Instant restore after a media failure

Media failures usually leave database systems unavailable for several hours until recovery is complete, especially in applications with large devices and high transaction volume. Previous work introduced a technique called single-pass restore, which increases restore bandwidth and thus substantially decreases time to repair. Instant restore goes further as it permits read/write access to any data on a device undergoing restore--even data not yet restored--by restoring individual data segments on demand. Thus, the restore process is guided primarily by the needs of applications, and the observed mean time to repair is effectively reduced from several hours to a few seconds. This paper presents an implementation and evaluation of instant restore. The technique is incrementally implemented on a system starting with the traditional ARIES design for logging and recovery. Experiments show that the transaction latency perceived after a media failure can be cut down to less than a second and that the overhead imposed by the technique on normal processing is minimal. The net effect is that a few "nines" of availability are added to the system using simple and low-overhead software techniques

Morphology of copper deposits obtained by metallic electrodeposition

Electrochemical deposition of copper from copper nitrate aqueous electrolyte on graphite substrate was investigated at current densities between 0.03 mA/cm2 - 1.36 mA/cm2 and in the voltage range of 3 V to 15 V. The surface morphology and elemental composition of the resultant deposit were characterized by electron microprobe analysis (EMPA). These images illustrate the influence of current density on the shape of copper electrodeposited on the electrode surface. Rods, polyhedral bodies, pentagonal pyramids, dendritics, spiked spheres or cauliflower-like shapes are observed depending on the electrodeposition conditions.Fil: González Mercado, Griselda Verónica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigación y Tecnología Química. Universidad Tecnológica Nacional. Facultad Regional Córdoba. Centro de Investigación y Tecnología Química; ArgentinaFil: Gonzalez, Carlos Jacinto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigación y Tecnología Química. Universidad Tecnológica Nacional. Facultad Regional Córdoba. Centro de Investigación y Tecnología Química; ArgentinaFil: Oliva, Marcos Iván. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; Argentina. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; ArgentinaFil: Brunetti, Veronica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Eimer, Griselda Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigación y Tecnología Química. Universidad Tecnológica Nacional. Facultad Regional Córdoba. Centro de Investigación y Tecnología Química; Argentin

Deposition and transport of graphene oxide in saturated and unsaturated porous media

In this work, sand and bubble column experiments were conducted to explore the deposition mechanisms of graphene oxide (GO) particles in porous media with various combinations of moisture content and ionic strength. Sand column experimental results indicated that retention and transport of GO in porous media were strongly dependent on solution ionic strength. Particularly, GO showed high mobility under low ionic strength conditions in both saturated and unsaturated porous media. Increasing ionic strength dramatically increased the retention of GO particles in porous media, mainly through secondary-minimum deposition as indicated in the XDLVO interaction energy profiles. Recovery rates of GO in unsaturated sand columns were lower than that in saturated columns under the same ionic strength conditions, suggesting moisture content also played an important role in the retention of GO in porous media. Findings from the bubble column experiments showed that the GO did not attach to the air–water interface, which is consistent with the XDLVO predictions. Additional retention mechanisms, such as film straining, thus could be responsible to the reduced mobility of GO in unsaturated porous media. The experimental data of GO transport through saturated and unsaturated porous media could be accurately simulated by an advection–dispersion-reaction model

Analysis of stress partitioning in biphasic mixtures based on a variational purely-macroscopic theory of compressible porous media: recovery of Terzaghi’s law

The mechanics of stress partitioning in two-phase porous media is predicted on the basis of a variational purely-macroscopic theory of porous media (VMTPM) with compressible constituents. Attention is focused on applications in which undrained flow (UF) conditions are relevant, e.g., consolidation of clay soils and fast deformations in cartilagineous tissues. In a study of the linearized version of VMTPM we have recently shown that, as UF conditions are approached (low permeability or fast loading), Terzaghi’s effective stress law holds as a general property of rational continuum mechanics and is recovered as the characteristic stress partitioning law that a biphasic medium naturally complies with. The proof of this property is obtained under minimal constitutive hypotheses and no assumptions on internal microstructural features of a particular class of material. VMTPM predicts that such property is unrelated to compressibility moduli of phases and admits no deviations from Terzaghi’s expression of effective stress, in contrast with most of the currently available poroelastic theoretical frameworks. This result is presently illustrated and discussed. Simulations of compressive consolidation tests are also presented; they are obtained via a combined analytical-numerical integration technique, based on the employment of Laplace transforms inverted numerically via de Hoog et al.’s algorithm. The computed solutions consistently describe a transition from drained to undrained flow which confirms that Terzaghi’s law is recovered as the limit UF condition is approached and indicate a complex mechanical behavior

Towards an Efficient Evaluation of General Queries

Database applications often require to evaluate queries containing quantifiers or disjunctions, e.g., for handling general integrity constraints. Existing efficient methods for processing quantifiers depart from the relational model as they rely on non-algebraic procedures. Looking at quantified query evaluation from a new angle, we propose an approach to process quantifiers that makes use of relational algebra operators only. Our approach performs in two phases. The first phase normalizes the queries producing a canonical form. This form permits to improve the translation into relational algebra performed during the second phase. The improved translation relies on a new operator - the complement-join - that generalizes the set difference, on algebraic expressions of universal quantifiers that avoid the expensive division operator in many cases, and on a special processing of disjunctions by means of constrained outer-joins. Our method achieves an efficiency at least comparable with that of previous proposals, better in most cases. Furthermore, it is considerably simpler to implement as it completely relies on relational data structures and operators

Effect of ozone, treatment temperature, and antimicrobials on inactivation of Escherichia coli O157:H7 and Salmonella spp. in apple cider and orange juice

The studies presented in this dissertation were conducted to determine the effect of ozone, treatment temperature, and antimicrobials on the inactivation of Escherichia coli O157:H7 and Salmonella spp. in apple cider and orange juice. In the first experiment, inactivation of£. coli O157:H7 and Salmonella in apple cider and orange juice treated with ozone was evaluated. A five-strain mixture of E.coli O157:H7 or Salmonella was inoculated (7 log cfu/ml) into apple cider and orange juice. Ozone (0.9 g ozone/h) was pumped into juices maintained at 4°C, ambient temperature (~20°C), and 50°C for up to 30 min (Salmonella/50°C), 75 min (E. coli/50°C), 180 min (apple cider/4°C) or 240 min (orangejuice/4°C and ambient). Samples were withdrawn, diluted in 0.1 % peptone water, neutralized with 1.0 N NaOH, and surface plated onto recovery media. Recovery of£. coli O157:H7 was compared on tryptic soy (TSA), sorbitol MacConkey (SMAC), hemorrhagic coli (HC), and modified eosin methylene blue (MEMB) agars; recovery of Salmonella was compared on TSA, bismuth sulfite (BSA), and XLT4 agars. After treatment at so·c, £. coli O157:H7 populations were reduced to the limit of detection ( 1.0 log cfu/ml) in 45, 30, 45, and 30 min in apple cider, and 75, 60, 60, and 45 min in orange juice, as determined on TSA, HC, MEMB, and SMAC, respectively