Development of an analytical dynamic model of a vibro‐compactor used in carbon anode production

The carbon anode quality has a significant impact on the production of primary aluminum. Their performance can be evaluated by their various mechanical, electrical, physical, and chemical, properties such as density, electric resistivity, C02 and air reactivities. The focus of this work is to study the various parameters of the vibro-compaction, which is one of the critical steps in the process of anode manufacturing. In this work, a dynamic model of a vibro-compactor is developed. The vibrocompactor is modeled as a rigid mass suspended on springs and dampers and subjected to harmonic external excitation. This model is used to identify the optimal conditions of the vibrocompacting process. These conditions are obtained through a correlation between the analytical vibro-compaction parameters and data from an industrial vibro-compactor. The use of optimum parameters will help improve the anode performance and, consequently, lead to better productivity and reduction on environmental impact

An anomalous wave formation at the Al/Cu interface during magnetic pulse welding

This paper reports an anomalous wave formation at an Al/Cu bimetallic interface produced by magnetic pulse welding. The mechanism of the anomalous wave formation is investigated using both metallurgical characterization and the interface kinematics. It reveals that the anomalous wave is formed with the combination of the intermediate zone and the interdiffusion zone with a thickness of 70 nm, wherein the intermediate zone is caused by the local melting due to the high shear instability, and the interdiffusion zone is formed below the melting point of aluminum combined with ultrahigh heating and cooling rates of about 1013 °C s−1. A multiphysics simulation of impact welding has been performed, and it is identified that the jetting kinematics and non-uniform distribution of shear strains during high-speed collision enable the formation of the anomalous wave. The numerical and experimental results comprehensively lead to understanding of the mechanism and the characteristics of the anomalous wave produced during an impact welding. This work is supported by the Co-operation Program of UTs and INSAs (France) and funded by the China Scholarship Council (No.201701810138). T. Sapanathan acknowledges F.R.S–FNRS (Belgium) during his postdoc at UCLouvain. The data that support the findings of this study are available from the corresponding author upon reasonable request

Measurement of the electric current distribution in an anode

Carbon anode, which carries the electricity and provides the carbon necessary for the electrochemical reaction in the electrolytic cell, is an essential component of the primary aluminum production. Energy efficiency and environmental impact are still the key issues in modern aluminum smelters; thus, it is important to control the quality of anodes which strongly influences the energy consumption and the greenhouse gas emissions. As the uniform current distribution appears to be one of the indicators of the anode quality, an experimental system has been developed to measure the current distribution in an anode. This article describes the measurement system used for laboratory anodes and presents the experimental results. The results are also compared with the electrical resistance distribution measurements in the anodes, and the comparison shows good agreement

Numerical investigation of the load free permanent strain in carbon anode during baking process

Baking is the final step of the anode production, which plays a major role in attaining the anode properties required by industry. However, the anode baking is a costly process during which various complex phenomena take place. It is therefore important to ensure good understanding of the impact of these phenomena on the baked anode quality. Regarding the mechanical aspect, various strain mechanisms occur in the anodes during the baking and evolve with respect to the spatial distribution of temperature and its rate of change in the baking furnace. Each of these mechanisms contributes to the stress equilibrium in the carbon anode and can lead, depending on the baking conditions, to poor mechanical properties including cracks when the failure limit is exceeded. In this paper, a specialized thermo-reactive visco-elastoplastic model is presented, which allow the numerical investigation of the stress distribution in the anode during baking. Each strain mechanism considered in the model is presented with a particular attention given to the permanent and non-recoverable strain mechanism occurring before the initial volatile release phase. Finally, the definition of a baking index is discussed to ensure the best approach to be used to quantify the evolution of anode properties during baking

Physical and mechanical characterizations of carbon anodes produced from different vibro-compactors

The aluminum industries in Quebec consume about 1.27 million tonnes per year of carbon for anode production. The anode quality is widely influenced by the quality of raw materials and the parameters of the manufacturing process which involves mixing, vibro-compacting, and baking. The anodes are regularly replaced at an interval of 20 to 30 days. This interval reduces when the anode quality is low. A better understanding of the vibro-compaction process would reduce the variation in the properties of formed anodes and thereby improve the anode performance during aluminum production. This, in turn, would reduce the cost and the greenhouse gas emissions. The focus of this work is to study the influence of vibro-compaction parameters on anode properties. The physical and mechanical characterization of anodes produced by different vibro-compactors was carried out. The article will present the results of this study

Hypoxia-activated genes from early placenta are elevated in preeclampsia, but not in Intra-Uterine Growth Retardation.

BACKGROUND: As a first step to explore the possible relationships existing between the effects of low oxygen pressure in the first trimester placenta and placental pathologies developing from mid-gestation, two subtracted libraries totaling 2304 cDNA clones were constructed. For achieving this, two reciprocal suppressive/subtractive hybridization procedures (SSH) were applied to early (11 weeks) human placental villi after incubation either in normoxic or in hypoxic conditions. The clones from both libraries (1440 hypoxia-specific and 864 normoxia-specific) were spotted on nylon macroarrays. Complex cDNAs probes prepared from placental villi (either from early pregnancy, after hypoxic or normoxic culture conditions, or near term for controls or pathological placentas) were hybridized to the membranes. RESULTS: Three hundred and fifty nine clones presenting a hybridization signal above the background were sequenced and shown to correspond to 276 different genes. Nine of these genes are mitochondrial, while 267 are nuclear. Specific expression profiles characteristic of preeclampsia (PE) could be identified, as well as profiles specific of Intra-Uterine Growth Retardation (IUGR). Focusing on the chromosomal distribution of the fraction of genes that responded in at least one hybridization experiment, we could observe a highly significant chromosomal clustering of 54 genes into 8 chromosomal regions, four of which containing imprinted genes. Comparative mapping data indicate that these imprinted clusters are maintained in synteny in mice, and apparently in cattle and pigs, suggesting that the maintenance of such syntenies is requested for achieving a normal placental physiology in eutherian mammals. CONCLUSION: We could demonstrate that genes induced in PE were also genes highly expressed under hypoxic conditions (P = 5 x 10(-5)), which was not the case for isolated IUGR. Highly expressed placental genes may be in syntenies conserved interspecifically, suggesting that the maintenance of such clusters is requested for achieving a normal placental physiology in eutherian mammals

Le Forum, Vol. 40 No. 3

https://digitalcommons.library.umaine.edu/francoamericain_forum/1088/thumbnail.jp

Le Forum, Vol. 41 No. 1

https://digitalcommons.library.umaine.edu/francoamericain_forum/1090/thumbnail.jp

Early Science with the Large Millimeter Telescope: Detection of Dust Emission in Multiple Images of a Normal Galaxy at z \u3e 4 Lensed by a Frontier Fields Cluster

We directly detect dust emission in an optically detected, multiply imaged galaxy lensed by the Frontier Fields cluster MACSJ0717.5+3745. We detect two images of the same galaxy at 1.1 mm with the AzTEC camera on the Large Millimeter Telescope leaving no ambiguity in the counterpart identification. This galaxy, MACS0717_Az9, is at z \u3e 4 and the strong lensing model (μ=7.5) allows us to calculate an intrinsic IR luminosity of 9.7 × 1010 Le and an obscured star formation rate of 14.6 ± 4.5 Me yr−1. The unobscured star formation rate from the UV is only 4.1 ± 0.3 Me yr−1, which means the total star formation rate (18.7 ± 4.5 Me yr−1) is dominated (75%–80%) by the obscured component. With an intrinsic stellar mass of only 6.9 × 109 Me, MACS0717_Az9 is one of only a handful of z \u3e 4 galaxies at these lower masses that is detected in dust emission. This galaxy lies close to the estimated star formation sequence at this epoch. However, it does not lie on the dust obscuration relation (IRX-β) for local starburst galaxies and is instead consistent with the Small Magellanic Cloud attenuation law. This remarkable lower mass galaxy, showing signs of both low metallicity and high dust content, may challenge our picture of dust production in the early universe