An Equalization Time Reduction Method Using a Pseudo‐Random Number Sequence for a Cell Voltage Equalization Circuit with an LC Series Circuit

When the cells of energy storage devices such as electric double‐layer capacitors are connected in series, it results in voltage imbalance in each cell because of the nonuniform properties of the individual cells. In a previous research, the authors proposed a novel cell voltage equalization circuit using an LC series circuit, and they examined the effectiveness of this circuit. However, the characteristics of the cell voltage equalization operation depend on each cell voltage difference. Therefore, the proposed circuit has a disadvantage that the equalization time tends to be longer than other cell voltage equalization circuits with a boosting circuit. This paper proposes an equalization time reduction method that uses a pseudo‐random number sequence generated by the linear congruential generators. The proposed method can reduce the average equalization time without adding any other active or passive elements. The effectiveness of the proposed method is verified through the experimental results. According to the experimental results, the proposed equalization time reduction method reduces the equalization time to 86.5% of the conventional method.     

Dental application of polyfunctional urethane comonomers to composite resin veneering materials

Urethane monomer/diluent monomer mixtures were used in dental composite resin veneering materials filled with various ratios of powder (filler)/liquid (comonomer), P/L. Hardness values of unfilled resins containing benzoyl peroxide only (BP0; 0.5 wt%), and filled resins (included trimethylol propane trimethacrylate (TMPT) composite filler) were tested. Significant increases in hardness were obtained with the use of TMPT composite filler in the resins. Also, their modulus values measured by bend test showed an increasing trend, compared to a commercial composite resin veneering material (a control sample; CONT) with a lower filler content (50 wt%). The DME–DPMDC/HPDM comonomer (dimethacryloxyethyl diphenylmethane-4,4-dicarbamate/hydroxypropyl dimethacrylate), which showed a smaller fraction of surface porosity, gave greater mechanical strength values at P/L ratios of 0.55 (17.8 wt% filler content) to 1.20 (27.3 wt%) than a CONT resin. The coefficient of thermal expansion was smaller in urethane-based filling materials than a CONT resin. Also, greater activation energy of thermal decomposition was observed in the resin samples with P/L ratio 0.75 to 1.20 than in a CONT resin. Thermally-induced decomposition occurred with smaller weight loss in the experimental filled resins than in a CONT resin.     

A New PV Converter for Grid Connection Through a High‐Leg Delta Transformer Using Cooperative Control of Boost Converters and Inverters

This paper proposes a new high‐efficiency photovoltaic (PV) converter for grid connection through a high‐leg delta transformer, which is composed of a symmetrically connected boost converter and three half‐bridge inverters. One of the three half‐bridge inverters is connected to the boost converter, and the others are directly connected to the PV terminals. This circuit configuration enables to reduce the power losses in both boost converter and inverter. This paper also proposes a new cooperative control method between the symmetrically connected boost converter and inverter. The control method can reduce the average switching frequency to 75% of that in a conventional one, resulting in a great reduction in switching power loss. Experimental results show that the proposed circuit improves its European efficiency from 91.6% to 94.5%.     

Approximate Synthesis of a Higher‐Order Passive Complex Coefficient Filter Using Autotransformers

In this paper, a new method for synthesizing a higher‐order passive complex filter using autotransformers is proposed. The proposed filter can be synthesized approximately by transforming the conventional one. Since the proposed transformation replaces all transformers with autotransformers, the proposed filter has no floating windings. As examples, both first‐order and third‐order complex filters are synthesized. The validity of the proposed method was confirmed through computer simulation and experiment. Due to approximate synthesis, the transfer function of the real output is different from that of the imaginary output. However, both of them have roughly the same response near the passband. Experimental results show good agreement with the theoretical value. It means that the proposed method is valid for the practical application.     

DEVELOPMENT OF SINGLE-WINDING LINEAR OSCILLATORY ACTUATOR

ABSTRACT

The Linear Oscillatory Actuator (“LOA”) uses very few components and has a highly simplified structure, and therefore promises to be a simpler and more reliable actuator. The authors have developed a single-winding LOA that provides high power output, includes a permanent magnet moving rod, has a simple structure.     

Adherent bacteria cells in five dental materials: sonication effect

Adherent bacterial cells on the surfaces of two dental porcelain ceramics, three composite resins and human enamel were examined using four types of bacteria strains. Their adherent cells were counted on saliva-coated and uncoated material surfaces after sonication, and contact angle and potential were measured for each adherent cell tested. A correlation between contact angle and bacterial cells on an uncoated surface was found to be higher in two Streptococcus sanguis cells than in S. mutans Ingbritt and S. sobrinus OMZ 176, whereas there appeared to be a higher correlation between S. mutans Ingbritt or S. sobrinus OMZ 176 and potential on the uncoated surface. On the saliva-coated surface, a significantly high correlation was found between the adherent cells, with the exception of S. sanguis ATCC 10 557, and the potential. Contact angle and potential values were small when the surfaces of the materials were coated with saliva, as compared with those on the uncoated surface. The sonication condition (120 s) of adherent cells on the surface of the material significantly depended on the types of bacteria cells, showing that S. mutans Ingbritt (>50–60%) had a greater removal percentage than the others (<50%). © 1998 Chapman & Hall     

Highly Efficient dc–dc Transformer Based on Multicell Converter Topology for Next Generation dc Distribution System

A multicell dc–dc transformer (DCX) with an efficiency of 98.0% is developed for a next generation dc distribution system. Input series output parallel (ISOP) and input parallel output series (IPOS) connection topologies of highly efficient dc–dc cell converters have been applied to realize DCXs that have arbitrary I/O voltages and a high transfer factor. The behavior of a DCX based on multicell topology using nonregulated dc–dc converters is analyzed, and the voltage stress in each cell converter is discussed quantitatively considering the variation in converter circuit parameters. Further, the availability of the applied topology and the validity of the analysis are confirmed by fabricating a prototype of a 384 V to 12 V 2400 W DCX. The multicell topology contributes to realizing a low‐carbon society pushing the promotion of highly efficient, space‐saving, and low cost dc power supplies with standardized, highly efficient cell converter modules.