• Environmental and Resource Economics Review
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• v.27 no.3
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• pp.421-461
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• 2018

Windpower turbines have positive values for visitors with regard to tourism and learning. On the other hand, it is clear that windpower turbines have negative impact on the landscape, particularly when the level of landscape is high. The impact of windpower turbines on the visitor's value is composed of two elements: the viewingvalue which is independent of the level of landscape and the landscape value which varies with the level of landscape. The net visitor's value of windpower turbines is the sum of these two values with opposite signs. This study used a choice experimentation method to value the impact of windpower turbine construction in the mountainous area in Korea. This study estimated the viewing value, the landscape value and the visit value as the sum of the two values. The estimated results demonstrated a significantly positive viewing value, a significantly negative landscape value, and weakly negative net visit value in average.

• Clean Technology
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• v.29 no.1
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• pp.71-75
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• 2023

In general, the presence of non-selective intercrystalline (grain boundary) defects in polycrystalline metal-organic framework (MOF) or zeolite membranes, which are known to be ca. 1 nm in size, causes lower membrane performance (selectivity) than the intrinsically expected. In this study we show that applying a thin polymeric coating of polydimethylsiloxane (PDMS) on a polycrystalline MOF membrane is effective to cap the non-selective intercrystalline defects and therefore improve membrane performance. To demonstrate the concept, first, polycrystalline UiO-66, one of Zr-based MOFs, membranes were prepared by an in-situ solvothermal growth. By controlling membrane growth condition with respect to growth temperature, we were able to obtain polycrystalline UiO-66 membranes at 150 ℃ with intercrystalline defects of which the quantity is not significant, so it can be plugged by the suggested PDMS deposition. Second, their performances were compared before and after the PDMS deposition. As expected, the PDMS deposition ended up with a noticeable increase in CO₂/N₂ ideal selectivity from 6 to 14, indicating successful intercrystalline defect plugging. However, the enhancement in CO₂/N₂ selectivity was accompanied by a significant reduction in CO₂ permeance from 5700 to 33 GPU because the PDMS deposition not only plugs defects but also forms a continuous coating on membrane surface, adding an additional transport resistance.

• Proceedings of the Membrane Society of Korea Conference
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• 1998.10a
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• pp.96-98
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• 1998

1. 서론 : 팔라듐이나 이의 합금막들은 높은 선택적 투과특성으로 인해 수소 정제나 분리막 반응기와 같은 산업응용 분야에서 매우 높은 관심을 갖고 있다. 상업적으로 이용되고 있는 이러한 막들은 통상적인 metallugical process에 의해 제조괸 self-supported type으로 수소 투과 속도가 낮을 뿐만 아니라 팔라듐 등은 고가의 귀금속이므로 비경제적이다. 따라서 현재 대부분의 연구자들은 기계적 강도를 유지하기 의한 다공성 지지체 위에 얇은 금속 박막을 코팅함으로서 투과성을 높이는 동시에 경제적인 복합막 형태의 막을 만드는데 연구의 촛점을 맞추고 있다. 이러한 형태의 막을 제조하기 위한 금속 박막 제조법은 무전해 도금법(electroless deposition), 화학증착법(CVD), 스퍼터링(sputtering), 전해도금법(electrodeposition) 등이 시도되었다. 그러나 수소에 대한 우수한 선택적 투과 특성을 갖기 의해서는 대부분 5$\mu$m 이상의 두꺼운 막을 제조하였으며 이보다 얇은 막의 제조에 한계가 있기 때문에 이들 막에 대한 기체 투과 특성에 대한 연구결과는 많지 않다. 본 연구에서는 기존의 전기도금법을 응용한 소위 'vacuum electrodeposition' 이란 새로운 기술을 도입함으로써 우수한 선택적 투과성을 갖는 2$\mu$m 이하의 팔라듐 합금 박막 제조를 가능하게 하였다. 지지체 표면의 거칠음 정도, 평균 기공 크기 등의 지지체 성질의 조절에 의한 금속 박막의 핀홀을 최소화함으로써 질소와 같은 inert gas의 투과도는 거의 없게 유지하는 동시에 금속 박막 두께, 결정 구조(e.g. grain size), 합금 조성 등을 조절함으로써 수소의 투과도를 높이고자 하였다. 있다. 후자의 경우, 미량의 과산화수소수 (1~10,000 ppm)를 이용해 처리 해주는 방법의 경우 경제적으로 큰 장점이 있고, 처리가 단순하다는 장점이 있으나 과산화수소수 자체에 포함하고 있는 높은 impurit level, 그리고 처리후 장시간의 flushing time을 가져야 한다는 단점등이 존재 하고 있다.요구된다. 몰입이 가능하여 임계치가 저하된 것으로 여겨진다. 또한 광학적 이득의 존재는 이 구조에 의한 극단파장 반도체 레이저다이오드의 실현 가능성을 나타내는 것이다.548 mL에 비해 통계학적으로 의의 있게 적었다(p<0.05). 결론: 관상동맥우회로 조성수술에서 전방온혈심정지액을 사용할 때 희석되지 많은 고농도 포타슘은 fliud overload와 수혈을 피하고 delivery kit를 사용하지 않음으로써 효과적이고 만족할 만한 심근보호 효과를 보였다.를 보였다.4주까지에서는 비교적 폐포는 정상적 구조를 유지하면서 부분적으로 소폐동맥 중막의 비후와 간질에 호산구 침윤의 소견이 특징적으로 관찰되었다. 결론: 분리 폐 관류는 정맥주입 방법에 비해 고농도의 cisplatin 투여로 인한 다른 장기에서의 농도 증가 없이 폐 조직에 약 50배 정도의 고농도 cisplatin을 투여할 수 있었으며, 또한 분리 폐 관류 시 cisplatin에 의한 직접적 폐 독성은 발견되지 않았다이 낮았으나 통계학적 의의는 없었다[10.0%(4/40) : 8.2%(20/244), p>0.05]. 결론: 비디오흉강경술에서 재발을 낮추기 위해 수술시 폐야 전체를 관찰하여 존재하는 폐기포를 놓치지 않는 것이 중요하며, 폐기포를 확인하지 못한 경우와 이차성 자연기흉에 대해서는 흉막유착술에 더 세심한 주의가 필요하다는 것을 확인하였다. 비디오흉강경수술

• Applied Microscopy
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• v.34 no.2
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• pp.145-157
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• 2004

The aim of the present study was to examine in detail, both at light and electron microscopical levels, the morphological variations in ameloblast of the fetal rat incisor enamel organ. Rats were started on distilled water at the beginning of pregnancy. The pups were sacrificed 11 days after delivery and animals were perfused intravascularly with glutaraldehyde and the incisors were removed. To examine on the ultrastructure of the ameloblast, the study employed primary light microscopy but electron microscopy was used to clarify some of the light microscopic finding. Longitudinal sections through the incisors of the rat show a continuous layer of ameloblasts on the labial surface of the tooth. This layer contains the entire sequence of developmental stages in enamel production. The ameloblast layer was divided into three main zones: 1) Presecretory zone, region of ameloblasts facing pulp. 2) Secretory zone, region of inner and outer enamel secretion. 3) Maturation zone, region of reduced ameloblasts. In particularly, the present study has shown that two distinctively different types of ameloblasts appear in the enamel organ during enamel maturation in the rat incisor. These two types have been designated ruffle-ended ameloblasts (rAB) and smooth-ended ameloblasts (sAB). The fluoride produces marked alteration in the fine structure of ameloblast from teeth of young rats, such as large confluent distensions of the endoplasmic reticulum and swelling of isolated mitochondria. This experimental data suggested that exposure prolonged of animal to high level of fluoride appears to induce a few dramatic changes in the normal appositional growth and initial mineralization of enamel created during amelogenesis.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.3-3
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• 2008

21 세기 제 3의 산업혁명을 가져올 것으로 기대되는 나노기술(NT), 정보기술(IT), 바이오기술(BT)은 전 세계 과학자들의 마음을 사로잡고 있다. 이 가운데 나노기술은 전자산업에 응용시 그 기대효과는 우리가 상상하는 이상의 것이라 예상하고 있다. 나노기술에 특히 관심을 가지는 이유는 물질이 마이크로미터 크기로 작아져도 벌크 물질의 물리적 특성이 그대로 유지되지만, 나노미터 크기가 되면서 우리가 경험하지 못했던 새로운 물리적 특성들이 발현되기 때문이다. 그 특성에는 양자구속효과, Hall-Petch 효과, 자기효과 등이 있다. 나노기술의 구현은 양자점과 같은 영차원 나노입자, 나노와이어, 나노막대, 나노리본 등과 같은 직경이 100nm 이하의 일차원 구조의 나노물질 및 나노박막과 기타 100nm 이하의 나노구조물들이 사용된다. 현재 일차원 구조를 이용한 전자디바이스화 연구는 결정성장을 정확하게 조절하는 합성기술 합성된 일차원 나노물질의 물리적 특성을 지배하는 각종 파라미터들과 물리적 특성들과의 상관관계 정립, 나노와이어를 이용한 Bottom-up 방식에 의한 조립기술 확보를 위해 활발히 진행 중이다. 하지만 나노구조의 특성을 확인하는 형태의 연구일 뿐, 실제 디바이스화에는 여전히 많은 과제를 안고 있다. 본 연구에서는 산화아연을 기반으로 한 고품위 능동형 산화물 나노구조의 다양한 성장방법 및 물성 평가에 대해 연구하였다. 성장장비로는 MOCVD와 스퍼터링을 이용하여 대면적 균일 성장을 이룰 수 있었다. 특히 실제 광전소자에 응용요구에 알맞은 Bottom-up 방식에 의한 수직성장 기술, 길이/직경 비 향상 기술, 결정성 향상 기술, 저온성장 기술, Dimension 조절 기술 Interfacial layer 제거 기술 등을 중점적으로 연구하였다. Dimension 조절 기술로 p-Si 기판위에 성장된 나노 LED에서는 밝은 emission을 관찰하였으며, 세계에서 최초로 스퍼터링을 이용하여 4인치 웨이퍼에 대면적 수직 성장하였다. 최근에는 선택적 삼원계 씨앗층을 이용한 길이/직경 비가 매우 향상된 MgZnO 나노와이어를 Interfacial layer 없이 수직으로 성장하여 산화물 전계방출 에미터로서의 가능성을 확인하였다.

• Journal of Advanced Marine Engineering and Technology
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• v.41 no.3
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• pp.276-280
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• 2017

In this study, we investigated the effect of sterilization and the neutralization of treated ballast water using seawater electrolysis. The electrolysis apparatus has a cation-selective membrane for passing the cation and a titanium electrode in each cell. We examined the sterilization effect after an incubation period of 24 hr. The oxidation reaction during electrolysis caused, the solution to become strongly acidic due to the generation of a hydroxyl group, and the oxidation reduction potentials(ORP) was increased to 800 - 1200mV. After the reduction reaction, the solution became alkaline(pH 9 - 12), and ORP was decreased to - 900 - - 750 mV. It might be possible to control the pH of ballast water through electrolysis. In addition, we demonstrated the effects of sterilization of ballast water containing generated hypochlorous acid using electrolysis under high ORP condition.

• Journal of Gifted/Talented Education
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• v.13 no.4
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• pp.65-94
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• 2003

The purpose of this study is to acquire the information on the current situation of students' selection process in order to renovate the system of picking up the students. As a first step of the study, we examined the validity of the factors of the single-out system such as qualification and the process for the application and the standards and proceeding of the selection. Then we analysed the result of the entrance examination of Hansung Science Highschool in 2002. The analysis was on the correlation between the result of entrance examination and the achievement in the school and the decision of the course after graduation. To know on the achievement of the students, we investigated the records of regular tests and asked the teachers' opinion in math and science classes. As a result, we gained the following points: First, the present single-out system has a danger of excluding students who are much talented in science and math field because it is based on students' achievements in middle schools; Second, the new selection system should consider the character and attitude of the applicants in addition to their knowledge; Third, the continuous observation of the teacher in middle school should be an important factor of the picking up system; Fourth, more questions requiring divergent thinking ability and inquiry skill should be developed as selective examination question. Also examination questions should cover the various contents from mathematics to science, and do not affect pre-learning; Finally, the system of present letting all students stand in one line should be changed into that of letting students in various lines. We can consider using multi-step selection system.

• Journal of Dental Rehabilitation and Applied Science
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• v.35 no.3
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• pp.160-169
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• 2019

Purpose: The purpose of this study was to evaluate the antimicrobial effects of a toothbrush with light-emitting diodes (LEDs) on periodontitis-associated dental biofilm attached to a zirconia surface by static and dynamic methods. Materials and Methods: Zirconia disks (12 mm diameter, 2.5 mm thickness) were inserted into a 24-well plate (static method) or inside a Center for Disease Control and Prevention (CDC) biofilm reactor (dynamic method) to form dental biofilms using Streptococcus gordonii and Fusobacterium nucleatum. The disks with biofilm were subdivided into five treatment groups-control, commercial photodynamic therapy (PDT), toothbrush alone (B), brush with LED (BL), and brush with LED+erythrosine (BLE). After treatment, the disks were agitated to detach the bacteria, and the resulting solutions were spread directly on selective agar. The number of viable bacteria and percentage of bacterial reduction were determined from colony counts. Scanning electron microscopy (SEM) was performed to visualize alterations in bacterial morphology. Results: No significant difference in biofilm formation was observed between dynamic and static methods. A significant difference was observed in the number of viable bacteria between the control and all experimental groups (P < 0.05). The percentage of bacterial reduction in the BLE group was significantly higher than in the other treated groups (P < 0.05). SEM revealed damaged bacterial cell walls in the PDT, BL, and BLE groups, but intact cell walls in the control and B groups. Conclusion: The findings suggest that an LED toothbrush with erythrosine is more effective than other treatments in reducing the viability of periodontitis-associated bacteria attached to zirconia in vitro.

• The korean journal of orthodontics
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• v.30 no.3 s.80
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• pp.287-296
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• 2000

It is well known that oral appliance could improve respiratory difficulty in patients with obstructive sleep apnea (OSA). To evaluate the effect of oral appliance, polysomnography and cephalometry were performed in OSA patients before and after oral appliance was used. Twenty four OSA patients were included in this study. Respiratory difficulty index (RDI) was obtained from polysomnography and the movement of soft palate, tongue, posterior pharygeal wall, hyoid bone, and mandible and the variables of the facial pattern were measured on the cephalogram. The changes of cephalometric parameters were compared to the RDI changes and the correlation was tested. After oral appliance was used, RDI decreased from 46.8 to 13.3. There was significant relationship between RDI improvement and the anterior movement of the mandible and superior movement of the hyoid bone. In 8 patients whose RDI was most improved, RDI improvement rate was correlated with the anterior movement of the tongue and anterior-posterior (AP) diameter of the airway at the levels between the lower portion of the soft palate and epiglottis. These results could conclude that anterior movement of the tongue and superior movement of the hyoid bone would be favorable cephalometric parameters for the improvement of OSA.

• Korean Journal of Environmental Biology
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• v.38 no.1
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• pp.114-126
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• 2020

Bloom-forming toxic cyanobacteria Microcystis spp. are common in the summer season in temperate freshwater ecosystems. Often, it leads to the degradation of water quality and affects the quality of drinking water. In a previous study, NQ (naphthoquinone) compounds were shown to be effective, selective, and ecologically safe algicides for Microcystis spp. blooms. To analyze the superiority of developed NQ derivatives, we conducted a microcosm experiment using clay, which is frequently used in South Korea. Similar to previous studies, the NQ 40 and NQ 2-0 compounds showed high algicidal activities of 99.9% and 99.6%, respectively, on Microcystis spp. at low concentrations (≥1 μM) and enhanced phytoplankton species diversity. However, when treated with clay, a temporary algicidal effect was seen at the beginning of the experiment that gradually increased at the end. In addition, treatment with the NQ compounds did not affect either the abiotic or biological factors, and similar trends were observed with the control. These results showed that the NQ 2-0 compound was more effective, with no ecosystem disturbance, and more economical than the currently used clay. These results suggest that NQ 2-0 compound could be a selective, economically and ecologically safe algicide to mitigate harmful cyanobacterial blooms in the field.