• Geomechanics and Engineering
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• 제4권2호
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• pp.79-90
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• 2012

Air pluviation method is widely adopted for preparation of large, uniform and repeatable sand beds of desired densities for laboratory studies to simulate in-situ conditions and obtain test results which are highly reliable. This paper presents details of a portable traveling pluviator recently developed for model sand bed preparation. The pluviator essentially consisted of a hopper, orifice plates for varying deposition intensity, combination of flexible and rigid tubes for smooth travel of material, and a set of diffuser sieves to obtain uniformity of pluviated sand bed. It was observed that sand beds of lower relative density can be achieved by controlling height of fall, whereas, denser sand beds could be obtained by controlling deposition intensity. Uniformity of pluviated sand beds was evaluated using cone penetration test and at lower relative densities minor variation in density was observed with depth. With increase in relative density of sand bed higher repeatability of uniform pluviation was achieved.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2006년도 International Symposium on GPS/GNSS Vol.1
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• pp.3-8
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• 2006

This paper discusses current challenges, as a result of the rapid increase in air travel, and future navigation needs of Civil Aviation. The objectives pursued by ANASTASIA, a sixth framework European Commission project, are presented. The methods used in the derivation of the navigation performance requirements are introduced and discussed in the context of precision approaches. High-level impacts on the avionics receiver of integrating additional multi-frequency ranging signals from a modernized GPS and Galileo into the current navigation architecture are investigated. Expected performance achievements are presented.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 추계학술대회 논문집
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• pp.750-761
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• 2008

The social and economical value assessment of railway facilities implies unaccountable values such as: reduction of travel time, reduction of car accident, reduction of air pollution. However, the value of railway facilities has been evaluated as the transportation and management results. The investment and management results of railway need to be considered objectively. Therefore, this study established the economical value assessment method of railway facilities composed of 10 items of economical value through the existing a preliminary assessment investigation, a manual of railway investment assessment, paper study. In addition, this study proposed the strategy for the value assessment of railway facilities before and after.

• 한국컴퓨터정보학회:학술대회논문집
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• 한국컴퓨터정보학회 2011년도 제44차 하계학술발표논문집 19권2호
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• pp.51-54
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• 2011

Telematics services include automatic location tracking for emergency rescue, which is available for use in case of a car accident due to falling off roadways. This paper presents a simulation study on how far a car will fall before it hits the ground, if dropped off the roadway due to an accident or a natural disaster. The greatest distance the falling car can travel is presented in this paper, on the assumption that air resistance as well as the direction and size of the acceleration due to gravity is negligible.

• 한국항만경제학회지
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• 제34권1호
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• pp.1-18
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• 2018

필리핀은 7000 개 이상의 섬으로 이루어진 아시아 개발 도상국 중 하나이다. 항공, 수로 및 육상 운송은 국내 내륙 여행 및 교통 수단이지만, 이들 7000여개가 넘는 섬들 사이의 사람, 상품 및 서비스 운송은 거의 대부분 RORO 선박을 통한 해송을 통해 이루어지고 있다. 현재 이러한 필리핀 섬들을 연결하는 전체 154 개의 RORO 노선이 구축되어 운항중에 있으며, 해당하는 항구 근처의 지방 자치 단체의 소득은 대략적으로 7 % 증가하는 것으로 나타났다. 그것은 관광객 수, 운송 비용 및 여행 시간의 증가 때문으로서 향후 지속적으로 증가할 것으로 분석되었다. 필리핀의 일부 주요노선을 개선하기 위해 본 연구에서는 필피핀 정부 (항만청), 지방정부, 항만 및 선박 회사가 지리적특성, 안전항로, 승하선, 항로보조시설 등 필요한 모든 사항들을 분석 및 제시하였으며 개선해야할 정책을 제안하였다. 향후 본 연구는 필리핀 전역에 해당하는 연구로 확대할 예정이며 이는 필리핀 섬들의 안전하고 효율적인 운송으로 이어질것으로 판단된다.

• 한국ITS학회 논문지
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• 제12권3호
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• pp.114-128
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• 2013

현재 온실가스 배출량 산정 방법은 온실가스 저감대책 효과 분석이 불가능하며 차량의 이동특성이 반영이 안 된 실정으로 이를 극복할 수 있는 온실가스 배출량 산정 방법의 필요로 본 연구가 시작되었다. 교통수요 분석을 통해 차종, 교통상황에 따른 HBEFA 배출계수로 배출량을 산정하는 방법을 통해 고양시에 적용하여 분석하였다. 본연구의 지자체단위 교통수요 추정방안을 통해 실질적인 교통 이용특성에 맞는 온실가스 배출량이 산출되었다. 온실가스 지자체별 통행요금, 속도제한 등 온실가스 저감 요인들이 교통수요 모형에 반영되어 온실가스 저감 대책에 대한 효과분석 후 환경영향을 줄일 수 있는 방안을 강구하여 온실가스 저감 대책 마련에 효율적으로 이용될 것으로 판단된다.

• 수면정신생리
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• 제3권2호
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• pp.18-31
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• 1996

Jet-lag can be defined as the cumulative physiological and psychological effects of rapid air travel across multiple time zones. Many reports have suggested that age-related changes in sleep reflect fundamental changes in the circadian system and in significant declines in slow wave sleep. Jet lag is a dramatic situation in which the changes of the phase of circadian process and homeostatic process of sleep occur. Thus the authors evaluatead the changes of sleep-wake cycle from jet lag by age. Thirty-eight healthy travellers were studied for 3 days before and 7 days after jet-flights across seven to ten time zone. They were aged 19-70, They trareled eastbound, Seoul to North America (USA, Canada). Sleep onset time, wake-up time, sleep latency, awakening frequency on night sleep, awakening duration on night sleep, sleepiness at wake-up and nap length were evaluated. Our results suggest that by the 7 to 10 time zone shift, the old age group was significantly influenced in sleep-wake cycles. The date on which subjective physical condition was recovered was $6.23{\pm}83$ day after arrivals for old age group, while for young and middle age group, $4.46{\pm}1.50$ day and $4.83{\pm}1.52$ day, respectively. In old age group, sleep onset time was later than baselines and could not recover untill 7th day. But in other groups, the recovery was within 5th day. Nap dura fion was longer in old age group through jet lag than younger age group. In other parameters, there was no definite difference among three age groups. Our results suggested that the old age was significantly influenced by the disharmony between internal body clock and sleep-wake cycle needed at the travel site. Thus we proved that recovery ability from jet lag was age-dependent as well as travelling direction-dependent. To demonstrate more definite evidence, EEG monitoring and staging of sleep were funthun encouraged.

• 대한교통학회지
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• 제27권5호
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• pp.7-16
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• 2009

본 연구는 도로사업의 경제적 타당성 분석시 적용되는 편익에 대한 정확성을 높이기 위한 방안을 제시하는 연구이다. 기존 경제적 평가방법의 문제점은 모형의 정산시 교통량만을 정산하기 때문에 실제 교통량과 비슷하게 모형이 정산되지만 모형에서 나오는 통행속도는 실제 속도와 차이를 나타낼 수 있다는 점이다. 실제통행속도와 다른 모형속도는 차량운행비, 통행시간, 대기오염 절감 편익들이 잘못 산정될 수 있게 한다. 따라서, 본 연구에서는 2개의 서로 다른 VDF를 가지고 도로망에서 비슷한 교통량 정산에 의해 서로 다른 속도로 산출된 후 서로 다른 모형속도 결과에 따른 경제적 편익의 차이가 크게 발생되는 문제점을 확인하였다. 이러한 문제점에 대한 개선방향으로 교통량에 따른 정확한 속도를 산출하는 VDF 함수 개발을 포함한 3가지 개선방안을 제시하여 향후 정확한 편익산정과 이로 인한 합리적인 경제성분석이 수행될 수 있는 토대를 마련하였다.

• 시스템엔지니어링학술지
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• 제19권1호
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• pp.64-78
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• 2023

This paper introduces urban air mobility (UAM) and the definition and types of vertiports required for UAM operations. It also examines domestic policy trends related to UAM and identifies UAM routes in Seoul currently planned by the government. To do so, we reviewed prior research on vertiports, analyzed new regulations from the European Aviation Safety Agency, and studied domestic vertiport specifications and deployment plans for UAM operations based on the size of the S-A1 airframe being developed by Hyundai, and applied them to Samsung Station, the core area of the demonstration routes. Next, using the 'Travel Time Savings Ratio', a method for evaluating transportation economics, we compared and analyzed the time taken by passenger vehicles and the time saved by using UAMs to derive a highly economical demonstration route. As a result, the Samsung Station↔Cheongnyangri Station section was found to be the most efficient. These findings are expected to be utilized for adjusting the distribution of UAMs when operating the demonstration route in the future.

• 한국정밀공학회지
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• 제26권2호
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• pp.109-117
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• 2009

This paper presents a linear air bearing stage with compensated motion errors by active control of preloads generated by magnetic actuators with combination of permanent and electromagnets. A 1-axis linear stage motorized with a linear motor with 240mm of travel range is built for verifying this design concept and tested its performances. The three motions of the table are controlled with four magnetic actuators driven by current amplifiers and a DSP based digital controller. Three motion errors were measured combined method with laser interferometer and two-probe method with $0.085{\mu}m$ of repeatability for straightness error. The measured motion errors were modeled as functions of the stage position, and compensation were carried out with feedforward control because the characteristics of the motion control with magnetic actuators are linear and independent for each degree-of-freedoms. As the results, the errors were reduced from $1.09{\mu}m$ to $0.11{\mu}m$ for the vertical motion, from 9.42 sec to 0.18 sec for the pitch motion and from 2.42 sec to 0.18 sec for roll motion.