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Evaluation of loss coefficient for an end plug with side holes in dual-cooled annular nuclear fuel
ChangHwan Shin,Tae-Hyun Chun,Dong-Seok Oh,인왕기 대한기계학회 2012 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.26 No.10
The Korea Atomic Energy Research Institute (KAERI) has been developing a dual-cooled annular fuel for a power uprate of 20% in an optimized pressurized water reactor (PWR) in Korea, OPR1000. The dual-cooled annular fuel is configured to allow coolant flow through the inner channel as well as the outer channel. Several thermal-hydraulic issues exist for the application of dual-cooled annular fuel to OPR1000. One is the hypothetical event of inner channel blockage because the inner channel is an isolated flow channel without the coolant mixing between the neighboring flow channels. The inner channel blockage could cause a departure from nucleate boiling (DNB) in the inner channel that eventually results in fuel failure. A long lower end plug for the annular fuel was invented to provide flow holes by perforating the side surface of the end plug body. The side holes in the lower end plug are expected to supply a minimum coolant in the inner channel to prevent the DNB occurrence in the event of partial or even complete blockage of the inner channel entrance. But due to the very unusual shape of the lower end plug, it is difficult to estimate the flow resistance of the side flow holes using empirical equations available in the open literature. An experiment and computational fluid dynamics (CFD) analysis were performed to investigate the bypass flow through the side holes of the end plug in the case of complete entrance blockage of the inner channel. The form loss coefficient in the side holes was also estimated using the pressure drop along the bypass flow path.
Shin, Changho,Kim, Jeong-Kyu,Kim, Gwang-Sik,Lee, Hyunjae,Shin, Changhwan,Kim, Jong-Kook,Cho, Byung Jin,Yu, Hyun-Yong IEEE 2016 IEEE transactions on electron devices Vol.63 No.11
<P>The impact of process-induced random dopant fluctuation (RDF)-induced threshold voltage (Vth) variation on the performance of 7-nm n-type germanium (Ge) FinFETs with and without a metal-interlayer-semiconductor (MIS) source/drain (S/D) structure is investigated using 3-D TCAD simulations. In order to reduce the RDF-induced Vth variation, an MIS S/D structure with a heavily doped n-type zinc oxide (ZnO) interlayer is used in the S/D region of the Ge FinFET. Thus, without performance degradation, the Ge FinFET with an MIS S/D structure achieves approximately threefold reduction in the RDF-induced Vth variation (versus without an MIS S/D structure). The impact of various fin parameters (i. e., fin height and fin width) on the RDF-induced Vth variation is also investigated. It is noteworthy that variation is suppressed as the fin height (fin width) increases (decreases).</P>
Shin, Changhwan The Institute of Electronics and Information Engin 2014 Journal of semiconductor technology and science Vol.14 No.2
There is a trade-off between read stability and writability under a full-/half-select condition in static random access memory (SRAM). Another trade-off in the minimum operating voltage between the read and write operation also exists. A new peripheral circuit for SRAM arrays, called a variation sensor, is demonstrated here to balance the read/write margins (i.e., to optimize the read/write trade-off) as well as to lower the minimum operation voltage for both read and write operations. A test chip is fabricated using an industrial 45-nm bulk complementary metal oxide semiconductor (CMOS) process to demonstrate the operation of the variation sensor. With the variation sensor, the word-line voltage is optimized to minimize the trade-off between read stability and writability ($V_{WL,OPT}=1.055V$) as well as to lower the minimum operating voltage for the read and write operations simultaneously ($V_{MIN,READ}=0.58V$, $V_{MIN,WRITE}=0.82V$ for supply voltage $(V_{DD})=1.1V$).
Changhwan Shin 대한전자공학회 2014 Journal of semiconductor technology and science Vol.14 No.2
There is a trade-off between read stability and writability under a full-/half-select condition in static random access memory (SRAM). Another trade-off in the minimum operating voltage between the read and write operation also exists. A new peripheral circuit for SRAM arrays, called a variation sensor, is demonstrated here to balance the read/write margins (i.e., to optimize the read/write trade-off) as well as to lower the minimum operation voltage for both read and write operations. A test chip is fabricated using an industrial 45-nm bulk complementary metal oxide semiconductor (CMOS) process to demonstrate the operation of the variation sensor. With the variation sensor, the word-line voltage is optimized to minimize the trade-off between read stability and writability (VWL,OPT = 1.055 V) as well as to lower the minimum operating voltage for the read and write operations simultaneously (VMIN,READ = 0.58 V, VMIN,WRITE = 0.82 V for supply voltage (VDD) = 1.1 V).
Shin, Jaemin,Ko, Eunah,Shin, Changhwan Institute of Electrical and Electronics Engineers 2018 IEEE transactions on electron devices Vol.65 No.1
<P>A negative differential resistance fin-shaped field-effect transistor (NDR-FinFET) using a Pb(Zr<SUB>0.52</SUB>Ti<SUB>0.48</SUB>)O<SUB>3</SUB> threshold selector (TS) is investigated. From the measured input transfer characteristic of NDR-FinFET, the following results are demonstrated: 1) superior reduction of off current by a factor of 350 (as compared to a baseline FinFET); 2) on current of NDR-FinFET comparable to that of the baseline FinFET; and 3) subthreshold slope of 3 mV/decade at 300 K. The operating principle of NDR-FinFET is demonstrated using MATLAB simulation. In the on-to-off and off-to-on switching processes, the existence of an unstable resistive switching region is verified through the comparison between simulation data and experimental results. The major device parameters that affect the formation of the unstable resistive switching region are revealed. Finally, it is proposed that: 1) lowering the hold voltage of the TS and 2) applying the drain voltage comparable to the threshold voltage can have the NDR-FinFET to work appropriately (i.e., not in unstable region).</P>
Ultra-thick semi-crystalline photoactive donor polymer for efficient indoor organic photovoltaics
Shin, Sang-Chul,Koh, Chang Woo,Vincent, Premkumar,Goo, Ji Soo,Bae, Jin-Hyuk,Lee, Jae-Joon,Shin, Changhwan,Kim, Hyeok,Woo, Han Young,Shim, Jae Won Elsevier 2019 Nano energy Vol.58 No.-
<P><B>Abstract</B></P> <P>An in-depth study on the photovoltaic characteristics under indoor lights, <I>i.e</I>., light-emitting diode (LED), fluorescent lamps, and halogen lamps, was performed with varying the photoactive layer thickness (120–870 nm), by comparing those under 1-sun condition. The semi-crystalline mid-gap photoactive polymer, poly[(2,5-bis(2-hexyldecyloxy)phenylene)-<I>alt</I>-(5,6-difluoro-4,7-di(thiophen-2-yl)benzo[<I>c</I>][1,2,5]thiadiazole)] (PPDT2FBT) and a fullerene derivative, [6,6]-phenyl C<SUB>71</SUB> butyric acid methyl ester (PC<SUB>70</SUB>BM) were used as a photoactive layer. In the contrary to the measurements under 1-sun condition, the indoor devices show a clearly different behavior, showing the thickness tolerant short-circuit current density (<I>J</I> <SUB>SC</SUB>) and fill factor (FF) values with 280–870 nm thick photoactive layers. The retained <I>J</I> <SUB>SC</SUB> and FF values of thick indoor devices were discussed in terms of the parasitic resistance effects based on the single-diode equivalent circuit model. The much lower series/shunt resistance (<I>R</I>s/<I>R</I> <SUB>P</SUB>) ratio was measured with thick photoactive layer (≥280 nm), resulting in negligible decreases in the <I>J</I> <SUB>SC</SUB> and FF values even with a 870-nm-thick active layer under the LED condition. Under 1000 lx LED light, the PPDT2FBT:PC<SUB>70</SUB>BM device showed an optimum power conversion efficiency (PCE) of 16% (max power density, 44.8 μW/cm<SUP>2</SUP>) with an open-circuit voltage of 587 mV, a <I>J</I> <SUB>SC</SUB> of 117 μA/cm<SUP>2</SUP>, and a FF of 65.2. The device with a 870-nm-thick active layer still exhibited an excellent performance with a PCE of 12.5%. These results clearly suggest that the critical parasitic resistance effects on the performance vary depending on the light illumination condition, and the large <I>R</I> <SUB>P</SUB> associated with the viable thick photoactive layer and the well-matched absorption (of photoactive layer) with the irradiance spectrum (of indoor light) are essential to realize efficient indoor photovoltaic cells with high <I>J</I> <SUB>SC</SUB> and FF.</P> <P><B>Highlights</B></P> <P> <UL> <LI> OPVs with a PPDT2FBT:PC<SUB>70</SUB>BM-based photoactive layer were fabricated. </LI> <LI> The thickness of the photoactive layers was varied from 120 nm to 870 nm. </LI> <LI> The <I>J</I> <SUB>SC</SUB> and fill factor remained high even with the 870-nm-thick photoactive layer. </LI> <LI> PPDT2FBT:PC<SUB>70</SUB>BM-based OPVs yielded 16.0 % efficiency under an 1000 lx LED lamp. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>The semi-crystalline polymer (PPDT2FBT) and a fullerene derivative (PC<SUB>70</SUB>BM) were used as a photoactive layer of organic photovoltaics. By varying the thickness of the photoactive layer (120–870 nm), we compared the performance under 1-sun and the indoor lights (LED, fluorescent and halogen). Unlike 1-sun condition, short-circuit current density and fill factor remained high under indoor illumination even as the active layer thickness was increased from 280 to 870 nm.</P> <P>[DISPLAY OMISSION]</P>
Uterine expression of tight junctions in the Canine uterus
Changhwan Ahn,Da-Hye Shin,Dongoh Lee,Hee Young Kang,Eui-Bae Jeung 충북대학교 동물의학연구소 2015 Journal of Biomedical and Translational Research Vol.16 No.3
Tight junctions (TJs) form continuous intercellular contacts in intercellular junctions. TJs involve integral proteins such as occludin (OCLN) and claudins (CLDNs) as well as peripheral proteins such as zona occludens-1 (ZO-1) and junctional adhesion molecules (JAMs). TJs control paracellular transportation across cell-to-cell junctions. Although TJs have been studied for several decades, comparison of the transcriptional-translational levels of these molecules in canine organs has not yet been performed. In this study, we examined uterine expression of CLDNs, OCLN, junction adhesion molecule-A, and ZO-1 in canine. Expression levels of canine uterine TJ proteins, including CLDN1, 2, 4, 5, JAM-A, ZO-1, and OCLN, were measured using reverse transcription PCR, real-time PCR, and Western blotting, whereas TJs distribution was determined by immunohistochemistry. The mRNA and protein expression levels of OCLN, CLDN-1, 4, JAM-1, and ZO-1 were identified in the uterus. Immunohistochemistry demonstrated that TJs were localized to the endometrium and/or myometrium of the uterus. Our results show that canine TJ proteins, including CLDNs, OCLN, JAM-A, and ZO-1, were expressed in the canine uterus. Taken together, these proteins may perform unique physiological roles in the uterus. Therefore, these findings may serve as a basis for further studies on TJ proteins and their roles in the physiological or pathological condition of the canine uterus.