up to 47.6%.

• 한국항해항만학회지
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• 제31권10호
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• pp.869-877
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• 2007

본 논문은 교행이 불가능한 두 대의 자동화 크레인을 운영하는 자동화 컨테이너 터미널의 장치장을 대상으로 국지적 탐색 알고리즘을 이용해 실시간 작업계획을 수립하는 방안을 제안한다. 제안방안은 실시간 제약조건을 만족시키기 위해 현재 이후 일정 시간의 작업만을 작업 계획의 대상으로 삼으며, 장치장의 동적인 작업 특성을 고려하여 새로운 작업이 요청될 때마다 작업 계획을 다시 수립한다. 또한, 교행이 불가능한 두 대의 크레인을 운영할 때 발생할 수 있는 크레인 간의 작업 부하 불균형을 해소하기 위해 작업 계획 과정에서 상대 크레인에 의한 사전 재취급과 사전 이적을 통한 두 크레인 간의 협업을 가능하게 하였다. 시뮬레이션을 이용한 실험 결과 제안 방안이 휴리스틱 방안에 비해 우수하며, 크레인 간의 협업이 작업 효율 향상에 도움이 됨을 확인하였다.

• Korean Circulation Journal
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• 제54권1호
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• pp.1-12
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• 2024

Background and Objectives: The objective of this study was to estimate the supply and demand for cardiologists in Korea and provide evidence for healthcare policy to ensure a stable and adequate workforce for optimal cardiovascular disease management. Methods: Past trends of inflow and outflow of cardiologists were used to make crude projections, which were then adjusted based on demands of services to obtain final projections. Inflow of cardiologists was estimated using second-order polynomial regression and demand for cardiology care was estimated using linear regression. Results: There were 1,139 active cardiologists who were under the age of 65 in clinical practice in Korea. The estimated number of cardiologists from 2022 to 2040 showed that the number of cardiologists would peak at 1,344 in 2032 and gradually decrease thereafter. We also estimated an increase of 947,811 cases of heart-related procedures annually from 2023 to 2032. The number of heart-related procedures per cardiologist would increase 1.4 times from 12,964 in 2023 to 17,862 in 2032. The estimated number of emergency patients per cardiologist under 50 years old would almost double from 544 in 2022 to 987 in 2032. Conclusions: We expect significant shortage of cardiologists in Korea within the next 10 years. The number of emergency patients per cardiologist will increase by nearly 50%, leading to high individual workload for cardiologists. To prevent this imbalance between supply and demand, an organized and collective approach by the specialty of cardiology is imperative to produce a balanced workforce.