• 터널과지하공간
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• 제10권3호
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• pp.486-491
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• 2000

발파 진동은 보통 지반진동속도로 계측되며, 발파설계나 구조물의 피해 산정에 적절하게 사용된다. 그러나 발파 진동에 의한 인체의 반응이나 가축의 피해 산정 등의 문제에서는 현행 소음진동규제법에서 명시하는 바, 인체의 감각적 감응척도에 충실한 진동레벨을 주로 사용하므로 변환문제가 발생한다. 본 연구에서는 발파 진동 계측기기로 계측한 데이터를 디지털 필터로 처리하여, 진동레벨로 변환하는 프로그램을 개발하고, 이를 단순조화진동과 실제 발파계측결과에 적용하였다. 그 결과, 단순조화진동은 물론이고 국내에서 널리 사용되고 있는 Instantel Inc.의 Blastmate series에서 계측된 진동데이터도 정밀도 높은 진동레벨로 변환이 가능하였다. 비슷한 정밀도로 계측결과를 ASCII file로 송출할 수 있는 기종에서 계측된 자료도 같은 정도로 처리할 수 있을 것으로 판정되었다.

• 한국암반공학회:학술대회논문집
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• 한국암반공학회 2000년도 암반공학문제의 수치해석(Numerical Analysis in Rock Engineering Problems)
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• pp.241-246
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• 2000

발파 진동은 보통 지반진동속도로 계측되며, 발파설계나 구조물의 피해 산정에 적절하게 사용된다. 그러나 발파 진동에 의한 인체의 반응이나 가축의 피해 산정 등의 문제에서는 현행 소음진동규제법에서 명시하는 바, 인체의 감각적 감응척도에 충실한 진동레벨을 주로 사용하므로 변환문제가 발생한다. 본 연구에서는 발파 진동 계측기기로 계측한 데이터를 디지털 필터로 처리하여, 진동레벨로 변환하는 프로그램을 개발하고, 이를 단순조화진동과 실제 발파계측결과에 적용하였다. 그 결과, 단순조화진동은 물론이고 국내에서 널리 사용되고 있는 Instantel Inc.의 Blastmate series에서 계측된 진동데이터도 정밀도 높은 진동레벨로 변환이 가능하였다. 비슷한 정밀도로 계측결과를 ASCII file로 송출할 수 있는 기종에서 계측된 자료도 같은 정도로 처리할 수 있을 것으로 판정되었다

• 한국소음진동공학회논문집
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• 제23권11호
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• pp.943-950
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• 2013

This paper discusses a harmonic response estimation method on the L$\acute{e}$vy plate with two opposite edges simply supported and the other two edges having free boundary conditions. Since the equation of motion of the plate is not self-adjoint, the modes are not orthogonal to each other on the domain. Noting that the L$\acute{e}$vy plate can be expressed using one term sinusoidal function that is orthogonal to other sinusoidal functions, this paper suggested the calculation method that is equivalent to finding a least square error minimization solution of the finite number of algebraic equations. Example problems subjected to a distributed area loading and a distributed line loading are defined and their solutions are provided. The solutions are compared to those of the commercial code, ANSYS. According to the verification results, it is expected that the suggested method will be useful to predict the forced response on the L$\acute{e}$vy plate with the distributed area or line loading conditions.

• 한국통신학회논문지
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• 제16권3호
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• pp.259-269
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• 1991

본 논문에서는 전력선 채널에서 가장 심각한 문제인 임펄스성 고조파 잡음을 제거하기 위한 디지털 신호 처리 기술을 LMS(Least Mean Square)와 ITLMS(Individual Tapped LMS)의 두 가지의 알고리즘을 사용한 선형 예측에 의한 전력선 고조파 잡음 제거 방식을 통해 다루었고 각종 재밍(jamming)에 강한 특징을 가지는 DS(Direct sequnce) 대역 확산 통신을 전력선 채널에 적용하여 전송 성능의 개선을 확인하였다.

• 한국융합학회논문지
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• 제4권1호
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• pp.33-41
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• 2013

This paper presents an adaptive recursive least squares algorithm (ARLS) for detecting voltage sag and voltage swell events in power systems. Different methods have been developed to detect voltage sag and voltage swell. Some of them use window techniques, which are too slow when voltage sag or swell mitigation is required. Others depend on the extraction of a single non-stationary sinusoidal signal out of a given multi-components input signal, and therefore they don't consider the harmonic components in calculating the voltage root mean square value (rms). The method, proposed in this paper, is capable of estimating the voltage rms taking into account all harmonic components. The method is tested by applying it to different, simulated signals using ATP program, and compared with voltage sag detection algorithms.

• 대한수학회지
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• 제61권1호
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• pp.183-205
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• 2024

In this paper, for an m-dimensional (m ≥ 5) complete non-compact submanifold M immersed in an n-dimensional (n ≥ 6) simply connected Riemannian manifold N with negative sectional curvature, under suitable constraints on the squared norm of the second fundamental form of M, the norm of its weighted mean curvature vector |H_f| and the weighted real-valued function f, we can obtain: • several one-end theorems for M; • two Liouville theorems for harmonic maps from M to complete Riemannian manifolds with nonpositive sectional curvature.

• 한국정보통신학회논문지
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• 제14권12호
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• pp.2818-2826
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• 2010

1985~2009년 동안 동북아시아해역 해수면온도의 시 공간변화특성을 연구하였는데, 먼저 기상청 부이 8곳의 자료와 위성 자료를 비교하였다. 제곱평균오차와 편차는 얕은 연안으로 갈수록 증가하였다. 연구해역은 일본기상청에서 나눈 방식에 따라 7해역으로 구분하고, NOAA/AVHRR 자료를 사용하여 조화분해를 수행하여 각 해역의 중점을 비교 분석하였다. 평균해수표면온도는 $8{\sim}26^{\circ}C$의 변화를 보였고, 연진폭은 $7{\sim}24^{\circ}C$까지 변하였다. 그리고 연위상은 7월말에서 8월말까지로 나타났다. 각 해역의 교차상관계수는 표면수온, 연진폭, 연위상이 각각 0.57~0.85, -0.04~0.81, 그리고 0.35~0.80으로 나타났다.

• Investigative Magnetic Resonance Imaging
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• 제22권1호
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• pp.37-49
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• 2018

Purpose: The effect of global inhomogeneity on quantitative susceptibility mapping (QSM) was investigated. A technique referred to as Simultaneous Unwrapping Phase with Error Recovery from inhomogeneity (SUPER) is suggested as a preprocessing to QSM to remove global field inhomogeneity-induced phase by polynomial fitting. Materials and Methods: The effect of global inhomogeneity on QSM was investigated by numerical simulations. Three types of global inhomogeneity were added to the tissue susceptibility phase, and the root mean square error (RMSE) in the susceptibility map was evaluated. In-vivo QSM imaging with volunteers was carried out for 3.0T and 7.0T MRI systems to demonstrate the efficacy of the proposed method. Results: The SUPER technique removed harmonic and non-harmonic global phases. Previously only the harmonic phase was removed by the background phase removal method. The global phase contained a non-harmonic phase due to various experimental and physiological causes, which degraded a susceptibility map. The RMSE in the susceptibility map increased under the influence of global inhomogeneity; while the error was consistent, irrespective of the global inhomogeneity, if the inhomogeneity was corrected by the SUPER technique. In-vivo QSM imaging with volunteers at 3.0T and 7.0T MRI systems showed better definition in small vascular structures and reduced fluctuation and non-uniformity in the frontal lobes, where field inhomogeneity was more severe. Conclusion: Correcting global inhomogeneity using the SUPER technique is an effective way to obtain an accurate susceptibility map on QSM method. Since the susceptibility variations are small quantities in the brain tissue, correction of the inhomogeneity is an essential element for obtaining an accurate QSM.

• 대한원격탐사학회지
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• 제27권3호
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• pp.329-338
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• 2011

The time-series normalized difference vegetation index (NDVI) product has proven to be a powerful tool to investigate the phenological information because it can monitor the change of the forests with very high time-resolution, This study described the application of the DFT analysis over the 9 year MODIS data for the identification of the two types of vegetation cover, Pinus densiflora(Pd) and Querqus mongolica(Qm) which are dominant species of evergreen and broadleaved deciduous forest, respectively, The total number of samples was 5148 reference cycles which consist of 2160 Pd and 2988 Qm. They were extracted from the pixel-based MODIS scenes over the 9 years from 2000 to 2008 of South Korea. The DFT analysis was mainly focused on the 0th and $1^{st}$ harmonic components, each of which represents the mean value and the variation amplitude of the NDVI over the years, respectively. The $0^{th}$ harmonic values of the vegetation Pd and Qm averaged over the 9 years were 0.74 and 0.65, respectively. This implies that Pd has a higher NDVI than Qm. Similarly obtained $1^{st}$ harmonic values of Pd and Qm were 0.19 and 0.27, respectively. This can be intuitively understood considering that the seasonal variation of Qm is much larger than Pd. This distinctive difference of the $1^{st}$ harmonic value has been used to identify evergreen and deciduous forests. Overall agreement between the Fourier analysis-based map and the actal vegetation map has been estimated to be as high as 75%. This study found that the DFT analysis can be a concise and repeatable method to separate and trace the changes of evergreen and deciduous forest using the annual NDVI cycles.

• 대한수학회보
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• 제54권6호
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• pp.1981-1990
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• 2017

Let R be a root system in $\mathbb{R}^d$ with Coxeter-Weyl group W and let k be a nonnegative multiplicity function on R. The generalized volume mean of a function $f{\in}L^1_{loc}(\mathbb{R}^d,m_k)$, with $m_k$ the measure given by $dmk(x):={\omega}_k(x)dx:=\prod_{{\alpha}{\in}R}{\mid}{\langle}{\alpha},x{\rangle}{\mid}^{k({\alpha})}dx$, is defined by: ${\forall}x{\in}\mathbb{R}^d$, ${\forall}r$ > 0, $M^r_B(f)(x):=\frac{1}{m_k[B(0,r)]}\int_{\mathbb{R}^d}f(y)h_k(r,x,y){\omega}_k(y)dy$, where $h_k(r,x,{\cdot})$ is a compactly supported nonnegative explicit measurable function depending on R and k. In this paper, we prove that for almost every $x{\in}\mathbb{R}^d$, $lim_{r{\rightarrow}0}M^r_B(f)(x)= f(x)$.