• Structural Engineering and Mechanics
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• v.52 no.2
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• pp.351-368
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• 2014

This study presents a hunting search based optimum design algorithm for engineering optimization problems. Hunting search algorithm is an optimum design method inspired by group hunting of animals such as wolves, lions, and dolphins. Each of these hunters employs hunting in a different way. However, they are common in that all of them search for a prey in a group. Hunters encircle the prey and the ring of siege is tightened gradually until it is caught. Hunting search algorithm is employed for the automation of optimum design process, during which the design variables are selected for the minimum objective function value controlled by the design restrictions. Three different examples, namely welded beam, cellular beam and moment resisting steel frame are selected as numerical design problems and solved for the optimum solution. Each example differs in the following ways: Unlike welded beam design problem having continuous design variables, steel frame and cellular beam design problems include discrete design variables. Moreover, while the cellular beam is designed under the provisions of BS 5960, LRFD-AISC (Load and Resistant Factor Design-American Institute of Steel Construction) is considered for the formulation of moment resisting steel frame. Levy Flights is adapted to the simple hunting search algorithm for better search. For comparison, same design examples are also solved by using some other well-known search methods in the literature. Results reveal that hunting search shows good performance in finding optimum solutions for each design problem.

• International Journal of Aeronautical and Space Sciences
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• v.1 no.1
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• pp.1-12
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• 2000

The wake geometries of a two-bladed rotor in axial flights using a time-marching free-wake method without a non-physical model of the far wake are calculated. The computed free-wake geometries of AH-1G model rotor in climb flight are compared with the experimental visualization results. The time-marching free-wake method can predict the behavior of the tip vortex and the wake roil-up phenomena with remarkable agreements. Tip vortices shed from the two-bladed rotor can interact with each other significantly. The interaction consists of a turn of the tip vortex from one blade rolling around the tip vortex from the other. Wake expansion of wake geometries in radial direction after the contraction is a result of adjacent tip vortices begging to pair together and spiral about each other. Detailed numerical results show regular pairing phenomenon in the climb flights, the hover at high angle of attack and slow descent flight too. On the contrary, unstable motions of wake are observed numerically in the hover at low angle of attack and fast descent flight. It is because of the inherent wake instability and blade-vortex-interaction rather then the effect of recirculation due to the experimental equipment.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.28 no.1
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• pp.7-13
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• 2020

A significant growth in local air traffic volume is leading to airway congestion and flight delays especially for Incheon-China and Incheon-Europe sectors. A key method to increase the airway capacity is to place a supplemental airway parallel to the existing one and in cooperation between the aviation authorities between China and Korea, a dual airway track was implemented on December 6, 2018. Here, we use airline A's flight data to analyze the congestion change effect of the new airway. Results show total delay time to Europe is reduced 51% (13.4 to 6.6 minutes) as the delay distribution for 16-30 minutes, 31 minutes and greater decreased from 23.2% to 8.2% and 8.7% to 1.0% respectively. The delay to China also decreased but the drop is not as significant as flights to Europe. This is caused by the difference in flight distance, traffic volume, and characteristics of flights landing and transiting China. Flights to Europe show a broad distribution in altitude allocation and reduction in aircraft separation demonstrating the effectiveness of a dual airway track.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.32 no.3
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• pp.205-214
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• 2024

The aircraft delay rate has increased nearly three times in 2023 due to change in Korea policy of delay criteria. One of the primary causes of delays in domestic flights is related to reactionary delays, with Turnaround Time being a key factor. To mitigate reactionary delays and reduce aircraft delays, it is essential to establish an appropriate Turnaround Time and integrate it into flight schedules. This study aims to analyze the appropriate Turnaround Time for aircraft operating at Gimpo, Gimhae, and Jeju International Airports, which handle a high frequency of domestic flights. The research applies air traffic simulation, using variables such as current flight schedules, actual flight times, Turnaround Time, and flight routes to simulate actual conditions. Based on this analysis, the study seeks to identify the fitting Turnaround Time across various scenarios. The findings are expected to address reactionary delays and help reduce overall delay rates in domestic flights.

• Journal of agricultural medicine and community health
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• v.27 no.1
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• pp.115-123
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• 2002

Objective: The aim of this study was to evaluate the patterns of helicopter emergency medical services (HEMS) in Ullung Island. Methods : The authors reviewed the records from emergency room diaries and the lists of helicopter transfers in the Ullung Public Health Medical Center over the 5-year period from Jan 1, 1997 to Dec 31, 2001. Results : One hundred thirteen cases were transferred by helicopters in 88 flights. According to year, the number of flights was 13(14.8%) and the number of cases was 15(13.3%) in 1997; 17(19.3%) and 21(18.6%) in 1998; 18(20.5%) and 20(17.7%) in 1999; 17(19.3%) and 20(17.7%) in 2000; and 23(26.1%) and 37(32.7%) in 2001. According to the kind of helicopter, the number of flights was 46(52.3%) and the number of cases was 60(53.1%) by Maritime police; and 19(21.6%) and 28(25.1%) by 119 rescue. According to time zone, there were no night flights. According to sex and age, there were 75 male cases(66.4%) and 28 cases(28.3%) of patients aged sixty years and over. The number of flights was 11(12.5%) and the number of cases was 15(13.3%) in November; 10 flights(11.4%) and 14 cases(12.4%) in March; and 7 cases(8.0%) in each of September, October and April. The most common season of helicopter transfer cases was autumn. According to transfer area, there were 48 cases (42.5%) in Pohang city, Gyeonsangbukdo; 35(31.0%) in Gangnung city, Gangwondo; and 17(15.0%) in Daegu metropolitan city. According to condition, there were 27 cases(23.9%) of cerebro-vascular accident, 13(11.5%) of fracture and 11(9.7%) of head injury. According to admission department, there were 42 cases(37.2%) in Neurosurgery, 21(18.6%) in Internal Medicine and 13(11.5%) in Orthopedic Surgery. According tothe Korea Standard Classification of Disease(3-KSCD), circulatory systemic disease(IX) and injury, intoxication and others (XIX) were the two most frequent categories with 34 cases(30.1%) each, followed by digestive system disease (XI) with 23 cases(20.4%). Conclusions : HEMS in Ullung Island leave much to be desired. Helicopters cannot make a night flight and are not equipped with medical facilities. HEMS in islands such as Ullung Island are essential. We hope that night flights, equipment-monitoring systems for emergency patients in the helicopters, and a law related to HEMS in the island will all be established.

• The Korean Journal of Air & Space Law and Policy
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• v.30 no.2
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• pp.249-277
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• 2015

Regulation (EC) No 261/2004 ("Regulation") is a common rule on compensation and assistance to passengers in the event of denied boarding and of cancellation or long delay of flights. In some recent cases of European nations, passengers sued the air carrier in order to obtain monetary compensation under Article 7(1) of the Regulation. Some courts dismissed the actions on the grounds that, unlike denied boarding or cancellation of the flight, the Regulation provides no compensation in relation to delayed flights. However, Court of Justice of the European Union(CJEU) ruled that Regulation 261/2004 must be interpreted to mean that passengers whose flights are delayed have a right to compensation in cases when the loss of time is equivalent to, or is in excess of three hours - where the passengers eventually reached their final destination three hours or more later than the originally scheduled arrival time. It is true that a strict interpretation of the regulation would suggest that passengers whose flight has merely been delayed are not entitled to compensation. They should only be offered assistance in accordance with the Articles 6 and 9. Nevertheless, the Court recognized the same right to the same compensation for passengers of flights delayed by more than three hours as that explicitly provided for passengers of cancelled flights. On the one hand, the Court bases this ruling on the recitals of the Regulation, in which the legislature links the question of compensation to that of a long delay, while indicating that the Regulations seek to ensure a high level of protection for passengers regardless of whether they are denied boarding or their flight is cancelled or delayed. On the other hand, the Court interprets the relevant provisions of the Regulation in light of the general principle of equal treatment. Furthermore, the Court delivered a ruling that the loss of time inherent in a flight delay, which constitutes an inconvenience within the intention of Regulation No 261/2004 and which cannot be categorized as 'damage occasioned by delay' within the meaning of Article 19 of the Montreal Convention, cannot come within the scope of Article 29 of that convention. Consequently, under this view, the obligation under Regulation No 261/2004 intended to compensate passengers whose flights are subject to a long delay is in line with Article 29 of the Montreal Convention. Although the above interpretation of the Court can be a analogical interpretation, the progressive attitude of the Regulation and the view of Court forward to protect passengers' interest is a leading role in the area of international air passenger transportation. Hopefully, after the model of the positive support in Europe, Korea can establish a concrete rule for protecting passengers' right and interest.

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.52-56
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• 2004

Unmanned Aerial Vehicles (UAVs) are remotely piloted or self-piloted aircraft by inputted program in advance or artificial intelligence. In this study Aileron and Elevator are used to control the movement of airplane for horizontal and vertical flights about its longitudinal and lateral axis. In an introduction, the drone was linearly modeled by extracting aerodynamic parameter through flight test and simulation, lift and drag coefficient corresponding to angle of attack, changes of pitching moment coefficient. In the main subject, the flight simulation was performed after constructing hardware using TMS320F2812 from TI company and PID with lateral and longitudinal controller for horizontal and vertical flights. Flying characteristics of two system were estimated and compared through real flight test with hardware equipped algorithm and adaptive algorithm that was applied to consider external factors such as turbulence. In conclusion the control performance of the controller with proposed algorithm was streamlined at lateral and longitudinal controller respectively, we will discuss guidance command to pass way point.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.824-828
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• 2002

Twin screw extruders are the heart of the polymer processing industry. The single most important mechanical element of a screw extruder is the screw. The proper design of the geometry of the excluder screw is of crucial importance to the proper functioning of the extruder. If material transport instabilities occur as a result of improper screw geometry, even the most sophisticated computerized control system cannot solve the problem. For this purpose, Tool shape design for the screw flights cutting in twin screw extruder.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2001.10a
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• pp.292-297
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• 2001

Twin screw extruders are the heart of the polymer processing industry. They are used at some stage in nearly all polymer processing operations. This paper is concerned with the basic elements of the extruder design. The proper design of the geometry of the extruder screw is of crucial importance to the proper functioning of the extruder. If the material transport instabilities occur as a result of improper screw geometry, even the most sophisticated computerized control system cannot solve the problem. For this purpose, a characteristic design on flights shape of the extruder screw. This paper presents cross section designs of a closely intermeshing twin screw extruder with double-flighted screw elements, and channel depth characteristics for a double flighted corotating self-wiping twin screw extruder.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.26 no.2
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• pp.123-131
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• 2018

Air transport industry tries to enhance punctuality, stability and amenity for customer's satisfaction. Especially airlines and airports do make an effort as the distance between these two stakeholders and passengers are close. This research has empirically discussed the relationship between duty free shop purchase of passengers and the number of flights and hours of schedule delay at the airport. According to the result, the total sales of duty free shop sales have meaningful influence on the number of flights and hours of delay. In order to decrease such an impact, close cooperation between airports and duty free shops required.