• Journal of Labour Economics
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• v.39 no.3
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• pp.75-97
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• 2016

This paper estimates the peer effect of how improving the under-performing students can affect the academic performance of other students, focusing on the ratio of students more than proficient. We take advantage of the regression discontinuity design of the policy assignment rule of School-for-Improvement (SFI), which targeted the under-performing schools as an identification strategy. The estimation results from the 2009-2010 NAEA (National Assessment of Educational Achievement) reveal that the decrease of the ratio of under-performing students tends to increase the ratio of excellent or proficient students at around the policy cutoff. The finding turns out to be robust to various falsification tests.

• Computational Structural Engineering
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• v.2 no.1
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• pp.79-86
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• 1989

This paper concentrates on the development of simplified and effective algorithm for optimum reinforced concrete(RC) member design. After constructing the data base of predetermined RC sections which are arranged in the order of increasing resistant capacity, the relationship between the section identification numbers and resistant capacities of sections is estabilished by regression and it can be used to obtain the initial solution(section) which satisfies the design constraints imposed. Assuming that there exists the optimum solution. The optimization of the entire structure is accomplished through the individual mumber optimization.

• Journal of the Korea Concrete Institute
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• v.14 no.6
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• pp.982-988
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• 2002

Current design equations for shear strength of reinforced concrete columns generally overestimate the shear strength contribution by the circular transverse reinforcement. This is due to the simplification of the discrete distribution of the reinforcement to the continuous one and the imprudent application of the classical truss model to the circular section, which is different in shear-resisting mechanism from the rectangular section. This study presents a rational model for the prediction of shear strength contribution by the circular transverse reinforcement considering the starting location of a diagonal crack, the number of transverse reinforcing bars crossing the main crack and the geometrical strength component of the transverse resistance. It was found that, for lower amount transverse reinforcement, the crack starting point and the number of crack crossing bars greatly influence the shear-resisting capacity. Proposed model leads to a reliable design equation which is derived using a linear regression method and is in good agreement with the lower bound of exact strength curve.

• The Journal of the Korea Contents Association
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• v.19 no.12
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• pp.647-659
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• 2019

The purpose of this study was to investigate the influence of children's elementary school entrance to working conditions of employed mothers. The data from 4th to 8th wave of Panel Study on Korean Children (PSKC) were used for analysis. Specifically, we examined changes in wages, working hours and regular employment of employed mothers after their children entered elementary schools. We adopted Heck selection model for unbalanced panel data after controlling sample selection bias, and compare results of analysis for unbalanced and balanced panel data. The results showed that children's elementary school entrance reduces employed mothers' wage, working hours and regular employment. These results indicate that mother tend to leave regular job and could not entry into decent job when their children are in elementary school.

• Information Systems Review
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• v.25 no.4
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• pp.1-25
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• 2023

The online fitness industry has experienced rapid growth in recent years, overcoming physical constraints of conventional fitness programs. The COVID-19 pandemic accelerated the trend as social distancing policies were implemented. However, as financial distress of offline gyms worsened, the Korean government implemented the "With-COVID19" policy, which lifted most of the restrictions and regulations on offline gyms, on November 1st, 2021, raising concerns about the loss of drivers for the growth of the online fitness industry. Using regression discontinuity design in time (RDDiT), this study investigates the causal effect of the "With-COVID19" policy on the viewer engagement of online fitness content. Contrary to expectations that viewer engagement would decrease, it increased by 21%. Additionally, subgroup analysis based on opportunity cost reveals heterogeneity, and the high-cost group experienced a greater increase of 32% compared to low-cost group. Based on these findings, the study provides possible mechanisms of the increase, theoretical contributions on using RDDiT in the Information Systems, and practical implications for guidelines on managing online fitness platforms and content in the era of digital transformation.

• Journal of the Korea Concrete Institute
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• v.19 no.1
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• pp.121-130
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• 2007

To investigate the enhancement in strength and deformation capacities of concrete confined by FRP composites, tests under axial loads were carried out on three groups of thirty six short columns in circular section with diverse GFRP confining reinforcement. The major test variables considered include fiber content or orientation, wrap or tube type by varying the end loading condition, and continuous or discontinuous confinement depending on the presence of vortical spices between its two halves. The circumferential FRP strains at failure for different types of confinements were also investigated with emphasis. Various analytical models capable of predicting the ultimate strength and strain of the confined concrete were examined by comparing to observed results. Tests results showed that FRP wraps or tubes provide the substantial increase in strength and deformation, while partial wraps comprising the vertical discontinuities fail in an explosive manner with less increase in strength, particularly in deformation. A bilinear stress-strain response was observed throughout all tests with some variations of strain hardening. The failure hoop strains measured on the FRP surface were less than those obtained from the tensile coupons in all tests with a high degree of variation. In overall, existing predictive equations overestimated ultimate strengths and strains observed in present tests, with a much larger scatter related to the latter. For more accuracy, two simple design- oriented equations correlated with present tests are proposed. The strength equation was derived using the Mohr-Coulomb failure criterion, whereas the strain equation was based on entirely fitting of test data including the unconfined concrete strength as one of governing factors.