• 센서학회지
• /
• 제17권3호
• /
• pp.217-222
• /
• 2008

$BaCl_2$ crystals were grown by using the Czochralski method, and their scintillation properties were measured. The emission spectrum was located in the range of $370{\sim}450$ nm, peaking at about 400 nm. The fluorescence decay time was approximately 75.9 ns for 662 keV ${\gamma}$-rays excitation. The energy resolution was about 24.4 % for $^{137}Cs$ 662 keV ${\gamma}$-rays, and the ${\alpha}/{\beta}$ ratio to $\alpha$ particles from a $^{210}Po$ 5.4 MeV was about 0.25.

• 방사성폐기물학회지
• /
• 제18권spc호
• /
• pp.1-19
• /
• 2020

Based on the current high-level radioactive waste management basic plan and the analysis results of spent nuclear fuel characteristics, such as dimensions and decay heat, an improved geological disposal concept for spent nuclear fuel from domestic nuclear power plants was proposed in this study. To this end, disposal container concepts for spent nuclear fuel from two types of reactors, pressurized water reactor (PWR) and Canada deuterium uranium (CANDU), considering the dimensions and interim storage method, were derived. In addition, considering the cooling time of the spent nuclear fuel at the time of disposal, according to the current basic plan-based scenarios, the amount of decay heat capacity for a disposal container was determined. Furthermore, improved disposal concepts for each disposal container were proposed, and analyses were conducted to determine whether the design requirements for the temperature limit were satisfied. Then, the disposal efficiencies of these disposal concepts were compared with those of the existing disposal concepts. The results indicated that the disposal area was reduced by approximately 20%, and the disposal density was increased by more than 20%.

• 한국추진공학회:학술대회논문집
• /
• 한국추진공학회 2008년도 제30회 춘계학술대회논문집
• /
• pp.163-167
• /
• 2008

30톤급 액체로켓엔진 연소기 연소시험을 통해 측정된 압력섭동 특성에 대한 결과를 제시하였다. 연소실 압력과 O/F비를 변화시키면서 수행된 46회의 연소시험의 결과를 바탕으로 30톤급 연소기의 연소 안정성을 대해 평가하였다. 정상 연소과정에서 발생하는 압력섭동 RMS 값이 연소실 압력의 2.6% 이내로서 정상상태에서 연소현상이 안정적임을 보여주었다. 또한 펄스건 강제교란을 통한 압력섭동의 감쇠 시간 계산결과가 3.5 msec 이내라는 것을 통해 동적으로 안정적인 연소기임을 확인하였다.

• 한국전기전자재료학회논문지
• /
• 제11권3호
• /
• pp.242-247
• /
• 1998

In this study, we have synthesized $ZnGa_2O_4$:Mn,X powder doped with Mn, MnO, $MnF_2$ and $MnCl_2$, low voltage green emitting phosphor, in vacuum atmosphere. From PL spectra, the intensity of the emission peak, the brightness with coactivator show that $ZnGa_2O_4$:Mn,Cl > $ZnGa_2O_4$:Mn,F > $ZnGa_2O_4$:Mn,O > $ZnGa_2O_4$:Mn. These improvement of the brightness are caused by the increase of the concentration of $Mn^{2+}$ ion. In case of $ZnGa_2O_4$:Mn,Cl and ZnGa$_2$O$_4$:Mn,F, the brightness is enhanced much more, which is owed to the decrease of defect of host material. For $ZnGa_2O_4$:Mn,Cl phosphor fabricated with optimized condition, the decay time becomes short from 30 ms of the $ZnGa_2O_4$:Mn and $ZnGa_2O_4$:Mn,O to 6 ms and the brightness of CL at 1 kV, 1 mA is 60 cd/$m^2$.

• 천문학회보
• /
• 제43권1호
• /
• pp.56.1-56.1
• /
• 2018

Tidal disruption events (TDEs) provide evidence for quiescent supermassive black holes (SMBHs) in the centers of inactive galaxies. TDEs occur when a star on a parabolic orbit approaches close enough to a SMBH to be disrupted by the tidal force of the SMBH. The subsequent super-Eddington accretion of stellar debris falling back to the SMBH produces a characteristic flare lasting several months. The theoretically expected bolometric light curve decays with time as proportional to $t^{-5/3}$. However, the light curves observed in most of the optical-UV TDEs deviate from the $t^{-5/3}$ decay rate especially at early time, while the light curves of some soft-X-ray TDEs are overall in good agreement with the $t^{-5/3}$ law. Therefore, it is required to construct the theoretical model for explaining these light curve variations consistently. In this paper, we revisit the mass fallback rates analytically and semi-analytically by taking account of the structure of the star, which is simply modeled by the polytrope. We find the relation between a polytropic index and the power law index of the mass fallback rate. We also discuss whether and how the decay curves, which we derived, fit the observed ones.

• 한국환경보건학회지
• /
• 제32권2호
• /
• pp.132-139
• /
• 2006

Number of aerosol, CO, $CO_2$ and TVOC after one-, two-, three-cigarettes smoking were monitored with time every 10 minute for 180 minutes in the seminar room (volume $51.1m^3$) when poorly-ventilated. IAQ monitor (IAQRAE, model PGM-5210) and PortCount (TSI, model 8020) were used for monitoring. Aerosol was decreased with exponential decay equation and it was estimated that number of aerosol would be long suspended (one cigarette 75/cc. two cigarettes 66/cc, three cigarettes 141/cc by 8hrs after smoking). While CO was also decreased with exponential or linear decay equation and correlated with number of aerosol strongly, TVOC and $CO_2$ were increased with linear equation in accordance with time lag. Most of TVOC and $CO_2$ were above standard levels of Korean Indoor Air Quality (Ministry of Environment) without regarding number of cigarettes. When naturally ventilated, all of CO, $CO_2$ and TVOC concentrations were dramatically decreased below standard levels of Korean Indoor Air Quality.

• 대한의용생체공학회:학술대회논문집
• /
• 대한의용생체공학회 1990년도 춘계학술대회
• /
• pp.39-42
• /
• 1990

지난 수년동안 MR을 이용한 생체내의 인의 분광을 얻기 위한 여러가지 방법들이 연구되었다. 그러나 대부분의 방법들은 선택시간의 지연으로 인하여 선택된 체적에서의 FID 신호가 짧은 T2 시간에 영향을 받았다. 본 논문에서는 인의 분광법으로 적절한 새로운 방법을 제시하였다. 이 방법은 k-공간을 방사형으로 스캔하면서 이루어지는 더 짧은 선택시간으로 T2 감쇄의 영향을 거의 받지 않으며, 좋은 선택도를 얻을 수 있었다.

• 한국정보디스플레이학회:학술대회논문집
• /
• 한국정보디스플레이학회 2009년도 9th International Meeting on Information Display
• /
• pp.127-130
• /
• 2009

High luminance 3D built-in PDP panel was developed with newly adopted fast-decaying phosphor. Luminance of 3D PDP was increased about 40% by reducing the particle size of RGB phosphors and using $Y_3(Al,Ga)_5O_{12}:Ce^{3+}$ phosphor. Decay time of developed 3D PDP was 5.2ms/4.9ms for Red/Green color.

• 한국세라믹학회지
• /
• 제35권10호
• /
• pp.1101-1106
• /
• 1998

Various $Zn_{2-x}SiO_4$:xMn based green phosphors were investigated in association with a co-dopant. The co-dopant incorporated into the phosphors are believed to alter the internal energy state of $Zn_{2-x}SiO_4$ : xMn So that the improvement in their intensity could be expected. Phosphor samples were prepared using the solid state reaction therein raw powders are mixed in the acetone and successively fired at $1300^{\circ}C$ for 4 hour. The fired powders are also heated up to $900^{\circ}C$ for 2 hour in the reduced atmoshpere and thereby giving The fired powders are also heated up to $900^{\circ}C$ for 2 hour in the reduced atmosphere and thereby giving rise to conspicuous enhancement of radiative efficiency. Basically the 0.08 mole ratio of the Mn con-centrations has the maximum value of the intensity so that a co-dopant are added to this Mn con-centration. When the Mg is co-doped with Mn luminescent intensity is proven to be promoted significantly.

• Journal of electromagnetic engineering and science
• /
• 제8권4호
• /
• pp.148-152
• /
• 2008

This paper describes the characteristics of lightning-induced voltages on subscriber telecommunication lines in Korea. Lightning parameters such as peak voltage, rise time, decay time, and steepness of the wave front were statistically analyzed from the measured results obtained using a waveform memory system. An induced voltage measurement system was also developed and installed at 286 sites in Korea to collect the induced voltage data. The distributions of lightning-induced voltages were also analyzed using these data.