• 천문학회지
• /
• 제24권2호
• /
• pp.129-149
• /
• 1991

An attempt has been made to examine the characteristics of acoustic and MHD waves generated in stellar convection zones($4000\;K\;{\leq}\;T_{eff}\;{\leq}\;7000\;K$, $3\;{\leq}\;\log\;g\;{\leq}\;4.5$). With the use of wave generation theories formulated for acoustic waves by Stein (1967), for MHD body waves by Musielak and Rosner (1987, 1988) and for MHD tube waves by Musielak et al.(l989a, 1989b), the energy fluxes are calculated and their dependence on effective temperature, surface gravity and megnetic field strength are analyzed by optimization techniques. In computing magneto-convection models, the effect of magnetic fields on the efficiency of convection has been taking into account by extrapolating it from Yun's sunspot models(1968; 1970). Our study shows that acoustic wave fluxes are dominant in F and G stars, while the MHD waves dominant in K and M stars, and that the MHD wave fluxes vary as $T_{eff}^4{\sim}T_{eff}^7$ in contrast to the acoustic fluxes, as $T_{eff}^{10}$. The gravity dependence, on the other hand, is found to be relatively weak; the acoustic wave fluxes ${\varpropto}\;g^{-0.5}$, the longitudinal tube wave fluxes ${\varpropto}\;g^{0.3}$ and the transverse tube wave fluxes ${\varpropto}\;g^{0.3}$. In the case of the MHD body waves their gravity dependence is found to be nearly negligible. Finally we assesed the computed energy fluxes by comparing them with the observed fluxes $F_{ob}$ of CIV(${\lambda}1549$) lines and soft X-rays for selected main sequence stars. When we scaled the corrected wave fluxes down to $F_{ob}$, it is found that these slopes are almost in line with each other.

• Current Optics and Photonics
• /
• 제6권5호
• /
• pp.497-505
• /
• 2022

Topological photonic nanocavities are considered to possess outstanding optical performance, and provide new platforms for realizing strong interaction between light and matter, due to their robustness to impurities and defects. Here hybrid plasmonic topological photonic nanocavities are proposed, by embedding various plasmon nanoantennas such as gold nanospheres, cylinders, and rectangles in a topological photonic crystal corner-state nanocavity. The maximum quality factor Q and minimum effective mode volume V_eff of these hybrid nanocavities can reach the order of 10⁴ and 10^-4 (𝜆/n)³ respectively, and the high figures of merit Q/V_eff for all of these hybrid nanocavites are stable and on the order of 10⁵ (𝜆/n)^-3. The relative positions of the plasmon nanoantennas will influence the coupling strength between the plasmon structures and the topological nanocavity. The hybrid nanocavity with gold nanospheres possesses much higher Q, but relatively large V_eff. The presence of a gold rectangular structure can confine more electromagnetic energy within a smaller space, since its V_eff is smallest, although Q is lowest among these structures. This work provides an outstanding platform for cavity quantum electrodynamics and has a wide range of applications in topological quantum light sources, such as single-photon sources and nanolasers.

• Nuclear Engineering and Technology
• /
• 제52권12호
• /
• pp.2733-2742
• /
• 2020

This paper presents an assessment of applicability of the multigroup cross sections generated with Monte Carlo tools to the fast reactor analysis based on transport calculations. 33-group cross section sets were generated for simple one- (1-D) and two-dimensional (2-D) sodium-cooled fast reactor problems using the SERPENT code and applied to deterministic steady-state and depletion calculations. Relative to the reference continuous-energy SERPENT results, with the transport corrected P₀ scattering cross section, the k-eff value was overestimated by 506 and 588 pcm for 1-D and 2-D problems, respectively, since anisotropic scattering is important in fast reactors. When the scattering order was increased to P₅, the 1-D and 2-D problem errors were increased to 577 and 643 pcm, respectively. A sensitivity and uncertainty analysis with the PERSENT code indicated that these large k-eff errors cannot be attributed to the statistical uncertainties of cross sections and they are likely due to the approximate anisotropic scattering matrices determined by scalar flux weighting. The anisotropic scattering cross sections were alternatively generated using the MC²-3 code and merged with the SERPENT cross sections. The mixed cross section set consistently reduced the errors in k-eff, assembly powers, and nuclide densities. For example, in the 2-D calculation with P3 scattering order, the k-eff error was reduced from 634 pcm to -223 pcm. The maximum error in assembly power was reduced from 2.8% to 0.8% and the RMS error was reduced from 1.4% to 0.4%. The maximum error in the nuclide densities at the end of 12-month depletion that occurred in ²³⁷Np was reduced from 3.4% to 1.5%. The errors of the other nuclides are also reduced consistently, for example, from 1.1% to 0.1% for ²³⁵U, from 2.2% to 0.7% for ²³⁸Pu, and from 1.6% to 0.2% for ²⁴¹Pu. These results indicate that the scalar flux weighted anisotropic scattering cross sections of SERPENT may not be adequate for application to fast reactors where anisotropic scattering is important.

• Nuclear Engineering and Technology
• /
• 제55권7호
• /
• pp.2613-2620
• /
• 2023

Excellent thermal neutron absorption performance of boron expands the potential use of boron rich slag to prepare epoxy resin matrix nuclear shielding composites. However, shielding attenuation behaviors and mechanism of the composites against gamma rays are unclear. Based on the radiation protection theory, Phy-X/PSD, XCOM, and ⁶⁰Co gamma ray source were integrated to obtain the shielding parameters of boron rich slag/epoxy resin composites at 0.015-15 MeV, which include mass attenuation coefficient (µ_t), linear attenuation coefficient (µ), half value thickness layer (HVL), electron density (N_eff), effective atomic number (Z_eff), exposure buildup factor (EBF) and exposure absorption buildup factor (EABF).µ_t, µ, HVL, N_eff, Z_eff, EBF and EABF are 0.02-7 cm²/g, 0.04-17 cm^-1, 0.045-20 cm, 5-14, 3 × 10²³-8 × 10²³ electron/g, 0-2000, and 0-3500. Shielding performance is BS4, BS3, BS3, BS1 in descending order, but worse than ordinary concrete. µ and HVL of BS1-BS4 for ⁶⁰Co gamma ray is 0.095-0.110 cm^-1 and 6.3-7.2 cm. Shielding mechanism is main interactions for attenuation gamma ray by BS1-BS4 are elements with higher content or higher atomic number via Photoelectric Absorption at low energy range, and elements with higher content via Compton Scattering and Pair Production in Nuclear Field at middle and higher energy range.

• 전자공학회논문지C
• /
• 제35C권4호
• /
• pp.21-29
• /
• 1998

As silicon geometry shrinks into deep submicron and the operating speed icreases, higher accuracy is required in the analysis of the propagation delays of the gates and interconnects in an ASIC. In this paper, the driving characteristics of a CMOS gate is represented by a gatedriver model, consisting of a linear resistor $R_{dr}$ and an independent ramp voltage source $V_{dr}$ . We drivered $R_{dr}$ and $V_{dr}$ as the functions of the timing data representing gate driving capability and an effective capacitance $C_{eff}$ reflecting resistance shielding effect by interconnet circuits. Through iterative applications of these equations and AWE algorithm, $R_{dr}$ , $V_{dr}$ and $C_{eff}$ are comuted simulataneously. then, the gate delay is decided by $C_{eff}$ and the interconnect circuit delay is determined by $R_{dr}$ and $V_{dr}$ . this process has been implemented as an ASIC timing analysis program written in C language and four real circuits were analyzed. In all cases, we found less than 5% of errors for both of gate andinterconnect circuit delays with a speedup factor ranging from a few tens to a few hundreds, compared to SPICE.SPICE.

• 한국광학회지
• /
• 제7권1호
• /
• pp.72-76
• /
• 1996

Metallic glass 1605SC, 2826MB 두 재질에 대해 세 가지 본딩 구조를 가지는 광섬유 자왜변환기를 구성하여 구조에 따른 여러가지 자왜응답특성을 측정해 보았다. 측정결과 두 재질 모두에서 양끝 본딩이 경우 가장 좋은 자왜응답특성을 보였다. 2605SC의 경우 양끝 본딩구조를 가진 자왜변환기의 유효자왜상수 $C_{eff}$, saturation magnetostriction .lambda.$_{s}$ , 최소감지자계 $H_{min}$은 각각 1.2*$10^{-5}$O $e^{-2}$ , 7.4*$10^{-4}$ , 1.6*$10^{-7}$ Oe/.root.Hz로 측정되었고, 2826MB재질의 경우 양끝 본딩구조에서의 유효자왜상수 $C_{eff}$, saturation magnetostriction .lambda.$_{s}$ 는 각각 7.6*$10^{-6}$ O $e^{-2}$ , 3.4*$10^{-4}$ 로 측정되었다.되었다.

• 한국안전학회지
• /
• 제6권4호
• /
• pp.81-87
• /
• 1991

We propose the crack growth rate equation which will model fatigue crack growth rate behavior such that constant stress amplitude fatigue crack growth behavior can be predicted. Constant stress amplitude fatigue tests are conducted for four materials under three stress ratios of R＝0.2, R＝0.4 and R＝0.6. Materials which have different mechanical properties i.e. stainless steel, low carbon steel, medium carbon steel and aluminum alloy are used. Through constant stress amplitude fatigue test by using unloading elastic compliance method, it is confirmed that crack closure is a close relationship with fatigue crack propagation. We describe simply fatigue crack propagation behavior as a function of the effective stress intensity factor range ($\Delta$ $K_{eff}$＝U .$\Delta$K) for all three regions (threshold region, stable region). The fatigue crack growth rate equation is given by da / dN＝A($\Delta$ $K_{eff}$­$\Delta$ $K_{o}$ )$^{m}$ / ($\Delta$ $K_{eff}$­$\Delta$K) Where, A and m are material constants, and $\Delta$ $K_{o}$ is stress intensity factor range at low $\Delta$K region. $K_{cf}$ is critical fatigue stress intensity factor.actor.

• 천문학회보
• /
• 제37권2호
• /
• pp.139.1-139.1
• /
• 2012

Wilson and Bappu (1957) found a significant relationship (WBR) between the absolute magnitude ($M_v$) and the width of the Ca II K emission line (W) for late type stars. In this study, we revisit the WBR to claim that WBR can be an excellent indicator of stellar surface gravity. We analyze 95 high-resolution spectra of G, K and M type stars obtained with UVES and BOES. WBR found in this work is $M_v$=34.22-18.34logW. In addition, stellar atmospheric parameters ($T_{eff}$, logg, [Fe/H], ${\xi}_{tur}$) are determined with the MOOG code and the Kurucz ATLAS9 model grids for G and K type stars. For M type stars, the method of Belle et al. (1999) is used to derive effective temperature which shows good agreement with other methods. Using the derived $T_{eff}$ and the measured logW,we find the relationship between logg and [logW, logT]; ${\log}g-_{fit}=-25.051-5.527{\log}W+10.254{\log}T_{eff}$. This relation can be applied to estimate the surface gravity of M type stars, which is difficult to be determined by other methods.

• 한국지역지리학회지
• /
• 제9권3호
• /
• pp.276-296
• /
• 2003

이 연구는 부산 김해평야 농업지역의 친환경농업에서 관련 행위자(actors)들이 어떠한 역할을 부여받으며 연결망을 형성하는가를 연구하고, 행위자-연결망 이론(Actors-Network Theory)이 우리나라 농촌 연구에서 지니는 유용성을 검토하고자 하였다. 인구지역에서 친환경 농업은 18농가만 수용하고 있어 수도권 등 타 지역에 비해 매우 미약하다. 친환경농업과 관련하여 형성되고, 또한 되어야 할 연결망들은 필수경로(OPP)의 형태에 의해 차단되거나 혹은 분산되어 있었고, 이 결과 지역내에서 연결망이 형성되지 못하고 있었다. 통과되지 못한 첫 번째 필수경로는 자연(수질 토양 오염)과 부정적인 지역 이미지였다. 두 번째 필수경로는 신뢰도였으며 이 중 농민과 정부관련기관간 신뢰도 결여가 가장 큰 장애요소였다. 이외의 극복되지 못한 필수경로는 유통망 및 정보 결여였다. 연결망에서 이와 같은 필수 경로를 통과하지 못하면, 연구지역에서 친환경농업에서 농민들의 이탈은 가속화될 것으로 사료되며, 작목반도 가까운 시일내에 해체될 것으로 생각된다. 친환경농업이 지속적으로 이루어지기 위해서는 정부 예산 집행기간의 탄력성, 지역환경에 어울리는 농법 개발과 지역내 행위자들의 협의체 구성을 통한 연결망의 상설 가동이 필요할 것으로 본다.

• Nuclear Engineering and Technology
• /
• 제55권12호
• /
• pp.4447-4464
• /
• 2023

This paper focuses on the development of a new computational model of the CNESTEN's TRIGA Mark II research reactor using the 3D continuous energy Monte-Carlo code TRIPOLI-4 (T4). This new model was developed to assess neutronic simulations and determine quantities of interest such as kinetic parameters of the reactor, control rods worth, power peaking factors and neutron flux distributions. This model is also a key tool used to accurately design new experiments in the TRIGA reactor, to analyze these experiments and to carry out sensitivity and uncertainty studies. The geometry and materials data, as part of the MCNP reference model, were used to build the T4 model. In this regard, the differences between the two models are mainly due to mathematical approaches of both codes. Indeed, the study presented in this article is divided into two parts: the first part deals with the development and the validation of the T4 model. The results obtained with the T4 model were compared to the existing MCNP reference model and to the experimental results from the Final Safety Analysis Report (FSAR). Different core configurations were investigated via simulations to test the computational model reliability in predicting the physical parameters of the reactor. As a fairly good agreement among the results was deduced, it seems reasonable to assume that the T4 model can accurately reproduce the MCNP calculated values. The second part of this study is devoted to the sensitivity and uncertainty (S/U) studies that were carried out to quantify the nuclear data uncertainty in the multiplication factor k_eff. For that purpose, the T4 model was used to calculate the sensitivity profiles of the k_eff to the nuclear data. The integrated-sensitivities were compared to the results obtained from the previous works that were carried out with MCNP and SCALE-6.2 simulation tools and differences of less than 5% were obtained for most of these quantities except for the C-graphite sensitivities. Moreover, the nuclear data uncertainties in the k_eff were derived using the COMAC-V2.1 covariance matrices library and the calculated sensitivities. The results have shown that the total nuclear data uncertainty in the k_eff is around 585 pcm using the COMAC-V2.1. This study also demonstrates that the contribution of zirconium isotopes to the nuclear data uncertainty in the k_eff is not negligible and should be taken into account when performing S/U analysis.