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Numerical study on the lubrication performance of compression ring-cylinder liner system with spherical dimples.

ABSTRACT: The effects of surface texture on the lubrication performance of a compression ring-cylinder liner system are studied in this paper. By considering the surface roughness of the compression ring and cylinder liner, a mixed lubrication model is presented to investigate the tribological behaviors of a barrel-shaped compression ring-cylinder liner system with spherical dimples on the liner. In order to determine the rupture and reformulation positions of fluid film accurately, the Jacoboson-Floberg-Olsson (JFO) cavitation boundary condition is applied to the mixed lubrication model for ensuring the mass-conservative law. On this basis, the minimum oil film thickness and average friction forces in the compression ring-cylinder liner system are investigated under the engine-like conditions by changing the dimple area density, radius, and depth. The wear load, average friction forces, and power loss of the compression ring-cylinder liner system with and without dimples are also compared for different compression ring face profiles. The results show that the spherical dimples can produce a larger reduction of friction in mixed lubrication region, and reduce power loss significantly in the middle of the strokes. In addition, higher reduction percentages of average friction forces and wear are obtained for smaller crown height or larger axial width.

SUBMITTER: Liu C

PROVIDER: S-EPMC5521801 | biostudies-other | 2017

REPOSITORIES: biostudies-other

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Project description:The abandoned Kam Kotia Mine (Canada) is undergoing remediation. A geosynthetic-clay-liner (GCL) cover system was installed in the Northern Impounded Tailings (NIT) area in 2008 to isolate acid-generating tailings from water and oxygen and to mitigate sulfide oxidation. The cover system includes a vegetated uppermost soil layer underlain by a granular protective layer (sand), a clay moisture-retaining layer, a GCL, a granular capillary-break material (cushion sand), and a crushed waste rock-capillary break layer installed above the tailings. The goal of this study was to characterize the microbiology of the covered tailings to assess the performance of the cover system for mitigating sulfide bio-oxidation. Tailings beneath the GCL were characterized by high sulfur and low carbon content. The bulk pH of the tailings pore water was circumneutral (?5.5 to 7.3). Total genomic DNA was extracted from 36 samples recovered from the constituent layers of the cover system and the underlying tailings and was analyzed in triplicates using high-throughput amplicon sequencing of 16S rRNA genes. Iron-oxidizing, sulfur-oxidizing, sulfate-reducing, and aerobic heterotrophic microorganisms were enumerated by use of most probable number enumeration, which identified heterotrophs as the most numerous group of culturable microorganisms throughout the depth profile. Low relative abundances and viable counts of microorganisms that catalyze transformations of iron and sulfur in the covered tailings, compared to previous studies on unreclaimed tailings, indicate that sulfide oxidation rates have decreased due to the presence of the GCL. Characterization of the microbial community can provide a sensitive indicator for assessing the performance of remediation systems.IMPORTANCE Mining activities are accompanied by significant environmental and financial liabilities, including the release of acid mine drainage (AMD). AMD is caused by accelerated chemical and biological oxidation of sulfide minerals in mine wastes and is characterized by low pH and high concentrations of sulfate and metal(loid)s. Microorganisms assume important roles in the catalysis of redox reactions. Our research elucidates linkages among the biogeochemistry of mine wastes and remediation systems and microbial community and activity. This study assesses the performance and utility of geosynthetic-clay-liner cover systems for management of acid-generating mine wastes. Analyses of the microbial communities in tailings isolated beneath an engineered cover system provide a better understanding of the complex biogeochemical processes involved in the redox cycling of key elements, contribute to the remediation of mine wastes, and provide a valuable tool for assessment of the effectiveness of the remediation system.

Project description:OBJECTIVES: This study investigated the radio-opacity of commercially available glass ionomer cements (GICs), flowable resin composites (FRCs) and calcium hydroxide cements (CHCs) and compared this with the radio-opacity of enamel, dentine and aluminium stepwedge. 16 GICs, 8 FRCs and 4 CHCs were analysed. METHODS: Three sets of three samples were prepared: 1 mm, 2 mm and 3 mm thickness for GIC and FRC and 1 mm thickness for CHC. Specimens of enamel and dentine with the same thicknesses were obtained. As a control, an aluminium stepwedge was used. Radiographs were taken with a digital Kodak RVG 5000 (0.32 s, 30 cm). The images were analysed using the Image Tool(®) program (v. 2.00; The University of Texas Health Science Center, San Antonio, TV) to obtain the mean grey values. RESULTS: Analysis of variance was used to investigate the significance of differences among the groups. For pairwise comparisons, the Tukey test was applied (p < 0.05). The GICs Ionomaster (Wilcos, Petrópolis, Brazil), Maxxion (FGM, Joinville, Brazil), Bioglass R (Biodinâmica, Ibiporã, Brazil), Bioglass F (Biodinâmica), Vidrion R (SS White, Rio de Janerio, Brazil) and Vidrion F (SS White), presented radio-opacity lower than that of dentine. All FRCs and CHCs studied showed radio-opacity higher than that of dentine. Vitro Fil (DFL, Rio de Janeiro, Brazil), Magic Glass (Vigodent, Rio de Janeiro, Brazil), Vitrebond (3M, Sumaré SP, Brazil), Riva Self Cure (SDI, Victoria, Australia), Riva Light Cure (SDI), Fill Magic (Vigodent), Opallis (FGM, Joinville, Brazil), Surefil SDR (Dentsply, Milford, DE), Tetric N (Ivoclar Vivadent, Schaan, Lichtenstein), Tetric (Ivoclar Vivadent), Hydro C (Dentsply, Petrópolis, Brazil), Hydcal (Technew, Madalena, Portugal) and Liner (Vigodent) showed radio-opacity similar to or greater than that of enamel for all thicknesses. CONCLUSIONS: The increased thickness of the materials studied increases their radio-opacity. Some commercially available GICs used as a base and liner for restorations have a very low radio-opacity (Ionomaster, Maxxion, Bioglass R, Bioglass F, Vidrion R and Vidrion F).

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Numerical study on the lubrication performance of compression ring-cylinder liner system with spherical dimples.

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