Flame Spread and Group-Combustion Excitation in Randomly Distributed Droplet Clouds with Low-Volatility Fuel near the Excitation Limit: a Percolation Approach Based on Flame-Spread Characteristics in Microgravity

Stable operation of liquid-fueled combustors requires the group combustion of fuel spray. Our study employs a percolation approach to describe unsteady group-combustion excitation based on findings obtained from microgravity experiments on the flame spread of fuel droplets. We focus on droplet clouds distributed randomly in three-dimensional square lattices with a low-volatility fuel, such as n-decane in room-temperature air, where the pre-vaporization effect is negligible. We also focus on the flame spread in dilute droplet clouds near the group-combustion-excitation limit, where the droplet interactive effect is assumed negligible. The results show that the occurrence probability of group combustion sharply decreases with the increase in mean droplet spacing around a specific value, which is termed the critical mean droplet spacing. If the lattice size is at smallest about ten times as large as the flame-spread limit distance, the flame-spread characteristics are similar to those over an infinitely large cluster. The number density of unburned droplets remaining after completion of burning attained maximum around the critical mean droplet spacing. Therefore, the critical mean droplet spacing is a good index for stable combustion and unburned hydrocarbon. In the critical condition, the flame spreads through complicated paths, and thus the characteristic time scale of flame spread over droplet clouds has a very large value. The overall flame-spread rate of randomly distributed droplet clouds is almost the same as the flame-spread rate of a linear droplet array except over the flame-spread limit.     

Experimental study of low-cycle fatigue of pipe elbows with local wall thinning and life estimation using finite element analysis

Low-cycle fatigue tests were conducted using elbow specimens with local wall thinning. Local wall thinning was machined on the inside of the elbow in order to simulate metal loss from erosion corrosion. The local wall thinning was located in three different areas known as the extrados, crown and intrados. The elbow specimens were subjected to cyclic in-plane bending under displacement control without internal pressure. In addition, three-dimensional elastic-plastic analyses were also carried out using the finite element method. As a result, the crack penetration area and the crack growth direction were successfully predicted by the analyses. The fatigue lives estimated by the analyses were close to those obtained by the experiments.     

Effect of Heavy Element Substitution and Off-Stoichiometric Composition on Thermoelectric Properties of Fe2VAl-Based Heusler Phase

The thermoelectric performance of Fe₂VAl-based alloys was improved by using the effects of (a) heavy element substitution and (b) off-stoichiometric (Fe/V ≠ 2) composition. The former method led to a significant reduction of lattice thermal conductivity, whereas the latter to an evolution of the Seebeck coefficient. As a result of sample preparation, we confirmed that the dimensionless figure of merit with n-type behavior was increased up to 0.25 at 420 K for the sample obtained at the optimized composition of Fe_1.98V_0.97Ta_0.05Al_0.9Si_0.1. Electronic structure calculations revealed that the increase of the Seebeck coefficient observed for Fe-poor samples was caused by a reduction of the density of states near the chemical potential.     

Microstructure and thermoelectric properties of Heusler Fe2VAl thin-films

Heusler-type Fe₂VAl thin-films were prepared on zirconia substrate by radio-frequency magnetron sputtering. The effect of deposition temperature on crystal structure and electrical properties was investigated. The degree of Heusler-type ordering in crystal structure was enhanced by the increase in deposition temperature. The enhanced Heusler-type ordering contributed to the formation of a steep density of state derived from pseudogap opening near Fermi level, resulting in large Seebeck coefficient. Since the film consisted of submicrometer-size grains, the electrical conductivity and the thermal conductivity of the film were both reduced by the grain boundary effect. The estimated thermoelectric power factor was 1.0 mW/mK² at 350 K.     

Country domain governance: an analysis by data-mining of country domains

Along with protocols, domain names are critical internet resources. To build a safe, secure, and globally ubiquitous internet, all entities responsible for the governance of domains must allocate their lower-level domains with competence and discipline following the basic principle of decentralized governance. The governance and operation of a country code top-level domain is delegated to the governing and operating entity of the relevant country or territory. There are great differences among these entities in domain allocation policy, fees, discipline, and technical competence. The undertaking of governing a global infrastructure requiring high integrity, such as the internet, on the basic principle of decentralized governance is unprecedented. To enable this governance to work well, it is necessary to set up proper objectives for the governance of country domains, and to use highly transparent criteria for a multi-faceted evaluation of how far these objectives have been achieved. This article presents a set of country domain governance indicators which is intended to be used for the construction of a safe and secure ubiquitous global network.     

Photocatalytic O2 evolution under visible light irradiation on BiVO4 in aqueous AgNO3 solution

BiVO₄ with a 2.3 eV band gap showed an activity for O₂ evolution from aqueous solutions containing Ag⁺ as an electron scavenger under visible light irradiation (λ > 520 nm). The quantum yield was 0.5% at 450 nm. This revised version was published online in July 2006 with corrections to the Cover Date.     

Inactivation of rifampin by Nocardia brasiliensis

Rifampin was glycosylated by a pathogenic species of Nocardia, i.e., Nocardia brasiliensis. The structures of two glycosylated compounds (RIP-1 and RIP-2) isolated from the culture broth of the bacterium were determined to be 3-formyl-23-(O-[beta-D-glucopyranosyl])rifamycin SV and 23-(O-[beta-D-glucopyranosyl])rifampin, respectively. Both compounds lacked antimicrobial activity against other gram-positive bacteria as well as the Nocardia species.