• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2014.10a
• /
• pp.125-130
• /
• 2014

High speed railroad car and high-rise apartment with development of railway technology cause different problems of noise contrary to the previous generation. It is the most efficient noise reduction countermeasure but we studied that is the way on noise propagation with sound proof wall or sound proof tunnel around railroad. But if it were railroad on bridge, additional cost which is more expensive than installing one on the ground is needed. So sound insulation material considering reducing weight of recent soundproof facilities must be selected. It is in this study that predicted and analyzed acoustical and structural effect for noise reduction by installing soundproof tunnel. If it were departmentalized into additional study, could be able to expect noise reduction effect of sound proof tunnel establishment on the bridge.

• Journal of Magnetics
• /
• v.6 no.4
• /
• pp.126-128
• /
• 2001

The effect of rapid thermal anneal (RTA) has been investigated on the properties of an FeMn exchange-biased magnetic tunnel junction (MTJ) using magnetoresistance and I-V measurements and transmission electron microscopy (TEM). The tunneling magnetoresistance (TMR) in an as-grown MTJ is found to be ∼27%, while the TMR in MTJs annealed by RTA increases with annealing temperature up to 300$\^{C}$, reaching ∼46%. A TEM image reveals a structural change in the interface of A1$_2$O$_3$layer for the MTJ annealed by RTA at 300$\^{C}$. The oxide barrier parameters are found to vary abruptly with annealing time within a few ten seconds. Our results demonstrate that the present RTA enhances the magnetoresistive properties of MTJs.

• Proceedings of the Korean Magnestics Society Conference
• /
• 2008.12a
• /
• pp.185.2-185.2
• /
• 2008

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2008.11a
• /
• pp.357-357
• /
• 2008

Spin injection experiment is conducted in epitaxially grown Fe/GaAs hybrid structure. For the formation of Schottky tunnel barrier between Fe and GaAs layers, highly n-doped GaAs layers are grown after n-doped channel layer. A non-local measurement, a voltage measurement probes do not contain a charge current path, is used for detecting only the chemical potential differences by the spin transport. As a result, the dips that are nicely matched with antiparallel region are obtained.

• Current Photovoltaic Research
• /
• v.12 no.2
• /
• pp.31-36
• /
• 2024

Passivating contacts are a promising technology for achieving high efficiency Si solar cells by reducing direct metal/Si contact. Among them, a polysilicon (poly-Si) based passivating contact solar cells achieve high passivation quality through a tunnel oxide (SiO_x) and poly-Si. In poly-Si/SiO_x based solar cells, the passivation quality depends on the amount of dopant in-diffused into the bulk-Si. Therefore, our study fabricated cells by inserting silicon oxide (SiO₂) as a doping barrier before doping and analyzed the barrier effect of SiO₂. In the experiments, p⁺ poly-Si was formed using spin on dopant (SOD) method, and samples ware fabricated by controlling formation conditions such as existence of doping barrier and poly-Si thickness. Completed samples were measured using quasi steady state photoconductance (QSSPC). Based on these results, it was confirmed that possibility of achieving high V_oc by inserting a doping barrier even with thin poly-Si. In conclusion, an improvement in implied V_oc of up to approximately 20 mV was achieved compared to results with thicker poly-Si results.

• Tunnel and Underground Space
• /
• v.17 no.6
• /
• pp.464-474
• /
• 2007

An enhancement in the performance and safety of a high-level waste repository requires a validation of its engineered barrier. An engineering-scale test (named "KENTEX") has been conducted to investigate the thermal-hydro-mechanical behaviors in the engineered barrier of the Korean reference disposal system The validation test started on May 31, 2005 and is still under operation. The experimental data obtained allowed a preliminary and qualitative interpretation of the thermal-hydro-mechanical behaviors in the bentonite blocks. The temperature was higher as it became closer to the heater, while it became lower as it was farther away from the heater. The water content had a higher value in the part close to the hydration surface than that in the heater part. The relative humidity data suggested that a hydration of the bentonite blocks might occur by different drying-wetting processes, depending on their position. The total pressure was continuously increased by the evolution of the saturation front in the bentonite blocks and thereby the swelling pressure. Near the heater region, there was also a significant contribution of the thermal expansion of bentonite and the vapor pressure in the pores of the bentonite blocks.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.28 no.4
• /
• pp.28-36
• /
• 2024

In this study, an analytical evaluation of evacuation safety in typical road tunnels was conducted. The Fire Dynamics Simulator (FDS) was employed to perform fire simulations with varying fire sizes to determine the allowable evacuation time in road tunnels. Additionally, evacuation simulations were performed using Pathfinder, considering the width of barrier doors and the spacing of evacuation passageways, to calculate the required evacuation time. A comparison between the allowable and required evacuation times was conducted to assess the impact of fire size, passageway spacing, and barrier door width on tunnel evacuation safety. The results from the fire and evacuation simulations indicated that an increase in fire size and passageway spacing, along with a decrease in door width, resulted in an increase in the number of casualties. Conversely, increasing the barrier door width to more than 1.2meters led to a reduction in casualties as passageway spacing increased.

• JSTS:Journal of Semiconductor Technology and Science
• /
• v.14 no.5
• /
• pp.572-578
• /
• 2014

In order to overcome small current drivability of a tunneling field-effect transistor (TFET), a TFET using Schottky barrier (SBTFET) is proposed. The proposed device has a metal source region unlike the conventional TFET. In addition, dopant segregation technology between the source and channel region is applied to reduce tunneling resistance. For TFET fabrication, spacer technique is adopted to enable self-aligned process because the SBTFET consists of source and drain with different types. Also the control device which has a doped source region is made to compare the electrical characteristics with those of the SBTFET. From the measured results, the SBTFET shows better on/off switching property than the control device. The observed drive current is larger than those of the previously reported TFET. Also, short-channel effects (SCEs) are investigated through the comparison of electrical characteristics between the long- and short-channel SBTFET.

• Wind and Structures
• /
• v.31 no.1
• /
• pp.43-57
• /
• 2020

Considering the wind barriers induced aerodynamic characteristic variations of both bridge deck and trains, this paper studies the effects of wind barriers on the safety and stability of trains as they run through an urban rail transit cable-stayed bridge which tends to be more vulnerable to wind due to its relatively low stiffness and lightweight. For the bridge equipped with wind barriers of different characteristics, the aerodynamic coefficients of trains and bridge decks are obtained from wind tunnel test firstly. And then, the space vibration equations of the wind-train-bridge system are established using the experimentally obtained aerodynamic coefficients. Through solving the dynamic equations, one can calculate the dynamic responses both the trains and bridge. The results indicate that setting wind barriers can effectively reduce the dynamic responses of both the trains and bridge, even though more wind forces acting on the bridge are caused by wind barriers. In addition, for urban rail transit cable-stayed bridges located in strong wind environment, the wind barriers are recommended to be set with 20% porosity and 2.5 m height according to the calculation results of cases with wind barriers porosity and height varying in two wide ranges, i.e., 10% - 40% and 2.0 m to 4.0 m, respectively.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2010.02a
• /
• pp.213-213
• /
• 2010

Magnetic random access memory (MRAM), based on magnetic tunnel junction (MTJ) and CMOS, is one of the best semiconductor memories because it can provide nonvolatility, fast access time, unlimited read/write endurance, low operating voltage and high storage density. For the realization of high density MRAM, the etching of MTJ stack with good properties is one of a key process. Recently, there has been great interest in the MTJ stack using MgO as barrier layer for its huge room temperature MR ratio. The use of MgO barrier layer will undoubtedly accelerate the development of MTJ stack for MRAM. In this study, high-density plasma reactive ion etching of MgO films was investigated in an inductively coupled plasma of $Cl_2$/Ar gas mixes. The etch rate, etch selectivity and etch profile of this magnetic film were examined on vary gas concentration. As the $Cl_2$ gas concentration increased, the etch rate of MgO monotonously decreased and etch slop was slanted. The effective of etch parameters including coil rf power, dc-bais voltage, and gas pressure on the etch profile of MgO thin film was explored, At high coil rf power, high dc-bais voltage, low gas pressure, the etching of MgO displayed better etch profiles. Finally, the clean and vertical etch sidewall of MgO films was achieved using $Cl_2$/Ar plasma at the optimized etch conditions.