• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.8
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• pp.1836-1842
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• 2010

Sensor network, which is technology to realize the ubiquitous environment, recently, could apply to the field of Mechanic & electronic Security System, Energy management system, Environment monitoring system, Home automation and health care application. However, feature of wireless networking of sensor network is vulnerable to eavesdropping and falsification about message. Presently, PKC(public key cryptography) technique using ECC(elliptic curve cryptography) is used to build up the secure networking over sensor network. ECC is more suitable to sensor having restricted performance than RSA, because it offers equal strength using small size of key. But, for high computation cost, ECC needs to enhance the performance to implement over sensor. In this paper, we propose the optimizing technique for multiplication, core operation in ECC, to accelerate the speed of ECC.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.8
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• pp.2117-2125
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• 2009

This paper describes an information system of operation adequacy in environmental facilities such as environmental contamination prevention and processing equipments, which is namely, an integrated management system for environmental facilities. By developing this system, we can improve environmental characteristics and maximize the efficiency throughout the life cycle from generation of contaminant source to contamination prevention processing, and to contaminant disappearance. In order to meet these objects, we have developed ubiquitous life cycle assessment(u-LCA) for environmental facilities, which is an ISO14001-based incineration facility information system. The developed system is currently operating for test at an incinerator in Koyang city. Due to this system, the managers can confirm the operation condition of the incinerator with real-time and they will be able to improve the problems immediately.

• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.2
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• pp.141-147
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• 2018

In this study, a cyclic loading test was carried out for a reinforced concrete frame installed a TS(tension-spring) damper for the purpose of verifying the seismic strengthening effect of the TS seismic reinforcing method. The test specimens are four specimens of non - reinforced frame and three reinforced frame specimens. Experimental parameters are Shape of damper and construction method of damper. As a result, the construction method of inserting type inside window was twice as much in terms of strength and stiffness, and the method of externally attached type showed a performance improvement of about 2 times in terms of energy dissipation. From these results, it can be confirmed that the TS seismic reinforcing method is a superior method for field application and seismic strengthening.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.97-98
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• 2007

A stoichiometric. mixture of evaporating materials for $CuGaSe_2$ single crystal thin films was prepared from horizontal electric furnace. Using extrapolation method of X-ray diffraction patterns for the polycrystal $CuGaSe_2$, it was found tetragonal structure whose lattice constant $a_0$ and $c_0$ were $5.615\;{\AA}$ and $11.025\;{\AA}$, respectively. To obtain the single crystal thin films, $CuGaSe_2$ mixed crystal was deposited on thoroughly etched semi-insulating GaAs(100) substrate by the hot wall epitaxy (HWE) system. The source and substrate temperatures were $610^{\circ}C$ and $450^{\circ}C$, respectively. The crystalline structure of the single crystal thin films was investigated by the photoluminescence and double crystal X-ray diffraction (DCXD). The carrier density and mobility of $CuGaSe_2$ single crystal thin films measured with Hall effect by van der Pauw method are $4.87{\times}10^{17}\;cm^{-3}$ and $129\;cm^2/V{\cdot}s$ at 293 K, respectively. The temperature dependence of the energy band gap of the $CuGaSe_2$ obtained from the absorption spectra was well described by the Varshni's relation, $E_g(T)\;=\;1.7998\;eV\;-\;(8.7489\;{\times}\;10^{-4}\;eV/K)T^2/(T\;+\;335\;K)$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.261-261
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• 2007

Wearable and ubiquitous micro systems will be greatly growing and their related devices should be self-powered in order to avoid the replacement of finite power sources, for example, by scavenging energy from the environment. With ever reducing power requirements of both analog and digital circuits, power scavenging approaches are becoming increasingly realistic. One approach is to drive an electromechanical converter from ambient motion or vibration. Vibration-driven generators based on electromagnetic, electrostatic and piezoelectric technologies have been demonstrated. Among various generator types proposed so far, piezoelectric generator possesses considerable potential in micro system. To overcome low mechanical-to- electric energy conversion, the piezoelectric device should activate in resonance mode in response to external vibration. Normally, the external vibration excretes at low frequency ranging 0.1 to 200 Hz, whereas the resonant frequencies of the devices are fixed as constant. Therefore, keeping their resonant mode in varying external vibration can be one of important points in enhancing the conversion efficiency. We investigated the possibility of use of multi-bender type piezoelectric devices. To match the external vibration frequency with the device resonant frequency, the various devices with different resonant frequency were chosen. Under an external vibration acceleration of 0.1G at 120 Hz, the device exhibited a peak-to-peak voltage of 2.8 V and a power of 0.5 mw in resonance mode.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.08a
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• pp.25-30
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• 2002

The ternary semiconducting compounds of the $A_{4}BX_{6}$(A=Cd, Zn, Hg; B=Si, Sn, Ge; X=S, Se, Te) type exhibit strong fluorescence and high photosensitivity in the visible and near infrared ranges, so these are supposed to be materials applicable to photoelectrical devices. These materials were synthesized and single crystals were first grown by Nitsche, who identified the crystal structure of the single crystals. In this paper. author describe the undoped and $Co^{2+}$-doped $Zn_{4}SnSe_{6}$ single crystals were grown by the chemical transport reaction(CTR) method using iodine of $6mg/cm^{3}$ as a transport agent. For the crystal. growth, the temperature gradient of the CTR furnace was kep at $700^{\circ}C$ for the source aone and at $820^{\circ}C$ for the growth zone for 7-days. It was found from the analysis of x-ray diffraction that undoped and $Co^{2+}$-doped $Zn_{4}SnSe_{6}$ compounds have a monoclinic structure. The optical absorption spectra obtained near the fundamental absorption edge showed that these compounds have a direct energy gaps. These temperature dependence of the optical energy gap were closely investigated over the temperature range 10[K]~300[K]

• Proceedings of the Korea Water Resources Association Conference
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• 2012.05a
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• pp.122-122
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• 2012

본 연구의 목적은 한국형 녹색성장 협력 모델을 기반으로 한국의 대(對) 메콩지역 진출 방안을 모색하는 것이다. 메콩 유역은 중국의 운남성 지방, 미얀마, 라오스, 태국, 캄보디아, 베트남 등 6개국이 위치하고 있는데 이 지역은 세계 경제 침체에도 불구하고 높은 경제 성장률을 달성하고 있다. 이에 따라 세계 각국이 개발사업 선점을 위한 치열한 경쟁을 벌이고 있으며 일본, 미국, 중국이 발 빠르게 영향력을 확장하고 있다. 한국은 지난해 메콩 5개국의 외교장관을 서울로 초청하여 회담을 개최하여 메콩 지역 진출의 교두보를 마련하였으나 최근 세계 각국이 메콩 지역의 개발사업 진출을 위해 적극적으로 노력하고 있는 상황에서 선진국과 차별적인 경쟁우위를 살릴 수 있는 방안의 모색이 필요하다. 따라서 본 연구는 2008년 이명박 정부가 제시한 신성장 패러다임인 녹색성장 모델과, 물관리 정책과 사업을 접목시킨 물과 녹색성장 공적개발원조 및 무나싱해(Munasinghe)의 지속가능한 경제(Sustainomics)가설을 이론적으로 고찰하여 대(對) 메콩유역 협력 방안 모델을 설계하였다. 이 지역이 급속한 경제 성장으로 전력수요가 증가하고 있고, 환경오염에 대한 우려를 잠식시키고 국가의 에너지 안보를 위해 높은 수입 석유 의존율을 낮춰야한다는 점 등을 고려해보았을 때 메콩 유역의 수력발전이 이 지역의 녹색성장을 위한 큰 동력이 될 수 있을 것으로 사료된다. 뿐만 아니라 홍수방재 효과, 전력 수출로 인한 소득 창출은 이 지역의 사회발전으로 이어질 수 있을 것으로 기대된다. 그러므로 본 연구는 자금조달 방식, 외교적 접근, 기술적 접근, 제도적 접근 방식을 제시하여 단계적으로 대(對) 메콩유역 한국형 물과 녹생성장 ODA의 나아가야 할 방향을 모색해 보았다. 제시된 협력 모델을 기반으로 점차 한국이 메콩 유역의 수력발전산업으로 진출하고 더 나아가 이지역의 영향력을 확대하는 데 큰 도움이 될 것으로 사료된다.

• Proceedings of the Korea Water Resources Association Conference
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• 2012.05a
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• pp.477-477
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• 2012

미생물 연료전지는 정부가 추진하고 있는 신성장 동력사업의 녹색성장 정책에 부합하는 환경융합 신기술로써 일상생활에서 배출되는 하 폐수와 같은 유기물질을 전자공여체로 이용하여 전기에너지를 생산 할 수 있다는 점에서 각광받고 있다. 미생물 연료전지는 산화전극부의 미생물이 공급된 유기물질 을 분해하여 전자와 수소이온을 생성시키며 이들은 산소가 존재하는 환원전극부로 이동하여 물로 환원 됨 으로써 전기를 생성한다. 전기 화학적 성능의 향상을 위해 미생물 연료전지에서는 환원전극부에 서의 산소와 전자 및 수소이온의 빠른 환원반응을 유도해 주는 Pt촉매를 이용한다. 하지만 고가의 Pt 촉매는 미생물 연료전지의 현장적용을 위한 규모확장 시 초기비용이 증가되는 문제점을 초래한다. 이에 미생물 연료전지의 대체촉매 개발에 대한 많은 연구가 진행되고 있다. 화학적 연료전지에 관한 논문에서 연료전지의 촉매로 산소 환원반응에 높은 성능을 보이는 Co-N/C 형태의 Cobalt poly-pyrrole carbon가 제시 되었다. 이는 가격적인 측면에서는 Pt촉매의 약1/10배 정도 수준이지만 셀 성능은 Pt촉매의 95%정도의 효율을 보인다는 측면에서 향후 Pt 대체촉매로 가능성을 보여주는 새로운 비금속 촉매물질이다. Cobalt poly-pyrrole carbon이 Pt-catalsyt 셀 전압 성능 대비 약 66 %의 효율을 보였고 내부저항과 최대전력 밀도에 있어서도 촉매를 사용하지 않은 경우와 비금속 촉매의 성능보다 높음을 알 수 있었다. 본 연구는 Pt-catalsyt를 대체할 수 있는 저가의 산소환원 촉매물질 발굴을 위해 미생물연료전지에서 사용된 전례가 없으며 현재 화학전지의 촉매로 널리 쓰이고 있는 Cobalt poly-pyrrole carbon의 산소환원 촉매로써의 이용가능성을 평가하기 위해 실시되었으며, 평가한 결과는 첫 번째로 Cobalt poly-pyrrole carbon을 사용한 경우가 촉매를 사용하지 않은 경우와 비금속 촉매보다 환원 전극부에서의 원활한 환원작용이 진행되고 있음을 추측할 수 있으며 Pt-catalyst와 비교하였을 때 성능 대비 저렴한 가격으로 가격 경쟁력에 있어서 우월하다고 판단되었고 두 번째로 전기화학적 성능평가 및 EIS를 이용한 환원전극부의 내부저항 평가를 실시한 결과 셀 전압에 있어서 가장 많은 도말량 ($2.0mg/cm^2$)이 높은 성능을 보이고 있음을 알 수 있었다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.12
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• pp.1035-1042
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• 2014

Reducing the friction of engine parts is an important issue in engine design. The loss of energy in the piston assembly due to mechanical friction ranges from 40 to 55%, and there is an increase in the total energy of about 5% if the friction of the piston can be removed. In order to reduce the friction loss at the level of each engine part, it is necessary to perform a comparative analysis with other engines to determine the important factors affecting the energy loss. Several studies have been performed to analyze the lubrication based on hydrodynamic modeling, since a piston lubrication system has dimensions in the nanoscale to microscale domain. Therefore, it is necessary to determine the correlations between the molecular and continuum systems. In this study, we investigated the friction changes due to the various interactions between molecules in the wall/fluid interface, where a microscopic movement of the oil film occurs along the cylinder liner of the engine.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.8
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• pp.3570-3577
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• 2012

Researches on the danger of nuclear power generation, the foundation of the development of national industry and one of the energy sources, as perceived by ordinary citizens, are very important to social acceptance of nuclear power generation. Accordingly, this study intends to understand how ordinary citizens perceive the social risk of nuclear power generation and radiation, and their misconceptions, and to propose ways to improve such perceptions. To achieve these goals, this study analyzed the perceptions of 251 ordinary citizens. The analysis showed that ordinary citizens have vague anxiety and suspicion about the safety of nuclear power generation, and little trust in government-affiliated organizations. The younger they were, the more influential they thought corporations and industries were. The result of this study suggests that the misconceptions of ordinary citizens should be corrected by professors and scientists in university research institutions they trust the most, and their intrinsic perceptions should be changed accordingly.