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991.
Jeom Sik Song Sukmin Lee Gook Chan Cha Sung Hee Jung Seo Yoon Choi Kyung Hoon Kim Mu Seong Mun 《应用聚合物科学杂志》2005,96(4):1095-1101
We studied the preparation of antimicrobial silicone rubbers of improved interfacial strength, which could be formed with the ion beam assisted deposition (IBAD) technique for coating metallic or inorganic materials (silver (Ag), Copper (Cu), and Hydroxyapatite(HAp)/TiO2) on the silicone surface. Those coating materials provide high product safety as well as outstanding antimicrobial activity. The deposition methodology is composed of pre‐etching with oxygen gas, vaporizing the coating materials, and post‐treatment with Ar ion. With the evaporation of the coating materials, the Ar beam was focused on the substrate to assist deposition. It was found out that the ion assisting depositions in the IBAD process give a prominent enhancement in adhesion between silicone rubbers and coatings of Ag and Cu. The HAp/TiO2 coating layer was easily dissolved in aqueous saline solution. All deposited layers display high antimicrobial activities against Staphlococcus aureus (ATCC 6538) and Escherichia coil (ATCC 25,922), showing 99.9% reduction of bacteria, respectively. In a cytotoxicity test, the Ag and HAp/TiO2 coated silicone shows a decrease of cytotoxicity, while the Cu coating leads to a slight increase of cytotoxicity. The result on the surface modifications of silicone rubber will be employed in further study for applications of medical or rehabilitation devices. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1095–1101, 2005 相似文献
992.
The glass transitions of acrylonitrile-butadiene rubber (NBR)/organoclay nanocomposites with various silicate contents were investigated using positron annihilation lifetime spectroscopy (PALS). The nanocomposites were prepared through melt intercalation of NBR with various concentrations of organoclay (OC30B) modified with the organic modifier, methyl tallow bis(2-hydroxyethyl) quaternary ammonium (MT2EtOH), i.e., Cloisite® 30B. X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HR-TEM) measurements of the NBR/OC30B nanocomposites showed that the NBR chains were intercalated between the silicate layers, thereby increasing the gallery heights of the organosilicates. The glass transition temperature of NBR was determined using differential scanning calorimetry (DSC). However, it seemed to be very difficult to clearly resolve the very small differences in Tgs caused from various loading of nanosized silicate in NBR/OC30B nanocomposites. Hence, we performed positron annihilation lifetime spectroscopy (PALS) on NBR/OC30B nanocomposites containing various amounts of OC30B (1-10 wt%). Significant changes in the temperature dependencies of free volume parameters (i.e., lifetimes and intensities) were observed at the transition temperature, Tg,PALS, and the Tg,PALS values were found to increase with increasing organoclay content in the samples. These observations are consistent with PALS having a higher sensitivity in the detection of very small changes in free volume properties. The present findings thus highlight the usefulness of PALS for studying phase transition phenomena in polymeric materials with nanoscale structural variations. 相似文献
993.
Youn-Woo Lee Myoung Seup So Ju Weon Lee Sung Taik Chung Kyung Ho Row 《Korean Journal of Chemical Engineering》1996,13(6):578-584
A Chromatographic retention behavior of five deoxyribonucleosides (dCyd, dUrd, dGuo, dThd, and dAdo) with respect to the mobile
phase composition was studied under isocratic conditions of reversed phase High Performance Liquid Chromatography (RP-HPLC).
The volume fraction (F) of organic modifier was changed from 0.05 to 0.30, and to 0.12 for methanol and acetonitrile, respectively.
The experimental data of nitro and steroid compound were also considered for comparison of five retention models with various
class of samples. The Langmuir-type retention model (k′= A+B/F) with two parameters shows excellect agreements between the
experimental capacity factors and calculated values although the values by the log-scale quadratic model with three parameters
(log k′= LF2+MF+N) are closer. Unlike the other four retention models, the slope B of the Langmuir-type retention model can characterize
the properties of solute and organic modifier simultaneously. For each solute, the intercepts A calculated for acetonitrile
and methanol as organic modifiers are coincident closely. 相似文献
994.
Soo Ho Kim Kwang Hoon Lee Baek Seok Seong Gyeung-Ho Kim Jong Sung Kim Young Soo Yoon 《Korean Journal of Chemical Engineering》2006,23(6):961-964
Recently, lithium titanium oxide material has gained renewed interest in electrodes for lithium ion rechargeable batteries.
We investigated the influence of excess Li on the structural characteristics of lithium titanium oxide synthesized by the
conventional powder calcination method, considering the potential for mass production. The lithium excess ratio is controlled
by using different weight of Li2CO3 powder during calcination. X-ray diffraction (XRD) measurement for the synthesized powder showed that the lithium titanium
oxide material with excess lithium content had a spinel crystal structure as well as a different crystal one. In addition,
high resolution transmission electron microscopy (HRTEM) and field emission scanning electron microscopy (FESEM) measurement
revealed that the lithium titanium oxide powders with a lithium excess ratio of 5–20% exhibited a two phase formation. Inductively
coupled plasma — atomic emission spectrometer (ICP-AES) and energy dispersive x-ray spectroscopy (EDX) measurements were used
to analyze composition of the lithium titanium oxide powder. These results suggested that the conventional calcination method,
considering the potential for mass production, formed two phases according to the Li excess amount in initial raw materials. 相似文献
995.
Fazli Akram Rizwan Ahmed Malik Salman Ali Khan Ali Hussain Soonil Lee Myang-Hwan Lee Choi Hai In Tae-Kwon Song Won-Jeong Kim Yeon Soo Sung Myong-Ho Kim 《Journal of Electroceramics》2018,41(1-4):93-98
In the present work, composition dependent crystal structure, ferroelectric, piezoelectric, and temperature dependent dielectric properties of the BiGaO3-modified (1–x)(0.65Bi1.05FeO3–0.35BaTiO3) (BFBT35–xBG, where x?=?0.00–0.03) lead-free ceramics were systematically investigated by solid-state reaction method, followed by water quenching process. The substitution of BG successfully diffuses into the lattice of the BFBT ceramics, without changing the pseudo-cubic structure of the samples. The scanning electron microscopy (SEM) results revealed that the average grain size was increased with BG-content in BFBT system. The BFBT–xBG ceramics showed a maximum in permittivity (?max) at temperatures (Tmax) above 500 °C in the compositional range of 0.00?≤?x?≤?0.03. The electro-strain is measured to be 0.125% (d*33 ~ 250 pm/V) under unipolar fields (5 kV/mm) for BFBT–0.01BG ceramics. The same composition (x?=?0.01), large static piezoelectric constant (d33 ~ 165 pC/N) and electromechanical coupling factor (kp ~ 25%) were obtained. The above investigated characterizations suggests that BFBT–BG material is favorable for piezoelectric and high temperature applications. 相似文献
996.
Jindeog Chung Jangyeon Lee Bongzoo Sung Samok Koo 《Journal of Mechanical Science and Technology》2003,17(5):776-783
A low speed wind tunnel test was conducted for full-scale model of an unmanned aerial vehicle (UAV) in Korea Aerospace Research
Institute (KARI) Low Speed Wind Tunnel (LSWT). The purpose of the presented paper is to illustrate the general aerodynamic
and performance characteristics of the UAV that was designed and fabricated in KARI. Since the testing conditions were represented
minor portions of the load-range of the external balance system, the repeatability tests were performed at various model configurations
to confirm the reliability of measurements. Variations of drag-polar by adding model components such as tails, landing gear
and test boom are shown, and longitudinal and lateral aerodynamic characteristics after changing control surfaces such as
aileron, flap, elevator and rudder are also presented. To explore aerodynamic characteristics of an UAV with model components
build-up and control surface deflections, lift curve slope, pitching moment variation with lift coefficients and drag-polar
are examined. The discussed results might be useful to understand the general aerodynamic characteristics and drag pattern
for the given UAV configuration. 相似文献
997.
Kyu-Il?HanEmail author Seok-?Su?Yee Sung?Hyun?Park Suk-?Ho?Lee Dong-?Hyun?Cho 《Journal of Mechanical Science and Technology》2002,16(9):1102-1111
The study focuses on the heat transfer performance of two-phase closed thermosyphons with plain copper tube and tubes having
50, 60, 70, 80, 90 internal grooves. Three different working fluids (distilled water, methanol, ethanol) are used with various
volumetric liquid fill charge ratio from 10 to 40%. Additional experimental parameters such as operating temperature and inclination
angle of zero to 90 degrees are used for the comparison of heat transfer performance of the thermosyphon. Condensation and
boiling heat transfer coefficients, heat flux are obtained using experimental data for each case of specific parameter. The
experimental results are assessed and compared with existing correlations. The results show that working fluids, liquid fill
charge ratio, number of grooves and inclination angle are very important factors for the operation of thermosyphons. The relatively
high rate of heat transfer is achieved when the thermosyphon with internal grooves is used compared to that with plain tube.
The optimum liquid fill charge ratio for the best heat transfer performance lies between 25% and 30%. The range of the optimum
inclination angle for this study is 20°-30° from the horizontal position. 相似文献
998.
A Defined and Flexible Pocket Explains Aryl Substrate Promiscuity of the Cahuitamycin Starter Unit–Activating Enzyme CahJ
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Dr. Ashootosh Tripathi Dr. Sung Ryeol Park Dr. Andrew P. Sikkema Dr. Hyo Je Cho Dr. Jianfeng Wu Brian Lee Dr. Chuanwu Xi Prof. Janet L. Smith Prof. David H. Sherman 《Chembiochem : a European journal of chemical biology》2018,19(15):1595-1600
Cahuitamycins are biofilm inhibitors assembled by a convergent nonribosomal peptide synthetase pathway. Previous genetic analysis indicated that a discrete enzyme, CahJ, serves as a gatekeeper for cahuitamycin structural diversification. Here, the CahJ protein was probed structurally and functionally to guide the formation of new analogues by mutasynthetic studies. This analysis enabled the in vivo production of a new cahuitamycin congener through targeted precursor incorporation. 相似文献
999.
An experimental apparatuses and measuring system have been made to obtain characteristics connected with evaporation, ignition delay, combustion of a freely falling liquid fuel droplet in high temperature and high pressure gas stream. In this study some systematic experiments were performed to test the utility of the system. The newly devised apparatus was ensured reliability and utility from the tentative experimental results. 相似文献
1000.
Ji?Hyuck?Yang Kang?Yong?LeeEmail author Taek?Sung?Lee She-Xu?Zhao 《Journal of Mechanical Science and Technology》2004,18(3):357-369
The purposes of the paper are to analyze the fracture phenomenon by delamination and cracking when the encapsulant of plastic
IC package with polyimide coating shows viscoelastic behavior under hygrothermal loading in the IR soldering process and to
suggest more reliable design conditions by the approaches of stress analysis and fracture mechanics. The model is the plastic
SOJ package with the polyimide coating surrounding chip and dimpled diepad. On the package without cracks, the optimum position
and thickness of polyimide coating to decrease the maximum differences of strains at the bonding surfaces of parts of the
package are studied. For the model delaminated fully between the chip and the dimpled diepad, C (t)-integral values are calculated
for the various design variables. Finally, the optimal values of design variables to depress the delamination and crack growth
in the plastic IC package are obtained. 相似文献