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유니몰프 압전소자를 이용한 발전 판넬의 출력특성에 관한 연구
김용혁,Kim, Yong-Hyuk 한국전기전자재료학회 2010 전기전자재료학회논문지 Vol.23 No.3
The ability for energy harvesting via the piezoelectric effect was studied for a unimorph element such as piezo buzzer. A simple equivalent circuit was proposed to predict the energy generated based on the internal stress. Unimorphs with a metal-cavity were used as a driving device of the generation panel. Both the AC open voltage and DC output voltage as a function of pressure period and number of element were measured. For the unimorph generation circuit, DC output voltage varies with pressure period, reaching a maximum value at $470{\mu}F$. The maximum output voltage a according to load resistance was measured at $1M{\Omega}$. Data analysis of the DC output voltage and time constant indicated that number of piezoelectric element of optimum was 60~80. It was found that piezoelectric unimorph has the possibility to be used as the driving element of the electric generation.
동시 진공증착한 Cu-Co 미세입상 합금박막의 자기 및 자기저항 특성
김용혁,이성래,오용주 대한금속재료학회(대한금속학회) 1995 대한금속·재료학회지 Vol.33 No.4
Magnetic and magnetoresistance properties as functions of Co composition and annealing temperatures were investigated in the Cu_(1-x)Co_x (x=0.2∼0.4) alloy films deposited by thermal co-evaporation. The MR ratio of 12.5% at room temperature which was the largest among the reported values was obtained in the 25 at.%Co-Cu granular alloy film aged at 500℃ for 140 minutes. At higher measuring temperature and limited external field, the maximum MR ratio occurs for larger Co size. In the low Co concentration($lt;25at.%) alloy films, they behaved mainly as paramagnetic in the as-deposited state at room temperature and above that composition, it showed the ferromagnetic character. The enhanced MR ratio up to annealing temperature of 500℃ was due mainly to the reduction of the Cu matrix resistivity, which resulted from the Co precipitation and Cu matrix grain growth. The MR ratio and the magnetization decreased by raising the annealing temperature from 500℃ to higher temperature. These were thought to be due to re-solution of precipitated Co back into the Cu matrix at higher temperature. The Co content of the diffused interface layer decreased and a result of that, the interface spin-dependent scattering power decreased.
Identification of a Novel Mutation in the ATP7A Gene in a Korean Patient with Menkes Disease
김용혁,이란,유한욱,염미선,배선환,정소정,박용민,손재성 대한의학회 2011 Journal of Korean medical science Vol.26 No.7
Menkes disease is an infantile-onset X-linked recessive neurodegenerative disorder caused by diverse mutations in a copper-transport gene, ATP7A. Affected patients are characterized by progressive hypotonia, seizures, failure to thrive and death in early childhood. Here, we report a case of Menkes disease presented by intractable seizures and infantile spasms. A 3-month-old male infant had visited our pediatric clinic for lethargy,floppy muscle tone, poor oral intake and partial seizures. His hair was kinky, brown colored and fragile. Partial seizures became more frequent, generalized and intractable to antiseizure medications. An EEG showed frequent posteriorly dominant generalized spikes that were consistent with a generalized seizure. From a genetic analysis, a c.2743C>T (p.Gln915X) mutation was detected and diagnosed as Menkes disease. The mutation is a novel one that has not been previously reported as a cause of Menkes disease.
김용혁,최명규,이원식,김재호 한국전기전자재료학회 1989 電氣電子材料學會誌 Vol.2 No.2
본 논문은 압전 세라믹스 재료를 사용한 장방형 압전 변압기의 승압특성에 관한 연구이다. 승압기구 분석을 위하여 진동모드에 따른 주파수 Spectrum을 구동부측곽 발전부측에 대해 각각 조사하였다. 시편구조(전극길이, 두께, 폭)에 따른 진동상태와 승압비를 평가하고 압전 변압기로써 가져야 될 최적조건을 제시하였다. 또한 부하저항에 병렬로 연결된 등가손실저항과 발전부 공진임피던스 사이의 관련성을 검토하였다.
김용혁,Kim, Yong-Hyuk 한국전기전자재료학회 2010 전기전자재료학회논문지 Vol.23 No.12
In this study, magnesium (Mg), zinc (Zn) and aluminium (Al) as anode electrode and the solution of NaCl dissolved with 2~20 wt% as electrolytes were used for the metal-air cell. The open circuit voltage, short circuit current and I-V characteristics upon different kinds of anode electrode and electrolyte concentration were investigated. The open circuit voltage, initially about 1.45 V, rises to 1.6 V during the first 10 minutes indicating the necessity of an induction time to activate the catalyst on the air cathode. The short circuit current increases with an increased concentration of NaCl, causes an increase in the conductivity of the electrolyte solution, but the open circuit voltage did not under undergo influence of electrolyte. From NaCl 20 wt% electrolyte, the maximum output power of the magnesium electrode materials was measured with 177mW. It is found that the power characteristics of metal-air cell could be improved by using magnesium electrode materials in the NaCl electrolyte.