• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.290.1-290.1
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• 2016

Grapehen, a single atomic layer of graphite, has been in the spotlight and researched in vaious fields, because its fine mechanical, electrical properties, flexibility and transparence. Synthesis methods for large-area graphene such as chemical vaper deposition (CVD) and mechanical, chemical exfoliation have been reported. In particular, chemical exfoliation method receive attention due to low cost process. Chemical exfoliation method require reduction of graphene oxide in the process of exfoliation such as chemical reduction by strong reductant, thermal reduction on high temperature, and optical reduction via ultraviolet light exposure. Among these reduction methods, optical reduction is free from damage by strong reductant and high temperature. However, optical reduction is economically infeasible because the high cost of short-wavelength ultraviolet light sorce. In this paper, we make graphene-oxide and lanthanoid ion mixture aqueous solution which has highly optical absorbency in selective wevelength region. Sequentially, we synthesize reduced graphene oxide (RGO) using the solution and visible laser beam. Concretely, graphene oxide is made by modified hummer's method and mix with 1 ml each ultraviolet ray absorbent Gd3+ ion, Green laser absorbent Tb3+ ion, Red laser absorbent Eu3+ ion. After that, we revivify graphene oxide by laser exposure of 300 ~ 800 nm layser 1mW/cm2 +. We demonstrate reproducibility and repeatability of RGO through FT-IR, UV-VIS, Low temperature PL, SEM, XPS and electrical measurement.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.352.2-352.2
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• 2016

In recent times, much effort has been concentrated on trivalent rare-earth ions activated ceramics or oxide phosphors to develop display industries due to their promising applications in optoelectronic devices and field-emission displays. To prepare efficient phosphors, citrate sol-gel method is one of the best synthetic methods. Green and blue emissive CaLa2ZnO5:RE3+ nanocrystalline materials are synthesized by a citrate sol-gel method. After the samples annealing at $1100^{\circ}C$, morphological and structural properties are investigated by scanning electron microscope images and X-ray diffraction patterns, respectively. At low electron beam voltage of <5 kV, the visible photoluminescence properties are obtained. Various concentrations of the RE3+ ions exhibited their characteristic emission peaks at different excitation wavelengths, respectively. Similarly, at high electron beam anodic voltage, the cathodoluminescence properties are studied as a function of acceleration voltage and filament current. The chromaticity coordinates are calculated for the optimized CaLa2ZnO5 nanocrystalline luminescent materials.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.5
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• pp.2367-2374
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• 2011

Today's digital broadcasting services based on DVB-SI standard are provided a two-way broadcast. However, using the power of STB if the user does not use a waste of time spent on standby power is becoming a serious problem. Accordingly, for energy savings both at home and abroad to actively promote green policies, but highly functional STB, the internal software to automatically update the appropriate scheduling techniques are not shown, power usage does not meet the standard can. Therefore, In this paper We analyze the current STB technology and the problems, as proper use of power to the standard STB design scheme and the automatic software installation method of operation is presented.

• Journal of Institute of Control, Robotics and Systems
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• v.8 no.7
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• pp.589-598
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• 2002

The color measuring/matching expert system is implemented with a new color measuring method that combines intelligent algorithms with image processing techniques. Color measuring part of the proposed system preprocesses the scanned original color input images to eliminate their distorted components by means of the image histogram technique of image pixels, and then extracts RGB(Red, Green, Blue)data among color information from preprocessed color input images. If the extracted RGB color data does not exist on the matching recipe databases, we can measure the colors for the user who want to implement the model that can search the rules for the color mixing information, using the intelligent modeling techniques such as fuzzy inference system and adaptive neuro-fuzzy inference system. Color matching part can easily choose images close to the original color for the user by comparing information of preprocessed color real input images with data-based measuring recipe information of the expert, from the viewpoint of the delta Eformula used in practical process.

• Journal of Korea Multimedia Society
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• v.19 no.5
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• pp.837-847
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• 2016

Tone mapping for High Dynamic Range(HDR) image provides matching human visual perception between real world scene and displayable devices. Recently, a tone mapping algorithm based on localized gamma correction is proposed. This algorithm is using human visual properties of contrast and colorfulness with background intensity, generating a weight map for gamma correction. However, this method have limitations of controlling enhancement region as well as generating halo artifacts caused by the weight map construction. To overcome aforementioned limitations, proposed algorithm in this paper modifies previous weight map, considering base layer intensity of input luminance channel. By determining enhancement region locally and globally based on base layer intensity, gamma values are corrected accordingly. Therefore, proposed algorithm selectively enhances local brightness and controls strength of edges. Subjective evaluation using z-score shows that our proposed algorithm outperforms the conventional methods.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.184-184
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• 2008

저온 동시 소성 세라믹(LTCC, Low Temperature Co-firing) 기술 중에서 테이프 캐스팅(tape casting)은 얇고 균일한 세라믹 그린 쉬트를 연속 성형할 수 있으며 성형된 쉬트의 밀도, 표면상태, 두께제어 등이 매우 중요하다. 얇고 균일한 세라믹 그린 쉬트를 제작하기 위해서 슬러리의 분산성과 레오로지 특성은 매우 중요한 요소이며 첨가되는 유기물 첨가제들의 종류와 함량비는 슬러리의 분산성과 점도에 큰 영향을 미친다. 본 연구에서는 유기물 첨가제의 종류와 함량에 따른 슬러리의 점도와 그린 쉬트의 밀도 및 두께 제어에 미치는 영향을 고찰하였다. 바인더로는 acryl, polyvinyl 계를 사용하였으며, 가소제는 glycol, phatalate 계를 사용하였다. 각각 2 종류의 바인더와 가소제의 함량에 따른 레올로지 거동과 그런 쉬트의 밀도를 측정하였다. 각 조성별로 준비된 슬러리를 사용하여 테이프 캐스팅 방법으로 제작된 그린 쉬트의 두께를 측정하여 유기물 첨가제 조성이 그린 쉬트의 두께제어에 미치는 영향을 평가하였다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.4
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• pp.524-532
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• 2012

In this paper, we used MOM-based BIM(Born Iterative Method) algorithm to implement the inverse scattering for the detection of cancer. We adopted two-dimensional breast structure, integral equations and two-dimensional Green's function is solved with MoM(Method of Moment) to analyzing electromagnetic scattering phenomena. In addition, verifying the calculation of developed inverse scattering algorithm and analyzing medical applicability and limitations of the algorithm.

• Current Photovoltaic Research
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• v.6 no.2
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• pp.39-42
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• 2018

When the PV module is illuminated in a high temperature region, solar cells are also exposed to the high temperature external environment. The operating temperature of the solar cell inside the module is increased, which causes the power drops. Various efforts have been made to reduce the operating temperature and compensate the power of solar cells according to the outdoor temperature such as installing of a cooling system. Researches have been also reported to lower the operating temperature of solar cells by improving the heat dissipation properties of the backsheet. In this study, we conducted a test to measure the internal temperature of each module components and the external temperature when the light was irradiated according to the surrounding temperature. Backsheets with different thermal conductivities were compared in the test. Finally, in order to explain the temperature difference between the solar cell and the outside of the module, we proposed an evaluation method of the heat transfer characteristics of photovoltaic modules with different backsheet.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.7
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• pp.91-98
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• 2009

A reliable tensile test technique for PDP's barrier rib materials was introduced. A tensile specimen was prepared by punching out of green sheet, curing the specimen in a high temperature furnace, attaching sand paper tabs on each grip ends, and then attaching two strain gages for the strain monitoring and specimen alignment. Preliminary tensile tests were successfully done with the specimens made from ZnO-based lead-free green sheet. The specimens cured at 3 different maximum curing temperatures were tested to demonstrate the applicability of the test method. The Young's modulus was 88 ${\pm}$ 4 GPa regardless of the maximum curing temperature. The ultimate tensile strength was decreased with increasing the temperature. The tensile test method proposed in this study was proven to be reliable, useful and easy to estimate the bulk mechanical properties of barrier rib materials.

• Proceedings of the IEEK Conference
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• 2001.10a
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• pp.342-348
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• 2001

This study was conducted to obtain granular crystalline gypsum that can be used as raw material for plaster boards or cements from waste Plaster board. We could disintegrate preferentially gypsum to gypsum needle in 10${\mu}{\textrm}{m}$ or less size among the contents of waste plaster board (gypsum, paper, fiber, and inorganic material .etc.) by hydration afterwards the dehydration of crushed waste plaster board. In this case, the optimum conditions for minimizing the size of gypsum were dehydration rate of 75%~ 85%, hydration concentration of 10~20%, agitation speed of 250~400rpm, crushing size of 2cm or less. Gypsum of 98.21% grade was recovered with 99.0% yield from under screenings of 325mesh wet screening which followed by the dehydration-hydration process performed in the conditions of dehydration rate of 80%, hydration concentration of 15%, agitation speed of 300rpm, crushing size of 2cm or less. Subsequently, Plate-like Crystalline gypsum of is 151${\mu}{\textrm}{m}$ size and the grade of 99.49% with the Yield of 98.0% from the upper screenings of 270mesh wet screening carried out after the re-crystallization of the recovered gypsum needle slurry.