• 한국ITS학회 논문지
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• 제17권2호
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• pp.142-151
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• 2018

제4차 산업혁명 시대가 도래하면서 전 세계적으로 자율주행자동차에 대한 연구개발이 활발히 진행되고 있다. 이러한 국제적인 기조 속에서 국토교통부는 2020년 SAE 기준 레벨 3이상의 자율주행자동차 상용화를 목표로 자율주행자동차 관련 연구개발을 적극적으로 추진하고 있다. 레벨 3 수준의 자율주행자동차에서는 운전자와 자동차 상호 간의 운행주체를 주고받는 제어권 전환이 필수적으로 발생하게 된다. 본격적인 자율주행자동차 시대에 앞서 본 연구에서는 우선적으로 고속도로를 대상으로 가상현실을 이용한 제어권 전환 안전성 평가를 위하여 대표 시나리오를 개발하였다. 이를 위해 자율주행자동차의 고속도로 주행 시나리오를 만들었고, 2014년 발생한 고속도로 교통사고 경위자료와 제어권 전환 특성을 고려하여 6개의 제어권 전환 시나리오를 개발하였다. 개발된 시나리오에서 고려된 변수는 운전자, 차량, 그리고 환경요인으로 크게 나눌 수 있으며, 총 36개의 변수가 포함되었다.

• Wind and Structures
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• 제19권5호
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• pp.505-522
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• 2014

While effects of the atmospheric boundary layer flow on engineering infrastructure are more or less known, some local transient winds create difficulties for structures, traffic and human activities. Hence, further research is required to fully elucidate flow characteristics of some of those very unique local winds. In this study, important characteristics of observed vertical velocity profiles along the main wind direction for the gusty Bora wind blowing along the eastern Adriatic coast are presented. Commonly used empirical power-law and the logarithmic-law profiles are compared against unique 3-level high-frequency Bora measurements. The experimental data agree well with the power-law and logarithmic-law approximations. An interesting feature observed is a decrease in the power-law exponent and aerodynamic surface roughness length, and an increase in friction velocity with increasing Bora wind velocity. This indicates an urban-like velocity profile for smaller wind velocities and rural-like velocity profile for larger wind velocities, which is due to a stronger increase in absolute velocity at each of the heights observed as compared to the respective velocity gradient (difference in average velocity among two different heights). The trends observed are similar during both the day and night. The thermal stratification is near neutral due to a strong mechanical mixing. The differences in aerodynamic surface roughness length are negligible for different time averaging periods when using the median. For the friction velocity, the arithmetic mean proved to be independent of the time record length, while for the power-law exponent both the arithmetic mean and the median are not influenced by the time averaging period. Another issue is a large difference in aerodynamic surface roughness length when calculating using the arithmetic mean and the median. This indicates that the more robust median is a more suitable parameter to determine the aerodynamic surface roughness length than the arithmetic mean value. Variations in velocity profiles at the same site during different wind periods are interesting because, in the engineering community, it has been commonly accepted that the aerodynamic characteristics at a particular site remain the same during various wind regimes.

• Steel and Composite Structures
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• 제7권6호
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• pp.487-502
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• 2007

In recent decades there has been a trend towards improved mechanical characteristics of materials used in footbridge construction. It has enabled engineers to design lighter, slender and more aesthetic structures. As a result of these construction trends, many footbridges have become more susceptible to vibrations when subjected to dynamic loads. In addition to this, some inherit modelling uncertainties related to a lack of information on the as-built structure, such as boundary conditions, material properties, and the effects of non-structural elements make difficult to evaluate modal properties of footbridges, analytically. For these purposes, modal testing of footbridges is used to rectify these problems after construction. This paper describes an arch type steel footbridge, its analytical modelling, modal testing and finite element model calibration. A modern steel footbridge which has arch type structural system and located on the Karadeniz coast road in Trabzon, Turkey is selected as an application. An analytical modal analysis is performed on the developed 3D finite element model of footbridge to provide the analytical frequencies and mode shapes. The field ambient vibration tests on the footbridge deck under natural excitation such as human walking and traffic loads are conducted. The output-only modal parameter identification is carried out by using the peak picking of the average normalized power spectral densities in the frequency domain and stochastic subspace identification in the time domain, and dynamic characteristics such as natural frequencies mode shapes and damping ratios are determined. The finite element model of footbridge is calibrated to minimize the differences between analytically and experimentally estimated modal properties by changing some uncertain modelling parameters such as material properties. At the end of the study, maximum differences in the natural frequencies are reduced from 22% to only %5 and good agreement is found between analytical and experimental dynamic characteristics such as natural frequencies, mode shapes by model calibration.

• 자동차안전학회지
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• 제8권4호
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• pp.12-17
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• 2016

NHTSA (National Highway Traffic Safety Administration) has offered consumers the vehicle safety information on their car since 1978. NHTSA believes that they contribute auto makers to develop safer vehicle for customers, which will result in even lower numbers of deaths and injuries resulting from motor vehicle crashes. NHTSA has been studied why people are still dying in frontal test despite of the use of many restraints system and they understand that current test does not reflect real world crash data such as oblique and corner impact test. As a result, NHTSA announced that a new test method will be introduced to use of enhanced biofidelic dummy and new crash avoidance technology evaluation from 2019. New and refined injury criteria will be applied to Head / Neck / Chest / Lower Leg. BrIC(Brain Injury Criterion)value in NHTSA test results using THOR dummy from 2014 to 2015 was average 0.91 and 1.24 in driver and passenger dummies. IIHS 64kph SOF test is the most likely to new frontal oblique test in an aspect of offset impact which is being studied by NHTSA. In this paper, we focused on head injury, especially brain injury - BrIC and conducted IIHS 64kph SOF (Small Offset Front) test with Hybrid III dummy to evaluate the injury for BrIC. Based on the test results, these data can be predicted BrIC level and US NCAP rating with current vehicle.

• 한국대기환경학회지
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• 제27권6호
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• pp.663-671
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• 2011

Although a scooter is a convenient transportation means for a short distance traveling with a light package in the congested urban center, it might be one of the significant sources of air pollutants to which many people can easily be exposed during its passing-by. In this paper, we measured concentrations of gases and particles emitted from a scooter at roadside with no other traffic. To understand the characteristics of scooter emissions with respect to driving speed (idling, 30 km/h) at the roadside, total particle number concentration, particle size distribution, average surface area of particles deposited in the alveolar region, and concentrations of black carbon, CO, and $NO_x$ were measured. The concentrations of the particle number, surface area of deposited particles, CO, and $NO_x$ were highly fluctuated in the scooter's idling condition. The trends of particle number concentration, CO, and $NO_x$ generation were similar to one another. When the scooter started to move, all of $NO_x$, CO and particle number concentrations increased and after it passed by at the speed of 30 km/h, the concentration peaks of the particles and gases appeared at the same time. Unimodal size distribution with ~70 and ~93 nm mode diameters was observed for the idling and cruising condition, respectively. From this work, we found that emission from a passing vehicle could be characterized using a roadside monitoring technique.

• 한국대기환경학회지
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• 제22권6호
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• pp.767-778
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• 2006

This study was carried out to evaluate the temporal variations of VOCs at an urban site, and to compare the concentrations of VOCs at an urban site in Daegu with those at a suburban site in Gyeongsan. Three hourly VOC samples in the ambient air were collected using a sequential tube sampler (STS 25, Perkin Elmer) throughout two weeks during May and July representing spring and summer seasons, respectively. The VOC concentrations were determined by an automatic thermal desorption apparatus with GC/MS analysis. A total of 12 VOCs of environmental concern were determined, which are chloroform, benzene, trichloroethylene, toluene, tetra-chloroethylene, ethylbenzene, m+p-xylenes, o-xylene, styrene, 1,3,5- and 1,2,4-trimethylbenzenes. Among 12 target VOCs, the most abundant compound appeared to be toluene, being followed by xylenes. The mean concentrations at the urbn site were 1.2 pub for benzene and 20.4 ppb for toluene (n=221) while the mean levels at the suburban site were 0.9 ppb and 4.3 ppb for benzene and toluene (n=96), respectively. The urban site concentrations were typically several-fold higher than those measured at the suburban site. It was found that general trends of VOC levels were significantly dependent on traffic conditions at the sampling site since VOC concentrations were at their maximum during rush hours, i.e. $9{\sim}12a.m$ and $6{\sim}9p.m$. Statistical investigations were conducted to investigate any significant relationships between VOC concentrations and affecting factors. Calculated correlation coefficients among VOCs were positively significant at a level of 0.05 in most cases. Increased concentrations of toluene in the urban site were estimated to reflect the effect of large industrial sources, mainly from textile industry.

• 한국콘텐츠학회논문지
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• 제14권9호
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• pp.45-53
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• 2014

본 연구에서는 차세대 ITS로 주목받고 있는 국내외 C-ITS 기술 동향을 현재 국내에서 진행 중인 프로젝트를 중심으로 분석하였으며, 해외 선진국들의 추진 사례를 바탕으로 국내 C-ITS 정책이 기존의 ITS 인프라와의 연계 모색이 미흡함을 지적한다. 이를 극복하기 위한 방안으로, 기존 ITS 인프라가 C-ITS에 대응이 가능하도록 세 가지 방향성을 제시한다. 첫째, 기존 인프라 설비의 성능을 고도화하고 자동화하는 기술을 개발(Performance-enhanced ITS)하고, 둘째, 능동형 센서 및 융합 센서를 개발하여 V2X 통신 기술과 더불어 선제적 안전 운행 지원 기술을 개발(Safety-enhanced ITS)하며, 셋째 Nomadic Device의 보급으로 발생하는 비정형 교통 데이터를 기존 ITS 설비로 수집한 데이터와 융합하여 고급 교통정보를 생성하는 기술 개발(Cloud-ITS)이다. 이와 같이 기존 ITS 인프라에 V2X 통신 환경에 필요한 기능을 추가하고 효율적인 유지관리 기술을 개발한다면 C-ITS에서 추구하는 차량과 차량, 차량과 노변 장비와의 상호 협력적인 기술 기반이 조성되고, 예산의 중복 투자 방지가 가능해져 C-ITS 도입 효과를 극대화할 수 있을 것으로 기대한다.

• 대한안전경영과학회지
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• 제19권1호
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• pp.237-243
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• 2017

Currently, Korea is actually increasing and increasing demand for leisure such as parts for A/S of automobile parts of the car, as well as trends in borrowing and finished parts are also required a steady increase in automobile traffic daetsu. There is one car and want to be driving a car A/S parts supplier smoothly for many years and that it is often the case if it is not supplied in a timely fashion, it is a reality that many eonseong hear from customers. These symptoms can be confirmed that the logistics systems of a system of selling auto parts supplier but above all a problem for several reasons, which will be considered as areas for improvement should be done urgently. Enterprises internally cooperation automotive supplier, but the need to get out to re-examine urgently complemented by the logistics system of systems to allow better respond to complex environmental changes of our customers grow, and now also the proliferation of small ship-run screen and Darvin, there is increasing distribution and logistics services, including logistics costs as a lack of work force that the company is itgetda can be called by the reality that the chances of getting a lot of jeyakreul own growth. Given this situation, the procurement of logistics enterprises. In-house logistics. Classified as sales logistics examined the long-term improvement of logistics distribution networks based on this part to derive into the problems of logistics and parts distribution system of Korean auto parts dealer.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2006년도 춘계학술대회 및 창립 30주년 심포지엄(논문집)
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• pp.301-307
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• 2006

컨테이너 물동량의 급격한 증가와 함께 컨테이너를 운송하는 선박들의 규모도 이전의 증가세와는 비교할 수 없을 정도로 규모는 커지고 있다. 이러한 추세와 함께 초대형선박에 대한 연구도 다양한 시각에서 활발하게 수행되어왔다. 그러나, 대부분의 기존 연구는 주로 선박의 설계, 운영 그리고 항만 하역시설 등 하드웨어적이고 개념적인 부문에 편중되어 있고, 실제 선박운항 측면에서 적정 선박 규모, 적정 기항 항만 수, 요구되는 하역 소요 시간 등 현실적인 연구는 극히 미흡한 실정이다. 따라서 본 논문은 초대형선박의 운영자인 선사들과 사용자인 포워딩업체들을 대상으로 초대형선의 예상 최대규모, 선호도, 이용 시 문제점과 예상 하역시간 등을 조사 분석하고, 초대형선의 출현으로 나타날 될 항만기항지 변화에 대하여 예측한다.

• 전자통신동향분석
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• 제37권3호
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• pp.74-84
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• 2022

The Korean mobile service market has persistently grown with the number of subscribers and volume of mobile traffic. It shows the slow diffusion of 5G subscribers, and rapid growth of both the MVNO(Mobile Virtual Network Operator) market and unlocked mobile phones. Therefore, this study derives the direction of telcos' strategies and policy implications by empirically analyzing the usage and attitude of LTE and 5G subscribers. Our major findings are as follows: First, our current mobile service subscription market constitutes most long-term customers for their incumbent carriers only by device change from lock-in with bundle services. Mobile tariffs, data speed, and benefits of bundle services are important factors affecting choices and customers' satisfaction with a provider and intentions of churning to another. Second, demand and satisfaction for using 5G are less because speeds and service tariffs act as pain points for 5G services. Third, the users' high preferences for MVNOs and unlocked mobile phones are linked to their subscription to MVNOs' low-cost plans with unlocked mobile phones on online channels. These streams lead to a big change in the market competition that MNO(Mobile Network Operator)s' market shares are expected to decrease and MVNOs' shares will be increased by two times, in the near future. Therefore, MNOs need to change their distribution strategies from offline to online channels and try to resolve the stereotype, "mobile tariffs are expensive," by enhancing their service values. Finally, as consumers prefer one-stop service in the same channel regardless of the distribution channel, policies should focus on the consumers' needs for convenience rather than on the channel separation for perfectly unlocked mobile phones.