Computation-oriented expression of a non-conservative condition for robust stability of sampled-data systems

A new expression of a non-conservative robust stability condition is derived for sampled-data systems taking into consideration its convenience in numerical computation. Our expression is described using a global maximum of a certain differentiable function, while the conventional expression includes a global maximum of a structured singular value, which is expensive to compute. When the sampling period is long, the advantages of our expression become clear. A possible problem is that the maximized function may be multimodal. However, the conventional expression has the same problem and even a local maximum is shown to give useful information. Our expression is applicable to a fairly large class of systems including the multi-input multi-output additive and multiplicative perturbation models. Using an example, we show how our expression is computed and make a comparison with the conventional expression.     

Dissolution in Ceramic Systems: III, Boundary Layer Concentration Gradients

By use of electron microbeam probe analysis on quenched samples, the concentration distribution of CaO, A1₂O₃, and SiO₂ was determined across the boundary layer between molten calcium aluminum silicates and dissolving or growing sapphire and fused silica. A definite shift in the concentration ratios of the solvent components was found near the interface. Analysis of diffusion flux equations for a ternary system successfully related the shift in concentration ratio to the intrinsic diffusion coefficient for each component. For alumina dissolution in a melt rich in CaO, evidence of incongruent dissolution was observed with the formation of new phases, CaO· 6Al₂O₃ and CaO· 2A1₂O₃.     

High-intensity laser-driven particle and electromagnetic wave sources for science, industry, and medicine

We simultaneously observed both the fast proton generation and terahertz (THz) radiation in the laser pulse interaction with a thin-foil target.The maximum proton energy of ～2.3 MeV and an intense THz radiation were observed at the pulse duration of ～30fs.We also measured the proton beam and UV harmonics from a thin-foil target by changing the laser pulse duration.In the case of the ～500 fs, peaks of UV harmonics up to fourth order appeared.This unique combination of the multiple beams will provide useful applications such as pump-probe experiments.     

Enhancement of MgO Evaporation from MgO-Stabilized ZrO2 by Grain-Boundary Diffusion

Preferential evaporation of MgO from cubic 14MgO·86ZrO₂ solid solution was determined for two polycrystals with different grain sizes at 1800° to 2100°C and 7 × 10^–3 Pa. The time dependence of the evaporation rate and the concentration in the solid phase indicated that the evaporation kinetics is controlled by cationic interdiffusion in the solid phase and enhanced by the presence of grain boundaries. The temperature dependence of the lattice diffusion coefficient calculated from the concentration distributions agreed with that previously determined for Mg-Zr interdiffusion in polycrystalline MgO-ZrO₂ solid solutions.     

RAPID DETECTION OF A SMALL NUMBER OF VIABLE CELLS BY THE FLUORESCENT GLUCOSE METHOD

A fluorescent glucose, 2NBDG, was rapidly consumed by 4 different species of microorganisms: Escherichia coli, Lactobacillus acidophilus, Saccharomyces cerevisiae, and Candida tropicalis. E. coli and L. acidophilus became fluorescent enough for microscopic observation within 1 min, while S. cerevisiae and C. tropicalis became fluorescent in a longer time span. All of the 14 coliforms that were isolated from various foods consumed 2NBDG and became fluorescent within 1 min. Therefore, 2NBDG is expected to be a useful indicator of viable cells irrespective of species as long as they could assimilate glucose. This 2NBDG method is valid in counting small amount of cells, such as 10–100 cells, accurately and carefully. Also, the 2NBDG method was successfully applied to the rapid detection of a small number of E. coli in milk. The feasibility of the 2NBDG method is discussed from the viewpoint of food safety control.     

Line identification of boron and nitrogen emissions in extreme-and vacuumultraviolet wavelength ranges in the impurity powder dropping experiments of the Large Helical Device and its application to spectroscopic diagnostics

An impurity powder dropper was installed in the 21 st campaign of the Large Helical Device experiment(Oct. 2019–Feb. 2020) under a collaboration between the National Institute for Fusion Science and the Princeton Plasma Physics Laboratory for the purposes of real-time wall conditioning and edge plasma control. In order to assess the effective injection of the impurity powders,spectroscopic diagnostics were applied to observe line emission from the injected impurity. Thus,extreme-ultraviolet(EUV) and vacuum-ultraviolet(VUV) emission spectra were analyzed to summarize observable impurity lines with B and BN powder injection. Emission lines released from B and N ions were identified in the EUV wavelength range of 5–300 ? measured using two grazing incidence flat-field EUV spectrometers and in the VUV wavelength range of 300–2400 ? measured using three normal incidence 20 cm VUV spectrometers. BI–BV and NIII–NVII emission lines were identified in the discharges with the B and BN powder injection, respectively. Useful B and N emission lines which have large intensities and are isolated from other lines were successfully identified as follows: BI(1825.89, 1826.40) ?(blended), BII 1362.46 ?, BIII(677.00, 677.14,677.16) ?(blended), BIV 60.31 ?, BV 48.59 ?, NIII(989.79, 991.51, 991.58) ?(blended), NIV765.15 ?, NV(209.27, 209.31) ?(blended), NVI 1896.80 ?, and NVII 24.78 ?. Applications of the line identifications to the advanced spectroscopic diagnostics were demonstrated, such as the vertical profile measurements for the BV and NVII lines using a space-resolved EUV spectrometer and the ion temperature measurement for the BII line using a normal incidence 3 m VUV spectrometer.     

A Hybrid DC Circuit Breaker Combining a Multilevel Converter and Mechanical Contactors: Verification of the Principles of Operation by Experiment and Simulation

This paper presents a new hybrid dc circuit breaker producing no conducting power loss under normal operating conditions and having the capability to interrupt a large amount of short‐circuiting current within several milliseconds. It consists of two reactors for current limiting and current control, two mechanical contactors, and a multilevel converter based on the cascade connection of multiple full‐bridge dc/dc converter cells. It is characterized by achieving current commutation from the main mechanical contactor to the multilevel converter with fast current control. This results in eliminating auxiliary power semiconductor switches that produce a nonnegligible conducting power loss under normal operating conditions. This paper discusses both principles of operation and control method of the new hybrid dc circuit breaker. Experimental verification is performed by a downscaled system rated at 300 V and 150 A, along with verification by computer simulation.     

Analysis of Liquid-State Interdiffusion in the System CaO-Al2O3-SiO2 Using Multiatomic Ion Models

Concentration profiles after liquid-state interdiffusion were determined using an electron probe microanalyzer for diffusion couples of ternary oxide systems with an average composition -40CaO₂OAl₂O₃-40SiO₂ (wt%) at r=1370° to 1550°C. Multicomponent diffusion equations were derived for three multiatomic ion models in terms of tracer diffusion coefficients of the constituent elements. The sizes of the diffusing units for silicate and aluminate ions were estimated by determining the structure parameters in the diffusion equations so as to provide the best fit of the theoretical calculations to the experimentally determined concentration profiles. The results were compared with the theoretical calculations for the monoatomic ion model and the oxide molecule model as diffusing species.     

Preparation of polyaniline-poly (p-styrenesulfonic acid) composite by post-polymerization and application as positive active material for a rechargeable lithium battery

Polyaniline (PANI)-poly (p-styrenesulfonic acid) (PSS) composite was prepared by thermal post-polymerization of PANI-p-styrenesulfonic acid (SSA) composite. A PANI–SSA composite was prepared by mixing PANI/N-methyl-2-pyrrolidinone solution with SSA aqueous solution. The PANI–SSA composite film was prepared by casting the composite onto an ITO glass plate. The cast film was converted to PANI-PSS film by heating at 100°C for 3h (post-polymerization process). The PANI–PSS modified ITO electrode showed electrochemical responses based on the redox reaction of PANI–PSS composite in the organic electrolyte solution, for example, propylene carbonate containing 1moldm–3 LiClO4. The PANI–PSS composite was a cation -doping polymer composite. The composite was also modified on a porous carbon material (Reticulated Vitreous CarbonTM, RVC, Energy Research and Generation, Inc.). The PANI–PSS modified RVC electrode showed similar electrochemical behaviour as the PANI–PSS modified ITO electrode. Model secondary lithium cells, Li|1moldm–3 LiClO4-propylene carbonate|PANI–PSS modified RVC electrode, were constructed and charge–discharge cycling tests were carried out. The cell showed about 60% coulombic efficiency under high current density cycling conditions (3.8Ag–1, per gram of PANI–PSS modified RVC electrode).