• Journal of the Institute of Electronics Engineers of Korea SD
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• v.45 no.4
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• pp.57-63
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• 2008

In this paper, the dependence of MOSFET performance on the channel stress is characterized in depth. The tensile and compressive stresses are applied to CMOSFET using a nitride film which is used for the contact etch stop layer (CESL). Drain current of NMOS and PMOS is increased by inducing tensile and compressive stress, respectively, due to the increased mobility as well known. In case of NMOS with tensile stress, both decrease of the back scattering ratio ($\tau_{sat}$) and increase of the thermal injection velocity ($V_{inj}$) contribute the increase of mobility. It is also shown that the decrease of the $\tau_{sat}$ is due to the decrease of the mean free path ($\lambda_O$). On the other hand, the mobility improvement of PMOS with compressive stress is analyzed to be only due to the so increased $V_{inj}$ because the back scattering ratio is increased by the compressive stress. Therefore it was confirmed that the device performance has a strong dependency on the channel back scattering of the inversion layer and thermal injection velocity at the source side and NMOS and PMOS have different dependency on them.

• Journal of the Korea Concrete Institute
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• v.21 no.5
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• pp.589-597
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• 2009

High Performance Fiber-reinforced Cement Composite (HPFRCC) shows the multiple crack and damage tolerance capacity due to the interfacial bonding of the fibers to the cement matrix. For practical application, it is needed to investigate the fractural behavior of HPFRCC and understand the micro-mechanism of cement matrix with reinforcing fiber. This study is devoted to the investigation of the AE signals in HPFRCC under monotonic and cyclic uniaxial compressive loading, and total four series were tested. The major experimental parameters include the type and volume fraction of fiber (PE, PVA, SC), the hybrid type and loading pattern. The test results showed that the damage progress by compressive behavior of the HPFRCC is a characteristic for the hybrid fiber type and volume fraction. It is found from acoustic emission (AE) parameter value, that the second and third compressive load cycles resulted in successive decrease of the amplitude as compared with the first compressive load cycle. Also, the AE Kaiser effect existed in HPFRCC specimens up to 80% of its ultimate strength. These observations suggested that the AE Kaiser effect has good potential to be used as a new tool to monitor the loading history of HPFRCC.

• Journal of the Korea Concrete Institute
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• v.13 no.5
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• pp.516-524
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• 2001

Among many connection methods of reinforcing bar, the grout-filled splice sleeve system is very effective method of precast concrete construction due to its superior construction efficiency, such as large allowable limit to arrangement of reinforcing bars, good application of large sized reinforcing bars. In this study, totally 20 full-sited specimens were made and tested under monotonic and cyclic loading in order to extend the usage range of grout-filled splice sleeve system. The experimental variables adopted in this study are size of reinforcing bars embedded in upper and lower part of sleeve and compressive strength of filled mortar etc. After test was performed, the results were compared and analyzed with respect to previous test of author. Following main conclusions are obtained : 1) The structural performance of splice sleeve system is improved with increasing compressive strength of filled mortar. And also it was verified that the splice sleeve system with over 700 kgf/㎠ mortar compressive strength and over 6.54 development length of reinforcing bar retains the structural performance of over A class(AIJ Criteria). 2) In the case of using different size of reinforcing bars embedded in upper and lower part of sleeve, the result show that splice sleeve matching with large sized reinforcing bar must be used. And also up to 2 level smaller size of reinforcing bar compared to large reinforcing bar embedded in sleeve can be used.

• Magazine of the Korean Society of Agricultural Engineers
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• v.45 no.3
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• pp.41-49
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• 2003

In this study, durability performance of blended cement mortars is evaluated when various mineral admixtures are used with the cement. A comprehensive evaluation of the effects of mineral admixtures on the mortar performance was made. The properties of fresh and hardened blended mortars investigated include slump flow and compressive strength. The durability characteristics of cement materials incorporating the mineral admixtures under various physical and chemical causes of deterioration was investigated. The laboratory test results indicate that mechanical and durability properties of blended cement mortars have superior performance rather than ordinary cement mortars.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.917-920
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• 2006

This paper reports a comparative study for performance evaluation guidelines for bridge bearings. Guidelines for bridge bearings such as KS, EN1337, AASHTO LRFD, and Japanese code were analyzed. In addition, fatigue tests of elastomeric bearing are being conducted for allowable shear deformation and compressive stress. Based on literature survey and tests, the innovative concept of performance evaluation guidelines for bridge bearings is suggested.

• The Journal of the Acoustical Society of Korea
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• v.39 no.3
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• pp.191-199
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• 2020

Currently, studies on the estimation algorithm based on compressive sensing are actively underway, but to the best of our knowledge, no study on the performance of the Sparse Spectrum Fitting (SpSF) algorithm in nonuniform sensor arrays has been made. This paper deals with the derivation of the compressive sensing based covariance fitting algorithm extended to the frequency domain. In addition, it shows the performance of directon-of-arrival estimation of the frequency domain SpSF algorithm in non-uniform linear sensor array system and the sensor array failure situation.

• Steel and Composite Structures
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• v.25 no.3
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• pp.299-314
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• 2017

The aim of this paper is to investigate the performance of Lightweight Aggregate Concrete Filled Steel Tube (LWCFST) columns experimentally and compare to the behavior of Self-Compacted Concrete Filled Steel Tube (SCCFST) columns under axial loading. Four different L/D ratios and three D/t ratios were used in the experimental program to delve into the compression behaviours. Compressive strength of the LWC and SCC are 33.47 MPa and 39.71 MPa, respectively. Compressive loading versus end shortening curves and the failure mode of sixteen specimens were compared and discussed. The design specification formulations of AIJ 2001, AISC 360-16, and EC4 were also assessed against test results to underline the performance of specification methods in predicting the compression capacity of LWCFST and SCCFST columns. Based on the behaviour of the SCCFST columns, LWCFST columns exhibited different performances, especially in ductility and failure mode. The nature of the utilized lightweight aggregate led to local buckling mode to be dominant in LWCFST columns, even the long LWCFST specimens suffered from this behaviour. While with the SCCFST specimens the global buckling governed the failure mode of long specimens without any loss in capacity. Considering a wide range of column geometries (short, medium and long columns), this paper extends the current knowledge in composite construction by examining the potential of two promising and innovative structural concrete types in CFST applications.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.2
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• pp.943-948
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• 2013

In this study, the characteristics of polymer-modified mortar which include UM resin, eco-friendly resin, was studied for improving the durability of concrete. UM and cement mortar were mixed with a certain percentage. Eco-friendly UM resin polymer-modified mortar was evaluated by compressive strength, splitting tensile strength, flexural strength, water absorption and chemical resistance experiments. The characteristics of eco-friendly UM resin polymer-modified mortar were evaluated by experiments. Performance of compressive strength and splitting tensile strength were decreasing. On the other hand, performance of flexural strength, water absorption and chemical resistance were increasing. Eco-friendly UM resin polymer-modified mortar reinforced concrete durability performance is excellent.

• Structural Engineering and Mechanics
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• v.71 no.3
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• pp.211-221
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• 2019

To study the eccentric compression behavior of ultra-high performance fiber reinforced concrete (UHPFRC) columns, six UHPFRC columns and one high-strength concrete (HSC) column were tested. Variation parameters include load eccentricity, volume of steel fibers and stirrup ratio. The crack pattern, failure mode, bearing capacity, and deformation of the specimens were studied. The results showed that the UHPFRC columns had different failure modes. The large eccentric compression failure mode was the longitudinal tensile reinforcements yielded and many horizontal cracks appeared in the tension zone. The small eccentric compression failure mode was the longitudinal compressive reinforcements yielded and vertical cracks appeared in the compressive zone. Because of the bridging effect of steel fibers, the number of cracks significantly increased, and the width of cracks decreased. The load-deflection curves of the UHPFRC columns showed gradually descending without sudden dropping, indicating that the specimens had better deformation. The finite element (FE) analysis was performed to stimulate the damage process of the specimens with monotonic loading. The concrete damaged plasticity (CDP) model was adopted to characterize the behaviour of UHPFRC. The contribution of the UHPFRC tensile strength was considered in the bearing capacity, and the theoretical calculation formulas were derived. The theoretical calculation results were consistent with the test results. This research can provide the experimental and theoretical basis for UHPFRC columns in engineering applications.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.11a
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• pp.69-70
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• 2023

The development of advanced 3D printing technologies has opened up new opportunities for customized digital designs in the construction industry. Using nano- and micro-scale additives is expected to improve the performance of cement-based materials in 3D printing. TiO₂ particles have been widely used as reinforcing additives in cement-based materials. Therefore, this study aims to investigate the application of cement-based materials containing multi-size TiO₂ particles in binder jet 3D printing and the effect of different-size TiO₂ particles on the performance of printed samples. TiO₂ particles exhibit an excellent filling effect, which increases the density of the printed samples and promotes hydration, thereby improving the compressive strength of the samples. In addition, larger TiO₂ particles exert more pronounced filling and photocatalytic effects on the resulting samples.