• 동력기계공학회지
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• 제17권5호
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• pp.64-68
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• 2013

One of the water management goals in PEM fuel cell is to avoid flooding and drying in the membrane, therefore the air humidification process is required. In order to increase water removal out of the membrane, the water management system may require the dehumidification process and it also requires a large space for application, moreover the process time is slow. In conformity with this fact, this present study proposes an advanced dynamic fuel cell water management which can be an intermittent optimization control using air flow rate instead of the air humidity as an variable in the optimization process. The results of this study have shown that the membrane flooding and drying can be avoided after being assisted by air velocity controlling method.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2021년도 추계학술대회
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• pp.376-378
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• 2021

세계기상기구가 발표한 2020년 글로벌 기후 보고서에 따르면, 2019년 지구의 평균 온도는 산업화 이전인 1850년에서 1900년사이에 측정된 온도보다 평균 1.1℃ 높게 측정되었다. 평균온도의 변화는 기온 상승이 식물 분포에 미치는 영향과 취약성 분석 논문의 따르면 평균온도의 상승시 식물의 분포되는 지역의 변화가 있다는 것을 알 수 있다. 본 논문에서는 이러한 환경 변화에 대응하기 위해, 아두이노와 센서를 사용하여 간헐흐름식 수경재배 스마트팜을 제작하고, PC와 어플리케이션을 통하여 제어하는 방법을 제안한다. 제작된 수경재배 스마트팜은 농장의 온습도, 양액의 ph농도, 조도, 수질의 정도를 파악하고, 양액의 양과 보충 필요 농도 확인, 조도의 따른 생장 LED 제어, 센서의 상태를 파악하여 농장의 전체적인 관리와, 식물의 모종 옮겨심기 이후의 적절한 환경에서 성장할 수 있도록 제어한다.

• Wind and Structures
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• 제5권2_3_4호
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• pp.115-126
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• 2002

A mesoscale meteorological model is applied to simulate turbulent airflow and eddy shedding over the Isle of Arran, SW Scotland, UK. Under conditions of NW flow, the mountain ridge of Kintyre, located upwind of Arran, induces gravity waves that also affect the airflow over the island. The possibility to nest domains allows description of the airflow over Arran with a very high resolution grid, while also including the effects of the surrounding mainland of Scotland, in particular of the mountain ridge of Kintyre. Initialised with a stably stratified NW flow, the mesoscale model simulates quasi-stationary gravity waves over the island induced by Kintyre. Embedded in the larger scale wave trains there is continuous development of small-scale transient eddies, created at the Arran hill tops, that move downstream through the stationary wave field. Although the transient eddies are more frequently simulated on the northern island where the terrain is more pronounced, they are also produced over Tighvein, a hill of 458 m on the southern island where measurements of surface pressure and 2 m meteorological variables have been recorded at intermittent intervals between 1996 and 2000. Comparison between early observations and simulations so far show qualitatively good agreement. Overall the computations demonstrate that turbulent flow can be modelled with a horizontal resolution of 70 m, and describe turbulent eddy structure on wavelength of only a few hundred metres.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년 영문 학술대회
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• pp.419-426
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• 2008

As pulse detonation engine(PDE) does not need compression mechanisms such as compressors because self-sustained detonation waves are able to compress propellant gases by their incident shock waves, the PDE can have a simple straight-tube structure. In this study, we propose an autonomous driving valve system of the PDE, which fill premixed gases into the PDE tubes at high frequency with high mass flow rate. The proposed valve is composed of only three parts: a piston, a cylinder, and a spring. This valve system can produce intermittent flow at high mass flow rate, and also can keep stable reciprocal motion by using the propellant-gas enthalpy. When the cylinder content product is assumed to be constant, experimental results of the mass flow rate were approximately equal to the calculation model. We confirmed the autonomous driving valve performance by experiments, and concluded that this extremely simple valve with no electrical power and controller can be used as the PDE propellant supply system.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2009년도 추계학술대회 논문집
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• pp.291-295
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• 2009

Economic and environmental concerns over fossil fuels encourage the development of photovoltaic(PV) energy systems. Due to the intermittent nature of solar energy. energy storage is needed in a stand-alone PV system for the purpose of ensuring continuous power flow. Grid-connected PV system that supply power in a critical load demand require to curb power fluctuation. In this case. SCB is a effectiveness in controlling power variation due to intrinsic PV system. We propose the Matlab/Simulink dynamic model and power flow characteristics of a hybrid energy system with PV and SCB.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2011년도 춘계학술대회 초록집
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• pp.165.2-165.2
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• 2011

Dye to recent development such as increasing price of fossil fuels and energy offers such a solution. Wave energy supplies. Weve energy offers such a solution. Wave energy is the most consistent of all the intermittent renewable energy sources. In addition to this, very large energy fluxes occur in the ocean waves and by using appropriate wave energy converters the energy can be harnessed. The present study looks at utilizing a direct drive turbine of cross flow type to extract energy from ocean waves indirectly. This novel design incorporates a turbine in an enclosed in a closed tank. utilizing the energy generated from sloshing.

• 한국연소학회:학술대회논문집
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• 대한연소학회 2003년도 제27회 KOSCO SYMPOSIUM 논문집
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• pp.35-41
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• 2003

Propagation speeds of turbulent premixed flames have been measured in a pulsed-flame flow reactor which generates flames propagating in nearly isotropic turbulent flow field with U'/$S_L$ ranging from 1.2 to 5.3. The measurement involved a high-speed digital imaging at 1000 frames/second to capture the flame propagation motion. In addition to the flame speed measurements, flame perimeter ratio was measured for comparison. The observed flame propagation speed is high ranging from 5 to 20 times the laminar flame speed for the range of U'/$S_L$. The flames observed at extreme equivalence ratios exhibit intermittent propagation in that only a small fraction of ignited flame kernel resulted in full propagation of the flame. Also, at low equivalence ratios the flame speed decreased substantially even at high turbulence intensities.

• Journal of Chest Surgery
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• 제26권10호
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• pp.808-811
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• 1993

Leriche syndrome ia a common entity which causes ischemia of the lower extremities. Since the introduction of aortic resection and homograft replacement by Oudot in 1951, reconstructive procedures to restore distal blood flow by either endarterectomy or, later, with prosthetic graft have become standardized. Recently we experienced a case of Leriche syndrome. A 50 year-old male patient admitted with intermittent claudication, impotence, and symmetrical atrophy at lower extremities. Aortogram revealed complete obstruction at infrarenal abdominal aorta and Doppler sonogram revealed only minimal blood flow at left femoral artery.Successful surgical treatment was accomplished with endarterectomy at proximal left renal artery and a bypass from abdominal aorta at the level of both renal arteries to both external iliac arteries with bifurcated Gore-tex vascular graft. After bypass operation, we did palpate with arterial pulse at both popliteal artery.He was recovered without complication.

• 한국산학기술학회논문지
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• 제17권5호
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• pp.203-212
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• 2016

본 연구는 뇌수술 후 부동 환자에게 부츠형 또는 무릎형 간헐적 공기 압박기 적용 후 심부정맥 혈전증 예방과 피부반응에 미치는 영향을 평가하기 위한 실험연구이다. 연구대상은 2015년 5월 부터 11월 까지 뇌수술 후 외과계 중환자실에 입실한 60명을 대상으로 하였다. 심부정맥 혈전증 평가는 7일 동안 대퇴정맥 혈류속도의 변화를 매일 측정하였고 피부 반응 정도도 매일 규칙적으로 관찰하였다. 그 결과 부츠형 간헐적 공기 압박기 적용군이 무릎형 간헐적 공기압박기 적용군보다 시간이 경과함에 따라 대퇴정맥 혈류속도가 증가함을 확인하였다. 즉, 7일 동안 측정한 평균 대퇴정맥 혈류속도는 시간경과에 따른 측정시기 오른쪽(F=64.41, p <.001), 왼쪽(F=58.21, p <.001)모두 통계적으로 유의한 차이를 나타내었다. 두 군 간의 발등 둘레는 측정시기와 집단 간의 상호작용에서 오른쪽(F=9.13, p <.001), 왼쪽(F=9.29, p<.001) 모두 통계적으로 유의한 차이를 보였다. 또한 부츠형 간혈적 공기 압박기 적용군은 피부 합병증도 발생하지 않았다. 이러한 결과는 뇌수술 후 부동환자에게 부츠형 간헐적 공기 압박기 적용이 심부정맥 혈전증을 예방하는데 보다 효과적임을 알 수 있다.

• Journal of Mechanical Science and Technology
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• 제16권7호
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• pp.986-998
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• 2002

Flow and spray characteristics are critical factors that affect the performance and exhaust emissions of a direct injection diesel engine. It is well known that the swirl control system is one of the useful ways to improve the fuel consumption and emission reduction rate in a diesel engine. However, until now there have only been a few studies on the effect of flow on spray. Because of this, the relationship between the flow pattern in the cylinder and its influence on the behavior of the spray is in need of investigation. First, in-cylinder flow distributions for 4-valve cylinder head of DI (Direct Injection) Diesel engine were investigated under steady-state conditions for different SCV (Swirl Control Valve) opening angles using a steady flow rig and 2-D LDV (Laser Doppler Velocimetry). It was found that swirl flow was more dominant than that of tumble in the experimented engine. In addition, the in-cylinder flow was quantified in terms of swirl/tumble ratio and mean flow coefficient. As the SCV opening angle was increased, high swirl ratios more than 3.0 were obtained in the case of SCV -70° and 90°. Second, spray characteristics of the intermittent injection were investigated by a PDA (Phase Doppler Anemometer) system. A Time Dividing Method (TDM) was used to analyze the microscopic spray characteristics. It was found that the atomization characteristics such as velocity and SMD (Sauter Mean Diameter) of the spray were affected by the in-cylinder swirl ratio. As a result, it was concluded that the swirl ratio improves atomization characteristics uniformly.