The linear electro-optic response of polymer-dispersed liquid crystal films has been studied. Micrometer-sized droplets of a cyanobiphenyl mixture (E7) were formed in a Norland Optical Adhesive 65 photopolymer by photopolymerization-induced phase separation. Samples with various average nematic droplet sizes were systematically investigated. The temperature dependence of the first-harmonic electro-optic spectra was obtained. Peculiar peaks and double peaks in the phase spectra were found at temperatures close to the clearing point. Samples with narrow distributions of droplet sizes were characterized by a double peak of the amplitude spectra in the low-frequency range. A flexoelectric origin of the first-harmonic spectra in confined nematic systems is discussed. 相似文献
The changes in weight, in elementary composition, in content of oxygen functional groups and in spin concentration of lignite, brown and black coal samples heated in a stream of humid air at a rate of 1 °C/min to various temperatures have been determined I.r. spectra of oxidized and non-oxidized brown coal are recorded and the yields of CO, CO2 and H2O were measured. The mixtures of low-molecular-weight hydrocarbons evolved before self-ignition were analysed by gas chromatography, and the temperatures of self-ignition were determined in an oxygen stream using a Leitz microscope. A region of coal oxidation was identified where the hydrogen content remained invariable or increased, indicating an interaction of coal with water in the presence of oxygen. For the next region the atomic ratio H/C of the overall gaseous product was found to be high (6 to 10). Self-ignition was found to occur in this region. The results permit coal oxidation to be considered as a redox process. The aromatic part of coal is believed to act as an oxidizing agent in the region where hydrogen is less affected by molecular oxygen. 相似文献
Summary: The effectiveness of some thermoplastic elastomers grafted with maleic anhydride (MA) or with glycidyl methacrylate (GMA) as compatibilizer precursors (CPs) for blends of low density polyethylene (LDPE) with polyamide‐6 (PA) has been studied. The CPs were produced by grafting different amounts of MA or GMA onto a styrene‐block‐(ethylene‐co‐1‐butene)‐block‐styrene copolymer (SEBS) (KRATON G 1652), either in the melt or in solution. A commercially available SEBS‐g‐MA copolymer with 1.7 wt.‐% MA (KRATON FG 1901X) was also used. The effect of the MA concentration and of other characteristics of the SEBS‐g‐MA CPs was also studied. The specific interactions between the CPs and the blends components were investigated through characterizations of the binary LDPE/CP and PA/CP blends, in the whole composition range. It was demonstrated that the SEBS‐g‐GMA copolymers display poor compatibilizing effectiveness due to cross‐linking resulting from reactions of the epoxy rings of these CPs with both the amine and the carboxyl end groups of PA. On the contrary, the compatibilizing efficiency of the MA‐grafted elastomers, as revealed by the thermal properties and the morphology of the compatibilized blends, was shown to be excellent. The results of this study confirm that the anhydride functional groups possess considerably higher efficiency, for the reactive compatibilization of LDPE/PA blends, than those of the ethylene‐acrylic acid and ethylene‐glycidyl methacrylate copolymers investigated in previous works.
SEM micrograph of the 75/25 LD08/PA blend (with 2 phr SEBSMA1). 相似文献
The initial phase arising at the interface with aluminum substrate during electroless deposition of amorphous high phosphorus (16–19 at.%) Ni–Cu–P alloy with alloyed copper 1.7–3.4 at.% is studied. Stripped deposit foils are inspected by Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy coupled with energy dispersive X-ray analysis (TEM-EDX). Depending on the plating conditions, various particles, some of them crystalline, are revealed at the foils sides formerly adhering to the substrate. EDX analysis of the crystallites shows diverse copper contents of about 34–64 at.%, without any phosphorus. Electron diffraction analysis indicates a lattice structure very close to that of Cu. The presence of a phase without phosphorus and enriched in copper at the interface with the Al substrate is also confirmed by Auger electron spectroscopy. This initially arising crystalline phase might exert a limited effect on the main properties of bulk Ni–Cu–P deposits: the composition uniformity through the thickness, amorphous structure and paramagnetic behavior. A modification of the plating process is recommended, which is decreasing the probability of inhomogeneities formation. 相似文献
The co-effects of two glass-formers in the TeO2-P2O5 system are studied on the basis of neutron diffraction data. The curves for the radial distribution function (RDF) obtained show a high extent of destruction of the short-range order in the tellurite matrix, while the basic co-ordination PO4 polyhedron remains unchanged. The co-ordination number (cn) of the Te atom changes from 4 to 3+1 and marked tendency towards elongation of the Te-O distances over 2.3 Å is observed. The considerably higher stability of the PO4 polyhedra and their strong influence on the TeO4 polyhedra is established. The observed smearing effect of the Te-Te, Te-second O and O-second O distances in the range of 3.8 to 3.9 Å in other tellurite glasses is also characteristic of this system. A structural interpretation of the liquid-liquid immiscibility on the short-range order level in the system is given. A critical composition with 26±5% of the second glass-former is established, above which concentration a stable immiscibility in the tellurite systems is observed. An attempt is made to construct two adequate structural models (microhomogeneous and microheterogeneous) for the short-range order in the glasses studied. 相似文献
This work deals with the development of a numerical method for solving an inverse problem for bending stiffness estimation in a Kirchhoff–Love plate from overdetermined data. The coefficient is identified using a technique called the Method of Variational Imbedding, where the original inverse problem is replaced by a minimization problem. The Euler–Lagrange equations for minimization comprise higher-order equations for the solution of the displacement and an equation for the bending stiffness. The correctness of the embedded problem is discussed. A difference scheme and a numerical algorithm for solving the parameter identification problem are developed. Numerical results for the obtained values of the bending stiffness as an inverse problem are presented. 相似文献
The electron beam technology (EBT), proven treatment for SO2 and NOx removal, is applied to different power stations as hot gas cleaning system. In this paper, an assessment of this technique installed in a Bulgarian power station on organic emissions is analyzed. The Polycyclic Aromatic Hydrocarbons (PAH) content, not only emitted in the gas phase but also trapped in the solid phase, has been carried out before and after the irradiation. The main aim has been to know whether the EBT affects organic emissions, like PAH, as it happens with inorganic pollutants, like SO2 and NOx, studying EBT effects from an organic environmental point of view. 相似文献
We develop a method for determinating the relative positions of the lidar transmitter (LT) and the local oscillator (LO) frequencies in Doppler CO(2) lidars. It uses the weak spectral asymmetry of TEA CO(2) laser pulses, defined by a number of secondary peaks at the high-frequency side of the main spectrum peak. Depending on the sign of the beat frequency, these peaks may appear in the demodulated spectrum at either the high- or the low-frequency side. Each laser pulse spectrum is compared with reference spectra with two types of asymmetry, with the cross-correlation coefficients used as criteria. The performance of the method at different values of signal-to-noise ratio is analyzed numerically. The method is also applied to raw data from the lidar reference channel and demonstrates good performance at noise levels lower than the secondary peaks in the pulse spectrum or at a signal-to-noise ratio of >/=20 dB. Application of the pulse spectrum asymmetry for lidar frequency stabilization is analyzed. Lidar operation without frequency stabilization is considered as well. The method offers a simple Doppler lidar hardware for the creation of low-cost coherent lidars, velocimeters-rangefinders, etc. 相似文献