• 한국항공운항학회지
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• 제31권3호
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• pp.50-58
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• 2023

Sudden wind changes at low altitudes pose a significant threat to aircraft operations. In particular, airports located in regions with complex terrain are susceptible to frequent abrupt wind variations, affecting aircraft takeoff and landing. To mitigate these risks, Low Level Wind shear Alert System (LLWAS) have been implemented at airports. This study focuses on understanding the characteristics of wind shear and developing a prediction model for Jeju International Airport, which experiences frequent wind shear due to the influence of Halla Mountain and its surrounding terrain. Using two years of LLWAS data, the study examines the occurrence patterns of wind shear at Jeju International Airport. Additionally, high-resolution numerical model is utilized to produce forecasted information on wind shear. Furthermore, a comparison is made between the predicted wind shear and LLWAS observation data to assess the prediction performance. The results demonstrate that the prediction model shows high accuracy in predicting wind shear caused by southerly winds.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제18권1호
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• pp.64-88
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• 2024

Security and reliability are the utmost importance facts in intelligent networked vehicles. Stochastic Petri Net and Z (SPZN) as an excellent formal verification tool for modeling concurrent systems, can effectively handles concurrent operations within a system, establishes relationships among components, and conducts verification and reasoning to ensure the system's safety and reliability in practical applications. However, the application of a system with numerous nodes to Petri Net often leads to the issue of state explosion. To tackle these challenges, a refinement and abstraction method based on SPZN is proposed in this paper. This approach can not only refine and abstract the Stochastic Petri Net but also establish a corresponding relationship with the Z language. In determining the implementation rate of transitions in Stochastic Petri Net, we employ the interval average and weighted average method, which significantly reduces the time and space complexity compared to alternative techniques and is suitable for expert systems at various levels. This reduction facilitates subsequent comprehensive system analysis and module analysis. Furthermore, by analyzing the properties of Markov Chain isomorphism in the case study, recommendations for minimizing system risks in the application of intelligent parking within the intelligent networked vehicle system can be put forward.

• Journal of Positioning, Navigation, and Timing
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• 제13권2호
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• pp.131-136
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• 2024

This paper deal with a method for calculating the continuity of Korea Augmentation Satellite System (KASS), which was completed in Korea in December 2023, and a plan to respond in the event that a continuity hazard situation occurs during operation. For this purpose, the International Civil Aviation Organization (ICAO) Satellite Based Augmentation System (SBAS) continuity standards, Wide Area Augmentation System (WAAS), and European Geostationary Navigation Overlay Service (EGNOS) continuity cases are examined in this paper. According to the measures recommended by the ICAO, when the number of continuity risks exceeds a certain level and the level drops drastically, various mitigation operations by country are implemented. Through this, if KASS does not meet ICAO continuity standards in the future, such measures can be referred to. In addition, this paper computes the short-term KASS continuity during the test broadcast period. Although continuity does not meet the ICAO standards, although this test period is too short, further meaningful analysis in the future is required. Additionally, this paper carried out an analysis of the timing and period to systematically calculate the meaningful value of continuity.

• 한국융합학회논문지
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• 제12권5호
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• pp.207-215
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• 2021

지게차는 전동 포크를 이용해 화물을 적재하고 운반하는 용도로 사용되는 산업용 장비로, 지게차로 인한 산업재해는 지속적으로 빈발하고 있다. 이러한 재해의 대다수는 작업자의 불안전한 행동에 기인하는 것으로 알려져 있으나, 지게차 작업에 초점을 두고 휴먼에러 관점에서 위험을 분석한 연구는 찾아보기 어렵다. 또한, 작업의 휴먼에러 위험을 파악하고 분석하기 위한 다양한 기법들이 개발되어 왔으나, 기법 간에 효과성이나 장단점을 직접적으로 비교한 연구는 드물다. 본 연구는 대표적인 휴먼에러 분석 기법인 SHERPA와 HE-HAZOP을 이용하여 지게차 작업에서의 불안전한 행동과 관련된 위험 요인을 분석하고 두 기법의 장단점을 비교한다. 지게차 작업 중 '하차작업', '자재이동 및 적재작업', '상차작업'의 3가지 대표적 작업을 대상으로 분석을 수행한 결과, SHERPA에 의해 118건의 에러와 34건의 개선대책이 도출되었으며 HE-HAZOP를 통해 139건의 에러와 54건의 개선대책이 도출되었다. 휴먼에러 위험 분석의 결과를 바탕으로 두 기법을 결과 건수, 접근방법, 원인분석, 위험성 평가, 개선방안 도출 방식 등 다양한 측면에서 비교하였다. 본 연구의 결과는 지게차를 사용하는 사업장에서 휴먼에러와 관련된 재해 위험을 줄이는 데 활용될 수 있다. 대상 작업과 여건에 맞는 휴먼에러 분석 기법을 선정하기 위한 가이드를 제공하기 위해서는 향후 다양한 작업을 대상으로 보다 많은 휴먼에러 분석 기법에 대한 비교 연구가 필요할 것으로 보인다.

• 한국항해학회지
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• 제21권2호
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• pp.47-58
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• 1997

The purpose of this study is to find out the impacts of VTS on the marine safety and users' opinion on the VTS which have been being operated in the port of Pohang for the last 3 years and is to suggest a guideline to the successful operation of VTS in the future. This study is based upon the questionnaire survey and the respondents include 236 masters/mates of merchant vessels who have visited the port of Pohang and 6 pilots who have been working in the port. From the questionnaire results, this study notes the following conclusions related to the VTS operations. (1) A few of the respondents (mainly foreigners) do not understand the entering procedure of the port and the fundamental concept of VTS. Accordingly, the more active VTS services have to be provided for the mariners. (2) It was found that themost dangerous factors in tehvicinity of the port were the floating materials, fishing nets, andillegal fishing activities inthe fairway. Therefore, the proper surveillance, stricter enforcement of Acts and the instructive education for the fishermen are required to avoid the risks. (3) A majority of the respondents agreed the VTS has contributed to the safety of vessel traffic, and they pointed out ' the assiatances in reduced visibililty conditions' is the most important task of VTS. The amount of 75.6% of the respondents answered that they have experienced the assistance from VTS more than 1 time since the system was established in the port of Pohang . Also 44.2% of the respondents considered they were able to avoid marine casualties such as collision, ramming or agrounding with the VTS assistances. (4) 49.2% of the respondents preferred the passive information services , while, 38.8% of them preferred the positive control advices in the case of encountering any potential risks. VTS iperators have to consider seriously when they provide the positive control advices of ship's course and speed. (5) A majority of the respondents confirmed that the prot and its approaches is suitable for the VTS coverge . To extend the service areas of the VTS and to improve radar detecting ability, the use of radar transponders are seen as the ideal method. (6) A minority of the respondents pointed out 'the improper orders or recommendatinos caused by the poor decision making' firstly, ' the language problem(sea-speaking in English)' secondly, as the deficiency of personal qualification. It seems, therefore, theat the personal efforts of the operators and systematic training programmes for them are necessary to solve the problems.

• Journal of Chest Surgery
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• 제31권7호
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• pp.668-673
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• 1998

최근 수년간에 Maze 수술은 만성 심방세동의 가장 효과적인 치료법이 되었다. 그러나 승모판질환 등 타 심질환의 수술에 병행하여 시행할 때 대동맥 차단시간의 연장, 술후 과다출혈 가능성, 그리고 술후 제세동 결과예측의 불확실성 등, 다소의 우려가 있는 것이 사실이다. 단국대학교 흉부외과에서는 1996년 9월부터 1997년 8월까지 6례에서 Cox-maze III 수술을 시행하여 양호한 결과를 얻었기에 초기 성적을 보고한다. 남녀 각각 3명으로 환자의 연령은 평균 49.6세이었다. 심방세동을 동반한 심질환은 승모판협착 또는 협착 및 폐쇄부전의 승모판질환 4례, 승모판과 대동맥판의 협착 및 폐쇄부전 1례, 관상동맥 협착 1례로서, 수술은 Cox-maze III 술식과 동시에 개방성 승모판교련절개술 3례, 승모판대치술 1례, 대동맥판 및 승모판대치술 1례, 그리고 관상동맥우회술 1례를 시행하였다. 대동맥 차단시간은 122~233분(평균 182.4), 체외순환시간은 202~346분(평균 273.8)으로 비교적 길었으나 술후 심장회복은 순조로우며 술후 출혈로인한 재개흉예는 없었다. 술후 전 예에서 수술직후 또는 술후 2~20일 사이에 동율동으로 전환되었으며 그 기간사이에 일시적인 상심실성 부정맥이 나타나기도 하였으나 약제에 잘 치료되었다. 추적검사상 모든 예가 동율동의 심전도 소견을 보였으며 심초음파검사상 우심방의 수축은 전 예에서, 좌심방의 수축은 가장 최근에 수술한 1례를 제외하고는 모든 예에서 확인되었다. 이상의 경험으로 Cox-maze III 술식은 큰 추가 수술위험성없이 시행될 수 있었으며 만성 심방세동의 제세동에 효과적이었다.

• International Journal of Railway
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• 제1권4호
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• pp.149-156
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• 2008

During maintenance or construction works in or at the tracks of railways, high risks for passengers and railway staff, especially for the workers on the construction site exist. The high risks result out of the movement of rail vehicles, like trains or construction vehicles, which must be faced by using any available technical and operational technologies for securing them against the environment. Therefore, it is necessary to evaluate the level of protection continuously and to identify new and innovative methods and technologies for the protection of the gang (construction worker, machines and material). Especially on construction sites at line sections with two or more parallel tracks but also with single tracks, there are still a lot of incidents and accidents mostly with seriously injured persons or fatalities. These were mainly gang members that breach the railway-loading gage. By using proper warning or protection systems, the avoidance of such accidents must be achieved. The latest developments. in gang protection systems concern on the one hand fixed barriers in the middle between the construction site and the operated track and on the other hand construction vehicles equipped with automatic warning systems. The disadvantage of such protection methods is that the gang can be warned against an approaching train but a monitoring of the gang members cannot be performed. Only one part of a potential dangerous situation will be detected. If the gang members will overhear the acoustic warning signal of the security staff and the workers will not leave the danger zone in the track, the driver of the approaching train had no chance to react to the dangerous situation. An accident is often inevitable. While the detection of acoustic warning signals by the gang members working on a construction site is very difficult, the acoustical planning of an automatic warning system has to be designed for an acoustic short range level of one meter besides the construction vehicle. The decision about the use of today's technical warning system (fixed systems, automatic warning systems, etc.) must be geared to the technical feasibility and the level of safety which is needed. Criteria for decision guidance to block a track should be developed by danger estimation and economical variables. To realize the actual jurisdiction and to minimize the hazards of railway operations by the use of construction vehicles near the tracks further developments are needed. This means, that the warning systems have to be enhanced to systems for protection, which monitor the realization of the warning signal as a precondition for giving a movement authority to a train. This method can protect against accidents caused by predictable wrongdoing. The actual state of the art technique of using a collective warning combined with additional security staff is no longer acceptable. Therefore, the Institute of Transportation System of the German Aerospace Center in Braunschweig (Germany) will develop a gang warning and protection system based upon imaging methods, with optical sensors such as video in visible and invisible ranges, radar, laser, and other. The advantage of such a system based on the possibility to monitor both the gang itself and the railway-loading gauge either of the parallel track or of the same track still in use. By monitoring both situations, the system will be able to generate a warning message for the approaching train, that there are obstacles in the track, so that the train can be stopped to prevent an accident. And also the gang workers will be warned, while they breach their area.

• 한국항행학회논문지
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• 제27권6호
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• pp.710-715
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• 2023

도시화가 가속화되면서 교통 혼잡, 주거 및 환경 문제 등의 사회적 이슈가 도출되고 있다. 이를 해결하기 위해 도심항공교통 (UAM; urban air mobility)과 같은 혁신적인 교통시스템 개발에 관한 연구가 활발하게 진행되고 있다. 초기 저밀도 운항 환경에서 기존의 항공교통시스템에 부담을 주지 않으면서도 안전하게 비행이 이루어져야 하고, 공역을 효율적으로 관리하고 운영하는 능력이 요구된다. 따라서 UAM은 회랑을 통한 경로의 운영으로 예측 가능성을 높여 초기 운영단계에서는 저밀도 상황에서의 운항에 대한 데이터를 축적해 나가는 것이 중요하다. 이를 위해서는 운영하기 전 각종 시뮬레이션을 활용한 시나리오를 생성하여 UAM 기체 간의 잠재적인 충돌 가능성을 예측하고 항공기 간격 즉 분리에 대한 손실 (LoS; loss of separation), 그리고 근접 공중충돌 (NMAC; near mid air collision) 위험에 대한 검토가 필요하다. 항적 난기류는 항공기 간의 안전한 분리를 보장하는 중요한 요소로, 기존 항공교통에서는 활주로와 항로의 분리에 필수적으로 사용되었다. UAM 비행체는 저고도에서 밀집된 공간에서 운영되기 때문에, 항적 난기류에 관한 추가적인 연구가 필요하며, 이를 위해 다양한 데이터를 활용하여 기체의 성능을 정밀하게 분석하고 있다. 본 논문에서는 국내외 연구 결과를 바탕으로 UAM의 분리 기준 설정에 필요한 요구사항과 고려해야 할 사항들을 확인하는 데 초점을 맞추고자 한다.

• Journal of Korean Neurosurgical Society
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• 제54권3호
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• pp.225-231
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• 2013

Objective : Spinal dysraphism defects span wide spectrum. Wound dehiscence is a common postoperative complication, and is a challenge in the current management of cerebrospinal fluid (CSF) leaks and wound healing. The purpose of this study is to evaluate the risks of CSF-related morbidity in the surgical treatment of spinal dysraphism. Methods : Ten patients with spinal dysraphism were included in this retrospective study. The median age of the cohort was 4.8 months. To assess the risk of CSF morbidity, we measured the skin lesion area and the percentage of the skin lesion area relative to the back surface for each patient. We then analyzed the relationship between morbidity and the measured skin lesion area or related factors. Results : The overall median skin lesion area was 36.2 $cm^2$ (n=10). The percentage of the skin lesion area relative to the back surface ranged from 0.6% to 18.1%. During surgical reconstruction, 4 patients required subsequent operations to repair CSF morbidity. The comparison of the mean area of skin lesions between the CSF morbidity group and the non-CSF morbidity group was statistically significant (average volume skin lesion of $64.4{\pm}32.5cm^2$ versus $27.7{\pm}27.8cm^2$, p<0.05). CSF morbidity tended to occur either when the skin lesion area was up to 44.2 $cm^2$ or there was preexisting fibrosis before revision with an accompanying broad-based dural defect. Conclusion : Measuring the lesion area, including the skin, dura, and related surgical parameters, offers useful information for predicting wound challenges and selecting appropriate reconstructive surgery methods.

• 정보처리학회논문지C
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• 제12C권4호
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• pp.481-488
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• 2005

현재 무선 네트워크 IP를 위한 이동성 자원의 표준인 Mobile IP는 이동 노드(Mobile Node, MN)의 접속에 관한 사용자 인증이 비효율적이다. 본 논문에서는 네트워크 구성원들의 상호 인증 및 보안 서비스를 위해서 인증(Authentication), 권한부여(Authorization) 및 과금(Accounting)을 지원하는 AAA 프로토콜에 기반하여 Mobile IP의 보안성을 유지하고 빠른 핸드오프를 수행하는 새로운 보안 핸드오프 방식을 제안한다. AAA 프로토콜은 QoS를 제한하는 비효율적인 인증 절차가 존재하여 MN이 핸드오프를 수행할 때마다 새로운 세션 키를 분배 받아야 한다. 본 논문에서는 MN이 핸드오프를 수행할 때 발생하는 지연 시간과 MN의 인증으로 인한 AAA 서버의 오버헤드를 줄이고자 공유(Overlap, 오버랩) 네트워크 구조 기반의 세션키 재사용 방법을 제안한다 본 방식에서는 MN의 보안성 향상을 위하여 공유 세션 키를 유선상에서 전달하는 방식에 기반하고, 그에 따라 신속하고 자연스러운 핸드오프 메커니즘을 제공한다. 분석적 모델링결과에 의하면 제안하는 방식은 기존 세션키 재사용 방식과 비교하여 핸드오프 시간을 고려하는 핸드오프 실패율에 있어서 $40\%$정도의 성능향상을 보인다.