• Korean Journal of Childcare and Education
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• v.11 no.5
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• pp.39-54
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• 2015

The purpose of this research is to examine the causal relationships between an infant's negative emotionality, the mother's reactive parenting, and the infant's problem-solving ability. This research used a Panel Study with Korean Children's 1st-3rd year data, and the subjects were 1789 infants and their mothers. To process the results, descriptive statistics, reliability verification, Pearson's product moment correlation analysis, and path analysis were conducted. The results of this research are as follows: First, the infant's negative emotionality had significant negative effects on the mother's reactive parenting. Second, the mother's reactive parenting had significant positive effects on the infant's problem-solving ability. Third, the infant's negative emotionality had indirect effects on the problem-solving ability. Through the results of this research, it could be interpreted that the path, the infant's negative emotionality, which is a personal factor, and the mother's reactive parenting, which is an environmental factor, had effects on the infant's problem solving ability. Furthermore, basic data to explore the ways of promoting the infant's problem solving ability could be introduced.

• Steel and Composite Structures
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• v.20 no.5
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• pp.1067-1085
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• 2016

Recent research on steel moment-resisting connection between steel beams and concrete filled steel tubes has shown that there are considerable advantages to be obtained by anchoring the connection to the concrete infill within the tube using anchors in blind bolts. In the research reported here, extensive experimental tests and numerical analyses have been performed to study the anchorage behaviour of cogged deformed reinforcing bars within concrete filled circular steel tubes. This data in essential knowledge for the design of the steel connections that use anchored blind bolts, both for strength and stiffness. A series of pull-out tests were conducted using steel tubes with different diameter to thickness ratios under monotonic and cyclic loading. Both hoop strains and longitudinal strains in the tubes were measured together with applied load and slip. Various lead-in lengths before the bend and length of tailed extension after the bend were examined. These dimensions were limited by the dimensions of the steel tube and did not meet the requirements for "standard" cogs as specified in concrete standards such as AS 3600 and ACI 318. Nevertheless, all of the tested specimens failed by bar fracture outside the steel tubes. A comprehensive 3D Finite Element model was developed to simulate the pull-out tests. The FE model took into account material nonlinearities, deformations in reinforcing bars and interactions between different surfaces. The FE results were found to be in good agreement with experimental results. This model was then used to conduct parametric studies to investigate the influence of the confinement provided by the steel tube on the infilled concrete.

• Journal of the Society of Naval Architects of Korea
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• v.32 no.3
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• pp.83-97
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• 1995

The aim of this study is to derive a simple formula for predicting ultimate strength of hull girders under vertical bending moment. The existing formulas have been reviewed and classified into analytical approach, empirical approach and linear approximate approach. It is known that the ship hull will reach the ultimate limit state if both collapse of the compression flange and yielding of the tension flange occur. Side shells in the vicinity of the compression and tension flanges will often fail also, but the material around the final neutral axis will remain in the elastic state. Based on this observation, a credible distribution of longitudinal stresses around the hull section at the overall collapse state is assumed, and an explicit analytical formula is derived. The accuracy of the formula has been verified by a comparison of the experimental and the numerical results.

• Journal of Korean Society of Steel Construction
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• v.18 no.5
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• pp.515-524
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• 2006

Cross-sectional distortions take place when steel box girders a re subjected to torsional moment, as a consequence of which distortional warping stresses are necessarily developed. Additional normal stresses due to the distortion are should be included at the design stage. The relative magnitude with respect to the maximum bending stress are kept less than the specific values, i.e., at 5~10%, by properly spaced intermediate diaphragms that could prevent the distortional deformation of the box girder. However, current design equations for the stiffness of intermediate diaphragms were derived based on BEF. In this study, the area required by the intermediate diaphragm members are investigated through three-dimensional finite element analyses. The results of the analyses indicate that the current equations give to conservative values for the intermediate diaphragm of box girder bridges. Finally, an improved equation for the area of the intermediate diaphragm is derived from a regression analysis from the finite element analysis results.

• Physical Therapy Korea
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• v.11 no.1
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• pp.1-17
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• 2004

The purposes of this study were to find correlations among Fugl-Meyer Assessment scale, gait speed, and Timed Up & Go test (TUG) and to predict gait ability from subscales of Fugl-Meyer Assessment scale. The study population consisted of 30 stroke patients referred to the Department of Rehabilitation Medicine in the Bundang Jaesang General Hospital. All subjects were ambulatory with or without an assistive device. All participants were assessed on Fugl-Meyer Assessment scale and gait speed (m/s), TUG (s). The data were analyzed using independent t-test, Pearson product moment correlation analysis and stepwise multiple regression. The results revealed that all items of Fugl-Meyer Assessment scale, except passive joint range of motion were significantly correlated with gait speed and TUG. In particular, sensation score, lower extremity motor and coordination score have a significant correlation with gait speed and TUG (p<.05). The sensation score and lower extremity motor score were important factors in comfortable gait and maximal gait speed. Their power of explanation regarding comfortable gait and maximal gait speed were 63.0% and 65.0%, respectively. The sensation score and lower extremity coordination score were important factors in TUG. Their power of explanation regarding TUG was 55.0%. These results showed that Fugl-Meyer Assessment scale is significantly correlated with gait speed and TUG. Therefore Fugl-Meyer Assessment scale is an appropriate assessment tool to predict gait ability of patients with stroke. Further study about gait speed and TUG by change of Fugl-Meyer Assessment score is needed using a longitudinal study design.

• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.2
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• pp.60-67
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• 2020

Recently, many studies have been conducted on the structural behavior of HPFRCC, but most of the studies focused on the flexural behavior while studies on the shear behavior are limited. In this study, a model has been developed to reasonably predict the shear strength of a HPFRCC beam without stirrups. To develop the model, a HPFRCC beam was simply idealized with upper & lower chords resisting bending moment and a web shear element resisting shear forces. Then, taking into the account of the tensile behavior of HPFRCC, the main diagonal compressive strut angle and shear stress of the web shear element were evaluated on shear failure. Then, the shear strength of the HPFRCC beam could be evaluated. For the verification of the proposed model, the predictions by the proposed model were compared with the test results of 48 HPFRCC beams exhibiting shear failure. The results showed that the proposed model reasonably predicted the actual shear strength with an average of 1.045 and CoV of 0.125. This study are expected to be useful for related researches and design of members or structures to which HPFRCC is applied.

• Korean Journal of Applied Biomechanics
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• v.26 no.3
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• pp.243-248
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• 2016

Objective: The aim of this study was to determine the kinematical characteristics of somersault with twist in the Lou Yun and Akopian motions and to provide useful information to gymnastic athletes in men's vault. Method: The study subjects were 12 male adult top athletes. After 12 trials (7 Lou Yun and 5 Akopian trials) filmed by using two digital high-speed camcorders set at 90 frames/sec, kinematical data were collected through the direct linear transformation (DLT) method. The mean differences in biomechanical variables were compared during the second flight upward phase. The kinematic characteristics of somersault with twist in the Lou Yun and Akopian motions were identified. Results: In Lou Yun motion, the vertical release velocity through horse breaking was not difficult to obtain, so the athletes had enough time to prepare for the twist. Therefore, the Lou Yun motion has an advantage to make a cat twist in the pike posture. In the Akopian motion, obtaining the horizontal velocity through horse pushing was so easy that the Akopian athletes attained a large angular impulse and angular momentum. Therefore, the Akopian motion has an advantage to making a tilt twist in the body tilting posture. Conclusion: This study suggests that gymnastic athletes should control their body segment movements in order to increase the twisting angular velocity of the whole body, which requires regulation of the longitudinal moment of inertia of the body. Moreover, athletes should prepare for the shoulder and hip twists early in order to make the landing position in advance.

• Earthquakes and Structures
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• v.19 no.4
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• pp.273-286
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• 2020

The pile group foundation is widely used for gravity pier of high-speed railway bridges in China. If a moderate or strong earthquake occurs, the pile-surrounding soil will exhibit obvious nonlinearity and significant pile group effect. In this study, an improved pushover analysis model for the pile group foundation with consideration of pile group effect is presented and validated by the quasi-static test. The improved model uses simplified springs to simulate the soil lateral resistance, side friction and tip resistance. PM (axial load-bending moment) plastic hinge model is introduced to simulate the impact of the axial force changing of pile group on their elastic-plastic characteristics. The pile group effect is considered in stress-stain relations of the lateral soil resistance with a reduction factor. The influence factors on nonlinear characteristics and plastic hinge distribution of the pile group foundation are discussed, including the pier height, longitudinal reinforcement ratio and stirrup ratio of the pile, and soil mechanical parameters. Furthermore, the displacement ductility factor, resistance increase factor and yielding stiffness ratio are provided to evaluate the seismic performance of soil-pile system. A case study for the pile group foundation of a railway simply supported beam bridge with a 32 m-span is conducted by numerical analysis. It is shown that the ultimate lateral force of pile group is not determined by the yielding force of the single one in these piles. Therefore, the pile group effect is essential for the seismic performance evaluation of the railway bridge with pile group foundation.

• Advances in aircraft and spacecraft science
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• v.7 no.6
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• pp.553-570
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• 2020

To address the problems caused by the strong coupling of an airbreathing hypersonic vehicle's airframe and propulsion to the integrated control system design, an integrated airframe-propulsion model is established, and the coupling characteristics between the aircraft and engine are analyzed. First, the airframe-propulsion integration model is established based on the typical nonlinear longitudinal dynamical model of an air-breathing hypersonic vehicle and the one-dimensional dual-mode scramjet model. Thrust, moment, angle of attack, altitude, and velocity are used as transfer variables between the aircraft model and the engine model. The one-dimensional scramjet model can accurately reflect the working state of the engine and provide data to support the coupling analysis. Second, owing to the static instability of the aircraft model, the linear quadratic regulator (LQR) controller of the aircraft is designed to ensure attitude stability and height tracking. Finally, the coupling relationship between the aircraft and the engine is revealed through simulation examples. The interaction between vehicle attitude and engine working condition is analyzed, and the influence of vehicle attitude on engine safety is considered. When the engine is in a critical working state, the attitude change of the aircraft will not affect the engine safety without considering coupling, whereas when coupling is considered, the attitude change of the aircraft may cause the engine unstart, which demonstrates the significance of considering coupling characteristics.

• Journal of the Korean Society of Hazard Mitigation
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• v.3 no.2 s.9
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• pp.127-137
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• 2003

In locations where the cost of concrete is relatively high, or in situations where the weight of concrete members is to be kept to a minimum, it may be economical to use hollow R.C. members. The ductility of circular hollow R.C. columns with one layer of longitudinal and spiral reinforcement placed near the outside face of the section and the steel tube placed on the inside face of the section is investigated. Such hollow sections are confined through the wall thickness since the steel tube is placed. In this study, moment-curvature analyses are conducted with Mander's confined concrete stress-strain relationship. The variables influenced on the ultimate strain is the ratio and yield strength of confining reinforcement and the compression strength for confined concrete. From this ultimate strain - the transverse reinforcement ratio relationship, the transverse reinforcement ratio for circular hollow reinforced columns with confinement is proposed. The proposed transverse reinforcement ratio is confirmed by experimental results.