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.     

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.     

A novel UV-mediated low-temperature sintering of TiO2 for dye-sensitized solar cells

Titania pastes were fired at 450 °C in oxygen to give white titania that was used to prepare dye-sensitized solar cells (DSSC). Titania fired at lower temperature and/or under inert atmosphere have brown stripes and cells made from these stripes had no measurable efficiency. When the titania paste was screen printed and then heated and simultaneously irradiated with UV light, white stripes were obtained. Improved efficiency was noted for PV cells made from pastes heated at lower temperature under irradiation vs. cells made from low-temperature heated paste but without irradiation. UV irradiation appears to facilitate clean oxidation of residual organic materials in the titania precursor pastes. The best cells in our study made with our titania paste treated at 450 °C in oxygen had the following characteristics: efficiency=3.45%; V_oc=630 mV; J_sc=8.5 mA/cm²; and a fill factor=0.64.     

A fuzzy logic‐based meningioma tumor detection in magnetic resonance brain images using CANFIS and U‐Net CNN classification

This article develops a methodology for meningioma brain tumor detection process using fuzzy logic based enhancement and co‐active adaptive neuro fuzzy inference system and U‐Net convolutional neural network classification methods. The proposed meningioma tumor detection process consists of the following stages as, enhancement, feature extraction, and classifications. The enhancement of the source brain image is done using fuzzy logic and then dual tree‐complex wavelet transform is applied to this enhanced image at different levels of scale. The features are computed from the decomposed sub band images and these features are further classified using CANFIS classification method which identifies the meningioma brain image from nonmeningioma brain image. The performance of the proposed meningioma brain tumor detection and segmentation system is analyzed in terms of sensitivity, specificity, segmentation accuracy, and Dice coefficient index with detection rate.