• 수산해양기술연구
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• 제28권2호
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• pp.164-170
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• 1992

In order to understand and explain the spary combustion, it was necessary to understand the disintegration mechanisms of liquid jet. To understand the disintegration mechanisms of liquid jet, the disintegration phenomena and uniform droplet production regions of testing liquid jet was investigated by means of longitudinally vibration capillary nozzle, which was injected the testing liquids. The testing liquids were light oil and light oil and light oil blended with 25wt% fish oil (File fish oil, Sardine fish oil, Alaska pollac oil) The results can be summarized as follows: 1. The uniform droplet phenomena have been changed according to the frequency of capillary tube, the jet velocity and physical properties of testing oils. 2. Within the region of uniform droplet, Reynold number was increased as Weber number increases. 3. The lower limit of wave length in which uniform droplet was produced 0.8d which was lower than Rayleigh wave length 4. The light oil blended with file fish oil which has lower viscosity and surface tension had the widest uniform droplet production region on the frequency and velocity among testing oils. But light oil blended with sardine fish oil were similar with light oil in the uniform production region.

• 한국가시화정보학회지
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• 제13권1호
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• pp.49-53
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• 2015

Recently, researches for droplet impact phenomena have been faced a new phase in the direction of studying the effect of complex external conditions (e.g. wettability, temperature, morphology, electric field, etc.) for depth understanding and precise controlling in various applications. Hence, here we investigated the electrified droplet impact phenomena, because there were few quantitative researches for electrified droplet impact when we considering many real applications such as electrospray, electrohydrodynamic (EHD) jet printing. To observe interaction effect of surface charge between substrate and droplet simultaneously, micro-droplets with various Reynolds number (Re) and Weber number (We) were dripped on super-hydrophobic surface with existence and nonexistence of electrical surface charge. It shows three kinds of impact behaviors, fully bouncing, partial bouncing, and splashing with different We. Also, charged droplet bounced higher on electrically charged surface than on non-charged surface. Additionally, transition regions of three impact behaviors were classified quantitatively with water hammer pressure value, which means instant pressure inside droplet at the impact moment.

• 대한기계학회논문집B
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• 제26권1호
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• pp.45-54
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• 2002

The breakup phenomena of a vertical laminar jet issuing from capillary tubes in a quiescent ambient air are investigated using a forced vibration analysis of the surface wave. Using a linear approach to the transient jet velocity, an approximate solution fur the longitudinal motion of a vertical liquid jet is theoretically derived, thus performing an instability analysis by a vibration method. The damping term of this equation is nonlinear as it depends on dimensionless parameters, a Weber number, and an Ohnesorge number. The instability condition is determined based on whether the coefficient of the damping term is less than zero or not. Uniform drop formation is dependent on the vibration frequency fur the forced vibration case.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 1999년도 유체기계 연구개발 발표회 논문집
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• pp.301-308
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• 1999

The present study investigates numerically particle laden flow through compressor cascades and a rocket nozzle. Engines are affected by various particles which are suspending in the atmosphere. Especially in the case of aircraft aviating in volcanic, industrial and desert region including many particles, each components of engine system are damaged severely. That damage modes are erosion of compressor blading and rotor path components, partial or total blockage of cooling passage and engine control system degradation. Numerical prediction and experimental data, erosion rates are predicted for two materials - ceramic, soft metal - on compressor blade surface. Aluminum oxide ($Al_2O_3$) Particles included in solid rocket propelant make ablative the rocket motor nozzle and imped the expansion processes of propulsion. By the definition of particle deposition efficiency, characteristics of particles impaction are considered quantitatively Stoke number is defined over the various particle sizes and particle trajectories are treated by Lagrangian approach. Particle stability is considered by definition of Weber number in rocket nozzle and particle breakup and evaporation is simulated in a rocket nozzle.

• 한국식품저장유통학회지
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• 제30권4호
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• pp.589-601
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• 2023

Malaysian honey is rich in nutrients and bioactive compounds, which can be a healthy alternative to refined sugar in food production. However, liquid honey's viscous and sticky nature makes it unpreferable in industrial handling. This study, an atomization system coupled with vacuum drying to produce honey powders to overcome the problem. Three types of Malaysian honey, namely Acacia, Gelam, and Tualang, were encapsulated in Ca-alginate gel beads using the atomization system. The density viscosity, and surface tension of the honey-alginate solutions were measured, and the concentration of honey and alginate influenced the physical properties of the solutions. Honey-encapsulated gel beads in the size range of 2.16-2.92 mm were produced using the atomization system with the air-liquid mass flow rate ratios of 0.22-0.31, Weber number (We) of 112-545, and Ohnersorges number (Oh) of 0.35-10.46. Gel bead diameter can be predicted using a simple mathematical model. After vacuum drying, the honey gel powder produced was in the size range of 1.50-1.79 mm. Results showed that honey gel powders with good encapsulation efficiency and high honey loading could be produced using the atomization system and vacuum drying.

• 전자공학회논문지
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• 제52권2호
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• pp.141-147
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• 2015

디스플레이의 대비는 일반적으로 디스플레이 최대 밝기와 최소 밝기의 비율을 이용하여 나타낸다. 그러나 이와 같은 명암비는 인간 시각의 인지 특성을 고려하지 않고 디스플레이의 물리적 특성만을 고려했기 때문에 인지 대비와 일치 하지 않는다. 본 논문에서는 디스플레이 밝기 범위 내에서 인지적으로 구별 가능한 밝기를 고려한 대비 측정 방법을 제안한다. 먼저, 디스플레이의 인지 밝기 범위를 측정하기 위해 CIECAM02 색 공간에서 최대 밝기와 최소 밝기 사이의 길이를 계산한다. 다음으로, Weber-Fechner 법칙을 기반으로 하여 각 밝기에서 인지적으로 동일한 밝기 범위를 결정하고, 각 범위 내에 존재하는 색의 수를 계산한다. 마지막으로, 각각의 동일하게 인지되는 밝기 범위내의 색의 수와 인지적 대비 길이의 비율로 인지적으로 구별 가능한 밝기를 계산한다. 주관적 실험에서 제안한 방법은 이전의 인지 대비 측정법에 비해 주관적 인지 대비 실험 결과와 일치하는 결과를 보였다.

• 인지과학
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• 제24권3호
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• pp.271-300
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• 2013

사람과 동물은 수량(numerosity)의 대략적인 많고 적음에 대한 직관적 판단 능력을 가지고 태어난다. 이를 대략적 수 감각(이하, 수 감각, number sense)이라 한다. 수 감각은 오래 전부터 동물의 수렵, 채취, 사냥 및 생존에 필수적인 능력으로 진화된 것으로 추정된다. 선행 연구에 따르면, 수학 발달 장애를 가진 아동은 수 감각이 정상적인 아동에 비해 매우 둔감하다. 반대로, 수 감각이 민감한 사람들은 수학적 성취도가 더 높다. 이러한 결과는 생애 초기부터 발달하는 수 감각 표상의 정확도가 학령기 이후 숫자에 기반한 수학적 인지 발달의 근간이 된다는 가설을 뒷받침한다. 최근 연구들은 수 감각 훈련을 통해 수학 성취도의 향상과 수학 관련 뇌 기능의 변화를 가져올 수 있는지를 검증하고 있다. 한편, 수량은 불연속적인 양(discrete quantity)으로서 길이, 면적, 시간 등 연속적인 양(continuous quantity)과 밀접한 관계가 있을 것으로 기대할 수 있다. 이와 같은 관점에서 수, 시간, 공간 등 다양한 차원의 양적인 표상의 정보처리는 후측 두정엽(posterior parietal cortex), 특히 두정 내 고랑(intraparietal sulcus, IPS)에 위치한 공통의 뇌 기제(common brain mechanism)에 기반한다는 가설이 대두되었다. 이 가설을 검증하는 실험적 증거와 후속 연구의 방향을 소개한다.

• 한국전산유체공학회지
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• 제21권4호
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• pp.90-95
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• 2016

Leidenfrost drops with ellipsoidal shaping can control the bouncing height by adjusting the aspect ratio(AR) of the shape at the moment of impact. In this work, we focus on the effect of the AR and the impact Weber number(We) on the non-axisymmetrical spreading dynamics of the drop, which plays an important role in the control of bouncing. To understand the impact dynamics, the numerical simulation is conducted for the ellipsoidal drop impact upon the perfect non-wetting solid surface by using volume of fluid method, which shows the characteristics of the spreading behavior in each principal axis. As the AR increases, the drop has a high degree of the alignment into one principal axis, which leads to the consequent suppression of bouncing height with shape oscillation. As the We increases, the maximum spreading diameters in the principal axes both increase whereas the contact time on the solid surface rarely depends on the impact velocity at the same AR. The comprehensive understanding of the ellipsoidal drop impact upon non-wetting surface will provide the way to control of drop deposition in applications, such as surface cleaning and spray cooling.

• 한국자동차공학회논문집
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• 제16권2호
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• pp.87-92
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• 2008

The breakup processes and spray plume characteristics of liquid jets injected in subsonic air cross-flows were experimentally studied. The behaviors of column, penetration, breakup of plain liquid jet and droplet sizes, velocities have been studied in non-swirling cross-flow of air. Nozzle has a 1.0 mm diameter and Lid ratio=5. Experimental results indicate that the breakup point is delayed by increasing air momentum, the penetration decreases by increasing Weber number and the split angle is increased by increasing air velocity or decreasing injection velocity. SMD increases according as increasing height or decreases in accordance with increasing air velocity. This phenomenon is related to the momentum exchange between column waves and cross-flow stream. Droplet vector velocities were varied from 11.5 to 33 m/s. A higher-velocity region can be identified in down edge region at Z/d=40, 70 and 100. Lower-velocity region were observed on bottom position of the spray plume.

• 한국분무공학회지
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• 제5권2호
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• pp.53-60
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• 2000

An aerodynamically progressed model, which is called APTAB model. has been proposed for more accurate prediction of the deformation and breakup of a spray. Especially, the effects of the droplet deformation on the droplet aerodynamic external force are considered in this model, which was neglected in TAB model. It is found that the predicted droplet deformation using APTAB model shows better agreement with experimental data than those of other models for the droplets in both bag-type and shear-type breakup regimes. A new breakup criterion has been proposed to predict more reasonable breakup quantities, such as breakup deformation length, time and so on; i.e., it is defined that the breakup occurs when the internal liquid phase pressure of the deformed droplet at the equator is greater than that of the pole. The proposed breakup criterion shows more physical relationship between the degree of droplet deformation at breakup and the corresponding breakup Weber number as compared with the results with TAB and DDB models. Therefore, it provides better predictions of the experimental data than TAB and DDB models for the droplet deformation and time in both bag-type and shear-type breakup regimes.