• Proceedings of the Korean Geotechical Society Conference
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• 2000.11b
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• pp.213-220
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• 2000

Numerical modeling of cut slope has some limits in simulating the real slopes. In the case of 2D analysis of slope stability, it is assumed that slope is simply straight even when it is concave or convex in plan view. In this study, 3D analysis in curved shape slopes has been conducted for the comparison with 2D analysis in terms of failure mode and factor of safety. For this, 3D analysis by FLAC3D was compared with 2D analysis in plane strain condition and axi-symmetric model condition by FLAC. It was also observed how safety factors of slopes were affected by the variation of the tensile strength and cohesion, which are important variables to decide whether the slope fails or not. 2D analysis of concave slopes under plane strain condition showed much smaller safety factors by 16-40 % errors depending on the radius of curvature of slopes, compared to the more realistic values from 3D analysis. In case of convex slopes, the lower values by 7-10 % has been reported. 2D analysis of axi-symmetric model showed also smaller safety factors by 6-10 % and by 2-4 %, in case of concave and convex slopes, respectively. Such results are expected to contribute to the better understanding of failure process and could be applied for improved design of slopes.

• Journal of Ocean Engineering and Technology
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• v.26 no.5
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• pp.87-93
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• 2012

Many longitudinally-arranged pipes in ships are equipped with loops as a measure to reduce stresses caused by displacement loads conveyed from the hull girder bending and/or thermal loads of carried fluid of non-ambient temperature. But as the loops have some negative effects such as causing extra manufacturing cost and occupying extra space, the number and the dimensions of the loops need to be minimized. In the meanwhile, a design formula for pipe loops has been developed by modeling them as a spring element of which stresses and axial stiffness are calculated based on the beam theory. But as the beam theory turns out to be inappropriate to deal with the complex structural behavior in the curved corner portion of the loop, this paper aims at improving the previously developed design formula by adopting correction factors which can allow for the gap between the results of beam theory and a more accurate analysis. This paper adopts a finite element analysis with two-dimensional shell elements with some validation work for it. The paper ends with a sample application of the proposed formulas showing their accuracy and efficiency.

• Proceedings of the KWS Conference
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• 2009.11a
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• pp.96-96
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• 2009

The purpose of this study is to clarify the transitional behavior and main factor of excessive welding distortion caused by fabrication process of STS 304 vacuum vessel having double curvature for the efficient quality control of vacuum vessel. In order to do it, the predictive equations of the welding distortion in simple weldment of vacuum vessel were established by conventional finite element analysis. And the principal factor controlling the welding distortion was identified by evaluating the welding distortion of vacuum vessel in each fabrication process with FEA and simplified thermo elastic method. Based on the results, the principal factors of distortion of vacuum vessel were clarified as angular distortion and transverse shrinkage which are a source of excessive out-of plane distortion in the double curved vacuum vessel. It was expected that the FE analysis results of this study could contribute to establish the proper control method of welding distortion for double curved vacuum vessel.

• Korean Journal of Remote Sensing
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• v.5 no.1
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• pp.41-56
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• 1989

Improvement of the multichannel sea surface temperature(MCSST) software, which had been developed for the purpose of operating under mainframe computer system, was seeked in order to operate effectively in a mini computer system. CPU time and processing time, which is not a major factor under mainframe computer system, become a critical factor in real time image processing under mini computer system. Due to fixed kernel size(3$\times$4) of the old MCSST software, high spatial resolution characteristics of the original image received from satellites were apparently degraded when images are transformed into a cartesian coordinate system after geometrical distortions of the image due to earth curvature are removed. CPU and processing time were reduced to 0.13 and 0.15~0.22 comparing with the old MCSST's, respectively, by applying disk block I/O and M/T queue I/O method under VAX-11/750 computer. The high resolution quality (1.1km in AVHRR) of the processed image was guaranted using 2$\times$2 kernel size and applying moving window techniques without sacrificing CPU and processing time much.

• Structural Engineering and Mechanics
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• v.69 no.6
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• pp.667-676
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• 2019

Minimizing the stress concentration around hypotrochoid hole in finite metallic plates under in-plane loading is an important consideration in engineering design. In the analysis of finite metallic plate, the effective factors on stress distribution around holes include curvature radius of the corner of the hole, hole orientation, plate's aspect ratio, and hole size. This paper aims to investigate the impact of these factors on stress analysis of finite metallic plate with central hypotrochoid hole. To obtain the lowest value of stress around a hypotrochoid hole, a swarm intelligence optimization method named ant lion optimizer is used. In this study, with the hypothesis of plane stress circumstances, analytical solution of Muskhelishvili's complex variable method and conformal mapping is employed. The plate is taken into account to be finite, isotropic and linearly elastic. By applying suitable boundary conditions and least square boundary collocation technique, undefined coefficients of stress function are found. The results revealed that by choosing the above-mentioned factor correctly, the lowest value of stress would be obtained around the hole allowing to an increment in load-bearing capacity of the structure.

• Journal of the Korea Concrete Institute
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• v.24 no.1
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• pp.15-23
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• 2012

This paper is about proposal of a calculation method and development of an analytical program for predicting crack width and deflection in structural concrete members. The proposed method numerically calculate stresses in steel rebar using a parabola-rectangle stress-strain curve and a modified tension stiffening factor considering the effect of the cover thickness. Based on the study results, a calculation method to predict crack width and deflection in reinforced concrete flexural members is proposed utilizing effective tension area and idealized tension chord as well as effective moment-curvature relationship considering tension stiffening effect. The calculation method was applied to the test specimens available in literatures. The study results showed that the crack width and deflections predicted by the proposed method were closed to the experimentally measured data compared the current design code provisions.

• Journal of the Korean Society of Clothing and Textiles
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• v.26 no.6
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• pp.901-910
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• 2002

This study is to classify somatotypes of the upper class boys in elementary school. The study is conducted through anthoropometric measurements and photometric measurements. The subjects are 320 boys in the age group of 10 to 11 years old. The following conclusions are drawn from this study. 1. The height items are increased along with age increase. The increases in the factors, which specify vertical sizes such as height and length, are a little larger than those of breadth, depth, and girth, which specify ; horizontal sizes. 2. The factor analysis on anthropometric measurements and photometric measurements reveals five somatic composition factors and those factors comprised 79.60% of total variance. 3. The torso shapes of the upper class boys in elementary school are classified into three categories. The first type is taller and heavier than the average elementary school upper class boys and has the highest rising shoulders. The shape of the back is about average and the chest is developed above average. The curvature of the lower back is gentle and lower abdomen protrudes the most of the three types. The second type is tall and slightly heavier than average and shoulders are raised a little. The shoulder blades protrude about average and the curvature of lower back is the most developed of all. The cheat is developed about average and the abdomen is a little protruding. The third type is the most common with the smallest height of the three and skinny with dropped shoulders. The chest is somewhat flat and the shoulder blades protrude about average.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.11
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• pp.927-933
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• 2012

The characteristics of two-dimensional supersonic coanda flow was experimentally investigated. For various ratios of slot height to coanda wall's radius of curvature, surface roughnesses, and jet stagnation pressures, the characteristics of the supersonic coanda flow such as shock structures and hysteresis were observed by flow visualization. It was found that the characteristics of hysteresis of the coanda jet was related to the surface roughness of the coanda wall. The study was further extended for application of the tangentially injected coanda jet to control co-flowing highly compressible main jet direction. It was noticed that the stagnation pressure of the main jet as well as the ratio of the slot height to coanda wall's radius of curvature wall was an influencing factor in the performance of the fluidic thrust vectoring method.

• Journal of Institute of Control, Robotics and Systems
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• v.5 no.5
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• pp.568-576
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• 1999

Using a laser sheet beam projector combined with a CCD-Camera, an efficient technique to recognize complex surface of curvature and lane has been demonstrated for the purpose of mobile robot navigation. In general, obstacles of indoor environments in the field of SLIT-RAY plane are captured as segments of an elliptical arc and a line in the camera image. The robot has been capable of moving along around the obstacle in front of it, by recognizing the original shape of each segment with the differential coefficient by means of least squares method. In this technique, the imaged pixels of each segment, particularly elliptical arc, have been converted into a corresponding circular arc in the real-world coordinates so as to make more feasible the image processing for the position and radius measurement than conventional way based on direct elliptical are analyses. Advantages over direct elliptical cases include 1) higher measurement accuracy and shorter processing time because the circular arc process can reduce the shape-specifying parameters, 2) no complicated factor such as the tilt of elliptical arc axis in the image plane, which produces the capability to find column position and radiua regardless of the camera location . These are essentially required for a mobile robot application. This technique yields an accuracy less than 2cm for a 28.5cm radius column located in the range of 70-250cm distance from the robot. The accuracy obtained in this study is sufficient enough to navigate a cleaning robot which operates in indoor environments.

• Journal of the Earthquake Engineering Society of Korea
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• v.3 no.2
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• pp.55-66
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• 1999

Eight RC bridge plers have been made on a 1/3.4 scale model and have been tested in a quasi-static cyclic load so as to investigate their seismic performance. The ultimate objective of this experimental study is to investigate the hysteretic behavior of reinforced concrete plers, which have been widely used for urban transportation facilities in Korea. Improtant test parameters are hoop ratio, axial load, load pattern, and etc. And noninear behaviors of test columns have been evaluated through their yield and ultimate strength, energy dissipation, ductility and load-deflection characteristics under quasi-static cyclic loads. From the quasi-static tests on 8 bridge piers, it is concluded that energy dissipation, ultimate strength and curvature for a given displacement factor ${\mu}={\Delta}/{\Delta}_y$ are higher for the seismically designed columns than for the nonseismically designed columns.