• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.17 no.4
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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.

• Journal of the Semiconductor & Display Technology
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• v.5 no.1 s.14
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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.

• Journal of the Semiconductor & Display Technology
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• v.6 no.1 s.18
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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.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.28 no.4
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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.

• Journal of the military operations research society of Korea
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• v.35 no.3
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• pp.1-15
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• 2009

Central supply depot of Air Force has been receiving and storing the goods from the inside and outside of the country. And it also has been distributing the goods to the air base by air, rail, road, etc. These goods have been called central goods. Among these central goods, 10% of them are transported by air and the amount of freight is increasing day by day. So, air transportation in the Air Force has been more important than ever. But, studies of demand estimation for activating air transportation are very difficient. This study verified the main factors affecting to air transportation and the function of regression model will be useful data for estimating air freight demand.

• Korea Trade Review
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• v.42 no.6
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• pp.131-154
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• 2017

In international trade, transportation generally has the largest and direct impact on freight costs. However, it is also sensitive to external factors such as global economic conditions, global trade volume and exchange rate. Therefore, it is necessary to examine the relationship and influence of international trade in terms of external factors that affect the change of imports and exports by marine and air transportation through empirical analysis. In particular, the analysis of the impact of these external factors on marine and air transportation is an important topic when recent exchange rate changes are significant, and it is also necessary to analyze what transportation means are more sensitive to exchange rate changes. In this study, we use the Vector Error Correction Model to analyze the dynamic effects of changes in exchange rate and domestic and international economic conditions on marine and air transportation from January 2000 to March 2017. Respectively. Alos, Impulse response function and variance decomposition were examined.

• The Korean Journal of Air & Space Law and Policy
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• v.15
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• pp.9-34
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• 2002

• Korea Trade Review
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• v.46 no.1
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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.

• The Korean Journal of Air & Space Law and Policy
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• v.23 no.2
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• pp.3-29
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• 2008

The volume of air passengers and cargo transportation has increased rapidly in recent years. This trend will be even more noticeable as the high-tech service industry expands and the globalization progresses. In an effort to reflect and to cope with this trend, many conventions concerning international air transportation have been concluded. The Republic of Korea has also acceded to the Montreal Convention of 1999 on September 20th, 2007 which became effective on December 29th 2007. However, Korea currently does not provide any private law on the liability of domestic air carrier, leaving the regulation wholly to the general conditions of carriage of private air lines. These general conditions of carriage, however, are not sufficient to regulate the liabilities of domestic air carriers, because they cannot be fully recognized as a legitimate source of law applicable in the court. This situation is inconvenient for both air carrier and their customers. Thus, the Ministry of Justice of Korea has decided to enact a law that will regulate domestic air transportation, namely, "Domestic Carriage by Air Act", as a part of the Korean Commercial Code. So was composed a special committee for legislation of the Domestic Carriage by Air Act. This writer has led the committee as a chairman. The committee has held in total 10 meetings so far and has completed a draft bill for the part VI of the Korean Commercial Code, "Air Carriage." The essentials of the draft are as follows: First, the establishment of Part VI in the Commercial Code. The Korean Commercial Code already includes a series of provisions on road transportation in part II and carriage by sea in part V. In addition to these rules regulating different types of transportation, the Domestic Carriage by Air Act will newly establish part VI to regulate air carriages. Eventually, the Commercial Code will provide an integrated legal system on the transportation industry. Second, the acceptance of the basic liability system which major international conventions, such as Montreal Convention of 1999 and Guadalajara Convention of 1961, have adopted. This is very important, because the law of air carriage is unified worldwide through various international conventions, making it necessary and significant for the new act to achieve conformity between rules of international air carriage and that of domestic air carriage. Third, the acceptance of Rome Convention system on damage caused by foreign aircraft to third parties on the surface. Fourth, the application of rules on domestic road carriage or carriage by sea mutatis mutandis with necessary modifications. This very point is the merit of inserting domestic air transportation law into the Commercial Code. By doing so, the number of articles can be reduced and the rules on air carriage can conform to that of road transportation and carriage by sea. The bill is expected to be passed by the parliament at the end of this year and is expected to be effective by end of July 2009.

• Journal of Environmental Health Sciences
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• v.46 no.2
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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.