• Journal of Korean Society of Steel Construction
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• v.15 no.3
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• pp.231-239
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• 2003

Many box girder bridges have been constructed during the past several decades due to their large bending and torsional rigidities as well as aesthetic considerations. However, box girders have shortcoming in that the cross section distorts under an eccentric loading and warps out of the section plane. Therefore, in order to reduce distortional stresses such as distortional warping and transverse bending normal stresses, diaphragms were generally installed in the box girders. Shapes of the diaphragms in steel-box-girder bridges constructed up to date were solid-plate, frame, and truss types. The objectives of this study using parametric study were to evaluate the appropriate stiffness ratio of intermediate diaphragms and then to propose the effective spacing and numbers of intermediate diaphragms based on the evaluated stiffness ratio. Target bridges for this study were straight continuous span bridges with a single-cell steel box section. The parameters for the parametric study were the shape of box section, the span numbers, the equivalent span length, the stiffness of intermediate diaphragms, and the spacing of intermediate diaphragms. From the results of the parametric study, the effective spacing and numbers as well as the stiffness ratio of the intermediate diaphragms will be presented.

• Polymer(Korea)
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• v.36 no.5
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• pp.555-563
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• 2012

Warpage of injection molded product is caused by non-uniform shrinkage during shaping operation and relaxation of residual stress. Robust part design and glass fiber reinforced reins have been adopted to prevent warpage of part. Warpages for part designs have been investigated in this study according to the injection molding conditions. Part design contains flat specimen and two different rib designs in the flat part. Resins used in this study were glass fiber reinforced amorphous plastics, PC and ABS. Different rib designs showed significant differences of warpages in the parts. Various warpages have been observed in the three regions of the part, near gate region, opposite region to the gate, and flow direction region. Results of computer simulation revealed that the warpages were strongly related to glass fiber orientation. Flat specimen showed the smallest warpage and the specimen with ribs to the flow direction showed a high resistance to warpage. Warpage highly depended upon part design rather than molding condition. It was concluded that the rib design and selection of gate location in injection molding would be the most important factors for the control of warpage since those are directly related to the fiber orientation during molding.

• The Journal of Engineering Geology
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• v.31 no.3
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• pp.295-306
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• 2021

This study used numerical modeling to investigate the stability of railway roadbed in areas with various underground cavities and rock conditions associated with mining activities. It compared combined loads from both passenger and freight trains with loads from only passenger trains. Stability was assessed with reference to the Korean government standards for railway subsidence allowance and railway warping repair. Sufficient stability regarding the railway subsidence allowance standard was not achieved when cavities were at depths of <5 m. The criteria for requiring railway warping repair were met when cavities were at depths of <15 m, depending on the rock fracture condition. This study provides the first report on systematic analysis land subsidence related to cavity size and rock fracture conditions associated with mining activities. We expect that this study could serve as an important reference for railway construction in mining areas.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.28 no.6
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• pp.256-262
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• 2018

A great amount of fly ash, which is a waste from a thermal power plant, has not been appropriately recycled until now. Landfill of flay ash causes environmental pollution and enormous economic costs. In this study, manufacturing of architectural ceramic tile was investigated replacing fly ash with clay raw material. The properties of porcelain tile was analyzed after manufacturing porcelain tile with mineral based glaze and fast firing process. In particular, the effect of the fly ash addition on the properties of ceramic tile was investigated by increasing the amount of limestone addition. Porcelain tile with fly ash showed excellent bending strength, water absorption, warping and abrasion resistance. However, a significant decrease in durability was observed through the autoclave test. Addition of limestone increased the water absorption, twisting and hydration expansion of the ceramic tile, but it was confirmed that the durability of the ceramic tile with fly ash was greatly improved. In conclusion, recycled architectural ceramic tiles, which can meet domestic construction standards, could be manufactured with the addition of fly ash and limestone.

• Journal of the Korean Wood Science and Technology
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• v.44 no.5
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• pp.726-735
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• 2016

This study was carried out to evaluate the high-temperature drying characteristics of douglas-fir, hemlock, and radiata pine square timber with dimensions of thickness 15 cm and 18 cm. As a result, radiata pine showed the lowest final moisture content followed by douglas-fir and hemlock without reference to the timber size. Moreover, when the longitudinal kerfing is processed, the final moisture content was lower than control. The kerfing treatment was effective to decreasing the twist of radiata pine and hemlock. When douglas-fir is processed to the shape like the edge-grained timber that does not include the pith, the decrease of drying defect was possible.

• Journal of the Society of Naval Architects of Korea
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• v.40 no.4
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• pp.16-21
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• 2003

The very large container ships have been built recently and those ships have very small structural rigidity compared with the other conventional ships. As a result, the destruction of ship hull is occurred by the springing including to warping phenomena due to encounter waves. In this study, the solutions of hydrodynamic coefficients are obtained by solving the three dimensional source distribution method and the forward speed Green function representing a translating and pulsating source potential for infinite water depth is used to calculating the integral equation. The vessel is longitudinally divided into various sections and the added mass, wave damping and wave exciting forces of each section is calculated by integrating the dynamic pressures over the mean wetted section surface. The equations for six degree freedom of motions is obtained for each section in the frequency domain and stiffness matrix is calculated by Euler beam theory. The computations are carried out for very large ship and effects of bending and torsional ridigity on the wave frequency and angle are investigated.

• The Journal of Korea CHUNA Manual Medicine
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• v.5 no.1
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• pp.135-139
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• 2004

Objectives : The objectives of this report is to introduce PTA. Methods : The examination of the leg length inequality gives us a useful tool for diagnosis of body imbalance. especially pelvic distortion. There are four steps in the process of the leg analysis, according to "The Standard Manual of Chuna Society (2nd ed., Seoul:KCA Press. 2001)". In the last step of the analysis, knee-flexing over $90^{\circ}$, we have often experienced a specific sign that the lower legs are attracted toward one side spontaneously. The authors call it 'Lower Leg Lateral Attraction'. This is a very significant sign that gives us which is the major part between pelvis and the upper parts over sacrum. Thus it is definded as "Pelvic Twist Analysis, PTA" by the authors. With PTA, first, you must check the side of short leg and next, check the side of lateral attraction in lower leg over-flexing. If both sides coincide with each other, then the major part you can correct first is pelvic distortion. If not, you must find another part for primary correction, instead of pelvis. Conclusions : PTA becomes a useful complement to the examination of the leg length inequality.

• Journal of Biomedical Engineering Research
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• v.21 no.6
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• pp.583-589
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• 2000

본 논문에서는 핵자기공명영상의 고해상도를 이루고, 영상의 신뢰성을 높이기 위해서 선형성이 증가된 경사자기장 코일의 설계와 제작에 목적을 두었다. Maxwell pair를 이용하여 Z-경사자계의 선형성을 증강시키기 위해 코일의 기하학적인 형태의 이론적인 계산과 몇 가지 형태의 코일로부터 예상되는 자기장 및 경사자기장의 분포를 구현했다. 즉, 코일 축 방향의 자기장을 구면좌표계에서 전개하는 방법으로 Maxwell pair의 크기와 위치를 계산하고, 유한요소법을 이용하여 자기장 및 경사자기장의 2차원 분포를 그렸다. 더불어 이론적인 계산 결과와 함께 자기장의 2차원 분포를 토대로 실제 경사자기장 코일을 제작하였고 이를 0.15 Τ 핵자기공명영상기에 적용하여, 영상을 획득하였다. 기존의 방법에 따른 Maxwell pair 형태를 이용한 경우에 코일지름의 40% DSV(diameter spherical volume)내에서 DSV의 5% 이내의 뒤틀림(distortion)을 갖는 선형성이 유지되었고, 새롭게 시도된 방법에 의한 경사자기장 코일의 경우는 코일지름의 70% DSV 내에서 DSV의 5% 이내의 뒤틀림을 갖는 선형성을 유지하였으며, 설계 제작된 경사자기장 코일과 RF-코일을 이용하여 이를 확인하였다. 본 연구에서 제작된 경사자기장 코일의 선형성은 Maxwell pair 코일보다 향상된 결과를 보았으며, 본 논문에서 제시하는 방법은 자기공명영상의 해상도 향상에 기여할 것으로 판단된다.

• Journal of the Korean Society for Nondestructive Testing
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• v.33 no.2
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• pp.154-159
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• 2013

In this paper, the effect of bolt clamping force and form accuray of contact surface between mirror and mount on mirror surface was studied. Normally, mirror used in reflecting optical system was assembled with mount by bolts or adhesive. In this case, the tension caused by bolt clamping force or adhesive force may distort the mirror surface. Also, form accuracy error of the contact surface have a negative impact on wrenched mirror surface which assembled by bolts or adhesive. In this study, stress and distorted displacements on mirror surface were analyzed according to the different contact surface form accuracies and bolt clamping forces by using the finite element analysis method.

• Journal of Korean Society of Steel Construction
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• v.14 no.2
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• pp.349-356
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• 2002

Cold-Formed C-section and Lipped C-section are commonly used as structural members of steel houses in Korea. Both are made of SGC41 steel. However, special Cold-Formed Sections with unique cross sectional shape have been developed and widely used in advanced countries. This research focused on the newly developed thin-walled Cold-Formed Sections which possess not only high strength and stiffness but also other advantages in construction. A series of compression tests was conducted to investigate the structural behavior of a compression member, including its load carrying capacity. Test results were compared with analytical study results.