• ETRI Journal
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• 제31권5호
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• pp.604-606
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• 2009

The primary dose effects on an insulated gate bipolar transistor (IGBT) irradiated with a $^{60}Co$ gamma-ray source are found in both of the components of the threshold shifting due to oxide charge trapping in the MOS and the reduction of current gain in the bipolar transistor. In this letter, the IGBT macro-model incorporating irradiation is implemented, and the electrical characteristics are analyzed by SPICE simulation and experiments. In addition, the collector current characteristics as a function of gate emitter voltage, VGE, are compared with the model considering the radiation damage of different doses under positive biases.

• Journal of Astronomy and Space Sciences
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• 제22권2호
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• pp.139-146
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• 2005

A model of advection-dominated accretion flows has been highlighted in the last decade. Most of calculations are based on self-similar solutions of equations governing the accreting flows. We revisit self-similar solutions of the simplest form of advection-dominated accretion flows. We explore the parameter space thoroughly and seek another category of self-similar solutions. In this study we allow the parameter f less than zero, which denotes the fraction of energy transported through advection. We have found followings: 1. For f > 0, in real ADAF solutions the ratio of specific heats ${\gamma}$ satisfies 1 < ${\gamma}$ < 5/3 for O ${\leq}$ f ${\leq}$ 1. On the other hands, in wind solutions a rotating disk does not exist. 2. For f < 0, in real ADAF solutions with ${\epsilon}$ greater than zero ${\gamma}$ requires rather exotic range, that is, ${\gamma}$ < 1 or ${\gamma}$ > 5/3. When -5/2 < ${\epsilon}$' < 0, however, allowable ${\gamma}$ can be found in ${\gamma}$ < 5/3, in which case 4{\Omega}_0$,_ is imaginary. 3. For a negative $u_0$,+ with f > 0, solutions are only allowed with exotic ${\gamma}$, that is, 1 < ${\gamma}$ or ${\gamma}$ > (5f/2-5/3)/(5f/2-1)when O < f < 2/5, (5f/2-5/3)/(5f/2-1) < ${\gamma}$ < 1 when f > 2/5. Since ${\epsilon}$' is negative, 4{\Omega}_0$,+ is again an imaginary quantity. For a negative $u_0$,+ with f < 0, ${\gamma}$ is allowed in 1 < 7 < (5|f|/2 + 5/3)/(5|f|/2 + 1). We briefly discuss physical implications of what we have found.

• Journal of Advanced Marine Engineering and Technology
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• 제36권1호
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• pp.126-132
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• 2012

본 연구에서는 강인한 성능을 가지는 모델추종형 H${\infty}$ 제어기의 설계법을 제시한다. 이를 위해 강인한 성능을 보장하는 해집단내에서 기준모델의 출력을 최적으로 추종하도록 유전 알고리즘을 사용하여 가중치 함수와 설계 파라미터 ${\gamma}$를 동시에 최적화한다. 설계된 H${\infty}$ 제어기는 강인한 성능에 관한 필요충분조건식을 만족함은 물론 설계사양에 따른 만족스러운 응답특성을 가진다. 제시된 방법을 보일러-터빈 제어 시스템에 적용하여 그 유용성을 확인한다.

• 천문학회지
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• 제29권spc1호
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• pp.99-102
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• 1996

I discuss implications of gamma-ray emission from blazars based on electron acceleration by shock waves in a relativistic jet. The number spectrum of electrons turns out to be a broken power law; while at low energies the power law index has a universal value of 2, at high energies it steepens to an index of 3 because of strong radiative cooling. This spectrum can basically reproduce the observed spectral break between X-rays and gamma-rays. I show that energetics of relativistic jets can be well explained by this model. I estimate physical quantities of the relativistic jets by comparing the prediction with observations. The results show that the jets are particle dominated and are comprised of electron-positron pairs. A connection between gamma-ray emission and radiation drag is also discussed.

• 천문학회보
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• 제42권2호
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• pp.45.1-45.1
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• 2017

A Korean VLBI Network Key Science Program, the Interferometric Monitoring of Gamma-ray Bright AGNs (iMOGABA) program continues to aim at revealing the origins of the gamma-ray flares that are often detected in active galactic nuclei (AGNs). Here in this presentation, we would like to present what we have learned about the Gamma-ray bright AGNs based on the recent results of the Korean VLBI Network Key Science Program: the iMGOABA. The results will include a) the source properties of the whole samples obtained from a single-epoch observation, and b) some of scientific highlights for the iMOGAGBA on specific sources. From those highlighted works, we find that the Gamma-ray bright AGNs become fainter at higher frequencies, yielding optically thin spectra at mm wavelengths. Based on the studies on specific sources, taking into account the synchrotron self-absorption model of the relativistic jet, we estimated the magnetic field strength in the mas emission region during the observing period.

• 한국식품영양학회지
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• 제11권6호
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• pp.635-639
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• 1998

The thermal degradation pattern of $\alpha$-, ${\gamma}$-and $\delta$-tocopherols in glycerol was investigated during heating at 100~25$0^{\circ}C$ for 5-60 min in the absence of oxyge. The tocopherols and thermally decomposed products were separated by HPLC with a reversed phase $\mu$-Bondapak C18-column. The degradation pattern of $\alpha$-tocopherol during the heating in the absence of oxygen was different from those of ${\gamma}$-and $\delta$-tocopherols. But the degradation patterns of ${\gamma}$-and $\delta$-tocopherols were similar to each other. The residual content of $\alpha$-tocopherol during the heating in the absence of oxygen decreased to the range 12~65% and those of ${\gamma}$-and $\delta$-tocopherols decreased to the range 4~96%. The thermal degradation of tocopherols in the absence of oxygen was less than that in the presence of oxygen.

• 한국세라믹학회지
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• 제23권1호
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• pp.1-6
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• 1986

The shrinkage rate of solid state sintering has been theoretically derived by combining the rate equation of material transport and the net free energy change resulting from the decrease of solid-vapor interface and the increase of grain boundary during sintering. For a sinteing model an idealized situation of the spherical particles with BCC packing was taken as the initial condition and the shrinkage was assumed to occur by forming the flat circualr grain boundaries on each particle. The plotted shrinkage rates as a function of grain boundary to surface energy ratio $(gamma_g/gamma_s)$ have shown that the relative density increases linearly at the initial stage of sintering but the shrinkage rate is decreased upon further sintering due to a decrease in driving force for densificaton. It has been also shown that the densification is critically affected by the $gamma_g/gamma_s$ ratio. In order to get the complete densificatin the ratio should be less than $sqrt{3}$. Any additive or atmospheric condition causing the decrease of$_g/gamma_s$ ratio will enhance sintering.

• IMMUNE NETWORK
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• 제14권2호
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• pp.89-99
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• 2014

Graft-versus-host disease (GVHD) is a fatal complication that occurs after allogeneic hematopoietic stem cell transplantation. To understand the dynamics of CD4 and CD8 T cell production of IFN-${\gamma}$ and IL-17 during GVHD progression, we established a GVHD model by transplanting T cell-depleted bone marrow (TCD-BM) and purified T cells from B6 mice into irradiated BALB.B, creating an MHC-matched but minor histocompatibility (H) antigen-mismatched transplantation (B6 ${\rightarrow}$ BALB.B GVHD). Transplantation-induced GVHD was confirmed by the presence of the appropriate compositional changes in the T cell compartments and innate immune cells in the blood and the systemic secretion of inflammatory cytokines. Using this B6 ${\rightarrow}$ BALB.B GVHD model, we showed that the production of IFN-${\gamma}$ and IL-17 by CD4 T cells preceded that by CD8 T cells in the spleen, mesenteric lymph node, liver, and lung in the BALB.B GVHD host, and Th1 differentiation predated Th17 differentiation in all organs during GVHD progression. Such changes in cytokine production were based on changes in cytokine gene expression by the T cells at different time points during GVHD development. These results demonstrate that both IFN-${\gamma}$ and IL-17 are produced by CD4 and CD8 T cells but with different kinetics during GVHD progression.

• 대한간호학회지
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• 제47권4호
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• pp.514-525
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• 2017

Purpose: The purpose of this study was to construct and test a structural equation model for Diabetes self-management (DSM) behavior and Quality of life (QoL) in older adults with diabetes who use Citizen Health Promotion Centers. The theory used this study was a combination of the Information-Motivation-Behavioral Model (IMB) and Self-Determination Theory (SDT) to reflect autonomous characteristics of participants. Methods: Data were collected from April 20 to August 31, 2015 using a self-report questionnaire. The sample was 205 patients with type 2 Diabetes who regularly visited a Citizen Health Promotion Center. SPSS 22.0 and AMOS 22.0 programs were used to analyze the efficiency of the hypothesized model and calculate the direct and indirect effects of factor affecting the participants' DSM behavior and QoL. Results: The supported hypotheses were as follows; 1) The variable that had a direct effect on QoL was health behavior adherence (${\gamma}=.55$, p=.007). 2) The variables that had a direct effect on DSM behavior were DSM information (${\gamma}=.15$, p=.023), DSM confidence (${\gamma}=.25$, p<.001), and autonomous motivation (${\gamma}=.13$, p=.048). 3) The variable that had a direct effect on DSM confidence was autonomy support (${\gamma}=.33$, p<.001). Conclusion: The major findings of this study are that supporting patient's autonomous motivation is an influential predictor for adherence to DSM behavior, and integrative intervention strategies which include knowledge, experience and psychosocial support are essential for older adults with diabetes to continue DSM behavior and improve QoL.

• 한국수자원학회논문집
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• 제32권3호
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• pp.265-279
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• 1999

본 연구에서는, Markov 연쇄 모형에 의해 산정된 모의 일 강우량을 일 유출모형인 Tand 모형에 입력시켜 모의 일유출량을 산정함으로써 저수유량계열을 확장하는 방법을 개발하였다. 또한, 모의된 일 유량계열로부터 지속기간별 연 최저치 계열을 작성하였으며, 지속기간별 연 최저치계열에 대한 빈도분석을 시행하였다. 분석에 사용된 분포형은 Lognormal-2, Lognormal-3, Gamma-2, Gamma-3, LogGamma-3, Gumbel-2, Weibull-2 분포이었으며, 모수추정은 모멘트법과 최우도법을 사용하였다. Kolmogorov - Sminorv 검정방법으로 지속기간별 연 최저치 계열에 적합한 확률분포형을 결정하고, 용담댐 지점을 대상으로 하여 지속기간별 갈수 빈도곡선을 산정하였다. 본 연구에서 제안된 방법을 적용하면 과거 저수 유량계열의 통계적 특성을 잘 나타내는 일 유량의 모의가 가능 하여, 갈수유량계열 자료가 빈곤한 유역에서 확률 갈수량을 추정하는데 유용하리라고 판단된다.