• Journal of the Korean Society of Radiology
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• v.17 no.6
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• pp.929-937
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• 2023

Human equivalent phantoms manufactured using 3D printers are cheaper and can be manufactured in a short time than conventional human phantoms. However, many phantoms are manufactured with less than 100 % of Infill Density, one of the 3D printer output setting variables. Therefore, this study compared the Bone Phantom CT number, which differs from the ratio of five Infill Density produced using a 3D printer, to the CT number of the actual human body Bone. In addition, the usefulness of the manufactured phantom was evaluated by producing a 100 % elbow joint phantom with Infill Density and setting the Infill Density to 100 % through CT number comparison for each tissue on computed tomography (CT). As a result, the Bone Phantom printed with 100 % Infill Density did not show the most statistically significant difference from the CT number value of the actual human Bone, and the CT number of each tissue did not show a statistically significant difference from the CT number value of each tissue of the actual human elbow joint.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.29 no.2
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• pp.83-91
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• 2017

In order to cope with the abnormally high waves during the storm surge due to climate change, various methods have been proposed for interlocking adjacent caissons to enhance stability of harbor structures. Among the methods, it was studied the method based on an open-cell caisson having reduction effect increasing the cohesion with adjunction caissons by filling materials such as crushed rocks in an inter-cell formed by two facing open-cells which consist of transverse walls. It is necessary to investigate the shear behaviors of an inter-cell to secure the stability using calculating shear forces on inter-cell under oblique wave loadings. It was analyzed the shear force share ratio with the length of internal and external wall and the number of internal walls. Numerical results show that 60~70% of the shear load is transmitted to adjacent caisson through the internal walls, more than 30% is through the external wall. It was applicable in the assumption that filling materials was uniformly distributed in inter-cells, and further studies were worth consideration on other conditions under construction.

• Journal of the Korean Society of Radiology
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• v.14 no.5
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• pp.651-660
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• 2020

The purpose of this study was to create a phantom with a HU value similar to that of the human Femur using a 3D printer to replace the existing pig bone. A total of 372 people were analyzed to determine the HU value of human Femur. Using a 3D printer, a human bone model phantom was fabricated using PLA-Cu 20% and subjected to CT examination. Pig bones were 6 months old pigs, and bones 2 days after slaughter were used. As a result of the examination, the 3D printing phantom made with 80% of the internal filling showed a similar value to all data of the human body (p<0.05), and there was a difference from the pig bone (p>0.05). In addition, in the case of the HU value of Femur by age group, it was confirmed that the value of HU decreased as the age group increased (p<0.05). 3D printing and HU values confirmed a weak negative correlation with respect to the stacking height, but confirmed a strong positive correlation (R² = 0.996) with 182.13±1.290 in the inner filling (p<0.05). In conclusion, it was confirmed that the human body model phantom using 3D printing can exhibit a similar level of HU value to the human body compared to the existing pig bone phantom, and this study will provide basic data for the production of a human body model phantom using a 3D printer.

• Journal of the Korean Society of Radiology
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• v.13 no.2
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• pp.185-192
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• 2019

DXA is the most commonly used BMD examination equipment with the best performance on reflecting the biological alteration with tiny change of bone density. In spite of the importance of the quality control to maintain the accuracy and precision of the examination, considerable number of hospitals are not conducting QC due to the difficulty and high cost of the phantom product. This study develops the cross revision phantom with 3D printer and the change of the degree of infilling filaments which can be readily secured, and provides the usefulness assessment of the developed phantom by comparing with existing products. The Hounsfield Units of ABS, TPU, PLA, 30% Cu-PLA, and 30% Al-PLA are assessed. The Hounsfield Units result at infilling rate 100% was $-149.74{\pm}2.36$, $-55.62{\pm}7.14$, $-7.68{\pm}3.82$, $87.53{\pm}1.07$, and $1795.20{\pm}16.15$. The L1, L2, L3 BMD of 3D printing phantom with linear regression model were $0.620{\pm}0.010g/cm^2$, $1.092{\pm}0.025g/cm^2$, $1.554{\pm}0.026g/cm^2$ which are statistically relevant to the existing phantom products. This result provides the base line data for various medical phantom produce and capability of proper quality control of DXA equipment.

• Journal of the Earthquake Engineering Society of Korea
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• v.4 no.4
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• pp.1-13
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• 2000

상부벽식 하부골조를 가진 복합구조물은 부족한 대지를 효율적으로 활용하기 위하여 건설되고 있다. 이러한 복합건물은 상부벽식-하부골조를 가지는 구조로써 일반적으로 전이보 또는 전이판으로 상하부를 연결하고 있다. 따라서 상하부 구조사이의 강성과 질량에 많은 차이가 발생하게 된다. 구보물의 고유주기는 지진하중과 밑면전단력을 결정하기 위한 중요한 변수이다. 그러나 현재 국내 규준에서 제안하는 고유주기 산정식은 이러한 건물에는 적용할 수 없다. 본 연구에서는 상부벽식-하부골조를 가진 복합구조물의 고유주기의 산정에 영향을 미치는 변수들 중 가장 큰 영향을 미치는 건물의 상하부 층수에 따른 변수만을 고려하여 고유주기산정식을 제안하였다. 하부는 2~5개 층을 가지고, 상부는 10~18개 층을 가지는 15~20층의 건물이면 정형적인 평면을 가지는 복합구조물로 한정하였다. 건물 내부의 채움벽에 대한 효과를 고려한 고유주기 제안식은 다음과 같다. 장변 방향 : $T_{L}$=($0.20H_{h}+0.05H_{i}$)/$sqrt{B}$-0.42 단변 방향 :$T_{S}$=($0.07H_{h}+0.12H_{i}$)/$sqrt{B}$-0.40

• Geophysics and Geophysical Exploration
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• v.3 no.3
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• pp.94-100
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• 2000

Many nondestructive test methods used for metallic materials have some limit in application to concrete materials due to their heterogeneity. Impact echo method utilizes the resonance frequency of reflected seismic waves from defects or the boundary between two materials and can be applied to investigate the interior of concrete structures. In this study, a field data acquisition system for the impact echo method was assembled and field tests under various conditions were performed. The impact echo method was applied for investigating thickness/defects/backfilling of concrete structures/tunnel lining/airport pavement. The applicability of the impact echo method to the civil engineering field was substantiated by providing results within $10\%$ errors.

• Journal of the Korean Geosynthetics Society
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• v.16 no.2
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• pp.165-174
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• 2017

There are natural disasters caused by abnormal climate in the world. In particular, there are frequent disasters such as floods and landslides caused by rainfall in summer. Rainfall will have a major impact on the stability of a retaining wall. If drainage during rainfall activities within the retaining wall is not made properly, permeated water brings a significant increase in pore pressure inside of the backfill soil and reduces the shear strength of the soil. Therefore, research how to install the drainage layers to reduce the infiltrated water inside of the backfill soil is very necessary. In this study, we performed a numerical modeling to find the optimum installation conditions of the location and number of drainage layer related to stability of the reinforced retaining wall during rainfall installed geosynthetics.

• Journal of the Korea Concrete Institute
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• v.26 no.1
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• pp.35-46
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• 2014

Two types of cast-in-place concrete-filled hollow PC (HPC1, HPC2) columns were developed to reduce lifting load of heavy-weight PC columns and to improve the structural integrity of joints. To form the hollow PC columns, a couple of prefabricated PC panels was used for HPC1, and special hoops were used for HPC2. Lateral pressure of wet concrete on PC faces was measured while placing the concrete inside the columns. To evaluate the seismic resistance, full scale specimens of two HPC columns and a conventional RC column were tested under combined axial compression and lateral cyclic loading. The test results showed that the structural performance of the proposed HPC columns such as intial stiffness, maximum strength, and displacement ductility was comparable to that of the conventional RC column, but the energy dissipation of HPC2 slightly decreased after rebar-buckling. However, all the test specimens satisfied the energy dissipation requirement specified in ACI 374.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.9 no.4
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• pp.165-175
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• 1997

This study qualitatively reviewed effect of the height of loading and the ratio of penetration on. the characteristics of deformation of cellular bulkhead by performing a model test of embedded steel plate cellular bulkhead which had different loading height and penetration ratio. And we also examined the effect of the loading height upon the shear behavior by performing two-dimensional model test making use of aluminum rods for a filler. Besides, test results and theoretical values based on Hansen's earth pressure theory were compared and reviewed. In consequence, it was ascertained that the yield moment of cells depended on the height of loading and the ratio of penetration, and the slip surface was located on the lower area of a cell interior according as the height of loading becomes lower. The theoretical consideration which was based on the theory of earth pressure proposed by Hansen revealed that the test results accorded with the theoretical values to some degree, and the same results were derived about the location change of the slip surface.

• Journal of Korean Society of Steel Construction
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• v.9 no.2 s.31
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• pp.249-257
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• 1997

This study will present the experimental research on the establishment of design considerations and structural integrity of the placed steel-plate cell methods for seawall and waterbreak, which have some benefits in the aspects of construction cost, time and equipments compared with the existing methods. The behavior of steel-plate cell structure is complicate due to stiffeners and cell-arc junction. There is also an ambiguity on lateral pressure by cell and arc filler. To resolve such problems, full scale cell $(D11.0^m{\times}H14.0^m{\times}12t)$ has been designed and fabricated, then placed on the seabed and filled. The strain measurement has also been performed to build up the design technology together with numerical analysis.