Uptake and recovery of gold by immobilized persimmon tannin

Some attempts were made to recover gold from aqueous systems using immobilized persimmon tannin. This adsorbent adsorbed gold from solutions containing hydrogen tetrachloroaurate(III) with high efficiency, whereas there was minimal adsorption from solutions containing gold(I) sodium thiomalate and sodium dicyanoaurate(I). The adsorption of gold was rapid, and was affected by the pH of the solution, temperature, external gold concentration and amount of adsorbent. Adsorbed gold was easily desorbed with 1 mol dm^?3 thiourea solution, indicating that immobilized persimmon tannin can be repeatedly re-used for the recovery of gold using adsorption-desorption cycles.     

Self-excited synchronous induction motor

A synchronous-induction motor, with the features of both a synchronous motor and a wound-rotor induction motor, far excels other synchronous motors in starting characteristics. However, a major drawback of the synchronous-induction motor is the need for an excitation power supply with low-voltage, large-current power rating. For this reason, its driving equipment becomes large, and increases overall cost. This paper proposes a new synchronous-induction motor, absent the problems involved in making the motor a self-excited type. It employs the second-space harmonic component of armature reaction field to obtain the self-excitation of the field system, and installs a harmonic winding, which is used for extraction of an excitation power, in the rotor. This new self-excited motor has the following advantages: (1) the driving equipment is small, since no excitation power supply is involved; and (2) due to the effect of the series characteristic by which the field current varies in proportion to the load current automatically, the motor can be operated with a good power factor. In the present paper the structure and operating principle of the new motor are explained and the basic characteristics are also investigated by means of a simple analysis and experimental results with a 1.5-kV trial machine.     

Development of kA-class alternating current superconducting conductors and fabrication of a prototype coreless superconducting autotransformer

Recently, multifilamentary superconducting wires with very low ac losses have been produced and practical applications will now be considered. To realize actualsize power machines and apparatuses, it is necessary to develop 1 - 10 kA ac conductors. However, the critical currents of multifilamentary wires at 1 T are several tens of A, and therefore it is necessary to use multistrand conductors consisting of several tens or several hundreds of strands. Such conductors sometimes show ac current degradation because of such factors as (1) nonuniform current distribution, (2) wire motion, (3) temperature increase, (4) longitudinal magnetic field effect, etc. Formerly, a coreless transformer was considered unpractical because of its large exciting current. However, Yamamoto and others proposed that a coreless superconducting transformer could be used as a stepdown autotransformer at the receiving side, utilizing its large exciting current as the reactive power source to cancel the charging current of an underground transmission line or UHV line, and therefore the shunt reactors could be eliminated. In this paper, development of ac-superconducting conductors aimed at prevention of current degradation are discussed, as well as quench test results of two small coils made with these conductors. In these conductors, low ac low strands with ultrafine NbTi filaments are twisted around a central bundle of stainless steel wires. One of the coils has been designed as a model coreless autotransformer, and its test result is also described.     

Self-Irradiation Damage of a Curium-Doped Titanate Ceramic Containing Sodium-Rich High-Level Nuclear Waste

The polyphase titanate ceramic containing sodium-rich simulated high-level nuclear waste was doped with 0.69 wt% of ²⁴⁴Cm to accelerate long-term self-irradiation due to α decays. α autoradiography showed that α emissions were almost uniformaly distributed throughout the curium-doped samples on a >20-μm scale although micropore surfaces and titanium oxide agglomerates were free of α-emitting nuclides. The phase assemblage of the curium-doped titanate ceramic included freudenbergite and loveringite in addition to the more abundant oxide phases: hollandite, perovskite, and zirconolite. Accumulation of α decays was accompanied by a gradual decrease in density. The increment of density was – 1% after an equivalent age of 5000 yr. Leach tests showed a slight trend toward higher total release of curium with equivalent age. The release of soluble nonradioactive elements (e.g., Na, Cs, Sr, and Ca) in the oldest specimens (equivalent age, 2000 yr) varied from specimen to specimen but, on average, were higher than specimens that had suffered a lower radiation dose.     

Application of the collocation method to vibration analysis of rectangular mindlin plates

The flexural vibration analysis of rectangular Mindlin plates using the collocation method is described. The results obtained by the present method are compared with published results for plates with uniform thickness and two opposite edges simply supported. The comparison shows that the method yields very good results with a relatively small number of collocation points, and that estimates for the higher modes can be obtained without any difficulties. Furthermore, the method is applied to plates with linearly varying thickness, and new findings are presented for the frequencies of plates.     

X-ray study of the new charge-density-wave phase in 1T-TaS2

Positions of both the first- and second-order satellite reflections in the newly found charge-density-wave phase of 1T-TaS₂ are measured by x-ray diffraction. The discommensuration network with a lower symmetry and its stacking sequence are determined. This phase appears on cooling from the nearly-commensurate phase as well as on heating from the commensurate phase, on contrast with results of previous measurements.     

Photografting of N‐isopropylacrylamide on polyethylene film in mixed solvents composed of water and organic solvent

The effects of a mixed solvent consisting of water and organic solvents such as acetone and methanol on the photografting (λ > 300 nm) of N‐isopropylacrylamide (NIPAAm) on linear low‐density polyethylene film (thickness = 30 μm) was investigated at 30°C and 60°C. Xanthone, which had been coated on the film, was used as a photoinitiator. The photografting initiated even in the system at 30°C by using a longer irradiation time. It was found that the maximum percentage of grafting was attained at a certain concentration of organic solvent in the mixed solvent, which shifted to a lower concentration of organic solvent in the system at 60°C compared with the system at 30°C. It was found that the grafted chains of the sample prepared in the system with the higher polymerization temperature and the use of mixed solvent penetrated into the center of the film compared with the sample prepared in the system with the lower polymerization temperature and use of a water solvent. Moreover, the NIPAAm‐grafted films exhibited temperature responsiveness, swelling and shrinking in water at 0°C and 50°C, respectively. The extent of this characteristic was found to be closely related to the location of the grafted chains in film substrate, which was measured by an attenuated total reflection infrared spectroscope and a scanning electron microscope. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 458–463, 2003     

Filter with variable transmission characteristics for determination of three-dimensional roughness

In this study, we propose a low-pass filter whose transmission characteristics are determined to be more than 99.99% identical to the designed transmission characteristics at wavelengths greater than the cut-off wavelength. This low-pass filter is realized using a frequency-domain method which uses down-sampling, a frequency filter, and a cubic B-spline. When the frequency characteristics of a Gaussian filter (GF) were used as the designed transmission characteristics, this low-pass filter perfectly replaced the GF. In addition, no end effects and directional characteristics developed, and high-speed computation was possible. Furthermore, we can easily realize a low-pass filter having transmission characteristics that rise sharply at a right angle like a step edge.