Polarized Raman spectra of doubly oriented poly(vinyl alcohol)

Polarized Raman spectra of doubly oriented samples of atactic poly(vinyl alcohol) have been measured. The great usefulness of such polarized spectra has been clarified for the vibrational analysis. The normal coordinate treatments of syndiotactic and isotactic poly(vinyl alcohol) chain models gave good agreement between the observed and calculated frequencies.     

Walking navigation system for the visually impaired using a guide stick

We have proposed an online navigation system for the visually impaired. In our previous system, we used a pedometer and a terrestrial magnetic sensor. This system has the problems of cumulative errors in the measurement of walking distance and errors in the detection of walking direction due to the lean of the terrestrial magnetic sensor. In this paper, we develop another navigation system that uses a guide stick to which is attached a small wheel at the end of the stick instead of a pedometer and a device for keeping the terrestrial magnetic sensor horizontal in order to improve the problems of the previous system. Thus, we can obtain a more exact walking locus. To navigate the visually impaired, we propose a method using auditory signals consisting of voice sound and buzzer. Further, we attach an answering machine to the guide stick to provide the required information whenever requested. To evaluate the navigation system, we conduct walking experiments using blindfolded and visually impaired individuals. It is seen that this system can guide them to a destination at a distance of about 620 m and is useful as a navigation system for the visually impaired. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 119(3): 69–80, 1997     

Electrical Conductivity of CeO2 Prepared from Nanosized Powders

Nanosized powders of cerium dioxide with controlled physical properties were prepared by the precipitation technique using ammonium hydroxide or oxalic acid as precipitating agent. The calcined precursors were studied by nitrogen adsorption to determine the specific surface area, X-ray diffraction for phase characterization and crystallite size determination, and by laser scattering for particle size distribution. The morphology of powder particles was observed by scanning electron microscopy. It is shown that both precipitating materials may be used for the preparation of nanocrystalline powders (< 10 nm) with high values of specific surface area (> 90 m² g^{– 1}). The observed differences between powders prepared from hydroxides or oxalates rely on the distribution of particle sizes and in the morphology of the agglomerated particles. Impedance spectroscopy experiments were carried out in the 5 Hz–13 MHz frequency range under controlled partial pressure of oxygen from 10 ppm to 1 atm. The analysis of these results allowed for the determination of the charge carriers responsible for the electrical transport in the ceria sintered pellets.     

The High-Temperature Thermoelectric Properties of Polycrystalline Ba8Ga x Al y Si46−x−y Type-I Clathrates

Thermoelectric materials suitable for practical thermoelectric power generators should, ideally, be based on light elements, for example Si and Al, which are abundantly available. For this reason, silicon clathrate compounds in which both Ga and Al were substituted for Si were synthesized and their thermoelectric properties were investigated. The temperature-dependent electrical resistivity of the samples indicated their metallic nature, and their negative Seebeck coefficient suggested that charge transport in the samples was mainly through electron transport. The maximum absolute value of the Seebeck coefficient achieved was ?180 μV/K at 1040 K for Ba_7.90Ga_13.8Al_2.29Si_30.0. Thus, these materials have potential for use in practical thermoelectric power generators.     

Formation and diffusion mechanism of histamine in the muscle of tuna fish

This study investigates the formation and accumulation of histamine in the fresh meat of tuna fish. Under sterilized conditions, histamine was not detected in the muscles of Thunnus obesus (T. obesus) stored at 20 °C and 25 °C for 72 h (data not shown). And histamine formation and the diffusion mechanism was studied in T. obesus meat inoculated with two histamine-forming bacteria, Morganella morganii NBRC 3168 (M. morganii NBRC 3168) and Photobacterium phosphoreum NBRC 13896 (P. phosphoreum NBRC 13896) and stored at 20 °C and 25 °C for 3 days. The histamine level of the inoculated A1 point accumulated at a level above 4000 mg/kg in the T. obesus sample inoculated with M. morganii NBRC 3168 for 48 h. And the most level of the histamine in the remote B point was 2000 mg/kg at the time the sample was inoculated with M. morganii NBRC 3168 and stored at 25 °C. For the P. phosphoreum NBRC 13896 however, the level of histamine at the inoculated point A was 1800 mg/kg for 48 h when it was stored at 25 °C, while the highest level of histamine distant from the inoculum site B point was found to be approximately 1800 mg/kg. In contrast, when stored at 20 °C, histamine level was higher for the sample inoculated with P. phosphoreum NBRC 13896 than with M. morganii NBRC 3168. While histamine was diffused from the inoculation point in the M. morganii NBRC 3168 sample, it was diffused not only from the inoculated point, but also the remote area in the P. phosphoreum NBRC 13896 sample.     

Corrosion resistance of molybdenum-containing titanium alloy for overpack in simulating underground environment

Crevice corrosion behavior of titanium (Ti) and binary Ti alloys containing 5-25 mass% of molybdenum (Mo) was investigated in 10% NaCl at 100 °C. Although a considerably large shift in crevice potential toward the active region and large current were observed with Ti, no change in crevice potential or current was observed with the Mo-Ti alloy. The resistance against crevice attack was found to depend on the Mo content of the alloys in the experiment. Further investigations by potentiodynamic polarization and the electrochemical impedance spectroscopy (EIS) method were conducted. Polarization measurements showed an increase in cathodic current density with the increase of Mo content in Ti alloys. As the Mo content was increased to around 10%, the corrosion potential was found to exist within the passive region even in highly acidic solutions. These results illustrated the more highly passivating behavior of 10-25% Mo-Ti alloys than pure Ti and 5% Mo-Ti alloys. The higher impedance values shown by EIS revealed the high ability of 15% and 25% Mo-Ti alloys to keep the passive film even in the acidic solutions. It was found that Mo-Ti alloy could keep the passive film even in a high chloride concentration environment at 100 °C. Hence, as for the crevice corrosion, this alloy could be useful for environments simulating the overpack near the coast.     

Deadbeat flux level control of direct-field-oriented induction motor

A method for the deadbeat flux level control of a direct-field-oriented induction motor with position control loop has been developed that employs an adaptive rotor flux observer. The observer is a full-order type and is used not only in the direct-field-oriented controller, but also to identify stator and rotor resistances of the motor. The observer reduces the sensitivity of a deadbeat controller to fluctuations in the motor parameters. The main advantage of this method is that it improves the efficiency of an induction motor without sacrificing dynamic performance. This paper describes the method as well as the fundamental characteristics of the system derived from experimental and simulation results.     

Cumulative pregnancy rates in couples with anovulatory infertility compared with unexplained infertility in an ovulation induction programme

Using a retrospective analysis, we compared cumulative pregnancy rates, early pregnancy failure rates and multiple pregnancy rates in couples with polycystic ovarian syndrome (PCOS) (n = 148), hypogonadotrophic or eugonadotrophic hypogonadism (n = 91) and unexplained infertility (n = 117), who were treated in an ovulation induction clinic between January 1991 and December 1995. The women were treated with either human menopausal gonadotrophin (HMG) or purified follicle stimulating hormone (FSH). The cumulative pregnancy rate (derived from life-table analysis) after four ovulatory treatment cycles was 70% in the PCOS group, 74% in the hypogonadism group and 38% in the unexplained infertility group. The cumulative pregnancy rate in the unexplained infertility group was significantly lower than the other groups (P < 0.001) but there was no significant difference between PCOS and hypogonadism using the log rank test. The early pregnancy failure rate was 25% in the PCOS group, 27% in the hypogonadism group and 26% in the unexplained infertility group (chi(2) = 0.132, not significant). The multiple pregnancy rate was 20% in the PCOS group, 30% in the hypogonadism group and 17% in the unexplained infertility group (chi(2) = 2.105, not significant). Treatment of anovulatory infertility using HMG or FSH is effective irrespective of the cause. Couples with unexplained infertility are less successfully treated using HMG: correction of unexplained infertility may involve more than simple correction of possible subtle ovulatory defects.