• Title/Summary/Keyword: 위상 민감도

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Variation and Structure of the Cold Water Around Ganjeol Point Off the Southeast Coast of Korea (하계 용승현상에 따른 간절곶 주변해역의 냉수역 구조와 변동)

  • Choo, Hyo-Sang
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.22 no.7
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    • pp.836-845
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    • 2016
  • The variation and structure of the cold water mass around Ganjeol Point during the summer of 2011 were studied using data from CTD observations and temperature monitoring buoys deployed at 20 stations off the southeast coast of Korea. There was a $-12^{\circ}C$ surface temperature difference between the cold water mass and normal water during the monitoring period. Variations in the isothermal lines for surface temperature along the coast showed that the seabed topography at Ganjeol Point played an important part in the distribution of water temperature. Cold water appeared when the wind components running parallel to the coast had positive values. The upwelling -response for temperature fluctuations was very sensitive to changes in wind direction. Vertical turbulent mixing due to the seabed topography at Ganjeol Point can reinforce the upwelling of cold bottom water. From wavelet analysis, coherent periods found to be 2-8 days during frequent upwelling events and phase differences for a decrease in water temperature with a SSW wind were 12-36 hours.

A Numerical Study on the Effect of Near Surface Inhomogeneity on Rayleigh Wave Propagation and Dispersion (천부 불균질대에 의한 레일리파 전파 및 분산특성 고찰)

  • Lee, Sang-Min;Park, Kwon-Gyu;Byun, Joong-Moo
    • Geophysics and Geophysical Exploration
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    • v.9 no.2
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    • pp.148-154
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    • 2006
  • The effect of small-scale near surface inhomogeneity on Rayleigh wave propagation and dispersion has been investigated in this study using two-dimensional FEM elastic modeling. Various inhomogeneity models with a variety of geometrical shape and embedment depth which exist in homogeneous half-space and two-layered media are considered. Results show that any near surface inhomogeneity greater than one wavelength in terms of minimum wavelength of Rayleigh wave shows dispersion characteristics. Such dispersion effect become stronger as the dimensions of the inhomogeneity increase. The effect of horizontal dimension is more dominant factor governing the dispersion characteristics than vertical dimension. However, the dispersion effect can not be identifiable in seismogram if the horizontal dimension is not wide enough. Nonetheless, even in this case, the existence of inhomogeneity can be inferred by the reflection or transmission event of Rayleigh wave. The results can be expected to provide insights on the behavior of Rayleigh wave which may be helpful for designating field work or new processing scheme to detect near surface inhomogeneity by surface wave method.

Analysis of time-series displacement using satellite SAR interferometry technique for Dam safety monitoring (댐 안전 관리를 위한 위성 SAR 간섭기법 활용 시계열 변위 분석)

  • Kang, Ki-mook;Hwang, EuiHo
    • Proceedings of the Korea Water Resources Association Conference
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    • 2022.05a
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    • pp.440-440
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    • 2022
  • 1970년대부터 집중 건설 된 우리나라의 다목적댐, 홍수조절댐, 용수전용댐 등의 대형 국가 수자원시설물들의 '고령화'가 급속히 진행되어 수리구조물에 대한 안정성을 주기적으로 파악할 수 있는 정밀안전모니터링 체계 구축이 시급한 시점이다. 주기적인 정밀안전모니터링 방법들 중에는 위성 등을 활용한 원격관측 기술들이 최근 시도되고 있다. 위성 영상레이더(SAR; Synthetic Aperture Radar)는 마이크로파 대역의 전자기파를 송·수신하는 능동센서로 날씨 및 주·야간에 영향을 받지 않고 지표면 관측이 가능한 장점이 있다. 특히, 고정산란체 영상레이더 간섭(PSInSAR; Permanent Scatterer Interferometry SAR)기법은 영상레이더 영상에서 긴밀도(coherence)가 상대적으로 높은 수자원시설물과 같은 고정산란체의 위상(phase) 정보를 이용하여 mm급의 측정민감도로 시계열 변위 분석이 가능하다. 또한, 여러 장의 InSAR 영상을 생성하였기 때문에 DEM 오차, 위성궤도 오차, 대기 성분에 의한 지연 오차 등을 보다 정밀하게 제거할 수 있는 장점이 있다 본 연구에서는 국내 중대형 수자원시설물의 정밀안전모니터링을 위하여 고정산란체 영상레이더 간섭 기법을 영암금호방조제, 영주댐, 소양강댐 등에 적용하여 시계열 변위 분석을 수행하였다. 2014년 11월부터 2022년 3월(현재)까지 획득된 Sentinel-1 SLC(Single Look Complex) 위성자료의 상승(Ascending) 궤도 126장 및 하강(Descending)궤도 187장을 각각 활용하였다. 두 위성궤도를 모두 활용하여 수직, 수평 변위 등 3차원 분석을 수행하였으며, 특히 소양강댐 GPS 관측 자료와 정확도 검증에서 연평균 2mm의 RMSE를 보였다. 이를 통해 위성 원격탐사 기술로도 댐, 보, 방조제와 같은 수자원시설물에 대한 시계열 변위 분석을 통한 댐 안전관리가 가능함을 보여주고 있다. 2025년 발사될 국내 C-밴드 SAR 탑재 수자원위성 개발을 통해 한반도 재방문주기를 단축시킴으로써, 한반도 전역의 수자원시설물 정밀안전진단체계 구축이 가능할 것으로 기대된다.

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Classification of Estuaries based on Morphological Convergence (형태적 수렴 특성을 이용한 하구 분류)

  • SHIN, Hyun-jung;RHEW, Hosahng;LEE, Guan-hong
    • Journal of The Geomorphological Association of Korea
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    • v.19 no.3
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    • pp.1-22
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    • 2012
  • The classification scheme of estuaries can be divided into two categories: qualitative classification based on geomorphic characteristics and quantitative classification based upon the physical properties of water body. While simple and intuitive scheme of the former is difficult to quantify, the latter is not easy to apply due to the lack of data. A classification scheme based on morphological convergence is very promising because it only requires easily accessible data such as width and depth of channels, as well as it can characterize estuaries in terms of tidal propagation. Thus, this paper examines the classification scheme based on estuarine morphological convergence using depth and width data obtained from 19 major Korean estuaries. Morphological convergence for each estuary was estimated with the estuarine length, width and depth data to get the convergence parameters, which includes the degree of funneling ${\nu}$ and the dimensionless estuarine length $y_0$. The transfer function ${\xi}({\nu},ky)$ is then deduced analytically from 1D depth-integrated hydrodynamic momentum equation and continuity equation for estuarine shapes. Tidal response of each estuary is finally calculated using ${\nu}$, $y_0$ and ${\xi}({\nu},ky)$ for comparison and classification. The 19 Korean estuaries were classified into three groups: tidal amplitude-dominated estuaries with standing wave-like tidal response (group 1), current-dominated estuaries with progressive wave-like tidal response (group 2), and the intermediate group (group 3) between groups 1 and 2. The sensitivity analysis revealed that uncertainties in determining the estuarine length can have a critical effect upon the results of classification, which indicates that the reasonable determination of the estuarine length is of critical importance. Once the estuarine length is feasibly determined, depth-convergence can be neglected without any negative effect on the classification scheme, which has an important ramification on the wide applicability of the classification scheme.

First-principles Study on the Magnetic Properties of Gd doped Bithmuth-Telluride (Gd 도핑된 비스무스 텔루라이드의 자기적 성질에 대한 제일원리 계산 연구)

  • Van Quang, Tran;Kim, Miyoung
    • Journal of the Korean Magnetics Society
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    • v.26 no.2
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    • pp.39-44
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    • 2016
  • Determination of the structural, electronic, and magnetic properties of the magnetically doped bismuth-telluride alloys are drawing lots of interest in the fields of the thermoelectric application as well as the research on magnetic interaction and topological insulator. In this study, we performed the first-principles electronic structure calculations within the density functional theory for the Gd doped bismuth-tellurides in order to study its magnetic properties and magnetic phase stability. All-electron FLAPW (full-potential linearized augmented plane-wave) method is employed and the exchange correlation potentials of electrons are treated within the generalized gradient approximation. In order to describe the localized f-electrons of Gd properly, the Hubbard +U term and the spin-orbit coupling of the valence electrons are included in the second variational way. The results show that while the Gd bulk prefers a ferromagnetic phase, the total energy differences between the ferromagnetic and the antiferromagnetic phases of the Gd doped bismuth-telluride alloys are about ~1meV/Gd, indicating that the stable magnetic phase may be changed sensitively depending on the structural change such as defects or strains.

A Calibration-Free 14b 70MS/s 0.13um CMOS Pipeline A/D Converter with High-Matching 3-D Symmetric Capacitors (높은 정확도의 3차원 대칭 커패시터를 가진 보정기법을 사용하지 않는 14비트 70MS/s 0.13um CMOS 파이프라인 A/D 변환기)

  • Moon, Kyoung-Jun;Lee, Kyung-Hoon;Lee, Seung-Hoon
    • Journal of the Institute of Electronics Engineers of Korea SD
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    • v.43 no.12 s.354
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    • pp.55-64
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    • 2006
  • This work proposes a calibration-free 14b 70MS/s 0.13um CMOS ADC for high-performance integrated systems such as WLAN and high-definition video systems simultaneously requiring high resolution, low power, and small size at high speed. The proposed ADC employs signal insensitive 3-D fully symmetric layout techniques in two MDACs for high matching accuracy without any calibration. A three-stage pipeline architecture minimizes power consumption and chip area at the target resolution and sampling rate. The input SHA with a controlled trans-conductance ratio of two amplifier stages simultaneously achieves high gain and high phase margin with gate-bootstrapped sampling switches for 14b input accuracy at the Nyquist frequency. A back-end sub-ranging flash ADC with open-loop offset cancellation and interpolation achieves 6b accuracy at 70MS/s. Low-noise current and voltage references are employed on chip with optional off-chip reference voltages. The prototype ADC implemented in a 0.13um CMOS is based on a 0.35um minimum channel length for 2.5V applications. The measured DNL and INL are within 0.65LSB and l.80LSB, respectively. The prototype ADC shows maximum SNDR and SFDR of 66dB and 81dB and a power consumption of 235mW at 70MS/s. The active die area is $3.3mm^2$.

A Design of Power Management IC for CCD Image Sensor (CCD 이미지 센서용 Power Management IC 설계)

  • Koo, Yong-Seo;Lee, Kang-Yoon;Ha, Jae-Hwan;Yang, Yil-Suk
    • Journal of IKEEE
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    • v.13 no.4
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    • pp.63-68
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    • 2009
  • The power management integrated circuit(PMIC) for CCD image sensor is presented in this study. A CCD image sensor is very sensitive against temperature. The temperature, that is heat, is generally generated by the PMIC with low efficiency. Since the generated heat influences performance of CCD image sensor, it should be minimized by using a PMIC which has a high efficiency. In order to develop the PMIC with high efficiency, the input stage is designed with synchronous type step down DC-DC converter. The operating range of the converter is from 5V to 15V and the converter is controlled using PWM method. The PWM control circuit consists of a saw-tooth generator, a band-gap reference circuit, an error amplifier and a comparator circuit. The saw-tooth generator is designed with 1.2MHz oscillation frequency. The comparator is designed with the two stages OP Amp. And the error amplifier has 40dB DC gain and $77^{\circ}$ phase margin. The output of the step down converter is connected to input stage of the charge pump. The output of the charge pump is connected to input of the LDO which is the output stage of the PMIC. Finally, the PMIC, based on the PWM control circuit and the charge pump and the LDO, has output voltage of 15V, -7.5V, 3.3V and 5V. The PMIC is designed with a 0.35um process.

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Water Governance and Basic Water Law (물거버넌스와 물관리기본법)

  • Lee, Seung-Ho;Kim, Sung
    • Proceedings of the Korea Water Resources Association Conference
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    • 2009.05a
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    • pp.385-389
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    • 2009
  • 본 연구의 목적은 물거버넌스 개념과 1997년, 2006년 물관리기본법안 분석을 통해 한국의 새로운 물관리 체제를 모색하는 것이다. 물거버넌스는 물관리정책과 계획의 수립, 시행, 평가에 있어 정부뿐만 아니라 일반 기업, 시민, 환경단체, 전문가 등 여러 이해당사자를 참여시키는 것을 핵심으로 한다. 거버넌스란 기존의 정부 주도의 정책 계획, 수립, 시행이 아닌 비정부 조직과의 타협, 협의, 논의를 통한 양방향 정책결정 과정을 뜻한다. 따라서 물거버넌스의 가장 중요한 원칙은 다양한 이해당사자 참여를 통한 정책결정의 복수화 과정이다. 한국의 물거버넌스를 시행하기 위해 가장 필요한 요건은 이해당사자 참여를 우선 중앙, 지방정부에서 그 필요성을 인식하고 법, 제도 등을 통해 제도화하는 것이다. 환경부 주도로 입안된 1997년 물관리기본법안은 물관리일원화, 적정사용, 유역관리, 비용부담, 균형배분의 5원칙을, 2006년 물관리기본법안은 물관리일원화 대신 통합물관리, 적정사용 대신 수요관리를 삽입하여 5원칙을 제시하였지만 이해당사자 참여는 원칙에 포함시키지 않았다. 이해당사자 참여 원칙의 제도화가 없이는 위의 두 법안이 제시한 원칙의 적용과 시행이 어려움에 봉착할 가능성이 높다. 왜냐하면 다른 원칙은 다양한 이해당사자 참여를 통한 사회적 합의 없이는 시행이 쉽지 않은 정치적으로 민감한 사항들이기 때문이다. 예를 들어 물의 균형배분 원칙 관련, 만약 상류와 하류 주민 간의 합의가 없이 어느 한 이해당사자의 일방적 행위가 있을 경우 큰 갈등을 유발할 수 있다. 물거버넌스을 실행하기 위해 중앙에 필요한 조직은 물이용 관련 물분쟁 발생 시 이를 조정하고 국가물관리계획을 수립하며 물관리 문제 전반을 총괄하는 조직이다. 1997년, 2006년 기본법안은 국가물관리위원회 설치를 제시하였고 2006년 기본법안에서 보다 구체적으로 위상, 운영, 역할 등에 대해 언급하였다. 하지만 국가물관리위원회는 물관련 중앙부처의 장, 지방행정조직의 장만을 포함하여 유역관리를 책임질 유역관리조직의 장에 대한 언급이 없다. 물거버넌스 실현을 위한 유역관리 시행이 바람직하기에 유역관리조직의 장도 국가물관리위원회에 참여하는 것이 바람직하다. 또한 두 기본법안 모두 국무총리실 산하에 위원회를 속하게 하였는데 이를 수정하여 대통령 직속기구로 규정하는 것이 국가물관리위원회가 정치, 행정, 재정적 압력에서 벗어나 일관성 있는 정책을 펼 수 있는 지름길이 될 것이다. 또한 지방의 물문제를 물관리계획에 적절히 반영하고 대응방안을 수립, 시행하기 위해서는 정부 관료뿐만 아니라 지방의회 의원, 환경단체, 기업, 시민, 전문가 등의 다양한 이해당사자가 참여하는 유역위원회가 필수적이다. 또한 유역 관련 물관리계획을 수립하고 사업을 추진하는 유역관리청도 필요하다. 유역위원회와 유역관리청은 유역 내 여러 이해당사자들이 물관리에 대해 다양한 의견을 개진하고 토론하며 합의점에 이르는 거버넌스를 수립할 수 있는 중요한 조직이다. 두 기본법안은 유역관리 원칙을 제시하긴 하였지만 유역관리 시행 관련 조직, 역할, 운영 등에 대해서는 언급이 없었다. 한국의 물관리는 소득, 문화 수준 향상으로 인한 양질의 물공급에 대한 요구, 시민사회의 발전, 지방분권화 등 정치, 경제, 사회의 변화를 수용하고 발전해 나가기 위해서는 여러 이해당사자의 참여와 합의에 바탕을 둔 물거버넌스 수립이 무엇보다 중요하다. 또한 이를 시행하기 위해서는 물관리기본법을 하루 속히 제정하여 제도적 기반을 갖춰 보다 효율적인 물관리시스템을 수립해야 한다.

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Estimation of source signal and channel response using ray-based blind deconvolution technique for Doppler-shifted underwater channel (음선 기반 블라인드 디컨볼루션 기법을 이용한 수중 도플러 편이 채널에서의 송신 신호 및 채널 응답 추정)

  • Byun, Gi Hoon;Oh, Se Hyun;Byun, Sung-Hoon;Kim, J.S.
    • The Journal of the Acoustical Society of Korea
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    • v.35 no.5
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    • pp.331-339
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    • 2016
  • This paper suggests an estimation method of the source signal and the channel impulse response (CIR) using ray-based blind deconvolution (RBD) in the underwater acoustic channel environment where Doppler effect exists by the relative motion between source and receiver. It is difficult to estimate the CIR on Doppler effect by the matched filter with a highly Doppler-sensitive waveform such as the m-sequence signal because Doppler shift can severely degrade the correlation between the received signal corrupted by Doppler effect and the original source signal. In this study, the Doppler-shifted source-signal's phase is estimated using the RBD, and the received signal is compensated by it to obtain the Doppler-corrected CIR. It is verified that using the matched filter with the received signal from the experimental data fails to estimate the CIR while the obtained CIR by the suggested method has the similarity to the propagation path of the ray model. Also, the results show that the reconstructed source signal using the RBD has the better Doppler shift compensation than the Doppler-shifted source signal derived from scattering function.

Evaluation of MR-SENSE Reconstruction by Filtering Effect and Spatial Resolution of the Sensitivity Map for the Simulation-Based Linear Coil Array (선형적 위상배열 코일구조의 시뮬레이션을 통한 민감도지도의 공간 해상도 및 필터링 변화에 따른 MR-SENSE 영상재구성 평가)

  • Lee, D.H.;Hong, C.P.;Han, B.S.;Kim, H.J.;Suh, J.J.;Kim, S.H.;Lee, C.H.;Lee, M.W.
    • Journal of Biomedical Engineering Research
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    • v.32 no.3
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    • pp.245-250
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    • 2011
  • Parallel imaging technique can provide several advantages for a multitude of MRI applications. Especially, in SENSE technique, sensitivity maps were always required in order to determine the reconstruction matrix, therefore, a number of difference approaches using sensitivity information from coils have been demonstrated to improve of image quality. Moreover, many filtering methods were proposed such as adaptive matched filter and nonlinear diffusion technique to optimize the suppression of background noise and to improve of image quality. In this study, we performed SENSE reconstruction using computer simulations to confirm the most suitable method for the feasibility of filtering effect and according to changing order of polynomial fit that were applied on variation of spatial resolution of sensitivity map. The image was obtained at 0.32T(Magfinder II, Genpia, Korea) MRI system using spin-echo pulse sequence(TR/TE = 500/20 ms, FOV = 300 mm, matrix = $128{\times}128$, thickness = 8 mm). For the simulation, obtained image was multiplied with four linear-array coil sensitivities which were formed of 2D-gaussian distribution and the image was complex white gaussian noise was added. Image processing was separated to apply two methods which were polynomial fitting and filtering according to spatial resolution of sensitivity map and each coil image was subsampled corresponding to reduction factor(r-factor) of 2 and 4. The results were compared to mean value of geomety factor(g-factor) and artifact power(AP) according to r-factor 2 and 4. Our results were represented while changing of spatial resolution of sensitivity map and r-factor, polynomial fit methods were represented the better results compared with general filtering methods. Although our result had limitation of computer simulation study instead of applying to experiment and coil geometric array such as linear, our method may be useful for determination of optimal sensitivity map in a linear coil array.