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이승호,정성균 서울産業大學校 1998 논문집 Vol.47 No.1
Shot peening is applied to machine structure, automobile, and aircraft part to improve the fatigue life. The increase of fatigue life is due to the compressive residual stress. Thus, the distribution of compressive residual stress and shot condition should be investigated. When the heat treated specimen is shot for 160sec, the maximum absolute compressive residual stress is -721.8MPa. When the heat treated specimen is shot for 70sec. we can obtain the maximum absolute compressive residual stress -529.6MPa on the surface of specimen. For the untreated specimen, the maximum absolute compressive residual stress can be obtained on the surface of specimen and the depth of residual stress was 0.45mm.
Polyimide Surface Modification by Low Energy Ion Beam Irradiation
Lee, Won Jun,Lee, Youn Seoung,Rha, Sa Kyun,Lim, Kwang Yong,Lee, Hee Soo,Whang, Chung Nam Trans Tech Publications, Ltd. 2005 Materials science forum Vol.492 No.-
<P>The surface modification of polyimide (PI) by the irradiation of 3 keV He+, Ne+ and Ar+ ions was studied using XPS and AFM at various ion dose ranging from 11014 to 11017 ions/cm2. The change of surface roughness of PI by 3 keV inert ions was closely connected to the change of surface composition. At low doses below 51015 ions/cm2, the surface of polyimide was carbonized by ion irradiations, showing rough surfaces. At higher ion doses, the surface composition was saturated due to the accumulation of damages, and the surface morphology became smoother as compared with the low dose case.</P>
Lee Seoung-Kyun,Yoon Bo-Hyun,Kim Kyungmin,Jung Ha-Ran,Kang Hangoeunbi,Jeong Yuran,Yun Hyunju,Song Jye-Heon,Sea Young-Hwa,Park Suhee 대한우울조울병학회 2023 우울조울병 Vol.21 No.3
Background: This study aimed to examine the influence of the coronavirus disease pandemic 2019 (COVID-19) by comparing the incidences of depression, suicidal ideation, and suicidal attempts before and after the outbreak of the pandemic among community-dwelling older adults. Methods: In total, 9,784 older adults were recruited from 22 counties in Jeollanam-do between 2019 and 2022. Self-reported questionnaires, including sociodemographic factors, suicidal ideation, suicidal attempt, and Geriatric Depression Scale-Short Form Korean version, were used. Results: The proportion of the depression high-risk group tended to increase since the COVID-19 outbreak, increasing to 16.3%, 23.1%, and 25.7% in 2019, 2020, and 2021, respectively; however, decreased to 21.8% in 2022. The incidence of suicidal ideation showed a similar pattern. The incidence of suicidal attempts showed a different pattern, rising to 1.3% and 2.6% in 2019 and 2020, respectively and then falling to 1.1% and 0.8% in 2021 and 2022, respectively. Conclusion: This study examined community-dwelling older adults and their mental states during the COVID-19 pandemic, and found that the risk of depression among older adults increased 1.708-fold in 2020, 1.877-fold in 2021, and 1.599-fold in 2022 compared to that in 2019, the year before the pandemic. Similarly, the risk of suicidal ideation increased by 1.582-fold in 2020, 1.913-fold in 2021, and 1.623-fold in 2022 compared with 2019 data. As the pandemic extended, mental health states improved; however, not to prepandemic levels. Suggesting that older people need continued support to alleviate the negative effects of the COVID-19 pandemic.
Remaining Oxide and Low-Energy Ion Implantation of BF2+ for Si (100)
Woo-Jung Lee,Sa-Kyun Rha,Ki-Man Kim,Kwang-Su Cheong,Won-Jun Lee,Youn-Seoung Lee 한국물리학회 2007 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.50 No.3
We investigated the behavior of boron by varying the $^{49}$BF$_{2}^{+}$ ion-implantation energy and the rapid thermal annealing (RTA) temperature with the remaining oxide. The $^{49}$BF$_{2}^{+}$ ions were implanted into p-type Si (100) without removal of the native oxide. The used $^{49}$BF$% _{2}^{+}$ ion-implantation energies were 0.5 keV, 1 keV, 2.5 keV, 5 keV, and 10 keV. The dose was fixed at 5 $\times$ 10$^{15}$ atoms/cm$^{2}$. RTA was performed under a N$_{2}$ ambient (760 Torr) at 1000 $^\circ$C and 1050 $^\circ$% C for 10 s. In order to investigate the boron behavior with $^{49}$BF$% _{2}^{+}$ ion implantation, we measured the surface roughness R$_{rms}$, the junction depth Xj, the dose, the sheet resistance Rs, and the thickness of the silicon oxide layer by using atomic force microscopy (AFM), secondary ion mass spectrometry (SIMS), ellipsometry, 4-point probe without removal of the native oxide layer. By these results, Rs in as-implanted samples increased abruptly (from 174 $\Omega $/cm$^{2}$ to 1706 $\Omega $/cm$^{2}$ for $^{49}$BF$_{2}^{+}$ implantation energy 0.5 keV and 10 keV, respectively) when Xj increased (from 27 nm for 0.5 keV to 57 nm for 10 keV) because of inactive dopants. After RTA, Rs decreased (from 128 $\Omega $/cm$% ^{2}$ for 0.5 keV to 70 $\Omega $/cm$^{2}$ for 10 keV at 1050 $^\circ$C) when Xj increased (from 147 nm for 0.5 keV to 221 nm for 10 keV at 1050 $^\circ$C). The inactive borons in as-implanted samples become the electrical active dopants after RTA treatment.
Large area thermal light emission from autonomously formed suspended graphene arrays
Park, Mina,Lee, Aram,Rho, Ho Kyun,Lee, Seoung-Ki,Bae, Sukang,Jeon, Dae-Young,Lee, Dong Su,Kim, Tae-Wook,Im, Yeon-Ho,Lee, Sang Hyun Elsevier 2018 Carbon Vol.136 No.-
<P><B>Abstract</B></P> <P>Since its discovery, the existence of graphene, a 2D extract of graphite, has been in the spotlight in the field of optoelectrical physics. Suspended graphene is potentially an ideal structure for utilizing intrinsic properties of the graphene by reducing the hindrance due to interaction with substrate. Here, an autonomous fabrication of suspended graphene is proposed where it only requires a single transfer which yields multiple arrays of micron-scale suspended graphenes all at once. Large area graphene sheets transferred onto a substrate of array-patterned 3D-electrodes easily tear into pieces due to the strain gradients induced by the step heights of the electrode patterns, and each torn graphene piece takes its position between individual electroplated Cu-microgap electrode pairs. With the absence of long-range scattering from randomly charged impurities in the substrate and the correspondingly enhanced carrier mobility of suspended graphene, our novel structure is demonstrated for the application of a visible light-emitting device. It is observed that the electrically driven thermal emission spectra spans the blue side of the visible band, which corresponds to a temperature of above 3000 K. The facile access to mass production of suspended graphene can bridge the current 2D materials research to the wide field of electronics and optoelectronics.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>