Hirotaka Sato

Multiple scattering of plane elastic waves in a fiber-reinforced composite medium with graded interfacial layers

In this study, we consider the multiple scattering of time-harmonic elastic waves in a metal matrix composite containing randomly distributed parallel fibers with graded interfacial layers. In-plane compressional and shear waves are considered. We assume same-size circular fibers of identical properties and same-thickness interface layers with nonhomogeneous elastic properties. The method of solution consists of first solving the scattering problem by a large number N of arbitrarily distributed fibers in an infinite matrix, the resulting equations are then averaged by considering the positions of the fibers to be random with a statistically uniform distribution, and these averaged equations are solved by using Laxs quasicrystalline approximation. Numerical calculations for a SiC-fiber-reinforced Al composite are carried out for a moderately wide range of frequencies and the effect of interface properties on the phase velocities, attenuations of coherent plane waves and the effective elastic moduli are shown graphically.

Multiple scattering of plane elastic waves in a particle-reinforced-composite medium with graded interfacial layers

Abstract In this study we consider the multiple scattering of time-harmonic elastic waves in a metal matrix composite containing randomly distributed particles with graded interfacial layers. Both continuously and multilayered graded interface layers can be designed and evaluated. The method of solution consists of first solving the scattering problem by a large number N of arbitrarily distributed particles in an infinite matrix, the resulting equations are then averaged by considering the positions of the particles and solved by using Lax’s quasicrystalline approximation. Numerical calculations for a SiC-particle-reinforced Al composite are carried out for a moderately wide range of frequencies and the effects of graded interface layers on the physical properties are shown graphically.

Influence of microstructure on scattering of plane elastic waves by a distribution of partially debonded elliptical inclusions

Scattering of elastic waves by a partially debonded elliptical inclusion is studied by using the boundary element method. We apply the results of the single scattering problem to the propagation of elastic waves in a composite material containing a dilute concentration of elliptical inclusions. Numerical calculations are carried out for a moderately wide range of frequencies, and the effects of microstructure and constituent properties on the scattering cross sections, the phase velocities and attenuations of coherent waves and the effective elastic moduli for a dilute composite material are shown graphically.

Boundary Element Analysis of Multiple Scattering Waves in High Performance Concretes

Advances in computing have allowed for the development of high performance concretes mathematically. We develop a method which combines the generalized self consistent model together with the boundary element method and the statistical averaging procedure to study the multiple scattering of plane elastic waves in concrete containing randomly distributed parallel fibers. In analysis, the concrete matrix is modeled by dispersed aggregate structure. The physical properties for a fiber-reinforced concrete are obtained numerically and shown in graphs for various microstructures at designated frequencies.

Contractile Skeletal Muscle Cells Cultured with a Conducting Soft Wire for Effective, Selective Stimulation

Contractile skeletal muscle cells were cultured so as to wrap around an electrode wire to enable their selective stimulation even when they were co-cultured with other electrically-excitable cells. Since the electrode wire was composed of the conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) and polyurethane (PU), which is soft and highly capacitive (~10 mF cm−2), non-faradaic electrical stimulation with charge/discharge currents could be applied to the surrounding cells without causing significant damage even for longer periods (more than a week). The advantage of this new culture system was demonstrated in the study of chemotactic interaction of monocytes and skeletal muscle cells via myokines.

Hydrogel-based electrical stimulation culture system to control the engineered cellular activities driven by nano biomolecules

The hydrogel-based electrical stimulation culture device composed of portable cellular micropatterns and the flexible and stretchable PEDOT/PU electrode arrays were developed to afford in vitro cell-based bioassay system. Electrical regulation of muscle cellular contraction driven by intracellular nano-actuator composed of biomolecules was successfully demonstrated by using this system.

DS-CDMA Downlink Site Diversity with Frequency-Domain Equalization and Antenna Diversity Reception

The use of frequency-domain equalization based on minimum mean square error criterion (called MMSE-FDE) can significantly improve the bit error rate (BER) performance of DS-CDMA signal transmission compared to the well-known coherent rake combining. However, in a DS-CDMA cellular system, as a mobile user moves away from a base station and approaches the cell edge, the received signal power gets weaker and the interference from other cells becomes stronger, thereby degrading the transmission performance. To improve the transmission performance of a user close to the cell edge, the well-known site diversity can be used in conjunction with FDE. In this paper, we consider DS-CDMA downlink site diversity with FDE. The MMSE site diversity combining weight is theoretically derived for joint FDE and antenna diversity reception and the downlink capacity is evaluated by computer simulation. It is shown that the larger downlink capacity can be achieved with FDE than with coherent rake combining. It is also shown that the DS-CDMA downlink capacity is almost the same as MC-CDMA downlink capacity.

Downlink Site Diversity with Frequency-Domain Equalization for a DS-CDMA Cellular System

In DS-CDMA high speed wireless signal transmissions, the bit error rate (BER) performance with coherent rake combining degrades due to inter-path interference (IPI) caused by a severe frequency-selective fading. The use of frequency-domain equalization (FDE) can significantly improve the BER performance. However, the local average received signal power slowly varies due to path loss and shadowing loss according to the movement of a mobile user. This variation degrades the link capacity particularly when the user is located close to the cell edge. To improve the link capacity, the well-known site diversity can be used in conjunction with FDE. In this paper, we present downlink site diversity with FDE for a DS-CDMA cellular system and derive the MMSE weight for site diversity combining. The downlink capacity is evaluated by computer simulation and compared to the case with coherent rake combining. Then it is shown that the link capacity with FDE is better than that with coherent rake combining