• Steel and Composite Structures
• /
• v.26 no.3
• /
• pp.255-263
• /
• 2018

A steel-concrete composite (SC) panel typically consists of two steel faceplates and a plain concrete core. This paper investigated the impact response of SC panels through drop hammer tests and numerical simulations. The influence of the drop height, faceplate thickness, and axial compressive preload was studied. Experimental results showed that the deformation of SC panels under impact consists of local indentation and overall bending. The resistance of the panel significantly decreased after the local failure occurred. A three-dimensional finite element model was established to simulate the response of SC panels under low-velocity impact, in which the axial preload could be considered reasonably. The predicted displacements and impact force were in good agreement with the experimental results. Based on the validated model, a parametric study was conducted to further discuss the effect of the axial compressive preload.

• Journal of Family Resource Management and Policy Review
• /
• v.18 no.2
• /
• pp.163-182
• /
• 2014

This study examined the effects of informal grandparent-provided child care and support on married women's additional birth plans. This study applied panel data analysis to three waves of the Korean Longitudinal Survey of Women and Family (KLoWF) and obtained two major findings, as follows. First, having a mother-in-law and co-residing with parents-in-law had a positive influence on married working women's additional birth plans. Child care provision from the parents of a married working woman also positively influenced her additional birth plans. Second, the analysis showed that housework assistance from a woman's mother-in-law or mother had no effect on her birth plans in both models investigated: the additional birth plan model for all women, both employed and unemployed, and the additional birth plan model for only working women. In conclusion, the findings of this study demonstrated that child care availability, with grandparents as the trusted providers, is a more important factor in married women's additional birth plans than housework assistance from their mothers-in-law and mothers.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.15 no.1
• /
• pp.106-115
• /
• 2007

In this study, first, child headform model was built up, satisfying requirement in the headform validation test. Also, for decreasing both acceleration peak and deformation, a new hood with dome shaped forming in inner panel was investigated. Next, headform impact, complying with draft of EEVC W/G 17, on the central portion of the newly proposed hood were simulated for a steel hood and three aluminum hoods with different thickness for examining the material and thickness effect on HIC value and inner panel deformation. The analysis results explained that aluminum hoods with dome shaped forming in inner panel were highly promising not only for meeting headform safety regulations but also for leading to weight savings. Finally, hood edge design technology in order to reduce pedestrian injury due to the high stiffness of beam type edge and the rigid support, was discussed. Various types of the foam filled edge were designed and their headform safety performance were evaluated. The edge structure with foam filled in upper one third of section exhibited excellent results.

• Asian Journal of Business Environment
• /
• v.11 no.1
• /
• pp.17-25
• /
• 2021

Purpose: This study extends previous empirical work on the threshold effects of institutions on the relationship between infrastructure and economic growth. It does so by using three sub-indices of institutions as the threshold variable in place of aggregate index. This is with a view to determining the roles of the sub-indices in the nexus between infrastructure and economic growth. Research design, data and methodology: The analysis is based on a dynamic panel threshold regression model using a panel data set comprising 41 countries in Sub-Saharan Africa over the sample period of 1996-2015. Data are obtained from Ogbaro (2019). Results: The study finds that infrastructure exerts significant positive effects on economic growth below and above the threshold values of the three sub-indices, with higher effects above the threshold values. Results also show that on average, the Sub-Saharan African countries are not able to satisfy any of the threshold conditions, which accounts for their poor growth experience. Conclusion: The study concludes that countries with weak institutions do not benefit maximally from infrastructure development policies. The paper, therefore, recommends that countries in Sub-Saharan Africa need to focus on improving their institutional patterns if they are to reap the optimum benefits from their infrastructure development efforts.

• Journal of Korea Technology Innovation Society
• /
• v.21 no.2
• /
• pp.663-683
• /
• 2018

This study aims to analyze the effectiveness of R&D tax credit for SMEs. We surveyed to collect the information on firm's financial statements and R&D tax credit during 2014-2016, and implemented fixed effect model, random effect model and panel negative binomial model. The results show that the effect of R&D tax credit is 5.3 times larger in terms of R&D expenditure and 4.3 times bigger in terms of number of researchers than that of R&D subsidy. In addition, the effect of tax credit on non-metropolitan area companies is higher than that in the metropolitan area. Based on these results, we suggests three ways to improve the R&D tax incentive system for SMEs; To convert unused R&D tax credit of the start-ups to tax points, to exempt the minimum tax rate on R&D expenditure in equipment, and to unify the operation of various R&D tax credit institution.

• The Mathematical Education
• /
• v.50 no.1
• /
• pp.103-118
• /
• 2011

The study examined whether the relation between mathematics self-efficacy and mathematics achievement was partially mediated by the learning strategies, using latent growth model analyses. It was also examined the auto-regressive, cross-lagged (ARCL) panel model for testing the stability and change in the relation of mathematics self-efficacy and learning strategy over time. The study analyzed the first-year to the third-year data of the Korean Educational Longitudinal Survey (KELS). The result of ARCL panel model analysis showed that earlier mathematics self-efficacy could predict later learning strategy use. There were linear trends in mathematics self-efficacy, learning strategy, and mathematics achievement. Specifically, mathematics achievement was increased over the three time points, whereas mathematics self-efficacy and learning strategies were significantly decreased. In the analyses of latent growth models, the mediating effects of learning strategies were overall supported. That is, both of initial status and change rate of rehearsal strategy partially mediated the relation of mathematics self-efficacy and mathematics achievement. However, in elaboration and meta-cognitive strategies, only the initial status of each variable showed the indirect relationship.

• Computers and Concrete
• /
• v.34 no.1
• /
• pp.1-14
• /
• 2024

The design of disturbed regions in reinforced concrete structures usually applies the well known Strut and Tie Method (STM). As an alternative, the Stringer-Panel Method (SPM), an intermediate model between STM and the Finite Element Method (FEM), consists in dividing a structure into two distinct elements: the stringers (which carry axial forces) and panels (which carry shear forces). SPM has already showed good applicability in manual calculations and computer implementations, and its most known application was SPanCAD, an AutoCAD plugin for linear and nonlinear analysis by SPM. Unfortunately, SPanCAD was discontinued by the developers, and it's not compatible with the most recent versions of AutoCAD. So, this paper aims to present a computer program that was developed as an upgrade to the latter: the Stringer Panel Modelling Tool (SPMTool), which is intended to be an auxiliary design tool and it presents improvements, in comparison to SPanCAD. It is possible to execute linear and nonlinear analysis by three distinct formulations: Modified Compression Field Theory (MCFT), Disturbed Stress Field Model (DSFM) and Softened Membrane Model (SMM). The nonlinear results were compared to experimental data of reinforced concrete elements that were not designed by SPM; these elements were also analyzed in SPanCAD. On overall, SPMTool made more realistic predictions to the behavior of the analyzed structures than SPanCAD. Except for DSFM predictions for corbels (1.24), in overall average, the ultimate load predictions were conservative (0.85 to 0.98), which is a good aspect for a design tool. On the other hand, the cracking load predictions presented overestimations (1.06 to 1.47) and higher variations (25.59% to 34.25%) and the post-cracking behavior could not be accurately predicted; for this use case, a more robust finite element software is recommended.

• Steel and Composite Structures
• /
• v.42 no.2
• /
• pp.277-288
• /
• 2022

A novel flat steel plate-concrete-corrugated steel plate (FS-C-CS) sandwich panel was proposed for resisting impact load. The failure mode, impact force and displacement response of the FS-C-CS panel under impact loading were studied via drop-weight impact tests. The combined global flexure and local indentation deformation mode of the FS-C-CS panel was observed, and three stages of impact process were identified. Moreover, the effects of corrugated plate height and steel plate thickness on the impact responses of the FS-C-CS panels were quantitatively analysed, and the impact resistant performance of the FS-C-CS panel was found to be generally improved on increasing corrugated plate height and thickness in terms of smaller deformation as well as larger impact force and post-peak mean force. The Finite Element (FE) model of the FS-C-CS panel under impact loading was established to predict its dynamic response and further reveal its failure mode and impact energy dissipation mechanism. The numerical results indicated that the concrete core and corrugated steel plate dissipated the majority of impact energy. In addition, employing end plates and high strength bolts as shear connectors could prevent the slip between steel plates and concrete core and assure the full composite action of the FS-C-CS panel.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2003.07a
• /
• pp.714-717
• /
• 2003

We have suggested several plasma display panel (PDP) cell structures for high luminance and low power consumption by our two-and three-dimensional fluid simulation codes. Generally, to improve luminous efficiency and discharge efficiency, it is known that it is lucrative to use long discharge path and to form low electric field. However, the problems are how to implement them effectively in the small PDP cell. Therefore, unlike conventional model, we suggest Front Three Electrodes (FTE) model. In this model, we tried to make long and V-shaped discharge path by geometry changes and driving pulse variations. Consequently, from our simulation results based on the model above, luminous efficiency has improved about 2.6 times.

• Journal of Korean Society of Transportation
• /
• v.30 no.1
• /
• pp.103-112
• /
• 2012

This research introduces a trip generation model reflecting time-series effects derived from a panel analysis with the data collected from the national household trip surveys conducted in 1996, 2002 and 2006. The existing methods are unable to reflect time-series effects from the change of socioeconomic conditions because the parameters applied to the model were basically from the base year of study - the parameter values were unchanged. This study proposes a new trip generation model developed through a panel analysis performed with the data collected from the last three national household trip surveys. From the results, it was found that the number of school trips increases and that the number of shopping trips decreases as time passes. The results showed that there are time-series effects affecting in trip generation.