Polymer films with nano- or microstructured surfaces have been widely applied to optical devices, bioplates, and printed electronics. Laser-assisted thermal imprinting (LATI), in which a laser directly heats the surfaces of a mold and a thermoplastic polymer, is one of the high-throughput methods of replicating nano- or microstructures on polymer films. Only the surfaces of the mold and polymer film are heated and cooled rapidly, therefore it is possible to replicate nano- or microstructures on polymer films more rapidly than by using conventional thermal nanoimprinting. In this study, microlens arrays (MLAs) were replicated on polymethylmethacrylate (PMMA) films using LATI, and the effects of the pressing pressure (10−50 MPa) and the pattern size (33- and 5-μm pitch) of the MLA on the filling ratio were investigated by analyzing a microlens replicated using different laser-irradiation times (0.1−2 ms). The filling ratio increased with increasing pressing pressure and laser-irradiation time in the replication of MLAs with varying sizes, while the flow of the PMMA varied with the pressing pressure and laser-irradiation time. It was found that during filling, the shape of the polymer cross-sectional surface demonstrated a double and single peak in the 33- and 5-μm-pitch patterns, respectively. This was because the depth of the heated area in the 33-μm-pitch pattern was smaller than the pattern size, whereas that of the 5-μm-pitch pattern was comparable to (or larger) than the pattern size.

Unmanned robot operation is highly anticipated for use in hazardous environments such as a nuclear accident and mine accident sites. We propose an automated construction system for robot locomotion and operation platform in a severely disturbed environment. In such an environment, the sensors and actuators that can be used are restricted. The platform is intended to enable specialized working robots to have access to any cube‐diced operation point, and to build a rail both for the platform itself and for specialized working robots. The entire platform structure is modularized, which means that the structure comprises multiple modules. They are assembled and constructed through cooperation of a transfer robot and a constructor robot. This paper describes the development of prototypes and explains experiments conducted to verify our fundamental concept. In particular, the feasibility of module‐transfer and connection motions in three prioritized positions is verified using the developed prototypes. The system design and experiments reveal that the most important technique to realize the proposed system is how to use guide structures to reduce the effects of mechanical error and misalignment among robots.

As a way of reducing the amount of particulate matter (PM) contained in the exhaust gas, diesel particulate filter (DPF) is widely used. To keep the condition of DPF normal and effective, estimation of the amount of PM deposits in the DPF is important. The estimation is mainly conducted based on the value of pressure drop across the DPF. Occasionally, the value of the pressure drop rises suddenly and it leads to overestimation of the amount of PM deposits. In order to elucidate the cause of the sudden pressure drop increase phenomenon, this paper first reveals the engine operating conditions which invoke this phenomenon. The authors also have developed a visualization method to realize the wide-perspective internal observation of the DPF. The observation experiment has been conducted with a commercial engine and DPF under the revealed conditions. Experimental results make clear that the phenomenon is caused by PM deposit layer collapse and channel plugging.

The authors have been offering a graduate level design course at the University of Tokyo. The students form groups of about 5 members to identify their own design goals and construct creative solutions to meet the product functional requirements (FRs). The course teaches Design Record Graph (DRG), a network diagram that starts with the product FR that divides into a number of sub-functions. The division continues until all functional elements are identified, and when every element functional requirement maps to a single element design parameter (DP), the design meets the independence axiom. The projects often start with heavily coupled designs that gradually turn into clean solutions towards their finalized design. The graph expression is easier for design students to get started with functional decomposition without having to work with design matrices