• Journal of the Korea Institute of Information Security & Cryptology
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• v.18 no.6A
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• pp.51-61
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• 2008

This paper suggests a new way to implement high speed AES on Intel Core2 processors and AMD Athlon64 processors, which are used all over the world today. First, Core2 Processors of EM64T architecture's memory-access-instruction processing efficiency are lower than calculus-instruction processing efficiency. So, previous AES implementation techniques, which had a high rate of memory-access-instruction, could cause memory-bottleneck. To improve this problem we present the partial round key techniques that reduce the rate of memory-access-instruction. The result in Intel Core2Duo 3.0 Ghz Processors show 185 cycles/block and 2.0 Gbps's throughputs in ECB mode. This is 35 cycles/block faster than bernstein software, which is known for being the fastest way. On the other side, in AMD64 processors of AMD64 architecture, by removing bottlenecks that occur in decoding processing we could improve the speed, with the result that the Athlon64 processor reached 170 cycles/block. The result that we present is the same performance of Matsui's unpublished software.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.3 no.1 s.4
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• pp.45-52
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• 2004

There are many cities installing ITS(Intelligent Transportation Systems) and running TMC(Trafnc Management Center) to improve mobility and safety of roadway transportation by providing roadway information to drivers. There are many devices in ITS which collect real-time traffic data. We can obtain many valuable traffic data from the devices. But it's impossible to avoid missing traffic data for many reasons such as roadway condition, adversary weather, communication shutdown and problems of the devices itself. We couldn't do any secondary process such as travel time forecasting and other transportation related research due to the missing data. If we use the traffic data to produce AADT and DHV, essential data in roadway planning and design, We might get skewed data that could make big loss. Therefore, He study have explored some imputation techniques such as heuristic methods, regression model, EM algorithm and time-series analysis for the missing traffic volume data using some evaluating indices such as MAPE, RMSE, and Inequality coefficient. We could get the best result from time-series model generating 5.0$\%$, 0.03 and 110 as MAPE, Inequality coefficient and RMSE, respectively. Other techniques produce a little different results, but the results were very encouraging.

• Journal of the Korean Society for Nondestructive Testing
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• v.25 no.1
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• pp.27-35
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• 2005

Ultrasonic inspection methods are widely used for detecting flaws in materials. The signal analysis step plays a crucial part in the data interpretation process. A number of signal processing methods have been proposed to classify ultrasonic flaw signals. One of the more popular methods involves the extraction of an appropriate set of features followed by the use of a neural network for the classification of the signals in the feature spare. This paper describes an alternative approach which uses the least mean square (LMS) method and exportation maximization (EM) algorithm with the model based deconvolution which is employed for classifying nondestructive evaluation (NDE) signals from steam generator tubes in a nuclear power plant. The signals due to cracks and deposits are not significantly different. These signals must be discriminated to prevent from happening a huge disaster such as contamination of water or explosion. A model based deconvolution has been described to facilitate comparison of classification results. The method uses the space alternating generalized expectation maximiBation (SAGE) algorithm ill conjunction with the Newton-Raphson method which uses the Hessian parameter resulting in fast convergence to estimate the time of flight and the distance between the tube wall and the ultrasonic sensor. Results using these schemes for the classification of ultrasonic signals from cracks and deposits within steam generator tubes are presented and showed a reasonable performances.

• Proceedings of the KIPE Conference
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• 2018.07a
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• pp.162-164
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• 2018

스위칭 주파수의 대역 확산 (Spread Spectrum) 기법은 전력 변환 장치의 전자 방해 잡음 (Electromagnetic Interference; EMI)를 줄일 수 있다. 하지만 공진형 컨버터는 스위칭 주파수 가변을 통해 출력 전압을 제어하기 때문에 스위칭 주파수의 대역 확산 기법을 적용하게 되면 출력 전압이 크게 흔들리게 된다. 본 논문은 LLC 공진형 컨버터에 대역 확산 기법을 사용함과 동시에 확산된 스위칭 주파수 대역의 위상 제어를 통해 출력 전압을 제어하는 방법을 제시하고자 한다. 제안하는 출력 전압 제어 성능 향상 및 전자방해잡음 감소 성능은 500 W 프로토타입 컨버터를 사용하여 검증하고자 한다.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2010.04a
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• pp.347-351
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• 2010

판과 같은 구조물의 손상 감지를 위해, 손상 전 구조물의 임피던스 신호를 기저신호(Baseline impedance signal)로 이용하여 직접적으로 비교하지 않는 새로운 개념의 무기저 손상진단 기법(Reference-free impedance method)을 제시한다. 박막 압전소자(이하 PZT)를 판의 상하 표면에 부착시킨 한 쌍의 병치 PZT를 이용하여 손상으로 인해 모드변환을 일으키는 전기역학적 신호(Electro Mechanical Signatures ; 이하 EMS)를 추출한다. 이 연구에서는 스펙트럼 요소법(Spectral Element Method ; 이하 SEM)을 이용하여 주파수 영역에서 병치된 PZT의 EMS를 파악하기 위한 수치해석을 수행한다. 특히, 손상에 의해 발생된 모드변환 EMSMC를 병치된 PZT의 극성에 기인한 신호분해 기법을 적용하여 추출하고, 분해된 모드변환 EMSMC가 손상의 위치와 크기에 따라 받는 영향을 추가로 분석한다.

• Geophysics and Geophysical Exploration
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• v.17 no.3
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• pp.129-136
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• 2014

Electromagnetic (EM) methods are generally divided into frequency-domain EM (FDEM) and time-domain EM (TDEM) methods, depending on the source waveform. The FDEM and TDEM fields are mathematically related by the Fourier transformation, and the TDEM field can thus be obtained as the Fourier transformation of FDEM data. For modeling in time-domain, we can use fast frequency-domain modeling codes and then convert the results to the time domain with a suitable numerical method. Thus, frequency-to-time transformations are of interest to EM methods, which is generally attained through fast Fourier transform. However, faster frequency-to-time transformation is required for the 3D inversion of TDEM data or for the processing of vast air-borne TDEM data. The diffusion expansion method (DEM) is one of smart frequency-to-time transformation methods. In DEM, the EM field is expanded into a sequence of diffusion functions with a known frequency dependence, but with unknown diffusion-times that must be chosen based on the data to be transformed. Especially, accuracy of DEM is sensitive to the diffusion-time. In this study, we developed a method to determine the optimum range of diffusion-time values, minimizing the RMS error of the frequency-domain data approximated by the diffusion expansion. We confirmed that this method produces accurate results over a wider time range for a homogeneous half-space and two-layered model.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.23 no.1
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• pp.8-13
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• 2015

In this paper, a simple algorithm is proposed to estimate wind speed and direction which can significantly improve the landing performance of an unmanned parafoil. The proposed algorithm is applied to flight test data along with other known algorithms and the results are compared and discussed. The proposed algorithm shows comparable performance while it can still be applied to the parafoil under control.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.9 no.5
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• pp.163-168
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• 2009

Most image segmentation methods are to represent observed feature vectors at each pixel, which are assumed as appropriated probability models. These models can be used by statistical estimating or likelihood clustering algorithms of feature vectors. EM algorithms have some calculation problems of maximum likelihood for unknown parameters from incomplete data and maximum value in post probability distribution. First, the performance is dependent upon starting positions and likelihood functions are converged on local maximum values. To solve these problems, we mixed the Gausian function and histogram at all the level values at the image, which are proposed most suitable image segmentation methods. This proposed algoritms are confirmed to classify most edges clearly and variously, which are implemented to MFC programs.

• Geophysics and Geophysical Exploration
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• v.11 no.1
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• pp.60-67
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• 2008

In this paper we consider an application of the method of electromagnetic (EM) migration to the interpretation of a typical marine controlled-source (MCSEM) survey consisting of a set of sea-bottom receivers and a moving electrical bipole transmitter. Three-dimensional interpretation of MCSEM data is a very challenging problem because of the enormous number of computations required in the case of the multi-transmitter and multi-receiver data acquisition systems used in these surveys. At the same time, we demonstrate that the MCSEM surveys with their dense system of transmitters and receivers are extremely well suited for application of the migration method. In order to speed up the computation of the migration field, we apply a fast form of integral equation (IE) solution based on the multigrid quasi-linear (MGQL) approximation which we have developed. The principles of migration imaging formulated in this paper are tested on a typical model of a sea-bottom petroleum reservoir.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.10
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• pp.1104-1114
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• 2008

In the output of a mixer, spurious appears with the desired signal, and a filter is necessary to suppress the spurious. In this paper, the planar filter for Ka-band frequency synthesizer was designed and fabricated. In this procedure, the frequency response becomes asymmetric because of discontinuities at the high frequency. Using this, we designed short-end PCLF by using a individual resonator tuning method. The fabricated 5th-order Ka-band pass filter is compared with the result of EM simulation through measurement. The performance agrees with the simulation. Finally spurious suppression was examined through the measurement of output spectrum of the mixer with the filter.