• Proceedings of the Materials Research Society of Korea Conference
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• 2009.05a
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• pp.22.2-22.2
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• 2009

Currently, metal silicides become increasingly more essential part as a contact material in complimentary metal-oxide-semiconductor (CMOS). Among various silicides, NiSi has several advantages such as low resistivity against narrow line width and low Si consumption. Generally, metal silicides are formed through physical vapor deposition (PVD) of metal film, followed by annealing. Nanoscale devices require formation of contact in the inside of deep contact holes, especially for memory device. However, PVD may suffer from poor conformality in deep contact holes. Therefore, Atomic layer deposition (ALD) can be a promising method since it can produce thin films with excellent conformality and atomic scale thickness controllability through the self-saturated surface reaction. In this study, Ni thin films were deposited by thermal ALD using bis(dimethylamino-2-methyl-2-butoxo)nickel [Ni(dmamb)2] as a precursor and NH3 gas as a reactant. The Ni ALD produced pure metallic Ni films with low resistivity of 25 $\mu{\Omega}cm$. In addition, it showed the excellent conformality in nanoscale contact holes as well as on Si nanowires. Meanwhile, the Ni ALD was applied to area-selective ALD using octadecyltrichlorosilane (OTS) self-assembled monolayer as a blocking layer. Due to the differences of the nucleation on OTS modified surfaces toward ALD reaction, ALD Ni films were selectively deposited on un-coated OTS region, producing 3 ${\mu}m$-width Ni line patterns without expensive patterning process.

• Journal of Hydrogen and New Energy
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• v.23 no.5
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• pp.455-460
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• 2012

This work describes the hydriding chemical vapor synthesis (HCVS) of the $MgH_2$ in a hydrogen atmosphere and the product's hydriding-dehydridng properties. Mg powder was used as a starting material to synthesize $MgH_2$ and uniformly heated to a temperature of $600^{\circ}C$ for Mg vaporization. The effects of hydrogen pressure on the morphology and the composition of HCVS-$MgH_2$ were examined by using X-ray diffraction (XRD) and scanning electron microscopy (SEM). It is clearly seen that after the HCVS process, the particle size of synthesized $MgH_2$ was drastically reduced to the submicron or micrometer-scale and these showed different shapes (needle-like nanofibers and angulated plate) depending on the hydrogen pressure. It was found that after the HCVS process, the $H_2$ desorption temperature of HCVS-$MgH_2$ decreased from 380 to $410^{\circ}C$, and the minimum hydrogen desorption tempreature of HCVS-$MgH_2$ powder with needle-like shape can be obtained. In addition, the enhanced hydrogen storage performance for needle-like $MgH_2$ was achieved during subsequent hydriding-dehydriding cycles.

• Journal of Hydrogen and New Energy
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• v.30 no.6
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• pp.593-600
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• 2019

The combustion characteristics of methane/hydrogen pre-mixed flame have been investigated with swirl stabilized flame in a laboratory-scale pre-mixed combustor with constant heat load of 5.81 kW. Hydrogen/methane fuel and air were mixed in a pre-mixer and introduced to the combustor through a burner nozzle with different degrees of swirl angle. The effects of hydrogen addition and swirl intensity on the combustion characteristics of pre-mixed methane flames were examined using particle image velocimetry (PIV), micro-thermocouples, various optical interference filters and gas analyzers to provide information about flow velocity, temperature distributions, and species concentrations of the reaction field. The results show that higher swirl intensity creates more recirculation flow, which reduces the temperature of the reaction zone and, consequently, reduces the thermal NO production. The distributions of flame radicals (OH, CH, C₂) are dependent more on the swirl intensity than the percentage of hydrogen added to methane fuel. The NO concentration at the upper part of the reaction zone is increased with an increase in hydrogen content in the fuel mixture because higher combustibility of hydrogen assists to promote faster chemical reaction, enabling more expansion of the gases at the upper part of the reaction zone, which reduces the recirculation flow. The CO concentration in the reaction zone is reduced with an increase in hydrogen content because the amount of C content is relatively decreased.

• Journal of the Korean Ceramic Society
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• v.52 no.5
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• pp.320-324
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• 2015

Optimization of the fabrication process of NiO-yttrium doped barium zirconate (BZY) composite anode substrates using tape-casting for high performance thin-film protonic ceramic fuel cells (PCFCs) is investigated. The anode substrate is composed of a tens of microns-thick anode functional layer laminated over a porous anode substrate. The macro-pore structure of the anode support is induced by micron-scale polymethyl methacrylate (PMMA) pore formers. Thermal gravity analysis (TGA) and a dilatometer are used to determine the polymeric additive burn-out and sintering temperatures. Crystallinity and microstructure of the tape-cast NiO-BZY anode are analyzed after the sintering.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.8
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• pp.553-561
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• 2017

The main motivation for this study was to establish a CFD-based procedure for the analysis of heating characteristics, particularly in industrial furnaces. As certain open-source software packages have gained popularity in dealing with complex industrial problems, the OpenFOAM framework was selected for further development of advanced physical models to meet industrial requirements. In this study, the newly developed comprehensive model was applied to simulate physical processes in the full-scale horizontal furnace of a continuous galvanizing line (CGL). The numerical results obtained indicate that the current approach predicts heating characteristics reasonably well. It was also found that radiative heat transfer plays a dominant role in heating the moving strip. To improve the predictability of our method, further work is required to model the turbulence-chemistry interaction realistically, as well as to impose a physically correct thermal wall boundary condition.

• Smart Structures and Systems
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• v.12 no.3_4
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• pp.415-426
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• 2013

Condition assessment and monitoring of bridges is critical for safe passenger travel, public transportation, and efficient freight. In monitoring, displacement measurement capability is important to keep track of performance of bridge, in part or as whole. One of the most important parts of a bridge is the expansion joint, which accommodates continuous cyclic thermal expansion of the whole bridge. Though expansion joint is critical for bridge performance, its inspection and monitoring has not been considered significantly because the monitoring requires long-term data using cost intensive equipment. Recently, a wireless smart sensor network (WSSN) has drawn significant attention for transportation infrastructure monitoring because of its merits in low cost, easy installation, and versatile on-board computation capability. In this paper, a rapid wireless displacement monitoring system, wireless hybrid sensor (WHS), has been developed to monitor displacement of expansion joints of bridges. The WHS has been calibrated for both static and dynamic displacement measurement in laboratory environment, and deployed on an in-service highway bridge to demonstrate rapid expansion joint monitoring. The test-bed is a continuous steel girder bridge, the Founders Bridge, in East Hartford, Connecticut. Using the WHS system, the static and dynamic displacement of the expansion joint has been measured. The short-term displacement trend in terms of temperature is calculated. With the WHS system, approximately 6% of the time has been spent for installation, and 94% of time for the measurement showing strong potential of the developed system for rapid displacement monitoring.

• Journal of the Korean Institute of Gas
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• v.19 no.5
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• pp.75-80
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• 2015

Aluminum dusts, from micro to nano-scale, are widely used in various applications such as propulsion and pyrotechnic compounds because of high burning rate. In this study, the pyrolysis hazard of aluminum dusts with different median size (sized by 70 nm, 100 nm, $6{\mu}m$, $15{\mu}m$) were investigated experimentally. The thermal decomposition characteristics of aluminum dusts with the variation of heating rate were investigated using TGA (Thermo gravimetric analysis) and was estimated the minimum ignition temperature from temperature of weight gain in nano and micro-sized aluminum dusts with different diameter. In the same condition of heating rate, the temperature of weight gain in aluminum dust layers increased with increasing of particle size and increased with increasing of heating rates in air. From the results, it was estimated that the pyrolysis hazard of aluminum dusts decrease with increasing of mean diameter.

• Journal of Biosystems Engineering
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• v.35 no.6
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• pp.401-407
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• 2010

In this study, computer simulations were conducted to assess the use of a circulating concurrent-flow dryer for rapeseed drying and to determined the effect of this drying method on the germination ratio of rapeseed after the drying process was complete. The simultaneous heat and mass transfer between air and rapeseed in a concurrent-flow dryer was examined by simulation. The drying simulation was based on several parameters with sequent time series. Equations concerning air psychrometrics, physical properties, thermal properties, equilibrium moisture content, thin layer drying of rapeseed, etc. were all combined to solve the simulation models. Based on energy and mass transfer in the concurrent-flow drying model, a simulation program for the circulating concurrent-flow rapeseed dryer was built along with a detailed description of the mathematical solution to the model. A pilot scale circulating concurrent-flow dryer(200 kg/batch) was used to verify the fitness of the simulation program. A comparison between the experimental data and the model predicted results was presented and discussed. The drying parameters and germination ratio were analyzed and the accuracy of the simulation program was evaluated. The simulation program proved to be reliable and was shown to be a convenient tool for predicting rapeseed drying and germination ratio of rapeseed in a concurrent-flow dryer.

• Journal of Biomedical Engineering Research
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• v.32 no.2
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• pp.127-133
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• 2011

Arteria radialis is a branch of the brachial artery extending down the forearm around the wrist where it closes to skin surface. In the oriental medicine, the skin above arteria radialis has an important role because oriental medicine practitioners put their finger tips on the area, and diagnose patient's health conditions by feeling the pulsation of the arterial contraction. The finger tip diagnostic method relies on subjective decision of the practitioner; and there is a need to develop an objective diagnostic modality. The pulsation of the arterial contraction appears not only a movement on the site but also as temperature fluctuation due to pulsatile feeding of warmer blood. The goal of this study is to demonstrate a feasibility of using an infrared camera quantitatively to detect the temperature fluctuation on the skin. Clinical important three different areas, called chon, gwan, chuk, near a wrist where the arteria radialis reaches close to skin surface are marked with small pieces of surgical tape. A high-speed and high-resolution infrared camera with a 3 cm of field of view measures these areas for 10 second at 200 frames per second with a 320*240 pixel size. The pulsatile temperature fluctuation is calculated after passing a band pass filter to remove any stationary temperature over 10 second. The temperature fluctuation of a healthy male volunteer is measured at a room temperature as a control, and is compared with another measurement performed after 20 minutes staying in a room at a 40 degree Celsius. This comparison is repeated for three times, and indicates that the fluctuation increases after staying 20 minutes in the warm room. This increase becomes smaller when the person stays in the warm room with an acupuncture treatment that decreases body temperature. So that an objective diagnostics on the site may become feasible.

• Tribology and Lubricants
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• v.31 no.2
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• pp.42-49
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• 2015

Because of the growing need for high-speed transport options such as trains and aircraft, there is increasing demand for technology related to high-speed trains. Among them, braking systems are important in high-speed trains in terms of reliability. Especially, the disk brake system, in use in most high-speed trains, transforms kinetic energy into thermal energy and noise. Therefore, the material properties of both the friction materials and disks are expected to influence the tribological characteristics. In this paper, the tribological characteristics depend on the hardness of the brake disks between the Cu-based sintered metallic friction material and the heat-treated heat-resisting steel disks. A lab-scale dynamometer used to perform braking tests at a variety of braking speeds using dry conditions. The test results revealed that the hardness of the disks affects the friction coefficients, friction stabilities, and wear rates. Thus, the brake system using the heat-resisting steel disk requires proper heat-treatment. These differences are considered to be caused by the change in tribological mechanisms and the generation of an oxide layer on the friction surfaces. The oxide layers on the friction surfaces are confirmed to Fe₂O₃ by x-ray diffraction (XRD) and scanning electron microscope-energy dispersive spectroscopy (SEM-EDS) analysis.