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951.
Wanneng Ye Chaojing Lu Yajun Qi Xiaolin Liu Stephan Senz Sung Kyun Lee Dietrich Hesse 《Applied Physics A: Materials Science & Processing》2008,91(2):323-326
Ferroelectric Bi3.15Nd0.85Ti3O12 (BNdT) thin films of predominant 100/010/119 orientation were grown through a cheap and simple sol–gel process both on Nb-doped
(011)SrTiO3 and on (011)SrRuO3/(011)SrTiO3. Using rapid heating rates during crystallization, films containing 28% (100)/(010)-oriented grains plus 19% (119)-oriented
grains were obtained on SrRuO3/SrTiO3, while 30% (100)/(010)- and 18% (119)-oriented grains were obtained on Nb:SrTiO3. The films consist of columnar grains and 90° a–b domains exist in large BNdT grains. The BNdT thin films exhibit excellent
ferroelectric and dielectric properties with a remanent polarization 2Pr=39.2 μC/cm2 and a dielectric constant εr=184.5.
PACS 77.80.Fm; 77.80.Dj; 68.60.Wm; 68.55.Jk; 68.37.Lp 相似文献
952.
This paper reports on analytic calculations of the lineshapes for polarization spectroscopy of rubidium atoms. Under the use of a weak circularly polarized pump beam, the time-dependent population of each magnetic sublevel was obtained analytically from the rate equations up to the lowest order of the pump beam intensity, and the associated circular birefringence experienced by a counterpropagating probe beam was calculated. In particular, analytic forms of the polarization spectroscopy spectra were obtained for 87Rb and 85Rb atoms using the mean transit time crossing the pump beam, and the analytic results were compared with the numerical data, experimental results and Nakayama model’s results, showing a good agreement one another. 相似文献
953.
We study the coupled dynamics of a network and a particle system. Particles of density rho diffuse freely along edges, each of which is rewired at a rate given by a decreasing function of particle flux. We find that the coupled dynamics leads to an instability toward the formation of hubs and that there is a dynamic phase transition at a threshold particle density rho c. In the low density phase, the network evolves into a star-shaped one with the maximum degree growing linearly in time. In the high density phase, the network exhibits a fat-tailed degree distribution and an interesting dynamic scaling behavior. We present an analytic theory explaining the mechanism for the instability and a scaling theory for the dynamic scaling behavior. 相似文献
954.
Application of Huygens-Fresnel diffraction principle for high aspect ratio SU-8 micro-/nanotip array
A high-aspect-ratio (approximately 30) SU-8 micro-/nanotip array whose shape is defined by diffraction was fabricated by a single UV photolithography procedure and its exposed dose control. The fabrication result of the tip agrees well with the Rayleigh-Sommerfeld solution of the Huygens-Fresnel principle at wide observation distances. In a near field below distance 2 microm (only several times of wavelength), necking points also agree with the solution, although it is assumed that the distance is much larger than wavelength. It can be also applied to control the shape of the tip and to determine the critical dose D(c) of SU-8 and other photocurable polymers. 相似文献
955.
Rira Jung Seok Ho Yoon Minsung Kang Hun-Sik Kim Hyoung-Joon Jin 《Current Applied Physics》2008,8(6):807-809
Electrically conducting polymeric microspheres having an average diameter of 92 μm were prepared from composites of multiwalled carbon nanotubes (MWCNTs) and suspension-polymerized poly(vinyl chloride) (PVC) particles. Cetyl trimethylammonium bromide and sodium dodecylbenzene sulfonate were selected as the surfactants to stably disperse the MWCNTs in water. Strong adhesion of MWCNTs on the surfaces of the PVC microspheres was observed from the images obtained by field emission scanning electron microscopy. The amount of MWCNTs adsorbed on the microspheres was approximately 2 wt.%, determined by thermogravimetric analysis. The electrical conductivity of these composite-microspheres was remarkably increased upto 1.5 × 10−4 S/cm compared with that of the pure PVC microspheres (less than 10−14 S/cm), because of the electrically conducting MWCNTs on their surfaces. These microspheres also showed an electrorheological (ER) effect under an electric field (1.8 kV/mm) owing to the interfacial polarization of the MWCNTs-adsorbed microspheres, when they were dispersed in silicone oil (20 wt.%). The MWCNT-adsorbed PVC microspheres formed linear structures by electric force; i.e. the individual microspheres were connected to neighboring microspheres. 相似文献
956.
Hun-Sik Kim Yun Seok Chae Byung Hyun Park Jin-San Yoon Minsung Kang Hyoung-Joon Jin 《Current Applied Physics》2008,8(6):803-806
Multiwalled carbon nanotubes (MWCNTs) are considered to be the ideal reinforcing agent for high-strength polymer composites, because of their fantastic mechanical strength, high electrical and thermal conductivity and high aspect ratio. Polymer/MWCNTs composites are easily molded, and the resulting shaped plastic articles have a perfect surface appearance compared with polymer composites made using usual carbon or glass fibers. Good interfacial adhesion between the MWCNTs and the polymer matrix is essential for efficient load transfer in the composite. The ultrahigh strength polymer composites demand the uniform dispersion of the MWCNTs in the polymer matrix without their aggregation and the good miscibility between MWCNT and polymer matrix. This approach can also be applied to biodegradable synthetic aliphatic polyesters such as poly(l-lactide) (PLLA), which has received a great deal of attention due to environmental concerns. In this study, PLLA was melt-compounded with MWCNTs. A high degree of dispersion of the MWCNTs in the composites was obtained by grafting PLLA onto the MWCNTs (PLLA-g-MWCNTs). After oxidizing the MWCNTs by treating them with strong acids, they were reacted with l-lactide to produce the PLLA-g-MWCNTs. The mechanical properties of the PLLA/PLLA-g-MWCNT composite were higher than those of the PLLA/MWCNT composite. The electrical conductivity of the composites was determined by measuring the volume resistivity, which is a value of the resistance expressed in a unit volume by two-probe method. The thermal diffusivity and heat capacity of composites was measured by laser flash method, and the effects of modification of the MWCNT in PLLA matrix are discussed. 相似文献
957.
Lee JS Lee YS Noh TW Oh SJ Yu J Nakatsuji S Fukazawa H Maeno Y 《Physical review letters》2002,89(25):257402
The optical conductivity spectra of the quasi-two-dimensional Ca2-xSrxRuO4 (0.0< or =x< or =2.0) system were investigated. In the Mott insulating state, two electron correlation-induced peaks were observed about 1.0 and 1.9 eV, which could be explained using the 3-orbital Hubbard model. The low frequency peak showed a shift toward higher frequency as temperature was lowered, indicating that electron-phonon interactions play an important role in the orbital arrangements. From the systematic analysis, it was suggested that the antiferro-orbital and the ferro-orbital ordering states could coexist. 相似文献
958.
Chin J Oh J Jon SY Park SH Walsdorff C Stranix B Ghoussoub A Lee SJ Chung HJ Park SM Kim K 《Journal of the American Chemical Society》2002,124(19):5374-5379
Ion selective electrodes (ISE) based on three different tripodal receptors (5, 6, and 7) have been investigated for sensing ammonium ion. Each receptor is based on three pyrazole groups that can accept three H-bonds from the bound ammonium ion. The receptor based on 4-bromo-3,5-dimethylpyrazole (6) is the most sensitive with a detection limit for ammonium ion of 2.5 x 10(-5) M at pH 8. The detection limits for the receptors based on 2,3-dimethylpyrazole (5) and unsubstitued pyrazole (7) are 1.0 x 10(-4) and 2.0 x 10(-4) M, respectively. The selectivities of the receptors 5, 6, and 7 for sensing ammonium ion over potassium ion (logK(NH)4+(/K)+) are -2.8, -2.3, and -1.7, respectively. In contrast, the detection limit and the selectivity of a nonactin-based ISE are 2.2 x 10(-5) M and -1.3, respectively. Crystallographic studies reveal that 6 accepts three H-bonds from the bound ammonium and singly protonated receptor 5 forms three H-bonds with the bound water molecule. 相似文献
959.
By using the diffracted field of the LP(11) mode of a hollow-core optical fiber, we have produced a micrometer-sized, focused dark laser spot in the near field of the fiber. The minimum half-width of the dark spot is less than 1 mum . In particular, by masking the hollow core and metal coating the cladding with a microsphere, we blocked the light propagating in the cladding and obtained a clean dark spot, which may be useful in atom-optical experiments such as with atomic lenses, atom traps, and atom switches. 相似文献
960.
Control of wettability by anion exchange on Si/SiO2 surfaces 总被引:1,自引:0,他引:1
Chi YS Lee JK Lee SG Choi IS 《Langmuir : the ACS journal of surfaces and colloids》2004,20(8):3024-3027