• 대한교통학회지
• /
• 제22권5호
• /
• pp.89-97
• /
• 2004

현재 군 수송기는 매주 일정 대수가 각 기지 간 물자수송, 인원수송 그리고 조종사들의 훈련목적으로 정해진 스케줄에 의해 운항하고 있다. 일일 수송기 운행 경로는 모 기지에서 이륙하여 몇 개의 기지를 경유하여 임무를 수행한 후, 다시 모 기지로 돌아오는 패턴을 취하고 있다. 본 연구는 공군의 중앙물자를 저장하는 창에서 각 기지로 물자를 수송할 때 물량예측 및 적정노선에 대해서 시계열분석과 차량경로모형이라는 두 가지 방법을 통해 접근한다. 먼저 현재 공군에서 사용하고 있는 각종 규정과 교범상의 항공수송에 대한 제약사항 자료를 수집하여, 이를 바탕으로 본 연구에서는 다회방문이 가능하고, 경우회수에 대한 제약을 갖는 모형시과 알고리즘을 제안하였다. 또한 지난 몇 년간의 수송물량을 시계열 분석을 이용하여 예측하고, 예측된 수송소요를 제안된 알고리즘에 적용하여 적정노선을 계획하는 방법을 제안하였다. 제안된 모형과 알고리즘의 적합성과 경제성을 파악하기 위해 본 연구에서는 모형에서 계산된 수송물량과 필요 수송기 대수와 실제 공군에서 수행된 항공화물 수송 물량과 투입 수송기 대수를 비교함으로써 객관적인 모형의 우수성을 입증하고자 하였다.

• 해양환경안전학회지
• /
• 제7권1호
• /
• pp.15-23
• /
• 2001

In regulation of IGC code 12.1 mechanical ventilation should be arranged to ensure sufficient air movement through the space to avoid the accumulation of flammable or toxic vapours and ensure a safe working environment, but in no case should the ventilation system have a capacity of less than 30 changes of air per hour baed upon the total volume of the space. In this study, a scaled mode chamber was constructed to investigate the ventilation characteristics and stagnation area in the hood room of LNG carrier and pump room in tanker. An experimental study was performed on the model by using visualization equipment with a laser apparatus and an image intensifier CCD camera. Twelve different kinds of measuring areas were selected as the experimental condition. Instant simultaneous velocity vectors in the whole fields were measured by a 2-D PIV system A three-dimensional numerical simulation was also carried out for three different Reynolds numbers. Then the CFD predictions were discussed with the experimental results. The results show the spiral L-shape flow that moves from the opening on the left wall diagonally to the upper right part dominates the ventilation structure. The stationary area of hood room in the velcoity distributions was located in the upper left stern part.

• 동력기계공학회지
• /
• 제20권3호
• /
• pp.5-10
• /
• 2016

The structure of the variable liquid column oscillator(VLCO) is analogous to that of the tuned liquid column damper used to suppress oscillatory motion in large structures like tall buildings and cargo ships. VLCO is using the technology which absorbs high potential energy made by process of accelerated motions effect of air spring by installation of inner air chamber. So, the application of VLCO can improve the efficiency of energy than that of wave energy converters made in Pelamis Company. In this research, experiments were performed for the models which have two different liquid column sizes. In order to find out the biggest motion response, two major conditions are taken into account. Two conditions are to open(or close) the valves and to differentiate the height of the liquid column.

• 항공산업연구
• /
• 통권49호
• /
• pp.3-40
• /
• 1999

In this paper, the types of airport operation are categorized four groups in context of ownership and operational management; full government ownership and operation; government ownership with privatization of selected service; government ownership and private management; private ownership and operation. The term,"Privatization" has a different definition when it is used in different contexts and cultures. In this paper, the definition of"Privatization" in the context of airport, is that the movement of an entity from the government sector to the private sector. To keep pace with the remarkable growth in the air traffic volume of passengers and cargo, more and more mega-international airports have been built or are under construction. As the air transport demand is expected to increase at an even greater rate in the 21st century, the need for new conception airport is merging to solve the current problems such as airport congestions and flight delays which will be essential factors to decide whether the competitive airports or not. Presently, we researched the type of the operational management to strengthen the competitiveness for Korea's airports. Specifically, It is focused on the government ownership with privatization of selected services. It seems to be evaluated as government ownership and private management when it is actively utilized within Korea Airport Authority's law or Inchon International Airport's public corporation law. To make more competitive airport in 21st Century, however, it is desirable to seek for the method to gradually evaluate to private ownership and operation.

• 대한교통학회지
• /
• 제29권1호
• /
• pp.7-15
• /
• 2011

오늘날 공항의 경쟁은 여객 및 화물 처리 능력 뿐 아니라 배후지역에서 부가가치를 창출 할 수 있는 공항도시 간의 경쟁으로 변화하고 있다. 즉, 공항의 경쟁이 공항과 공항간의 경쟁에서 공항과 연계한 배후단지와 다양한 자족적 기능을 갖는 공항 도시를 형성하여 경쟁하고 있는 것이다. 본 연구는 공항을 중심으로 한 공항도시와 배후단지의 클러스터 형성에 대해 인천국제공항을 대상으로 한 실증분석을 하였다. 본 연구에서는 인천국제공항이 항공물류산업 클러스터로 발전하기 위해서는 전문 인력 확보의 용이성, 클러스터 형성을 도모하는 제도정비, 정부의 정책적 지원, 의존산업 및 연관 산업의 입지, 협력업체와의 정보공유에 대한 부분에 대해 추가적인 노력을 기울여야 할 것으로 나타났다.

• 한국가시화정보학회지
• /
• 제9권2호
• /
• pp.54-60
• /
• 2011

This paper is a basic study on volatile organic compounds(VOC) recovery system in a crude oil carrier. VOC is easily evaporated in cargo tankers during loading and transportation of crude oil, causes serious environmental contamination and a huge economic loss. An ejector system is designed to mix VOC gas into crude oil flow to reduce VOC concentration. Detail two-phase flow inside the ejector is simulated using a commercial CFD code. To verify the numerical prediction, a scale-down experiment is conducted. Instead of crude oil and VOC, water and air are used as the working fluids. Flow characteristics and main parameters are obtained by two-phase flow visualization and PIV measurements. Air volume flow rate induced by the ejector is compared with respect to the volume flow rate of water using experimental and numerical results. Overall performance of the two-phase ejector predicted by the CFD simulation agrees well with that of the experiment.

• 한국항공운항학회지
• /
• 제13권3호
• /
• pp.85-97
• /
• 2005

The objective of this study is to investigate freight forwarders' airline choice behaviors in the Korean air cargo transportation market. This study identifies the major factors affecting airline choice and their relative importance by analyzing the data gathered by the survey from freight forwarders in Seoul. The questionnaire of the survey is composed of two parts; the first part is to identify the significant variables of airline choice and the second part is to gather the data about airline choice using stated preference techniques. The relative importance of major variables considered in forwarders' airline choice is estimated by the logit models calibrated with stated preference data. To strength the reliability of the analysis, this study segments the market by three routes; Seoul-Los Angeles, Seoul-Amsterdam and Seoul-Hongkong. The five major variables that are considered seriously in airline choice are reliability, space availability, frequency, cost and flight schedule. The utility trade-offs between variables are estimated by the ratio analysis of coefficients of logit model of each route, and the results of ratio analysis is interpreted as reflecting the reality of market conditions.

• 한국해양공학회지
• /
• 제23권4호
• /
• pp.12-18
• /
• 2009

The present study focused on the compressibility of partially filled fluids in a sloshing tank. Filling ratios ranging from 18% to 26% were used to find compressible impact on a vertical wall. The model test was for 1/25 scale of a 138 K LNGC cargo tank. To investigate the two dimensional phenomenon of sloshing, a longitudinal slice model was tested. A high speed camera was used to capture the flow field, as well as the air pocket deformation. The pressure time history synchronized with the video images revealed the entire compressible process. Three typical impact phenomena were observed: hydraulic jump, flip through, and plunging breaker. In particular, the pressure time history and flow pattern details for flip through and plunging breaker are presented.

• 한국해양공학회지
• /
• 제27권6호
• /
• pp.27-31
• /
• 2013

The structure of a variable liquid column oscillator(VLCO) is analogous to that of the tuned liquid column damper used to suppress oscillatory motion in large structures like tall buildings and cargo ships. The VLCO is a system for absorbing the high kinetic energy of the accelerated motions of multiple floating bodies using an air-spring effect produced the installation of inner air chambers. Thus, a VLCO can improve the energy efficiency of the activating object type of wave energy converters made by the Pelamis Company. In this research, an experiment was performed in two cases: with the top valves closed and open. The floating bodies were connected by hinges. The effect of the internal flow was estimated by comparing the results for the closed and open valves.

• 한국기계가공학회지
• /
• 제20권3호
• /
• pp.53-59
• /
• 2021

In vibration-free vehicles such as limousine buses, the vibration is minimized by installing an air spring instead of the leaf spring used in the existing freight cars to prevent the damage to the loaded cargo from shocks generated during movement. In the existing vehicles, steel structures support the air spring system. This study was aimed at replacing the steel structures used in the Z-spring by carbon fiber and glass fiber reinforced plastics. In addition, the mechanical properties (elastic modulus, tensile strength, and shear strength) of carbon fiber and glass fiber prepreg were derived using specimens molded with the corresponding prepreg. The final goal was to develop a material lighter than the conventional steel material but with enhanced mechanical properties. Although the CF prepreg exhibited excellent mechanical properties, the production cost was extremely high. To overcome this limitation, hybrid composites with GF prepreg were examined, which are expected to be promising future materials.