Advances in Liquid Crystals

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Authors: Shan Wei, Chun Juan Ou Yang, Si Min Wei
Abstract: According to analyzing the different wavelet coefficients' transmission property of signals and noises under different scales of the wavelet transform, LEFC denoising algorithm based on fuzzy clustering and wavelet transform is proposed. Our experimental evaluations show that the algorithm is effective and robust to restore the images compared with the other wavelet soft-thresholding algorithms. When the ratio exceeds 40 %, LEFC gives superior performance.
Authors: Guo Zhong Lai, Xi Yao Chen, Yu Fei Wang, Hong Lin
Abstract: A Fabry-Perot self-collimation interferometer (FPSI) constructed in a two-dimensional photonic crystal (2D PhC) by liquid crystal infiltration has been proposed and demonstrated theoretically. The resonant cavity of FPSI is infiltrated with a nematic liquid crystal (LC) 5CB with ordinary and extraordinary refractive indices 1.522 and 1.706, respectively. The transmission spectrum of the FPSI has been investigated with the 2D finite-difference time-domain method. Calculation results show that resonant transmission peaks have nearly equal frequency spacing 0.0090c/a. When the effective refractive index neff of the liquid crystal is increased from 1.522 to 1.706, the peaks shift to the lower frequencies over 0.0071c/a while the peak spacing is almost kept unchanged. Thus this FPSI by LC infiltration can work as a tunable attenuator or an optical switch. For the central operating wavelength around 1.55m, its dimensions are only about tens of microns. Thus this device may be applied to photonic integrated circuits.
Authors: Fu Fang Zhou, Bao Gai Zhai, Chun Xu Pan, Yuan Ming Huang
Abstract: By varying the dopant-to-pyrrole ratio in a wide range from 0 to 60% a series of 5-sulfosalicylic acid sodium doped polypyrrole was synthesized in situ in aqueous solution with ferric chloride as the oxidant. The resulting polypyrroles were characterized with the four-probe, laser light scattering and thermo-gravimetry analysis, differential thermal analysis, respectively. Our results indicate that the particle size plays a determinative role to tune the conductivity in the studied range of dopant concentration; and this series of polypyrrole with size-tuned-conductivity exhibits little less thermal-stability although its size and conductivity changes simultaneously and acutely with the dopant concentration. The association of the conductivity with particle size was interpreted in terms of a theoretical model proposed by Baughman and Shacklelette.
Authors: Xiao Shu Zeng, Yi Wu Yi, Zao Hong Du, Chao Luo
Abstract: A novel technology is explored, using which an aligned array carbon nanotube film (aacf) can be perfectly peeled off from itself growing substrate as well as transferred onto an aluminum tape substrate, being assembled a composite film together with the Al tape. The electrical conductance and the field emission behaviors have been tested for the composite films. Experimental results show that the composite film has electrical resistance between 10 ohm and 1127 ohm, which depends on thickness and quality of the sticky glue layer between the carbon nanotub (cnt) film and the Al substrate. F-N curve proves the electronic emission of the composite film is field emission. I-V measurement curves demonstrate that the composite film with good electrical conductance has better field emission behavior and that the turn-on field and threshold field of sample 1 are 1.1 V/um and 1.8 V/um respectively. The technology datum show the composite film can meet the requirements of the emission cathode in flat panel displays.
Authors: Yuan Ming Huang, Fu Fang Zhou, Bao Gai Zhai
Abstract: With the ultraviolet-visible spectrophotometry, we have investigated the effects of red laser (633 nm) and green laser (532 nm) irradiations on the optical absorption of the ethyl alcohol solutions of an azo-containing bent-core liquid crystal. As the irradiation duration increases, the optical absorptions at about 360 nm of the bent-core compound exhibit concentration dependent and irradiation-time dependent features. The absorptions of dilute solutions (~2.2 mg/litter) are not sensitive to the laser irradiation duration whereas the absorptions of higher concentrations (~10 mg/litter) decrease as the laser irradiation continues. Our results have demonstrated that laser irradiation induced thermolysis is responsible for the dissociation of the azo-linkages in azo-containing bent-core compound. The mechanisms on the red and green light irradiations are discussed.
Authors: Xiao Xi Chen, Zi Qiang Huang, Wen Jun Yang, Jin Bi Leng
Abstract: This research is to develop a black-white liquid crystal adjustable grating using the period distributed electronic field pulsing on guest-host liquid crystal. The transmission properties of parallel or twisted-alignment liquid crystal cells have been investigated by means of numerical simulating and experiencing the guest-host liquid crystal cells, and analyze how the parameters of the LC cell effects such basic characteristics of LCDs as the contrast, brightness and polarity of the viewing angles. The result is the alignment impact on the transmittance of the liquid crystal cell. A good agreement between the experimental result and the calculated data was achieved.

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