Hydrogel of biodegradable cellulose derivatives. I. Radiation‐induced crosslinking of CMC

Radiation crosslinking of carboxymethylcellulose (CMC) with a degree of substitution (DS) from 0.7 to 2.2 was the subject of the current investigation. CMC was irradiated in solid‐state and aqueous solutions at various irradiation doses. The DS and the concentration of the aqueous solution had a remarkable affect on the crosslinking of CMC. Irradiation of CMC, even with a high DS, 2.2 in solid state, and a low DS, 0.7 in 10% aqueous solution, resulted in degradation. However, it was found that irradiation of CMC with a relatively high DS, 1.32, led to crosslinking in a 5% aqueous solution, and 20% CMC gave the highest gel fraction. CMC with a DS of 2.2 induced higher crosslinking than that with a DS of 1.32 at lower doses with the same concentration. Hence, it was apparent that a high DS and a high concentration in an aqueous solution were favorable for high crosslinking of CMC. It is assumed that high radiation crosslinking of CMC was induced by the increased mobility of its molecules in water and by the formation of CMC radicals from the abstraction of H atoms from macromolecules in the intermediate products of water radiolysis. A preliminary biodegradation study confirmed that crosslinked CMC hydrogel can be digested by a cellulase enzyme. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 278–283, 2000     

Economic evaluation of independent power producers viewed from total generating costs of electric power systems

In Japan, electric power utilities purchase electricity from independent power producers (IPPs) through competitive bidding; the IPP evaluation is based on the avoided costs of corresponding generators of utilities. In this evaluation, however, nonpricing factors such as power flow constraints in the electric power system cannot be considered. In this paper, we propose a new approach to evaluate economic impacts of IPPs, the IPP electricity being priced on the basis of total generating costs of the electric power utilities. Such a price to purchase the electricity of IPPs is referred to as the “break‐even cost.” The main results are summarized as follows: 1) Break‐even cost depends on not only the power flow constraints in the system, but also various IPP factors such as generating pattern, location, and capacity, 2) Break‐even cost for the base‐type IPP is higher than the avoided cost of corresponding utility generators, because IPPs located on demand sides can reduce the transmission power loss in the electric power system, 3) Break‐even cost is affected by available capacity of utility generators, especially for the peak‐type IPP generating only during peak demand periods. © 2000 Scripta Technica, Electr Eng Jpn, 133(2): 20–30, 2000     

Weighting matrix of quadratic performance index and design method of optimal deadbeat control system

A method of determination of the weighting matrix of the quadratic performance index and a method of design of an optimal deadbeat control system are discussed. First, the relationship between the weighting matrix of the quadratic performance index and the extra poles of the overparametrized pulse transfer function model is indicated. Next, a method of design of an optimal deadbeat control system is explained. Lastly, to demonstrate the effectiveness of the proposed method, some numerical examples are presented. © 2000 Scripta Technica, Electr Eng Jpn, 133(1): 53–63, 2000     

Construction and power generation characteristics of H2O turbine power generation system utilizing waste heat from factories

A new gas turbine power generation system has been proposed, in which the steam (H₂O) produced by utilizing waste heat from factories is used as the working fluid of gas turbine. A simulation model has been constructed to estimate power generation characteristics of the proposed system by adopting C++ language. It has been shown from simulation results that the proposed system has high exergetic efficiency, that is, the total exergetic efficiency is 46.3% and fuel‐based efficiency is 56.3% for a case where steam with a temperature of 275 °C produced from a garbage incineration plant is used. Sensitivity analysis has also been carried out when usable steam temperature and pressure is changed, together with the case when condenser outlet pressure is changed. Characteristics of a dual fluid gas turbine cycle power generation system (DFGT) have also been estimated in this study. It has been shown that the proposed system has 16.9% higher exergetic efficiency and 41.8% higher fuel‐base exergetic efficiency compared with DFGT. © 1999 Scripta Technica, Electr Eng Jpn, 130(1): 38–47, 2000     

Field test and EMTP simulation of transient voltages when clearing a transformer secondary fault

A field test was carried out to investigate a fault clearing transient due to current interruption of a three‐phase to ground fault at the secondary side of a 3‐MVA, 22/6.6‐kV transformer by a vacuum circuit breaker. EMTP simulations in comparison with the measured results have made it clear that the capacitance C_p of a CR divider to measure voltages reduces dv/dt of transient recovery voltage across the circuit breaker by the ratio of (C_t/(C_t + C_p) where C_t is the transformer stray capacitance. The leakage inductance evaluated from the transformer rating has been found to be noticeably greater than that determined from the measured fault current possibly due to the transformer saturation. Considering the transformer magnetizing conductance and selecting an appropriate interrupted current, EMTP simulation gives a satisfactory result compared with a field test. © 1999 Scripta Technica, Electr Eng Jpn, 130(2): 40–48, 2000     

Parallel operation of four‐switch full‐bridge power amplifiers and a unique digital control scheme for advanced magnetic resonance imaging

In recent years, magnetic resonance imaging (MRI) systems have been in demand to diagnose moving parts in the human body such as the heart or the blood in angiography, where images should be taken in milliseconds instead of minutes. Gradient power amplifiers, which are small but vital components for advanced MRI, require higher output power capacity as well as faster rise/fall dynamic response characteristics under a variety of specified current reference signals. This paper presents a novel switch‐mode gradient power amplifier using IGBTs which are connected in parallel to a conventional four‐switch full‐bridge power conversion circuit at their inputs/outputs in order to realize a higher power density. To satisfy the design specifications, which require minimized ripple and improved rise/fall dynamic response characteristics of the current in the gradient coil, a unique digital control scheme based on an optimal type 1 servo system is proposed and described in detail. The effectiveness of the above is discussed and evaluated through computer‐aided analysis. It is expected that the proposed techniques will greatly expand the diagnostic targets and improve the image quality of MRI. © 2000 Scripta Technica, Electr Eng Jpn, 132(1): 64–72, 2000     

A one‐converter contactless charger for electric vehicles

A simple and reliable contactless battery charger for electric vehicles is proposed. Its feature is a unitized power factor correcting (PFC) converter and a high‐frequency inverter (HFI) where the low‐side switch of the HFI also works as the boost switch of the PFC in discontinuous conduction mode, which results in a high input power factor and low harmonic distortion without any feedforward control. The exiting current of the inductive connector, compliant with SAEJ1773, works effectively to make the converter operate in zero voltage switching (ZVS) condition. Another feature is that the charger is controlled by a single magnetically coupled variable frequency oscillator developed by the authors. This paper analyzes the circuits, gives a design example, describes the inductive connector and the oscillator, and presents experimental results. A 1.7‐kW output prototype charger achieved a charging efficiency of 87.4% for total one cycle charging, an overall efficiency of 90% at heavy load, and an input power factor of over 98%. © 2000 Scripta Technica, Electr Eng Jpn, 132(2): 73–81, 2000     

Bisanthracene‐Based Donor–Acceptor‐type Light‐Emitting Dopants: Highly Efficient Deep‐Blue Emission in Organic Light‐Emitting Devices

Deep‐blue fluorescent compounds are particularly important in organic light‐emitting devices (OLEDs). A donor–accepotor (DA)‐type blue‐emitting compound, 1‐(10‐(4‐methoxyphenyl)anthracen‐9‐yl)‐4‐(10‐(4‐cyanophenyl)anthracen‐9‐yl)benzene ( BD3 ), is synthesized, and for comparison, a nonDA‐type compound, 1,4‐bis(10‐phenylanthracene‐9‐yl)benzene ( BD1 ) and a weak DA‐type compound, 1‐(10‐phenylanthracen‐9‐yl)‐4‐(10‐(4‐cyanophenyl)anthracen‐9‐yl)‐benzene ( BD2 ), are also synthesized. The twisted conformations of the two anthracene units in the compounds, confirmed by single crystal X‐ray analysis, effectively prevent π‐conjugation, and the compound shows deep‐blue photoluminescence (PL) with a high PL quantum efficiency, almost independent of the solvent polarity, resulting from the absence of an intramolecular charge transfer state. The DA‐type molecule BD3 in a non‐doped device exhibits a maximum external quantum efficiency (EQE) of 4.2% with a slight roll‐off, indicating good charge balance due to the DA‐type molecular design. In the doped device with 4,4′‐bis(N‐carbazolyl)‐1,1′‐biphenyl (CBP) host, the BD3 exhibits higher EQE than 10% with Commission International de L'Eclairge (CIE) coordinates of (0.15, 0.06) and a narrow full‐width at half‐maximum of 45 nm, which is close to the CIE of the high definition television standard blue.