• Journal of the Korean Wood Science and Technology
• /
• 제19권1호
• /
• pp.71-80
• /
• 1991

This study was carried out to investigate replaceable species with the conventional sounding board sitka spruce. by comparing the dynamic properties such as density, dynamic Young's modulus and internal friction Dynamic Young's modulus. internal friction of longitudinal and radial direction measured in free mass-free boundary condition for facile vibration analysis and measured by forced vibration method. Dynamical properties of four species were measured on squared plate specimen that the four edges were hung vertically by threads and driven magnetically through an iron piece glued on the specimen, by the use of condenser microphone as vibration transducer, and analyzed by FFT analyzer. The results obtained were as follows: 1. Chaldni method using aluminum powder was proper to identify the vibration mode in the plate vibration and it was possible to verify the resornance mode. 2. It was considered that it was necessary to investigate the influence of adhesive part on the plate vibration when the sounding board was made by two or three small board adhesion. 3. It was considered that plate vibration method, which was a superior to the vibration test of beam, was suitable for selecting suounding board because dynamic Young's modulus and internal friction show different order according to longitudinal and radial direction. 4. Paulownia tomentosa Thunb.) Steudel has been considered to be replaceable species with sitka spruce because it has high dynamic Young's modulus compared with low density, low internal friction, and K value of Paulownia tomentosa (Thunb.) Steudel is greater than that of sitka spruce.

• 한국재료학회:학술대회논문집
• /
• 한국재료학회 2011년도 추계학술발표대회
• /
• pp.17.2-17.2
• /
• 2011

Double-walled carbon nanotubes (DWCNTs) were grown with vertical alignment on a Si wafer by using catalytic thermal chemical vapor deposition. This study investigated the effect of pre-annealing time of catalyst on the types of CNTs grown on the substrate. The catalyst layer is usually evolved into discretely distributed nanoparticles during the annealing and initial growth of CNTs. The 0.5-nm-thick Fe served as a catalyst, underneath which Al was coated as a catalyst support as well as a diffusion barrier on the Si substrate. Both the catalyst and support layers were coated by using thermal evaporation. CNTs were synthesized for 10 min by flowing 60 sccm of Ar and 60 sccm of H2 as a carrier gas and 20 sccm of C2H2 as a feedstock at 95 torr and $750^{\circ}C$. In this study, the catalyst and support layers were subject to annealing for 0~420 sec. As-grown CNTs were characterized by using field emission scanning electron microscopy, high resolution transmission electron microscopy, Raman spectroscopy, and atomic force microscopy. The annealing for 90~300 sec caused the growth of DWCNTs as high as ~670 ${\mu}m$ for 10 min while below 90 sec and over 420 sec 300~830 ${\mu}m$-thick triple and multiwalled CNTs occurred, respectively. Several radial breathing mode (RBM) peaks in the Raman spectra were observed at the Raman shifts of 112~191 cm-1, implying the presence of DWCNTs, TWCNTs, MWCNTs with the tube diameters 3.4, 4.0, 6.5 nm, respectively. The maximum ratio of DWCNTs was observed to be ~85% at the annealing time of 180 sec. The Raman spectra of the as-grown DWCNTs showed low G/D peak intensity ratios, indicating their low defect concentrations. As increasing the annealing time, the catalyst layer seemed to be granulated, and then grown to particles with larger sizes but fewer numbers by Ostwald ripening.

• 한국항공우주학회지
• /
• 제41권8호
• /
• pp.665-672
• /
• 2013

적층된 복합재 구조물의 강도와 강성 저하를 발생시키는 중요원인 중의 하나는 복합재 층 사이에 발생하는 층간 분리이다. 적용되는 대부분의 복합재 구조물은 어느 정도 곡률을 가지고 있다. 만약 굽은 복합재 구조물이 굽힘 하중을 받게 되면 평평하게 되려는 현상 때문에 두께 방향의 수직응력이 발생하게 되며, 최대 응력이 발생되는 곳에서 층간 분리가 발생한다. 본 논문에서는 굽은 복합적층 보의 반경방향 응력을 결정하는 방법을 설명하고, 층간 분리 응력에 미치는 적층 순서의 영향을 검토하였다. 그리고 층간분리 응력의 크기와 위치를 이론적인 해와 유한요소 방법을 이용하여 해석하고 비교하였다.

• 한국자기학회지
• /
• 제13권2호
• /
• pp.47-52
• /
• 2003

DC 마그네트론 스파터법과 RLSA(Radial Line Slot Antenna)을 이용한 마이크로파 여기 프라즈마를 이용하여 Ta/Cu/Ta/NiFe/Cu/Mn$_{75}$Ir$_{25}$/ $Co_{70}$Fe$_{30}$/Al-oxide 구조의 접합을 제조한 후, contact-mode AM(Atomic Force Microscope)을 이용하여 Al 산화막의 국소전도 특성의 평가를 수행하였다. AFM 동시전류측정으로부터, 얻어지는 표면상과 전류상은 대응하지 않는다. 국소 전류-전압(I-V)의 측정 결과, 전류상은 절연층의 barrier height의 분포를 나타내고 있다는 것을 알았다.다.다.

• 자동차안전학회지
• /
• 제8권1호
• /
• pp.26-30
• /
• 2016

The steel road wheel on ventilation holes was cracked in the vehicle durability test. But the component durability test by uni-axial, CFT(Cornering Fatigue Test) and RFT(Radial Fatigue Test) had been satisfied. That is, the uni-axial component test could not forecast the crack of vehicle. Therefore this study developed the bi-axial test mode to reflect a vehicle condition(to reflect both vertical and lateral force simultaneously) based on real load data which was measured in Europe and China and developed CAE simulation too. It reproduced the cracks same as vehicle's and verified by bi-axial test machine in the LBF(Fraunhofer Institute for Structural Durability and System Reliability) durability research center in Germany. Finally this the durability CAE simulation by using HMC(Hyundai Motor Company)'s the bi-axial test mode predicts feasibly the steel wheel's durability performance before vehicle durability test.

• 한국추진공학회:학술대회논문집
• /
• 한국추진공학회 2008년도 제30회 춘계학술대회논문집
• /
• pp.125-128
• /
• 2008

이중모드 위상도플러속도계(Dual-mode Phase Doppler Anemometry, DPDA)를 이용하여 소형 액체 로켓엔진 인젝터 분무의 미립화 특성을 고찰하였다. 분무액적의 반경방향 이동에 따른 속도, 크기, 수밀도, 부피플럭스 등을 다양한 분사압력에서 측정하여 인젝터 분무의 공간분포 특성을 규명한다. 분사 압력이 증가함에 따라 분무액적의 속도, 난류강도, 수밀도, 그리고 부피플럭스는 증가하지만, 산술평균 직경($D_{10}$)과 분무액적의 증발율에 대한 척도인 Sauter Mean Diameter($D_{32}$)로 표현되는 액적의 크기는 감소하였다. 또, 속도와 부피플럭스는 Sauter 평균직경(Sauter mean diameter, SMD)에 비례하는 것을 알 수 있었다.

• 대한기계학회논문집A
• /
• 제34권7호
• /
• pp.851-858
• /
• 2010

함수구배재료에서 구배방향을 따라 전파하는 천이모드 III 균열에 대한 일반적인 탄성해를 근접해법으로 얻었다. 함수구배재료의 전단계수 및 밀도는 구배방향을 따라 지수형적으로 변화한다고 가정하였다. 균열선단의 응력과 변위장은 응력확대계수 및 균열선단속도의 시간변화율에 의존하는 계수들을 갖는 방사상 좌표계의 누승으로 얻었다. 비균질성과 천이계수들이 응력 및 변위장의 고차항에 미치는 영향에 대하여 토론하였다.

• 로봇학회논문지
• /
• 제3권3호
• /
• pp.186-193
• /
• 2008

We propose a novel real-time obstacle avoidance method for rescue robots. This method, named the ELA(Emergency Level Around), permits the detection of unknown obstacles and avoids collisions while simultaneously steering the mobile robot toward safe position. In the ELA, we consider two sensor modules, PSD(Position Sensitive Detector) infrared sensors taking charge of obstacle detection in short distance and LMS(Laser Measurement System) in long distance respectively. Hence if a robot recognizes an obstacle ahead by PSD infrared sensors first, and judges impossibility to overcome the obstacle based on driving mode decision process, the order of priority is transferred to LMS which collects data of radial distance centered on the robot to avoid the confronted obstacle. After gathering radial information, the ELA algorithm estimates emergency level around a robot and generates a polar histogram based on the emergency level to judge where the optimal free space is. Finally, steering angle is determined to guarantee rotation to randomly direction as well as robot width for safe avoidance. Simulation results from wandering in closed local area which includes various obstacles and different conditions demonstrate the power of the ELA.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제10권6호
• /
• pp.2801-2816
• /
• 2016

Owing to their low scalability, weak support on big data, insufficient data collaborative analysis and inadequate situational awareness, the traditional methods fail to meet the needs of the security data analysis. This paper proposes visualization methods to fuse the multi-source security data and grasp the network situation. Firstly, data sources are classified at their collection positions, with the objects of security data taken from three different layers. Secondly, the Heatmap is adopted to show host status; the Treemap is used to visualize Netflow logs; and the radial Node-link diagram is employed to express IPS logs. Finally, the Labeled Treemap is invented to make a fusion at data-level and the Time-series features are extracted to fuse data at feature-level. The comparative analyses with the prize-winning works prove this method enjoying substantial advantages for network analysts to facilitate data feature fusion, better understand network security situation with a unified, convenient and accurate mode.

• 천문학회보
• /
• 제40권2호
• /
• pp.33.3-34
• /
• 2015

We present the spectroscopic study of the globular clusters (GCs) in the massive elliptical galaxy M86 in the Virgo galaxy cluster. Using the spectra obtained from the Multi-Object Spectroscopy (MOS) mode of Faint Object Camera and Spectrograph (FOCAS) on the Subaru Telescope, we measure the radial velocities for 56 GCs in M86. The mean velocity of the GCs is derived to be $<v_p>=-335{\pm}41km/s$, which is different from the velocity of the M86 nucleus ($<v_{gal}>=-224{\pm}5km/s$) within ${\sim}2.5{\sigma}$. The mean velocity ($<v_p>=-342{\pm}60km/s$) of 33 blue GCs in M86 is similar to that ($<v_p>=-314{\pm}71km/s$) of 23 red GCs. We also derive the mean velocities of the GC systems in other 16 nearby early-type galaxies (ETGs) from the radial velocity data in the literature. The mean value of the differences between the mean velocity of the GC systems in each galaxy and the nucleus velocity of their host galaxies, is almost zero except the M86 GC system. But the scatter of the differences in the blue GC system is larger than that in the red GC system. We will discuss these results in the context of GC formation in ETGs.