Multistability and multiperiodicity of delayed Cohen-Grossberg neural networks with a general class of activation functions

In this paper, by using analysis approach and decomposition of state space, the multistability and multiperiodicity issues are discussed for Cohen-Grossberg neural networks (CGNNs) with time-varying delays and a general class of activation functions, where the general class of activation functions consist of nondecreasing functions with saturation’s including piecewise linear functions with two corner points and standard activation functions as its special case. Based on the Cauchy convergence principle, some sufficient conditions are obtained for checking the existence and uniqueness of equilibrium points of the n-neuron CGNNs. It is shown that the n-neuron CGNNs can have 2ⁿ locally exponentially stable equilibrium points located in saturation regions. Also, some conditions are derived for ascertaining equilibrium points to be locally exponentially stable or globally exponentially attractive and to be located in any designated region. As an extension of multistability, some similar results are presented for ascertaining multiple periodic orbits when external inputs of the n-neuron CGNNs are periodic. Finally, three examples are given to illustrate the effectiveness of the obtained results.     

Large‐Scale Fluctuation Behavior Prior to the Crystallization of Poly(ethylene terephthalate) Glass: A Small‐Angle Light Scattering Study

The crystallization processes of amorphous, glassy‐state poly(ethylene terephthalate) (PET) at two temperatures, a low temperature near T _g where PET has a slow crystallization speed and a middle temperature (about 55°C above T _g ) where PET crystallization is rapid, were monitored in situ by a time‐resolved small‐angle light scattering (SALS) device. It was found that large‐scale fluctuations happened prior to the crystallization at both temperatures, but the kind of fluctuation had a temperature dependence: at the middle temperature, pure density fluctuation took place during the induction period, whereas at low temperature, both density fluctuation and orientation fluctuation occurred, but the latter was the dominant factor. Analyses of the kinetics of these two kinds of fluctuation processes demonstrated that the spinodal decomposition (SD) type of phase‐separation character was undistinguishable in the SALS scale, while the nucleation‐growth (NG) type of phase behavior could describe the scattering results as well.     

相变乳状液的储冷模型与参数分析

本文建立了一种乳化的非牛顿相变功能流体的循环储冷模型,对影响其储冷性能的各项参数进行了模拟计算和分析。得出了描述不同储冷条件下与初始温度相关联的显热段和与乳液浓度相关联的潜热段储冷性能特征的无量纲关联式,以及储冷速率的相对比较。计算结果与有限条件下的测试结果基本吻合。该研究结果对采用潜热型功能相变流体储冷装置的设计具有参考价值。     

Harmonic operation of high gain harmonic generation free electron laser

In high gain harmonic generation (HGHG) free electron laser (FEL), with the right choice of parameters of the modulator undulator, the dispersive section and the seed laser, one may make the spatial bunching of the electron beam density distribution correspond to one of the harmonic frequencies of the radiator radiation, instead of the fundamental frequency of the radiator radiation in conventional HGHG, thus the radiator undulator is in harmonic operation (HO) mode. In this paper, we investigate HO of HGHG FEL.Theoretical analyses with universal method are derived and numerical simulations in ultraviolet and deep ultraviolet spectral regions are given. It shows that the power of the 3rd harmonic radiation in the HO of HGHG may be as high as 18.5% of the fundamental power level. Thus HO of HGHG FEL may obtain short wavelength by using lower beam energy.     

剖面不变性与非局部扰动电子温度响应

在ＴＦＴＲ及ＴＥＸＦ等装置上观测到的边界电子冷脉冲的输运现象是通常基于局部热导的瞬态输运理论所无法解释的。利用一个与电子温度剖面不变性相「容的且与在ρ＝ρＬ（ρＬ≈０．７～０．８）处的局部电子热导相关的非局部电子热导模型来描述边界冷脉冲引起的电子温度变化的瞬态过程,发现此模型可定性地解释边界冷脉冲实验现象的几乎所有主要特征。     

Some selected problems of nonaqueous microemulsions — phase diagrams and variation of the composition in the quaternary and ternary systems

A variety of quaternary and ternary systems of the type of dodecane/aliphatic alcohols/Na-dodecyl sulphate/water or a water-replacing component (formamide, ethylene glycol, propylene glycol, propylene carbonate, dimethylsulfoxide, acetonitrile) were subjected to a comparative analysis of microemulsification. The compositions of the systems of the type of oil/surfactant/cosurfactant/water or nonaqueous liquid were changed with respect to surfactant (Na-dodecyl sulfate and triton X 114) concentration, cosurfactant (homologous aliphatic alcohols) concentration and mixing ratio of water and water-replacing component. The appertaining phase diagrams were plotted and compared with those of aqueous systems.The experimental results suggest that the phase regions, which are designated as nonaqueous microemulsions, probably represent, not only microemulsions in the usual sense, but a separate kind of mixed phase whose microstructure is examined by special studies. Analogously to aqueous microemulsion systems, transparency and spontaneous formation of homogeneous multicomponent systems cannot serve as the sole criteria for waterless microemulsion formation. But they are important guiding properties of microemulsion formation in multicomponent systems.The variety of components involved in the chemical composition and the current insufficient knowledge do not permit to generally decide whether nonaqueous systems can be assigned to microemulsions or to molecular solutions. For clarifying this problem a detailed examination of the miscibility behavior, especially that of binary systems as a function of temperature, and the role that surfactant and cosurfactant play in the formation of homogeneous systems will be necessary.     

冷态德士古气化炉流场与停留时间分布的研究

测定了德士古气化炉的冷态速度分布和停留时间分布。结果表明：德士古气化炉内在轴向２．５～３．０倍直径范围内存在回流，最大回流量为射流量的３．５倍左右；在平均停留时间之前，已有５０％左右的物料逸出炉外。本文指出，德士古气化炉中存在的问题，如结渣、耐火砖寿命短、有效气体成分偏低均与炉内流场有关。     

DSC study of cold and heat denaturation processes of β-lactoglobulin A with guanidine hydrochloride

The cold and heat denaturations of bovine P-lactoglobulin A ((β-lg A) has been studied in solutions of guanidine hydrochloride (GuHCI) by differential scanning calorimetry (DSC). The experimental results are presented and discussed. It is shown that the number of protons bound by the monomeric molecules of β-lg A was unchanged before and after its heat denaturation below pH 3, and that the activation energy of the heat denaturation was depressed owing to the presence of GuHCI. In the solutions with 2.50 and 3.06 mol/L of GuHCI, both the cold and heat denaturations of P-lg A were observed. In comparison with the heat denaturation, the activation energy of cold denaturation was far lower and the number of GuHCl molecules bound by the unfolded polypeptide chains after culd denaturation increased a lot. The absolute value of the enthalpy of cold denaturation was larger than that of heat denaturation. It was found by the analysis that the contribution to the total denaturational enthalpy of conformational change itself of the monomeric molecules of β-lg A was the lowest among the globulins, according to the average of the number of heavy atoms. Project supported by the National Natural Science Foundation of China, and by the fund for excellent items under Director of the Institute of Chemistry.     

Syntheses and properties of related polyoxadiazoles and polytriazoles

New aromatic poly-1,2,4-triazoles and poly-1,3,4-oxadiazoles are studied as thermally stable membrane materials. Various groups were introduced onto the pendant phenyl groups of poly-1,2,4-triazoles. Glass transition temperature, degradation temperature, and cold crystallization behavior were studied as a function of these groups. Cold crystallization appeared to be highly sensitive to macromolecular regularity. The solubility of poly-1,3,4-oxadiazoles was highly improved upon incorporation of 5-t-butylisophthalic, 1,1,3-trimethyl-3-phenylindane, 4,4′-(2,2′-diphenyl) hexafluoro propane, and diphenyl ether groups into the polymeric main chain, whereas the high glass transition temperatures and degradation temperatures typical for aromatic poly-1,3,4-oxadiazoles were maintained. © 1994 John Wiley & Sons, Inc.     

Effects of Deformation Rate on the Necking of an Amorphous Copolyester Studied by Modulated DSC

The tensile loading-induced necking in notched specimens of an amorphous copolyester (aCOP) was studied by modulated differential scanning calorimetry (MDSC). It was shown that necking occurred by cold drawing since the enthalpy of cold crystallization and that of the subsequent melting agreed fairly with each other. Increasing deformation in the necking zone and increasing deformation rate of the specimens shifted the onset of cold crystallization toward lower temperatures and yielded a slightly higher glass transition temperature (T_g). This was attributed to the molecular orientation caused by mechanical loading. The finding that the melting contained a non-reversing part was considered as appearance of possible microcrystallinity. The T_g range was strongly influenced by the deformation rate and reflects the thermomechanical history of the samples accordingly. This revised version was published online in August 2006 with corrections to the Cover Date.