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排序方式: 共有480条查询结果,搜索用时 31 毫秒
121.
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123.
Yirang Lim Seung-Heon Lee Yan Li Seung-Hyun Kim Tae Hui Kang Yung Doug Suh Soojin Lee Yongjin Kim Gi-Ra Yi 《Particle & Particle Systems Characterization》2020,37(4):1900405
For an optically transparent, UV-reflective film, hollow silica nanospheres smaller than the visible wavelength (<λvis) are prepared and assembled into colloidal glasses, of which interstices are then backfilled with a polymer. The polymer refractive index is matched with the silica shell to minimize backscattering in the visible range, and the average distance between the hollow silica particles is adjusted by tuning the shell thickness to satisfy the interference resonance condition for a UV selective reflection. The resulting composite film shows a strong UV reflection as expected, but it is translucent in visible light due to non-negligible backscattering, which may be caused by large defects or fluctuation of the particle concentration. In order to avoid such backscattering, another polymer is introduced of which the refractive index is matched with the average refractive index of the hollow nanospheres. This allows an optically transparent film that selectively reflects the UV light. Furthermore, spherical aggregates of hollow silica nanospheres called “supraballs” are prepared and their average refractive index is matched with a solvent by adjusting the mixture ratio of water and ethylene glycol, which yields an optically transparent solution, selectively reflecting UV. 相似文献
124.
Kaliyamoorthy Panneerselvam Tian‐Huey Lu Ta‐Yung Chi Shu‐Fang Tung Chung‐Sun Chung 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(4):e128-e129
The crystal structure of the title compound, [CoCl(C18H37N4O2){ZnCl3}], has been determined by X‐ray diffraction.C‐meso‐5,5,7,12,12,14‐Hexamethyl‐1,4,8,11‐tetraazacyclotetradecane‐N‐acetate acts as a bridging ligand to coodinate with CoIII and ZnII ions. The CoIII ion is six‐coordinate in a nearly octahedral environment provided by one Cl atom, four N atoms of the bridging ligand, and one O atom. The ZnII ion is four‐coordinate in a distorted tetrahedral environment completed by three Cl atoms and an O atom of the bridging ligand. 相似文献
125.
R. S. Chen D. X. Wang A. H. Yang Edward K. N. Yung 《International Journal of Infrared and Millimeter Waves》2001,22(8):1223-1242
In this paper, A numerical technique, called short-open calibration (SOC), in conjunction with edge-based finite element method (FEM) is employed to analyze millimeter wave circuit that can be segmented into two distinct section: static model of feedlines and dynamic model of circuit discontinuity. The derivation of reflection coefficient of 3D discontinuities is arranged in two steps. In the first step, this SOC technique is incorporated into the FEM for mesh truncation of computaional domain. In this way, much faster convergence is achieved for large-sparse linear matrix equations from FEM by this termination than by perfectly matching layers (PML). The field distribution of the dominated mode in uniform feedlines and entire circuit is obtained individually by exciting a pair of even and odd impressed voltages along the struture. In step two, Scattering parameters based on the voltages and current defintion is calculated by integral of electric and magnetic fields. Numerical solutions for a class of planar circuit discontuities are very well compared with those published in the available literatures. 相似文献
126.
R. S. Chen Z. Liu K. N. Yung 《International Journal of Infrared and Millimeter Waves》1996,17(11):1937-1945
In this article the theoretical and experimental performances of a Gunn harmonically synchronized frequency divider are presented. The results show that such a divider has a 96-32GHz division, with 15-mW output power over the operating band greater than 1400MHz at 10-mW input power level. 相似文献
127.
Three‐dimensional computations have been performed to study the flow through a symmetric sudden expansion with an expansion ratio of 3 at low Reynolds numbers. The aspect ratio of the flow channel is allowed to vary within a wide range to examine its influence on the flow which bifurcates from a symmetric state to an asymmetric state. The results reveal that the critical Reynolds number of the symmetry‐breaking bifurcation increases while the aspect ratio is reduced. The flow behaviour near the side walls is illustrated by using limiting streamlines. The origin of the singular points identifiable on the side wall can be traced back to the recirculating flows and the relevant reattachment/separation points in the core of the channel. It is seen that the determination of the exact critical Reynolds number is not trivial because it depends on how to define asymmetric flow. Computations have also been conducted to show that a slight asymmetry in the channel geometry causes a smooth transition from symmetric to non‐symmetric states. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
128.
Scanning tunnelling microscopy and X-ray Photoelectron Spectroscopy were conducted on magnetron sputtered WO3 thin films, following a sequence of ultra high vacuum anneals from 100 °C to 900 °C. Annealing from 100 °C to 400 °C induced an upward surface band bending of about 0.3 eV, attributed to the oxygen migration from the bulk to the surface, but no changes in the surface topography. Chemical changes occurred from 600 °C to 800 °C, associated with the formation of secondary oxide species. STM imaging showed that the film surface consists of amorphous particles 35 nm in size up to 600 °C, while higher temperatures resulted in an increase in particle size. Crystallisation of the nanoparticles started to occur after annealing at 600 °C. The implications in terms of gas sensing are discussed. 相似文献
129.
Dettlaff-Weglikowska U Skákalová V Graupner R Jhang SH Kim BH Lee HJ Ley L Park YW Berber S Tománek D Roth S 《Journal of the American Chemical Society》2005,127(14):5125-5131
Chemical modification by SOCl2 of an entangled network of purified single-wall carbon nanotubes, also known as 'bucky paper', is reported to profoundly change the electrical and mechanical properties of this system. Four-probe measurements indicate a conductivity increase by up to a factor of 5 at room temperature and an even more pronounced increase at lower temperatures. This chemical modification also improves the mechanical properties of SWNT networks. Whereas the pristine sample shows an overall semiconducting character, the modified material behaves as a metal. The effect of SOCl2 is studied in terms of chemical doping of the nanotube network. We identified the microscopic origin of these changes using SEM, XPS, NEXAFS, EDX, and Raman spectroscopy measurements and ab initio calculations. We interpret the SOCl2-induced conductivity increase by p-type doping of the pristine material. This conclusion is reached by electronic structure calculations, which indicate a Fermi level shift into the valence band, and is consistent with the temperature dependence of the thermopower. 相似文献
130.
Yung‐Sen Lin Huang‐Ming Liu Chung‐Wei Tsai 《Journal of Polymer Science.Polymer Physics》2005,43(15):2023-2038
Surface modification of polyimide films Kapton E(N) and Upilex S by nitrogen plasmas were investigated for their enhanced adhesion strength with sputtered coppers. Peel tests demonstrate this improvement, with peel strengths of 7 and 12 N/m for unmodified Kapton E(N) and Upilex S, and 1522 and 1401 N/m for nitrogen plasma‐modified Kapton E(N) and Upilex S at certain plasma conditions. Atomic force microscopy (AFM) and the sessile drop method indicated the surface roughness, and the surface energy of polyimide films were highly increased by nitrogen plasmas. This study shows the enhanced adhesion strengths of polyimide films with sputtered coppers by nitrogen plasmas, and these nitrogen plasmas were strongly affected by the surface characteristics of polyimide films. Electron spectroscopy for chemical analysis (ESCA) observed the increased surface energy on polyimide films by nitrogen plasmas was due to the increased surface composition of O and the increased chemical bond of C? O. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2023–2038, 2005 相似文献