Yasuhiro Sato

120-GHz-Band Wireless Link Technologies for Outdoor 10-Gbit/s Data Transmission

Our progress in 120-GHz-band wireless link technologies enables us to transmit 10-Gbit/s data transmission over a distance of more than 1 km. The 120-GHz-band wireless link uses high-speed uni-traveling carrier photodiodes (UTC-PD) and InP high-electron mobility transistor (HEMT) millimeter-wave (MMW) monolithic integrated circuits (MMICs) for the generation of MMW signals. We investigate the maximum output power of these devices and compare the phase noise of MMW signals generated by UTC-PDs and InP HEMT MMICs. We describe the antennas we used and their operation technologies. Finally, we investigate the dependence of transmission distance on availability using the statistical rain attenuation data. The calculation results show that the 120-GHz-band wireless link can transmit 10-Gbit/s data over a distance of 1 km with availability of 99.999%.

Creep force characteristics between rail and wheel on scaled model

Abstract In order to carry out the research project, which we call “Development of Intelligent Active Wheel,” a test facility of roller stand with 1/5 scaled truck is developed. Creep force characteristics between the roller rail and wheel at varied contact conditions are measured. From the measured results it is found that, in clean contact condition, creep force characteristics become negative as the creep rate becomes larger than 0.7%. In friction modifier high positive friction (HPF) applying condition, creep force characteristics do not show any negative property even if the creep rate increases up to 1.2%. The maximum F / Q , which is considered as friction coefficient at clean condition, is about 0.46, and the rate is about 0.16 at HPF applying condition as the creep rate increasing to about 1.2%.

Continuous observation of wheel/rail contact forces in curved track and theoretical considerations

By using non-contact gap sensors equipped on non-rotating parts of a bogie, a new measuring method of wheel/rail contact forces has been developed. The developed system has been verified to have sufficient durability for continuous measurement on in-service trains and sufficient practical accuracy after various stand tests and train running tests. After a long-period of continuous measurement on a commercial subway line, some important characteristics of wheel/rail contact mechanics were found by the analysis of measured data. Numerical simulations of curving with a full vehicle model using multi-body dynamics software were carried out, and according to the comparison with measured data, simulation results agree well with measured data in the steady-state values of derailment coefficients considering friction coefficient.

Analysis of Electret-Based MEMS Vibrational Energy Harvester With Slit-and-Slider Structure

This paper describes an analysis and a performance limit of a vibrational energy harvester with a novel slit-and-slider structure. This structure has a separable electret and microelectromechanical systems (MEMS) parts. In the MEMS parts, movable electrodes slide due to external vibration and receive electrical field that is periodically modulated by slits of fixed electrodes. The structure was fabricated based on MEMS technology and produced an ac current of 170 pA with an external vibration of amplitude of 1 m/s2 at a frequency of 1166 Hz. Since the structure is separable, individual characterization of the electret and movable electrodes was performed. On the basis of their quantitative analyses, a structural model was constructed and validated. The model showed a way to optimize structural and material parameters for enhancement of output power and predicted a performance limit of 2.5 × 10-3 μW and 6.1% as output power and harvester effectiveness, respectively. This value of effectiveness is comparable to that of conventional non-MEMS-based large energy harvester around 1 cm3, which indicates feasibility of MEMS-based small energy harvesters around 0.01 cm3 by appropriate designing.

Curving performance evaluation for active-bogie-steering bogie with multibody dynamics simulation and experiment on test stand

The authors propose a new concept of the active steering bogie, which has simple mechanism and high curving performance. Active-bogie-steering bogie has the steering mechanism only between car-body and bogie frame and no mechanism in wheelsets. On curved track, the bogie frames are steered towards radial steering direction by actuators according to active control law. In this paper, we show that the lateral contact force of the leading-outside wheel can be reduced to zero even on very sharp curve by this mechanism. Validity tests were carried out by using a full-size test bogie on the rolling test stand, which can simulate curve-running condition. Bogie parameters and steering actuator characteristics are identified in order to compare the experimental results with multibody dynamics simulation. After these stand tests and simulation, we successfully verified the effectiveness of the proposed bogie mechanism and control.

Novel Mapping Technique for Localization of Focal and Reentrant Activation During Atrial Fibrillation

Identification of wavefront propagation pattern during AF remains challenging in ablation procedures. We sought to test a novel combination of a new mapping technology called Ripple Map and high‐density mapping to distinguish focal and reentrant activation during atrial fibrillation (AF).

Development of low-energy and high-current-density ion beam system

A low-energy ion beam system operating at a dc voltage of less than 300 V was developed using an ion source with a multicusp magnetic field. A high-current-density ion beam of 6.9 mA∕cm(2) was successfully extracted at the electrode. The beam extraction characteristics for flat and concave electrodes were compared. In the case of a concave electrode with a designed focal length of 350 mm, it was observed that the beam profile was sharper than that obtained using a flat electrode.

Suppression of Radial Divergence of Extremely Low Energy Ion Beam by an Electron Beam Injection to a Grounded Electrode

Transition to a highly focused state is observed in a hydrogen ion beam extracted from an ion source using concave-shaped electrodes. The beam has a low energy (~95 eV) and a high current (~60 mA) with a ~60 mm diameter. The transition is induced by electron beam injection (1 keV and up to 50 mA) to a grounded electrode of an ion source from a direction obliquely opposite to the ion beam velocity. Probably, secondary electrons emitted from the electrode play an effective role in cancelling the beam ion space charge, since they are produced in the core region of ion beam immediately after the extraction. Comparison between the cases with and without an electron beam exhibits great improvements not only in a total ion beam current reaching a target, but also in the focusing of ion beam. The sudden transition to this highly focused state, which is triggered by a low electron beam current (~9 mA), suggests that some kind of a nonlinear process plays an essential role in this focusing.

A Multilevel CMOS–MEMS Design Methodology Based on Response Surface Models

We have developed a novel methodology to design systems composed of complementary metal-oxide-semiconductor (CMOS) and microelectromechanical systems (MEMS) parts. This multiscale methodology combines bottom-up modeling and top-down design-space exploration through the following steps: 1) In bottom-up modeling, characteristics of CMOS circuits and MEMS structures are accurately simulated at the circuit and MEMS device level; 2) on the basis of the results of a statistical regression method, these characteristics are abstracted into individual response surface models (RSMs), each with a set of coefficients of design parameters; 3) the models are mathematically connected to describe an elemental unit comprising CMOS and MEMS components; 4) the characteristics of the whole system of elemental units are abstracted into another RSM to cover the system performance; and 5) in top-down design-space exploration, the system requirements are connected to a set of design parameters for the CMOS circuits and MEMS structures by utilizing the RSMs in the reverse direction. To verify the concept, our design methodology was applied to a CMOS-MEMS fingerprint sensor.

Synchronized Multiple-Array Vibrational Device for Microelectromechanical System Electrostatic Energy Harvester

In this paper, we describe a novel structure of a vibrational micro-electro-mechanical system (MEMS) device for power generation enhancement. A synchronized multiple-array vibrational device, in which movable plates are connected by rods, increases the area of the movable plate in the energy conversion region and couples the phase of movement. The fabricated device resonates at approximately 1430 Hz with an acceleration amplitude of 6 m/s2 and nanoampere-order AC current is generated. These results confirm that this MEMS vibrational device will contribute to the progress in energy harvesting.