• Journal of the Korean Geotechnical Society
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• v.22 no.11
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• pp.55-64
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• 2006

It is very Important to predict the damage zone of a rock mass induced by blasting for the excavation of an underground cavity such as a tunnel, as the damage zones incur mechanical and hydraulic instability of the rock mass potentially. Complicated blasting processes that can hinder the proper characterization of the damage zone can be effectively represented by two loading mechanisms. The first mechanism is the dynamic impulsive load-generating stress waves that radiate outwards immediately after detonation. This load creates a crushed annulus along with cracks around the blasthole. The second is the gas pressure that remains for an extended time after detonation. As the gas pressure reopens some arrested cracks and extends these, it contributes to the final structure of the damage zone induced by the blasting. This paper presents a simple method to evaluate the damage zone induced by gas pressure during rock blasting. The damage zone is characterized by analyzing crack propagations from the blasthole. To do this, a model of a blasthole with a number of radial cracks that are equal in length in a homogeneous infinite elastic plane is considered. In this model, crack propagation is simulated through the use of only two conditions: a crack propagation criterion and the mass conservation of the gas. The results show that the stress intensity factor of a crack decreases as the crack propagates from the blasthole, which determines the crack length. In addition, it was found that the blasthole pressure continues to decrease during crack propagation.

• Korean System Dynamics Review
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• v.8 no.2
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• pp.253-273
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• 2007

To measure the effect of school zone on housing cost, Linear Regression Model is widely used, and school zone is known as a key determinant of housing cost in Korea. However, when the Hierarchical Linear Model (HLM) is applied with the same data, school effect on housing cost becomes statistically non-significant. It is because HLM effectively separates the effect of individual housing's attributes from the group effect. In sum, the housing cost of Kangnam, where good public schools are located, is apparently is higher than that of Kangbuk. However, the school effect on housing cost (Level 2) becomes non-significant when individual housing's attributes (Level 1) are controlled with HLM.

• Economic and Environmental Geology
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• v.28 no.2
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• pp.155-164
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• 1995

The kriging model, one of the geostatistical models, has been used to evaluate the deep-sea manganese nodule deposits until now. The distribution of the manganese nodule deposits estimated by the model shows the smooth surface as well as much difference from the actual distribution. Subsequently, it estimates the deposit distribution roughly in terms of the limited data of surveyed zone. Therefore, this paper presents the interpretation methodology of the deep-sea manganese nodule deposit distribution by using the fractal model to overcome the problems caused by the geostatistical model. Also, the manganese nodule distributions are interpreted by using the manganese nodule data sampled in the GH82-4 zone, west longitude $165^{\circ}40^{\prime}-169^{\circ}00^{\prime}$, and south latitude $0^{\circ}00^{\prime}-2^{\circ}40^{\prime}$ neighboring Nova-Canton Trough in the Pacific Ocean which was surveyed by the Geological Survey of Japan in 1982.

• Structural Engineering and Mechanics
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• v.7 no.1
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• pp.69-80
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• 1999

The purpose of this study is to propose an analytical model for the simulation of the hysteretic behavior of RC (reinforced concrete) beam-column subassemblages under various loading histories. The discrete line element with inelastic rotational springs is adopted to model the different locations of the plastic hinging zone. The hysteresis model can be adopted for a dynamic two-dimensional inelastic analysis of RC frame structures. From the analysis of test results it is found that the stiffness deterioration caused by inelastic loading can be simulated with a function of basic pinching coefficients, ductility ratio and yield strength ratio of members. A new strength degradation coefficient is proposed to simulate the inelastic behavior of members as a function of the transverse steel spacing and section aspect ratio. The energy dissipation capacities calculated using the proposed model show a good agreement with test results within errors of 27%.

• Transactions of Materials Processing
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• v.10 no.2
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• pp.130-136
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• 2001

The mathematical set-up model was developed to reduce the mechanical property deviation in annealed and slightly rolled steel strip. The mechanical peculiarities of skin pass rolling process, such as high friction value and non-circular contact arc, low reduction and non-negligible entry and exit elastic zones as well as central restricted deformation zone are all taken into account. The deformation of work rolls is calculated with the influence function method and arbitrary contact arc shape is permitted. The strip deformation is modeled by slab method and the entry and exit elastic deformation zones are included. The strip restricted deformation zone near the neutral point is also considered. It was revealed that the new model has better accuracy than present regression model by statistical analysis with actual mill rolling data.

• Journal of Environmental Science International
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• v.11 no.12
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• pp.1321-1326
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• 2002

A numerical model is investigated to predict a behavior of the gaseous volatile organic compounds and a subsurface contamination caused by them in the unsaturated zone. Two dimensional advective-dispersion equation caused by a density difference and two dimensional diffusion equation are computed by a finite difference method in the numerical model. A laboratory experiment is also carried out to compare the results of the numerical model. The dimensions of the experimental plume are 1.2m in length, 0.5m in height, and 0.05m in thickness. In comparing the result of 2 methods used in the numerical model with the one of the experiment respectively, the one of the advective-dispersion equation shows better than the one the diffusion equation.

• Journal of Mechanical Science and Technology
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• v.15 no.9
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• pp.1292-1301
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• 2001

The mean-line method using empirical models is the most practical method of predicting off-design performance. To gain insight into the empirical models, the influence of empirical models on the performance prediction results is investigated. We found that, in the two-zone model, the secondary flow mass fraction has a considerable effect at high mass flow-rates on the performance prediction curves. In the TEIS model, the first element changes the slope of the performance curves as well as the stable operating range. The second element makes the performance curves move up and down as it increases or decreases. It is also discovered that the slip factor affects pressure ratio, but it has little effect on efficiency. Finally, this study reveals that the skin friction coefficient has significant effect on both the pressure ratio curve and the efficiency curve. These results show the limitations of the present empirical models, and more resonable empirical models are reeded.

• Journal of The Korean Society of Agricultural Engineers
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• v.48 no.4
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• pp.33-40
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• 2006

In present study, the principal stress condition needed to conduct cubical large-scale triaxial test which can reflect three dimensional stress condition (or plain strain condition) in a dam was investigated by performing model test and numerical analysis and the principal stress ratio varying with the height of CFRD was examined. Also, the principal stress ratio in CFRD body was investigated from the monitoring results of horizontal and vertical earth pressure gages, installed in the center zone and lower part of transition zone of the dam body, respectively, in order to consider the principal stress condition in the large-scale triaxial test to model the behavior of CFRD. The result of the study indicated that the principal stress ratio decreased gradually from the lower to the upper part in the dam body for its center axis and was about 0.5 and 0.2 in the lower and upper part, respectively.

• Coupled systems mechanics
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• v.7 no.6
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• pp.669-690
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• 2018

This paper deals with numerical modeling of dynamic failure phenomena in rate-sensitive brittle and/or ductile materials. To this end, a two-dimensional continuum viscodamage-embedded discontinuity model, which is based on our previous work (see Do et al. 2017), is developed. More specifically, the pre-peak nonlinear and rate-sensitive hardening response of the material behavior, representing the fracture-process zone creation, is described by a rate-dependent continuum damage model. Meanwhile, an embedded displacement discontinuity model is used to formulate the post-peak response, involving the macro-crack creation accompanied by exponential softening. The numerical implementation in the context of the finite element method exploiting the second-order mid-point scheme is discussed in detail. In order to show the performance of the model several numerical examples are included.

• Journal of Korean Association for Spatial Structures
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• v.20 no.2
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• pp.87-94
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• 2020

The present study is aimed to calculate the optimal damping according to the seismic load on the structure with a non-seismic design to perform structure analysis considering the deformation of structural joint connection and panel zone; to develop design program equipped with structural stability of the steel frame structures reinforced with the panel zone and viscous dampers, using the results of the analysis, in order to systematically integrate the seismic reinforcement of the non-seismic structures and the analysis and design of steel frame structures. The study results are as follows: When considering the deformation of the panel zone, the deformation has been reduced up to thickness of the panel double plate below twice the flange thickness, which indicates the effect of the double plate thickness on the panel zone, but the deformation showed uniform convergence when the ration is more than twice. The SMRPF system that was applied to this study determines the damping force and displacement by considering the panel zone to the joint connection and calculating the shear each floor for the seismic load at the same time. The result indicates that the competence of the damper is predictable that can secure seismic performance for the structures with non-seismic design without changing the cross-section of the members.