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.     

Effect of copper addition on the β-phase formation rate in FeSi2 thermoelectric materials

The transformation kinetics of the β-phase from an as-solidified structure composed of α and ε in the Fe–Si system was investigated by using rapidly, unidirectionally or conventionally solidified FeSi₂ alloys containing a small amount of Cu (0.1–1 at%). The addition of Cu decreased the size of primary ε and slightly changed the solidified eutectic morphology. The solubility of Cu in the α-Fe₂Si₅ phase was estimated to be less than 0.2 at%. A needle-like Cu enriched phase was newly formed in the conventionally solidified alloys containing more than 0.2 at % Cu. Microdifferential thermal analysis (DTA) clearly showed that the addition of Cu drastically accelerated β-phase formation. X-ray diffraction analysis and microstructural observation of the isothermally heat-treated specimens showed that Cu addition was effective in increasing the rate of eutectoid decomposition (α → β + Si) and the initial stage of the peritectoid reaction (α + ε → β). For complete β formation, heat treatment for a long time was still required because it took a long time for the coarse ε-phase in the slowly solidified alloy to be eliminated by peritectoid reaction. The effect of Cu depended on the annealing temperature. The decomposition rate of α in the Cu-added cast specimen was about 15 times higher at 1073 K than that of the binary cast specimen and exceeded more than 30 times at 873 K. This revised version was published online in November 2006 with corrections to the Cover Date.     

Chiral Electrodeposition by the Rotation in a Vertical Magnetic Field

The roles of the rotations in the process of chirality appearance in magnetoelectrodeposition were theoretically clarified.Electrodeposition in a vertical magnetic field induces a macroscopic fluid rotation called vertical MHD flow(VMHDF)over the electrode surface.Inside the rotation,minute numerous micro-vortexes called micro-MHD flow(MMHDF)arise from 2D and 3D nucleation,which interact with the mass flux of metallic ion,yielding chiral deposits with the characteristic features called micro-and nano-mystery circles.Generally,numerous vortexes always keep chiral symmetry,forming four types of vortexes,i.e.,with the combination of upward or downward and clockwise or counterclockwise.However,ionic vacancy acting as an atomic scale lubricant is created in electrodeposition,which gives a restriction to the vortexes;the bottom of an upward vortex covered with ionic vacancies becomes a free surface without friction,whereas the bottom of a downward vortex exposed without ionic vacancies remains rigid with friction.The rotation of VMHDF donates a precession to the upward vortexes to rotate in the same direction,which finally yield a chiral deposit.The similar effect to that of VMHDF can be expected for the system rotation(SR),where an electrolytic cell rotates in a vertical magnetic field.In this case,the SR gives the reverse rotation to the upward vortexes,so that a deposit with reverse chirality is obtained.     

Pigment Changes in Parsley Leaves during Storage in Controlled or Ethylene Containing Atmosphere

Pigments were monitored in parsley leaves stored in air, air + 10 ppm C₂H₄, or 10% O₂+ 10% CO₂ controlled atmosphere (CA). Chlorophylls a and b, as determined with HPLC, decreased sharply in leaves held in air or air + 10 ppm C₂H₄. The decrease was less in leaves held in 10% O₂ and 10% CO₂ CA. The oxidized product of chlorophyll a, 10-hydroxychlorophyll a, did not accumulate and chlo-rophyllide accumulated minimally. Xanthophylls decreased but new pigments, suspected to be esterified xanthophylls, formed with yellowing of leaves. Neither the pathway of Chl degradation or xantho-phyll products were altered by C₂H₄ or CA.     

Debittering Mechanism in Bitter Peptides of Enzymatic Hydrolysates from Milk Casein by Aminopeptidase T

The bitter peptide fraction present in casein hydrolysates obtained by using three proteases (subtilisin, papain and trypsin) was treated with aminopeptidase T from Thermus aquaticus YT-1. The bitterness of the bitter peptide fraction could be decreased, and it sometimes disappeared completely, with an increase in free amino acids. The percentages of total free amino acids released from each bitter peptide fraction (subtilisin, papain and trypsin) by aminopeptidase digestion for 20 hr were approximately 11%, 8.7%, and 6.5%, respectively. Bitter peptide (α_s1-CN f91-100) was isolated from a tryptic hydrolysate of casein by HPLC, its threshold value of bitterness being 2.9 ppm (w/v). The peptide (α_s1-CN f96-100) obtained from the amino peptidase digestion of this bitter peptide showed no bitterness.     

Milk Curdling by Rennet under High Pressure

The effect of pressure on milk curd formation initiated by rennet was studied under high pressures. The milk used was a 20% solution of skim milk powder in 0.02M CaCl₂. After holding the milk with rennet at 35°C for given periods under high pressure, up to 1300 kglcm², the extent of proteolytic digestion and the curd tension were measured under atmospheric pressure. Rennet and milk protein were not denatured by pressure under the experimental conditions used. The primary phase reaction of milk curdling by rennet (hydrolysis of casein) was not affected by compression. The secondary phase reaction (core formation of casein micelle aggregates) was delayed under high pressure and the tertiary phase reaction (milk curd formation) was accelerated.     

Optimized Logarithmic Roller Crowning Design of Cylindrical Roller Bearings and Its Experimental Demonstration

A logarithmic profile is essentially an optimal geometry for rolling machine elements such as bearing rollers and raceways. Under most conditions of loading, it yields lower stresses to give longer endurance. Lundberg first suggested the basic profile, and some researchers followed him by modifying it to satisfy engineering requirements. In this article, the authors propose a mathematical optimization method for logarithmic profiles in roller bearing applications. Moreover, rolling contact fatigue life tests are carried out to make a comparison among logarithmically crowned, standard partially crowned, and modified partially crowned rollers. Results show that the logarithmically crowned rollers are beyond the modified partially crowned rollers in fatigue life, especially in poor lubrication conditions, although the logarithmic rollers require less workload to process the crowning.     

Study on Construction of Industrial Large‐Scale Battery System

This paper proposes a construction method for battery systems that are widely used in industries. The battery system uses a building block structure combined with a battery module, whose capacity is less than 1 kWh. To manage the building block structured system, we propose a hierarchical structured management method. In each hierarchy, the voltage and temperature of the battery are monitored, and the information necessary for calculating charge states and detecting faults are sent to the upper hierarchy for the state management of the lower hierarchy. Furthermore, to ensure the safety during maintenance activities, we provide a guidance for understanding the insulation structure for the battery module, and develop a ground fault detection method that detects a decline in the insulation performance by using a rising method. For the experiment, we use a 30‐kWh trial manufacture battery system combined with the hierarchical management method. We verify that charge states and faults are detected in the battery of the system, and confirm that the system can be charged and discharged safely.     

Solid Solutions in the System Taeniolite-Sodium Taeniolite and Their Properties

Solid solutions in the system taeniolite (KMg₂LiSi₄O₁₀F₂)-sodium taeniolite (NaMg₂LiSi₄O₁₀F₂) were synthesized to study the solid solubility and swelling characteristics. Based on their melting behavior, crystals were grown for X-ray structural analysis. A complete solid solution series does not form in this system; there are two types of micas, K-rich taeniolite (0≤ x <0.5, x = Na/Na + K) and Na-rich taeniolite (0.8< x ≤l). The Na-rich taeniolite exhibits swelling properties, which become less pronounced with increasing potassium content. Melting and crystallization behavior were investigated by DTA. Solid solutions with higher sodium content melted at lower temperatures and crystallization occurred over a wide range of temperatures. To obtain larger crystals, the samples containing small crystallites were remelted at slightly above their melting points, then cooled slowly.     

Increase in Curd Tension of Milk Coagulum Prepared with Immobilized Proteases

Curd tension of milk clotted by nine proteases in immobilized or soluble forms was measured by a curd tension meter. In the curd prepared by trypsin, α-chymotrypsin, papain, thermolysin or alkaline-protease in a soluble form, the increasing rate of curd tension was definitely smaller than that of curd formed by rennet. However, curd tension increased linearly when the extent of proteolysis was controlled by employing these proteases in an immobilized form. The amounts of TCA-soluble nitrogenous compounds and sialic acid released at the beginning of clotting were kept constant throughout the incubation time.