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971.
The liquid crystalline properties of two series of non-symmetric liquid crystal dimers consisting of cholesterol and Schiff base moieties interconnected by ω-oxyalkanoyl spacers of varying length are compared: one series (SBOC- n ) carry the octyloxy tail on the Schiff base mesogen, and the other (SBOF- n ) a perfluoroheptylmethyloxy tail. In general, compounds with the fluorinated alkoxy tail exhibited mesophases over a much wider temperature range than those with the alkoxy tail. The latter series favoured the formation of more diverse mesophases than the former. SBOC-4, -5 and -7, and SBOF-4, -5 and -10 formed the chiral smectic C phase. 相似文献
972.
Won Seok Chung Ohmyoung Kwon Du Seon Choi Seungho Park Young Ki Choi Joon Sik Lee 《Superlattices and Microstructures》2004,35(3-6):325
This paper suggests and demonstrates a novel flow measurement technique: tunable AC thermal anemometry, that allows simple integration, robust measurement and extremely high accuracy. The principle and simple theoretical analysis of the technique are presented. To find the optimal condition at which the phase lag becomes most sensitive to the flow speed change, the phase lag was measured scanning the heating frequency from 1 to 100 Hz, while the flow speed of ethanol was increased stepwise from 0 to 40 mm/s. The sensitivity of the phase lag depended on the heating frequency and the flow speed. It was possible to measure the average flow speed of 0.7 mm/s with the resolution of 0.1 mm/s at 4 Hz. 相似文献
973.
974.
Yuan Li Eun J. Park Kwon T. Lim Keith P. Johnston Peter F. Green 《Journal of Polymer Science.Polymer Physics》2007,45(11):1313-1324
It has recently been shown that thin polymer films in the nanometer thickness range exhibit anomalous swelling maxima in supercritical CO2 (Sc‐Co2) in the vicinity of the critical point of CO2. The adsorption isotherm of CO2 on carbon black, silica surfaces, porous zeolites, and other surfaces, is known to exhibit anomalous maxima under similar CO2 conditions. It is believed that because CO2 possesses a low cohesive energy density, there would be an excess amount of CO2 at the surfaces of these materials and hence the CO2/polymer interface. This might cause excess CO2 in the polymer films near the free surface, and hence the swelling anomaly. In addition, an excess of CO2 would reside at the polymer/substrate and polymer/CO2 interfaces for entropic reasons. These interfacial effects, as have been suggested, should account for an overall excess of CO2 in a thin polymer film compared to the bulk, and would be responsible for the anomalous swelling. In this study, we use in situ spectroscopic ellipsometry to investigate the role of interfaces on the anomalous swelling of polymer thin films of varying initial thicknesses, h0, exposed to Sc‐CO2. We examined three homopolymers, poly(1,1′‐dihydroperflurooctyl methacrylate) (PFOMA), polystyrene (PS), poly(ethylene oxide) (PEO), that exhibit very different interactions with Sc‐CO2, and the diblock copolymer of PS‐b‐PFOMA. We show that the anomalous swelling cannot be solely explained by the excess adsorption of CO2 at interfaces. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1313–1324, 2007 相似文献
975.
We report the implementation of a transponder to transmit eight channels of a Gigabit Ethernet signal transparently in an Optical Transport Network(OTN). This transponder is based on framing technologies for Ethernet over SDH over OTN. This framing structure offers an attractive option for carrying data traffic over the OTN. 相似文献
976.
977.
Nak Eun Cho Oh Sang Kwon H.M. Srivastava 《Journal of Mathematical Analysis and Applications》2004,300(2):353-520
Making use of a multiplier transformation, which is defined here by means of the Hadamard product (or convolution), the authors introduce some new subclasses of meromorphic functions and investigate their inclusion relationships and argument properties. Some integral-preserving properties in a given sector are also considered. 相似文献
978.
S. Fähler U. Hannemann M. Weisheit V. Neu S. Melcher S. Leinert S.C. Wimbush A. Singh A. Kwon B. Holzapfel L. Schultz 《Applied Physics A: Materials Science & Processing》2004,79(4-6):1529-1531
Pulsed laser deposition from elemental targets was used to prepare highly textured hard magnetic Nd–Fe–B and Fe–Pt films with coercivities of 2 T and 5.2 T, respectively. In situ methods such as reflection high energy electron diffraction and Auger electron spectroscopy were applied to analyse film composition and structure during growth. Optimisation of the hard magnetic properties is discussed together with the specific advantages of pulsed laser deposition. PACS 81.15.Fg; 75.50.Ww; 75.50.Vv 相似文献
979.
Yong Hee Kim Young June Hong Ku Youn Baik Gi Chung Kwon Jin Joo Choi Guang Sup Cho Han Sup Uhm Do Young Kim Eun Ha Choi 《Plasma Chemistry and Plasma Processing》2014,34(3):457-472
Non-thermal atmospheric pressure plasma jet could generate various kinds of radicals on biosolution surfaces as well as inside the biosolutions. The electron temperature and ion density for this non-thermal plasma jet have been measured to be about 0.8~1.0 eV and 1 × 1013 cm?3 in this experiment, respectively, by atmospheric pressure collisional radiative model and ion collector current. In this context, the hydroxyl OH radical density inside the biosolutions has been also investigated experimentally by ultraviolet absorption spectroscopy when the Ar non-thermal plasma jet has been bombarded onto them. It is found that the emission and absorption profiles for the other reactive oxygen species such as NO (226 nm) and O2*? (245 nm) are shown to be very small inside the biosolution in comparison with those for the OH radical species. It is found that the densities of OH radical species inside the biosolutions are higher than those on the surface in this experiment. The densities of the OH radical species inside the deionized water, Dulbecco’s modified eagle medium, and phosphate buffered saline are measured to be about 2.1 × 1016, 1.1 × 1016, and 1.0 × 1016 cm?3, respectively, at 2 mm downstream from the surface under optimized Ar gas flow of 200 sccm. It is also found that the critical hydroxyl OH radical density for the lung cancer H460 cells to experience an apoptosis is observed to be around 0.3 × 1016 cm?3 under 1 min plasma exposure in this experiment. 相似文献
980.
Ji‐Hong Kim Zhaomo Tian Min‐Gyu Kim Soon‐Ju Kwon 《Surface and interface analysis : SIA》2014,46(5):289-292
Adsorption/interaction of Carbon monoxide (CO) on a catalytic surface is the key step in electrochemical conversion of CO2 for environmental consideration. Copper (Cu) is known to be the most efficient catalyst for this purpose. Thus, this paper investigates effects of CO adsorption on the electronic/atomic state of polycrystalline Cu surface by using x‐ray absorption spectroscopy (XAS). X‐ray absorption near‐edge structure (XANES) tells that the Cu K‐edge shift +0.2 eV on adsorbing CO. Extended x‐ray absorption fine structure (EXAFS) analysis informs that CO adsorption disturbs Cu surface, i.e. increase of Cu‐Cu bonding distance and decrease of the coordination number of the first nearest neighbor. Both the results of XANES and EXAFS imply decrease of d‐electron density of Cu on the adsorption. Demonstrated is that XAS is very useful in studying the surface phenomena of a catalyst but requires further efforts. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献