Competitive oxidation of formaldehyde and formate on amorphous copper-palladium-zirconium alloy electrodes in alkaline media

Raney-type Cu–Pd alloy electrodes were prepared from amorphous Cu–Pd–Zr ternary alloys by treatment with aq. HF, and competitive anodic oxidation reactions of HCHO and HCOO^– were studied on these electrodes in alkaline media. The initial HCHO oxidation product was HCOO^– even on Pd or Pd-rich alloy electrodes which should be more active to the HCOO^– oxidation than to HCHO. The product HCOO^– was oxidized only after a large decrease of the HCHO concentration in the electrolyte. The oxidation rate of HCOO^– was considerably lowered by the existence of even a small amount of HCHO, as well as by the introduction of CO. These results suggest that the HCHO electro-oxidation is accompanied by production of a surface contaminant such as adsorbed CO. The optimum nominal Pd atomic fraction in the Cu–Pd alloy electrodes suitable for the steady simultaneous oxidation of HCHO and HCOO^– in mixed solution was shown to be 0.25 and 0.4 in 1.0 M NaOH (M=moldm^–3) and 0.5 M K₂CO₃, respectively.     

A sinusoidal PAM-PWM inverter

A new strategy, using both PAM (pulse amplitude modulation) and PWM (pulsewidth modulation) in combination for a power inverter is described. The output waveforms in the proposed PAM-PWM inverter are investigated both theoretically and experimentally. The line-to-line voltage waveform includes the fundamental component and the sidebands of the carrier frequency. Lower-order harmonics are not included in the output waveform. The amplitude of the fundamental component increases 15 percent more than that of a conventional sine-wave inverter. Since each inverter arm does not operate during two-thirds of the period, the heat generated in the devices is reduced, i.e., the size of the inverter system can be minimized because of the reduction in the heat dissipating equipment.     

Critical current test results of 13 T-46 kA Nb3Al cable-in-conduit conductor

In the framework of ITER-EDA, a 13 T-46 kA Nb₃Al conductor with stainless steel jacket has been developed in order to demonstrate applicability of an Nb₃Al conductor with react-and-wind technique to ITER-TF coils. Using a 3.5 m sample consisting of a pair of conductors with 0% and 0.4% bending strain, the critical current performances of the Nb₃Al conductors were studied to verify that the conductor achieves the expected performance and the bending strain of 0.4% does not originate degradation. The critical currents were measured at background magnetic fields of 7, 9, 10 and 11 T at temperatures from 6 to 9 K. The expected critical currents were evaluated taking into account the variation of the strain in the cross-section due to the bending strain as well as self-field and non-uniform current distribution as results of an imbalance in the joint resistance and inductances. The calculation results indicate that the current distribution is almost uniform and the experimental results showed good agreement with the expected critical currents. Accordingly, we can conclude that the fabrication process of this conductor is appropriate and the react-and-wind technique using the Nb₃Al conductor is applicable to ITER-TF coils. In addition, the critical current of the Nb₃Al conductor is expected to be 108 kA at 13 T and 4.5 K, resulting in a sufficient margin against the nominal current of 46 kA. Furthermore, it was found that the decrease in the critical current by thermal strain can be made small by applying the bending strain to the conductor so as to reduce the compressive strain at higher fields, i.e. inner side of the coil, in the conductor cross-section.     

Implications of the ability to learn simple actions on the efficiency of the evolution of social behavior of agents

We investigate the effect of the ability to learn simple actions on the performance characteristics of the evolution of social behavior in agents situated in an inherently cooperative environment. Using a continuous predator–prey pursuit problem, we verified that relatively complex social behavior emerges from simple, implicit, locally defined, and thus robust and scalable interactions between the predator agents. Considering a distinct aspect of the phenomenon of emergence, we hypothesize that the ability of agents to learn how to perform simple, atomic acts of implicit interaction might facilitate the evolution of more complex behavior. The empirical results indicate that incorporation of the proposed approach to learning in genetic programming (employed as an algorithmic paradigm to evolve the social behavior of the agents) is associated with about a two-fold decrease in the computational effort of evolution.This work was presented, in part, at the 9th International Symposium on Artificial Life and Robotics, Oita, Japan, January 28–30, 2004     

Synthesis of EDTA-monoalkylamide chelates and evaluation of the surface-active properties

New chelating agents were synthesized from long-chain amines and ethylenediaminetetraacetic acid (EDTA) monoanhydride which was prepared by partial hydrolysis of EDTA anhydride. The equivalent reactions between the chelating agents and several metal ions gave the corresponding 1:1 metal chelates in good yield. These chelates and the sodium salts of the chelating agents were found to have good surface active properties, especially dispersing power and emul-sifying power.     

Development of a new pH-swing CO2 mineralization process with a recyclable reaction solution

A new CO₂ mineral sequestration process using the pH swing of a weak base–strong acid solution was proposed. In this process, an alkaline-earth metal was extracted selectively from silicate waste material, such as steelmaking slag or waste concrete, in an acidic condition using a weak base–strong acid solution. The reacted solution containing alkaline-earth metal ions and a weak-base, behaves as a CO₂ absorbent. The acidic extraction solution was regenerated from the basic absorbent solution by precipitating the alkaline-earth metal with CO₂ as the carbonate. The thermodynamic analysis of this process shows that a series of reactions proceeds spontaneously and the overall reaction is exothermic. The feasibility of the proposed process was confirmed using steelmaking slag as a silicate material and ammonium chloride solution as a weak base–strong acid solution. It was confirmed that this series of reaction proceeds successfully under mild conditions. Calcium ions were extracted selectively from steelmaking slag using an ammonium chloride solution, and the reacted solution absorbed CO₂ followed by the precipitation of CaCO₃ at 80 °C. On the basis of these experimental analyses, the energy consumption of the proposed process was roughly estimated as 300 kWh/ton-CO₂.     

High-density formation of Ge quantum dots on SiO2

We formed high-density Ge quantum dots (QDs) on an ultrathin SiO₂ layer by controlling the early stages of low-pressure chemical vapor deposition (LPCVD) with a germane gas (GeH₄) assisted by a remote plasma of pure H₂. We then characterized the electronic charged states of the QDs by an AFM/Kelvin probe technique. The formation of single crystalline Ge-QDs with an areal dot density of ∼2.0 × 10¹¹ cm⁻² was confirmed after examining the surface morphology and lattice by atomic force microscopy and transmission electron microscopy, respectively. It has been suggested that an increase in the flux of deposition precursors due to efficient decomposition of GeH₄ by a supply of hydrogen radicals and the dehydration reaction of surface OH bonds plays a role in nucleation of Ge-QDs on SiO₂. Surface passivation with hydrogen may also promote the surface migration of deposition precursors during LPCVD. The surface potential of the dots changed in a stepwise manner with respect to the tip bias due to multistep electron injection into and extraction from the Ge-QDs.     

Flowability measurement of pulverized and granulated materials using vibrating tube method

To develop a method for measuring the flowability of MOX (mixed oxide of uranium and plutonium) particles used in the simplified MOX pellet fabrication process, the flowability of model particles has been investigated by the vibrating tube method. As model particles, pulverized ZrO₂ and granulated WO₃ were used. To prepare a variety of samples, coarse particles of 106–250 μm in diameter were mixed with fine particles smaller than 45 μm in diameter in different concentrations. The prepared particles were put into the vibrating tube and the amplitude of vibration was increased at a constant rate for a period of time and then decreased. The mass of particles discharged from the tube was measured at constant time intervals. From the experimental data, the relationships between the mass flow rate and the vibration acceleration (i.e. flowability profiles) were obtained. Two factors (i.e. ‘critical vibration acceleration’ to make the particles flow and ‘characteristic mass flow rate’) were selected to analyze the flowability profiles. The hysteresis of the flowability between increasing and decreasing vibration accelerations was also evaluated.