• 한국항공우주학회지
• /
• 제42권4호
• /
• pp.351-359
• /
• 2014

본 논문에서는 저궤도 소형인공위성에서 위성의 각 부에 전원을 공급하기 위한 리튬이온 배터리 시스템의 신뢰성 확보를 위해 수행한 우주인증시험들의 결과를 나타내었다. 리튬이온 배터리 시스템의 신뢰성을 검증하기 위하여 구조해적, 성능시험, 우주 및 발사환경에서의 환경시험 등을 수행하였다. 모든 해석 및 시험 결과가 요구조건에 만족함을 보임으로써 리튬이온 배터리를 적용한 소형인공위성의 신뢰성을 검증하고 제고할 수 있었다.

• 대한안전경영과학회:학술대회논문집
• /
• 대한안전경영과학회 2004년도 춘계학술대회
• /
• pp.247-257
• /
• 2004

Electrodes were fabricated based on activated carbon powder BP-20, conducting agent such as Super P, vapor grown carbon fiber (VGCF) and acetylene black (AB), and the mixed binders of flexible poly(vinylidenefluoridehexafluoropropylene) [P(VdF-co-HFP)] and cross linking dispersion agent of polyvinylpyrrolidone (PVP) to increase mechanical strength. According to impedance measurement of the electrode with the addition of conducting agent, we found that it was possible to charge rapidly by the fast steady-state current convergence due to low equivalent series resistance (AC-ESR, fast charge transfer rate at interface between electrode and electrolyte and low RC time constant. The self-discharge of unit cell showed that diffusion process was controlled by the ion concentration difference of initial electrolyte due to the characteristics of Electric Double Layer Capacitor (EDLC) charged by ion adsorption in the beginning, but this by current leakage through the double-layer at the electrode/electrolyte interface had a minor effect and voltages of curves were remained constant regardless of electrode material. We found that the 2.3V/230F grade EDLC would be applied to industrial safety usage such as uninterrupted power supply (UPS) because of the constant DC-ESR by IR drop regardless of discharge current.

• 대한안전경영과학회지
• /
• 제4권4호
• /
• pp.137-146
• /
• 2002

In order to investigate the effect of irradiation by $^{60}Co-\gamma$rays as well as the e thermal treatment on the dielectric deterioration in ethylene propylene rubber, insulating material for electric cables used in atomic power plants, charging discharging current, residual built- up voltage and dielectric properties are measu discussed in this study. Variance in the characteristic of relative dielectric constant as a function of tem was observed in relatively high dose of irradiation. Since glass transition tem appeared at tens of degree Celsius below zero, the characteristic is attributed orientation polarization. Dielectric loss is generally increased, with increasing d irradiation in the characteristic of dielectric loss as a function of temperature, No d loss by thermal treatment was observed. Dielectric resistance decreases with increa of irradiation in the characteristic of charging current as a function of temperature be considered that dielectric resistance seems to be recovered by thermal treatm characteristic of discharging current as a function of time in the specimen less ir become similar to that of the unirradiated, when thermal treated. A peak is shown residual built- up voltage as a function of time, and the corresponding time of the shorten as increasing dose of irradiation. It is also observed that the corresponding the peak is lengthened by thermal treatment.

• 유통과학연구
• /
• 제22권1호
• /
• pp.69-78
• /
• 2024

Purpose: This study is undertaken from the standpoint of student-centered learning and theoretical paradigms that have developed in the business world and display conceptual affinities: the transfer of knowledge and training. Research design, data and methodology: Utilizing questionnaire surveys and multivariate data analysis are two research methodologies (CFA, SEM). Around 201 undergraduate students who were studying in Vietnam provided the data. Results: The results show importance of the faculty role in students' knowledge acquisition. The findings show that Ability to form a good relationship positively influences the development of competence. Additionally, neither ability to develop a good relationship nor learning drive or knowledge acquisition are significantly correlated with one another. The growth of competencies is positively impacted by the suitability of teaching approaches. Knowledge acquisition is favorably impacted by learning motivation, and knowledge acquisition in turn is positively impacted by competence development. Conclusions: Research has shown the important role of lecturers in students' knowledge acquisition. From this result, some implications related to lecturers are also given to help improve students' ability to acquire knowledge. Building good relationships with students (ready to answer questions, positive relationships) and good expertise will help increase learning motivation, ability to acquire knowledge as well as improve development for students.

• 정보처리학회논문지C
• /
• 제13C권1호
• /
• pp.1-10
• /
• 2006

최근 새로운 형태의 네트워크 환경인 유비쿼터스 컴퓨팅에 대한 연구가 활발하게 진행되고 있다. 특히 유비쿼터스 컴퓨팅에서 중요한 요소는 센서 네트워크로써, 저전력 Ad-hoc 네트워크에 기반한 센서와 센서 노드들로 구성되며, 실제의 환경과 유비쿼터스 컴퓨팅과의 매개 역할을 한다. 현재의 유비쿼터스와 관련된 연구는 주로 RFID를 이용해 경량화된 하드웨어를 통한 네트워크 관리에 대한 연구가 진행중에 있다. 그러나 실생활에 적용하기 위해서는 보다 현실적인 시나리오와 더불어 안전성과 효율성을 고루 갖춘 보안적인 연구가 필수적으로 요구되고 있다. 따라서 본 논문에서는 현재 연구가 진행중인 RFID 이외에 개인 네트워크에서 가장 많은 활용성을 제공하고 있는 PTD를 기반으로 다중 사용자들의 무선 네트워크 구성하고 이를 관리하는 방식을 제안하고자 한다. 제안된 방식은 사용자 주변의 신뢰된 기기를 기반으로 무선 네트워크에서 요구되는 다양한 서비스와 관련된 보안과 효율성을 높이기 위한 방식으로 기존 논문에서 전자 상거래에 사용하던 PTD를 이용해 다양한 서비스를 제공하고 임시 그룹을 설정하여 동적인 환경에 적합한 관리방식을 제안하였다.

• 한국측량학회지
• /
• 제35권6호
• /
• pp.453-460
• /
• 2017

고압 송전선은 전선을 느슨하게 가선하여 약간의 이도를 유지하도록 되어있다. 현재 송전선의 이도를 측정하는 방법은 직접 측량에 의존하고 있고 비교적 정확한 값을 얻을 수 있지만, 송전탑에 직접 승탑하거나 가까이 접근해야하는 위험성 및 어려움이 있다. 본 연구에서는 대상체에 접근하지 않고 3차원 측정을 수행하기 위해 저가의 드론을 활용한 항공사진측량 기법을 사용하였다. 선형 구조물인 송전선은 매핑을 위한 특징점이 존재하지 않기 때문에, 송전선의 방향과 수직이 되도록 에피폴라 라인을 형성하여 입체 사진 처리기법을 통해 송전선의 3차원 매핑을 수행하고, 송전선의 처짐량을 도출하였다. 사진측량기법에 의한 측정 결과 무타겟 토탈스테이션을 사용하여 직접 측정한 두 지점의 송전선의 처짐량과 비교하였을 때 수직 정확도가 15~16cm로 파악되었고 이는 해당 지점 처짐량 대비 5% 이내 및 대상 송전선 이도량의 3% 이내에 해당하는 값이다.

• 한국기계가공학회지
• /
• 제16권2호
• /
• pp.7-15
• /
• 2017

Recently, an electricity sensor system has been installed and operated to prevent failures and accidents by identifying whether a transformer is normal in advance of failure. This electricity sensor system is able to both measure and monitor the transformer's power and voltage remotely and send information to a manager when unusual operation is discovered. However, a battery is required to operate power detection devices, and battery systems need ongoing management such as regular replacement. In addition, at a maintenance cost, occasional human resources and worker safety problems arise. Accordingly, we apply a linear electromagnetic generator using vibration energy from a transformer for an electric sensor system's drive in this research and we conduct optimal design to maximize the linear electromagnetic generator's power. We consider design variables using the provided design method from Process Integration, Automation, and Optimization (PIAnO), which is common tool from process integration and design optimization (PIDO). In addition, we analyze the experiment point from the design of the experiments using "MAXWELL," which is a common electromagnet analysis program. We then create an approximate model and conduct accuracy verification. Finally, we determine the optimal model that generates the maximum power using the proven approximate kriging model and evolutionary optimization algorithm, which we then confirm via simulation.

• 한국신재생에너지학회:학술대회논문집
• /
• 한국신재생에너지학회 2009년도 춘계학술대회 논문집
• /
• pp.361-364
• /
• 2009

KEPRI has studied planar type SOFC stacks using anode-supported single cells and kW class co-generation systems for residential power generation. A 1kW class SOFC system consisted of a hot box part, a cold BOP part and a water reservoir. A hot box part contains a SOFC stack made up of 48 cells with $10{\times}10cm^2$ area and ferritic stainless steel interconnectors, a fuel reformer, a catalytic combustor and heat exchangers. Thermal management and insulation system were especially designed for self-sustainable operation. A cold BOP part was composed of blowers, pumps, a water trap and system control units. When a 1kW class SOFC system was operated at $750^{\circ}C$ with hydrogen, the stack power was 1.2kW at 30 A and 1.6kW at 50A. Turning off an electric furnace, the SOFC system was operated using hydrogen and city gas without any external heat source. Under self-sustainable operation conditions, the stack power was about 1.3kW with hydrogen and 1.2kW with city gas respectively. The system also recuperated heat of about 1.1kW by making hot water. Recently KEPRI developed stacks using $15{\times}15cm^2$ cells and tested them. KEPRI will develop a 5 kW class CHP system using $15{\times}15cm^2$ stacks by 2010.

• 한국자동차공학회논문집
• /
• 제20권6호
• /
• pp.46-51
• /
• 2012

Fuel Cell Hybrid Vehicles (FCHVs) have become a major topic of interest in the automotive industry owing to recent energy supply and environmental problems. Several types of power management strategies have been developed to improve the fuel economy of FCHVs including optimal control strategy based on optimal control theory, rule-based strategy, and equivalent consumption minimization strategy (ECMS). The ECMS is applied in this study. This strategy is based on the heuristic concept that the usage of the electric energy can be exchanged to equivalent fuel consumption. This strategy is known as one of the promising solutions for real-time control of hybrid vehicles. The ECMS for an FCHV is introduced in this paper as well as the equivalent fuel consumption parameter. The relationship between the battery final state of charge (SOC) and the fuel consumption while changing the equivalent fuel consumption parameter is obtained for three different driving cycles. The function of the equivalent fuel consumption parameter is also discussed.

• 유기물자원화
• /
• 제10권3호
• /
• pp.110-116
• /
• 2002

음식물쓰레기를 처리하는 과정에서 발생하는 이물질이나 오폐수 등이 적절하게 처리되지 않아 주변 환경을 오염시키는 사례들이 발생하고 있어서 본 연구에서는 공정부산물의 처리가 음식물쓰레기의 처리비용에 미치는 영향을 분석하였다. 비용을 분석하기 위해 전력사용량, 오폐수발생량 등을 조사하고 1일 50톤 처리용량에서 처리비용을 분석하였다. 총처리비에서 공정부산물의 처리비가 차지하는 비중은 하수병합, 혐기성퇴비화, 건식사료화 등 공정부산물의 발생이 많은 방법들은 14~39%, 호기성퇴비화, 습식발효사료화, 습식파쇄사료화 등 공정부산물의 발생이 적은 방법은 5~11%의 범위를 보였다. 따라서 공정부산물의 발생이 많은 처리방법일수록 그에 소요되는 비용을 충분히 수수료에 반영하거나 하수처리장과 매립지 등을 저가로 활용하게 하여 공정부산물의 부적절한 처리를 예방할 필요가 있다고 판단되었다.