• Journal of Korean Society of Coastal and Ocean Engineers
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• v.28 no.3
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• pp.117-123
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• 2016

One of the major characteristics of the swell-like high waves, which occur in the East Sea mostly in winter with large height and long period, is its suddenness associated with the rapid development of high waves from a calm state of sea. To represent such suddenness, in this study, the term sudden high waves is introduced. To propose the criterion of sudden high waves, comparisons were made between the wave measurement data at Gangneung and Wangdolcho for eight years from 2005 and the record of marine accidents and property damage on the coast of Gangwon-do Province and Gyeongsangbuk-do Province during the same period. It was found that most of the accidents occurred when ${\Delta}(H^2L)/{\Delta}t$ was approximately greater than the top 20% or $88.6m^3/hr$, which is therefore proposed as the criterion of sudden high waves. The used variable represents the rate of increase of the wave energy in one wavelength, including not only height and period but also suddenness of high waves.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2007.10a
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• pp.170-174
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• 2007

Although research efforts for brain waves have prospered in medicine and engineering, acupuncture still has a long way to go regarding researches on brain waves analysis. Thus this study set out to analyze brain waves stimulated by indirect mugwort moxibustion, which was part of acupuncture techniques, and to investigate their correlations with the automatic nervous system. For the experiments, stimulation was given to Jungwan, Shingwol and Gwanwon, which were some of the spots on the body suitable for acupuncture, through indirect mugwort moxibustion. The subjects' brain waves were measured before the stimulation, during the stimulation, and one hour and two hours after the stimulation. The measurements were analyzed with Matlab 7.0 for FFT and frequency power spectrum. Then the ${\alpha}$, ${\beta}$, ${\delta}$, and ${\theta}$ waves were analyzed and examined for changes to the percentage of each frequency and to the amplitude of vibration according to the stages of stimulation. The EEG data of the entire brain were translated into FFT to analyze the percentage of the ${\alpha}$, ${\beta}$, ${\delta}$, and ${\theta}$ waves. As a result, the ${\alpha}$ waves recorded a double increase after the stimulation. The power spectrum analysis results of the entire brain decreased the ${\alpha}$ and ${\beta}$ waves dropping in the energy level, which suggested that the parasympathetic nerves were activated. When the results of the study were compared with those of the previous study, it's confirmed that indirect moxibustion stimulation could cause changes to the automatic nervous system and bring stability to those who were nervous or under stress due to the proportionate increase of the ${\alpha}$ waves.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.6
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• pp.1800-1805
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• 2008

Shiro-abhyanga is one of treatments of Ayurveda, which is the ancient system of health care and medicine in India. In this essay, I examined the effect of Shiro-abhyanga for relaxing stress of women in twentieth by the means of the brain wave test. The brain wave test showed that Shiro-abhyanga reduced Delta and Theta waves of the left brain but increased $\alpha$, SMR, Low-$\beta$ waves of the right brain. Delta and Theta waves are usually found in sleeping time. Their high measurement in awakening instructs the stress and depressing situations of objects. However the treatment of Shiro-abhyanga made the decrease of Delta and Theta waves and the increase of Alpha wave in working time. Alpha wave appears while objects are comfortable and peaceful from the relaxation of body and mind. Therefore the growth of Alpha wave says that the treatment of Shiro-abhyanga has an effect on mitigation of stress.

• Interaction and multiscale mechanics
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• v.6 no.3
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• pp.287-300
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• 2013

In this paper, the effect of impulsive line on the propagation of shear waves in non-homogeneous elastic layer is investigated. The rigidity and density in the intermediate layer is assumed to vary quadratic as functions of depth. The dispersion equation is obtained by using the Fourier transform and Green's function technique. The study ends with the mathematical calculations for transmitted wave in the layer. These equations are in complete agreement with the classical results when the non-homogeneity parameters are neglected. Various curves are plotted to show the effects of non-homogeneities on shear waves in the intermediate layer.

• Science of Emotion and Sensibility
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• v.27 no.2
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• pp.105-112
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• 2024

Forward head posture (FHP) is a representative postural deformation problem in people today, causing various physical and mental problems, but the effect of FHP on discomfort or distraction during rest is not well known. Accordingly, this study aims to demonstrate the effect of FHP on these brain functions by analyzing brain wave signals at rest. Thirty-three heavy users of computers participated in this study, and all of them exhibited functional FHP when using computers. All participants performed using both normal posture and FHP, and their brain waves were measured at rest while maintaining each posture for five minutes without stimulation. Brain wave signals were acquired using EEG with 32 channels, and through frequency analysis, changes in delta and beta waves, known to be closely related to discomfort and attention, were compared and analyzed depending on the posture. As a result, FHP showed a significant decrease in delta waves in nine channels compared to the normal posture, and a significant increase in beta waves in 14 channels, showing that FHP does affect brain function at rest. These changes are consistent with those that occur under conditions of psychological discomfort and distraction, and they appear to be because the increased discomfort caused by musculoskeletal changes in the FHP also affects brain activity. These can provide important results showing that posture correction can help improve brain function and psychological state at rest.

• Journal of Astronomy and Space Sciences
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• v.23 no.3
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• pp.209-216
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• 2006

Ion acoustic solitary wave in a plasma consisting of electrons and ions with an external magnetic field is reinvestigated using the Sagdeev's potential method. Although the Sagdeev potential has a singularity for n < 1, where n is the ion number density, we obtain new solitary wave solutions by expanding the Sagdeev potential up to ${\delta}n^4$ near n = 1. They are compressiv (rarefactive) waves and shock type solitary waves. These waves can exist all together as a superposed wave which may be used to explain what would be observed in the solar wind plasma. We compared our theoretical results with the data of the Freja satellite in the study of Wu et al. (1996). Also it is shown that these solitary waves propagate with a subsonic speed.

• Journal of Korean Institute of Industrial Engineers
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• v.23 no.3
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• pp.609-619
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• 1997

The concept of human emotion is recently demanded to be imbedded in industrial product and environment for enhancing quality of life. Human emotion is attempted to be qualified and quantified by physiological measurements. EEG variation, one of the physiological measurement, is observed to characterize psychological response in this study. This study is to find function and process of brain according to emotion. Twenty university students participated in this study and experienced positive and negative emotion by auditory stimulus. Delta, theta, alpha and beta waves showed characteristic variation in normalized sense according to positive and negative emotion. Local area showing significant difference between positive and negative emotion decreases with stimulus duration. Delta, theta and beta waves increase with negative emotion while alpha wave does with positive emotion.

• Earthquakes and Structures
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• v.9 no.2
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• pp.305-320
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• 2015

The present paper is devoted to study SH-wave propagation in heterogeneous layer laying over an inhomogeneous isotropic elastic half-space. The dispersion relation for propagation of said waves is derived with Green's function method and Fourier transform. As a special case when the upper layer and lower half-space are homogeneous, our derived equation is in agreement with the general equation of Love wave. Numerically, it is observed that the velocity of SH-wave increases with the increase of inhomogeneity parameter.

• Pediatric Infection and Vaccine
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• v.31 no.1
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• pp.83-93
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• 2024

Purpose: Since the start of the coronavirus disease 2019 (COVID-19) pandemic, various variants of concern have emerged. We divided the representative COVID-19 mutation period into four waves and aimed to analyze the clinical and laboratory features of children with COVID-19 from pre-mutation wave to the middle of omicron wave. Methods: We retrospectively reviewed the medical records of hospitalized patients aged ≤19 years with laboratory confirmed COVID-19. Clinical and laboratory findings during pre-mutation (February 1st 2020 to September 30th 2020), alpha/beta (October 1st 2020 to May 31st 2021), delta (June 1st 2021 to October 31st 2021), and omicron (November 1st 2021 to May 31st 2022) waves were compared. Results: Among total 827 patients, 163 (19.7%) were asymptomatic, and the frequency of fever and cough was 320 (38.7%) and 399 (48.2%), respectively. The proportion of fever ≥38.5℃ was observed to be high during the omicron wave in the age group under 12 years. Lymphopenia was observed highly in the omicron wave in the age group under 12 years, and in the delta wave in the age group older than 12 years. Neutropenia was highly observed in the delta wave in the 0-4 years age group. Conclusions: There were distinct characteristics during all epidemic waves of COVID-19. Children with COVID-19 had more frequent persistent fever during delta wave and children during the omicron wave had a higher peak fever.

• Bulletin of the Korean Mathematical Society
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• v.50 no.1
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• pp.201-216
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• 2013

In this note, we consider the Riemann problem for a two-dimensional nonstrictly hyperbolic system of conservation laws. Without the restriction that each jump of the initial data projects one planar elementary wave, six topologically distinct solutions are constructed by applying the generalized characteristic analysis method, in which the delta shock waves and the vacuum states appear. Moreover we demonstrate that the nature of our solutions is identical with that of solutions to the corresponding one-dimensional Cauchy problem, which provides a verification that our construction produces the correct global solutions.