Dead Beat Microprocessor Control of PWM Inverter for Sinusoidal Output Waveform Synthesis

A new control technique based on dead beat control theory to obtain a nearly sinusoidal PWM inverter output voltage is described. The closed-loop digital feedback system measures the output and controls the inverter switches to generate the required pulsewidth-modulated (PWM) pattern to produce low total harmonic distortion (THD) sinusoidal output voltage. This scheme inherently provides very good voltage regulation, phase positioning, and compensation for load disturbances and nonlinear loads. A theoretical analysis, computer simulation, and experimental results for a single-phase bridge inverter controlled by an Intel 8086 microprocessor-based system is presented.     

Synthesis of bulk silicon oxynitride glass through nitridation of SiO2 aerogels and determination of Tg

The development of transparent glass for use in high-temperature applications is continuing. In this study, we synthesized bulk silicon oxynitride glasses (a-Si(O,N)_x) through the nitridation of SiO₂ aerogels containing methyl (CH₃-) groups and evaluated their bulk properties, including their glass transition temperature (T_g). Tetramethyl orthosilicate and methyltrimethoxysilane were added into the precursor gels, and those gels were subjected to a supercritical CO₂ drying process. The presence of CH₃-group in the gel avoided cracking during ammonolysis at 750°C–1400°C, and the transparency of the gel was remained even after ammonolysis at 1300°C. The ammonolysis successfully introduced nitrogen into the gels even at relatively low temperatures, for example, 750°C, and the highest nitrogen content (11.7 mass%) was achieved in the gel after ammonolysis at 1300°C. As the nitrogen-related signals in electron spectroscopy indicated presence of nitride ions (N³⁻) after ammonolysis and the infrared absorption signals attributed to Si–N bonds were enhanced with the increase of nitrogen concentration, we successfully obtained oxynitride glasses. Those oxynitride glasses showed increase of T_g with their nitrogen concentration.     

Characterization and Adsorption Behavior of ZSM-5 Zeolite Film on Cordierite Honeycombs Prepared by a Novel in situ Crystallization Method

Thin films of ZSM-5 zeolite prepared on three types of cordierite ceramic honeycomb substrates by a novel in situ crystallization method were characterized by XRD, FTIR, XRF, SEM-EDX, NH₃-TPD and propane gas adsorption to examine the effect of the substrate on various properties of the ZSM-5 films. The substrates were both as-prepared and acid treated cordierite honeycombs. The XRD, FTIR and XRF results showed that silica-rich surface layers were formed on the surface of the honeycombs by the acid treatments. The SiO₂/Al₂O₃ ratios of the ZSM-5 zeolite formed on these layers increased with increasing time of acid treatment. Both Al₂O₃ and SiO₂ from the substrates were found to contribute to the formation reaction of the zeolite films corresponding to the composition of the interfacial layer. The porous properties of the honeycomb substrates also varied in relation to the amount of zeolite film, which increased linearly with acid treatment time. The presence of the silica-rich interfacial layer between the substrate and zeolite film increased the amount of ZSM-5 and the physical adsorption but decreased the solid acidity and amount of chemisorption.     

Synthesis of fluoride-releasing carbonate apatites for bone substitutes

Fluoride (F⁻)-substituted B-type carbonate hydroxyapatite (CHAP) powders were prepared for application as bone substitute materials having the ability to enhance bone formation and to suppress bone resorption due to the therapeutic effect of F⁻. F⁻ was adsorbed on CHAP in a sodium fluoride solution followed by heating at 700°C in carbon dioxide flow to substitute F⁻ for the hydroxyl ion in the CHAP structure. The F⁻ contents in the F-substituted CHAP powders were 16–22 times greater than that in normal adult human bones. The carbonate ion contents in the F-substituted CHAP powders corresponded to or were higher than that in normal adult human bones. F-substituted CHAP powder with CO₃²⁻ and F⁻ contents of 11.03 and 0.66 wt%, respectively, slowly released F⁻ in a physiological salt solution to a sufficiently high F⁻ level. The F⁻ concentration slowly increased and reached 67.20 ± 4.81 μg l⁻¹, which was 1.5–9.3 times higher than that in the body fluid of normal adult humans, near the therapeutic window of F⁻, and far lower than the estimated toxic level. Therefore, the F-substituted CHAP can promote bone formation. The present F-substituted CHAP has the advantage of slow F⁻ release over sodium fluoride and sodium monofluorophosphate which are highly soluble salts and cannot be sintered into a ceramic body.     

A Methodology for the Performance Evaluation of Inertial Measurement Units

This paper presents a methodology for a reliable comparison among Inertial Measurement Units or attitude estimation devices in a Vicon environment. The misalignment among the reference systems and the lack of synchronization among the devices are the main problems for the correct performance evaluation using Vicon as reference measurement system. We propose a genetic algorithm coupled with Dynamic Time Warping (DTW) to solve these issues. To validate the efficacy of the methodology, a performance comparison is implemented between the WB-3 ultra-miniaturized Inertial Measurement Unit (IMU), developed by our group, with the commercial IMU InertiaCube3? by InterSense.     

Extraction of Exotic Fullerenes and Purification of Single-Walled Nanotubes

In this report, we presented a novel and simple extraction method, namely Hydrothermally Initiated Dynamic Extraction (HIDE) method, which allows the extraction of exotic fullerenes remaining in the fullerene soot. In the HIDE method, the soot was treated in boiling water that neither dissolved fullerenes nor produced minimal by-products but untangles the fullerenes from the soot, prior to the extraction by organic solvent. As a result, the HIDE method allowed the extraction of exotic fullerenes, such as dimeric fullerene oxides, higher fullerenes having a low symmetry and oxidized higher fullerenes. Accordingly, the single walled nanotubes (SWNTs) with a purity of 99% by wt was achieved for the first time with the application of the HIDE method.     

Thermonuclear fusion neutrons under “Currentless plasmas” in Heliotron E

Thermonuclear fusion neutron emissions of up to 3 × 10⁹ neutrons/s have been observed in Heliotron E deuterium plasmas. “Currentless plasmas” were produced by electron cyclotron resonance (53 GHz, 150 kW) and further heated by hydrogen neutral beam injection (2.2 MW, H⁰→D⁺). It is found that all observed neutron emissions have thermonuclear origin due to the absence of hard X-ray background. Agreement between neutron and charge exchange ion temperature measurements (500 eV < T_i(0) × 900 eV) have been found at intermediate densities $\text{(1.5 ×}\text{n}{}_{\mathrm{<mtext>e</mtext>}}\text{× 3 × 10}{}^{13}\text{cm}{}^{\mathrm{?3}}\text{)}$. The neutrons reported in this paper are the first observations of pure thermonuclear fusion neutrons in a helical heliotron plasma confinement device.     

Relationships among display features, eye movement characteristics, and reaction time in visual search

The relative contribution of number of fixations and fixation duration to reaction time in visual search was investigated. Ten participants (age 20-24 years) took part in each of two experiments. In Experiment 1, the experimental factors were display type (icon and file name), organization (arrangements with and without grouping), and number of stimuli presented (4, 8, and 16). In Experiment 2, a search task for a target stimulus (three prespecified random letters) was conducted, and the experimental factor was the display's layout complexity. Multiple regression analysis was used to examine whether reaction time was explained by a mediational model in which reaction time is mediated by eye movements and display features are not directly related to reaction time. The mediational model was not supported, and the effects of display features on reaction time were not attributable solely to eye movements. The interaction between number of fixations and fixation duration was also explored as a function of display features. As the display feature changed and the task became more difficult, the contribution of the number of fixations to explain the variation in reaction time became dominant for both experiments. Potential applications include measurements of cognitive ability, eye muscle balance disorders, and binocular fusion ability.     

Positioning in Releasing Manipulation by Iterative Learning Control

In order to improve the positioning precision of the stop posture (position and orientation) of an object and decrease the trial numbers in our proposed releasing manipulation, two iterative learning control (ILC) schemes, learning control based on convergent condition (LCBCC), and learning control based on optimal principle (LCBOP) are designed in experimental-oriented way. These two methods are all based on a linearized system model. The experimental results show that these methods are effective. Having discussed the characteristics of these control methods, we conclude that in the case there is no enough system knowledge, LCBCC is the only choice to be used to learn the system knowledge; after the enough experience has been acquired, LCBOP is better than LCBCC, in the view of both of the convergent rate and the precision.     

Proposal of 98.5% high‐efficiency chopper circuit QRAS for the electric vehicle and the verification

A high‐efficiency and high‐power chopper based on a novel soft switching scheme QRAS (Quasi‐resonant Regenerating Active Snubber) has been proposed in this paper. Operating efficiency of the proposed QRAS has been investigated by simulation and experiments. For the purposes of this study we fabricated a one‐tenth prototype model and tested it under the rated load, light load, current discontinuous mode, and under operation out of the resonant stable operational region. The overall evaluation of these test results is provided and the possibility of implementation of an 80‐kW practical model is demonstrated by these successful test results. In addition, as an approach to the next study, the feasibility of 8‐kW SiC‐QRAS is examined and a preliminary evaluation of the efficiency enhancement due to the use of silicon carbide (SiC) power devices is given based on successful experimental results. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 158(4): 68– 80, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20439