• Journal of the Korea Concrete Institute
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• v.22 no.5
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• pp.641-650
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• 2010

The concrete cracking from the restrained stress caused by the shrinkage may play significant cause of deterioration of concrete structures by allowing the permeation of sulphate and chloride ions which in turn triggers corrosion of steel reinforcement. In particular, the cracking becomes more critical as water binder ratio (W/B) is reduced and concrete strength increases. Therefore, it needs to evaluate correctly the comprehensive shrinkage behavior of concrete with high strength: high-strength concrete (HSC), ultra-highstrength concrete (UHSC). The unrestrained shrinkage tests, however, cannot estimate the net shrinkage effectively which affects cracking after full development of strength and stiffness because it does not consider the degree of restraint, strength development, stress relaxation, and so on. Therefore, in this study, both free and restrained shrinkage tests with variables of W/B (W/B of 30, 25 and 16%) and admixtures (fly ash (FA) and granulated blast-furnace slag (BFS)) for HSC, very-high-strength concrete (VHSC) and UHSC were performed. The test results indicated that the autogenous shrinkage and total shrinkage at drying condition were reduced as W/B increased and FA, BFS were added, and the cracking behavior was suppressed as W/B increased and FA was added.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.1920-1925
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• 2007

A transformer is a device that changes the current and voltage by electricity induced between coil and core steel, and it is composed of metals and insulating materials. In the core of the transformer, the thermal load is generated by electric loss and the high temperature can make the break of insulating. So we must cool down the temperature of transformer by external radiators. According to cooling fan's usage, there are two cooling types, OA(Oil Natural Air Natural) and FA(Oil Natural Air Forced). For this study, we used Fluent 6.2 and analyzed the cooling characteristic of radiator. we calculated 1-fin of detail modeling that is similar to honeycomb structure and multi-fin(18-fin) calculation for OA and FA types. For the sensitivity study, we have different positions(side, under) of cooling fans for forced convection of FA type. The calculation results were compared with the measurement data which obtained from 135.45/69kV ultra transformer flowrate and temperature test. The aim of the study is to assess the Fluent code prediction on the radiator calculation and to use the data for optimizing transformer radiator design.

• The Journal of Asian Finance, Economics and Business
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• v.7 no.6
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• pp.525-535
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• 2020

The study aims to investigate the roles of financial education (FE) as a moderator to financial attitude (FA), parental financial socialisation (PFS), and financial literacy (FL) to ensure the success of prudent financial management practices (PFMP) among Malaysian youth. The study was designed quantitatively and employed self-administered questionnaires, which were adopted from previous studies and distributed to 480 youths in Malaysia. The data were analyzed using Partial Least Squares Structural Equation Modeling (PLS-SEM) to test hypotheses of the study. The results showed FA, PFS and FL have significant and positive relationship with PFMP. However, as regards moderating interaction of FE, results showed that FE does not significantly moderate the relationship between FA, PFS and FL with PFMP. The results further highlighted serious concerns on the effectiveness of FE towards improving youth capability in managing their financial affairs prudently. This proved that mandated FE prior to graduation has less effect and does not lead to behavior changes among Malaysian youth. It shows the challenges faced by the country stakeholders to strengthen FE, enhance the effectiveness and encompass the right FE elements to ensure today's young Malaysians are able to apply what they learned in the classroom to their real life.

• Steel and Composite Structures
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• v.51 no.5
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• pp.529-543
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• 2024

The bonding efficacy of steel I-section embedded in metakaolin-fly ash-based geopolymer concrete (MK-FA-GC) was investigated in this study. Push-out tests were conducted on nine column specimens to evaluate the influence of compressive strength of concrete, embedded length of steel I-section, thickness of concrete cover, and stirrup ratio on the bond performance. Failure patterns, load-slip relationships, bond strength, and distribution of bond stress among the specimens were analyzed. The characteristic bond strength of geopolymer concrete (GC) increased with higher compressive strength, longer embedded steel section length, thicker concrete cover, and larger stirrup ratio. Empirical formulas for bond strength at the loading end were derived based on experimental data and a bond-slip constructive model for steel-reinforced MK-FA-GC was proposed. The calculated bond-slip curves showed good agreement with experimental results. Furthermore, numerical simulations using ABAQUS software were performed on column specimens by incorporating the suggested bond-slip relationship into connector elements to simulate the interface behavior between MK-FA-GC and the steel section. The simulation results showed a good correlation with the experimental findings.

• Journal of the Korean Geotechnical Society
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• v.16 no.3
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• pp.5-13
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• 2000

In this study, the Disturbed State Concept (DSC) constitutive model is calibrated and modified for steel-sand interface by using the HiS S model for relative intact (Rl) state and the critical state model for the fuBy adjusted (FA) part in the material. The general formulation for implementation is developed. Then, the DSC model with modification for interface is implemented in finite element program based on the generalized Biot's theory. The interface test under one-way monotonic and two-way cyclic loading were numerically simulated using the finite element program modified in this study. The DSC predictions show improved agreement with the observed results from laboratory test. Overall, the computer procedure with the DSC allows relatively improved simulation ofthe soil-structure interaction problems.oblems.

• Journal of Korean Neurosurgical Society
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• v.55 no.5
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• pp.267-272
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• 2014

Objective : Differentiation of demyelination in white matter from axonal damage can be determined using diffusion tensor imaging (DTI). In this study using meningioma patients an attempt was made to evaluate the relationship between preoperative weakness and the changes of diffusion parameters in the corticospinal tract (CST) using DTI. Methods : Twenty-six patients with meningioma were enrolled in this study. Eleven of them suffered from objective motor weakness and were classified as Group 1. The remaining 15 patients did not present motor weakness and were classified as Group 2. Fiber tractography and CST diffusion parameters were obtained using DTIStudio. The ratios (lesion side mean value/contralateral side mean value) of CST diffusion parameters were compared with 1.0 as a test value using a one-sample t-test. Results : In Group 1, fractional anisotropy (FA), tensor trace (TT), and radial diffusivity (RD, ${\lambda}2$ and ${\lambda}3$) of the CST were significantly different between two hemispheres, but axial diffusivity (AD, ${\lambda}1$) of the CST was not significantly different between two hemispheres. In Group 2, FA and ${\lambda}3$ of CST did not differ significantly between the hemispheres. In Group 2, TT, ${\lambda}1$, and ${\lambda}2$ of CST in the ipsilateral hemisphere were significantly higher than those of the unaffected hemisphere. However, the differences were small. Conclusion : Motor weakness was related to a low FA and high TT resulting from increased RD of the CST fibers. CST diffusion changes in patients with weakness are similar to those for demyelination.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.9
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• pp.967-973
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• 2003

This paper presents a new predistortion method which injects the 2nd low-frequency intermodulation signal of RF signals into the input bias line of the amplifier. New 2nd intermodulation signal extraction circuit is also proposed. We have shown that this method can suppress the 3rd IM apparently and sometimes do the 5th IM, through mathematical analysis, then confirmed it with simulation and verified it on the desk test. When the input signal CDMA IS-95 lFA is applied, measured ACPR improvements are 25 dBc, 22.5 dBc, and 6 dBc at 0.885 MHz, l.25 MHz and 2.25 MHz offset respectively. Also, when applying the CDMA IS-95 3FA, the measured ACPR improvement is 20 dBc at 0.885 MHz offset.

• Journal of the Korean Society of Radiology
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• v.12 no.2
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• pp.253-260
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• 2018

Diffusion tensor images were obtained to investigate the damage of brain white matter in non-smokers and an adequate drinking group (less than 10 points) selected by scores of the Korean versions of alcohol use disorders identification test questionnaire. Factional anisotropy (FA) values, according to the variables of age and body mass index (BMI), were not statistically significant in all regions of the brain white matter after measurement of factional anisotropy (FA) values by the tract-based spatial statics (TBSS) method. In other words, age and body mass index (BMI) do not significantly affect the microstructural changes of the brain white matter.

• The korean journal of orthodontics
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• v.51 no.5
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• pp.329-336
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• 2021

Objective: To compare the magnitude of external apical root resorption (EARR) 6 months after starting orthodontic treatment using orthodontic aligners (OAs) and fixed appliances (FAs). Methods: This parallel randomized clinical trial included 40 patients randomized into two groups: OA group (n = 20, 160 incisors) and FA group (n = 20, 160 incisors). For evaluation of the tooth length, periapical radiographs and standardized linear measurements of the maxillary and mandibular incisors were acquired before (T0) and 6 months after treatment initiation (T1). EARR was calculated through the difference in length between the two time points (T1-T0). Statistical comparisons were performed by means of using t-tests, chi-squared test and covariance analysis (a = 5%). Results: Rounding of the root apex was observed in both groups; the resorption involved 2.88% of the root length, so 97.12% of the tooth length remained intact. Intragroup comparisons between the two time points revealed a significant difference, with (T1-T0) ranging from -0.52 to -0.88 mm in the FA group and from -0.52 to -0.85 mm in the OA group. In the intergroup comparisons, only tooth #21 presented a statistically significant difference (OA: -0.52 ± 0.57 mm, FA: -0.86 ± 0.60 mm); however, the overall differences between groups were not clinically relevant, ranging from 0.03 to 0.35 mm. Conclusions: OA and FA treatment resulted in a similar degree of EARR in the maxillary and mandibular incisors at 6 months after treatment initiation. However, the amount of resorption was small and does not impair tooth longevity.

• Journal of the Korean Recycled Construction Resources Institute
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• v.1 no.3
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• pp.211-218
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• 2013

Cyclic wet and dry conditions in the marine environment structures corrosion is known to be the fastest rising. For that reason, accelerated corrosion test methods for the reproduction of tidal environment has been actively conducted. However, many studies have estimated threshold value for steel corrosion or concentrated in chloride penetration analysis. In this study, cyclic wet and dry conditions to reproduce the structure of the environment in accelerated corrosion and chloride penetration test analysis was performed. Corrosion was determined by the result of reinforcement corrosion monitoring based on galvanic potential measurement and half-cell potential method. Accelerated corrosion test results for each formulation was different corrosion periods, the order OPC> FA> BS> High-strength concrete. FEM durability interpretation program DuCOM was conducted under the same conditions as in accelerated corrosion test. The experimental RCPT tests demonstrated the validity of the result.