• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.2823-2828
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• 2007

Numerical simulation on the two-stage centrifugal compressor with Low Solidity Vaned Diffuser LSVD) for HFC-134a Turbo-chiller was performed using a commercial code. The comparative study with experimental results from other compressor was also investigated to testify the simulation schemes. The numerical analysis was separately simulated for each stage of the compressor and the effect of impeller-diffuser flow interaction was considered. Setting angle of the diffuser vane changed in the range of 15 deg. and the effects on its variation were discussed in detail including the flow analysis in the passage of the compressor. The vane setting angle obtained from the preliminary design was slightly adjusted to the optimal value by the performance enhancement in terms of pressure recovery and flow characteristics.

• 한국유체기계학회 논문집
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• 제15권2호
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• pp.57-62
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• 2012

The constant air volume flow fan can maintain constant flow rate to the wide range of exit pressure. Therefore, the use of this fan is increasing recently for ventilation of high building. Brushless DC motor is adopted to this fan because that has advantages of compactness and performance. But this type of motor protrude from impeller hub side to fan inlet. The Impeller inlet flow is influenced by size of this obstacle called hub. In this paper, the influence of hub shape on the fan performance characteristics are experimentally and numerically analyzed. CFX 12.0 is used to perform the fan internal flow analysis and numerical results are compared with the experiments. Depending on hub shape, internal loss is generated and the performance and efficiency are reduced. The best performance is occurred around $h/b_1$ = 0.25. The results of this study will be contribute to initial design of constant air volume flow fan development.

• The Korean Journal of Pain
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• 제10권1호
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• pp.97-100
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• 1997

We treated a 56 year old male ailing of painful herpetic eruption on his 2nd, 3rd and 4th left cervical spinal segment. On the 18th day, patient also suffered an abrupt left facial palsy, accompanied with ongoing postherpetic neuralgia even though the skin eruption had been cured. This patient visited our pain clinic on his 46th day of illness and was teated with continuous cervical epidural block for 9 days, and stellate ganglion block plus oral analgesics and antidepressant for 12 days. The combination of treatments resulted in marked improvement of facial palsy and postherpetic neuralgia. A possible explanation of facial palsy accompanied with herpes zoster on cervical spinal segment could be related to Hunt's hypothesis that geniculate ganglion forms a chain connecting the high cervical ganglion below. Another possibility may be related to a compression injury of the facial nerve by long-term severe edema on the soft tissue of the face, the periauricular area and parotid gland around the facial nerve, and edema on the facial nerve itself emerging out from the cranium.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1994년도 추계학술대회
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• pp.43-46
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• 1994

A new spatial localization technique using high-order surface gradient coil (SGC) is proposed. Although the Spatial Selection with High-Order gradient (SHOT) can provide a 2-D selection with only one selective RF pulse, the high-order gradient produced by cylindrical-shape coils has not been clinically useful for clinical systems due to the large minimum selection size caused by the limited radial gradient intensity. However, by using the proposed high-order SGCs located near the imaging region, the size of volume selection can be reduced to a clinically useful 1-4 cm in diameter by applying stronger radial gradient with much less gradient driving power. A 40 cm-by-40 cm $r^{2}$ SGC has been designed and constructed, and phantom and volunteer studies have been performed. Experimental results using spatially localized MRI show good agreement to the theoretically predicted behavior.

• 전자공학회논문지SC
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• 제40권4호
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• pp.291-298
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• 2003

질병을 진단하기 위하여 환부를 가시화하는 것은 매우 중요하다. 많은 경우 환부의 형태학적 변화를 동반하기 때문이다. 혈관에서의 이러한 형태학적 특성을 가시화하는 기법을 혈관 조영기법 이라 한다. 혈관조영기법은 TOF 기법과 위상대조도 기법, 조영제 증강 기법이 있다. 본 논문에서는 혈관 조영기법에 대한 각각의 원리와 관련된 시퀸스 및 특성에 대하여 소개하고 촬영을 통한 데이터 획득후의 데이터 후처리의 과정을 기술하였으며 인체에 응용의 최근 사례들을 소개하였다.

• 한국유체기계학회 논문집
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• 제10권4호
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• pp.29-38
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• 2007

In this study, flow structure in a two-stage centrifugal compressor for a turbo-chiller with the refrigerant, R134a, was numerically investigated at the design point of the compressor using a commercial code. Flow characteristics in the passages of impeller, diffuser and return channel were analyzed in detail including velocity vector, secondary flow, Mach number and pressure contours in blade spanwise and meridional plane for each stage. The estimation on the one-dimensional output from the preliminary design and three-dimensional shape of the impeller blade and the meridional shape of the return channel were performed through the flow analysis, while some numerical schemes and techniques including Multiple Frames of Reference technique, real gas property data and inlet boundary condition changes, which were used in CFD, were compared with their features. The results will be used as reference data for a new design of 3-D impeller shape to improve R134a compressor performance.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2010년 춘계학술대회논문집
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• pp.167-173
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• 2010

In this study, flow structure in a three-stage centrifugal compressor for LNG Plant with the refrigerant, Propane, was numerically investigated at the design point of the compressor using a commercial code. Flow characteristics in the passages of impeller and vaneless diffuser were analyzed in detail including velocity vector, Mach number and pressure contours in blade spanwise and meridional plane for each stage. The estimation on the one-dimensional output from the preliminary design and three-dimensional shape of the impeller blade was performed through the flow analysis. The verification for designed compressor was carried out from three-dimensional Navier-Stokes analysis. The results will be used as reference data for a new design of 3-D impeller shape to improve propane refrigerant compressor performance.

• 한국연초학회지
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• 제23권2호
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• pp.156-161
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• 2001

This study was carried out to evaluate the effect of bulk fermentation on chemical, chromatic, and organoleptic characteristics of burley leaf tobacco. The pile of ferment processing was taken up 32 days under the conolitions of leaf moisture contents of $28\pm1%$, with a pressure of some 200kg/$m^2$ within a closed room (mean air temperature and relative humidity ; 20.5$^{\circ}C$ and 58.7%). The pile was opened up and reconstructed two times when the maximum inside temperature reached at $45~46^{\circ}C$. The nicotine content was decreased, but amomnia contents and pH were significantly increased by bulk fermentation. Otherwise, the contents of total nitrogen, total volatile base, organic acids, and fatty acids were not affected by same treatment. The value of L(black to white), a(red to green) and b(yellow to blue) in chromatic characteristics were significantly decreased by bulk fermentation. In sensory test of the cigarettes made by addition of the tormented tobacco leaves after toasting in proportion of 19-25%, no negative characteristics in irritation, taste, and preference were detected in comparison with normally processed cigarettes(19%, 2 years fermentation, toasting). The results suggest that bulk fermentation may be useful to increase the proportion of burley leaf tobacco in the cigarettes and to shorten the period of storage for aging.

• 디지털융복합연구
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• 제11권11호
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• pp.169-175
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• 2013

스마트 유연근무는 개인이 직장과 가정에서 요구되는 역할 균형을 가능하도록 하는 주요 정책수단으로 최근 관심을 받아 왔다. 본 연구는 유연근무를 시범적으로 시행하고 있는 광역자치단체 공무원들을 대상으로 스마트 유연근무제 유형에 대해 살펴보고, 조직단위 별 스마트 유연근무 유형을 분석하고 근로 장소 유연성, 근로시간 유연성 과 근로 장소 및 시간 융합 유연성 등 스마트 유연근무제 유형별 성공요인을 분석하였다. 분석결과 직장영역과 가정영역 별 유연근무의 특성에 차이가 있는 것으로 나타났고 구체적으로 가정 및 직장 융합 영역이 유연근무에 가장 중요한 성공요인으로 밝혀졌으며 이에 따른 정책적 시사점을 도출하였다.

• 한국터널지하공간학회 논문집
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• 제20권1호
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• pp.225-234
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• 2018

국내 대도시 도심지역은 지속적인 인구증가와 교통량의 증가로 심각한 교통혼잡 문제가 발생하고 있다. 교통혼잡 등의 문제를 해결하기 위한 방안으로 서울, 부산 등의 도심지에서는 지하공간을 활용한 소형차 전용 대심도 복층터널 연구가 활발히 이루어지고 있다. 이러한 소형차 전용 대심도 복층터널의 특징은 비교적 단면의 높이가 낮아 터널 내 화재 발생시 화재연기의 전파가 전 차종이 통행 가능한 일반적인 도로 터널보다 빠르게 전파되어 인명피해 발생이 우려된다. 따라서, 소형차 전용 대심도 복층터널에 화재 발생시 화재연기의 확산을 지연시켜 인명피해 발생을 최소화시키는 화재연기 확산지연장치가 필요하다. 선행하여 연구된 대심도 복층터널 화재시 연기확산 방지연구에서 3차원 CFD 해석을 통하여 화재연기 확산지연장치 작동 시 차단 면적에 따라 확산 효과를 분석하였고, 대심도 복층터널 화재연기 확산지연장치 연구개발에서는 대심도 복층터널에 적용성이 뛰어나며 경제적으로 상품가치가 높은 스프링 탄성을 이용한 화재연기 확산지연장치에 대하여 연구하였다. 이에, 본 연구에서는 화재연기 확산을 지연시키기 위한 화재연기 확산지연장치 시제품을 제작하여 화재연기 확산지연 효과를 실험하였으며, 분석 결과 화재연기 확산지연장치 작동 시 화재연기 지연효과가 나타났다. 따라서, 화재연기 확산지연 장치를 대심도 복층터널에 적용시 대피자들의 인명피해를 최소화시킬 수 있을 것으로 판단된다.