• Smart Structures and Systems
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• v.21 no.2
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• pp.195-205
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• 2018

Research on Lamb wave-based damage identification in plate-like structures depends on precise knowledge of dispersive wave velocity. However, boundary reflections with the same frequency of interest and greater amplitude contaminate direct waves and thus compromise measurement of Lamb wave dispersion in different materials. In this study, non-reflecting boundaries were proposed in both numerical and experimental cases to facilitate time-frequency characterization of Lamb wave dispersion. First, the Lamb wave equations in isotropic and laminated materials were analytically solved. Second, the non-reflecting boundaries were used as a series of frames with gradually increased damping coefficients in finite element models to absorb waves at boundaries while avoiding wave reflections due to abrupt property changes of each frame. Third, damping clay was sealed at plate edges to reduce the boundary reflection in experimental test. Finally, the direct waves were subjected to the slant-stack and short-time Fourier transformations to calculate the dispersion curves of phase and group velocities, respectively. Both the numerical and experimental results suggest that the boundary reflections are effectively alleviated, and the dispersion curves generated by the time-frequency analysis are consistent with the analytical solutions, demonstrating that the combination of non-reflecting boundary and time-frequency analysis is a feasible and reliable scheme for characterizing Lamb wave dispersion in plate-like structures.

• Computers and Concrete
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• v.23 no.2
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• pp.133-143
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• 2019

The paper presents the experimental investigations into the effect of ground granulated blast furnace slag (GGBFS) on the time-dependent tensile strength of concrete. The splitting and flexural tensile strength of concrete was determined at the ages of 3, 7, 28, 56, 90, 150 and 180 days using the cylindrical and prism specimens respectively for plain and GGBFS concrete. The amount of cement replacement by GGBFS was 0%, 40% and 60% on the weight basis. The maximum curing age was kept as 28 days. The results showed that the splitting and flexural tensile strength of concrete containing GGBFS has been found lower than the plain concrete at all ages and for all mixes. The tensile strength of 40 percent replacement has been found higher than the 60 percent at all ages and for all mixes. The rate of gain of splitting and flexural tensile strength of 40 percent GGBFS concrete is found higher than the plain concrete and 60 percent GGBFS concrete at the ages varying from 28 to 180 days. The experimental results of time-dependent tensile strength of concrete are compared with the available models. New models for the prediction of time-dependent splitting and flexural tensile strength of concrete containing GGBFS are proposed. The present experimental and analytical study will be helpful for the designers to know the time-dependent tensile properties of GGBFS concrete to meet the design requirements of liquid retaining reinforced and pre-stressed concrete structures.

• Journal of the Society of Naval Architects of Korea
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• v.61 no.1
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• pp.1-7
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• 2024

Underwater sound speed is an important analysis parameter on an estimation of the underwater radiated noise (URN) emitted from vessels. This paper aims to present an underwater sound speed measurement procedure using a cross-correlation of time-domain acoustic signals and validate the procedure through an experiment in a reverberant water tank. For the purpose, time-domain acoustic signals transmitted by a Gaussian pulse excitation from an acoustic projector have been measured at 20 hydrophone positions in the reverberant water tank. Then, the sound speed in water has been calculated by a linear regression using 190 cross-correlation cases of distances and time lags between the received signals and the result has been compared with those estimated by the existing empirical formulae. From the result, it is regarded that the presented experimental procedure to measure an underwater sound speed is reliably applicable if the time resolution is sufficiently high in the measurement.

• Proceedings of the Korean Society for Quality Management Conference
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• 1998.11a
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• pp.361-377
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• 1998

The measurement of welding temperature of connector is usually performed with an infra red temperature gauge. However, the factors, which influence the temperature measurement, are rarely known. This research used the welding temperature measurement of the connector as an example, applying the experimental design, in two-phase experiments, to search the affecting factors. In phase-I experiment, we used a resolution III, seven-factor fractional factorial design with two levels for each factor. The result showed that none of the factor was significant in affecting the welding temperature when the type I error ${\alpha}$ was 0.05. Next, we did the phase-II factorial experiment with three factors and each factor had three levels. The experiment showed the experimental time was significant in affecting the temperature measurement when the type I error ${\alpha}$ was 0.05. Further Duncan's multiple range tests on the second experimental data showed that the later the experimental time, the weaker the light intensity could have on the temperature measurement and the average of the highest temperatures was lower. Moreover, the later the experimental time, the smaller was the variance of the temperature measurement and the difference between the averages of the highest and the lowest temperatures was also lower.

• Journal of Korean Academy of Nursing
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• v.31 no.3
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• pp.454-466
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• 2001

Purpose: The purpose of this study was to determine the effects of exercise program on cardiopulmonary functions and shoulder joint functioning in breast cancer patients who under- went radiation therapy after surgery. Method: Subjects in the experimental group(N=12) participated in an exercise program for eight weeks. The Exercise program consisted of shoulder stretching, arm weight training, and walking on treadmill. Maximal oxygen uptake (v2max), maximal running time, shoulder joint range of motion, and shoulder functional assessment were determined before and after the exercise program. Baseline sociodemographic and medical data were compared between experimental group and control group using the Fisher's exact test and Mann- Whitney U test. For effects of the exercise program, repeated measures ANOVA were used. Result: 1) Following the exercise program for eight weeks, both v$\alpha$ max and maximal running time tended to increase in experimental group comparing with the control group. 2) Shoulder abduction, extension and flexion of the operated upper extremity in the experimental group comparing with control significantly increased after the exercise program(p<0.05). 3) Shoulder flexion of the normal upper extremity in the experimental group comparing with control significantly increased after the exercise program(p<0.05). Conclusion: The results suggest that the exercise program for breast cancer patients undergoing radiation therapy after breast surgery can improve shoulder functions and increase cardiopulmonary functions, which are maximal oxygen uptake and maximal running time.

• Bulletin of the Society of Naval Architects of Korea
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• v.38 no.3
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• pp.88-92
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• 2001

H. Kim, B.K. Lee and C.K. Rheem have been experimentally studied to clarified the mechanism of thrust force generated by sculling motion for the propulsion of Korean small boats. The experimental investigations have been conducted under the bollard condition by installing a scull at the end of a trimming tank of towing tank. The sculling motion produced by the skilful fisherman and the resultant venerated forces have been measured in respect to the Cartesian coordinate fitted to the pivot point of the scull. ("An Experimental Study on the Propulsive Characteristics of Sculls". J. of the Soc. of Naval Arch. of Korea, Vol. 26, No. 3, 1989, pp.13-24) Through these experiments the trajectory of the blade tip and the angular displacement of the blade section have been measured as shown in Fig. 1 and 2 of this paper. And at the same time the resultant hydrodynamic force components are expressed in Fig. 3 and 4. These three dimensional data of sculling motion and generated real time force components are the unique experimental information which could clarify the thrust force generating mechanism of sculling motion. The experimental results have been reanalyzed by focusing the relation between instantaneous attack angle of blade section and the resultants real time force components. Through these investigation it is found out that the conventional imagination that the 7cull motion should be effective in generating lift force must be reconsidered because the attack angle of scull blade are too great to free from stall phenomena during the sculling operation.

• Journal of the Korean Society of Clothing and Textiles
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• v.27 no.5
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• pp.496-504
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• 2003

The purpose of this study was (1) to identify the experimental bias which could appear person perception as results of presentation methods (2) to find out the most desirable method in presentation of stimulus. The research was a quasi experiment and the subjects were 773 male and female undergraduate students. The experimental instruments consisted of a set of stimulus and semantic differential scales of 7- point hi-polar adjectives. The collected data were analyzed by Factor Analysis, ANOVA(analysis of variance), Scheffe＇s multiple range test. The independent variables were presentation orders and presentation time of stimulus. The results were as follows: First, five factors which were potency, sociality, appearance, evaluation, activity impression dimensions emerged to account for the methods of development of stimulus. Second, the presentation order of stimulus in the combination of four stimuli sets had significant effects on the 3 impressional factors(sociality, appearance, evaluation). The presentation order of stimuli in the combination of eight stimuli set had significant effects on the 3 impressional factors(potency, sociality, appearance) and the presentation order of stimuli in the combination of eight stimuli set showed a significant effect on memorization of stimulus and the results support the recency effect. Third, the presentation time of stimuli had significant effects on the 2 impressional factors(potency, activity). 30 seconds presentation as well as free duration time resulted less experimental bias than 3 seconds presentation.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.36 no.8
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• pp.529-538
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• 1987

The time optimal position control scheme based on the Pontryagin's minimum principle is proposed in the current source inverter(CSI) fed induction motor system. The field oriented induction motor system is modelled with a second order plant and a switching curve is obtained by solving Hamiltonian equation. The validity of time optimal control solution has been verified by experimental tests carried out with a prototype MC68000 based microcomputer system, and 5Hp induction motor. Experimental results are in a close agreement with those the digital simulation ones.

• Women's Health Nursing
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• v.27 no.3
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• pp.196-208
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• 2021

Purpose: This study aimed to test the efficacy of a nurse-led postpartum self-care (NLPPSC) intervention at reducing postpartum fatigue (PPF) and depressive mood and promoting maternal functioning among first-time mothers in Bangladesh. Methods: A non-synchronized quasi-experimental design was used. First-time mothers were recruited during postpartum and assigned to the experimental or control group (34 each). The experimental group received the NLPPSC in the hospital, a 1-day intervention that focused on increasing self-efficacy. The control group received usual care. Data on PPF, depressive mood, maternal functioning, self-care behaviors, postpartum self-efficacy, and self-care knowledge were collected at postpartum 2 weeks (attrition 23.5%) and 6 weeks (attrition 16.1%). Data were analyzed using descriptive statistics, bivariate statistics, and linear mixed model analysis. Results: One-third (33.3%) of new mothers experienced depressive mood (Edinburgh Postnatal Depression Scale scores of ≥13 points). The NLPPSC intervention was statistically significant in decreasing PPF (β=-6.17, SE=1.81, t=-3.39, p<.01) and increased maternal functioning at postpartum 6 weeks in the experimental group (β=13.72, t=3.73, p<.01) compared to the control. Knowledge was also statistically significant for increased maternal functioning over time (β=.37, SE=.18, t=2.03, p<.05). However, there were no statistically significant differences in depressive mood over time. Conclusion: The NLPPSC intervention was feasible and effective in improving fatigue and maternal functioning in Bangladeshi mothers by postpartum 6 weeks and thus supports implementing the NLPPSC intervention for new mothers after childbirth.

• Women's Health Nursing
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• v.27 no.4
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• pp.278-285
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• 2021

Purpose: This study aimed to examine the effect of a newborn care education program using ubiquitous learning (UL-NCEP) on exclusive breastfeeding and maternal role confidence of first-time mothers in Vietnam. Methods: This quasi-experimental study with a nonequivalent control group design was conducted at a university hospital in Hue city, Vietnam, between June and July 2018. Eligible first-time mothers were conveniently allocated to the experimental (n=27) and the control group (n=25). Mothers in the control group received only routine care, whereas mothers in the experimental group received UL-NCEP through tablet personal computers in addition to routine care in the hospital. Then, the educational content was provided to mothers by their smartphone for reviewing at home. UL-NCEP was developed based on the World Health Organization's "Essential Newborn Care Course" guidelines. The exclusive breastfeeding rate and maternal role confidence level after birth and at 4 weeks postpartum were assessed in both groups to assess the effect of UL-NCEP. Results: At 4 weeks postpartum, the experimental group showed a significantly higher level than the control, for exclusive breastfeeding rate (p<.05) as well as mean maternal role confidence (p<.05). Conclusion: UL-NCEP was a feasible and effective intervention in increasing first-time Vietnamese mothers' exclusive breastfeeding rate and maternal role confidence level. This program may be integrated into routine care for postpartum mothers to promote mother and infant health among first-time mothers in Vietnam.