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1.
Novel polyurethane insulating coatings were prepared from the reaction of glycerin‐terminated polyurethane prepolymers (GPUPs) and a blocked isocyanate curing agent (BIC). The GPUPs were prepared from the reaction of one equivalent of polycaprolactone polyol (CAPA 210) with an excess amount of 4,4′‐methylene bis(phenyl isocyanate) (MDI) and subsequent reaction of the NCO‐terminated polyurethane with glycerin. The BIC was prepared from the reaction of trimethylol propane (TMP), toluene diisocyanate (TDI) and N‐methylaniline (NMA). The polyols and curing agent were characterized by conventional methods while the curing condition was optimized via gel content measurements. The curing kinetics of the polyurethane coating were investigated and the kinetic parameters derived. The crosslink densities of the samples were determined via the equilibrium swelling method, using the Flory–Rehner equation. The relationships between the crosslink density and the electrical, physical, mechanical and dynamic mechanical properties of the coatings were also studied. Copyright © 2005 Society of Chemical Industry 相似文献
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3.
Survival of rotavirus on lettuce, radishes, and carrots was studied to evaluate the potential of rotavirus transmission by vegetables irrigated with wastewater. The vegetables were contaminated with rotavirus SA-11 and stored at 4°C and room temperature in covered and uncovered containers to simulate post harvest conditions. Virus decay rates were greater on radishes and carrots than lettuce. Decay rates of rotavirus on lettuce, radish, and carrot ranged from ?0·057 to ?0·479 (log10 pfu/day). Rotavirus SA-11 survived on lettuce, radish, and carrot for 25 to 30 days at 4°C but at room temperature survival was very different for the various vegetables varying from 5 to 25 days. Greatest survival was always observed on the lettuce. These data suggest that rotaviruses can survive long enough on contaminated vegetables as to be transmitted by this vehicle. 相似文献
4.
A novel interference suppression scheme for global navigation satellite systems using antenna array 总被引:2,自引:0,他引:2
This paper considers interference suppression and multipath mitigation in Global Navigation Satellite Systems (GNSSs). In particular, a self-coherence anti-jamming scheme is introduced which relies on the unique structure of the coarse/acquisition (C/A) code of the satellite signals. Because of the repetition of the C/A-code within each navigation symbol, the satellite signals exhibit strong self-coherence between chip-rate samples separated by integer multiples of the spreading gain. The proposed scheme utilizes this inherent self-coherence property to excise interferers that have different temporal structures from that of the satellite signals. Using a multiantenna navigation receiver, the proposed approach obtains the optimal set of beamforming coefficients by maximizing the cross correlation between the output signal and a reference signal, which is generated from the received data. It is demonstrated that the proposed scheme can provide high gains toward all satellites in the field of view, while suppressing strong interferers. By imposing constraints on the beamformer, the proposed method is also capable of mitigating multipath that enters the receiver from or near the horizon. No knowledge of either the transmitted navigation symbols or the satellite positions is required. 相似文献
5.
A generalized kinematic viscosity-temperature correlation for undefined liquid heavy petroleum fractions has been developed to represent the data for a wide range of temperature from 100°C to 200°C. The correlation is based on the experimental kinematic viscosity data of true boiling point fractions of four Arabian crude oils. The characterization property required for estimation is 50% boiling point. The proposed correlation fits the experimental data with an overall absolute error of 6.1%. Experimental measurements of kinematic viscosity of heavy true boiling point fractions of Arabian crude oils were also obtained in order to develop the proposed correlation. 相似文献
6.
This paper contributes to extend the minimax disparity to determine the ordered weighted averaging (OWA) model based on linear programming. It introduces the minimax disparity approach between any distinct pairs of the weights and uses the duality of linear programming to prove the feasibility of the extended OWA operator weights model. The paper finishes with an open problem. 相似文献
7.
M. A. A. Issa F. A. A. Amin A. M. Hasstb Z. H. Dughaish 《Journal of Materials Science》1989,24(7):2300-2304
Germanium-silicon alloys doped with phosphorus were prepared in vacuum by rapidly pouring the molten alloy into cooled copper moulds containing the phosphorus dopant. Without any further treatment, the ingots are milled into powder of grain size (L 5 µm) and hot pressed. It is shown that a high degree of homogenization of the alloy constituents can be obtained in the final compacts, thus eliminating the need for zone-levelled starting material. It is also shown that this work is in agreement with the plastic flow model of sintering known as the Mackenzie-Shuttleworth-McClelland model. Electrical measurements indicate that the dopant is effectively and uniformly incorporated into the alloy. 相似文献
8.
Shoko Yoshikawa Toshitaka Ota Robert Newnham Ahmed Amin 《Journal of the American Ceramic Society》1990,73(2):263-267
Composite materials composed of randomly dispersed semiconducting ceramic particles in an insulating polymer matrix show a pronounced change in resistivity with pressure. Different amounts of iron oxide (Fe3 O4 ) powder and antimony-doped tin oxide (SnO2 :Sb) powder were dispersed in an epoxy polymer matrix to form pressure-sensitive composites. In each family of materials, an insulator-to-semiconductor transition is observed in agreement with percolation theory. Composites within a certain range of filler content showed substantial piezoresistive effect under both uniaxial and hydrostatic pressure in which sensitivity is controlled by the choice of filler material and the volume fraction. The effect of temperature on the piezoresistance effect was also examined. Piezoresistors made from Fe3 O4 composites showed larger temperature changes than those filled with Sb-doped SnO2 . 相似文献
9.
Muhammad Asfand-e-yar Amin Anjomsho Edgar R. Weippl A Min Tjoa 《International Journal of Software and Informatics》2010,4(1):89-100
Software end-users need to sign licenses to seal an agreement with the product
providers. Habitually, users agree with the license (i.e. terms and conditions) without fully
understanding the agreement. To address this issue, an ontological model is developed to
formulate the user requirements and license agreements formally. This paper, introduces
ontological model that includes the abstract license ontology of common features found in
di?erent license agreements. The abstract license ontology is then extended to a few real
world license agreements. The resulting model can be used for di?erent purposes such as
querying the appropriate licenses for a speciˉc requirement or checking the license terms and
conditions with user requirements. 相似文献
10.