280 research outputs found
AVALANCHE PHENOMENA IN TWO-DIMENSIONAL FOAM SYSTEMS(Session III : Complex Fluids, The 1st Tohwa University International Meeting on Statistical Physics Theories, Experiments and Computer Simulations)
この論文は国立情報学研究所の電子図書館事業により電子化されました
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
Dissipative flows of 2D foams
We analyze the flow of a liquid foam between two plates separated by a gap of
the order of the bubble size (2D foam). We concentrate on the salient features
of the flow that are induced by the presence, in an otherwise monodisperse
foam, of a single large bubble whose size is one order of magnitude larger than
the average size. We describe a model suited for numerical simulations of flows
of 2D foams made up of a large number of bubbles. The numerical results are
successfully compared to analytical predictions based on scaling arguments and
on continuum medium approximations. When the foam is pushed inside the cell at
a controlled rate, two basically different regimes occur: a plug flow is
observed at low flux whereas, above a threshold, the large bubble migrates
faster than the mean flow. The detailed characterization of the relative
velocity of the large bubble is the essential aim of the present paper. The
relative velocity values, predicted both from numerical and from analytical
calculations that are discussed here in great detail, are found to be in fair
agreement with experimental results
Determination of the internal quantum efficiency for photoelectrochemical reaction in a semiconductor photoelectrode by photoacoustic detection
We showed for the first time the validity of photothermal measurement for determination of internal quantum efficiency, which is one of the most fundamental parameters for energy conversion systems. The measurement method using photoacoustic detection in the present study can be applied to a wide variety of samples and measurement conditions
Application of transparent microperforated panels to acrylic partitions for desktop use: A case study by prototyping
There are various measures currently in place to prevent the spread of coronavirus (COVID-19); however, in some cases, these can have an adverse effect on the acoustic environment in buildings. For example, transparent acrylic partitions are often used in eating establishments, meeting rooms, offices, etc., to prevent droplet infection. However, acrylic partitions are acoustically reflective; therefore, reflected sounds may cause acoustic problems such as difficulties in conversation or the leakage of conversation. In this study, we performed a prototyping of transparent acrylic partitions to which a microperforated panel (MPP) was applied for sound absorption while maintaining transparency. The proposed partition is a triple-leaf acrylic partition with a single acrylic sheet without holes between two MPP sheets, as including a hole-free panel is important to prevent possible droplet penetration. The sound absorption characteristics were investigated by measuring the sound absorption in a reverberation room. As the original prototype showed sound absorption characteristics with a gentle peak and low values due to the openings on the periphery, it was modified by closing the openings on the top and sides. The sound absorption performance was improved to some extent when the top and sides were closed, although there remains the possibility of further improvement. For this study, only the sound absorption characteristics were examined in the prototype experiments. The effects during actual use will be the subject of future study
有限要素法による室内音場解析に関する研究 : 大規模多目的ホール内部音場の試行的解析
1.はじめに 2.FEMによる室内音場解析手法 3.大規模多目的ホール内部の音場解析 4.まと
Nonlinear Stress Fluctuation Dynamics of Sheared Disordered Wet Foam
Sheared wet foam, which stores elastic energy in bubble deformations, relaxes
stress through bubble rearrangements. The intermittency of bubble
rearrangements in foam leads to effectively stochastic drops in stress that are
followed by periods of elastic increase. We investigate global characteristics
of highly disordered foams over three decades of strain rate and almost two
decades of system size. We characterize the behavior using a range of measures:
average stress, distribution of stress drops, rate of stress drops, and a
normalized fluctuation intensity. There is essentially no dependence on system
size. As a function of strain rate, there is a change in behavior around shear
rates of .Comment: accepted to Physical Review
Spacial and temporal dynamics of the volume fraction of the colloidal particles inside a drying sessile drop
Using lubrication theory, drying processes of sessile colloidal droplets on a
solid substrate are studied. A simple model is proposed to describe temporal
dynamics both the shape of the drop and the volume fraction of the colloidal
particles inside the drop. The concentration dependence of the viscosity is
taken into account. It is shown that the final shapes of the drops depend on
both the initial volume fraction of the colloidal particles and the capillary
number. The results of our simulations are in a reasonable agreement with the
published experimental data. The computations for the drops of aqueous solution
of human serum albumin (HSA) are presented.Comment: Submitted to EPJE, 7 pages, 8 figure
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