• 한국인터넷방송통신학회논문지
• /
• 제10권6호
• /
• pp.113-118
• /
• 2010

주행 중인 자동차 타이어의 손상을 검출하기 위해 타이어에서 발생하는 초음파 신호에 대한 스플릿 스펙트럼 처리 알고리즘을 연구하였다. 스플릿 스펙트럼의 최대값을 추정하는 알고리즘을 사용하여 정상적인 타이어와 손상 물질에 의해 손상된 타이어에 대한 처리 결과를 비교하였다. 자기상관함수를 이용한 결과, 실험에 사용된 손상된 타이어에서는 주행속도 50km/h 일 때 162.9ms, 100km/h 일 때 84.81ms 주기로 손상 특이점을 검출 할 수 있었으며, 이에 의해 자동차 주행속도에 따른 손상 특징 점의 주기성을 이용하여 손상 물질에 의한 타이어의 손상 판단이 가능하였다.

• BMB Reports
• /
• 제30권6호
• /
• pp.426-430
• /
• 1997

The helical periodicity of the triple-stranded $(dT)_n{\cdot}(dA)_n{\cdot}(dT)_n$ sequence was determined by measuring gel-mobilities of bent DNA fragments containing the sequence. In the bent DNA fragments, a $GA_{22}G$ $CT_{22}C$ sequence was located between two bent DNA loci composed of six $A_{6}{\cdot}T_{6}$ repeats. and the DNA length between the bent DNA loci was varied by 1 base pair over a full helical turn. The gel mobility of each bent DNA fragment reflected the overall extent of DNA bending and varied with the DNA length between the two bent loci. Mobilities of the bent DNA fragments in 5% polyacrylamide gel were measured after preincubating the DNA fragments both in the presence and absence of $CT_{22}C$ oligonucleotide. By comparing the bent DNA fragments containing an intermolecular triplex structure with those of a genuine duplex structure in the gel mobilities, the helical periodicity of the $T_n{\cdot}A_n{\cdot}T_n$ triplex DNA was determined to be $11.5({\pm}0.3)bp/turn$.

• 한국소음진동공학회논문집
• /
• 제19권7호
• /
• pp.719-725
• /
• 2009

An efficient time-domain numerical method for the analysis of broadband noise generation and propagation due to turbulence-cascade interaction is developed. The core algorithm of the present method is based on the B-periodicity of the acoustic response function of the flat-airfoil cascade to the ingesting gust(B denotes the number of airfoils in the cascade). To confirm this periodicity, gust-cascade interaction problem are solved by using the time-domain method, which shows that the incident gust with the circumferential mode number having the same remainders when divided by the airfoil number excites the same acoustic response of the cascade. Using the proposed fast algorithm with this periodicity, we show that the total computation time for the model broadband problem using the total 525 incident gust modes can be reduced to about 1/4 of that taken in using the previous time-domain program.

• Journal of Astronomy and Space Sciences
• /
• 제28권2호
• /
• pp.103-108
• /
• 2011

The latitudinal variation of sunspots appearing during the period from 1874 to 2009 has been studied in terms of centerof-latitude (COL). The butterfly diagram has been used to study the evolution of the magnetic field and the dynamics at the bottom of the solar convection zone. Short-term periodicities have been of particular interest, in that they are somehow related to the structure and dynamics of the solar interior. We thus have focused our investigation on shortterm periodicities. We first calculated COL by averaging the latitude of sunspots with the weight function in area. Then, we analyzed the time series of COL using the wavelet transform technique. We found that a periodicity of ~5 years is the most dominant feature in the time series of COL, with the exception of the ~11 year solar cycle itself. This periodicity can be easily understood by considering small humps between the minima in the area-weighted butterfly diagram. However, we find that periodicities of ~1.3 (0.064), ~1.5 (0.056), or ~1.8 (0.046) years ($\frac{1}{month}$), month ), which have been previously suggested as evidence of links between the changing structure of the sunspot zone and the tachocline rotation rate oscillations, are insignificant and inconsistent. We therefore conclude that the only existing short-term periodicity is of ~5 years, and that periodicities of ~1.3, ~1.5, or ~1.8 years are likely to be artifacts due to random noise of small sunspots.

• 한국우주과학회:학술대회논문집(한국우주과학회보)
• /
• 한국우주과학회 2003년도 한국우주과학회보 제12권2호
• /
• pp.85-85
• /
• 2003

We examined the hypothesis that the crater formation rate exhibits periodicity, employing data sets of Grieve (1991), Moon et al. (2001), and the Earth Impact Database (2002; DB02). DB02 is known to supercede previous compilations in terms of its accuracy and precision of the ages; it is the first time that this database has been used for periodicity analysis. For data sets comprising impact structures with D$\geq$5km (and also those with $\geq$20km), there is no convincing evidence for periodicities in the crater ages, according to our Fourier analysis. However, we detected two peaks at 16.1Myr and 34.7Myr for craters with D$\geq$30km; we confirm that the age distribution of impact craters with D$\geq$45km has dominant power at 16.1Myr. Thus, we may conjecture a probable periodic shower of Earth impactors with sizes d$\geq$1.5km. In addition, we found that the selection of data sets, the lower limits on the ages and diameters of impact craters, as well as the accuracy and precision of the ages, all constitute crucial factors in reconstructing the impact cratering history of the Earth.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2009년도 춘계학술대회 논문집
• /
• pp.477-482
• /
• 2009

An efficient time-domain numerical method for the analysis of broadband noise generation and propagation due to turbulence-cascade interaction is developed. The core algorithm of the present method is based on the B-periodicity of the acoustic response function of the flat-airfoil cascade to the ingesting gust (B denotes the number of airfoils in the cascade). To confirm this periodicity, gust-cascade interaction problem are solved by using the time-domain method, which shows that the incident gust with the circumferential mode number having the same remainders when divided by the airfoil number excites the same acoustic response of the cascade. Using the proposed fast algorithm with this periodicity, we show that the total computation time for the model broadband problem using the total 525 incident gust modes can be reduced to about 1/4 of that taken in using the previous time-domain program.

• 대기
• /
• 제29권5호
• /
• pp.599-607
• /
• 2019

The change and periodicity of Korean winter temperature in the period 1979-2018 are investigated. It is shown that the winter temperature is on a long-term rise, with two regime shifts of winter temperature during 40 years. In addition, the decrease in cold days is confirmed along with the rise in temperature. Analysis of the periodicity of daily temperature in winter is carried out by means of power spectral analysis. Of the spectral peaks that are statistically significant, the most frequent detection exists on the time scale between 7 and 8 days. It is found that the number of significant periods have decreased since 2014, particularly no longer existent around the period of 7 day. The longer periods than 7 days gradually increase during 40 years, while the shorter periods show the tendency of decrease but recently rebound. Spectral analysis calculated from high/low-pass filtered daily temperature data also shows similar results.

• Journal of Information Processing Systems
• /
• 제8권2호
• /
• pp.359-374
• /
• 2012

In this paper, we propose a new machine vision algorithm for automatic defect detection on patterned textures with the help of texture-periodicity and the Jensen-Shannon Divergence, which is a symmetrized and smoothed version of the Kullback-Leibler Divergence. Input defective images are split into several blocks of the same size as the size of the periodic unit of the image. Based on histograms of the periodic blocks, Jensen-Shannon Divergence measures are calculated for each periodic block with respect to itself and all other periodic blocks and a dissimilarity matrix is obtained. This dissimilarity matrix is utilized to get a matrix of true-metrics, which is later subjected to Ward's hierarchical clustering to automatically identify defective and defect-free blocks. Results from experiments on real fabric images belonging to 3 major wallpaper groups, namely, pmm, p2, and p4m with defects, show that the proposed method is robust in finding fabric defects with a very high success rates without any human intervention.

• 천문학회보
• /
• 제29권2호
• /
• pp.22.1-22.1
• /
• 2004

• Kyungpook Mathematical Journal
• /
• 제24권1호
• /
• pp.51-53
• /
• 1984