Analytical performance study of solar blind non-line-of-sight ultraviolet short-range communication links

Motivated by recent advances in solid-state incoherent ultraviolet sources and solar blind detectors, we study communication link performance over a range of less than 1 km with a bit error rate (BER) below 10(-3) in solar blind non-line-of-sight situation. The widely adopted yet complex single scattering channel model is significantly simplified by means of a closed-form expression for tractable analysis. Path loss is given as a function of transceiver geometry as well as atmospheric scattering and attenuation and is compared with experimental data for model validation. The BER performance of a shot-noise-limited receiver under this channel model is demonstrated.     

Preparation of nano-hydroxyapatite/poly(<Emphasis Type="SmallCaps">l</Emphasis>-lactide) biocomposite microspheres

Nano-hydroxyapatite (HA)/poly(l-lactide) (PLLA) composite microspheres with relatively uniform size distribution were prepared by a solid-in-oil-in-water (s/o/w) emusion solvent evaporation method. The encapsulation of the HA nanopaticles in microshperes was significantly improved by grafting PLLA on the surface of the HA nanoparticles (p-HA) during emulsion process. This procedure gave a possibility to obtain p-HA/PLLA composite microspheres with uniform morphology and the encapsulated p-HA nanoparticle loading reached up to 40 wt% (33 wt% of pure HA) in the p-HA/PLLA composite microspheres. The microstructure of composite microspheres from core-shell to single phase changed with the variation of p-HA to PLLA ratios. p-HA/PLLA composite microspheres with the diameter range of 2–3 μm were obtained. The entrapment efficiency of p-HA in microspheres could high up to 90 wt% and that of HA was only 13 wt%. Surface and bulk characterizations of the composite microspheres were performed by measurements such as wide angle X-ray diffraction (WAXD), thermal gravimetric analysis (TGA), environmental scanning electron microscope (ESEM) and transmission electron microscopy (TEM).     

Versatile Graphene-Isolated AuAg-Nanocrystal for Multiphase Analysis and Multimodal Cellular Raman Imaging

Main observation and conclusion Surface-enhanced Raman spectroscopy(SERS)-based bioanalytical technique involves the interaction of SERS-active substrate with c...     

Optical pattern simulations for closed cylinders of liquid crystals

Abstract

Optical patterns for the polarizing microscope textures of closed cylinders of liquid crystals (CCLCs) are studied by the Jones vector formulation. The simulated director configuration diagram of a CCLC with normal orientation at the walls contains four kinds of stable director configurations. The resulting texture under some approximations depends only on phase shifts. The patterns are characterized by dark brushes that coincide with the directions of the crossed polarizers. Additionally, there are concentric circle fringes. For the ring defect structure, the centre region of the cylinder exhibits a black extinction. However, this is not distinguishable as between the hyperbolic and radial structures for both the point and the ring defect patterns. Comparing the observed patterns with the simulated ones, we find that the dark cross brushes and the centre black extinction of simulated patterns are similar to those that are observed. However, the concentric circle fringes of the observed pattern are not in accordance with the simulated pattern.     

On the non-symmetric planar aligned NLC cell

The planar aligned nematic liquid crystal cell with different anchoring for the two substrates (i.e. a non-symmetric NLC cell) is investigated by an analytical method. We deduce the basic equations and the boundary conditions of the tilt angle θ of the LC director. Expressions for threshold and saturation magnetic field are obtained, and numerical results of these two quantities with variation in anchoring parameters of the two substrates are given. A symmetry breaking parameter Δ is introduced and the relations between Δ and applied field, as well as the two sets of anchoring parameters are discussed in detail. A feasible experimental plan for measurement of anchoring strengths of a series of different substrates is proposed.     

An effective method for evaluating the image-sticking effect of TFT-LCDs by interpretative modelling of optical measurements

The conventional method of evaluating the image-sticking effect of a LCD module is inspection by sight, because the residual optical difference between two stressing areas is small and viewing angle-dependent, so that it is difficult to obtain a significant optical difference value by instrumental measurement. We propose an effective method for evaluating the image-sticking effect of a TFT-LCD module by directly measuring its time evolution of transmission with the TFT glass turned off after a period of pattern stress. In this way, the liquid crystal system under charge equilibrium in constant-charge mode shows a dramatically amplified optical difference. Further, we interpret the measured results by a modelling that combines the calculation of liquid crystal director orientation and ionic charge distribution. It is supposed that there are four time constants that dominate the overall sticking phenomenon and belong to four transient processes: adsorption of ions, desorption of free ions, desorption of stuck ions, and TFT leakage. The modelling shows good accordance between measured and simulated results when fitting parameters are properly chosen.     

Preparation of sol–gel materials doped with ionic liquid and extractant for cerium(III) extraction

Silica materials (ILDEHPASGs) consisting of ionic liquids and di-(2-ethylhexyl)phosphoric acid (DEHPA) for Ce(III) extraction was prepared by a sol–gel method using the hydrophobic ionic liquid 1-octyl-3-methylimidazolium hexafluorophosphate ([C₈mim]PF₆) as porogen and solvent medium. The ILDEHPASGs were characterized by scanning electron microscopy, Brunauer–Emmett–Teller surface area, Fourier transform infrared, and thermogravimetric analyses. The results indicated the doping of DEHPA and [C₈mim]PF₆ in ILDEHPASG-3 would evidently affect the formation of porous structure of sol–gel materials. ILDEHPASG-3 also possessed more channels and macropores than the blank sorbent; the surface area and pore volume of ILDEHPASG-3 were 409 m² g^?1 and 0.444 cm³ g^?1, respectively. [C₈mim]PF₆ and DEHPA were only physically confined or entrapped in the growing covalent silica network rather than chemically bound to the inorganic matrix. The majority of [C₈mim]PF₆ and DEHPA were stably immobilized in the gel. Then, the effects of contact time and pH were determined. The results showed the sorption of Ce(III) strongly depended on the contact time and pH, and ILDEHPASGs had high sorption ability for Ce(III). The results were analyzed by both Langmuir and Freundlich adsorption isotherm models, and the latter was found to give a better fit.     

Intrinsic properties of active sites for hydrogen production from alcohols without coke formation

The detailed reaction pathway and coke formation mechanism over Pt/metal oxide nanoparticles during the steam reforming of ethanol（SRE） at 300℃were studied.The catalysts were prepared by incipient wetness impregnation method and were characterized with CO pulse chemisorption, BET surface measurement,oxygen adsorption,ethanol-TPD,NH₃-TPD,and TPO.The SRE activity of the catalysts with steam/ethanol molar ratio of 3/1 was tested using a continuous fixed-bed reactor.Strong interaction between Pt and supports causes lower H₂ production temperatures and no C₂H₄ formation,while weak interaction leads to C₂H₄ formation and strong bonded CO on Pt particles during ethanol-TPD. H₂ production over Pt-based catalysts is mainly resulted from the decomposition and dehydrogenation of ethanol,and decarbonylation of acetaldehyde.Meanwhile,coke can be formed from acetaldehyde,acetone,C₂H₄ and CO.However,when the interaction between Pt and supports is weak,more coke is formed especially from acetone,C₂H₄ and CO.When the interaction is strong,no coke formation is observed due to high oxygen storage capacity of the catalyst.     

Determination of the B1-B2 transition path in RbCl by Möbius pair potentials

Using Chen-Möbius lattice inversion, we derive the interionic pair potentials from pseudopotential total-energy curves of the RbCl polymorph. Based on the potentials, the B1-B2 transition pathways have been analysed by calculating the activation energy and saddle point at transition pressure. The intermediate structures along the transition path were obtained within the different symmetric restrictions. By comparing the four pathways under the different restricted conditions, the intermediate structures with space groups Cmcm and P2 1 / m were predicted to explain the B1-B2 phase transition in RbCl.     

A modified procedure for synthesis of the side chain of ceftazidime-activated thioester

A modified procedure for synthesis of the side chain of ceftazidime-activated thioester has been established. This key intermediate of ceftazidime was obtained by a more eco-friendly process than conventional methods, and the yield was much higher (up to 92.4 %). It was found that different organic bases (triethylamine or pyridine) used in this reaction had different effects. The reaction conditions were also optimized to make the route more competitive and suitable for large-scale industrial production.