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Kangho Lee,Tae-Hak Lee,Chang-Soo Ahn,Young-Sik Kim,Juseop Lee THE INSTITUTE OF ELECTRICAL ENGINEERS 2015 IEEE Microwave and Wireless Components Letters Vol. No.
<P>This letter proposes a new design method for a bandstop filter with two stopbands. Contrary to a conventional method, the presented method allows for achieving two stopbands without increasing the number of the couplings between resonators and the transmission line connecting the input and output ports. In addition, a filter designed using the presented method can not only have different center frequencies but also have different bandwidths by adjusting the resonant frequencies of the resonators. For verification of the proposed approach a dual-stopband filter using four tunable substrate-integrated waveguide resonators has been designed and measured.</P>
Exposure assessment of workers in printed electronics workplace
Lee, Ji Hyun,Sohn, Eun Kyung,Ahn, Jin Soo,Ahn, Kangho,Kim, Keun Soo,Lee, Jong Hwan,Lee, Taik Min,Yu, Il Je Informa Healthcare USA, Inc. 2013 Inhalation toxicology Vol.25 No.8
<P>Printed electronics uses converging technologies, such as printing, fine mechanics, nanotechnology, electronics and other new technologies. Consequently, printed electronics raises additional health and safety concerns to those experienced in the traditional printing industry. This study investigated two printed electronics workplaces based on a walk-through survey and personal and area sampling. All the printed electronics operations were conducted in a cleanroom. No indication of exposure to excess silver nanoparticles or carbon nanotubes (CNTs) was found. While the organic solvents were lower than current occupational exposure limits, there was a lack of engineering controls, such as local exhaust ventilation, correct enclosure and duct connections. There was also an insufficient quantity of personal protective equipment, and some organic solvents not described in the safety data sheets (SDSs) were detected in the air samples. Plus, the cleaning work, a major emissions operation, was not conducted within a hood, and the cleaning waste was not properly disposed of. Therefore, the present exposure assessment results from two printed electronics workplaces suggest that the printed electronics industry needs to take note of the occupational safety and health risks and hazards already established by the traditional printing industry, along with new risks and hazards originating from converging technologies such as nanotechnology.</P>
InGaP/GaAs 이중접합 기반의 고효율 플렉시블 태양전지 제조기술 연구
문승필(Seungpil Moon),김영조(Youngjo Kim),김강호(Kangho Kim),김창주(Chang Zoo Kim),정상현(Sang Hyun Jung),신현범(Hyun-Beom Shin),박경호(Kyung Ho Park),박원규(Won-Kyu Park),안연식(Yeon-Shik Ahn),강호관(Ho Kwan Kang) 한국태양광발전학회 2016 Current Photovoltaic Research Vol.4 No.3
III-V compound semiconductor based thin film solar cells promise relatively higher power conversion efficiencies and better device reliability. In general, the thin film III-V solar cells are fabricated by an epitaxial lift-off process, which requires an AlxGa1-xAs (x≥0.8) sacrificial layer and an inverted solar cell structure. However, the device performance of the inversely grown solar cell could be degraded due to the different internal diffusion conditions. In this study, InGaP/GaAs double-junction solar cells are inversely grown by MOCVD on GaAs (100) substrates. The thickness of the GaAs base layer is reduced to minimize the thermal budget during the growth. A wide band gap p-AlGaAs/n-InGaP tunnel junction structure is employed to connect the two subcells with minimal electrical loss. The solar cell structures are transferred on to thin metal films formed by Au electroplating. An AlAs layer with a thickness of 20 nm is used as a sacrificial layer, which is removed by a HF:Acetone (1:1) solution during the epitaxial lift-off process. As a result, the flexible InGaP/GaAs solar cell was fabricated successfully with an efficiency of 27.79% under AM1.5G illumination. The efficiency was kept at almost the same value after bending tests of 1,000 cycles with a radius of curvature of 10 mm.
Han, Sung Gu,Lee, Jong Seong,Ahn, Kangho,Kim, Yong Soon,Kim, Jin Kwon,Lee, Ji Huyn,Shin, Jae Hoon,Jeon, Ki Soo,Cho, Wan Seob,Song, Nam Woong,Gulumian, Mary,Shin, Beom Soo,Yu, Il Je Springer-Verlag 2015 Archives of toxicology Vol.89 No.7
<P>Gold nanoparticles are known to be distributed to many tissues following their oral, inhalation, or intravenous exposure. Information on the biodistribution and clearance of gold nanoparticles from these tissues is, therefore, important to understand their behavior in vivo. To study the effect of size on the biodistribution of gold nanoparticles, Sprague-Dawley rats were exposed by inhalation to small gold nanoparticles (13?nm in diameter on average) at an exposure concentration of 12.8??2.42??g/m(3), and to large gold nanoparticles (105?nm in diameter on average) at an exposure concentration of 13.7??1.32??g/m(3). The experimental animals were exposed to the gold nanoparticles and the control animals to fresh air for 5?days (6?h/day), followed by a recovery period of 1, 3, and 28?days in fresh air. None of the exposed animals exhibited any toxic response to the gold nanoparticles. Despite the difference in size, both small and large gold nanoparticles deposited mainly in rat lungs. Their biodistribution from the lungs to secondary target organs was significantly higher with the small compared to the large gold nanoparticles. While the large gold nanoparticles were only found in the blood, the small gold nanoparticles were detected in the liver, spleen, brain, testes, and blood. In addition, the elimination half-life of the small gold nanoparticles from the lungs was significantly shorter than that of the large gold nanoparticles. The present data may, therefore, suggest that the smaller gold nanoparticles are able to translocate from the lungs, the primary exposure organ to extrapulmonary organs at a faster rate than the larger gold nanoparticles and thus confirming previous observations reported in the literature.</P>
Peranantham, Pazhanisami,Park, Gye Hyun,Kim, Kangho,Ahn, Kwang Jun,Hwangbo, Chang Kwon,Lee, Jaejin,Rotermund, Fabian American Scientific Publishers 2017 Journal of Nanoscience and Nanotechnology Vol.17 No.6
<P>We report a 4.8% absolute efficiency enhancement for a single-junction GaAs solar cell fabricated with ZnO nanorod arrays (NRAs) as an antireflection (AR) layer. The efficiency enhancement, compared to a bare solar cell, mainly stems from the increase in current density due to AR effects caused by ZnO NRAs. The seed layer necessary for ZnO NR growth was deposited by RF magnetron sputtering without fill factor degradation, and ZnO NRAs of different lengths were subsequently fabricated by using the hydrothermal method. The reflectance, external quantum efficiency, and current density-voltage characteristics were measured for the fabricated GaAs solar cells. The reflectance measurement showed that the ultraviolet-to-near infrared reflectance was significantly suppressed for GaAs solar cells with ZnO NRAs. A GaAs solar cell with ZnO NRAs with lengths of 620 nm and a mean diameter of 30 nm shows the highest efficiency of 19.9%.</P>
콘크리트 구조체 균열 탐지에 대한 Mask R-CNN 알고리즘 적용성 평가
배병규(Bae, Byongkyu),최용진(Choi, Yongjin),윤강호(Yun, Kangho),안재훈(Ahn, Jaehun) 한국지반공학회 2024 한국지반공학회논문집 Vol.40 No.3
구조물의 상태를 파악하기 위한 균열조사는 정밀안전 진단에 필수적인 검사 항목이다. 그러나 육안으로 이루어지는 균열조사 방식은 현장 상황의 변화에 따라 주관적으로 수행될 수 있다. 이러한 육안검사의 한계를 극복하기 위해 본 연구에서는, ResNet, FPN, Mask R-CNN을 백본(Backbone), 넥(Neck), 헤드(head)로 구성한 합성곱 신경망을 바탕으로, 이미지 데이터에서의 콘크리트 균열 탐지를 자동화하고. 그 성능을 IoU 값을 바탕으로 분석하였다. 해석에 사용된 데이터는 총 1,203개의 이미지 데이터로 구성하였으며, 이 중 70%를 훈련(Training)에, 20%를 검증(Validation)에, 그리고 10%의 데이터를 시험(Testing)에 사용하였다. 시험 결과의 평균 IoU값은 95.83%로 산정되었고, 또한 이미지 내 균열이 전혀 탐지되지 않는 경우는 존재하지 않아, 본 연구에 가정한 모델이 콘크리트의 균열 탐지를 성공적으로 수행하는 것을 확인하였다. Inspecting cracks to determine a structure’s condition is crucial for accurate safety diagnosis. However, visual crack inspection methods can be subjective and are dependent on field conditions, thereby resulting in low reliability. To address this issue, this study automates the detection of concrete cracks in image data using ResNet, FPN, and the Mask R-CNN components as the backbone, neck, and head of a convolutional neural network. The performance of the proposed model is analyzed using the intersection over the union (IoU). The experimental dataset contained 1,203 images divided into training (70%), validation (20%), and testing (10%) sets. The model achieved an IoU value of 95.83% for testing, and there were no cases where the crack was not detected. These findings demonstrate that the proposed model realized highly accurate detection of concrete cracks in image data.
Kim, Ellen,Lee, Ji Hyun,Kim, Jin Kwon,Lee, Gun Ho,Ahn, Kangho,Park, Jung Duck,Yu, Il Je Hindawi Limited 2015 Journal of nanomaterials Vol.2015 No.-
<P>This study evaluated the risk of silver nanoparticle (AgNP) exposure from antibacterial sprays containing AgNPs. Using an exposure simulation chamber as the setting for the experiment, various instruments, including a scanning mobility particle sizer (SMPS), condensation particle counter (CPC), dust monitor, and mixed cellulose esters (MCE) filters, are connected to the chamber to measure the exposure levels of AgNPs when using the sprays. To assess potential risks to consumers, margin of exposure (MOE) approach was used to assess risk in which a calculated MOE was compared with a target MOE. When evaluating the risk of antibacterial sprays to inhalation exposure using the MOE, spraying a whole can and spraying an air conditioner both resulted in a high-risk concern level with a MOE ranging from 59 to 146 that was much lower than the no-risk concern level of 1000, while some spray showed a MOE 2049 with no-risk concern level. The dermal exposure levels with a single layer of clothing were estimated at 2–50 <I>μ</I>g/kg/day with a MOE ranging from 20,000 to 500,000. Therefore, the current results showed the possibility of high-risk inhalation exposure to AgNPs released when using antibacterial sprays.</P>