• 한국전자통신학회논문지
• /
• 제15권6호
• /
• pp.1037-1044
• /
• 2020

윈드프로파일러(RWP, radar wind profiler)는 기상 상태와 관계없이 시공간 분해능이 높은 바람장 자료를 제공하며 생산된 바람의 정확도나 품질에 대한 검증이 필수적이다. 기존 정확도 검증 방식은 레윈존데와의 동시 관측을 통해 윈드프로파일러에서 생성된 바람 벡터를 기준 자료로 활용하는 것이다. 본 연구에서는 평균 모멘트 자료로부터 스펙트럼과 원시 시계열 자료를 시뮬레이션하는 알고리즘을 통해 윈드프로파일러의 신호처리 알고리즘을 단계별로 검증하는 방안을 제시하고, LAP-3000의 원시 자료와의 비교를 통해 해당 알고리즘의 가능성을 확인하였다. 기상 신호의 밀도 함수를 모멘트값을 인자로 하는 왜곡된 정규 분포의 밀도 함수로 가정하여 생성하였고, 난수를 통해 시뮬레이션 스펙트럼을 생성하였다. 또한, 난수 위상과 역 이산푸리에 변환으로 간섭 평균된 시뮬레이션 원시 시계열 자료를 생성하고 최종적으로 디리클레 분포(Dirichlet distribution)를 통해 간섭 평균 전 단계의 원시 시계열 자료를 생성하였다.

• 국제초고층학회논문집
• /
• 제11권4호
• /
• pp.277-286
• /
• 2022

In this study, The POD technique was applied to the fluctuating wind pressure of high aspect ratio circular cylinder to consider about its organizational structure, and considered about the characteristics of the fluctuating wind force obtained by synthesized the POD modes.

• 전기전자학회논문지
• /
• 제17권1호
• /
• pp.10-15
• /
• 2013

정상적인 불꽃 점화 시스템과 관통형 세라믹 콘덴서를 부가한 불꽃 점화 시스템에서 복사되는 전자파의 전력 스펙트럼의 측정 데이터를 분석한 결과 관통형 세라믹 콘덴서를 부가한 불꽃 점화 시스템에서 복사되는 전자파는 정상적인 불꽃 점화 시스템에서 복사되는 전자파 보다 약하고, 스펙트럼 밀도 또한 소하였다. 이것은 불꽃 점화 시스템에서 복사되는 불요 전자파를 관통형 세라믹 콘덴서가 감소시키는 것이라고 할 수 있으며, 고압의 펄스를 발생하는 점화 코일은 고주파를 발생하는 무선 주파 발진기라고 할 수 있다.

• 천문학회보
• /
• 제41권1호
• /
• pp.38.2-38.2
• /
• 2016

The mapping of dark matter clustering from real to redshift spaces introduces the anisotropic property to the measured density power spectrum in redshift space, known as the Redshift Space Distortion (hereafter RSD) effect. The mapping formula is intrinsically non-linear, which is complicated by the higher order polynomials due to the indefinite cross correlations between the density and velocity fields, and the Finger-of-God (hereafter FoG) effect due to the randomness of the peculiar velocity field. Furthermore, the rigorous test of this mapping formula is contaminated by the unknown non-linearity of the density and velocity fields, including their auto- and cross-correlations, for calculating which our theoretical calculation breaks down beyond some scales. Whilst the full higher order polynomials remains unknown, the other systematics can be controlled consistently within the same order truncation in the expansion of the mapping formula, as shown in this paper. The systematic due to the unknown non-linear density and velocity fields is removed by separately measuring all terms in the expansion using simulations. The uncertainty caused by the velocity randomness is controlled by splitting the FoG term into two pieces, 1) the non-local FoG term being independent of the separation vector between two different points, and 2) the local FoG term appearing as an indefinite polynomials which is expanded in the same order as all other perturbative polynomials. Using 100 realizations of simulations, we find that the best fitted non-local FoG function is Gaussian, with only one scale-independent free parameter, and that our new mapping formulation accurately reproduces the observed power spectrum in redshift space at the smallest scales by far, up to k ~ 0.3 h/Mpc, considering the resolution of future experiments.

• Structural Engineering and Mechanics
• /
• 제49권1호
• /
• pp.129-145
• /
• 2014

In order to investigate the characteristics of torsional wind loads on rectangular tall buildings, five models with different rectangular cross-sections were tested in a boundary wind tunnel. Based on the test results, the RMS force coefficients, power spectrum densities as well as vertical correlation functions of torsional wind loads were analyzed. Formulas that took the side ratio as parameters were proposed to fit the test results above. Comparisons between the results calculated by the formulas and the wind tunnel measurements were made to verify the reliability of the proposed formulas. An simplified expression to evaluate the dynamic torsional wind loads on rectangular tall buildings in urban terrain is presented on basis of the above formulas and has been proved by a practical project. The simplified expressions as well as the proposed formulas can be applied to estimate wind-induce torsional response on rectangular tall buildings in the frequency domain.

• 대한전자공학회논문지
• /
• 제26권12호
• /
• pp.1903-1909
• /
• 1989

In this paper, the mobile communication CH simulator is implemented in the baseband, using the Digital Signal Processor(TMS320C25), A/D and D/A converters. The Rayleigh CH is modeled by shaping the random noise source power spectrum. The statistical characteristics(Level Crossing Rate, Cumulative distribution Function, Probability Density Function) and the received fading signal's power's spectrum is observed when the doppler frequency is varied according to the variation of the vehicular velocity at the 222MHz band. And also the BER is measured when the baseband mobile CH simulator is applied to the GMSK(Gaussian Minimum Shift Keying` transmission rate: 16kbps, Bb T=0.25) modulator. The results shows the similar characteristics to be compared with the theoritically derived BER values of the discriminator type GMSK detection.

• 천문학회보
• /
• 제44권2호
• /
• pp.53.2-53.2
• /
• 2019

The genus of the matter density eld, as traced by galaxies, contains information regarding the nature of dark energy and the fraction of dark matter in the Universe. In particular, this topological measure is a statistic that provides a clean measurement of the shape of the linear matter power spectrum. As the genus is a topological quantity, it is insensitive to galaxy bias and gravitational collapse. Furthermore, as it traces the linear matter power spectrum, it is a conserved quantity with redshift. Hence the genus amplitude is a standard population that can be used to test the distance-redshift relation. In this talk, I present measurements of the genus extracted from the SDSS DR7 LRGs in the local Universe, and also slices of the BOSS DR12 data at higher redshift. I show how these combined measurements can be used to place cosmological parameter constraints on m, wde.

• 전기전자학회논문지
• /
• 제13권4호
• /
• pp.9-14
• /
• 2009

이 논문에서는 혼성 신호 집적회로 상의 온칩 전원전압 잡음을 측정하는 회로에 대해 기술하였다. 온칩 상의 전원전압 잡음을 측정함으로서 잡음이 아날로그 회로에 미치는 영향을 확인하고 이를 보상하는 정보로도 사용할 수 있다. 이 회로는 동일하지만 독립적인 두 개의 채널로 구성되어 있다. 각 채널은 샘플 앤 홀드와 전압 제어 발진기를 포함한 주파수-디지털 변환 블록으로 구성되어 있다. 간단한 아날로그-디지털 변환 방법을 사용해서 시간 기준 전압 정보와 주파수 기준 전력 스펙트럼 밀도를 얻을 수 있다. 버퍼는 넓은 대역폭을 갖는 유닛 게인 버퍼로 동작하고, 전압 제어 발진기는 해상도를 높이기 위한 높은 증폭도를 가지고 있다. 이 회로는 0.18um CMOS 공정으로 설계되었으며 측정된 해상도는 2.06mV/count 이다. 전원잡음 측정회로는 15mW의 전력을 소모하며 $0.768mm^2$의 면적을 차지한다.

• 한국정보처리학회논문지
• /
• 제7권7호
• /
• pp.2246-2253
• /
• 2000

In this paper, we show that one can enhance the performance of blind segmentation of phoneme boundaries by adopting the knowledge of Korean syllabic structure and the regions of voiced/unvoiced sounds. eh proposed method consists of three processes : the process to extract candidate phoneme boundaries, the process to detect boundaries of voiced/unvoiced sounds, and the process to select final phoneme boundaries. The candidate phoneme boudaries are extracted by clustering method based on similarity between two adjacent clusters. The employed similarity measure in this a process is the ratio of the probability density of adjacent clusters. To detect he boundaries of voiced/unvoiced sounds, we first compute the power density spectrum of speech signal in 0∼400 Hz frequency band. Then the points where this paper density spectrum variation is greater than the threshold are chosen as the boundaries of voiced/unvoiced sounds. The final phoneme boundaries consist of all the candidate phoneme boundaries in voiced region and limited number of candidate phoneme boundaries in unvoiced region. The experimental result showed about 40% decrease of insertion rate compared to the blind segmentation method we adopted.

• 한국자동차공학회논문집
• /
• 제8권4호
• /
• pp.85-92
• /
• 2000

The pulsating pressure waves are composed of fundamental frequency and higher order harmonics in exhaust pipe of engines. The nonlinearity in exhaust pipe is caused by their interactions. The error which is between prediction and measurement is induced by the nonlinearity. We can not explain this phenomenon using linear acoustic theory which is existing theory. So power spectrum which was used in linear theory is not useful. Bispectrum and bicoherence functions which are a higher order spectrum are applicable to explain this phenomenon. This paper proposes a nonlinear effect of pulsating pressure waves. The phenomenon proposed here is identified by using of higher order spectrum density functions.