• Transactions on Electrical and Electronic Materials
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• 제8권3호
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• pp.121-124
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• 2007

The $Zn_2SiO_4:Mn$ phosphors were prepared using polymer matrix technique in order to improve the performance of green emitting phosphors for plasma display panel(PDP). $Zn_2SiO_4:Mn$ phosphor exhibits a strong green emission around 520-530 nm. The emission intensity and particle size of powders were controlled by sintering temperature and raw material composition. The zinc silicate $Zn_2SiO_4:Mn$ single phase were obtained at lower temperature than prepared by solid-state reaction method. PL luminance of $Zn_2SiO_4:Mn$ phosphor was similar to the commercial material.

• 한국유기농업학회지
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• 제17권4호
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• pp.483-499
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• 2009

This research is to establish a theme-type organic edu-farm model and provide ways to practically apply it so as to vitalize urban-rural exchange through the emerging concept of green tourism. This research also traces the practical development of organic edu-farm programs. Organic edu-farm(OEF) should be some of the ideas to develop organic agriculture resources according to the local features, and learn by direct and actual experience a life of organic farm. A few policy suggestions to put OEF model in practical use are proposed. What the state needs to do through direct involvement are to put efforts at demand expansion on organic farm products, to clean and beautify the green rural environmental settings, to build more urban-rural exchange facilities. What is more important, however, is financial support, to create the network and to develop program contents for each OEF operation unit. The OEF model proposed in this research will be applied as a relevant reference in planning and realizing sustainable green tourism at the village level.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2009년도 9th International Meeting on Information Display
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• pp.476-477
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• 2009

The smallest green laser containing a built-in temperature controlling unit has been demonstrated. The device volume was just 0.5 cubic centimeters, which is nearly the same size as existing red and blue diode lasers, has an electrical-to-optical conversion efficiency of 10% and 150 mW power output. Furthermore as an alternative approach for compact green laser development, a quasi-phase matching method with wide spectral bandwidth for the reduction of speckle noise will be presented.

• 한국전기전자재료학회논문지
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• 제26권4호
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• pp.264-270
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• 2013

$CaMoO_4:Tb^{3+}$ green phosphor powders and thin films were successfully prepared by using the solid-state reaction method and the radio-frequency magnetron sputtering technique, respectively. The crystalline structure of all phosphor powders with different $Tb^{3+}$ ion concentrations was found to be a tetragonal system with the maximum diffraction intensity at $28.58^{\circ}$, while that of the phosphor thin films, irrespective of the type of substrate, was amorphous. As for the phosphor powders, the grain particles showed the chain-like patterns with inhomogeneous size distribution, the excitation spectra were composed of a broad band peaked at 307 nm and two small narrow bands centered at 381 and 492 nm, and the highest green emission spectrum was observed at 0.01 mol of $Tb^{3+}$ ions. As for the phosphor thin films, the average transmittance exceeding 85% was measured in the 400~1,100 nm range and the optical band gap showed a significant dependence on the type of substrate.

• Current Photovoltaic Research
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• 제2권2호
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• pp.53-58
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• 2014

$Tb^{3+}$ - or $Ce^{3+}$-doped $LaBO_3$ phosphors were synthesized by a solid-state reaction process with different concentrations of activator ions. The XRD spectra showed the monoclinic $LaBO_3$ pattern with the main peak occurring at (014) plane, irrespective of the kind of activator ions. The crystallite size was determined by using the Scherrer formula, and the maximum was obtained with an activator concentration of 0.05 mol for both phosphors. The emission spectra of $LaBO_3$ phosphors doped with $Tb^{3+}$ ions under excitation at 269 nm exhibited three major emission bands at 488, 544, and 587 nm. The strongest emission was green at 544 nm owing to the $^5D_4-^7F_5$ transition at a $Tb^{3+}$ ion concentration of 0.05 mol. For the $Ce^{3+}$-doped $LaBO_3$ phosphors, one strong blue band centered at 469 nm and weak multipeaks were observed. These results suggest that the optimum green and blue emission can be realized by controlling the concentration and type of activator ions incorporated in the host crystal.

• Journal of Communications and Networks
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• 제18권4호
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• pp.600-609
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• 2016

In this paper, we propose a two-stage base station (BS) sleeping scheme to save energy consumption in cellular networks. The BS sleeping mode is divided into a light sleeping stage and a deep sleeping stage according to whether there is a user in the BS's coverage. In the light sleeping stage, a BS will retain its coverage and frequently switch between the on state and the doze state according to the service characteristics. While in the deep sleeping stage analysis, the BS will shut down its coverage, and neighbor BSs will patch the coverage hole. Several closed-form formulas are derived to demonstrate the power consumption in each sleeping stage and the stage switching conditions are discussed to minimize the average power consumption. The average traffic delay caused by BS sleeping and the average deep sleeping rate under a given traffic load have also been studied. In addition, it is shown that BS sleeping is not always possible because of the limited quality of service (QoS) requirements. Simulation results show that the proposed scheme can effectively reduce the average BS power consumption, at the cost of some extra traffic delay. In summary, our proposed framework provides an essential understanding of the design of future green networks that aim to take full advantage of different stages of BS sleeping to obtain the best energy efficiency.

• 한국조경학회지
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• 제39권5호
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• pp.111-118
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• 2011

건강과 삶의 질 향상에 대한 관심이 커짐에 따라 도시녹지가 가져다 주는 건강편익이 크게 주목되고 있지만, 이에 관한 객관적이고 과학적인 데이터는 매우 부족한 실정이다. 따라서 본 연구에서는 도시녹지가 가져다 주는 건강편익에 대한 과학적 자료를 얻기 위해 생리적, 심리적 지표를 활용하여 실험을 실시하였다. 과거병력이 없는 20대 남자 대학생 20명이 실험에 참가하였고, 자극은 녹지와 도시에서 실제의 경관을 15분간 감상하는 것으로 하였다. 이번 연구는 충남대학교 의학전문대학원 생명윤리심사위원회의 승인을 받은 후 실시되었다. 녹지와 도시에 대한 생리반응을 분석한 결과, 도시에 비해 녹지에서 심박동수가 현저히 감소하였고, 안정상태에서 증가하는 부교감신경활동이 유의하게 향상되었으며, 스트레스호르몬의 일종인 코티솔 농도가 낮아지는 경향이 보였다. 심리반응에 있어서는 부정적인 감정과 정신상태가 녹지에서 보다 유의하게 낮아진 반면, 활력은 유의하게 증가하였다. 이번 연구의 결과는, 녹지를 접하는 것이 심리적 변화뿐만 아니라 인체의 자율신경계와 내분비계 활동에 긍정적 변화를 가져다 준다는 것을 보여주는 것으로써, 녹지가 도시민의 건강증진과 관련하여 매우 직접적인 환경요인이 될 수 있음을 과학적으로 뒷받침한다고 할 수 있다.

• 한국실천공학교육학회논문지
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• 제4권1호
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• pp.119-131
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• 2012

본 연구에서는 미국의 그린직업훈련체계 및 정책동향을 연방정부 및 주정부 차원에서 분석하고, 다양한 그린스킬 수요에 대응한 수준별 훈련프로그램체계와 관련 사례들을 조사하였다. 이러한 조사 분석에 기반 하여 우리나라 신성장동력분야의 향후 인력양성 정책방향을 다각도에서 제시하였다. 신성장동력분야는 우리나라의 경쟁력을 제고시킬 고부가가치 산업이지만, 첨단 기술력이 요구되고 투자 위험성이 크며 신속한 시장대응이 필요하기 때문에 적절한 인력공급체계를 갖추기 어려운 실정이다. 따라서 본 연구결과가 정부 인력양성정책의 문제점을 찾고 개선방안을 모색하는데 도움이 될 것으로 기대한다.

• 환경영향평가
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• 제8권1호
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• pp.51-59
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• 1999

This study was conducted to evaluate the functions of green spaces for the environment amelioration in Chongju City. The results obtained from this study were as follows; 1. Total amounts of $SO_2$ and $NO_2$ which can be absorbed by green spaces in Chongju City from EPA model were calculated as 27,655 tons and l,551 tons per year, respectively. 2. It was estimated that more green spaces were needed to mitigate the effect of air pollutants emitted from industrial complex at Songjung-Dong, Bokdae-Dong and Sachang-Dong in Chongju City. This is acquired as a result of overlaying the map of administrative district, forest state, and $SO_2$ isoline using GIS method. 3. The amounts of green spaces and the selection of their proper location have to be considered at the stage of city planning and in this case, the amounts of air pollutants are also considered.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제5권1호
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• pp.55-78
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• 2001

Given the anisotropic Poisson equation $-{\nabla}{\cdot}{\mathcal{K}}{\nabla}p=f$, one can convert it into a system of two first order PDEs: the Darcy law for the flux $u=-{\mathcal{K}{\nabla}p$ and conservation of mass ${\nabla}{\cdot}u=f$. A very natural mixed finite volume method for this system is to seek the pressure in the nonconforming P1 space and the Darcy velocity in the lowest order Raviart-Thomas space. The equations for these variables are obtained by integrating the two first order systems over the triangular volumes. In this paper we show that such a method is really a standard finite element method with local recovery of the flux in disguise. As a consequence, we compare two approaches in analyzing finite volume methods (FVM) and shed light on the proper way of analyzing non co-volume type of FVM. Numerical results for Dirichlet and Neumann problems are included.