• KSII Transactions on Internet and Information Systems (TIIS)
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• 제12권4호
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• pp.1760-1778
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• 2018

For image segmentation with intensity inhomogeneity, many region-based level set methods have been proposed. Some of them however can't get the relatively ideal segmentation results under the severe intensity inhomogeneity and weak edges, and without use of the image gradient information. To improve that, we propose a new level set method combined with local direction gradient in this paper. Firstly, based on two assumptions on intensity inhomogeneity to images, the relationships between segmentation objects and image gradients to local minimum and maximum around a pixel are presented, from which a new pixel classification method based on weight of Euclidian distance is introduced. Secondly, to implement the model, variational level set method combined with image spatial neighborhood information is used, which enhances the anti-noise capacity of the proposed gradient information based model. Thirdly, a new diffusion process with an edge indicator function is incorporated into the level set function to classify the pixels in homogeneous regions of the same segmentation object, and also to make the proposed method more insensitive to initial contours and stable numerical implementation. To verify our proposed method, different testing images including synthetic images, magnetic resonance imaging (MRI) and real-world images are introduced. The image segmentation results demonstrate that our method can deal with the relatively severe intensity inhomogeneity and obtain the comparatively ideal segmentation results efficiently.

• 대한기계학회논문집
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• 제14권1호
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• pp.172-178
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• 1990

본 연구에서는 스터링기관의 예비설계에 편리하게 적용될 수 있는 경제적이며 타당한 해석방법을 확립하기 위하여, Urieli등에 의하여 정립된 이상적인 단열모델에 대하여 해석적 근사해를 구하고자 한다.이미 발표된 연구에서는 근사해를 얻기 위 해 피스턴운동을 가장 간단한 톱날파로 가정한 바 있으나 실제의 정현파형 등과는 현 저한 차이가 있으므로 이를 개선하여 크랭크각도에 대한 임의의 구간선형함수(piecew- ise linear function)로 취급한다. 또한, 해석의 결과로서 결정되는 기관내의 압력 및 각 실린더내의 질량 또는 온도 등 열역학적 변수로부터 기관성능평가를 위한 열 및 일의 계산 과정을 포함한다.

• 한국생활과학회지
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• 제23권2호
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• pp.251-268
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• 2014

Applying the data from 64 single(26 men and 38 women) and 71 childless married men and women(37 men and 34 women) aged between 30 and 45, this study is to understand their future fertility intention. For this purpose, ideal and real number of children that participants plan to have were compared using paired t-test. Second, demographic variables(sex, age, marital status), child care related variables(thoughts about caring children, child care value), individual characteristics(gender role attitude, relation orientation) and social context variables(perceived economic condition, recognition of low fertility policies) were included in a stepwise regression model to explain expected number of children participants plan to have in the future. Results showed that ideal number of children participants wish to have was significantly higher than real number of children they expect to have in the Korean society. The stepwise regression model explained 35% of the variance of the dependent variable. Among four types of variables, child care related variables most powerfully explained expected number of children study participants plan to have in the future. Finally, age, child care value, gender role attitude, and relation orientation significantly explained expected number of children in the future.

• Structural Engineering and Mechanics
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• 제28권5호
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• pp.525-548
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• 2008

This article deals the theory for solving an inverse problem of plate structures using the frequency-domain information instead of classical time-domain delays or free vibration eigenmodes or eigenvalues. A reduced set of output parameters characterizing the defect is used as a regularization technique to drastically overcome noise problems that appear in imaging techniques. A deconvolution scheme from an undamaged specimen overrides uncertainties about the input signal and other coherent noises. This approach provides the advantage that it is not necessary to visually identify the portion of the signal that contains the information about the defect. The theoretical model for Quantitative nondestructive evaluation, the relationship between the real and ideal models, the finite element method (FEM) for the forward problem, and inverse procedure for detecting the defects are developed. The theoretical formulation is experimentally verified using dynamic responses of a steel plate under impact loading at several points. The signal synthesized by FEM, the residual, and its components are analyzed for different choices of time window. The noise effects are taken into account in the inversion strategy by designing a filter for the cost functional to be minimized. The technique is focused toward a exible and rapid inspection of large areas, by recovering the position of the defect by means of a single accelerometer, overriding experimental calibration, and using a reduced number of impact events.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1994년도 Proceedings of the Korea Automatic Control Conference, 9th (KACC) ; Taejeon, Korea; 17-20 Oct. 1994
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• pp.488-493
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• 1994

The global stability of model reference adaptive control system (MRACS) in the ideal case was resolved in the 1980's. Hoever the improvement of the transient, behaviour of MRACS has not been discussed sufficiently even in the ideal case. Only a few attempts have so far been made at the application of MRACS to the practical systems in contrast to the theoretical systematization. Therefore, when we consider the practical usage of MRACS it is necessary to develop an improved design scheme with respect to transient behaviour. In this paper, we propose two design schemes improving transient behaviour of MRACS by mollifying the input synthesis in the conventional design scheme of MRACS. We present a design scheme of MRACS in which we utilize the design approach of variable structure system(VSS). After describing the above design scheme, we also propose the improved design scheme in which we introduce the dead-zone decided by the magnitude of the output-error between the plant and the reference model. The effectiveness of the proposed two design schemes are shown through computer simulations. As the results, by using these methods, the convergence of the transient response is greatly improved in comparison with the conventional one.

• 대한기계학회논문집
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• 제16권4호
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• pp.787-794
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• 1992

본 연구에서는 이미 알려진 이상적인 단열모델에 대한 해석적 근사해를 기본 해로 취하고, 열교환과정의 손실 및 작동유체의 유동손실 등 성능에 미치는 영향이 비교적 큰 인자만을 고려하여, 성능을 쉽게 예측할 수 있는 2차단열해석법의 하나를 개발하고자 한다. 방법의 타당성및 적용예를 보이기 위하여 기존의 스터링기관중 각 종제원및 실험결과가 발표되어 있어 비교의 기준으로서 적합한 GPU-3(ground power unit)기관을 대상으로 해석방법을 실제 적용하고 결과를 고찰하기로 한다.

• 설비공학논문집
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• 제21권8호
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• pp.448-455
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• 2009

A performance analysis of the regenerative gas turbine system with afterfogging is carried out. Because of the high temperature at the outlet of air compressor, afterfogging has a potential of improved recuperation of exhaust heat than inlet fogging. Thermodynamic analysis model of the gas turbine system is developed by using an ideal gas assumption. Using the model, the effects of pressure ratio, water injection ratio, and ambient temperature are investigated parametrically on thermal efficiency and specific power of the cycle. The dependency of pressure ratio giving peak thermal efficiency is also investigated. The results of numerical computation for the typical cases show that the regenerative gas turbine system with afterfogging can make a notable enhancement of thermal efficiency and specific power. In addition, the peak thermal efficiency is shown to decrease almost linearly with ambient temperature.

• 한국세라믹학회지
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• 제48권6호
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• pp.549-558
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• 2011

Application of a generalized equivalent circuit including the electrode condition for the Hebb-Wagner polarization in the frequency domain proposed by Jamnik and Maier can provide a consistent set of material parameters, such as the geometric capacitance, partial conductivities, chemical capacitance or diffusivity, as well as electrode characteristics. Generalization of the shunt capacitors for the chemical capacitance by the constant phase elements (CPEs) was applied to a model mixed conducting system, $Ag_2S$, with electron-blocking AgI electrodes and ion-blocking Pt electrodes. While little difference resulted for the electron-blocking cell with almost ideal Warburg behavior, severely non-ideal behavior in the case of Pt electrodes not only necessitates a generalized transmission line model with shunt CPEs but also requires modelling of the leakage in the cell approximately proportional to the cell conductance, which then leads to partial conductivity values consistent with the electron-blocking case. Chemical capacitance was found to be closer to the true material property in the electron-blocking cell while excessively high chemical capacitance without expected silver activity dependence resulted in the electron-blocking cell. A chemical storage effect at internal boundaries is suggested to explain the anomalies in the respective blocking configurations.

• 한국측량학회지
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• 제34권2호
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• pp.161-169
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• 2016

This paper is intended to propose a novel approach to select an optimal site for a small-scaled artificial recharge system installation using TOPSIS (Technique for Order Preference by Similarity to Ideal Solution) with geospatial data. TOPSIS is a MCDM (Multi-Criteria Decision Making) method to choose the preferred one of derived alternatives by calculating the relative closeness to an ideal solution. For applying TOPSIS, in the first, the topographic shape representing optimal recovery efficiency is defined based on a hydraulic model experiment, and then an appropriate surface slope is determined for the security of a self-purification capability with DEM (Digital Elevation Model). In the second phase, the candidate areas are extracted from an alluvial map through a morphology operation, because local alluvium with a lengthy and narrow shape could be satisfied with a primary condition for the optimal site. Thirdly, a shape file over all candidate areas was generated and criteria and their values were assigned according to hydrogeologic attributes. Finally, TOPSIS algorithm was applied to a shape file to place the order preference of candidate sites.

• 한국광학회지
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• 제4권4호
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• pp.464-473
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• 1993

본 논문에서는 광섬유에 아르곤 레이저 빔이 입사될 때 생기는 위상격자 형성에 관한 역학을 다룬다. 간단한 쌍광자 표백모델(two-photon bleaching model)을 이용하여 위상격자가 시간이 지남에 따라 이상적인(ideal) 격자로 자기조직됨(self-organized)을 보인다. 광섬유의 각점에서의 시간에 따른 상태전개는 하나의 보편 매개변수(universial parameter)에 의해 나타내어지고 또한 이 광섬유계를 기술하는 연립편미분 방정식이 이 매개변수에 의해 연립 상 미분 방정식으로 간소화 된다. 이 연립 상 미분 방정식을 이용하여 위상격자가 자라나는 상태는 한 고정점(a fixed point)를 향해 가는 과정이고 이 고정점은 완벽히 위상맞춤(phase-matched)된 격자에 해당된다는 것을 보인다.