• 한국분무공학회지
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• 제22권3호
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• pp.116-121
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• 2017

Pre-combustion chamber type indirect diesel engines have different combustion characteristics compared with those of common rail direct injection engine. The CONVERGE, specific engine CFD program, was used to simulate hollow cone spray model and combustion. The air-fuel mixture flow propagating from pre-combustion chamber to cylinder was concentrated at top half and center of the pre-combustion chamber throat. Stronger mixture flow was formed at smaller and longer throat cases. As a result, thermal efficiency and fuel consumption were improved for modified throat shape and the soot emission was also reduced.

• 대한기계학회논문집B
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• 제25권4호
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• pp.507-513
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• 2001

Time averaged pressure distributions in a high-speed centrifugal compressor channel diffuser at design and off-design flow rates are investigated. Pressure distributions from the impeller exit to the channel diffuser exit are measured for various flow rates from choke to near surge condition, and the effects of operating condition are discussed. The strong non-uniformity in the pressure distribution is obtained over the vaneless space and semi-vaneless space caused by the impeller-diffuser interaction. As the flow rate increases, flow separation near the throat, due to large incidence angle at the vane leading edge, increases aerodynamic blockage and reduces the aerodynamic flow area downstream. Thus the minimum pressure location occurs downstream of the geometric throat, and it is named as the aerodynamic throat. And at choke condition, normal shock occurs downstream of this aerodynamic throat. The variation in the location of the aerodynamic throat is discussed.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집B
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• pp.548-554
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• 2000

The aim of this paper is to understand the time averaged pressure distributions in a high-speed centrifugal compressor channel diffuser at design and off-design flow rates. Pressure distributions from the impeller exit to the channel diffuser exit are measured and discussed far various flow rates from choke to near surge condition, and the effect of operating condition is discussed. The strong non-uniformity in the pressure distribution is obtained over the vaneless space and semi-vaneless space caused by the impeller-diffuser interaction. As the flow rate increases, flow separation near the throat, due to large incidence angle at the vane leading edge, increases aerodynamic blockage and reduces the aerodynamic flow area downstream. Thus the minimum pressure location occurs downstream of the geometric throat, and it is named as the aerodynamic throat. And at choke condition, normal shock occurs downstream of this aerodynamic throat. The variation in the location of the aerodynamic throat is discussed.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.2035-2040
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• 2004

A cone cylinder is used to obtain variable operation conditions for the sonic ejector-diffuser system. The cone cylinder is designed to move upstream and downstream to change the ejector throat area ratio, thus obtaining variable mass flow rates. The present study investigates the effects of ejector throat area ratio and operating pressure ratio on the entrainment of secondary stream for the variable sonic ejector system. In experiment, the ejector throat area is varied in the range from ${\psi}=11.88$ to 66.69, and the operating pressure ratio from $p_{0p}/p_a=1.25$ to 9.0. The results show that the variable sonic ejector system is suitable for a required entrainment ratio of secondary stream by altering the ejector throat area ratio and operating pressure ratio.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2004년도 제22회 춘계학술대회논문집
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• pp.414-417
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• 2004

A cone cylinder is used to obtain variable operation conditions for the sonic ejector-diffuser system. The cone cylinder is designed to be shifted upstream and downstream to change the ejector throat area ratio, thus obtaining variable mass flow rates. The present study investigates the effects of ejector throat area ratio and operating pressure ratio on the entrainment of secondary stream for the variable sonic ejector system. The study is carried out experimentally. The ejector throat area is varied at the range from Ψ= 11.88 to 66.69, and the operating pressure ratio is changed from $P_{op}$ / $P_{a}$=1.25 to 9.0. The results show that the variable sonic ejector system can be operated to obtain specific entrainment ratio of secondary stream by altering the ejector throat area ratio and operating pressure ratio.o.

• 한국추진공학회지
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• 제14권6호
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• pp.25-30
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• 2010

최근 이중목 노즐(Dual Throat Nozzle, DTN)을 사용하여 추진체의 추력을 제어하는 방법이 많은 주목을 받고 있다. 이중목 노즐은 공동을 사이에 두고 두 개의 노즐 목을 가지도록 설계된다. 본 연구에서는 DTN의 유동특성을 조사하기 위하여, 수치해석적인 방법을 적용하였으며, 2차 유동의 질량유량과 노즐 압력비를 변화시켰다. 수치해석에서는 2차원, 압축성 Navier-Stokes 방정식을 풀기 위하여, 유한체적법을 적용하였다. 그 결과 본 수치해석은 실험결과를 잘 예측하였으며, DTN을 이용한 추력벡터 제어는 추력계수와 유출계수의 항으로 상세하게 설명하였다.

• 한국의사학회지
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• 제25권1호
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• pp.81-91
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• 2012

Objectives : "Yayaoyuanfang" is a prescription book, compiled by Xuguozhen in 1267. In "Yayaoyuanfang", there are 13 chapters including "Throat, Mouth and Teeth". Because there are few prescription books focused only on mouth and teeth disease in traditional medicine, "Throat, Mouth and Teeth" in "Yayaoyuanfang" is distinctive. Methods : We try to analyze prescriptions by form, effectiveness and report experiences in "Yayaoyuanfang". Results : There are 95 prescriptions with 77 powder, 5 paste, 5 liquid, 2 granule and 5 other forms. Effectiveness of those are divided into teeth, gum and mouth. Effectiveness for teeth are about pains, weakness, cavity, discoloration and so on. Effectiveness for gum are about pain, swelling, weakness, shrinking, etc. Effectiveness for mouth is about bad breath. Conclusions : "Throat, Mouth and Teeth" in "Yayaoyuanfang" has professional prscriptions for throat, mouth and teeth with several form and effectiveness.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2010년도 제34회 춘계학술대회논문집
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• pp.339-342
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• 2010

최근 이중목 노즐(Dual Throat Nozzle, DTN)을 사용하여 추진체의 추력을 제어하는 방법이 많은 주목을 받고 있다. 이중목 노즐은 공동을 사이에 두고 두 개의 노즐 목을 가지도록 설계된다. 본 연구에서는 DTN의 유동특성을 조사하기 위하여, 수치해석적인 방법을 적용하였으며, 2차유동의 질량 유량을 변화시켰다. 수치해석에서는 2차원, 압축성 Navier-Stokes방정식을 풀기 위하여, 유한체적법을 적용하였다. 그 결과 본 수치해석은 실험결과를 잘 예측하였으며, DTN을 이용한 추력벡터 제어는 추력계수와 유출계수의 항으로 상세하게 설명하였다.

• 한국정보과학회논문지:소프트웨어및응용
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• 제34권3호
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• pp.226-234
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• 2007

본 논문은 환경 노이즈를 원천적으로 차단하는 성대 마이크를 이용한 명령어 인식기를 개발한다. 성대마이크는 환경 노이즈의 효과를 최소화하는 장점이 있다. 그러나 고주파의 부재와 부분적인 포먼트 정보 손실 때문에, 성대마이크를 이용해서 개발된 ASR시스템은 표준마이크를 이용한 시스템에 비해 낮은 성능을 보인다. 이러한 문제 때문에 ASR시스템 개발에 성대마이크를 이용한 경우는 표준 마이크로 낮은 성능을 보인다. 이러한 문제 때문에 ASR시스템 개발에 성대마이크를 이용한 경우는 표준 마이크로부터 입력되는 정보 보안하는데 주로 사용된다. 본 논문은 한국어의 음운적 특정과 신호 분석을 통해 성대마이크만을 사용한 높은 성능의 ASR 시스템을 개발 할 수 있음을 보인다. 주파수 대역내 에너지 합을 이용하는 MFCC 알고리즘이 갖는 성대신호 분석의 문제점을 제시하고, 성대신호를 대상으로 보다 높은 성능을 갖는 특정추출 알고리즘의 조건을 제시한다. 이러한 조건은 (1) 민감한 band-pass filter와 (2) 유/무성음 분리를 위해 사용하는 특정벡터의 사용이다 실험 결과 제안된 조건을 만족하는 ZCPA 알고리즘을 적용한 경우가 MFCC를 적용한 경우보다 약 16%정도의 높은 성능을 보인다. 그러고 CMS와 RASTA와 같은 channel normalization 알고리즘을 적용한 경우 약 2%의 성능 향상이 있다.

• 대한기계학회논문집B
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• 제28권10호
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• pp.1231-1237
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• 2004

Determination of geometric design parameters of a second-throat type annual supersonic ejector is described. Tested geometric parameters were primary nozzle area ratio, cross-sectional area of second-throat, L/D ratio of second-throat and primary flow injection angle. Varying these four geometric parameters, we build a test matrix made of 81 test conditions, and experimental apparatus was fabricated to accommodate them. For each test condition, the stagnation pressure of primary flow and the static pressure of the secondary flow were measured simultaneously along with their transition to steady operation and finally to unstarting condition. Comparing the performance curve of every case focused on starting pressure, the unstarting pressure and the minimum secondary pressure, we could derive correlations that the parameters have on the performance of the ejector and presented the optimal design method of the ejector. Additional experiments were carried out to find effects of temperature and mass flow rate of the secondary flow.