Mass transfer in polycrystalline ytterbium monosilicate under oxygen potential gradients at high temperatures

Mass transfer in polycrystalline Yb₂SiO₅ wafers with precise composition control was evaluated and analyzed by oxygen permeation experiments at high temperatures using an oxygen tracer. Oxygen permeation proceeded due to mutual grain boundary diffusion of oxide ions and Yb ions without synergistic effects such as acceleration or suppression. The oxygen shielding properties of Yb₂SiO₅ were compared with those of the other line compounds such as Yb₂Si₂O₇ and Al₂O₃ based on the determined mass transfer parameters. It was found that the more preferentially an oxide ion diffuses in the grain boundary compared to the interior of the grain, the greater the effect of suppressing the movement of the oxide ion by applying an oxygen potential gradient becomes.     

Systematic packaging design tools integrating functional and environmental consequences on product life cycle: Case studies on laundry detergent and milk

This study presents systematic packaging design tools integrating functional and environmental consequences on product life cycle. To design packaging for sustainability, the trade-offs between functional and environmental aspects of packaging throughout the product life cycle should be considered. However, it is difficult for packaging designers to understand the overall trade-offs because the extent of the design consequences on the entire life cycle of packaging and its contents is unclear. We developed two tools for packaging design: the Life Cycle Association Matrix (LCAM) and the Function Network Diagram (FND). The following three steps, based on literature reviews and interviews with industrial experts, were applied. Firstly, we listed the product functions and design variables related to the functions as the attributes allocated to the product life cycle. Secondly, the attributes were connected appropriately based on causal relationships. Lastly, we identified the factors to support decision making in the packaging design procedure. As a result, the LCAM depicts the design consequences on the life cycle, and the FND determines the stakeholders affected by the design consequences. Two case studies were demonstrated to analyze the trade-offs by using our tools. In the case studies, a liquid laundry detergent bottle and a milk carton were redesigned. The tools identified the design consequences and stakeholders affected by the redesign of the usability and protective function for the detergent and milk cases, respectively. The results showed the significance of understanding the design consequences on the product life cycle by integrating the functional and environmental aspects.     

Hydrogen production through dry reforming of biogas using a porous electrochemical cell: Effects of a cobalt catalyst in the electrode and mixing of air with biogas

This paper reports the performance of porous Gd-doped ceria (GDC) electrochemical cells with Co metal in both electrodes (cell No. 1) and with Ni metal in the cathode and Co metal in the anode (cell No. 2) for CO₂ decomposition, CH₄ decomposition, and the dry reforming reaction of a biogas with CO₂ gas (CH₄ + CO₂ → 2H₂ + 2CO) or with O₂ gas in air (3CH₄ +?1.875CO₂ +?1.314O₂ → 6H₂ +?4.875CO +?0.7515O₂). GDC cell No. 1 produced H₂ gas at formation rates of 0.055 and 0.33?mL-H₂/(min?m²-electrode) per 1?mL-supplied gas/(min?m²-electrode) at 600?°C and 800?°C, respectively, by the reforming of the biogas with CO₂ gas. Similarly, cell No. 2 produced H₂ gas at formation rates of 0.40?mL-H₂/(min?m²) per 1?mL-supplied gas/(min?m²) at 800?°C from a mixture of biogas and CO₂ gas. The dry reforming of a real biogas with CO₂ or O₂ gas at 800?°C proceeded thermodynamically over the Co or Ni metal catalyst in the cathode of the porous GDC cell. Faraday's law controlled the dry reforming rate of the biogas at 600?°C in cell No. 2. This paper also clarifies the influence of carbon deposition, which originates from CH₄ pyrolysis (CH₄ → C + 2H₂) and disproportionation of CO gas (2CO → C + CO₂), on the cell performance during dry reforming. The dry reforming of a biogas with O₂ molecules from air exhibits high durability because of the oxidation of the deposited carbon by supplied air.     

Generation of gas bubbles in microflow using micropipette with ultrasound

Ultrasound was applied to a micropipette micromixer to improve dispersion of gas and liquid in a microchannel. Flow visualization using a high-speed camera was performed to examine the effect of ultrasonic irradiation on bubble generation in the microchannel. Basically, nitrogen gas was injected using a (0.5 µm ID) glass micropipette into ethanol flowing in a rectangular (100 µm×200 µm) microchannel on polydimethylsiloxane (PDMS). Gas and liquid flow rates were regulated using mass flow controllers. At aflow condition that is typical of bubbly flow, ultrasound was transmitted into the microchannel using a piezo-electric (PZT) transducer over a range of operating voltages (2 to 200 Vp-p) and frequencies (50 to 60 kHz). Images captured during the action of the PZT transducer indicate that bubble formation is influenced by ultrasound. When subjected to ultrasound above 50 Vp-p and at the resonant frequency of the PZT transducer, bubbles formed that were smaller and closer together, signifying enhanced shearing of the gas at the micropipette tip by the liquid. The observation of gas slugs occurring sooner might be attributed to the coalescence of gas bubbles that became closely spaced.     

InxGa1−xAs ohmic contacts to n-type GaAs with a tungsten nitride barrier

Significant reduction of the contact resistance of In_0.7Ga_0.3As/Ni/W contacts (which were previously developed by sputtering in our laboratory) was achieved by depositing a W₂N barrier layer between the Ni layer and W layer. The In_0.7Ga_0.3 As/Ni/W₂N/W contact prepared by the radio-frequency sputtering technique showed the lowest contact resistance of 0.2 Ωmm after annealing at 550°C for 10 s. This contact also provided a smooth surface, good reproducibility, and excellent thermal stability at 400°C. The polycrystalline W₂N layer was found to suppress the In diffusion to the contact surface, leading to improvement of the surface morphology and an increase in the total area of the In_xGa−As between metal and the GaAs substrate. These improvements are believed to reduce the contact resistance.     

Power swing analysis in a future metropolitan electric power system on a contingent trip of cryogenic high-power cables

A cryogenic power cable is expected to be capable of carrying bulk power as a main transmission line in a future metropolitan electric power system. It is important to establish a strategy of how to sustain power supply when such a highly densified power supply route trips from the network due to contingency. It is proposed here that the bulk power transmitted by the cryogenic cable could be distributed into the parallel conventional transmission lines by suitable circuit breaker operations in the system. In this process, power-flow routes are forced to be changed with a remarkable modification in the system configuration. In this paper, the power swings associated with the large power-flow change following contingent faults are analyzed by means of a transient network analyzer. It is found that the proposed system modification could be realized without any harmful power swing if the parameters in generators as well as in control devices have conventional magnitudes. It is shown also by simulations that the margin to occurrence in an unstable power swing is left sufficient even if the parameters deviate somewhat from the present magnitudes.     

A 160-kDa Protein Is Essential for Hemocyanin-derived Melanosis of Prawn

ABSTRACT A purified 160-kDa protein, isolated from the cuticle of kurama prawn and named melanosis collaborating factor (MCF), was a key factor in promoting melanosis by a cooperative reaction with hemocyanin-derived phenoloxidase but hemocyanin itself was incapable of producing black pigment. The enzymatic activity of MCF in the body of the prawn was very stable against the process of freezing and thawing; the enzyme maintained more than 80% of its activity after 3 mo of storage at −2 5 °C. These results indicated that MCF, acting in conjunction with hemocyanin-derived phenoloxidase, played a crucial role in postharvest melanogenesis in prawn.     

Wake and aerodynamics loads in multiple bodies—application to turbomachinery blade rows

Two-dimensional, unsteady flow around bodies of complex geometry (or multiple bodies) at high Reynolds number is simulated using the vortex method. This method is modified to take into account the sub-grid scale phenomena through a second order velocity structure function model adapted to the Lagrangian scheme. The dynamics of the body wake is computed using the convection-diffusion splitting algorithm; the convection process is carried out with a Lagrangian Adams-Bashforth time-marching scheme and the diffusion process is simulated using the random walk method. The pressure distribution is obtained using an integral equation derived from the pressure Poisson equation, which was first developed for a single body. Results for the numerical simulation around a linear cascade of airfoils are presented. As the flow is periodic in the y direction, the discrete vortex shedding need only be considered for a reference airfoil. The flow characteristics around the NACA 65-410 series airfoils are calculated and comparisons are made with results available in the literature.