• Journal of Korean Tunnelling and Underground Space Association
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• v.20 no.5
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• pp.855-867
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• 2018

When a weak zone exists ahead of tunnel face, the stress in the adjacent area would increase due to the longitudinal arching effect and the stability of the tunnel is affected. Therefore, it is critical to prepare a countermeasure through the investigation of the frontal weakness zone of the excavated face. Although there are several researches to predict the existence of weak zone ahead of tunnel face, such as geophysical exploration, numerical analysis and tunnel support, lack of studies on the relaxation zone depending on the width or distance from the vulnerable area. In this study, the impact of the weak zone on the formation of the relaxation zone was investigated. For this purpose, a series of laboratory test were carried out varying the width of the weak zone and the separation distance between tunnel face and weak zone. In the model test, sand with a water content of 3.8% was used to form a model ground. The model weak zone was constructed with dry sand curtains. The tunnel face was adjusted to allow a sequential excavation of upper and lower half part. load cells were installed on the bottom of the foundation and the tunnel face and measuring instruments for displacement were installed on the surface of the model ground to measure the vertical stress and surface displacements due to tunnel excavation respectively. The test results show that the width of weak zone did not affect the ground settlement while the ground subsidence drastically increased within 0.25D. The vertical stress and horizontal stress increased from 0.5D or less. In addition, the longitudinal arching effect is likely within the 1.0D zone ahead of the tunnel face, which may reduce the vertical stress in the ground following tunneling direction.

• Journal of the Korean Association of Geographic Information Studies
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• v.15 no.4
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• pp.124-137
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• 2012

Climate analysis is important in urban planning for human comfort. Synoptic weather conditions can only resolve the 30% of local variance of wind conditions whereas 70% of the variance arise from local terrain, buildings, and other small scale thermal conditions. Climate Analysis Seoul (CAS) was developed to resolve such micro-scale climate. The Local-scale air temperature Deviation (LD) analysis map from CAS showed the co-existence of built-up and suburban areas in the study region (CR, Cold-air analysis Region) despite its small extent. Temperature, humidity, wind speed, and wind direction were monitored in CR. Hourly observed cooling rate agreed well with LD. Cold air production, transportation, and stagnation was visualized by the observed Vertical Temperature Gradient (VTG) along the small stream in CR. VTG observed at the upper-most stream can be divided into two components: radiative cooling and cold air inflow from outside. Radiative cooling exists regardless of the wind speed whereas cold air inflow occurs only with calm wind. From the regression analyses based on the wind speed, the inflow portion was determined as 84% of radiative cooling. Climate analysis in the future will be able to characterize the changes in cold air by urban development plan to support the human comfort.

• Fire Science and Engineering
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• v.31 no.3
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• pp.25-30
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• 2017

Because of the vertical combustion characteristics of combustible substances, accurate substance safety information for their safe use, handling and transportation is essential. The flash point, fire point, explosion limits and autoignition temperature (AIT) are important safety parameters which need special attention in chemical plants and laboratories that handle dangerous materials. In this study, tert-butylbenzene which is widely used as an intermediate material in the chemical industry was selected. For the reliability of the flammable properties of tert-butylbenzene, this study was investigated the explosion limits of tert-butylbenzene in the reference data. The flash points, fire points and AITs by the ignition delay time for tert-butylbenzene were experimented. The lower flash points of tert-butylbenzene by using the Setaflash and Pensky-Martens closed-cup testers measured $39^{\circ}C$ and $44^{\circ}C$, respectively. The flash points of tert-butylbenzene by using the Tag and Cleveland open cup testers are measured $51^{\circ}C$ and $54^{\circ}C$. And the fire points of tert-butylbenzene by the Tag and Cleveland open cup testers were $54^{\circ}C$ and $58^{\circ}C$ respectively. The AIT of tert-butylbenzene measured by the ASTM 659E tester was measured as $450^{\circ}C$. The lower explosion limit of $39^{\circ}C$ which measured by the Setaflash flash point tester was calculated to be 0.68 vol%.

• Journal of Korea Port Economic Association
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• v.24 no.4
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• pp.71-96
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• 2008

The purpose of this study is to suggest the new strategies for West coast ports, especially Mokpo Port development. This paper also analyzes the recently evolving change of shipping environment such as upsizing of vessels, horizontal and vertical integration strategies in the liner shipping industries through the mergers and acquisitions or strategic alliances, establishment of dedicated terminal and surging bunker charge. With shipping environment is rapidly changing, we examine how to cope with the current situation and suggest the solutions how to tackle shippers' and shipping companies' request. As a result of an empirical study, we found out that Mokpo Port suffers from the shortage of container cargo, container imbalance, insufficient forwarders and inland trucking service providers and hinterland transportation network system. With these obstacles settled, the number of container cargo can be induced to Mokpo Port and the regular container services between Mokpo and Chinese ports and Japanese ports loops were found to be competitive.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.53 no.2
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• pp.177-186
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• 2017

This study is intended to provide navigator with specific information necessary to assist in the avoidance of collision and in operation of ships to evaluate the maneuverability of research vessel Jera. Authors carried out full-scale sea trials for turning test, zig-zag test, and spiral test at actual sea-going condition, which were performed on starboard and port sides with 10-20 rudder angle at service speed of 10 knots. The turning circle was much different at both of the turning of port and starboard which was longer at the starboard than at the port. In the zig-zag test results, the port and starboard was $10^{\circ}$ the first and second overshoot angles were $6.0^{\circ}$, $5.8^{\circ}$ and $6.3^{\circ}$, $7.1^{\circ}$ respectively and the first overshoot angles were $16.4^{\circ}$, $17.6^{\circ}$ when using $20^{\circ}$. Her maneuverability index T and N can be easily determined by using an analogue computer with the data obtained from the zig-zag tests where K is a constant representing the turning ability and T is a constant representing her quick response. In the zig-zag tests under $10^{\circ}$ or $20^{\circ}$ at rudder angle, the value K is 0.149. 0.123 sec- and T is 11.853 and 6.193 sec and angular velocity is $0.937^{\circ}/sec$ and $1.636^{\circ}/sec$. In the spiral test, the loop width was unstable at $+0.51^{\circ}$ and $-1.19^{\circ}$ around the midship of rudder, but the tangent line at $0^{\circ}$ was close to vertical. From the sea trial results, we found that she did comply with the present criterion in the standards of maneuverability of IMO.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.11
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• pp.617-623
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• 2020

Urban railroad vehicles carry many passengers and are the core of an urban railroad transportation system. Therefore, the dynamic performance of the vehicle must be ensured. Dynamic behaviors such as the vibration and ride comfort of railway vehicles are affected by the structure of the suspension system. We analyzed the dynamic behavior of a railway vehicle according to the suspension system of an urban railway vehicle, which is mainly operated in Korea. For two types of vehicles with different suspension structures, the vibration of the vehicles on railway tracks was measured, and dynamic behavior characteristics such as vibration, ride, and vibration reduction rate were analyzed. The result of the test shows that the vibration performance of the body is superior to that of B-bogie in the lateral direction and that of A-bogie in the vertical direction. Overall, the ride quality of the A-bogie car is superior to that of B-bogie. When analyzing the vibration attenuation rate of primary suspension system, the vibration attenuation performance of B-bogie with coil spring was superior to that of A-bogie with a conical rubber spring. The secondary suspension system has better vibration attenuation performance for A-bogie with air springs compared to coil springs.

• Journal of the Korean association of regional geographers
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• v.17 no.6
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• pp.698-709
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• 2011

Wedding shops, which had been located in Jung-gu, Jongno-gu, Seodaemun-gu, and Mapo-gu in 1990, have been shown a rapid change in light of location since the year of 1995. Thus, most of shops are concentrated on Gangnam-gu in 2010. Wedding dress shops in Gangnam-gu were distributed between Kanglim Church and Apgujeong station in the early 1990s, and then moved gradually to Dosan park and then to Cheongdam-dong after passing through Hakdong intersection. Luxury image in Cheongdam-dong was the main reason for integration of wedding businesses. This intergration of shops showed the peak at the Cheongdam intersection. A motive of having come to start business in Cheongdam-dong was selected the high awareness and image in district, and was taken the ease for business-based cooperation and connection. High rent and inconvenient transportation were reasons for dissatisfaction. The business-based cooperation and connection were mostly formed through a consulting company. Level and reputation of relevant shops were important elements. Even the connective and associative shops are located the most in Cheongdam-dong followed by Nonhyeon-dong, Shinsa Apgujeong-dong in order. The cluster relationship was most noticeable in wedding studio, wedding dress, wedding consulting, and hanbok(Korean traditional clothes) business. Frequency of vertical cluster was indicated to be more than horizontal cluster. User behavior of wedding businesses in Seoul has been collecting wedding information through internet and wedding consulting business.

• Journal of the Korean Institute of Landscape Architecture
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• v.40 no.4
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• pp.51-61
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• 2012

Kyong-Eui Railway used to be one of the major cross-country railways connecting Busan and Shineuiju. Being the central axis of logistics and transportation in Korea, it also signifies a symbolic meaning of the people's desire for the unification of divided Korean peninsula. A steam locomotive that had stopped in Jangdan Station was bombed out during the Korean War. The locomotive has been neglected and covered with rust in DMZ over a half century, and now is becoming a historic reminder of divided Korea. The initial design approach was based on the three main perspectives of the relocation plan of the steam locomotive in Jangdan Station which is designated as the registered cultural asset no. 78: historical significance, role of a monumental space, and influence on and from the local culture and tourism. Three design subjects were especially highlighted which would represent the identity of the cultural asset, the stream locomotive. First, a vertical watching deck was installed to provide various view points toward the locomotive while ensuring the security of visitors as well as the cultural asset. Second, the Dokgae bride area has good design potentials being on the railway. However, the site is too narrow. Thus, a new ramp and a stairway were placed responding to the existing topography so that the pedestrian environment could be secured last, to respect the local context where the locomotive was originally located, mulberry trees in the locomotive were transplanted as well. Flowering plants were planted around the display area for better ventilation to minimize the negative impact on the locomotive.

• Journal of Navigation and Port Research
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• v.28 no.1
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• pp.1-8
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• 2004

The final goal of this research is to establish the relative dangerousness D/B for factors on seakeeping performance. This D/B is, essential to develope the seakeeping performance evaluation system built-on-ship. The system is composed of the apparatus for measuring a vertical acceleration to be generated by the ship's motions, computer for calculating the synthetic seakeeping performance index and monitor for displaying the evaluating diagram of navigational safety of ship. In this paper, a methodology on the establishment of the relative dangerousness D/B for factors on seakeeping performance is presented by a numerical simulations, playing an important role on the algorithm of the program for calculating the synthetic seakeeping performance index. Finally, It is investigated whether the relative dangerousness D/B can be realized an accurate values according to the loading conditions, weather conditions, wave directions and present ship's speed of a model ship.

• Journal of the Korean GEO-environmental Society
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• v.17 no.8
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• pp.17-27
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• 2016

High-speed trains have been developed widely in European countries and Japan in order to transport large quantity of people and commodities in short time. Additionally, a high speed train is one of the most desirable and environmentally friendly transportation methods. When a high speed train enters a tunnel, aerodynamic resistance is generated suddenly. This resistance causes micro pressure wave and discomfort to passengers. Due to this aerodynamic pressure against the train, a large amount of traction is required for the operation of a train in a tunnel. Therefore, it is essential to incorporate a pressure relief system in a tunnel in order to reduce aerodynamic resistance caused by a high-speed train. A pressure relief duct and a vertical shaft are representative measures in a tunnel. This study represents the effect of pressure relief ducts in order to alleviate positive and negative normal pressures acting on a train. One-dimensional numerical simulations were carried out in order to estimate the effect of pressure relief systems.