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The thermal resistances of epoxy resins cured with complexes of boron trifluoride with benzylamine, 2-benzylaminoethanol and 2-anilinoethanol were examined. Thermal analysis data were used to compare the thermal resistances of epoxy compusitions cured with polyamines (aliphatic and aromatic), acid anhydrides and complexes of boron trifluoride with the above amines.
Analytical as well as computer aided thermal optimization of a construction of a stripegeometry double-heterostructure GaAs/(AlGa)As diode laser were performed in the present work. The influence of various construction parameters of the laser on its thermal resistance is shown.
Abstract
This paper reports the synthesis and study of some Co(II) coordination polymers with the following acids as ligands: 2,8-dimethylphenoxyphosphinic, diphenyloxyphosphinacetic, diphenylthiophosphinacetic and dihexylphosphinic acids. The study was performed by means of chemical analysis, gel chromatography, IR spectroscopy, ESR, X-ray diffraction, thermogravimetry and electric resistance measurements. The experimental results were used to propose the structural formulae of these compounds and to calculate the kinetic parameters of the thermal decomposition reactions.
Abstract
PEEK is characterised by high impact and fatigue resistance andT g of 145‡C. Blends of PEEK and PEI have been made and scanning electron micro-graphs of the broken specimen show that the two polymers are completely miscible in all proportions. The study also shows that PEEK∶PEI 50∶50 blend, can be used as matrix for composite applications with appreciable enhancement ofT g to 177‡C.
Abstract
The adsorption kinetics of H2O in a clinoptilolite rich zeolitic tuff was experimentally investigated at 18°C. In the identification of the diffusion mechanism the isothermal adsorption model equation was used. It was found out that the intraparticle mass transfer becomes more dominant over the heat transfer with increase in particle size and the adsorptive dose pressure. Although initially intraparticle mass transfer was the controlling resistance later external heat transfer also contributes to the transfer mechanism.
The effects of mechanical perforation densities by extracting soil cores through an aerator Vertidrain with a working width of 1.6 m and equipped with hollow tines spaced of 65 mm, were studied on a sandy soil of a grassy sward in the Golf Course El Kantaoui in Sousse (Tunisia). The mechanical aeration was performed at two densities: 250 and 350 holes/m2. The cone penetration resistance and soil water infiltration were measured. These parameters were performed at initial state before aeration (E0) and then on the 10th, 20th and 30th day after aeration. These results showed that perforation density of 350 holes/m2 had a positive effect on the soil by reducing its cone resistance to penetration compared to the initial state (Rp = 14.8 daN/cm2). At 5 cm depth the decrease in resistance to penetration was 34% and 43% on the 10th and 20th day after aeration, respectively. However, on the 30th day after aeration the soil resistance to penetration tended to grow and its value compared to the initial state decreased only by 21 and 26%, respectively, at 5 and 15 cm of depth only by 10% and 9% with 250 holes/m2 density. The soil water infiltration made a good improvement after aeration compared to the initial state. This parameter increased from 4.8 cm/h to 8.3, 10.9 and 13.1 cm/h with 250 holes/m2 density and to 10, 12.9 and 14.8 cm/h with 350 holes/m2 density on the 10th, 20th and 30th day following the aeration.
Abstract
Various methods (e.g. spreading resistance and C-V measurements, neutron activation analysis, SIMS) have been used to determine concentration distributions of antimony dopant and charge carriers in single and double epitaxial silicon layers. Comparing the results obtained by the methods, an increased dopant diffusion process could be observed in the epitaxial layer during neutron irradiation of the sample, which arose as a systematic error in the NAA method. The origin of the deviations is discussed.
Abstract
The influence of copper on adults of the Colorado potato beetle (Leptinotarsa decemlineata Say) was studied. The adults were treated by the contact fungicide Kuprikol 50, which is used to control down powder mildew (Phytophtora infestans de Bary). Copper content was determined by radio-nuclide X-ray fluorescence analysis using a 238Pu exciting source. The obtained results contribute to the control measures against the Colorado potato beetle and to the question of the resistance of Colorado potato beetle towards pyrethroide insecticides.
Abstract
The radiolytic products of the DCH18C6 obtained after 
-irradiation have been determined, and the seven main structures have been separated and analyzed. The radiolytic product yields range from about 0.01 to nearly 0.3 molecules per 100 eV absorbed by the DCH18C6 at an energy of 3290 kGy. From the viewpoint of radiation decomposition rate, the DCH18C6 presents a considerable resistance and its radiolytic products have little or no extraction power.
Abstract
Biological resistance of coatings can be regarded as one of the main properties in automotive industries. This study aims to investigate the effects of biological materials on the mechanical performance of an automotive clear coat. To this end, two acrylic melamine clear coats containing different melamine cross-linker contents were used. In addition, biological resistance of these clear coats were studied at two different ageing processes including pre-ageing and post-ageing which involve various hot-cold, humid shockings and UV radiation of sunlight. By the aid of optical microscopy, micro Vickers and DMTA analyses, different optical and mechanical properties such as micro hardness, T g, cross-linking density and storage modulus were studied. Results revealed an inverse impact of both biological materials to decrease the clear coats mechanical attributes. In addition, a complicated effect of ageing conditions was observed for both clear coats exposed to these materials. It was shown that the coating having a higher mechanical properties and T g even resulted in a lower biological resistance.
