세관 양광주 방전에서 플라즈마 확산의 완전 해

김동준,정종문,김정현,황하청,정재윤,조윤희,임현교,구제환,최은하,조광섭,Jin, D.J.,Jeong, J.M.,Kim, J.H.,Hwang, H.C.,Chung, J.Y.,Cho, Y.H.,Lim, H.K.,Koo, J.H.,Choi, E.H.,Cho, G.S. 한국진공학회 2010 Applied Science and Convergence Technology Vol.19 No.1

관경이 수 mm인 세관 램프 내부에서 플라즈마의 확산을 조사하기 위하여 이극성(ambipolar) 확산방정식을 해하였다. 반경 방향의 확산에 의한 유리관 벽에서의 플라즈마 소멸 특성시간은 $\tau_r\;=\;(r_0/2.4)^2/D_a$로 주어진다. 반경 $r_0{\sim}1\;mm$이고 이극성 확산계수 $D_a{\sim}0.01\;m^2/s$ 이면, $\tau_r{\sim}17\;{\mu}s$이다. 이는 램프의 교류전원 구동에서 플라즈마를 유지하기 위한 구동 최소 주파수 ~30 kHz에 해당한다. 고전압이 인가되는 전극부에 발생한 고밀도의 플라즈마가 양광주로 확산되는 특성시간은 $\tau_z{\sim}0.1\;s$이다. 고밀도 플라즈마 경계에서의 시간에 대한 확산속도는 $t{\sim}10^{-6}\;s$일 때 $u_D{\sim}10^2\;m/s$이고, $t{\sim}10^{-3}\;s$이면 그 속도는 $u_D{\sim}1\;m/s$로 느려진다. 따라서 램프 길이 ~1 m에 대하여 전극부에서 생성된 고밀도 플라즈마가 양광주 전체로 확산되는 시간은 수 초가 걸린다. The ambipolar diffusion equation has been solved in a fine-tube lamp of a few mm in diameter. In the diffusion of radial direction, the plasma diffuses and vanishes away at the glass wall by recombination with the characteristic time of plasma loss is given by $\tau_r\;=\;(r_0/2.4)^2/D_a$. With the radius $r_0{\sim}1\;mm$ and the ambipolar diffusion coefficient $D_a{\sim}0.01\;m^2/s$, the vanishing time is calculated $\tau_r{\sim}10\;{\mu}s$ which corresponds to the least value of frequency 30 kHz for the sustaining the plasma in the operation of high voltage AC-power. In the diffusion of longitudinal z-direction, a high density plasma generated at the area of a high voltage electrode, diffuses into the positive column with the characteristic time $\tau_z{\sim}0.1\;s$. The plasma diffusion velocity at the boundary of high density plasma is $u_D{\sim}10^2\;m/s$ at the time $t{\sim}10^{-6}$ s and the diffusion velocity becomes slow as $u_D{\sim}1\;m/s$ at $t{\sim}10^{-3}\;s$. Therefore, for the long lamp of 1 m, it takes about several seconds for the high density plasma at the area of electrode to diffuse through the whole positive column space.

Electrocatalytic activity of chemically deposited Cu_xS thin film for counter electrode in quantum dots-sensitized solar cells

Lim, I.,Lee, D.Y.,Patil, S.A.,Shrestha, N.K.,Kang, S.H.,Nah, Y.C.,Lee, W.,Han, S.H. Elsevier Science Publishers 2014 Materials chemistry and physics Vol.148 No.3

The compact (c-Cu<SUB>x</SUB>S) and the porous (p-Cu<SUB>x</SUB>S) with particle decorated films of coppers-ulfidearesynthesized using a chemical bath deposition technique, and the films are characterized using electrochemical techniques. In addition, the chemically deposited Cu<SUB>x</SUB>S films are investigated as a counter electrode in quantum dots-sensitized solar cells (QSSCs). The available redox active reaction sites of the p-Cu<SUB>x</SUB>S film are found to be 57.9% higher than those available in the c-Cu<SUB>x</SUB>S film. From the electrochemical impedance spectroscopy, the effective diffusion coefficients of the polysulfide electrolyte in the c-Cu<SUB>x</SUB>S and p-Cu<SUB>x</SUB>S films are estimated to be 3.67 x 10<SUP>-5</SUP> and 6.35 x 10<SUP>-5</SUP> cm<SUP>2</SUP> s<SUP>-1</SUP>, respectively. These results can be ascribed to the improvement in the available redox active reaction sites and the electrocatalytic activity of the Cu<SUB>x</SUB>S counter electrode. As compared to the c-Cu<SUB>x</SUB>S film, the p-Cu<SUB>x</SUB>S film as a counter electrode exhibits an enhanced photovoltaic performance of the QSSCs with the power conversion efficiency of 3.17%, short-circuit current of 11.89 mA c<SUP>-</SUP>m<SUP>2</SUP>, open-circuit voltage of 0.50 V, and fill factor of 53.29. The improved performance of the QSSCs is ascribed to the improvements on the available redox active reaction sites, electrocatalytic activity and the diffusion coefficients, which are directly related to the surface morphology of the sulfide films.

Experimental evidence of hydrogen-oxygen decoupled diffusion into BaZr_0.6Ce_0.25Y_0.15O_3-δ

Lim, D.K.,Im, H.N.,Jeon, S.Y.,Park, J.Y.,Song, S.J. Elsevier Science 2013 ACTA MATERIALIA Vol.61 No.4

The electrical properties of BaZr<SUB>0.6</SUB>Ce<SUB>0.25</SUB>Y<SUB>0.15</SUB>O<SUB>3-δ</SUB> (BZCY) were studied as a function of both oxygen partial pressure (-2.65≤log(P<SUB>O'2</SUB>atm<SUP>-1</SUP>)≤-0.62) and water vapor activity (-3.33≤log(P<SUB>H'2O</SUB>atm<SUP>-1</SUP>≤-1.3)) in the temperature range of 973-1073K. The total conductivity slightly increased in reducing atmospheres with increasing water vapor activity because of the relative contribution to the total conductivity by the redox reaction at the given thermodynamic conditions. The partial conductivities of protons, holes and oxygen vacancies were successfully calculated, and the activation energy determined for proton transport was 0.3+/-0.1eV. The chemical diffusivity of oxygen at a fixed water vapor activity, D~<SUB>vO</SUB>, could only be evaluated from Fick's second law during oxidation and reduction at the fixed water vapor activity. However, twofold nonmonotonic conductivity relaxation behaviors were clearly confirmed in the temperature range investigated during hydration/dehydration. If P<SUB>O'2</SUB> represents the fixed oxygen partial pressure, D~<SUB>iH</SUB> is the hydrogen chemical diffusivity at P<SUB>O'2</SUB> and D~<SUB>vH</SUB> is the oxygen chemical diffusivity at P<SUB>O'2</SUB>, it was observed that D~<SUB>iH</SUB>>D~<SUB>vH</SUB> at all experimental conditions, suggesting that the hydrogen chemical diffusion is always faster than oxygen on hydration/dehydration in the temperature range studied.

Predictive risk factors for Listeria monocytogenes meningitis compared to pneumococcal meningitis: a multicenter case–control study

Lim, S.,Chung, D. R.,Kim, Y. S.,Sohn, K. M.,Kang, S. J.,Jung, S. I.,Kim, S. W.,Chang, H. H.,Lee, S. S.,Bae, I. G. Springer Science + Business Media 2017 Infection Vol.45 No.1

<P>Patients with a prior history of receiving immunosuppressive therapy within 1 month and chronic liver disease have 8.1-fold and 5-fold increased risk of meningitis by L. monocytogenes compared to S. pneumoniae, respectively.</P>

RF Interference Analysis for KOMPSAT-II Spacecraft

Lim, S.B.,Kim, D.Y.,Chang, Y.K. 통신위성우주산업연구회 2001 Joint Conference on Satellite Communications Vol.2001 No.-

In general, LEO satellite uses S-band communication link for the whole satellite management, whereas the satellite payload frequently implements X-band and/or Ku-band transmitter for payload data transmission. The transmission system should have out-band rejection filter (protection circuit) to prevent any interference with the satellite receiver, so that the receiver can be normally operated. It is usually implemented in the transmitter itself but the vendor of a transmitter could not take it into account whole out of band frequency because a variety of individual satellites utilize different RF communication systems. The KOMPSAT-II, which is an earth observation satellite, is being developed by Korea Aerospace Research Institute and Korean industries. It has S-band communication system for the bus and X-band transmission system for payload data. In addition, L-band GPS Receiver is being incorporated to achieve the KOMPSAT-II mission goal. Unfortunately, the KOMPSAT-2 payload system does not have external out-band rejection~ filter nor transmitter for S-band and L-band protection. The transmitter only has band rejection filter for TDRSS. In addition, it has high gain directional antenna whose directional beam has to pass over the S-band antenna. In this paper, the analysis method is described to calculate the interference effects of the S-band spurious noise power on X-band transmitting system to S-band receiver. The S-band antenna is positioned very closely to the X-band Antenna by I .2m. We will also introduce general simple RF interference analysis method applicable to a traditional system, including advantage and disadvantages. The X-band transmitting system is often required to add the specified filter to suppress the S-band spurious signal for the safety of the receiver performance. The analysis result shows that the performance of S-band receiver is satisfied with no implementation of the specified filter.

Preparation and characterization of sulfonated amine-poly(ether sulfone)s for proton exchange membrane fuel cell

Seo, D.W.,Lim, Y.D.,Lee, S.H.,Jeong, Y.G.,Hong, T.W.,Kim, W.G. Pergamon Press ; Elsevier Science Ltd 2010 International journal of hydrogen energy Vol.35 No.23

Sulfonated amine-poly(ether sulfone)s (S-APES)s were prepared by nitration, reduction and sulfonation of poly(ether sulfone) (ultrason<SUP>(</SUP>R)-S6010). Poly(ether sulfone) was reacted with ammonium nitrate and trifluoroacetic anhydride to produce the nitrated poly(ether sulfone), and was followed by reduction using tin(II)chloride and sodium iodide as reducing agents to give the amino-poly(ether sulfone). The S-APES was obtained by reaction of 1,3-propanesultone and the amino-poly(ether sulfone) (NH<SUB>2</SUB>-PES) with sodium methoxide. The different degrees of nitration and reduction of poly(ether sulfone) were successfully synthesized by an optimized process. The reduction of nitro group to amino was done quantitatively, and this controlled the contents of the sulfonic acid group. The films were converted from salt to acid forms with dilute hydrochloric acid. Different contents of sulfonated unit of the S-APES were studied by FT-IR, <SUP>1</SUP>H NMR spectroscopy, differential scanning calorimetry (DSC), and thermo gravimetric analysis (TGA). Sorption experiments were conducted to observe the interaction of sulfonated polymers with water and methanol. The ion exchange capacity (IEC), a measure of proton conductivity, was evaluated. The S-APES membranes exhibit conductivities (25 <SUP>o</SUP>C) from 1.05 x 10<SUP>-3</SUP> to 4.83 x 10<SUP>-3</SUP> S/cm, water swell from 30.25 to 66.50%, IEC from 0.38 to 0.82 meq/g, and methanol diffusion coefficients from 3.10 x 10<SUP>-7</SUP> to 4.82 x 10<SUP>-7</SUP> cm<SUP>2</SUP>/S at 25 <SUP>o</SUP>C.

Comparison of solvent@?wetted and kneaded l-sulpiride@?loaded solid dispersions: Powder characterization and in vivo evaluation

Kim, D.S.,Choi, J.S.,Kim, D.W.,Kim, K.S.,Seo, Y.G.,Cho, K.H.,Kim, J.O.,Yong, C.S.,Youn, Y.S.,Lim, S.J.,Jin, S.G.,Choi, H.G. Elsevier/North Holland 2016 International journal of pharmaceutics Vol.511 No.1

The purpose of this study was to compare the powder properties, solubility, dissolution and oral absorption of solvent@?wetted (SWSD) and kneaded (KNSD) l-sulpiride@?loaded solid dispersions. The SWSD and KNSD were prepared with silicon dioxide, sodium laurylsulfate and D-α-tocopheryl polyethylene glycol 1000 succinate (TPGS) using a spray dryer and high shear mixer, respectively. Their powder properties, solubility, dissolution and oral absorption were assessed compared to l-sulpiride powder. The drug in SWSD was in the amorphous state; however, in KNSD, it existed in the crystalline state. The SWSD with a drug/sodium laurylsulphate/TPGS/silicon dioxide ratio of 5/½/12 gave the higher drug solubility and dissolution compared to the KNSD with the same composition. The oral absorption of drug in the SWSD was 1.4 fold higher than the KNSD and 3.0 fold higher than the l-sulpiride powder (p<0.05) owing to better solubility and reduced crystallinity. Furthermore, the SWSD at the half dose was bioequivalent of commercial l-sulpiride@?loaded product in rats. Thus, the SWSD with more improved oral absorption would be recommended as an alternative for the l-sulpiride@?loaded oral administration.

Prevalence and characterization of Salmonella in pigs from conventional and organic farms and first report of S. serovar 1,4,[5],12:i:- from Korea

Tamang, M.D.,Gurung, M.,Nam, H.M.,Moon, D.C.,Kim, S.R.,Jang, G.C.,Jung, D.Y.,Jung, S.C.,Park, Y.H.,Lim, S.K. Elsevier Scientific Pub. Co 2015 Veterinary microbiology Vol.178 No.1

<P>This study compared the prevalence of Salmonella spp. and their antimicrobial susceptibilities in pigs from conventional and organic farms during 2012-2013 in Korea and characterized them by molecular methods. Altogether, 100 nontyphoid Salmonella were isolated: 47 from 1324 pigs (3.5%) from conventional farms and 53 from 641 pigs (8.3%) from organic farms. The most frequent serovar was Typhimurium (49%) followed by Panama (24%), 1,4,[5],12:i:- (5%), and Virchow (5%). Overall, the isolates were most often resistant to tetracycline (75%) followed by ampicillin (66%), streptomycin (57%), and gentamicin (44%). The prevalence of antimicrobial resistance, multi-drug resistance phenotype, and resistance to tetracycline, ampicillin, and gentamicin were significantly higher in swine Salmonella from conventional farms than those from organic farms. The most common resistance pattern was ampicillin-gentamicin-tetracycline (n = 16). All eight ceftiofur-resistant Salmonella identified produced CTX-M-15. Overall, decreased susceptibility to ciprofloxacin was observed in 39 isolates. Among them, a single isolate was positive for qnrS1 gene. An insertion sequence ISEcp1 was detected upstream of bla(CTX-M) gene in all isolates. The spread of bla(CTX-M-15) gene was attributed to combination of clonal expansion and horizontal dissemination mediated by IncHI2 plasmid. Multilocus variable number of tandem repeats analysis demonstrated clonal dissemination of S. Typhimurium and S. 1,4,[5],12:i:- strains in pigs. To our knowledge, this is the first report of bla(CTX-M-15) gene in S. Virchow from pigs and qnrS1 gene in S. Rissen from animals. This study also reports the first occurrence of Salmonella serovar 1,4,[5],12:i:- from Korea and CTX-M-15 producing Salmonella from pigs in Korea. (C) 2015 Elsevier B.V. All rights reserved.</P>

Characteristics of Adherence and Invasion of Staphylococcus lugdunensis to Human Oral Epithelial Cells

Cha, J. D.,Lee, S. H.,Jung, K. Y.,Lim, D.S.,Woo, W. H.,Kim, K. J. Korean Academy of Oral Biology and the UCLA Dental 1999 International Journal of Oral Biology Vol.24 No.2

Staphulococcus lugdunensis is one of the most common pathogens in coagulase-negative staphylococci. Adhesion and invasion of S. lugdunensis to oral epithelial cells were demonstrated by recovery of viable organisms from gentamicin-treated KB cells, human oral epidemoid carcinoma cells. Adhesion was found to be time dependent and increased linearly with increasing number of bacteria added (10^3-10^5 CFU/well). Bacterial adhesion to the KB cells occurred via a cytochalasin B- and D-insensitive process. To clarify the time point and characteristics of S. lugdunensis invasion of KB cells, bacteria (10^4 CFU/well) were cocultered for several different times (1-5 hr) with or without cytochalasin B (1 ㎍/ml), follwed by additional coculture for 2hr in the presence of gentamicin (100㎍/ml). No bacteria were recovered at 2 hr, but a few colonies were detected after 3 hr of coculture. In addition, cytochalasin B also did not affect invasion of S. lugdunensis into KB cells. The data obtained here demonstrate that S. lugdunensis can adhere to the KB cells via a cytoskeletal actin protein-independent process; however its invasion through the cellular membrane is unclear. These data suggest a tissue-specific characteristic of pathogenesis for S. lugdunensis in in vivo.

Rational Design of Low Cost and High Energy Lithium Batteries through Tailored Fluorine-free Electrolyte and Nanostructured S/C Composite

Agostini, M.,Lim, D.-H.,Sadd, M.,Hwang, J.-Y.,Brutti, S.,Heo, J. W.,Ahn, J. H.,Sun, Y. K.,Matic, A. Wiley (John WileySons) 2018 ChemSusChem Vol.11 No.17

<P>We report a new Li-S cell concept based on an optimized F-free catholyte solution and a high loading nanostructured C/S composite cathode. The Li2S8 present in the electrolyte ensures both buffering against active material dissolution and Li+ conduction. The high S loading is obtained by confining elemental S (approximate to 80%) in the pores of a highly ordered mesopores carbon (CMK3). With this concept we demonstrate stabilization of a high energy density and excellent cycling performance over 500 cycles. This Li-S cell has a specific capacity that reaches over 1000 mA hg(-1), with an overall S loading of 3.6 mg cm(-2) and low electrolyte volume (i.e., 10 mu L cm(-2)), resulting in a practical energy density of 365 Wh kg(-1). The Li-S system proposed thus meets the requirements for large scale energy storage systems and is expected to be environmentally friendly and have lower cost compared with the commercial Li-ion battery thanks to the removal of both Co and F from the overall formulation.</P>