• Proceedings of the Korean Magnestics Society Conference
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• 2008.12a
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• pp.41.1-41.1
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• 2008

• Journal of Korean Society for Atmospheric Environment
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• v.25 no.2
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• pp.133-140
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• 2009

In order to examine the effects of micrometeorological and climatological influences on urban scale particulate air pollutants observed in Busan, power spectrum analysis was applied to the observed particulate matter with aerodynamic diameter ${\le}10{\mu}m$ ($PM_{10}$) for the period from 1991 to 2006. Power spectrum analysis has been employed to the daily mean $PM_{10}$ concentrations obtained at 13 sites to identify different scales of periodicities of $PM_{10}$ concentrations. The results show that, aside from the typical and well-known periodicities such as diurnal and annual variations caused by anthropogenic emission influences, another two significant peaks of power spectrum density were identified: 21 day and $3{\sim}4$ year of periodicities. Cospectrum analysis indicates that the intraseasonal 21 day periodicity are found to be negatively correlated with wind speed and surface pressure but shows consistently positive with relative humidity and temperature. This result implied that 21 day periodicity is presumably relevant to the secondary aerosol formation processes through the photochemical reaction that can be subsequently resulted from hygroscopic characteristics of aerosol formation. However, the interannual $3{\sim}4$ year of periodicity is found to have positive correlation with pressure, and negative with temperature and relative humidity, which is rather consistent with both characteristics of air mass during the Asian dust event and the occurrence frequency of Asian dust whose periodicities have been recorded inter-annually over the Korean peninsula.

• Journal of the Korean association of regional geographers
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• v.21 no.3
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• pp.593-607
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• 2015

This study examined the Holocene environmental changes by OSL dating and magnetic susceptibility (MS) in 12 sediment cores from estuarine tidal flat, Mosan Bay Estuary, west coast of Korea. For the complexity of the geomorphic characteristics of estuaries, it is difficult to obtain a series of data. The following significant results were derived using relatively simple methods. First, MS data shows sensitive changes in pattern according to the precipitation change during mid to late Holocene. Second, MS data show periodicity of 250 yr. when they were wavelet transformed. This periodicity is related with the intensifying of solar intensity, the East Asian Summer Monsoon and ENSO. Thus, MS data from estuarine sediments are valuable data which can explain mechanism of climate change in East Asia and worthy as proxy data.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.2
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• pp.227-232
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• 2013

This study proposes a method for predicting the reliability of the barrel in small arms by analyzing the dispersion. The periodicity with which the barrel needs to be changed can be determined by detecting the inner surface directly or by inspecting scratches inside the barrel using an optical sensor. However, soldiers and directors in the logistics command need a more easy way to check the periodicity of barrel. Therefore, this study focuses on the relation between the firing round and the dispersion. A simple equation can be experimentally derived from pre-tests and analyses. This equation is confirmed through firing tests. In this sense, it can be easily applied to determine the periodicity with which the barrel of small arms needs to be changed in the field army.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.11 no.3
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• pp.41-46
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• 2011

The tire damage classification method is researched by periodicity detection of ultrasonic envelope signals to occur at the driving vehicle tire. Because periodic signals is generated by rotations of the damaged tire, it should convert to pulse for using the density function. After time intervals of pulses are represented by the density function, the dominant periodicity is detected. The threshold to make a pulse is calculated by moving average of envelope signals. The result of time density function in case of one damage material, the first peak's time is equals to tire's rotation period, 162ms and 102ms, about the speed of 50km/h and 80km/h. In case of more than one damage material, the sum of each peak's time is equals to tire's rotation period about the speed.

• Journal of Environmental Science International
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• v.6 no.2
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• pp.95-106
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• 1997

The characteristics on the transtion probabilities and periodicity for the daily precipitation occurrence in Korean peninsula are investigated by applying the Markov chain properties to daily precipitation occurrence. In order to examine the responses of Markov Chain properties to the applied period and their magnitudes, three cases (Case A: 1956~ 1985 at 14 stations, Case B: 1965~ 1994 at 14 stations, and Case C: 1985~ 1994 at 63 stations) are considered In this study. The transition probabilities from wet day to wet day for all cases are about 0.50 and in summer, especially July, are higher. In addition, considering them in each station we can find that they are the highest at Ullung-do and lowest at Inchon for all cases. The annual equilibrium probabilities of a wet day appear 0.31 In Case A, 0.30 Case B, and 0. 29 Case C, respectively. This may explain that as the data-period used becomes shorter, the higher the equilibrium probability is. The seasonal distributions of equilibrium probabilities are appeared the lowest(0.23~0.28) in winter and the highest(more than 0.39) in spring and monthly in .truly and in October, repectively. The annual mean wet duration for all cases is 2.04 days in Case A, 1.99 Case B, and 1.89 Case C, repectively. The weather cycle obtained from the annual mean wet and dry duration is 6.54~6.59 days, which are closely associated with the movement of synoptic systems. And the statistical tests show that the transitions of daily precipitation occurrence for all cases may have two-state first Markov chain property, being the stationarity in time and heterogeneity in space.

• Water for future
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• v.15 no.3
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• pp.23-36
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• 1982

The stochastic variations and structures of time series data on water quality were examined by employing the techniques of autocorrelation function, variance spectrum, Fourier series, autoregressive model and ARIMA model. These time series included hourly and daily observation on DO, turbidity, conductivity pH and water temperature. The measurement was made by automatic recording instrument at Noryangjin and Dook-do located in the downstream part of Han River during 1975 and 1976. Hourly water quality time series varied with the dominant 24-hour periodicity, and the 12-hour periodicity was also observed. An important factor affecting 24-hour periodic variation of DO is believed to be photosynthesis by algae. These phenomena might be attributable to periodic discharges of municipal sewage. Noryangjin site showed the more distinct 12-hour periodicity than Dook-do site did, and tidal effect might be responsible for the difference. The water quality, as measured by DO and turbidity, was better in the afternoon compared with the quality in the morning. This change can be explained by the periodic variation of DO, temperature and the amount of municipal wewage discharge. It was also observed that the water temperature at Noryangjin was higher than the temperature at Dook-do. This difference might have been caused by the pollutants that were added to the section between two sites. The correlation coefficients between some of the variables were fairly high. For example, the coefficient was -0.88 between DO and water temperature, 0.75 between turbidity and river flow, and 0.957 between water temperature and air temperature. The lag time of heat transfer from the air to the water was estimated as 24 days. The first order auto-regressive model was appropriate for explaning standardized hourly DO time series. The ARIMA model of (1, 0, 0) type provided relatively satisfactory results for daily DO time series after the removal of significant harmonic value.

• The Journal of the Korea institute of electronic communication sciences
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• v.6 no.4
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• pp.479-485
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• 2011

A video flame detection method analyze the temporal and spatial characteristics of the regions which have the flame-like color and moving objects in the input video. The video flame detector should be able to reduce a false alarm rate without the degradation of flame detection capability. The conventional methods can reject the false alarm caused by the car lights and some electric lights. However they make the false alarm caused by the warning lights, neon sign, and some periodic flickering lights which have the flame-like color and temporal features. This paper propose the video flame detection method with periodicity analysis based false alarm rejection. The proposed method can detect the periodicity of the flickering electric lights and can reject the false alarm caused by the periodic electric lights. The computer simulation showed that the proposed method did not make the false alarm in the test video with the periodic electric lights. But the conventional methods made a false alarm in the same test video.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.9 no.6
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• pp.591-598
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• 2016

For the mobile healthcare environment, it is important to measure the exact biomedical signals in real time, and another key point is to design mobile healthcare devices with low power consumption. In this paper, we propose a method in which the piezo film sensor(PFS), having a low power characteristic, is used to measure the pulse signal synchronized with the heart rate from the radial artery. The critical issue in the bio-signal processing is the existence of the motion artifacts. To dissolve this problem, we have applied the periodic moving average filter using the quasi-periodicity of the pulse signal in addition to the conventional method of the adaptive filtering using the reference signal. Results of simulation and experiments are presented to confirm that the quasi-periodicity of the PFS signal can be used to eliminate completely the motion artifacts which still appears after the adaptive filtering.

• Journal of the Korean Society of Costume
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• v.12
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• pp.39-54
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• 1988

The purposes of this study were to identify the periodicity of fashion in modern society and to find the correlation between each detail and bustle constitution through the bustle styles that have been recently revived. For the study of periodicity, fashion plates or pictures in Vogue or in the books related Vogue since 1930 were selected, and were analyzed into bell, tubular and bustle silhouettes that were devided by Young (1937). And for the study of the correlation of detail and bustle constitution, fashion plates and pictures that were related to the bustle in the 19th century and the 20th century were selected, and according to the epoch (19C, 20C) and the use (daytime dress or evening dress), each of them was analyzed. The results were as follows: 1. After 1930, $24{\sim}33$ year amplitude was founded at tubular and bell shape, that proved shorter cycles than Young's. 2. In each characters of clothing details, deep decolletage, undivided waistline, spaced bodice in daytime dress were partly identified the characteristics of 20th century costume. 3. The form of bustle was converted from the complex ornament of the 19th century to the simple shape of the 20th century. In other words, it is necessary that the definition of bustle be changed not the previous definition as the silhouette and instrument but that as the emphasis dimension. 4. The dimensions that showed difference at daytime dress and evening dress were 'existence of collar', 'neckline', 'length of sleeve', 'kind of sleeve' for 19th century, and 'neckline', 'length of sleeve', 'kind of sleeve,' 'length of skirt' for 20th century. 5. Correlations with the bustle constitution and details were shown at bodice and waistline with the complex bustle in the 19th century and at collar and neckline with the simple bustle in the 20th century.