• Explosives and Blasting
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• v.25 no.1
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• pp.31-43
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• 2007

In most tunnel constructions in South Korea, blasting has been widely used as an excavation method. In tunnel blasting, the center-cut to induce first free surface is very important for enhancing excavation efficiency and reducing vibration caused by exploding. This paper introduces new center-cut method named SAV-cut (Stage Advance V-cut) developed on the concept of V-cut. Significant features of SAV-cut are the center hole and stepwise ignition. Many field tests and numerical analysis were carried out to analyze the mechanical behavior and blasting vibration. From the results, the newly developed SAV-cut was proved as an effective center-cut method for both increasing blasting efficiency and decreasing blasting vibration.

• Journal of the Korean Society of Marine Environment & Safety
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• v.18 no.3
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• pp.199-205
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• 2012

In this study, wave transformation by damping due to the permeable bed of finite depth is investigated. The relationship between wave damping rate and relative water depth are presented. The damping rate is used in the eigenfunction expansion method to calculate the wave dissipation over the permeable bed. For a permeable shoal, the eigenfunction expansion model result is compared with that of the integral equation method to show good agreement. The model is also used to examine the wave reflection over the permeable planar slope of various frequency. It has been found that in general relatively short waves are more influenced by the permeability of the permeable seabed than relatively long waves unless the water depth is so large that the influence of permeable bed on surface water waves disappears.

• The Journal of the Korea Contents Association
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• v.18 no.7
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• pp.577-589
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• 2018

The future of ROK-US alliance has not been discussed in detail by both governments since early 2000s. However, it is becoming more apparent that ROK-US alliance is facing various daunting challenges. The new administrations both in ROK and US might have different perspectives about the future of alliance. In the process of resolving outstanding North Korean nuclear issue, the alliance can face challenges to change its fundamental features such as halting joint military exercise. ROK-US governments also agreed to transfer wartime operational control as soon as possible. All those factors indicates the growing necessity to articulate the future of ROK-US alliance. ROK and US needs to facilitate to dialogue for future alliance with the possible scenarios of changing security environment such as maintaining status quo, reconciliation of North and South Korea, and entering the reunification stage. In each phase, ROK-US has to develop the goal for the alliance, military institution to implement the alliance, role of USFK, and etc. It is imperative to develop the road map for future ROK-US alliance at this stage to avoid unnecessary folly.

• The Journal of the Petrological Society of Korea
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• v.23 no.2
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• pp.119-138
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• 2014

There are various ways to monitor active volcanoes, such as the method of observing the activity of a volcano with the naked eye, the method of referring to the past eruptive history based on the historic records and the method of monitoring volcanoes by using observation equipment. The most basic method from the observation equipment-using methods to monitor volcanoes is seismic monitoring. In addition to this, the ways to monitor volcanoes are as follows: resonance observation which may be effective to remove artificial noises from the seismic activities that are recorded in the seismograph, ground deformation by using precision leveling, electronic distance measurement, tiltmeter, GPS, and InSAR observation method, volcanic gas monitoring, hydrologic and meteorological monitoring, and other geophysical monitoring methods. These monitoring methods can make volcanic activities effectively monitored, determine the behavior of magmas in magma chambers and help predict the future volcanic eruptions more accurately and early warning, thus, minimize and mitigate the damage of volcanic hazards.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.36 no.5
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• pp.915-926
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• 2016

The purpose of this study is to classify debris flow hazard zones in urbanized areas using multivariate statistical analyses and to suggest customized management strategies to each areal type. Using field survey data set in Seoul, 49 sample debris hazard zones are selected. Clustering and discriminant analyses show that debris flow hazard zones are classified into two types. Surrounding land use and land slope are major factors influencing to the categorization. The results suggest that, by considering the characteristics of each areal type, more customized management strategies for debris flow hazard are necessary. Particularly, in addition to traditional structural measures, non-structural measures including land use and development control for downstream built-up areas should be emphasized in urbanized areas to mitigate human and property damages from debris flow hazard more fundamentally.

• Journal of Korean Society of Steel Construction
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• v.21 no.4
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• pp.393-401
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• 2009

The flexural-stiffness formula of the wale for the innovative prestressed support (IPS) system was precisely derived, and the equivalent beam stiffness was introduced for application in the actual design of the IPS wale. The cable tension forces of the IPS wale were calculated in both cases, and the axial-deformation effects were included and ignored, respectively. The central displacements of the 1-post, 2-post, 3-post, and 4-post IPS wales were calculated based on the principle of virtual work. The effects of the IPS wale length and cable inclination angle were also investigated using the derived central displacements. The simplified equivalent flexural stiffness of the IPS wale is presented herein for design purposes, and the validity of the proposed design formula was verified through its comparison with the FE and analysis solutions.

• Journal of the Korean GEO-environmental Society
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• v.3 no.1
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• pp.27-36
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• 2002

This study is about the applicability of copper slag as the ground improvement material. By the geo-technical characteristics of the copper slag and by the effect of consolidation and under drainage condition, it is proved that the copper slag can be used for ground improvement material as substitution for sand. As a result of laboratory tests, it was shown that the permeability of the copper slag was similar to that of sands under the vertical drainage condition. In addition, the copper slag showed higher critical hydraulic gradient than that of sand under up-ward vertical flow state. The copper slag has potential safety against piping and it has internal stability of particles. The conclusion is that the copper slag is suitable for drainage and filter material.

• Journal of the Korean GEO-environmental Society
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• v.19 no.10
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• pp.5-11
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• 2018

The PBD (Plastic Board Drain) method is one of effective ground improvement methods on the soft dredging reclamation ground. This method has outstanding economic efficiency and constructability, and it is widely used for the soft ground improvement. However, the PBD method reduces permeability and drainage capacity of the ground due to the long construction period. Therefore, the nano coated Plastic drain board (PDB) was developed to solve problems. It is the non-metallic electrode and improves the weakness of the PBD method by using electric force of the electro-osmosis method. Various researches have been conducted to apply the nano coated PDB, but these researches were limited to model tests in laboratory. In this study, model and field tests were conducted to assess field applicability of the nano coated PDB. The result showed that the nano coated PDB had the better effect on the ground improvement compared to the normal PDB.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.8 no.4
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• pp.11-21
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• 1988

In twentieth century, a rigid pavement composed of a series of thin Portland Cement Concrete has been accepted due to the desirable structural strength of concrete, durability and economy. However, despite of precise design and construction of concrete highway pavements, some of concrete pavements (example : Interstate-l0 and 75 in U.S.A, 88 Olympic express highway and Jung-bu express highway in Korea) has already shown severe signs of longitudinal and transverse cracking, faulting, and pumping before the end of their intended service life. This highlights the need for better understanding of concrete pavement behavior using structural analysis program. For these reasons, this research was performed to study an analytical behavior of concrete pavements, especially for the effects of skewed joints on concrete pavements. Subsequently, this research should give better understanding of concrete pavement behavior to the highway engineers and provide effective remedies to the concrete highway pavements.

• Composites Research
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• v.17 no.4
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• pp.68-73
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• 2004

An analytical study was conducted to characterize the fatigue crack growth behavior of pre-cracked aluminum plates repaired with asymmetric bonded composite patch. For single-sided repairs, due to the asymmetry and the presence of out-of$.$plane bending, crack front shape would become skewed curvilinear started from a uniform through-crack profile, as observed from Previous studies. Therefore, for the accurate investigation of fatigue behavior, it is necessary to predict the actual crack front evolution and take it into consideration in the analysis. In this study, the fatigue analysis of single-sided repairs considering crack front shape development was conducted by implementing three-dimensional successive finite element method coupled with linear elastic fracture mechanics (LEFM) concept, which enables the growing crack front to be directly traced and modeled in a step by step way. Through conducting present analysis technique, crack path of the patched plate as well as the fatigue life was evaluated with sufficient accuracy. The analytical predictions of both the crack front shape evolution and the fatigue life were in good agreement with the experimental observations.