• 한국정밀공학회지
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• 제13권1호
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• pp.143-152
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• 1996

The vibratory bowl feeder is the most versatile of all hopper feeding devices for small engineering parts, and the typical nonlinear dynamic system experiencing repeated impacts with friction. We model and analyze the dynamic behavior of a single part on the vibrating track of the bowl feeder. While the previous studies are restricted to the sliding regime, we focus our analysis on the hopping regime where the high conveying rate is available. We present the numerical analysis results for conveying rate and frictional impact process both in periodic and chaotic regimes. We examined the dynamic effects from the variation of several physical parameters, and presented the important features for the design of the vibratory bowl feeder. This research holds much potential for leverage over design problems of wide range of mechanisms and tools with repeated collisions.

• International Journal of Advanced Culture Technology
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• 제11권3호
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• pp.182-189
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• 2023

This study investigates the psychological effects of positive/negative valence order in repeated exposure to a suspenseful text. Specifically, the study seeks to understand how the order in which positive and negative elements are presented in a narrative impacts the experience of suspense, arousal, and enjoyment in readers or listeners. Using a suspenseful short story, participants were exposed to narratives with varying valence orders in a repeated-measures design. The study employed self-report questionnaires and psychophysiological measurements to capture participants' psychological responses. The results supported the hypothesis that repeated exposure impacts suspense, with negative valence enhancing suspense and arousal. Moreover, the order of valence influenced participants' psychological responses, indicating that positive valence can mitigate the impact of repeated exposure. However, the influence on enjoyment was not significant. Psychophysiological measures, specifically skin conductance level (SCL), revealed trends of habituation over repeated exposure. The findings underscore the significance of negative valence in heightening suspense and suggest directions for future research in exploring diverse factors that contribute to suspense in both fictional and real-life contexts.

• International Journal of Naval Architecture and Ocean Engineering
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• 제10권6호
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• pp.670-682
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• 2018

This paper presents the experimental and numerical investigation results of the response of low-temperature steel (LT-FH32 grade steel) beams under repeated impacts at room temperature and a single impact at a sub-zero temperature. After conducting tensile tests at room and sub-zero, repeated impact tests were conducted on two clamped single-beam models at room temperature, and single-impact tests of two other clamped single-beam models were conducted at $-50^{\circ}C$. The single and repeated impact tests were conducted by releasing a knife-edge striker using a drop testing machine. The permanent deflection of the model measured after each impact gradually increased with increasing number of impacts. Under the reduced temperature, the permanent deflection of the models slightly decreased. The numerical analyses were also performed to predict the damage response of the tested single-beam models. A comparison of the numerical prediction with those of experiments showed quite reasonable agreement.

• 대한가정학회지
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• 제46권8호
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• pp.85-95
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• 2008

This study examined the revictimization of wives from repeated husband violence and how that affected their depression. It also explored whether social support networks can have moderating effects. Sixty-four wives participated in the research group, 72.3% of whom had experienced repeated verbal violence, and 29.2% experienced repeated physical violence since their husbands participated in the correction and rehabilitation program for family violence perpetrators. Revictimization from repeated husband-to-wife violence was proven to significantly influence wife depression. To moderate the harmful effects of repeated domestic violence on depression, social support networks were observed to provide protective reinforcements. However, the findings of this study did not support the notion that social support networks have moderating effects on wife depression, while a strong negative relationship was established between professional networks of social support networks. Based on these results, the research discussion here advocates for an intervention that promotes psychological health to wives who are exposed to repeated domestic violence.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 추계학술대회 논문집
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• pp.1025-1028
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• 2005

Generally, fiber-reinforced composites have the highest possibilities of impact damages with external object collisions. Also, resulting in fatigue fracture considering the continued impact load. For the reasons mentioned above, the accurate understanding of interactions between the impact of composites and the fatigue load will be essential to understand the safety level of material structures. Furthermore, the composite materials and structures, due to the geometrical effect, vary the life in connection with the impact-fatigue. Therefore, I have reached the point that a focus of this study will be to evaluate fatigue fracture characteristics by the impacts-fatigue load of fiber-reinforced composites. Thus, in this paper, I have tried to work on impacts-fatigue load causing aspects and impact characteristics through impact-fatigue test on HTV-5Hl Black 9250 material made- structure, along with to evaluate the expected lift of real structures, the FEM analysis was carried out.

• Computers and Concrete
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• 제30권1호
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• pp.19-32
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• 2022

This paper presents an investigation into the failure of RC columns under impact loadings. A numerical simulation of 19 identical RC columns subjected to single and repeated impact loadings was performed. A free-falling hammer was dropped at midspan with the same total kinetic energy input but varying mass and momentum. The specimens under the repeated impact test were struck two times at the same location. The colliding index, defined as the impact energy-momentum ratio, was proposed to explain the different impact responses under equal-energy impacts. The increase of colliding index from low to high indicates the transition of the impact response from static to dynamic and failure mode from flexure to shear. This phenomenon was more evident when the column had a greater axial load and was impacted with a high colliding index. The existence of the axial load had an inhibitory effect on the crack development and increased the shear resistance. The second impact changes the failure mode from flexural to brittle shear as found in the specimen with 20% axial load subjected to high a colliding index. Moreover, a deflection prediction equation based on the impact energy and force was limited to the low colliding index impact.

• Structural Engineering and Mechanics
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• 제85권6호
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• pp.755-764
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• 2023

The article examines the impact response of the sandwich beam furnished by a novel bilayer core as inspired by the woodpecker's head architecture under different repeatedly exerted low-velocity impact loadings by employing the finite element package, ABAQUS. The sandwich beam forms four essential parts comprising bottom and top carbon fiber reinforced polymer laminates encasing bilayer core made of laterally arched solid hot melt adhesive material and aluminum honeycomb. Impact loadings are implemented repeatedly with a steel hemisphere impactor for various impact energies, 7.28 J, 9.74 J, and 12.63 J. Essentially, the commonly concentrated stresses at the impact region are regulated away by the arched core in all considered cases thus reducing the threat of failure. The sandwich beam can resist up to 5 continual impacts at 7.28 J and 9.74 J but only up to 3 times repeated loads at 12.63 J before visible failure is noticed. In the examination of several key impact performance indicators under numerous loading cases, the proposed beam demonstrates favorably up to 1.3-11.2 higher impact resistance efficacies compared to existing designs, therefore displaying an improvement in repeated impact resistance of the new design.

• 환경영향평가
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• 제19권3호
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• pp.335-345
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• 2010

This paper assessed environmental impacts of marine sand mining on coastal areas and Exclusive Economic Zones (EEZs) of Korea, and diagnosed problems of the related assessment statements for suggesting key assessment items (scoping) and system improvement. To mitigate conflicts and environmental impacts caused by large-scale, concentrated sand mining, we suggest it is critical to promote sustainable and eco-friendly utilization of marine resources while listening opinions from various stakeholders and analyzing alternative plans. Especially, it should be mandatory as a scoping item to provide verifiable data on the amount of sand, potential and accumulative impacts by mining, and key assessment items (e.g. erosion and sedimentation by submarine topography, benthic change, spreading of suspended solids, water pollution, grain-size change, and impact on fisheries resources). We also suggest that postassessment and monitoring should be improved to enable tracking of environmental impacts caused by sand mining through seasonal monitoring together with intermittent short-term surveys. In addition, effective measures to mitigate the impacts is also essential. As repeated sand mining at large-scale can damage marine ecosystems by long-term accumulated impacts, we suggest that assessment systems and regulatory policies should be developed and established, especially for ensuring reliability of assessment and review on selected major sandmining projects.

• 대한기계학회논문집A
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• 제32권8호
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• pp.642-653
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• 2008

In this paper, we propose a 3-D finite element (FE) analysis model with combined physical behavior and kinematical impact factors for evaluation of residual stress in multi-impact shot peening. The FE model considers both physical behavior of material and characteristics of kinematical impact. The physical parameters include elastic-plastic FE modeling of shot ball, material damping coefficient, dynamic friction coefficient. The kinematical parameters include impact velocity and diameter of shot ball. Multi-impact FE model consists of 3-D symmetry-cell. We can describe a certain repeated area of peened specimen under equibiaxial residual stress by the cell. With the cell model, we investigate the FE peening coverage, dependency on the impact sequence, effect of repeated cycle. The proposed FE model provides converged and unique solution of surface stress, maximum compressive residual stress and deformation depth at four impact positions. Further, in contrast to the rigid and elastic shots, plastically deformable shot produces residual stresses closer to experimental solutions by X-ray diffraction. Consequently, it is confirmed that the FE model with peening factors and plastic shot is valid for multi-shot peening analyses.

• 한국산업보건학회지
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• 제33권2호
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• pp.156-170
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• 2023

Objectives: This study conducted practical training to improve the proper usage of personal protective equipment(PPE), which greatly impacts workplace safety and health management. Personal protective equipment education was conducted through active participation, without theoretical modules, and aimed to identify the effects of repeated practical education and determine ways to increase participant satisfaction. Methods: Study data were analyzed using the IBM SPSS Statistics ver.29 software. First, participants' general characteristics were analyzed with frequency analysis. Second, the normality and equality of variances (Leven's test) were tested for the dependent variables prior to statistical analyses to determine the use of parametric tests. In general, normality is assumed when the sample size is 30 or more per the central limit theorem (Park et al., 2014). As our sample size of health management workers was 43, normality can be assumed. However, to ensure rigor of the study, we examined skewness and kurtosis. The results confirmed that the data were normally distributed. Third, the effects of repeated PPE training were analyzed using paired t-tests. Fourth, differences in satisfaction with PPE training according to the safety and health job position and safety and health certification were analyzed with t-test and Welch's t-test. For parameters that did not meet the assumption of equal variances, the Welch's t-test was performed. Results: Repeated PPE training improved the educational outcomes, and the improvements were significant in the 1st and 2nd respiratory PPE and safety and hygiene PPE training evaluations (p<.001). In terms of safety and health job position, repeated training led to improvements in educational outcomes, with significant improvements observed among supervisors and specialized health management institution workers in the 1st and 2nd training evaluations (p<.005). In terms of safety certification, repeated training led to improvements in educational outcomes, with significant improvements observed among both certified and non-certified individuals (p<.005). Regarding satisfaction with PPE training according to safety and health job positions, specialized health management institution workers showed greater satisfaction than supervisors, with significant differences in the satisfaction for expertise of lecture, work relevance, and lecturer's attitude (p<.001). Regarding satisfaction with PPE training according to safety and health certification, satisfaction was higher among certified individuals, with significant differences in satisfaction for work relevance and lecture attitude (p<.05) Conclusions: PPE education should be recommended to be provided as practical training. Repeated training can enhance educational outcomes for individuals with inadequate knowledge and understanding of PPE prior to education. For individuals with high levels of pre-existing knowledge and understanding of PPE, the results show that various training experiences should be provided to enhance their satisfaction. Therefore, it suggests that the workplace should actively seek educational media and methods to acquire expertise and skills in wearing personal protective equipment and improve the ability to use