Kogakuin University

A (0001) α-Ga2O3 film was grown by the mist chemical vapor deposition method on a (0001) α-Cr2O3 template (100 μm thick α-Cr2O3 layer formed on an α-Al2O3 substrate). Benefiting from the small a-axis lattice mismatch between α-Ga2O3 and α-Cr2O3, a high-quality α-Ga2O3 film with a small twist distribution, and consequently a low edge dislocation density, was coherently grown on an α-Cr2O3 template. The edge dislocation density of 7 × 107 cm−2, estimated from the full-width at half-maximum value of the X-ray rocking curve (XRC) in X-ray diffraction (XRD), was more than two orders of magnitude lower than that of the film grown on an α-Al2O3 substrate, and was almost consistent with that of the α-Cr2O3 template. The bright-field transmission electron microscopy (TEM) image supports the dislocation density estimated from the XRD measurements. The high-angle annular dark-field scanning TEM and inverse fast Fourier transform images indicate coherent growth, with almost no misfit dislocations generated at the α-Ga2O3/α-Cr2O3 interface.

A palladium-complex-catalyzed cross-coupling reaction was achieved between benzyl diazo esters and aryl iodides bearing ortho-substituents, which had previously not been tolerated for such reactions. In the quest for an optimal catalyst for reactions with ortho-iodobenzaldehyde, the yields of the desired coupling compound were unsatisfactory in many catalyst systems, and the aldol reaction frequently occurred competitively. However, the catalyst prepared from Pd(dba)2 and P(2-furyl)3 promoted the cross-coupling reaction, generating α-diazophenyl acetate in excellent yield. The cross-coupling was also acceptable for aryl iodides with various ortho-substituents, delivering a variety of coupling products in moderate to good yields.

Loudspeaker arrays are commonly used for personal audio systems. Alternatively, panel loudspeakers can be employed in place of conventional loudspeaker arrays. The advantage of panel loudspeakers is that they preserve the appearance and aesthetic quality of products. Specifically, structural actuators can be mounted on the rear side of a product enclosure and thus remain concealed. However, directivity control on the front side may be undesirably accompanied by sound leakage on the rear side because the enclosure acoustically couples the two sides. To address this issue, acoustic actuators, i.e., loudspeakers, are introduced inside the enclosure and used in conjunction with the structural actuators. The array signal processing of the structural and acoustic actuators is based on acoustic contrast control, which simultaneously aims to achieve directivity control in the exterior space and sound reduction in the interior space. The performance of the proposed methods is verified through computer simulations and experiments using a rectangular plate-cavity model.

Inclusive design requires empathy for users with diverse needs, yet designers often find it difficult to consider perspectives and needs they have not personally experienced. This study investigated whether simulating left-handedness through human augmentation could enhance design awareness and reduce unconscious bias. The “left-handed experience device,” a wearable robot that simulates left-handedness by mirroring right-handed movements, was developed. Engineering students were divided into three groups: (1) no information about left-handedness, (2) explanation of left-handedness, and (3) experiential learning using the device. Each group conducted product redesign tasks focusing on usability and inclusivity using everyday tools such as calipers and kitchen tools. Design outcomes were evaluated using a self-assessment rubric. The group that used the device (Group 3) demonstrated higher awareness and generated more inclusive and symmetrical designs. Participants also reported increased confidence and empathy toward minority users. These results suggest that human augmentation can serve as a valuable educational tool for fostering inclusive design thinking. While experiential learning was effective in raising awareness, sustainable behavioral change remains a challenge.

Solar radiation pressure (SRP) introduces non-negligible perturbations to periodic orbits around libration points in the Earth–Moon circular-restricted three-body problem (CR3BP), affecting their stability and dynamical structure. This study investigates periodic orbits around libration points in the Earth–Moon CR3BP under the influence of SRP. When considering SRP in the Earth–Moon system, the Sun follows a circular motion with a synodic lunar period in the rotating frame of the Earth–Moon system. To handle the time-dependent nature of SRP, we render the non-autonomous system an autonomous one by augmenting state vector with the Sun's phase angle and the spacecraft's two attitude angles. This transformation enables stability and bifurcation analysis using conventional tools, such as monodromy matrix evaluation. Through this augmented framework, we can design and analyze families of periodic orbits, connecting solutions with fixed attitude angles to those exhibiting time-varying attitude angles. The analysis in this study, which takes into account the time variation of SRP, contributes to a deeper understanding of dynamical structures and bifurcation phenomena in dynamical systems influenced by SRP.

This paper reports on the application of DP-AA-PSP to unsteady shock wave phenomena. PSP measurements were performed under sub-microsecond exposure conditions to enable the clear visualization of shock waves. The superior temporal response of DP-AA-PSP was evaluated by comparing its performance to conventional PSPs in high-speed unsteady fluid measurements.

This study investigates how incorporating a twisted wall structure into a lattice structure improves sound absorption performance based on the numerical and experimental investigation. The twisted wall structure is expected to lengthen the flow path of sound waves inside the sound-absorbing structure. In this study, finite element simulations have been conducted to compare the sound absorption characteristics at twisted angles of 0 deg, 180 deg and 360 deg. Note that the direct and homogenization methods are also applied in the simulations, and sound absorption measurements were also performed to confirm the same trends as the numerical and experimental results. As a result, an increase in the peak sound absorption coefficient and an improvement in the sound absorption coefficient at low frequencies were confirmed as the torsional angle increases. Furthermore, by calculating the flow length passing inside the sound-absorbing structure, the frequency at the peak sound absorption coefficient can be predicted.