Development of Reference Shunt for Short‐Time Alternating High Current Tests and Study of Measuring System

Short‐circuit tests for power circuit breakers and others require alternative short‐time current measurement, from a few kA to over several tens kA. However, the reference measurement system as a national standard or a specified secondary standard instrument to directly perform comparative test as a complete calibration test in high current class has not yet been established globally. The Japan Short‐Circuit Testing Committee (hereinafter referred to as “JSTC”) has therefore developed a shunt resistor that can be used as a standard instrument for high current measurement. Reference system using this shunt resistor is also considered by JSTC. The performance of the newly developed shunt resistor has been checked through several methods, such as resistance measurement, high power current test, high frequency current test, temperature rise test, and interference test. The results of the tests proved satisfactory performance. Resistance of the shunt resistor before and after the tests was invariant and stable. This makes the shunt resistor adequate for a reference in practical use. In addition, evaluation of uncertainty of the whole reference system including this shunt resistor satisfactorily fulfills the requirements of IEC 62475 edition 1.0, 2010.     

ESTIMATION OF DAILY INTAKE OF FOUR KINDS OF TRIHALOMETHANE BY JAPANESE HOUSEWIVES

Duplicate portions of the daily meals consumed by 30 housewives were collected for 3 consecutive days in the cities of Nagoya and Yokohama in Japan.
Meals were analyzed for chloroform, bromodichloromethane (BDCM), chlorodibromomethane (CDBM) and bromoform by using a purge-trap procedure. The average concentration (and the range) of these four kinds of trihalomethane in each of the 24 h duplicate meals were, chloroform 19.6±18.1 ppb(n.d.-106.8 ppb), BDCM 0.3±0.3 ppb(n.d.-1.7 ppb), CDBM 0.1±0.2 ppb(n.d.-0.6 ppb) and bromoform 0.5±1.3 ppb(n.d.-8.1 ppb).
The mean daily dietary intake of the four kinds of trihalomethane by housewives were, chloroform 40.0±25.4 μg, BDCM 0.6±0.5 μg, CDBM 0.3±0.3 μg and bromoform 0.9±1.3 μg.     

Improvement of the Half-embryo Test for Detection of Gamma-irradiated Grapefruit and Its Application to Irradiated Oranges and Lemons

The duration of the half-embryo test used for identification of gamma-irradiated grapefruit was shortened by increasing germination temperature to 35°C. Maximum shooting percentages were reached within 3 days. Gibberellin application reduced the required incubation time to 2 days. Half-embryos extracted from irradiated orange and lemon gave similar results to those of grapefruit. This half-embryo test is proposed as an identification method for irradiated citrus. Assessment can be made after 3 to 4 days when shooting percentage is greater than 50%.     

A Half-Embryo Test for Identification of Gamma-Irradiated Grapefruit

Whole grapefruit were exposed to 5, 15, 30, 50, and 100 krad doses of gamma-radiation. Seeds were removed and half-embryos, consisting of one cotyledon and embryo axis, dissected from the surrounding tissue. Nonirradiated half-embryos germinated faster than intact or partially dissected (outer seed coat removed) seeds. Shoot elongation was also quicker, occurring within 6 days. Irradiated half-embryos over 15 krad doses showed markedly reduced root growth and shoot elongation was almost totally retarded. Differences between irradiated and nonirradiated half-embryo were not affected when variety, harvest date, and fruit storage conditions were varied. This test could thus discriminate between irradiated and non irradiated grapefruit.     

A Low‐Speed,High‐Torque Motor Drive Using a Modular Multilevel Cascade Converter Based on Triple‐Star Bridge Cells (MMCC‐TSBC)

This paper provides an experiment‐based discussion on a modular multilevel cascade converter based on triple‐star bridge cells (MMCC‐TSBC) for a low‐speed high‐torque motor drive. The TSBC is a direct ac‐to‐ac power converter capable of achieving bidirectional power flow as well as drawing and feeding three‐phase sinusoidal input (supply‐side) and output (motor‐side) currents with any power factor at both sides. This paper discusses active dc‐capacitor‐voltage control applied to the low‐speed, high‐torque motor drive. A specially designed downscaled system combining a 320‐V, 38‐Hz, 6‐pole, 15‐kW induction motor with a 400‐V, 15‐kW TSBC is constructed and tested to confirm the validity of the motor drive. Experimental waveforms obtained from the downscaled system confirm stable operation with the rated load torque across a range from a standstill to the rated speed, including satisfactory start‐up performance.     

Introduction of High Pressure to Food Processing: Preferential Proteolysis of β-Lactoglobulin in Milk Whey

Various proteins were subjected to thermolysin digestion at 2000 atm. Casein and soy protein were extensively digested at both atmospheric and high pressures, but the tetrameric proteins alcohol dehydrogenase and hemoglobin and the monomeric protein β-lactoglobulin were degraded only upon pressurization. Globular proteins with many disulfide bonds (RNase A, lysozyme, and α-lactalbumin) resisted the proteolysis at both pressures. These observations led to the preferential digestion of β-lactoglobulin in cow's milk whey, thus simulating human milk protein. The versatility of pressure-induced proteolysis in food processing is also proposed.     

Study on Mechanism of Hydrogen Generation from Lubricants

To establish fundamental countermeasures for hydrogen embrittlement that occurs to several kinds of bearings, the mechanism of hydrogen generation from lubricants was studied. Sliding tests were conducted, and the amount of hydrogen generated from several kinds of lubricants during sliding was measured. It is concluded that the lubricant is decomposed and hydrogen is generated through a catalytic reaction with the fresh steel surface. The amount of hydrogen generated from each lubricant depends on its lubricity, not on its chemical structure. It is also confirmed that the lubricant with the larger wear brings more generated hydrogen into steel. Based on the above mechanism of hydrogen generation, methods of inhibiting hydrogen brittle flaking with additives were investigated. It is clarified that the addition of corrosion inhibitors that form a passive state film on the steel surface effectively inhibits generation of hydrogen from lubricants and penetration of hydrogen into steel.