• Composites Research
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• 제26권6호
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• pp.343-348
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• 2013

본 연구에서는 발포 폴리프로필렌(Expanded polypropylene)과 발포 폴리스티렌(Expanded polystyrene)의 준정적 시험(Quasi-static test) 및 계장화 충격 시험(Instrumented impact test)을 수행하였다. EPP와 EPS는 4가지의 다른 밀도에 대해 원통형 시편이 준비되었다. 준정적 시험에는 MTS 858을 사용하여 0.001 $s^{-1}$과 0.1 $s^{-1}$ 두 가지 변형률속도 조건으로 진행되어 결과를 분석하였다. 계장화 충격 시험에서는 Instron dynatup 9250HV를 사용하여, 각각 100 J, 200 J, 300 J의 서로 다른 충격에너지를 가했을 때의 응력-변형률 선도 결과를 비교 분석하였다.

• 한국응급구조학회지
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• 제24권2호
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• pp.111-121
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• 2020

Purpose: The purpose of this study was to compare visual blood loss estimation and subjective emergency according to clothing color. Methods: This is a quasi-experimental study which involved the use of mock bleeding patients wearing different colors tops. Results: Differences in visual estimates according to clothing color were significant in both paramedic students (F=6.69, p=.002) and the general department students (F=20.92, p=.000). When looking specifically at the accuracy of visual estimates, the paramedic students group tended to underestimate (50% white, 62.5% black, 32.5% yellow) the actual blood volume in all experimental conditions. On the other hand, the general department group tended to overestimation (45% white, 40% black, 67.5% yellow). The subjective emergency was also found to differ between paramedic students (F=13.58, p=.000) and general department students (F=9.67, p=.000). Conclusion: Paramedics treating bleeding patients at pre-hospital stages need to pay attention to blood loss estimations depending on clothing color, a factor not to be neglected or underestimated.

• Structural Engineering and Mechanics
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• 제72권2호
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• pp.191-201
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• 2019

Finite element analysis is one of the most used tools for studying femoral neck fracture. Nerveless, consensus concerning either the choice of material characteristics, damage law and /or geometric models (linear on nonlinear) remains unreached. In this work, we propose a numerical quasi-brittle damage model to describe the behavior of the proximal femur associated with two methods to evaluate the Young modulus. Eight proximal femur finite elements models were constructed from CT scan data (4 donors: 3 women; 1 man). The numerical computations showed a good agreement between the numerical curves (load - displacement) and the experimental ones. A very encouraging result is obtained when a comparison is made between the computed fracture loads and the experimental ones ($R^2=0.825$, Relative error =6.49%). All specific numerical computation provided very fair qualitative matches with the fracture patterns for the sideway fall simulation. Finally, the comparative study based on 32 simulations adopting linear and nonlinear meshing led to the conclusion that the quantitatively results are improved when a nonlinear mesh is used.

• 한국항해학회지
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• 제14권3호
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• pp.15-33
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• 1990

In recent years, propellers with various blade configurations such as highly skewed propellers are often fitted to ships from the viewpoint of reduction of vibration and noise. In the design of such propellers, design charts based on methodical series tests are to be complemented by theoretical calculations for accurate estimation of propeller open-water characteristics. The author intended to develop a method to estimate propeller open-water characteristics based on Quasi -Vortex - Lattice Method originally developed by Lan for solving planar thin wings, The Quasi - Vortex - Lattice Method has the simplicity and flexibility of Vortex - Lattice Method. Its accuracy is comparable to that of the Vortex - Lattice Method. Converged solution can be obtained with a small number of control points and further, leading edge suction force can be calculated directly. In the present paper, a numerical method to estimate propeller open-water characteristics based on the Quasi - Vortex - Lattice Method is reviewed and its application to marine propellers is described in detail. Comparison of propeller open-water characteristics obtained by the present method with experimental data showed good agreement for a wide variety of propellers including highly skewed propellers.

• Journal of Power Electronics
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• 제17권4호
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• pp.860-873
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• 2017

The present article reports an analysis and investigation of a direct AC-AC quasi-resonant converter. A bidirectional power device, whose switching frequency is lower than the frequency of the current passing through the load, is used for its realization. The zero voltage switching mode is described when zero voltage on the power device is available by measuring it with the control system. The continuous current in the resonant inductance by switching the power device at zero voltage is considered, and it is characterized by two sub-modes. A mathematical analysis of the processes has been made and comparative results from the computer simulation and experimental study have been brought. The converter can be used in a wide areas of power electronics: induction heating, wireless power transfer, AC-DC converters, etc.

• Structural Engineering and Mechanics
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• 제70권2호
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• pp.153-168
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• 2019

In this paper, energy absorption characteristics of circular windowed tubes with different section shapes (circular, ellipse, square, hexagon, polygon and pentagon) are investigated numerically and experimentally. The tube possesses the same material, thickness, height, volume and average cross sectional area which are subjected under axial and oblique quasi-static loading conditions. Numerical model was constructed with FE code ABAQUS/Explicit, the obtained outcome of simulation is in good matching with the experimental data. The energy absorbed, specific energy absorption, crash force efficiency, peak and mean loads along with the collapse modes with their initiation point of simple and windowed tubes were evaluated. The technique for order of preference by similarity ideal solution (TOPSIS) approach was employed for assessing their overall crushing performances. The obtained results confirm that efficacy of crash force indicators have improved by introducing windows and tubes with pentagonal and circular windows achieves the maximum ranking about 0.528 and 0.517, it clearly reveals the above are best window shapes.

• Earthquakes and Structures
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• 제13권6호
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• pp.599-611
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• 2017

This paper improves seismic fragility of a typical steel-concrete composite bridge with the deck-to-pier connection joint configuration at the concrete crossbeam (CCB). Based on the quasi-static test on a typical steel-concrete composite bridge model under the SEQBRI project, the damage states for both of the critical components, the CCB and the pier, are identified. The finite element model is developed, and calibrated using the experimental data to model the damage states of the CCB and the bridge pier as observed from the experiment of the test specimen. Then the component fragility curves for both of the CCB and the pier are derived and combined to develop the system fragility curves of the bridge. The uncertainty associated with the mean system fragility has been discussed and quantified. The study reveals that the CCB is more vulnerable than the pier for certain damage states and the typical steel-concrete composite bridge with CCB exhibits desirable seismic performance.

• Journal of Korean Biological Nursing Science
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• 제26권1호
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• pp.16-25
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• 2024

Purpose: This study aimed to investigate the effect of a video-based enteral nutrition education program using QR codes on the perception, knowledge, and performance of enteral nutrition for intensive care unit (ICU) nurses. Methods: This was a quasi-experimental study with a nonequivalent control group pre- and post-test design. The participants were nurses working at six ICUs within a single university hospital, with 55 nurses in the experimental group and 55 nurses in the control group. The video-based enteral nutrition education program using QR codes was repeated three times to the experimental group. Results: There was a statistically significant pre-post difference in perceptions between the two groups (Z = -4.04, p < .001) with 2.00 points (± 5.57) for the control group and 7.89 points (± 7.95) for the experimental group, in knowledge (Z = -7.48, p < .001) with 0.02 points (± 1.91) for the control and 4.18 points (± 2.33) for the experimental, and in performance (Z = -2.20, p = .028) with 0.06 points (± 3.96) for the control and 2.00 points (± 5.14) for the experimental. Conclusion: The video-based enteral nutrition education program using QR codes was effective in improving the perceptions, knowledge, and performance of enteral nutrition among ICU nurses. This enteral nutrition education program using QR codes in clinical education can contribute to evidence-based nursing practice by improving perceptions and knowledge of enteral nutrition.

• Geomechanics and Engineering
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• 제21권3호
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• pp.227-236
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• 2020

Non-destructive exploration using elastic waves has been widely used to characterize rock mass properties. Wave propagation in jointed rock masses is significantly governed by the characteristics and orientation of discontinuities. The relationship between spatial heterogeneity (i.e., joint spacing) and wavelength for elastic waves propagating through jointed rock masses have been investigated previously. Discontinuous rock masses can be considered as an equivalent continuum material when the wavelength of the propagating elastic wave exceeds the spatial heterogeneity. However, it is unclear how stress-dependent long-wavelength elastic waves propagate through a repetitive rock-joint system with multiple joints. A preliminary numerical simulation was performed in in this study to investigate long-wavelength elastic wave propagation in regularly jointed rock masses using the three-dimensional distinct element code program. First, experimental studies using the quasi-static resonant column (QSRC) testing device are performed on regularly jointed disc column specimens for three different materials (acetal, aluminum, and gneiss). The P- and S-wave velocities of the specimens are obtained under various normal stress levels. The normal and shear joint stiffness are calculated from the experimental results using an equivalent continuum model and used as input parameters for numerical analysis. The spatial and temporal sizes are carefully selected to guarantee a stable numerical simulation. Based on the calibrated jointed rock model, the numerical and experimental results are compared.

• 여성건강간호학회지
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• 제27권4호
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• pp.388-404
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• 2021

Purpose: The purpose of this study was to examine the effects of team-based learning (TBL) on nursing students' communication ability, problem-solving ability, self-directed learning, and nursing knowledge related to high-risk pregnancy nursing. Methods: This quasi-experimental study used a nonequivalent control group pretest-posttest design. The participants were 91 nursing students allocated to an experimental group (n=45) and a control group (n=46). The experimental group received TBL lectures three times over the course of 3 weeks (100 minutes weekly) and the control group received instructor-centered lectures three times over the course of 3 weeks (100 minutes weekly). Data were collected by questionnaires from September to November, 2019. Data were analyzed using the chi-square test, paired t-test, and independent t-test. Results: After the intervention, the mean scores of problem-solving ability (t=-2.59, p=.011), self-directed learning (t=4.30, p<.001), and nursing knowledge (t=3.18, p=.002) were significantly higher in the experimental group than in the control group. No significant difference in communication ability was found between the experimental and control group (t=1.38, p=.171) Conclusion: The TBL program was effective for improving nursing students' problem-solving ability, self-directed learning, and nursing knowledge. Thus, TBL can be considered an effective teaching and learning method that can improve the learning outcomes of high-risk pregnancy nursing in women's health nursing classes. The findings suggest that TBL will be helpful for future nursing students to develop the nursing expertise necessary for providing nursing care to high-risk pregnant women.