• Title/Summary/Keyword: Quasi-Experimental Study

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Aeroelastic forces on yawed circular cylinders: quasi-steady modeling and aerodynamic instability

  • Carassale, Luigi;Freda, Andrea;Piccardo, Giuseppe
    • Wind and Structures
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    • v.8 no.5
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    • pp.373-388
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    • 2005
  • Quasi-steady approaches have been often adopted to model wind forces on moving cylinders in cross-flow and to study instability conditions of rigid cylinders supported by visco-elastic devices. Recently, much attention has been devoted to the experimental study of inclined and/or yawed circular cylinders detecting dynamical phenomena such as galloping-like instability, but, at the present state-of-the-art, no mathematical model is able to recognize or predict satisfactorily this behaviour. The present paper presents a generalization of the quasi-steady approach for the definition of the flow-induced forces on yawed and inclined circular cylinders. The proposed model is able to replicate experimental behaviour and to predict the galloping instability observed during a series of recent wind-tunnel tests.

Development and evaluation of a pediatric nursing competency-building program for nursing students in South Korea: a quasi-experimental study

  • Koo, Hyun Young;Lee, Bo Ryeong
    • Child Health Nursing Research
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    • v.28 no.3
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    • pp.167-175
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    • 2022
  • Purpose: The present study aimed to develop and examine the effectiveness of a pediatric nursing competency-building program for nursing students. Methods: This was a quasi-experimental study with a nonequivalent control group pretest-posttest design conducted between October and December 2021. The participants included 40 nursing students (20 each in the experimental and control groups) at a university in a South Korean city. The pediatric nursing competency-building program integrated problem-based learning and simulation into clinical field practice. The experimental group participated in the program, while the control group did not. Data were analyzed using the 𝑥2 test, the independent t-test, and repeated-measures analysis of variance. Results: Pediatric nursing competency and clinical performance showed a greater increase in the experimental group than in the control group. However, the change in problem-solving ability in the experimental group was not significantly different from that in the control group. Conclusion: The pediatric nursing competency-building program effectively improved students' pediatric nursing competency and clinical performance.

Mixed-Mode Fracture Analysis of Quasi-Brittle Material Considering Fracture Energy (파괴에너지를 고려한 유사취성재료의 혼합모드 균열해석)

  • Lim, Yun-Mook;Kim, Moon-Kyum;Cho, Seok-Ho;Shin, Seung-Kyo
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.6 no.4
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    • pp.129-137
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    • 2002
  • In this study, mixed-mode fracture behavior is simulated effectively through the numerical method using the axial defomation link elements which can predict the behavior of quasi-brittle material. The behavior of quasi-brittle material is modeled numerically using the exponential tension softening constitutive equation and verified by comparing with the result of published experimental result. In order to verify the mixed-mode fracture behavior through the developed numerical method, analysis of mode I is formulated and the result is compared with those of FEM first, and then mixed-mode analysis is analyzed and compared with existing theories and experimental data. Also the characteristics of fracture behavior is examined through the analysis of crack generation with respect to various mode mixity.

Experimental and Numerical Studies on Composite Tubes for the Energy Absorber of High-speed Train (복합재 튜브를 이용한 고속 열차의 에너지 흡수장치에 대한 실험 및 수치해석 연구)

  • Nguyen, Cao-Son;Jang, Hong-Kyu;Shin, Jae-Hwan;Son, Yu-Na;Kim, Chun-Gon
    • Composites Research
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    • v.24 no.1
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    • pp.1-9
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    • 2011
  • This paper presents an experimental and numerical study on composite tubes for the energy absorber of the high-speed train. The purpose of the experimental study is to find out which lay-up is the best lay-up for the energy absorber. Four lay-ups were tested using quasi static method: $[0/45/90/-45]_4$, $[0]_{16}$, $[0/90]_8$, $[0/30/-30]_5$. Two triggering methods were used to create initial damage and guarantee the progressive collapse mode: bevel edge and notch edge. As a result, $[0/45/90/-45]_4$ lay-up was find out the best lay-up among the laminates being tested. In the numerical study, a parametric analysis was done to find out the most proper way to simulate the quasi static test of a composite tube using LS-DYNA program. A single composite tube was modeled to be crashed by a moving wall. Comparison between simulation and experiment was done. Reasonable agreement between experiment and analysis was obtained. Dealing with parameter TFAIL and the mass scaling factor, this parametric study shows the ability and the limitation of LS-DYNA in modeling the quasi static test for the composite tube.

MODELING OF DIRECT INJECTION DIESEL ENGINE EMISSIONS FOR A QUASI-DIMENSIONAL MULTI-ZONE SPRAY MODEL

  • Jung, D.;Assanis, D.N.
    • International Journal of Automotive Technology
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    • v.5 no.3
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    • pp.165-172
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    • 2004
  • Phenomenological models for direct injection diesel engine emissions including NO, soot, and HC were implemented into a full engine cycle simulation and validated with experimental data obtained from representative heavy-duty DI diesel engines. The cycle simulation developed earlier by Jung and Assanis (2001) features a quasi-dimensional, multi-zone, spray combustion model to account for transient spray evolution, fuel-air mixing, ignition and combustion. In this study, additional models for HC emissions were newly implemented and the models for NO, soot, and HC emissions were validated against experimental data. It is shown that the models can predict the emissions with reasonable accuracy. However, additional effort may be required to enhance the fidelity of models across a wide range of operating conditions and engine types.

A Study on the Axial Crush Analysis of a Rectangular Tube with Experimental Comparison (사각관의 붕괴해석 및 실험에 관한 연구)

  • 강신유;한동철
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.17 no.10
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    • pp.2555-2562
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    • 1993
  • In this paper, the axial crush of the rectangular STS304 tube is analyzed using DYNA3D, and 10 models are tested under quasi-static load. The deformed shapes of analysis and test are present, and the analysis results are compared with the results of quasi-static test. This paper describes that free rotational boundary condition causes a very similar deformed shapes to expermental results, and using the elastic buclking modes as initial imperfecion shapes, the deformed shapes are very close to the experimental shapes.

Experimental and numerical study on energy absorption of lattice-core sandwich beam

  • Taghipoor, Hossein;Noori, Mohammad Damghani
    • Steel and Composite Structures
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    • v.27 no.2
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    • pp.135-147
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    • 2018
  • Quasi-static three-point bending tests on sandwich beams with expanded metal sheets as core were conducted. Relationships between the force and displacement at the mid-span of the sandwich beams were obtained from the experiments. Numerical simulations were carried out using ABAQUS/EXPLCIT and the results were thoroughly compared with the experimental results. A parametric analysis was performed using a Box-Behnken design (BBD) for the design of experiments (DOE) techniques and a finite element modeling. Then, the influence of the core layers number, size of the cell and, thickness of the substrates was investigated. The results showed that the increase in the size of the expanded metal cell in a reasonable range was required to improve the performance of the structure under bending collapse. It was found that core layers number and size of the cell was key factors governing the quasi-static response of the sandwich beams with lattice cores.

Effects of a hybrid online and offline program for facilitating father-infant interactions in South Korea: a quasi-experimental study

  • Park, Sae-Eun;Bang, Kyung-Sook
    • Child Health Nursing Research
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    • v.28 no.2
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    • pp.132-141
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    • 2022
  • Purpose: This study examined the effects of an educational program for fathers on improving father-infant interactions, child-rearing knowledge, and attachment. Methods: In this quasi-experimental study, the participants were recruited by convenience sampling among fathers with infants (2-6 months of age) residing in three districts of Seoul. Fifteen participants in the experimental group and 17 participants in the control group completed the follow-up investigation. A 5-week online and offline intervention program with five sessions was provided to the experimental group. The data were analyzed using generalized estimating equations (GEEs). Results: There was a significant difference in the change in father-infant interaction scores of the experimental group, especially in the caregiver aspect with a significance level of .100 in time and group-to-group interactions (B=6.46, p=.051, 95% confidence interval [CI]=-0.02-12.94). The changes between the groups and times were not statistically significant when it came to infant development knowledge and father-infant attachment. Conclusion: We conclude that hybrid online and offline education should be implemented as an effective method to improve fathers' interactions with their children based on accurate knowledge about infant development.

The Effect of a Social Skills Program on Violent Behaviors in Children Aged 60~72 Months

  • Kuzlu Ayyildiz, Tulay;Cimete, Guler
    • Journal of Korean Academy of Nursing
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    • v.49 no.6
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    • pp.771-782
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    • 2019
  • Purpose: To determine the effects of a child and parent program on developing social skills for preventing violent behaviors in children aged 60~72 months through a specially developed pre and posttest, control group, quasi-experimental study. Methods: A social skills development program based on Gardner's Multiple Intelligence Theory was used. The data were collected using the Social Skills Assessment Scale (SSAS), a Chart to Monitor Verbal and Behavioral Violence in Children, the Parental Attitude Scale and the Parent Interview Form. This quasi-experimental study that included a pretest, posttest, and control group had a sample comprising 67 children and parents, with 36 in the experimental group, and 31 in the control group. Results: Over a six-month period, while the social skill scores of the children in the experimental and control groups increased, their violent behaviors decreased (p<.050). Increase in social skill scores and decrease in violent behaviors were higher in the experimental than in the control group children (p<.050). The parents in the experimental group stated that they had started to empathize with their children, using "I" language, and applied rules more consistently after the program. Conclusion: This program was successful in preventing violent behaviors in children through the development of social skills. Hence, it can be effectively implemented through a teacher/nurse collaboration.

A Study on Residual Strength of Carbon/Epoxy Face Sheet and Honeycomb Core Sandwich Composite Structure after Quasi Static Indentation Damage (탄소섬유/에폭시 면재, 알루미늄 허니컴 코어 샌드위치 복합재 구조의 압입 손상에 의한 잔류강도 연구)

  • Kong, Chang-Duk;Park, Hyun-Bum;Lee, Seoung-Hyun
    • Composites Research
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    • v.22 no.2
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    • pp.24-29
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    • 2009
  • This study aims to investigate the residual strength of sandwich composites with Al honeycomb core and carbon fiber face sheets after the quasi-static indentation damage by the experimental investigation. The 3-point bending test and the edge-wise compressive strength test were used to find the mechanical properties, and the quasi-static point load was applied to introduce the simulated damage on the specimen. The damaged specimens were finally assessed by the 3-point bending test and the compressive strength test. The investigation results revealed the residual strength of the damaged specimens due to the quasi-static indentation. The both test results showed that the residual strength of the damaged specimen was decreased according to increases of the damaged depth.