High-performance combinatorial optimization based on classical mechanics.

Quickly obtaining optimal solutions of combinatorial optimization problems has tremendous value but is extremely difficult. Thus, various kinds of machines specially designed for combinatorial optimization have recently been proposed and developed. Toward the realization of higher-performance machines, here, we propose an algorithm based on classical mechanics, which is obtained by modifying a previously proposed algorithm called simulated bifurcation. Our proposed algorithm allows us to achieve not only high speed by parallel computing but also high solution accuracy for problems with up to one million binary variables. Benchmarking shows that our machine based on the algorithm achieves high performance compared to recently developed machines, including a quantum annealer using a superconducting circuit, a coherent Ising machine using a laser, and digital processors based on various algorithms. Thus, high-performance combinatorial optimization is realized by massively parallel implementations of the proposed algorithm based on classical mechanics.

Seasonal changes in activity levels among nursing care insurance service users in areas with different climates.

[Purpose] To clarify seasonal changes in activity levels among nursing care insurance service users in areas with different climates using the Life Space Assessment. [Subjects] A total of 72 nursing care insurance service users aged ≥65 years, who were from areas along the Sea of Japan or those around the Inland Sea. [Methods] The subjects were divided into 2 groups according to their home prefecture, and each survey was conducted over two successive seasons (Survey I: fall and winter, n=48, Survey II: winter and spring, n=24). We investigated the subjects' basic information, and determined their FIM, the Life Space Assessment, and Modified Falls Efficacy Scale scores. These scores were subjected to between-group and -season comparisons. [Results] In Survey I, there were no significant differences in any investigation item between the 2 groups, but the Japan Sea group showed decreases in the Life Space Assessment, Independent Life space, and Minimal Life space scores in winter. In Survey II, we did not note any between-group or -season differences. [Conclusion] Our findings suggest that the Life Space Assessment, whose scores are influenced by outdoor environments, may be used as a tool to clarify seasonal changes in activity levels of nursing care insurance service users.