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Lee S.,Inha Technical College | Lee B.-J.,Namseoul University
Surface and Coatings Technology | Year: 2012

In the present work, we report the formation of residual oxide layer during chemical-mechanical-planarization (CMP) process in the carbon nanotube (CNT) via interconnects and some feasible solutions for its removal. Residual oxide layer makes electrically poor contact between CNTs and metal resulting in high contact resistance in CNT via interconnects. We adopt post-CMP processes such as hydrofluoric acid (HF) or Ar plasma treatment to remove the residual oxide layer. X-ray photoelectron spectroscopy (XPS) was used to confirm the chemical state of samples before and after the post-CMP process. Silicon and oxygen peaks from silicon-based oxide layer observed after the CMP process were disappeared and reduced in its intensity by the post-CMP process, respectively. Furthermore, via resistance decreased more than 1 order of magnitude after the post-CMP process. It is found that the post-CMP process provides good electrical contact between CNTs and metal by removing the residual oxide layer. © 2011 Elsevier B.V.


Yang K.-H.,Kyonggi University | Yi S.-T.,Inha Technical College
Magazine of Concrete Research | Year: 2016

The tensile characteristics of lightweight aggregate concrete under direct tension were examined with a view to enhancing the utilisation of artificially expanded clay granules as secondary aggregates. Ready-mixed concrete specimens were classified into two groups: all-lightweight concrete (ALWC) and sand-lightweight concrete (SLWC). The test parameters considered for each group were the maximum aggregate size (4-19 mm) and the lateral depth of specimens with a rectangular section (100-500 mm). The complete stress-crack mouth opening displacement (CMOD) response was measured under direct tension. The results show that the slope of the ascending branch of the stress-CMOD curve is slightly smaller for SLWC specimens than for ALWC specimens. The displacement at peak stress tends to increase with the lateral depth of the specimen, whereas the tensile strength of the concrete decreases, revealing the size effect phenomenon. However, the tensile strength of concrete and the softening slope at the descending branch of the stress-CMOD curve are marginally affected by the specimen's lateral depth and maximum aggregate size, owing to the reduced aggregate interlocking capacity across the crack. Gopalaratnam and Shah's model was modified to evaluate the stress-CMOD responses of the lightweight aggregate concretes, and the suggested and existing models were compared with the test results. © 2016, ICE Publishing. All rights reserved.


do Lee C.,Inha Technical College
Metals and Materials International | Year: 2014

The aim of the present study was to investigate the contribution of the strain rate to the transition of elastic-plastic deformation behavior and the difference between the fatigue strength coefficient and monotonic tensile strength in terms of the modified Basquin’s relation, which considers microporosity variation. The transition phenomena of elastic-plastic deformation were evaluated through comparison of the overall contour of the hysteresis loops measured in high cycle fatigue tests of a low-pressure die-cast A356 alloy. The increase of the alternating stress amplitude at a given excitation frequency causes a variation in the strain rate per unit time interval that depends fundamentally on the excitation frequency. In addition, the transition of elastic-plastic deformation behavior is induced by variation of strain rate in high cycle fatigue test, i.e., typically, a variation of the elastic modulus and extension of the elastic deformation region, compared with monotonic deformation under a very slow strain rate. The dependence of the elastic modulus on the strain rate due to the variation of the stress amplitude can be described in an exponential form of strain rate. The modified Basquin’s equation which includes the contribution of the strain rate and microporosity to the fatigue strength coefficient and fatigue life was re-established, including the dependence of the elastic modulus and transition of elastic-plastic deformation on the variation of the strain rate. © 2014, The Korean Institute of Metals and Materials and Springer Science+Business Media Dordrecht.


Lee J.-I.,Inha Technical College
International Journal of Precision Engineering and Manufacturing | Year: 2012

This paper addresses the prediction of the distributed material properties of a microstructure. Predictions were made by measuring the dynamic response of fabricated materials used in the microstructures. When these distributed material properties are used to estimate the mechanical performance of microstructures, differences between computer simulations and the experimental results can be reduced, and reliable design can be developed. The distributed material properties of a micro-electromechanical system(MEMS)-based gyroscope were obtained numerically using the proposed method and experimentally using dynamic testing. The natural frequency of the numerical analysis was slightly higher (first mode: - 0.43 Hz, second mode: 0.33 Hz) than the result from the dynamic testing because some properties such as the microstructure porosity were neglected. © KSPE and Springer 2012.


The variability in the tensile elongation of squeeze-cast Al-10%Si-2%Cu-0.4%Mg alloy was investigated in terms of the defect susceptibility to the effective void area fraction, which is the sum of the additional void area caused by damage evolution of eutectic Si particles and the void area of pre-existing microvoids. Additional theoretical verification was performed by constitutive prediction. The tensile elongation of as-cast and T6-treated alloys is described as a power law relationship to the variation of the effective void area fraction. The anisotropic fracture damage of eutectic Si particles has a significant contribution to the total effective void area fraction when compared with the variation of load-bearing capacity by microporosity. The constitutive model can precisely predict the defect susceptibility of tensile elongation to the variation of effective void area fraction. Additionally, the model suggests that the tensile deformation of Al-10%Si-2%Cu-0.4%Mg alloy is affected by the maximum effective void area, which corresponds with extremes of the distribution frequency, rather than the average value of the microstructural characteristics, especially over a wide-range distribution of aspect ratio of Si particles. © 2010.


Lee C.D.,Inha Technical College
Metals and Materials International | Year: 2010

The variability in the tensile strength of as-cast AM60 and AZ91 alloys was investigated in terms of the defect susceptibility to the variation in grain size and microporosity. The microporosity was measured from the quantitative fractography analysis through scanning electron microscopy (SEM) observation on fractured surface after tensile test. The ultimate tensile strength (UTS) of both alloys can be characterized as a power law relationship to microporosity variation in terms of the defect susceptibility and maximum strength achievable in the defect-free condition. The defect susceptibility of tensile strength to microporosity variation is decreased remarkably with grain refinement. The defect susceptibility of AZ91 alloy to microporosity variation exhibits more sensitive dependence on the variation in grain size than AM60 alloy. Also, the dependence of UTS on the variation in grain size is described as a power law relationship for various levels of microporosity. The variation on effective void area fraction by the damage evolution of Mg17Al12 phase may introduce a practically significant decrease of load bearing capacity, less than by microporosity variation. The Hall-Petch relation of both alloys in the defect-free condition could be suggested as maximum values of friction stress and locking parameter. ©KIM and Springer.


Kim D.W.,Inha Technical College
ICCAS 2015 - 2015 15th International Conference on Control, Automation and Systems, Proceedings | Year: 2015

Intelligent humanoid robot (IHR) consisting of intelligent software components is proposed in this paper. The framework of an IHR requires reliable and stable network connection with real-time response between software components. In the developed service platform, intelligent software components work on the resources that are distributed in the network, and the IHR uses the results from the resources. In this way, the IHR is able to provide high-quality and intelligent service to users. In this framework, middleware CORBA (Common Object Request Broker Architecture) are designed to integrate software components into an IHR system. © 2015 Institute of Control, Robotics and Systems - ICROS.


Kang S.Y.,Inha Technical College
Journal of Korean Institute of Metals and Materials | Year: 2012

Carbon diffusion of ultra low carbon steel treated at 880°C and 930°C for 10, 30, 60 and 120 minutes was investigated using optical microscopy, SAM, EPMA, and Micro Vickers. The martensite patterns of the specimens treated at 880°C and 930°Cwere different. Martensite in the ferrite region was found in the specimen treated at 8801C because of grain boundary diffusion. Such phenomena is explained by a carbon diffusion model. Copyright © 2012 The Korean Institute of Metals and Materials.


Kang S.Y.,Inha Technical College
Journal of Korean Institute of Metals and Materials | Year: 2012

Strength change in ultra low carbon steel carburized at 880°C and 930°C for 10, 30, 60 and 120 minutes was investigated. The results were analyzed by a tensile test, chemical composition analysis, optical microscopy and scanning electron microscopy. Stress in the 0.5% strain specimen in the tensile test increased as the time treated at 880°C and 930°C increased, because the carbon diffusion layer and the martensite of the specimen increased with increasing treatment time. Martensite was found in the ferrite region in the specimen treated at 880°C, which is attributed to grain boundary diffusion. Copyright ©2012 The Korean Institute of Metals and Materials.


The present study aimed to optimize the conditions for the T6 heat treatment of low-pressure die-cast A356 alloy in terms of the dependence of fatigue properties on microporosity variation. The fatigue property was evaluated using a high cycle fatigue test, and the microporosity was based on the fractographic porosity measured through SEM imaging of a fractured surface. The number of cycles to failure for the A356 alloy depends on the variations in microporosity through an exponential relationship. Because the fatigue strength coefficient and exponent of the S-N curve is always underestimated in the presence of microvoids, the evaluation of the number of cycles to failure achievable in a defect-free condition has practical significance. Detailed suggestions for improving the number of cycles to failure were accomplished based on the modified Basquin's equation, which fundamentally determines the number of cycles to failure from both the defect susceptibility of the tensile strength and the maximum achievable tensile strength in a defect-free environment. A T6 heat treatment with solutionizing and aging treatment times of 6. h at 540 °C and 16. h at 160 °C, respectively, is proposed as the optimal conditions for improving the number of cycles of A356 alloy at stress amplitudes of less than 200. MPa. © 2012 Elsevier B.V.

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