A study of the loss characteristics of the amorphous magnetic material under nonsinusoidal wave magnetic flux

This paper presents a study on iron loss characteristics of an amorphous magnetic material under nonsinusoidal wave magnetic flux. The iron loss characteristics of the amorphous magnetic material have been compared to those of grain‐oriented magnetic steel sheets. Measurements of the iron loss have been carried out by means of an SST. It was found that the ratio of the iron loss increase of the amorphous magnetic material under the excitation by distorted waveforms and symmetric PWM waveforms is lower than that of grain‐oriented magnetic steel sheets. On the other hand, the ratio of the iron loss increase of the amorphous magnetic material under the excitation by asymmetric PWM waveforms is higher than that of grain‐oriented magnetic steel sheets. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 150(3): 11–18, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20004     

Mechanical Property Evolution during Autoclaving Process of Aerated Concrete Using Slag: I, Tobermorite Formation and Reaction Behavior of Slag

The chemical reactions in the formation of autoclaved aerated concrete (AAC) block were investigated. The samples were prepared using blast furnace slag at 180°C under saturated steam pressures for various times from 1 to 128 h. Autoclaving for 1 h yielded 1.1-nm tobermorite with higher Al substitution and lower Ca/(Al + Si) ratio than that made without slag, due to the high solubility of the slag during the initial stage of reaction. This suggests that the utilization of slag has an advantage of reducing processing time. On further reaction, the crystallinity of the tobermorite increases and its Ca/(Al + Si) ratio decreases, becoming constant after 64 h. After a long period of autoclaving. thick reaction rims are formed around unreacted slag particles, interrupting the diffusion of Ca from slag to matrix.     

Seismic reflector imaging by prestack time migration in the Kakkonda geothermal field, Japan

We show that a prestack migration method improves the S/N ratio of seismic reflection profiling in the Kakkonda geothermal field where seismic reflection data are of poor quality. We use non-iterative prestack time migration (PSTM), which does not require multiple iterations to determine the velocity structure for prestack time migration. The optimum constant migration velocity can be determined at each image point from a migration velocity analysis based on primary diffraction patterns. Our results delineate a strong reflector beneath a zone of high seismicity. According to the correspondence between the fracture distribution, the distribution of microearthquakes, and geothermal structure, this reflector is interpreted to be a zone of low-angle fractures saturated with hydrothermal fluids, and to be strongly controlled by the geothermal structure.     

Effect of ATRX and G‐Quadruplex Formation by the VNTR Sequence on α‐Globin Gene Expression

ATR‐X (α‐thalassemia/mental retardation X‐linked) syndrome is caused by mutations in chromatin remodeler ATRX. ATRX can bind the variable number of tandem repeats (VNTR) sequence in the promoter region of the α‐globin gene cluster. The VNTR sequence, which contains the potential G‐quadruplex‐forming sequence CGC(GGGGCGGGG)_n, is involved in the downregulation of α‐globin expression. We investigated G‐quadruplex and i‐motif formation in single‐stranded DNA and long double‐stranded DNA. The promoter region without the VNTR sequence showed approximately twofold higher luciferase activity than the promoter region harboring the VNTR sequence. G‐quadruplex stabilizers hemin and TMPyP4 reduced the luciferase activity, whereas expression of ATRX led to a recovery in reporter activity. Our results demonstrate that stable G‐quadruplex formation by the VNTR sequence downregulates the expression of α‐globin genes and that ATRX might bind to and resolve the G‐quadruplex.     

Promotion Effect of Hydrogen on Grain Refinement in Pure Fe by High-Pressure Torsion-Straining

Metallurgical and Materials Transactions A - We revealed that hydrogen (H) in pure Fe promotes grain refinement during plastic deformation, which is caused by the increase in dislocation density by...     

Control of cathodic potential for deposition of ZnO by constant-current electrochemical method

For the preparation of functional films and crystals, the electrochemical deposition method has advantages of large-area deposition at low temperature and high efficiency in terms of the raw materials used. However, crystallization through electrochemical processes is not currently well understood. To apply the electrochemical deposition method, it is necessary to better understand the crystallization and the growth mechanism. To investigate the mechanism, it is essential to ensure the reproducibility of the growth process. We focused on cathodic potential as a parameter that affects the reproducibility of the galvanostatic method. The repeatability of cathodic potentials during deposition was drastically improved by optimizing the mask pattern on the electrode and the pre-treatment conditions. As the result, the cathodic potential was able to be controlled by the current density. Furthermore, nucleation and grain growth of ZnO crystals by the galvanostatic electrochemical method are discussed in association with the change of cathodic potential. Changes in grain size at various cathodic currents are also discussed.     

A common‐source active clamped complex type converter

This paper presents a novel common‐source active clamped complex type converter. This converter is the intermediate isolated bus converter for the distributed power supply system in telecommunications equipment. Using active clamped circuits, the switching loss and switching noise can be reduced by means of the soft switching techniques. By adding an auxiliary winding to the transformer, the proposed converter is a common‐source type having direct connection of sources of the two MOSFET switches. As a result, the pulse transformer becomes unnecessary, and the drive circuit is simplified. In the experiment, at 48 V ratings input voltage, 36 to 72 V worldwide input voltage, and 12 V output voltage, the ZVS operation is performed on the main switch and auxiliary switch, and highest efficiency 92.7% is obtained. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 167(2): 64–70, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20682     

Magnetic characteristics analysis of permanent magnet motor by using complex approximation taking account of two‐dimensional magnetic properties

This paper presents a complex E&S modeling approach, which is developed with a complex approximation for conventional E&S modeling. Complex E&S modeling is used to analyze a permanent magnet motor and the validity of complex E&S modeling is demonstrated. The computation time of complex E&S modeling can be considerably reduced in comparison with conventional E&S modeling. © 2012 Wiley Periodicals, Inc. Electr Eng Jpn, 180(2): 9–16, 2012; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.21268     

Fabrication of CuZr(Al) bulk metallic glasses by high pressure torsion

In this paper, pure Cu, Zr and Al metal sheets were alternatively stacked and, then, cold roll-bonded. The overall compositions of the stacks were Cu₇₁Zr_29, Cu₆₂Zr_38, Cu₅₃Zr₄₇ and Cu₅₂Zr₃₈Al₁₀. The bonded materials were subsequently sliced into disks and, then, used for high pressure torsion (HPT) process. After HPT process up to maximum equivalent strain of about 1200 at ambient temperature, bulk materials with 10 mm in diameter and 0.30 mm in thickness were obtained. The phase constitution and microstructural evolutions of the HPTed samples with various rotations ranging from 0.5 to 20 were studied by XRD, FESEM and TEM. Thermal properties of the HPTed samples were analyzed by DSC. It was found that CuZr(Al) BMGs could be fabricated with a wide composition range by the HPT process. Tensile tests were used to measure the mechanical properties of the HPT processed samples. The mechanism of the solid-state amorphization during the HPT process was put forward and discussed.