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김원재(Weon Jae Kim),권용대(Yong Dae Kwon) 대한치과의사협회 2019 대한치과의사협회지 Vol.57 No.5
Obstructive sleep apnea syndrome (OSAS) is characterized by obstructive events of the upper airway (UAW) during sleep, which can be associated with clinical signs and symptoms such as snoring, excessive daytime sleepiness, impaired memory, and fatigue. 1)It is associated with many problems like psychosocial problems, physiologic alterations in the cardiovascular and respiratory systems as a result of hypoxia and repeated awakenings during sleep. 29)Conservative treatments such as weight loss, sleep positioning, improvement of sleep hygiene, CPAP and MAD can be performed for the obstructive sleep apnea. However, their effect for the OSA is limited and differs by patient’s individual properties. Accordingly, surgical reconstructions of the upper airway must be carried out for the treatment of OSA.
Optimizing Total Transport Cost Incurred under Specific Port System
Weon Jae Kim(김원재) 한국항만경제학회 2010 韓國港灣經濟學會誌 Vol.26 No.3
본 논문의 핵심은 일정한 전용항만을 운용하는데 있어 발생되는 물유비용을 크게 3가지로 나누어 이들의 합계가 최소화 될 수 있는 선박톤수 별 연간 발주 항차 수를 최적화하는 것이다. 즉 항만에서 적항과 양항간을 오가며 발생되는 해상수송비용, 도착 선박이 항만에서 선석을 기다리며 발생되는 대기비용, 그리고 수입된 화물이 하역되어 야적장에 보관된 상태에서 발생되는 재고유지비용 등의 비용발생 행태가 대, 중, 소 3가지 선급별 연간 항차 수의 배정에 따라 상이한 만큼, 이들 비용의 합계가 최소화 될 수 있는 최적 항차 배정 의사결정이 요구된다. 이때 해상수송비용은 주어진 선급 별, 항만 별 요율로써 확정할 수 있고, 항만 대기비용은 시뮬레이션 모델로써 추정할 수 있다. 그리고 야적장의 화물 재고유지비용은 연간 평균재고량에 화물 별 單價와 이자율 등을 감안하여 추정할 수 있다. 포항제철㈜의 원료수입 전용부두를 운영하는 사례 분석 결과에서 규모의 경제 효과에 의한 해상수송비용을 최소화하기 위해 대형선박의 연간 항차 배정 율을 증가시킬 경우, 일정 비율을 지나면 선박 대기비용이 급격히 상승하고 야적장의 재고비용도 다소 상승되어 결국 총비용이 증가하는 것으로 나타났다. 따라서 현재의 전용항만 구조하에서 물류비용을 최소화하기 위해서는 중형선은 연간 총 배정 항차 수의 약 50% 정도의 비중으로, 대형선은 약 33% 정도, 그리고 소형선은 약 17% 내외로 구성하는 것이 최적인 것으로 나타났다. 물론 이러한 분석 결과는 추후 새로운 선석의 건설, 수입화종과 화물량, 단가 등의 변수에 따라 달라질 수 있다. This paper primarily deals with a decision-making for determining the number of voyages in each ship size under a specific port structure in order to minimize the total transport cost consisting of transport cost at sea, queuing cost in port, and inventory cost in yard. As a result of computer simulation using queuing model characterized by inter-arrival time distribution, we were able to find out some combination of voyage numbers of 3 ship-size(50,000-ton, 100,000-ton, and 200,000-ton), where the total transport cost can be minimized under a specific port structure. The simulation model also allows us to figure out any trade-off relationship among sea transport cost, queuing cost in port, and inventory cost in yard. Put it differently, an attempt to reduce the sea transport cost by increasing the number of voyages of the largest ship size, the transport cost incurred in both port and yard is hypothesized to be increased and vice versa. Consequently, Port managers are required to adjust the number of annual number of voyages allocated in each ship size, put into the sea lines for importing raw materials, in order to optimize the transport costs incurred under the specific port system. We may consider a net present value(NPV) model for performing an economic feasibility analysis on port investment project. If a total discounted net benefit, including cost savings, exceeds the initial investment for an additional berth construction, then we accept the port investment project. Otherwise, we reject the proposed port investment plan.
가압펌프와 공기포화탱크를 연계한 하이브리드형 미세기포 발생장치의 운전특성
김원재 ( Weon-jae Kim ) 한국수처리학회(구 한국수처리기술연구회) 2021 한국수처리학회지 Vol.29 No.3
Dissolved air flotation (DAF) process has been applied to the entire environmental fields. The micro-bubble generator, which is a key facility in DAF process, can be classified according to its generation methodology. In Korea, saturator and DAF-pump types are widely utilized. The feature of saturator type is the application of an air saturation tank (AST), and it has a disadvantage in that operation and maintenance are not easy due to relatively complicated facilities. On the other hand, DAF-pump type uses a micro-bubble generating pump (MGP) alone, so the device configuration is very simple, but the ranges of optimal operating conditions are narrow. In this study, a new hybrid-type microbubble generator has been developed by linking a pressure pump and an AST by converging the advantages of the existing saturator and DAF-pump types. As a result of examining the operation characteristics of this microbubble generator including operating pressure, air flow rate, water flow rate, power consumption, A/W ratio (air/water ratio), DO, and particle size distribution, the appropriate operating conditions could be determined as operating pressure of 4.0 - 6.0 kgf/㎠, air flow rate of 4.0 - 5.0 L/min, water flow rate of 57 - 68 L/min, and A/W ratio of 5.9 - 8.7%. The average diameter of the generated microbubbles showed a stable distribution in the range of 25.0 - 26.7 μm. Based on the above results, it could be verified that the novel hybrid-type microbubble generator had excellent performance at a level that can be applied to the field.
김원재(Weon Jae Kim),이광남(Kwang Nam Lee) 한국수산경영학회 1993 수산경영론집 Vol.24 No.2
Since the last decade, the fisheries industry in Korea has faced many difficulties in terms of comparative economic advantage partly because of marine environmental damage caused by pollution and coastal reclamation, and partly because of too expensive production factors like labor. In addition, new order of world trade created by Uruguay Round will force the Korean fisheries industry to prepare some remedies including a joint - venture business with China for international compatativeness. As a result, this paper mainly deals with an analysis on feasibility of Sino - Korean joint cooperation in fisheries business. Especially, the Shandong Province in China is expected to take advantage of its geographical proximity to Korea as well as of its abundance in marine natural resources in order to achieve a fast economic growth. Thus, for the next decade to come, it would be very important for the Korean fisheries industry to cope with the international fisheries market by the Sino - Korean joint - venture combining the capital and technology from Korea with the cheap labor and favorable marine environment for aquaculture from China.