• Journal of Korean Society of Transportation
• /
• v.16 no.2
• /
• pp.169-176
• /
• 1998

버스운행시격은 주어진 고정된 승객수요와 버스운행시간에 대해 최적의 버스운행시격을 결정하고, 이러한 운행시격을 요일과 시간대에 관계없이 그대로 유지하는 것이 일반적이다. 여기에 첨두시와 비첨두시의 운행시격으로 구분하여 결정하기도 한다. 그러나 실제 버스운행시간과 승객수요는 요일별 시간대별로 변화하고 이에 맞는 운행시격으로 조정하지 못함에 따라 버스운영의 비효율성을 초래하기 쉽다. 본 연구의 목적은 요일별, 시간대별로 변화하는 시내버스의 승객수요 및 버스운행 소요시간을 변수로 하여 운영자비용과 이용자비용의 합으로 본 총교통비용 모형을 수립하고, 요일별, 시간대별 최적의 버스운행시격을 구하는데 있다. 또한 최적의 버스보유대수를 구하고, 이에 따른 운행시격 조정 방법을 제안하였다. 또한 서울시에서 운행되고 있는 시내버스 노선 1개에 대한 사례연구를 통해 요일별, 시간대 별로 버스운행시격을 탄력적으로 조정함에 따라, 총교통비용을 상당히 절감할 수 있음을 입증하였고, 버스보유대수의 최적화도 유사한 결과를 나타내었다.

• Journal of Korean Society of Industrial and Systems Engineering
• /
• v.22 no.52
• /
• pp.117-139
• /
• 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.

• Journal of Advanced Navigation Technology
• /
• v.4 no.2
• /
• pp.114-131
• /
• 2000

An airline should consider the number of seats or size of aircraft, when it composes fleet or selects a type of aircraft for some routes. There are two major factors considered for this choice problem under the assumption that the objectives of an airline is a profit maximization: the operating cost and revenue from the aircraft operated. This research tries to solve the problem of aircraft size selection by airline. The study applies four steps to get optimal choice of aircraft size: (1) cost analysis for the relationship between airline operation cost and aircraft size: (2) market share and revenue analysis: (3) flight segment-level analysis, based on the derived cost, demand and revenue functions: and (4) network-level analysis to see how airlines make choice of aircraft size systematically at a network level. An airline can accommodate the increasing air travel demand by either increasing operation frequency, or increasing aircraft size that is represented by seat capacity, or both. Airport runway capacity and productivity depend on the size of aircraft used at airport. This paper presents the understanding of how airlines make decisions on the size of aircraft to operate, how they will adjust their choices when airport capacity is constrained, and how public regulation such as policy for landing fees could influence airlines' aircraft choice.

• Wind and Structures
• /
• v.11 no.4
• /
• pp.257-273
• /
• 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.

• Journal of Fisheries and Marine Sciences Education
• /
• v.27 no.1
• /
• pp.308-318
• /
• 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.

• Journal of the Korean Institute of Navigation
• /
• v.14 no.1
• /
• pp.21-38
• /
• 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.

• Journal of the Korean Institute of Navigation
• /
• v.15 no.3
• /
• pp.1-11
• /
• 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.

• Journal of the Society of Naval Architects of Korea
• /
• v.42 no.2 s.140
• /
• pp.151-158
• /
• 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.

• Journal of the Korea Institute of Military Science and Technology
• /
• v.25 no.4
• /
• pp.425-433
• /
• 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
• /
• v.23 no.4
• /
• pp.1-16
• /
• 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.