• The Journal of Korean Academy of Prosthodontics
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• v.52 no.4
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• pp.279-286
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• 2014

Purpose: The aim of this study was to investigate the effect of implant thread profile on the marginal bone stresses which develop during implant insertion. Materials and methods: Four experimental implants were created by placing four different thread systems on the body ($4.1mm{\times}10mm$) of the ITI standard implant. The thread types studied in this study included the buttress, v-shape, reverse buttress, and square shape threads. In order to examine the insertion stress generation, 3D dynamic finite element analysis was performed which simulated the insertion process of implants into a 1.2 mm thick cortical bone plate (containing 3.5 mm pilot hole) using a PC-based DEFORM 3D (ver 6.1, SFTC, Columbus, OH, USA) program. Results: Insertion stresses higher than human cortical bone developed around the implants. The level of insertion stresses was much different depending on the thread. Stress level was lowest near the v-shape thread, and highest near the square shaped thread. Difference in the interfacial bone stress level was more noticeable near the valley than the tip of the threads. Conclusion: Among the four threads, the v-shape thread was turned out to minimize the insertion stress level and thereby create better conditions for implant osseointegration.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.10C
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• pp.935-941
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• 2007

In this paper, we suggest the power allocation method which enhances the performance in high SNR for LDPC codes. In this method, bit power is unequally allocated proportionally to the difference of the degree distributions of variable and check nodes of Tanner graph between practically used codes and the codes optimized by density evolution. Simulation is performed to the codes in IEEE 802.16e standards, and the results show that the proposed method works well in high SNR.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.29 no.1
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• pp.85-93
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• 2016

In this study, finite element analyses of masonry infilled frames using a general purpose FE program, ABAQUS, were conducted. Analysis models consisted of the bare frame, infilled frames with masonry wall thickness of 0.5B and 1.0B, respectively. The masonry walls were constructed using the concrete bricks which were generally used in Korea as infilled wall. The material properties of frames and masonry for the analysis were obtained from material tests. However, four times increased the tensile strength was used for 1.0B wall, which is seemingly due to the differences in locating the bricks. The force-displacement relation and development of crack from the FE analysis were very similar to those from the experiments. From the FEA results, contact force between the frame and masonry, distribution of shear force and bending moments in frame members were analyzed. Obtained contact stress shows a trianglur distribution, and the contact length for 0.5B speciment and 1.0B specimen were close to the value estimated using ASCE 41-06 equation and ASCE 41-13 equation, respectively. Obtained shear force and bending moment distribution seems to replicate actual behavior which originates from the contact stress and gap between the frame and masonry.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.1
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• pp.21-29
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• 2017

In this paper, the total procedure for composite laminate mechanical joint (ASTM D5961 Proc. A, B) from fixture design to test analysis was showed. Composite laminate mechanical joints were analyzed using the FEM(Finite Element Method) and compared to test results. A progressive failure analysis was applied to FEM to analyze the failure behavior of test specimens. Three failure theories - maximum stress, maximum strain, and Tsai-Wu were applied to FEM to predict test failure load. General parameters for composite laminate joints were reviewed and the differences of bearing strength were compared with major parameters.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.13 no.4
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• pp.227-237
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• 1993

This paper dealt with numerical analysis of sand drain considering the smear effect around drain wells and discontinuous deformation behavior due to difference in rigidity between drain materials and adjacent clayey soils. Biot's equation was selected as governing equation coupled with MODCAM (Modified Cam-clay) model or EVP(Elasto-Viscoplastic) model as constitutive equation. The validity as well as the accuracy of the method developed by author was checked by comparing the proposed method with those by Siriwardane and Ghaboussi using joint element. The FEM analysis developed in this study was applied to both 2-dimensional model foundation and actual foundation. the result of which proved to be satisfactory.

• Journal of the Korean Society for Railway
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• v.14 no.4
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• pp.333-340
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• 2011

The purpose of this paper is to develop two kinds of finite element models for the heavy deformable obstacle defined in grade crossing collision scenario of the Europe TSI and the Korean rolling stock safety regulations and to apply the crashworthiness evaluation for the Korean high-speed EMU with the FE model. The numerical models of the heavy obstacle were changed from a past rigid one to a current deformable one whose stiffness requirement should be verified by a collision simulation defined in the regulations. Through several trial simulations, two types of numerical models for the heavy obstacle were developed, which satisfied physical properties specifies in the regulations. One is a solid-type obstacle with uniform density and the other is a shell-type. With the obstacles developed in this study, the grade crossing collision scenario for Korean high-speed EMU was simulated and evaluated for the two-type obstacle models. From the simulation results, the shell and solid-type obstacles showed quite different behaviors after collision, and the shell type model gave more severe results.

• International Journal of Highway Engineering
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• v.10 no.3
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• pp.209-220
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• 2008

This paper presents the differences in the analysis results according to the underlying layer modeling methods when analyzing the curling behaviors of the concrete slabs on grade under environmental loads. The models of the slab on grade system considered in this study included a three-dimensional(3D) model, a model composed of 3D slab and springs for underlying layers, and a model composed of 2D slab and springs for underlying layers. First, when the underlying layer consisted of one layer, the curling behaviors according to the different models were compared. Then, the underlying layers that consisted of two different materials and thicknesses were considered. The results of this study showed that the tensionless spring model for the underlying layer gave very accurate results when the underlying layer consisted of one layer. However, when the underlying layers consisted of two layers, the spring model for the underlying layers could overestimate the displacements and underestimate the maximum stress with a large elastic modulus of upper underlying layer, a small elastic modulus of under underlying layer, and thick underlying layers.

• Journal of Genetic Medicine
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• v.6 no.2
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• pp.146-154
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• 2009

Multiplex ligation dependent probe amplification (MLPA) is a PCR-based method to detect gene dosage. Since its introduction, MLPA has been used to test a large number of genes for major deletions or duplications. Genetic testing, as a diagnostic tool for genetic disease, has been used primarily to identify point mutations, including base substitutions and small insertions/deletions, using PCR and sequence analysis. However, it is difficult to identify large deletions or duplications using routine PCR- gel based assays, especially in heterozygotes. The MLPA is a more feasible method for identification of gene dosage than another routine PCR-based methods, and better able to detect deleterious deletions or duplications. In addition to detection of gene dosage, MLPA can be applied to identify methylation patterns of target genes, aneuploidy during prenatal diagnoses, and large deletions or duplications that may be associated with various cancers. The MLPA method offers numerous advantages, as it requires only a small amount of template DNA, is applicable to a wide variety of applications, and is high-throughput. On the other hand, this method suffers from disadvantages including the possibility of false positive results affected by template DNA quality, difficulties identifying SNPs located in probe sequences, and analytical complications in quantitative aspects.

• Transactions of the Korean Society of Mechanical Engineers
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• v.10 no.6
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• pp.876-888
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• 1986

The Study is concerned with the analysis of unconstrained axisymmetric piercing as a nonsteady forging process by the rigid-plastic finite element method. In the numerical analysis of axisymmetric piercing, the initial velocity field is generated by assuming the material as a linear viscous material to begin with in order to facilitate the input handling and to ensure better convergencey. The strain-hardening effect for nonsteady deformation and the friction of the die-material interial interface are considered in the formulation. Rigid body treatment is also incorporated in the developed program. The experiments are carried out for aluminum alloy specimens (A1204) with different specimen heights. It is shown that the experimental results are in excellent agreement with the finite element simulations is deformed configuration. For load prediction the theoretical prediction shows excellent agreement with th eexperimental laod in the initial stage of loading before fracture of the specimen is not initiated. Distribution of stresses, strains and strain rates has been found for the given cases in computation. On this basis several fracture criteria are introduced in order to check the fracture initiation. It is found that maximum shear criterion is capable of good fracture prediciton.

• Journal of the Korean Society of Hazard Mitigation
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• v.11 no.2
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• pp.31-37
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• 2011

Understanding of the phase distribution in a multi-phase polycrystalline material is important because it can affect material properties and mechanical behaviors significantly. In this research, probability functions (two-point correlation and lineal-path functions) are used to represent the phase distributions of microstructures. The two-phase microstructures with random phase distribution are reconstructed using probability functions and compared with original samples. Mechanical behaviors of the virtual samples for different directions are evaluated using a finite element method. It is confirmed that microstructures with the same statistical characteristics can be generated using the reconstruction method. It is also demonstrated that the characteristics of the probability functions and mechanical reponses between the original and reconstructed microsturctures are statistically identical.