Direct synthesis of H2O2 acid solutions on carbon cathode prepared from activated carbon and vapor-growing-carbon-fiber by a H2/O2 fuel cell

Direct synthesis of H₂O₂ acid solutions was studied using a gas-diffusion cathode prepared from activated carbon (AC), vapor-growing-carbon-fiber (VGCF) and poly-tetra-fluoro-ethylene (PTFE) powders, with a new H₂/O₂ fuel cell reactor. O₂ reduction to H₂O₂ was remarkably enhanced at the three-phase boundary (O₂(g)-electrode(s)-acid(l)) at the [AC + VGCF] cathode. Fast diffusion processes of O₂ to the active surface and of H₂O₂ to the bulk acid solutions were essential for H₂O₂ accumulation. Synergy of AC and VGCF was observed for the H₂O₂ formation. RRDE and cyclic voltammetry studies indicated that the surface of AC functioned as the active phase for O₂ reduction to HO₂, and VGCF functioned as an electron conductor and a promoter to convert HO₂ to H₂O₂. A maximum H₂O₂ concentration of 353 mM (1.2 wt%) was accomplished under short-circuit conditions (current density 12.7 mA cm⁻², current efficiency 40.1%, geometric area of cathode 1.3 cm², reaction time 6 h).     

A three-dimensional,clothed human thermal model

We have developed a three-dimensional clothed human thermal model for predicting physiological responses to temperature and humidity within clothing by considering the thermal properties of fabrics, clothing ensembles, and their designs. The model is a coupled simulation system of a human thermal model and a clothing thermal model. The model performance was investigated by comparing its predictions with experimental data. The following results were obtained. (1) The model predictions of skin temperature distributions and the micro-climate within clothing basically agreed with experimental data. (2) The skin temperatures of clothed body parts were higher than the corresponding body parts in the nude condition, and the skin temperatures of the hand and foot were higher than those in the nude condition, both in the model predictions and in the experimental data. (3) The model prediction of total moisture transfer was almost the same as obtained from the experimental data. 1998 Scripta Technica, Heat Trans Jpn Res, 26(8): 554–566, 1997     

Mechanical behavior of a single polymer chain in a non-solvent

Mechanical properties of a single polystyrene chain in mixtures of dioxane and methanol were measured with AFM. The effect of the solubility of the surrounding liquid on mechanical behavior of a polymer chain was examined. In good and Θ solvents, the force-extension curves exhibit a freely jointed chain (FJC)-like trend with good reproducibility. In a non-solvent, the profile of force-extension curve was dependent on the extension speed: an FJC-like nature emerged at the lower speed of 200 nm/s while saw-toothed curves were obtained at the higher speed of 2000 nm/s. The shape of saw-toothed curves varied from measurement to measurement. A force relaxation was also observed in the non-solvent under a fixed extension distance after 2000 nm/s extension. The mechanical behavior in non-solvents suggests that inhomogeneous deformation of a PS chain occurs due to reduction of the chain mobility.     

Development of µGC (micro gas chromatography) with high performance micromachined chip column

A micro gas chromatography (µGC) instrument applying a high performance chip column fabricated on a silicon wafer was developed. Experimental results of the chip column and protyping of a µGC instrument are described. Approximately 35 000 theoretical plates were generated with the chip column coated liquid phase (5% phenyl-/95% dimethyl-polysiloxane). The theoretical plates of the chip column were close to those of the capillary column. Experimental minimum height equivalent to a theoretical plate (HETP, H_min) of the chip column was 1.2 times higher than the calculated H_min. A prototype µGC applying the chip column was developed. The µGC generated approximately 35 000 theoretical plates, similar to the theoretical plates obtained by a commercial GC instrument. Copyright © 2009 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Soluble and colorless polyimides with polyalicyclic structures [1]

Two tetracarboxylic dianhydrides with polyalicyclic structure, bicyclo[2.2.2]octane-2-endo, 3-endo, 5-exo, 6-exo-2,3:5,6-dianhydride (5a) and the all-exo isomer (5b), were synthesized in six steps using phthalic acid as a starting material. The dianhydrides were polymerized at 85–105°C in well-purified DMAc with aromatic diamines which were purified by two recrystallizations and then sublimation. The polyimides formed flexible and tough films, and were soluble in aprotic polar solvents such as DMAc. The 5%-weight loss temperatures were over 450°C. The polyimides possessed glass-transition temperatures in the range from 211 to 385°C. The polyimides films had a tensile modulus range of 1.5–2.6 GPa, a tensile strength range of 52–96 MPa, and an elongation range at break of 3–11%. The polyimide films showed cutoffs at wavelengths shorter than 320 nm and were entirely colorless. The colorlessness of the polyimide films was maintained up to 200°C when heated in air and to 400°C in a N₂ atmosphere.     

Shape from Shading with Interreflections Under a Proximal Light Source: Distortion-Free Copying of an Unfolded Book

We address the problem of recovering the 3D shape of an unfolded book surface from the shading information in a scanner image. This shape-from-shading problem in a real world environment is made difficult by a proximal, moving light source, interreflections, specular reflections, and a nonuniform albedo distribution. Taking all these factors into account, we formulate the problem as an iterative, non-linear optimization problem. Piecewise polynomial models of the 3D shape and albedo distribution are introduced to efficiently and stably compute the shape in practice. Finally, we propose a method to restore the distorted scanner image based on the reconstructed 3D shape. The image restoration experiments for real book surfaces demonstrate that much of the geometric and photometric distortions are removed by our method.     

An investigation of the effect of fatigue deformation on the residual mechanical properties of Ti-6Al-4V ELI

Tensile properties, hardness, and Charpy impact toughness of Ti-6Al-4V extralow interstitial (ELI) with equiaxed α and Widmanstätten α structures at various stages of fatigue were investigated. Fatigue crack initiation characteristics of the same alloy were also investigated in this study. In the equiaxed α structure, fatigue cracks initiated mainly at the interface between primary-α grains, while in the Widmanstätten α structure, they initiated across α plates at an angle of around 45 deg to the stress axis. Specimens with the Widmanstätten α structure fractured before adequate fatigue hardening was achieved because a multitude of microcracks readily formed. Specimens with the equiaxed α structure fractured after adequate fatigue hardening developed. Tensile strength, 0.2 pct proof stress, and hardness increased clearly with increasing stress cycles and fatigue steps, particulary in the low-cycle fatigue (LCF) region, while impact toughness and elongation showed a reverse trend. It is suggested, therefore, that the dislocation density multiplies more rapidly near the specimen surface during the early stages of fatigue, while during the later stages of fatigue, dislocation density increases near the center of the specimen. Also, the dislocation multiplication will continue until saturation of the entire specimen has occurred.     

Effects of microstructure on the short fatigue crack initiation and propagation characteristics of biomedical α/β titanium alloys

This article presents the results of a study of the effects of microstructure on the fatigue strength and the short fatigue crack initiation and propagation characteristics of a biomedical α/β titanium alloy, Ti-6Al-7Nb. The results are compared to those obtained from a Ti-6Al-4V extra-low interstitial (ELI) alloy. Fatigue crack initiation occurs mainly at primary α grain boundaries in an equiaxed α structure, whereas, in a Widmanst?tten α structure, initiation occurs within the α colonies and prior β grains, where α plates are inclined at around 45 deg to the stress-axis direction. In an equiaxed α structure, the short fatigue crack initiation and propagation life, where the length of the crack (a) is in a microstructurally short fatigue-crack regime (2a < 50 μm), occupies around 50 pct of the total fatigue life. On the other hand, the fatigue crack in a Widmanst?tten α structure initiates at very early stages of fatigue, and, therefore, the fatigue crack-initiation life occupies a few percentages of the total fatigue life in an α structure. Then, the short fatigue crack propagates rapidly and is arrested at the grain boundaries of α colonies or prior β grains for a relatively long period, until the short crack passes through the boundaries to specimen failure. Therefore, the short fatigue crack-arrest life occupies more than 90 pct of the total fatigue life in a Widmanst?tten α structure. These trends are similar between the Ti-6Al-7Nb and Ti-6Al-4V ELI alloys and biomedical α/β titanium alloys. The total fatigue life for the Ti-6Al-7Nb alloy with an equiaxed α structure is changed by the volume fraction of primary α phase and the cooling rate after solution treatment. By increasing the volume fraction of the primary α phase from 0 to 70 pct, the fatigue limit of the Ti-6Al-7Nb alloy is raised. Changing the cooling rate after solution treatment by switching from air cooling to water quenching improves the fatigue limit of the Ti-6Al-7Nb alloy significantly.     

Numerical simulation of fracture of model Al-Si alloys

Hypoeutectic Al-Si alloys consist of primary α-Al and Al-Si eutectic phases and show typical elasticplastic fracture. To understand their fracture behavior, fracture processes were simulated using an elastic-plastic finite-element method. The validity of the J-integral-based criterion was verified and applied to the simulations. A complicated model was used to simulate the fracture in an idealized dendritic microstructure, and four simplified models were intended to more clearly understand the interaction between a crack and individual α phases. Results show that the crack is attracted to the soft α phase when passing by the α phase, whereas it is repelled when the α phase is close in front of or behind the crack tip. The presence of α phase close in front of or behind the crack tip leads to an amplification of the driving force. However, the α phase beside the tip reduces the driving force. Furthermore, the fracture behavior is mainly affected by the adjacent α phase on one side around the crack tip, while the remote α phase on the opposite side has an offsetting effect. The local stress-strain fields were examined to analyze the simulated behavior. The simulated crack-growth path in the dendritic model was compared and verified with the experimentally observed path.