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Graphene-Incorporated Nanofibrous Hybrid Membrane with Enhanced Properties
신원상,박정순,오준성,이은정 한국고분자학회 2017 Macromolecular Research Vol.25 No.11
Graphene has been highlighted as an additive material to ameliorate functions of biomaterials due to its unique structure and superelasticity. In this study, graphene at different concentration (up to 10%) was incorporated into a hybrid membrane composed of chitosan and silica xerogel to enhance the functionality of the hybrid membrane for guided bone regeneration (GBR) through in situ sol-gel technique. The effect of graphene incorporation was evaluated in terms of morphology, mechanical property, and biological property. In SEM observation, graphene (G)-incorporated membranes showed macroporous structure and nanofibrous microstructure which could allow protein to attach onto membrane more efficiently. The hybrid membrane containing 10% graphene was found to have highly porous and nanofibrous structure with the highest level of protein adsorption. These G-incorporated membranes also showed improved mechanical properties compared to hybrid membrane only (control) in wet state. However, the tensile strength and elongation were decreased when 10% graphene was incorporated into the hybrid membrane. Both in vitro and in vivo tests confirmed that G-incorporated membranes had similar biological properties to those of osteogenic hybrid membrane with excellent GBR ability. These findings demonstrate that prop
신원상,백승우,김윤준 대한금속·재료학회 2022 대한금속·재료학회지 Vol.60 No.6
Nodular graphite cast iron is used in the railway and automobile industries because of its excellent workability, abrasion resistance, mechanical strength, and hardenability. To use nodular graphite cast iron in harsh environments, it is essential to examine their friction–wear properties in conjunction with the surface hardness of the materials. Therefore, in this study, a pin–on–disk type method was used to investigate specimens whose surface hardness was improved by the addition of Sn alloying element, followed by high-frequency heat treatment. The results revealed that Sn inhibited the growth of nodular graphite by acting as a barrier to the movement of carbon and promoted the transformation of some matrix from ferrite to pearlite. In contrast, most of the matrix of the high-frequency heat treated specimen was transformed into pearlite. Consequently, the specimens prepared using both methods achieved higher surface hardness than the as-cast state. With regards to the friction–wear properties, the Sn added alloy exhibited a relatively weak matrix, and therefore, delamination of the surface and spalling on the nodular graphite occurred, with significant wear width and depth. In contrast, surface delamination was not observed in the specimen after high-frequency heat treatment.
신원상,김종규 대한화학회 2012 Bulletin of the Korean Chemical Society Vol.33 No.7
We describe herein a three-dimensionally diverse micropatterning of poly(lactic acid), as a biopolymer, using 1-butyl-3-methylimidazolium-based room-temperature ionic liquids (bmim-based RTILs), [bmim]X (X = SbF6, PF6, NTf2, Cl). Utilizing the hydrophobic bmim-based RTILs, [bmim]X (X = SbF6, PF6, NTf2) and a phase separation technique, we were able to produce white and opaque membranes with a three-dimensional structure closely packed with particles (10-50 μm in diameter). The particlulate structure, made by the assistance of [bmim]NTf2 and DCM, interestingly transformed to a fibrous structure by using a cosolvent, e.g., DCM/CF3CH2OH. When we used an increased amount of [bmim]NTf2, the particles were effectively detached and macrosized (100-500 μm in diameter) and the oval-shaped beads were obtained in a powder form. By varying the counter-anion type of the imidazolium-based RTIL, for example from NTf2 − to Cl−, the particulate 3D-morphology was once more transformed to a porous structure. These reserch results could be potentially useful, as a method to fabricate particulate scaffolds, fibrous or porous scaffolds, and beads as a biopolymer device in diverse fields including drug delivery, tissue regeneration, and biomedical engineering.
신원상,조나단놀리스,김해원 대한화학회 2011 Bulletin of the Korean Chemical Society Vol.32 No.5
An efficient and novel positive charge-doping on the sidewalls of multi-walled carbon nanotubes has been achieved in the presence of tetrahydrofuran as a dopant and Lewis acidic ionic liquids, [bmim]Sb_nF_(5n+1) (n ≥ 2;bmim = 1-butyl-3-methylimidazolium), as an activator, leaving air-stable derivatives having positively charged sidewalls and the counter anions, [MWCNT^(y+)][SbF6_^−]y (MWCNT = multi-walled carbon nanotube). The derivatization took place very fast in one-pot and under mild reaction conditions. The ionic structure enabled a tunable dissolution of the derivatives in various solvents through anion exchange.
신원상,Hyun-Ki Hong,김해원,공명선 대한화학회 2011 Bulletin of the Korean Chemical Society Vol.32 No.5
Silver nanoparticles (<10 nm) were prepared in ultrasonic vibration-induced nanodroplets of isopropyl alcohol (IPA) in combination with hydrophobic room temperature ionic liquids (RTILs). The Ag-precursor used were silver (I) complex, Ag_2(ehac)_2(eha)_2 (ehac = 2-ethylhexylammonium carbamate; eha = 2-ethylhexylamine), in IPA, while 1-butyl-3-methylimidazolium-based ionic liquids bearing SbF_6^−, PF_6^− and NTf_2^− as counter anions were used as RTILs. During sonication for 10-90 min at room temperature, uniform silver nanoparticles with mean sizes of 2 to 8 nm were rapidly synthesized. Transmission electron micrographs also confirmed that silver nanoparticles have a spherical shape and diverse sizes depending on the reaction time (10-90 min).
건설프로젝트의 설계안전성 검토에 대한 인식 분석 및 개선방안
신원상,손창백 한국건축시공학회 2019 한국건축시공학회지 Vol.19 No.4
Recognizing that the fundamental cause of construction safety accidents was a lack of safety management activities in the planning and design phases, the government made the Design for Safety (DFS) system mandatory in May 2016. However, awareness among ordering parties and designers regarding this system is significantly low, and the system has not been properly established due to reasons such as the need for additional work and a lack of professional manpower. In this study, the awareness of ordering parties and designers of the DFS system was analyzed through a survey, various problems in DFS work execution were identified and measures for improvement were presented. Measures to improve the efficiency in DFS work execution involve the discovery of risk factors and establishment of countermeasures, and here the establishment of a DFS work support system that enables the sharing of informationbetween institutions is the most urgent priority. In addition, it is also urgently necessary to establish a dedicated organization in charge of DFS work, cultivate professional manpower, develop the relevant education programs and establish a proper cost calculation standard for DFS work execution by design offices. 정부는 안전사고의 근본원인을 기획 및 설계단계의 안전관리활동 부재라고 인식하고, 2016년 5월 DFS 제도를 의무화하였다. 그러나 아직까지 발주자 및 설계자들의 인지도는 매우 낮고, 추가적인 업무수행, 전문인력 부족 등의 다양한 사유로 제대로 정착되지 못하고 있다. 본 연구는 발주자 및 설계자에게 설문조사를 수행하여 DFS에 대한 인식을 분석하고, 업무수행상의 문제점을 도출하여 이에 대한 개선방안을 제시하였다. DFS 업무 수행의 효율성 제고를 위한 개선방안은 위험요소 및 대책 발굴이 가능하고, 기관별 정보공유가 가능한 DFS업무 지원시스템의 구축이 가장 시급하다. 이와 동시에 DFS업무를 전담하여 수행할 전담조직의 구축 및 전문 인력의 양성과 이를 위한 교육프로그램의 개발, 그리고, 설계사무소에서 DFS업무 수행 시 필요한 비용에 대한 적정 대가 산정기준 정립이 시급히 요구된다.