• Water for future
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• v.18 no.2
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• pp.175-185
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• 1985

This paper discusses the posibility of synthesizing flood hudrographs by the stroage function model. Eight small watersheds from Han, Gum, Nakdong, Youngsan river system were selected for this purpose. The optimum constants are computed from the chi square criterion by the SDFP methods Based on these constants, equations for the storage constant and Lag time are derived from the kinematic wave theory and storage function theory. These relations are examined by using optimum constants of the storage function model and assumptive constant of the kinematic wave model. Main results are sumarized as follows. 1. Constants of the storage function model are closely related to those of the kinematic wave model. The formula obtained theoretically is difficult to use practically because of the unclaified definition of factors. 2. In order to estimate constants of the storage function model for the practical purpose, new equations are also proposed for mountaneous area. 3. The verification of proposed equation is made for several recorded floods for mountaeous areas.

• Journal of the Korean Society of Propulsion Engineers
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• v.20 no.6
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• pp.29-37
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• 2016

This paper proposes a shape optimization of the metal boss for a composite motor case using finite element analysis. For the structural safety and the weight reduction of the composite motor case, under the internal pressure, the fiber stress in the dome area and the tightening bolt stress are constrained and the boss weight is set to objective function, respectively. The response surface models are constructed for the performance characteristics by using response surface method. The significance of the design variables about the performance characteristics is evaluated through the ANOVA(analysis of variance) and the goodness of fit test for the constructed model is performed through the regression analysis. The SQP(sequential quadratic programming) algorithm is used for the optimization and the proposed method is verified by performing structural analysis for the optimum shape.

• Journal of Ginseng Research
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• v.24 no.2
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• pp.58-63
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• 2000

To develop the production of ginseng root using plant tissue culture technology, submerged culture conditions were optimized by means of the fractional factorial design with 4 factors and 3 levels by a RSM computer program. The ginseng (Panax ginseng C. A. Meyer) roots induced by plant growth regulators were cultured on SH medium and the effects of various pH of medium, sucrose concentration, nitrogen concentration and phosphate concentration on fresh weight of the ginseng root were investigated. The fresh weight of ginseng root increased with a decrease in nitrogen concentration and fresh weight of ginseng root varied from 1.00 to 2.33g under various conditions. The optimum pH of medium and sucrose concentration determined by a partial differentiation of the model equation, nitrogen and phosphate concentration were pH 5.6, sucrose 3.8%, nitrogen 50 mg/L and phosphate 80.7 mg/L, respectively. Under these conditions, the predicted growth of ginseng root was estimated to be 2.36g.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.20 no.6
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• pp.683-690
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• 2007

Topology optimization techniques have been developed as a very efficient design tool and utilized for design engineering processes in many industrial sections during the past decade. And topology optimization has become the focus into structural optimization design up to now. Recently, thermally actuated compliant mechanisms have a wide range of applications. In this research, the thermo-elastic problem is a coupled problem which has to consider heat transfer analysis and structural analysis. Hence, the thermo-elastic problem has to deal with heat transfer material properties and structural material properties at the same time. The numerical examples are presented. From the results, it was shown that in terms of the displacement after optimization. Moreover, this paper compared thermo-system, elastic-system with thermo-elastic system and was shown a good result of topology optimization while thermo-elastic system was used.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.12
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• pp.1811-1820
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• 2010

Most components in the real world show nonlinear response. The nonlinearity may arise because of contact between the parts, nonlinear material, or large deformation of the components. Structural optimization considering nonlinearities is fairly expensive because sensitivity information is difficult to calculate. To overcome this difficulty, the equivalent load method was proposed for nonlinear response optimization. This method was originally developed for size and shape optimization. In this study, the equivalent load method is modified to perform topology optimization considering all kinds of nonlinearities. Equivalent load is defined as the load for linear analysis that generates the same response field as that for nonlinear analysis. A simple example demonstrates that results of the topology optimization using equivalent load are very similar to the numerical results. Nonlinear response topology optimization is performed with a practical example and the results are compared with those of conventional linear response topology optimization.

• Tuberculosis and Respiratory Diseases
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• v.43 no.5
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• pp.755-762
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• 1996

Background : Continuous positive airway pressure(CPAP) is doubtlessly using as a medical treatment of choice for patients with obstructive sleep apnea (OSA) syndrome. CPAP is effective in OSA patients as a physical "pneumatic pressure splint" mechanism. We have done this study for two purposes, first to seek for the factors to determine the optimal CPAP titer, second to predict the minimal CPAP titer using the determined factors. Methods: We studied a 72 OSA patients who were treated with CPAP. All of them were studied by using a two nights polysomnographic rests in hospital. We compared the patients requiring CPAP over $10cmH_2O$ with those who required CPAP under 5cm $H_2O$ to determine the factors affecting the minimal CPAP titer. Results : The high CPAP group is characterized by a significantly higher body mass index(BMI), apnea index(AI) and apnea and hyponea index(AHI) and significantly lower lowest $SaO_2$. Regression analysis using the optimal four variables resulted in the following prediction equation for CPAP titer. CPAPtiter=8.382 + 0.064 ${\times}$ BMI + 0.077 ${\times}$ AI - 0.004 ${\times}$ AHI - 0.077 ${\times}$ lowest $SaO_2$ When this regression equation was applied to the 72 patients, the mean CPAP titer as predicted by the above equation was $7.80{\pm}2.96$ mmHg. Compared this value with actually determined CPAPtiter, $7.93{\pm}4.00$mmHg, there was no significant difference between the two values. Conclusion: Obesity, apnea severity and lowest Sa02 were strongly correlated with CPAP titer. Linear regression equation for CPAP titer using these indices predicted very closely the actually measured values in the sleep laboratory.

• Journal of Biomedical Engineering Research
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• v.25 no.4
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• pp.235-242
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• 2004

In this paper, we proposed the algorithm for detection of microtalcification by automatic threshold decision based on region growing method. The region for optimal threshold is grown from local maximum pixel by increasing repeatedly threshold in microralcification candidate region. Then, the optimal threshold is automatically decided at the maximum value of the contrast and edge sharpness in this region. Microcalcifications could be efficiently detected as satisfied result that true positive ratio is 81.5% and average false positive numbers are 1.1 about total 299 microcalcifirations in real image. In a result, we showed that this algorithm can be used to aid diagnostic-radiologist for the diagnosis of the early phase of breast cancer.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2014.10a
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• pp.145-147
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• 2014

대부분 이진화 알고리즘은 임계치를 결정하기 위해 히스토그램을 사용하여 밝기 분포를 분석한다. 배경과 물체의 명암 차이가 큰 경우는 분할을 위해 양봉 히스토그램으로 표현하여 최적의 임계치를 찾기 위해 히스토그램 골짜기를 선택하는 것으로도 양호한 임계치를 찾을 수 있지만 배경과 물체의 밝기 차이가 크지 않거나 밝기 분포가 양봉 특성을 보이지 않을 때는 히스토그램 분석만으로 적절한 임계치를 얻기 어렵다. 이 문제점을 개선하기 위해 삼각형 타입의 소속 함수를 적용하여 임계치를 동적으로 설정하고 영상을 이진화 하는 퍼지 이진화 방법이 제안되었다. 퍼지 이진화 방법은 소속 함수에 적용된 소속도를 a-cut에 적용하여 영상을 이진화 한다. 그러나 기존의 퍼지 이진화 방법은 a-cut값을 경험적으로 설정하기 때문에 다양한 영상을 이진화하는 과정에서 정보 손실이 많이 발생하는 문제점이 있다. 따라서 본 논문에서는 FCM 클러스터링 알고리즘을 이용하여 퍼지 이진화 방법의 a-cut값을 동적으로 설정하여 이진화하는 방법을 제안한다. 제안된 방법을 다양한 영상에 적용한 결과, 배경과 물체의 명암도 차이가 크게 나지 않는 영상의 경우에는 기존의 퍼지 이진화 방법보다 정보 손실이 적은 상태로 이진화되는 것을 확인하였다.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.27 no.2
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• pp.63-70
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• 2014

Design sensitivity analysis and topology design optimization for a piezoelectric crystal resonator are developed. The piezoelectric crystal resonator is deformed mechanically when subjected to electric charge on the electrodes, or vice versa. The Mindlin plate theory with higher-order interpolations along thickness direction is employed for analyzing the thickness-shear vibrations of the crystal resonator. Thin electrode plates are masked on the top and bottom layers of the crystal plate in order to enforce to vibrate it or detect electric signals. Although the electrode is very thin, its weight and shape could change the performance of the resonators. Thus, the design variables are the bulk material densities corresponding to the mass of masking electrode plates. An optimization problem is formulated to find the optimal topology of electrodes, maximizing the thickness-shear contribution of strain energy at the desired motion and restricting the allowable volume and area of masking plates. The necessary design gradients for the thickness-shear frequency(eigenvalue) and the corresponding mode shape(eigenvector) are computed very efficiently and accurately using the analytical design sensitivity analysis method using the eigenvector expansion concept. Through some demonstrative numerical examples, the design sensitivity analysis method is verified to be very efficient and accurate by comparing with the finite difference method. It is also observed that the optimal electrode design yields an improved mode shape and thickness-shear energy.

• Journal of KIISE:Computing Practices and Letters
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• v.15 no.12
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• pp.943-947
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• 2009

To support an efficient management of software verification and validation activities, many defect prediction models have been proposed based on object oriented metrics. In order to apply defect prediction models, we need to determine a threshold value. Because we cannot know actually where defects are, it is difficult to determine threshold. Therefore, we performed a series of experiments to explore the issue of determining a threshold. In the experiments, we applied defect prediction models to other systems different from the system used in building the prediction model. Specifically, we have applied three models - Olague model, Zhou model, and Gyimothy model - to four different systems. As a result, we found that the prediction capabilities varied considerably with a chosen threshold value. Therefore, we need to perform a study on the determination of an appropriate threshold value to improve the applicably of defect prediction models.