• 한국재료학회지
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• 제29권9호
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• pp.559-566
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• 2019

$Lu(Nb,Ta)O_4:Eu^{3+}$ powders are synthesized by a solid-state reaction process using LiCl and $Li_2SO_4$ fluxes. The photoluminescence (PL) excitation spectra of the synthesized powders consist of broad bands at approximately 270 nm and sharp peaks in the near ultraviolet region, which are assigned to the $Nb^{5+}-O^{2-}$ charge transfer of $[NbO_4]^{3-}$ niobates and the f-f transition of $Eu^{3+}$, respectively. The PL emission spectra exhibit red peaks assigned to the $^5D_0{\rightarrow}^7F_J$ transitions of $Eu^{3+}$. The strongest peak is obtained at 614 nm ($^5D_0{\rightarrow}^7F_2$), indicating that the $Eu^{3+}$ ions are incorporated into the $Lu^{3+}$ asymmetric sites. The addition of fluxes causes the increase in emission intensity, and $Li_2SO_4$ flux is more effective for enhancement in emission intensity than is LiCl flux. The substitution of $Ta^{5+}$ for $Nb^{5+}$ results in an increase or decrease in the emission intensity of $LuNb_{1-x}Ta_xO_4:Eu^{3+}$ powders, depending on amount and kind of flux. The findings are explained using particle morphology, modification of the $[NbO_4]^{3-}$ structure, formation of substructure of $LuTaO_4$, and change in the crystal field surrounding the $Eu^{3+}$ ions.

• 상하수도학회지
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• 제28권4호
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• pp.473-478
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• 2014

Microalgae is known as one alternative energy source of the fossil fuel with the small size of $5{\sim}50{\mu}m$ and negative charge. Currently, the cost of microalgae recovery process take a large part, about 20 - 30% of total operating cost. Thus, the microalgae recovery method with low cost is needed. In this study, the optimum current for Scenedesmus dimorphus recovery process using electrocoagulation techniques was investigated. Under the electrical current, Al metal in anode electrode is oxidized to oxidation state of $Al^{3+}$. In the cathode electrode, the water electrolysis generated $OH^-$ which combine with $Al^{3+}$ to produce $Al(OH)_3$. This hydroxide acts as a coagulant to harvest microalgae. Before applying in 1.5 L capacity electrocoagulation reactor, Scenedesmus dimorphus was cultured in 20 L cylindrical reactor to concentration of 1 OD. The microalgae recovery efficiency of electrocoagulation reactor was evaluated under different current conditions from 0.1 ~ 0.3 A. The results show that, the fastest and highest recovery efficiency were achieved at the current or 0.3 A, which the highest energy efficiency was achieved at 0.15 A.

• 한국전기전자재료학회논문지
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• 제30권11호
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• pp.710-716
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• 2017

New white-light-emitting $SrSnO_3:Dy^{3+}$ phosphors were prepared using different concentrations of $Dy^{3+}$ ions via a solid-state reaction. The phase structure, luminescence, and morphological properties of the synthesized phosphors were investigated using X-ray diffraction analysis, fluorescence spectrophotometry, and scanning electron microscopy, respectively. All the synthesized phosphors crystallized in an orthorhombic phase with a major (020) diffraction peak, irrespective of the concentration of $Dy^{3+}$ ions. The excitation spectra were composed of a broad band centered at 298 nm, ascribed to the $O^2-Dy^{3+}$ charge transfer band and five weak bands in the range of 350~500 nm. The emission spectra of $SrSnO_3:Dy^{3+}$ phosphors consisted of three bands centered at 485, 577, and 665 nm, corresponding to the $^4F_{9/2}{\rightarrow}^6H_{15/2}$, $^4F_{9/2}{\rightarrow}^6H_{13/2}$, and $^4F_{9/2}{\rightarrow}^6H_{11/2}$ transitions of $Dy^{3+}$, respectively. As the $Dy^{3+}$ concentration increased from 1 to 15 mol%, the intensities of all the emission bands gradually increased, reached maxima at 15 mol% of $Dy^{3+}$ ions, and then decreased rapidly at 20 mol% due to concentration quenching. The critical distance between neighboring $Dy^{3+}$ ions for concentration quenching was calculated to be $9.4{\AA}$. The optimal white light emission by the $SrSnO_3:Dy^{3+}$ phosphors was obtained when the $Dy^{3+}$ concentration was 15 mol%.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 추계학술대회 논문집 Vol.17
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• pp.683-686
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• 2004

In recent years, the supercapacitor and hybrid capacitor have related with substitutional energy source focused of many scientists because of their usage in power sources for electric vehicles, computers and other electric devices. The storage energy of electrical charge is based on electrostatic interactions in the electric double layer at the electrode/electrolyte interface, resulting in high rate capability and long cycle performance compared with batteries based on Faradaic electrode reactions. So we have been considered to carbon nanofibers as the ideal material for supercapacitors due to their high utilization of specific surface area, good conductivity, chemical stability and other advantages. In this work, we aimed to find out that the capacitance have increased because of electrochemical capacitance to provide by carbon nanofibers. Also carbon nanofibers based on chemical method and water treatment have been resulted larger capacitances and also exhibit better electrochemical behaviors about 15% than before of nontreated state. And also optical observations with treated and nontrteated carbon nanofibers discussed by the TEM, SEM, EDX, BET works and specific surface area analyzer. Their results also focused on the surface area of electrode and electrical capacitance was also improved by the effect of surface treatments.

• 한국화재소방학회논문지
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• 제24권5호
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• pp.150-158
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• 2010

도매시장은 20년 이상의 노후화 된 건물이 많고, 구조적 특성상 건물의 밀집도가 높아 방화구획 등 연소확대 차단시설 및 소방시설의 설치 곤란, 안전의식의 부재, 불특정다수인의 출입 등으로 인하여 대형화재가 발생할 수 있는 시설이다. 이러한 취약요소 등으로 인하여 수백억원의 재산피해가 발생한 2005년 서문시장 화재, 7명의 사상자가 발생한 2005년 서울 동문상가 도매시장 화재 등 시장에서 대형 화재가 자주 발생하고 있어 이에 대한 대책이 절실한 상황이다. 본 연구에서는 도매시장의 현황 및 구성주체별 특성, 화재사례 및 방재적 특성을 통계자료 등을 통해 도출하였고, 도매시장의 방화관리 현황과 화재안전관리 실태 등을 도매시장 방화관리자 및 종사자를 대상으로 설문조사를 실시하여 분석하였다. 그 결과 방화관리업무의 전문성 확보, 건물의 구조적 취약요소 개선 및 소방시설의 성능적 신뢰성 확보, 시장 종사자 소방교육의 내실화 등이 필요한 것으로 분석되었다.

• 한국정보통신학회논문지
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• 제18권4호
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• pp.861-866
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• 2014

국가 연구개발 사업은 그 규모가 점차 확대되고, 대형화되어가고 있어 연구 영역간의 융복합화 등이 활발하게 진행됨에 따라, 보다 객관적이고 공정한 사업선정과 예산관리의 투명성이 담보될 수 있는 시스템구축의 필요성이 대두되고 있다. 본 연구에서는 이기종간의 정보연계를 위한 표준 프레임워크를 제안하고, 이를 기반으로 국가 재정의 예산과 회계를 총괄하는 디지털예산회계시스템과 국가 연구개발 성과관리 및 성과평가를 담당하는 국가과학기술지식정보시스템의 정보연계를 위한 시스템을 고찰하여 연계를 위한 현황과 문제점을 해결하는 표준 정보연계 프레임워크의 활용방안을 제시하고자 한다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1990년도 하계학술대회 논문집
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• pp.227-230
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• 1990

The addition of titanium has come to produce an increase in the conductivity of ${\alpha}-Fe_2O_3$ and has been shown NTC ( negative temperature coefficient ) characteristics. Titanium enters the ${\alpha}-Fe_2O_3$ lattice substitutionally as $Ti^{4+}$,thus producing an $Fe^{2+}$ and maintaining the average charge per cation at three. Thus the $Fe^{2+}$ acts as a donor center with respect to the surrounding $Fe^{3+}$ ions. The sintering temperature, compacting pressure and sintering tire have an effect on the electrical properties. C-V and other properties have been measured on polycrystalline samples of ${\alpha}-Fe_2O_3$ containing small deviations from stoichiometry and small amounts of added Titanium. This measurment was made in the course of an investigation of the NTC mechanism in oxides whose cations have a partially filled d-level. C-V and frequency properties have been applied to the measurement of the trap barrier properties at the grain boundary. The double Schottky barrier at the grain boundary is the major cause of the NTC mechanism in NTC thermistor of ${\alpha}-Fe_2O_3$ containing N-type impurity.

• 의료ㆍ복지 건축 : 한국의료복지건축학회 논문집
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• 제17권1호
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• pp.7-14
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• 2011

This paper is intended to suggest some reference materials for future specialization of university education about healthcare facility design in Korea, by reviewing the degree systems and curriculum of 5 universities where architecture departments have specialized program for healthcare facility design in USA. Research method includes the navigation of related homepages, the e-mail contacts with the professors in charge, and the analysis of collected materials. Some conclusions can be summarized as following : Degrees of the specialized programs under concentration or track system are awarded as the same title as master program in the department of Architecture. Specialized education programs can be largely classified by concentration/track systems( Clemson University, University of Kansas and Arizona State University) which are operated independently in general and certificate system(Texas A&M University and Texas Tech University) which adds some healthcare related courses to general master program in the department of Architecture. As distinctive curriculum from 5 Universities, Clemson University which offers almost courses related to healthcare facility design, University of Kansas which provides internships(6 credits each) for summer term & fall semester of 2nd year, and Texas Tech University where certificate program is co-operated by architecture and nursing department can be mentioned. In order to pursuit the specialization of university education about healthcare facility design in the department of Architecture, it would be desirable to proceed it after setting the direction such as concentration, track or certificate system according to the various circumstances & conditions of the department concerned.

• 드라이브 ㆍ 컨트롤
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• 제10권4호
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• pp.1-6
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• 2013

With aggravation of environmental contamination and energy resource exhaustion, Hybrid Electric Vehicles (HEV) that can be economically operated with low fuel consumption are receiving greater attention. For performance improvement of such HEV, the development of efficient transmission can be seen as one of core technologies such as performance of components and driving strategy. Dual clutch transmission (DCT) is actively studied as a transmission type for HEV due to its advantages of having excellent power transmission efficiency based on manual transmission characteristic, resolving the problem of power interruption, and realizing driving convenience of automatic transmission (AT). In this paper, one diesel HEV equipped with 6-Speed DCT, modelled using MATLAB/Simulink, and a performance simulator developed for this vehicle are introduced. Driving simulation with driving cycles such as FTP75 and NYCC was performed using the developed performance simulator, and the simulated results regarding state of charge and fuel economy, when AT and DCT are applied to this diesel hybrid vehicle respectively, are compared. This performance simulator can be utilized to develop a control algorithm for improving the fuel economy of HEV with DCT.

• 공업화학
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• 제34권6호
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• pp.633-639
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• 2023

We synthesized 2-(10-methyl-10H-phenothiazin-3-yl)-5-phenyl-1,3,4-oxadiazole (MPPO) and 5,5-(10-methyl-10H-phenothiazin-3,7-diyl)-bis-(2-phenyl-1,3,4-oxadiazole) (DPPO). MPPO has both electron-donating and electron-accepting substituents with asymmetric molecular geometry. By incorporating one extra electron-accepting group into MPPO, we created a symmetric molecule, which is DPPO. The optical and electrochemical properties of these compounds were measured. The lowest unoccupied molecular orbital (LUMO) level of DPPO was lower than that of MPPO. The excited-state dipole moment of DPPO, with symmetric geometry, was calculated to be 4.1 Debye, whereas MPPO, with asymmetric geometry, had a value of 7.0 Debye. The charge-carrier mobility of both compounds was similar. We fabricated non-doped organic light-emitting diodes (OLEDs) using D-A type molecules as an emitting layer. The current efficiency of the DPPO-based device was 7.8 cd/A, and the external quantum efficiency was 2.4% at 100 cd/m², demonstrating significantly improved performance compared to the MPPO-based device. The photophysical and electroluminescence (EL) characteristics of the two D-A type molecules showed that molecular symmetry, as well as the lowered LUMO level of DPPO, played critical roles in the enhancement of EL performance.