A Method for Reducing the Dead‐Time Voltage and Impedance Voltage in a Series Voltage Compensator

Many research groups are developing series voltage compensators. In a series converter, since a transformer is used in series in the power system, the power system current flows into the voltage source inverter through the transformer. The inverter current, which is determined by the transformation ratio, gives rise to an error voltage that consists of a dead‐time voltage and an impedance voltage. The error voltage is generated even when the reference voltage is zero. This paper describes the mechanism by which the error voltage occurs and proposes a method for reducing the error voltage. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 186(3): 85–93, 2014; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.22333     

添加合金元素对奥氏体不锈钢等离子渗氮和渗碳的影响

奥氏体不锈钢众所周知有良好的耐蚀性,但是在工业上没有用于承受摩擦的工件上,因为它的硬度低,摩擦磨损性能差。奥氏体不锈钢经低温等离子体渗氮或渗碳能生成一层特殊的氮化物或碳化物层,称为S相,它具有高的硬度和优良的耐蚀性。这项研究中各种奥氏体不锈钢都经低温等离子体渗氮或渗碳,用各种分析技术研究了添加合金元素对S相特性的影响,用了光学显微镜和电子显微镜观察,做了X射线衍射分析,在5%H2SO4溶液中测量阳极极化,用球对平面摩擦装置做摩擦磨损测试。氮化物或碳化物层厚度随处理温度增加而加厚,AISI316钢上生成的渗层厚度是所有的基体钢材中最厚的。超过临界温度,由于氮化铬工碳化铬沉淀使耐蚀性降低。临界温度由渗氮的基材决定。另一方面,在渗碳层中临界温度不随基材变化。大部分样品上S相层的耐蚀性比没有处理的不锈钢的低。但是,AISI316和JIS-SUS304J3钢在400℃渗碳后都有和未处理钢一样优良的耐蚀性。每种不锈钢经渗氮或渗碳后耐磨性都有明显的改进。     

Rapid erasing of wettability patterns based on TiO2-PDMS composite films

TiO₂-polydimethylsiloxane (TiO₂-PDMS) composite films are prepared using the sol–gel method from a Ti(OBu)₄–benzoylacetone solution containing PDMS. The prepared films are cured by irradiation with ultraviolet (UV) light. Structural changes in the films after UV irradiation are confirmed by UV–vis absorption experiments, which show that an absorption band characteristic of the benzoylacetonate chelate rings disappears. This finding is ascribed to structural changes associated with the dissociation of the chelate rings. The IR spectra of the thin films exhibit a broad absorption band after UV irradiation, indicating that a Ti–O–Ti network forms in the thin film. Contact angles are measured for the TiO₂-PDMS thin films, showing wettability conversion from hydrophobic to superhydrophilic states by irradiation with oxygen plasma for 1 s. This phenomenon is explained by XPS experiments which reveal that the number of carbon atoms decreases, whereas the number of oxygen atoms increases on the surface of the TiO₂-PDMS composite films. Finally, hydrophobic–superhydrophilic patterns are fabricated based on a patterned TiO₂-PDMS composite film. The film displays a rapid change to superhydrophilicity over the whole film surface upon plasma irradiation for 1 s, which means that the wettability patterns are rapidly erasable.     

The complex aerodynamic footprint of desert locusts revealed by large-volume tomographic particle image velocimetry

Particle image velocimetry has been the preferred experimental technique with which to study the aerodynamics of animal flight for over a decade. In that time, hardware has become more accessible and the software has progressed from the acquisition of planes through the flow field to the reconstruction of small volumetric measurements. Until now, it has not been possible to capture large volumes that incorporate the full wavelength of the aerodynamic track left behind during a complete wingbeat cycle. Here, we use a unique apparatus to acquire the first instantaneous wake volume of a flying animal''s entire wingbeat. We confirm the presence of wake deformation behind desert locusts and quantify the effect of that deformation on estimates of aerodynamic force and the efficiency of lift generation. We present previously undescribed vortex wake phenomena, including entrainment around the wing-tip vortices of a set of secondary vortices borne of Kelvin–Helmholtz instability in the shear layer behind the flapping wings.     

Effect of fluorine contamination on barrier metal oxidation

We clarified that interfacial barrier metal oxidation with inter layer dielectric (ILD) could be revealed by X-ray photoelectron spectroscopy (XPS) on the peeled-side of the barrier metal, and the barrier metal oxidation was promoted by fluorine contamination which adsorb to the ILD surface during etching. To consider the effect of fluorine contamination on barrier metal oxidation, hydrolysable property of fluorine contamination was evaluated by measuring the change of F 1s spectrum after dipping in boiling water. Moreover, fluoride ions and the acidity of water in which fluorine contamination was dipped were measured by Ion chromatography and pH measurement, respectively. According to our experiments, it was suggested that hydrofluoric acid (HF) acted as an oxidizing catalyst to promote barrier metal oxidation at the interface of barrier metal and ILD.     

Influence of Water on the Compression Behavior of Decomposed Granite Soil

In order to investigate the influence of water on compression characteristics of decomposed granite soils, single-particle crushing and one-dimensional compression tests were carried out on three types of decomposed granite soils as well as on quartz-rich silica sand under both dry and wet conditions. Results showed that the initial crushing strength of a single particle was reduced and strength variability increased due to the weakening effects induced by the presence of water. Moreover, it was observed that the one-dimensional compression behavior of decomposed granite soil was related to the initial crushing strength. Finally, the magnitude of initial crushing strength was also affected by the degree of weathering of the soil.     

Augmented proliferation of human alveolar macrophages after allogeneic bone marrow transplantation

After allogeneic bone marrow transplantation (allo-BMT), recipient alveolar macrophages (AM) are gradually replaced by AM of the donor origin. An influx of mononuclear phagocytes of donor origin to the lung is responsible for the repopulation, but the detailed kinetics remain unclear. We therefore studied 24 BMT recipients who underwent bronchoalveolar lavage (BAL) from 24 to 83 days after BMT. AM cell number, size, morphology, proliferating ability, and genotype of AM were measured. Before day 50, the number and size of AM in BAL fluid were similar to those of normal nonsmokers. However, after day 50, the mean number of AM increased threefold and the mean cell size decreased due to the increase of small AM. These small cells are presumably of donor origin based on DNA fingerprinting analysis and based on fluorescence in situ hybridization for the Y chromosome in a sex-mismatched case. Immunohistochemistry and cell cycle analysis demonstrated that the increase in AM number coincided with a remarkable increase of AM expressing proliferating cell nuclear antigen, suggesting that small AM are proliferating. This is the first report representing that augmented proliferation of donor AM in situ may contribute to the reconstitution of AM population after BMT.