Bioleaching of Rare Metals from Manganese Nodules by Thiobacillus Ferrooxidans

Manganese nodules, which constitute a potential future resource of rare metals, are composed mainly of oxides of manganese and iron, with various metals such as copper, nickel, and cobalt. Although physical and chemical processes have been developed for extracting the rare metals from manganese nodules, another possible process is the leaching of metals by microbial means.

This paper describes leaching of raw manganese nodules by sulfurous acid and sulfuric acid which are biologically produced by oxidation of elemental sulfur by Thiobacillus ferrooxidans. The bioleaching behavior of each metal from nodules was measured at 30°C and pH 2 in a well-mixed batch reactor. The metal content of the nodules used in this work was 0.29% Cu, 0.49% Ni, 0.27% Co, 16% Fe and 17% Mn by weights. For both the microbial system and the control culture containing no T.ferrooxidans, copper and nickel exhibited close to 100% leaching in two weeks and less than 5% for iron and manganese. On the other hand, leaching of cobalt was markedly accelerated in the microbial system reaching 50% in two weeks compared with the sterile control. The bioleaching rate of cobalt was enhanced as the initial sulfur-liquid loading ratio became higher, but is was practically independent of the nodule size which was less than 330 mesh. Moreover, there was an optimal relation between the bioleaching rate and the initial cell concentration, and the addition of T.ferrooxidans cells in excess of the optimal concentration resulted in a decrease in the leaching rate of cobalt.     

Experimental Services of Energy Management for Energy Users in Business Region on Miyakojima City All‐Islands EMS Demonstration Project

Smart grid and demand response (DR) had been attracting attention and evaluated in several demonstration projects. Many DR experimental results for residential and large‐scale buildings had been evaluated, while evaluation for small size buildings seems to be not enough. In this paper, a new energy service combined EMS method is proposed for small size buildings. Then results of its application to Miyako Island All‐Islands EMS Demonstration Project are introduced. The experimental services include not only DRs but also peak cutting recommendations and energy analysis reports. The results show combination of services can realize more effects than individual service. Especially the peak cutting recommendations and energy analysis reports help energy consumers to learn and understand how to save and manage energy usages that lead to effective DR potentials. Also the experimental system developed for energy data measurement and DR management as an island community EMS is intrduced.     

Development of Multiresonant ZVS High‐Frequency Inverter

A novel multiresonant zero‐voltage switching (ZVS) high‐frequency inverter has been developed. This inverter is capable of supplying a current of large amplitude to a load as a result of suppression of the main switch current. The principle of the ratio of the main switch current to the load current is theoretically demonstrated using the capacitance ratio. High‐frequency operation with ZVS is verified experimentally.     

Design Method for Improving Motor Efficiency of Switched Reluctance Motor

The motor efficiencies of switched reluctance motors (SRMs) are inferior to those of permanent magnet synchronous motors. This paper describes a design procedure for an SRM to obtain a higher motor efficiency. The first step in the design procedure makes clear the principle for improving the motor efficiency. The cross‐sectional and axial shapes of the rotor and stator cores are designed by magnetic field analysis with the two‐dimensional (2D) and 3D finite element method. A high‐efficiency SRM with 12 stator poles and eight rotor poles is designed. The designed SRM was produced experimentally, and was tested to verify its performance. The motor efficiency was improved in comparison to the standard SRM with six stator poles and four rotor poles.     

ISOLATION OF INTACT TYPE V COLLAGEN FROM FISH INTRAMUSCULAR CONNECTIVE TISSUE

A purification method for intact type V collagen from fish intramuscular connective tissue was developed. Collagens were extracted with 0.5 M acetic acid from fish intramuscular connective tissue. Intact type V collagen could not be isolated by conventional salt fractionation which has been used for isolation of pepsinized collagens. Isolation was achieved by ion-exchange chromatography in the presence of 5 M urea. This is the first report on isolation of intact type V collagen from muscle tissue.     

Reversible Optical Change of Amorphous Red Phosphorus in Reduced Phosphate Glasses

Amorphous red phosphorus formed in reduced phosphate glasses was found to show a photodarkening effect by illuminating the glasses with light approximately equivalent to its absorption edge; the optical transmission edge shifts toward longer wavelengths on illumination, and then a distinct deepening of the reddish color is observable visually. The photo-darkened specimen recovers its original transmission when it is heated at 300° to 350°C. This darkening-restoring process is confirmed to be reversible by repeated illumination and heating. Transmission measurements over a range of elevated temperatures suggest that this optical characteristic of red phosphorus is unique to its amorphous state.     

Photosensitive Mechanism of Dopant-Free, Ultraviolet-Sensitive Calcium Aluminate Glasses

Calcium aluminate glasses show high sensitivity to ultraviolet radiation without the doping of optically active components. A mechanism is proposed to account for their photosensitivity on the basis of the result that the cause of UV-induced coloring is the emergence of two kinds of paramagnetic centers, an aluminum-oxygen hole center (Al-OHC) and an ozonide (O^-₃). In this model, a peroxy linkage connecting tetrahedrally coordinated Al³⁺s and a physically dissolved O₂ molecule are assumed to be present in the glasses as structural defects. On exposure to UV rays, the peroxy linkage homolvtically dissociates into a pair of A1-OHC's by absorbing UV quanta and one of the two resulting A1-OHC's combines with a nearby O₂ to form an ozonide. Experimental evidences substantiating the mechanism are also reported.     

Solution convexity of a system of linear interval equations

A necessary and sufficient condition for a convex solution set to a system of linear interval equations is presented. The relation between the convexity and feasibility of an optimization problem is also discussed. An extended Leontief system is proposed as an application of the results.     

Valency Control of Glow Discharge Produced a-SiC:H and its Application to Heterojunction Solar Cells

A new type of amorphous silicon solar cell having a conversion efficiency of 8% level is introduced. The cell has a wide band gap window layer made of hydrogenated amorphous silicon carbide, (a-SiC:H), with a good valency control. Electrical, optical and optoelectronic properties of a-SiC:H have been investigated, together with their valency controllability. A design concept and some key technologies to improve solar cell performance with this new material are demonstrated. A series of technical data on material preparation and cell performance are presented. Clear improvements in cell performance, not only I_DC but also V_DC, have been obtained. The realistic limit of the conversion efficiency in a-Si solar cells is estimated and discussed.     

Photosensitive Characteristics of Dopant-Free, Ultraviolet-Sensitive Calcium Aluminate Glasses

Calcium aluminate glasses show high sensitivity to ultraviolet radiation without the doping of optically active components. In this paper, photosensitive characteristics and the cause of UV-induced coloring were investigated for these glasses. Ultraviolet rays below 270 nm were effective for inducing the coloring. The most effective wavelength agreed with that of the apparent absorption edge. In the ternary system with SiO₂ or GeO₂, the sensitivity was monotonically reduced with the amount of the third component and almost vanished for the compositions containing 40 mol%. On the basis of the establishment of a close correlation between two optical absorption bands and two electron spin resonance signals induced by UV illumination, the UV-induced coloring was concluded to be due to the emergence of an aluminum-oxygen hole center (Al-OHC) and an ozonide (O₃^-).