An upgraded version of the Particle and Heavy Ion Transport code System, PHITS2.52, was developed and released to the public. The new version has been greatly improved from the previously released version, PHITS2.24, in terms of not only the code itself but also the contents of its package, such as the attached data libraries. In the new version, a higher accuracy of simulation was achieved by implementing several latest nuclear reaction models. The reliability of the simulation was improved by modifying both the algorithms for the electron-, positron-, and photon-transport simulations and the procedure for calculating the statistical uncertainties of the tally results. Estimation of the time evolution of radioactivity became feasible by incorporating the activation calculation program DCHAIN-SP into the new package. The efficiency of the simulation was also improved as a result of the implementation of shared-memory parallelization and the optimization of several time-consuming algorithms. Furthermore, a number of new user-support tools and functions that help users to intuitively and effectively perform PHITS simulations were developed and incorporated. Due to these improvements, PHITS is now a more powerful tool for particle transport simulation applicable to various research and development fields, such as nuclear technology, accelerator design, medical physics, and cosmic-ray research.

The potential of three-dimensional (3D) metal-halide perovskites to sensitize organic triplets is unveiled. Nanocrystals of surface-modified inorganic cesium lead halide perovskites (CsPbX, X = Br/I) are found to work as efficient triplet sensitizers for photon upconversion based on triplet-triplet annihilation (TTA-UC) at low excitation intensity.

A new family of surface-functionalized CdSe/ZnS core-shell quantum dots (csQD) has been developed, which work as triplet sensitizers for triplet-triplet annihilation-based photon upconversion (TTA-UC). The surface modification of csQD with acceptor molecules plays a key role in the efficient relay of the excited energy of csQD to emitter molecules in the bulk solution, where the generated emitter triplets undergo triplet-triplet annihilation that leads to photon upconversion. Interestingly, improved UC properties were achieved with the core-shell QDs compared with core-only CdSe QDs (cQD). The threshold excitation intensity, which is defined as the necessary irradiance to achieve efficient TTA process, decreases by more than a factor of four. Furthermore, the total UC quantum yield is enhanced more than 50-fold. These enhancements should be derived from better optical properties of csQD, in which the non-radiative surface recombination sites are passivated by the shell layer with wider bandgap.

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The Multi-agent Path Finding (MAPF) problem consists in all agents having to move to their own destinations while avoiding collisions. In practical applications to the problem, such as for navigation in an automated warehouse, MAPF must be solved iteratively. We present here a novel approach to iterative MAPF, that we call Priority Inheritance with Backtracking (PIBT). PIBT gives a unique priority to each agent every timestep, so that all movements are prioritized. Priority inheritance, which aims at dealing effectively with priority inversion in path adjustment within a small time window, can be applied iteratively and a backtracking protocol prevents agents from being stuck. We prove that, regardless of their number, all agents are guaranteed to reach their destination within finite time, when the environment is a graph such that all pairs of adjacent nodes belong to a simple cycle of length 3 or more (e.g., biconnected). Our implementation of PIBT can be fully decentralized without global communication. Experimental results over various scenarios confirm that PIBT is adequate both for finding paths in large environments with many agents, as well as for conveying packages in an automated warehouse.

The first example of green (λ > 500 nm)-to-ultraviolet (λ < 400 nm) triplet–triplet annihilation-based photon upconversion sensitized by lead halide perovskite nanocrystals is achieved.

In this work, we demonstrate that useful C-C bond-forming photoredox catalysis can be performed in air using easily prepared gel networks as reaction media to give similar results as are obtained under inert atmosphere conditions. These reactions are completely inhibited in homogeneous solution in air. However, the supramolecular fibrillar gel networks confine the reactants and block oxygen diffusion, allowing air-sensitive catalytic activity under ambient conditions. We investigate the mechanism of this remarkable protection, focusing on the boundary effect in the self-assembled supramolecular gels that enhances the rates of productive reactions over diffusion-controlled quenching of excited states. Our observations suggest the occurrence of triplet-sensitized chemical reactions in the gel networks within the compartmentalized solvent pools held between the nanofibers. The combination of enhanced viscosity and added interfaces in supramolecular gel media seems to be a key factor in facilitating the reactions under aerobic conditions.