Formation of a large‐scale shish‐kebab structure of polyoxymethylene in the melt spinning and the crystalline morphology evolution after hot stretching

Polyoxymethylene (POM) fiber was produced by melt spinning with a high take‐up speed, which imposed a strong flow field. An unexpected formation of a shish‐kebab morphology with multiple shish of POM fibers was reported for the first time. This morphology is a large‐scale shish kebab with a diameter of 10.5 µm. Further orientation of the POM fiber was obtained by hot stretching twice at 160°C. Two crystalline morphology evolution processes were also observed: (i) the process from the large‐scale shish‐kebab to the deformed small shish‐kebab and (ii) the process from the deformed small shish‐kebab to the perfect whiskers. Compared with the melt spinning fiber, fiber tensile strength with first and second hot stretching increased by 976% and 1705%, respectively. The crystalline melting behavior of fibers significantly changes after the first and second hot stretching. The flow field induces a large number of extended chain crystals. Copyright © 2014 John Wiley & Sons, Ltd.     

Nano Carbon Doped Polyacrylamide Gel Electrolytes for High Performance Supercapacitors

Novel polyacrylamide gel electrolytes (PGEs) doped with nano carbons with enhanced electrochemical, thermal, and mechanical properties are presented. Carboxylated carbon nanotubes (fCNTs), graphene oxide sheets (GO), and the hybrid of fCNT/GO were embedded in the PGEs to serve as supercapacitor (SC) electrolytes. Thermal stability of the unmodified PGE increased with the addition of the nano carbons which led to lower capacitance degradation and longer cycling life of the SCs. The fCNT/GO-PGE showed the best thermal stability, which was 50% higher than original PGE. Viscoelastic properties of PGEs were also improved with the incorporation of GO and fCNT/GO. Oxygen-containing functional groups in GO and fCNT/GO hydrogen bonded with the polymer chains and improved the elasticity of PGEs. The fCNT-PGE demonstrated a slightly lower viscous strain uninform distribution of CNTs in the polymer matrix and the defects formed within. Furthermore, ion diffusion between GO layers was enhanced in fCNT/GO-PGE because fCNT decreased the aggregation of GO sheets and improved the ion channels, increasing the gel ionic conductivity from 41 to 132 mS cm⁻¹. Finally, MnO₂-based supercapacitors using PGE, fCNT-PGE, GO-PGE, and fCNT/GO-PGE electrolytes were fabricated with the electrode-specific capacitance measured to be 39.5, 65.5, 77.6, and 83.3 F·g⁻¹, respectively. This research demonstrates the effectiveness of nano carbons as dopants in polymer gel electrolytes for property enhancements.     

带导管鱼雷层流与湍流绕流计算

用分块耦合求解方法和自编三维软件计算了带导管鱼雷整体流场无冲角和有冲角的绕流问题,湍流计算采用Baldwin-Lomax湍流模型.计算雷诺数从103到107.计算冲角0～20°.在各种雷诺数计算,头部滞止压力（无黏流理论值为1.5）误差在10％范围内,总流量误差在5％范围内.对于不同冲角计算表明,升力系数在冲角15°范围内基本上线性增加,超过15°后升力系数缓慢减少.而摩擦阻力系数几乎与冲角无关,但压差阻力随冲角的增加而迅速增长.     

关于功的一种新的教学思路*--从概念起源和科学方法的角度学习

针对“功”的教学现状,在查阅资料中,我们认为不仅可以引导学生从概念起源的角度来学习功,更可以让学生在学习功的概念之中体会和感悟物科学方法。我们提出全新的教学设计,并在教学实践之中进行尝试。在这样的教学设计和实践中,学生们明确功的概念起源之后,在头脑中自然形成判断一个力是否做功的逻辑依据,并且按照逻辑顺序自然掌握了计算一个力做功多少的方法。     

The fractal research and predicating on the times series of sunspot relative number

In this paper, with the theory of nonlinear dynamic systems, It is analyzed that the dynamic behavior and the predictabilityfor the monthly mean variationsof the sunspot relative number recorded from January 1891 to December 1996. Inthe progress, the fractal dimension (D=3. 3±0.2) for the variation process wascomputed. This helped us to determine the embedded dimension [2×D+1]=7.By computing the Lyapunov index (λ₁=0.863), it was indicated that the variationprocess is a chaotic system. The Kolmogorov entropy (K=0.0260) was also computed, which provides, theoretically, the predicable time scale. And at the end, according to the result of the analysis above, an experimental predication is made,whose data was a part cut from the sample data.     

太阳黑子数时间序列的分形研究及预测

本文应用非线性动力系统理论分析了１８９１年１月至１９９６年１２月间太阳黑子月平均数变化的动力行为及其可预测性·计算了它的分形维数（Ｄ＝３３±０２）·确定了预测的嵌入维数［２×Ｄ＋１］＝７;计算了Ｌｙａｐｕｎｏｖ指数（λ１＝０８６３）,揭示了该系统的混沌特性;并计算了Ｋｏｌｍｏｇｏｒｏｖ熵（Ｋ＝００２６０）,用以从理论上分析这组数据可预报的时间尺度·最后根据分析的结果,从采样数据中截取一段数据进行了试验性的预测     

华蟾素注射液有效组份的分离和鉴别

分别用水、50%乙醇洗脱HP-20大孔树脂分离华蟾素注射液,得到0.125%非极性组份和0.3625%极性组份。薄层色谱检测发现,极性组份用Dragendoff显色剂喷洒有斑点呈桔红色,推断为生物碱类物质;非极性组份喷洒20%乙酸-硫酸溶液有紫色斑点出现,推断为甾体强心甙类物质。高效液相色谱检测发现,非极性组份在40min以后出现紫外吸收峰,尤以47、51和53min以后出现的吸收峰明显;极性组份在10min以前有明显的紫外吸收峰,且与华蟾素注射液相应位置出现的紫外吸收峰相似。     

Synthesis of nanosized BaSO4 and CaCO3 particles with a membrane reactor: effects of additives on particles

Nanosized BaSO(4) particles, about 15 nm in size, were synthesized successfully by a membrane reactor at the aids of additives, in which Na(2)SO(4) solutions were added into BaCl(2) solutions gradually through the micropores of ultrafiltration membranes to control the saturation ratio, subsequently the nucleation and growth rates. The effects of additives species, additives concentrations, and membranes molecular weight cut-off (MWCO) on the particle morphology, along with the formation processes of particles, were investigated. CaCO(3) nanoparticles of 30-60 nm in size were also prepared by the reactor. The results revealed that the addition of methyl alcohol, ethanol etc. favor the synthesis of nanoparticles with small size. The particles size decreases with the increase in ethanol concentrations. With the increase in membrane MWCO, the products tend from nanoparticles towards aggregates.     

Propagation of instability in dielectric elastomers

When an electric voltage is applied across the thickness of a thin layer of an dielectric elastomer, the layer reduces its thickness and expands its area. This electrically induced deformation can be rapid and large, and is potentially useful as soft actuators in diverse technologies. Recent experimental and theoretical studies have shown that, when the voltage exceeds some critical value, the homogenous deformation of the layer becomes unstable, and the layer deforms into a mixture of thin and thick regions. Subsequently, as more electric charge is applied, the thin regions enlarge at the expense of the thick regions. On the basis of a recently formulated nonlinear field theory, this paper develops a meshfree method to simulate numerically this instability.     

关于4-苯基-2-丁酮与饱和亚硫酸氢钠加成反应的探讨

亚硫酸氢钠与醛酮的加成是比较经典的反应 ,但在与 4 苯基 2 丁酮的反应中 ,传统的实验反应条件并不一定是最佳选择