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991.
Blends of linear polyethylene (LPE) and branched polyethylene (BPE) display very good mechanic properties that can be beneficial for various applications such as shear thinning and melt elasticity. LPE, BPE and amorphous polyethylene can be produced using nickel diimine (DMN) catalyst under various polymerization conditions, while LPE can be obtained using metallocene catalyst. Thus, LPE/BPE blends can be achieved by in situ polymerization using a hybrid DMN/metallocene catalyst. A novel hybrid catalyst made of DMN and Cp2TiCl2 was designed and used for ethylene polymerization. A synergistic effect of the two active sites in the hybrid DMN/metallocene catalyst was observed. Blends of linear and low branched polyethylene were synthesized when polymerization was conducted at low temperature (0 °C), while blends of linear and highly branched polyethylene were obtained at high temperature (50 °C). However, the miscibility of the polymers obtained at 50 °C was dramatically reduced as compared to those obtained at 0 °C. Mesoporous particles (MCM‐41) consisting of aluminosilicate with cylindrical pores were used to support the hybrid catalyst, in which MCM‐41 provides sufficient nanoscale pores to facilitate the polymerization in well‐controlled confined spaces. Blends of LPE and BPE were synthesized by in situ polymerization without adding comonomer and characterized. The miscibility of the polymer blends can be improved by supporting the hybrid catalyst on MCM‐41. Copyright © 2009 Society of Chemical Industry 相似文献
992.
Energetic thermoplastic elastomers containing energetic groups, such as azido, nitrato, nitro, and so forth, are emerging as attractive binder systems for advanced solid rocket propellants. Poly[3,3‐bis(Azidomethyl) oxetane (BAMO)‐co‐3‐azidomethyl‐3‐methyl oxetane (AMMO)] comprising hard crystalline BAMO segment and the soft/amorphous AMMO segment in various molar ratios (80 : 20, 50 : 50 and 20 : 80) were synthesized during the present work. The homo polymers namely Poly‐BAMO and Poly‐AMMO were also synthesized. All the polymers and copolymers were characterized by spectral and thermal methods. They were found to be thermally stable. The most promising 80 : 20 copolymer softened at 56°C with Tg of −36°C. Rheological studies were also carried out to determine their suitability as a binder in explosive and propellant formulations. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 相似文献
993.
AbstractThe microsegregation of Mn, Cu, Cr, Mo, Ni and Si has been measured in ductile iron which has been quenched during solidification. Effective segregation coefficients have been determined for each of the elements, and used to calculate the segregation on the basis of the Scheil equation. The calculated values agree reasonably well with the measured values of solute concentration as a function of the solid fraction. On the basis of the measured segregation of the alloying elements, the mechanisms by which the segregation affects the as-cast microstructure are considered, and an explanation for the effect of the segregation on the hardenability of ductile iron is proposed. 相似文献
994.
《Energy Policy》2013
In this paper, life cycle analysis has been carried out to evaluate overall performance of given rated stand-alone solar photovoltaic (SAPV) in terms of basic energy matrices, life cycle cost analysis, and earned carbon credit. Further, the experimentally calculated actual on-field life cycle performance results of existing outdoor SAPV system (i.e. almost 20 years old) have been represented with respect to the potential (max.) performance of same SAPV system estimated under same environmental conditions of solar intensity, ambient temperature, PV operating temperature as obtained during actual on-field performance evaluation. This new approach of overall performance evaluation by considering the on-field SAPV system installation as new (i.e. with potential/max. performance) and old (i.e. with actual performance) under same environmental conditions provides an inclusive comparative life cycle assessment of on-field PV system. 相似文献
995.
H. Ziari 《Petroleum Science and Technology》2013,31(17-18):1627-1632
In this research study, Sasobit as warm additive was used to modify original binder (60/70 penetration grade). The binder fatigue and rutting performance was evaluated through linear amplitude sweep (LAS) and multiple stress creep and recovery test, respectively. Results indicated that 3% Sasobit modified binder has the highest percent recovery value and the lowest Jnr value, but had the highest sensitivity to a sudden increase in the stress level inside the asphalt mixture. The LAS test results demonstrated that the fatigue behavior of asphalt binders modified with 1% Sasobit is the highest one. 相似文献
996.
Aaron Robertson James Allen Robin Laney Alison Curnow 《International journal of molecular sciences》2013,14(7):14024-14063
Radon-222 is a naturally occurring radioactive gas that is responsible for approximately half of the human annual background radiation exposure globally. Chronic exposure to radon and its decay products is estimated to be the second leading cause of lung cancer behind smoking, and links to other forms of neoplasms have been postulated. Ionizing radiation emitted during the radioactive decay of radon and its progeny can induce a variety of cytogenetic effects that can be biologically damaging and result in an increased risk of carcinogenesis. Suggested effects produced as a result of alpha particle exposure from radon include mutations, chromosome aberrations, generation of reactive oxygen species, modification of the cell cycle, up or down regulation of cytokines and the increased production of proteins associated with cell-cycle regulation and carcinogenesis. A number of potential biomarkers of exposure, including translocations at codon 249 of TP53 in addition to HPRT mutations, have been suggested although, in conclusion, the evidence for such hotspots is insufficient. There is also substantial evidence of bystander effects, which may provide complications when calculating risk estimates as a result of exposure, particularly at low doses where cellular responses often appear to deviate from the linear, no-threshold hypothesis. At low doses, effects may also be dependent on cellular conditions as opposed to dose. The cellular and molecular carcinogenic effects of radon exposure have been observed to be both numerous and complex and the elevated chronic exposure of man may therefore pose a significant public health risk that may extend beyond the association with lung carcinogenesis. 相似文献
997.
Surendra Kumar Roy 《International Journal of Electronics》2013,100(6):703-707
Although more rigorous treatments have been developed for the microstrip elements, the purpose of this transmission line model is to provide a numerically efficient substitute for them. The rectangular resonator is replaced by two equivalent radiating slots. In most practical cases the approximations are acceptable. It is obvious that the efficiency of the transmission model can be used to include mutual coupling in practical analysis. The calculated results are in good agreement with observed results. 相似文献
998.
《纺织学会志》2013,104(5):429-434
Abstract Engineering of spun yarns having specific tensile, evenness and hairiness characteristics is a long-cherished dream of spinning technologists. Selection of suitable raw materials at minimum cost and optimisation of process parameters are the two major tasks to be achieved to manufacture engineered yarn. Advent of high-speed fibre-testing machines and development of powerful modelling tools such as artificial neural network (ANN) have provided a great impetus in the yarn engineering research. This article demonstrates the feasibility of yarn engineering by developing a yarn-to-fibre ‘reverse’ model, using ANN. This approach is entirely different from the prevailing forward models, which predict the properties of final yarn using the fibre properties as inputs. The cost minimisation of cotton fibre mix was ensured by using the classical linear programming approach in combination with ANN. The engineered yarns demonstrated good agreement with the target yarn properties. 相似文献
999.
1000.
Piotr Macech 《Thin solid films》2009,517(18):5399-5403
Nanoscopic defects present in ultrathin (~ 6 nm) silica films covalently attached to gold substrates through a gold oxide layer exhibit a voltammetric response consistent with a random array of ultramicroelectrodes. These pinholes can be passivated via electrochemical polymerization of phenol to create insulating poly(phenylene) oxide plugs as documented by atomic force microscopy and infrared reflectance-absorbance spectroscopy. Passivation of pinholes is ~ 99.5% complete after 550 voltammetric cycles of oxidative electropolymerization. 相似文献