• 제목, 요약, 키워드: Effect size

Search Result 11,164, Processing Time 0.07 seconds

Size-Effect Analyses of Shear Behavior in Reinforced Concrete Beams (철근콘크리트 보의 전단거동의 크기효과 해석)

  • 변근주;하주형;송하원
    • Proceedings of the Korea Concrete Institute Conference
    • /
    • /
    • pp.321-326
    • /
    • 1998
  • Shear failure of reinforced concrete beams is serious problem due to sudden brittle failure and many experimental results proved that size effect in shear behavior is an important feature of reinforced concrete members. For this reason, the structural safety of the reinforced concrete beams for shear has been checked by applying empirical design formula, which includes the size-effect, derived from experimental data. However, as the sizes of reinforced concrete members become extremely large, experiments sometimes become very difficult so that the formula or the experimental data could not be obtained and size-effect analyses of shear behavior become significant. In this study, size-effect analysis of shear behavior in reinforced concrete beams is performed by modeling tension stiffening/shear stiffening on reinforced concrete and the tension softening/shear softening on plain concrete. Then, the influences of models in the size-effect analyses of shear behavior in reinforced concrete beams are analyzed.

  • PDF

A Meta-analysis of the Variables related to the Emotional Labor of Nurses (간호사의 감정노동과 관련된 변인의 메타분석)

  • Kim, Sin Hayng;Ham, Younsuk
    • Journal of Korean Academy of Nursing Administration
    • /
    • v.21 no.3
    • /
    • pp.263-276
    • /
    • 2015
  • Purpose: The study was done to verify the effect size of the variables related to the emotional labor of nurses. Methods: A total of 47 article on variables related to the emotional labor of nurses and published from 2006 to 2014 were used for the meta-analysis. Results: Variables with the largest effect size related to emotional labor were identified as the variables of work task, organization and individual characteristics in descending order of effect size. The sub-factors with the greatest effect size in the work task variable were exhaustion and work commitment, while for organization variables, intention to change jobs had the largest effect size. For individual characteristics, physical symptoms had the largest effect size. Conclusion: The results of this study are meaningful as the first study to integrate research results on variables related to the emotional labor of Korean nurses, providing practical data for the management of emotional labor.

Size-effect of fracture parameters for crack propagation in concrete: a comparative study

  • Kumar, Shailendra;Barai, S.V.
    • Computers and Concrete
    • /
    • v.9 no.1
    • /
    • pp.1-19
    • /
    • 2012
  • The size-effect study of various fracture parameters obtained from two parameter fracture model, effective crack model, double-K fracture model and double-G fracture model is presented in the paper. Fictitious crack model (FCM) for three-point bend test geometry for cracked concrete beam of laboratory size range 100-400 mm is developed and the different fracture parameters from size effect model, effective crack model, double-K fracture model and double-G fracture model are evaluated using the input data obtained from FCM. In addition, the fracture parameters of two parameter fracture model are obtained using the mathematical coefficients available in literature. From the study it is concluded that the fracture parameters obtained from various nonlinear fracture models including the double-K and double-G fracture models are influenced by the specimen size. These fracture parameters maintain some definite interrelationship depending upon the specimen size and relative size of initial notch length.

Size Effect on Axial Compressive Strength of Concrete (콘크리트의 축압축강도에 대한 크기효과)

  • 이성태;김민욱;김진근
    • Journal of the Korea Concrete Institute
    • /
    • v.13 no.2
    • /
    • pp.153-160
    • /
    • 2001
  • In this study, the size effect on axial compressive strength for concrete members was experimentally investigated. Experiment of mode I failure, which is one of the two representative compressive failure modes, was carried out by using double cantilever beam specimens. By varying the eccentricity of applied loads with respect to the axis on each cantilever and the initial crack length, the size effect of axial compressive strength of concrete was investigated, and new parameters for the modified size effect law (MSEL) were suggested using least square method (LSM). The test results show that size effect appears for axial compressive strength of cracked specimens. For the eccentricity of loads, the influence of tensile and compressive stress at the crack tip are significant and so that the size effect is present. In other words, if the influence of tensile stress at the crack tip grows up, the size effect of concrete increases. And the effect of initial crack length on axial compressive strength is present, however, the differences with crack length are not apparent because the size of fracture process zone (FPZ) of all specimens in the high-strength concrete is similar regardless of differences of specimen slenderness.

A Meta-Analysis of Variables Related to Parenting Efficacy (부모효능감 관련변인에 대한 메타분석)

  • Lee, Hwe Seong;Yoo, Soon Hwa
    • Korean Journal of Child Studies
    • /
    • v.34 no.1
    • /
    • pp.35-51
    • /
    • 2013
  • The purpose of this study is to synthesize research findings on the relationship between parenting efficacy and the variables related to it, as well as to produce results using meta-analysis. The following questions guide this study : Which variables are frequently conducted in research related to parenting efficacy? What is the effect size of each variable? The 65 studies whose results are analyzed in this paper were collected via a search for investigations focusing on 'parenting efficacy'. The studies were used for meta-analysis in which eleven variables were selected. The results of the analysis indicate that a large effect size is produced by the parenting stress in a negative direction. A higher than medium effect size occurs on the basis of parenting beliefs in a negative direction. A higher than medium effect size is also caused by the father's involvement in child care and social support. A medium effect size is produced on the basis of children's temperament, and a small effect size is the result of the mother's academic background, parenting knowledge, and parent's income. There is no relationship between parenting efficacy and children's gender.

Size Effect of Concrete Structures without Initial Cracks (초기균열이 없는 콘크리트 구조물의 크기에 따른 응력감소효과에 관한 연구)

  • Kim, Jin Keun;Park, Hong Kyee
    • Journal of The Korean Society of Civil Engineers
    • /
    • v.7 no.2
    • /
    • pp.29-36
    • /
    • 1987
  • In most of the structural members with initial cracks, the strength tends to decrease as the member size increases. This phenomenon is known as size effect. Among the structural materials of glass, metal or concrete, etc., concrete represents the size effect even without initial crack. According to the previous size effect law, the concrete member of very large size can resist little stress. Actually, however, even the large size member can resist some stress if there is no initial notch. This means that the fracture mechanism of very small or very large size member follows strength criterion, but the medium size member follows non-linear fracture mechanics (NLFM). In this study, the empirical models which are derived based on nonlinear fracture mechanics are proposed according to the regression analysis with the existing test data of large size specimens for uni-axial compression test, splitting tensile test and shear test of reinforced concrete beams.

  • PDF

The Effect of Aquatic Exercise Therapy on Balance in Patients with Chronic Stroke : Meta-Analysis of Studies in Korea (수중운동치료가 만성 뇌졸중 환자의 균형에 미치는 효과 : 국내연구의 메타분석)

  • Lee, Dongjin;Cho, Sunghyoun
    • Journal of The Korean Society of Integrative Medicine
    • /
    • v.6 no.2
    • /
    • pp.1-16
    • /
    • 2018
  • Purpose : This meta-analysis was aimed at guiding future research in stroke treatment and to provide real-world data relating to the effects of aquatic exercise therapy on balance in patients with chronic stroke. Methods : We performed a meta-analysis comprising 22 studies involving aquatic exercise therapy performed between 2006 and 2017. A meta-analysis software program was used to calculate the mean effect size, effect size by intervention, and effect size by outcome. We also performed a meta-regression analysis and an analysis of publishing bias. Results : The mean effect size was 0.563. The effect size by outcome was observed to be the largest for the functional reach test, followed by the Berg balance scale, balance equipment, the Timed Up and Go test and one leg standing. Meta-regression analysis showed that effect size increased with an increase in the duration, number, length of exercise session. Conclusion : Aquatic exercise therapy appears to show a moderate effect on balance in patients with chronic stroke. A meta-analysis is warranted for further research to determine the effects of aquatic exercise on walking, muscle strength, and range of motion.

A Meta-analysis of the effects of cardiopulmonary resuscitation training (심폐소생술 교육 효과에 대한 메타분석 연구)

  • Yoou, Soon-Kyu;Lee, Ji-Eun
    • The Korean Journal of Emergency Medical Services
    • /
    • v.21 no.1
    • /
    • pp.17-44
    • /
    • 2017
  • Purpose: This study aimed to identify the effects of cardiopulmonary resuscitation (CPR) training using a meta-analysis by effect size. Methods: The effect sizes for each variable and the overall effect size for the collected data were identified. The homogeneity verification of the effect size and the difference among the average effect sizes for each mediation variable were determined. Results: The overall average effect size for CPR training was 1.747. Homogeneity verification of the overall effect size was a Q-value of 3716.962, which was statistically significant (p=.000) when${\alpha}=.05$. CPR training showed statistically significant differences depending on age (p=.002), sex (p=.006), number of trainees (p=.000), research design (p=.000), training method (p=.027), and practical training tools (p=.000). Conclusion: CPR training can effectively improve knowledge, skills, and attitudes about CPR. The results of this meta-analysis contribute to the development of more effective educational guidelines for future CPR training and the advancement of the CPR education field.

Meta-Analysis of Constraint-Induced Movement Therapy in Hemiplegic Stroke Patient in Korea (국내 뇌졸중 편마비 환자를 대상으로 한 건측억제-환측유도 치료효과의 메타분석)

  • Park, So-Yeon;Shin, In-Soo
    • Physical Therapy Korea
    • /
    • v.19 no.2
    • /
    • pp.59-68
    • /
    • 2012
  • This meta-analysis investigated the effects on arm motor impairment, arm motor function and disability, and psychological aspects of constraint-induced movement therapy (CIMT) for upper extremity hemiparesis following stroke, based on Korean studies. A comprehensive search of the complete Korean studies information service system (KISS), Research Information Sharing Service (RISS), Korea National Library, and the Korean Medical Database to September 2011 was conducted. Eleven eligible controlled clinical trials compared CIMT to a control group or an alternative treatment. All outcome measures of arm motor impairment, arm motor function and disability, and psychological aspects were pooled for calculating effect size. The overall effect size of CIMT was .700 (95% confidence interval=.482~.918). The CIMT programs showed large effect on the aspect of arm motor function and disability (the effect size is .920) and the psychological aspect (the effect size is .946). The effect of CIMT on arm motor impairment was moderate (the effect size is .588). These results show that CIMT may improve upper extremity motor impairment, function and disability, and psychological aspects following stroke. However, these results were based on a small number of studies, and not all of them were randomized control trials. Additional research is needed to include larger well-designed trials to resolve these uncertainties.

Electro-mechanical vibration of nanoshells using consistent size-dependent piezoelectric theory

  • Ebrahimi, Narges;Beni, Yaghoub Tadi
    • Steel and Composite Structures
    • /
    • v.22 no.6
    • /
    • pp.1301-1336
    • /
    • 2016
  • In this paper, the free vibrations of a short cylindrical nanotube made of piezoelectric material are studied based on the consistent couple stress theory and using the shear deformable cylindrical theory. This new model has only one length scale parameter and can consider the size effects of nanostructures in nanoscale. To model size effects in nanoscale, and considering the nanotube material which is piezoelectric, the consistent couple stress theory is used. First, using Hamilton's principle, the equations of motion and boundary condition of the piezoelectric cylindrical nanoshell are developed. Afterwards, using Navier approach and extended Kantorovich method (EKM), the governing equations of the system with simple-simple (S-S) and clamped-clamped (C-C) supports are solved. Afterwards, the effects of size parameter, geometric parameters (nanoshell length and thickness), and mechanical and electric properties (piezoelectric effect) on nanoshell vibrations are investigated. Results demonstrate that the natural frequency on nanoshell in nanoscale is extremely dependent on nanoshell size. Increase in size parameter, thickness and flexoelectric effect of the material leads to increase in frequency of vibrations. Moreover, increased nanoshell length and diameter leads to decreased vibration frequency.