Phase-transformation and grain-growth kinetics in yttria-stabilized tetragonal zirconia polycrystal doped with a small amount of alumina

Microstructure development during sintering in 3 mol% Y₂O₃-stabilized tetragonal zirconia polycrystal doped with a small amount of Al₂O₃ was investigated in the isothermal sintering conditions of 1300–1500 °C. At the low sintering temperature at 1300 °C, although the density was relatively high, the grain-growth rate was much slow. In the specimen sintered at 1300 °C for 50 h, Y³⁺ and Al³⁺ ions segregated along grain boundaries within the widths of about 10 and 6 nm, respectively. In grain interiors, the cubic-phase regions were formed by not only a grain-boundary segregation-induced phase-transformation mechanism but also by spinodal decomposition. The grain-growth behavior was kinetically analyzed using the grain-size data in 1300–1500 °C, which indicated that the grain-growth rate was enhanced by Al₂O₃-doping. These phase-transformation and grain-growth behaviors are reasonably explained by the diffusion-enhanced effect of Al₂O₃-doping.     

Simulation on contact between the droplet and the slider at head-disk interface based on water-hammer pressure model

To understand the cause of read/write error due to lube accumulation, a model to simulate the slider’s response to the contact impact, which can occur between a lubricant droplet on the disk and a slider, was developed. The contact impact model is based on the water-hammer pressure model with an additional damping force, where the wave-shock pressure is assumed to function as the contact pressure, and the damping force defines the damping characteristics of the impact which are due to the lubricant’s high viscosity and squeeze between the droplet and slider contact area along the slider local velocity direction. The transient contact impact is dependent on lube droplet density, disk velocity, pitch angle of the slider, and contact area between the droplet and the slider. The measured read/write signal jump due to lube pickup can be explained by the simulation results. This modeling and simulation are helpful to us in understanding the read/write signal loss due to a lube droplet at head disk interface.     

Self‐Organized Nanoporous Anodic Titania Films and Ordered Titania Nanodots/Nanorods on Glass

We report a new method to fabricate self‐organized nanoporous titania films (pore diameter ≈ 30 nm; ≈ 1100 nm thick) and ordered titania nanorod arrays (rod diameter ≈ 30–60 nm; 70–260 nm high) by combined anodizing of superimposed Al/Ti layers sputter‐deposited on glass substrates. The titania nanostructures mimic the ordered nanoporous anodic alumina films via a through‐mask anodization. We propose a new anodizing electrolyte, i.e., a diluted nitric acid solution, for fabricating uniform, self‐organized, ordered nanoporous titania films with parallel cylindrical pores and without any thickness limit. More significantly, the nanoporous titania films contain a small amount of titanium nitride and dissociated nitrogen, and exhibit a moderate transparency and an enhanced absorption throughout the UV and visible light regions of the electromagnetic spectrum. After heating at 600 °C for 2 h, the nanoporous titania films develop a small absorption red‐shift and exhibit high photocatalytic activity under UV illumination.     

Tensile strain dependence of Brillouin frequency shift in silicaoptical fibers

Brillouin frequency shift in a single-mode optical fiber has been measured as a function of tensile strain. The strain coefficient of normalized Brillouin frequency shift C≡(dv_B/ dϵ)/v_B is found to be 4.4 for silica fibers. This result shows the potential of Brillouin spectroscopy to evaluate tensile strain in the fiber with the strain resolution of about 2×10^-4. The origin of the large strain coefficient is discussed     

Grasp and Delivery for Moving Objects on Broken Lines

This paper studies the following variant of the Vehicle Routing Problem that we call the Grasp and Delivery for Moving Objects (GDMO) problem, motivated by robot navigation: The input to the problem consists of n products, each of which moves on a predefined path with a fixed constant speed, and a robot arm of capacity one. In each round, the robot arm grasps one product and then delivers it to the depot. The goal of the problem is to find a collection of tours such that the robot arm grasps and delivers as many products as possible. In this paper we prove the following results: (i) If the products move on broken lines with at least one bend, then the GDMO is MAXSNP-hard, and (ii) it can be approximated with ratio 2. However, (iii) if we impose the “straight line without bend” restriction on the motion of every product, then the GDMO becomes tractable. Y. Asahiro’s research was supported in part by Grant-in-Aid for Young Scientists 15700021, and Research on Priority Areas 16092223. E. Miyano’s research was supported in part by Grant-in-Aid for Research on Priority Areas 16092223. Presently, S. Shimoirisa is with the Software Development Engineering Department, Products Development Center, Retail Information Systems Company, Toshiba TEC Corporation.     

Control of nano-sized interlayer space of lamellar vanadyl benzylphosphate

Nano-sized interlayer space of lamellar vanadyl benzylphosphate was controlled by water content in starting solution. Depending on the water content, three types of lamellar vanadyl benzylphosphate having basal spacings of 1.4 nm, 1.9 nm and 2.3 nm were obtained. It was suggested that the difference in the concentrations of benzyl and hydroxyl groups in the interlayer leads to the variation of the interlayer space.     

A Coupled MPM-FDM Analysis Method for Multi-Phase Elasto-Plastic Soils

The Material Point Method (MPM), as proposed by Sulsky et al. (1994), has been developed to simulate large deformations and failure evolution involving different material phases in a single computational domain. A continuum body is divided into a finite number of subregions represented by Lagrangian material points, while the governing equations are formulated and solved with the Eulerian grid. Since this grid can be chosen arbitrarily, mesh tangling does not appear in the MPM. To design a simple but robust spatial discretization procedure, the MPM is coupled with the finite difference method (FDM) in the present study for simulating fully and partially saturated elasto-plastic soil responses based on the simplified three-phase method. Governing equations for the soil skeleton and the pore fluid are discretized by the MPM and FDM, respectively. Soil-water coupled analyses for fully saturated soils and seepage-deformation coupled analyses for unsaturated soils are performed, and the potential of the proposed method is demonstrated via numerical examples.     

Exposure and risk assessment of zinc in Japanese surface waters

In recent years, due to concerns on the potential effects of zinc on aquatic biota, zinc is receiving particular attention from regulatory agencies. A comprehensive exposure and risk assessment of zinc in Japanese surface waters was conducted to provide a scientific basis for developing realistic risk reduction measures for zinc. Emissions from corrosion contribute approximately 37% of the total zinc emissions to surface water in Japan. The zinc concentration distributions estimated using 12 years of monitoring data from 2075 sites by a maximum likelihood method indicated that the mean concentrations have gradually declined. The threshold concentrations (HC5 and PHC5) derived from organism- and population-level species sensitivity distributions were estimated to be 27 and 107 μg/L for total zinc, respectively. The risk characterization identified that during 1991-2002, 14.5-26.8% of the monitoring sites likely exceeded the HC5, whereas only 0.7-3.5% likely exceeded the PHC5. Evaluation of the effect of stormwater runoff to zinc concentrations in a river showed that zinc concentrations in river water increased significantly from roadway drainage flowing into the river. The cost-effectiveness analyses demonstrated that enforcement of the zinc national effluent standard may be effective at a certain level for public water areas in Japan; however, the degree of the effectiveness is highly dependent on the characteristics (e.g., sources and background) of the watersheds. An emissions and exposure assessment along with cost-effectiveness analysis is crucial for developing realistic and appropriate ecological risk management of zinc. The zinc RAD in Japan illustrated that in any “state-of-the science” method used, some degree of ecological risk from zinc can be observed in some Japanese water environments. On the other hand, zinc is a beneficial material for human industrial activities. Because zinc is an element, its role in industrial activities would be difficult to be substituted by other metals with less toxicity. In addition to improving science-based risk assessment methodologies which often focus on the toxicological perspectives, it is important to develop a more robust framework considering a trade-off between a damage in ecosystem and a benefit in human activities. Zinc can be a role model for it.     

Preparation of mesoporous silica replica using ordered mesoporous carbon by vapor phase transport of silica source

A new vapor phase transport (VPT) technique to prepare an inverse silica replica of an ordered mesoporous carbon was developed. Tetraethyl orthosilicate (TEOS) was infiltrated in mesoporous carbon CMK-3 as the hard template at 180 °C for 48 h under an autogenous pressure in an autoclave in the presence of water. The samples obtained by removal of CMK-3 retained structural regularity of CMK-3 with little shrinkage of framework, which were characterized by SAXRD, N₂ adsorption, TG-DTA, and SEM. Influence of preparation temperature on the loading amount of silica was investigated. The multi-step replication process was monitored by characterizing the replicated materials as well as intermediate composites.