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Microchannel plates for field emission displays
Sunghwan Jin,SeGi Yu,Jungna Heo,Taewon Jeong,Junghee Lee,Whikun Yi,Yongsoo Choi,Jongmin Kim 한국진공학회(ASCT) 2000 Journal of Korean Vacuum Science & Technology Vol.4 No.4
Microchannel plates (MCPs) have been developed by introducing new materials and process technologies. Main body was made of alumina by programmable punching, laminating, and firing. The channel walls of pore arrays of an MCP were deposited with thin films by electro1ess copper plating and sol-gel process. Our MCP has advantages such as easy fabrication, durability, high temperature endurance, and applicability to the large size comparing with the conventional MCPs. Experiments on the brightness of an MCP incorporated FED revealed that the FED with a MCP is three to four times brighter than a conventional FED. Moreover, the focusing in a FED is improved. Incorporating an MCP into a FED is one of promising methods to enhance the characteristics of the FED. In addition, amplification yield of the MCP is measured for varying the aspect ratio and the input current.
Colossal grain growth yields single-crystal metal foils by contact-free annealing
Jin, Sunghwan,Huang, Ming,Kwon, Youngwoo,Zhang, Leining,Li, Bao-Wen,Oh, Sangjun,Dong, Jichen,Luo, Da,Biswal, Mandakini,Cunning, Benjamin V.,Bakharev, Pavel V.,Moon, Inyong,Yoo, Won Jong,Camacho-Mojica American Association for the Advancement of Scienc 2018 Science Vol.362 No.6418
<P><B>Turning many into one</B></P><P>Single-crystal metal foils are valuable for their surface properties that allow for synthesis of materials like graphene. Jin <I>et al.</I> present a strategy for creating colossal single-crystal metal foils called “contact-free annealing” (see the Perspective by Rollett). The method relies on hanging and heating commercially available, inexpensive, cold-rolled metal foils. Almost as if by magic, the polycrystalline grains rotate and anneal into a large single-crystal sheet with a specific crystal orientation. The strategy allows for the creation of much larger and much cheaper single-crystal metal foils.</P><P><I>Science</I>, this issue p. 1021; see also p. 996</P><P>Single-crystal metals have distinctive properties owing to the absence of grain boundaries and strong anisotropy. Commercial single-crystal metals are usually synthesized by bulk crystal growth or by deposition of thin films onto substrates, and they are expensive and small. We prepared extremely large single-crystal metal foils by “contact-free annealing” from commercial polycrystalline foils. The colossal grain growth (up to 32 square centimeters) is achieved by minimizing contact stresses, resulting in a preferred in-plane and out-of-plane crystal orientation, and is driven by surface energy minimization during the rotation of the crystal lattice followed by “consumption” of neighboring grains. Industrial-scale production of single-crystal metal foils is possible as a result of this discovery.</P>
Jin Sunghwan,전광훈,전석우,Hong Soon Hyung 나노기술연구협의회 2016 Nano Convergence Vol.3 No.8
Commercialization of organic solar cell (OSC) has faltered due to their low power conversion efficiency (PCE) compared to inorganic solar cell. Low electrical conductivity, low charge mobility, and short-range light absorption of most organic materials limit the PCE of OSCs. Carbon nanomaterials, especially carbon nanotubes (CNTs) and graphenes, are of great interest for use in OSC applications due to their high electrical conductivity, mobility, and unique optical properties for enhancing the performance of OSCs. In this review, recent progress toward the integration of carbon nanomaterials into OSCs is described. The role of carbon nanomaterials and strategies for their integration into various layers of OSCs, including the photoactive layer and charge transport layer, are discussed. Based on these, we also discuss the prospects of carbon nanomaterials for specific OSC layers to maximize the PCE.
Sunghwan Ji,Hee-Won Jung,Jeounghee Kim,Younghye Kwon,Yeonmi Seo,Semin Choi,Hyoun Jin Oh,백지연,Il-Young Jang,Eunju Lee,for the Asan Multidisciplinary Committee for Seniors (AMCS) 대한노인병학회 2023 Annals of geriatric medicine and research Vol.27 No.2
Background: Falls are a major concern among hospitalized adults, and it is essential to identify high-risk patients to prevent falls. This retrospective cohort study conducted at the Asan Medical Center, Korea, compared the screening abilities of the at-point Clinical Frailty Scale (CFS) and Morse Fall Scale (MFS) to identify patients at high risk for falls among hospitalized adults. Methods: We assessed the records of at-point CFS, MFS, and fall incidence during hospitalization of 2,028 patients aged 18 or older included in this study. We calculated the sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and area under the curve (AUC) for each tool. Results: Twenty-five patients (1.23%) experienced falls during hospitalization. The mean at-point CFS score was significantly higher in those with falls than in those without falls. The mean MFS score did not differ significantly between the two groups. The optimal cutoff points for the at-point CFS and MFS scores were 5 and 45, respectively. At these cutoffs, the at-point CFS demonstrated a sensitivity of 76.0%, specificity of 54.0%, PPV of 2.0%, and NPV of 99.4%, whereas the MFS demonstrated a sensitivity of 60.0%, specificity of 68.1%, PPV of 2.2%, and NPV of 99.4%. The AUC values for the at-point CFS and MFS were 0.68 and 0.63, respectively, with no significant difference (p=0.31). Conclusion: The at-point CFS is a valid screening tool for assessing fall risk in hospitalized adults, as it effectively identifies fall risk with a performance similar to that of the MFS.
The Effects of Related Party Transactions on Market Returns of IPO firms in China
Jin Tan,Sunghwan Kim 한국재무학회 2016 한국재무학회 학술대회 Vol.2016 No.11
In this study, we investigate the effects of related party transactions of IPO firms on their market returns around their IPOs. We separately study them in various types of related party transactions: sales and purchases of goods and services between affiliated firms, related party funding – lending and borrowing of funds between affiliated firms, and the provision of credits, collaterals and mortgages between affiliated firms on initial and long-term market returns of IPO firms, using an extensive sample of 1,609 Chinese firms that went public by now. The sales to related party has a significant U-shaped effect on initial returns of both high-return and low-return IPOs, while the asset trading between related parties has a significant reverse U-shaped effect on initial returns of lowreturn IPOs. In addition, lending to related party has a significant U-shaped effect on initial returns of both high-return and low-return IPOs while debt financing from related party has a significant Ushaped effect on initial returns of high-return IPOs. Lastly, the guarantee provided for related party has a significant U-shaped effect on initial returns of high-return IPOs, while high-return firms get guaranteed from related party have higher initial returns of IPOs than not.
Jin, Jang Mi,Choi, Suhee,Kim, Young Hwan,Choi, Man Ho,Kim, Jongwon,Kim, Sunghwan Springer-Verlag 2012 Journal of the American Society for Mass Spectrome Vol.23 No.9
<P>The structural effect of a nanoporous gold (NPG) surface on the signal intensities of laser desorption ionization-mass spectrometry (LDI-MS) were investigated using NPG surfaces with controlled structures. The relationship between surface area and LDI efficiency was compared and evaluated. Comparisons between bare flat gold and NPG surfaces show that nanostructures increased LDI efficiency. We also found that the LDI signal decreased with increasing depth of nanoporous layers, thus increasing the surface area. This result agrees with a previous report (Shin J. A. et al., <I>J. Am. Soc. Mass Spectrom.</I> 2010, 21, 989) in which the LDI efficiency of small molecules decreased for ZnO wires with longer lengths. This observation was explained by the penetration and deposition of samples into locations inaccessible to photons because of structural screening. The LDI-MS analysis of oils with NPG surfaces (but without matrix) showed the same trend whereby the NPG with about a 200 nm depth of porous area showed the highest sensitivity. This study clearly shows that the active surface area for solution chemistry can differ from LDI-MS and that NPGs can function as a substrate for LDI oil analysis.</P>
Sunghwan Shin,유인영,Hyang Jin Shim,On-Kyun Kang,Byung Woo Jhun,Won-Jung Koh,허희재,Nam Yong Lee 대한진단검사의학회 2020 Annals of Laboratory Medicine Vol.40 No.2
The GENEDIA MTB/NTM Detection Kit (GENEDIA MTB/NTM; Green Cross Medical Science Corp., Chungbuk, Korea) is a multiplex real-time PCR assay used for differential identification of Mycobacterium tuberculosis complex (MTBC) and nontuberculous mycobacteria (NTM). While the importance of differential identification of MTB/NTM is recognized, there is limited data on the performance of GENEDIA MTB/NTM assay to date. A total of 687 consecutive sputum specimens were cultured and analyzed with the GENEDIA MTB/NTM and GENEDIA MTB assays. Nineteen specimens (2.8%) were MTBC-positive, and 69 (10.0%) were NTM-positive based on mycobacterial culture. All specimens showed concordant results for MTBC using both assays, with a kappa value of 1.00, overall sensitivity of 63.2% (12/19), and specificity of 100% (668/668). The overall NTM sensitivity and specificity were 23.2% (16/69) and 99.7% (616/618) for GENEDIA MTB/NTM. The association between NTM-positivity using GENEDIA MTB/NTM and the diagnosis of NTM pulmonary disease was not statistically significant. In conclusion, the two real-time PCR assays showed similar diagnostic performance for MTBC detection. However, the sensitivity for NTM detection was lower than that for MTBC detection.
The Causes and Effects of Post-IPO Underperformance in China
Jin Tan,Sunghwan Kim 한국재무학회 2016 한국재무학회 학술대회 Vol.2016 No.05
In this study, we test whether the initial returns (IR) or the phenomena of underpricing of IPOs is also one of the causes of Post- IPO Underperformance in China. We study the market information effect on the underpricing of IPOs first and study the effect of the other causes of Post-IPO Underperformance such as the Post-IPO initial stock return volatility and lock-up policy. Multivariate regressions are conducted using all the IPOs of firms listed on the Shanghai and Shenzhen exchanges from 1987 to 2015. The main results of this study are as follows. First, while that the magnitudes of weighted (equally or value weighted) IPO volumes in the past have a positive effect on the magnitude of IPO returns in the future, the IPO volume itself has a negative effect on the magnitude of IPO returns in the future. Second, the magnitude of weighted IPO returns in the past has a positive effect on the magnitude of IPO returns, while simultaneously reflecting the effects of both time-span and magnitude in returns and volume for most of the information used in Lowry and Schwert (2002). Third, in most situation, Post-IPO underperformance following the high initial returns (IR) in China. Fourth, for high lung-run return IPOs, high Post-IPO initial stock return volatility exacerbates the Post-IPO Underperformance while for low lung-run return IPOs, high Post-IPO initial stock return volatility eases the Post-IPO Underperformance. Fifth, the lock-up policy partial eases the Post-IPO Underperformance and the stock return volatility after open-up the locked trading stock can exacerbate the Post-IPO Underperformance.