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排序方式: 共有251条查询结果,搜索用时 33 毫秒
51.
Daniel A. Vega John M. Sebastian Yueh‐Lin Loo Richard A. Register 《Journal of Polymer Science.Polymer Physics》2001,39(18):2183-2197
Triblock copolymers in midblock‐selective solvents can form physical gels. However, at low triblock contents (near the percolation threshold), the bridging of chains between micelles can lead to macrophase separation. Adding a styrene–isoprene diblock to a styrene–isoprene–styrene triblock copolymer in squalane can eliminate macrophase separation, yielding a wide range of stable, single‐phase gels with a disordered arrangement of micelles. The plateau modulus of these triblock gels scales with the 2.2 power of polymer content, indicating the importance of entanglements in dictating the modulus. Comparing gels made from the midblock‐saturated derivative of the same polymer [styrene‐(ethylene‐alt‐propylene)‐styrene] in squalane reveals that the modulus differences in the gels are a direct consequence of the difference in the entanglement molecular weight of the midblock homopolymer in bulk. Finally, the broad relaxation spectrum of these triblocks is well‐described by a recent theory for the dynamics of entangled star polymers, with the breadth of the relaxation spectrum dictated by the number of entanglements per midblock in the gel. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2183–2197, 2001 相似文献
52.
Parviz Ghandforoush James C. Loo 《The Journal of the Operational Research Society》1992,43(11):1087-1093
This paper presents a procurement model for a multinational oil company with affiliate plants located worldwide. The proposed model uses a quantity discount relationship to reduce the total procurement cost. We use a non-linear programming method to solve the model and make comparisons with the current approach used by the oil company. The proposed approach has several distinct advantages: assured minimum cost, ease of data management, flexibility in design, and accuracy in results. 相似文献
53.
This paper presents a Hybrid Particle Swarm Optimization (HPSO) to solve the Unit Commitment (UC) problem. Problem formulation of the unit commitment takes into consideration the minimum up and down time constraints, start up cost and spinning reserve, which is defined as the minimization of the total objective function while satisfying all the associated constraints. Problem formulation, representation and the simulation results for a 10 generator-scheduling problem are presented. Results shown are acceptable at this early stage. 相似文献
54.
Zhaohui Chen Boon H Loo Ying Ma Yunwei Cao Amin Ibrahim Jiannian Yao 《Chemphyschem》2004,5(7):1020-1026
Novel inorganic/organic composite films of molybdates with photochromic properties have been prepared by self-assembly using alkylammonium ions as a supramolecular template. Both 1-hexadecylammonium/polyoxomolybdate (C16-Mo) and 1-octadecylammonium/polyoxomolybdate (C18-Mo) composite films have been successfully fabricated. The elemental analysis and thermal gravimetric analysis show that the main product in the C16-Mo film was (C16H33NH3)4Mo8O26. The X-ray diffraction (XRD) results indicate that the composite films were lamellar in nature. The IR, Raman and X-ray photoelectron spectroscopy (XPS) results show that the polyoxomolybdate anions present as MoO6 octahedra and that the Mo species exists as Mo6+ in the freshly prepared films. The alkyl chains in the 1-hexadecylammonium chains were linear and the alkyl groups are an all-trans configuration. Upon UV irradiation of the C16-Mo films, some Mo6+ was reduced to Mo5+, some -NH3+ became -NH2 with a concomitant increase in the concentration of -OH groups on the molybdate moieties, and the films were colored. Thus, the photochromism of the films involves the reduction of Mo6+ to Mo5+, coupled with a proton transfer from 1-hexadecylammonium ions to an oxygen atom at the Mo site. In contrast to thin films of transition-metal oxides, which all show photochromism in the blue region of the electromagnetic spectrum, these composite films show photochromism in the violet region with the greatest absorbance change at 472 nm. 相似文献
55.
A.D. Modestov Guo-Ding Zhou Hong-Hua Ge B.H. Loo 《Journal of Electroanalytical Chemistry》1995,380(1-2)
The electrochemical behavior of Cu electrodes in Cl− solutions was studied in a wide range of pH. The results were compared with those obtained in solutions containing F−, Br−, I− and So2−4 ions at pH 8.5, and discussed in terms of the competitive formation of Cu2O and CuCl films on the Cu surface and the influence of CuCl on the properties of Cu2O. At pH 8.5 or higher, Cu2O was formed first, whereas at pH 5.7 or lower the Cu2O film was formed on the Cu surface under the CuCl layer which was formed initially. It is believed that the Cu2O films doped with Cl− ions exhibited poor protective properties against Cu corrosion. 相似文献
56.
57.
In this paper, we classify the real hypersurfaces in a non-flat complex space form with ??-parallel shape operator. 相似文献
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