• Analytical Science and Technology
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• v.18 no.3
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• pp.232-240
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• 2005

The total PCBs level in the transformer insulation oil samples using GC/ECD and HRGC/HRMS were ranged from 0.087 to $223.6{\mu}g/g$ and ranged from N.D. to $154.04{\mu}g/g$, respectively. The calculated TEQ values were ranged from 0.00067 to 6.8 ng WHO-TEQ/g. Among the samples, 6 samples showed higher than 2 ppm concentration (specific waste criterion of Korea). A variety in the concentration of total PCBs were observed between ECD and HRMS analysis. This is maybe due to quantification mehtod. The Aroclor 1248 wasn't present in the samples. The distribution pattern of Co-PCB congeners showed that the ratio of monoortho substituted congeners were higher than non-ortho substituted congeners. Among that, PCB-167 congener was predominant. In addition, the distribution of Co-PCBs congeners was different with that of flue gas and ambient air samples as well as commercial PCB formulations (Aroclor, Kanechlor).

• Korean Journal of Food Science and Technology
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• v.32 no.3
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• pp.481-490
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• 2000

Modified atmosphere packaging was applied to oriental melon(Cucumis melo L. var. makuwa Mak.) to extend its freshness during distribution. Gas composition and ethylene content in the film bags changed rapidly at the early stage of storage. Within 10 days, weight loss of the unpackaged increased upto 7.68% while those of the packaged remained less than 1.0% except LDPE film modified by addition of 5%(w/w) zeolite with $20\;{\mu}m$ thickness(20CK, 2.38%). Firmness was effectively maintained in the LDPE film modified by addition of 5%(w/w) zeolite with $40\;{\mu}m$ thickness(40CK) and the LDPE film with $40\;{\mu}m$ thickness containing ethylene absorber sachet(40LP). Peel color of the fruit changed rapidly in control and a little in 40CK. Oriental melon packages using 40CK provided better visual and sensory quality retention compared with others. Results suggested that packaging treatment such as 40CK could be used for extending freshness of oriental melon during transport period at ambient temperature.

• Journal of the Semiconductor & Display Technology
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• v.6 no.3
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• pp.19-23
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• 2007

The NiSi is very promising candidate for the metallization in 45 nm CMOS process such as FUSI(fully silicided) gate and source/drain contact because it exhibits non-size dependent resistance, low silicon consumption and mid-gap workfunction. Ni film was first deposited by using ALD (atomic layer deposition) technique with Bis-Ni precursor and $H_2$ reactant gas at $220^{\circ}C$ with deposition rate of $1.25\;{\AA}/cycle$. The as-deposited Ni film exhibited a sheet resistance of $5\;{\Omega}/{\square}$. RTP (repaid thermal process) was then performed by varying temperature from $400^{\circ}C$ to $900^{\circ}C$ in $N_2$ ambient for the formation of NiSi. The process temperature window for the formation of low-resistance NiSi was estimated from $600^{\circ}C$ to $800^{\circ}C$ and from $700^{\circ}C$ to $800^{\circ}C$ with and without Ti capping layer. The respective sheet resistance of the films was changed to $2.5\;{\Omega}/{\square}$ and $3\;{\Omega}/{\square}$ after silicidation. This is because Ti capping layer increases reaction between Ni and Si and suppresses the oxidation and impurity incorporation into Ni film during silicidation process. The NiSi films were treated by additional thermal stress in a resistively heated furnace for test of thermal stability, showing that the film heat-treated at $800^{\circ}C$ was more stable than that at $700^{\circ}C$ due to better crystallinity.

• Fire Science and Engineering
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• v.25 no.6
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• pp.168-177
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• 2011

The combustion test for real box of AC outdoor unit has been performed in this study in order to estimate the fire hazard in multi-system type of AC outdoor unit which is currently used for commercial use. The result showed that in test, there was explosion inside of AC outdoor unit, and flame erupted and fire spread through upper side grill. And then this fire burnt the combustibles such as wires, electronic control board, heat exchange copper plate and plastics etc inside the unit, refrigerant gas pipe was burst due to fire, and accelerated the explosion and flame eruption to outside while the refrigerant was erupting. It is found in this test that the maximum heat release rate of AC outdoor unit is 5,830 kW, the maximum internal temperature measured with infrared camera and thermocouple is $1,201^{\circ}C$, maximum ambient temperature is $881^{\circ}C$, and flame rose higher than about 5 m. It is concluded that the fire in AC outdoor unit cause fire to combustibles around the unit, and may give big damage by generating the secondary fire. It is expected that the result obtained from the test on the real object may be applied to fire realization of AC outdoor unit and estimation of fire spreading to the combustibles around in the future computer simulation.

• Korean Journal of Materials Research
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• v.8 no.12
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• pp.1182-1189
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• 1998

High quality $TiN/TiSi_2$-bilayers were formed on the Si(100) substrate at room temperature and at $600^{\circ}C$ first by coevaporation of stoichiometric Si and Ti(Si:Ti = 2:1) fellowed by Ti reactive deposition in N, gas ambient, and in situ annealing in ultrahigh vacuum. Stoichiometric $Ti_{0.}N_{0.5}$, films with (111) texture and $C54-TiSi_2$ films were grown by annealing at temperatures above $700^{\circ}C$. $TiN/C54-TiSi_2$/Si(100) interface was clear and flat without agglomoration, and $CS4-TiSi_2$ film was epitxailly grown. The sheet resistance of the $TiN/TiSi_2$- bilayer decreased as the annealing temperature increased and about $2.5\omega/\textrm{cm}^2$ was obtained from the sample annealed over $700^{\circ}C$.

• Journal of Korean Society for Atmospheric Environment
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• v.21 no.4
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• pp.439-458
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• 2005

An automated analysis system for water soluble constituents in $PM_{2.5}$ has been developed. The system consists of a high capacity multi tube diffusion scrubber (MTDS), a low temperature particle impactor (LTPI), and two ion (anion and cation) chromatography (IC) systems. Atmospheric particles have been collected by passing sample air through a thermostated MTDS followed by a LTPI. This system allows simultaneous measurements of soluble ions in $PM_{2.5}$ at 30 minutes interval. At the air sampling flow rate of 1.0L/min, the detection limits of the overall system are in the order of tens of $ng/m^3$. This system has been successfully used for the measurement of particulate components of Seoul air from April 2003 to January 2004. $SO_4^{2-},\;NO_3^-,\;NH_4^+,\;NO_2^-,\;Cl^-,\;Na^+,\;K^+,\;Ca^{2+},\;and\;Mg^{2+}$ are the major ionic species for $PM_{2.5}$ at Seoul. Among them, $SO_4^{2-},\;NO_3^-\;and\;NH_4^+$ are the most abundant ions, contributed up to $86\%$ of the total and the concentrations were higher than those in any other urban sites in the world except for Chinese cities. There are high pollutant episodes which contribute about $15\~20\%$ of annual average values of the major ions. During the episode, the all parcels were transported from the asian continent and $PM_{2.5}$ were significantly neutralized. This suggests that aged and long range transported pollutants caused the high pollutant episodes. They showed a distinct daily and seasonal variations:they showed a peak in the early morning caused by the night-time accumulation of particulate matters. Atmospheric reactions including gas-to-particle reactions and inter-particle reactions and meteorological parameters including relative humidity and ambient temperature were described with related to the $PM_{2.5}$ 5 concentrations. All of the ionic species showed higher concentrations during the spring than those for summer and winter.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.1
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• pp.538-545
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• 2020

The outdoor coal storage sheds of thermal power plants are being converted to indoor coal storage sheds worldwide because of the environmental pollution problems in the surrounding areas. On the other hand, indoor coal storage sheds are causing problems, such as indoor coal scattering and harmful gas generation. In this study, the ventilation method of indoor coal storage sheds was analyzed in terms of the internal flow characteristics and ventilation according to the outside wind velocity and direction. CFD analysis was performed based on the actual flow measurement information inside the indoor coal storage sheds. A comparison of the wind speed of 6 m/s and 2 m/s when the outside wind direction was easterly showed that the stream velocity to the monitor louver was faster and the recirculation area was clearer at 6 m/s than at 2 m/s. In addition, the trend of a westerly wind was similar to that of the easterly wind. The ventilation rate according to the wind speed was 13.1 times and 4.4 times for a wind speed of 6 m/s and 2 m/s, respectively. If the wind speed is 2 m/s, the situation does not meet the required number of ventilations per hour in a general plant, and needs to be improved.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.78-78
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• 2013

Recently, many platinoid metals like platinum and ruthenium have been used as an electrode of microelectronic devices because of their low resistivity and high work-function. However the material cost of Ru is very expensive and it usually takes long initial nucleation time on SiO2 during chemical deposition. Therefore many researchers have focused on how to enhance the initial growth rate on SiO2 surface. There are two methods to deposit Ru film with atomic layer deposition (ALD); the one is thermal ALD using dilute oxygen gas as a reactant, and the other is plasma enhanced ALD (PEALD) using NH3 plasma as a reactant. Generally, the film roughness of Ru film deposited by PEALD is smoother than that deposited by thermal ALD. However, the plasma is not favorable in the application of high aspect ratio structure. In this study, we used a bis(ethylcyclopentadienyl)ruthenium [Ru(EtCp)2] as a metal organic precursor for both thermal and plasma enhanced ALDs. In order to reduce initial nucleation time, we use several methods such as Ar plasma pre-treatment for PEALD and usage of sacrificial RuO2 under layer for thermal ALD. In case of PEALD, some of surface hydroxyls were removed from SiO2 substrate during the Ar plasma treatment. And relatively high surface nitrogen concentration after first NH3 plasma exposure step in ALD process was observed with in-situ Auger electron spectroscopy (AES). This means that surface amine filled the hydroxyl removed sites by the NH3 plasma. Surface amine played a role as a reduction site but not a nucleation site. Therefore, the precursor reduction was enhanced but the adhesion property was degraded. In case of thermal ALD, a Ru film was deposited from Ru precursors on the surface of RuO2 and the RuO2 film was reduced from RuO2/SiO2 interface to Ru during the deposition. The reduction process was controlled by oxygen partial pressure in ambient. Under high oxygen partial pressure, RuO2 was deposited on RuO2/SiO2, and under medium oxygen partial pressure, RuO2 was partially reduced and oxygen concentration in RuO2 film was decreased. Under low oxygen partial pressure, finally RuO2 was disappeared and about 3% of oxygen was remained. Usually rough surface was observed with longer initial nucleation time. However, the Ru deposited with reduction of RuO2 exhibits smooth surface and was deposited quickly because the sacrificial RuO2 has no initial nucleation time on SiO2 and played a role as a buffer layer between Ru and SiO2.

• Korean Journal of Food Science and Technology
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• v.49 no.4
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• pp.369-376
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• 2017

Maturation of distilled spirit can generate diverse flavors and tastes. Rice Soju was matured in oak casks (MSO) and stainless steel containers (MSS) for one year at ambient temperature. Ipguk (Aspergillus luchuensis) and Saccharomyces cerevisiae Y88-4 were used, and reduced pressure ($110{\pm}20Torr$) distillation was applied to brew Soju. Acidity and conductivity were increased in both MSO and MSS. MSO reduced alcohol content (from 43 to 40%) and volume (from 18,000 to 12,730 mL), and significantly altered yellowness (from 0.2 to 30.2). Furthermore, MSO increased the isoamyl alcohol (from 276.7 to $339.2{\mu}g/mL$) and isobutyl alcohol (from 122.3 to $144.2{\mu}g/mL$) content. Gas chromatography-mass spectrometry was used to detect volatile compounds in Soju, which included 20 esters, 7 alcohols, 2 acids, and 5 miscellaneous compounds. Oak lactone was detected only in MSO and was considered as a specific flavor component associated with oak maturation. Thus, maturation materials contribute to the physicochemical property of distilled spirits.

• Korean Journal of Optics and Photonics
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• v.14 no.3
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• pp.312-320
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• 2003

The basic mechanistic aspects of the interaction and practical considerations related to polymer ablation were briefly reviewed. Photochemical and photothermal effects, which highly depend on laser wavelength have close correlation with each other. In this study, multi-scanning laser ablation processing of polymer with a DPSS (Diode Pumped Solid State) 3rd harmonic Nd:YVO$_4$ laser (355 nm) was developed to fabricate a three-dimensional micro shape. Polymer fabrication using DPSSL has some advantages compared with the conventional polymer ablation process using KrF and ArF laser with 248 nm and 193 nm wavelength. These advantages include pumping efficiency and low maintenance cost. And this method also makes it possible to fabricate 2D patterns or 3D shapes rapidly and cheaply because CAD/CAM software and precision stages are used without complex projection mask techniques. Photomachinability of polymer is highly influenced by laser wavelength and by the polymer's own chemical structure. So the optical characteristics of polymers for a 355 nm laser source is investigated experimentally and theoretically. The photophysical and photochemical parameters such as laser fluence, focusing position, and ambient gas were considered to reduce the plume effect which re-deposits debris on the surface of substrate. These phenomena affect the surface roughness and even induce delamination around the ablation site. Thus, the process parameters were tuned to optimize for gaining precision surface shape and quality. This maskless direct photomachining technology using DPSSL could be expected to manufacture tile prototype of micro devices and molds for the laser-LIGA process.