• 한국방사선학회논문지
• /
• 제8권7호
• /
• pp.417-422
• /
• 2014

본 연구에서는 방사선의 투사에너지에 따라 달라지는 산란선의 영향정도를 객관적이고 정량적인 방법인 PSNR로 평가할 수 있는 새로운 방법은 제시하고자 하였다. Target을 CR로 두었을 때와 Target을 DR로 두었을 때의 MSE와 PSNR의 값에는 변화가 없었으며, 관전압에 따란 MSE와 PSNR값에 변화가 나타났다. CR과 DR 모두 관전압 변화에 따라서 MSE와 PSNR의 변화가 있는 것으로 보아 Computon 산란선 영향이 있는 것으로 나타났다. CR과 DR의 경우 80 kVp영역에서 MSE와 PSNR의 변화가 급격하게 일어나는 현상이 발생하는 것은 광전효과에 의한 광전자와 Computon 산란에 의한 Computon 전자, 그리고 Computon 산란선이 동시에 검출기에 영향을 미친 것으로 나타났다. 향후 CR과 DR장치의 영상에서 광전효과의 에너지 대역인 60 kVp를 기준으로 하여 70 kVp, 80 kVp, 90 kVp, 100 kVp의 MSE와 PSNR 의 값을 비교하여 관전압의 변화에 따라 CR과 DR의 장치의 산란선과 화질저하에 대한 연구가 이루어지길 제안한다.

• 마이크로전자및패키징학회지
• /
• 제24권4호
• /
• pp.85-90
• /
• 2017

페로브스카이트 태양전지의 전자수송층(ETL)인 다공성 $TiO_2$에 $TiCl_4$를 흡착시켜 FTO 전극과 광활성층의 직접 접촉을 방지하고, 페로브스카이트 광활성층과 $TiO_2:TiCl_4$ 전자수송층 간의 전자 이동을 쉽게 함으로써 소자의 광전변환 효율을 높이고자 했다. 제작한 페로브스카이트 태양전지의 구조는 FTO/$TiO_2:TiCl_4$/Perovskite($CH_3NH_3PbI_3$)/spiro-OMeTAD/Ag이다. $TiCl_4$ 수용액에 다공성 $TiO_2$를 침지하는 시간을 변화시켜 제작한 소자의 광전기적 특성에 미치는 영향을 비교 평가하였다. $TiO_2:TiCl_4$ 전자수송층을 갖는 페로브스카이트 태양전지의 광전변환효율은 $TiCl_4$ 수용액에 $TiO_2$ 전자수송층을 30분 동안 침지하여 제작한 소자에서 가장 높은 10.46%를 얻었으며, 이는 $TiO_2$만의 전자수송층을 갖는 소자에 비해 27% 향상되었다. SEM, EDS, XPS 측정으로 $TiCl_4$ 흡착으로 인한 $TiO_2$ 층의 다공성 감소와 Cl 성분의 검출, 페로브스카이트 광활성층의 큐브형 모폴로지와 $PbI_2$ 피크의 이동을 관찰하였으며, $TiO_2:TiCl_4$ 층과 페로브스카이트 광활성층이 형성되었음을 확인하였다.

• 한국전기전자재료학회논문지
• /
• 제29권12호
• /
• pp.814-818
• /
• 2016

DSSCs (dye-sensitized solar cells) based on $TiO_2/SiO_2$ multi layer AR (anti-reflection) coating on the outer glass FTO (fluorine-doped tin oxide) substrate are investigated. We have coated an AR layer on the surface of a DSSCs device by using an IAD (ion beam-assisted deposition) system and investigated the effects of the AR layer by measuring photovoltaic performance. Compared to the pure FTO substrate, the multi layer AR coating increased the total transmittance from 67.4 to 72.9% at 530 nm of wavelength. The main enhancement of solar conversion efficiency is attributed to the reduction of light reflection at the FTO substrate surface. This leads to the increase of Jsc and the efficiency improvement of DSSCs.

• 한국화재소방학회논문지
• /
• 제23권4호
• /
• pp.98-103
• /
• 2009

본 논문은 연기감지기의 응답특성을 분석하여 주택용 화재감지기로 적합한지를 분석하고자 광전식연기감지기, 아날로그연기감지기, 단독경보형연기감지기를 시험체로 선정하여 UL 268에서 정하는 화재시험방법을 응용하여 화재성상(종이화재와 인화성액체화재)에 따른 연기감지기의 응답특성을 분석하고자 화재실험을 실시하였다. 실험결과 화재성상에 따라 연기감지기의 응답특성 차이가 나타나는 것을 확인할 수 있었다.

• Journal of Power Electronics
• /
• 제19권2호
• /
• pp.519-528
• /
• 2019

The unified power quality conditioner (UPQC) is an effective custom power device that is used at the point of common coupling to protect loads from voltage and current-related PQ issues. Currently, most researchers have studied series unit and parallel unit models and an idealized transformer model. However, the interactions of the series and parallel converters in AC-link are difficult to analyze. This study utilizes an equivalent transformer model to accomplish an electric connection of series and parallel converters in the AC-link and to establishes a precise unified mathematical model of the UPQC. The strong coupling interactions of series and parallel units are analyzed, and they show a remarkable dependence on the excitation impedance of transformers. Afterward, a feed-forward decoupling method based on a unified model that contains the uncertainty components of the load impedance is applied. Thus, this study presents an adaptive method to estimate load impedance. Furthermore, simulation and experimental results verify the accuracy of the proposed modeling and decoupling algorithm.

• 한국융합학회논문지
• /
• 제10권8호
• /
• pp.53-58
• /
• 2019

최근 만성질환자 건강관리의 목적으로 혈압측정에 대한 접근성을 높이는 제품 연구가 지속적으로 이루어지고 있다. 기존 연구에서는 심전도(ECG)와 광전용전맥파(PPG)를 분석하여 수축기혈압과 이완기 혈압을 산출하는 방식을 사용하고 있다. 주 과제는 정확도와 재현성을 위한 분석 알고리즘 개발이다. 본 연구에서는 초소형 혈압측정장치를 개발하는 단계에서 장치의 크기를 줄이고 측정방법도 간단히 하는 동시에 알고리즘도 두 개의 PPG만을 이용하여 최고혈압(SBP)을 추출하고 이에 따른 최저혈압(DBP)을 구하고자 하였다. 이를 위해 두 개의 PPG에서 얻은 측정값과 SBP, DBP 관계를 통계적으로 추적하여 상호관계를 분석하였다. PPG의 차이 값인 DF_P는 SBP와 반비례 관계가 있으며, DBP와는 비례적 관계가 성립되어 알고리즘에 의해 혈압값을 유추할 수 있으며, SBP를 통해 DBP를 추적할 수 있다.

• 전기학회논문지
• /
• 제67권10호
• /
• pp.1370-1374
• /
• 2018

A heterojunction $SnS_2/p-Si$ photodetector was fabricated by RF magnetron sputtering system. $SnS_2$ was formed with 2-inch $SnS_2$ target. Al was applied as the front and the back metal contacts. Rapid thermal process was conducted at $500^{\circ}C$ to enhance the contact quality. 2D material such as $SnS_2$, MoS2 is very attractive in various fields such as field effect transistors (FET), photovoltaic fields such as photovoltaic devices, optical sensors and gas sensors. 2D material can play a significant role in the development of high performance sensors, especially due to the advantages of large surface area, nanoscale thickness and easy surface treatment. Especially, $SnS_2$ has a indirect bandgap in the single and bulk states and its value is 2 eV-2.6 eV which is considerably larger than that of the other 2D material. The large bandgap of $SnS_2$ offers the advantage for the large on-off current ratio and low leakage current. The $SnS_2/p-Si$ photodetector clearly shows the current rectification when the thickness of $SnS_2$ is 80 nm compared to when it is 135 nm. The highest photocurrent is $19.73{\mu}A$ at the wavelength of 740 nm with $SnS_2$ thickness of 80 nm. The combination of 2D materials with Si may enhance the Si photoelectric device performance with controlling the thickness of 2D layer.

• 전기학회논문지
• /
• 제67권1호
• /
• pp.68-74
• /
• 2018

All transparent UV photodetector based on ZnO was fabricated with structure of NiO/ZnO/$SnO_2$/ITO by using RF and DC magnetron sputtering system. ZnO was deposited with 4 inch ZnO target (purity 99.99%) for a quality film. In order to build p-n junction up, p-type NiO was formed on n-type ZnO by using reactive sputtering method. The indium tin oxide (ITO) which is transparent conducting oxide (TCO) was applied as a transparent electrode for transporting electrons. To improve the UV photodetector performance, a functional $SnO_2$ layer was selected as an electron transporting and hole blocking layer, which actively controls the carrier movement, between ZnO and ITO. The photodetector (NiO/ZnO/$SnO_2$/ITO) shows transmittance over 50% as similar as the transmittance of a general device (NiO/ZnO/ITO) due to the high transmittance of $SnO_2$ for broad wavelengths. The functional $SnO_2$ layer for band alignment effectively enhances the photo-current to be $15{\mu}A{\cdot}cm^{-2}$ (from $7{\mu}A{\cdot}cm^{-2}$ of without $SnO_2$) with the quick photo-responses of rise time (0.83 ms) and fall time (15.14 ms). We demonstrated the all transparent UV photodetector based on ZnO and suggest the route for effective designs to enhance performance for transparent photoelectric applications.

• 한국정보디스플레이학회:학술대회논문집
• /
• 한국정보디스플레이학회 2008년도 International Meeting on Information Display
• /
• pp.620-621
• /
• 2008

Transparent electronics has been one of the key terminologies forecasting the ubiquitous technology era. Several researchers have thus extensively developed transparent oxide-based thin-film transistors (TFTs) on glass and plastic substrates although in general high voltage operating devices have been mainly studied considering transparent display drivers. However, low voltage operating oxide TFTs with transparent electrodes are very necessary if we are aiming at logic circuit applications, for which transparent complementary or one-type channel inverters are required. The most effective and low power consuming inverter should be a form of complementary p-channel and n-channel transistors but real application of those complementary TFT inverters also requires electrical- and even photo-stabilities. Since p-type oxide TFTs have not been developed yet, we previously adopted organic pentacene TFTs for the p-channel while ZnO TFTs were chosen for n-channel on sputter-deposited $AlO_x$ film. As a result, decent inverting behavior was achieved but some electrical gate instability was unavoidable at the ZnO/$AlO_x$ channel interface. Here, considering such gate instability issues we have designed a unique transparent complementary TFT (CTFTs) inverter structure with top n-ZnO channel and bottom p-pentacene channel based on 12 nm-thin nano-oxide/self assembled monolayer laminated dielectric, which has a large dielectric strength comparable to that of thin film amorphous $Al_2O_3$. Our transparent CTFT inverter well operate under 3 V, demonstrating a maximum voltage gain of ~20, good electrical and even photoelectric stabilities. The device transmittance was over 60 % and this type of transparent inverter has never been reported, to the best of our limited knowledge.

• 한국표면공학회지
• /
• 제53권4호
• /
• pp.182-189
• /
• 2020

Indium tin oxide (ITO) used a transparent electrode of a photoelectric device has a low sheet resistance and a high transmittance. However, ITO is disadvantageous in that the process cost is expensive, and the process time is long. Silver nanowires (AgNWs) transparent electrodes are based on a low cost solution process. In addition, it has attracted attention as a next-generation transparent electrode material that replaces ITO because it has similar electrical and optical characteristic to ITO, it is noted as a. AgNW thin films are mainly produced by spin-coating. However, the spin-coating process has a disadvantage of high material loss. In this study, the material loss was reduced by using about 2~10 ㎕ of AgNW solution on a (25 × 25) ㎟ substrate using the shear-coating method. It was also possible to align AgNWs in the drag direction by dragging the meniscus of the solution. The electro-optical properties of the AgNW thin film were adjusted by changing the experimental parameters that the amount of AgNWs suspension, the gap between the substrate and the blade, and the coating speed. As a result, AgNW thin films with a transmittance of 90.7 % at a wavelength of 550 nm and a sheet resistance of 15 Ω/□ was deposited and exhibited similar properties to similar AgNW transparent electrodes studied by other researchers.