Molecular dynamics study on the effect of molecular orientation on polymer welding

Coarse-grained molecular dynamics simulation of a bead-spring polymer model was conducted for interdiffusion of two polymer flow fronts flowing parallel to one another as would be found in a weld-line. The effect of molecular orientation of the flow fronts on the interfacial structure was simulated. It was observed that the time evolution of the interfacial thickness was suppressed by shear flow for a chain whose length was longer than entanglement length. According to the analysis of autocorrelation function of end-to-end vector, it was revealed that anisotropic motion of chain was responsible for the growth of interfacial thickness and relaxation of the chain orientation was an important mechanism to explain the effect of shear flow on the growth of interfacial thickness. From the analysis of the segment motion at the interface with taking the density profile of end beads and center beads during the diffusion, it was found that interdiffusion of the end segment was always faster than that of center segments and significantly suppressed in oriented long chain.     

Effect on Wettability of FEP Teflon Surface Morphology

Wettability of FEP Teflon® (a perfluorinated ethylene-propylene copolymer) is vastly improved by heterogeneous nucleation and crystallization in contact with gold, a high surface free energy substrate. The critical surface tension of wetting (γ_e) increases from 18.8 dynes/cm to 40.4 dynes/cm. We compute that this rise in γ_e results from a 20 percent increase in the surface density of gold-nucleated FEP Teflon®. The increase in critical surface tension from 18.8 dynes/cm to 20.6 dynes/cm, for as received FEP Teflon which had been crosslinked by helium in a glow discharge (CASING technique), suggests an increase of the surface density with crosslinking. The critical surface tension of the gold-nucleated FEP Teflon® is sharply decreased from 40.4 dynes/cm to 22.0 dynes/cm by short exposure to the CASING treatment in helium. The results of ATR infrared spectroscopy show that in the surface region of the polymer there are no chemical changes such as the presence of unsaturated groups or the introduction of polar groups by oxidation. We conclude from this study that wettability of the polymer surface is affected by the surface morphology.     

Correlations among FBR core characteristics for various fuel compositions

In the design of a fast breeder reactor (FBR) core for the light water reactor (LWR) to FBR transition stage, it is indispensable to grasp the effect of a wide range of fuel composition variations on the core characteristics. This study finds good correlations between burnup reactivity and safety parameters, such as the sodium void reactivity and Doppler coefficient, for various fuel compositions and determines the mechanisms behind these correlations with the aid of sensitivity analyses. It is clarified that the Doppler coefficient is actually correlated with the other core characteristics by considering the constraint imposed by the requirement of sustaining criticality on the fuel composition variations. These correlations make it easy to specify the various properties ranges for core reactivity control and core safety, which are important for core design in determining the core specifications and performance. They provide significant information for FBR core design for the transition stage. Moreover, as an application of the above-mentioned correlations, a simplified burnup reactivity index is developed for rapid and rational estimation of the core characteristic variations. With the use of this index and these correlations, the core characteristic variations can be estimated for various fuel compositions without repeating the core calculations.     

Biodegradable supramolecular composites of poly(ε‐caprolactone) and low‐molecular‐weight organic gelators

When a homogeneous hot liquid of poly(ε‐caprolactone) (PCL) with (R)‐12‐hydroxystearic acid (HSA) or N‐carbobenzyloxy‐L ‐isoleucylaminooctadecane (CIA) was gradually cooled to room temperature, the mixture became gelatinous material and then solidified to give a PCL/HSA or PCL/CIA composite. The rheological measurements of the mixtures of PCL with HSA and CIA revealed that the organogels are formed at around 70–50°C and 100–73°C during the cooling process, respectively. Furthermore, the formation of supramolecular fibrillar networks was confirmed by the microscopic and differential scanning calorimetric analyses. The tensile moduli of both the composites were improved by the addition of CIA and HSA. Both the composites showed so high biodegradability as PCL. The fibrillar networks of the composites were also regenerated during the repeated cooling process from the isotropic liquid. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Processing‐structure‐property relationships in solid‐state shear pulverization: Parametric study of specific energy

Solid‐state shear pulverization (SSSP) is a unique processing technique for mechanochemical modification of polymers, compatibilization of polymer blends, and exfoliation and dispersion of fillers in polymer nanocomposites. A systematic parametric study of the SSSP technique is conducted to elucidate the detailed mechanism of the process and establish the basis for a range of current and future operation scenarios. Using neat, single component polypropylene (PP) as the model material, we varied machine type, screw design, and feed rate to achieve a range of shear and compression applied to the material, which can be quantified through specific energy input (E_p). As a universal processing variable, E_p reflects the level of chain scission occurring in the material, which correlates well to the extent of the physical property changes of the processed PP. Additionally, we compared the operating cost estimates of SSSP and conventional twin screw extrusion to determine the practical viability of SSSP. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers     

Regeneration of granular activated carbon with adsorbed trichloroethylene using wet peroxide oxidation

The objective of this study is to clarify the regeneration of granular activated carbon (GAC) adsorbed trichloroethylene (TCE) using wet peroxide oxidation (WPO). TCE and TOC concentrations decreased during WPO, whereas Cl(-) accumulated in water indicating that TCE was not only decomposed but was also mineralized to Cl(-) and CO(2) using WPO. Regeneration efficiencies (q/q(0)) of GAC regenerated at 150, 165 and 180 degrees C (initial pH 4) were 0.36, 0.45, 0.48, respectively. In addition, regeneration efficiencies of GAC regenerated in the solution of various initial pH (2.5, 3.0, 4.0) at 180 degrees C were 0.71, 0.60, 0.48, respectively. These results suggest that regeneration of GAC is more effective at higher reaction temperature and lower initial pH of the solution. In the repeated regeneration of GAC, the adsorption capacity of GAC for TCE gradually decreased and regeneration efficiency of the regenerated GAC at sixth step was 0.40. The adsorption capacity loss of regenerated GAC is probably due to oxidation of GAC during WPO.     

Power swing damping control by HVDC power modulation in an ac/dc hybrid transmission system

This paper describes power swing damping control by HVDC power modulation. In a hybrid system (where the ac transmission system and the HVDC system compose a loop transmission system), damping control of power swing by control of HVDC power is called power modulation control. The new HVDC link between the Shokoku and Kansai power systems forms a loop transmission system consisting of the existing ac transmission system and the new HVDC transmission system; therefore, power modulation control can be applied for stabilization of the ac system. This paper deals with a newly developed power modulation control system to damp two power-swing modes occurring in a 60-Hz interconnected system and the neighboring power system to the HVDC converter station. Characteristics of power swings in an ac systems, principles of power swing damping control by power modulation, the control system design method, and the results of verification tests by digital and analog simulators are described. It is shown that the developed power modulation system applied to the HVDC link is effective for damping two power swing modes.     

Tapered Multimode Interference Combiners for Coherent Receivers

报道了一个新的基于锥形多模干涉的相干光波合波器.对锥形多模波导中的模式行为给出了完整的理论分析,并给出了该锥形合波器在不同结构下的输出特性.在一个绝缘体上硅的基板上实现了该器件.鉴于无后向反射,容易扩展为多口配置,对实验误差有大的允许度和尺寸紧凑等优点,这种锥形多模干涉的合波器是大型光子集成中所用的相干光波合波器的理想选择.     

Manufacturing technology for continuous high-density coils for brushless motors

This paper reports on our development of a manufacturing technology for continuous high-density coils and terminal processing for high performance motor stators. We have developed a “series winding and collective forming method”. The coils are wound in series, and their slot insertion parts are collectively formed and clung. Four continuous and high-density coils with a slot-fill rate of 75% were prepared using the developed winding form and manufacturing facilities. Moreover, terminal insulation of the continuous coils was established with the developed wiring board. A 60% decrease in man-hours and 95% decrease in the cost of the board can be expected by using our technique rather than conventional printed circuit board manufacturing techniques.