• Tunnel and Underground Space
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• v.29 no.5
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• pp.332-345
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• 2019

Maximum dip vector of individual joint plane, which can be uniquely defined on the hemispherical projection plane, has been established by considering its dip and dip direction. A new stereographic projection method for the rock slope analysis which employs the maximum dip vector can intuitively predict the failure modes of rock slope. Since the maximum dip vector is uniquely projected on the maximum dip point of the great circle, the sliding direction of discontinuity plane can be recognized directly. By utilizing the maximum dip vector of discontinuity both the plane sliding and toppling directions of corresponding blocks can be discerned intuitively. Especially, by allocating the area of high dip maximum dip vector which can form the flanks of sliding block the potentiality for the formation of virtual sliding block has been estimated. Also, the potentiality of forming the triangular-sectioned sliding block has been determined by considering the dip angle of joint plane the dip direction of which is nearly opposite to that of the slope face. Safety factors of the different-shaped blocks of triangular section has been estimated and compared to the safety factor of the most hazardous block of rectangular section. For the wedge analysis the direction of crossline of two intersecting joint planes, which has same attribute of the maximum dip vector, is used so that wedge failures zone can be superimposed on the stereographic projection surface in which plane and toppling failure areas are already lineated. In addition the maximum dip vector zone of wedge top face has been delineated to extract the wedge top face-forming joint planes the orientation of which provides the vital information for the analysis of mechanical behavior of wedge block.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.6
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• pp.19-26
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• 2021

The lattice structure is attracting attention from industry because of its excellent strength and stiffness, ultra-lightweight, and energy absorption capability. Despite these advantages, widespread commercialization is limited by the difficult manufacturing processes for complex shapes. Additive manufacturing is attracting attention as an optimal technology for manufacturing lattice structures as a technology capable of fabricating complex geometric shapes. In this study, a unit cell was formed using a three-dimensional coordinate method. The relative density relational equation according to the boundary box size and strut radius of the unit cell was derived. Simple cubic (SC), body-centered cubic (BCC), and face-centered cubic (FCC) with a controlled relative density were designed using modeling software. The accuracy of the equations for calculating the relative density proposed in this study secured 98.3%, 98.6%, and 96.2% reliability in SC, BCC, and FCC, respectively. A simulation of the lattice structure revealed an increase in compressive yield load with increasing relative density under the same cell arrangement condition. The compressive yield load decreased in the order of SC, BCC, and FCC under the same arrangement conditions. Finally, structural optimization for the compressive load of a 20 mm × 20 mm × 20 mm structure was possible by configuring the SC unit cells in a 3 × 3 × 3 array.

• Journal of the Korean GEO-environmental Society
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• v.12 no.3
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• pp.5-12
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• 2011

In this paper, after studying structural performance for the representative corrugated steel plate used in Korea, we proposed the optimum shape for section of corrugated steel plate considering a width of steel plates that can be produced currently in the factory. Using AISI(1986) in examination for the performance of the corrugated steel plate, we determined the mechanical limit of the optimum sections considering shear force and bending moment of corrugated steel plate and also determined the geometric limit of them considering formability, shapes and ratio between width of steel plate before forming and that after forming. As a result of examination for performance of steel plate applying algorithm for searching optimal sections algorithm developed in this study to the existing representative corrugated steel plate, allowable force and moment of inertia indicated the maximum values at bending radius 76mm and internal bending angle $50^{\circ}$. And as an application result of the optimum design system that used SS490 with 1,550mm of width and 4,700mm of length considering current production situation in Korea, we developed the new section with more than 2 times of structural performance comparing with existing corrugated steel plate.

• Journal of the Korean Geotechnical Society
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• v.38 no.2
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• pp.29-38
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• 2022

The friction anisotropy of shear resistance can be selectively used in geo-structures. For example, larger axially loaded deep foundation, soil nails, and tiebacks increase load carrying capacity due to induced large shear resistance while pile penetration and soil sampling produce minimal shear resistance. Previous studies confirmed direction-dependent shear resistance induced by interface between soil and surface asperity of plate inspired by geometrical shape of snake scale. The aim of this paper is to quantitatively evaluate interface friction angle with different surface asperities. Using the modified direct shear test, a total of 51 cases, which sand are prepared at the relative density of 40%, are conduced including 9 plates, two shear direction (shearing direction against the height of surface asperity is increased or decreased during shearing test), and three initial vertical stress (100 kPa, 200 kPa, 300 kPa). Experimental results show that shear stress is increased with higher height of surface asperity, shorter length of surface asperity, and the shearing direction that the height of surface asperity increases. Also, interface friction angle is decreased with larger surface asperity ratio, and shearing direction with increasing height of surface asperity produces larger interface friction angle regardless of the surface asperity ratio.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.1A
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• pp.105-113
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• 2008

Solar radiation induces non-uniform temperature distribution in the bridge structure depending on the shape of the structure and shadows cast on it. Especially in the case of curved steel box girder bridges, non-uniform temperature distribution caused by solar radiation may lead to unusual load effects enough to damage the support or even topple the whole curved bridge structure if not designed properly. At present, it is very difficult to design bridges in relation to solar radiation because it is not known exactly how varying temperature distribution affects bridges; at least not specific enough for adoption in design. Standard regulations related to this matter are likewise not complete. In this study, the thermal behavior of curved steel box girder bridges is analyzed while taking the solar radiation effect into consideration. For the analysis, a method of predicting the 3-dimensional temperature distribution of curved bridges was developed. It uses a theoretical solar radiation energy equation together with a commercial FEM program. The behavior of the curved steel box girder bridges was examined using the developed method, while taking into consideration the diverse range of bridge azimuth angles and radii. This study also provides reference data for the thermal design of curved steel box girder bridges under solar radiation, which can be used to develop design guidelines.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.5A
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• pp.887-899
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• 2006

The aim of this study is to investigate a correlation between fundamental data on aerodynamic characteristics of bridge girder cross-sections, such as aerodynamic force coefficients and flutter derivatives, and their aerodynamic behaviour. The section model tests were carried out in three stages. In the first stage, seven deck configurations were studied, namely; Six 2-edge girders and one box girder. In this stage, changes in aerodynamic force coefficients due to geometrical shape of girders, incidence angle of flow, wind directions and turbulence intensities were studied by static section model tests. In the second stage, the dynamic section model tests were carried out to investigate the relativity of static coefficients to dynamic responses. And finally, the two-dimensional (lift-torsion) aerodynamic derivatives of three bridge deck configurations were investigated by dynamic section model tests. The aerodynamic derivatives can be best described as a representation of the aerodynamic damping and the aerodynamic stiffness provided by the wind for a given deck geometry. The method employed here to extract these unsteady aerodynamic properties is known as the initial displacement technique. It involves the measurement of the decay in amplitude with time of an initial displacement of the deck in heave and torsion, for various wind speeds, in smooth flow. It is suggested that the proposed aerodynamic force coefficients and flutter derivatives of bridge girder sections will be potentially useful for the aeroelastic analysis and buffeting analysis.

• Journal of Korea Water Resources Association
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• v.33 no.3
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• pp.331-340
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• 2000

This study aims to develop a methodology of real time forecasting of mundation risk based on DAMBRK model and Kalman filter. The model is based on implicit, nonlinear finite difference approximatIons of the one-dimensional dynamic wave equations. The stochastic estimator uses on extended Kalman filter to provide optimal updating estimates. These are accomplished by combining the predictions of the determurustic model with real time observauons modified by the Kalman filter gain ractor. Inundation risks are also estimated by applying Monte Carlo simulation to consider the variability in cross section geometry and Manning's roughness coefficient. The model calibrated by applying to the floods ot South Han River on September, 1990 and August, 1995. The Kalman tilter model indicates that significant improvement compared to deteriministic analysis in flood routing predictions in the river. Overtopping risk of levee is also presented by comparing levee height with simulated flood level. level.

• Journal of the Korea Convergence Society
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• v.9 no.3
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• pp.257-263
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• 2018

Hyperthermia supplies RF high-frequency energy above 1MHz to the tumor tissue through the electrodes. And the temperature of the tumor tissue is increased to $42^{\circ}C$ or more to cause thermal necrosis. A mathematical model can be derived a human body model for absorption and transmission of electromagnetic energy in the human model and It is possible to evaluate the distribution of temperature fields in biological tissues. In this paper, we build the human model based on the adult standard model of the geometric shape of the 3D model and use the FVM code. It is assumed that Joule heat is supplied to the anatomical model to simulate the magnetic field induced by the external electrode and the temperature distribution was analyzed for 0-1,200 seconds. As a result of the simulation, it was confirmed that the transferred energy progressively penetrates from the edge of the electrode to the pulmonary tumors and from the skin surface to the subcutaneous layer.

• Food Engineering Progress
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• v.21 no.1
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• pp.29-35
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• 2017

Quality changes of dried sea cucumber (Stichopusjaponicus) after applying a cyclic rehydration and retorting process were investigated during 4 weeks of storage. The length, volume, and weight of dried sea cucumber increased significantly as the number of rehydration cycles increased. Sea cucumber (SC) was bottled in the glass jar and a retort thermal process ($121.1^{\circ}C$, 0.15 MPa) was applied. The total thermal processing time (TTT) was 24 min based on the temperature at the cold point. The size and texture of retorted SC were significantly changed until the first week of storage. However, regardless of the number of rehydration cycles, the size and texture of samples at different rehydration cycles showed no significant difference during the whole storage. The length, volume, weight, rehydration ratio ($R_R$), hardness, and chewiness at the maximum degree of swelling during rehydration of dried SC were estimated as 100.86 mm, 38.62 mL, 41.05 g, 6.39 of $R_R$, $249.19g_f$, and 4.05 mJ, respectively.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.10
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• pp.150-161
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• 2013

This paper presents a new system which produces high resolution 3D contents by capturing multiview images of an object using multiple cameras, and estimating geometric and texture information of the object from the captured images. Even though a variety of multiview image-based 3D reconstruction systems have been proposed, it was difficult to generate high resolution 3D contents because multiview image-based 3D reconstruction requires a large amount of memory and computation. In order to reduce computational complexity and memory size for 3D reconstruction, the proposed system predetermines the regions in input images where an object can exist to extract object boundaries fast. And for fast computation of a visual hull, the system represents silhouettes and 3D-2D projection/back-projection relations by chain codes and 1D homographies, respectively. The geometric data of the reconstructed object is compactly represented by a 3D segment-based data format which is called DoCube, and the 3D object is finally reconstructed after 3D mesh generation and texture mapping are performed. Experimental results show that the proposed system produces 3D object contents of $800{\times}800{\times}800$ resolution with a rate of 2.2 seconds per frame.