• Structural Engineering and Mechanics
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• 제75권6호
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• pp.713-722
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• 2020

This article aims to illustrate the damped dynamic responses of layered functionally graded (FG) thick 2D beam under dynamic pulse sinusoidal load by using finite element method, for the first time. To investigate the response of thick beam accurately, two-dimensional plane stress problem is assumed to describe the constitutive behavior of thick beam structure. The material is distributed gradually through the thickness of each layer by generalized power law function. The Kelvin-Voigt viscoelastic constitutive model is exploited to include the material internal damping effect. The governing equations are obtained by using Lagrange's equations and solved by using finite element method with twelve -node 2D plane element. The dynamic equation of motion is solved numerically by Newmark implicit time integration procedure. Numerical studies are presented to illustrate stacking sequence and material gradation index on the displacement-time response of cantilever beam structure. It is found that, the number of waves increases by increasing the graduation distribution parameter. The presented mathematical model is useful in analysis and design of nuclear, marine, vehicle and aerospace structures those manufactured from functionally graded materials (FGM).

• 한국기계가공학회지
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• 제16권5호
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• pp.141-149
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• 2017

Due to the inaccuracy of micro-machining, various special processing methods have been investigated recently. Among them, pulse electrochemical machining is a promising machining method with the advantage of no residual stress and thermal deformation. Because the cross section of the wire electrode used in this study is circular, wire-pulse electrochemical machining is suitable for micro-hole machining. By applying the response surface methodology, the experimental plan was made of three factors and three levels: machining time, duty factor, and voltage. The regression equation was obtained through experiments. Then, by referring to the main effect diagram, we fixed the duty factor and machining time with little relevance, and solved the equation for the target 900 microns to obtain the voltage value. The results obtained from the response surface methodology were approximately those of the target value when the actual experiment was carried out. Therefore, it is concluded that the optimal conditions for hole processing can be obtained by the response surface methodology.

• 전기학회논문지
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• 제64권5호
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• pp.799-804
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• 2015

This study aims at the new analysis of heart beat fluctuations by applying physiological Heart Rate Variability Model with representing the cardiac control system in sympathetic and parasympathetic-coupling oscillator constants, C_s and C_p. To find the effects of coupling constants on the beat-to-beat fluctuations, Integral Pulse Frequency Modulation (IPFM) model is adopted to generate the time series data of ECG R-peaks and represent them by poincaré scattergram plot in the time domain and HRV in the frequency domain, respectively. The actual poincaré plots and HRV spectrum are also analyzed by acquiring the experimental data from the subjects exposed to the emotional-stress invoking environment and the function of the coupling constants are verified in terms of antagonism in sympathetic and parasympathetic activity.

• 대한조선학회논문집
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• 제57권5호
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• pp.271-277
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• 2020

Recoverability and vulnerability of navy ships under underwater explosion are critical verification factors in the acquisition phase of navy ships. This paper aims to establish numerical analysis techniques for the underwater explosion of navy ships. Doubly Asymptotic Approach (DAA) Equation of Motion (EOM) of primary shock wave and secondary bubble pulse proposed by Geers-Hunter was introduced. Assuming a non-compressive fluid, reference solution of the DAA EOM of Geers-Hunter using Runge-Kutta method was derived for the secondary bubble pulse phase with an assumed charge conditions. Convergence analyses to determine fluid element size were performed, suggesting that the minimum fluid element size for underwater explosion analysis was 0.1 m. The spherical and cylindrical fluid domains were found to be appropriate for the underwater explosion analyses from the fluid domain shape study. Because the element size of 0.1 m was too small to be applied to the actual navy ships, a very slender beam with the square solid section was selected for the study of fluid domain existence effect. The two underwater explosion models with/without fluid domain provided very similar results in terms of the displacement and stress processes.

• 대한간호학회지
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• 제17권2호
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• pp.137-144
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• 1987

The main purpose of this study was to examine the validity of the vital sign as an instrument of stress reaction measurement. From July to August 1986, stress reaction was evaluated by the difference of endoscopic vital sign on 93 G-I troubled out-patients who underwent endoscopy for the first time and did not have any evidence of cardiovascular disease. The data were analysed by x$^2$-test, Paired . t-test, ANCOVA and Multiple Comparison Test. The result of study were as follows: 1. The frequency of gastric disease was differed by the family type, and the mobility of gastritis and gastric cancer were more increased in nuclear family than in large family (p=0.019). 2. In a comparison of before with after 5 minutes endoscopic vital sign, and a Pulse rate (P=0.0001), respiration rate (p=0.0001), systolic blood pressure (p=0.0002) and diastolic blood Pressure (P=0.006) were significantly increased after 5minutes by endoscopy in contrast with before 5minutes. 3. The control of before 5 minutes of endoscopic vital sign, after 5 minutes of endoscopic systolic (p=0.024) and diastolic blood pressure (p=0.0146) were more elevated in biopsyed group than in non-biopsyed, group. And after 5minutes of endoscopic respiration rate was more increased in gastric cancer than in gastritis (p=0.0406) or gastric ulcer (p=0.0073). And after 5 minutes of endoscopic systolic blood pressure was elevated over 50years old men (P=0.0238). In short, the increase of a pulse rate af ter 5 minutes of endoscopy was not influenced by general characteristics of samples in this experiment. And systolic blood pressure over 50years old men must be considered of physiological hypertension.

• Corrosion Science and Technology
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• 제5권5호
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• pp.168-172
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• 2006

Alloy 600 having a superior resistance to a corrosion is used as a steam generator tubing in nuclear power plants. In spite of its high corrosion resistance, there are many tubings which experience corrosion problems such as a SCC under the high temperature and high pressure environments of nuclear power plants. The Alloy 600 tubing can be repaired by using a Ni electroplating having an excellent SCC resistance. In order to carry out a successful Ni electrodeposition inside a steam generator tubing, the effects of various parameters on the material properties of the electrodeposit should be elucidated. Hence this work deals with the effects of an applied current density, duty cycle($T_{on}/(T_{on}+T_{off})$) of a pulse current, bath temperature and solution pH on the material properties of Ni electrodeposit obtained from a Ni sulphamate bath by analyzing the current efficiency, potentiodynamic curve, hardness and stress-strain curve. Hardness, YS(yield strength) and TS(tensile strength) decreased whereas the elongation increased as the applied current density increased. This was thought to be by a concentration depletion at the interface of the electrodeposit/solution, and a fractional decrease of the hydrogen reduction reaction. As the duty cycle increased, the hardness, YS and TS decreased while the elongation increased. During an off time at a high duty cycle, the concentration depletion could not be recovered sufficiently enough to induce a coarse grain sized electrodeposit. With an increase of the solution temperature and pH, the YS and TS increased while the elongation decreased. The experimental results of the hardness and the stress-strain curves can be supplemented by the results of the potentiodynamic curve.

• 재활간호학회지
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• 제7권1호
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• pp.68-77
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• 2004

The Purpose of this study is to explore the effects of Craniosacral therapy(CST) on the chronic headache patients, and the research was used the one-group pretest-posttest design. The subjects were 31 chronic headache patients, who received Craniosacral therapy by once per week for 6 weeks. The data were collected from July 1, 2003 to August 28, 2003. In order to evaluate the effects of craniosacral therapy, Visual Analogue Scale(VAS) for headach intensity, blood pressure, pulse rate, respiration rate, craniosacral rhythm rate, depression and stress perception were measured before and after treatment. The results are as follows : 1) The mean score of intensity of headache (VAS) significantly decreased after each session of Craniosacral therapy(F=86.14, p<.001). 2) The mean score of systolic blood pressure significantly decreased after each session of craniosacral therapy(F=6.99, p<.001), and the mean score of diastolic blood pressure significantly decreased after 3rd session of Craniosacral therapy(t=5.710, p<.001). The means of pulse(F=6.19, p<.001), respiration (F=7.93, p<.001) and craniosacral impulse rate(F=22.84, p<.001) significantly decreased after each session of Craniosacral therapy. 3) The means score of depression significantly decreased after Craniosacral therapy(t=6.627, p<.001) and stress also significantly decreased after Craniosacral therapy(t=5.987, p<.001). Therefore, these results of this study suggest that Craniosacral therapy could be an effective nursing intervention to reduce the intensity of headache.

• 산업융합연구
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• 제22권9호
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• pp.169-177
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• 2024

연구는 사무직 근로자를 대상으로 척추온열마사지 기기의 사용이 신체적･정신적 이완에 미치는 효과를 규명하는데 목적이 있다. 30~40대 사무직 근로자 15명이 연구에 참여하였으며, 연구참여자들은 자택에서 한 달 동안 주 5회, 회당 40분씩 척추온열마사지 기기를 사용하였다. 주관적 지표는 시각적상사척도(visual analog scale, VAS)를 이용하여 사용 전과 후의 피로, 스트레스, 근육통, 혈액순환, 소화불량, 불면증의 변화를 분석하였으며, 객관적 지표는 혈압(이완기/수축기) 및 맥압의 변화를 분석하였다. 연구결과, 주관적 지표에서 피로(-51.5%), 근육통(-49.6%), 혈액순환(-23.1%), 스트레스(-20.9%) 척도가 유의하게 감소하였고, 불면증(-20%) 및 소화불량(-7.4%) 증상도 기준선 대비 감소하는 경향을 보였다. 객관적 지표에서 혈압은 수축기 혈압에서 유의한 감소를 보였으며, 이완기 혈압과 맥압에서도 감소하는 경향을 보였다. 결론적으로 사무직 근로자의 척추온열마사지 기기 사용은 온열요법과 물리적 마사지의 동시 적용으로 부교감 신경계를 활성화시켜 신체적 이완 및 정신적 이완에 도움이 될 수 있음을 확인하였다.

• 대한간호학회지
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• 제36권1호
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• pp.179-188
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• 2006

Purpose: This study was aimed to identify the effects of a self-foot reflexology massage on depression, stress responses and functions of the immune system of middle-aged women, Method: This study was a one group pretest-postlest experimental design and the data was collected from August $1^{st}$ 2004 to May $31^{st}$ 2005. The subjects consisted of 46 middle-aged women (40 - 64 years) who were recruited from the Community Health Center in Busan city. Subjects were not treated for 4 weeks, subsequently they were trained in self foot reflexology massage for 2 weeks, and then they did their own daily for 6weeks (2 days at the research center, 5 days at home).The outcome variables were measured 4 times, at baseline, pre training, after training, and after the intervention. The collected data was analyzed using repeated measure ANOVA by the SPSS/WIN program. Result: There was a statistically significant difference in depression, perceived stress, systolic blood pressure, natural-killer cells and Ig G. However, there was not a statistically significant difference in dyastolic blood pressure, pulse or serum cortisol. Conclusion: These results suggest that a self-foot reflexology massage could be utilized as an effective nursing intervention to reduce depression and stress responses, and to strengthen immune systems in middle-aged women.

• 성인간호학회지
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• 제19권3호
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• pp.353-364
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• 2007

Purpose: The purpose of this study was to investigate the effects of health promotion program on physiological stress, perceived stress and menopausal symptoms in menopausal women. Methods: This study followed a nonequivalent control group pretest-post test design. The subjects consisted of 57 middle-aged women(30 in the experimental group and 27 in the control group) who were recruited from the community health center in J city. The subjects in the experimental group participated in a health promotion program for 8 weeks, which was composed of yoga and teaching for 1 session per week. Results: The health promotion program showed a statistical difference in blood pressure, pulse rate and perceived stress. However, there was not a statistical difference in serum cortisol, or menopausal symptoms. Conclusion: This health promotion program was partially effective for reducing stress and it was not effective for reducing menopausal symptoms in menopausal women. It is necessary to conduct a future study using a different time period, measurement time, and target population.