• Composites Research
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• v.34 no.3
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• pp.155-160
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• 2021

Metamaterials are complexes of elements that can create properties not found in naturally occurring materials, such as changing the direction of forces, creating negative stiffness, or altering vibration and impact properties. In the case of wood pile metamaterials that are easy to manufacture and have excellent performance in reducing vibration and shock in the vertical direction, basic research on variables affecting shock transmission is needed to reduce shock. Although research on impact reduction according to geometrical factors is being conducted recently, studies on the effect of material variables on impact reduction are insufficient. In this paper, finite element analysis was carried out by variablizing the geometrical properties (lamination angle, diameter, length) and material properties (modulus of elasticity, specific gravity, Poisson's ratio) of wood pile cylinders. Through finite element analysis, the shape of the wooden pile cylinder delivering impact was confirmed, and the effect of each variable on the reduction of impact force and energy was considered through main effect diagram analysis, and frequency band analysis was performed through fast Fourier transform. proceeded In order to reduce the impact force and vibration, it was found that the variables affecting the contact area of t he cylinder have a significant effect.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.42 no.6
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• pp.825-836
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• 2022

Micropiles can be used to support additional load in extended building structures. However, their use brings about a risk of exceeding the bearing capacity of existing piles. In this study, pre-compression was applied to distribute the load of an existing building to micropiles, and an indoor loading test was performed to confirm the structural applicability of a wedge-type anchorage device designed to improve its capacity. According to the test results, the maximum strain of the anchorage device was 0.63 times that of the yield strain, and the amount of slip generated at the time of anchorage was 0.11 mm, satisfying structural standards. In addition, using MIDAS GTS, a geotechnical finite element analysis software, the effect of the size of the pre-compression, the thickness of the soil layer, and the ground conditions around the tip on the reaction force of the existing piles and micropiles were analyzed. From the numerical analysis, as the size of the pre-compression load increased, the reaction force of the existing pile decreased, resulting in a reduction rate of up to 36 %. In addition, as the soil layer increased by 5 m, the reduction rate decreased by 4 %, and when the ground condition at the tip of the micropile was weathered rock, the reduction rate increased by 14 % compared with that of weathered soil.

• The korean journal of orthodontics
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• v.27 no.5 s.64
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• pp.815-824
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• 1997

The purpose of this study is to develop the basic algorithm for the finite element method modeling of individual malocclusions. Usually, a great deal of time is spent in preprocessing. To reduce the time required, we developed a standardized procedure for measuring the position of each tooth and a program to automatically preprocess. The following procedures were carried to complete this study. 1. Twenty-eight teeth morphologies were constructed three-dimensionally for the finite element analysis and saved as separate files. 2. Standard brackets were attached so that the FA points coincide with the center of the brackets. 3. The study model of a patient was made. 4. Using the study model, the crown inclination, angulation, and the vertical distance from the tip of a tooth was measured by using specially designed tools. 5. The arch form was determined from a picture of the model with an image processing technique. 6. The measured data were input as a rotational matrix. 7. The program provides an output file containing the necessary information about the three-dimensional position of teeth, which is applicable to several finite element programs commonly used. The program for a basic algorithm was made with Turbo-C and the subsequent outfile was applied to ANSYS. This standardized model measuring procedure and the program reduce the time required, especially for preprocessing and can be applied to other malocclusions easily.

• The Journal of Information Technology and Database
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• v.6 no.2
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• pp.71-86
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• 1999

The performance of relational database is measured by the number of disk accesses necessary to transfer data from disk to main memory. The paper proposes to vertically partition relations into fragments and to allow attribute replication to reduce the number of disk accesses. To reduce the computational time, heuristic search method using genetic algorithm is used. Genetic algorithm used employs a rank-based-sharing fitness function and elitism. Desirable parameters of genetic algorithm are obtained through experiments and used to find the solutions. Solutions of attribute replication and attribute non-replication problems are compared. Optimal solutions obtained by branch and bound method and by heuristic solutions(genetic algorithm) are also discussed. The solution method proposed is able to solve large-sized problems within acceptable time limit and shows solutions near the optimal value.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1804_1805
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• 2009

최근 여러 산업 분야에서는 품질의 향상과 생산성을 높이기 위해 자동화 검사 장치 개발이 활발하게 연구 되고 있다. 본 연구에서는 비전을 이용한 신뢰도 높은 슬라브(Slab) 표면 검사 자동화 알고리즘의 전처리 단계인 오실레이션 마크(Oscillation mark) 검출을 목표로 한다. 슬라브 영상의 경우 조업시에 발생하는 산화 물질인 스케일(Scale)이 영상 전체에 분포하고 있으며, 이러한 스케일은 형태적 특징 및 밝기 특징이 일정치 않기 때문에 오실레이션 마크 검출 성능을 저하 시킨다. 따라서 스케일의 영향을 최소화 하고 효과적으로 오실레이션 마크를 검출하기 위해 가버 필터(Gabor filter)와 수직 투영 프로파일(Vertical projection profile)을 이용한 노이즈 제거 방법을 사용한다.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2010.07a
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• pp.337-340
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• 2010

본 논문은 H.264/AVC를 이용한 근접 무손실 화면내 부호화에서 기존의 라인 기반 예측 방법에서 발생할 수 있는 오류 전파 문제를 해결하기 위한 방법을 제안한다. H.264/AVC의 화면내 예측 부호화는 주변 블록의 복원 화소들을 현재 부호화하려는 블록의 예측값으로 사용하여 공간적 상관성을 제거하고 부호화 효율을 향상시킨다. 기존의 라인 기반 예측 방법에서는 일반적으로 화소 간 거리가 멀어질수록 화소 간 상관성이 떨어지므로 라인 단위로 예측을 수행하여 예측의 정확도를 높였다. 하지만, 이 경우 오류 전파 문제에 취약하다는 단점이 있다. 본 논문에서는 화면내 $16{\times}16$ 수직 및 수평 예측 모드에 대해 매크로블록을 라인 단위로 예측하면서 정해진 서브 블록마다 참조 화소를 업데이트하는 방법을 제안한다. 따라서, 라인 기반 예측 방법의 예측 정확도는 유지하면서 오류 전파 문제를 예방할 수 있다. 실험을 통해, 제안하는 방법이 High 프로파일에서 H.264/AVC 표준 소프트웨어 JM 12.2에 비해 평균 약 5.8%의 비트율을 감소시킬 수 있음을 보였다.

• Journal of Industrial Technology
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• v.28 no.B
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• pp.209-214
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• 2008

Set-valued attributes appear in many applications to model complex objects occurring in the real world. One of the most important operations on set-valued attributes is the set join, because it provides a various method to express complex queries. Currently proposed set join algorithms are based on block nested loop join in which inverted files are partitioned horizontally into blocks. Evaluating these joins are expensive because they generate intermediate partial results severely and finally obtain the final results after merging partial results. In this paper, we present an efficient processing of set join algorithm. We propose a new set join algorithm that vertically partitions inverted files into blocks, where each block fits in memory, and performs block nested loop join without producing intermediate results. Our experiments show that the vertical bitmap nested set join algorithm outperforms previously proposed set join algorithms.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2012.11a
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• pp.207-210
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• 2012

본 논문에서는 스테레오스코픽 3D 동영상에서 왼쪽과 오른쪽 영상 사이의 프레임 동기가 맞지 않아 시청에 어려움을 주는 문제를 해결하기 위해서, 두 영상에서 물체의 움직임에 따른 차이를 이용한 프레임 동기화 방법을 제안한다. 제안 방식은 교정화 과정을 통해 수직 시차를 보정한 왼쪽과 오른쪽 입력 영상에서 각각 전 영상과의 차분 값에 대한 수평 방향 투영 프로파일을 구하고, 이들의 절대 오차에 대한 평균 (mean of absolute difference(MAD))를 계산해 최소값이 되는 프레임 조합을 찾아 프레임 동기를 맞추는 방법이다. 실험결과, 프레임 동기가 맞는 프레임 조합에서 최소 MAD 값을 기록하여 스테레오스코픽 3D 동영상에서의 프레임 동기화가 가능하다는 것을 볼 수 있으며, 특정 잡음이나 영상 압축 조건에 대해서도 동작함을 알 수 있다.

• Journal of the military operations research society of Korea
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• v.22 no.1
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• pp.81-96
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• 1996

In a relational database environment, partitioning of data is directly concerned with the amount of data that needs to be required in a query or transaction. In this paper, we consider non-overlapping, vertical partitioning. Vertical partitioning algorithm in this paper is composed of two phases. In phase 1, we cluster the attributes with zero-one integer program that maximize affinity among attributes. The result of phase 1 is called 'Initial Fragments'. In phase 2, we modify Initial Fragments that is not directly considered by cost factors, making use of a transaction-based partitioning method. A transaction-based partitioning method is partitioning attributes according to a set of transactions. In this phase we select logical accesses which needs to be required in a transaction as comparison criteria. In phase 2, proposed algorithm consider only small number of modification of Initial Fragments in phase 1. This algorithm is so insensible to number of transactions and of attributes that it can applied to relatively large problems easily.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2001.04a
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• pp.121-127
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• 2001

To investigate the stability and integrity of offshore structures, it is necessary to estimates the significant ocean environmental loadings. They include hydrostatic pressure, wind, wave, current, tide, ice, earthquake, temperature, marine growth and scouring. Waves are of major importance among them because of the large forces acting on submerged parts of the structure caused by accompanying water motions. For the comparison of stress and deflection analysis tools, a vertical pile is applied under environmental loads. The analysis is concerned with SACS(Structural Analysis Computer System), ANSYS and C program. SACS and C program have nearly the same results but not ANSYS. This study shows the comparison of results obtained from 3 different approaches.