• Journal of the Korean Society for Railway
• /
• v.10 no.5
• /
• pp.607-612
• /
• 2007

In this paper, operation mode of train was divided into powering, coasting, and braking and rail wear phenomenon has been done comparative analysis by each section. Data of train velocity is transferred to acceleration and deceleration from ATO Logging data. Amount of rail wear has been done comparative analysis by traction force of acceleration and braking force of deceleration and a plan for management of track irregularity is come up with by the result of the analysis.

• Proceedings of the KIPE Conference
• /
• 2019.07a
• /
• pp.121-123
• /
• 2019

본 논문에서는 실시간 시뮬레이터를 이용하여 DC 전력시스템의 모델링하고, Power Hardware-in-the-Loop (PHIL) 모의 테스트를 통해 DC 마이크로그리드에 적용 가능한 컨버터의 전력제어 알고리즘의 실효성을 검증하고자 한다. PHIL 모의시험 테스트 기법을 이용해 DC 마이크로그리드의 자율운전을 모사할 수 있는 Test-Bed를 제안하고자 한다. 이를 통해 부하 변화에 따른 운전 모드, 사고 상황 대처 알고리즘 등 DC 마이크로그리드에 연계된 전력변환장치의 전력제어 방법 및 실효성을 검증을 하고자 한다. 모의시험과 3 kW급 컨버터 시작품을 이용하여 제안하는 DC 마이크로그리드의 시험환경을 검증하고 전력제어 알고리즘의 신뢰성 및 안정성을 검증한다.

• Proceedings of the KIPE Conference
• /
• 2019.07a
• /
• pp.475-476
• /
• 2019

본 논문에서는 다기능 ESS의 제어알고리즘 및 운영 전략에 따른 모드 천이 안정성 및 경제성 등 장시간 시뮬레이션을 수행할 수 있는 소프트웨어 테스트베드 모델설계 결과를 제시한다. 전력변환장치의 순시 응답 특성을 확인하기 위해서 인버터 전력반도체 스위치, 인덕터 및 커패시터 등의 부품에 대한 모델링이 필요하고, 이는 전력계통에서 활용되고 있는 상용 소프트웨어인 Matlab/Simulink/SimPowerSystems의 라이 브러리를 활용하여 구현할 수 있다. 하지만 평균모델을 사용하는 경우에도 각 요소 회로의 시정수로 인해 시뮬레이션의 샘플링 시간을 줄이는 데는 한계가 있다. 따라서 본 논문에서는 신재생 에너지의 하루 발전 특성에 대한 제어로직에 따른 결과 및 경제성 분석등에 활용할 수 있는 기능모델(functional model)의 설계 방법을 제시하고, 개발된 모델을 상용소프트웨어의 결과와 비교함으로써 본 연구결과의 타당성을 보인다.

• Proceedings of the Korean Society of Broadcast Engineers Conference
• /
• 2021.06a
• /
• pp.311-312
• /
• 2021

최근 VVC(Versatile Video Coding) 표준 완료 이후 JVET(Joint Video Experts Team)은 NNVC(Neural Network-based Video Coding) AhG(Ad-hoc Group)을 구성하고 인공지능을 이용한 비디오 압축 기술들을 탐색하고 있다. 본 논문에서는 VVC 복원 영상의 DCT 계수를 기반으로 복원 영상을 분류하고, 분류된 각 클래스에 따라 적응적으로 CNN(Convolutional Neural Network) 기반의 화질 개선을 수행하는 VVC 후처리 기법을 제안한다. 실험결과, 제안기법은 AI(All Intra) 부호화 모드에서 1.23% BD-rate 이득을 보였다.

• Proceedings of the Korea Information Processing Society Conference
• /
• 2022.11a
• /
• pp.977-979
• /
• 2022

본 논문에서는 시중에서 판매되는 점자학습 기기의 단점들을 보완한 점자학습 보드를 제안한다. 학습 보드는 다음과 같은 기능을 수행한다. 첫째, 자음, 모음 등의 기초적인 글자 학습, 단어와 문장 학습, 게임학습, 총 세 가지의 학습 모드를 지원하는 기능. 둘째, 사용자의 학습 데이터를 분석하여 마지막 학습 일자, 학습 진행 상황 등의 다양한 요소를 고려한 학습, 복습 내용을 자동으로 업로드하는 기능. 셋째, 기기에 연동된 애플리케이션을 통해 학습상태를 확인하고 기기를 조작하는 기능. 넷째, 학습 보드와 앱의 음성안내, 생체인식을 사용한 로그인, 음성인식을 통한 언어 변환, 보드 자동 교체 등의 사용자 편의성을 위한 기능이다. 본 논문은 이를 통해 점자학습에 대한 접근성을 높여 시각장애인의 문맹률 감소를 목표로 한다.

• Journal of Broadcast Engineering
• /
• v.17 no.2
• /
• pp.374-387
• /
• 2012

In this paper, we implement a new hardware for finding the significant coefficients of a digital hologram and ciphering them using discrete wavelet packet transform (DWPT). Discrete wavelet transform (DWT) and packetization of subbands is used, and the adopted ciphering technique can encrypt the subbands with various robustness based on the level of the wavelet transform and the threshold of subband energy. The hologram encryption consists of two parts; the first is to process DWPT, and the second is to encrypt the coefficients. We propose a lifting based hardware architecture for fast DWPT and block ciphering system with multi-mode for the various types of encryption. The unit cell which calculates the repeated arithmetic with the same structure is proposed and then it is expanded to the lifting kernel hardware. The block ciphering system is configured with three block cipher, AES, SEED and 3DES and encrypt and decrypt data with minimal latency time(minimum 128 clocks, maximum 256 clock) in real time. The information of a digital hologram can be hided by encrypting 0.032% data of all. The implemented hardware used about 200K gates in $0.25{\mu}m$ CMOS library and was stably operated with 165MHz clock frequency in timing simulation.

• Geophysics and Geophysical Exploration
• /
• v.12 no.4
• /
• pp.361-366
• /
• 2009

Layered-earth Green's functions in electormagnetic (EM) surveys play a key role in modeling the response of exploration targets. They are computed through the Hankel transforms of analytic kernels. Computational precision depends upon the choice of algebraically equivalent forms by which these kemels are expressed. Since three-dimensional (3D) modeling can require a huge number of Green's function evaluations, total computational time can be influenced by computational time for the Hankel transform evaluations. Linear digital filters have proven to be a fast and accurate method of computing these Hankel transforms. In EM modeling for 3D inversion, electric fields are generally evaluated by the secondary field formulation to avoid the singularity problem. In this study, three components of electric fields for five different sources on the surface of homogeneous half-space were derived as primary field solutions. Moreover, reflection coefficients in TE and TM modes were produced to calculate EM responses accurately for a two-layered model having a sea layer. Accurate primary fields should substantially improve accuracy and decrease computation times for Green's function-based problems like MT problems and marine EM surveys.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.20 no.4
• /
• pp.314-321
• /
• 2000

A gap between a $Al_2O_3/Fe$ thermite and lower head vessel is formed in the lower-plenum arrested vessel attack(LAVA) experiment which is the 1st phase study of simulation of naturally arrested vessel attack in vessel(SONATA-IV). The gap measurement using a conventional ultrasonic method would be lack of a reliability due to the structure complexity and the metallurgical grain size change of the lower head HAZ occurred by a thermite $Al_2O_3/Fe$ melt or a $Al_2O_3$ melt at $2300^{\circ}C$. The grain echoes having false signals and lower S/N ratio signals are detected due to a multiple scattering, a mode conversion and an attenuation of a ultrasonic resulted from at the interface of increased grain size zone. In this test, the signals pattern was classified to understand the behavior of the ultrasonic in a multi-layer specimen of solid-liquid-solid of assuming that the thermite and the lower head vessel is immersed. The polarity threshold algorithm of frequency diversity gives us the enhancement about 6dB of the ratio S/N.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.16 no.2
• /
• pp.173-182
• /
• 2003

In equivalent static nonlinear analysis and in energy-based design, the structures are generally transformed into an equivalent SDOF system. In this study the seismic energy demands in multi story structures, such as three-, eight-, and twenty-story steel moment-resisting frames(MRF), buckling restrained braced frames(BRBF) and a damage tolerant braced frame(DTBF), are compared with those of equivalent single degree of freedom(ESDOF) systems. Sixty earthquake ground motions recorded In different soil conditions, which are soft rock, soft soil, and neat fault, were used to compute the input and hysteretic energy demands in model structures. In case the modal mass coefficient is less than 0.8, the effects of higher modes are considered in the process of converting into ESDOF According to the analysis results, the hysteretic and input energies obtained from 3 story and 8 story MRF and DTBF agreed well with the results from analysis of equivalent SDOF systems. However in the 20 story BRBF the results from ESDOF underestimated those obtained from the original structures.

• Journal of the Institute of Electronics Engineers of Korea SP
• /
• v.47 no.6
• /
• pp.1-9
• /
• 2010

In this paper, we propose an efficient compression method of the integral images. The integral imaging is a well-known technique to represent and record three-dimensional images. The proposed method is based on three dimensional discrete cosine transform (3D-DCT). The 3D-DCT techniques for the integral images have been reported as an efficient coding method for the integral images which reduces the redundancies between adjacent elemental images. The proposed method is a compression method efficient to integral images using adaptive block mode(ABM), based on the 3D-DCT technique. In the ABM, 3D-DCT blocks adaptive to the characteristics of integral images are constructed, which produces variable block size 3D-DCT blocks, and then 3D-DCTs for the 3D blocks are performed. Experimental results show that the proposed method gives significant improvement in coding efficiency. Especially, at the high bit-rates, the proposed method is more excellent since the overhead incurred by the proposed method take less part of the total bits.