• Tribology and Lubricants
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• 제38권2호
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• pp.33-40
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• 2022

In this study, we present rotor dynamic analysis and operation test of a turbo expander for a hydrogen liquefaction plant. The turbo expander consists of a turbine and compressor wheel connected to a shaft supported by two hydrostatic radial and thrust bearings. In rotor dynamic analysis, the shaft is modeled as a rigid body, and the equations of motion for the shaft are solved using the unsteady Reynolds equation. Additionally, the operating test of the turbo expander has been performed in the test rig. Pressurized helium is supplied to the bearings at 8.5 bar. Furthermore, we monitor the shaft vibration and flow rate of the helium supplied to the bearings. The rotor dynamic analysis result shows that there are two critical speeds related with the rigid body mode under 40,000 rpm. At the first critical speed of 36,000 rpm, the vibration at the compressor side is maximum, whereas that of the turbine is maximum at the second critical speed of 40,000 rpm. The predicted maximum shaft vibration is 3 ㎛, whereas sub-synchronous vibration is not presented. The operation test results show that there are two critical speeds under the rated speed, and the measured vibration value agrees well with predicted value. The measured flow rate of the helium supplied to the bearing is 2.0 g/s, which also agrees well with the predicted data.

• Asian Journal of Atmospheric Environment
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• 제7권2호
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• pp.95-104
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• 2013

The study of carbonaceous aerosols in the atmosphere is critical to understand the role of aerosols in human health and climate. Using standardized thermal optical transmittance methods, organic carbon (OC), elemental carbon (EC), and water soluble organic carbon (WSOC) were determined using a combustion sampling system for four types of agricultural crop residues (rice straw, red pepper stems, soybean stems, and green perilla stems) and eight types of forest trees (pine stems, pine needles, ginkgo stems, ginkgo leaves, maple stems, maple leaves, cherry stems, and cherry leaves). The aerosol particles between 0.056 and $5.6{\mu}m$ in size were analyzed using a Micro-Orifice Uniform Deposit Impactor (MOUDI). In the current study, the Carbonaceous Thermal Distribution (CTD) by carbon analyzer was discussed in order to understand the carbon fractions from the twelve types of biomass burning. Also, the concentration of OC, EC, WSOC, and water insoluble organic carbon (WIOC) detected in the emissions were described.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집B
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• pp.121-126
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• 2001

In this study, the 4-way spool valve characteristics are clearly defined and proposed new type of spool valve. This paper presents governing equations of the flow through clearances between sleeve and spool as a model of orifice flow for null characteristic analysis, and programmed analysis software of it. This software is possible to basically analysis that not only which case of open center, closed center or critical center but +,- displacement of spool, lab position, boundary region and spool opening of the valve, and to estimate the pressure variation in the spool and external leak flow variation. We are convinced that the scale of load pressure difference is changed as lab condition of spool valve, and this scale is changed with boundary point on the annular clearance. It is vary useful to designer and user of spool valve with this design data and analysis software.

• Tuberculosis and Respiratory Diseases
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• 제61권5호
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• pp.484-489
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• 2006

원발성 기관지내 평활근육종은 폐에 원발하는 매우 드문 악성 종양으로 통상적인 생검방법으로는 육종의 진단이 쉽지 않고 수술적 폐생검이 필요한 경우가 많으며 치료는 근치적 절제술로 완치를 기대할 수 있다. 저자들은 대량객혈을 주소로 내원한 21세 남자에서 좌폐하엽 기관지에서 발생한 원발성 기관지내 평활근육종을 진단하고 좌하엽 수상절제술을 시행하였으나 3개월 후에 국소 재발하였다. 1차 수술 후 4개월 째 좌측 전폐절제술을 시행하였으나 2차 수술 후 11개월 째 다시 국소재발과 기관지흉막루가 발생하였고 이와 관련된 농흉과 패혈증으로 사망하였던 환자를 경험하여 이를 보고하는 바이다.

• 대한관절경학회지
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• 제2권1호
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• pp.1-3
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• 1998

The PCL reconstruction in chronic isolate PCL reconstruction was still controversy. 1) In isolate PCL deficient knee, functionally not so bad as like ACL deficient knee. 2) The result of the PCL reconstruction was not as good as ACL reconstruction. Therefore, isolate PCL injuries has been treated as nonoperatively. Hey Grovere, who was the first to attempt an intra-articular reconstruction of the PCL, utilized the semi-tendinous tendon other static procedures have been described in only a few cases with very limited follow-up. Dynamic procedures utilizing the medial head of the gastrocnemius has been reported by Hugston and Degenhardt, Kennedy and Grainger, and Insall and Hood. These procedures did not improve static stability. Dr Clancy, who was introduce the use of BPTB for the PCL reconstruction transtibial and femoral tunnel. From 1995, untill early 1990 PCL reconstruction was done as tend as placement of the isometric point. Physiometic placement of Anatomical placement of the femoral tunnel in PCL reconstruction were introduced in 1995. Tibial Inlay Technique was reported by Dr Berg in 1995. The main advantage of the tibial Inlay Technique was to avoid fraying of the graft at the posterior tibial tunnel orifice. In complete PCL ruptured and severely posterior unstable knee, dual femoral tunnel technique will be to get better result than one bundle technique. To achieve restoration of normal posterior laxity, it is critical to address the posterior as well as the posterolateral structures. Futher research is necessary to evaluate new surgical approches such as double-bundle reconstructions and tibial inlay techniques as well as improved techniques for capsular and collateral ligament injuries.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년도 제30회 춘계학술대회논문집
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• pp.281-284
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• 2008

스크램제트 엔진의 연소기 내부 유동은 초음속이므로 유동의 잔류시간과 혼합율의 증대가 효과적인 연소를 가능하게 하는 주요 요인으로 작용한다. 본 연구에서는 연료-공기 혼합기로써 개방형 공동 모델을 사용하였고, 공동 앞에서의 경사 연료 분사 시 분사구 주위와 공동 주위의 유동특성을 살펴보기 위하여 레이저 슐리렌 기법과 압력측정을 실시하였다. 레이저 슐리렌은 10 ns의 광원 지속시간으로 공동 부근의 비정상 유동 현상을 효과적으로 관찰 할 수 있었다. 또한, 압력측정은 연료 분사 J(운동량비)를 변화시켜 가며 측정하였으며, 운동량비에 따른 연소기 내부 주요 연소발생 지점의 변화를 살펴 볼 수 있었다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.43-46
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• 2002

The HANARO, multi-purpose research reactor, 30 MWth open-tank-in-pool type, is under 24 MWth of power operation since it reached to the initial critical in February, 1995. Many useful experiments should be safely performed to activate the utilization of the HANARO, but there is a radioactive risk of using the HANARO. To reduce the risk, a test facility, which is not reacted by nuclear fuel, is being developed to simulate similar flow characteristics with the HANARO. This paper describes the computational flow analysis to determine each shape of simulating fuels for simulating the flow similarities of 36 elements hexagonal fuels assembly and 18 elements circulating fuels assembly loaded in HANARO. The shares of orifices were determined by the trial and error method and the structural integrities of them were verified by the finite element method assuming that the flow rate and pressure differences of reactor core are constant. The analysis results will be verified with the results of the flow test to be performed after the installation of this test facility.

• International Journal of Automotive Technology
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• 제5권1호
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• pp.9-16
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• 2004

An experimental study was carried out to characterize the spray atomization process of micro-machined port fuel injectors with a piezoelectric atomization device, which can generate pressure pulsations through vibration of a piezoelectric transducer. In this study, several types of micro-machined arrays such as 30∼200-microns of hole arrays were tested. Both a dual-stream and a central-port injectors with micro-machined arrays were tested and compared with normal port fuel injectors. The spray visualization was conducted to characterize overall spray structure and phase Doppler particle analyzer (PDPA) system was used to quantify the droplet size and velocity. In addition, the pressure history was recorded by using digitized signal from pressure transducer. The results showed that modulation is effective to the spray atomization for tested injectors and atomization performance depends on injector design factors, orifice sizes, and frequency and power of the modulator. A number of resonance frequencies of the modulator was modified by injector parameters and temperature. In addition, our results suggested that design of sufficient space among holes is critical to avoid droplet coalescence in the multi-hole micro-machined injectors.

• 대한안전경영과학회지
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• 제12권4호
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• pp.93-98
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• 2010

본 연구에서는, 반도체, LCD 공정에서 금속막을 증착하기 위하여 PECVD장비에 화재, 폭발 위험성과 독성을 가진 Silane가스를 사용하게 되는 장비인 gas cabinet, pipeline, VMB(Valve manifold box), MFC(mass flow controller)장비 등, 전반적인 시스템에 대하여 영국 HES의 ALARP개념을 도입하여 위험성 평가를 실시하여 문제점을 도출하고 대책을 강구 하는데 목적이 있고, 여러 가지 문제점중 절대적으로 수용 할 수 없는 Critical Risk로는 Gas Cylinder를 사용하여 Silane을 공급하고자 할 때에는 필히 Gas Cabinet을 사용하여 공급하여야 하고, Tube Trailer를 사용하여 공급하고자 할 때에는 필수적으로 Purge System을 갖추어 공급하여야 한다. 선택적으로 수용할 수 있는 High, Medium Risk로는 Gas Cylinder 또는 Tube Trailer를 사용하여 Silane을 공급하고자 할 때는 Inlet 부분에 RFO(Resticted Flow Orifice)를 설치하여 사용하고 Gas Supply Room에는 CO2소화설비를 적용하지 말고 Water Mist등 물 분무설비를 적용하여야한다.

• 한국추진공학회지
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• 제13권4호
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• pp.9-15
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• 2009

스크램제트 엔진의 연소기 내부 유동은 초음속이므로 유동의 잔류시간과 혼합율의 증대가 효과적인 연소를 가능하게 하는 주요 요인으로 작용한다. 본 연구에서는 연료-공기 혼합기로써 L/D=4.8인 개방형 공동 모델을 사용하였고, 공동 앞에서의 경사 연료 분사 시 분사구 주위와 공동 주위의 유동특성을 살펴보기 위하여 레이저 슐리렌 기법과 압력측정을 실시하였다. 측정에 사용된 레이저 슐리렌은 10 ns의 매우 짧은 광원 지속시간을 보유하여 공동부근의 비정상 유동 현상을 효과적으로 관찰할 수 있었다. 압력측정은 연료 분사비 J(운동량비)를 변화시켜 가며 측정하였으며, 운동량비에 따른 연소기 내부 주요 압력상승 지점의 변화를 살펴 볼 수 있었다.