• 한국분말재료학회지
• /
• 제17권1호
• /
• pp.13-22
• /
• 2010

The unique features of spark plasma sintering process are the possibilities of a very fast heating rate and a short holding time to obtain fully dense materials. $\beta$-SiC powder with 0, 2, 6, 10 wt% of $\alpha$-SiC particles (seeds) and 4 wt% of Al-B-C (sintering aids) were spark plasma sintered at $1700-1850^{\circ}C$ for 10 min. The heating rate, applied pressure and sintering atmosphere were kept at $100^{\circ}C/min$, 40 MPa and a flowing Ar gas (500 CC/min). Microstructural development of SiC as function of seed content and temperature during spark plasma sintering was investigated quantitatively and statistically using image analysis. Quantitative image analyses on the sintered SiC ceramics were conducted on the grain size, aspect ratio and grain size distribution of SiC. The microstructure of SiC sintered up to $1700^{\circ}C$ consisted of equiaxed grains. In contrast, the growth of large elongated SiC grains in small matrix grains was shown in sintered bodies at $1750^{\circ}C$ and the plate-like grains interlocking microstructure had been developed by increasing sintering temperature. The introduction of $\alpha$-SiC seeds into $\beta$-SiC accelerated the grain growth of elongated grains during sintering, resulting in the plate-like grains interlocking microstructure. In the $\alpha$-SiC seeds added in $\beta$-SiC, the rate of grain growth decreased with $\alpha$-SiC seed content, however, bulk density and aspect ratio of grains in sintered body increased.

• 감성과학
• /
• 제7권2호
• /
• pp.107-121
• /
• 2004

본 연구에서는 생활용품이면서 의복과 함께 생활필수품인 신발을 대상으로 감성만족도 요소의 추출과 분류체계를 개발하였다. 제화류의 감성만족도 요소는 감각성(sense), 적합성(fitness), 묘사성(description), 평가성(evaluation), 선호성(attitude)의 5개 그룹으로 구성되었으며, 각 그룹에는 형태감, 볼륨감 등 29개 요소가 포함되었다. 이들 중에서 일반 제화의 평가에 적합한 요소들로 형태감, 볼륨감, 균형감, 색감, 인체적합성, 안락성, 안정성, 여유성, 개념적 이미지, 품위감, 고급감, 조화감, 견고성, 주목성, 간편성, 신뢰성, 선호도, 수용도, 만족성, 매력성 등 20개의 요소들을 선택하여 이들에 대한 평가양식을 개발하였다. 본 연구에서 제시한 감성만족도 요소는 제화류의 고객만족도 평가 모델링에서 종속변수로 활용될 수 있다.

• International Journal of Aeronautical and Space Sciences
• /
• 제13권1호
• /
• pp.117-125
• /
• 2012

This paper presented the design of SRPS, ground function test, and the deployment test on a high speed taxi of KC-100 airplane. KAI has developed a spin recovery system in collaboration with Airborne Systems for KC-100 general aviation airplane. Spin mode analysis, rotary balance and forced oscillation tests were performed to obtain the rotational, dynamic derivatives in the preliminary design phase. Prior to the detailed design process of SRPS, approximations for initial estimation of design parameters- fineness ratio, parachute porosity, parachute canopy filling time, and deployment method- were considered. They were done based on the analytical disciplines such as aerodynamics, structures, and stability & control. SRPS consists of parachute, tractor rocket assembly for deployment, attach release mechanism (ARM) and cockpit control system. Before the installation of SRPS in KC-100 airplane, all the control functions of this system were demonstrated by using SBTB(System Breakout Test Box) in the laboratory. SBTB was used to confirm if it can detect faults, and simulate the firing of pyrotechnic devices that control the deployment and jettison of SRPS. Once confirmed normal operation of SRPS, deployment and jettison of parachute on the high speed taxiing were performed.

• 한국정보통신학회논문지
• /
• 제17권5호
• /
• pp.1138-1144
• /
• 2013

최대주기를 갖는 수열들의 상호상관함수에 대한 연구는 수십년간 이루어져 왔다. 본 논문에서는 n=2m을 만족하고 최대주기 $2^n-1$을 가지면서 Niho type의 데시메이션 $d=2^{m-2}(2^m+3)$에 대하여 비선형수열$S_a^r(t)=Tr_1^m\{[Tr_m^n(a{\alpha}^t+{\alpha}^{dt})]^r\}$의 상호상관함수 값을 구한다. 특히, $d{\equiv}1(mod\;2^m-1)$을 만족하는 d를 Niho type의 데시메이션 이라고 한다. 그리고 위상이동차 ${\tau}=(2^m+1)k(0{\leq}k{\leq}2^m-2)$인 경우에 대하여 $S_a^r(t)$의 상호상관함수 값의 분포를 분석하고 실험 결과를 제시한다.

• 한국운동역학회지
• /
• 제24권4호
• /
• pp.375-383
• /
• 2014

The purpose of this study was to assess the inter-segmental trunk motion during which multi-segmental movements of the spinal column was designed to interpret the effect of segmentation on the total measured spine motion. Also it analyzed the relative motion at three types of the spine models in drop landing. A secondary goal was to determine the intrinsic algorithmic errors of spine motion and the usefulness of such an approach as a tool to assess spinal motions. College students in the soccer team were selected the ten males with no history of spine symptoms or injuries. Each subject was given a fifteen minute adaptation period of drop landing on the 30cm height box. Inter-segmental spine motion were collected Vicon Motion Capture System (250 Hz) and synchronized with GRF data (1000 Hz). The result shows that Model III has a more increased range of motion (ROM) than Model I and Model II. And the Lagrange energy has significant difference of at E3 and E4 (p<.05). This study can be concluded that there are differences in the three models of algorithm during the phase of load absorption. Especially, Model III shows proper spine motion for the inter-segmental joint motion with the interaction effects using the seven segments. Model III shows more proper observed values about dynamic equilibrium than Model I & Model II. The findings have shown that the dynamic stability strategy of Model III toward multi-directional spinal motion supports for better function of the inter-segmental motor-control than the Model I and Model II.

• 한국광학회지
• /
• 제16권4호
• /
• pp.361-365
• /
• 2005

표면거칠기가 큰 가공면의 표면형상을 비접촉 고속 측정 하기 위해 고안된 점광원 절대간섭계는 점광원의 위치가 시스템 변수로 정의된다. 시스템 오차인 점광원의 위치 오차가 측정 결과에 미치는 영향을 분석하며, 이를 보정하기 위해 CCD 카메라를 이용한 보정법을 제안한다. 제안된 방법을 검증하기 위해 기준면을 측정하여 측정 정밀도의 향상을 확인하며, 이를 거친 표면형상의 특징을 가진 칩모듈 측정에 적용하였다. 측정 결과 기존의 촉침식 측정기와 $50mm{\time}50mm$의 영역에서 $9.8{\mu}m$의 측정 차이를 보임을 확인하였다.

• Bulletin of the Korean Chemical Society
• /
• 제15권9호
• /
• pp.713-718
• /
• 1994

Manganese-incorporated neodymium oxide systems with a variety of Mn mol% were prepared to investigate the effect of doping on the electrical properties of neodymium oxide. XRD, XPS, SEM, DSC, and TG techniques were used to analyze the specimens. The systems containing 2, 5, 8, and 10 mol% Mn were found to be solid solutions by X-ray diffraction analysis and the lattice parameters were obtained for the single-phase hexagonal structure by the Nelson-Riley method. The lattice parameters, a and c, decreased with increasing Mn mol%. Scanning electron photomicrographs of the specimens showed that the grain size decreased with increasing Mn mol%. The curves of log conductivity plotted as a function of 1/T in the temperature range from 500 to 1000$^{\circ}C$ at $PO_2$'s of $10^{-5}$ to $10^{-1}$ atm for the specimens were divided into high-and low-temperature regions with inflection points near 820-890$^{\circ}C$. The activation energies obtained from the slopes were 0.53-0.87 eV for low-temperature region and 1.40-1.91 eV for high-temperature region. The electrical conductivities increased with increasing Mn mol% and $PO_2$, indicating that all the specimens were p-type semiconductors. At $PO_2$'s below $10^{-3}$ atm, the electrical conductivity was affected by the chemisorption of oxygen molecule in the temperature range of 660 to 850$^{\circ}C$. It is suggested that electron holes generated by oxygen incorporation into the oxide are charge carriers for the electrical conduction in the high-temperature region and the system includes ionic conduction owing to the diffusion of oxygen atoms in the low-temperature region.

• Advances in aircraft and spacecraft science
• /
• 제4권2호
• /
• pp.145-167
• /
• 2017

The presented paper gives an overview of several projects addressing the experimental characterization and control of the buffet phenomenon on 3D turbulent wings in transonic flow conditions. This aerodynamic instability induces strong wall pressure fluctuations and therefore limits flight domain. Consequently, to enlarge the latter but also to provide more flexibility during the design phase, it is interesting to try to delay the buffet onset. This paper summarizes the main investigations leading to the achievement of open and closed-loop buffet control and its experimental demonstration. Several wind tunnel tests campaigns, performed on a 3D half wing/fuselage body, enabled to characterize the buffet aerodynamic instability and to study the efficiency of innovative fluidic control devices designed and manufactured by ONERA. The analysis of the open-loop databases demonstrated the effects on the usual buffet characteristics, especially on the shock location and the separation areas on the wing suction side. Using these results, a closed-loop control methodology based on a quasi-steady approach was defined and several architectures were tested for various parameters such as the input signal, the objective function, the tuning of the feedback gain. All closed-loop methods were implemented on a dSPACE device able to estimate in real time the fluidic actuators command calculated mainly from the unsteady pressure sensors data. The efficiency of delaying the buffet onset or limiting its effects was demonstrated using the quasi-steady closed-loop approach and tested in both research and industrial wind tunnel environments.

• Wind and Structures
• /
• 제28권1호
• /
• pp.31-47
• /
• 2019

The accurate prediction of snow distributions under the wind action on roofs plays an important role in designing structures in civil engineering in regions with heavy snowfall. Affected by some factors such as building shapes, sizes and layouts, the snow drifting on roofs shows more three-dimensional characteristics. Thus, the research on three-dimensional snow distribution is needed. Firstly, four groups of stepped flat roofs are designed, of which the width-height ratio is 3, 4, 5 and 6. Silica sand with average radius of 0.1 mm is used to model the snow particles and then the wind tunnel test of snow drifting on stepped flat roofs is carried out. 3D scanning is used to obtain the snow distribution after the test is finished and the mean mass transport rate is calculated. Next, the wind velocity and duration is determined for numerical simulations based on similarity criteria. The adaptive-mesh method based on radial basis function (RBF) interpolation is used to simulate the dynamic change of snow phase boundary on lower roofs and then a time-marching analysis of steady snow drifting is conducted. The overall trend of numerical results are generally consistent with the wind tunnel tests and field measurements, which validate the accuracy of the numerical simulation. The combination between the wind tunnel test and CFD simulation for three-dimensional typical roofs can provide certain reference to the prediction of the distribution of snow loads on typical roofs.

• Journal of Nutrition and Health
• /
• 제53권6호
• /
• pp.563-569
• /
• 2020

Purpose: The vascular smooth muscle cells (VSMCs) in mature animals have implicated to play a major role in the progression of cardiovascular diseases such as atherosclerosis. This study aimed at optimizing the protocol in culturing primary VSMCs (pVSMCs) from rat thoracic aorta and investigating the effect of cellular zinc (Zn) deficiency on cell proliferation of the isolated pVSMCs. Methods: The thoracic aorta from 7-month-old Sprague Dawley rats was isolated, minced and digested by the enzymatic process of collagenase I and elastase, and then inoculated with the culture Dulbecco Modified Eagle Medium (DMEM) at 37℃ in an incubator. The primary cell culture morphology was observed using phase-contrast microscopy and cellular Zn was depleted using Chelex-100 resin (extracellular zinc depletion only) or 3 µM N,N,N',N'-tetrakis(2-pyridinylmethyl)-1,2-ethanediamine (TPEN) (extracellular and intracellular zinc depletion). Western blot analysis was used for the detection of SM22α and calponin as smooth muscle cell marker proteins and von Willebrand factor as endothelial cell marker protein to detect the culture purity. Cell proliferation by Zn depletion (1 day) was measured by MTT assay. Results: A primary culture protocol for pVSMCs from rat thoracic aorta was developed and optimized. Isolated cultures exhibited hill and valley morphology as the major characteristics of pVSMCs and expressed the smooth muscle cell protein markers, SM22α and calponin, while the endothelial marker von Willebrand factor was hardly detected. Zn deprivation for 1 day culture decreased rat primary vascular smooth muscle cell proliferation and this pattern was more prominent under severe Zn depletion (3 µM TPEN), while less prominent under mild Zn depletion (Chelexing). Conclusion: Our results suggest that cellular Zn deprivation decreased pVSMC proliferation and this may be involved in phenotypic modulation of pVSMC in the aorta.