Some considerations on the use of space sound absorbers with next-generation materials reflecting COVID situations in Japan: additional sound absorption for post-pandemic challenges in indoor acoustic environments

In this study, we first point out the possible acoustic problems associated with the post-pandemic operation of built environments. In particular, we focus on the problem of acoustic deficiency due to the lack of absorption. This deficiency, which is likely to be encountered in most enclosed spaces in a range of establishments, is due to the reduced number of audience members or users of the space as a result of social distancing. As one of the promising solutions to this problem, we introduce a sound absorption technique using three-dimensional (3D) space sound absorbers developed through our recent research projects. Significantly, the type of sound absorber proposed herein is made of materials that are especially suited to hygiene considerations. The materials are microperforated panels (MPPs) and permeable membranes (PMs), both of which are easily washable and sanitised. Furthermore, we point out that 3D-MPP or PM space absorbers possess the additional value of aesthetic designability

Effects of long rarefied plasma on fast electron generation for FIREX-I targets

Long-scale preformed plasmas are generated inside the cone by the pre-pulse of the heating laser in the cone-guided fast ignition scheme and it is found that coupling efficiency from the heating laser to fast electrons especially suitable for core heating is drastically reduced by the preformed plasmas. To mitigate this serious problem, an extremely thin film is suggested to cover the entrance of the cone. This method, however, introduces long rarefied plasmas around the entrance of the cone and the main pulse must propagate through these plasmas. Therefore, fast electron characteristics produced by the main pulse could be affected, and effects of long rarefied plasmas on fast electron generation are investigated. It is found that the electron beam intensity becomes larger than that without the rarefied plasma, but the energy coupling rate from the heating laser to the core decreases due to lack of appropriate electrons for core heating. To achieve less than 10% degradation of the core electron temperature, the thin film must be expanded by irradiation of the pre-pulse so that the length and the density of rarefied plasmas become less than 500 ?m and one-tenth of the critical density. A thickness of the thin film can be determined by these criteria and the intensity of the pre-pulse

Collisional Effects on Fast Electron Generation and Transport in Fast Ignition

As the binary collision process requires much more computation time, a statistical electron-electron collision model based on modified Langevin equation is developed to reduce it. This collision model and a simple electron-ion scattering model are installed into one-dimensional PIC code, and collisional effects on fast electron generation and transport in fast ignition are investigated. In the collisional case, initially thermal electrons are heated up to a few hundred keV due to direct energy transfer by electron-electron collision, and they are also heated up to MeV by Joule heating induced by electron-ion scattering. Thus the number of low energy component of fast electrons increase than that in the collisionless case

Immunological Pathogenesis of Endolymphatic Hydrops and Its Relation to Meniere\u27s Disease

This study was designed to investigate an immunologically induced endolymphatic hydrops (ELH) and to focus on the issue of its pathogenesis in relation to Meniere\u27s disease. The time course of ELH was evaluated by light microscopy in a 2-hour to 7-month period following direct antigen challenge to the endolymphatic sac (ELS) in systemically pre-sensitized guinea pigs. ELH began to appear in the vestibule and the basal turn 5-7 hours after inner ear challenge and developed gradually. During the interval from the second day to the first week, ELH rapidly developed in all the cochlear turns and reached a maximum size. During the period from the second week to the eighth week, ELH gradually reduced. After 9 weeks, ELH of the saccule and the cochlea gradually recurred. During the interval from the first week to the eighth week, the time course of ELH correlated well with the grade of cellular infiltration of the perisaccular tissue. These results suggest that recurrent immunological reaction in the ELS may result in disorders of the ELS which finally lead to the onset of Meniere\u27s disease