Volume-type holographic antenna

A new type of holographic antenna based on the principle of the volume hologram is proposed. The characteristics of the prototype are examined. The antenna has a unidirectional beam with a front-to-back ratio of 20 dB. The practical frequency handwidth is about 10 percent of the center frequency. The antenna is unique in that the feed point is placed in the plane of the holographic plate so that both feeder and the holographic plate could be made out of one printed circuit board for easy flush mount installation or mass production, although the feeder of the prototype antenna was a pyramidal horn.     

Inhibitory effect of 1,3-diglycerides during adsorption of β-carotene onto attapulgite and sepiolite

The adsorption isotherms of β-carotene on attapulgite and sepiolite were measured in the presence of 1,3-diglyceride in n-hexane to elucidate the relative inhibitory power of the diglycerides, hydroxyl group, carbon number, and double bond for adsorption bleaching. The adsorption mode of β-carotene was the Langmuir type. The inhibition of β-carotene adsorption may be caused by the polarity of diglycerides and the formation of diglyceride micelles. The relative inhibitory power of 1,3-diolein, 1,3-distearin, and 1,3-dipalmitin toward β-carotene adsorption was 1.49, 1.40, and 0.99, respectively. Therefore, the relative inhibitory power due to the hydroxyl group and increase in the carbon atom of the fatty acid in glyceride was 0.41–0.49.     

Wind velocity and rotor position sensorless maximum power point tracking control for wind generation system

In order to perform maximum power point tracking control of wind generation system, it is necessary to drive windmill at an optimal rotor speed. For that purpose, a rotor position and a wind velocity sensors become indispensable. However, from the aspect of reliability and increase in cost, rotor position sensor and wind velocity sensor are not usually preferred. Hence, wind velocity and position sensorless operating method for wind generation system using observer is proposed in this paper. Moreover, improving the efficiency of the permanent magnet synchronous generator is also performed by optimizing d-axis current using the Powell method.     

Surrogate thrombopoietin

To evaluate the practical value of natural beta-carotene (NbetaC) and to elucidate the apparent discrepancy between epidemiological observations and intervention trials on the role of beta-carotene (betaC) in tumor prevention, the genotoxicity and the antigenotoxicity of NbetaC and synthetic betaC crystal (SbetaCC) stereoisomers were studied comparatively using chromosome aberration analysis and the micronucleus test in human lymphocytes in vitro. NbetaC was extracted from the halotolerant algae Dunaliella salina. The NbetaC crystal (NbetaCC) preparation is about 70% all-trans (TbetaC) and 8% 9-cis (CbetaC). The NbetaC oil (NbetaCO) preparation is about 40% all-trans and 38% 9-cis. SbetaCC is more than 97% all-trans, and the 9-cis can not be detected. The mixture of betaC (betaCM) preparation is 74% SbetaCC and 26% NbetaC. Our results show no genotoxicity of 1-30 microg/ml NbetaCC, but this concentration of NbetaCC inhibited significantly gamma-ray-induced micronucleus formation in human lymphocytes in vitro. One to thirty microg/ml NbetaCO was most effective against both gamma-ray-induced and spontaneous micronucleus formation. However, no influence of NbetaCO on spontaneous chromosome aberrations in human lymphocytes in vitro was observed. NbetaCO suppressed significantly mitomycin C (MMC)-induced chromosome aberrations. One to thirty microg/ml SbetaCC induced a dose-dependent increase in micronucleus frequency, and also inhibited gamma-ray-induced micronucleus formation. No effect of betaCM on spontaneous chromosome aberrations was found. One to thirty microg/ml betaCM is more effective against MMC-induced chromosome aberrations than NbetaCO. These results suggest that CbetaC might play a critical role in the genotoxicity and antigenotoxicity of SbetaCC and NbetaC. The genotoxic activity of SbetaCC might be involved in carcinogenesis. NbetaC or betaCM could be of practical value in tumor prevention and supplementary treatment.     

An adaptive dead-time compensation strategy for voltage source inverter fed motor drives

This paper presents an adaptive dead-time compensation strategy to obtain fundamental phase voltage for inverter fed vector controlled permanent magnet synchronous motor drives. The amplitude of phase dead-time compensation voltage (DTCV) to compensate disturbance voltage due to undesirable characteristics of inverter, such as dead-time, turn-on/off time of switching devices, and on-voltages of switching devices and diodes is adaptively determined according to a dead-time compensation time (DTCT). DTCT is identified on-line with using a /spl delta/-axis disturbance voltage in the current reference frame that is synchronized with current vector. The /spl delta/-axis disturbance voltage is estimated by a disturbance observer. The accuracy of identified DTCT is experimentally confirmed by calculating the mean absolute percentage error (MAPE) between a calculated active power and a measured one. MAPE for adaptive DTCT is almost within 5% at any operating point.     

Relationship of parallel model and series model for permanent magnet synchronous motors taking iron loss into account

This paper investigates the relationship of parallel model and series model for permanent magnet synchronous motor taking iron loss into account. The expressions of flux linkage, terminal voltage, and electromagnetic torque are compared. It follows from the investigation that the parallel and series models are mathematically the same. In addition, the properties of the models are exhibited. The parallel model is superior in understanding the physical meaning to the series model. The series model is superior in low order of the state variables to the parallel model.     

Position sensorless control for ultrasonic motors based on input voltage information

This paper presents a method of position sensorless control of ultrasonic motors (USM). The position sensorless control method is useful for reducing the cost and size of drive system. The position estimation method is based on the input voltage information of the ultrasonic motor. The characteristic of input voltage versus rotor position is expressed by a quadratic function which is used to estimate a rotor position based on input voltage information. This estimation method, which uses only the drive voltage of the ultrasonic motor, is a very simple algorithm and shows good estimation ability. The parameters of the quadratic function are adjusted by using the recursive least squares method and are obtained on‐line. Since it can correspond to parameter change, the estimated rotor position shows good agreement with the measured rotor position against load torque and motor temperature changes. Sensorless position control is achieved by using the estimated rotor position instead of the measured rotor position. The validity of the proposed method is confirmed by experimental results. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 163(1): 57–64, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20626     

A novel calculation method for iron loss resistance suitable in modeling permanent-magnet synchronous motors

This paper proposes a calculation method for iron loss resistance, suitable for modeling permanent-magnet synchronous motors. The proposed method is based on the linear feature between semi-input power and square of speed electromotive force. The iron loss resistance is calculated from the slope of this linear function in the offline manner. The advantage of the proposed method is that the iron loss resistance can be calculated directly without any measurements related to mechanical loss. In addition, the proposed method can be executed at any load conditions. The validity of the proposed method is experimentally confirmed by the comparison between the actual torque and the calculated torque containing the iron loss resistance.     

Torsional torque suppression of decentralized generators using H∞ observer

The output power fluctuations of renewable energy plants such as wind turbine generators and photovoltaic systems cause frequency deviations and terminal voltage fluctuations. Furthermore, these power fluctuations also affect the turbine shaft of diesel generator and gas-turbine generators which are usually the main electric power systems in isolated islands. This paper presents a control strategy that achieves torsional torque suppression and power system stabilization. Since the measurement of the torsional torque is technically difficult and there is uncertainty in mechanical constants of the shaft torsional system, the torsional torque is estimated by using a H_∞ observer. The simulation results validate the effectiveness of the proposed control system.