• 한국지능시스템학회논문지
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• 제12권3호
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• pp.239-245
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• 2002

본 논문에서는 입력에 제한이 있는 시간지연 비선형 시스템에 대한 퍼지 $H_2/H_{\infty}$ 제어기 설계 방법을 제시한다. 포화입력을 갖는 시간지연 비선형 시스템을 시간지연과 포화입력을 갖는 Takagi-Sugeno 퍼지 모델로 표현하고 병렬분산보상(PDC)의 개념을 이용하여 제어기를 설계한다. Lyapunov 함수를 이용하여 시간지연과 포화입력을 갖는 $H_2/H_{\infty}$ 퍼지모델에 대한 폐루프 시스템의 안정성 조건과 LQ 성능을 최소화하는 조건을 유도하고, 퍼지 $H_2/H_{\infty}$ 제어기가 존재할 충분조건을 선형행렬부등식(LMI: liner matrix inequality)을 이용하여 구한다. 제어기는 선형행렬부등식의 해를 구하므로써 바로 구할 수 있으며, 설계된 퍼지 $H_2/H_{\infty}$ 제어기는 $H_{\infty}$ 노옴 한계값을 만족하면서 LQ성능의 상한값을 최소화한다. 마지막으로 포화압력으로 포화압력을 가지는 시간지연 비선형 시스템에 대해 퍼지 $H_2/H_{\infty}$ 제어기 설계 사례를 보인다.

• 한국정보과학회논문지:데이타베이스
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• 제29권3호
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• pp.217-229
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• 2002

정규경로표현은 전통적 스키마를 가정하지 않는 준구조적 데이타에 대해 질의를 고안하기 위한 기본적 질의 요소이다. 그리고 질의전지는 정규경로표현의 처리에 있어 불필요한 탐색을 제거하기 위한 중요한 최적화 기법이다. 그러나 기존 질의전지는 다중 정규경로표현들은 완전히 최적화하지 못하는 경우가 많으며, 기존 질의전지의 결과를 후처리하는 기존의 방법은 지수적으로 증가하는 많은 부분결과들의 조합들을 확인해야 한다. 본 논문에서는 전처리 단계와 전지 단계로 구성된 두 단계 질의전지라 부르는 새로운 기법을 소개한다. 우리의 두 단계 질의전지는 다중 정규경로표현의 최적화에 효과적이며, 지수적으로 증가하는 많은 부분결과들의 조합들을 화인하지 않는다는 점에서 기존의 방법보다 더 확장성이 있다.

• 미생물학회지
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• 제29권6호
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• pp.408-415
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• 1991

TOL plsmid size of Flavobacterium odoratum SUB53 was estimated as 83 Md and the optimum concentration of m-toluate degradation by TOL plasmid was 5 mM. $H_{2}$ production by Rhodopseudomonas sphaeroides KCTC1425 was largely dependent on nitrogenase activity and showed the highest at 30 mM malate with 7 mM glutamate as nitrogen source. Nitrogenase activities were inhibited by 0.3 mM $NH_{4}^{+}$ions, to be appeared the decrease of $H_{2}$ production. Conjugation of TOL plasmids from F. odoratum SUB53 and Pseudomonas putida mt-2 to R. sphaeroides showed the optimum at the exponential stage of recipient cells in presence of helper plasmid pRK2013. According to the investigation of catechol-1,2-oxygenase (C-1, 2-O) and catechol-2,3-oxygenase (C-2,3-O) activities of R. sphaeroides C1 (TOL SUB53) and C2 (TOL mt-2), the gene for C-2,3-O is located on TOL plasmid and gene for C-1, 2-O on the chromosome of R. sphaeroides. m-Toluate was biodegraded by TOL plasmid in R. sphaeroides C1 and C2, presumably to be produced $H_{2}$ gas from the secondary metabolites of m-toluate.e.

• Geomechanics and Engineering
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• 제34권5호
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• pp.481-489
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• 2023

Drained cyclic triaxial tests were conducted on a saturated sand to examine its deformation characteristics under either axial or lateral cyclic loading condition. To apply lateral cyclic loading, the cell pressure was cycled while maintaining a constant vertical stress. The strain accumulations and flow direction in the soil were presented and discussed considering various initial stress ratios (η₀), cyclic stress amplitudes and cyclic stress paths. The results indicate that axial strain accumulation shows an exponential increase with the maximum stress ratio (η^max). The initial deviatoric stress has comparable effects with lateral cyclic stress amplitude on the accumulated axial strain. In contrast, the accumulated volumetric strain is directly proportional to the lateral cyclic stress amplitude but not much affected by η₀ values. Due to the anisotropy of the soil, the accumulated axial and lateral bulging strains are greater in lateral cyclic loading when compared to axial cyclic loading even though η^max is the same. It is also found that η^max affects soil's lateral deformation and increasing the ratio could change the lateral deformation from contraction to bulging. The flow direction depends on η^max in the sand under lateral cyclic loading, regardless of η₀ values and the cyclic stress amplitudes, and a large η^max could lead to great deviatoric strain but a little volumetric strain accumulation.

• 대한화학회지
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• 제54권2호
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• pp.192-197
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• 2010

형광체나 반도체의 소자로 사용되는 전이금속화합물 중에서 나노(nano) 크기를 가지는 스피넬 화합물을 합성하였다. 스피넬 화합물의 크기, 합성여부, 열적분석과 화합물의 특성을 확인하기 위하여 열 중량 분석기(TGA), X-선 회절 분석기(XRD), 적외선 흡수 분광기(IR)를 사용하였다. Scherrer식을 이용하여 화합물의 평균 입자 크기가 13~16 nm임을 예측할 수 있었다. 본 논문에 사용된 실험방법은 졸-겔(sol-gel)법을 사용하였으며, 소성 온도는 낮은 온도에서 진행 되었다($350^{\circ}C$). Kinetic 함수인 활성화 에너지와 전환인자를 계산하기 위해서 Kissinger방법과 Arrhenius식을 이용하여 계산하였다. $ZnCo_2O_4$와 $NiCo_2O_4$의 활성화 에너지는 163.42 kJ/mol와 147.01 kJ/mol 값을 가지는 있음을 확인하였다. 그리고 spinel 화합물들의 열역학적 함수(${\Delta}G^{\varphi}$, ${\Delta}H^{\varphi}$, ${\Delta}S^{\varphi}$)를 결정하였다.

• 한국해양학회지
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• 제3권2호
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• pp.55-62
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• 1968

The distributions of average water color and the transparency in the seas around Korea show two patterns: the one is the East Sea and the South Ses, the other is the Yellow Sea. In the East Sea and the South Sea, the water colors C$\sub$E/ in Forel scales change from green to greenish blue with distance x in miles from the seashore, an average color is bluish green, 3.7 in Forel scales, and the relationship is given by C$\sub$E/ = 5e$\^$-0.056.root.x; an average transparency is 15m and the transparency T$\sub$E/ shows following formula with distance x, E$\sub$E/=0.9.root.x+10. In the Yellow Sea, the water color C$\sub$Y/ changes from green yellow to bluish green with distance, an average color is light green, 5.6 in Forel scales, and the relationship is given by C$\sub$Y/= 8.5e$\^$-0.086.root.x; an average transparency is 7m, the farther it is from the seashore, the deeper transparency T$\sub$Y/ is as following, T$\sub$Y/=1.2 .root.x+1. Along the seashore, the transparency T$\sub$Y/ is only 10% that of the East Sea and the South Sea. The distributions of the water color and the transparency by depth change in values within the continental shelf. The water color in Forel scales decreases with the distance from the seashore and depth; the transparency increases with the distance and depth. They are caused by suspended particles, especially suspended clay, and it is the major factor in the change in color and transparency, particularly in the Yellow Sea. In September, the sea water is the clearest in the seas around Korea, transparency shows the maximum and water color the minimum in forel scales. The water color shows green yellow when transparency is 1m, green at 10m, and greenish blue at 20m. the relationship between the water color and the transparency shows an exponential distribution as following, C=9e$\^$-kT/, k=0.0625m$\^$-1/. This formula agrees with calculated formulas between the water color and the transparency from the emprircal formulas C$\sub$E/ and T$\sub$E/, C$\sub$Y/ and T$\sub$Y.

• 유통과학연구
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• 제11권10호
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• pp.73-79
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• 2013

Purpose - This study examines the impact of oil price volatility on economic activities in Korea. The new millennium has seen a deregulation in the crude oil market, which invited immense capital inflow into Korea. It has also raised oil price levels and volatility. Drawing on the recent theoretical literature that emphasizes the role of volatility, this paper attends to the asymmetric changes in economic growth in response to the oil price movement. This study further examines several key macroeconomic variables, such as interest rate, production, and inflation. We come to the conclusion that oil price volatility can, in some part, explain the structural changes. Research design, data, and methodology - We use two methodological frameworks in this study. First, in regards to the oil price uncertainty, we use an Exponential-GARCH (Exponential Generalized Autoregressive Conditional Heteroskedasticity: EGARCH) model estimate to elucidate the asymmetric effect of oil price shock on the conditional oil price volatility. Second, along with the estimation of the conditional volatility by the EGARCH model, we use the estimates in a VECM (Vector Error Correction Model). The study thus examines the dynamic impacts of oil price volatility on industrial production, price levels, and monetary policy responses. We also approximate the monetary policy function by the yield of monetary stabilization bond. The data collected for the study ranges from 1990: M1 to 2013: M7. In the VECM analysis section, the time span is split into two sub-periods; one from 1990 to 1999, and another from 2000 to 2013, due to the U.S. CFTC (Commodity Futures Trading Commission) deregulation on the crude oil futures that became effective in 2000. This paper intends to probe the relationship between oil price uncertainty and macroeconomic variables since the structural change in the oil market became effective. Results and Conclusions - The dynamic impulse response functions obtained from the VECM show a prolonged dampening effect of oil price volatility shock on the industrial production across all sub-periods. We also find that inflation measured by CPI rises by one standard deviation shock in response to oil price uncertainty, and lasts for the ensuing period. In addition, the impulse response functions allude that South Korea practices an expansionary monetary policy in response to oil price shocks, which stems from oil price uncertainty. Moreover, a comparison of the results of the dynamic impulse response functions from the two sub-periods suggests that the dynamic relationships have strengthened since 2000. Specifically, the results are most drastic in terms of industrial production; the impact of oil price volatility shocks has more than doubled from the year 2000 onwards. These results again indicate that the relationships between crude oil price uncertainty and Korean macroeconomic activities have been strengthened since the year2000, which resulted in a structural change in the crude oil market due to the deregulation of the crude oil futures.

• 한국대기환경학회지
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• 제20권5호
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• pp.671-683
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• 2004

This study was carried out to understand long-range transport of $SO_2$ using aircraft measurements for the identification of it's horizontal and vertical concentration and distribution pattern. Thirteen missions of aircraft measurements have been done around 37$^{\circ}$00'/124$^{\circ}$30' from October 1997 to November 2001. Concentrations of $SO_2$ was 1.5~2.0 ppb in the below mixing layer, 0.6~1.1 ppb in the above mixing layer. $SO_2$ was found to be relatively higher than marine background level, 0.08~0.2ppb, indicating the western coast being influenced by long-range transport except for the summer season. The vertical distribution of $SO_2$ was classified into 3 groups using its vertical sounding and meteorology pattern; the first is linear decay pattern, the second is exponential decay pattern, and the last is gaussian distribution pattern in the below mixing layer, 2 patterns of linear decay and gaussian distribution patterns in the upper layer. It is founded that vertical distribution pattern is strongly dependent on meteorological condition, for example atmospheric stability and predominant air flow.

• 한국산학기술학회논문지
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• 제12권2호
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• pp.600-604
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• 2011

본 Czochralski 방법으로 새로운 섬광체인 $LaCl_3:Eu^{2+}$ 결정을 육성하고, 육성된 섬광체의 섬광 특성을 조사하였다. 육성한 $LaCl_3:Eu^{2+}$ 결정 구조는 육방정계로서 $P_63$/m 공간군에 속함을 확인할 수 있었으며, 격자상수는 각각 a = b = $7.48{\AA}$, c = $4.37{\AA}$이었다. 335 nm로 여기시킨 $LaCl_3:Eu^{2+}$ 결정의 발광 스펙트럼 파장 범위는 약 370 ~ 640 nm 이었으며, 중심 파장은 430 nm이었다. 형광 감쇠 곡선은 $2.82{\pm}0.72{\mu}s$의 단일 성분으로 구성되었으며, $^{137}Cs$ 662 keV ${\gamma}$-선에 대한 에너지 분해능은 약 8.8%이었다.

• 한국재료학회지
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• 제29권7호
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• pp.412-424
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• 2019

Global fitting functions for Fe-selective chlorination in ilmenite($FeTiO_2$) and successive chlorination of beneficiated $TiO_2$ are proposed and validated based on a comparison with experimental data collected from the literature. The Fe-selective chlorination reaction is expressed by the unreacted shrinking core model, which covers the diffusion-controlling step of chlorinated Fe gas that escapes through porous materials of beneficiated $TiO_2$ formed by Fe-selective chlorination, and the chemical reaction-controlling step of the surface reaction of unreacted solid ilmenite. The fitting function is applied for both chemical controlling steps of the unreacted shrinking core model. The validation shows that our fitting function is quite effective to fit with experimental data by minimum and maximum values of determination coefficients of $R^2$ as low as 0.9698 and 0.9988, respectively, for operating parameters such as temperature, $Cl_2$ pressure, carbon ratio and particle size that change comprehensively. The global fitting functions proposed in this study are expressed simply as exponential functions of chlorination rate(X) vs. time(t), and each of them are validated by a single equation for various reaction conditions. There is therefore a certain practical merit for the optimal process design and performance analysis for field engineers of chlorination reactions of ilmenite and $TiO_2$.