• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 춘계학술대회 논문집 방전 플라즈마 유기절연재료 초전도 자성체연구회
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• pp.25-29
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• 2004

Corona on polymer materials causes deterioration by the combined action of the discharge striking the surface and the action of certain chemical compounds that are formed by the discharges. In the design and manufacture of polymer insulators must be sufficiently large to avoid corona discharges, otherwise a shielding or corona ring (grading ring) needs to be installed on the insulator. To conduct this purpose, many researchers have investigated end-fitting of polymer insulator by voltage distribution simulation and electrical test. Grading rings are used to improve the performance of the insulator in multiple ways. They can reduce corona and associated audible noise and radio influence and television interference. The factors determining the uses of a grading ring are line voltage, geometry and dimensions of end fittings, geometry and dimensions of line hardware, and environmental conditions. In this paper, electrical property of polymer insulator with end-fitting design have been investigated by electrical field analysis, various end-fitting design, tracking wheel test, corona inception voltage and extinction voltage. Electrical field analysis is conducted by FEM program and various end-fitting is designed through this result. Designed end-fittings are manufactured and their performance is conducted by electrical performance test.

• 한국분말재료학회지
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• 제15권2호
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• pp.114-118
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• 2008

Functional nanomaterial is expected to have improved capacities on various fields. Especially, metal nanoparticles dispersed in polymer matrix and metal nanofiber, one of the functional nanomaterials, are able to achieve improvement of property in the electric and other related fields. In this study, the fabrication of metal (Ag) nanoparticle dispersed nanofibers were attempted. The Ag nanoparticle dispersed polymer nanofiber and Ag nanofiber were fabricated by electrospinning method using electric force. First, PVP/$AgNO_3$ nanofibers were synthesized by electrospinning in $18{\sim}22kV$ voltage with the starting materials (Ag-nitrate) added polymer (PVP; poly (vinylpyrrolidone)). Then Ag nanoparticle dispersed polymer nanofibers were fabricated to reduce hydrogen reduction at $150^{\circ}C$ for 3hr. And Ag nanofibers were synthesized by the decomposited of PVP at $300{\sim}500^{\circ}C$ for 3hr. The nanofibers were analyzed by XRD, TGA, FE-SEM and TEM. The experimental results showed that the Ag nanofibers could be applied in many fields as an advanced material.

• 한국분말재료학회지
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• 제27권4호
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• pp.311-317
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• 2020

In this study, the effects of Co content on the microstructure and Charpy impact properties of Fe-Cr-W ferritic/martensitic oxide dispersion strengthened (F/M ODS) steels are investigated. F/M ODS steels with 0-5 wt% Co are fabricated by mechanical alloying, followed by hot isostatic pressing, hot-rolling, and normalizing/tempering heat treatment. All the steels commonly exhibit two-phase microstructures consisting of ferrite and tempered martensite. The volume fraction of ferrite increases with the increase in the Co content, since the Co element considerably lowers the hardenability of the F/M ODS steel. Despite the lowest volume fraction of tempered martensite, the F/M ODS steel with 5 wt% Co shows the highest micro-Vickers hardness, owing to the solid solution-hardening effect of the alloyed Co. The high hardness of the steel improves the resistance to fracture initiation, thereby resulting in the enhanced fracture initiation energy in a Charpy impact test at - 40℃. Furthermore, the addition of Co suppresses the formation of coarse oxide inclusions in the F/M ODS steel, while simultaneously providing a high resistance to fracture propagation. Owing to these combined effects of Co, the Charpy impact energy of the F/M ODS steel increases gradually with the increase in the Co content.

• 한국염색가공학회지
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• 제29권2호
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• pp.97-103
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• 2017

Polyketone fiber, a newly developed high strength fiber, has a tenacity and modulus similar to the p-aramid fiber, and can be used for reinforcing mechanical rubber goods(MRG), such as tires, hoses, and technical textiles. It will be expected for replacement of super fiber such as aramids and increasing the technical textile market share. This paper surveys the mechanical properties of polyketone fiber for technical textiles. For this purpose, dyed polyketone fabric is prepared, mechanical properties of coated and uncoated polyketone fabrics such as tensile strength, elongation and tear strength were examined before and after weather resistance test(temperature $63{\pm}3^{\circ}C$, humidity 60%, amount of power $0.35w/m^2$). The differences of mechanical properties between uncoated and coated fabrics for high functional technical textiles and composite materials are estimated through this study. The UV-stability of polyketone fabric showed obvious improvement after coating. After 168h(7day) of UV exposure, the coated fabric showed less deterioration in mechanical properties with the retained tensile strength and elongation at break greater than 22 and 17% of the uncoated polyketone fabrics values, respectively.

• 한국재난정보학회 논문집
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• 제5권1호
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• pp.78-100
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• 2009

This study is to protect peoples' life, minimize the property damage by coping with threats quickly and take more preventive measures in advance against nuclear bomb, CBR, and potential explosive. For this, CBRNE(Chemical, Biological, Radiological, Nuclear, Explosive) program research was used. Thanks to advance in technology, terrorist groups and even individuals make or keep nuclear and CBR weapons. And also it's likely that disaster and threats from a toxic gas, acute pathogens, accidents in the nuclear power plants and a high explosive could be happened a lot. Recently more organized terrorist groups maintain random attacks for unspecified individuals and also it's highly likely that a large-scale terrorist attack by WMD and CBRNEwill be done. To take strict measures against CBRNE attacks by terrorists is on the rise as an urgent national task. Moreover biological weapons are relatively easy and inexpensive to obtain or produce and cause mass casualties with a small amount. For this reason, more than 25 countries have already possessed them. In the 21 st century, the international safety environment marks the age of complicated threats : transnational threats such as comprehensive security and terror, organized crime, drug smuggling, illegal trade of weapons of mass destruction, and environmental disruption along with traditional security threats. These cause military threats, terror threats, and CBRNE threats in our daily life to grow. Therefore it needs to come up with measures in such areas as research development, policy, training program. Major industrial nations on CBRNE like USA, Canada, Switzerland, and Israel have implemented various educational programs. These researches could be utilized as basic materials for drawing up plans for civil defense, emergency services and worldwide countermeasures against CBRNE.

• Design & Manufacturing
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• 제10권2호
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• pp.18-23
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• 2016

Injection molded thermoplastic parts may need to be coated to facilitate paint adhesion, or to satisfy other surface property requirements, such as appearance, durability, and weather resistance. In this paper, a two-component polyurethane metering system was developed for the simultaneous injection and surface coating of a plastic substrate. The system was composed of storage tanks, feed pumps, axial piston pumps, mixing head. The tank was designed to be double-jacket structured and fabricated for polyol and isocyanate, respectively. A temperature chamber was used to maintain the material temperature to be $80^{\circ}C$ during flowing from storage tank to mixing head. Inside the chamber, feed pump, low pressure filter, high pressure pump, high pressure filter, pressure sensor, flow meter were installed. A mixing head of L-type was used for homogeneous mixing of polyol and isocyanate. Inside the mixing head, a cartridge heater and a temperature sensor were installed to control the temperature of the materials. The flow rate of axial-piston pump was controlled by using closed-loop feedback control algorithm. The input flow-rates were compared with the measured values. The output error was 6.7% for open-loop control, whereas the error was below 2.2% for closed-loop control. In addition, the pressure generated through mixing-head nozzle increased with increasing flow rate. It was found that the pressure drop between metering pump and mixing-head nozzle was almost 10 bar.

• 한국실내디자인학회논문집
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• 제21권5호
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• pp.3-11
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• 2012

The first visual contact in architecture happens in surface, and it could be significant object as well as the starting point to recognize the essence and perceive the buildings. Architecture surface could not get out of the restriction of structures and materials that support buildings for a long time in the past. Architecture surface in the past should fulfill the structural role to form are appearance of buildings and support buildings at the same time, so it was difficult to get out of logic for material and thickness of walls, arrangements and sizes of windows. However, since the modern age, architecture surface came to be freer according to the development of building technology, and development of technology changes shows tendencies to express role of new design factor as an architectural element emphasized expression and autonomy,s which was escaped from the subordinate relationship that the surface of building must do the structural function. In this study, it would be examined the expressive characteristics of various epidermis that are expressed in architecture of Herzog & de Meuron since the end of 20thcentury focused on comprehended and analyzed results of changes and characteristics of contemporary society. Through this, it would be comprehended the epidermis of architecture that has particular character expressed in modern buildings of Herzog & de Meuron, and it would be composed a certain linkage between this and characteristics of contemporary society and it would be investigated that the establishing process of inner spaces. Identification through case analysis for this would perform a role of catalyst for the new possibility and development of contemporary architecture's surface expression in the future.

• 한국산학기술학회논문지
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• 제16권5호
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• pp.3587-3595
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• 2015

본 연구에서는 저비용의 저심도 도시철도시스템을 구축하기 위하여 산업부산물인 고로슬래그 미분말, 플라이애시 및 급냉 전기로 산화슬래그를 사용하여 개발된 저탄소 친환경 PC 박스용 콘크리트의 역학적 성능 및 내구성을 평가 하였다. 역학적 특성을 평가한 결과, 재령 1일 압축강도는 모든 조건에서 설계기준강도($f_{ck}$) 35MPa의 90% 이상 강도 발현 하는 것으로 나타나 공기단축 가능으로 건설비용을 절감할 수 있을 것으로 판단된다. 또한, 소요의 물성 및 설계기준강도($f_{ck}$) 35MPa를 만족하는 범위에서 시멘트 단독 사용 조건보다 염소이온침투성 및 확산계수가 낮게 나타나 내염성능이 우수한 것으로 나타났으며, 동결융해 저항성 및 화학저항성의 경우에도 내구성능이 우수한 것으로 나타났다. 따라서 저탄소 친환경 PC 박스용 콘크리트를 사용할 경우, 시멘트 제조 시 발생되는 이산화탄소 및 환경부하를 저감할 수 있을 것으로 기대된다.

• 한국산학기술학회논문지
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• 제12권7호
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• pp.2939-2944
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• 2011

용융탄산염형 연료전지 시스템의 성능 향상을 위해 핵심 부분인 스택을 수치적으로 모사할 필요성이 대두되고 있다. 스택은 다양한 재질, 즉 금속, 세라믹, 폴리머 등으로 이루어져 있고 또한 단위전지 수백 장이 적층되어 제작되기 때문에 이를 전부 세세히 모델링하여 고려하는 것은 거의 불가능하다. 이에 따라 스택 전체를 하나의 균질한 물질로 대체할 수 있는 균질 물성치 도출이 요구되고 있다. 본 논문에서는 단위전지 압축률을 도입하고 모든 압축 변형이 분리판과 매트릭스에서만 일어난다는 등의 몇 가지 기본 가정 하에서 스택의 두 가지 영역, 즉 활성 영역과 매니폴드 영역에서 각각 균질 물성치를 추정하였다. 추정된 물성치를 실제 문제에 적용하여 성공적인 결과를 얻을 수 있었다.

• Restorative Dentistry and Endodontics
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• 제40권2호
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• pp.113-122
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• 2015

Objectives: The aim of this paper was evaluating the ratios of electrical impedance measurements reported in previous studies through a correlation analysis in order to explicit it as the contributing factor to the accuracy of electronic apex locator (EAL). Materials and Methods: The literature regarding electrical property measurements of EALs was screened using Medline and Embase. All data acquired were plotted to identify correlations between impedance and log-scaled frequency. The accuracy of the impedance ratio method used to detect the apical constriction (APC) in most EALs was evaluated using linear ramp function fitting. Changes of impedance ratios for various frequencies were evaluated for a variety of file positions. Results: Among the ten papers selected in the search process, the first-order equations between log-scaled frequency and impedance were in the negative direction. When the model for the ratios was assumed to be a linear ramp function, the ratio values decreased if the file went deeper and the average ratio values of the left and right horizontal zones were significantly different in 8 out of 9 studies. The APC was located within the interval of linear relation between the left and right horizontal zones of the linear ramp model. Conclusions: Using the ratio method, the APC was located within a linear interval. Therefore, using the impedance ratio between electrical impedance measurements at different frequencies was a robust method for detection of the APC.