Electric field dependence of the mode I energy release rate in single-edge cracked piezoelectric ceramics: effect due to polarization switching/dielectric breakdown

This study presents the results of the mode I energy release rate of a rectangular piezoelectric material with a single-edge crack under electromechanical loading. A crack was created normal or parallel to the poling direction, and electric fields were applied parallel and antiparallel to the poling. A nonlinear plane strain finite element analysis was carried out, and the effect of localized polarization switching on the energy release rate was discussed for the permeable, impermeable, open, and discharging cracks under a high-negative electric field. The effect of dielectric breakdown on the energy release rate was also examined under a high-positive electric field.     

Efficient growth of multi-walled carbon nanotubes by continuous-wave laser vaporization of graphite containing B4C

Multi-walled carbon nanotubes (MWCNTs), 7–70 nm thick and up to 30 μm long, were efficiently grown by room-temperature continuous-wave laser vaporization of a graphite target containing B₄C in an ambient Ar gas. Adjusting the boron content in the target and Ar gas pressure resulted in a maximum fraction of ∼60% of MWCNTs in the deposits. The straightness of the MWCNTs and graphene layers with an interlayer spacing of ∼0.35 nm indicated that the degree of graphitization was fairly high in the grown MWCNTs. However, the features of D, G, and 2D bands in the Raman spectrum of a deposit suggested boron doping in the MWCNTs. An apparent Young’s modulus of a grown MWCNT was measured to be 0.68 TPa and comparable to those of heat-treated vapor grown carbon nanofibers. MWCNTs are thought to grow on molten boron carbide particles acting as seeds at high temperatures of up to ∼2400 °C.     

不同含水率粘土在不同试验条件下的应力-应变特性

采用单轴固结试验和三轴剪切试验对饱和、湿润、风干以及烘干的藤森粘土进行了应力-应变特性研究。在试验过程中,进行了不同轴向应力水平下的恒应变率加载试验、蠕变试验以及卸载与重复加载试验。局部变形测量传感器(LDT)被用于三轴剪切试验中的轴向变形测量以提高小应变测量的精度。试验结果表明,不同含水率与饱和度的藤森粘土在单轴固结试验与三轴剪切试验条件下都表现出明显的粘塑性。它们的加载速率效应、蠕变效应都相似;而且在蠕变结束后的一小段邻域内藤森粘土的强度有明显的提高。笔者提出用参数β来描述藤森粘土的粘性。对试验结果的计算分析表明,在单轴和三轴试验条件下不同含水率与饱和度的藤森粘土的β值介于0.034到0.064之间;而且,含水率高的藤森粘土的β值大于含水率低的藤森粘土的β值,单轴试验条件下的β值大于三轴试验条件下的β值。     

Mechanochemical synthesis of indium complex oxides (InAO4; A = P, V, Nb, Ta, Sb) and their solid solutions

Indium complex oxides, InAO₄ (A = P, V, Nb, Ta, Sb), were synthesized by milling of the In₂O₃ and A ₂O₅ mixture using planetary ball mill at room temperature. Formation of these compounds was monitored by powder X-ray diffraction (XRD) and was found to be complete with 240 or 480 min. This method has been successfully extended to the synthesis of solid solutions, InP_1−x V _x O₄ and InTa_1−x Nb _x O₄, between these indium complex oxides.     

Cholesterol-lowering activity of plant sterol-egg yolk lipoprotein complex in rats

Free plant sterols cannot be dissolved in oil or water. Using free plant sterols and egg yolks, we developed a plant sterol-egg yolk lipoprotein complex (PSY) that can be dispersed in water and considered suitable for use in processed foods. The cholesterol-lowering activity of PSY was equal to that of free plant sterols and plant sterol esters. Consumption of a freeze-dried PSY-containing omelet reduced serum and hepatic cholesterol concentrations. The results suggest that PSY has cholesterol-lowering activity equivalent to that of free plant sterols and plant sterol esters. Moreover, the cholesterol-lowering activity of PSY was maintained in processed foods.     

Particle growth of magnesium alkoxide as a carrier material for polypropylene polymerization catalyst

Images from scanning electron microscopy, transmission electron microscopy and X-ray diffraction profiles of typical magnesium diethoxide (MGE) particles obtained by the reaction of ethanol, metal magnesium and iodine showed the round MGE particle (tertiary particle) had a layer structure consisting of many crystalline fragments (secondary particles) comprising many minute crystals (primary particles). It was clearly shown that each precipitated secondary particle had not agglomerated, but had repeatedly grown and combined with others. From the investigation of the course of a reaction, it was suggested the MGE crystals grown on Mg metal exfoliated as “lump-like” seeds, and crystal growth on seeds proceeded such that the shapes of the final MGE particles were more spherical than those of their seeds. It was presumed from a model reaction that the enhancement of MGE solubility by I₂ addition to form the quasi-stable complex nMg(OEt)₂·MgI₂·mEtOH was the key process in the formation of plate crystals. The relationship between the size of crystalline fragments and crystallization rate (reaction rate, MGE solubility) was discussed.The catalyst, when prepared using MGE as the carrier material, exhibited exceptionally high polymerization activity than when it was prepared with MgCl₂ alcohol complex (MgCl₂·ROH). We presume that this is because particles of the MGE-based catalyst are porous, and because the formation of active species of the supported Ti and monomer diffusion progressed adequately from the surface of the particle to its internal parts.     

Residual Deformation of Geosynthetic-Reinforced Sand in Plane Strain Compression Affected by Viscous Properties of Geosynthetic Reinforcement

A series of plane strain compression (PSC) tests were performed on large sand specimens unreinforced or reinforced with prototype geosynthetic reinforcements, either of two geogrid types and one geocomposite type. Local tensile strains in the reinforcement were measured by using two types of strain gauges. Sustained loading (SL) under fixed boundary stress conditions and cyclic loading (CL) tests were performed during otherwise monotonic loading at a constant strain rate to evaluate the development of creep deformation by SL and residual deformation by CL of geosynthetic-reinforced sand and also residual strains in the reinforcement by these loading histories. It is shown that the creep deformation of geosynthetic-reinforced sand develops due to the viscous properties of both sand and geosynthetic reinforcement, while the residual deformation of geosynthetic-reinforced sand during CL (defined at the peak stress state during CL) consists of two components: i) the one by the viscous properties of sand and reinforcement; and ii) the other by rate-independent cyclic loading effects with sand. The development of residual deformation of geosynthetic-reinforced sand by SL and CL histories had no negative effects on the subsequent stress-strain behaviour and the compressive strength was maintained as the original value or even became larger by such SL and CL histories. The local tensile strains in the geosynthetic reinforcement arranged in the sand specimen subjected to SL decreased noticeably with time, due mainly to lateral compressive creep strains in sand during SL of geosynthetic-reinforced sand. This result indicates that, with geosynthetic-reinforced soil structures designed to have a sufficiently high safety factor under static loading conditions because of seismic design, it is overly conservative to assume that the tensile load in the geosynthetic reinforcement is maintained constant for long life time. Moreover, during CL of geosynthetic-reinforced sand, the residual tensile strains in the geosynthetic reinforcement did not increase like global strains in the geosynthetic-reinforced sand that increased significantly during CL. These different trends of behaviour were also due to the creep compressive strains in the lateral direction of sand that developed during CL of geosynthetic-reinforced sand.     

Degradation of bisphenol A using sonochemical reactions

The sonochemical degradation of bisphenol A in aqueous solution, a suspected endocrine disruptor, which can cause several damages for humans, animals and the environment, was investigated at different ultrasonic intensities under air atmosphere. Bisphenol A (0.50mM) was completely degraded after 10, 3 and 2h of ultrasonic irradiation at a frequency of 404kHz, and intensities of 3.5, 9.0 and 12.9kW/m(2), respectively. During ultrasonic irradiation, some aromatic intermediates such as 2-(4-hydroxyphenyl)-2-(3,4-dihydroxyphenyl)propane, commonly known as 3-hydroxybisphenol A were detected. Further cleavage of the aromatic rings resulted in other products, like formaldehyde and organic acids, also being detected. The proposed pathways of bisphenol A degradation by ultrasonic irradiation are based on the above-mentioned intermediates. The relationship between bisphenol A degradation and formation of hydrogen peroxide and nitric acid was taken into account, correlating this to the radicals that take part in the degradation process. In order to optimize the performance of the ultrasonic system, additional experiments using Fenton-like reactions were also carried out. However, the addition of iron (II) sulfate (FeSO(4)) did not increase bisphenol A degradation rates. Compared with the system without iron (II) sulfate, the total organic carbon concentration (TOC) was reduced by about 30%, at 404kHz and 9.0kW/m(2).     

Targeted proteome analysis of microalgae under high-light conditions by optimized protein extraction of photosynthetic organisms

1. Download high-res image (294KB)
2. Download full-size image

     

Large Tunnel Magnetoresistance in Epitaxial Oxide Spin‐Filter Tunnel Junctions

A high‐performance spin filter tunnel junction composed of an epitaxial oxide heterostructure is reported. By independently controlling the magnetic orientations of ferromagnetic tunnel barrier and electrode layers, a tunnel magnetoresistance ratio exceeding 120% is obtained purely by the spin filtering effect. A newly introduced spin filter material, Pr_0.8Ca_0.2Mn_1‐yCo_yO₃, is shown to be useful for building novel multibarrier spintronic tunnel devices due to its composition‐controlled magnetic hardness.