Overview of light degradation research on crystalline silicon solar cells

Recent research on light degradation of crystalline Si materials and solar cells is reviewed. The first paper on the issue was published in 1973 when efficiency of solar cells using 1 Ω cm, B‐doped CZ wafers degraded under illumination and recovered by annealing at a low temperature of around 200°C. In the 1990's, several studies have been performed to investigate the mechanism of the light degradation and also to provide practical solutions to suppress the degradation. Numerous experiments have been carried out regarding the effects of impurities including B, Ga, P, O and processing parameters such as oxidation temperature. To suppress the degradation, reducing the concentration of B and O or substituting boron by gallium as dopant was found to be effective. These findings are in agreement with a model attributing the lifetime degradation to oxygen and boron. Copyright © 2000 John Wiley & Sons, Ltd.     

Experimental studies of the improvement of power system stability by superconducting fault current limiters

With increasing demands for electric power, the electric power system is becoming more and more complicated, and the stable, highly reliable delivery of electric power is encountering two major problems, namely, large fault currents and power system instability. In particular, the fault currents occurring in power systems are tending to increase. To solve this problem, superconducting fault current limiters (SCFCLs) have been developed, and it is hoped that they will also solve the problem of power system stability. This paper describes the results of experiments on the improvement of power system stability and the suppression of fault currents with SCFCLs, performed with power transmission simulators. An experiment using an R‐type SCFCL in a power system was performed. An R‐type SCFCL was simulated by using a resistor and an electromagnetic contactor with thyristors. It was found that the inclusion of an SCFCL in the electric power system gives improved suppression of fault currents and improved power system transient stability. © 2000 Scripta Technica, Electr Eng Jpn, 133(4): 41–52, 2000     

Effects of external stress on magnetic properties in motor cores

The effects of shrink fitting on the magnetic properties of iron cores are investigated in order to simulate the magnetic behavior of iron cores mounted in motor frames. Shrink fittings, of course, decrease permeability and increase effective magnetostriction and magnetic loss. It is well known that the magnetostriction increment and the permeability decrement are explained by the increase of magnetoelastic energy due to compressive stress by shrink fitting. The magnetic loss increases, however, cannot be explained by this energy. We demonstrate experimentally that the magnetic loss increases result from mechanical work due to the magnetostrictive movement of the iron core under compressive stress. © 1998 Scripta Technica, Electr Eng Jpn, 123(1): 15–22, 1998     

Electrical conduction in highly resistive polyolefin films modified by polar groups

Electrical conduction and space charge distribution in oxidized low-density polyethylene (samples A1–A6) and copolymers of ethylene and carbon monoxide (samples B1–B3) with different carbonyl contents have been studied. A V-shaped dependence of conduction current on carbonyl content was observed for samples A1–A6, while the current decreases monotonically with an increase in carbonyl content for samples B1–B3. The effect for polar groups on electrical conduction is discussed, focusing on their bonding forms in polymer molecules. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 120(3): 9–16, 1997     

Extraction Kinetics of Organic Acids with Tri-n-octylphosphine Oxide

The extraction kinetics of organic acids with tri-n-octylphosphine oxide (TOPO) was investigated to determine the extraction mechanism. It was found that the species were in equilibrium at the interface and the extraction rate was limited by the mass transfer, except for crotonic acid. In crotonic acid, the observed rates were analysed by considering the film diffusion of the acid and the reaction between the acid and TOPO in organic solution.     

Association between Equol Production Status and Nonalcoholic Steatohepatitis

Equol is a metabolite of daidzein, a major soybean isoflavone with estrogenic and antioxidant activities. As the production of equol depends on the presence of certain members of the intestinal microflora, not all individuals can produce equol. We examined the relationship between NASH histological features and equol production. In an animal model, obese OLETF rats were intraperitoneally injected with a porcine serum to augment liver fibrogenesis. Equol-rich soy product, SE5-OH was orally administered during the experimental period. Treatment with SE5-OH markedly attenuated the development of liver fibrosis and expression of alpha-smooth muscle actin. In clinical research, 38 NAFLD patients (13 men and 25 women) were included. The degree of fibrosis and ballooning in equol-nonproducers was significantly higher than in equol-producers in women. The percentage of nonproducers with NAFLD activity score (NAS) ≥ 5 was significantly higher than that of producers. None of the histological features were significantly different between nonproducers and producers in men. Decision tree analysis identified predictors for NAS ≥ 5 in women. The status of equol production was the strongest predictor, followed by fasting glucose. Since equol can be noninvasively detected in urine, it can be applied as a screening tool for the progression of NASH in women.     

Evaluation of radiation damaged p-in-n and n-in-n siliconmicrostrip detectors

Two p-in-n and one n-in-n silicon microstrip detectors were radiation-damaged and tested in a beam. A comparison was made between the p-in-n and the n-in-n in high resistivity wafers, and the p-in-n in a low and a high resistivity wafer. The charge collection showed a clear difference in the n-in-n and the p-in-n detectors, which suggested that the signals were shared between strips more in the irradiated p-in-n detectors. Although a difference of the low and the high resistivity wafers was observed in the body capacitance measurement, little difference was observed in the beam test results     

A comparison of the performance of irradiated p-in-n and n-in-n silicon microstrip detectors read out with fast binary electronics

Both n-strip on n-bulk and p-strip on n-bulk silicon microstrip detectors have been irradiated at the CERN PS to a fluence of 3×10¹⁴ pcm⁻² and their post-irradiation performance compared using fast binary readout electronics. Results are presented for test beam measurements of the efficiency and resolution as a function of bias voltage made at the CERN SPS, and for noise measurements giving detector strip quality. The detectors come from four different manufacturers and were made as prototypes for the SemiConductor Tracker of the ATLAS experiment at the CERN LHC.     

Effect of Ca contamination on apatite formation in a Ti metal subjected to NaOH and heat treatments

It has long been known that titanium (Ti) metal bonds to living bone through an apatite layer formed on its surface in the living body after it had previously been subjected to NaOH and heat treatments and as a result had formed sodium titanate on its surface. These treatments were applied to a porous Ti metal layer on a total hip joint and the resultant joint has been in clinical use since 2007. It has been also demonstrated that the apatite formation on the treated Ti metal in the living body also occurred in an acelullar simulated body fluid (SBF) with ion concentrations nearly equal to those of the human blood plasma, and hence bone-bonding ability of the treated Ti metal can be evaluated using SBF in vitro. However, it was recently found that certain Ti metals subjected to the same NaOH and heat treatments display apatite formation in SBF which is decreased with the increasing volume of the NaOH solution used in some cases. This indicates that bone-bonding ability of the treated Ti metal varies with the volume of the NaOH solution used. In the present study, this phenomenon was systematically investigated using commercial NaOH reagents and is considered in terms of the structure and composition of the surface layers of the treated Ti metals. It was found that a larger amount of the calcium contamination in the NaOH reagent is concentrated on the surface of the Ti metal during the NaOH treatment with an increasing volume of the NaOH solution, and that this inhibited apatite formation on the Ti metal in SBF by suppressing Na ion release from the sodium titanate into the surrounding fluid. Even a Ca contamination level of 0.0005 % of the NaOH reagent was sufficient to inhibit apatite formation. On the other hand, another NaOH reagent with a nominal purity of just 97 % did not exhibit any such inhibition, since it contained almost no Ca contamination. This indicates that NaOH reagent must be carefully selected for obtaining reliable bone-bonding implants of Ti metal by the NaOH and heat treatments.