Harmonic analysis of the output voltage of a third‐harmonic‐injected inverter for LSM drives

The superconducting magnetic leviation railway system (MAGLEV) under development in Japan uses pulse‐width‐modulation (PWM) inverter for driving a linear synchronous motor (LSM). The inverter output voltage contains nonnegligible harmonics which cause harmonic resonances in the LSM system, and therefore harmonics of the output voltage have been analyzed in order to control such harmonic resonances. This paper applies a third‐harmonic injection method to the inverter for the purpose of enhancing the output voltage without changing the circuit configuration. It performs harmonic analysis of the output voltage of the inverter based on the third‐harmonic injection. Validity of the harmonic analysis is verified by computer simulation. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 160(1): 71–78, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ).     

Development of a low-noise analog front-end ASIC for CdTe detectors

This paper describes the recent development of a low-noise analog front-end ASIC for CdTe detectors. The ASIC is designed on the basis of the Open-IP LSI project led by JAXA and implemented using TSMC 0.35-μm CMOS technology. The ASIC contains eight identical channels, each of which includes a charge-sensitive amplifier, band-pass filters, and a sample-and-hold circuit. Preliminary testing of the ASIC achieved noise performance of 188e^-+7.5e^-/pF. In order to verify the low-noise characteristics, the ASIC was connected to a guard-ring-equipped CdTe diode detector with dimensions of and having a thickness of 0.5 mm. As a result, the gamma-ray spectra of radioactive sources were obtained with good energy resolutions of 2.51 and 2.35 keV (FWHM) for gamma rays of 59.5 and 122 keV, respectively, at room temperature.     

Model analysis of an inter-industrial and inter-regional waste recycling system in Japan

In this study, we investigate an inter-industrial and inter-regional recycling system for industrial waste by the cement industry in Japan. We develop a linear programming model that represents cement production processes and waste transportation of all cement factories in Japan. We simulate cost and CO₂-minimizing systems. The result implies that making waste transportation more efficient in cost is an effective means for CO₂ reduction.     

Active Harmonic Filters

Unlike traditional passive harmonic filters, modern active harmonic filters have the following multiple functions: harmonic filtering, damping,isolation and termination, reactive-power control for power factor correction and voltage regulation, load balancing, voltage-flicker reduction, and/or their combinations. Significant cost reductions in both power semiconductor devices and signal processing devices have inspired manufactures to put active filters on the market. This paper deals with general pure active filters for power conditioning, and specific hybrid active filters for harmonic filtering of three-phase diode rectifiers.     

Independence of older adults in performing instrumental activities of daily living (IADLs) and the relation of this performance to visual abilities

A questionnaire study was undertaken of more than 2800 elderly people aged 60 years and over and living at home, to investigate the relationship between their performance of some instrumental activities of daily living (IADLs) and their visual abilities. The IADL measured the ability of elderly participants to pick up coins, manage monthly financial matters, use the telephone and take medication as recommended. Visual abilities were assessed by means of each subject's answers to questions relating to resolution, focus, adaptation to bright or to dim lighting, dynamic acuity, distance perception and colour vision. The types of visual functions that, together with age and gender, contribute to determining the level of independence in the performance of IADL activities were identified using logistic regression analysis. The results indicated that elderly participants who had problems with either distance perception or yellowish vision also tended to have difficulties in picking up coins, using the telephone and taking medication as recommended. In addition, problems with adaptation and dynamic acuity were associated with difficulty in managing monthly financial matters. From an analysis of all subjects, distance perception was the significant factor that determined whether an elderly subject could pick up coins or use a telephone unaided. Yellowish vision was also significantly associated with a need for assistance or with an inability to manage monthly financial matters, use the telephone or take medication as recommended.     

Direct measurement of the group refractive index of air with interferometry between adjacent femtosecond pulses

The group refractive index of air in laboratory conditions is measured directly between adjacent femtosecond laser pulses by a new interferometry technique. Measurement of the repetition rate of the mode-locked pulse train that gives the maximum amplitude of the interference-signal envelope enables us to determine the group refractive index of air within a standard deviation of 2 x 10(-7). This simple method without vacuum reference is attractive for measuring the group refractive index needed for precise distance measurements in open fields.     

Microscopic time-resolved two-dimensional imaging with a femtosecond amplifying optical Kerr gate

We demonstrate microscopic time-resolved two-dimensional (2D) imaging that is based on a femtosecond amplifying optical Kerr gate (fs-amp OKG). The contribution of the optical nonlinear effects to the transverse imaging performance and the limit of the transverse resolving power are investigated. The optical Kerr effect in the excited state with amplification, used in the fs-amp OKG, does not deteriorate the quality of the time-resolved image at transverse resolutions up to at least 5.5 microm. We obtain a femtosecond-time-resolved 2D image of a microscopic object with a transverse resolution of 1.7 microm.     

Photonic encoder and decoder for optical code-division multiplexing with time-to-space converters and angle-multiplexed holograms

A photonic encoder-decoder pair for optical code-division multiplexing (OCDM) that uses time-to-space converters and angle-multiplexed holograms is proposed. The encoder converts the pulse from each input port into a specific code and multiplexes input signals into the output port. The hologram in the decoder generates a correlation waveform between the transmitted code and the recorded code. The performance of the OCDM system with the encoder-decoder pair is estimated. The maximum spectral efficiency for 8-bit length orthogonal codes in the worst case at a bit-error rate of 10(-9) is 0.17 (bits/s)/Hz when the number of channels is 8.     

Synchronization between audiovisual and haptic feeling for constructing edutainment systems

Virtual reality (VR) technology has become more and more mature over the last decade. Development of a virtual environment for training purpose is considered to be one of the most practical applications of the VR technology. Since the VR technology involves all kinds of sensors in exchanging information between the real world and the virtual environment, it is computationally intensive in terms of data processing at an individual sensor and information integration among all the sensors. In general, the information integration has to be well synchronized in order to meet the training needs. At the same time, real-time processing capability is also considered to be critical. Many more practical issues could be uncovered only when a virtual training environment is actually being developed. Based on this belief, this study experiments on the development of a virtual environment for training billiards players. The technical difficulties encountered and the corresponding resolutions are considered beneficial to the development of other practical virtual training environments. This paper summarizes the design and implementation details about our experimental virtual training environment for edutainment systems such as virtual billiard game, virtual air hockey game and virtual drum performance with the algorithms for the synchronization of the information from different sources.