Ab initio study of Kr in hcp Ti: Diffusion, formation and stability of small Kr-vacancy clusters

Ab initio electronic structure calculations have been performed to study the formation and migration of Kr impurities, and the stability of small Kr-vacancy clusters for clusters with up to four vacancies and four Kr atoms, in hcp Ti. Both the substitutional and the interstitial configurations of Kr are found to be stable. The octahedral configuration is however found to be more stable than the tetrahedral. Interstitial Kr atoms are shown to have attractive interactions and a low migration barrier, suggesting that, at low temperature, Kr bubble formation is possible, even in the absence of vacancies. We also find vacancy clusters to be stable. The binding energies of an interstitial Kr atom and a vacancy to a Kr-vacancy cluster are obtained from the calculated formation energies of the clusters. The stability of small-vacancy clusters is found to be dependent on Kr-vacancy ratio. The trends of the calculated binding energies are discussed in terms of providing further insights on the behaviour of Kr in implanted Ti.     

Polarization and power density trends of a soil-based microbial fuel cell treated with human urine

Microbial fuel cells (MFCs) are bio-electrochemical devices that use microbial metabolic processes to convert organic substances into electricity with high efficiency. In this study, the performance of a soil-based MFC using urine as a substrate was assessed using polarization and power density curves. A single-chamber, membrane-less MFC with a carbon-felt air cathode and a carbon-felt anode fully buried in biologically active soil was constructed to examine the impact of urine treatment on the performance of the MFC. The peak power of the urine-treated MFC was 124.16 mW/m² and was obtained 24 hours after the first urine addition; a control MFC showed a value of 65.40 mW/m² in the same period. The treated MFC produced an average power of 70.75 mW/m² up to 21 days after the initial urine addition; the control MFC gave an average value of 4.508 mW/m² over the same period. The average internal resistances of the treated MFC and the control MFC obtained after the initial treatment were 269.94 and 1627.89 Ω, respectively. This study demonstrates the potential of human urine to reduce internal losses in soil MFCs and to provide stable power densities across various external resistors. These results are propitious for future advancements in soil MFCs for power generation utilizing human urine (a readily available source of nutrients) as a substrate.     

Dynamic output feedback stabilization of deterministic finite automata via the semi-tensor product of matrices approach

This paper deals with the dynamic output feedback stabilization problem of deterministic finite automata (DFA).The static form of this problem is defined and so...     

Preparation of cellular SiBOC foams by thermo-foaming of polymethylvinylborosiloxane–wheat flour dough

A novel method for the preparation of SiBOC foams from a polymethylvinylborosiloxane (MVBS) solution in ethanol using wheat flour as a foam stabilizer and pore template has been reported. A dough prepared by mixing the MVBS solution and wheat flour undergoes foaming at 180°C due to the stabilization of bubbles created by ethanol vapor by the adsorption of wheat flour particles on their surface. The ceramization of the foamed body at 1500°C followed by burnout of carbon produced from the wheat flour results in SiBOC foams of hierarchical pore structure. The foam density (.68–.44 g cm⁻³), average cell size (1.81–.58 mm), compressive strength (3.9–1.7 MPa), and thermal conductivity (.33–.21 W m⁻¹ K⁻¹) decrease with an increase in wheat flour to MVBS weight ratio from .25 to 1. The population of smaller pores (∼5–50 μm) created by wheat flour particles on cell walls and struts increases with an increase in wheat flour to MVBS weight ratio. The presence of β-SiC and turbostratic graphite nanodomains in amorphous SiBOC is evidenced by X-ray diffraction and transmission electron microscopy analysis.     

Kaolin modified with sodium salt of rubber seed oil as a reinforcing filler for blends of natural rubber,polybutadiene rubber and acrylonitrile–butadiene rubber

Blends of natural rubber (NR) and synthetic rubbers are widely used in the rubber industry to meet specific performance requirements. Further, the emerging field of organomodified clay/rubber nanocomposites could provide a host of novel materials having a unique combination of properties to meet various stringent service conditions. Previous studies have shown that at very low dosages, china clay (kaolin) modified with sodium salt of rubber seed oil (SRSO) improved the cure characteristics and physico‐mechanical properties of NR. Results of the present study show improved cure characteristics and physico‐mechanical properties for blends of NR with butadiene rubber and nitrile rubber containing 4 phr of SRSO‐modified kaolin as indicated by reduction in optimum cure time along with higher tensile strength, tensile modulus and elongation at break for their vulcanizates as compared to those containing unmodified kaolin. The SRSO‐modified kaolin/rubber nanocomposites showed improved flex resistance, reduced heat build‐up, tan delta and loss modulus and higher chemical crosslink density index, indicating a reinforcing effect of the SRSO‐modified kaolin, enabling the nanocomposites to have potential industrial applications. © 2015 Society of Chemical Industry     

First-principles Study of the Impact of Hydrogen Passivation on the Charge State Transition Levels of the CiOi(Sii)n Defect Complexes in Silicon

Silicon - Density functional theory (DFT) with the Heyd-Scuseria-Ernzerhof hybrid functional has been used to predict the stability, formation energy, geometric structure, and the charge state...