• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년 추계학술대회논문집
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• pp.262-267
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• 2008

Numerical investigations were performed with an external-compression inlet with a three-dimensional bump at Mach 2 to scrutinize the geometrical effects of the bump in controlling the interaction of a shock wave with a boundary layer. The inlet was designed for two oblique shock waves and a terminal normal shock wave followed by a subsonic diffuser, with a circular cross-section throughout. The bump-type inlet that replaced the aft ramp of the conventional ramp-type inlet was optimized with respect to the inlet performance parameters as well as compared with the conventional ramp-type inlet. The current numerical simulations showed that a bump-type inlet can provide an improvement in the total pressure recovery downstream of the shock wave/boundary layer interaction over a conventional ramp-type inlet.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 1999년도 춘계 학술대회논문집
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• pp.85-89
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• 1999

Numerical Analysis has been done for the supersonic off-design jet flow due to the pressure difference between the jet and the ambient fluid. The difference of pressure generates an oblique shock or an expansion wave at the nozzle exit, The waves reflect repeatedly at the center axis and on the sonic surface in the shear layer, and the pressure difference is resolved across these waves interacted with the turbulence mixing layer. In this paper, the axi-symmetric Navier-Stokes equation has been used with two equation $k-{\varepsilon}$ turbulence closure model. The second order TVD scheme with flux limiters, based on the flux vector split by the smooth eigenvalue split, has been used to capture internal shocks and other discontinuities. The correction term for the compressible flow and the damping function are used in the turbulence model. Numerical calculations have been done to analyze the off-design jet flow due to the pressure difference. The variation of pressure along the flow axis is compared with an experimental result and other numerical result. The characteristics of the interaction between the shock cell and the turbulence mixing layer have been analyzed.

• 한국전산유체공학회지
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• 제2권2호
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• pp.59-72
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• 1997

A numerical model is constructed to simulate the interactions of oblique shock wave / turbulent boundary layer on a strongly heated wall. The heated wall temperature is two times higher than the adiabatic wall temperature and the shock wave is strong enough to induce boundary layer separation. The numerical diffusion in the finite volume method is reduced by the use of a higher order convection scheme(UMIST scheme) which is a TVD version of QUICK scheme. The turbulence model is Chen-Kim two time scale model. The comparison of the wall pressure distribution with the experimental data ensures the validity of this numerical model. The effect of strong wall heating enlarges the separation region upstream and downstream. In order to eliminate the separation, wall suction is applied at the shock foot position. The bleeding slot width is about same as the upstream boundary layer thickness and suction mass flow is 10% of the flow rate in the upstream boundary layer. The final configuration of the shock reflection pattern and the wall pressure distribution approach to the non-viscous value when wall suction is applied.

• 한국전자파학회논문지
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• 제18권11호
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• pp.1217-1223
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• 2007

5.8 GHz의 DSRC(Dedicated Short Range Communication) 시스템을 사용하는 ITS(Intelligent Transport System)에 전자파 환경 문제가 발생하면서 광각 경사 입사 대책용 전파 흡수체의 사용이 요구된다. 5.8 GHz 주파수에서 경사 입사된 전파에 대해 낮은 반사 손실을 보이는 2층형의 전파 흡수체(유전 복합 재료/자성 복합 재료)를 설계하였다. 흡수층에는 iron flake를 filler로 사용하였다. 임피던스 정합 기능의 표면층에는 유전상수가 낮은 carbon black을 사용하였다. 각 층의 sheet는 일반적인 세라믹 혼합물 제조 공정에 의해 제작되었고, 지지재로는 가황고무를 사용하였다. 전송 선로 이론에 근거하여 TE(Transverse Electric)와 TM(Transverse Magnetic) 편파에 대해 입사각을 변화시키며 반사 손실을 계산하였고, 자유공간법에 의해 반사 전력을 실측하였다. 입사각 $55^{\circ}$까지 낮은 반사 손실(-10 dB 이하)을 갖는 2층형 흡수체가 설계되었다. 자유공간법에 의한 반사 전력의 실측치가 이론적 계산치와 비슷한 값을 보여 설계 방법의 타당성을 입증할 수 있었다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.426.1-426.1
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• 2016

We report high work function Aluminum doped zinc oxide (AZO) films as insertion layer as a function of O2 flow rate between transparent conducting oxides (TCO) and hydrogenated amorphous silicon oxide (a-SiOx:H) layer to improve open circuit voltage (Voc) and fill factor (FF) for high efficiency thin film solar cell. However, amorphous silicon (a-Si:H) solar cells exhibit poor fill factors due to a Schottky barrier like impedance at the interface between a-SiOx:H windows and TCO. The impedance is caused by an increasing mismatch between the work function of TCO and that of p-type a-SiOx:H. In this study, we report on the silicon thin film solar cell by using as insertion layer of O2 reactive AZO films between TCO and p-type a-SiOx:H. Significant efficiency enhancement was demonstrated by using high work-function layers (4.95 eV at O2=2 sccm) for engineering the work function at the key interfaces to raise FF as well as Voc. Therefore, we can be obtained the conversion efficiency of 7 % at 13mA/cm2 of the current density (Jsc) and 63.35 % of FF.

• 대한한의학회지
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• 제32권3호
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• pp.1-9
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• 2011

Objectives: This study was carried out to observe the foot gworeum meridian muscle from a viewpoint of human anatomy on the assumption that the meridian muscle system is basically matched to the meridian vessel system as a part of the meridian system, and further to support the accurate application of acupuncture in clinical practice. Methods: Meridian points corresponding to the foot gworeum meridian muscle at the body surface were labeled with latex, being based on Korean standard acupuncture point locations. In order to expose components related to the foot gworeum meridian muscle, the cadaver was then dissected, being respectively divided into superficial, middle, and deep layers while entering more deeply. Results: Anatomical components related to the foot gworeum meridian muscle in human are composed of muscles, fascia, ligament, nerves, etc. The anatomical components of the foot gworeum meridian muscle in cadaver are as follows: 1. Muscle: Dorsal pedis fascia, crural fascia, flexor digitorum (digit.) longus muscle (m.), soleus m., sartorius m., adductor longus m., and external abdominal oblique m. aponeurosis at the superficial layer, dorsal interosseous m. tendon (tend.), extensor (ext.) hallucis brevis m. tend., ext. hallucis longus m. tend., tibialis anterior m. tend., flexor digit. longus m., and internal abdominal oblique m. at the middle layer, and finally posterior tibialis m., gracilis m. tend., semitendinosus m. tend., semimembranosus m. tend., gastrocnemius m., adductor magnus m. tend., vastus medialis m., adductor brevis m., and intercostal m. at the deep layer. 2. Nerve: Dorsal digital branch (br.) of the deep peroneal nerve (n.), dorsal br. of the proper plantar digital n., medial br. of the deep peroneal n., saphenous n., infrapatellar br. of the saphenous n., cutaneous (cut.) br. of the obturator n., femoral br. of the genitofemoral n., anterior (ant.) cut. br. of the femoral n., ant. cut. br. of the iliohypogastric n., lateral cut. br. of the intercostal n. (T11), and lateral cut. br. of the intercostal n. (T6) at the superficial layer, saphenous n., ant. division of the obturator n., post. division of the obturator n., obturator n., ant. cut. br. of the intercostal n. (T11), and ant. cut. br. of the intercostal n. (T6) at the middle layer, and finally tibialis n. and articular br. of tibial n. at the deep layer. Conclusion: The meridian muscle system seemed to be closely matched to the meridian vessel system as a part of the meridian system. This study shows comparative differences from established studies on anatomical components related to the foot gworeum meridian muscle, and also from the methodical aspect of the analytic process. In addition, the human foot gworeum meridian muscle is composed of the proper muscles, and also may include the relevant nerves, but it is as questionable as ever, and we can guess that there are somewhat conceptual differences between terms (that is, nerves which control muscles in the foot gworeum meridian muscle and those which pass nearby) in human anatomy.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2011년도 춘계학술대회 및 Fine pattern PCB 표면 처리 기술 워크샵
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• pp.125-125
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• 2011

티타늄 화합물은 뛰어난 물리적 특성과 인체 무해성을 가지고 있어 생체, 내식 및 내마모 재료 등에 널리 응용되고 있으며, 금(gold)색의 색상 구현을 통해 미적 기능성 향상을 위한 표면처리 분야에도 많은 관심을 받고 있다. 본 연구에서는 아크 방전법을 이용해 밀착력이 우수한 다층 TiN 박막을 제조하고 미세조직 변화에 따른 특성을 알아보고자 한다.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2012년도 춘계학술발표회 논문집
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• pp.143-143
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• 2012

질화 티타늄(Titanium Nitride)은 뛰어난 물리적 특성이 있어 내마모 재료의 표면처리 분야에 많이 사용되고 있다. 본 연구에서는 음극 아크 방전을 이용하여 빗각 증착을 실시하고 증착 시 기판에 bias 인가 여부에 따라 주상정의 방향성이 변하는 단층 및 다층의 TiN 박막을 제조하였으며 동일한 두께의 다양한 다층구조에서 경도의 증가를 확인하였다.

• 한국항공우주학회지
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• 제50권11호
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• pp.747-754
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• 2022

유체진동기에서 분출되는 초음속 진동제트를 이용하여 충격파에 의한 경계층 박리유동을 제어하는 실험적 연구가 이루어졌다. 유체진동기의 위치와 제어압력의 변화가 경사충격파에 의하여 발생되는 경계층 박리유동의 특성에 미치는 영향이 관찰되었고, 이를 위하여 고속 슐리렌, 표면유동가시화, 벽압력 측정, 그리고 정밀 피토관 측정 기법이 적용되었다. 본 연구의 초음속 진동제트의 박리유동 제어 특성은 공기제트 와류를 이용한 기존 제어기법과 정량적으로 비교 분석되었다.

• 한국자동차공학회논문집
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• 제6권2호
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• pp.12-20
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• 1998

Exter ballistics of a typical high-speed projectile is studied through a flow-visualization experiment and an unstructured grid Navier-Srokes computation. Experiment produced a schlieren photograph that adequately shows the characteristic features of this complex flow, namely two kinds of oblique cone shocks and turbulent wake developing into the downstream. A hybrid scheme of finite volume-element method is used to simulate the compressible Reynolds-Averaged Navier-Stok- es solution on unstructured grids. Osher's approximate Riemann solver is used to discretize the cinvection term. Higher-order spatial accuracy is obtained by MUSCL extension and van Albada ty- pe flux limiter is used to stabilize the numerical oscillation near the solution discontinuity. Accurate Gakerkin method is used to discretize the viscous term. Explict fourth-order Runge-Kutta method is used for the time-stepping, which simplifies the application of MUSCL extension. A two-layer k-$\varepsilon$ turbulence model is used to simulate the turbulent wakes accurately. Axisymmetric folw and two-dimensional flow with an angle of attack have been computed. Grid-dependency is also checked by carrying out the computation with doubled meshes. 2-D calculation shows that effect of angle of attack on the flow field is negligible. Axi-symmetric results of the computation agrees well with the flow visualization. Primary oblique shock is represented within 2-3 meshes in numerical results, and the varicose mode of the vortex shedding is clearly captured in the turbulent wake region.