• Title/Summary/Keyword: 차분

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Improvement of Small Baseline Subset (SBAS) Algorithm for Measuring Time-series Surface Deformations from Differential SAR Interferograms (차분 간섭도로부터 지표변위의 시계열 관측을 위한 개선된 Small Baseline Subset (SBAS) 알고리즘)

  • Jung, Hyung-Sup;Lee, Chang-Wook;Park, Jung-Won;Kim, Ki-Dong;Won, Joong-Sun
    • Korean Journal of Remote Sensing
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    • v.24 no.2
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    • pp.165-177
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    • 2008
  • Small baseline subset (SBAS) algorithm has been recently developed using an appropriate combination of differential interferograms, which are characterized by a small baseline in order to minimize the spatial decorrelation. This algorithm uses the singular value decomposition (SVD) to measure the time-series surface deformation from the differential interferograms which are not temporally connected. And it mitigates the atmospheric effect in the time-series surface deformation by using spatially low-pass and temporally high-pass filter. Nevertheless, it is not easy to correct the phase unwrapping error of each interferogram and to mitigate the time-varying noise component of the surface deformation from this algorithm due to the assumption of the linear surface deformation in the beginning of the observation. In this paper, we present an improved SBAS technique to complement these problems. Our improved SBAS algorithm uses an iterative approach to minimize the phase unwrapping error of each differential interferogram. This algorithm also uses finite difference method to suppress the time-varying noise component of the surface deformation. We tested our improved SBAS algorithm and evaluated its performance using 26 images of ERS-1/2 data and 21 images of RADARSAT-1 fine beam (F5) data at each different locations. Maximum deformation amount of 40cm in the radar line of sight (LOS) was estimated from ERS-l/2 datasets during about 13 years, whereas 3 cm deformation was estimated from RADARSAT-1 ones during about two years.

Enhanced and Practical Alignment Method for Differential Power Analysis (차분 전력 분석 공격을 위한 향상되고 실제적인 신호 정렬 방법)

  • Park, Jea-Hoon;Moon, Sang-Jae;Ha, Jae-Cheol;Lee, Hoon-Jae
    • Journal of the Korea Institute of Information Security & Cryptology
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    • v.18 no.5
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    • pp.93-101
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    • 2008
  • Side channel attacks are well known as one of the most powerful physical attacks against low-power cryptographic devices and do not take into account of the target's theoretical security. As an important succeeding factor in side channel attacks (specifically in DPAs), exact time-axis alignment methods are used to overcome misalignments caused by trigger jittering, noise and even some countermeasures intentionally applied to defend against side channel attacks such as random clock generation. However, the currently existing alignment methods consider only on the position of signals on time-axis, which is ineffective for certain countermeasures based on time-axis misalignments. This paper proposes a new signal alignment method based on interpolation and decimation techniques. Our proposal can align the size as well as the signals' position on time-axis. The validity of our proposed method is then evaluated experimentally with a smart card chip, and the results demonstrated that the proposed method is more efficient than the existing alignment methods.

Design and Implementation of Biological Signal Measurement Algorithm for Remote Patient Monitoring based on IoT (IoT기반 원격환자모니터링을 위한 생체신호 측정 알고리즘 설계 및 구현)

  • Jung, Ae-Ran;You, Yong-Min;Lee, Sang-Joon
    • Asia-pacific Journal of Multimedia Services Convergent with Art, Humanities, and Sociology
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    • v.8 no.6
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    • pp.957-966
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    • 2018
  • Recently, the demand for remote patient monitoring based on IoT has been increased due to aging population and an increase in single-person household. A non-contact biological signal measurement system using multiple IR-UWB radars for remote patient monitoring is proposed in this paper. To reduce error signals, a multilayer Subtraction algorithm is applied because when the background subtraction algorithm was applied to the biological signal processing, errors occurred such as voltage noise and staircase phenomenon. Therefore, a multilayer background subtraction algorithm is applied to reduce error occurrence. The multilayer background subtraction algorithm extracts the signal by calculating the amount of change between the previous clutter and the current clutter. In this study, the SVD algorithm is used. We applied the improved multilayer background subtraction algorithm to biological signal measurement and computed the respiration rate through Fast Fourier Transform (FFT). To verify the proposed system using IR-UWB radars and multilayer background subtraction algorithm, the respiration rate was measured. The validity of this study was verified by obtaining a precision of 97.36% as a result of a control experiment with Neulog's attachment type breathing apparatus. The implemented algorithm improves the inconvenience of the existing contact wearable method.

Tensile Force Estimation of Externally Prestressed Tendon Using SI technique Based on Differential Evolutionary Algorithm (차분 진화 알고리즘 기반의 SI기법을 이용한 외부 긴장된 텐던의 장력추정)

  • Noh, Myung-Hyun;Jang, Han-Taek;Lee, Sang-Youl;Park, Taehyo
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.29 no.1A
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    • pp.9-18
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    • 2009
  • This paper introduces the application of DE (Differential Evolutionary) method for the estimation of tensile force of the externally prestressed tendon. The proposed technique, a SI (System Identification) method using the DE algorithm, can make global solution search possible as opposed to classical gradient-based optimization techniques. The numerical tests show that the proposed technique employing DE algorithm is a useful method which can detect the effective nominal diameters as well as estimate the exact tensile forces of the externally prestressed tendon with an estimation error less than 1% although there is no a priori information about the identification variables. In addition, the validity of the proposed technique is experimentally proved using a scale-down model test considering the serviceability state condition without and with the loss of the prestressed force. The test results prove that the technique is a feasible and effective method that can not only estimate the exact tensile forces and detect the effective nominal diameters but also inspect the damping properties of test model irrespective of the loss of the prestressed force. The 2% error of the estimated effective nominal diameter is due to the difference between the real tendon diameter with a wired section and the FE model diameter with a full-section. Finally, The accuracy and superiority of the proposed technique using the DE algorithm are verified through the comparative study with the existing theories.

Experimental Analysis of MESD Attack on Smartcard. (스마트카드의 MESD 공격에 대한 실험적 분석)

  • 안만기;이훈재;하재철;김동렬;문상재
    • Proceedings of the Korea Institutes of Information Security and Cryptology Conference
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    • 2002.11a
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    • pp.575-579
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    • 2002
  • 스마트카드는 내부의 암호 알고리듬이 수행될 때, 비밀키와 관련된 여러 가지 물리적인 정보가 누출될 가능성이 있다. 이러한 물리적 정보 중에서 소비되는 전력을 측정하고 분석하는 차분 전력분석 공격은 매우 강력한 방법이다. 본 논문에서는 시차공격과 단순전력분석 공격에 대응하는 몽고메리 멱승 알고리듬과 스칼라 상수배 알고리듬이 구현된 스마트카드에서 차분 전력 분석 공격의 방법 중에서 동일한 메시지를 이용하는 MESD 공격을 실험하고 실험과정에서 소모전력의 측정 개수와 표본화율 그리고 잡음의 관계를 분석한다.

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효율적 시장가설과 서브마팅게일의 검증

  • Ok, Gi-Yul;Song, Yeong-Hyo
    • The Korean Journal of Financial Management
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    • v.14 no.1
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    • pp.207-217
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    • 1997
  • 본 연구에서는 효율적 시장가설을 검증할 때 일반적으로 이용하는 주가의 로그변환방법은 마팅게일과 서브마팅게일을 구분할 수 없다는 것을 이론적으로 보여주고, 이러한 문제를 해결하기 위해서는 로그변환없이 일차 차분을 한 시계열 데이타를 이용하는 것이 바람직하다는 것을 제시한다. 또한 마팅게일과 서브마팅게일의 구분하기 위해서는 주가 차분 시계열 데이타의 공분산이라는 검정통계량을 이용하는데, 이 공분산이라는 검정통계량을 이용하여 실증적으로 검증을 하기 위해서는 이 통계량의 분포를 알아야 한다. 본 연구에서는 bootstrap방법론을 이용하여 이 공분산의 분포를 구하는 방법론을 제시한다.

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Human·Livestock Classifier Using Spatial Integration (공간적분을 이용한 인간.가축 분류)

  • Oh, Myung-Jae;Kim, Jin-Kyo;Tak, Myung-Hwan;Joo, Young-Hoon
    • Proceedings of the KIEE Conference
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    • 2011.07a
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    • pp.1912-1913
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    • 2011
  • 본 논문은 공간적분을 이용한 인간 가축 분류를 위한 실시간 영상처리 방법을 제안한다. 입력 영상에 장면 차분 방법을 이용해 차분 영상을 구하고 잡음 제거를 위해 EM 알고리즘을 이용한다. 잡음 제거된 템플릿 영상에 대해 KLT 알고리즘을 이용하여 특징 벡터를 구한다. 추출된 이동 객체의 움직임 벡터 기반으로 히스토그램을 생성한다. SA 알고리즘을 이용하여 히스토그램을 분석 하여, 최종적으로 인간과 가축을 분류한다.

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유한차분법을 이용한 볼스크류 시스템의 열팽창 해석

  • 박정균;정성종
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 1991.11a
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    • pp.101-104
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    • 1991
  • Bal1 screw systems has been used for positioning elements of machine tools. In order to maintain high rigidity and accuracy, preload is applied between nut and screw. However, large amount of preload increases frictional heat. Temperature rises remarkably at high speed notion, Thermal expansion degrades positioning accuracy, In this paper, finite differance method is applied to compute temperature distributions and thermal expansions of ball screw systems according to preload condition and rotational steed. Some simulation results show that the developed methodology is good to study thermal expansion of ball screw systems.

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Item Difference Difficulty & Item Discrimination based Item Suitability Verification for Test Bank System (문제은행 시스템의 문항 차분 난이도 및 변별도를 기반으로 한 문항 적합성 검증)

  • 전병호
    • Proceedings of the Korea Multimedia Society Conference
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    • 2001.06a
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    • pp.403-406
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    • 2001
  • 문제은행 시스템은 피험자의 조건에 따라 데이터베이스에서 문항을 추출하여 가상공간에서 평가를 수행한다. 가상 공간에서의 평가는 피험자에게 적용하는 경우 출제 빈도에 따라 운항의 난이도 및 변별력에 영향을 주게 된다 출제 빈도에 따라 난이도나 변별력이 낮아지는 문항은 출제를 제한하는 기준이 필요하다. 본 논문에서는 문항 사후 난이도와 문항 변별도를 기반으로 하여, 문항 차분 난이도를 주기적으로 측정하고 난이도 차이가 일정 수준 이상이 되는 문항에 대해 출제를 제한하는 방안과 전체 피험자에 대한 운항의 변별력을 측정하러 변별력이 떨어지는 문항을 출제자에게 문항을 수정하게 하거나 삭제하도록 하는 방안들 제안한다.

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The Analysis of Microwave Amplifier using an Extended FDTD Method (확장된 시간영역 유한차분법을 이용한 고주파 증폭기 해석)

  • 강희진;노범석;최재훈
    • Proceedings of the Korea Electromagnetic Engineering Society Conference
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    • 2000.11a
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    • pp.130-134
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    • 2000
  • 본 논문에서는 확장된 시간영역 유한차분법(Extended finite difference time domain method)을 이용하여 마이크로파 중폭기를 해석하였다. 회로에 포함되어 있는 능동 소자는 고주파 등가 회로를 이용하여 모델링 하였다. 고주파 등가 회로를 통하여 계산한 게어트와 드레인의 전류를 FDTD의 전계 계산식에 첨가향으로개 마이크로스트립 회로의 전자기파와 능동 소자와의 상호 작용을 특성 지었다. 해석 결과는 주파수 영역 회로 해석법(Frequency-domain circuit analysis)을 이용한 결과와의 비교를 통하여 정확성을 입증했다.

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