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One-step synthesis of nano-porous monolithic polyimide aerogel
Kim, Jinyoung,Kwon, Jinuk,Kim, Seung-Ik,Kim, Myeongsoo,Lee, Daero,Lee, Sangrae,Kim, Gunhwi,Lee, Juheon,Han, Haksoo Elsevier 2016 Microporous and mesoporous materials Vol.234 No.-
<P><B>Abstract</B></P> <P>A facile one-step method for synthesis of a porous monolithic polyimide aerogel was successfully developed. The specific thermal curing, slow desiccating process and swelling method were used in synthesizing monolithic polyimide aerogel without any additional chemical reaction to create a connected structure among the polyimide-based spherical aerogel microparticles. Using this method, the monolithic polyimide aerogel can be easily fabricated whilst using no additional chemicals for crosslinking. This type of polyimide aerogel was produced homogeneously by the polyimidization of pyromellitic dianhydride (PMDA) and 4,4′-oxydianiline (ODA). The synthesized porous monolithic polyimide aerogel has many good properties which could be used in various industries, as it maintained a high thermal decomposition temperature (10% weight decomposition temperature: T<SUB>d10%</SUB>) of approximately 577 °C and a glass transition temperature (T<SUB>g</SUB>) of 432 °C, with bulk density of 490.7 kg/m<SUP>3</SUP>, porosity of approximately 45% and average pore size of 4 nm (by nitrogen adsorption test) of polymer and 157 nm (by mercury intrusion method) of space observed in FE-SEM image. Also, the monolithic polyimide aerogel had an excellent oil-adsorbing capacity of 150%, and the adsorbed oil could be separated easily using a simple drying process. The dried monolithic polyimide aerogel showed significant recoverability and reusability of adsorbed oil. In addition, the monolithic polyimide aerogel exhibited high mechanical resistance such that the structure can withstand a high pressure greater than 122.3 kPa, under which the monolithic polyimide aerogel (MPA) was compressed but did not break. This type of MPA shows excellent thermal, mechanical properties and great processability, and could be the new candidate for high performance materials in various industries, especially catalyst field.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Unlike other aerogel synthesis, in this study, the polyimide aerogel monolith is created without adding any other chemicals. </LI> <LI> The polyimide aerogel monolith has excellent thermal, mechanical properties and great processability for application in various industries. </LI> <LI> The polyimide aerogel monolith synthesized with homogeneity fully maintained in very convenient and easy method. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Kim, Kwangin,Yoo, Taewon,Lee, Juheon,Kim, Myeongsoo,Lee, Sangrae,Kim, Gunhwi,Kim, Jinyoung,Han, Patrick,Han, Haksoo Elsevier Sequoia 2017 Progress in organic coatings Vol.112 No.-
<P><B>Abstract</B></P> <P>In this study, transparent thin films for coating material are synthesized by adding bulky CF<SUB>3</SUB> and hydroxyl groups intro into poly(amide-imide)s. As expected, these poly(amide-imide)s show higher shear adhesion and higher glass transition temperatures than the neat poly(amide-imide) due to hydrogen bonding of the hydroxyl groups. In addition, the modification to the poly(amide-imide) structure leads to only slight decreases in transmittance and yellow index.</P> <P>Consequently, the successful synthesis of poly(amide-imide)s with wide applications as transparent coating materials due to their optical properties and high adhesion is demonstrated. Transparent flexible display and coating products can be manufactured with poly(amide-imide)s having high reliability and a low chance of cracking due to their favorable thermal properties.</P>
Kim, Myeongsoo,Kim, Gunhwi,Kim, Jinyoung,Lee, Daero,Lee, Sangrae,Kwon, Jinuk,Han, Haksoo Elsevier 2017 Microporous and mesoporous materials Vol.242 No.-
<P><B>Abstract</B></P> <P>In this study, the improvement of synthesizing method of sponge-type polyimide (PI) membrane and its newly developed pore size control techniques are mainly described. The sponge-type polyimide membrane with large pore size (0.1–10 µm) and high permeability was successfully synthesized by using non-solvent phase separation method (NIPS) in continuous process and its full polyimidization is confirmed via Fourier-transform infrared technique. The theoretical approach in this research induced by Jurin's law which describes the height of a liquid within a thin capillary tube. In this theory, the pore size of membrane is highly influenced by the interactive tension between the polymer and solvents during synthesizing process of polymer membrane. There are two ways of controlling pore size established from Jurin's law. The validity of the application of Jurin's law was proven via comparison with theoretical and experimental data. Its inner structure of membrane and pore size are identified by field emission-scanning electron microscopy.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Synthesis of sponge-type polyimide membrane for continuous system using non-solvent phase separation (NIPS) method. </LI> <LI> Two ways of controlling pore size established from Jurin's law. </LI> <LI> Comparison of pore size with theoretical and experimental data. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
차량용 레이더의 각도 추정 성능향상을 위한 안테나의 보정 기법
문건휘(Gunhwi Moon),박정훈(Jeong Hoon Park),조완제(Wanjei Cho),김진욱(Jinwook Kim),윤영준(Young-Jun Yoon),김성철(Seong-Cheol Kim) 한국통신학회 2022 한국통신학회 학술대회논문집 Vol.2022 No.2
본 논문은 차량용 레이더를 기반으로 각도 추정의 성능향상을 위한 안테나 보정 방식을 제안한다. 건물 옥상에서 레이더 기준으로 전방에서 타깃을 0°, 10°, 20°, 30° 씩 기울이며, 해당 각도마다 레이더와 타깃 간의 거리를 2.5m, 5m, 7.5m 로 설정하여 데이터를 취득하였다. 이후 측정 데이터를 기반으로 수신 안테나를 보정하고 각도 추정을 통해 성능을 비교하였다. 측정 데이터를 이용해 분석했을 때, 제안한 방법으로 수신 안테나를 보정한 경우 DOA 피크값이 각 실험 시나리오에 대해 평균적으로 0.025dB 높아짐을 보였다.
Action Recognition Model to Monitor Illegal Dumping using Zoom-In Image Sequence Data
Kyoungmin Ko,Hyunmin Gwak,Eunseok Lee,Gunhwi Kim,Donghyeon Moon,Youngjoo Cho,SungHwan Kim 계명대학교 자연과학연구소 2021 Quantitative Bio-Science Vol.40 No.2
In this study, we propose an action recognition model that provides generalized performance regardless of camera location and distance between the camera and human. The proposed model consists of two-stage networks, namely, human detection and action recognition. The proposed method operates on video frames that are resized by a new zoom-in method using pretrained Yolo v3. To use temporal information, which is regarded as a critical factor in action recognition, we adopt the R(2+1)D model, which is a factorized model capable of representing more complex networks. The proposed Zoom-In method yields generalized performance regardless of distance. In an experiment, the proposed method exhibited accuracies of 96.07%, 96.61%, and 94.55% in the short, medium, and long ranges in which our datasets were employed, respectively.