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A Case of Giant Hydronephrosis Hidden by Obesity in an 11-year-old Boy
Hwang, Gumbich,Hwang, Inchan,Choo, Seol Ho,Kim, Hyun Gi,Pai, Ki Soo Korean Society of Pediatric Nephrology 2017 Childhood kidney diseases Vol.21 No.2
Giant hydronephrosis (GH) is a rare urological entity and usually presents with more than a liter of fluid in the collecting system. It may mimic a progressive and benign abdominal cystic tumor. We report a case of GH in an 11-year-old obese boy who presented with abdominal distension and dyspnea on exercise. Hydronephrosis was caused by ureteropelvic junction obstruction, with 2,300 mL of fluid in the collecting system. Diagnostic and therapeutic features of this case are discussed, with reference to current literature.
Hwang, Inchan,Um, Han-Don,Kim, Byeong-Su,Wober, Munib,Seo, Kwanyong The Royal Society of Chemistry 2018 Energy & environmental science Vol.11 No.3
<P>Much attention has been paid to thin crystalline silicon (c-Si) photovoltaic devices due to their excellent flexibility characteristics, stable efficiency, and possibility of use as highly efficient next-generation flexible photovoltaic devices (FPVs). To fabricate thin c-Si FPVs, it is important to improve their light-absorption properties while maintaining the flexible characteristics. In this study, vertically aligned microwires (MWs) on a 50 μm-thick thin c-Si substrate are designed for novel FPVs. Increasing the length of the MWs enhances the optical properties of the thin c-Si without affecting its flexibility. To maximize the efficiency of the thin c-Si FPVs with MWs, tapered MWs and a localized back-contact structure are devised. This device shows a maximum efficiency of 18.9%. In addition, the proposed thin c-Si FPV with MWs shows high stability without any change in efficiency, even with 1000 bending cycles with a bending radius of 12 mm. Thus, we successfully demonstrate battery-free flexible electronic devices integrated with our thin c-Si FPVs with MWs.</P>
Enhancement of Light Absorption in Photovoltaic Devices using Textured Polydimethylsiloxane Stickers
Hwang, Inchan,Choi, Deokjae,Lee, Sojeong,Seo, Ji hoon,Kim, Ka-Hyun,Yoon, Ilsun,Seo, Kwanyong American Chemical Society 2017 ACS APPLIED MATERIALS & INTERFACES Vol.9 No.25
<P>We designed and fabricated a random-size inverted-pyramid structured polydimethylsiloxane (RSIPS-PDMS) sticker to enhance the light absorption of solar cells and thus increase their efficiency. The fabricated sticker was laminated onto bare glass and crystalline silicon (c-Si) surfaces; consequently, low solar-weighted reflectance values were obtained for these surfaces (6.88 and 17.2%, respectively). In addition, we found that incident light was refracted at the PDMS air interface of each RSIPS, which redirected the incident power and significantly increased the optical path length in the RSIPS-PDMS sticker which was 14.7% greater than that in a flat-PDMS sticker. Moreover, we investigated power reflection and propagation through the RSIPS-PDMS sticker using a finite-difference time-domain method. By attaching an RSIPS-PDMS sticker onto both an organic solar cell (OSC) based on a glass substrate and a c-Si solar cell, the power conversion efficiency of the OSC and the c-Si solar cell were increased from 8.57 to 8.94% and from 16.2 to 17.9%, respectively. Thus, the RSIPS-PDMS sticker is expected to be universally applicable to the surfaces of solar cells to enhance their light absorption.</P>
Hwang, Gaeun,Park, Hyungmin,Bok, Taesoo,Choi, Sinho,Lee, Sungjun,Hwang, Inchan,Choi, Nam-Soon,Seo, Kwanyong,Park, Soojin The Royal Society of Chemistry 2015 Chemical communications Vol.51 No.21
<P>Nanostructured micrometer-sized Al-Si particles are synthesized via a facile selective etching process of Al-Si alloy powder. Subsequent thin Al2O3 layers are introduced on the Si foam surface via a selective thermal wet oxidation process of etched Al-Si particles. The resulting Si/Al2O3 foam anodes exhibit outstanding cycling stability (a capacity retention of 78% after 300 cycles at the C/5 rate) and excellent rate capability.</P>
Hwang, Yeong-Hyeon,Hwang, Inchan,Cho, Won-Ju American Scientific Publishers 2014 Journal of Nanoscience and Nanotechnology Vol.14 No.11
<P>The influence of composition ratio on the bipolar resistive switching behavior of resistive switching memory devices based on amorphous indium-gallium-zinc-oxide (a-IGZO) using the spin-coating process was investigated. To study the stoichiometric effects of the a-IGZO films on device characteristics, four devices with In/Ga/Zn stoichiometries of 1:1:1, 3:1:1, 1:3:1, and 1:1:3 were fabricated and characterized. The 3:1:1 film showed an ohmic behavior and the 1:1:3 film showed a rectifying switching behavior. The current-voltage characteristics of the a-IGZO films with stoichiometries of 1:1:1 and 1:3:1, however, showed a bipolar resistive memory switching behavior. We found that the three-fold increase in the gallium content ratio reduces the reset voltage from -0.9 to - 0.4 V and enhances the current ratio of high to low resistive states from 0.7 x 10(1) to 3 x 10(1). Our results show that the increase in the Ga composition ratio in the a-IGZO-based ReRAM cells effectively improves the device performance and reliability by increasing the initial defect density in the a-IGZO films.</P>
슐리렌 장치를 활용한 기상 냉매 주입 과정의 유동 가시화
황인찬(Inchan Hwang),이상욱(Sangwook Lee),김민수(Min-Soo Kim) 대한기계학회 2022 대한기계학회 춘추학술대회 Vol.2022 No.11
In this study, we investigate the flow behavior of refrigerant R134a vapor injection process in a pressurizing chamber. We conducted experiments under various injection pressures using a image processing. In order to observe the flow behavior, the injection process was filmed with short term images through high speed camera. By using schlieren method, we can distinguish R134a and CO₂ by the difference of density of gases. From the injection images, we marked the boundary of R134a according to the change in light intensity levels to investigate injection characteristics such as the tip penetration and cone angle. The results showed that the velocity of injection tip is affected by the injection pressure and the chamber pressure. The cone angle of the injection was also investigated with various pressure conditions. Furthermore, we could observe that the injection stream was depleted as the pressure difference decreases.