• 한국산학기술학회논문지
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• 제12권11호
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• pp.4819-4825
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• 2011

이 연구는 노인들의 성격유형이 스트레스 저항에 미치는 영향이 있는지를 개인이 지닌 뇌신경 생리학적 지표인 뇌파 측정을 이용하여 비교하여 보았다. 대상자는 한국정신과학연구소에 2007년 9월에서 2010년 12월까지 뇌파측정을 실시한 노인(만 65세 이상)들을 기준으로 선정한 자료이며, 총 1108명이다. 행동성향의 분포도는 긍정 적극성향이 552명, 부정 소극성향이 556명이었으며, 정서성향의 분포도는 명랑(외향)성향이 735명, 우울(내향)성향이 373명이었다. 분석 결과 노인들의 행동성향과 스트레스 저항과는 무관하였으며, 정서성향과 스트레스 저항과는 (p=.000)으로 유의미한 차이가 있었다. 즉, 명랑(외향)성향이 우울(내향)성향에 비하여 항 스트레스지수에서 평균이 높게 차이가 났으며, 이는 스트레스를 이겨낼 수 있는 능력이 높다고 할 수 있겠다. 이 연구 결과 정서성향과 스트레스 저항능력이 관련이 있음을 보여주었으며 미치는 영향이나 작용기전을 규명하는 연구가 필요하다고 사료된다.

• Smart Structures and Systems
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• 제15권1호
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• pp.135-150
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• 2015

Large concrete structures are prone to cracks and damages over time from human usage, weathers, and other environmental attacks such as flood, earthquakes, and hurricanes. The health of the concrete structures should be monitored regularly to ensure safety. A reliable method of real time communications can facilitate more frequent structural health monitoring (SHM) updates from hard to reach positions, enabling crack detections of embedded concrete structures as they occur to avoid catastrophic failures. By implementing an unconventional mode of communication that utilizes guided stress waves traveling along the concrete structure itself, we may be able to free structural health monitoring from costly (re-)installation of communication wires. In stress-wave communications, piezoelectric transducers can act as actuators and sensors to send and receive modulated signals carrying concrete status information. The new generation of lead zirconate titanate (PZT) based smart aggregates cause multipath propagation in the homogeneous concrete channel, which presents both an opportunity and a challenge for multiple sensors communication. We propose a time reversal based pulse position modulation (TR-PPM) communication for stress wave communication within the concrete structure to combat multipath channel dispersion. Experimental results demonstrate successful transmission and recovery of TR-PPM using stress waves. Compared with PPM, we can achieve higher data rate and longer link distance via TR-PPM. Furthermore, TR-PPM remains effective under low signal-to-noise (SNR) ratio. This work also lays the foundation for implementing multiple-input multiple-output (MIMO) stress wave communication networks in concrete channels.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 춘계학술대회논문집
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• pp.675-678
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• 2008

The effect of wave and current interactions on jet-like current flowing against waves was investigated based on numerical simulations. The numerical simulations are conducted by a combined model system of REF/DIF(a wave model) plus SHORECIRC(a current model) and a Boussinesq equation model, FUNWAVE. In the simulations, regular and irregular waves refracted due to the jet-like opposing current were focused along the core region of current, and the jet-like current was earlier spreaded when the waves had larger wave heights. The numerical results show that the rapid change of wave height distribution in transverse direction near current inlet plays a significant role to spread the jet-like current. In other words, the gradients of radiation stress forcing in transverse direction have a more significant effect on the jet-like current than its relatively small gradients forcing in flowing direction, which tend to accelerate the current, do. In conclusion, it is indispensible to take into account the interaction effect of wave transformation and current characteristics when waves meet the opposing jet-like current such as river mouth.

• Structural Engineering and Mechanics
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• 제90권2호
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• pp.209-218
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• 2024

The present paper is focused on the study of the propagation of plane waves in thermoelastic media under a modified Green-Lindsay (MG-L) model having the influence of non-local and two temperature. The problem is formulated for the considered model in dimensionless form and is explained by using the reflection phenomenon. The plane wave solution of these equations indicates the existence of three waves namely Longitudinal waves (LD-Wave), Thermal waves (T-wave), and Shear waves (SV-wave) from a stress-free surface. The variation of amplitude ratios is computed analytically and depicted graphically against the angle of incidence to elaborate the impact of non-local, two temperature, and different theories of thermoelasticity. Some particular cases of interest are also deduced from the present investigation. The present study finds applications in a wide range of problems in engineering and sciences, control theory, vibration mechanics, and continuum mechanics.

• 한국식품영양학회지
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• 제13권6호
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• pp.602-610
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• 2000

Taekukkwon was practiced far health previously. The experimental group consisted of undergraduate and graduate students practising in the above disciplines at Myong Ji University. The group consisted of three female and three male students and the aim of this research was to measure the brain wave change for opened and closed eyes. The result of this research are as follows. Firstly, when students were subjected to basic open eye brain wave tests, beta-waves displayed for all regions of the brain. In the frontal region fast beta-waves were displayed and in the central region alpha-waves were displayed. Secondly, in the closed eye brain wave tests, the control group displayed beta-waves in some regions and alpha waves in external and internal regions. For all students\` brain-wave patterns, the amplitude of the alpha-wave was low and the frequency was high. In some students theta-waves were displayed. Taekukkwon practice relaxes the mind and body and helps relieve social stress which shows that taichichuan practices is beneficial. Finally, characteristics of the subjects were mostly type A so the personalities of the subjects were fast and aggressive. This research shows a definite link between personality and personal relationships with beta-waves emissions. So, further research is required in the future to investigate this relationship. The subjects consumed too large amount of foods so it was necessary to change their dietary habits taking into consideration on total calories, fats, and protein. It was also necessary to carrying out nutrition education to the students in emphasizing appropriate attitudes in general health and dietary behavior.

• Journal of the Korean Wood Science and Technology
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• 제27권1호
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• pp.50-55
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• 1999

Since ultrasonic stress wave velocity varies with wood temperature and moisture content, ultrasonic stress wave could be a tool to predict wood moisture content if temperature effect could be eliminated. This temperature effect was investigated by measuring the velocities of ultrasonic stress waves transmitting through air, a metal bar and a dimension lumber at various temperatures. For air the velocity and amplitude of the ultrasonic stress wave increase with temperature, while for a metal bar and a dimension lumber those decrease as temperature increases. However all three materials showed velocity hystereses with a temperature cycle. The effect of temperature and moisture content on stress wave velocity of a dimension lumber was depicted in the form of a three dimensional graph. The plot of stress wave velocity vs. wood moisture content was well fitted by two regression equations: a exponential equation below 46% and a linear equation above 46%.

• 한국소음진동공학회논문집
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• 제22권1호
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• pp.81-87
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• 2012

This paper establishes a modeling and simulation procedure for structural response and reliability of a cylindrical array sensor on submarines under the shock generated by underwater explosion. The structural reliability of SONAR is important because the submarine could get out of combat ability by the structural damage of the SONAR upon explosion. A cylindrical array sensor was first modeled using the finite element method. Modal analysis was then performed for the check of the reliability of the modeling. The shock resistance simulations were performed for the responses to the structural shock waves and for the responses to the directly applied underwater shock waves, according to BV-043 and MIL-STD-901D, respectively. The stresses of the structure were evaluated with von-Mises scheme. Vulnerable regions were exposed through mapping the maximum stress to the structural model. Maximum stress of the SONAR was compared with the yield stress of the material to examine the structural reliability.

• 조명전기설비학회논문지
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• 제21권9호
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• pp.1-6
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• 2007

In this study, tests of brain waves were carried out to investigate the physiological characteristics of drivers during a change of headlight brightness. The participants were 20 males in their 20s. Twenty-three different conditions combining the waveform of light, voltage, and alteration time were used. The measurement of brain waves was performed by an internationally standardized 10-20 method using LXE3232-RF. The results were as follows. 1. From the results of the brain wave map analysis, it was suggested that waveform A increases mental stress and waveform B affects mental and visual stress. The longer the stimulation time, the more stress level was detected. 2. The voltage alteration time of the B waveform should be kept to less than 1500msec, while the voltage should not fall below 11.5[V].

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 춘계 학술발표회 초청강연 및 논문집
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• pp.442-451
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• 2008

The evaluation of field degree of consolidation on soft clays has been an important problem in geotechnical areas. Monitoring either settlements or pore water pressures has been widely applied in the filed, but occasionally they have some problems. This study addresses the suggestion and application of another method for evaluating the degree of consolidation using shear wave velocities. A research site where soft clay layers were consolidated by surcharging loads was chosen. Laboratory tests were performed to determine the relation between shear wave velocity and effective stress. Field seismic tests were conducted several times during the consolidation of the clay layers. The tests results show that the shear wave velocity increased significantly as clays consolidated. The shear wave velocities at each field stress states were derived from the laboratory results and the degree of consolidation was evaluated by comparing the shear wave velocities obtained by laboratory and field seismic methods. In most stress states, the degree of consolidation evaluated using the shear wave velocity matched well with that obtained from field settlement record, showing the potential of applying the method using shear waves in the evaluation of field degree of consolidation on soft clay deposits.

• 대한기계학회논문집A
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• 제20권12호
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• pp.3892-3898
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• 1996

In this study, the prediction of the fatigue life as well as the extimation of the characteristics of fatigue cumulative damage on GFRP under random loading were performed. The constant amplitude tests and the ramdom loading test were carried on notched GFRP specimens with a circular hole. Random waves were generated with a micro-computer and had wide band spectra. Since it is useful that the prediction of fatigue life ot the given load sequences is based on S-N curves under constant amplitude loading, the estimation of equivalent stress is done on every random waves. The equivalent stress wasat first estimated by Miner's rule and then by the proposed model which was based on Hashin-Rotem's comulative damage theory regarding nonlinear fatigue cumulative damage behavior. The fatigue lives were predicted from each equivalent stress evaluated. And each predicted fatigue llife was compared with experimental results. The number of cycles of random loads were counted by mean-cross counting method. The reuslts showed that the fatigue life predicted by proposed model was correlated well with the experimental results in comparison with Miner's model.