• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.205-205
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• 2013

테라헤르쯔(terahertz: THz)파는 0.1~10 THz 의 범위로 적외선과 방송파 사이에 광대역 주파수 스펙트럼을 차지하고 있으며 직진성, 투과성, 그리고 낮은 에너지 (meV)를 가지고 있어 비 파괴적이고 무해한 장점을 지니고 있다. Ti:sapphire laser와 같은 femto-pulse source 등이 많은 발전이 되어 현재 많은 연구와 발전이 이루어지고 있다. femto-pulse source를 이용한 THz 응용에서는 높은 저항, 큰 전자 이동도, 그리고 아주 짧은 전하수명의 기판을 요구하는데 저온에서 성장한 (low-temperature grown : LT) GaAs는 격자 내에 Gallium 자리에 Arsenic이 치환 하면서 AsGa antisite가 발생하여 전하수명을 짧아지는 것을 응용하여 가장 많이 이용되고 있다. 현재 THz 응용분야에서 보다 작고 가격경쟁력이 있는 광통신을 이용한 THz photomixer등이 활발히 연구 하고 있다. 광섬유 내에서 손실과 분산이 최소값을 가지는 부분이 1.55 ${\mu}m$ 부근이고 In0.53Ga0.47As 기판을 이용하였을 때 여기에 완벽하게 만족하게 된다. 하지만 LT-InGaAs 의 경우 AsGa antisite로 인하여 carrier lifetime은 짧아지지만 높은 n-type 전하밀도를 가지게 된다. 이때 Be을 doping하여 전하밀도를 보상하여 높은 저항을 유지해야 하는데 Be의 활성화를 위해서는 열처리를 필요로 한다. 하지만 열처리를 하면 carrier lifetime이 길어지기 때문에 carrier lifetime과 저항을 적절히 조율해야 한다. 이는 물질자체의 특성이기 때문에 InGaAs는 GaAs보다 낮은 amplitude와 짧은 cut-off frequency를 가진다. 본 연구에서는 보다 높은 저항을 얻기 위하여 molecular beam epitaxy를 이용하여 semi-insulating InP:Fe 기판위에 격자 정합된 InGaAs:Be/InAlAs multi quantum well (MQW)를 온도별 ($250{\sim}400^{\circ}C$), 주기별 (50~150)로 성장을 하였고 이때 InGaAs layer의 Be doping level은 $2{\times}1018\;cm^{-3}$, Ex-situ annealing은 $550^{\circ}C$에서 10분으로 고정 하였다. THz 발생 실험에서는 InGaAs/InAlAs MQW은 4000 pA로 1,000 pA를 가지는 InGaAs epilayer보다 4배 높은 전류 신호를 얻을 수 있었고 모든 샘플이 2 THz에서 cut-off frequency를 가지고 있었다. THz 검출 실험에서는 LT-InGaAs:Be epilayer LT-InGaAs:Be/InAlAs, HT-InGaAs/InAlAs 샘플이 각각 180, 9000, 12000 pA의 전류신호를 가지고 있었고 모든 샘플이 2 THz에서 cut-off frequency를 가지고 있었다. HT-InGaAs/InAlAs MQW를 이용한 검출실험에서는 InGaAs layer가 defect free이지만 LT-InGaAs:Be/ InAlAs MQW 보다 높은 전류 신호를 얻을 수 있었다. 이는 InAlAs layer가 저항만 높이는 것뿐만 아니라 carrier trapping layer로써의 역할도 하는 것으로 사료된다.

• Journal of Wetlands Research
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• v.20 no.1
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• pp.63-71
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• 2018

The particle filtration mechanisms in an infiltration trench should be varying due to the different hydraulic conditions during stormwater runoff. The understanding of these variations associated with different filtration mechanisms and their effect on the particle removal efficiency is of vital importance. Therefore, a LID (Low Impact Development) system comprising of an infiltration trench packed with gravel and woodchip was investigated during the monitoring of several independent rainfall events. A typical rainfall event was divided into separate regimes and their corresponding flow conditions as well as filtration mechanisms in the trench were analyzed. According to hydraulic conditions, it was found out that filtration changes between vertical and horizontal flows as well as between unsaturated, saturated, and partially-saturated flows. Particle separation efficiency was high (55-76%) and was mainly governed by physical straining during the unsaturated period. It was then enhanced by diffusion during the saturated period (75-95%). When the trench became partially saturated at the end of the rainfall event, the efficiency decreased which was believed to be due to the existence of a negatively charged air-water interface which limited the removal to positively charged particles.

• Journal of Nutrition and Health
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• v.44 no.1
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• pp.16-28
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• 2011

Oxidative stress leads to the induction of cellular oxidative damage, which may cause adverse modifications of DNA, proteins, and lipids. The production of reactive species during oxidative stress contributes to the pathogenesis of many diseases. Antioxidant defenses can neutralize reactive oxygen species and protect against oxidative damage. The aim of this study was to assess the antioxidant status and the degree of DNA damage in Korean young adults using glutathione s-transferase (GST) polymorphisms. The GSTM1 and GSTT1 genotypes were characterized in 245 healthy young adults by smoking status, and their oxidative DNA damage in lymphocytes and antioxidant status were assessed by GST genotype. General characteristics were investigated by simple questionnaire. From the blood of the subjects, GST genotypes; degree of DNA damage in lymphocytes; the erythrocyte activities of superoxide dismutase, catalase, and glutathione peroxidase; plasma concentrations of total peroxyl radical-trapping potential (TRAP), vitamin C, ${\alpha}$- and ${\gamma}$-tocopherol, ${\alpha}$- and ${\beta}$-carotene and cryptoxanthin, as well as plasma lipid profiles, conjugated diene (CD), GOT, and GPT were analyzed. Of the 245 subjects studied, 23.2% were GSTM1 wild genotypes and 33.4% were GSTT1 wild genotype. No difference in erythrocyte activities of superoxide dismutase, catalase, or glutathione peroxidase, and the plasma TRAP level, CD, GOT, and GPT levels were observed between smokers and non-smokers categorized by GSTM1 or GSTT1 genotype. Plasma levels of ${\alpha}$- and ${\gamma}$-tocopherol increased significantly in smokers with the GSTT1 wild genotype (p < 0.05); however, plasma level of ${\alpha}$-carotene decreased significantly in non-smokers with the GSTM1 wild genotype (p < 0.05). DNA damage assessed by the Comet assay was significantly higher in non-smokers with the GSTM1 genotype; whereas DNA damage was significantly lower in non-smokers with the GSTT1 genotype. Total cholesterol and LDL cholesterol levels were significantly higher in non-smokers with the GSTT1 genotype than those with the GSTT1 wild genotype (p < 0.05). In conclusion, the GSTM1 genotype or the GSTT1 wild genotype in non-smokers aggravated their antioxidant status through DNA damage of lymphocytes; however, the GSTT1 wild type in non-smokers had normal plasma total cholesterol and LDL-cholesterol levels. This finding confirms that GST polymorphisms could be an important determinant of antioxidant status and plasma lipid profiles in non-smoking young adults. Further study is necessary to clarify the antioxidant status and/or lipid profiles of smokers with the GST polymorphism and to conduct a study with significantly more subjects.

• Nuclear Engineering and Technology
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• v.52 no.12
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• pp.2860-2866
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• 2020

Oxide dispersion-strengthened materials W-1wt%Pr₂O₃ and W-1wt%La₂O₃ were synthesized by wet chemical method and spark plasma sintering. The field emission scanning electron microscopy (FE-SEM) analysis, XRD and Vickers microhardness measurements were conducted to characterize the samples. The irradiations were carried out with a 5 keV helium ion beam to fluences up to 5.0 × 10²¹ ions/m² under 600 ℃ using the low-energy ion irradiation system. Transmission electron microscopy (TEM) study was performed to investigate the microstructural evolution in W-1wt%Pr₂O₃ and W-1wt%La₂O₃. At 1.0 × 10²⁰ He⁺/m², the average loops size of the W-1wt%Pr₂O₃ was 4.3 nm, much lower than W-1wt% La₂O₃ of 8.5 nm. However, helium bubbles were not observed throughout in both doped W materials. The effects of pre-irradiation with 1.0 × 10²¹ He⁺/m² on trapping of injected deuterium in doped W was studied by thermal desorption spectrometry (TDS) technique using quadrupole mass spectrometer. Compared with the samples without He⁺ pre-irradiation, deuterium (D) retention of doped W materials increased after He⁺ irradiation, whose retention was unsaturated at the damage level of 1.0 × 10²²D₂⁺/m². The present results implied that irradiation effect of He⁺ ions must be taken into account to evaluate the deuterium retention in fusion material applications.

• Korean journal of applied entomology
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• v.60 no.4
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• pp.431-448
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• 2021

We decided the efficient application timings of organo-synthetic insecticides for controlling the first generation larvae of O. furnacalis through investigations of insect stage-specific densities, damage aspects in maize, and effects of insecticides. A waxy maize cultivar, Ilmichal, was cultivated from April 20 (sowing) to July 26 (harvest, dough stage of maize) in Suwon, 2016. The maximum and 50% cumulative catch dates of the overwintering generation adults in the sex pheromone trapping were May 29 and May 31, respectively. Most of the first generation larvae finished their occurrence till the early reproductive stage of maize. The first generation larvae fed on leaves inside the whorl leaves before tassel and stem development of maize, sequentially moved to tassel and stem, and then moved finally to stem and ear parts. In the results of insecticide applications at different dates, the 9-11 leaf stage (June 10~17) and the 6-7 leaf stage (June 3) of maize were the most efficient application timings for direct spray of Etofenprox EC to maize, and for application of Carbofuran granules onto soil surface, respectively, which resulted in suppression of tunnelling damages. The timings for the two insecticides were 12-19 days and 5 days after the adult maximum catch date, respectively. Those timings after the 50% cumulative adult catch date were advanced 2 days.

• 한국노년학
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• v.38 no.2
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• pp.291-308
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• 2018

The purpose of this study is to analyze the factors influencing financial preparedness for retirement of the middle-aged North Korean defectors (resettling in South Korea) using concepts of 'financial literacy' and 'financial inclusion'. Those questioned were 100 North Korean defectors of 40-60 years-old residing in Seoul and Gyeonggi-do Province selected by convenience sampling, one of the non-probability sampling. Path analysis is used as a main analysis method. The results of the study show a direct effect in which increased financial literacy resulted in better financial preparedness for retirement among middle-aged North Korean defectors at a statistically significant level. In addition, by boost-trapping method, financial inclusion has its mediating effect on the relationship between financial literacy and financial preparedness for retirement. However, this study shows that influence of financial literacy on financial preparedness for retirement is different across economic statues. The mediating effect of financial inclusion on the relationship between financial literacy and financial preparedness is statistically significant only for the low-income group. Meanwhile, for the above average income group, financial literacy has a direct effect on the financial preparedness after retirement at a statistically significant level. Based on these results, this study suggests practical and policy implementation such as necessity of customized financial education suited to their economic status, development of financial instruments for retirement, introduction of financial social workers to prepare stable old age of North Korean defectors.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.6
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• pp.14-18
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• 2019

The conductivity of a semiconductor is primarily determined by the carriers. To achieve higher conductivity, the number of carriers should be high, and an energy trap level is created so that the carriers can cross the forbidden zone with low energy. Carriers have a crystalline binding structure, and interfacial mismatching tends to make them less conductive. In general, high-concentration doping is typically used to increase mobility. However, higher conductivity is also observed in non-orthogonal conjugation structures. In this study, the phenomena of higher conductivity and higher mobility were observed with space charge limiting current due to tunneling phenomena, which are different from trapping phenomena. In an atypical structure, the number of carriers is low, the resistance is high, and the on/off characteristics of capacitances are improved, thus increasing the mobility. ZTO thin film improved the on/off characteristics of capacitances after heat treating at $150^{\circ}C$. In charging and discharging tests, there was a time difference in the charge and discharging shapes, there was no distinction between n and p type, and the bonding structure was amorphous, such as in the depletion layer. The amorphous bonding structure can be seen as a potential barrier, which is also a source of space charge limiting current and causes conduction as a result of tunneling. Thus, increased mobility was observed in the non-structured configuration, and the conductivity increased despite the reduction of carriers.

• The Journal of Korea Assosiation for Disability and Oral Health
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• v.15 no.1
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• pp.60-64
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• 2019

Swyer-James syndrome (SJS), also known as Swyer-James-MacLeod syndrome and unilateral hyperlucent lung syndrome, is rare acquired pulmonary disorder develops secondary to infectious etiologies in early childhood. Viral respiratory infection such as adenoviruses or Mycoplasma pneumoniae in infancy or early childhood rarely cause Swyer-James syndrome. It is generally characterized on radiographs by a unilateral small lung with hyperlucency and air trapping on expiration. In many cases unaffected lung tissue functions normally, compensating for affected lung portion. Preoperative assessment is needed to determinate individual's pulmonary function. A 4-year-old boy with Swyer-James syndrome visited Seoul National University Dental Hospital Department of pediatric dentistry for caries treatment. Clinical and radiographic examinations revealed multiple carious lesions on deciduous teeth. Considering patient's underling disease, age, and level of cooperation, dental treatment under general anesthesia was scheduled. Dental treatment was done with composite resin and stainless-steel crown. Since ventilation of Swyer-James syndrome patients was diminished because of airway obstruction, close monitoring of ventilation is necessary during dental treatment. Considering pulmonary pathology, general anesthesia rather than sedation is recommended when special behavior management is required for dental treatment. Swyer-James syndrome patients can tolerate general anesthesia and surgery well, according to several reports.

• Journal of Adhesion and Interface
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• v.22 no.3
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• pp.91-97
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• 2021

By introducing an organic interlayer on the Parylene C dielectric surface, the electrical device performances and the operating stabilities of organic field-effect transistors (OFETs) were improved. To achieve this goal, hexamethyldisilazane (HMDS) and octadecyltrichlorosilane (ODTS), as the organic interlayer materials, were used to control the surface energy of the Parylene C dielectrics. For the bare case used with the pristine Parylene C dielectrics, the field-effect mobility (μ_FET) and threshold voltage (V_th) of dinaphtho[2,3-b:2',3'-f ]thieno[3,2-b]- thiophene (DNTT) FET devices were measured at 0.12 cm²V^-1s^-1 and - 5.23 V, respectively. On the other hand, the OFET devices with HMDS- and ODTS-modified cases showed the improved μ_FET values of 0.32 and 0.34 cm²V^-1s^-1, respectively. More important point is that the μ_FET and V_th of the DNTT FET device with the ODTS-modified Parylene C dielectric presented the smallest changes during a repeated measurement of 1000 times, implying that it has the most stable operating stability. The results could be meaned that the organic interlayer, especially ODTS, effectively covers the Parylene C dielectric surface with alkyl chains and reduces the charge trapping at the interface region between active layer and dielectric, thereby improving the electrical operating stability.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.24 no.1
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• pp.69-80
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• 2021

The new town in Korea, developed as a large-scale housing plan, has created urban ecological corridors to provide habitat and movement routes to wildlife and to promote natural ecological flow. This study aimed to investigate the use of wildlife in 10 ecological corridors in Gwanggyo New Town through camera trap technology and confirm effectiveness by identifying environmental factors affecting the use of wildlife's urban ecological corridors. Our researchers installed 20 unmanned sensor cameras at each the entrance and exit of the ecological corridors, and monitored urban wildlife for 10 weeks. According to the monioring results, the main species in Gwanggyo New Town were identified not only raccons, cats, water deer, korean hare and avain but also magpies, dove, eurasian tree sparrow, ring-necked pheasant, and eurasian jay. The number of uses ecological corridors of urban residents was 801(13.49%), as high as that of urban wildlife (1,140, 19.20%), which was judged to have disturbed the use of ecological corridors by wildlife. However, most dominant species of urban wildlife are nocturnal so that, it was judged that they share home range with urban residents at a time interval. In addition, according to the correlation analysis results between the mammal using rate of the urban ecological corridors and environmental factors(ecological corridor-specific length, ecological corridor-specific width, cover degree, shielding degree, connected green area, separation of movement routes, and presence of streetlights), environmental factors were not statistically significant. However, the more the area of green space connected to ecological corridors, the more increasing the mammal using rate of ecological corridor(r=0.71, p<0.05). Therefore, the area of green space connected to the ecological corridors that is associated with rate of wildlife using corridors should be considered as a priority when developing an urban ecological corridors. In the future, this study will extend the observation period of the ecological corridors and continuously accumulate data by adding the number of observation cameras. Furthermore, it is expected that the results of this study can be used as basic data for the standards for urban ecological corridors installation.