Masayuki Nishi

While the benefits of using visual programming environments at the level of K-12 education have been well-studied, little is known about the plausibility of using visual programming in higher education settings. This empirical study compares the merits and demerits of using textual programming environments (e.g., Android Studio) and visual programming environments (e.g., MIT App Inventor) in an Android app development course targeting first year university students in a faculty of engineering. The analysis is based on instructors' reflection as well as feedback from students. Our findings show that a visual programming environment was useful even for university students. It allowed beginners to focus on the logic of apps without facing the barrier of too many technical details. They could quickly develop functional apps with complex features. On the other hand, textual programming takes an upper hand when it comes to providing an authentic learning experience as well as supporting efficient source code management in collaborative development. We discuss the implications of the findings within the framework of the distributed cognition theory and point out directions for future research.

The Soret effect is a diffusion phenomenon driven by a temperature gradient in a multicomponent system. This effect in condensed systems is not fully understood. Previously, we reported a theoretical model called “adjusted Kempers model” to predict the Soret coefficient in glass melts, and compared the experimental value to the theoretical value for 11Na ₂ O‐89B ₂ O ₃ (mol%) melts. Here, molecular dynamics calculations, as well as theoretical and experimental values, are quantitatively compared in 10Na ₂ O‐90GeO ₂ melts. We used a vertical tubular furnace to cause a temperature gradient and heated the sample from top side to reduce the natural convection. We measured the composition of 10Na ₂ O‐90GeO ₂ glass samples after 45, 90, and 180 hours of heat treatment under a temperature gradient, and estimated the steady‐state Soret coefficient near 1373 K to be 1.09 × 10 ⁻³ K ⁻¹ . In addition, we calculated Soret coefficients to be 3.65 × 10 ⁻³ K ⁻¹ and 1.85 × 10 ⁻³ K ⁻¹ in theory and molecular dynamics calculation, respectively. The ratios between the experimental and theoretical Soret coefficients were 1.2 and 3.3 for 11Na ₂ O‐89B ₂ O ₃ melts and 10Na ₂ O‐90GeO ₂ melts, respectively. The difference in ratios may be attributed to the mass and size of diffusion species in the glass melts.

Fracture of dissimilar materials is generally caused in the vicinity of the interface end. This is because the singular stress is induced at the interface end. In this study, in order to improve the adhesive strength, the adhesive bonded round bar with circumferential notch near the interface is considered. The small crack at the interface are strongly controlled by the singular stress field at the interface end without the crack. Then, the intensity factor of the interface edge crack. The effect of the position of circumferential notch on the stress intensity factor of the interface crack is analyzed. As a result, it is found that the singular stress at the interface end can be reduced significantly when the circumferential notch is close to the interface of the bonded bar.

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A single gold nanostructure is successfully deposited at the tip apex of a silicon probe for atomic force microscopes (AFM) in an electroless and area-selective manner. The tip apex of a commercially available silicon AFM probe is irradiated with a focused ion beam (FIB) to remove the native oxide layer, and then the probe was exposed to chloroauric acid (HAuCl₄) aqueous solution containing sodium chloride (NaCl). A single gold nanostructure selectively grows at the FIB-irradiated apex as a consequence of electron transfer from silicon to the solution through the FIB-irradiated silicon surface. This electron transfer is driven by the difference in the electrochemical potential of electrons. NaCl, added to a pure HAuCl₄ aqueous solution, improves the area-selectivity of gold growth and decreases the size of gold, resulting in desired geometry of gold as the tip apex for tip-enhanced Raman spectroscopy (TERS) in terms of the spatial resolution and the enhancement of the electric field. Our probes provide TERS imaging of a carbon nanotube with a spatial resolution of 10 nm, and enhancement factors up to 2.2 × 10⁵ for an azobenzene thiol self-assembled monolayer in the gap-mode configuration with a side-illumination optical setup.

We describe and experimentally verify the mechanism of area-selective electroless deposition of gold nanostructures at interfaces between locally induced naked silicon surfaces and pure HAuCl₄ solution. We previously demonstrated that gold nanostructures selectively grow on focused ion beam (FIB)-irradiated areas of a silicon substrate when the substrate is exposed to pure HAuCl₄ solution. We revealed that silicon dangling bonds formed by FIB irradiation reduce Au(III) ions and initiate the nucleation of gold. Here, we focus on the growth stage. Quantitative estimate of the amount of gold grown reveals that silicon dangling bonds explain only a fraction of the total amount of gold. Thus, the growth mechanism is different from the nucleation mechanism. In the growth stage, soon after silicon/gold interfaces form via gold nucleation, electrons in the crystalline silicon near the interfaces reduce Au(III) ions through the interfaces and the growing gold. This mechanism is consistent with the Fermi level (chemical potential of electrons), which decreases in the order silicon > gold > HAuCl₄ solution in the isolated form. Double exposure to the same and different HAuCl₄ solutions shows the results that support the mechanism, and allows further control of gold morphology.