• Journal of the Korean Wood Science and Technology
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• 제24권3호
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• pp.18-27
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• 1996

The feasibility of using stress-wave technique in the transverse direction for the assessment of early stages of decay was investigated using compression test specimens having different annual ring orientations subjected to decay by Tyromyces palustris for various time intervals. Decay detection, quantitative assessment of decay, and the prediction of residual strength of decayed wood with less than five percent weight loss can be feasible using stress-wave parameters (wave velocity, wave impedance, and stress-wave elasticity) and their percent reduction due to decay, measured by stress-wave technique in the transverse direction. The use of stress-wave technique in the transverse direction for the application of this technique to structural members in service is desirable, when considering the easiness of attachment of accelerometers of stress-wave measuring device on the surface of members and also accurate detection of localized decayed areas. In stress-wave technique in the transverse direction, stress-wave parameters measured were different according to the angles between wave propagation path and annual ring, due to the anisotropy of wood structure. Therefore, it is recommended to use percent reduction in stress-wave parameters instead of stress-wave parameters. This evaluation method using percent reduction in stress-wave parameters is ideal when it is impossible to observe annual ring orientation on the transverse surface of wood.

• 한국소음진동공학회논문집
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• 제11권4호
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• pp.71-77
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• 2001

In this paper, stress wave propagation characteristics of MR(Magneto-rheological) inserts are experimentally investigated. Generally, stress waves of structures such as warships or submarines are induced by shock waves from underwater explosion. Their fatal effects on the shipboard equipments or structures damage the performance of warships. But, such a problem can be solved by controlling the stress waves propagating through structures by means of MR inserts. MR insert consists of two aluminum layers and MR fluid filled in between. Two piezoceramic disks are embedded on the host plate as a transmitter and a receiver of stress waves. Pulse waves are generated by the transmitter and they reach to the receiver through the MR insert. Permanent magnet and magnetic coil are used to produce magnetic field at the MR insert. In the presence of magnetic field, MR particles are arranged in chains parallel to the magnetic field such that the transmitted stress waves are reduced. Attenuation of stress waves is experimentally investigated.

• Journal of the Korean Wood Science and Technology
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• 제24권2호
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• pp.1-6
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• 1996

This study was performed to investigate the feasibility of using sonic stress-wave technique in the longitudinal direction for the assessment of incipient decay of radiata pine wood. Decayed bending specimens by Tyromyces palustris and Gloeophyllum trabeum for varoious periods were tested nondestructively using stress-wave technique in the longitudinal direction and destructively. Decay detection, quantitative assessment of decay, and the prediction of residual strength of decayed wood with less than five percent weight loss can be feasible using stress-wave parameters (wave velocity, wave impedance, stress-wave elasticity) measured by stress-wave technique in the longitudinal direction and their percent reduction due to decay.

• 한국방사선학회논문지
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• 제6권6호
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• pp.515-520
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• 2012

스트레스는 현대 사회의 가장 큰 관심 분야로서 만병의 원인이라고 여겨지고 있다. 이러한 스트레스는 뇌파에서도 특이한 영향을 미치는데 특히, 알파파의 감소가 일어난다는 점이다. 본 연구에서는 스트레스에 관하여 EDT 기법이 뇌파중 알파파에 긍정적 영향을 미치는지 알아보기 위함에 있다. 기법의 적용은, 주 2회 10분간 2주 동안 실시하며 EDT 대체의학 기법 적용이 초등학교 교사의 뇌파에 안정을 의미하는 알파파의 증가와 베타파의 감소를 보였으며, 유의한 효과는 없었으나 감마파 감소에 일부 도움이 있는 것으로 사료된다. EDT 기법이 스트레스에 있어서 관련된 뇌파인 알파파에 개선에 유의한 효과가 있으므로 스트레스 관리에 적극적 활용의 필요성을 제기한다.

• 동력기계공학회지
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• 제11권2호
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• pp.32-37
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• 2007

The present study describes the effects of music and vibroacoustic stimuli to the relaxation of human body. We have carried out the experiment on 6 human subjects of which are composed 3 men and 3 women. We have investigated the electroencephalogram(EEG) of all subjects before and after the stimuli of which are made a strong noise or the meditatiom music and the acoustic vibration. The vibroacoustic device has transmitted meditation music as vibration between 20Hz and 250Hz to the body. From the experimental results, we made sure the effects that the meditation music and vibroacoustic stimuli influenced the stress reduction of human body for good as alpha wave was increased continuously during the good stimuli and after that.

• 가정과삶의질연구
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• 제26권4호
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• pp.13-25
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• 2008

This study of a music therapy program for the 18 subjects residing in Jeollanam-do province was conducted two times per week during 4 months totalling 17 times in order to evaluate the reduction of the characteristics of patients suffering from stress disorder patients such as depression, and anxiety, Though the experiment for non-symmetric level the concentration and appearance of Alpha wave were determine to be stable but the findings from non-symmetric level according to the left-right brain activity were not significant for T-test, though its effective intermission of music therapy due to variation of the mean values was demonstrated, and the variation of the Alpha wave appearance rate was also significant for the statistics of the T-test for the effectiveness of the music therapy. And for the reduction of depression, emotion, and state-trait anxiety between groups divided into the control group and the experiment, pre-measurement and post-measurement comparisons through psychological tess, validated the effectiveness of music therapy for Posttraumatic stress disorder patients. First of all, this study was conducted in the situation of scarce study cases and program developments for the efficacy of music therapy for the patients suffering from Posttraumatic stress disorders without precedent studies of scientific identification through brain wave measurement. Because this study is insightful in the context of validating the efficacy of musical treatment, we expect that these kinds of studises will be continued.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2002년도 추계 학술발표회 논문집
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• pp.123-130
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• 2002

The ground-borne vibration from pile driving is causing many public discontents. However, because of the fact that the characteristics of wave propagation and attenuation are not well understood, systematic and effective vibration reduction measures can not be taken. This paper attempts to study the propagation of stress waves induced by the pile driving. To simulate the wave propagation in a semi-infinite domain, the so-called absorbing boundaries are incorporated in the finite element method and a series of numerical simulations is performed. Numerical results show that the surface displacement and velocity increase first and then decrease as the pile penetration depth becomes larges.

• Biomolecules & Therapeutics
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• 제22권6호
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• pp.570-576
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• 2014

Studies have demonstrated that electromagnetic waves, as the one of the most important physical factors, may alter cognitive and non-cognitive behaviors, depending on the frequency and energy. Moreover, non-ionizing radiation of low energy waves e.g. very low frequency waves could alter this phenomenon via alterations in neurotransmitters and neurohormones. In this study, short, medium, and long-term exposure to the extremely low frequency electromagnetic field (ELF-EMF) (1 and 5 Hz radiation) on behavioral, hormonal, and metabolic changes in male Wistar rats (250 g) were studied. In addition, changes in plasma concentrations for two main stress hormones, noradrenaline and adrenocorticotropic hormone (ACTH) were evaluated. ELF-EMF exposure did not alter body weight, and food and water intake. Plasma glucose level was increased and decreased in the groups which exposed to the 5 and 1Hz wave, respectively. Plasma ACTH concentration increased in both using frequencies, whereas noradrenaline concentration showed overall reduction. At last, numbers of rearing, sniffing, locomotor activity was increased in group receiving 5 Hz wave over the time. In conclusions, these data showed that the effects of 1 and 5 Hz on the hormonal, metabolic and stress-like behaviors may be different. Moreover, the influence of waves on stress system is depending on time of exposure.

• 한국산학기술학회논문지
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• 제18권2호
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• pp.374-382
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• 2017

본 연구에서는 고등학생을 대상으로 배꼽힐링 프로그램을 개발하고 적용한 후, 뇌파 검사를 통해 뇌파 활성도를 측정함으로써 그에 따른 효과성을 검증하는데 그 연구의 목적이 있다. 본 연구에 A고등학생 19명(남학생 8명, 여학생 11명)이 참여 하였으며 실험에 참여한 학생들은 2주 동안 매일 2회씩(아침, 저녁) 5분간 배꼽힐링 프로그램을 실시하였다. 효과검증을 위해 피험자의 각성상태 및 안정상태에서의 뇌파를 측정하였으며 스트루프 과제중의 뇌파의 변화를 관찰하였다. 이후 배꼽힐링을 약 5분간 실시하고 1분간의 휴식을 취한 후 동일한 과정을 반복하였다. 연구 결과, 배꼽힐링 프로그램을 통해 스트루프 과제 중 각성상태 대비 M-Beta파, H-Beta파, 그리고 Gamma파의 감소량이 줄어들었으며 안정상태 대비 Alpha파, SMR파의 감소량이 감소하는 것으로 나타났다. 이는 배꼽힐링을 통해 피험자들이 스트레스 상황에서의 집중력, 몰입력 등이 향상되었으며 심리적 안정상태도 유지한다는 것을 시사한다. 이는 학생들의 연구 후 인터뷰 내용과도 일치 한다. 따라서, 본 연구의 결론을 제시하면 다음과 같다. 첫째, 배꼽힐링 프로그램은 고등학생의 스트레스 해소에 효과가 있기 때문에, 학업 스트레스를 많이 받는 수험생을 대상으로 배꼽힐링 프로그램을 실시할 필요가 있다. 둘째, 배꼽힐링 프로그램은 고등학생의 집중력과 몰입력을 증가시키는 효과가 있기 때문에, 복잡하거나 어려운 특정 과제를 해결하기 전에 배꼽힐링 프로그램을 실시할 필요가 있다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.1063-1068
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• 2007

개인마다 소음, 음악과 음향진동 자극에 대한 인체의 반응은 상당한 차이가 발생하는 것을 고려하여 뇌파 파워의 상대적인 비율로 비교.고찰하였다. 우선 강한 소음 자극에 대한 뇌파의 변화는 긴장과 스트레스 증가를 의미하는 베타파의 증가 및 긴장완화와 안정을 의미하는 알파파의 감소를 보였고, 좋은 자극에 대해서는 그 반대의 효과를 보였다. 즉, 좋은 자극에 의한 스트레스저감의 효과가 있음을 확인하였다. 자극 후의 변화에서는 좋은 자극시와 마찬가지로 대체로 알파파가 증가하는 경향이 있지만 이와 반대의 경우도 발생하고있어 이 역시 개인차가 있음을 알았다.