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921.
Yoshiteru Amemiya Tomohiro Tokunaga Yuichiro Tanushi Shin Yokoyama 《Optical Review》2009,16(3):247-251
Electric-field drive optical modulators using a Si ring resonator were fabricated on silicon-on-insulator (SOI) wafers. The
fabricated resonators consisted of Si waveguides with width and thickness of 1.0 and 0.3 μm, respectively. In order to induce
the linear electro-optic (EO) effect in the Si core layer, the strain was applied by covering the layer with Si3N4 film (0.26 μm thick) deposited by low pressure chemical vapor deposition (LPCVD) at 750 °C. The vertical electric-field was
applied to the Si waveguide through the top and bottom cladding layers, and the optical output from the drop port at the resonance
wavelength was measured. At a wavelength of 1501.6 nm, the optical modulation of 33% was obtained at 200V (electric-field
at the silicon surface ∼3 × 105 V/cm, nearly the breakdown field). The resonance wavelength was shifted toward the short wavelength side by applying both
positive and negative voltages, this shift was explained by carrier concentration modulation. The linear EO effect in the
Si core layer was not observed, presumably because the strain in the Si core layer was too small. 相似文献
922.
Yonggang Gao Lin Gu Yusheng Qin Xianhong Wang Fosong Wang 《Journal of polymer science. Part A, Polymer chemistry》2012,50(24):5177-5184
Low‐molecular weight oligo(carbonate‐ether) diols are important raw materials for polyurethane formation, which with tunable carbonate unit content (CU) may endow new thermal and mechanical performances to polyurethane. Herein, facile synthesis of oligo(carbonate‐ether) diols with number average molecular weight (Mn) below 2000 g mol?1 and CU tunable between 40% and 75% are realized in high activity by immortal copolymerization of CO2/propylene oxide (PO) using zinc‐cobalt double metal cyanide complex (Zn‐Co‐DMCC) in the presence of sebacic acid (SA). Mn of the oligomer is in good linear relationship to the mole ratio of PO and SA (PO/SA) and hence can be precisely controlled by adjusting PO/SA. Besides, the molecular weight distribution is quite narrow due to the rapid reversible chain transfer in the immortal copolymerization. High pressure and low temperature are favorable for raising CU. In all the reactions, the weight fraction of propylene carbonate (WPC) can even be controlled as low as 2.0 wt %, and the catalytic activity of Zn‐Co‐DMCC is above 1.0 kgg?1 cat. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 相似文献
923.
M. Ivković M.A. Gonzalez S. Jovićević M.A. Gigosos N. Konjević 《Spectrochimica Acta Part B: Atomic Spectroscopy》2010
The results of an experimental study of the He I 447.1 nm line and its forbidden component at high electron number density are presented and compared with profiles calculated using computer simulation method. Michelson interferometer at 632.8 nm was used to measure plasma electron number density in the range (1–7) × 1023 m− 3 while electron temperatures for the same experimental conditions in the range of 25 000 K to 35 000 K were determined using several spectroscopic techniques. The agreement of experimental overall line shape with computer simulation results is within 10% of what is well within theoretical and experimental uncertainty. This favorable comparison enabled the development of a simple approximate formula for the evaluation of electron number density from the measurement of wavelength separation between peaks of allowed and forbidden lines. This technique of plasma diagnostics is not sensitive to the presence of self-absorption of strong He I allowed line. The derivation of approximate formula with estimated accuracy of 15% was followed by detailed comparison with other experimental and theoretical data. 相似文献
924.
Po‐Sheng Chen Yi‐Chang Liu Chia‐Her Lin Bao‐Tsan Ko 《Journal of polymer science. Part A, Polymer chemistry》2010,48(16):3564-3572
Two novel sulfonate phenol ligands—3,3′‐di‐tert‐butyl‐2′‐hydroxy‐5,5′,6,6′‐tetramethyl‐biphenyl‐2‐yl 4‐X‐benzenesulfonate (X?CF3, LCF3 ‐H, and X?OCH3, LOMe ‐H)—were prepared through the sulfonylation of 3,3′‐di‐tert‐butyl‐5,5′,6,6′‐tetramethylbiphenyl‐2,2′‐diol with the corresponding 4‐substituted benzenesulfonyl chloride (1 equiv.) in the presence of excess triethylamine. Magnesium (Mg) complexes supported by sulfonate phenoxide ligands were synthesized and characterized structurally. The reaction of MgnBu2 with L‐H (2 equiv.) produces the four‐coordinated monomeric complexes ( LCF3 )2Mg ( 1 ) and ( LOMe )2Mg ( 2 ). Complexes 1 and 2 are efficient catalysts for the ring‐opening polymerization of ε‐caprolactone (ε‐CL) and trimethylene carbonate (TMC) in the presence of 9‐anthracenemethanol; complex 1 catalyzes the polymerization of ε‐CL and TMC in a controlled manner, yielding polymers with the expected molecular weights and narrow polydispersity indices (PDIs). In ε‐CL polymerization, the activity of complex 1 is greater than that of complex 2 , likely because of the greater Lewis acidity of Mg2+ metal caused by the electron‐withdrawing substitute trifluoromethyl (? CF3) at the 4‐position of the benzenesulfonate group. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3564–3572, 2010 相似文献
925.
Guowei Wang Xiaoshan Fan Junlian Huang 《Journal of polymer science. Part A, Polymer chemistry》2010,48(23):5313-5321
4μ‐A2B2 star‐shaped copolymers contained polystyrene (PS), poly(isoprene) (PI), poly(ethylene oxide) (PEO) or poly(ε‐caprolactone) (PCL) arms were synthesized by a combination of Glaser coupling with living anionic polymerization (LAP) and ring‐opening polymerization (ROP). Firstly, the functionalized PS or PI with an alkyne group and a protected hydroxyl group at the same end were synthesized by LAP and then modified by propargyl bromide. Subsequently, the macro‐initiator PS or PI with two active hydroxyl groups at the junction point were synthesized by Glaser coupling in the presence of pyridine/CuBr/N,N,N ′,N ″,N ″‐penta‐methyl diethylenetri‐amine (PMDETA) system and followed by hydrolysis of protected hydroxyl groups. Finally, the ROP of EO and ε‐CL monomers was carried out using diphenylmethyl potassium (DPMK) and tin(II)‐bis(2‐ethylhexanoate) (Sn(Oct)2) as catalyst for target star‐shaped copolymers, respectively. These copolymers and their intermediates were well characterized by SEC, 1H NMR, MALDI‐TOF mass spectra and FT‐IR in details. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010 相似文献
926.
927.
928.
929.
对于静电场,由普遍的格林互易定理得出特殊情形下的格林互易定理.应用该定理推导出均匀带电圆环的数种在形式上互不相同的静电势分布解式. 相似文献
930.