3D flexible Si based-composite (Si@Si₃N₄)/CNF electrode with enhanced cyclability and high rate capability for lithium-ion batteries

Kim, Si-Jin,Kim, Min-Cheol,Han, Sang-Beom,Lee, Gyu-Ho,Choe, Hui-Seon,Kwak, Da-Hee,Choi, Sun-Yong,Son, Byung-Goo,Shin, Myoung-Sun,Park, Kyung-Won Elsevier 2016 Nano energy Vol.27 No.-

<P><B>Abstract</B></P> <P>Despite extremely high capacity of Si-based anodes in lithium-ion batteries (LIB), Si-based materials have shown a structural collapse caused by a volumetric expansion/contraction during the cycling process. The conventional electrode structure, which consists of active materials, a current collector, a conducting agent, and a binder, actually showed a low loading of active material due to the other heavy components. In this study, we prepared a 3D flexible Si-composite electrode consisting of core (Si)-shell (Si<SUB>3</SUB>N<SUB>4</SUB>) NPs (Si@Si<SUB>3</SUB>N<SUB>4</SUB>) and carbon nanofibers (denoted as Si-composite/CNF). The Si-composite/CNF was directly utilized as an anode in the absence of the other components was electrochemically evaluated using a coin-type cell. The Si-composite/CNF showed a high capacity of 665mAhg<SUP>−1</SUP> at a fairly high current density of 10Ag<SUP>−1</SUP> and an extremely low capacity loss for 2000 cycles.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We prepared Si-composite/CNF exhibits a 3D flexible Si-composite electrode. </LI> <LI> The electrode consists of core (Si)-shell (Si<SUB>3</SUB>N<SUB>4</SUB>) NPs (Si@Si<SUB>3</SUB>N<SUB>4</SUB>) and carbon nanofibers. </LI> <LI> The Si-composite/CNF was directly utilized as an anode. </LI> <LI> Si-composite /CNF exhibited high specific capacity and improved high rate cycling performance. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Association Among Self-Injury, Suicidal Tendency, and Personality and Psychological Characteristics in Korean Adolescents

Kyojin Yang,Si Young Kim,Hyejin Kim,Jun-Won Hwang 대한신경정신의학회 2022 PSYCHIATRY INVESTIGATION Vol.19 No.1

Objective To compare mental health problems and personality characteristics between adolescents with self-injury (SI) and suicidal tendency (ST), including suicidal ideation and suicide planning. Methods The participants completed the Adolescent Personality and Mental Health Problems Screening Questionnaire, Third version (AMPQ-III), and Korean version of the Strengths and Difficulties Questionnaire (SDQ-Kr), and gave their demographic information. Based on the answered SI and ST items in AMPQ-III, the participants were divided into groups: without SI and ST, with SI and without ST, without SI and with ST, and with SI and ST. Analysis of variance (ANOVA) and post-hoc Scheffe test were used to determine group differences, stepwise multiple linear regression, and factors associated with SI and ST. Results ANOVA yielded results for all categories of mental health problems. Significant differences were observed between the four groups. Conversely, for personality characteristics, only the sense of community item between the group without SI and with ST and the group without SI and ST were significantly different; sense of community was associated with ST (β=-0.054, p=0.005). Among the mental health subscales, SI was significantly associated with conduct problems (β=0.211, p<0.001), emotional problems (β=0.173, p<0.001), peer problems (β=0.085, p<0.001), and prosocial behavior (β=0.073, p<0.001). ST was significantly associated with emotional symptoms (β=0.317, p<0.001), peer problems (β=0.130, p<0.001), conduct problems (β=0.106, p<0.001), hyperactivity (β=0.050, p=0.010), and prosocial behavior (β=0.062, p<0.001). Conclusion The findings highlight the necessity of assessing psychological strength, difficulties, and personality characteristics for the prevention and early intervention of adolescent SI.

The Change of Skeletal Muscle Mass Is Associated with Hepatic Steatosis in Non-Alcoholic Fatty Liver Disease

( Do Seon Song ),( U Im Chang ),( Seong Woo Go ),( Jeong Won Jang ),( Si Hyun Bae ),( Seung Kew Yoon ),( Jin Mo Yang ) 대한간학회 2018 춘·추계 학술대회 (KASL) Vol.2018 No.1

Aims: We aimed to investigate the association between the change of muscle mass and change of fibrosis and steatosis in NAFLD patients. Methods: We analyzed 2,893 NAFLD subjects who had health check-up more than twice in St. Vincent’s Hospital between November 2009 and December 2017. NAFLD was diagnosed by ultrasound, and appendicular muscle mass (ASM) was assessed by Inbody 720, and Sarcopenia index was calculated as ASM divided by weight (SI%) and ASM divided by body mass index (SI-BMI). Non-invasive markers were used to evaluate the severity of hepatic fibrosis and steatosis; NAFLD fibrosis score (NFS), Fibrosis-4 (Fib-4) score, and Forn’s index for fibrosis, and hepatic steatosis index (HSI) and fatty liver index (FLI) for steatosis. Results: The mean age was 47.3±10.4 years, and 1956 subjects (67.6%) were male. Diabetes, hypertension, metabolic syndrome were more prevalent in sarcopenic subjects (P<0.01), and non-invasive fibrosis and steatosis markers were higher in sarcopenic subjects (P< 0.01). The mean interval between two health check-up was 39.8±21.9 months. There was no significant association between the change of NFS, Fib-4, and Forn’s index and the change of SI% and SI-BMI (all P >0.1). However, the changes of HIS and FLI were significantly associated with the change of SI% and SI-BMI (all P<0.01). Multivariate logistic analysis demonstrated the independent association between the change of skeletal muscle mass and the changes of non-invasive steatosis markers after adjusting for other confounding factors (all P< 0.001). However, the changes of non-invasive fibrosis markers did not show an independent association with the change of appendicular muscle mass after adjusting for other confounders (all P >0.1) Conclusions: The change of muscle mass is strongly associated with the change of hepatic steatosis, but not the change of fibrosis.

SiC 단결정의 TSSG 공정을 위한 전이금속 특성 연구

이승준,유용재,정성민,배시영,이원재,신윤지,Lee, Seung-June,Yoo, Yong-Jae,Jeong, Seong-Min,Bae, Si-Young,Lee, Won-Jae,Shin, Yun-Ji 한국결정성장학회 2022 한국결정성장학회지 Vol.32 No.2

본 연구에서는 SiC 단결정의 TSSG 공정중 결정 품질을 저하시키지 않으면서도 의도하지 않은 질소 도핑(N-UID)을 쉽게 제어하기 위해 지금까지 Co 또는 Sc 전이금속을 첨가한 신규 용융조성을 제안한다. Co 또는 Sc의 특성을 파악하기 위해 Ar 분위기에서 1900℃ 온도에서 약 2시간 동안 열처리 실험을 수행했다. 용융조성은 Si-Ti 10 at% 또는 Si-Cr 30 at%를 비롯하여, 탄소 용해도에 효과적이라고 알려진 Co 또는 Sc을 각각 3 at% 첨가하였다. 열처리 후 도가니 단면을 가공하여 도가니-용융물 계면에서 발생한 Si-C 반응층을 관찰하고, 탄소황분석을 통해 조성에 따른 탄소 용해도를 간접적으로 분석하였다. 그 결과, Si-Sc 기반 용융조성이 TSSG 공정에 적합한 특성을 갖는 Si-C반응층을 형성하고 있었다. 또한 탄소황분석 결과에서도 Cr 다음으로 높은 탄소량이 갖는 것으로 분석되었다. Sc는 Cr에 비해 질소와의 반응성이 낮은 이점을 가지므로 TSSG 공정에 Si-Sc 용융조성을 적용하면, 본 연구에서 의도한 대로 SiC 단결정 성장속도와 질소 UID를 모두 제어할 수 있는 것으로 고려된다.

1T DRAM with Raised SiGe Quantum Well for Sensing Margin Improvement

Si-Won Lee,Seongjae Cho,Il Hwan Cho,Garam Kim 대한전자공학회 2023 Journal of semiconductor technology and science Vol.23 No.1

In this paper, a novel one-transistor dynamic random-access memory (1T DRAM) with a raised SiGe quantum well (QW) under one gate in the double-gate (DG) structure is proposed. The proposed structure can improve the poor performance of the retention time and sensing margin which is the problem of the conventional 1T DRAM. In write operation, the performance is improved through the band to band tunneling (BTBT) between body and drain and through valence band offset between SiGe and Si. Also by utilizing the physical barrier of oxide, read “1” retention time can be increased. The fabrication process is also proposed.

쥘 쉬페르비엘의 시에 나타난 지리적 상상력 : 여행과 정주, 새로운 세계

김시원(Si-Won KIM) 프랑스학회 2017 프랑스학연구 Vol.0 No.83

Au cours des derniéres décennies, la poésie française est caractérisée par «l’ouverture au monde», mise en relief par Michel Collot. Pourtant, pour ce qui est de cette tendance, nous nous intéressons moins à la jeune génération de poétes qu’à un de ses précurseurs de la premiére moitié du XXe siécle, Jules Supervielle. Chez celui-ci la poésie s’unit, en acceptant les diverses localités de pays lointains, à la géographie. La poésie superviellienne est remarquable non seulement pour son excellente véracité géographique mais aussi pour son imagination féconde géographique. L’expression «entre l Europe et l Amérique du Sud» s’accorde à la situation géographique, psychologique de Supervielle. Et comme suggére bien l’expression “Ulysse Montévidéen”, il rêve du retour à l’Amérique du Sud, sa véritable patrie. Par ailleurs, nous tentons d’interpréter son imagination géographique s’appuyant sur «la dialectique du voyage et de l’habitation» proposée par Kenneth White. Il s agit de l imagination par laquelle Supervielle s identifie à Christophe Colomb qui a quitté l Europe et découvert le Nouveau Monde. Son imagination géographique concerne alors moins la dimension biographique que celle d’historique et de collectif. En fait, son imagination géographique imprégne sa poésie d expérience historique des Pionniers qui ont exploité les terres inconnues, comme le montrent plusieurs de ses poémes. Chez ce poéte l Europe et l Amérique du Sud s’affrontent comme un lieu de départ et un lieu à atteindre. D’ailleurs, Supervielle représente son désir de traverser une distance interstellaire au lieu d une mer entre deux continents. Ce poéte-astronome qui rêve d un « nouveau monde » à travers le télescope astronomique serait le conquérant de l Univers qui porte déjà une «carte du ciel» dans son intérieur. Pourtant, Supervielle vise moins une conquête physique que la communication cosmique par laquelle il accueille tous les êtres dans l’Univers, s’approprie toutes les maisons cosmiques. Soit le nouveau continent, soit l’espace interstellaire, Supervielle l’aspire paradoxalement pour finir son errance. Il veut y atteindre pour une véritable installation et communication, en tournant le dos aux maisons européennes étroitement fermées.

생존 페르스와 19세기 말의 앤틸리스 제도: 「찬사」의 공간에 대한 문화지리학적 연구

김시원(KIM, Si-Won) 프랑스학회 2015 프랑스학연구 Vol.71 No.-

Éloges est une œuvre au tobiographique de Saint-John Perse. Il est né en 1887 aux Anti lles et i l y a grandi avant son départ pour la France. M algré l'ambiguïté intentionnelle, le poète nous pr ésente à travers le paysage une géographie des Anti lles. Il décrit un paysa ge qui rappelle les Antille s et nous constato ns dans É loges l'environnem ent tropique, climat, topogra phie, végétation, mais au ssi des paysages des pet ites villes modernisées, p ort, route, école , Hal le, etc. Nous tentons d'aborder l'espace d'Éloge s, au regard de la "géographi e de vérité", rapporté e à l'exp loration critique de la société et de la cultu re, au-delàde la "géographi e objective". N otr e lecture de cet espace poétique est associée donc à une moralité. Quo i que soit l'intention du p oète lui-même, il est inévitabl e, pour le lecte ur d'Éloges, qu'il y tro uve des sujets critique s, import ants pour la géo graphie culturelle contemporaine. Nous constat ons, dan s "Pour fêter un e enfance", "Eloges", quel ques élémentssugg éra nt la hiér archisation social e, économique, ainsi que raciale, celle-ci est raccrochée au pouvoir qui domine dans les îles, es pace d'Éloges. Le modernisme p orté par les Bla ncs européens divise blanc et non-blanc, gouvern ants et gouvernés, ains i que "nous" et "les autres". Enfin, nous étudions le poète lui-même comme un sujet de la diaspora, à travers la noti on de "l 'identité", une des plus importantes pour la géographie cultur elle contemporaine. N ous recherchons comment se forme-t-elle son identité c ulturelle dans la vie quotidienne aux îl es, société multi-ra ciale et multi-culturelle. Nous avons recours à l'analys e d' Images à Crusoé pour ap profondir le prob lème de l'identité segmentée du sujet de la di aspora qu i a immigré de la France aux Antilles, pour rep artir enfin pour la France. Nous faisons ainsi val oir que le recuei l Éloges est profondément lié aux sujets princi paux de la géographie culturelle contemporaine.

수원 일월저수지에서 Microcystis aeruginosa (K$\ddot{u}$tzing) K$\ddot{u}$tzing 수화현상 시 환경요인들의 변화

김지은,박정원,조기안,김시균,Kim, Ji-Eun,Park, Jung-Won,Jo, Ki-An,Kim, Si-Kyoon 한국하천호수학회 2013 생태와 환경 Vol.46 No.2

본 연구는 수원 일월저수지에서 수화현상 시 환경요인들의 변화와 한국형 부영양화 지수를 이용하여 영양단계를 평가하였다. 수화현상 종은 남조류의 Microcystis aeruginosa Kutz.였으며 조사기간 내내 우점하였다. 수온은 평균 $25.7{\sim}28.4^{\circ}C$, pH는 8.4~11.17, CODcr는 4.25~$72.0mg\;L^{-1}$, 전기전도도는 333.1~$749.0{\mu}S\;cm^{-1}$, Chl-a는 22.0~$185.0mg\;L^{-1}$였다. 정체 수역인 정점 2에서 CODcr는 다른 정점에 비해 2.9배 정도로 높아 내부기원 유기물의 기여도가 높은 것으로 판단된다. 영양염인 TN은 평균 28.86~$56.75mg\;L^{-1}$, TP는 0.2~$1.24mg\;L^{-1}$로 매우 높았고, Fe는 0.11~$1.05mg\;L^{-1}$이었고, Si는 3.13~$7.46mg\;L^{-1}$이었다. TN과 TP는 일월저수지 내에 지속적으로 누적된 것으로 파악되었고, Fe도 높은 농도가 유지되었다. 한국형 부영양화지수는 37.19~147.22였다. 영양단계는 중영양에서 과영양 단계로 평가되었고, 같은 저수지 내에서도 시기 및 지점에 따라 영양단계가 다름을 나타내므로 많은 자료가 추적된다면 한국형 영양단계 분석은 저수지의 영양단계 분석 시 매우 유용하게 활용될 것으로 판단된다. Variances in environmental factors were followed in Ilwol reservoir, Suwon, during bloom of Microcystis aeruginosa (K$\ddot{u}$tzing) K$\ddot{u}$tzing, Cyanophtya from August to October, 2011. M. aeruginosa dominated the water column throughout the investigation period. The water temperature varied from $25.7^{\circ}C$ to $28.4^{\circ}C$, pH 8.40 to 11.17, CODcr 4.25 to $72.00mg\;L^{-1}$, electrical conductivity 333.1 to $749.0{\mu}g\;cm^{-1}$, and Chl-a 22 to $185mg\;L^{-1}$. In particular, the high levels of CODcr is likely indicate high contribution of autochthonous organic matters in the reservoir. TN varied from 28.86 to $56.75mg\;L^{-1}$, TP 0.20 to $1.24mg\;L^{-1}$, Fe 0.11 to $1.05mg\;L^{-1}$, and Si 3.13 to $7.46mg\;L^{-1}$. These increases imply constant accumulation in Ilwol reservior, and reinforce the idea of autochthonous organic matters input in the reservoir. The Korea Trophic Status Index ($TSI_KO$) varied from 37.19 to 147.22. Trophic levels varied from mesotrophic to hypertrophic level, and differed spatio-temporally. Therefore, it is concluded that $TSI_KO$ is useful for analyzing trophic status of reservoirs.

고품질 4H-SiC 단결정 성장을 위한 다공성 흑연 판의 역할

이희준,이희태,신희원,박미선,장연숙,이원재,여임규,은태희,김장열,전명철,이시현,김정곤,Lee, Hee-Jun,Lee, Hee-Tae,Shin, Hee-Won,Park, Mi-Seon,Jang, Yeon-Suk,Lee, Won-Jae,Yeo, Im-Gyu,Eun, Tai-Hee,Kim, Jang-Yul,Chun, Myoung-Chul,Lee, Si-Hyun 한국결정성장학회 2015 한국결정성장학회지 Vol.25 No.2

본 연구에서는 PVT법으로 4H-SiC 단결정 성장 시 다공성 흑연판을 사용하여 Si/C 비율이나 온도구배, 물질전달의 향상시킴으로써 고품질의 SiC 단결정 기판 제작을 목적으로 연구를 진행하였다. 연구에 사용된 SiC 소스 물질은 흑연 도가니에 넣어 흑연 단열재로 쌓인 구조로 실험을 하였다. 성장온도는 $2100{\sim}2300^{\circ}C$, 그리고 성장압력은 10~30 Torr의 압력으로 아르곤과 질소 분위기에서 성장시켰다. 종자정은 2인치의 $4^{\circ}$ off-axis 4H-SiC의 C면 (000-1)을 사용하였고 다공성 흑연판은 SiC 소스 물질 위에 삽입하였다. 4H-SiC 결정다형 안정화를 위한 C-rich 조건이나 균일한 온도구배를 만들어주기 위해 다공성 흑연판을 삽입하여 실험을 진행하였다. 일반적인 도가니의 경우, 성장된 wafer에서 6H-, 15R-SiC와 같은 다양한 결정다형이 관찰된 반면에 다공성 흑연판을 삽입한 도가니에서는 4H-SiC만 관찰되었다. 또한 다공성 흑연판을 삽입한 도가니에서 성장된 결정에서 MP나 EP의 낮은 결함밀도를 보였으며 결정성 또한 향상된 것을 학인하였다. The present research is focused on the effect of porous graphite what is influenced on the 4H-SiC crystal growth by PVT method. We expect that it produces more C-rich and a change of temperature gradient for polytype stability of 4H-SiC crystal as adding the porous graphite in the growth cell. The SiC seeds and high purity SiC source materials were placed on opposite side in a sealed graphite crucible which was surrounded by graphite insulator. The growth temperature was around $2100{\sim}2300^{\circ}C$ and the growth pressure was 10~30 Torr of an argon pressure with 5~15 % nitrogen. 2 inch $4^{\circ}$ off-axis 4H-SiC with C-face (000-1) was used as a seed material. The porous graphite plate was inserted on SiC powder source to produce a more C-rich for polytype stability of 4H-SiC crystal and uniform radial temperature gradient. While in case of the conventional crucible, various polytypes such as 6H-, 15R-SiC were observed on SiC wafers, only 4H-SiC polytype was observed on SiC wafers prepared in porous graphite inserted crucible. The defect level such as MP and EP density of SiC crystal grown in the conventional crucible was observed to be higher than that of porous graphite inserted crucible. The better crystal quality of SiC grown using porous graphite plate was also confirmed by rocking curve measurement and Raman spectra analysis.

초정밀 가공기계 베드 구조물용 에폭시 : 그래나이트재의 특성에 관한 연구

원시태,박영일,맹희영,김종호 서울산업대학교 산업대학원 1993 大學院論文集 Vol.2 No.-

The machine tool structures for ultra-precision machining must be manufactured with materials which have high static and dynamic stiffness, high damping, a long term dimensional and thermal stability. This study aims at the development of new composite material Epoxy-Granite which exhibits the satisfactory characteristics as a material of ultra-precision mchine tool bed. The Epoxy-Granite testpieces that use epoxy resins as a binder and granite particles as a aggregate have been manufactured so as to examine the material properties about mechanical, thermal and damping characteristcs. Experiments were carried out to obtain the proper manufacturing conditions of Epoxy-Granite specimens by varying the several testing conditions such as types of epoxy resins, particle sizes of granite and mixture ratio of epoxy resin and aggregate. Also, when Epoxy-Granite was compared with cast iron, GRANITAN which was imported from CMS of U.K. and granite materials, it has exhibited the superior or almost the same mechanical and damping properties and thermal conductivity, except for the thermal expansion.