• 한국항공우주학회지
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• 제48권1호
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• pp.1-11
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• 2020

항공기에서 발생한 후류의 거동은 항공기의 성능과 비행안정성에 큰 영향을 미친다. 본 연구에서는 푸리에-스펙트럴법을 사용하여 근접 편대비행을 하고 있는 항공기 날개 후류 거동에 관하여 연구하였다. 초기와의 순환강도, 상대위치 등에 따라 와들의 거동이 복잡한 양상으로 나타났다. 와의 순환강도 값이 큰 경우 와들의 이동이 크게 나타났다. 초기에는 가까이 위치한 와의 영향을 받아 이동하지만 이동하는 과정에서 다른 와와 가깝게 되면 새로운 경로를 형성하였다. 점성이 클수록 와의 반경이 증가하여 와 반경 근처로 새롭게 진입하는 와와 상호작용이 강해진다. 향후 항공기가 이착륙 시에 발생하는 지면 효과를 고려한 후류 거동 해석 연구를 수행하고자 한다.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2002년도 proceedings of the second asia international conference on tribology
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• pp.425-426
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• 2002

Lineal and angular movements of many engine components make the lubricant absorb air and the aerated lubricant greatly influences the clearance performance of contacting behaviors of engine components such as big-end bearing, cam and tappet, etc. This study investigates the behaviors of aerated lubricant in the gap between con-rod bearing and proceeding which is one of the most frictional energy consuming components in the engine. Our assumption for the analysis of aerated lubricant film is that the film formation is influenced by the two major factors. One is the density characteristics of the lubricant due to the volume change of lubricant by absorbing the bubbles and the other is the viscosity characteristics of the lubricant due to the surface tension of the bubble in the lubricant. In our investigation, it is found that these two major factors surprisingly increase the load capacity in certain ranges of bubble sizes and densities. Frictional forces are also influenced by the aerated bubble size and density, which eventually enlarge the shear resistance due the surface tension, Modified Reynolds' equation is developed for the computation of fluid film pressure with the effects of aeration ratio under the dynamic loading condition. From the calculated load capacity by solving modified Reynolds' equation, proceeding locus is computed with Mobility method at each time step.

• Bulletin of the Korean Chemical Society
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• 제33권8호
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• pp.2489-2493
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• 2012

A new fluorescent system (acridine/RTIL hybrid gel) confined in the 3D micro-structure of a poly(lactic acid) membrane were prepared from 1-butyl-3-methylimidazolium-based ionic liquids ([bmim]X (X = $SbF_6$, $NTf_2$, Cl); RTILs), poly(lactic acid) (PLA), and acridine via the sol-gel route. SEM images showed that, in the presence of [bmim]$SbF_6$ and [bmim]$NTf_2$, 3D-ly paticulated structures were created inside the PLA membranes and acridine/RTIL hybrid gels were confined in gabs of particulates. However, the use of [bmim]Cl induced the formation of a 3D-ly porous structure containing the hybrid gel of acridine/[bmimCl in the micropores. The three fluorescent systems exhibited different fluorescence behaviors (fluorescence maximum and intensity) depending on the C2-H acidity scale of the RTILs (or their anion type). Acridine gels hybridized with [bmim]$SbF_6$ and [bmim]$NTf_2$ showed blue fluorescence with relative high intensity, whereas the hybrid gel with [bmim]Cl exhibited almost no fluorescence under dry conditions. However, the acridine/[bmim]Cl hybrid system in the micro-porous PLA membrane started to emit fluorescent light under humid conditions and showed a possible response, indicating that it could be applied as a humidity sensor.

• 한국자동차공학회논문집
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• 제9권5호
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• pp.96-104
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• 2001

The present study experimentally investigates the concentration distribution of liquid and vapor phase with different injection timings in the in-cylinder flow field of a optically accessible engine. The conventional MPI, DOHC engine was modified into DI gasoline engine. The images of liquid and vapor phases in the motoring engine were captured by using exciplex fluorescence method. Dopants used in this study were 2% fluorobenzene and 9% DEMA(diethyl-methyl-amino) in 89% solution of hexane by volume respectively. Two dimensional spray fluorescence images of liquid and vapor phases were acquired to analyze spray behaviors and fuel distribution in the in-cylinder flow field. Measurements were carried out fur four different injection timings, namely BTDC 270$^{\circ}$, 180$^{\circ}$, 90$^{\circ}$, and 50$^{\circ}$. Experimental results indicate that behaviors and distribution of vapor phase were largely affected by in-cylinder tumble flow, and mixture formation process was also greatly affected by in-cylinder flow at early injection mode and by ambient pressure at late injection mode.

• Korea-Australia Rheology Journal
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• 제16권3호
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• pp.117-128
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• 2004

The effect of molecular parameters on the steady vortex behaviors in the inertial viscoelastic flow past a cylinder has been investigated. FENE-CR model was considered as a constitutive equation. A recently developed iterative solution method (Kim et al., (in press)) was found to be successfully applicable to the computation of inertial viscoelastic flows. The high-resolution computations were carried out to understand the detailed flow behaviors based on the efficient iterative solution method armed with ILU(0) type pre-conditioner and BiCGSTAB method. The discrete elastic viscous split stress-G/streamline upwind Petrov Galerkin (DEVSS-G/SUPG) formulation was adopted as a stabilization method. The vortex size decreased as elasticity increases. However, the vortex enhancement was also observed in the case of large extensibility, which means that the vortex behavior is strongly dependent upon the material parameters. The longitudinal gradient of normal stress was found to retard the formation of vortex, whereas the extensional viscosity played a role in the vortex enhancement. The present results are expected to be helpful for understanding the inertial vortex dynamics of viscoelastic fluids in the flow past a confined cylinder.

• 한국실내디자인학회:학술대회논문집
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• 한국실내디자인학회 2007년도 춘계학술대회 논문집
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• pp.181-187
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• 2007

The world is changing drastically by digital information technology and ubiquitous networking. Meanwhile, with the demographic avalanche, South Korea officially became an 'ultra-aging society' in 2026. Simultaneously, this demographic change will also stimulate a cultural climate which facilitates the formation and dissemination of 'slow culture' from the existent urban 'fast culture' which has been weakening the retirement living. One of the fundamental connections with the slow movement appears in the cooking and dining area. With this point of view, this study aims to identify the needs and behaviors of the elderly in current restaurants and a digitally planned multi-purpose one for the future. Small group workshop was employed for this study. In order to elicit detailed information from the elderly group members, scenarios were developed. A group facilitator kept the discussion on track by asking a series of open-ended questions meant to stimulate discussion. As the results, it was revealed that the elderly were interested in digitally planned restaurant which provides one-stop service including entertainment activities, health related contents and socializing with family. Even though this study took restaurant scenarios, the ideas in them also provide holistic perspectives on the direction of marketing and planning strategies on various future environments and services.

• 한국재료학회지
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• 제13권5호
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• pp.323-327
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• 2003

Properties of nanoparticles synthesized during gas phase reaction were studied in terms of particle behaviors using real-time particle characterization method. For this study, $TiO_2$ nanoparticles were synthesized in the chemical vapor condensation process(CVC) and their in-situ measurement of particle formation and particle size distribution was performed by scanning mobility particle sizer(SMPS). As a result, particle behaviors in the CVC reactor were affected by both of number concentration and thermal coagulation, simultaneously. Particularly, growth and agglomeration between nanoparticles followed two different ways of dominances from coagulations by increase of number concentration and sintering effect by increased temperature.

• 대한기계학회논문집A
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• 제27권10호
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• pp.1686-1694
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• 2003

The foam-filled tube beams can be used for the front rail and firewall structures to absorb impact energy during frontal or side collision of vehicles. In the case of side collision where bending is involved in the crushing mechanism, the foam filler would be effective in maintaining progressive crushing of the thin-walled structures so that much impact energy could be absorbed. In this study, bending behaviors of the closed-cell-aluminum-alloy-foam-filled stainless steel tube were investigated. The various foam-filled specimens including piecewise fillers were prepared and tested. The aluminum-alloy-foam filling offered the significant increase of bending resistance. Their suppression of the inward fold formation at the compression flange as well as the multiple propagating folds led to the increase of load carrying capacity of specimens. Moreover, the piecewise foams would provide the easier way to fill the thin-walled shell structures without the drawback of strength.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2003년도 제20회 춘계학술대회 논문집
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• pp.87-90
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• 2003

압축성 유동장의 주된 특징은 유동장의 형성과정에 의존한다는 것은 잘 알려져 있다. 본 연구의 목적은 비평형 응축을 수반하는 초음속 제트유동장의 발달에 미치는 제트의 시간이력을 조사하는 것이다. 특히 초음속 습공기 제트에서 마하디스크 직경과 위치의 거동이 노즐압력비와 초기 상대습도의 항으로 소개된다. 대기흡입식 풍동설비에 장착된 노즐의 출구에서 부족팽창된 습공기 제트를 얻기 위해 노즐의 압력비와 초기상대습도를 변화시켰다. 마하디스크의 직경은 동일한 압력비에서 상대습도가 증가함에 따라 증가하지만, 그 위치는 상류로 이동하는 것으로 나타났다. 또한 노즐의 작동압력비가 증가하는 경우의 마하디스크 직경과 발생위치가 감소하는 경우보다 더 크다.

• Nuclear Engineering and Technology
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• 제44권8호
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• pp.945-952
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• 2012

The sorption of selenium ions onto iron and iron compounds as a disposal container material and its corrosion products, and onto bentonite as a buffer material, was studied to understand the behaviors of selenium in a waste repository. Selenite was sorbed onto commercial magnetite very well in solutions at around pH 9, but silicate hindered their sorption onto both magnetite and ferrite. Unlike commercial magnetite and ferrite, flesh synthesized magnetite, green rust and iron greatly decreased selenium concentration even in a silicate solution. These results might be due to the formation of precipitates, or the sorption of selenide or selenite onto an iron surface at below Eh= -0.2 V. Red-colored Se(cr) was observed on the surface of a reaction bottle containing iron powder added into a selenite solution. Silicate influences on the sorption onto magnetite and iron for selenide are the same as those for selenite. Even though bentonite adsorbed a slight amount of selenite, the sorption cannot be ignored in the waste repository since a very large quantity of bentonite is used.