• 대한기계학회논문집A
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• 제26권6호
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• pp.1107-1113
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• 2002

This study presents the hydrogen emblittlement in the metal, which decreases the ductility and then induces the brittle fracture. The contribution deals with the effect of strain rate and notch geometry on hydrogen emblittlement of 1.25Cr-0.5Mo and 2.25Cr-1Mo steels, which are in use at high pressure vessel. Smooth and notched specimens were examined to obtain the elongation and tensile strength. For charging the hydrogen in the metal, the cathodic electrolytic method was used. In this process, current density is maintained constant. The amount of hydrogen penetrated in the specimen was detected by the hydrogen determenator(LECO RH404) with the various charging time. The distribution of hydrogen concentration penetrated in the specimen was obtained by finite element analysis. The amount of hydrogen is high in smooth specimen and tends to concentrate in the vicinity of surface. The elongation and tensile strength decreased with the passage of charging time in 1.25Cr-0.5Mo and 2.25Cr-1Mo steels. The elongation increased and tensile strength decreased as strain rate increased. As a result of this study, it is supposed that 1.25Cr-0.5Mo steel is more sensitive than 2.25Cr-lMo steel in hydrogen embrittlement. Hydrogen embrittlement susceptibility of notched specimen after hydrogen charging is more remarkable than that of smooth specimen.

• 정보관리학회지
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• 제32권3호
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• pp.317-340
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• 2015

이 연구는 한국의 정신의학 국제공동연구 협력망 구축을 위하여, 네트워크 분석에 중점을 두어 정신의학 국제공동연구의 공저관계를 반영하는 지식구조를 규명하였다. 먼저 국가 레벨에서의 지식구조 분석 결과는 다음과 같다. 첫째, 5년 간 공동연구 비율은 89.97%로 높은 편이며, 시간의 경과에 따라 국제공동연구의 비율은 증가함을 확인하였다. 둘째, 아시아 국가들 간의 협업은 저조한 상태임을 확인하였다. 셋째, 국제공동연구 논문 수 및 중심성 값이 가장 높은 국가(또는 집단)는 EU-28로 확인되었다. 또한 연구성과 레벨에서의 지식구조 분석 결과는 다음과 같다. 중심성과 연구성과와의 상관관계를 분석하였으며, 분석 결과 세 가지 중심성 지표간에는 정적 상관관계가 나타났고 중심성이 높은 국가는 연구성과도 좋았다.

• 한국항공우주학회지
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• 제31권6호
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• pp.72-78
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• 2003

액체로켓용 터보펌프 인듀서에 대한 수치해석적 연구가 수행되었다. 5,000RPM 및 6,000RPM의 회전속도 조건에서 여러 가지 유량조건에 대하여 수치해석이 수행되었다. 이에 대한 입구유동각, 쉬라우드 표면 정압분포, 수두 및 효율에 대한 분석이 수행되었으며, 실험값과 비교하였다. 쉬라우드 정압의 분포는 실험과 비교하여 잘 일치하는 결과를 얻을 수 있었으나, 입구의 역류가 심한 지역에서는 실험값과 차이를 보였다. 전체성능, 즉, 수두 및 효율은 대체로 실험값과 잘 일치하였지만, 유량계수 0.08이상의 고유량에서 계산값이 실험치에 비하여 낮게 예측하는 것이 확인되었다. 본 연구에 채택된 인듀서의 경우, 유량계수가 0.074일 경우에 수력성능이 최고가 되었으나, 유량계수가 0.085이상에서 입사각이 양의 값을 가지게 되었다. 흡입성능의 측면에서는 입사각이 양의 값을 가지는 것이 권장되므로 설계자는 성능과 흡입성능에서 적절한 유량계수를 선택하여야 할 것이다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 1995년도 춘계학술대회논문집; 전남대학교, 19 May 1995
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• pp.196-201
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• 1995

The broadband and discrete sources of sound in small cooling fans of propeller type and centrifugal type were investigated to understand the turbulent vortex structures from many bladed fans using ANSI test plenum for small air-moving devices (AMDs). The noise measurement method uses the plenum as a test apparatus to determine the acoustic source spectral density function at each operating conditions similar to real engineering applications based on acoustic similarity laws. The characteristics of fans including the head rise vs. volumetric flow rate performance were measured using a performance test facility. The sound power spectrum is decomposed into two non-dimensional functions: an acoustic source spectral distribution function F(St,.phi.) and an acoustic system response function G(He,.phi.) where St, He, and .phi. are the Strouhal number, the Helmholtz number, and the volumetric flow rate coefficient, respectively. The autospectra of radiated noise measurements for the fan operating at several volumetric flow rates,.phi., are analyzed using acoustical similarity. The rotating stall in the small propeller fan with a bell-mouth guided is mainly due to a leading edge separation. It creates a blockage in the passage and the reduction in the flow rate. The sound power levels with respect to the rotational speeds were measured to reveal the mechanisms of stall and/or surge for different loading conditions and geometries, for example, fans installed with a impinging plate. Lee and Meecham (1993) studied the effect of the large-scale motions like impinging normally on a flat plate using Large-Eddy Simulation(LES) and Lighthill's analogy.[ASME Winter Annual Meeting 1993, 93-WA/NCA-22]. The dipole and quadrupole sources in the fans tested are shown closely related to the vortex structures involved using cross-correlations of the hot-wire and microphone signals.

• 음성과학
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• 제9권4호
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• pp.93-103
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• 2002

The purpose of this study was to establish preliminary data on the speech rates in groups of normal speaking adults and children. The results of the present study are intended to serve as clinical measurement guidelines for diagnosis, assessment, treatment planning, and therapy progresses of stuttering. Thirty-one adults (16 females, 15 males), aged 18-30 years and thirty normally developing children (15 females, 15 males), aged 8-10, participated in the study. The subjects' reading of the Stroll (Jeong, 1994) passage and l-minute portion of talking about the daily routine were sampled. The adult speakers had rates of $308.29\pm22.57$ syllables per minute (SPM) or $108.06\pm6.17$ words per minute (WPM) during reading, and $252.87\pm40.86$ SPM and $92.26\pm17.12$ WPM during talking. The children had rates of $176.67\pm33.65$ SPM or $64.07\pm12.62$ WPM during reading, and $149.30\pm33.14$ SPM and $56.60\pm11.36$ WPM during talking. The results of t-tests for reading and talking tasks in adults showed that SPM in reading (t=2.211, p< .05) and WPM in talking (t=-2.284, p< .05) differed significantly by the gender. To answer the questions whether the rate is different across children' s gender and age, a two-way ANOVA was performed. Both SPM and WPM in reading tasks were significantly different between groups of children aged 8 and 10 (p< 01), In speaking tasks, both SPM and WPM were significantly different between groups of children aged 8 and 10, and between 9 and 10.

• 설비공학논문집
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• 제17권10호
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• pp.898-906
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• 2005

The present study has been conducted to investigate convective heat/mass transfer in the cooling passage with bleed holes. The rotating square channel has 40.0 mm hydraulic diameter and the bleed holes on the leading surface of the channel. The hole diameter of bleed hole is 4.5mm and its spacing is ( p/d:4.9) about five times of hole diameter. Exit mass flow rate through bleed holes is $10\%$ of the main mass flow rate and relation number is changed form 0.0 to 0.4. A naphthalene sublimation technique is employed to determine the detailed local heat transfer coefficients using the heat and mass transfer analogy The cooling performance is influenced by exit mass flow rate through bleed holes and Coriolis force of rotating channel for fixed Reynolds number. The heat transfer on the leading surface is decreased due to Coriolis force. However the total heat transfer is enhanced around holes on the leading surface because of trapping flow by bleeding.

• International journal of advanced smart convergence
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• 제8권3호
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• pp.27-38
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• 2019

I reviewed about dyeing fastness and functional properties of the non-mordant dyed cotton and iron mordant dyed cotton with astringent persimmon juice. In the UV-VIS spectrum of astringent persimmon juice, the maximum absorption wavelength of the juice was 272.0 nm, which was a characteristic peak of tannin. In dyeing fastness, light fastness of the non-mordant dyed cotton was a little low at grade 2~3. But by the iron mordant treatment, the light fastness was good at grade 4. Dry cleaning fastness to discoloration and contamination was excellent at grade 4~5 for both the non-mordant dyed cotton and iron-mordant dyed cotton. Their rub fastness were grade 3 and grade 2~3 respectively, in the dry condition, and grade 2~3 and grade 3 respectively, in the wet condition. In the perspiration fastness of the non-mordant dyed cotton, the discoloration from acidity and alkalinity was grade 3~4 and grade 3, respectively, and contamination from acidity and alkalinity was relatively good at grade 4. Meanwhile, in the perspiration fastness of the non-mordant dyed cotton, discoloration from acidity and alkalinity was fair, both recording grade 3~4, and contamination from acidity and alkalinity was very good, both recording grade 4~5. In the ultraviolet protection effect of the non-mordant dyed cotton and iron-mordant dyed cotton, the ultraviolet protection factor was both 50+, both of which showed an excellent ultraviolet blocking effect. And the protection rate of UV-A appeared 98.4% and 99.1%, respectively, and the protection rate of UV-B showed 98.7% and 99.2, respectively. In addition, both exhibited an excellent deodorization rate over 99.9% or more, irrespective of the passage of time. Also, both showed an excellent antimicrobial activity over 99.9% or more against Staphylococcus aureus and Klebsiella pneumoniae.

• 한국약용작물학회지
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• 제1권1호
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• pp.10-15
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• 1993

본 연구는 1991년부터 1992년까지 2개년간 경상북도 농촌진흥원 특용작물 시험포장에서 풍기종과 의성종을 공시하여 채종시기와 종자 후숙방법별 100립중과 출현율을 경시적으로 조사한 바 그 결과를 요약하면 다음과 같다. 1. 풍기종은 의성종에 비해 100립중이 무거운 대립 종이었는데 두 품종 모두 7월 25일경 100립중이 최대가 되었고 이후 점차 감소되어 7월 25일 이후 종자가 등숙되는 시기로 판단되었다. 2. 채종시기에 따른 출현율은 풍기종이 7월 5일 채종한 종자에서 7.8%의 출현율을 나타내었고 의성종은 10일정도 늦었는데 두 품종 모두 8월 15일 채종에서 평균 출현율은 풍기종이 96.7%, 의성종은 94.0%로 가장 높았다. 3. 종실채종과 협실채종에서 후숙시킨 것은 후숙시키지 않고 즉시 파종한 것 보다 출현율이 높았는데 특히, 7월 5일${\sim}$8월 5일 사이의 조기 채종에서 출현율이 높고 8월(月) 15일(日) 이후 채종에서 일정한 경향은 없었다. 또한 종실 및 협실 후숙에 있어서 7월 5일과7월 15일 채종한 것은 10일간 후숙한 것보다 $20{\sim}30$일 후숙시킨 것이 출현율이 약간 높은 경향이고 7월 25일 이후 채종에서는 차이를 볼 수 없었다.

• 한국가축번식학회지
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• 제24권1호
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• pp.49-57
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• 2000

본 연구는 소 태아섬유아세포를 이용하여 핵이식 후 세포의 휴면처리, 세포의 passage 수 및 세포의 기원이 복제란의 발육에 미치는 영향을 검토하였다.3.57개 월령 한우 수컷 태아의 피부 및 간 조직에서 세포를 채취하여 체외에서 4∼6 회 계대배양 후 동결하였다가 핵이식에 사용하였다. 세포는 핵이식 전에 혈청기아처리를 하였으며, 대조구로는 활발히 분열 중의 무처리 세포를 사용하였다. Donor 세포는 미수정란의 탈핵세포질에 이식 후 전기융합 및 활성화를 실시하였고, 재구축배는 7∼9 일간 체외배양하여 발육농을 검토하였다. 배반포로 발육된 일부 복제란은 발정 7∼8 일째의 수란우에 이식하였다. 복제란의 배반포 발육율은 혈청기아 처리구 (25.3%)가 무처리구 (15.9%)에 비하여 유의적으로 높았으나 (P＜0.05), 세포의 passage 수 (4∼6회) 에 관계없이 23.1∼25.0%로 나타났고, 피부 및 간유래 복제란의 배반포 발육율도 23.8∼25.2% 로 두 조직세포 간에 차이가 없었다. 복제란의 이식 후 60일 및 120일에 수란우의 34.4% 및 15.6%가 각각 임신이 확인되었으며, 초자화동결된 태아 피부세포 복제란으로부터 1두의 수컷 송아지가 생산되었다. 본 연구의 결과는 복제란의 체외발육능이 세포의 휴면처리에 의하여 향상되었으나, 세포의 passage 수 (4∼6 회) 및 세포의 두 기원 (피부 및 간) 에 의해서는 영향을 받지 않으며, 태아 피부세포 유래 복제란으로부터 산자가 생산될 수 있음을 확증한다.

• 대한기계학회논문집B
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• 제27권12호
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• pp.1750-1757
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• 2003

This paper describes the flow measurements inside the blade passage of an axial flow fan by using a rotating hot-wire probe sensor from a relative flame of reference fixed to the rotor blades. The validity of fan rotor designed by a streamline curvature equation was performed by the measurement of the three-dimensional flow upstream and downstream of the fan rotor using a 5-hole pitot tube. The vortical flow structure near the rotor tip can be clearly observed by the measurements of a relative velocity and its fluctuation on quasi-orthogonal planes to a tip leakage vortex. Larger vortical flow, which results in higher blockage in the main flow, is formed according to decrease a flow rate. The vortical flow spreads out to the 30 percent span from the rotor tip at near stall condition. In the design operating condition, the tip leakage vortex is moved downstream while the center of the vortex keeps constant in the spanwise direction. Detailed characteristics of a velocity fluctuation with relation to the vortex were also analyzed.