• 대한전자공학회논문지TC
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• 제47권12호
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• pp.104-110
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• 2010

일본 TV 방송 선호의 전파월경 실태를 파악하기 위하여 지난 2003년 2월부터 2009년 10월까지 약 44개월간 일본 TV 방송 신호를 측정한 후 분석하였다. 국내에 유입되는 신호세기를 부산지역의 고정측정시스템을 이용하여 측정하였고 전파 분석모델 예측치와 측정치와의 상관성을 연도별 계절별로 분석하였다. 분석결과 일본방송신호의 전파월경 현상이 심각한 수준으로 평가되어 향후 디지털 전환 시 이에 대한 적절한 대응이 필요할 것으로 예측되었다.

• 한국유체기계학회 논문집
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• 제20권2호
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• pp.5-10
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• 2017

In this study, the Coanda effect inducing bump was applied to improve the film cooling effectiveness on the flat plate with $30^{\circ}$ and $45^{\circ}$ angled rectangular slots. The slot length to width ratio was 6. A cylindrical cap shaped structure, called Coanda bump, was installed at the exit of the slot to generate Coanda effect. The width and height of the bump was 10.5 mm and 1 mm, respectively. The film cooling effectiveness was measured at the fixed blowing ratio, M=2.0, using pressure sensitive paint (PSP) technique. The mainstream velocity was 10 m/s and the turbulence intensity was about 0.5%. Results showed that the film cooling effectiveness for case of $30^{\circ}$ angled slot was higher than that of $45^{\circ}$ angled slot. It was found that there was no positive effect of Coanda effect on the overall averaged film cooling effectiveness for the $30^{\circ}$ angled slot. On the other hand, for the $45^{\circ}$ angled slot, the film cooling effectiveness was improved with the installation of the Coanda bump.

• 한국전기전자재료학회논문지
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• 제11권8호
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• pp.646-651
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• 1998

In this present study, the luminescence characteristics and mechanism of energy $CaTiO_3$:Pr phosphor were studied using disk specimens sintered at various temperatures and envirenment. A single-phase $CaTiO_3$:Pr was synthesized by sintering above 140$0^{\circ}C$ and its crystal structure was found to be perovskite orthorhombic. A dominant peak around 360 nm and a broad peak around 395 nm were observed in the PLE(Photoluminescence Excitation) spectrum of $CaTiO_3$:Pr with fixed emission wavelength at 612 nm, the decay time of 360 nm excitation was found to be longer than that of 395 nm excitation. From this result, it is assumed that the free carrier excited to 360 nm is transferred to 395 nm energy level. Therefore, the decrease in 395 nm intensity observed in CaTiO$_3$:Pr specimens sintered in Ar gas environment induced shorter decay time and improved CL luminescence.

• 한국의학물리학회지:의학물리
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• 제13권3호
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• pp.176-180
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• 2002

방사선 치료 분야에서 환자를 고정시킬 수 있는 더 나은 도구에 대한 요구가 증가하고 있다. 특히, 전신방사선 수술과 세기 조절 방사선 치료 등의 치료 방법에서는 확실하면서도 실용적인 고정 기구가 필요하다. 외부 빔 방사선 치료시 복부를 고정하는 새로운 방법으로, 공기 주입형 풍선 담요(air-injected balloon blanket, AIBB)를 설계, 제작하였다. 공기가 풍선 담요의 내부로 주입되며 환자의 복부를 눌러 환자를 고정시킨다. AIBB는 환자의 움직임을 고정시키는데 유용한 역할을 하여, 환자의 복부에서 호흡에 의해 가장 많이 움직이는 앞뒤 방향 움직임을 5 mm 이상 감소시킬 수 있었다. 이러한 고정 기구의 이용으로 호흡에 따르는 환자의 움직임이 감소되었고, 실험 결과는 AIBB를 임상에서 사용하는 것이 가능하다는 것을 보여주었다.

• 대한기계학회논문집B
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• 제32권3호
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• pp.190-197
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• 2008

It was experimentally studied that the stabilization mechanism of turbulent, lifted jet flames in a non-premixed condition to reveal the newly found liftoff height behavior of hydrogen jet. The objectives are to report the phenomenon of a liftoff height decreasing as increasing fuel velocity, to analyse the flame structure and behavior of the lifted jet, and to explain the mechanisms of flame stability in hydrogen turbulent non-premixed jet flames. The hydrogen jet velocity was changed from 100 to 300m/s and a coaxial air velocity was fixed at 16m/s with a coflow air less than 0.1m/s. For the simultaneous measurement of velocity field and reaction zone, PIV and OH PLIF technique was used with two Nd:Yag lasers and CCD cameras. As a result, it was found that the stabilization of lifted hydrogen diffusion flames is correlated with a turbulent intensity and Karlovitz number.

• Journal of Magnetics
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• 제22권2호
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• pp.326-332
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• 2017

The effects of exposure to an extremely low-frequency magnetic field (25 Hz 20G) on animal cells have been studied. In some reports, stimulation was performed for fixed frequency and variations in magnitude; however, animal-cell experiments have established that both parameters play an important role. The present work undertook the modeling, simulation, and development of a uniform-magnetic-field generation system with variable frequency and stimulation intensity (0-60 Hz, 1-25G) for experimentation with cell cultures in situ. The results showed a coefficient of variation less than 1 % of the magnetic-field dispersion at the working volume, which is consistent with the corresponding simulation results demonstrating a uniform magnetic field. On the other hand, long-term tests during the characterization process indicated that increments of only $0.4^{\circ}C$ in the working volume temperature will not be an interfering factor when experiments are carried out in in situ cell cultures.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2017년도 제48회 춘계학술대회논문집
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• pp.814-819
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• 2017

본 논문에서는 점화 위치 및 시간에 따른 점화 지연 및 연소 불안정에 미치는 영향을 관찰하는 것이 목표이다. 산화제는 기체 산소를 사용하였고 연료는 액체 케로신을 사용하였다. 점화 지연 및 연소 불안정 정도를 관찰하기 위해 압력 트랜스듀서를 이용하여 정압을 측정하였다. 점화 위치는 분사기 스페이서를 이용하여 변경하였다. 모든 경우의 점화기 작동 시기를 제외한 점화 시퀀스는 동일하게 설정하였고 점화 시간은 25 ms 간격으로 설정하였다. 점화 시간이 늦어질수록 초기 압력 피크값과 점화 지연 시간이 증가하는 경향을 보였다. 점화 위치가 분사기로부터 멀어질수록 초기 압력 피크 이후 불안정한 화염 발달 구간이 존재하였다.

• 한국세라믹학회지
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• 제50권4호
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• pp.280-287
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• 2013

Plate-type phosphor is a promising substitute in overcoming the issues related to the powder phosphor paste mixed with resin. In this research, $Ca-{\alpha}-SiAlON:Eu^{2+}$ plate phosphor ($Ca_xSi_{12-(m+n)}Al_{m+n}O_nN_{16-n}:Eu_y$) was investigated for the varied compositions (m,n) of the host crystal with the fixed Eu content (y). Densification was promoted for the compositions with increasing 'm' values for the m=2n relationship. Dictated by the Eu concentration inside the phosphor crystal, photoluminescence intensity was stronger in ${\alpha}2$ specimen (m = 3.0, n = 1.5) containing the second phases when compared to ${\alpha}1$ specimen (m = 1.5, n = 0.75) comprising a single-phase ${\alpha}$-SiAlON. The concentration of Eu in the non-emitting amorphous interfacial glass phase was 2~4 times of the designed Eu concentration inside the ${\alpha}$-SiAlON crystal.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 추계학술대회 논문집 Vol.16
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• pp.124-127
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• 2003

The stochiometric $AgGaSe_2$ polycrystalline mixture of evaporating materials for the $AgGaSe_2$ single crystal thin film was prepared from horizontal furnance. To obtain the single crystal thin films, $AgGaSe_2$ mixed crystal and semi-insulating GaAs(100) wafer were used as source material and substrate for the Hot Wall Epitaxy (HWE) system, respectively. The source and substrate temperature were fixed at $630^{\circ}C$ and $420^{\circ}C$, respectively. The thickness of grown single crystal thin films is $2.1{\mu}m$. The single crystal thin films were investigated by photoluminescence and double crystal X-ray diffraction(DCXD) measurement. From the photoluminescence measurement of $AgGaSe_2$ single crystal thin film, we observed free excition ($E_x$) observable only in high quality crystal and neutral bound excition ($D^{\circ}$,X) having very strong peak intensity. And, the full width at half maximum and binding energy of neutral donor bound excition were 8 meV and 14.1 meV, respectively. By Haynes rule, an activation energy of impurity was 141 meV.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 B
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• pp.1775-1777
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• 2005

In this paper, maximum output of three different temperature conditions of the photovoltaic modules have been tested and compared to obtain the optimum conditions for the maximum power operation. Temperatures of the cell and module have been set to $20^{\circ}C$, $25^{\circ}C$ and $30^{circ}C$ under the constant light intensity of 1kW/$m^2$. 125${\times}$125mm 36 single crystal solar cells having 80 [W] each have been serially connected in the module. From the results, maximum output deviation of 4.67% has been obtained under the ceil temperature of $20^{\circ}C$ and module temperature of $30^{\circ}C$ while minimum deviation of 0.41${\sim}$0.92% has been measured under the same temperatures of cell and module. Therefore it has been found that the temperature of both cell and module should be fixed to $25^{\circ}C$ to obtain stable data unless the temperature coefficient should be compensated for the testing sample.