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排序方式: 共有325条查询结果,搜索用时 15 毫秒
61.
Sue Ann Campbell Jacques Bélair Toru Ohira John Milton 《Journal of Dynamics and Differential Equations》1995,7(1):213-236
We analyze a second-order, nonlinear delay-differential equation with negative feedback. The characteristic equation for the linear stability of the equilibrium is completely solved, as a function of two parameters describing the strength of the feedback and the damping in the autonomous system. The bifurcations occurring as the linear stability is lost are investigated by the construction of a center manifold: The nature of Hopf bifurcations and more degenerate, higher-codimension bifurcations are explicitly determined. 相似文献
62.
<正> 关于多分散性对丁基橡胶加工行为的影响,有人进行了研究,近年来人们对丁基橡胶的分子量分布与加工性能的研究,又有新的报道,结果表明,丁基橡胶的分子量分布对其加工时收缩变形有很大的影响,我们曾用过渡金属卤化物和卤代烷基铝-加氢汽油催化体系合成了丁基橡胶,但在加工时收缩率大和不均匀,我们利用高聚物沉淀分级原理,在烷烃溶剂中添加氯代烃(CH_2Cl_2,CH_3Cl),混合溶剂制备的丁基橡胶,其分子量分布及加工收缩性能比单用汽油溶剂时有显著改进,其综合性能基本上达到了Polvsar 301水平。 相似文献
63.
Solid–liquid equilibrium was measured for benzene + cyclohexane, trans-decahydronaphthalene + naphthalene and cis-decahydronaphthalene + naphthalene under the atmospheric pressure in the temperature range from 226.69 to 353.14 K. The apparatus was specially designed in this study, and it was based on a cooling method. The phase diagram with the complete immiscible solids was observed for the three systems, and the eutectic point was found at x2 = 0.2709 and Teu = 232.11 K for benzene + cyclohexane, x2 = 0.9816 and Teu = 241.98 K for trans-decahydronaphthalene + naphthalene, and x3 = 0.9822 and Teu = 225.74 K for cis-decahydronaphthalene + naphthalene, respectively. Hydrogen solubility was also measured for the two pure substances, trans-decahydronaphthalene and cis-decahydronaphthalene, and the three mixtures, trans-decahydronaphthalene + cis-decahydronaphthalene, trans-decahydronaphthalene + naphthalene, and cis-decahydronaphthalene + naphthalene, in the pressure range from 1.702 to 4.473 MPa at 303.15 K. Considering the solid–liquid equilibrium data, mole ratio of trans-decahydronaphthalene:cis-decahydronaphthalene was set to 50:50, and those of trans-decahydronaphthalene + naphthalene, and cis-decahydronaphthalene + naphthalene to 85:15. The hydrogen solubility increased linearly with the pressure following the Henry's law for all systems. The experimental solubility data were correlated or predicted with the Peng–Robinson equation of state [D.Y. Peng, D.B. Robinson, Ind. Eng. Chem. Fundam. 15 (1976) 59–64; R. Stryjek, J.H. Vera, Can. J. Chem. Eng. 64 (1986) 323–333]. 相似文献
64.
The status and main problems in the cultivation of master degree graduate training in materials and chemical engineering (chemical engineering field) of Harbin Institute of Technology were analyzed by applying the concept of engineering education paradigm. Combined with the professional directions of chemical engineering discipline in HIT, i.e. "one field" (new chemical material field) and "two industries" (electrochemical engineering and polymer material engineering), the revision of training program, the course constructions and the measures for engineering practice ability and innovation ability training were explored and practiced with the purpose of the cultivation of industry leaders and high-level talents in chemical engineering filed. 相似文献
65.
A. Everaerts Sue Roberts H. K. Hall 《Journal of polymer science. Part A, Polymer chemistry》1986,24(7):1703-1716
A new class of poly-conjugated polymers has been obtained by condensation of anthraquinones with aromatic diamines in polyphosphoric acid. The polymers are black, intractable powders. Toward obtaining tractable materials, the effect of monomer structure on polymer tractability has been studied. Copolymerizations were also carried out to “soften” these materials. Electrical conductivities in the semiconducting range, 10?4- 10?8 (ohm cm)?1 were observed. Doping with iodine showed small increases. 相似文献
66.
La_2Ti_6O_(15)-CeTi_(21)O_(38)-PbTiO_3 ceramics formed in gaseous penetration of La-Ce into PbTiO_3 and their electric properties 总被引:2,自引:0,他引:2
PbTiO3 ceramics, which are typical ferroelectric materials, are useful in various applied fields. For example, it has a very good candidacy for piezoelectric materials for high temperature and high sensibility. In recent years, the studies on doped PbTiO3 ceramics have received consid-erable attention[1—3]. The modified PbTiO3 ceramics doped with Ca2+, Sm3+, Y3+, Ce4+ etc. have some better properties: their Curies temperature decreases, their tetragonal distortion degree de-grades and th… 相似文献
67.
68.
Dazhi Sun Minhao Wong Luyi Sun Yuntao Li Nobuo Miyatake Hung-Jue Sue 《Journal of Sol-Gel Science and Technology》2007,43(2):237-243
Purification and stabilization of colloidal ZnO nanoparticles synthesized from zinc acetate dihydrate and potassium hydroxide
in methanol have been performed. Isopropanol and hexane were utilized to achieve the precipitation-redispersion washing procedure
in methanol. The results from atomic absorption spectroscopy show that the concentration of K+ cation can be dramatically reduced by washing. X-ray diffraction and transmission electron microscopy results show that zinc
layered double hydroxide formed in the ZnO precipitate can be effectively removed through concentrating the unpurified ZnO
colloids by solvent evaporation. The purified ZnO nanoparticles can be fully redispersed in methanol, but become unstable
with time due to the low concentration of acetate in the colloids. Fortunately, the unstable ZnO methanol colloids are found
to become stable after addition of a small amount of hexane. The present study is of particular significance for the preparation
of purified colloidal ZnO nanoparticles for device fabrication, functional ZnO coatings and polymer nanocomposite applications. 相似文献
69.