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We propose a design for asymmetric acoustic transmission using mode conversion in a waveguide with gratings. First, we studied dispersion diagrams to determine the waveguide widths and clarified the mechanism of asymmetric acoustic transmission using the cutoff of a higher-order mode. Then we analyzed the sound pressure level and showed that asymmetric acoustic transmission is feasible by utilizing the mode conversion and cutoff. In addition, we investigated the structural dependence of the transmission rates for bidirectional propagation.

We investigated the dispersion characteristics of the propagation modes that progress on the tectorial membrane (TM). Recent studies have uncovered complex TM behavior and a possibility that TM might play an important role in the hearing system. An interaction between the TM and the fluid induces propagation modes, which are called TM modes. We found that there are several kinds of TM modes and analyzed the direction of the displacement of the TM that is caused by each mode. We also investigated the structural dependency of the angular wavenumber of each mode.

This study focuses on the attenuation characteristics of the waves that propagate on the tectorial membrane (tectorial membrane waves). The traveling wave on the basilar membrane (basilar membrane wave) plays a main role in transmitting acoustic signals. However, slow waves can propagate on the tectorial membrane other than the basilar membrane. If the tectorial membrane waves also progress along the cochlea from the base to the apex, they could have influence on the signal that is transmitted by the basilar membrane wave. We discuss the difference of the propagation characteristics between two types of the tectorial membrane waves and the basilar membrane wave by comparing the attenuation constants. First, we showed the difference of the displacement of the basilar and tectorial membranes between these waves. Then, we investigated their propagation characteristics including the phase constants and attenuation constants. Finally, we studied the structural dependence of the attenuation constants of the tectorial membrane waves.

Apart from Von Bekesy's traveling wave theory, this paper introduces our new comprehension on auditory system based on acoustic resonance in hair cells. Focusing on a rootlet inductance L and a membrane capacitance C of the hair cell, a real-sized cell model is designed so as to form a series LC resonant circuit for the incident soundwaves. In simulation, acoustic resonance is observed successfully at 1120 Hz together with 148-times sound pressure enhancement inside the cell. This model is useful to explain OAE responses, frequency shifts of absolute pitch for aging, pure-tone tinnitus, and even apoptosis of outer hair cells by huge sound exposure.

This paper proposes an acoustic frequency selective curtain composed of two membranes and periodically connected elastic pillars. This new architecture, which was inspired by the structure of sensory hair cells in human auditory system, generates a pass band at a certain frequency, and can be used as a curtain which allows only a specific sound pass through.

Different from human’s ears, injured hearing system of birds can be regenerated within two weeks even if their hair cells are damaged by exposure of large sounds. In terms of the regenerative process of birds’ ears, it is pointed out that the hair cells hearing the lower frequency are cured first, and then, those for higher frequencies are gradually recovered [1]. However, are the damaged hair cells repaired like this In other words, do the birds regain hearing from the lower frequencies to the higher ones When we assume that the hair cells had their own resonant frequency and detected sounds based on such resonance, different comprehension might be possible on the experimental results in [1]. In this paper, we would like to argue the regenerative process of the injured birds’ ears under the hypothesis that the hair cells have resonant system for incoming sounds.

Apart from medical/biological understandings and widely accepted V. Bekesy’s traveling wave theory for human hearing system, this paper proposes a new sound detection theory based on extraordinary acoustic transmission. From engineering point of view, resonance on enlarged hair cell models including a set of membrane and pin-hole are demonstrated theoretically. This new idea can be applied to μm-scale super compact hair cells to account for mechanism of human hearing system.

This invited talk introduces how extraordinary acoustic transmission plays an important role to detect sounds in human hearing system. This new approach from engineering point of view is totally different from that of V. Bekesy's traveling wave theory which has been widely accepted up to today. To elucidate human hearing mechanism, we focus on architecture of sensory hair cells. That is, the wall of the cell has three-layered structure consisting of plasma membrane, cortical lattice, and subsurface cisternae. Our theoretical study indicates that the plasma membrane and cortical lattice form an extraordinary acoustic transmission system to detect sounds with extremely high resolution and sensitivity, and subsurface cisternae works as a sound reflector to protect DNA in nucleus against damages caused by higher sound pressures for resonance.

This paper discusses hearing system of human from engineering point of view, and reports four questions we have now; 1) why eardrum is so sensitive and broadband, 2) how middle ear compensates significant impedance mismatching, 3) how sounds are detected by such a small cochlea, and 4) how the sounds are absorbed perfectly without ringing. Discussion is focused on question 3), and new hypothesis based on extraordinary transmission in acoustic metamaterials is proposed.

The coupling coefficients of two parallel metal-insulator-metal (MIM) plasmonic waveguides are investigated using the analysis of the coupled-mode equations. The frequency characteristics of the power transmittance of a MIM waveguide coupled with a resonant cavity are studied and compared with the simulation results obtained from the FDTD method into which motion equations of free electrons are installed.

A ridged-circular nanoaperture is investigated through three-dimensional (finite-difference time-domain) FDTD method. The motion equations of free electrons are inserted to analyze a metallic material. The electromagnetic field distributions of optical near-field around the aperture are investigated. The phase change disk illuminated by a near-field optical light through a ridged-circular nanoaperture is also analyzed. The far-field scattering patterns from the phase change disk and the crosstalk characteristics between plural marks are studied.

The recording density of optical storage systems has been increased by using the shorter wavelength of laser light and the higher numerical apertures of the objective lenses. However, the optical diffraction limit restricts these methods to get the higher recording density. Near-filed optical recording is one of the promising techniques because it has the potential to overcome this limitation. Many types of nano-apertures and nano-antennas have been proposed in order to obtain near-field of high emission intensity and a small spot size. In this study, the three-dimensional optical disk structure utilizing a metallic nano-aperture with ledges is analyzed by using FDTD method. The motion equations of free electrons have been installed to analyze the metallic material. First, the nano-aperture with ledges is analyzed and the near-field through the aperture and the far-field scattering patterns are studied. It is demonstrated that the narrow beam width can be achieved by adding the ledges on the aperture. Next, the readout characteristics of the near-field optical disk are investigated. The structure is composed of the rectangular nano-aperture with ledges and the recording layer that is sandwiched between the two protective layers. The dependency of the characteristics on the recorded-mark size is studied and the crosstalk characteristics between adjacent recorded marks are investigated when the plural recorded marks are arranged. It is shown that the crosstalk can be reduced by using the proposed aperture. The readout characteristics of the continuously arranged recorded-marks are also studied and the minimum recorded-mark size that can be distinguished is discussed.

Surface plasmon polaritons (SPPs), which carry the electromagnetic energy along the metal-dielectric interface, have received much attention in the field of the photonic devices because they have potential to realize nanoscale photonic devices with the dimension smaller than the diffraction limit. There are mainly two types of configurations that are composed of metal-insulator-metal (MIM) and insulator-metal-insulator (IMI). Among of these, MIM configurations have been attracting much interest because they can realize strong field localization and their fabrication process is simpler and easier compared with the IMI ones. Many types of MIM plasmonic devices have been proposed so far, such as ring resonators, Bragg gratings, splitters and demultiplexers, filters utilizing cascaded transverse cavities. Analytical modeling of resonant cavities for MIM waveguide junctions has also been investigated. In this study, MIM waveguide resonant cavities that include metallic nano-cylinders in them are investigated through FDTD analysis. In the FDTD method, special handling of the metallic material is required because the permittivity is dispersive and has a negative value in the optical frequency. To overcome this difficulty, the motion equations are introduced into the FDTD method in order to evaluate the conducting current. The MIM waveguide consists of silver and air. The fundamental mode of the MIM waveguide is excited at the input port and the frequency characteristics of the power transmittance through the output port are investigated. It is shown that the drastic change of the power transmittance characteristics occur by slightly changing the location of the nano-cylinders inside the cavity. The field pattern inside the cavity is analyzed and the association with the power transmittance characteristics is demonstrated. It is shown that a wide variety of filtering characteristics can be obtained by arranging the nano-cylinders properly.

There is an optical diffraction limit for the recording density of conventional optical recording systems. There has been a lot of recent interest in the field of optical storage technologies for the recording methods that are based on near-field optical principles because they have the potential to overcome the limitation by using the localized optical near-field for writing and reading recorded marks. Many types of nano-apertures and nano-antennas have been investigated to achieve the high throughput of the optical near field. It is also well-known that the near-field is observed when the incident light is illuminated to a metallic nano-sphere. This study focuses on a ridged-circular nano-aperture with metallic nano-spheres for a near-field optical disk. The analysis is accomplished by a three-dimensional FDTD method, which combines the motion equations of the free electrons. This method can be applied to the analysis of various plasmonic devices and also handle Drude dispersion easily. First, nearfield distributions through the nano-aperture are analyzed and it is shown that the transmitted light intensity increases by adding the nano-spheres near the ridged-circular nano-aperture. It is thought to be due to the surface plasmon resonance between two adjacent nano-spheres. Phase distributions of the nearfield are also analyzed and the relevance to the near-field enhancement is investigated. Next, the near-field optical disk structures are analyzed and the readout characteristics are studied. The structure is composed of the ridged-circular nano-aperture with nano-spheres and the recording layer that is sandwiched between the two protective layers. The dependency of the readout characteristics on the recorded-mark size is studied and the crosstalk when using the plural recorded marks is also analyzed and the advantage for using the nano-spheres for the near-field optical disk nano-apereture is confirmed through FDTD simulations.

This paper proposes a spiral-shaped dispersive delay structure (Spiral-DDS) composed of vertically stacked spiral coils and vertical vias. This all-pass network architecture can produce a large group delay peak at a certain frequency in a few GHz range. Basic performance of the Spiral-DDS are studied theoretically, and the group delay with more than 6 ns was successfully generated by a compact multilayered architecture with dimensions of 6.0 × 6.0 × 1.18 mm3. This paper also reports that the most of losses occurred in DDS comes from conductor loss, not from dielectric loss.

Readout characteristics of a near-field optical disk with an acute-edged metallic nano-aperture were investigated. The electromagnetic field distributions of the near field around the aperture were analyzed, and the far-field scattering of the waves transmitted through the phase change disk was calculated by finite-difference time-domain method into which motion equations of free electrons were incorporated. Adjusting the edge angle of the aperture increased the field intensity of near-field light. The influence of the edge angle on output through the recorded mark was also investigated. It was found that there is an optimum edge angle that differs depending on the aperture width.

Scattering characteristics of a domain wall displacement detection (DWDD) disk with a control layer were investigated by finite-difference time-domain (FDTD) analysis. DWDD is one of the high-density storage technologies of magneto-optical (MO) disks and the control layer is used to suppress ghost signals due to a rear process. The effects of the control layer on the scattering characteristics were studied.

Parallel programs for distributed memory machines are not easy to create and maintain, especially when they involve sparse matrix computations. In this paper, we propose a program translation system for generating parallel sparse matrix computation codes utilizing PSBLAS. The purpose of the development of the system is to offer the user a convenient way to construct parallel sparse code based on PSBLAS. The system is build up on the idea of bridging the gap between the easy-to-read program representations and highly-tuned parallel executables based on existing parallel sparse matrix computation libraries. The system accepts a MATLAB program with annotations and generates subroutines for an SPMD-style parallel program which runs on distributed-memory machines. Experimental results on parallel machines show that the prototype of our system can generate fairly efficient PSBLAS codes for simple applications such as CG and Bi-CGSTAB programs.

We propose a new type of miniaturized filter to be constructed in multilayer structure. The filter consists of a couple of quarter-wavelength resonators. Each resonator is composed of two segments of coplanar waveguide(CPW) which are fabricated face to face on both surfaces of the substrate. The two resonator segments are connected to each other with a piece of bonding wire at an open end. It possesses sharp band-pass characteristics with an attenuation pole around the passband. We investigate the filtering characteristic through experiments as well as numerical simulations by means of the FD-TD method, and discuss the attenuation pole characteristics in terms of the input susceptance.

In this paper, we propose microstrip filters with a loaded capacitance of which frequency band can be changed by light-induced plasma in a silicon chip buried in part of a substrate. We analyze the frequency characteristics of the filters by using the (FD)2 TD method.

This paper proposes a new type of multi-stratified comb-line filters of narrow pass band utilizing conductor-backed coplanar waveguides. It is shown through numerical simulations by means of FD-TD method that the filtering characteristics can be controlled effectively by introducing a grounding conductor with a window between the coupled two resonators. It is demonstrated that, by changing the dimensions of the window on the grounding conductor, we can change, without affecting the odd mode, the input susceptance of the even mode independently and that we can adjust the frequency of attenuation pole. An interesting feature of this filter is that an additional window on the grounding conductor makes another attenuation pole appear around the passband.

A new band elimination filter for coplanar waveguide using a patch of conductor is proposed. The proposed structure is composed of a coplanar waveguide (CPW) to which a patch of conductor on the opposite surface of the substrate is wired through a narrow hole drilled in the substrate. It is shown through numerical simulations by means of the FD-TD method that the structure provides excellent bandstop characteristics and that frequencies of stopband can be controlled by dimensions of the patch. We also investigate, both numerically and experimentally, the characteristics of a filter with several patches aligned periodically.

This paper proposes a new type of comb-line filter suitable for miniaturization utilizing stratifying technology. The filter consists of a couple of quarter-wavelength resonators. Each resonator is composed of two sections of CPW (coplanar waveguide) and MSL (microstrip line) which is fabricated on the other side of the CPW. Both sections are connected to each other with a piece of bonding wire at an open end to set up a new type of folded comb-line filter. The filtering characteristics are investigated through experiments as well as numerical simulations by means of the FD-TD method. It is shown that the filtering characteristics are improved by adjusting coupling between the resonators. It is also shown that the filter can be miniaturized by introducing stepped impedance structure in the resonators.

This paper presents a new 2-stage dual plane comb-line filter. It is shown by experiment as well as by numerical simulations with FD-TD method that this filter has a wide pass-band and attenuation poles just below and above the pass-band. It is also shown that the characteristics of attenuation poles can be explained by considering the 2-stage filter as a series connection of two 1-stage filters and that the attenuation characteristics of the 2-stage filter can be improved by a simple combination of two 1-stage filters adjusted appropriately.

In this paper, a dual-plane comb-line filter having plural attenuation poles is proposed. We investigate the filtering characteristics from both experiments and numerical simulations by means of the finite-difference time-domain method. It is shown that this filter has attenuation poles just above, as well as below the passband and that intersections between the curves of input susceptance of the even and odd modes agree with the attenuation-pole frequencies. Furthermore, it is demonstrated that, by changing the position of the metal pin, which connects two resonators, we can change the input susceptance of the odd mode alone and, hence, regulate the attenuation-pole frequencies.

This paper presents a concept of real-time parallel volume rendering system for time-varying scientific visu-alization based on the scalable architecture of ReVolver/C40 developed by Kyoto University. A preliminary experimental environment using the rendering pipeline of ReVolver/C40 and newly designed DataProbe which is an additional hardware for parallel volume data transfer is also presented. In terms of the load balancing in parallel volume rendering, a block cyclic data assignment with the early ray termination technique is also discussed.

We propose a new element containing a two-mode nonlinear waveguide consisting of Kerr-like material for all-optical logic circuits. The proposed element, incorporated into the Mach-Zehnder interferometer, functions like a phase shifter. Although the optical waves propagating in the proposed element are monochromatic and identical in polarization, its function is insensitive to the relative phase difference between the incident beams. Using this element, we can realize various logic functions. In this paper, we demonstrate such logic circuits as inverters, distributors, and AND gates.

A compact ultra-wideband (UWB) bandpass filter using a multilayered structure is proposed.The proposed filter is composed of a pair of parallel plates, a meander line, and a thin conductor column that connects the parallel plates. The fabricated filter has a small size of 5 × 6 × 1.818 mm3 that amounts to 0.19 λg × 0.22 λg × 0.07 λg, where λg is the guided wavelength at the center frequency of the passband (6.95 GHz). UWB bandpass characteristics from 1.9 to 12.0 GHz with two attenuation poles at 0.4 and 12.8 GHz were achieved. Experimental results are in good agreement with the numerical ones that are obtained from a simulation and an equivalent circuit. Flat group delay characteristics in the wide frequency range are also shown. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:557–559, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25816

The influence of ground terminal shape on the resonant frequency of a microstrip resonator is investigated through numerical simulations and experiments. Resonators are one of the basic components of very small high-dielectric stripline filters, named the laminated-planar filter. The resonant frequencies are calculated by means of the finite-difference time-domain (FDTD) method and compared with experimental results. It is also shown that the resonant frequency is directly related to the square root of its line inductance when the resonator is regarded equivalently as a series LC circuit.

We propose a new type of comb-line filter that is suitable for miniaturization utilizing stratifying technology. It consists of a couple of composite resonators. Each resonator is composed of two sections of a microstrip and a coplanar waveguide fabricated on the microstrip ground plane which are connected through a piece of wire at an open end to set up a new folded comb-line filter. The filtering characteristics are investigated through experiments as well as numerical simulations by means of the FD-TD method. It is shown that the filtering characteristics can be much improved by removing part of the barrier in the coplanar-line portion of the resonator to alter the coupling.

This paper presents full-wave analysis of the cylindrical striplines and the cylindrical microstrip lines utilizing the finite difference time-domain method in a circular-cylindrical coordinate system. Numerical results on the normalized characteristic impedance are in good agreement with the available results. Furthermore, the junctions of the coaxial transmission line and the cylindrical microstrip line are analyzed to show the usefulness of this method. >

Multilayered monolithic microwave integrated circuits (MMIC) have been proposed with a view to reducing the size and increasing the degree of integration of the MMIC. It has been demonstrated that new circuit configurations can be realized and the design capability can be improved. By the use of a multilayered MMIC, the circuit can be laminated so that the circuit size can be made smaller. However, since the circuit is laminated, qualitative evaluation of the crosstalks between the upper and lower transmission lines becomes important. Most of the previous analyses on the microstrip line crossover focused on the case where the two lines cross orthogonally. In this research, the finite-difference time-domain (FD-TD) method applicable to an arbitrary coordinate system is used for the analysis of the crosstalk when two transmission lines cross at an arbitrary angle. First, the FD-TD method that can be applied to an arbitrary coordinate system is summarized. Next, it is confirmed that the results of the present analysis for a single microstrip line do not depend on the mesh shape and that the present analysis results agree with those by other methods for a microstrip bend with an arbitrary angle. Finally, a three-dimensional crossover of micro-strip lines with an arbitrary angle is analyzed. the normalized frequency characteristics, cross-angle dependence, and the interdistance dependence of the s parameters are presented.