Preparation of polyimide-epoxy composites

The formation of a three dimensional network of crosslinked epoxy leads all unmodified epoxies to have inherent brittleness and relatively low degradation temperatures. Polyimides, on the other hand, are widely used for applications that require high degrees of flexibility and thermal resistance. Here, we have focused on the preparation of epoxy systems cured with polyamic acids instead of traditional amino-group-containing hardening agents. The cure behavior and potential reaction mechanisms of EPON 828 resin and polyamic acid mixtures were evaluated by DSC and TGA. Thermal analysis showed a complex reaction sequence taking place in the mixture and also determined the extent of reaction of the polyamic acid with itself and the competitive reaction of the polyamic acid with the epoxy. The compositions of the mixtures were varied to see the dependence of the cure behavior on component concentrations. Solutions of the two components did not phase separate and also phase separation was not apparent either optically or microscopically in the cured samples. This phase behavior was attributed to a unique in situ reaction. A novel solvent system for the polyamic acid precursor was also used.     

Expert system for dispatch control in restoration of ehv power system after complete blackout

Present-day power systems operate with high reliability, and it is rare that a blackout will extend over an entire system swiftly and securely. This paper considers automatic power supply to loads after a complete blackout of a system. First, taking into account characteristics of generators, loads, and initial power sources, a method is proposed of allocating several generators to each load in parallel to the system and supplying power to the load sequentially. Second, to remove the imbalance between supply and demand of power, a method is proposed of adjusting the amount of supply and generation according to a present imbalance and the sum of past ones. Third, to automatically issue orders for start-up, parallel, follow-up, stand-by, and stoppage of generators, several rules for each power station are set and an expert system is made based on them. Finally, the expert system is applied to a model power system, and it is verified that it can restore loads without any trouble for a complete blackout which occur at any time of a day and in any restoration pattern.     

Order-disorder transition and its effect on microwave quality factor Q in Ba(Zn1/3Nb2/3)O3 system

Influences of composition deviation from stoichiometry and heat treatment on crystal phases and Q factor in Ba(Zn_1/3Nb_2/3)O₃(BZN) were studied. The structural order and the crystal phases strongly depended on the slight composition deviation from stoichiometric BZN. The maximum Q factor was obtained at the vicinity of the stoichiometric BZN. In the other regions, non-stoichiometric disordered BZN or ordered BZN with secondary phase were formed, and their Q factors were found to be low. For the stoichiometric BZN, the order-disorder phase transition occurred between 1300 and 1400^°C. The crystal-structural ordering of the stoichiometric BZN was improved by post-annealing at below its transition temperature, conserving the density and the grain size. However, no significant Q factor improvement was found. The Q factor of the stoichiometric BZN strongly depends on the density and grain size not on the crystal-structural order. These results suggest that the ceramic microstructure such as the pore and grain boundary, the secondary phase and lattice defect caused by non-stoichiometry affect the variation of the Q factor in BZN system than the crystal-structural ordering.     

Piezoelectric properties of langasite group based on the ionic size of cation

As langasite A₃BC₃D₂O₁₄ compounds group with piezoelectric properties has no phase transition up to the melting point of 1400–1500 °C, they have been applied for the combustion pressure sensor. As they also have a larger electromechanical coupling factor compared to quartz and nearly the same temperature stability as quartz, the surface acoustic wave (SAW) filters are expected based on the digital transformation of wider bandwidth and higher-bit rates. In the case of three-element compounds such as [R₃]_A[Ga]_B[Ga₃]_C[GaSi]_DO₁₄ (R=La, Pr and Nd), the piezoelectric constant increases with the ionic radius R. In the case of four-element compounds such as [A₃]_A[B]_B[Ga₃]_C[Si₂]_DO₁₄ (A=Ca or Sr, B=Ta or Nb), |d₁₁| and k₁₂ values as a function of A_L/B_L ratio showed a linear relationship completely. There are two effects for the substitutions of A- and B-site cations: the substitution of Sr for Ca brings expansion toward [100] and enlargement in |d₁₁| and k₁₂. On the other hand, as the substitution of Ta for Nb brings not much change, the properties are similar. In this study, five-element compounds such as La_3?xSr_xTa_yGa_5?x+ySi_1+x?2yO₁₄ (0≤x≤3, 0≤y≤1) solid solutions analysed by a single crystal X-ray diffraction are compared with the three- and four-element compounds on the coordinates of oxygen ions. As the coordinates positions are located on the extended line of coordinate positions on the three-element compounds as increasing ionic radius of R-ions in A-site, the piezoelectric properties |d₁₁| and k₁₂ are expected become large.     

Glare Generation Based on Wave Optics

This paper proposes a novel and general method of glare generation based on wave optics. A glare image is regarded as a result of Fraunhofer diffraction, which is equivalent to a 2D Fourier transform of the image of given apertures or obstacles. In conventional methods, the shapes of glare images are categorized according to their source apertures, such as pupils and eyelashes and their basic shapes (e.g. halos, coronas, or radial streaks) are manually generated as templates, mainly based on statistical observation. Realistic variations of these basic shapes often depend on the use of random numbers. Our proposed method computes glare images fully automatically from aperture images and can be applied universally to all kinds of apertures, including camera diaphragms. It can handle dynamic changes in the position of the aperture relative to the light source, which enables subtle movement or rotation of glare streaks. Spectra can also be simulated in the glare, since the intensity of diffraction depends on the wavelength of light. The resulting glare image is superimposed onto a given computer‐generated image containing high‐intensity light sources or reflections, aligning the center of the glare image to the high‐intensity areas. Our method is implemented as a multipass rendering software. By precomputing the dynamic glare image set and putting it into texture memory, the software runs at an interactive rate.     

Heat and mass transfer during crystal growth

Quality of semiconductor and oxide crystals which are grown from the melts plays an important role for electronic and/or optical devices. The crystal quality is significantly affected by the heat and mass transfer in the melts during crystal growth in a growth furnace such as Czochralski or horizontal Bridgman methods. This paper reviews the present understanding of phenomena of the heat and mass transfer of the melts, especially instability of melt convection from the detailed numerical calculation, which helps to understand the melt convection visualized using X-ray radiography. Large scale simulation of melt convection during crystal growth is also reviewed.

Characteristics of flow instabilities of melt convection with a low Prandtl number (ratio between momentum and thermal diffusivities) are also reviewed by focusing on the instabilities of baroclinic, the Rayleigh-Benard and the Marangoni-Benard, from the points of view of temperature, rotating and/or magnetic field effects during crystal growth. Oxygen concentration in grown crystals is also discussed how melt convection affects.     

Evaluation of method for simultaneous determination of pesticide residues in fruits and vegetables by collaborative study

A collaborative study involving 8 laboratories was conducted to evaluate a method for the simultaneous determination of pesticide residues in 6 types of fruits and vegetables (spinach, tomato, apple, radish, cabbage and carrot). The method of analysis was the same as reported by Kakimoto et al. in 2003. One hundred and thirty-nine pesticides were spiked by each of 8 laboratories at levels of 0.1 microg/g (pesticides analyzed by GC/MS) or 0.5 microg/g (pesticides analyzed by HPLC) into the 6 kinds of samples. Statistical analysis showed that 111 pesticides could be analyzed with practical precision by this method. For screening purposes, the method could analyze 118 pesticides. The median values of the limits of detection were 0.001-0.041 microg/g. The calibration curves were linear in the range of 0.5-5 microg/mL for most pesticides with median correlation coefficients of 0.983-1.000.     

Conventional detection of 2,4-dinitrophenol using quartz crystal microbalance

We present conventional detection of 2,4-dinitrophenol (DNP) for using the competitive reaction between DNP and DNP-conjugated albumin onto DNP antibody immobilized quartz crystal microbalance (QCM). This QCM method allows detection of DNP concentration in the range of 0.01 to 100 ng/ml; linear correlation obtains DNP concentration from 1 to 100 ng/ml.     

Information-theoretic investigation of impact of huggable communication medium on prefrontal brain activation*

This paper examines the effect of mediated hugs that are achieved with a huggable communication medium on the brain activities of users during conversations. We measured their brain activities with functional near-infrared spectroscopy (NIRS) and evaluated them with two information theoretic measures: permutation entropy, an indicator of relaxation, and multiscale entropy, which captures complexity in brain activation at multiple time scales. We first verify the influence of lip movements on brain activities during conversation and then compare brain activities during tele-conversation through a huggable communication medium with a mobile phone. Our analysis of NIRS signals shows that mediated hugs decrease permutation entropy and increase multiscale entropy. These results suggest that touch interaction through a mediated hug induces a relaxed state in our brain but increases complex patterns of brain activation.