• 대한설비공학회지:설비저널
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• 제17권4호
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• pp.466-472
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• 1988

Pneumatic transportation systems are operated most economically, if the transportation velocity is somewhat greater than the limit velocity. Therefore it is very important to find out this limit velocity. That is well known for coarse and fine particles, but not yet for long ribbon type material. In this study a formula for the mass ratio of transported material to air in limit load point is derived for ribbon type material from the pneumatic transportation theory and the model theory. A relationship for estimating the limit velocity is also found out through experiments. The possibility of the generalization of this formula, which is obtained from a given pneumatic transportation system, should be estimated through further systematic studies.

• 반도체디스플레이기술학회지
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• 제5권1호
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• pp.27-31
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• 2006

Non-contact transportation system using air cushion for the manufacturing of large-sized LCD panels was considered. Flow characteristics between air pad and glass plate was analyzed using computational fluid dynamics method to obtain optimized air pad configurations. Effects of the design variables such as hole arrays from which gas is injected, gas-feeding method into the gas supplying channels, and horizontal and vertical pitches of clusters of holes were studied. Optimized air pad unit gave evenly distributed pressure contour on the glass surface and well-suspended levitation height in the experiment.

• 반도체디스플레이기술학회지
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• 제6권1호
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• pp.59-64
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• 2007

Non-contact transportation of a large-sized glass plate using air cushion for the vertical sputtering system of liquid crystal display (LCD) panel was considered. The objective of the study was to design an air pad unit which was composed of multiple injection and exhaust holes and mass flow supplying pipe. The gas was injected through multiple small holes to maintain the force for levitating glass plate. After hitting the plate, the air was vented through exhaust holes. Complex flow field and resulting pressure distribution on the glass surface were numerically studied to design the air injection pad. The exhaust hole size was varied to obtain evenly distributed pressure distribution at fixed diameter of the injection hole. Considering the force for levitating glass plate, the diameter of the exhaust hole of 30 to 40 times of the gas injection hole was recommended.

• 한국항공운항학회지
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• 제28권4호
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• pp.164-170
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• 2020

Recently, the aviation industry faced a major crisis due to the impact of COVID-19. However, despite the sluggish passenger transportation, the cargo transportation sector is relatively maintained or increasing depending on the item. In this study, we will look at the trends before and after COVID-19, focusing on the cargo export field, which is a concern of the aviation industry. First, it analyzes the entire air cargo and then analyzes the trends of each item and country in detail. In particular, it examines the process of changes in air transport costs, which increased significantly immediately after COVID-19, and conducts future trends and prospects in the cargo export field. As a result of the study, some characteristics of air cargo exports before and after COVID-19 were found in an analysis by item and country, and transportation costs varied according to route distance.

• 한국국방경영분석학회지
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• 제35권3호
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• pp.1-15
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• 2009

현재 공군은 중앙창에서 국내 조달물자와 해외 도입물자를 공급받아 보관하고 전국 각 기지로 수송하여 기지별로 필요한 물자를 공급하고 있다. 이러한 물자를 중앙물자라고 부르며 항공, 철도, 육로 등 다양한 방편을 이용하여 수송한다. 이 중 항공이 차지하는 비중은 전체 물자의 10% 정도이며, 그 물량이 날로 증가하고 있다. 이렇듯 군에서 항공수송의 비중이 점점 커져가고 있지만, 항공수송을 활성화시키기 위한 수요예측이나 노선설계와 같은 연구는 매우 미흡한 실정이다. 본 연구는 회귀분석을 통하여 항공수송에 미치는 주요 요인과 영향력을 검증하였고 산출된 회귀모형식은 군 항공화물수요 예측에 있어 유용한 자료가 될 것이다.

• 무역학회지
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• 제42권6호
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• pp.131-154
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• 2017

국제무역에서 운송수단의 선택은 일반적으로 화물의 운임이 가장 큰 직접적인 영향을 주지만 그 외 세계경기의 상황과 글로벌 무역규모 그리고 환율 등의 외부변수에 의해서도 민감하게 반응한다. 따라서 국제무역에서 해상 및 항공운송 수출입의 변화에 이러한 외부적 요인 등을 고려하여 어떠한 관계 또는 영향이 있는지를 실증분석을 통해 살펴보고 시사점을 도출하고자 한다. 최근과 같이 환율의 변화가 심할 경우 해상 및 항공운송에 미치는 영향에 대한 분석은 중요한 주제이며 어떠한 운송수단이 환율변화에 더 민감하게 반응하는지에 대한 분석도 필요하다. 본 연구에서는 2000년 1월~2017년 3월까지 월별 자료를 이용하여 환율의 변화와 국내외 경기수준이 해상 및 항공운송에 미치는 동태적 영향을 분석하기 위해 벡터오차수정모형을 이용하였으며, 충격반응함수 및 예측오차 분산분해도 함께 분석하였다.

• 항공우주정책ㆍ법학회지
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• 제15권
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• pp.9-34
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• 2002

• 무역학회지
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• 제46권1호
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• pp.135-154
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• 2021

This study aims to investigate the difference in the perception of shippers on the quality of air freight service between air express and air freight forwarders. This study suggests hypothesis verification and implications on importance-performance between two groups of air express and air freight forwarders. In this study, we find that important variables through paired t-test and importance-performance analysis. As a result of paired t-test, there was a difference in the use variables of the document work variables through computerization in the importance area. In the satisfaction area, there was a difference between the groups in the response to customer request and the response to accidents. The variables that need to improve the focus derived from the importance-performance analysis are document work through computer and response to accidents. It is necessary to observe and manage the response of shippers continuously by holding various transportation schedules in the schedule area, possibility of adjustment of transportation schedule, regular freight and schedule provision.

• 항공우주정책ㆍ법학회지
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• 제23권2호
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• pp.3-29
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• 2008

항공운송과 관련하여 우리나라는 1955년 헤이그 의정서에 의하여 개정된 바르샤바협약과 1999년 몬트리올 협약에 가입하여 국제운송에 관하여는 적용할 법률을 가지고 있지만, 현재 국내항공운송에 관하여는 적용될 법률이 없는 실정이다. 법무부는 상법 내에 항공운송편을 제정하기로 결정하고, 항공운송편제정 특별위원회를 구성하였다. 동 위원회는 2008년 여름 항공운송편 초안을 완성하여 동 초안은 현재 법제처의 심의를 받고 있다. 항공운송편을 제정함에 있어서는 현재까지 성립된 항공운송관련 대부분의 조약을 수용하였다. 항공운송법의 편제는 1장 통칙, 제2장 운송, 제3장 지상 제3자의 손해에 대한 책임 등 총 3개의 장을 두었다. 우리나라가 항공운송에 관한 단행법을 제정하지 않고 상법 제6편에 항공운송편을 두어 제2편 상행위편에 육상운송을 규정하곤 제5편에 해상운송에 관한 규정을 둔 것과 함께! 통합적인 운송법체계를 가진 것은 입법례가 없는 매우 독특한 입법형식을 취한 것이다. 특히 항공기운항자의 지상 제3자의 손해에 대한 책임에 관한 로마조약체계까지도 수용하여 함께 규정한 것은 국내항공운송법체계를 완성한 것으로서 매우 의미 있는 일이라고 생각한다.

• 한국환경보건학회지
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• 제46권2호
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• pp.204-213
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• 2020

Objective: This study is aimed at investigating indoor air quality on public transportation (subway, train, and bus) according to changes in season and time. Methods: We evaluated TVOC and HCHO on public transportation based on the un-controlled parameters of the Ministry of Environment. We also measured temperature and humidity since they affect the concentration of TVOC and HCHO. For public transportation classification, subway lines were classified into Lines 1 to 4. Additionally, trains were classified as ITX and KTX. Results: When comparing summer and winter on public transportation, the concentrations of TVOC and HCHO did not show any particular tendency. However, the concentrations of TVOC and HCHO during traffic congestion was higher than levels during times of non-congestion on most public transportation. In summer and winter, the measurement results for temperature and humidity showed a normal range, so temperature and humidity did not affect the concentrations of TVOC and HCHO. In the case of TVOC, TVOC concentrations on new trains were found to be relatively higher than on older ones, but there was no statistically correlation. Conclusions: A survey was conducted on the indoor air quality on public transportation. This study also analyzed data based on TVOC and HCHO for designing policies and managing indoor air quality.