• Journal of Astronomy and Space Sciences
• /
• v.24 no.2
• /
• pp.91-98
• /
• 2007

The existence of the North-South asymmetry of the solar activity is widely accepted even though the phenomenon is not yet satisfactorily understood. We have studied the temporal variations in the North-South asymmetry of the sunspot area during the period from May in 1874 to April in 2007. The combined data have been examined for periodicity in the solar activity North-South asymmetry. We have found that (i) solar northern and southern hemispheres show an asymmetric behavior, in terms of a sunspot area, (ii) sunspot areas in northern and southern hemispheres show clearly the 11 year periodicity when they were analyzed separately, as they do when analyzed together, (iii) in addition to the general 11 year periodicity in both northern and southern hemisphere solar activities, there are also noticeable shorter periodicities other than the 11 year periodicity in the asymmetry in North-South activity. Finally, we conclude by pointing out the importance of studying the North-South asymmetry of the solar activity.

• Korean Journal of Ecology and Environment
• /
• v.38 no.spc
• /
• pp.17-21
• /
• 2005

We investigated the diel periodicity in the drift in relation to body size by field survey using the fourth instar grazing larvae of Micrasema quadriloba Martynov (Trichoptera, Brachycentridae) as a material. Although the larvae showed nocturnal drift periodicity, drift density in the nighttime was only twice that in the daytime. In both time periods, smaller individuals drifted significantly more, and the drift individuals in the daytime was the smallest in size (P< 0.05 in Sheffe's F). We discussed whether the drift of the fourth instar larvae drift behaviorally or accidentally considering larval size and food depletion.

• Journal of Korea Water Resources Association
• /
• v.43 no.5
• /
• pp.483-493
• /
• 2010

In this study, for the purpose of analyzing variability and periodicity of Korean hydrologic weather parameters, 5 hydrologic weather parameters data such as annual precipitation, annual rainy days, annual average temperature, annual average relative humidity, annual duration of sunshine are collected from 63 domestic meteorological stations that has the hydrologic weather parameters records more than 30 years. And in this study the variability and periodicity using the statistical methods like Wald-Wolfowitz test, Mann-Whitney test, and Wavelet Transform about hydrologic weather parameters is analyzed. The results of statistical analysis of variability and periodicity can be summarized as follows: 1) Variability commonly appeared in annual average temperature and annual average relative humidity. 2) Annual precipitation, annual rainy days and annual duration of sunshine showed different results according to area. 3) Periodicity appeared in annual precipitation and annual rainy days but did not appeard in annual average temperature, annual average relative humidity and annual duration of sunshine.

• Korean Journal of Applied Biomechanics
• /
• v.27 no.1
• /
• pp.45-52
• /
• 2017

Objective: The aim of this study was to investigate the periodicity of the lower extremity joint flexion/extension angle to compare the local stability between young and elderly women during walking on a treadmill. Method: Eighteen young women (mean $age=21.2{\pm}1.6y$; mean $mass=57.1{\pm}6.1kg$; mean $height=1.61{\pm}0.04m$) and 18 elderly women (mean $age=66.4{\pm}1.2y$; mean $mass=55.4{\pm}8.3kg$; mean $height=1.56{\pm}0.04m$) participated in this study. Approximate entropy (ApEn) was used to determine the periodicity in the lower limb joint angles. Results: The ApEn values of the two groups were statistically greater in the surrogate data test than in the original time series data (p<.05). The periodicity of the hip and ankle flexion/extension angles decreased in the elderly women group compared with the young women group (p<.05). The periodicity of the lower extremity joint flexion/extension angle showed that the ankle joint increased dominatingly in both groups (p<.05); the hip joint decreased compared with the knee joint in the young women group; and the knee joint decreased compared with the hip joint in the elderly women group (p<.05). Conclusion: These results suggest that the lower extremity joint flexion/extension angles of the young and elderly women during walking contained random noises as well as biological signals. In addition, the differences in the periodicity in the lower extremity joint between the young and elderly women may provide some insight in predicting potential falls and be used as a characteristic indicator for determining local stability in elderly women during walking.

• Journal of Veterinary Clinics
• /
• v.22 no.2
• /
• pp.79-83
• /
• 2005

Six dogs including 4 dogs living in different geographic locations of Kangwon province and 2 client-owned dogs were used to determine the periodicity of microfilariae of D. immitis using a trigonometric model. The calculated periodicity index was ranged from 25.6 to $95.5\%$ with mean of $57.6\%$, and the estimated hour of peak was approximately 21:00 hrs (range, 20:04-21:29 hrs) and minimum counts at 09:00 hrs (range, 08:04 - 09:29 hrs). Correlation coefficient between the observed and the expected count from the model varies depending on dogs, ranging from 6.4 to $49.2\%$. Based on this study, the periodicity of microfilariae of D. immitis was considered as nocturnally sub-periodic for all dogs employed. This result is in consistent with previous report in peak hour but different in minimal hour, indicating that further studies on the periodicity need to be performed to better understanding the dynamics of the periodicity and to help practitioners in the choice of the time for examination of the dogs.

• Journal of applied mathematics & informatics
• /
• v.26 no.1_2
• /
• pp.263-273
• /
• 2008

For the discrete version of an artificial neural network of two neurons with piecewise constant argument, we obtain some sufficient conditions that every solution is either periodic or convergent.

• Journal of applied mathematics & informatics
• /
• v.35 no.5_6
• /
• pp.449-457
• /
• 2017

In this paper, we shall provide several properties of Dedekind sums with quasi-periodicity Euler functions. In particular, we present a representation of these Dedekind sums in terms of the Eulerian functions and the tangent functions.

• Journal of applied mathematics & informatics
• /
• v.19 no.1_2
• /
• pp.191-201
• /
• 2005

In this paper, the existence of periodic positive solution and the attractivity are investigated for the rational recursive sequence $x_{n+1} = (A + ax_{n_k})/(b + x{n-l})$, where A, a and b are real numbers, k and l are nonnegative integer numbers.

• Journal of Astronomy and Space Sciences
• /
• v.25 no.2
• /
• pp.71-76
• /
• 2008

Study of terrestrial impact craters is important not only in the field of the solar system formation and evolution but also of the Galactic astronomy. The terrestrial impact cratering record recently has been examined, providing short- and intermediate-term periodicities, such as, ${\sim}26$ Myrs, ${\sim}37$ Myrs. The existence of such a periodicity has an implication in the Galactic dynamics, since the terrestrial impact cratering is usually interpreted as a result of the environmental variation during solar orbiting in the Galactic plane. The aim of this paper is to search for a long-term periodicity with a novel method since no attempt has been made so far in searching a long-term periodicity in this research field in spite of its great importance. We apply the cepstrum analysis method to the terrestrial impact cratering record for the first time. As a result of the analysis we have found noticeable peaks in the Fourier power spectrum appear ing at periods of ${\sim}300$ Myrs and ${\sim}100$ Myrs, which seem in a simple resonance with the revolution period of the Sun around the Galactic center. Finally we briefly discuss its implications and suggest theoretical study be pursued to explain such a long-term periodicity.

• Proceedings of the KIEE Conference
• /
• 2004.11a
• /
• pp.194-196
• /
• 2004

$BaTiO_3/SrTiO_3$ heterolayered thick films on the $Al_2O_3$ substrate by screen printing method with stacking periodicity. The stacking periodicity of $BaTiO_3/SrTiO_3$ heterolayer structure was varied from $(BaTi_O_3)_1/(SrTiO_3)_1$ to $(BaTi_O_3)_3/(SrTiO_3)_3$. The total thickness of the $BaTiO_3/SrTiO_3$ films was about $120{\mu}m$. There was an interdiffusion at the interface of the $BaTiO_3$ and $SrTiO_3$ layers. The dielectric constant of $BaTiO_3/SrTiO_3$ heterolayered thick films was increased with decreasing stacking periodicity of the $BaTiO_3/SrTiO_3$. The dielectric constant of the ($(BaTi_O_3)_1/(SrTiO_3)_1$ herterolayered thick films was about 1780.