• 산업경영시스템학회지
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• 제22권52호
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• pp.117-139
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• 1999

This paper is concerned about the hybrid tandem configuration as the design of the automated guided vehicle system(AGVs). The hybrid tandem configuration is that the manufacturing system is divided into several non-overlapping zones, workstations of each zone are linked by network configuration including loop. That is, the manufacturing system is divided into several non-overlapping small size networks, and at most two automated guided vehicles can be available in each network. The transit point is located at proper point between adjacent networks. The parts are transported to workstations in other network through the transit points. One of the objective functions in dividing into the hybrid tandem configuration is to minimize the maximum travel time of the divided networks, and other is to minimize the total travel distance of parts moved to workstations in other networks for the next processing. The model formulation is presented, and a numerical example is shown. Also, the performances of system for the hybrid tandem, tandem and network configuration are compared through the simulation. The results of this research will contribute to the development of material handling systems in the manufacturing system. Also, it will be applied in determining the transportation area of transportation vehicles and the number and size of the transportation fleet in the transportation problem of logistics management.

• 한국항행학회논문지
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• 제4권2호
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• pp.114-131
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• 2000

항공사는 항공기단을 편성하거나 특정노선에 투입할 항공기종을 결정할 때 항공기 좌석수가 어느 정도인 항공기로 선택할 것인지 심각하게 고려하지 않을 수 없다. 또한 공항의 혼잡 완화 정책과 같은 외부요인도 항공기 크기 선정에 작용하기도 한다. 이때 두 가지 요인을 고려하여 항공기의 크기를 결정하게 되는데, 첫째는 항공기의 운영비용이고 둘째는 예상되는 수익과 시장 점유율이다. 항공사를 이윤 극대화를 목표로 하는 기업이라고 가정하면 좌석 수에 의한 항공기종별 비용과 수익을 이용해 최적의 항공기종을 선택할 수 있다. 본 연구는 다음과 같은 4단계의 분석을 통하여 항공사의 항공기 크기 선택 행위를 분석한다: (1) 항공기 좌석 수에 따른 운영비 분석 (2) 시장점유율과 수익분석 (3) 비용, 수익분석에 의한 단위노선의 항공기 크기 선정 (4) 네트워크 단위의 항공기 크기 선정, 항공사는 증가하는 수요를 수용하기 위해 운항횟수를 늘리거나, 대형기종으로 교체해야 하는데 이때 항공기 크기 선정 방법을 잘 선택하여 대처해야 할 것이다. 공항이 혼잡한 경우는 운항횟수 증가가 어려워 대형기로의 교체가 불가피한데 이때도 이윤율 증가를 고려한 의사결정이 필요할 것이다.

• Wind and Structures
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• 제11권4호
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• pp.257-273
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• 2008

A number of passive aerodynamic drag reduction methods were applied separately and then in different combinations on an intercity bus model, through wind tunnel studies on a 1:20 scale model of a Mercedes Benz Tourismo 15 RHD intercity bus. Computational fluid dynamics (CFD) modelling was also conducted in parallel to assist with flow visualisation. The commercial CFD package $CFX^{TM}$ was used. It has been found that dramatic reductions in coefficient of drag ($C_D$) of up to 70% can be achieved on the model using tapered and rounded top and side leading edges, and a truncated rear boat-tail. The curved front section allows the airflow to adhere to the bus surfaces for the full length of the vehicle, while the boat-tails reduce the size of the low pressure region at the base of the bus and more importantly, additional pressure recovery occurs and the base pressures rise, reducing drag. It is found that the CFD results show remarkable agreement with experimental results, both in the magnitude of the force coefficients as well as in their trends. An analysis shows that such a reduction in aerodynamic drag could lead to a significant 28% reduction in fuel consumption for a typical bus on intercity or interstate operation. This could translate to a massive dollar savings as well as significant emissions reductions across a fleet. On road tests are recommended.

• 수산해양교육연구
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• 제27권1호
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• pp.308-318
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• 2015

In order to improve the competitiveness of Korean large purse seine fishery, the purpose of this study is to find out the problems and present the improvement of the production structure of Korean large purse seine fishery by comparing to the production structure of Norwegian purse seine fishery. Norwegian purse seine fishery has been operating labor and energy-saving systems through a single wire operation and avoiding fishing competition through the introduction of IVQ system with different types of fishing vessel and obtaining benefits from Leading fishery management integrated with fish pumps and cooling water systems. In contrast, our country has a large purse seine fishery issues such as high cost and low efficiency of production structures, the volatility of mackerel resources, the lack of leading fishery management after catching fishes, the reduction of fishing ground in accordance with the North East Asia EEZ system. To solve these problems, initiatives to improve the structure of our large purse seine fishery are as follows: First, Implementing the promotion of the effective immature fishes management and establishing Korea-China-Japan resource management system. Second, the promotion of reduction of fleet size, the review of possible single fishing operation, leading out to strengthen its competitiveness by switching to energy-efficient production systems through enhanced efforts at fisheries catches steps. Third, it is necessary to realize corporate through the diversification of business areas and the large-scale commercialization of production structure.

• 한국항해학회지
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• 제14권1호
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• pp.21-38
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• 1990

This paper discusses the various modes of operations of cargo ships which are liner operations, tramp shipping and industrial operations, and mathematical programming, simulation , and heuristic method that can be used to solve ships routing and scheduling problems for each of these operations. In particular, this paper put emphasis on a crude oil tanker scheduling problem. The problem is to achieve an optimal sequence of cargoes or an optimal schedule for each ship in a given fleet during a given period. Each cargo is characterized by its type, size, loading and discharging ports, loading and discharging dates, cost, and revenue. Our approach is to enumerate all feasible candidate schedate schedules for each ship, where a candidate schedule specifies a set of cargoes that can be feasibly carried by a ship within the planning horizon , together with loading and discharging dates for each cargo in the set. Provided that candidate schedules have been generated for each ship, the problem of choosing from these an optimal schedule for each ship is formulated as a set partitioning problem, a set packing problem, and a integer generalized network problem respectively. We write the PASCAL programs for schedule generator and apply our approach to the crude oil tanker scheduling problem similar to a realistic system.

• 한국항해학회지
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• 제15권3호
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• pp.1-11
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• 1991

As increasing needs of marine transportation , world merchant fleet and ship's size were enlarged and it caused frequent disasters in human lives and natural environment. By the reason of the above, they started to establish the Vessel Traffic System (VTS) at the European coast in 1960' and most of advanced contries established and managed it to prevent the sea traffic accidents in these days. The concept of traffic control at sea can be divided into three types. First, the initial gathering of informations about ship's identity and movement etc.. Second, monitoring of the traffic flow and amendment of instructions. Third , organization and direction of ships by allocating routes and speeds. Where the goal of traffic control is safety of traffics and developing effectiveness of navigation channel, if traffic volume is less tan channel capacity then the above first or second level of control would be sufficient but if it is bigger than that , more positive policy of control should be adopted as same as third type of the above. In this paper where the strategy of VTS is focused on the control of traffic density to be spread equality, as possible , all over the navigation channels and also improvement of effectiveness , it suggests algorithm to assign the vessels to the channels with balanced traffic density , and other algorithms using D.P. to sequence the vessels assigned to one channel in optimum order which decreases the mean waiting time in sense of channel effectiveness with numerical examples.

• 대한조선학회논문집
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• 제42권2호
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• pp.151-158
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• 2005

The concept of recent cruise ship design is changing rapidly according to the expansion of cruise fleet sizes, emphasis on passenger safety and tightened requirements for ecotourism. In this view point, this study focuses on investigative analysis for the recent trends in cruise ship design and construction. Based on the shipyard production logs and the cruise industry's annual news, the data for principal dimensions of newly built cruise ships, their hull forms and propulsion devices and the characteristics of cabin and public spaces are collected and analysed. As expected, it is found that the size of cruise ships is growing and the design concept is becoming more leisure-oriented for all ages rather than lust sightseeing. For producing a greater ton/pax ratio, the adoption of podded electric propulsion system, outside cabins and balcony spaces is a common trend in recent cruise ship design.

• 한국군사과학기술학회지
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• 제25권4호
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• pp.425-433
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• 2022

This paper studies the method of delivering munitions using both drones and UGVs that are developing along with the 4th Industrial Revolution. While drones are more mobile than UGVs, their loading capacity is small, and UGVs have relatively less mobility than drones, but their loading capacity is better. Therefore, by simultaneously operating these two delivery means, each other's shortcomings may be compensated. In addition, on actual battlefields, time constraints are an important factor in delivering munitions. Therefore, assuming an actual battlefield environment with a time limit, we establish delivery routes that minimize delivery time by operating both drones and UGVs with different capacities and speeds. If the delivery is not completed within the time limit, penalties are imposed. We devised the hybrid genetic algorithm to find solutions to the proposed model, and as results of the experiment, we showed the algorithm we presented solved the actual size problems in a short time.

• Journal of Korea Trade
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• 제23권4호
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• pp.1-16
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• 2019

Purpose - This research empirically proves that global shipbuilding industry leadership has moved to China from Korea. Design/Methodology - Competitiveness is measured by AHP for the weights of comprehensive competitiveness, which is the output mixture of three attributive factors: shipbuilding technology, shipbuilding contract price, and export credit. Findings - China is far ahead of Korea for standard vessels such as bulkers and containerships with competitiveness weights of 0.762 and 0.612, respectively, against 0.238 and 0.388 of Korea. Korea is maintaining its competitiveness only in LNG carriers (174k CBM) with a competitiveness weight 0.621. China and Korea have similar competitiveness for chemical carriers, complex vessels with a small hull size. The sources of Chinese competitiveness are shipbuilding contract price and export credit. With the majority share of standard vessel types in the world fleet, China will hold a bigger market share than Korea in the global shipbuilding industry in the forthcoming years. Implications - The swing factors of market power are shipbuilding technology and contract price. If China fails to further develop shipbuilding technology for shipowners worried about the reliability of the Chinese-built vessels, shipowners may swing back to Korea. The rising Chinese labor cost will expedite this swing in the forthcoming competition. Originality/value - To the best of the author's knowledge, this is the first paper that quantitatively examines the competitiveness of shipbuilding between China and Korea by comparing attributive factors for competitiveness.

• 수산해양기술연구
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• 제25권2호
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• pp.61-69
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• 1989

한국 제주도와 대마도 주변해역을 중심으로 고등어와 정어리를 주어획대상으로 선단조업을 하고 있는 건착망어업의 어선의 성능, 어패의 크기, 어획성능, 조업해역별 단위노력당 어획량등을 조업어선의 톤급별로 분석, 검토한 결과는 다음과 같다. 1. 망선의 총톤수(x)와 건착망의 면적(y)간에는 y=538.8x+99657.3의 관계가 있었다. 2. CPUE의 계절변동지수는 11~4월은 기분보다 높고, 5~10월은 낮은 현상을 나타내었다. 3. 각 해역에 있어서 톤급별 어획성능지수는 톤급별, 해역별 CPUE는 1%의 유음수준에서 차가 인정되었다. 4. 톤급별 망어패의 효율은 A와 D급선 보다 B와 C급선이 높은 현상을 나타내었다