• Proceedings of the Korean Geotechical Society Conference
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• 2009.03a
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• pp.361-367
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• 2009

The criteria such as ASTM recommends that the zero reading process of CPT must be performed in the same temperature condition with underground in order to reduce the effect of temperature. However, this method can not consider the change of temperature occurred during penetration. In this study, ultra small size temperature sensor with 0.5mm in diameter is manufactured to estimate and compensate the effect of temperature by using FBG sensor. The continuous temperature changes are monitored during cone penetration by using FBG temperature sensor installed in cone penetrometer. The temperature compensated tip resistances show the uniform and similar distributions with depth in different with originally measured tip resistance in cohesive soil. This study verifies that the tip resistances measured by previous zero reading method are affected by the change of underground temperature, and suggests the new temperature compensation technique using by FBG temperature sensor.

• Journal of Magnetics
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• v.6 no.4
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• pp.132-141
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• 2001

The switching characteristics and the magnetization-flop behavior in magnetic tunnel junctions exchange biased by synthetic antiferromagnets (SyAFs) are investigated by using a computer simulations based on a single-domain multilayer model. The bias field acting on the free layer is found to be sensitive to the thickness of neighboring layers, and the thickness dependence of the bias field is greater at smaller cell dimensions due to larger magnetostatic interactions. The resistance to magnetization flop increases with decreasing cell size due to increased shape anisotropy. When the cell dimensions are small and the synthetic antiferromagnet is weakly, or not pinned, the magnetization directions of the two layers sandwiching the insulating layer are aligned antiparallel due to a strong magnetostatic interaction, resulting in an abnormal magneto resistance (MR) change from the high-MR state to zero, irrespective of the direction of the free-layer switching. The threshold field for magnetization-flop is found to increase linearly with increasing antiferromagnetic exchange coupling in the synthetic antiferromagnet. Irrespective of the magnetic parameters and cell sizes, magnetization flop does not exist near zero applied field, indicating that magnetization flop is driven by the Zeeman energy.

• Proceedings of the KSR Conference
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• 2008.11b
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• pp.1078-1083
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• 2008

In this paper, assessed are the stability of vehicle and track according to vertical support stiffness difference on the transition between conventional and zero-longitudinal resistance (ZLR) rail fastener on bridge. For this, the spring constants of rail fastener have been determined according to different load ranges - KTX load (with or without impact factor) and test load of EN standards - from results of laboratory test on rail pad, the stability analysis of vehicle and track has been performed according to numbers or installation length of ZLR fasteners using vertical vehicle-track coupled model to consider train-track interaction. The analysis results reveal that only the wheel load variation slightly exceed the limit value when 2 ZLR fasteners are used with spring constant determined within the EN test load range, but, in all other cases, all evaluation items are satisfied. Thus, it can be said that the stability of vehicle and track will not be degraded by ZLR fastener.

• Journal of the Microelectronics and Packaging Society
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• v.29 no.4
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• pp.77-82
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• 2022

During etching process of PCB, the electroplated copper line and seed layer copper have different etching rates and it caused the over etching of copper line as well as undercut of lines. In this research, the effects of etchants composition on copper etching characteristics were investigated. The optimum concentration of hydrogen peroxide and sulfuric acid of etchants were obtained using polarization and OCV (open circuit voltage) analysis for both rolled copper and electroplated copper. The inhibiting effects of different inhibitors were investigated using OCV and ZRA (zero resistance ammeter) analysis. The galvanic current between electroplated copper and seed layer copper were measured using ZRA method. Inhibitors for least galvanic current could be chosen based on galvanic coupling in ZRA analysis.

• Journal of the Korean Society of Marine Environment & Safety
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• v.22 no.5
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• pp.564-575
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• 2016

The present study provides numerical simulations to predict the added resistance and ship motion of the KVLCC2 in regular waves using the unsteady Reynolds-Averaged Navier-Stokes (URANS) and 3-D potential methods. This numerical analysis is focused on added resistance and vertical ship motions (heave and pitch) under a wide range of wave conditions at three ship speeds (design, operating and zero speeds). Firstly, the characteristics of the CFD and 3-D potential flow methods are presented to predict added resistance and ship motions in regular waves taking into account various wave conditions at design speed to provide a validation study as well as at operating and zero speeds. Secondly, analyses of added resistance and ship motion with unsteady wave patterns and time history results as simulated by CFD were performed at each ship speed. Systematic validation and verifications of the numerical computations in this study were made against available Experimental Fluid Dynamics (EFD) data including grid convergence tests to demonstrate that reliable numerical results were obtained for the prediction of added resistance and ship motion in waves. Relationships between added resistance, vertical motion and changes in ship speeds were also found.

• Advances in concrete construction
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• v.8 no.2
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• pp.127-137
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• 2019

Roller Compacted Concrete (RCC) is a zero slump concrete consisting of a mixture of cementitious materials, sand, dense graded aggregates and water. In this study, an attempt has been made to investigate the effect of aggregate type on strength and abrasion resistance of RCC made by using granulated blast furnace slag (GGBS) as partial replacement of cement. Mix proportions of RCC were finalized based upon the optimum water content achieved in compaction test. Two different series of RCC mixes were prepared with two different aggregates: crushed gravel and limestone aggregates. In both series, cement was partially replaced with GGBS at a replacement level of 20%, 40% and 60%. Strength Properties and abrasion resistance of the resultant mixes was investigated. Abrasion resistance becomes an essential parameter for understanding the acceptability of RCC for rigid pavements. Experimental results show that limestone aggregates, with optimum percentage of GGBS, perform better in compressive strength and abrasion resistance as compared to the use of crushed gravel aggregates. Observed results are further supported by stoichiometric analysis of the mixes by using basic stoichiometric equations for hydration of major cement compounds.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.6
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• pp.876-885
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• 2000

A new and simple method is presented for determining the parasitic resistances of MESFET and HEMT from the measured S-parameters under normal active bias without depending on additional DC measurements or iteration or optimization process. The presented method is based on the fact that the difference between source resistance(Rs) and drain resistance(Rd) can be obtained from the measured Z-parameters under zero bias condition. It is possible to define the new internal device including intrinsic device and 3 parasitic resistances by elimination the parasitic inductances and capacitances from the measured S-parameters. Three parasitic resistances are calculated easily from the fact that the real parts of Yint,11 and Yint,12 of intrinsic Y-parameters are zero theoretically and the relations between S-,Z-, Y-matrices. The calculated parasitic resistances using the presented method and successively calculated equivalent circuit parameters give modeled S-parameters which are in good agreement with the measured S-parameters up to 400Hz.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2000.02a
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• pp.109-111
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• 2000

A magnetic field sensor is fabricated with superconducting ceramics of Y-Ba-Cu-O system. The prepared material shows the superconductivity at about 95K. The sensor at liquid nitrogen temperature shows the increase in electrical resistance by applying magnetic field. Actually, the voltage drop across the sensor is changed from zero to a value more than 100$\mu$V by the applied magnetic field. The change in electrical resistance depends on magnetic field. The sensitivity of this sensor is 2.9 ohm/T. The sensing limit is about $1.5\times$$10^{-5}$ (=1.5$\times$$10^{-1}$ G). The increase in electrical resistance by the magnetic field is ascribed to a modification of the Josephson junctions due to the penetrating magnetic flux into the superconducting material.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07a
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• pp.115-118
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• 2003

The sensor at liquid nitrogen temperature showed the increase of electrical resistance by applying magnetic field. Actually, the voltage drop across the sensor was changed from zero to a value more than $100\;{\mu}V$ by the applied magnetic field. The change of electrical resistance depended on magnetic field. The sensitivity of this sensor was $2.9\;{\Omega}/T$. The sensing limit was about $1.5{\times}10^{-5}\;T$. The increase of electrical resistance by the magnetic field was ascribed to a modification of the Josephson junctions due to the penetrating magnetic flux into the superconducting material. Considering the observed properties of the superconductor with trapped magnetic flux, a magnetic sensor was fabricated to detect simultaneously both the intensity and the direction of the magnetic field.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2003.10a
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• pp.69-71
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• 2003

The magnetic field sensor was fabricated with superconducting ceramics of YBaCuO system. The sensor at liquid nitrogen temperature showed the increase of electrical resistance by applying magnetic field. Actually the voltage drop across the sensor was changed from zero to a value more than 100 $mutextrm{V}$ by the applied magnetic field. The change in electrical resistance depended on magnetic field. The sensitivity of this sensor was 2.9 $\Omega$/T. The sensing limit was about $1.5\times$10$^{-5}$. The increase of electrical resistance by the magnetic field was ascribed to a modification of the Josephson junctions due to the penetrating magnetic flux into the superconducting material. Considering the observed properties of the superconductor with trapped magnetic flux, a magnetic sensor was fabricated to detect simultaneously both the intensity and the direction of the magnetic field.