波形碳纳米管增强复合材料的有效刚度和局部应力的宏微观均质化数值模拟

采用分子动力学方法简化的碳纳米管等效纤维模型,利用具有精确周期性边界条件的均质化理论和宏微观均质化法分析正弦波形非连续碳纳米管的有效刚度和局部应力分布规律.结果表明,纳米增强复合材料的有效刚度和局部应力对碳纳米管的波形非常敏感,碳纳米管稍有弯曲就会导致复合材料有效刚度降低和应力传递能力的下降,为揭示复合材料中碳纳米管的增强机制和改善增强效果提供理论依据.     

A LRT Control Method Using Sensor Information in Distribution Systems with a Large Amount of PVs and EVs

It is of prime importance to maintain voltage profile within the proper range in distribution systems with a large amount of photovoltaics and electric vehicles (EVs). In particular, there is a possibility that line drop compensation (LDC) logic, which is utilized for the control of load ratio tap transformer (LRT) does not work properly when reverse power flow is included partially. Hence, in this paper, we have developed a new LRT control method based on the sensor information supposing that some section switchgears with sensors are introduced in the future distribution systems. Specifically, the extreme value of voltage profile is estimated by convergence calculation in the section between the section switchgear with sensor and LRT. Moreover, the voltage at the end node can be estimated by LDC method using sensor information of section switchgear. The proposed method was tested using a distribution system model and its effectiveness was shown.     

Gel-Forming Characteristics and Rheological Properties of Kefiran

A water soluble polysaccharide “kefiran” produced by Lactobacillus kefiranofaciens was examined for its gel-forming and rheological properties. Kefiran (3%) formed gel in the presence of ethanol (4–10%). The gel strength in 8% ethanol was comparable to that of 3% gelatin gel in water. Addition of casein (3%) increased gel strength 1.5–2.0 fold. The unique properties of kefiran may make it a useful food additive.     

Fabrication of particulate reinforced magnesium composites by applying a spontaneous infiltration phenomenon

A new fabrication method of particulate reinforced magnesium matrix composites using a spontaneous infiltration phenomenon was developed. By mixing infiltration agent powder with reinforcement powder, the magnesium melt spontaneously infiltrated into the powder mixture. In this study, pure magnesium, SiO2 and SiC particle (SiCp, 1.2,2,3,4 and 8 m) powders were used as the matrix metal, infiltration agent and reinforcements, respectively. Experiments to clarify the conditions in which the spontaneous infiltration occurred were carried out under pure argon atmosphere at 973 K. Furthermore, the infiltration velocity was measured. Spontaneous infiltration occurred in the 2,3,4 and 8 m SiCp systems. A minimum SiO2 content necessary for spontaneous infiltration existed and it depended on SiCp diameter. Microstructural observation of the composites revealed that SiCp dispersed homogeneously, even though the diameter of SiCp was fine, and MgO and Mg2Si reaction products were observed. During infiltration, a temperature rise was observed, caused by Mg–SiO2 thermit reaction. Consequently, spontaneous infiltration was caused by improvement of wettability between the magnesium melt and SiCp, which resulted from Mg–SiO2 thermit reaction at the infiltration front.     

基于平面应变试验的修正塑性功硬化软化模型

以改良型平面应变仪为基础,通过一系列平面应变和三轴压缩试验,对砂土的应力应变特性进行了研究,推导出以修正塑性功为硬化参数的本构关系。改良型平面应变仪较好地解决了加载面的摩擦及约束问题,能保证ε2的控制精度,并采用了合理的变形量测整理方法。本文提出的弹塑性模型仍以传统塑性理论为框架,其弹性特性、破坏准则、硬化参数及塑性势等均直接从试验曲线推导,以修正塑性功为硬化参数的硬化准则函数能反映硬化及软化的全过程曲线,并从试验结果推导了非关联流动准则塑性势函数。该模型结构较为清晰,参数选取规范,模型验证表明计算结果与试验结果较为吻合。     

Canonic form state space realization of two dimensional transfer functions having separable denominator

In this paper a procedure is developed for the computation of a state space realization from two dimensional transfer functions with separable denominator. The procedure relies on a canonic form for the state space realization.     

Learning automaton as a model to simulate and analyse learning behaviour in rats

A technique is presented for using a learning automaton as a model to simulate and analyse learning behaviour in rats, and the usefulness of this model is illustrated. This automaton was proposed as a learning machine by Tsetlin (1961) and refined by Aso and Kimura (1976). Some learning properties of such an automaton are first examined and it is shown that the automaton can be used to simulate a variety of learning behaviour, composed of several kinds of action, by the proper selection of parameters. Secondly, a mathematical model of the learning experiment carried out in our laboratory with rats is formulated as an interactive system between a learning automaton and its environment. Finally, the effectiveness of the mathematical model is discussed and proved through the simulation and analysis of learning behaviour with multiple actions in a specific rat.     

Self-propagating high-temperature synthesis of AlN in a graphite crucible in air by mechanical activation

Powders of Al and C were mixed in a molar ratio of Al :C = 3:1 and were then ground in a planetary ball mill. When the thus mechanically activated mixtures were transferred into a graphite crucible and exposed to air, they spontaneously ignited and self-propagating high-temperature synthesis took place in two successive steps. The products were sliced along the depth direction and examined by X-ray diffraction. Depending on the depth of the crucible, aluminium nitride, aluminium carbide, aluminium oxynitride, aluminium oxycarbide and alpha alumina were detected. From measurements of the lattice constant, it was found that aluminium nitride with a 97% purity could be obtained at the bottom of the graphite crucible. This revised version was published online in November 2006 with corrections to the Cover Date.     

过二硫酸铵法从LiMn_2O_4中萃取锂及所获得的吸附剂对锂同位素的选择性

本文对采用过二硫酸铵 (NH4) 2 S2 O8法从 Li Mn2 O4中萃取锂离子进行了研究 ,并就所获得吸附剂 (Mn O2 (Li) )的特性 ,特别是对于分离锂同位素的能力进行了测试。在良好的控制条件下 ,(NH4) 2 S2 O8是一种优良的锂吸附剂 ,它具有非常高的锂萃取度 ,同时保持锰的最小溶解性。所制备的 Mn O2 (Li)在 2 5°C时最大的 7Li/ 6Li同位素分离因子为 1 .0 1 4,它是那些商品有机离子交换剂的几倍。     

Thermal Transitions of Myosins/Subfragments from Black Marlin (Makaira mazara) Ordinary and Dark Muscles

Thermal transitions were studied by means of differential scanning calorimetry (DSC) and a spectrophotometric method. Three endothermic peaks (40, 43, 50°C: ordinary muscle; 46, 54, 62°C: dark muscle) were observed in DSC thermograms of both myosins. Thermograms of S-l fragments showed one peak (41°C: ordinary muscle, 43°C: dark muscle). But ordinary and dark muscle rod fragments gave two peaks (41, 62°C) and one peak (58°C), respectively. The spectrophotometric results also showed two thermal transitions for both myosins and one transition for their S-1 fragments. However, the rod from ordinary muscle myosin had two transitions, whereas that from dark muscle myosin had one transition.