• Proceedings of the KIEE Conference
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• 2003.11c
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• pp.445-448
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• 2003

This paper presents a novel iris recognition method using wavelet transform and curve simplification. One-dimensional signals, which are calculated over circles on the iris, are decomposed into a multiple frequency bands. Each decomposed signal is approximated by a piecewise linear curve connecting node points. The curve is simplified by progressively removing unimportant node points while keeping the shape of the curve. Finally, a small number of node points represent features of each signal. Experiment results show that the presented method results in good performance in various noise environments.

• Geomechanics and Engineering
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• v.28 no.1
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• pp.77-87
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• 2022

Many geotechnical analyses require the investigation of water flow within partially saturated soil zone to incorporate the effect of climatic conditions. It is widely understood that the hydraulic properties of the partially saturated soil should be included in the transient seepage analyses. However, the characteristics of dual porosity soils with dual-mode water retention curve are normally modelled using single-mode mathematical equation for simplification of the analysis. In reality, the rainwater flow can be affected significantly by the dual-mode hydraulic properties of the soil. This paper presents the variations of safety factor for dual porosity soil slope with dual-mode water retention curve and dual-mode unsaturated permeability. This paper includes the development of the new dual-mode unsaturated permeability to represent the characteristics of soil with the dual-mode water retention curve. The finite element analyses were conducted to examine the role of dual-mode water retention curve and dual-mode unsaturated permeability on the variations of safety factor under rainfall loading. The results indicate that the safety factor variations of dual porosity soil slope modelled using the dual-mode water retention curve and the unsaturated permeability equation are lower than those of dual porosity slope modelled using single-mode water retention curve and unsaturated permeability equations.

• Journal of the Korean Institute of Intelligent Systems
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• v.20 no.5
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• pp.722-727
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• 2010

This paper is presented to study simplification of face image using cubic spline interpolation for a business card with 2D barcode. People often forget business card's owner because business cards don't be included a face picture generally. To solve such problem, many applications have be developed through mobile devices, Internet and so on. But they couldn't caught up with value of existing business card mad by paper. Hence, some methods which can put information on business card using 1D or 2D barcode had suggested. but they couldn't include information like face image or company logo image which have too much data. Therefore, we study the simplification method of face image to encode from a face image to 2D barcode. The simplification method using spline curves defined by feature points which we dotted on face, ears, hair, eyebrows, nose, lips, neck, etc.. on a face area. for experiment, we see real face image and simplified face image made by proposed method after we automatically extract face watch through camera. In experimental results, data of simplified face image was reduced as small as it can be expressed by 2D barcode, and confirmed that it can effectively express features.

• Journal of Power Electronics
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• v.19 no.6
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• pp.1429-1439
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• 2019

Buck-Boost LLC (BBLLC) converters based on a PWM + phase control strategy are good candidates for high efficiency, high power density and wide input range applications. Nevertheless, they suffer from large computational complexity when it comes to calculating the optimal phase for ZVS of all the switches. In this paper, a method is proposed for a microcontroller unit (MCU) to calculate the optimal phase quickly and accurately. Firstly, a 2-D lookup table of the phase is established with an index of the input voltage and output current. Then, a bilinear interpolation method is applied to improve the accuracy. Meanwhile, simplification of the phase equation is presented to reduce the computational complexity. When compared with conventional curve-fitting and LUT methods, the proposed method makes the best tradeoff among the accuracy of the optimal phase, the computation time and the memory consumption of the MCU. Finally, A 350V-420V input, 24V/30A output experimental prototype is built to verify the proposed method. The efficiency can be improved by 1% when compared with the LUT method, and the computation time can be reduced by 13.5% when compared with the curve-fitting method.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.05a
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• pp.271-276
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• 2002

Existing design equations generally overestimate the shear strength of the circular transverse reinforcement. This is due to the simplification of the discrete distribution of the reinforcement to the continuous one and the inappropriate application of the classical truss model to the circular section, which is different in shear-resisting component from the rectangular section. The present study introduces a new model considering the starting point of the diagonal crack, the number of transverse reinforcing bars crossing the crack and the effective strength component of the transverse resistance. This model leads to a simple design equation which is derived using the linear regression method and is in agreement with the lower bound of exact strength curve.

• Proceedings of the Korea Water Resources Association Conference
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• 2018.05a
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• pp.284-284
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• 2018

대부분의 물분쟁의 경우 강 또는 호수를 공유하고 있는 국가 간에 발생하고 있으며 국내에도 제한된 물로 인하여 다양한 지역에서 물 분쟁이 발생하고 있다. 이렇듯 물 부족으로 인한 물분쟁 현상은 점차 심화되고 있으며 특히 강을 공유하고 있는 인접지역에서 발생할 가능성이 높아지고 있다. 본 연구에서 Water Rights Analysis Package (WRAP) 모델의 국내 적용을 위한 기초자료 구축단계로서 수위별로 되어 있는 수위-유량 관계 곡선식을 단순화하여 자연하천유량 산정을 위한 절차를 간편화하였다. 첫째, 확률 분포곡선을 이용한 수위 자료 구간별 구분; 둘째, 구분된 수위 자료에 대한 회귀 분석 실시; 셋째, 실측 유량 자료 및 모의 유량 자료를 이용한 신뢰도 산정 및 비교를 통한 본 연구결과에 대한 타당성 검토를 수행하였다.

• Geomechanics and Engineering
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• v.34 no.6
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• pp.683-696
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• 2023

The destruction and fracture of rock masses are crucial components in engineering and there is an increasing demand for the study of the influence of rock mass heterogeneity on the safety of engineering projects. The numerical manifold method (NMM) has a unified solution format for continuous and discontinuous problems. In most NMM studies, material homogeneity has been assumed and despite this simplification, fracture mechanics remain complex and simulations are inefficient because of the complicated topology updating operations that are needed after crack propagation. These operations become computationally expensive especially in the cases of heterogeneous materials. In this study, a heterogeneous model algorithm based on stochastic theory was developed and introduced into the NMM. A new fracture algorithm was developed to simulate the rupture zone. The algorithm was validated for the examples of the four-point shear beam and semi-circular bend. Results show that the algorithm can efficiently simulate the rupture zone of heterogeneous rock masses. Heterogeneity has a powerful effect on the macroscopic failure characteristics and uniaxial compressive strength of rock masses. The peak strength of homogeneous material (with heterogeneity or standard deviation of 0) is 2.4 times that of heterogeneous material (with heterogeneity of 11.0). Moreover, the local distribution of parameter values can affect the configuration of rupture zones in rock masses. The local distribution also influences the peak value on the stress-strain curve and the residual strength. The post-peak stress-strain curve envelope from 60 random calculations can be used as an estimate of the strength of engineering rock masses.

• The Journal of Korean Association of Computer Education
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• v.9 no.1
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• pp.89-95
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• 2006

The local geometric properties such as curvatures and normal vectors play important roles for analyzing the local shape of objects in the fields of computer graphics and computer vision. The result of the geometric operations such as mesh simplification and mesh smoothing is dependent on how to compute the curvatures of meshes because there is no exact mathematical definition of curvature at vertices on 3D meshes. Therefore, In this paper, we indicate the fatal error in computing the sectional curvatures of the most previous discrete curvature estimations. Moreover, we present a discrete curvature estimation to overcome the error, which is based on the parabola interpolation and the geometric properties of Bezier curves. Therefore, We can well distinguish between the sharp vertices and the flat ones, so our method may be applied to a variety of geometric operations.

• Computers and Concrete
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• v.15 no.6
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• pp.903-919
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• 2015

The flow of freshly mixed cement-based material shows thixotropy, which implies some difficulties on robust measurement of its rheological properties: The flow curve of thixotropic materials depends on the used protocol. For examples, higher viscosity is obtained when the rate of shear strain is more quickly increased. Even though precise measurement and modelling of the concrete rheology needs to consider the thixotropic effect, engineers in the concrete field prefer considering as a non-thixotropic Herschel-Bulkley fluid, even more simply Bingham fluid. That is due to robustness of the measurement and application in casting process. In the aspect of simplification, this papers attempts to mimic the thixoropic flow by the non-thixotropic Herschel-Bulkley model. Disregarding the thixotropy of cement based materials allows us to adopt the rheological concept in the field. An optimized protocol to measure the Bingham parameters was finally found based on the accuracy and reproducibility test of cement paste samples, which minimizes the error of simulation stemming from the assumption of non-thixotropy.

• Journal of Biomedical Engineering Research
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• v.38 no.3
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• pp.95-101
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• 2017

In this study, photoplethysmography(PPG) was suggested as a way to replace the ankle-brachial index(ABI) in diagnosing PAD. The method using the PPG was presented for the simplification of the PAD diagnosis method which was used before. And the index related to the health condition of the artery from the PPG measured in both big toes of the subjects through the experiment was drawn. The indexes showing the significant relativeness in the Pearson correlation analysis with the ABI were the stiffness index(SI), reflection index(RI); it was confirmed each of them had the correlation coefficient of 0.688, and 0.637 at p < 0.05. The explanation ability of the linear regression equation derived using ABI, SI and RI was 52.5%. The explanation ability of the secondary curve regression equation derived using ABI, squared SI was 54.7%. It is expected to provide patients with significant results and draw the index associated with PAD by measuring PPG easily in the real life instead of the ambulatory care field.