• Smart Structures and Systems
• /
• 제20권2호
• /
• pp.175-180
• /
• 2017

The load-carrying capacity and structural behavior of concrete-filled steel tube (CFST) structures is highly influenced by the grouting compactness in the steel tube. Due to the invisibility of the grout in the steel tube, monitoring of the grouting progress in such a structure is still a challenge. This paper develops an active sensing approach with combined piezoceramic-based smart aggregates (SA) and piezoceramic patches to monitor the grouting compactness of CFST bridge structure. A small-scale steel specimen was designed and fabricated to simulate CFST bridge structure in this research. Before casting, four SAs and two piezoceramic patches were installed in the pre-determined locations of the specimen. In the active sensing approach, selected SAs were utilized as actuators to generate designed stress waves, which were detected by other SAs or piezoceramic patch sensors. Since concrete functions as a wave conduit, the stress wave response can be only detected when the wave path between the actuator and the sensor is filled with concrete. For the sake of monitoring the grouting progress, the steel tube specimen was grouted in four stages, and each stage held three days for cement drying. Experimental results show that the received sensor signals in time domain clearly indicate the change of the signal amplitude before and after the wave path is filled with concrete. Further, a wavelet packet-based energy index matrix (WPEIM) was developed to compute signal energy of the received signals. The computed signal energies of the sensors shown in the WPEIM demonstrate the feasibility of the proposed method in the monitoring of the grouting progress.

• 한국양식학회지
• /
• 제9권1호
• /
• pp.93-100
• /
• 1996

물고기에서 효과적인 발현 vector의 구성을 위해, 미꾸라지 MAR로부터 ARS를 cloning하여, 그 염기서열을 분석하였다. 총 443 염기들로 구성된 미꾸라지의 ARS는 다른 여러종들의 DNA 복제원점에서 나타나는 것 처럼, AT가 풍부하고, ARS consensus sequences, topoi-somerase II consensus sequences, 그리고 A 흑은 T-box등을 포함하고 있다. 그리고 그 DNA 단편은 복제원점에서 일반적인 양상으로 나타나는 반복적인 inverted sequence들을 가지고 있고, 5개의 가능한 hairpin loop 구조들을 내포하고 있다. 이들 구조는 DNA 복제개시에 관여하는 단백질들의 인지부위로 작용할 것으로 생각된다.

• Computers and Concrete
• /
• 제19권4호
• /
• pp.429-434
• /
• 2017

Failure of basic structures material is usually accompanied by expansion of interior cracks due to stress concentration at the cracks tip. This phenomenon shows the importance of examination of the failure behavior of concrete structures. To this end, 4 types of mortar samples with different amounts of nano-silica (0%, 0.5%, 1%, and 1.5%) were made to prepare twelve $50{\times}50{\times}50mm$ cubic samples. The goal of this study was to describe the failure and micro-crack growth behavior of the cement mortars in presence of nano-silica particles and control mortars during different curing days. Failure of mortar samples under compressive strength were sensed with acoustic emission technique (AET) at different curing days. It was concluded that the addition of nano-silica particles could modify failure and micro-crack growth behavior of mortar samples. Also, monitoring of acoustic emission parameters exposed differences in failure behavior due to the addition of the nanoparticles. Mortar samples of nano-silica particles revealed stronger shear mode characteristics than those without nanoparticles, which revealed high acoustic activity due to heterogeneous matrix. It is worth mentioning that the highest compressive strength for 3 and 7 test ages obtained from samples with the addition of 1.5% nano-silica particles. On the other hand maximum compressive strength of 28 curing days obtained from samples with 1% combination of nano-silica particles.

• 대한토목학회논문집
• /
• 제6권2호
• /
• pp.121-131
• /
• 1986

?(warping)의 효과(効果)가 포함된 원형곡선부재(圓形曲線部材)의 부재강도(部材剛度)매트릭스를 미분방정식(微分方程式)의 해석적(解析的)인 해(解)를 사용(使用)하여 유도(誘導)하고, 원형곡선부재(圓形曲線部材)의 변위법(變位法)에 의(依)한 정적탄성해석방법(靜的彈性解析方法)을 제시(提示)하였다. 예제(例題)를 통하여 얻어진 결과(結果)는 다른 방법(方法)에 의(依)한 해석결과(解析結果)와 잘 일치(一致)하고 있어, 본(本) 논문(論文)의 정당성을 입증하였고 원형곡선부재(圓形曲線部材)로 구성(構成)된 구조물(構造物)을 해석(解析)할 때 곡선좌표계(曲線座標系)를 사용(使用)하므로써, 한 절점에 연결된 양쪽 부재축(部材軸)의 접선(接線)이 일치(一致)한다면, 국부좌표계(局部座標系)로부터 전체좌표계(全體座標系)로의 변환(變換)이 필요(必要)없음을 보였다. 본(本) 논문(論文)에서 유도(誘導)된 이론(理論)은 P.S. 상자형(箱子桁)의 폐단면(閉斷面) 또는 부재평면(部材平面)과 수직(垂直)인 축(軸)에 대하여 대칭인 개단면(開斷面)을 갖는 수평원형곡선부재(水平圓形曲線部材)로 이루어진 구조물(構造物)의 엄밀(嚴密)한 해석(解析)에 적용(適用)할 수 있다.

• 한국정보통신학회논문지
• /
• 제17권4호
• /
• pp.953-958
• /
• 2013

본 논문에서는 고성능 HEVC 복호기를 위한 효율적인 $32{\times}32$ 역변환기 하드웨어 구조를 제안한다. HEVC는 4k, 8k 이미지와 같이 기존의 이미지코덱에 비해 훨씬 더 큰 크기의 이미지를 처리할 수 있는 새로운 영상 압축 표준이다. 큰 이미지의 데이터를 효과적으로 처리하기 위해 다양한 새 블록 구조를 채택하였으며, 이 블록들은 $4{\times}4$, $8{\times}8$, $16{\times}16$, $32{\times}32$으로 구성되었다. 이 논문에서는 $32{\times}32$ 역변환기의 효과적인 구조를 제안하며, 역변환기의 구조는 $32{\times}32$ 행렬을 $16{\times}16$ 행렬로 재구성하고 쉬프트와 덧셈기로 구성된 곱셈기를 사용하여 연산을 단순화 하였으며 멀티 사이클 패스를 구현하여 낮은 주파수에서도 동작이 가능하도록 설계하였다. 또한 HEVC 코덱의 다양한 크기의 변환이나 순방향 변환 블록에 쉽게 적용할 수 있다.

• 한국해안해양공학회지
• /
• 제1권1호
• /
• pp.93-101
• /
• 1989

본 논문에서는 가이드 타워, 텐션 레그 프랫폼, 무어링 부이, 해저 케이블, 사장교, 현수교, 케이블 루프 등과 같은 해상 및 육상 구조물의 유한요소 모델에 사용하기 위한 기하학적 비선형 케이블 요소를 연구 제시하였으며, 케이블 요소는 평면내에서 임의의 하중과 기하형상을 갖는 케이블에 대한 탄성현수 케이블 이론으로부터의 적합방정식과 연성행렬을 직접 이용하여 유도하였다. 또한, 유도된 케이블 유한요소에 근거하여, 케이블 부재를 사용하는 구조물들의 유한요소 해석을 위해 전산 프로그램을 개발하였으며, 시간영역 동적 해석을 위해 뉴마크-베타의 직접적분법을 사용하였고, 각 시간간격에서의 비선형 평형방정식 및 적합방정식을 풀기 위한 방법으로서 뉴톤-랩슨의 반복법을 사용하였다. 이상과 같이 개발된 전산 프로그램을 이용하여 케이블 부재에 대한 정적 및 동적 해석을 수행한 후 그 결과를 분석ㆍ고찰하여 보았다.

• 열처리공학회지
• /
• 제13권4호
• /
• pp.231-238
• /
• 2000

Flake graphite cast irons with the high damping capacity have been used for the control of vibration and noise occurring in the members of various mechanical structures under vibrating conditions. However, the damping capacity which is morphological characteristics of graphite is one of the important factors in reducing the vibration and noise, but hardly any work has deal with this problem. Therefore, the authors have examined the damping capacity of various cast irons with alloying elements and studied the influences of the matrix structures, mechanical properties and morphological characteristics of graphite. The main results obtained are as follows: Effects of pouring temperature on the damping capacities and mechanical properties were investigated in 3.6%C cast iron. At $1400^{\circ}C$, specific damping capacity showed the maximum value, and decreased with increase pouring temperature. Mechanical properties showed opposite trend with the damping capacity. And then, effects of Ni on the damping capacities and mechanical properties have been investigated in 3.6%C gray cast iron. At 0.2%Ni content, specific damping capacity showed the maximum value, and decreased with further increase in Ni content. Graphite length also showed same behavior. This indicates that the specific damping capacity has a close relation with graphite length. In case of Mo addition in 3.6%C-0.2%Ni cast iron, specific damping capacity and tensile strength was 27% and $20kgf/mm^2$ at 3.6%C-0.2%Ni-0.3%Mo cast iron respectively.

• 열처리공학회지
• /
• 제14권6호
• /
• pp.330-335
• /
• 2001

Flake graphite cast irons with the high damping capacity have been used for the control of vibration and noise occurring in the members of various mechanical structures under vibrating conditions. However, the damping capacity which Is morphological characteristics of graphite is one of the important factors in reducing the vibration and noise, but hardly any work has deal with this problem. Therefore, the authors have examined the damping capacity of various cast irons with alloying elements and studied the influences of the matrix structures, mechanical properties and morphological characteristics of graphite. The main results obtained are as follows: Effects of Sb on the damping capacities and mechanical properties have been investigated in 3.6%C-0.2%Ni gray cast iron. At 0.02%Sb, specific damping capacity showed the maximum value, and decreased with further increase in Sb content. Mechanical properties showed opposite trend with the damping capacity. And then, effects of Ti on the damping capacities and mechanical properties have been investigated in 3.6%C-0.2%Ni-0.02%Sb gray cast iron. Specific damping capacity increased with increase in Ti content. Graphite length also showed same behavior. Tensile strength increased with Ti content due to refinement of pearlite. In the case of 0.14%Ti addition in 3.6%C-0.2%Ni-0.02%Sb cast iron, specific damping capacity and tensile strength was 36% and 25 $kgf/mm^2$ which are higher than 32% and 15 $kgf/mm^2$ at 3.6%C-0.2%Ni cast iron respectively.

• 대한조선학회논문집
• /
• 제29권1호
• /
• pp.135-142
• /
• 1992

선박이나 해양구조물과 같은 접수구조물의 진동해석은 구조계와 유체계를 연성시켜 접수면에서의 적합조건을 만족시키는 해를 구하게 된다. 잘 알려진 바와 같이 이러한 유력탄성해석은 구조계는 유한요소법을, 유체계는 경계요소법을 적용하여 두 계를 연성시켜 효과적으로 풀 수 있는데, 이 방법은 부가수질량 행렬의 모든 자유도가 접수면에 완전연성되어 있기 때문에 실용화하기에는 어려움이 있다. 본 논문에서는 이와같은 단점을 보완하기 위해서 재해석방범에 기초한 유체-구조 연성진동 해석방법을 제시하였다. 이 방법은 전통적으로 보거동 진동해석에 사용해 온 2차원 부가수질량과 3차원 수정계수 J를 이용한 비연성 진동해석 방법과 비교해 볼때, 3차원 수정계수 J의 고려없이 보거동 진동은 물론 고차진동해석에 좋은 해석 결과를 보여 주었다. 이 방법의 타당성과 계산 효율성을 수치예를 통해 입증하였다.

• International Journal of Naval Architecture and Ocean Engineering
• /
• 제7권1호
• /
• pp.128-141
• /
• 2015

Independent Component Analysis (ICA), one of the blind source separation methods, can be applied for extracting unknown source signals only from received signals. This is accomplished by finding statistical independence of signal mixtures and has been successfully applied to myriad fields such as medical science, image processing, and numerous others. Nevertheless, there are inherent problems that have been reported when using this technique: instability and invalid ordering of separated signals, particularly when using a conventional ICA technique in vibratory source signal identification of complex structures. In this study, a simple iterative algorithm of the conventional ICA has been proposed to mitigate these problems. The proposed method to extract more stable source signals having valid order includes an iterative and reordering process of extracted mixing matrix to reconstruct finally converged source signals, referring to the magnitudes of correlation coefficients between the intermediately separated signals and the signals measured on or nearby sources. In order to review the problems of the conventional ICA technique and to validate the proposed method, numerical analyses have been carried out for a virtual response model and a 30 m class submarine model. Moreover, in order to investigate applicability of the proposed method to real problem of complex structure, an experiment has been carried out for a scaled submarine mockup. The results show that the proposed method could resolve the inherent problems of a conventional ICA technique.