• Proceedings of the KIEE Conference
• /
• 2015.07a
• /
• pp.1171-1172
• /
• 2015

송전선이나 전기기기의 나선(裸線)부분을 절연하고 동시에 기계적으로 유지 또는 지지하기 위한 절연체와 이것과 일체로 조립된 금구류로 구성된 절연지지물인 애자는 전기적으로 충분한 절연내력을 가지게 하기 위하여 다수의 주름을 만들어 표면에 따른 거리를 크게 한다. 이는 표면이 습하였을 때, 염분이나 먼지 등이 부착하였을 때 절연내력이 저하되는 것을 방지하는 데 효과가 있다. 그리고 재질별(세라믹, 유리, 합성수지 등), 모양별(원판형, 원주형, 중공, 갓형 등), 용도별(전차 선로용, 발전소 또는 변전소용, 통신 선로용 등) 및 사용방법(현수용, 내장용, 인류용, 고정용 등)에 따라 다양하게 분류된다. 본 논문에서는 복합 애자류(composite insulators)의 여러 가지 성능평가 시험방법 중에서 복합 애자의 여러 계면과 연결 금구의 접속부(interfaces and connections of end fittings)에 대한 이상 유무를 확인하는 시험인 수분침투시험평가기술에 대해 고찰하였다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 1997.11a
• /
• pp.31-31
• /
• 1997

우수한 비강성과 비강도를 지닌 복합재료를 이용한 자동차용 추진축(Propeller Shaft)의 사용은 자동차의 구조정량화, 소음/진동 감소, 승차감 향상 측면에서 개선된 효과를 기대할 수 있다. 본 연구에서는 탄소섬유/에폭시 필라멘트 와인딩(Filament Winding) 공빔을 적용한 복합재료 튜브와 금속재 플랜지 그리고 유니버셜 조인트로 구성된 상용 차의 추진축 개발과정 중 축의 진동특성에 대한 적합한 형상과 물성을 찾기 위해 유한요소법을 적용한 자유진동 해석과 FFT 해석장비를 이용한 진동실험 그리고 축을 운용속도까지 회전시켜 공진(Resonance) 현상 발생 유무를 소음량의 측정으로 판단하는 시험이 수행되었다. 그 결과 요구조건에 적합한 진동특성을 나타내는 추진축의 형상을 결정할 수 있었다.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.38 no.7
• /
• pp.765-770
• /
• 2014

This paper describes the study on a method for improving the structural durability of bolted joints applied to a composite bogie frame. In this study, three bolted joints with and without inserts and screw threads were selected for determining the effect of the inserts, using experiment and analysis. The structural performances of the proposed bolted joints were compared and evaluated using the test method prescribed by the ASTM D5961 standard. The results revealed that the bolted joint having an insert shape without the screw thread offered improved durability for application to a composite bogie frame. Furthermore, the structural integrity of the frame comprising the bolted joints was evaluated using finite element analysis according to the JIS E 4207 standard. The Tasi-Wu and Von-Mises failure criteria were used for determining the failure of the composite structure and bolted joints, respectively. A sub-modeling technique was introduced for investigating the performance of the bolted joints in greater detail. The analysis results demonstrated that the Tasi-Wu failure index of the composite structure near the bolted joints was reduced by approximately one-half after applying an insert without the screw thread. This implies that the structural durability of the bolted joints of a composite bogie frame could be improved by using a metal insert without the screw thread.

• Journal of Digital Convergence
• /
• v.11 no.12
• /
• pp.725-734
• /
• 2013

This paper aimed to verify the current status of adolescents' donations and predictors influencing their donation behaviors. First, the result revealed that adolescents' donations were higher in the order of time, material, and talent donation. Second, donation motives, attitude towards donation, self-esteem, a sense of community, and trust in charitable organization were positively correlated. Third, the predictors of material donation behaviors of adolescents were gender, age, extrinsic motives, attitude towards donation, sense of community, and trust in charitable organization. And the predictors of time donation behaviors were gender and sense of community, and those of talent donation were age, intrinsic motives and sense of community. The strategies for the activation of adolescents' donations were suggested.

• Journal of KIISE:Computing Practices and Letters
• /
• v.14 no.8
• /
• pp.778-782
• /
• 2008

The performance in combination of wired and wireless mesh network which will be a main access network in future internet is directly linked with service quality to users. In this paper, we evaluate variant TCP performance and analyze traffic characteristics on Wireless (Seoul National University Mesh testbed) - Wired (KOREN/Abilene) - Wireless (HP Mesh testbed in the USA) Network. We found that RTT is proper in this network to serve a VoIP service. Also we propose an enhanced TCP protocol which can perform well in both wireless network which has many packet losses and wired network which has high bandwidth and long delay.

• Journal of Digital Convergence
• /
• v.15 no.8
• /
• pp.247-256
• /
• 2017

The purpose of this study was to identify the convergent influence of social awareness and health status on social support in Korean echo generation by using Korea adult psycho-social anxiety survey data. Korea adult psycho-social anxiety survey data were collected from August to September 2015 and included 1,653, who responded to the question regarding social support. The data were analyzed by t-test, chi-square and hierarchial multiple regression using SPSS WIN 23.0 program. The mean score of social support was 19.60. The influencing factors on social support were neighborhood relations, perceived class, euphoria, equality in society, stability in society, self Esteem, communication, and stress, respectively. Therefore, it is necessary to establish strategies to strengthen social support of echo generation. A more careful examination may be warranted.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.48 no.11
• /
• pp.935-943
• /
• 2020

This paper presents a methodology for evaluating suitability of a manned-unmanned aerial vehicle team for a complicated mission. The study identified vehicle performance, equipment performance and level of autonomy as the key factors that affect the mission effectiveness. A manned and an unmanned aircraft were compared, and their performance was quantized in these respects. SEAD was chosen as a representative manned-unmanned team mission. The SEAD mission was broken down to a sequence of tasks. Mission experts evaluated the importance of each mark item for the mission legs. Combining the results showed proper type of aircraft for each leg depending on the complexity, safety, and importance of the task. Finally, the whole mission plan was laid out as a time-based sequence which alleviate pilot workload significantly.

• Membrane Journal
• /
• v.23 no.1
• /
• pp.80-91
• /
• 2013

Metal-templated condensation of cyclohexanedione dioxime and phenylboronic acid in the presence of Fe(II) sulfate heptahydrate proceeds cleanly in methanol to furnish the Fe(II) clathrochelate. An organic/inorganic hybrid membranes composed of Fe(II) clathrochelate and polyethersulfone was prepared by using phase inversion method. For membrane preparation, the Fe(II) clathrochelate was highly soluble (3~5 g/L) in DMF, NMP, and DMAc, which meets the requirements for the solubility of metal complexes in polar aprotic solvent used in membrane preparation. It was stable even in the presence of strong acids, such as trifluorosactic acid (pKa = 0.3). It was characterized by UV-vis spectroscopy, and their stability in solution phase studied in the presence of (i) strong acids or (ii) competing chelates. Organic/inorganic hybrid membranes were prepared with polyethersulfone, polyvinylpyrrolidone, p-toluenesulfonic acid, Fe(II) clathrochelate and DMF by using nonsolvent induced phase inversion method. The addition of Fe(II) clathrochelate leads increase of surface pore density, mean pore size and flux. We can obtain highly asymmetric membranes by addition of Fe(II) clathrochelate.

• Membrane Journal
• /
• v.22 no.3
• /
• pp.155-170
• /
• 2012

Fuel cells have been considered as alternative power generation system in the twenty-first century because of eco-friendly system, high power density and efficiency compare with petroleum engine system. Proton exchange membranes (PEMs) are the key components in fuel cell system. Currently, Nafion has been used in fuel cell system. However, Nafion has disadvantages such as low conductivity at high temperature and high cost. The researchers have focused to reach the high properties such as high proton conductivity, low permeability to fuel, good chemical/thermal stability, good mechanical properties and low manufacturing cost. Various methods have been developed for preparation of proton exchange membrane with high performance and commercialization of fuel cell system. The hybrid organic/inorganic membrane has the potentials to provide a unique combination of organic and inorganic properties with improved proton conductivity and mechanical property at high temperatures. So, this paper presents an overview of research trend for the composite membranes prepared by organic/inorganic system using various inorganic materials.

• Proceedings of the Korean Operations and Management Science Society Conference
• /
• 2004.05a
• /
• pp.131-134
• /
• 2004

무선시장의 급격한 확장과 유무선간 복합/결합서비스 등장추세에 따라 OECD 및 EU 각국을 중심으로 통신시장 경쟁구도 개편과 규제정책방향을 재검토하고 유무선간 대칭규제 방향을 지향해 가고 있다. 그러나 국내의 경우 유선사업의 성장세 둔화와 시장개방에 대한 비대칭 규제가 계 속되고 있는 상황에서 무선망 개방 등 통신시장의 합리적 경쟁구도 설정을 위한 방안 연구가 시급히 요청되고 있다. 따라서 본 고에서는 주파수 부족으로 여전히 경쟁이 부재한 이동전화 시장을 중심으로 경쟁을 활성화시키기 위한 여러가지 방안들을 살펴보고 이를 이미 실행하고 있는 외국의 사례를 통해 이들 정책의 도입 및 경제적 효과를 살펴보고자 한다.