• 한국정밀공학회지
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• 제26권6호
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• pp.68-73
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• 2009

One of the traditional optical methods to monitor a tool is a CCD sensor-based vision system which captures an aspect of the tool in real time. In the case using the CCD sensor, specific lens-modules are necessary to monitor the tool with higher resolution than its pixel size, and a microprocessor is required to attain desired data from captured images. Thus theses additional devices make the entire measurement system complex. Another method is to use a pair of an optical source and a detector per measuring axis. Since the method is based on the intensity modulation, the structure of the measurement system is simper than the CCD sensor-based vision system. However, in the case measuring the three dimensional position of the tool, it is difficult to apply to micro machine-tools because there may not be space to integrate three pairs of an optical source and a detector. In this paper, in order to develop a tool-origin measurement system which is employed in micro machine-tools, the improved method to measure a tool origin in x, y and z axes is introduced. The method is based on the intensity modulation and employs one pair of an optical source radiating divergent beams and a quadrant photodiode to detect a three dimensional position of the tool. This paper presents the measurement models of the proposed tool-origin sensor. The models were verified experimentally The verification results show that the proposed method is possible and the induced models are available for design.

• 반도체디스플레이기술학회지
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• 제22권2호
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• pp.1-5
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• 2023

In the past, display devices have undergone many changes, such as plasma TVs and LCDs, and have continued to develop. Recently, new display technologies, such as Organic Light Emitting Diode displays and Inorganic Light Emitting Diode displays, have been developed. Among them, Micro LED displays have the potential to improve performance more than LCDs and OLEDs, but a lot of effort and time are needed until the mass production technology (transfer and bonding) of Micro LED displays is developed. We have developed a new Micro LED display light source that can be produced using existing transfer and bonding process technologies to enable faster commercialization of Micro LED in the industry. This light source is TFT deposition on LED. TFT deposition on LED has the advantage of being able to produce displays using existing process technology, making early commercialization of display application products possible. In this study, we applied the Active Driving method to verify the performance of TFT deposition on LED as a display to determine its commercialization potential. Additionally, to facilitate faster application of Micro LED in the industry, we applied TFT deposition on LED to Optical Wireless Communication systems, which are widely used in application service areas such as safety/security and sensors, to verify its communication performance. The experimental results confirmed that TFT deposition on LED is not only capable of AM driving but can also be applied to OWC systems.

• 대기
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• 제23권3호
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• pp.265-273
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• 2013

To investigate properties of cloud and rainfall occurred at Boseong on 10 July 2012, Raindrop Size distributions (RSDs) and other parameters were analyzed using observation data collected by Micro Rain Radar (MRR) and PARticle SIze and VELocity (PARSIVEL) disdrometer located in the National center for intensive observation of severe weather at Boseong in the southwest of the Korean peninsula. In addition, time series of RSD parameters, relationship between reflectivity-rain rate, and vertical variation of rain rates-fall velocities below melting layer were examined. As a result, good agreements were found in the reflectivity-rain rate time series as well as their power relationships between MRR and PARSIVEL disdrometer. The rain rate was proportional to reflectivity, mean diameter, and inversely proportional to shape (${\mu}$), slope (${\Lambda}$), intercept ($N_0$) parameter of RSD. In comparison of the RSD, as rain rate was increased, the slope of RSD became less steep and the mean diameter became larger. Also, it was verified that reflectivities are classified in three categories (Category 1: Z (reflectivity) > 40 dBZ, Category 2: 30 dBZ < Z < 40 dBZ, Category 3: Z < 30 dBZ). As reflectivity was increased, rain rate was intensified and larger raindrops were existed, while reflectivity was decreased, shape (${\mu}$), slope (${\Lambda}$), intercept ($N_0$) parameter of RSD were increased. We expected that these results will lead to better understanding of microphysical process in convective rainfall system occurred during short-term period over Korean peninsula.

• 한국균학회지
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• 제44권3호
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• pp.132-137
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• 2016

A unrecorded hyphomycete species of Phialocephala was isolated for the first time during the investigation of fungal community in the soil samples collected from different regions of Korea. The fungal isolate was identified as Phialocephala lagerbergii, based on the morphological characteristics and phylogenetic analysis of the ribosomal DNA sequence. In addition, cultural and micro-morphological features were described in detail.

• Journal of Mechanical Science and Technology
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• 제18권9호
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• pp.1604-1613
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• 2004

This paper presents an effective and reliable evaluation method for fracture strength and material degradation of the micro-structure of high temperature service steel weldment using advanced small punch (ASP) test developed from conventional small punch (CSP) test. For the purpose of the ASP test, a lower die with a minimized ${\Phi}$1.5 mm diameter loading ball and an optimized deformation guide hole of ${\Phi}$3 mm diameter were designed. The behaviors of fracture energy (E$\_$sp/), ductile-brittle transition temperature (DBTT) and material degradation from the ASP test showed a definite dependency on the micro-structure of weldment. Results obtained from ASP test were compared and reviewed with results from CSP test, Charpy impact test, and hardness test. The utility and reliability of the proposed ASP test were verified by investigating fracture strength, behavior of DBTT, and fracture location of each micro-structure of steel weldment for test specimen in ASP test. It was observed that the fracture toughness in the micro-structure of FL＋CGHAZ and ICHAZ decreased remarkably with increasing aging time. From studies of all micro-structures, it was observed that FGHAZ microstructure has the most excellent fracture toughness, and it showed absence of material degradation.

• 한국산업융합학회 논문집
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• 제26권4_1호
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• pp.517-527
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• 2023

Many techniques have been proposed and investigated for microlens array manufacturing in three-dimensional (3D) structures. We present fabricating a microlens array using selective laser etching and a CO₂ laser. The femtosecond laser was employed to produce multiple micro-cracks that comprise the predesigned 3D structure. Subsequently, the wet etching process with a KOH solution was used to produce the primary microlens array structures. To polish the nonoptical surface to the optical surface, we performed reflow postprocessing using a CO₂ laser. We confirmed that the micro lens array can be manufactured in three primary shapes (cone, pyramid and hemisphere). Compared to our previous study, the processing time required for laser processing was reduced from approximately 1 hour to less than 30 seconds using the proposed processing method. Therefore, micro lens arrays can be manufactured using our processing method and can be applied to mass productionon large surface areas.

• 한국재료학회지
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• 제16권4호
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• pp.225-230
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• 2006

Nanoimprint lithography (NIL) is a novel method of fabricating nanometer scale patterns. It is a simple process with low cost, high throughput and resolution. NIL creates patterns by mechanical deformation of an imprint resist and physical contact process. The imprint resist is typically a monomer or polymer formulation that is cured by heat or UV light during the imprinting process. Stiction between the resist and the stamp is resulted from this physical contact process. Stiction issue is more important in the stamps including narrow pattern size and wide area. Therefore, the antistiction layer coating is very effective to prevent this problem and ensure successful NIL. In this paper, an antistiction layer was deposited and characterized by PECVD (plasma enhanced chemical vapor deposition) method for metal stamps. Deposition rates of an antistiction layer on Si and Ni substrates were in proportion to deposited time and 3.4 nm/min and 2.5 nm/min, respectively. A 50 nm thick antistiction layer showed 90% relative transmittance at 365 nm wavelength. Contact angle result showed good hydrophobicity over 105 degree. $CF_2$ and $CF_3$ peaks were founded in ATR-FTIR analysis. The thicknesses and the contact angle of a 50 nm thick antistiction film were slightly changed during chemical resistance test using acetone and sulfuric acid. To evaluate the deposited antistiction layer, a 50 nm thick film was coated on a stainless steel stamp made by wet etching process. A PMMA substrate was successfully imprinting without pattern degradations by the stainless steel stamp with an antistiction layer. The test result shows that antistiction layer coating is very effective for NIL.

• 한국전자통신학회논문지
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• 제16권2호
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• pp.219-226
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• 2021

LED-to-LED VLC(: Visible Light Communications) 기술은 기존의 VLC 기술과 달리 송신부와 수신부를 모두 LED로 사용한 기술이다. 본 논문에서는 Micro LED를 송신부로 사용한 Micro LED-to-LED VLC 기술을 연구하였다. Red, Yellow, Green, Blue, White 색상의 송/수신부 LED에 따라 통신 시스템의 상승 시간과 신호 대 잡음비를 측정하여 채널 용량을 비교하였다. 본 실험 결과에 따르면, 송신부 Micro LED가 Blue이고 수신부 LED가 Green일 때에 통신 시스템 중에서 가장 좋은 결과인 125 kbps의 채널 용량을 갖는 것을 확인하였다. 또한, OFDM(: Orthogonal Frequency Division Multiplexing) 신호를 사용하여 비트 에러율을 확인한 결과, 250 kbps까지는 통신이 가능함을 실험적으로 확인하였다.

• 원예과학기술지
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• 제33권4호
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• pp.479-485
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• 2015

본 연구는 배 '만수' 품종의 열과 발생의 원인과 재배 조건을 구명하여 발생을 경감시킬 수 있는 재배 방법을 제안하고자 수행하였다. 미세 열과는 성숙기 과실에서 발견되었다. 미세 열과의 발생은 8월 중의 일조 시간과 밀접한 관련을 나타내었다. 발생이 심했던 해에는 일조 시간이 부족하였으며, 발생이 적었던 해에는 일조 시간이 길고 일조량이 많은 날이 연속되어 광 조건이 우수하였다. Y자 수형보다는 평덕식에서 많이 발생하였고, 인공 관수구와 무관수 처리구에서 미세 열과 발생률의 차이는 나타나지 않았다. 무대 처리구에서는 미세 열과가 전혀 발생하지 않았으나, 외피가 흑색과 황색인 봉지를 이용한 처리구에서의 미세 열과 발생은 각각 62.2% 및 17.3%로 흑색 봉지 처리구에서 미세 열과가 심하게 발생하였다. 따라서 '만수' 과실의 미세열과 발생은 일조 시간, 수형 및 봉지 색에 따라 차이를 보여 광 조건이 가장 크게 작용하는 것으로 판명되었다. '만수' 과실의 미세열과를 방지하기 위해서는 적합한 수형 및 봉지 색을 선택하고, 하계전정 등을 통해 광 조건을 개선하는 것이 요구된다.

• 열처리공학회지
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• 제33권3호
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• pp.117-123
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• 2020

Due to high corrosion resistance, Zinc has been widely used in the automobile, shipping or construction industries as a galvanizing material. Zinc is popular as a coating element, but its low mechanical strength impede the expansion of applications as a load-bearing structure. The mechanical strength of Zinc can be increased through zinc based alloy process, but the ductility is significantly reduced. In this study, the mechanical strength and ductility of Zinc-Magnesium alloys with respect to heat treatment hold time was investigated. In order to enhance the mechanical strength of Zinc, a Zinc-Magnesium alloy was fabricated by a melting process. The heat treatment process was performed to improve the ductility of Zinc-Magnesium alloy. The microstructure of the heat-treated alloy specimen was analyzed using SEM. The hardness and compressive strength of the specimen were measured by a micro-hardness tester and a nano-indenter, respectively.