Desynchronization of large scale delayed neural networks

We consider a ring of identical neurons with delayed nearest neighborhood inhibitory interaction. Under general conditions, such a network has a slowly oscillatory synchronous periodic solution which is completely characterized by a scalar delay differential equation with negative feedback. Despite the fact that the slowly oscillatory periodic solution of the scalar equation is stable, we show that the associated synchronous solution is unstable if the size of the network is large.

     

To transform maifanite powders from insulators to conductors by Sm gaseous penetration technology

Research on Chemical Intermediates - For the preparation of low-cost and eco-friendly conductive powders, a novel rare earth gaseous penetration technology was applied to modify maifanite powders....     

Some observations on practising successful operational research

Much has been written about the decline of Operational Research. In the 1960s it had already been proclaimed dead and the decreasing number of OR departments in industrial enterprises seems to support this thesis. The question seems to be: ‘Why is OR apparently disappearing at a time when the major obstacles to OR applications in the past, namely lack of computer-readable data, lack of software and hardware have been overcome?’ I report on 30 years of successful external OR activities and offer some observations which I have made while being active at a university and in OR companies in Germany.     

Modifying a branched surface to carry a foliation

We consider C¹ nonsingular flows on a closed 3-manifold under which there is no transverse disk that flows continuously back into its own interior. We provide an algorithm for modifying any branched surface transverse to such a flow ? that terminates in a branched surface carrying a foliation F precisely when F is transverse to ?. As a corollary, we find branched surfaces that do not carry foliations but that lift to ones that do.     

Limit cycles,tori, and complex dynamics in a second-order differential equation with delayed negative feedback

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.     

在烃类溶剂中制备丁基橡胶的研究

<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。     

Solid–liquid equilibrium and hydrogen solubility of trans-decahydronaphthalene + naphthalene and cis-decahydronaphthalene + naphthalene for a new hydrogen storage medium in fuel cell system

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 T_eu = 232.11 K for benzene + cyclohexane, x₂ = 0.9816 and T_eu = 241.98 K for trans-decahydronaphthalene + naphthalene, and x₃ = 0.9822 and T_eu = 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].     

哈工大材料与化工(化学工程领域)专业硕士研究生培养的探索与实践

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.     

Synthesis and properties of semiconducting aromatic polyquinonediimines

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.     

Effect of headgroup size on permeability of Newton black films

Gas permeability and thin-film interferometry are used as a tool to elucidate the orientation of polymeric headgroups in free-standing foam films. Nonionic polyoxyethylene (EO) surfactants were used to stabilize the foam films, keeping the size of the hydrophobic part constant (C12) and varying the size of the hydrophilic (EO numbers) part. The effect of headgroup size on the gas permeability of Newton black foam films was studied. Thickness, contact angle, and surface tension were measured to understand the permeation mechanism. Increase of film thickness and surface tension was observed while increasing the headgroup size, but the contact angle remains small and constant. Upon increasing the headgroup size, the permeability decreases showing that the headgroups provide a resistance to permeation. For smaller headgroups, the permeability follows a linear dependence on the film thickness, whereas for larger headgroups, the permeability essentially deviates from linearity. We use the conventional "coil model" of the EO chains to explain the observed results providing a detailed picture of the orientation of this important molecule in a confined volume of foam films.