• 한국가스학회지
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• 제26권3호
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• pp.27-37
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• 2022

최근 ESS(전기저장장치)의 보급이 늘어나면서 ESS에 의한 지속적인 화재발생으로 인명 및 재산의 피해 또한 급증하고 있다. ESS에 활용되는 우레탄 샌드위치 패널에 제조에 있어 난연 성능의 향상이 필요한 실정이다. 본 연구에서는 연질 폴리우레탄 폼의 난연 특성을 구현하고자 제품의 물성을 변화시키는 이소시아네이트 관능기 파라미터의 변화로 인한 제품의 조직 치밀도가 화재성능에 미치는 영향을 연구하였다. 우레탄 조직의 치밀도를 변화시켜가며 제품을 제작하여 연소성능 시험, 가스유해성 시험, 연기밀도 시험을 진행하였다. 그 결과 총 방출열량은 이소시아네이트 관능기 그룹이 높은 경우 성능이 우수하고, 최대 열 방출율과는 상관이 없는 것을 확인하였다. 이소시아네이트 관능기 그룹의 값이 2.7이상에서 형상의 붕괴를 방지할 수 있었다. 가스유해성 시험에서는 이소시아네이트 관능기 그룹이 상대적으로 높아 조직이 치밀하면서 탄화 막 형성이 용이한 Char시스템용 난연제가 추가적으로 투입되어야 성능이 상승하였고, 연기밀도 시험에서는 이소시아네이트 관능기 그룹의 값이 2.75이상에서 성능이 증가되는 것을 확인하였다. 따라서 본 연구의 결과로 기존에 사용되던 저렴한 우레탄 샌드위치 패널을 대체할 난연제 개발에 기반을 마련할 수 있을 것으로 생각된다.

• 한국정밀공학회지
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• 제29권12호
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• pp.1272-1278
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• 2012

The micro barrier rip array structures have been applied in a variety of areas including as privacy films, micro heat sinks, touch panel and optical waveguide. The increased aspect ratio (AR) of barrier rip array structures is required in order to increase the efficiency and performance of these products. There are several problems such as burr, defect of surface roughness and deformation and breakage of barrier rip structure with machining high-aspect ratio micro barrier rip array structure using orthogonal cutting method. It is essential to develop technological methods to solve these problems. The optimum machining conditions for machining micro barrier rip array structures having high-aspect ratio were determined according to lengths ($200{\mu}m$ and $600{\mu}m$) and shape angles ($2.89^{\circ}$ and $0^{\circ}$) of diamond tool, overlapped cutting depths ($5{\mu}m$ and $10{\mu}m$), feed rates (100 mm/s) and three machining processes. Based on the optimum machining conditions, micro barrier rib array structures having aspect ratio 30 was machined in this study.

• IMMUNE NETWORK
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• 제15권2호
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• pp.83-90
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• 2015

Evaluation and screening of vaccines against tuberculosis depends on development of proper cost effective disease models along with identification of different immune markers that can be used as surrogate endpoints of protection in preclinical and clinical studies. The objective of the present study was therefore evaluation of subcutaneous model of M.tuberculosis infection along with investigation of different immune biomarkers of tuberculosis infection in BALB/c mice. Groups of mice were infected subcutaneously with two different doses : high ($2{\times}10^6CFU$) and low doses ($2{\times}10^2CFU$) of M.tuberculosis and immune markers including humoral and cellular markers were evaluated 30 days post M.tuberculosis infections. Based on results, we found that high dose of subcutaneous infection produced chronic disease with significant (p<0.001) production of immune markers of infection like $IFN{\gamma}$, heat shock antigens (65, 71) and antibody titres against panel of M.tuberculosis antigens (ESAT-6, CFP-10, Ag85B, 45kDa, GroES, Hsp-16) all of which correlated with high bacterial burden in lungs and spleen. To conclude high dose of subcutaneous infection produces chronic TB infection in mice and can be used as convenient alternative to aerosol models in resource limited settings. Moreover assessment of immune markers namely mycobacterial antigens and antibodies can provide us valuable insights on modulation of immune response post infection. However further investigations along with optimization of study protocols are needed to justify the outcome of present study and establish such markers as surrogate endpoints of vaccine protection in preclinical and clinical studies in future.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.159-159
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• 2016

Vertically-aligned carbon nanotubes (VCNT) have attracted much attention due to their unique structural, mechanical and electronic properties, and possess many advantages for a wide range of multifunctional applications such as field emission displays, heat dissipation and potential energy conversion devices. Surface modification of the VCNT plays a fundamental role to meet specific demands for the applications and control their surface property. Recent studies have been focused on the improvement of the electron emission property and the structural modification of CNTs to enable the mass fabrication, since the VCNT considered as an ideal candidate for various field emission applications such as lamps and flat panel display devices, X-ray tubes, vacuum gauges, and microwave amplifiers. Here, we investigate the effect of surface morphology of the VCNT by water vapor exposure and coating materials on field emission property. VCNT with various height were prepared by thermal chemical vapor deposition: short-length around $200{\mu}m$, medium-length around $500{\mu}m$, and long-length around 1 mm. The surface morphology is modified by water vapor exposure by adjusting exposure time and temperature with ranges from 2 to 10 min and from 60 to 120oC, respectively. Thin films of SiO2 and W are coated on the structure-modified VCNT to confirm the effect of coated materials on field emission properties. As a result, the surface morphology of VCNT dramatically changes with increasing temperature and exposure time. Especially, the shorter VCNT change their surface morphology most rapidly. The difference of field emission property depending on the coating materials is discussed from the point of work function and field concentration factor based on Fowler-Nordheim tunneling.

• Nuclear Engineering and Technology
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• 제49권7호
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• pp.1442-1450
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• 2017

In liquid metal fast breeder reactors, postulated failures of the plant protection system may lead to serious unprotected accidental consequences. Unprotected transients are generically categorized as transient overpower accidents and transient under cooling accidents. In both cases, core meltdown may occur and this can lead to a molten fuel coolant interaction (MFCI). The understanding of MFCI phenomena is essential for study of debris coolability and characteristics during post-accident heat removal. Sodium is used as coolant in liquid metal fast breeder reactors. Viewing inside sodium at elevated temperature is impossible because of its opaqueness. In the present study, a methodology to depict MFCI phenomena using a flat panel detector based imaging system (i.e., real time radiography) is brought out using a woods metal-water experimental facility which simulates the $UO_2-Na$ interaction. The developed imaging system can capture attributes of the MFCI process like jet breakup length, jet front velocity, fragmented particle size, and a profile of the debris bed using digital image processing methods like image filtering, segmentation, and edge detection. This paper describes the MFCI process and developed imaging methodology to capture MFCI attributes which are directly related to the safe aspects of a sodium fast reactor.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2011년도 추계학술발표대회
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• pp.35.1-35.1
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• 2011

New photovoltaic (PV) materials and manufacturing approaches are needed for meeting the demand for lower-cost solar cells. The prototypal thin-film photovoltaic absorbers (CdTe and $Cu(In,Ga)Se_2$) can achieve solar conversion efficiencies of up to 20% and are now commercially available, but the presence of toxic (Cd,Se) and expensive elemental components (In, Te) is a real issue as the demand for photovoltaics rapidly increases. To overcome these limitations, there has been substantial interest in developing viable alternative materials, such as $Cu_2ZnSnS_4$ (CZTS) is an emerging solar absorber that is structurally similar to CIGS, but contains only earth abundant, non-toxic elements and has a near optimal direct band gap energy of 1.4~1.6 ev and a large absorption coefficient of ${\sim}10^4\;cm^{-1}$. The CZTS absorber layers are grown and investigated by various fabrication methods, such as thermal evaporation, e-beam evaporation with a post sulfurization, sputtering, non-vacuum sol-gel, pulsed laser, spray-pyrolysis method and electrodeposition technique. In the present work, we report an alternative method for large area deposition of CZTS thin films that is potentially high throughput and inexpensive when used to produce monolithically integrated solar panel modules. Specifically, we have developed an aqueous chemical approach based on chemical bath deposition (CBD) with a subsequent sulfurization heat treatment. Samples produced by our method were analyzed by scanning electron microscopy, X-ray diffraction, transmission electron microscopy, absorbance and photoluminescence. The results show that this inexpensive and relatively benign process produces thin films of CZTS exhibiting uniform composition, kesterite crystal structure, and good optical properties. A preliminary solar cell device was fabricated to demonstrate rectifying and photovoltaic behavior.

• 한국건설순환자원학회논문집
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• 제5권2호
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• pp.83-90
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• 2010

As a reinforced fabric, asbestos has been utilized as a fire-resistant material as it has a superior flexural stiffness and heat resistance up to $1500^{\circ}C$. However, due to its harmfulness, its use has been prohibited recently and the even the installed asbestos materials are being repaired or supplemented if there is a concern about flying. Asbestos is mainly used for construction panels as a reinforced fabric and coating materials to ensure the fire-resistance of steel frames. Asbestos was used as fire-resistant materials for steel frames until 1991 and then prohibited as Act on Industrial Safety and Health limits the concentration of asbestos in the air. Classified as a designated waste according to Act on Waste Control, asbestos must be buried if there is no possibility of flying (panel-type materials) or cement-solidified and then buried if there is a possibility of flying (spray coating material) In general, it is required that a new waste landfill include a certain landfill facility for designated waste, but in reality there is an absolute storage of landfill facilities for designated waste as they only install facilities of the size required by the regulations. This could result in the 2nd environmental pollution as they cannot process asbestos wastes which will be generated in large volume in the future. This study explores a method that melts asbestos wastes at $700^{\circ}C$ rather than cement-solidifying the waste asbestos from construction sites, especially asbestos-containing spray coating. The study results showed that there was no change in the composition and shape even though asbestos wastes was melted at $1300^{\circ}C$, but there was a change for the specimen which was process in advance for low temperature melting and then melt at $900^{\circ}C$.

• 한국산학기술학회논문지
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• 제13권3호
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• pp.961-966
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• 2012

고유가 시대를 맞아 에너지 절약이 사회적으로 이슈화됨에 따라 진공유리에 대한 관심이 높아지고 있다. 진공유리 개발을 위한 핵심 공정 중 유리모서리 접합공정은 두 장의 유리 사이를 진공으로 유지하기 위해 높은 신뢰도를 요한다. 본 논문에서는 유리 모서리 접합 시 기존 프릿을 이용하여 접합하는 방법과 달리 고밀도열원인 수소혼합가스를 이용하여 모서리를 접합하는 공정을 제시하였다. 또한 유리의 파손 및 변형방지를 위해 전기로내의 분위기 온도를 설정하고 균일도를 측정하였다. 기초시험을 통해 모서리접합 공정변수를 설정하고 공정변수에 따른 유리 모서리 접합부 면적과의 수학적관계식을 다중회귀분석으로 도출하였다.

• 한국산학기술학회논문지
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• 제11권8호
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• pp.2999-3004
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• 2010

LED는 다른 광원에 비해 동작수명이 길고, 친환경적이며, 에너지 효율이 높은 장점을 가지고 있다. 최근 LED 기술의 발전으로 인해 고휘도, 고용량의 LED가 개발됨에 따라, 표시장치에만 적용되던 LED를 조명장치에도 적용하는 기술이 확산되고 있다. 조명장치에 적용되는 파워 LED는 발열문제로 인한 소손을 막기 위해 구동전류를 일정한 전류값 이하로 제어할 필요성이 있다. 본 논문은 파워 LED의 구동전류를 설정된 값 이하로 제어하는 전류제 한 기능을 갖는 파워 LED 태양광 보안등 개발에 관한 연구이다. 태양광 발전에 의해 생산된 전력을 DC12[V] 축전지에 저장한 후, 야간에 승압형 DC-DC 컨버터를 통해 DC24[V]로 승압시켜 파워 LED로 공급한다. 태양광 보안등 제어기, 승압형 DC-DC 컨버터, 72[W]급 파워 LED 램프를 개발하여 동작을 확인하고 관련 데이터를 도출함으로써 제안된 시스템의 타당성을 입증하였다.

• 한국농촌건축학회논문집
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• 제20권2호
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• pp.49-56
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• 2018

The vernacular houses with 田-shaped floor plan at Gangreung have been played important roles in tracing the vernacular living cultures including housing life. But due to the adoption of convenient facilities in vernacular housing lives caused by modernization and urbanization, many changes and transformations have happened at residential space of vernacular houses. This thesis targets to extract basic data to prepare and prevent various problems in process of renovation, extension and function change as installing housing life facilities, and to identify the changes and transformations of them to prepare the proper balances between their original form preservation and residents' convenience living. The results are as follows. The inner wall removal of rooms, the fuel change of cooking and heating, the leveling change of kitchen floor made possible the sedentary lifestyles. And its residential rooms were transformed from two row to one row by inner wall removal, the fuel heating change, the heating method change and the heat insulating materials. The residential extension materials were changed from the traditional materials such as soil, wood, etc to the modern materials such as cement block or brick, sandwich panel, etc. And the modern materials were used and attached to widen residential spaces to the vernacular house because of the easiness of execution. So, it is necessary for 田-shaped floor plan vernacular house owners to distribute printed execution guide book to prevent and minimize the various problems to be shown by extension, renovation and function change.