In this study, the mechanisms of jet atomization were analyzed based on a frequency analysis of atomization sounds in the audible range (∼20 kHz). Jet atomization is a two-dimensional, high-speed atomization using a diaphragm, and interesting acoustic signals and atomization phenomena were detected on hydrophobic and hydrophilic diaphragms. The hydrophilic diaphragm strongly interacted and resonated with the surface wave, resulting in symmetrical jet atomization relative to the diaphragm. The resonance between the diaphragm and the surface wave was supported by a calculation of the eigenfrequency of the diaphragm and the coincidence of the droplet diameters as calculated from Lang's equation. Notably, the diaphragm excited by the ultrasonic transducer acted as a new transducer vibrating perpendicular to the transducer. As a result, when the diaphragm and the surface wave were in resonance at 2.4 MHz, a symmetrical two-dimensional high-speed jet atomization was generated in the direction perpendicular to the transducer’s vibration direction. This study also revealed that the atomization state can be determined based on the acoustic analysis. This acoustic analysis of atomization sounds can be applied in more advanced atomization control, such as for providing uniform dispersions of droplets containing DNA, drugs, or microplastics.

A university course on mechanical design utilizing CAE structural analyses is reported. To develop students’ skills to solve practical open-ended engineering problems, a project-based learning (PBL) approach was adopted. The course taught not only technical skills to use CAE software but also fundamental knowledge that links theoretical and practical problems in engineering. Each segment of this course consisted of a lecture and workshop. The basic concepts of structural analysis and the background theory of finite element analysis were described in the lecture. Students conducted structural analyses in a CAE software through workshop problems and compared its results to the theory learned in the lecture. CAE structural analyses were conducted in the integrated environment of the 3D CAD software Autodesk Inventor. As the final project of the course, groups of students designed an original structure under restrictions based on functionality, strength and weight. Data of the students’ performance in related courses were collected to analyse the improvement of skills needed to solve engineering problems, and a short survey was conducted to summarize responses from the students after the course had finished. The results of the data analysis and short survey indicated that the combination of the theoretical lectures and the PBL workshop improved the students’ motivation and performance.

A series of finite element analyses were conducted to clarify the effect of contact and interfacial resistance between constituents on effective thermal conductivities of dispersed composites. Equally dispersed fillers in FCC (face-centered cubic) and BCC (body-centered cubic) material systems were extracted from cyclic microstructures as unit cell models. In addition to spherical fillers, a polyhedron called the Wigner–Seitz cell that can realize a fully packed microstructure was chosen as the shape of the filler to investigate the effect of contact between the high volumetric fraction of fillers. The effective thermal conductivities of the resulting composites were calculated based on the FEA results and compared to the theoretical results for various volume fractions of the fillers including the maximum packing fraction. The following conclusions were obtained from the present study: 1. The effect of the contact depending on the shape and configuration of the fillers has more of a significant influence on the effective thermal conductivity than the influence of the increase in the volume fraction of the fillers. 2. When the contact occurred, the effective thermal conductivity became more than double that without contact. 3. Interfacial thermal resistance must be less than the order of 10−4 m2K/W to obtain improvement in the effective thermal conductivity by compounding the fillers.