• 대한교통학회:학술대회논문집
• /
• 대한교통학회 1998년도 Proceedings The 4th International Transport Symposium
• /
• pp.141-151
• /
• 1998

Provision of Passing Sight Distance (PSD) is an important component in two-lane highway design and has a critical impact on capacity of highway and safety of drivers. Many models have been developed to estimate PSD reasonably. However, each of them has a number of shortcomings for reflecting the real traffic conditions. This paper introduces a revised model that reflects the characteristics of the passing maneuver. The changes in passing sight distances under different assumptions about acceleration and vehicle length, which are related to vehicle types, are presented. The results obtained by the revised model are compared with those obtained from the existing models. There is an important link between geometric design decisions which determine the available sight distance and the quality of service which the road provides. In this paper, we examine one aspect of this relationship. That is to determine whether the passing sight distance is provided by improving horizontal alignment for a specific roadway section or passing may be restricted to save the road construction cost. To do so, a simple method for estimating traffic delay in no-passing is introduced.

• 대한원격탐사학회지
• /
• 제26권6호
• /
• pp.675-680
• /
• 2010

Temperature is one of the main issues in climate change, and the urban heat island effect in highly developed urban areas is an important issue that we need to deal with. This study analyzed the extent of the cooling effects of urban green spaces. The study used a surface temperature map of Seoul. It found that the cooling effects of green space was observed within limited distances, although it varied a little depending on the parks investigated. The cooling effect distance ranged from 240m to 360m, averaging about 300m. It also found the size of an urban green space does not make much difference in cooling the surrounding areas. Although further investigation with diverse urban areas should be conducted on this matter, the results did imply that many small green spaces in the neighborhood are more effective than a single big green space in mitigating the heat island effects of cities.

• 4차산업연구
• /
• 제1권2호
• /
• pp.1-8
• /
• 2021

Purpose - By suggesting relational distance between supervisor and subordinate, this study examines the boundary condition of the impact of transformational leadership and organizational commitment in Korea. Research design, data, and methodology - We collected survey data from employees in various industries in Korea. A total of 241 employees participated in this study. We conducted the hierarchical linear regression and confirmed moderating effects of relational distances (democratic, structural and affective distance) on the relationship between transformational leadership and organizational commitment. Result - The results from 241 Korean employees show that transformational leadership is positively related to organizational commitment. Further, this relationship was moderated by structural distance and affective distance between supervisor and subordinate. Conclusion - This study shed new light on how exercising transformational leadership can help raise employees' organizational commitment. Organizations should be concerned about the various relational distance between supervisor and subordinate.

• Structural Engineering and Mechanics
• /
• 제81권2호
• /
• pp.117-129
• /
• 2022

This research evaluated the different types of deck to pier connections effects (one or two elastomeric bearing lines and rigid) on a concrete bridges. Three-dimensional bridge models behavior with different deck to pier connections and different distances of two bearing lines were studied under the service load. Also, the detailed connection system with two elastomeric bearing lines was modeled to evaluate the effect of changing distance between two-lines. Results indicated that the proper location of elastomeric bearings has a major impact on the transferring forces to the substructure. Double elastomeric bearing lines have a behavior between one line and rigid connections. Transferring bending moment to the substructure in two-lines is more than the corresponding value of the one line. Moreover, an increase in the distance of two-lines lead to a significant increase in the rotational stiffness of the connection, and an analytical solution was investigated for their relation. In fact, the semi-rigidity effect of this connection and its change due to the distance of bearings should be considered in the design process.

• Earthquakes and Structures
• /
• 제22권3호
• /
• pp.289-304
• /
• 2022

During strong ground motions, adjacent structures with insufficient separation distances collide with each other causing considerable architectural and structural damage or collapse of the whole structure. Generally, existing design procedures for determining the separation distance between adjacent buildings subjected to structural pounding are based on approximations of the buildings' peak relative displacement. These procedures are based on unknown safety levels. This paper attempts to evaluate the influence of foundation flexibility on the structural seismic response by considering the variability in the system and uncertainties in the ground motion characteristics through comprehensive numerical simulations. Actually, the aim of this study is to evaluate the influence of foundation flexibility on probabilistic evaluation of structural pounding. A Hertz-damp pounding force model has been considered in order to effectively capture impact forces during collisions. In total, 5.25 million time-history analyses were performed over the adopted models using an ensemble of 25 ground motions as seismic input within OpenSees software. The results of the study indicate that the soil-structure interaction significantly influences the pounding-involved responses of adjacent structures during earthquakes and generally increases the pounding probability.

• 천문학회보
• /
• 제46권1호
• /
• pp.58.4-59
• /
• 2021

This presentation introduces Korea's SNIPE (Small scale magNespheric and Ionospheric Plasma Experiment) mission, formation flying CubeSat constellation. Observing particles and waves on a single satellite suffers from inherent space-time ambiguity. To observe spatial and temporal variations of the micro-scale plasma structures on the topside ionosphere, four 6U CubeSats (~ 10 kg) will be launched into a polar orbit of the altitude of ~500 km in 2021. The distances of each satellite will be controlled from 10 km to more than 100 km by formation flying algorithm. The SNIPE mission is equipped with identical scientific instruments, solid-state telescope, magnetometer, and Langmuir probe. All the payloads have a high temporal resolution (sampling rates of about 10 Hz). Iridium modules provide an opportunity to upload changes in operational modes when geomagnetic storms occur. SNIPE's observations of the dimensions, occurrence rates, amplitudes, and spatiotemporal evolution of polar cap patches, field-aligned currents (FAC), radiation belt microbursts, and equatorial and mid-latitude plasma blobs and bubbles will determine their significance to the solar wind-magnetosphere-ionosphere interaction and quantify their impact on space weather.

• 화약ㆍ발파
• /
• 제23권2호
• /
• pp.57-66
• /
• 2005

A major concern with blasting at surface mines is generation of ground vibration, air blast, flyrock, dust & fume and their impact on nearby structures and environment. A study was conducted at a coal mine in India which produces 10 million tonne of coal and 27 million cubic meter of overburden per annum. Draglines and shovels with dumpers carry out the removal of overburden. Detonation of 100 tonnes of explosives in a blasting round is a common practice of the mine. These large sized blasts often led to complaints from the nearby inhabitants regarding ground vibrations and their affects on their houses. Eighteen dragline blasts were conducted and their impacts on nearby structures were investigated. Extended seismic arrays were used to identify the vibration characteristics within a few tens meters of the blasts and also as modified by the media at distances over 5 km. 10 to 12 seismographs were deployed in an array to gather the time histories of vibrations. A signature blast was conducted to know the fundamental frequency of the particular transmitting media between the blast face and the structures. The faster decay of high frequency components was observed. It was also observed that at distances of 5km, the persistence of vibrations in the structures was substantially increased by more 10 seconds. The proximity of the frequency of the ground vibration to the structure's fundamental frequencies produced the resonance in the structures. On the basis of the fundamental frequency of the structures, the delay interval was optimized, which resulted into lower amplitude and reduced persistence of vibration in the structures.

• 대한치과교정학회지
• /
• 제50권2호
• /
• pp.75-85
• /
• 2020

Objective: The aim of this study was to evaluate changes in the nasal soft tissues, including movements of landmarks, changes in linear distances, and volumetric changes, using three-dimensional (3D) stereophotogrammetry after microimplant-assisted rapid palatal expansion (MARPE) in adult patients. Methods: Facial data were scanned using a white light scanner before and after MARPE in 30 patients. In total, 7 mm of expansion was achieved over a 4-week expansion period. We determined 10 soft tissue landmarks using reverse engineering software and measured 3D vector changes at those points. In addition, we calculated the distances between points to determine changes in the width of the nasal soft tissues. The volumetric change in the nose was also measured. Results: All landmarks except pronasale and subnasale showed statistically significant movement on the x-axis. Pronasale, subnasale, alar right, and alar left showed significant movement on the y-axis, while all landmarks except subnasale showed significant movement on the z-axis. The alar base width, alar width, and alar curvature width increased by 1.214, 0.932, and 0.987 mm, respectively. The average volumetric change was 993.33 ㎣, and the amount of increase relative to the average initial volume was 2.96%. Conclusions: The majority of soft tissue landmarks around the nasal region show significant positional changes after MARPE in adults. The nose tends to widen and move forward and downward. The post-treatment nasal volume may also exhibit a significant increase relative to the initial volume. Clinicians should thoroughly explain the anticipated changes to patients before MARPE initiation.

• 대한환경공학회지
• /
• 제39권12호
• /
• pp.685-688
• /
• 2017

장외영향평가의 정량적 위험성평가에 사용되는 ALOHA와 PHAST 프로그램으로 화학물질관리법상 사고대비물질로 지정하고 있는 염소의 누출 사고 시나리오를 가정하여 모델링 하였다. 연평균 기온, 풍속, 습도, 대기안정도를 변화시키면서 ERPG-2 농도에 해당하는 끝점거리를 산출하였으며, 산출된 끝점거리 값을 비교하여 각각의 기상요소와 끝점거리 간의 상관관계와 ALOHA와 PHAST의 장단점 분석하였다. 연구결과 ALOHA는 연평균 기온과 습도와의 상관관계는 없거나 작고, 풍속과 대기안정도와의 상관관계가 큰 것으로 조사되었다. PHAST의 경우 연평균 기온, 풍속, 습도, 대기안정도 모든 기상요소와의 상관관계가 있었으며, 그 중 대기안정도의 영향을 가장 크게 받는 것으로 조사되었다.

• 대한의생명과학회지
• /
• 제24권4호
• /
• pp.411-417
• /
• 2018

The aim of this study was to investigate the impact of participation in the 622 km hyper-ultra-marathon on hepatic metabolism and renal function in middle-aged men. Healthy middle-aged male amateur ultra-marathoners between the ages of 40 and 60. Blood was collected at the pre-race, immediately after 300 km, 622 km hyper-ultra marathon race, 72 hours (3 day) and 144 hours (6 day) after the race, AST (aspartate aminotransferase), ALT (alanine aminotransferase), ALP (alkaline phosphatase), ${\gamma}$-GTP (gamma glutamyl transferase), T-Bil (total bilirubin), D-Bil (direct bilirubin), T-protein (total protein), albumin, uric acid, BUN (blood urea nitrogen), creatinne were analyzed. ALP was significantly increased at 300 km, 622 km, day 3 and day 6 than the pre-race. ${\gamma}$-GTP, T-protein, albumin, uric acid, BUN and creatinine were not significantly different between the distances and the recovery period respectively. AST and ALT were significantly increased at 300 km, 622 km, day 3 and day 6 than the pre-race, respectively (P<0.05) at day 3 and day 6 they showed significant decrease from 300 km and 622 km, respectively (P<0.05). T-Bil and D-Bil increased significantly at 300 km and 622 km, respectively (P<.05) and significantly decreased at day 3 (P<0.05) compared to the pre-race, at day 3 and day 6 they were decreased significantly than 300 km and 622 km, respectively (P<0.05). In conclusion, no disturbance of renal function was observed according to the distances and between the recovery period of 622 km hyper-ultra marathon race, but reversible hepatocyte function could be degraded and some hemolysis of blood vessels was induced.