• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.77-77
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• 2000

Titanium oxide (TiO2) thin films have valuable properties such as a high refractive index, excellent transmittance in the visible and near-IR frequency, and high chemical stability. Therefore it is extensively used in anti-reflection coating, sensor, and photocatalysis as electrical and optical applications. Specially, TiO2 have a high dielectric constant of 180 along the c axis and 90 along the a axis, so it is highlighted in fabricating dielectric capacitors in micro electronic devices. A variety of methods have been used to produce patterned self-assembled monolayers (SAMs), including microcontact printing ($\mu$CP), UV-photolithotgraphy, e-beam lithography, scanned-probe based micro-machining, and atom-lithography. Above all, thin film fabrication on $\mu$CP modified surface is a potentially low-cost, high-throughput method, because it does not require expensive photolithographic equipment, and it produce micrometer scale patterns in thin film materials. The patterned SAMs were used as thin resists, to transfer patterns onto thin films either by chemical etching or by selective deposition. In this study, we deposited TiO2 thin films on Si (1000 substrateds using titanium (IV) isopropoxide ([Ti(O(C3H7)4)] ; TIP as a single molecular precursor at deposition temperature in the range of 300-$700^{\circ}C$ without any carrier and bubbler gas. Crack-free, highly oriented TiO2 polycrystalline thin films with anatase phase and stoichimetric ratio of Ti and O were successfully deposited on Si(100) at temperature as low as 50$0^{\circ}C$. XRD and TED data showed that below 50$0^{\circ}C$, the TiO2 thin films were dominantly grown on Si(100) surfaces in the [211] direction, whereas with increasing the deposition temperature to $700^{\circ}C$, the main films growth direction was changed to be [200]. Two distinct growth behaviors were observed from the Arhenius plots. In addition to deposition of THe TiO2 thin films on Si(100) substrates, patterning of TiO2 thin films was also performed at grown temperature in the range of 300-50$0^{\circ}C$ by MOCVD onto the Si(100) substrates of which surface was modified by organic thin film template. The organic thin film of SAm is obtained by the $\mu$CP method. Alpha-step profile and optical microscope images showed that the boundaries between SAMs areas and selectively deposited TiO2 thin film areas are very definite and sharp. Capacitance - Voltage measurements made on TiO2 films gave a dielectric constant of 29, suggesting a possibility of electronic material applications.

• Korean Journal of Weed Science
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• v.31 no.1
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• pp.96-102
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• 2011

The objective of this study was to find herbicidal compounds in the essential oil of palmarosa (Cymbopogon martini). Of essential oils from basil (Ocimum basilicum), blackpepper (Piper nigrum), clary sage (Salvia sclarea), ginger (Zingiber pfficinale), hyssop (Hyssopus officinalis), nutmag (Myristica fragrance), palmarosa (Cymbopogon martini), fennel (Foeniculum vulgare), sage (Salvia leucantha), and spearmint (Mentha spicta), the herbicidal activity of palmarosa essential oil, which was determined by a seed bioassay using rapeseed (Brassica napus L.), was highest ($GR_{50}$ value, $201{\mu}g\;mL^{-1}$). In palmarosa essential oil, 11 volatile organic chemicals were identified by gas chromatography-mass spectometry with solid-phase micro-extraction apparatus and the major constituents were geraniol (40.23%), geraniol acetate (15.57%), cis-ocimene (10.79%), and beta-caryophyllene (8.72%). The $GR_{50}$ values of geraniol, citral, nerol, and geranyl acetate were 151, 224, 452, and $1,214{\mu}g\;mL^{-1}$, respectively. In greenhouse and field experiments, foliar application of palmarosa essential oil at the level of $80kg\;ha^{-1}$ controlled weeds effectively. Overall results of this study showed that the herbicidal activity of palmarosa essential oil could be due to geraniol and citral which had lower $GR_{50}$ values.

• Weed & Turfgrass Science
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• v.1 no.4
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• pp.44-49
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• 2012

The objective of this study was to know the herbicidal activity of the essential oil from amyris (Amyris balsamifera). In a seed bioassay experiment, the amyris essential oil inhibited the growth of rapeseed (Brassica napus) by fifty percent at 8.8 ${\mu}g\;g^{-1}$. And in a greenhouse experiment, sorghum, barnyard grass and Indian jointvetch, which was applied in above-ground parts, with the amyris essential oil at 4,000 ${\mu}g\;ml^{-1}$ showed visual injuries of 90, 70, and 70, respectively (0, no damage; 100, total damage). However, soil application of the essential oil did not show such herbicidal injuries. In a field experiment, foliar application of the amyris essential oil at 5% controlled effectively weeds such as barnyardgrass, shepherd's purse, and clover in 24 hours. Our results indicated that the amyris essential oil had herbicidal activity. To understand the composition of the amyris essential oil, the oil was analyzed by gas chromatography-mass spectometry with solid-phase micro-extraction apparatus. There were 15 organic chemicals in the oil and the major constituents were calarene, elemol, ${\gamma}$-eudesmol, curcumene, ${\beta}$-sesquiphellandrene, zingiberene, selina-3,7(11)-diene, 1,3-diisopropenyl-6-methyl-cyclohexene, ${\beta}$-bisabolene, and ${\beta}$-maaliene. Overall results suggest that the amyris essential oil had a herbicidal activity with fast, contact, and non-selective mechanism.

• Korean Journal of Materials Research
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• v.9 no.3
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• pp.244-250
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• 1999

MOCVD TiN films were prepared from a new TiN precursor, tetrakis(etylmethylamino)titanium (TEMAT) and ammonia. Deposition of TiN films from a single precursor, TEMA T yielded the growth rates of $70 to 1050\AA$/min, depending on the deposition temperature. Furthermore, the excellent bottom coverage of -90% over $0.35\mu\textrm{m}$ contacts was obtained at $275^{\circ}C$. The addition of ammonia to TEMA T lowered the resistivity of as- deposited TiN film to ~ $800\mu\omega-cm$ from $3500~6000\mu\omega-cm$ and improved the stability of TiN film in air. Examination of the films by Auger electron spectroscopy(AES) showed that the oxygen and carbon contents decreased with the addition of ammonia. However, increasing ammonia flow rate decreased the bottom coverage of TiN films over $0.5\mu\textrm{m}$ contacts, probably due to the high sticking coefficient of intermediate species produced from the gas phase reaction of TEMA T and ammonia. Based on the byproduct gases detected by the quadrupole mass spectrometer (QMS), the transammination reaction was proposed to be responsible for TiN deposition. In addition, XPS analysis revealed that the carbon in the films made from TEMA T and ammonia was metallic carbon, suggesting that $\beta$-hydrogen activation process occurs competitively with the transammination reaction.

• Korean Journal of Materials Research
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• v.21 no.11
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• pp.587-591
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• 2011

The effect of the precipitator (NaOH, $NH_4OH$) and the amount of the precipitator (150, 200, 250, 300 ml) on the formation of $Fe_3(PO_4)_2$, which is the precursor used for cathode material $LiFePO_4$ in Li-ion rechargeable batteries was investigated by the co-precipitation method. A pure precursor of olivine $LiFePO_4$ was successfully prepared with coprecipitation from an aqueous solution containing trivalent iron ions. The acid solution was prepared by mixing 150 ml $FeSO_4$(1M) and 100 ml $H_3PO_4$(1M). The concentration of the NaOH and $NH_4OH$ solution was 1 M. The reaction temperature (25$^{\circ}C$) and reaction time (30 min) were fixed. Nitrogen gas (500 ml/min) was flowed during the reaction to prevent oxidation of $Fe^{2+}$. Single phase $Fe_3(PO_4)_2$ was formed when 150, 200, 250 and 300 ml NaOH solutions were added and 150, 200 ml $NH_4OH$ solutions were added. However, $Fe_3(PO_4)_2$ and $NH_4FePO_4$ were formed when 250 and 300 ml $NH_4OH$ was added. The morphology of the $Fe_3(PO_4)_2$ changed according to the pH. Plate-like lenticular shaped $Fe_3(PO_4)_2$ formed in the acidic solution below pH 5 and plate-like rhombus shaped $Fe_3(PO_4)_2$ formed around pH 9. For the $NH_4OH$, the pH value after 30 min reaction was higher with the same amount of additions of NaOH and $NH_4OH$. It is believed that the formation mechanism of $Fe_3(PO_4)_2$ is quite different between NaOH and $NH_4OH$. Further investigation on this mechanism is needed. The prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and the pH value was measured by pH-Meter.

• 한국가시화정보학회:학술대회논문집
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• 2002.11a
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• pp.1-6
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• 2002

How is the flow in a rotating impeller. About 35 years have passed since one experimentalist rotating with the impeller. of a huge centrifugal blower made the flow measurements using a hot-wire anemometer (Fowler 1968). Optical measurement methods have great advantages over the intrusive methods especially for the flow measurement in a rotating impeller. One is the optical flow visualization (FV) technique (Senoo, et al., 1968) and the other is the application of laser velocimetry (LV) (Hah and Krain, 1990). Particle image velocimetries (PIVs) combine major features of both FV and LV, and are very attractive due to the feasibility of simultaneous and multi-points measurements (Hayami and Aramaki, 1999). A high-pressure-ratio transonic centrifugal compressor with a low-solidity cascade diffuser was tested in a closed loop with HFC134a gas at 18,000rpm (Hayami, 2000). Two kinds of measurement techniques by image processing were applied to visualize a flow in the compressor. One is a velocity field measurement at the inducer of the impeller using a PIV and the other is a pressure field measurement on the side wall of the cascade diffuser using a pressure sensitive paint (PSP) measurement technique. The PIV was successfully applied for visualization of an unsteady behavior of a shock wave based on the instantaneous velocity field measurement (Hayami, et al., 2002b) as well as a phase-averaged velocity vector field with a shock wave over one blade pitch (Hayami, et al., 2002a. b). A violent change in pressure was successfully visualized using a PSP measurement during a surge condition even though there are still some problems to be overcome (Hayami, et al., 2002c). Both PIV and PSP results are discussed in comparison with those of laser-2-focus (L2F) velocimetry and those of semiconductor pressure sensors. Experimental fluid dynamics (EFDs) are still growing up more and more both in hardware and in software. On the other hand, computational fluid dynamics (CFDs) are very attractive to understand the details of flow. A secondary flow on the side wall of the cascade diffuser was visualized based either steady or unsteady CFD calculations (Bonaiuti, et al.,2002). EFD and CFD methods will be combined to a hybrid method being complementary to each other. Measurement techniques by image processing as well as CFD calculations give a huge amount of data. Then, data mining technique will become more important to understand the flow mechanism both for EFD and CFD.

• Korean Journal of Food Science and Technology
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• v.48 no.5
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• pp.430-436
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• 2016

Solid phase microextraction and gas chromatography-mass spectrometry (SPME/GC-MS), electronic nose, and electronic tongue were used to characterize the sensory profiles of cider vinegars from Korea (K1-2), China (C1-2), Japan (J1-2), and US (U1-2). SPME-GC/MS detected acetic acid as the common volatile compound in all vinegars, in addition to isovaleric acid, octanoic acid, and phenethyl acetate. Acids and acetic esters were the major components of Korean and US vinegar samples, respectively. Chinese vinegars had high ethyl acetate content, while Japanese samples were characterized by a low content of acetic acid. Principal component analysis (PCA) pattern provided a clear categorical discrimination of Chinese vinegars by E-nose and E-tongue analyses. The instrumental sensory scores and the taste attributes for flavor ($r^2=0.9431$), sourness ($r^2=0.9515$), and sweetness ($r^2=0.8325$) were highly correlated. Therefore, SPME/GC-MS, E-nose, and E-tongue analyses may be useful tools to discriminate the sensory profiles of cider vinegars of different origins.

• Nuclear Engineering and Technology
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• v.53 no.10
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• pp.3367-3378
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• 2021

The design phase and safety assessment of Generation IV liquid metal-cooled fast reactors calls for the improvement of fuel pin performance codes, in particular the enhancement of their predictive capabilities towards uranium-plutonium mixed oxide fuels and stainless-steel cladding under irradiation in fast reactor environments. To this end, the current capabilities of fuel performance codes must be critically assessed against experimental data from available irradiation experiments. This work is devoted to the assessment of three European fuel performance codes, namely GERMINAL, MACROS and TRANSURANUS, against the irradiation of two fuel pins selected from the SUPERFACT-1 experimental campaign. The pins are characterized by a low enrichment (~ 2 wt.%) of minor actinides (neptunium and americium) in the fuel, and by plutonium content and cladding material in line with design choices envisaged for liquid metal-cooled Generation IV reactor fuels. The predictions of the codes are compared to several experimental measurements, allowing the identification of the current code capabilities in predicting fuel restructuring, cladding deformation, redistribution of actinides and volatile fission products. The integral assessment against experimental data is complemented by a code-to-code benchmark focused on the evolution of quantities of engineering interest over time. The benchmark analysis points out the differences in the code predictions of fuel central temperature, fuel-cladding gap width, cladding outer radius, pin internal pressure and fission gas release and suggests potential modelling development paths towards an improved description of the fuel pin behaviour in fast reactor irradiation conditions.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.31 no.4
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• pp.154-158
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• 2021

The optical transmittance of Mn-doped SnO₂ monolayer film increased gradually from 80.9 to 85.4 % at 550 nm wavelengths upon increasing the O₂/Ar+O₂ concentration rate from 0 to 7.9 % and the band gap energy changed from 3.0 to 3.6 eV. The resistivity tended to decrease from 3.21 Ω·cm to 0.03 Ω·cm, reaching a minimum at 2.7 %, and then gradually increased from 0.03 to 52.0 Ω·cm at higher O₂/Ar+O₂ gas concentration ratio. Based on XPS spectra analysis, the Sn 3d_5/2 peak of Mn-doped SnO₂ single layer shifted slightly from 486.40 to 486.58 and O_1s peak also shifted from 530.20 to 530.33 eV with increase the O₂/Ar+O₂ concentration ratio. Therefore, the XPS spectra results indicate that a multiphase with SnO and SnO₂ coexisted in the sputtered Mn-doped SnO₂ monolayer film.

• Economic and Environmental Geology
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• v.52 no.2
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• pp.119-128
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• 2019

About 300,000 tones of oyster shell are annually produced in Korea and, thus, a massive recycling plan is required. Many desulfurizing studies using oyster shells with chemical composition of $CaCO_3$ have been performed so far; however, most of them have focused on dry desulfurization. This study investigates the possibility of using oyster shells for wet desulfurization after calcination. For this, a simulated wet desulfurization facility of spray type was devised and compared the SOx-stripping characteristics of calcined oyster shell with those of limestone. The calcined oyster shell slurry indicate a better desulfurizability than the slurries of raw shell or limestone because the oyster shell transformed to a more reactive phase ($Ca(OH)_2$) by the calcination and hydration. Because of this reason, when the calcined oyster shell slurries were used, the reaction residue showed the higher gypsum ($CaSO_4{\cdot}2H_2O$) contents than any other cases. In the continuous desulfurization experiments, calcined oyster shell slurry showed a wider pH variation than limestone or raw oyster shell slurries, another clear indication of high reactivity of calcined oyster shells for $SO_2$ absorption. Our study also shows that the efficiency of wet desulfurization can be improved by the use of calcined oyster shells.