• Korean Journal of Optics and Photonics
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• v.10 no.3
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• pp.181-187
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• 1999

We prepared the side-chain type nonlinear optical NPP(N-(6-nitrophenyl)-(L)-prolinol) polymer films by spin coating method. Ellipsometric spectra were in situ collected by using spectroscopic phase modulated ellipsometer while the NPP polymer films were being corona poled at the temperature above glass transition. We calculated film thickness and the refractive index dispersion by modeling the spectro-ellipsometry data in transparent region. We also calculated the refractive index and the extinction coefficient of the polymer films by numerically inverting the spectro-ellipsometry data in absorbing region, while the previously determined film thickness was used. The independently determined extinction coefficient spectra from the analysis of transmission spectra were compared with those by spectro-ellipsometry and they showed an excellent agreement with each other. From the analysis of the complex refractive index change of the NPP polymer thin films induced by the corona poling, we could determine the vertical complex refractive index and the horizontal complex refractive index separately. Using the volume fraction of the vertical component f⊥, the degree of poling of poled NPP polymer films was quantitatively addressed. It is suggested that the present method can be used to quantitatively address the degree of poling in an absolute manner and to depth profile the poled fraction of thick polymer films. It will be useful to understand the structural change of polymer films and hence the poling mechanism during the poling process.

• Journal of the Korean Geotechnical Society
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• v.19 no.6
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• pp.363-369
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• 2003

The purpose of this study is to understand the dissipation pattern of excess pore pressure after liquefaction and to estimate the variation in permeability during shaking load, which should be known for settlement predictions of the ground undergoing liquefaction. In this study, 1-g shaking table tests were carried out for 5 different kinds of sands, all of which had high liquefaction potentials. During the tests excess pore pressure at various depths, and surface settlements were measured. The measured dissipation curve of the excess pore pressure after liquefaction was linearly simulated using the solidification theory, and from the analysis of the slopes of linearly simulated curves, the correlation between dissipation velocity and the gradation characteristics was obtained. By substituting this correlation and the measured settlement to the dissipation velocity equation recommended in solidification theory, the permeability during dissipation was calculated, which was used for estimating the permeability variation during shaking load. The dissipation velocity of excess pore pressure after liquefaction had a linear correlation with the effective grain size divided by the coefficient of uniformity. The permeability during dissipation and liquefaction increased by 1.1∼2.8 times and 1.4∼5 times compared to the initial permeability of the original ground, respectively. And the amount of increase became greater as the effective grain size of the test sand increased and the coefficient of uniformity decreased.

• Proceedings of the Korea Water Resources Association Conference
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• 2009.05a
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• pp.74-78
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• 2009

우리 사회가 발전함에 따라 재해의 위험으로부터도 안전하게 살고자 하는 대중들의 욕구 또한 증가하고 있다. 하지만 최근의 기후변화와 이상홍수의 사례에서 볼 때 현재 우리가 처해 있는 자연재해로부터의 위협은 과거와는 상이하다는 것을 알 수 있다. 이러한 위협에 대처하기 위해서는 우리에게 노출된 재해의 특성을 평가하는 과정이 무엇보다 선행되어져야 한다. 홍수로 인한 피해는 대부분이 인명이나 재산피해가 주를 이루기 때문에 홍수위험도의 평가결과도 발생 가능한 인명이나 재산피해로 표현되는 것이 적절하다고 판단된다. 따라서 본 연구에서는 지역회귀분석을 적용하여 가능 홍수 피해금액을 추산하고, 이를 통해 각 지역별 홍수위험도를 평가하는 방법을 제안하였다. 지역회귀분석은 강우유출모형이나 확률분포모형의 매개변수들을 유역 특성인자들로 표현하기 위해 수문학 분야에서 사용되어져 왔으며 본 연구에서는 이 방법을 홍수 피해금액 추정에 응용하였다. 지역회귀방법의 절차는 먼저 계측지역에서는 홍수 피해금액과 시강우량 자료를 바탕으로 비선형회귀분석을 실시한 후 이 회귀식의 계수를 다시 해당 지역의 인문 사회 경제학적 인자들로 표현하였다. 이러한 방법을 통해 지역적 인자들이 홍수 피해에 미치는 영향을 정량적으로 분석할 수 있었으며 궁극적으로 미계측지역에서도 지역적 인자들을 통해 특정 빈도에 발생 가능한 홍수 피해금액을 추정할 수 있었다. 최종적으로 추정된 홍수 피해금액과 지역 총 자산의 비를 통해 홍수위험지도를 작성하였다. 본 연구결과를 수자원장기종합계획에서 홍수위험도 평가를 위해 사용된 홍수피해잠재능(Potential Flood Damage; PFD)과 비교해 보면 PFD에서는 각 인자들의 가중치 산정에서 전문가의 주관이 개입될 수 있다는 단점이 있었으나 과거 피해금액과의 상관관계를 분석한 본 연구에서는 이러한 단점을 극복할 수 있었다.

• Tunnel and Underground Space
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• v.17 no.6
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• pp.453-463
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• 2007

Terzaghi's tunnel pressure theory is generally used to estimate primary design pressures on tunnel support for shield and urban NATM tunnels until now. A trial is made in this paper to investigate the interaction between the ground deformation behavior and Terzaghi's tunnel pressure, which assumes pound's limit (or critical) state, by considering results of 'Terzaghi's tunnel pressure theory. two-dimensional reduced-scale model tunnel tests and nonlinear numerical analysis based on strain softening modeling. A full understanding between tunnel pressure and ground deformation behavior under the tunnel excavation and an effective utilization of this interaction lead to an economical tunnel support design and a safe construction of tunnel.

• Korean Journal of Ecology and Environment
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• v.34 no.3 s.95
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• pp.215-222
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• 2001

A statistical analysis was performed to evaluate relationships among the pollutant concentrations in non-urban area. The data obtained from two subcatchments in Hwa-Ong watershed during 1999 was used for correlation and regression analyses. Strong correlations were observed among the SS, COD, and TP, while it was not significant with TN. The reason fer weak correlation with TN might be that TN was high in dry-days and runoff in wet-days could not increase enough to change it substantially like in other pollutants. The correlations were stronger for the data in wet-days than in dry-days, and it was influenced by watershed characteristics. While TP-COD showed linear relationship from the regression analysis, SS-TP and SS-COD shelved intrinsically linear relationship between log-transformed TP and COD data and non-transformed SS data. The TP-COD showed strong relationship for all the combinations of monitored data, which implies that these two constituent concentrations varied in a similar pattern. The regression equations reported in the paper might be used to estimate one pollutant concentration from the other in pollutant loading estimates, and its application could be expanded to other non-urban watersheds if their characteristics are not significantly different from the study area. In water quality management projects, rigorous monitoring and its thorough evaluation are recommended to develop more reliable relationships among the pollutant concentrations which could be used in other area.

• Korean journal of applied entomology
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• v.47 no.4
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• pp.407-411
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• 2008

This study was conducted to estimate the economic injury level (EIL) and economic threshold (ET) of the green peach aphid, Myzus persicae, on Chinese cabbage (Brassica campestris var). The changes of biomass of Chinese cabbage and M. persicae density were investigated after introduction of M. persicae at different density (0, 2, 5, 10, 15, and 20 per plant; inoculated at 10d after planting). The densities of M. persicae largely increased from the above initial densities to 0, 92.3, 177.4, 406.9, 440.4, and 471.3 aphids per plant at 18d after the initial inoculation, respectively. The biomass of Chinese cabbage significantly decreased with increasing the initial inoculated density of M. persicae: 602.0, 264.2, 262.0, 109.3, 151.0, and 67.3 g in above plots with different initial densities, respectively. The relationship between cumulative aphid days (CAD) and yield loss (%) of Chinese cabbage was well described by a nonlinear logistic equation. Using the estimated equation, EIL of M. persicae on Chinese cabbage was estimated 25 CAD per plant based on the yield loss 13%, which take into account of an empirical gain threshold 5% and marketable rate 92% of spring Chinese cabbage. Also, ET was calculated at 80% of EIL: 20 aphids per plant. Until a more elaborate EIL-model is developed, the present result may be useful for M. persicae management at early growth stage of Chinese cabbage.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.18 no.7
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• pp.1028-1035
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• 1993

The signed regressor (SR) algorithm employs one bit quantization on the input regressor (or tap input) in such a way that the quantized input sequences become +1 or -1. The algorithm is computationally more efficient by nature than the popular least mean square (LMS) algorithm. The behavior of the SR algorithm unfortunately is heavily dependent on the characteristics of the input signal, and there are some Inputs for which the SR algorithm becomes unstable. It is known, however, that such a stability problem does not take place with the SR algorithm when the input signal is Gaussian, such as in the case of speech processing. In this paper, we explore a statistical analysis of the SR algorithm. Under the assumption that signals involved are zero-mean and Gaussian, and further employing the commonly used independence assumption, we derive a set of nonlinear evolution equations that characterizes the mean and mean-squared behavior of the SR algorithm. Experimental results that show very good agreement with our theoretical derivations are also presented.

• Journal of Korean Society of Steel Construction
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• v.12 no.1 s.44
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• pp.65-73
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• 2000

The behavior of double angle connections is analyzed by 3D finite element method using ABAQUS(ver 5.8). Moment-rotation curves for the connections are generated, as well as stress distribution for angle and bolt. Double angle connections have various angle thickness, gage distance and number of bolt. Parameters, such as initial stiffness, plastic tiffness, reference load and curve shape parameter were obtained by regression method using Richard's formula. These parameter lead to predict nonlinear behavior of double angle connection. Design curves giving the parameters of the moment-rotation curves are generated. These parameters are primarily a function of the angle thickness, gage distance and the number of bolts in the connection. Using these parameters, connection moment and its ratio to the full plastic moment capacity Mp of the beam are calculated.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.44 no.6
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• pp.1-8
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• 2007

In this paper, research on joint optimization of the image spatial registration and the exposure compensation is conducted. The exposure compensation is performed in a frame work of the intensity compensation based on the polynomial approximation of the relationship between images. This compensation is jointly combined with the registration problem employing the Gauss-Newton nonlinear optimization method. In this paper, to perform for a simple and stable optimization, the block-coordinate method is combined with the Gauss-Newton optimization and extensively compared with the traditional approaches. Furthermore, regression analysis is considered in the compensation part for a better stable performance. By combining the block-coordinate method with the Gauss-Newton optimization, we can obtain a compatible performance reducing the computational complexity and stabilizing the performance. In the numerical result for a particular image, we obtain a satisfactory result for 10 repeats of the iteration, which implies a 50% reduction of the computational complexity. The error is also further reduced by 1.5dB compared to the ordinary method.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.2
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• pp.697-703
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• 2017

This paper examines the flexure behavior of FRP-concrete composite structure that can replace conventional reinforced concrete structure types. In order to investigate the structural performance and behavioral characteristics in numerical analysis means, ABAQUS, a general purpose finite element analysis program, was utilized for nonlinear finite element analysis, and the various variables and their influences were analyzed and compared with experimental results to suggest values optimized to this composite structure. The concrete damage plasticity model and Euro code for concrete were used. In the implicit finite element analysis, the convergence was ambiguous when geometrical and material nonlinearity were large, so the explicit finite element analysis used in this study was deemed to be appropriate. From the comparison with the experiment about concrete damaged plasticity model, 20mm for the mesh size, $30^{\circ}$ for the dilation angle, $100Nmm/mm^2$ for the value of fracture energy, 0.667 for Kc value, and the consideration of damage parameter were suggested believed to be appropriate. The numerical model suggested in this study was able to imitate the ultimate load and cracking pattern very well; therefore, it is expected to be utilized in research of various new material composite structures.