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Cho, Yongjoon,Lee, Hae Rang,Jeong, Ayoung,Lee, Jungho,Lee, Sang Myeon,Joo, Se Hun,Kwak, Sang Kyu,Oh, Joon Hak,Yang, Changduk American Chemical Society 2019 ACS APPLIED MATERIALS & INTERFACES Vol.11 No.43
<P>A family of copolymers (P(NDIOD-T2F<I>x</I>)) based on naphthalenediimide (NDI) and 2,2′-bithiophene (T2) units with different amounts of 3,3′-difluoro-2,2′-bithiophene (T2F) decoration were synthesized, characterized, and used in n-type organic field-effect transistors (OFETs). With increasing T2F content in the backbone, we observe increased melting and crystallization transitions, blue-shifted absorptions, and deeper-lying highest occupied molecular orbital (HOMO)/lowest unoccupied molecular orbital (LUMO) levels, together with improved hydrophobicity. The highest electron mobility of 4.48 × 10<SUP>-1</SUP> cm<SUP>2</SUP> V<SUP>-1</SUP> s<SUP>-1</SUP> was obtained for P(NDIOD-T2F0) without a T2F unit, which is attributed to the larger domain grains and crystallites, as well as a more tightly packed and oriented crystalline structure, as evidenced from the morphological study. In contrast, P(NDIOD-T2F100) with the highest T2F content has superior air stability, showing greater than 25% electron mobility retention after 30 days in wet conditions of 100% relative humidity without encapsulation. Even P(NDIOD-T2F100) is able to operate normally after 30 min of immersion in water, which is due to the synergistic contributions from the deep HOMO/LUMO levels and improved hydrophobicity. This study advances our fundamental understanding of how the morphology/crystallinity, device performance, and device stability of n-type copolymers are tuned by incorporating different concentrations of T2F in the backbone, shedding light on an important modification for air- and water-stable n-type materials for future OFET applications.</P> [FIG OMISSION]</BR>
Jiwon Jeong,Chul Hoon Chung,Yongjoon Chang,Kuylhee Kim,Soyeon Jung 대한수부외과학회 2024 대한수부외과학회지 Vol.29 No.1
The incidence of high-pressure injection injuries is increasing with the development of industry and use of injectors. Although high-pressure injection injuries are relatively rare, they commonly lead to complications such as skin necrosis, infection, and amputation. Moreover, the initial presentation is prone to be underestimated because of the small entry point at the patient’s first encounter in emergency care. A prompt surgical intervention is required, with appropriate and rapid initial treatments, including broad-spectrum antibiotics and tetanus toxoid. The surgical treatment involves wide debridement for foreign material removal and subsequent reconstruction. In this case report, we present three cases we encountered and the ensuing complications. All three patients who received the same treatments are discussed in detail.
Sural nerve grafts in subacute facial nerve injuries: a report of two cases
Jiwon Jeong,Yongjoon Chang,Chul Hoon Chung,Soyeon Jung 대한두개안면성형외과학회 2024 Archives of Craniofacial Surgery Vol.25 No.2
Because facial nerve injuries affect the quality of life, leaving them untreated can have devastating effects. The number of patients with traumatic and iatrogenic facial nerve paralysis is considerably high. Early detection and prompt treatment during the acute injury phase are crucial, and immediate surgical treatment should be considered when complete facial nerve injury is suspected. Symptom underestimation by patients and clinical misdiagnosis may delay surgical intervention, which may negatively affect outcomes and in some cases, impair the recovery of the injured facial nerve. Here, we report two cases of facial nerve injury that were treated with nerve grafts during the subacute phase. In both cases, subacute facial nerve grafting achieved significant improvements. These cases highlight surgical intervention in the subacute phase using nerve grafts as an appropriate treatment for facial nerve injuries.
고강도강 다층 용접금속 재가열부의 미세조직 및 기계적 특성
강용준(Yongjoon Kang),박기태(Gitae Park),정성훈(Seonghoon Jeong),이창희(Changhee Lee) 대한용접·접합학회 2017 대한용접·접합학회지 Vol.35 No.6
A large fraction of reheated weld metal is formed during multi-pass welding, which significantly affects the reliability and stability of the welded structures. In this study, the effect of reheating on the mechanical properties and microstructure of high-strength steel welds during multi-pass welding was investigated. Two kinds of high-strength steel welds with different hardenabilities, i.e., welds L (low hardenability) and H (high hardenability), were produced by single-pass, bead-in-groove welding, and both welds were thermally cycled to various peak temperatures to simulate the reheated welds using a Gleeble simulator. In as-welded weld L, acicular ferrite developed extensively in the grain interior, while grain boundary ferrite and Widmanstätten ferrite formed along the prior austenite grain boundaries. The microstructure of as-welded weld H consisted mainly of bainite, with some acicular ferrite and coalesced bainite. The microstructural changes due to thermal cycling were observed by scanning electron microscopy and correlated with the mechanical properties.
Control of liquid crystal pretilt angles by using organic/inorganic hybrid interpenetrating networks
Ahn, Dowon,Jeong, Yong-Cheol,Lee, Seungwoo,Lee, Jihye,Heo, Yongjoon,Park, Jung-Ki The Optical Society 2009 Optics express Vol.17 No.19
<P>A new photoalignment method of controlling the pretilt angle of liquid crystals (LCs) by using organic/inorganic hybrid interpenetrating polymer networks (IPNs) is proposed and demonstrated. In the hybrid IPN alignment layer system, the competition between poly(vinyl cinnamate) (PVCi) favoring planar alignment and poly(dimethyl siloxane) (PDMS) favoring vertical alignment made it possible to achieve pretilt angle in a wide range from 0 degrees to 90 degrees, and adjust pretilt angle as a function of PDMS content. In addition, we achieved the high azimuthal anchoring energy at the intermediate pretilt angle by using PDMS as the vertical-aligning component.</P>
페라이트계 스테인리스강 재현 용접 열 영향부의 석출거동 및 열피로 특성에 미치는 구속응력의 영향
한규태(Kyutae Han),강용준(Yongjoon Kang),이상철(Sangchul Lee),홍승갑(Seunggab Hong),정홍철(Hongchul Jeong),이창희(Changhee Lee) 대한용접·접합학회 2015 대한용접·접합학회지 Vol.33 No.6
Thermal fatigue life of the automobile exhaust manifold is directly affected by the restraint force according to the structure of exhaust system and bead shape of the welded joints. In the present study, the microstructural changes and precipitation behavior during thermal fatigue cycle of the 18wt% Cr ferritic stainless steel weld heat affected zone (HAZ) considering restraint stress were investigated. The simulation of weld HAZ and thermal fatigue test were carried out using a metal thermal cycle simulator under complete constraint force in the static jig. The change of the restraint stress on the weld HAZ was simulated by changing the shape of notch in the specimen considering the stress concentration factor. Thermal fatigue properties of the weld HAZ were deteriorated during cyclic heating and cooling in the temperature range of 200℃ to 900℃ due to the decrease of Nb content in solid solution and coarsening of MX type precipitates, laves phase, M6C with coarsening of grain and softening of the matrix. As the restraint stress on the specimen increased, the thermal fatigue life was decreased by dynamic precipitation and rapid coarsening of the precipitates.
Proinvasive extracellular matrix remodeling in tumor microenvironment in response to radiation
Yoo, Ki-Chun,Suh, Yongjoon,An, Yoojeong,Lee, Hae-June,Jeong, Ye Ji,Uddin, Nizam,Cui, Yan-Hong,Roh, Tae-Hoon,Shim, Jin-Kyoung,Chang, Jong Hee,Park, Jong Bae,Kim, Min-Jung,Kim, In-Gyu,Kang, Seok-Gu,Lee, Nature Publishing Group UK 2018 Oncogene Vol.37 No.24
<P>Ionizing radiation is widely used for patient with glioblastoma (GBM). However, the effect of radiation on patient survival is marginal and upon recurrence tumors frequently shift toward mesenchymal subtype adopting invasiveness. Here, we show that ionizing radiation affects biomechanical tension in GBM microenvironment and provides proinvasive extracellular signaling cue, hyaluronic acid (HA)-rich condition. In response to radiation, HA production was increased in GBM cells by HA synthase-2 (HAS2) that was transcriptionally upregulated by NF-kappa B. Notably, NF-kappa B was persistently activated by IL-1 alpha-feedback loop, making HA abundance in tumor microenvironment after radiation. Radiation-induced HA abundance causally has been linked to invasiveness of GBM cells by generating movement track as an extracellular matrix, and by acting as a signaling ligand for CD44 receptor, leading to SRC activation, which is sufficient for mesenchymal shift of GBM cells. Collectively, our findings provide an explanation for the frequent brain tumor relapse after radiotherapy, and potential therapeutic targets to block mesenchymal shift upon relapse.</P>
이종혁 ( Lee Jonghyuk ),이상익 ( Lee Sangik ),정영준 ( Jeong Yongjoon ),김동수 ( Kim Dongsu ),이승재 ( Lee Seung-jae ),최원 ( Choi Won ) 한국농공학회 2021 한국농공학회논문집 Vol.63 No.2
Agriculture is most closely related to weather, and the government pursues stable food production by weather research. However, abnormal weather conditions have occurred frequently around the world in recent years, and stable food production has been threatened. Among them, heavy snow in winter tends to increase in frequency and size, which causes serious damage to greenhouses. Therefore, it is imperative to build a system reflecting various demands to reduce the damage to agricultural facilities caused by heavy snow. A business model can realize this as a way of commercialization, however, no suitable model has been presented to date. Therefore, this study aims to design a representative business model that can establish a safety system by distributing a greenhouse disaster prevention warning system for heavy snow to farms.