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김광락,정흥석,강희석,이한수,안도희,백승우,이성호 한국공업화학회 1998 응용화학 Vol.2 No.2
Effect of cross-linking agent and solvent on pore characteristics of styrene-divinylbenzene copolymer was investigated experimentally. Influence of cross-linking agent on surface area of the polymeric support was dominant over all the others. Surface area and pore volume of the polymeric support were decreased and the second peak was shifted to large pore size in the pore size distribution with increasing the content of poor solvent in the solvent mixture. When toluene was used as a good solvent, and n-heptane as poor solvent, the optimum range of good/poor solvent ratio was 1.5∼0.7 for styrene-divinylbenzene copolymer of large surface and micropore area and pore volume.
기광석,김현섭,정하연,이현준,안병석,김준식,강수원,김용국,하종규 한국동물자원과학회 2003 한국축산학회지 Vol.45 No.5
This study was carried out to survey operation system of self-making TMR and particle size of self-making and commercial TMR, then to compare TMR particle size recommended by Penn State particle Size Separator. Daily mixing time in self-making TMR averaged 48.6±28.0min, 2 angar type of mixer was most by 55.5% and daily 2 times of mixing in summer and other season was 44.4 and 22.2%, respectively. Percentage of residual feed in upper sieve(19㎜ diameter), middle sieve(8 ti 18㎜ diameter) and lower pen was 21.5~25.6%, 16.0~25.8%, 52.8~61.4%, respectively, at self-making TMR mixer. Percentage of particle sizes of more than 19㎜ in self-making and commercial TMR was 24.9±1.4 and 26.2±1.7%, that of 8-10㎜ 22.8±1.0 and 12.8±1.2 and that of less than 8㎜ 52.3±1.7 and 61.0±1.5, respectively, which in particle length of 8~13㎜ in self-making and commercial TMR was lower by 82.6 and 100% compared to that recommended by Penn State particle separator, respectively. Especially there was not particle length of more than 19㎜ in commercial TMR at all. It is necessary to check the number of cows ruminating in a farm in order to estimate the particle size of TMR; it is recommended to change the TMR mixing time or the TMR formulae if the proportion of ruminating cows in a farm is less than 40%.
Bi-2223계 초전도 선재의 임계전류밀도 향상을 위한 연구
임성우,박종광,안용호,박준채,한병성,송재주 전북대학교 공업기술연구소 1998 工學硏究 Vol.29 No.-
There have been a lot of studies to improve the characteristic of Bi-2223 tape by PIT method which is considered as one of the best way for applying superconductor. These improved characteristic of Bi-2223 tape is able to be acqured by control of mechanical defromation and heat treatment. Particulary, the rolling reduction rate during mechanical processing affects the alinement of grain structure and sauseging betyween Ag-sheath and superconductor core and these affect Jc of tape seriouly that is the most important factor of superconductor tape. In this work, we examined the variation of Jc in Bi-2223 tape due to various rolling reduction rate.
Large-scale pattern growth of graphene films for stretchable transparent electrodes
Kim, Keun Soo,Zhao, Yue,Jang, Houk,Lee, Sang Yoon,Kim, Jong Min,Kim, Kwang S.,Ahn, Jong-Hyun,Kim, Philip,Choi, Jae-Young,Hong, Byung Hee Macmillan Publishers Limited. All rights reserved 2009 Nature Vol.457 No.7230
Problems associated with large-scale pattern growth of graphene constitute one of the main obstacles to using this material in device applications. Recently, macroscopic-scale graphene films were prepared by two-dimensional assembly of graphene sheets chemically derived from graphite crystals and graphene oxides. However, the sheet resistance of these films was found to be much larger than theoretically expected values. Here we report the direct synthesis of large-scale graphene films using chemical vapour deposition on thin nickel layers, and present two different methods of patterning the films and transferring them to arbitrary substrates. The transferred graphene films show very low sheet resistance of ∼280 Ω per square, with ∼80 per cent optical transparency. At low temperatures, the monolayers transferred to silicon dioxide substrates show electron mobility greater than 3,700 cm<SUP>2</SUP> V<SUP>-1</SUP> s<SUP>-1</SUP> and exhibit the half-integer quantum Hall effect, implying that the quality of graphene grown by chemical vapour deposition is as high as mechanically cleaved graphene. Employing the outstanding mechanical properties of graphene, we also demonstrate the macroscopic use of these highly conducting and transparent electrodes in flexible, stretchable, foldable electronics.
Static behavior of a laterally loaded guardrail post in sloping ground by LS-DYNA
Woo, Kwang S.,Lee, Dong W.,Yang, Seung H.,Ahn, Jae S. Techno-Press 2018 Geomechanics & engineering Vol.15 No.5
This study aims to present accurate soil modeling and validation of a single roadside guardrail post as well as a single concrete pile installed near cut slopes or compacted sloping embankment. The conventional Winkler's elastic spring model and p-y curve approach for horizontal ground cannot directly be applied to sloping ground where ultimate soil resistance is significantly dependent on ground inclination. In this study, both grid-based 3-D FE model and particle-based SPH (smoothed particle hydrodynamics) model available in LS-DYNA have been adopted to predict the static behavior of a laterally loaded guardrail post. The SPH model has potential to eliminate any artificial soil stiffness due to the deterioration of the node-connected Lagrangian soil mesh. For this purpose, this study comprises two parts. Firstly, only 3-D FE modeling has been tested to show the numerical validity for a single concrete pile in sloping ground using Mohr-Coulomb material. However, this material option cannot be implemented for SPH elements. Nevertheless, Mohr-Coulomb model has been used since this material model requires six input soil data that can be obtained from the comparative papers in literatures. Secondly, this work is extended to compute the lateral resistance of a guardrail post located near the slope using the hybrid approach that combines Lagrange FE elements and SPH elements by the suitable node-merging option provided by LS-DYNA. For this analysis, the FHWA soil material developed for application to road-base soils has been used and also allows the application of SPH element.
Impact Behavior of a Laterally Loaded Guardrail Post near Slopes by Hybrid SPH Model
Woo, Kwang S.,Lee, Dong W.,Ahn, Jae S. Hindawi Limited 2018 Advances in civil engineering Vol.2018 No.-
<P>Based on the assumption that guardrail systems are placed in soil with horizontal ground, interaction behavior between soil and a post has been presented using some relevant theories such as the theory of subgrade reaction, Winkler’s spring theory, and the nonlinear <I>p</I>-<I>y</I> curve method. However, they can be constructed on cut slopes or compacted sloping embankments beside the roadway. Thus, the theory based on the conventional discrete spring models cannot be directly applied to the sloping ground since the ground inclination significantly affects the ultimate soil resistance. In this study, two approaches for comparison of them are adopted to present the interaction behavior between soil and the post. One of them is the three-dimensional Lagrangian approach, and the other is the hybrid approach that combines the finite elements and the particles based on SPH (smoothed particle hydrodynamics) modeling. The SPH method is expected to overcome drawbacks of large mesh distortion in soil regions consisting of node-connected finite elements due to lateral movement of the guardrail post. The soil-post interaction in the sloping ground under conditions of quasi-static and dynamic loads is investigated according to ground inclination, embedment length, and embedment location of the post near the slope.</P>
김광원(Kwang Won Kim),최인선(In Seon S . Choi),박석채(Seog Chea Park),장안수(Ahn Soo Jang),임호(Ho Lim) 대한내과학회 1999 대한내과학회지 Vol.57 No.1
N/A Researches on the characteristics of fatality-prone asthmatics have been performed in western countries, but there are few reports in this field in Korea. The purposes of this study were to clarify the magnitude of the problem and to identify the risk factors of near-fatal asthma(NFA). Methods : The records of patients admitted due to asthma attack were analyzed retrospectively. Results :1) The subjects had NFA in 50.6% and PaCO2 > 45mmHg in 22.9%. Five(11.1%) among NFA patients and 3 out of 19(15.8%) subjects with PaCO2 > 45mmHg required mechanical ventilation. 2) There were no significant differences between NFA and non-NFA in age, sex, resident place, academic career, familial and personal history of atopic diseases, serum total IgE level, positive skin prick test to house dust mites, accompanying allergic rhinitis and aspirin intolerance, emphysema on chest high resolution computerized tomogram, dyspnea perception, previous asthma education, regular OPD follow-up, and use of antiinflammatory drugs. 3) However, cigarette smoking(62.2% vs 38.6%), accompanying paranasal sinusitis(66.7% vs 45.3%), chronic asthma severity(severe persistent: 55.5% vs 29.5%), hospitalization frequency(2.93 vs 1.58), and duration of recent asthma exacerbation(6.6 vs 18.8 days) in NFA were significantly different from those in non-NFA.4) The relative risk for NFA was high in patients with history of hospitalization > 3, severe persistent asthma, exacerbation period < 3 days, smoking, or sinusitis in the order of frequency. Conclusion : Near-fatal asthma is a prevalent problem in clinical practice and asthma admission history, severe persistent asthma, short exacerbation period < 3 days, smoking, and paranasal sinusitis are the risk factors warning near-fatal asthma attack in advance.