• Economic and Environmental Geology
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• v.50 no.2
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• pp.129-143
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• 2017

The shallow sediments in the southwestern Ulleung Basin consist of mass flow deposits such as slide/slump and debris flow deposits (DFD), caused by slope failure. These sediments are proven to be important in studying geological disaster and stability of the seafloor. In this paper, we analysised the flow accumulation and slope failure susceptibility of the Ulleung Basin on the basis of multi-beam data, collected in this area. We also studied the distribution pattern and the seismic characteristics of the DFD in the uppermost layer of the Ulleung Basin on the basis of seismic data. The slope susceptibility was calculated as the frequency ratio of each factors including slope, aspect, curvature and stream power index (SPI), which causes the slope failure. These results indicate that the slope failure is frequently to occur in the southern and western continental slope of the Ulleung Basin. The sediment flow (mass flow) caused by the slope failure converges to the north and northwest of the Ulleung Basin. According to the seismic characteristics, the uppermost layer in study area can be divided into four sedimentary unit. These sedimentary units develop from the south and southwest to the north and northwest in association with slope susceptibility and flow accumulation.

• Geophysics and Geophysical Exploration
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• v.10 no.4
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• pp.229-240
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• 2007

In this study, seismic anisotropic tomography algorithm was developed for imaging the seismic velocity anisotropy of the subsurface. This algorithm includes several inversion schemes in order to make the inversion process stable and robust. First of all, the set of the inversion parameters is limited to one slowness, two ratios of slowness and one direction of the anisotropy symmetric axis. The ranges of the inversion parameters are localized by the pseudobeta transform to obtain the reasonable inversion results and the inversion constraints are controlled efficiently by ACB(Active Constraint Balancing) method. Especially, the inversion using the Fresnel volume is applied to the anisotropic tomography and it can make the anisotropic tomography more stable than ray tomography as it widens the propagation angle coverage. The algorithm of anisotropic tomography is verified through the numerical experiments. And, it is applied to the real field data measured at limestone region and the results are discussed with the drill log and geological survey data. The anisotropic tomography algorithm will be able to provide the useful tool to evaluate and understand the geological structure of the subsurface more reasonably with the anisotropic characteristics.

• Journal of Korean Society of Forest Science
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• v.112 no.3
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• pp.340-351
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• 2023

Landslides are major natural geological hazards that cause enormous property damage and human casualties annually. The vulnerability of mountainous areas to landslides is further exacerbated by the impacts of climate change. Soil depth is a crucial parameter in landslide and debris flow analysis, and plays an important role in the evaluation of watershed hydrological processes that affect slope stability. An accurate method of estimating soil depth is to directly investigate the soil strata in the field. However, this requires significant amounts of time and money; thus, numerous models for predicting soil depth have been proposed. However, they still have limitations in terms of practicality and accuracy. In this study, 71 seismic survey results were collected from domestic mountainous areas to estimate soil depth on hill slopes. Soil depth was estimated on the basis of a shear wave velocity of 700 m/s, and a database was established for slope angle, elevation, and soil depth. Consequently, the statistical characteristics of soil depth were analyzed, and the correlations between slope angle and soil depth, and between elevation and soil depth were investigated. Moreover, various soil depth prediction models based on slope angle were investigated, and corrected linear and exponential soil depth prediction models were proposed.

• Tunnel and Underground Space
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• v.10 no.2
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• pp.237-248
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• 2000

Based on the preliminary results from the therm analysis, which is currently carrying, three-dimensional computer simulations using a finite element code, ABAQUS Ver. 5.8, were designed to determine the mechanically stable cavern and deposition hole spacing. Linear elastic modeling for the cases with different cavern and deposition hole spacing were carried out under three different in situ stress conditions. From the simulations, the response of the rock to the stress redistribution after the excavation of the openings could be investigated. Also the optimum cavern and deposition hole spacing could be estimated based on the factor of safety. When the in situ stress determined from the actual stress measurements in Korea were used, the case with cavern spacing of 40m and deposition hole spacing of 3m was in very stable condition, because the factor of safety was calculated as 3.42., When the in situ stress conditions for Sweden and Canada were used, the previous case, they seem to be in stable condition, since the factors of safety are still higher than 1.0. From these results, it was concluded that the rock will not fail even after the stress redistribution.

• Journal of Korean Society of Forest Science
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• v.94 no.6
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• pp.377-386
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• 2005

This study was carried out to analyse the landslide characteristics by ground investigation, borehole image processing system, field seismic test, laboratory test and ground stability analysis at the landsliding area occurred in Maeri, Sangdong-myeon, Gimhaesi, Gyeongsangnam-do. Region I needs to install data logger system to monitor a land displacement during the heavy rainfall events because the region can be liable to occur the land slide by land creeping. It is needed to restore rapidly, if the land displacement occurs in Region I. Region II needs to monitor and repair because of the possibility of slope failure by long-term soil loss. Region III needs constructions to remove ground runoff and ground water to be infiltrated from talus. Region IV where is a stable region, needs to be protected from land cutting or other man-made damage.

• International Journal of Highway Engineering
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• v.9 no.4
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• pp.11-20
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• 2007

This thesis develops a fatigue model for the asphalt black base using the APT(Accelerated Pavement Testing) and analyzes the correlation of the APT analysis result with results of previous laboratory tests. For the APT testing, aggregate of the maximum grain size of 25mm(BB-3) was used as the material for the asphalt black base. The result of the APT revealed that the variable of the fatigue model, i.e. the maximum tensile stress on the bottom part of the pavement, increased as the number of loading increased while the modulus of elasticity for the pavement layer decreased gradually. The tensile strain was obtained from a strain gauge, and it was used to derive the values of $k_1=1.29{\times}10^{-6}$ and $k_2=3.02$ from the basic equation of the asphalt fatigue model, $N_f=k_1(\frac{1}{\epsilon})^{k_2}$. The fatigue life predicted from the asphalt fatigue model was greater than that obtained from laboratory experiments, given the same tensile strain. Additionally, a theory to estimate the remaining life of the pavement was developed using FWD, a non-destructive experiment.

• Geotechnical Engineering
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• v.12 no.3
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• pp.109-126
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• 1996

In this study, the chemical fluid considered is sodium chloride sloutions. The concentrations for the sodium chloride solutions are varied from 0 to 20%. A series of lab oratory triaxial tests are performed on the cylindrical specimens of sand bentonite mixture with different (5, 10, 15%) sodium chloride content solutions. Deformation(elastic modulus, E) and strength (cohesion, c', and angle of friction, f') parameters are obtained from the triaxial tests and they are expressed as functions of conf'ming pressure and sodium chloride solution concentrations. The stress-strain-strength behavior based on the above strength parameters is introduced to the finite element method with a residual flow procedure (RFP). By integrating a slope stability (limit equilibrium) procedure in the finite element method, factors of safety with time are computed.

• Journal of Korean Society of Steel Construction
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• v.13 no.2
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• pp.153-162
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• 2001

A direct design method of three-dimensional frames using practical advanced analysis is presented. In this method. separate member capacity checks encompassed by the code specifications are not required. because the stability of separate members and the structure as a whole can be rigorously treated in determining the maximum strength of the structures. Advanced analysis accounts for geometric and material nonlinearities. The geometric nonlinearlity is considered by the use of stability function. The material nonlinearity is accounted for using CRC tangent modulus and parabolic function. The load-displacements predicted by the proposed analysis compare well with those given by other approaches. A design example has been presented for a 22-story frame. The analysis results show that the proposed method is suitable for adoption in practice.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.354.1-354.1
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• 2014

Hafnium nitride (HfN) 박막은 고온에서의 안정성과 낮은 비저항 그리고 산소확산에 대한 억제력을 가지고 있기 때문에 확산방지막으로 많은 연구가 진행 되고 있다. 현재까지 진행된 대부분의 연구는 HfN 박막의 전기적인 특성과 구조적인 특성에 대한 것이었고 다양한 연구 결과가 보고되었다. 하지만 기존의 연구들은 박막의 nano-electrotribology 특성에 대한 연구가 부족하여 박막 적층 공정시 요구되는 물성에 대한 연구가 절실하다. 따라서 본 연구에서는 HfN 박막의 증착조건 및 열처리조건에 따른 nano-electrotribology 특성 변화를 확인하고자 하였다. HfN박막은 rf magnetron sputter를 이용하여 Si 기판위에 Hf target으로 질소 유량을 변화시키며 증착하였고 가열로에서 $600^{\circ}C$와 $800^{\circ}C$로 20분간 열처리를 실시하였다. 열처리한 박막과 as-deposited 상태의 박막을 nano-indenter를 통하여 나노기계 전기적인 특성을 분석하였다. nano-indenter는 박막에 인가된 stress와 탄성계수(elastic modulus), 표면경도(surface hardness)와 같은 특성을 직접적인 tip 접촉을 통하여 in-situ로 분석할 수 있는 장비이다. 실험결과 HfN박막을 $600^{\circ}C$로 열처리 한 경우 표면경도가 16.20에서 18.59 GPa로 증가하였다. 표면경도의 증가는 열처리 시 박막내에 compressive stress가 생성되었기 때문이라고 생각된다. 그러나 $800^{\circ}C$로 열처리 한 경우 표면경도가 16.93 GPa로 감소하였는데 이는 표면균열 발생으로 인한 stress relaxation 때문인 것으로 생각된다. 증착 시 주입되는 질소의 유량과 열처리 온도는 HfN박막의 기계적 안정성에 영향을 미치는 중요한 요소임을 본 실험을 통해 확인하였다.

• Proceedings of the Materials Research Society of Korea Conference
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• 2010.05a
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• pp.7-7
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• 2010

형상기억합금은 합금이 갖는 형상기억효과 및 초탄성효과 때문에 학문적으로 공업적으로 큰 흥미를 끌어왔다. 형상 기억효과는 Au-Cd 합금과 Cu-Zn 합금에서 최초로 발견되었지만 당시에는 크게 주목을 받지 못하였다. 그 후 1962년 Ti-Ni 합금에서 형상기억효과가 발견된 이래로 크게 주목을 받게 되었고, 곧바로 상용화를 위한 노력이 이어져 리벳, 열엔진, 커플링, 회로차단기 등에 적용이 시도되었다. 현재까지 약 300여종에 이르는 형상기억합금이 개발되어 있지만 형상기억효과의 안정성, 우수성, 내식성, 가공성, 내피로성, 내마모성이 우수한 Ti-Ni 합금이 가장 실용화에 적합한 합금으로 인식되고 있다. Ti-Ni합금은 1960년대에 개발되었지만 의료분야에 적용되기 시작한 것은 1980년대이고, 그 후 미국의 FDA가 Ti-Ni 합금으로 제조된 몇몇 3급(Class III) 임플란트를 인증하면서 시장규모도 폭발적으로 증가하고 있다. 일본의 경우 1980년대 초부터 Ti-Ni 합금을 치과용 임플란트로써 사용하여 왔, 독일, 중국, 러시아도 1980년대부터 임상에 적용해 왔다. 우리나라는 2004년 식약청(식품의약안정청)으로부터 제조 및 판매가 허가되어 현재 실제 임상에 적용되고 있다. 이와 같이 Ti-Ni 합금이 의료용 금속재료로서 널리 쓰이게 된 가장 근본적인 이유는 말할 나위 없이 합금이 갖는 형상기억효과 및 초탄성효과 때문이다. 본 강연에서는 Ti-Ni 합금을 의료용 금속재료의 입장에서 재조명해보고, 본 합금이 의료용 금속재료로서 어떠한 장점이 있으며, 그러한 장점을 의료분야에서 어떻게 응용하고 있는가에 대해 소개하고자 한다. 또한 의료용 Ti-Ni 합금에서 향후 개선되어야 할 요소에 대해서도 논의하고자 한다.