• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.170-170
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• 2010

Thin-film transistors (TFT) have become the key components of electronic and optoelectronic devices. Most conventional thin-film field-effect transistors in display applications use an amorphous or polycrystal Si:H layer as the channel. This silicon layers are opaque in the visible range and severely restrict the amount of light detected by the observer due to its bandgap energy smaller than the visible light. Therefore, Si:H TFT devices reduce the efficiency of light transmittance and brightness. One method to increase the efficiency is to use the transparent oxides for the channel, electrode, and gate insulator. The development of transparent oxides for the components of thin-film field-effect transistors and the room-temperature fabrication with low voltage operations of the devices can offer the flexibility in designing the devices and contribute to the progress of next generation display technologies based on transparent displays and flexible displays. In this thesis, I report on the dc performance of transparent thin-film transistors using amorphous indium tin zinc oxides for an active layer. $SiO_2$ was employed as the gate dielectric oxide. The amorphous indium tin zinc oxides were deposited by RF magnetron sputtering. The carrier concentration of amorphous indium tin zinc oxides was controlled by oxygen pressure in the sputtering ambient. Devices are realized that display a threshold voltage of 4.17V and an on/off ration of ${\sim}10^9$ operated as an n-type enhancement mode with saturation mobility with $15.8\;cm^2/Vs$. In conclusion, the fabrication and characterization of thin-film transistors using amorphous indium tin zinc oxides for an active layer were reported. The devices were fabricated at room temperature by RF magnetron sputtering. The operation of the devices was an n-type enhancement mode with good saturation characteristics.

• Proceedings of the KWS Conference
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• 2009.11a
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• pp.43-43
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• 2009

단련용 다결정 Ni기 초내열합금은 우수한 가공성, 내산화성, 고온특성 등으로 가스터빈 연소기, 디스크, 증기발생기 전열관 등 발전용 고온부품 소재에 널리 적용되고 있다. 최근 발전설비의 고효율화를 꾀하기 위해 작동 온도를 현격히 증가시키는 기술방향으로 발전하고 있고, 소재측면에서는 기존의 초내열합금 대비 고기능성을 확보할 수 있는 차세대 Ni기 초내열합금 개발이 유럽, 미국, 일본, 중국 등을 중심으로 활발히 이루어지고 있다. 이러한 소재의 고온강도 (온도수용성)를 향상시키기 위해서는 통상 규칙격자 금속간화합물인 $Ni_3(Al,Ti)-{\gamma}'$상의 분율을 증가시킬 수 있지만, ${\gamma}'$상분율이 증가할 경우 용접 및 후열처리 동안 용접열영향부 (HAZ)에서 액화균열이 발생할 가능성이 높아진다. 결정립계를 따라 발생하는 HAZ 액화균열은 입계특성에 의해 크게 영향을 받을 것으로 판단된다. 한편, 본 연구자들은 최근 입계 serration 현상을 단련용 합금에 도입시키는 특별한 열처리를 이론적 접근법을 통해 개발하였다. 형성된 파형입계는 결정학적인 관점에서 조밀 {111} 입계면을 갖도록 분해 (dissociation)되어 낮은 계면에너지를 갖게 됨을 확인하였으며, 입계형상 변화뿐만 아니라 탄화물 특성변화까지 유도하여 크리프 수명을 기존대비 약 40% 정도 향상시킴을 확인하였다. 이러한 직선형 입계 대비 'special boundary'로 간주되는 파형입계가 도입될 경우, HAZ 결정립크기 변화 및 액화거동에 미치는 영향을 고찰하고, 아울러 입계특성 제어가 용접성/용접부 품질 향상에 기여할 수 있는 가능성도 토의하고자 하였다. 본 연구에서는 재현 HAZ 열사이클 시험을 통해 미세구조를 정량적으로 비교하였다. 상대적으로 입계구조가 안정된 파형입계의 이동속도가 高계면 에너지를 갖는 직선형 입계보다 느려 HAZ 결정립 성장이 효과적으로 억제됨을 확인할 수 있었다. 입계 액화거동을 살펴보면, 두 시편 모두 $M_{23}C_6$, MC 등 입계탄화물 계면이 빠른 승온중 액화반응 (constitutional liquation)에 의해 입계가 액화되었으며, 이후 급냉에 의해 입계에 액상막이 존재한 흔적이 발견되었다. 최고온도별로 입계액화 폭/비율을 정량적으로 비교한 결과, 파형입계가 직선입계 대비 대체로 낮음을 확인할 수 있었으며, 때때로 액화되지 않고 잔존하는 입계 탄화물이 관찰되었다. 재현 HAZ 미세조직을 통해 Hot ductility 시험 결과를 유추하자면, 파형입계가 직선입계 보다 좁은 취성온도영역 (Brittle Temperature Range)을 나타낼 것으로 예상되어, 입계특성제어에 의해 Ni기 초내열합금의 용접성을 향상 가능성을 확인하였다.

• Korean Journal of Veterinary Research
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• v.37 no.3
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• pp.541-546
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• 1997

There are two conserved regions with a significantly high amino acid sequence homology among the A subunits of STX, SLTs and ricin. To produce an inactive Verotoxin-2 (VT-2), two different mutants, pE167D and pDE5A, were constructed by site-directed mutagenesis, respectively, on the basis of the previous reports that two regions lie within the active-site clefts of the A subunits of ricin and STX family. The cytotoxicity ($10^3$ $CD_{50}/ml$) of VT-2 holotoxin with E167D mutation was reduced by $10^3$-fold compared with wild-type level. In addition, VT-2 with DE5A ($Trp_{202}GlyArgIleSer_{206}$) deletion mutation showed a significantly low cytotoxicity ($10^1$ $CD_{50}/ml$), resulting in $10^5$- and $10^2$-fold reductions, respectively, compared with the wild-type and E167D mutatant. SDS-PAGE for protein samples showed a 33-kDa band corresponding to the A subunit of VT-2. These results indicate that reduction in cytotoxic activity was affected not by amount of VT-2 protein produced but by mutation.

• Journal of Preventive Medicine and Public Health
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• v.22 no.1 s.25
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• pp.153-161
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• 1989

Authors studied on the prevalence of 94 cases of pneumoconiosis who were found out through the screening test on 1,062 workers engaged in welding process at 36 shipyard in Pusan area from March 1st, 1986 to November 30th, 1986. The result were as follows; 1. Dust concentration was measured $4.49{\pm}0.54mg/m^3$ in the small scale shipyard while it was $6.25{\pm}1.08mg/m^3$ in the large one. 2. The prevalence of welder's lung was 8.9% (male:8.5%, female:12.0%) and this is consist of 4.9% suspected pneumoconiosis and 4.0% pneumoconiosis more than category 1/0. 3. The prevalence was significantly increased according to the duration of dust exposure(p<0.05), and it showed the increasing tendency by the age group. 4. The prevalence was significantly higher in the large scale shipyard than is the small scale one(p<0.01). 5. The type and shape of opacities were 71.4% of p type and 28.6% of q type, however no pneumoconiosis with r type observed in this study. 6. The main subjective symptoms were the sputum(29.8%), coughing(25.5%), shortness of breath(20.2%), fatique(6.4%), and chest pain(5.3%). In other hand, 57.4% of pneumoconiosis were asymptomatic. 7. The prevalence of pulmonary tuberculosis was radiologically 1.7% in all subjects including 5.3% in pneumoconiosis and 1.3% in no pneumoconiosis(p<0.01).

• Parasites, Hosts and Diseases
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• v.27 no.1
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• pp.41-46
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• 1989

This study was performed to observe the infection rate and infection intensity of fresh water fish such as pale chub (Z. platypus) and dark chub (Z. temminckii) with the metacercariae of C. armatus. The fish were caught in several rivers and streams from June to September, 1988 and examined by artificial digestion technique. Total 370 fish were caught at 19 rivers. The metacercarial (C. armatus) infection rate and average burden in Z. Platypus were 86.8% and 224, and those in Z. tsmminckii were 78.5% and 131. The infection rate and burden per fish were 73.4% and 32 in the fish caught from the Han river, and 88.0% and 44 from the Youngsan river. All fish caught from the Keum and the Tamjin river were infected and their mean metacercarial density was 45 and 59 respectively. The infection rate and density in fish caught from the Seomjin and Nagdong rivers were 100% and 119, and 81.0% and 348 respectively. From this study, it is confirmed that C. armatus is widely distributed along 5 major rivers in Korea.

• Parasites, Hosts and Diseases
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• v.26 no.4
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• pp.229-238
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• 1988

In vitro culture of Toxoplasma gondii in HL-60 cells and cell-mediates immunity against Toxoplasma in dimethylsulfoxide(DMSO) -induced HL-60 cells, i.e., differentiation into granulocytes, were pursued. HL-60 calls were treated with various concentrations of DMSO, and 1.3%(v/v) for 3 day incubation was chosen as the optimal condition icy differentiation into granulocytes. The degree of differentiation was assayed in physiological and functional aspects in addition to morphological point. When treated with 1.3% DMSO for 3 days, HL-60 cells did not synthesiar DNA materials beyond background level, and showed active chemotactic response to chemotactic peptide, formal-methionyl-leucyl-phenylalanine(FMLP). Morphologically promyelocytes of high nuclearlcytoplasmic(NIC) ratio changed to granulocytes of relatively low WJC ratio. The relationships between HL-60 cells or DMSO-induced HL-60 cells and Toxoplasma were examined after stain with Giemsa and Buorescent dye (acridine orange). HL-60 cells did not show any sign of torso- plasmacidal activity but showed intracellular proliferation of Texoplasma to form rosette for 72 hr co-culture. In contrast, OMSO-induced HL-60 cells phagocytosed Toxoplasma within 1 hr, and performed a process of intracellular digestion of Toxoplasma thereafter. With the above results, it is suggested that phagosome-Iysosome fusion is one of the critical events for the parasitism by Toxoplasma or for susceptibility of host cells. The in vitro culture system of this study has offered a defined condition to study the protozoan parasite-host cell interactions.

• Korean Journal of Weed Science
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• v.9 no.2
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• pp.154-167
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• 1989

This study was conducted to determine the influence of various extracts from 21 medicinal plants including Bupleurm falcatum on the germination and growth of Lactuca sativa, Oryza native and E. crus-galli var. crus-galli, and the amount of their phenolic acids, fatty acids and organic acids, Water extract(5%) of all the medicinal plants, particularly Acorus gramineus, Cnidium officinale, Aconitum carmicheali, Bulpeurum falcatum, Zingiber officinale, Angelica gigas and Curcuma zeodaria inhibited over 90% of the lettuce seed germination and growth, indicating that medicinal plants contained the biologically active substances. The highest amount of phenolic compounds was observed in Prunus crmenica var, ansu(30.6013mg/g) followed by Aconitum ciliare(29.1008mg/g) and Cnidium officienale(27.2943mg/g) which inhibited markedly the germination of testing plants, showing the close relation of phenolic compounds to inhibitory effects. Cnidium officinale contained the highest amount of fatty acids(24.10mg/g) and organic acids(21.04mg/g) which may be partly related to inhibitory effects.

• Korean Journal of Weed Science
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• v.9 no.2
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• pp.141-148
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• 1989

Echinochloa species collected from 13 places of Korea appeared to be morphologically very different. They were classified by Yabuno's seed morphology method into two species such as Echinochloa oryzicola and Echinochloa crus-galli which have two varieties such E. crus-galli var, cuss-galli and var, praticola. Among them, E. oryzicola was morphologically similar to Oryza sativa, but it had small leaf length with straight from, no awn, late heading and little interspecific variance. As compared with E. oryzicola, E. eras-galli var. crus-galli, and var, praticola showed a great variance exerting so difficulty in classifing them morphologically, particularly a great variance in leaf length, tiller number and grain size. E. oryzicola species showed the more sensitive response to butachor and thiobencarb herbicides than E. eras-galli var. praticola and var. eras-galli. However, E. eras-galli var. praticola was themore sensitive one to pretilachloa herbicide than such as E. oryzicola and E. eras-galli var. eras-galli, indicating that Echinochloa species might have a selective response to the annual herbicides tested.

• Korean Journal of Microbiology
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• v.35 no.2
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• pp.158-163
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• 1999

A ploygalacturonase-produchg yeast was isolated from Cheju soil by selective eivichment media. One strain which has the highesl activity of polygalacturonase was selected. The characle~ishcs of the strain CS-2 were as follows: CS-2 utilized xylose. sucrose, maltose, u.ehalose, cellobiose. melibiose, lactose, raffinose, inosiiol, dulicilol, and dextrose, but did not utilized galactose, nitrate. nit~te, and lysine. Growth of CS-2 was inhibited by cyclohexamide, 1% acetic acid, and high concenaation (over 50%) of glucose. It grew at $30^{\circ}C$ but did 'IIOL $35^{\circ}C$. The cell size ofthe strain CS-2 was 2.9 p ~ n in length and 1.3 $\mu$ in diameter. Vegetable reproductmn was multiple budding and ascospre was present I to 4. Pseudomycelia or true myceliua formation were not observed In any of the cullureq. These results suggest that strain CS-2 is most likely a strain related Cryptococcus spp. (Cryptococcu spp. CS-2). When polygalacturonase or ihe yeast was induced by addition of polygalactoronic acid, polygalacturonase activity was detected in culture supernatent. There was a peak of specific activity a1 he mid-stationary phase(3 days culture) of growth. Polygalacturonase specific activity of Crylmcoccus sp. CS-2 was 2.96 unitsling. The molecular weighl ol'polygalacturonase was showed to be 46 KDa by both SDS-PAGE and activity stailling.

• Korean Journal of Agricultural and Forest Meteorology
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• v.7 no.2
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• pp.148-155
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• 2005

An accurate prediction of blooming date is crucial for many authorities to schedule and organize successful spring flower festivals in Korea. The Korea Meteorological Administration (KMA) has been using regression models combined with a subjective correction by forecasters to issue blooming date forecasts for major cities. Using mean monthly temperature data for February (observed) and March (predicted), they issue blooming date forecasts in late February to early March each year. The method has been proved accurate enough for the purpose of scheduling spring festivals in the relevant cities, but cannot be used in areas where no official climate and phenology data are available. We suggest a thermal time-based two-step phenological model for predicting the blooming dates of spring flowers, which can be applied to any geographic location regardless of data availability. The model consists of two sequential periods: the rest period described by chilling requirement and the forcing period described by heating requirement. It requires daily maximum and minimum temperature as an input and calculates daily chill units until a pre-determined chilling requirement for rest release. After the projected rest release date, it accumulates daily heat units (growing degree days) until a pre- determined heating requirement for flowering. Model parameters were derived from the observed bud-burst and flowering dates of cherry tree (Prunus serrulata var. spontanea) at KMA Seoul station along with daily temperature data for 1923-1950. The model was applied to the 1955-2004 daily temperature data to estimate the cherry blooming dates and the deviations from the observed dates were compared with those predicted by the KMA method. Our model performed better than the KMA method in predicting the cherry blooming dates during the last 50 years (MAE = 2.31 vs. 1.58, RMSE = 2.96 vs. 2.09), showing a strong feasibility of operational application.