Na₂S 하부층을 이용한 Cu(In,Ga)Se₂ 광흡수층의 저온증착 및 Cu(In,Ga)Se₂ 박막태양전지에의 응용

신해나라,신영민,김지혜,윤재호,박병국,안병태,Shin, Hae Na Ra,Shin, Young Min,Kim, Ji Hye,Yun, Jae Ho,Park, Byung Kook,Ahn, Byung Tae 한국태양광발전학회 2014 Current Photovoltaic Research Vol.2 No.1

High-efficiency in $Cu(In,Ga)Se_2$ (CIGS) solar cells were usually achieved on soda-lime glass substrates due to Na incorporation that reduces deep-level defects. However, this supply of sodium from sodalime glass to CIGS through Mo back electrode could be limited at low deposition temperature. Na content could be more precisely controlled by supplying Na from known amount of an outside source. For the purpose, an $Na_2S$ layer was deposited on Mo electrode prior to CIGS film deposition and supplied to CIGS during CIGS film. With the $Na_2S$ underlayer a more uniform component distribution was possible at $350^{\circ}C$ and efficiency was improved compared to the cell without $Na_2S$ layer. With more precise control of bulk and surface component profile, CIGS film can be deposited at low temperature and could be useful for flexible CIGS solar cells.

Na₂S 하부층을 이용한 Cu(In,Ga)Se₂ 광흡수층의 저온증착 및 Cu(In,Ga)Se₂ 박막태양전지에의 응용

신해나라(Hae Na Ra Shin),신영민(Young Min Shin),김지혜(Ji Hye Kim),윤재호(Jae Ho Yun),박병국(Byung Kook Park),안병태(Byung Tae Ahn) 한국태양광발전학회 2014 Current Photovoltaic Research Vol.2 No.1

High-efficiency in Cu(In,Ga)Se₂ (CIGS) solar cells were usually achieved on soda-lime glass substrates due to Na incorporation that reduces deep-level defects. However, this supply of sodium from sodalime glass to CIGS through Mo back electrode could be limited at low deposition temperature. Na content could be more precisely controlled by supplying Na from known amount of an outside source. For the purpose, an Na₂S layer was deposited on Mo electrode prior to CIGS film deposition and supplied to CIGS during CIGS film. With the Na₂S underlayer a more uniform component distribution was possible at 350°C and efficiency was improved compared to the cell without Na₂S layer. With more precise control of bulk and surface component profile, CIGS film can be deposited at low temperature and could be useful for flexible CIGS solar cells.

Facile and fast Na-ion intercalation employing amorphous black TiO_2-x/C composite nanofiber anodes

Lee, Na-Won,Jung, Ji-Won,Lee, Jun-Seo,Jang, Hye-Yeon,Kim, Il-Doo,Ryu, Won-Hee Elsevier 2018 ELECTROCHIMICA ACTA Vol.263 No.-

<P><B>Abstract</B></P> <P>Structural and electronic modification of titanium oxide (TiO<SUB>2</SUB>) nanomaterials induced by the co-introduction of fully disordered glass phase and oxygen vacancies can lead to remarkable advances in the electrode performance in emerging energy storage systems. We report on the effective co-creation of fully amorphous nanofibers (NFs) composed of black TiO<SUB>2-x</SUB> and conductive carbons throughout the NF structure, and evaluate the materials as potential anodes in sodium-ion batteries. The black TiO<SUB>2-x</SUB> nanofiber is successfully fabricated by electrospinning a precursor solution followed by a two-step sequential thermal treatment in an air and reducing atmosphere. The NF electrode could deliver approximately two-fold higher 2nd discharge capacity and an excellent kinetic performance even under high rates compared to that delivered by anatase-structured white TiO<SUB>2</SUB> NFs used as reference, because of (i) an inherent free volume in the glass phase corresponding to the enlarged Na<SUP>+</SUP> sites, (ii) increased electrical conductivity (low bandgap) resulting from the presence of Ti<SUP>3+</SUP>, (iii) introduction of conductive carbon agents around the TiO<SUB>2-x</SUB> domain, and (iv) one-dimensional NF feature allowing numerous Na<SUP>+</SUP> reaction sites at the electrochemical interface. We also elucidate the morphological and structural changes in the nanofibers after discharge and charge by <I>ex-situ</I> characterizations.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We succeed in co-creating amorphous nanofiber structure composed of black TiO<SUB>2-x</SUB> and conductive carbons. </LI> <LI> Black TiO<SUB>2-x</SUB>/carbon nanofibers are prepared by electrospinning followed by a two-step thermal treatment. </LI> <LI> Black TiO<SUB>2-x</SUB>/carbon nanofiber delivers excellent electrochemical performance compared to those of anatase TiO<SUB>2</SUB> nanofiber. </LI> <LI> The benefits and reaction mechanism of the black TiO<SUB>2-x</SUB>/carbon nanofiber anode in the Na-ion cell operation is elucidated. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

대학생의 우울정도 : 간호학전공과 타전공대학생을 중심으로

김지연,류나은,이소라,이지희,정윤정,주지연,황인혜 이화여자대학교 간호과학대학 2012 이화간호학회지 Vol.- No.46

Purpose: This study was designed to investigate sample’s general characteristics and compare depression degree among sample’s general characteristics and students’ major(nursing vs. other major). Methods: The subjects consisted of 318 university students. Data was collected by self-reported questionnaires, which were constructed BDI score. Data was analyzed by the SPSS/PC WIN 19.0 program. Results: The depression of nursing students and other major students was not significantly different according to BDI score. Statistically significant difference was identified among sleeping. Conclusion: Specific study focused on the practice time should be done to confirm the depression of nursing major and other majors. Detailed support programs which specifically deal with sleeping should be developed to effectively reduce the harmful effects of individual vulnerability. Therefore, prevention and management system to reduce depression degree for university students is needed.

Hierarchically nanoporous pyropolymer nanofibers for surface-induced sodium-ion storage

Yoon, Hyeon Ji,Lee, Min Eui,Kim, Na Rae,Yang, Seung Jae,Jin, Hyoung-Joon,Yun, Young Soo Pergamon Press 2017 Electrochimica Acta Vol. No.

<P><B>Abstract</B></P> <P>Surface-driven charge storage materials based on both electrochemical double layer (EDL) formation and pseudocapacitive behavior can deliver high energy and power capabilities with long-lasting cycling performance. On the other hand, the electrochemical performance is strongly dependent on the material properties, requiring sophisticated electrode design with a high active surface area and a large number of redox-active sites. In this study, hierarchically nanoporous pyropolymer nanofibers (HN-PNFs) were fabricated from electrospun polyacrylonitrile nanofibers by simple heating with KOH. The HN-PNFs have a hierarchically nanoporous structure and an exceptionally high specific surface area of 3,950.7m<SUP>2</SUP> g<SUP>−1</SUP> as well as numerous redox-active heteroatoms (C/O and C/N ratio of 10.6 and 16.8, respectively). These unique material properties of HN-PNFs resulted in high reversible Na-ion capacity of ∼292mAhg<SUP>−1</SUP> as well as rapid kinetics and stable cycling performance in the cathodic potential range (1-4.5V vs. Na<SUP>+</SUP>/Na). Furthermore, energy storage devices based on HN-PNFs showed a remarkably high specific energy of ∼258 Wh kg<SUP>−1</SUP> at ∼245Wkg<SUP>−1</SUP> as well as a high specific power of ∼21,500Wkg<SUP>−1</SUP> at ∼78 Wh kg<SUP>−1</SUP>, with long and stable cycling behaviors over 2,000 cycles.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Hierarchically nanoporous pyropolymer nanofibers (HN-PNFs) were fabricated. </LI> <LI> HN-PNFs have a high specific surface area of ∼3,950m<SUP>2</SUP> g<SUP>−1</SUP> and numerous heteroatoms. </LI> <LI> HN-PNFs exhibit high capacities of ∼292mAhg<SUP>−1</SUP> and great rate/cycling performances. </LI> <LI> High energy (258Whkg<SUP>−1</SUP>) and high power (21,500Wkg<SUP>−1</SUP>) are achieved. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>Hierarchically nanoporous pyropolymer nanofibers (HN-PNFs) fabricated from electrospun polyacrylonitrile nanofibers by simple heating with KOH exhibited high electrochemical performance for Na-ion storage.</P> <P>[DISPLAY OMISSION]</P>

Chitosan/oleamide Nanofluid for Enhancing Gas Utilization Efficiency in C1-gas Bioconversion

Eungsu KANG,Hyunsuk CHOI,Ji Yeong LEE,Min-sik KIM,Jeong Geol NA,Yoo Seong CHOI 한국생물공학회 2021 한국생물공학회 학술대회 Vol.2021 No.10

Microbial biotransformation using C1-gases (CH₄, CO) is a notable technique for sustainable, carbon-neutral chemical and fuel production. However, the low mass transfer coefficient (KLa) of C1-gases in biological processes has hampered the efficient production of value-added materials, despite efficient, nonnative strains having been recently developed. Here, we constructed a nanofluid material mainly composed of chitosan and oleamide (CS/OA), which was stably suspended with a particle size of 120.7 ± 39.0 ㎚ in aqueous culture media below pH 7.5. The kLa value was enhanced more than 1.5-fold with a reduction of surface tension even in the 0.0001 % (w/v) CS/OA nanofluid. In addition, when the nanofluid was applied into media for seed-cultivation of three C1-gas utilizing strains such as Methylomonas sp. DH-1, M. trichosporium OB3b, and Thermococcus onnurineus NA1 156T, the CS/OA nanoparticles attached to the cell surface, leading to a morphological change in the cell surface at extended lag-phase, and enhanced the specific cell growth rates (μmax), gas utilization efficiency in log-phase. Remarkably, the adapted strains from the seed culture using the CS/OA nanofluid media also had enhanced μmax in a subsequent subculture and the main culture using conventional culture media, resulting in higher C1 gas consumption, cell growth, and metabolite production such as formate and succinate. These results showed that the CS/OA nanofluid could be an effective medium component to enhance the gas utilization efficiency in C1-gas microbial bioconversion.Microbial biotransformation using C1-gases (CH₄, CO) is a notable technique for sustainable, carbon-neutral chemical and fuel production. However, the low mass transfer coefficient (KLa) of C1-gases in biological processes has hampered the efficient production of value-added materials, despite efficient, nonnative strains having been recently developed. Here, we constructed a nanofluid material mainly composed of chitosan and oleamide (CS/OA), which was stably suspended with a particle size of 120.7 ± 39.0 ㎚ in aqueous culture media below pH 7.5. The kLa value was enhanced more than 1.5-fold with a reduction of surface tension even in the 0.0001 % (w/v) CS/OA nanofluid. In addition, when the nanofluid was applied into media for seed-cultivation of three C1-gas utilizing strains such as Methylomonas sp. DH-1, M. trichosporium OB3b, and Thermococcus onnurineus NA1 156T, the CS/OA nanoparticles attached to the cell surface, leading to a morphological change in the cell surface at extended lag-phase, and enhanced the specific cell growth rates (μmax), gas utilization efficiency in log-phase. Remarkably, the adapted strains from the seed culture using the CS/OA nanofluid media also had enhanced μmax in a subsequent subculture and the main culture using conventional culture media, resulting in higher C1 gas consumption, cell growth, and metabolite production such as formate and succinate. These results showed that the CS/OA nanofluid could be an effective medium component to enhance the gas utilization efficiency in C1-gas microbial bioconversion.

품종별 무화과의 영양성분 비교

나환식 ( Hwan Sik Na ),김진영 ( Jin Young Kim ),박학재 ( Hak Jae Park ),최경철 ( Gyeong Cheol Choi ),양수인 ( Soo In Yang ),이지헌 ( Ji Heon Lee ) 한국식품저장유통학회(구 한국농산물저장유통학회) 2013 한국식품저장유통학회지 Vol.20 No.3

국내에서 주로 재배되는 무화과 품종인 도후인(Dauphine)2종, 봉래시(Horaish)2종, 바나네(Banane) 1종을 대상으로 이화학적 특성을 분석한 결과, 무화과의 수분은 85.37~87.28%, 회분 0.38~0.43%, 조지방 0.20~0.26%, 조단백질 0.39~0.81%로 품종별 차이는 보이지 않았으며 조섬유는 바나네가 7.55±0.13%로 다른 품종 5.12~7.60%에 비해 다소 높은 결과를 보였다. 무기성분 함량은 모든 품종에서 K>Ca>Mg>Na순으로 나타났으며 전체 함량의 경우 도후인 품종이 타 품종에 비해 조금 높은 결과를 보였다. 바나네 품종과 봉래시 품종의 총 유리아미노산 조성은 glutamic acid>proline>aspartic acid 순으로 높은 분포를 보였으며, 전체 함량의 51.68~58.71%를 차지하고 있으며, 도후인 품종의 경우 glutamic acid>aspartic acid>alanine이 전체의 약 50%를 차지하고 있었다. 또한 기억력 감퇴 예방 등 학습 능력에 도움을 주는 기능성 물질인 γ-aminobutyric acid(GABA) 함량은 바나네에서 26.69mg/100g으로 상당히 높은 함량을 보였다. 총 폴리페놀 함량은 도후인이 198.91~261.64mg/kg, 봉래시 품종이 169.90~174.33mg/kg, 바나네 품종이 211.07mg/kg으로 나타났으며 총 플라보노이드 함량은 바나네(84.95mg/kg), 도후인(60.47~68.71mg/kg), 봉래시(44.12~44.60mg/kg)순으로 바나네가 가장 높았으며 품종간의 차이를 보였따. 플라보노이드성분 중 quercetin과 kaempferol은 각각 2.40~3.54mg/kg, 1.09~1.16mg/kg으로 분석되었다. In this study, the proximate compositions, minerals, free amino acids, total polyphenol and flavonoids of figs were analyzed according to their cultivars. The proximate compositions showed moisture at 85.37~87.28%, crude ash at 0.38~0.43%, crude lipid at 0.20~0.26%, crude protein at 0.39~0.81%, carbohydrate at 11.23~13.66% and crude fiber at 5.12~7.55% (dry base). The amounts of the following minerals in the figs were highest, in this order: K > Ca > Mg > Na. The total polyphenol contents were highest in this order: Dauphine (198.91~261.64mg/kg), Banane (211.07 mg/kg) and Horaish (169.90~174.33 mg/kg). The total flavonoid contents were highest in this order. Banane (84.52 mg/kg) > Dauphine (60.47~68.71 mg/kg) > Horaish (44.12~44.60mg/kg). The quercetin contents were highest in this order. Dauphine, 2.40~3.54 mg/kg; Banane, 3.54 mg/kg; and Horaish, 2.40~2.75 mg/kg; but the flavonoid contents were lowest in this order. Dauphine, 1.11~1.16 mg/kg; Banane, 1.14 mg/kg; and Horaish, 1.09~1.11 mg/kg. The free amino acid content of the figs was 199.70~328.77 mg/100g; their essential free amino acid contents, 46.45~67.46 mg/100 g; and their GABA (γ-aminobutyric acid) contents, 13.57~26.69 mg/100 g.

Energy storage capabilities of nitrogen-enriched pyropolymer nanoparticles fabricated through rapid pyrolysis

Yun, Young Soo,Kim, Yu Hyun,Song, Min Yeong,Kim, Na Rae,Ku, Kyojin,An, Ji Su,Kang, Kisuk,Choi, Hyoung Jin,Jin, Hyoung-Joon Elsevier 2016 Journal of Power Sources Vol.331 No.-

<P><B>Abstract</B></P> <P>Nanostructured pyropolymers contain significant amounts of redox-active heteroatoms, have high specific surface areas, and a defective carbon microstructure, indicating good potential for pseudocapacitive charge storage. In this study, nitrogen-enriched pyropolymer nanoparticles (N-PNs-50) are fabricated from polyaniline nanotubes through rapid pyrolysis at 50 °C min<SUP>−1</SUP>. N-PNs-50 exhibit a nitrogen content of 9.8 wt%, a high specific surface area of 875.8 m<SUP>2</SUP> g<SUP>−1</SUP>, and an amorphous carbon structure with an I<SUB> <I>D</I> </SUB>/I<SUB> <I>G</I> </SUB> intensity ratio of 0.95. These unique characteristics lead to good electrochemical performances, in which reversible capacities of 660 and 255 mAh g<SUP>−1</SUP> are achieved for Li-ion and Na-ion storage, respectively, with favorable voltage characteristics (<1.5 V for Li-ions and <1.2 V for Na-ions). This study provides a more feasible production method for nitrogen-doped pyropolymers and their practicable electrochemical performances for use as an anode in energy storage devices.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Nanostructured pyropolymers (N-PNs-50) were fabricated by rapid pyrolysis. </LI> <LI> N-PNs-50 exhibited a nitrogen content of 9.8 wt% and amorphous carbon structure. </LI> <LI> N-PNs-50 exhibited a high specific surface area of 875.8 m<SUP>2</SUP> g<SUP>−1</SUP>. </LI> <LI> 660 and 255 mAh g<SUP>−1</SUP> were achieved for Li-ion and Na-ion storage, respectively. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>Nitrogen-enriched pyropolymer nanoparticles (N-PNs-50) were fabricated from polyaniline nanotubes through rapid pyrolysis at 50 °C min<SUP>−1</SUP>, showing superior electrochemical performances.</P> <P>[DISPLAY OMISSION]</P>

보리순의 영양성분 조성

서혜지,최용민,김상천,이준수,이기택,정명근,천지연,황진봉,남진식,서우덕,황영,김행란,김세나 忠北大學校 農業科學硏究所 2015 農業科學硏究 Vol.31 No.2

경계조건변화에 따른 동력전달관로의 동특성

나기대,유영태,김지환 한국공작기계학회 2002 한국생산제조학회지 Vol.11 No.6

Design for a quiet operation of fluid power system requires the understanding of noise and vibration characteristics of the system. It's not easy to analyze noise problem in hydraulic cylinder used in typical actuator Because they've got complex fluid dynamics. One of the fundamental problems associated with the hydraulic system is the pulsating flow in pipe lines, which can e tackled by the analysis under simplifying assumptions. The present study focuses on theoretic analysis and experimental study on the dynamics of laminar pulsating flow in a circular pipe. We analyze the propagation characteristics of the pressure pulse within a hydraulic pipe line taking into account the pulsating flow frequency variation. We also measure instantaneous pressure pulses within pipe line to identify the transfer functions. We conduct series of experiments to investigate the propagation characteristics of pressure pulse for various pressure of pulsating flow. The working fluid of the present study is ISO VG46 and the temperature ranges from 20 to 60℃ with normal pressure at 4000kPa. The flow rate is measured by using an ultrasonic flow meter. Pressures at fixed upstream and downstream positions are measured concurrently. The electric signals of the pressure sensor are stored and analyzed using a system analyzer(PKE 983 series). The frequency is varied in the range of 10~500Hz. The Reynolds number is kept below 2,000. In the present study, boundary condition was varied by installing a surge tank and an orifice at the end of pipe. Experimental and theoretical results were compared each other under various boundary conditions.