Nano-Welding of Ag Nanowires Using Rapid Thermal Annealing for Transparent Conductive Films

Oh, Jong Sik,Oh, Ji Soo,Shin, Jae Hee,Yeom, Geun Young,Kim, Kyong Nam American Scientific Publishers 2015 Journal of nanoscience and nanotechnology Vol.15 No.11

Fabrication of high-performance graphene nanoplatelet-based transparent electrodes <i>via</i> self-interlayer-exfoliation control

Oh, Jong Sik,Oh, Ji Soo,Sung, Da In,Yeom, Geun Young The Royal Society of Chemistry 2018 Nanoscale Vol.10 No.5

<P>Graphene nanoplatelets (GNP) have attracted considerable attention due to their high yield and fabrication route that is scalable to enable graphene production. However, the absence of a means of fabricating a transparent and conductive GNP film has been the biggest obstacle to the replacement of pristine graphene. Here, we report on a novel means of fabricating uniform and thin GNP-based high-performance transparent electrodes for flexible and stretchable optoelectronic devices involving the use of an adhesive polymer layer (PMMA) as a GNP layer controller and by forming a hybrid GNP/AgNW electrode embedded on PET or PDMS. Relative to the commercially available indium tin oxide (ITO) film on a PET substrate, a GNP-based electrode composed of hybrid GNP/AgNW on PET exhibits superb optical, physical, and electrical properties: a sheet resistance of 12 Ω sq<SUP>−1</SUP> with 87.4% transmittance, a variable work function from 4.16 to 5.26 eV, an ultra-smooth surface, a rate of resistance increase of only 4.0% after 100 000 bending cycles, stretchability to 50% of tensile strain, and robust stability against oxidation. Moreover, the GNP-based electrode composed of hybrid Cl-doped GNP/AgNW shows outstanding performance in actual organic light-emitting diodes (OLEDs) by exhibiting an increased current efficiency of 29.5% and an increased luminous efficiency of 36.2%, relative to the commercial ITO electrode on PET.</P>

Effects of Step-up Training on Walking Ability of Stroke Patients by Different Support Surface Characteristics

( Geun-sik Oh ),( Yu-ran Choi ),( Dae-hyouk Bang ),( Yong-jun Cha ) 대한물리의학회 2017 대한물리의학회지 Vol.12 No.3

PURPOSE: Gait disturbances in patients with hemiplegic stroke involve asymmetry of stance time. Step box training is used to supplement the limitations of stair walking training and increasing the torque value of the paralyzed lower leg`s strength. This study aimed to investigate whether step-up training on unstable support could change walking ability in patients with chronic stroke. METHODS: Thirty stroke patients were randomly assigned to the step-up training group (experimental group), that performed training on an unstable surface, and the control group, that performed training on a stable surface. Walking speed, step length, and cadence were measured before and after training. Paired t-tests were used to compare pre- and post-intervention data, while the independent samples t-test was used to determine intergroup differences. Values of p < .05 were considered statistically significant. RESULTS: There was a significant difference in walking ability before versus after the intervention in both groups, although the experimental group showed greater differences than the control group (walking velocity by 8.1%; step length of the non-paralyzed side by 6.9%, respectively; p<.05). CONCLUSION: Step-up training might be more effective on an unstable surface than on a stable surface for increasing walking speed and step length of the non-paralyzed side.

Alcaligenes latus 에 의한 PHB 의 생합성에 관한 연구

김우식,오준택,조근도,윤정열 한국화학공학회 1997 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.35 No.3

본 논문은 Alcaligenes latus DSM 1123 균주의 최적 증식조건 및 PHB 생합성을 위한 효과적인 배양방법에 관한 연구이다. 최적 균증식 조건에 대한 실험은 진탕배양기를 이용하였으며, 얻어진 최적 조건 하에서 2.5L 용량의 호기성 배양 장치를 사용하여 회분식 배양과 pH 조절 용액을 달리한 유가식 배양을 행하였다. 배양에 있어 탄소원 및 질소원은 각각 저가의 탄소원인 sucrose및 (NH₄)₂SO₄를 사용한 경우가 가장 효율적이었다. 최적의 C/N비는 탄소원 및 질소원 농도에 비례하여 증가하였으며, sucrose농도 30g/L일 경우 C/N비 30에서 최대의 비증식속도를 보였다. Yeast extract 0.5 g/L와 polypeptone 1.0 g/L를 배지 중에 첨가한 결과 지연시간의 감소 및 2배 이상의 비증식 속도 향상을 보였다. 또 A. latus는 A. eutrophus와 달리 균증식기에도 PHB를 합성하였다. 초기에는 NH₄OH용액을, 균증식기 중반부터는 NaOH용액을 이용하여 2단 유가식 배양을 하였을 경우가 NH₄OH 용액과 NaOH 용액을 각각 이용하여 pH를 조절한 경우에 비하여 비증식속도와 균체량 및 PHB 축적량이 증가하였으며, 이때의 최종균체량, PHB 합성량 및 최종 균체량에 대한 PHB 축적률은 각각 17.6 g/L, 8.04 g/L 및 46%이었다. Culture conditions for the optimum growth and biosynthesis of PHB in Alcaligenes latus DSM 1123 were investigated. Optimum carbon and nitrogen sources and their concentrations for growth were determined, and batch and fed-batch fermentations were performed in a 2.5 L jar type aerobic fermenter with various pH control solutions. Sucrose and (NH₄)₂SO₄ were found to be the most effective carbon and nitrogen sources for the growth of A. latus, respectively. Optimum C/N ratio was found to be varied with the concentrations of carbon and nitrogen sources. The maximum specific growth rate was obtained at the sucrose concentration of 30 g/L and C/N ratio of 30. The specific growth rate increased more than two times and lag time was reduced when yeast extract and polypeptone were added. PHB could be synthesized in the logarithmic growth phase. By using NH₄OH and NaOH solutions in the first and second stage as pH control solution, significant increases in the specific growth rate, biomass and PHB concentrations were observed. Under the optimal conditions, the maximum biomass and PHB accumulation yield(Y_(P/X) attained after 40 hours were 17.6 g/L and 46 %, respectively.

High-speed etching of SiO₂ using a remote-type pin-to-plate dielectric barrier discharge at atmospheric pressure

Oh, Jong Sik,Park, Jae Beom,Gil, Elly,Yeom, Geun Young Institute of Physics [etc.] 2010 Journal of Physics. D, Applied Physics Vol.43 No.42

<P>High speed etching of SiO<SUB>2</SUB> has been investigated using a remote-type dielectric barrier discharge (DBD) in-line system with a multi-pin-to-plate power electrode configuration as functions of N<SUB>2</SUB>/NF<SUB>3</SUB> gas combination, added gases and operating frequency of a pulse power supply. The SiO<SUB>2</SUB> etch rate increased with an increase in NF<SUB>3</SUB> flow rate (0.2–1.0 slm) in N<SUB>2</SUB> (60 slm)/NF<SUB>3</SUB> but showed a maximum with an increase in N<SUB>2</SUB> (30–80 slm) at 60 slm in the N<SUB>2</SUB>/NF<SUB>3</SUB> (1 slm) gas mixture. The SiO<SUB>2</SUB> etch rate was also increased with the addition of up to 0.6 slm of He or Ar gas and it was also related to the increase in fluorine atomic density in the plasma. The addition of He or Ar to the N<SUB>2</SUB> (60 slm)/NF<SUB>3</SUB> (1 slm) and the increase in the frequency of the pulse power increased the fluorine atomic density through the increased Penning ionization/dissociation and the increased ionization by the increased pulse-on time, respectively.</P>

高下島의 植物相과 植生에 關한 硏究

오장근,김진식 木浦大學校 沿岸環境硏究所 1995 沿岸環境硏究 Vol.12 No.1

Phytosociological investigation of the vegetation was carried out in Kohado island at the period of October 1996 by Braun-Blanquet's method. Vascular plants identified in these investigations were 95 families, 257 genera, 291 species, 52 varieties and 3 forma summing up to 346 species total. The forest vegetation was classified into 5 communities, Pinus thunbergii, Pennisetum alopecuroides, Erigeron canadensis, Phragmites communis, Suaeda japonica community. Based on the classification of communities the actual vegetation map was drawn in 1 : 50,000 scale.

A case of right sided aortic arch with atrial septal defect

Geun Jin Ha,Myeung Joon Sung,Jung Hyeun Kim,Jin Wook Jung,So Yeon Kim,Jin Bae Lee,Jae Kean Ryu,Sub Lee,Ji Young Choi,Oh Chun Kwon,Kee Sik Kim,Sung Gug Chang,Young Soo Lee 대한내과학회 2009 대한내과학회 추계학술대회 Vol.2009 No.-

SAW를 이용한 ZnSe의 TAV 연구

오재근,손인호,채건식,김영국 경남대학교 환경문제연구소 1993 환경연구 Vol.15 No.-

The energy gap in ZnSe sing1e crystal epilayer have been studied by measuring Transverse Acoustoelectric Voltage(TAV). The energy gap of ZnSe was 2.6eV at room temperature. Trap levels were calculated by Heating rate, Peak shape and Initial rise methods respectively. Also we can calculated cross section of ZnSe.

Ceramic Direct Rapid Tooling with FDM 3D Printing Technology

Geun-Sik Shin(신근식),Hyun-Kyu Kweon(권현규),Yong-Goo Kang(강용구),Won-Taek Oh(오원택) 한국기계가공학회 2019 한국기계가공학회지 Vol.18 No.7

In the conventional casting and forging method, there is a disadvantage that a mold is an essential addition, and a production cost is increased when a small quantity is produced. In order to overcome this disadvantage, a metal 3D printing production method capable of directly forming a shape without a mold frame is mainly used. In particular, overseas research has been conducted on various materials, one of which is a metal printer. Similarly, domestic companies are also concentrating on the metal printer market. However, In this case of the conventional metal 3D printing method, it is difficult to meet the needs of the industry because of the high cost of materials, equipment and maintenance for product strength and production. To compensate for these weaknesses, printers have been developed that can be manufactured using sand mold, but they are not accessible to the printer company and are expensive to machine. Therefore, it is necessary to supply three-dimensional casting printers capable of metal molding by producing molds instead of conventional metal 3D printing methods. In this study, we intend to reduce the unit price by replacing the printing method used in the sand casting printer with the FDM method. In addition, Ag paste is used to design the output conditions and enable ceramic printing.

Efficient metallic nanowire welding using the Eddy current method

Oh, Ji Soo,Oh, Jong Sik,Kim, Tae Hyung,Yeom, Geun Young IOP 2019 Nanotechnology Vol.30 No.6

<P>In this study, metallic nanowires (M-NWs) such as silver nanowires (AgNWs) and copper nanowires (CuNWs) were welded only at junctions resistively by a novel method using an indirect Eddy current through an inductive power transfer. By applying an inductive power of 45 kHz alternating current power indirectly for 6 s to the M-NW network deposited on polymer substrates, a decrease of sheet resistance up to ∼67.9% for AgNWs and ∼49.9% for CuNWs could be obtained without changing the optical transmittance. For AgNWs, after the welding a decrease of surface roughness could also be observed from 44.5 nm to 26.3 nm, which is similar to the height of a single layer AgNW (22.2 nm) for a bilayer junction. For AgNWs coated on a transparent flexible substrate, after the cyclic bending of 10 000 times, no change of resistance (ΔR/R0) of the AgNWs after the welding was observed and the welded AgNWs were not easily peeled off from the substrate. It is believed that this novel welding method can be applied not only to all kinds of M-NWs on various flexible low-temperature polymer substrates, but also to large areas at a short time and at low cost.</P>