Finding consistent global checkpoints in a distributed computation

Consistent global checkpoints have many uses in distributed computations. A central question in applications that use consistent global checkpoints is to determine whether a consistent global checkpoint that includes a given set of local checkpoints can exist. Netzer and Xu (1995) presented the necessary and sufficient conditions under which such a consistent global checkpoint can exist, but they did not explore what checkpoints could be constructed. In this paper, we prove exactly which local checkpoints can be used for constructing such consistent global checkpoints. We illustrate the use of our results with a simple and elegant algorithm to enumerate all such consistent global checkpoints     

Vapor-Phase Alkylation of Toluene with Isopropanol over Mg/Al, Ni/Al and Cu/Al Hydrotalcites (Layered Double Hydroxide)

Vapor-phase isopropylation of toluene has been carried out over Mg/Al, Ni/Al and Cu/Al calcined hydrotalcites (CHTs). Reaction conditions were optimized for alkylation by varying temperature, weight hourly space velocity and reactant mole ratio. Side-chain alkylation is found to be more predominant than ring alkylation over Mg/Al CHT, while Ni/Al and Cu/Al CHTs favored ring alkylation. The main products were isobutylbenzene and cymene. The combined participation of acidic and basic sites of the materials is found to be crucial for both side-chain and ring alkylation of toluene with isopropanol. An X-ray diffraction pattern of the resulting oxide indicates a diffuse MgO structure. The incorporation of small amounts of Al³⁺ to MgO generates new surface Lewis acid--base pair sites.     

Solution combustion synthesis of (La,K) FeO<Subscript>3</Subscript> orthoferrite ceramics: structural and magnetic property studies

Polycrystalline La_1−x K _x FeO₃ ceramic oxides were synthesized by a solution combustion process using glycine as a fuel. The synthesized ceramic powders were characterized for structural features applying characterization techniques such as powder X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and magnetic and optical property studies applying characterization techniques such as SQUID magnetometer and diffuse reflectance (DR). The changes in magnetic properties are correlated to changes in structural features resulting from Rietveld structural refinement.     

Properties of surface treated transparent conducting single walled carbon nanotube films

Transparent conducting single-walled carbon nanotube (SWCNT) films were fabricated using the spin coating technique. UV-ozone treated and poly(3,4-ethylenedioxythiophene) doped with poly(styrenesulfonate) coated glass substrates together with SWCNT dispersed in 1,2-dichlorobenzene were used to promote the adhesion of SWCNT at room temperature. The produced film had a sheet resistance of 430 Ω/□ for 80% optical transparency at 550 nm. The spin coated SWCNT film after a post fabricated treatment in a mixer of isopropyl alcohol and nitric acid solution had a sheet resistance as low as 120 Ω/□ for 80% optical transparency at 500 nm. Besides reduction in sheet resistance, we obtained stable and strongly adherent SWCNT films on substrate that could serve as an alternative to transparent conducting oxides in display and optoelectronic applications.     

Synthesis,characterization, and electrochemical performance of the ternary layered composite (1-x-y) LiNi1/3Co1/3Mn1/3O2·xLi2MnO3·yLiCoO2

Composite ceramic cathodes represented by the formula (1-x-y) LiNi_1/3Co_1/3Mn_1/3O₂·xLi₂MnO₃·yLiCoO₂ were studied. A ternary compositional diagram was built with these ceramic materials as end-members, and selected points were chosen to represent the compositional space. Synthesized ceramic composite materials were investigated as to whether integration of structurally compatible units leads to improved electrochemical performance. Detailed structural (X-ray diffraction – XRD), elemental (X-ray photoelectron spectroscopy-XPS), microstructure (Scanning electron microscopy – SEM), and electrochemical (galvanostatic testing of half-cells) studies were performed and are presented. Within eight samples studied three compositions are found to exhibit first discharge capacity of around 230 mAh/g.     

Aqueous Gelcasting of Fused Silica Using Colloidal Silica Binder

An aqueous‐based gelcasting of fused silica ceramics by using colloidal silica binder was developed. Fused silica slurries having different volume percentage of solid loading from 63 to 74 vol% in colloidal silica were made and the rheological properties were evaluated. It was found that the slurry with 73 vol% of solid loading with viscosity 0.70 Pa.s is suitable for this gelcasting system. The influence of solid loading on physical and mechanical properties of gelcast green and sintered bodies has been studied. The fabricated green body by using colloidal silica binder exhibited a flexural strength of 9 MPa and 88% of theoretical density with 2.2% of drying shrinkage while the sintered sample exhibited flexural strength of 60 MPa and 95% of theoretical density with 4.3% of sintering shrinkage. It was observed that, the nano silica particles from the colloidal silica binder is filling the interstitial positions in the consolidated fused silica green body and enhancing physical and mechanical properties.     

Magnetic and electrical characterization of heavily boron-doped diamond

For a heavily boron-doped diamond (BDD) film, temperature variations of the electrical conductivity σ and magnetic susceptibility χ are reported. The room temperature σ 143 (Ω-cm)⁻¹ corresponds to a carrier concentration 10³ ppm, and its temperature variation yields an activation energy E_a 28 meV from 140 to 300 K and E_a0.88 meV from 40 to 80 K. It is argued that larger boron doping leads to lower magnitudes of E_a. The χ vs. T data (1.8–350 K) fits the Curie–Weiss law, with the concentration of paramagnetic species 120 ppm and a diamagnetic susceptibility −0.4×10⁻⁶ emu/g Oe. The results obtained from the measurements of σ and χ are discussed and compared.     

Holographic characterization of azo-dye doped poly (methyl methacrylate) films

Many holographic techniques have been developed for non-destructive studies and characterization of materials. In this paper, discussion will be made about the employed holographic technique to characterize the poly(methyl methacrylate) (PMMA) matrices doped with azo-dyes. In this manner we were able to study the effect of the thickness of the samples, the effect of concentration of the azo-dyes and of PMMA and the effect of aging (storage time) on the holographic efficiency (diffraction efficiency) of these materials. Auto-erasable holographic gratings have been successfully recorded on azo-dye doped PMMA films and the dynamic diffraction efficiency was monitored with light different from that used for the recording.