• Journal of Korean Medical classics
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• v.21 no.1
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• pp.183-203
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• 2008

"Uihakdokseogi(醫學讀書記)" is a casual work which mentions Ujaekyeong(尤在涇)'s thoughts on various problems found through extensive studying or in practice. The book does not focus on a single topic, thus the spectrum of the work is broad and is filled with problems which would interest most medical professionals. The major contents of the first volume of "Uihakdokseogi(醫學讀書記)" include differences of view on health preservation, the Five Circuit Phases[五運] and Six Atmospheric Influences[六氣], diseases, and the "Naegyeong(內經)", mentions on errors in transcription , and the gap between certain contents in "Yeongchu(靈樞)" and "Somun(素問)". U[尤在涇] asserts that Eum and Yang(陰陽) in a human should be in harmony as is the Gi(氣) of the sky and earth[天地] is, and that one should live according to the Gi(氣) of the four seasons to live a healthy life. He does not vary largely from the context of other writers on the matter of the Five Circuit Phases [五運] and Six Atmospheric Influences[六氣], and focuses on the concepts of predominant Gi[主氣], guest Gi[客氣], corresponding years[天符] , correlating years[歲會], and Taeeul corresponding years[太乙天符]. He mentions causes, symptoms, and treatments of various diseases such as cough due to asthenia of the viscera, stagnation of Yang(陽), stagnation of Eum(陰), abscess of the stomach, hard abscess of the intestines, upper emaciation, edema of the limbs, inability to raise the limbs, broken thigh, turbid fluid, inversion of Gi(氣) flow, sudden onset of fainting with cold extremities, diarrhea due to disorder of Gi(氣), and malaria. U[尤在涇] also points out faults of "Classic of Acupuncture and Moxibustion[甲乙經]" in the understanding of "Naegyeong(內經)".

• Journal of Drive and Control
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• v.11 no.2
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• pp.30-35
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• 2014

The pumps of electro-hydrostatic actuators operate most frequently in boundary lubrication speed range, as they compensate for the position control errors as a control element. When conventional swash plate type piston pumps are applied to electro-hydrostatic actuators, the frictional power losses as well as the wear rate of sliding components, such as piston shoes can increase drastically under the boundary friction condition. In this paper, the power losses of the piston shoes were investigated which were engendered by a frictional solid-to-solid contact and leakage flow rate of their hydrostatic bearing. In order to reduce them, DLC-coating was applied to the swash plate and the ball joint of pistons along with its effects were demonstrated. In addition, it was also shown that the wear rate of the piston shoes could be markedly reduced using the DLC-coated swash plate.

• Journal of Aerospace System Engineering
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• v.13 no.5
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• pp.32-38
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• 2019

The flying wing configuration with high sweep angles and rounded leading edge represent a complex flow of structures by the leading edge vortex. For control of the tailless flying wing configuration with unstable directional stability, flaperon is used. In this study, we conducted numerical simulations for a non-slender flying wing configuration with a rounded leading edge and analyzed the effect of the sideslip angle and flaperon. Through aerodynamic coefficient analysis, it was found that the effect of AoS on lift and drag coefficient was minimal and the side force and moment coefficient were markedly influenced by AoS. As the sideslip angle increased, the pitch break, which is related to the pitching moment coefficient, was delayed. Through stability analysis, the directional and lateral static stability of the flying wing configuration were increased by flaperon. Also, the structure and behavior of the leading edge vortex were analyzed by observing the contour of the pressure coefficient and the skin friction line.

• Journal of the Korean Society of Propulsion Engineers
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• v.14 no.4
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• pp.1-9
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• 2010

Fuel shutoff valve of a gas generator controls propellant mass flowrate of a rocket engine, by using pilot pressure and spring force. The developing fuel shutoff valve can be self sustained even though pilot pressure is removed in an actuator. Therefore, it is necessary to analyze the characteristics of the forces with respect to the opening and closing of the valve in order to evaluate its performance. In light of this, the valve has been designed to adjust the control pressure for the opening of the poppet and to determine the working fluid pressure at which the valve starts to close. This paper also has been designed dynamic model using the AMESim and predicted flow coefficient of the valve by Fluent CFD analysis. Various results from the prediction and the analysis have been compared with experiments. Finally, dynamic characteristics of the valve have been verified with experimental results.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.20 no.5
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• pp.304-313
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• 2008

This paper investigates the indoor-air-quality (IAQ) characteristics of the interior space equipped with system air-conditioner. The behaviors of individual variables such as temperature, humidity and concentration of carbon dioxide ($CO_2$) that influence on IAQ of the interior space were characterized under various cooling conditions by numerical and experimental studies. The numerical analysis predicting the temperature behavior of the interior space was conducted, and its results showed a good agreement with the experimental ones. The $CO_2$ concentration and humidity were measured and their time dependent behaviors were monitored and analyzed. From the results, it was found that there existed the differences of the time-dependent behaviors of IAQ variables according to the locations. In addition, it is demonstrated that the large discharge angle of $45^{\circ}$ made the temperature profile more irregular and the high discharge flow of 5.34 m/s produced similar temperature profiles at three different sensing locations. Finally, the humidity of interior space was less sensitive to the changes of the air cooling conditions than the case of temperature and the $CO_2$ concentration increase mainly depended on the number of individuals inside the space.

• Journal of Ship and Ocean Technology
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• v.12 no.3
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• pp.36-54
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• 2008

A jet stream applied tangential to a curved surface in fluid increases lift force by strengthening circulation around the surface and this phenomenon is known as the Coanda effect. Many experimental and numerical studies have been performed on the Coanda effect and the results found to be useful in various fields of aerodynamics. Recently, preliminary studies on Coanda control surface are in progress to look for practical application in marine hydrodynamics since various control surfaces are used to control behaviors of ships and offshore structures. In the present study, the performance of a Coanda control surface with different geometries of the jet injection nozzle was surveyed to assess applicability to ship rudders. A numerical simulation was carried out to study flow characteristics around a section of a horn type rudder subjected to a tangential jet stream. The RANS equations, discretized by a cell-centered finite volume method were used for this computation after verification by comparing to the experimental data available. Special attentions have been given to the sensitivity of the lift performance of a Coanda rudder to the location of the slit (outlet) and intake of the gap between the horn and rudder surface at the various angles of attack. It is found that the location of the water intake is important in enhancing the lift because the gap functions as a conduit of nozzle generating a jet sheet on the rudder surface.

• Journal of the Society of Naval Architects of Korea
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• v.57 no.1
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• pp.35-44
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• 2020

Propeller cavitation extent, pressure fluctuation induced by cavitation, pressure distribution on propeller blade, total velocity distribution and nominal wake distribution for a MR Taker were computed in both conditions of model test and sea trial using a code STAR-CCM⁺. Then some of the results were compared with model test data at LCT and full-scale measurement (Ahn et al (2014); Kim et al (2014)] in order to confirm the availability of a numerical prediction method and to get the physical insight of local flow around a ship and propeller. The nominal wake distributions computed and measured by LDV velocimeter on the variation of on-coming velocity show the wake contraction characteristics proposed by Hoekstra (1974). The numerical prediction of propeller cavitation extent on a blade angular position and pressure fluctuation level on each location of pressure sensors are very similar with the experimental results.

• Journal of the Semiconductor & Display Technology
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• v.18 no.4
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• pp.69-74
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• 2019

The aim of this work is to investigate the effect of the microtip length in a slot-die head on coating of a fine poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) stripe. To this end, we have employed a meniscus guide with a 150-㎛-wide microtip and performed roll-to-roll slot-die coatings by varying its length between 500 ㎛ and 50 ㎛. When the microtip length is 150 ㎛ or shorter, we have observed three unexpected phenomena; 1) though the solution spreads much wider than the microtip width, yet the coated stripe width is almost the same as the microtip width, 2) the stripe width decreases, but the stripe thickness is rather increased with increasing coating speed at a fixed flow rate, 3) we obtain stripes much narrower than the microtip width at high coating speeds. It is due to the fact that 1) the meniscus is not well controlled by a short microtip, 2) the main stream of solution from the outlet is very close to the substrate and thus the distributed solution along the head lip merges with the main stream, and 3) the solution is not spread over the entire microtip end at high coating speeds, causing a tiny wobble in the meniscus. Using the 150-㎛-wide and 250-㎛-long microtip, we have fabricated 153-㎛-wide and 94-nm-thick PEDOT:PSS stripe at the maximum coating speed of 13 mm/s. To demonstrate its applicability in solution-processable organic light-emitting diodes (OLEDs), we have also fabricated an OLED device with the fine PEDOT:PSS stripe and obtained strong light emission from it.

• Nuclear Engineering and Technology
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• v.42 no.6
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• pp.620-635
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• 2010

In this paper we describe current activities on the project Multi-Scale Modeling and Analysis of convective boiling (MSMA), conducted jointly by the Paul Scherrer Institute (PSI) and the Swiss Nuclear Utilities (Swissnuclear). The long-term aim of the MSMA project is to formulate improved closure laws for Computational Fluid Dynamics (CFD) simulations for prediction of convective boiling and eventually of the Critical Heat Flux (CHF). As boiling is controlled by the competition of numerous phenomena at various length and time scales, a multi-scale approach is employed to tackle the problem at different scales. In the MSMA project, the scales on which we focus range from the CFD scale (macro-scale), bubble size scale (meso-scale), liquid micro-layer and triple interline scale (micro-scale), and molecular scale (nano-scale). The current focus of the project is on micro- and meso-scales modeling. The numerical framework comprises a highly efficient, parallel DNS solver, the PSI-BOIL code. The code has incorporated an Immersed Boundary Method (IBM) to tackle complex geometries. For simulation of meso-scales (bubbles), we use the Constrained Interpolation Profile method: Conservative Semi-Lagrangian $2^{nd}$ order (CIP-CSL2). The phase change is described either by applying conventional jump conditions at the interface, or by using the Phase Field (PF) approach. In this work, we present selected results for flows in complex geometry using the IBM, selected bubbly flow simulations using the CIP-CSL2 method and results for phase change using the PF approach. In the subsequent stage of the project, the importance of effects of nano-scale processes on the global boiling heat transfer will be evaluated. To validate the models, more experimental information will be needed in the future, so it is expected that the MSMA project will become the seed for a long-term, combined theoretical and experimental program.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.11
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• pp.909-917
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• 2021

In this work, a one-dimensional combustor solver was constructed for the scramjet control m odel. The governing equations for fluid flow, Arrhenius based combustion kinetics, and the inje ction model were implemented into the solver. In order to validate the solver, the zero-dimensi onal ignition delay problem and one-dimensional scramjet combustion problem were considered and showed that the solver successfully reproduced the results from the literature. Subsequentl y, a ramjet analysis algorithm under subsonic speed conditions was constructed, and a study o n the inlet Mach number of the combustor was carried out through the thermal choking locatio ns at ram conditions. In such conditions, a model for precombustion shock train analysis was i mplemented, and the algorithm for transition section analysis was introduced. In addition, in or der to determine the appropriateness of the ram mode analysis in the code, the occurrence of a n unstart was studied through the length of the pseudo-shock in the isolator. A performance a nalysis study was carried out according to the geometry of the combustor.