• Journal of the Institute of Electronics Engineers of Korea SD
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• v.40 no.8
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• pp.580-587
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• 2003

In this paper, we introduce a novel model to analyze the linearity of a TW-EAM (traveling-wave electroabsorption modulator). The device length, microwave loss (ML), and internal reflection (IR) due to impedance mismatch have effect on the linearity of a TW-EAM. The longer devices have characteristics of lower biases with minimum IMDS (intermodulation distortions). ML decreases the output power as well as the IMD value. Internal reflection has different nonlinear characteristics according to the wavelength of the input frequency and the device length. There is little change in SFDR (spurious-free dynamic range) due to ML or IR. As a result, for a 50 GHz band RF-optical communication system, a 0.8 mm-long TW-EAM with the lowest ML would have better properties by using n, which is caused by impedance, mismatch at the output port.

• Journal of Korean Society of Transportation
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• v.20 no.4
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• pp.163-175
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• 2002

Fatalities from traffic accidents constitute one of the major health issues as well as safety ones in Korea. It has been reported that traffic accident is affected by the combined effects of road. vehicle. and human factors. Over the past few decades, a number of studies have been conducted to find the impact of road geometric factors on traffic safety. The purpose of this study is to investigate the effect of road geometric factors on traffic safety on Korean expressways. Detailed geometric design data were available from Korea Highway Corporation. Five-year traffic accident data on Honam expressway were collected and analyzed. It was found that following geometric factors influence traffic safety on expressways : radius of curve, curve length, and length of straight section. Furthermore, the existence of I.C. turned out to have a significant impact on traffic safety level. Based on the data analysis several multiple regression forms that relate traffic accident frequencies and geometric factors on expressways are developed.

• The Journal of the Korean dental association
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• v.39 no.10 s.389
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• pp.854-865
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• 2001

• Proceedings of the Korea Water Resources Association Conference
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• 2007.05a
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• pp.428-432
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• 2007

댐 제방 등의 붕괴로 인하여 발생하는 급격한 유량의 변화와 흐름영역의 변화로 인한 천이류 및 도수의 발생, 불규칙한 하천단면에서 갈수기 저수기의 흐름해석은 기존의 수치해법의 한계로 인하여 수리모형실험 및 경험식 또는 단면의 단순화 등에 의존하고 있는 실정이다. 본 연구에서는 자연하천에서 비선형 흐름율 계산에 불연속초기조건의 해석해인 Riemann 근사해법을 사용하여 수치적으로 안정되고 정확한 1차원 모형을 개발하고자 한다. 이를 위하여 유한체적법을 사용하였고, 수위와 유량의 계산을 위하여 요구되는 유한체적을 유출입하는 흐름율의 계산에 HLL Riemann 해법을 사용하였으며, MUSCL 기법으로 2차 정확도기법으로 확장하였다. Riemann 해법을 통하여 계산된 비선형의 흐름율과 보존 특성을 만족시켜줄 수 있는 하상 및 하폭변화로 인한 생성항을 처리하는 기법을 제안함으로서 새로운 1차원 수치해석모형을 개발하였다. 개발된 모형의 실제하천의 적용성을 확인하기 위하여 하상과 하폭이 변화하는 부정류 흐름에 적용하여 모형의 적용성 및 정확성을 검증하였다.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.7
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• pp.1295-1301
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• 2010

In this note, a systematic general design of a new robust nonlinear variable structure controller based on state dependent nonlinear form is presented for the control of uncertain affine nonlinear systems with mismatched uncertainties and mismatched disturbance. After an affine uncertain nonlinear system is represented in the form of state dependent nonlinear system, a systematic design of a new robust nonlinear variable structure controller is presented. To be linear in the closed loop resultant dynamics, the nonlinear integral-type sliding surface is applied. A corresponding control input is proposed to satisfy the closed loop exponential stability and the existence condition of the sliding mode on the nonlinear integral-type sliding surface, which will be investigated in Theorem 1. Through a design example and simulation studies, the usefulness of the proposed controller is verified.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.8
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• pp.1947-1954
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• 2013

Previous works for detecting arrhythmia have mostly used nonlinear method such as artificial neural network, fuzzy theory, support vector machine to increase classification accuracy. Most methods require accurate detection of P-QRS-T point, higher computational cost and larger processing time. But it is difficult to detect the P and T wave signal because of person's individual difference. Therefore it is necessary to design efficient algorithm that classifies different arrhythmia in realtime and decreases computational cost by extrating minimal feature. In this paper, we propose arrhythmia detection based on binary coding using QRS feature varibility. For this purpose, we detected R wave, RR interval, QRS width from noise-free ECG signal through the preprocessing method. Also, we classified arrhythmia in realtime by converting threshold variability of feature to binary code. PVC, PAC, Normal, BBB, Paced beat classification is evaluated by using 39 record of MIT-BIH arrhythmia database. The achieved scores indicate the average of 97.18%, 94.14%, 99.83%, 92.77%, 97.48% in PVC, PAC, Normal, BBB, Paced beat classification.

• Journal of the Korean Institute of Telematics and Electronics
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• v.27 no.10
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• pp.60-67
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• 1990

This paper proposes a model-based fault detection method for linear/nonlinear system having modelling errors, nonlinearities and measurement noise. The system model is represented by the unified operator [5] in order to apply to both the continuous-time and discrete-time problems. The fault detection method suggested here accounts for the effects of noise, model mismatch and nonlinearities. Modelling errors are depicted by additive forms and the nominal model denominator is fixed via prior experiments in order to quantify the nucertainty bound on the parameter estima-tion. The least square method is used to estimate the numerator parameters of the nominal model. performance than traditional methods.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.18 no.2
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• pp.123-131
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• 2005

According to ow previous study, we confirmed That the Petrov-Galerkin natural element method(PG-NEM) completely resolves the numerical integration inaccuracy in the conventional Bubnov-Galerkin natural element method(BG-NEM). This paper is an extension of PG-NEM to two-dimensional geometrically nonlinear problem. For the analysis, a linearized total Lagrangian formulation is approximated with the PS-NEM. At every load step, the grid points ate updated and the shape functions are reproduced from the relocated nodal distribution. This process enables the PG-NEM to provide more accurate and robust approximations. The representative numerical experiments performed by the test Fortran program, and the numerical results confirmed that the PG-NEM effectively and accurately approximates The large deformation problem.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.7
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• pp.762-768
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• 2003

This paper reports the effects of gain flatness for linearity improvement of feedforward power amplifier fur IMT-2000 band. To investigate the operational characteristics for gain flatness of each amplifier, WCDMA 4FA input signal was used and measured 10 W output power. Especially, linearity improvement for variation of gain flatness of each amplifier was investigated that have an effect on linearity improvement such as delay line, phase, and amplitude imbalances. Variation of gain flatness of main amplifier is 40 MHz and of error amplifier is 40 MHz and 80 MHz bandwidth, respectively. Measured results, gain flatness of main amplifier is less than 1.5 dB and of error amplifier is less than 0.5 dB for more than 20 dB improvement at 5 MHz offset. In addition to that results, the characteristics of feedforward amplifier are drastically varied by gain flatness of error amplifier and it is shown that gain flatness of error amplifier is more important factor for linearity improvement.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.14 no.4
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• pp.423-434
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• 2001

In this paper, a three-span continuous box girder is analysed by using elastic equation based on energy method, concerning the behaviour with the effects of bending and pure torsional moment. The statically indeterminate forces of a three-span continuous curved box girder are calculated by applying the principle of least work to this elastic equation. The influence line of shear force, bending moment, pure torsion, displacement and angle of rotation due to unit vortical load and unit torque for curved box girder are obtained. The internal forces of the curved box girder which the actual load is applied can be calculated using the influence line obtained from this study.