A web-based e-learning system for increasing study efficiency by stimulating learner’s motivation

Due to the opportunities provided by the Internet, more and more people are taking advantage of distance learning courses and during the last few years enormous research efforts have been dedicated to the development of distance learning systems. So far, many e-learning systems are proposed and used practically. However, in these systems the e-learning completion rate is about 30%. One of the reasons is the low study desire when the learner studies the learning materials. In this research, we propose an interactive Web-based e-learning system. The purpose of our system is to increase the e-learning completion rate by stimulating learner’s motivation. The proposed system has three subsystems: the learning subsystem, learner support subsystem, and teacher support subsystem. The learning subsystem improves the learner’s study desire. The learner support subsystem supports the learner during the study, and the teacher support subsystem supports the teacher to get the learner’s study state. To evaluate the proposed system, we developed several experiments and surveys. By using new features such as: display of learner’s study history, change of interface color, encourage function, ranking function, self-determination of the study materials, and grouping of learners, the proposed system can increase the learning efficiency.

Voltammetric study of electrocatalysis for dioxygen reduction by trinuclear rutheniumammine complex confined in a polymer membrane

Electrocatalytic O₂ reduction was studied using a modified electrode coated with a Nafion membrane (Nf) dispersing a trinuclear ruthenium ammine complex ([(NH₃)₅Ru^IIIORu^IV(NH₃)₄ORu^III(NH₃)₅]Cl₆, Ru-red). When measuring cyclic voltammogram under O₂ atmosphere (at 0.5 mV s⁻¹), catalytic currents due to O₂ reduction were found to develop below −0.2 V (vs. Ag/AgCl). Since Ru-red undergoes irreversible decomposition into the mononuclear complexes via the reduced state (Ru^III-Ru^III-Ru^III) (∼−0.1 V), it is suggested that the electrocatalysis originates from the decomposed species (initial active species: Ru^II(NH₃)₅(OH₂) and Ru^II(NH₃)₄(OH₂)₂) rather than from the Ru-red. Although the present electrocatalyst was also applied to H₂O₂ reduction system, the catalytic activity was found to be poor from the voltammetric behavior. It appeared that the kinetics of the electrocatalysis is much faster in the O₂ reduction than in the H₂O₂ one. A selective and direct catalysis for O₂ reduction into H₂O was suggested from a ring-disk voltammogram to take place by an aggregate of the mononuclear ruthenium complexes in the polymer matrix. In addition, it was found that electrocatalytic O₂ reduction involves a slow kinetic process, so that factors affecting the overall kinetics were discussed in terms of the catalysis mechanism.     

Bubble wake visualization by using photochromic dye

Wake structure of a single “clean bubble”, rising in rectilinear, zigzagging or spiraling path, is experimentally investigated. A single nitrogen gas bubble was produced in a silicone oil pool and the wake structure development in the rear of the rising bubble was visualized by using photochromic dye. The flexibility of this visualization method enabled us to distinguish wake from drift easily. Both bubble motion and wake structure were recorded by using stereo high-speed video camera simultaneously. We present the first experimental support for the existence of the standing eddy at the rear of the clean bubble, as predicted by a previous numerical study by Ryskin and Leal [1984. Journal of Fluid Mechanics 148, 19-35], Dandy and Leal [1986. Physics of Fluids 29(5), 1360-1366] and Blanco and Magnaudet [1995. Physics of Fluids 7(6), 1265-1274]. We study motion of a pair of vortex filaments, which is called double-threaded type wake, in the case of bubble rising in an axi-asymmetric path. Visualization results of multiple formations of horse-shoe type vortices in one period of zigzag motion of rising bubble with shape oscillations, which has not been observed in previous studies are also presented.     

Helium gas permeability of montmorillonite/epoxy nanocomposites

Helium gas permeability of silicate clay (montmorillonite) particles/epoxy nanocomposites was examined. The incorporation of increasing amounts of montmorillonite particles reduced the helium gas permeability. Based on Fick’s law, gas permeation behavior of the nanocomposite was evaluated. With the increase of montmorillonite loading, gas diffusivity decreased, while gas solubility increased. Helium diffusion behavior is in agreement to the numerical results based on the Hatta–Taya–Eshelby theory. It has been revealed that dispersion of nanoscale platelets in polymer is effective in improving gas barrier property.     

Effect of gravity on InGaSb crystal growth

The effect of gravity on dissolution of GaSb in InSb melt and growth of InGaSb was experimentally investigated. Experiments were carried out in a GaSb(seed)/InSb/GaSb(feed) sandwich system under an imposed temperature gradient. In the experiments, the GaSb feed crystal dissolved into the InSb melt to supply the required GaSb component for the growth of In_0.1Ga_0.9Sb crystal. Two parameters were considered: (1) the inclination angle (θ) of the sample for gravity as 0° and 53°, and (2) the sample diameter (D) as 9 mm and 5mm. When θ was 0°, the interface was almost flat, indicating that convection was axisymmetric and stable. Whereas the interface was distorted towards gravitational direction when θ was 53°, indicating that solutal convection was dominant. The decrease of growth temperature and sample diameter reduced the distortion of interface and the dissolution amount of GaSb feed. The homogeneous crystals were grown at the initial growth stage by supplying the GaSb component during growth.     

Relationship between electrode surface roughness and impulse breakdown voltage in vacuum gap of Cu and Cu-Cr electrodes

The relationship between the impulse breakdown voltage of vacuum gaps and electrode surface roughness was investigated for the purpose of controlling the surface roughness on HV conductors. The roughness of mechanically polished Cu and Cu-Cr electrodes was measured with a roughness meter, and the relationship between the breakdown voltage and surface roughness was obtained for plate-to-plate gaps. The discharge-conditioning effect increased with reduction in the surface roughness. The breakdown voltage depended not only on the roughness of the cathode but also on the anode surfaces. Reducing the surface roughness was found not to be an effective way to increase the breakdown voltage for non-uniform field gaps after discharge conditioning.     

Properties of novel diallyl phthalate resin modified with sulfur‐containing allyl ester compounds

Sulfur‐containing allyl ester, which reacts with diallyl phthalate (DAP) resin to have allyl groups, was synthesized by the reaction of allyl phthalic acid with bisphenol having sulfur atoms. The sulfur‐containing allyl ester compound was blended with DAP resin to improve the adhesive properties to copper. By modification with sulfur‐containing allyl ester compound, the T‐peel adhesive strength and the lap shear adhesive strength to copper was improved. In particular, the adhesive strength was greatly improved when the resin was modified with the allyl ester compound having a disulfide bond (?S?S?) (DADS). It is concluded that this result is due to the improvement of the interfacial adhesive strength because the sulfur atom was found to be located in the surface of the copper by Fourier transform infrared (FTIR) analysis. The glass transition temperature (T_g) and the thermal decomposition temperature (T_d) of the cured DAP resin modified with DADS slightly decreased with increasing concentration of DADS. The lowering of T_g is because the crosslinking density of the DAP resin modified with DADS is smaller than that of DAP resin. Moreover, from thermogravimetric analysis, the lowering of Td of the DAP resin modified with DADS is because DADS is likely to pyrolyze. © 2013 Society of Chemical Industry     

Colorless polyimides with low coefficient of thermal expansion derived from alkyl‐substituted cyclobutanetetracarboxylic dianhydrides

Alkyl‐substituted cyclobutanetetracarboxylic dianhydrides (CBDAs) were synthesized by photo‐dimerization of alkyl‐substituted maleic anhydrides to obtain novel colorless polyimides (PIs). Dimethyl‐substituted CBDA (DM‐CBDA) showed much higher polymerizability with various diamines than conventional cycloaliphatic tetracarboxylic dianhydrides and led to high molecular weights of PI precursors. Polyaddition of non‐substituted CBDA and trans‐1,4‐cyclohexanediamine (t‐CHDA) was completely inhibited by salt formation in the initial reaction stage. The use of DM‐CBDA allowed the formation of a homogeneous/viscous PI precursor solution by overcoming the salt formation problem. The prominent substituent effect probably reflects how the methyl substituents of DM‐CBDA contributed to increasing the salt solubility. Some of the thermally imidized DM‐CBDA‐based systems simultaneously possessed non‐coloration, low coefficient of thermal expansion (CTE), very high T_g exceeding 300 °C and very low dielectric constant. Copolymerization was very effective for improving the solubility of DM‐CBDA‐based PIs. The copolyimide cast films prepared via chemical imidization displayed a further decreased CTE without sacrificing other target properties, suggesting that the present materials can be useful as plastic substrates in display devices. The mechanism of self‐chain orientation behavior during solution casting is also discussed. A potential application of the copolyimide systems as optical compensation film materials in liquid crystal displays is proposed. © 2013 Society of Chemical Industry .     

Experimental validation with field circuit by changing start voltage of salient pole synchronous motor

This paper reports on the experimental validation characteristics of a salient pole synchronous motor with the starting field circuit in contact. The starting characteristics were experimentally evaluated at voltages of 100%, 75%, and 50% using a 1.5 kVA salient pole synchronous motor. The signal for pulling into step was applied to the field circuit by using the control module for all test conditions. The results confirmed the proper pulling into step at 100% of voltage, and the results of the tests at 50% and 75% of voltage revealed that the pulling into step under these conditions becomes stable at the suitable slip condition.