A novel bifluoro-monomer containing naphthalene moieties was synthesized and characterized by using FTIR, MS and NMR. Different poly(aryl ether ketone)s based on 1,4-bis(4,4′-fluorobenzoyl) naphthalene were prepared ...A novel bifluoro-monomer containing naphthalene moieties was synthesized and characterized by using FTIR, MS and NMR. Different poly(aryl ether ketone)s based on 1,4-bis(4,4′-fluorobenzoyl) naphthalene were prepared via aromatic nucleophilic substitution reaction. The polymers with a high molecular weight can be readily obtained due to the highly activity of the used monomer. 3F-PEEK-nK and 6F-PEEK-nK polymers were determined to exhibit good thermal stabilities with high T-g of 450 K and 457 K, respectively. Moreover, these polymers show a satisfactory solubility and can be cast into flexible and transparent films.展开更多
A kind of highly fluorinated bisphenol monomer was synthesized. It was characterized by FTIR, 1H NMR and MS. 6F PEEK and 6F PEEKK were prepared via aromatic nucleophilic substitution, based on [3,5 di(trifluoromethyl)...A kind of highly fluorinated bisphenol monomer was synthesized. It was characterized by FTIR, 1H NMR and MS. 6F PEEK and 6F PEEKK were prepared via aromatic nucleophilic substitution, based on [3,5 di(trifluoromethyl)] phenylhydroquinone and difluoro monomers. The T gs of 6F PEEK and 6F PEEKK are 423 and 436 K, respectively. The 6F polymers exhibit a high thermal stability and good solubility. The flexible, creasable and transparent thin films were easily obtained by compression moulding and solution casting.展开更多
Negative refraction and subwavelength imaging properties of a two-dimensional （2D） photonic crystal （PC） slab are studied by the finite-difference time-domain method. The PC consists of a triangular lattice of air...Negative refraction and subwavelength imaging properties of a two-dimensional （2D） photonic crystal （PC） slab are studied by the finite-difference time-domain method. The PC consists of a triangular lattice of air holes immersed in a dielectric. For a certain frequency range in the third photonic band, the directions of the group velocities and the phase velocities can be opposite, so the PC can work as a kind of negative refractive-index material. The light radiated from a point source can form a subwavelength image spot through the PC slab. Negative refraction and an effective refractive index of the PC slab n = -1 can be achieved for the incident wave with its incident angle within a certain range.展开更多
The fluorescence spectra of synthetic food dyes of sunset yellow and tartrazine are analyzed. The fluorescence peak wavelengths of sunset yellow and tartrazine are 576 and 569 nm, respectively, while the fluorescence ...The fluorescence spectra of synthetic food dyes of sunset yellow and tartrazine are analyzed. The fluorescence peak wavelengths of sunset yellow and tartrazine are 576 and 569 nm, respectively, while the fluorescence spectra widths are 480-750 and 500 750 nm induced by ultraviolet light between 310-400 nm. The fluorescence spectra of sunset yellow overlap heavily with those of tartrazine, so it is difficult to distinguish them. Based on the principle of radial basis function neural network, a neural network is obtained from the training of the 14 groups of experimental data. The results show that the species of sunset yellow and tartrazine could be recognized accurately. This method has potential applications in other synthetic food dyes detection and food safety inspection.展开更多
A four-level tripod active-Raman-gain scheme is analyzed for obtaining phase-controlled gain, phase shift, and group velocity at room temperature. The scheme can be used to eliminate significant probe field atten- uat...A four-level tripod active-Raman-gain scheme is analyzed for obtaining phase-controlled gain, phase shift, and group velocity at room temperature. The scheme can be used to eliminate significant probe field atten- uation or distortion which is unavoidable in the scheme based on electromagnetically induced transparency. It is shown that the intensity gain, phase shift, and group velocity of a probe field can be simultaneously manipulated by changing the relative phase of two pump fields. The scheme is also different from that proposed recently by Deng et al. where a probe-field gain always exists. New features of the scheme presented here raise the possibility of designing rapidly responding optical switches and gates for optical information processing.展开更多
文摘A novel bifluoro-monomer containing naphthalene moieties was synthesized and characterized by using FTIR, MS and NMR. Different poly(aryl ether ketone)s based on 1,4-bis(4,4′-fluorobenzoyl) naphthalene were prepared via aromatic nucleophilic substitution reaction. The polymers with a high molecular weight can be readily obtained due to the highly activity of the used monomer. 3F-PEEK-nK and 6F-PEEK-nK polymers were determined to exhibit good thermal stabilities with high T-g of 450 K and 457 K, respectively. Moreover, these polymers show a satisfactory solubility and can be cast into flexible and transparent films.
文摘A kind of highly fluorinated bisphenol monomer was synthesized. It was characterized by FTIR, 1H NMR and MS. 6F PEEK and 6F PEEKK were prepared via aromatic nucleophilic substitution, based on [3,5 di(trifluoromethyl)] phenylhydroquinone and difluoro monomers. The T gs of 6F PEEK and 6F PEEKK are 423 and 436 K, respectively. The 6F polymers exhibit a high thermal stability and good solubility. The flexible, creasable and transparent thin films were easily obtained by compression moulding and solution casting.
基金supported by the National Key Basic Research Special Foundation of China(Nos.2006CB921702 and 2007CB310403)the National Natural Science Foundation of China(Nos.10674185 and 10801017) the Youth Foundation of Minzu University of China.
文摘Negative refraction and subwavelength imaging properties of a two-dimensional （2D） photonic crystal （PC） slab are studied by the finite-difference time-domain method. The PC consists of a triangular lattice of air holes immersed in a dielectric. For a certain frequency range in the third photonic band, the directions of the group velocities and the phase velocities can be opposite, so the PC can work as a kind of negative refractive-index material. The light radiated from a point source can form a subwavelength image spot through the PC slab. Negative refraction and an effective refractive index of the PC slab n = -1 can be achieved for the incident wave with its incident angle within a certain range.
文摘The fluorescence spectra of synthetic food dyes of sunset yellow and tartrazine are analyzed. The fluorescence peak wavelengths of sunset yellow and tartrazine are 576 and 569 nm, respectively, while the fluorescence spectra widths are 480-750 and 500 750 nm induced by ultraviolet light between 310-400 nm. The fluorescence spectra of sunset yellow overlap heavily with those of tartrazine, so it is difficult to distinguish them. Based on the principle of radial basis function neural network, a neural network is obtained from the training of the 14 groups of experimental data. The results show that the species of sunset yellow and tartrazine could be recognized accurately. This method has potential applications in other synthetic food dyes detection and food safety inspection.
基金supported by the National Natural Science Foundation of China (Nos. 10674060 and10874043)the National "973" Program of China(Nos. 2005CB724508 and 2006CB921104)
文摘A four-level tripod active-Raman-gain scheme is analyzed for obtaining phase-controlled gain, phase shift, and group velocity at room temperature. The scheme can be used to eliminate significant probe field atten- uation or distortion which is unavoidable in the scheme based on electromagnetically induced transparency. It is shown that the intensity gain, phase shift, and group velocity of a probe field can be simultaneously manipulated by changing the relative phase of two pump fields. The scheme is also different from that proposed recently by Deng et al. where a probe-field gain always exists. New features of the scheme presented here raise the possibility of designing rapidly responding optical switches and gates for optical information processing.
