Implicit Methods for Equation-Free Analysis: Convergence Results and Analysis of Emergent Waves in Microscopic Traffic Models

We introduce a general formulation for an implicit equation-free method in the setting of slow-fast systems. First, we give a rigorous convergence result for equation-free analysis showing that the implicitly defined coarse-level time stepper converges to the true dynamics on the slow manifold within an error that is exponentially small with respect to the small parameter measuring time scale separation. Second, we apply this result to the idealized traffic modeling problem of phantom jams generated by cars with uniform behavior on a circular road. The traffic jams are waves that travel slowly against the direction of traffic. Equation-free analysis enables us to investigate the behavior of the microscopic traffic model on a macroscopic level. The standard deviation of cars' headways is chosen as the macroscopic measure of the underlying dynamics such that traveling wave solutions correspond to equilibria on the macroscopic level in the equation-free setup. The collapse of the traffic jam to the free flow then corresponds to a saddle-node bifurcation of this macroscopic equilibrium. We continue this bifurcation in two parameters using equation-free analysis.Comment: 35 page

4D topology optimization: Integrated optimization of the structure and self-actuation of soft bodies for dynamic motions

Topology optimization is a powerful tool utilized in various fields for structural design. However, its application has primarily been restricted to static or passively moving objects, mainly focusing on hard materials with limited deformations and contact capabilities. Designing soft and actively moving objects, such as soft robots equipped with actuators, poses challenges due to simulating dynamics problems involving large deformations and intricate contact interactions. Moreover, the optimal structure depends on the object's motion, necessitating a simultaneous design approach. To address these challenges, we propose "4D topology optimization," an extension of density-based topology optimization that incorporates the time dimension. This enables the simultaneous optimization of both the structure and self-actuation of soft bodies for specific dynamic tasks. Our method utilizes multi-indexed and hierarchized density variables distributed over the spatiotemporal design domain, representing the material layout, actuator layout, and time-varying actuation. These variables are efficiently optimized using gradient-based methods. Forward and backward simulations of soft bodies are done using the material point method, a Lagrangian-Eulerian hybrid approach, implemented on a recent automatic differentiation framework. We present several numerical examples of self-actuating soft body designs aimed at achieving locomotion, posture control, and rotation tasks. The results demonstrate the effectiveness of our method in successfully designing soft bodies with complex structures and biomimetic movements, benefiting from its high degree of design freedom.Comment: 36 pages, 27 figures; for supplementary video, see https://youtu.be/sPY2jcAsNY

A modular approach to large-signal modeling of an interconnected AC/MTDC system

Y. Susuki, N. Kawamoto, Y. Ohashi, A. Ishigame, T. Funaki and S. D’Arco, "A Modular Approach to Large-Signal Modeling of an Interconnected AC/MTDC System," 2020 IEEE PES Innovative Smart Grid Technologies Europe (ISGT-Europe), The Hague, Netherlands, 2020, pp. 945-949, doi: 10.1109/ISGT-Europe47291.2020.9248890

Stiff deployable structures via coupling of thick Miura-ori tubes along creases

Origami-based structures play an important role in the realization of deployable mechanisms and unique mechanical properties via programmable deformation by folding. Among origami-based structures, tessellation by the coupling of origami tubes enriches the variations in geometry and mechanical properties. However, thickness accommodation is a critical problem in engineering applications involving the coupling of thick origami tubes. To solve this problem, this study proposes the coupling of thick Miura-ori tubes along the creases for facile fabrication, which sustains the one-degree-of-freedom (DOF) motion of thick Miura-ori tubes owing to the local mirror symmetry around the coupling interfaces. Furthermore, the coupling method contributes to the high stiffness of the coupled Miura-ori tubes, as evidenced by the wide gap in the eigenvalues between the one-DOF mode and the elastic modes obtained by the bar-and-hinge models. Finally, meter-scale coupled Miura-ori tubes were fabricated to demonstrate one-DOF motion and high stiffness. The findings of this study enable the rapid construction of structures by one-DOF motion and enhancement of transportability via flat-foldability.Comment: 41 pages, 16 figure

Efficacy of Combination Treatment with Tadalafil and Mirabegron in Patients with Benign Prostatic Hyperplasia Who Presented with Persistent Storage Symptoms After Tadalafil Monotreatment: A Prospective, Multicenter, Open-Labeled Study

Background: The aim of this study is to evaluate the efficacy and safety of tadalafil, a phosphodiesterase type 5 inhibitor, plus mirabegron, a β3-adrenoreceptor agonist, in patients with benign prostatic hyperplasia who presented with persistent storage symptoms after tadalafil monotreatment. Methods: The registration of this study started in August 2016 and ended in July 2019. The inclusion criteria included patients aged ? 50 years who were diagnosed with benign prostatic hyperplasia and who presented with overactive bladder symptoms. Patients were treated with oral tadalafil 5 mg once daily for 4 weeks. Then, its efficacy was evaluated. Patients who responded to the treatment received oral tadalafil 5 mg once daily for 4 more weeks (monotreatment group). Meanwhile, those who did not respond received oral tadalafil 5 mg and mirabegron 50 mg, which is an add-on treatment, once daily for 4 more weeks (combination therapy group). Results: After 8 weeks, the monotreatment group (n = 19) and the combination group (n = 56) had significantly better total Overactive Bladder Symptom Score and International Prostate Symptom Score and International Prostate Symptom Score voiding and storage subscale scores. Moreover, the two groups experienced significant improvements in the total Overactive Bladder Questionnaire and Nocturia Quality of Life Questionnaire scores, and Nocturia Quality of Life Questionnaire Bother/Concern subscale score after 8 weeks. However, there were no cases of urinary retention or serious adverse events. Conclusion: Combination treatment with tadalafil and mirabegron is effective and safe for patients with benign prostatic hyperplasia who presented with persistent storage symptoms after tadalafil monotreatment. Hence, tadalafil plus mirabegron is a promising therapeutic option, and it can improve overactive bladder related-quality of life

Magnetic Field-Induced Superconductor-Insulator-Metal Transition in an Organic Conductor: An Infrared Magneto-Optical Imaging Spectroscopy

The magnetic field-induced superconductor-insulator-metal transition (SIMT) in partially deuterated $\kappa$-(BEDT-TTF)$_2$Cu[N(CN)$_2$]Br, which is just on the Mott boundary, has been observed using the infrared magneto-optical imaging spectroscopy. The infrared reflectivity image on the sample surface revealed that the metallic (or superconducting) and insulating phases coexist and they have different magnetic field dependences. One of the magnetic field dependence is SIMT that appeared on part of the sample surface. The SIMT was concluded to originate from the balance of the inhomogenity in the sample itself and the disorder of the ethylene end groups resulting from fast cooling.Comment: 5 pages, 5 figures, to appear in Phys. Rev.