• Nuclear Engineering and Technology
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• 제56권5호
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• pp.1895-1901
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• 2024

The fission model, G4ParaFissionModel, was enhanced in this study, mainly focusing on refining the energy dependence of the peak-to-valley ratio in the mass distribution and the energy dependence of the average total kinetic energy (TKE). The enhanced model was employed to investigate the characteristics of fission products from ²³⁵U(n, f) reaction. The calculated results, including fission yield, TKE distribution, prompt fission neutron and gamma spectra, were compared with both evaluated and experimental data. The comparison shows that these physical observables related nuclear data, which are of importance for developments of the nuclear power and physics, can be reasonably well reproduced.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2012년도 자성 및 자성재료 국제학술대회
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• pp.104-105
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• 2012

The temperature dependence of the effective magnetic anisotropy constant K(T) of ferrite nanoparticles is obtained based on the measurements of SQUID magnetometry. For this end, a very simple but intuitive and direct method for determining the temperature dependence of anisotropy constant K(T) in nanoparticles is introduced in this study. The anisotropy constant at a given temperature is determined by associating the particle size distribution f(r) with the anisotropy energy barrier distribution $f_A(T)$. In order to estimate the particle size distribution f(r), the first quadrant part of the hysteresis loop is fitted to the classical Langevin function weight-averaged with the log?normal distribution, slightly modified from the original Chantrell's distribution function. In order to get an anisotropy energy barrier distribution $f_A(T)$, the temperature dependence of magnetization decay $M_{TD}$ of the sample is measured. For this measurement, the sample is cooled from room temperature to 5 K in a magnetic field of 100 G. Then the applied field is turned off and the remanent magnetization is measured on stepwise increasing the temperature. And the energy barrier distribution $f_A(T)$ is obtained by differentiating the magnetization decay curve at any temperature. It decreases with increasing temperature and finally vanishes when all the particles in the sample are unblocked. As a next step, a relation between r and $T_B$ is determined from the particle size distribution f(r) and the anisotropy energy barrier distribution $f_A(T)$. Under the simple assumption that the superparamagnetic fraction of cumulative area in particle size distribution at a temperature is equal to the fraction of anisotropy energy barrier overcome at that temperature in the anisotropy energy barrier distribution, we can get a relation between r and $T_B$, from which the temperature dependence of the magnetic anisotropy constant was determined, as is represented in the inset of Fig. 1. Substituting the values of r and $T_B$ into the $N{\acute{e}}el$-Arrhenius equation with the attempt time fixed to $10^{-9}s$ and measuring time being 100 s which is suitable for conventional magnetic measurement, the anisotropy constant K(T) is estimated as a function of temperature (Fig. 1). As an example, the resultant effective magnetic anisotropy constant K(T) of manganese ferrite decreases with increasing temperature from $8.5{\times}10^4J/m^3$ at 5 K to $0.35{\times}10^4J/m^3$ at 125 K. The reported value for K in the literatures is $0.25{\times}10^4J/m^3$. The anisotropy constant at low temperature region is far more than one order of magnitude larger than that at 125 K, indicative of the effects of inter?particle interaction, which is more pronounced for smaller particles.

• 한국가스학회지
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• 제1권1호
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• pp.7-13
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• 1997

최소발화에너지의 압력의존성을 고찰하기 위해 열발화이론, 열전달개념, 이상기체법칙, 그리고 반응속도론에 의해 시도하였다. 최소발화에너지와 압력의 상관관계식을 문헌자료의 다중회귀분석을 통하여 수식화하였다. 이 방법에 적용한 물질은 대표적인 탄화수소인 프로판과 노말펜탄이었다. 제시된 방법론에서 압력변화에 따른 예측된 최소발화에너지는 아주 작은 평균오차에서 문헌값과 일치하고 있다. 따라서 제시된 방법론은 탄화수소의 최소발화 에너지를 예측하는 일반적인 방법으로 제시하고 있다.

• 전기학회논문지P
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• 제52권2호
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• pp.68-73
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• 2003

$Zn_4SnSe_6$ and $Zn_4SnSe_6:Co^{2+}$ single crystals were grown by the chemical transport reaction(CTR) method. They were crystallized in the monoclinic structure. These temperature dependence of the optical energy gap were closely investigated over the temperature range 10[K]~300[K]. The direct energy gaps of $Zn_4SnSe_6$ and $Zn_4SnSe_6$:$Co^{2+}$ single crystals were given by 2.146[eV] and 2.042[eV] at 300[K]. The temperature dependence of the optical energy gap is well presented by the Varshni equation.

• 대한방사선기술학회지:방사선기술과학
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• 제16권2호
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• pp.51-60
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• 1993

The $CaSO_4$ : Tm-PTFE TLDs have been prepared and their energy dependences of TL intensity to X-rays have been investigated. The dose dependence of the prepared $CaSO_4$ : Tm-PTFE TLDs is linear within the range of $100{\mu}Gy-10Gy$ for X-rays and gamma rays. The spectral peaks of TL emission spectrum are at about 350nm and 475nm. The fading rate of the main peak has been found to be about 2% for 30days when $CaSO_4$ : Tm-PTFE TLDs stored in the dark room at room temperature. The energy dependence of $CaSO_4$ : Tm-PTFE TLD has been compensated by combining the TL responses of one bare TLD and five TLDs filtered with 1.0mm Al, 0.2mm Cu, 0.5mm Cu, 1.5mm Cu, 2.0mm Pb respectively. The determined correction coefficients for filter combination are $a_0=0.078,\;a_1=-0.009,\;a_2=-0.235,\;a_3=0.588,\;a_4=0.568\;and\;a_5=0.180$ respectively. From the results of these studies, the prepared TLD badge of six dosimeter combination may be useful as a radiation dosimeter for personal and environmental monitoring.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1998년도 추계학술발표회요약집
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• pp.208-208
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• 1998

• Journal of Astronomy and Space Sciences
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• 제30권4호
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• pp.247-253
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• 2013

It has long been known that the magnetospheric particles can precipitate into the atmosphere of the Earth. In this paper we examine such precipitation of energetic electrons using the data obtained from low-altitude polar orbiting satellite observations. We analyze the precipitating electron flux data for many periods selected from a total of 84 storm events identified for 2001-2012. The analysis includes the dependence of precipitation on the Kp index and the electron energy, for which we use three energies E1 > 30 keV, E2 > 100 keV, E3 > 300 keV. We find that the precipitation is best correlated with Kp after a time delay of < 3 hours. Most importantly, the correlation with Kp is notably tighter for lower energy than for higher energy in the sense that the lower energy precipitation flux increases more rapidly with Kp than does the higher energy precipitation flux. Based on this we suggest that the Kp index reflects excitation of a wave that is responsible for scattering of preferably lower energy electrons. The role of waves of other types should become increasingly important for higher energy, for which we suggest to rely on other indicators than Kp if one can identify such an indicator.

• 대한전자공학회논문지
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• 제21권2호
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• pp.36-46
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• 1984

Ga1-xlnxSe 단결정을 X=0.0∼0.1영역과 X=0.8-1.0영역에서 Bridgman방법으로 성장시켰다. 성장된 Ga1-xlnxSe 단결정은 X=0.0∼0.1영역에서는 hexagonal구조, X=0.8∼1.0영역에서는 rhombohedral 구조를 가지고 있었다. CaInSe 단결정은 간접천이형 energy gap을 가지고 있었으며, 15°K에서 250°K로 시편의 온도가 상승할 때 energy gap 은 감소되었고, 온도계수는 (-2.4∼-4.3)×10-4eV/K으로 주어졌다. Ga1-xlnxSe 단결정의, energy gap에 온도 의존성은 Schmid의 electron-phonon 상호작용의 이론으로 설명할 수 있었다.

• Radiation Oncology Journal
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• 제17권3호
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• pp.256-260
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• 1999

목적 : 얇은 박막을 위에 얹은 TLD 선량계의 반응 값에 영향을 미치는 인자를 조사하였고, 특히, 금속박막을 얹은 TLD 선량계의 광자에너지와 표면 흡수선량에 대한 의존성을 조사하였다. 방법 및 재료 : 본 연구에서는 TLD-100과 TLD-100 위에 얹은 Slt은 물질로는 주석, 금, 그리고 TE 플라스틱 판을 사용하였다. 각 금속 박막의 두께는 0.1 mm, TE 플라스틱 판의 두께는 1 mm였고 각 박막의 면적은 TLD-100의 면적과 같이 하였다. 방사선치료에 많이 산이는 6 MV에서 15 MV사이의 광자에너지에 대한 TLD-100의 반응감도와 금박막을 얹은 TLD-100의 반응감도, 그리고 주석 박막을 얹은 TLD-100의 반응감도를 비교해 보았다. 결과 : 금속 박막을 얹은 TLD의 경우 표면 흡수선량의 증가가 명백히 나타나고, 금 박막을 얹은 TLD의 경우 10MV에서 정상 TLD보다 약 1.83배 정도 과잉 반응하는 것으로 관측되었으며, 흡수선량에 따른 반응감도의 변화는 주석을 얹은 TLD의 경우가 가장 작았다 금속 박막을 얹은 TLD의 일반 TLD에 대한 상대 반응감도는 에너지에 대한 의존성을 거의 나타내지 않았다. 그리고 311은 박막의 조직에 대한 등가 두께에 따라 반응감도가 증가하였다. 결론 : 금속박막을 얹은 TLD 선량계의 반응값이 고 에너지(6-15 MV)에 대한 의존성을 거의 나타내지 않았으며, 흡수선량에 대한 선형성도 뛰어난 것으로 관측되었다. 따라서 금속박막을 얹은 TLD 선량계는 매우 작은 크기의 광자빔과 표면흡수선량의 측정에 매우 적합한 것으로 사료된다.

• Journal of Electrical Engineering and Technology
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• 제8권3호
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• pp.421-427
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• 2013

The dependence between wind speeds in multiple wind sites has a considerable impact on the reliability of power systems containing wind energy. This paper presents a new method to generate dependent wind speed time series (WSTS) based on copulas theory. The basic feature of the method lies in separating multivariate WSTS into dependence structure and univariate time series. The dependence structure is modeled through the use of copulas, which, unlike the cross-correlation matrix, give a complete description of the joint distribution. An autoregressive moving average (ARMA) model is applied to represent univariate time series of wind speed. The proposed model is illustrated using wind data from two sites in Canada. The IEEE Reliability Test System (IEEE-RTS) is used to examine the proposed model and the impact of wind speed dependence between different wind regimes on the generation system reliability. The results confirm that the wind speed dependence has a negative effect on the generation system reliability.