Heat conduction tuning using the wave nature of phonons

The world communicates to our senses of vision, hearing and touch in the language of waves, as the light, sound, and even heat essentially consist of microscopic vibrations of different media. The wave nature of light and sound has been extensively investigated over the past century and is now widely used in modern technology. But the wave nature of heat has been the subject of mostly theoretical studies, as its experimental demonstration, let alone practical use, remains challenging due to the extremely short wavelengths of these waves. Here we show a possibility to use the wave nature of heat for thermal conductivity tuning via spatial short-range order in phononic crystal nanostructures. Our experimental and theoretical results suggest that interference of thermal phonons occurs in strictly periodic nanostructures and slows the propagation of heat. This finding broadens the methodology of heat transfer engineering by expanding its territory to the wave nature of heat

CMA-ES with Learning Rate Adaptation: Can CMA-ES with Default Population Size Solve Multimodal and Noisy Problems?

The covariance matrix adaptation evolution strategy (CMA-ES) is one of the most successful methods for solving black-box continuous optimization problems. One practically useful aspect of the CMA-ES is that it can be used without hyperparameter tuning. However, the hyperparameter settings still have a considerable impact, especially for difficult tasks such as solving multimodal or noisy problems. In this study, we investigate whether the CMA-ES with default population size can solve multimodal and noisy problems. To perform this investigation, we develop a novel learning rate adaptation mechanism for the CMA-ES, such that the learning rate is adapted so as to maintain a constant signal-to-noise ratio. We investigate the behavior of the CMA-ES with the proposed learning rate adaptation mechanism through numerical experiments, and compare the results with those obtained for the CMA-ES with a fixed learning rate. The results demonstrate that, when the proposed learning rate adaptation is used, the CMA-ES with default population size works well on multimodal and/or noisy problems, without the need for extremely expensive learning rate tuning.Comment: Nominated for the best paper of GECCO'23 ENUM Track. We have corrected the error of Eq.(7

Improvement of Cylindrical Deep Drawability in Hot Stamping

AbstractDeep drawability of steel sheets in hot stamping was investigated. In the case of deep drawing with a conventional die, the forming limit was significantly lower because the temperature of the sheet metal at the flange part decreased during the forming and the flow resistance increased. Therefore, the blank holding method to avoid temperature decrease at flange part of sheet metal was studied. In this study, application of gap supports and forming without blank holder were investigated. In the former method, the gap supports made clearance at the flange part. In the latter method, the blank holder was located at the lower dead point from the beginning of forming and the flange part of the blank was free during forming. The forming limit in both cases was improved as compared with that in the conventional blank holding method. For the application of gap supports, the limiting drawing ratio was also evaluated. In this experiment, the maximum value of limiting drawing ratio was 1.71

Comparison of crystal structures and effects of Co substitution in a new member of Fe-1111 superconductor family AeFeAsF(Ae = Ca and Sr): a possible candidate for higher Tc superconductor

We refined crystal structures of newly found members of the Fe-1111 superconductor family, CaFe\_{1-x}Co\_{x}AsF and SrFe\_{1-x}Co\_{x}AsF (x = 0, 0.06, 0.12) by powder synchrotron X-ray diffraction analysis. The tetragonal to orthorhombic phase transitions were observed at ~120 K for unsubstituted CaFeAsF and at ~180 K for unsubstituted SrFeAsF, the transition temperatures agreeing with kinks observed in temperature-dependent resistivity curves. Although the transition temperature decreases, the structural phase transitions were observed below 100 K in both samples of x = 0.06, and finally they were suppressed in the doping level of x = 0.12. The refined structures reveal that distortions of the FeAs4 tetrahedron from the regular tetrahedron likely originate from mismatches in atomic radii among the constituent elements. In this system, the enlarged FeAs4 tetrahedron resulting from larger radius of Sr than that of Ca is flattened along a-b plane, whereas the smaller radius of Ca makes the tetrahedron closer to regular one, and their characteristic shapes are further enhanced by Co substitution. These results suggest that the CaFeAsF compound is a promising candidate for higher-Tc superconductor.Comment: 17 pages, 8 figures, 2 tables, Supplementary information is included at the end of the documen

Brugada ショウコウグン ノ トリアツカイ : Brugadaガタ シンデンズ オ ドウ カンリスルカ

Brugada et al . reported that electrocardiogaraphic finding of ST elevation and right bundle branch block in the right precordial lead are closely associated with cardiac sudden death during sleep in 1992, and these finding is an important substrate of idiopathic ventricular fibrillation, since then we became call this clinical condition Brugada syndrome. Brugada type ECG is not so rare abnormality in Japan, especially saddle-back type ST elevation is often encountered in mass examination or daily clinic, and lethal arrhythmias are occurred in these some cases. Several percentage of asymptomatic Brugada syndrome complicate sudden cardiac death. Therefore, diagnosis and evaluation of prognosis of Brugada type ECG become important issue for daily clinic. Various suggestions for Brugada syndrome and asymptomatic Brugada type ECG are proposed, and implantable cardioverter defibrillator （ICD） is only therapy for Brugada syndrome, but there is not yet an agreed opinion about management of Brugada type ECG. Appropriate prevention for sudden death is necessary since some asymptomatic cases with Brugada type ECG complicate ventricular fibrillation. In our daily clinic, we examine signal averaged ECG, 123I-MIBG myocardial scintigarphy and adoministration test of pilsicanide for the case with Brugada type ECG as a screening test, and perform foreknowledge of sudden death. In near future, the standardized screening test for asymptomatic Brugada type ECG will be established by further study