Metallic slabs: Perturbative treatments based on jellium

We examine first-order perturbative results based on jellium for the surface energy of slabs of simple metals, using various local pseudopotentials (Ashcroft, Heine-Abarenkov and evanescent core). The difference between the pseudopotential and the jellium potential is averaged along the plane parallel to the surface. We compare these perturbative results with those of the stabilized jellium model (a modification of the regular jellium model in which the perturbation appears in the energy functional right from the outset) and with the output of other perturbative and non-perturbative calculations.Comment: 15 pages, 2 figures, to appear in Prog. Surf. Sc

An Approach to Sustainable Metrics Definition and Evaluation for Green Manufacturing in Material Removal Processes

[EN] Material removal technologies should be thoroughly analyzed not only to optimize operations but also to minimize the different waste emissions and obtain cleaner production centers. The study of environmental sustainability in manufacturing processes, which is rapidly gaining importance, requires activity modeling with material and resource inputs and outputs and, most importantly, the definition of a balanced scorecard with suitable indicators for different levels, including the operational level. This paper proposes a metrics deployment approach for the different stages of the product life cycle, including a conceptual framework of high-level indicators and the definition of machining process indicators from different perspectives. This set of metrics enables methodological measurement and analysis and integrates the results into aggregated indicators that can be considered for continuous improvement strategies. This approach was validated by five case studies of experimental testing of the sustainability indicators in material removal operations. The results helped to confirm or modify the approach and to adjust the parameter definitions to optimize the initial sustainability objectives.This research was funded by the Escuela Politecnica Nacional (Ecuador) Research Project: PIS 16-15, the Universitat Politecnica de Valencia UPV (Spain) and the Carolina Foundation (Spanish Government Scholarships) Call 2017.Ayabaca-Sarria, C.; Vila, C. (2020). An Approach to Sustainable Metrics Definition and Evaluation for Green Manufacturing in Material Removal Processes. Materials. 13(2):1-21. https://doi.org/10.3390/ma13020373S121132Brundtland, G. H. (1987). Our Common Future—Call for Action. Environmental Conservation, 14(4), 291-294. doi:10.1017/s0376892900016805Berke, P. R., & Conroy, M. M. (2000). Are We Planning for Sustainable Development? 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An integrated approach for analysing the enablers and barriers of sustainable manufacturing. Journal of Cleaner Production, 142, 4412-4439. doi:10.1016/j.jclepro.2016.11.123Eastwood, M. D., & Haapala, K. R. (2015). A unit process model based methodology to assist product sustainability assessment during design for manufacturing. Journal of Cleaner Production, 108, 54-64. doi:10.1016/j.jclepro.2015.08.105Garretson, I. C., Mani, M., Leong, S., Lyons, K. W., & Haapala, K. R. (2016). Terminology to support manufacturing process characterization and assessment for sustainable production. Journal of Cleaner Production, 139, 986-1000. doi:10.1016/j.jclepro.2016.08.103Helleno, A. L., de Moraes, A. J. I., & Simon, A. T. (2017). Integrating sustainability indicators and Lean Manufacturing to assess manufacturing processes: Application case studies in Brazilian industry. Journal of Cleaner Production, 153, 405-416. doi:10.1016/j.jclepro.2016.12.072Kluczek, A. (2017). An Overall Multi-criteria Approach to Sustainability Assessment of Manufacturing Processes. Procedia Manufacturing, 8, 136-143. doi:10.1016/j.promfg.2017.02.016Latif, H. H., Gopalakrishnan, B., Nimbarte, A., & Currie, K. (2017). Sustainability index development for manufacturing industry. Sustainable Energy Technologies and Assessments, 24, 82-95. doi:10.1016/j.seta.2017.01.010Moldavska, A., & Welo, T. (2017). The concept of sustainable manufacturing and its definitions: A content-analysis based literature review. Journal of Cleaner Production, 166, 744-755. doi:10.1016/j.jclepro.2017.08.006Winroth, M., Almström, P., & Andersson, C. (2016). Sustainable production indicators at factory level. Journal of Manufacturing Technology Management, 27(6), 842-873. doi:10.1108/jmtm-04-2016-0054Linke, B., Das, J., Lam, M., & Ly, C. (2014). Sustainability Indicators for Finishing Operations based on Process Performance and Part Quality. 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Towards sustainability assessment of machining processes. Journal of Cleaner Production, 170, 694-703. doi:10.1016/j.jclepro.2017.09.197Kadam, G. S., & Pawade, R. S. (2017). Surface integrity and sustainability assessment in high-speed machining of Inconel 718 – An eco-friendly green approach. Journal of Cleaner Production, 147, 273-283. doi:10.1016/j.jclepro.2017.01.104Benedicto, E., Carou, D., & Rubio, E. M. (2017). Technical, Economic and Environmental Review of the Lubrication/Cooling Systems Used in Machining Processes. Procedia Engineering, 184, 99-116. doi:10.1016/j.proeng.2017.04.075Zhao, G. Y., Liu, Z. Y., He, Y., Cao, H. J., & Guo, Y. B. (2017). Energy consumption in machining: Classification, prediction, and reduction strategy. Energy, 133, 142-157. doi:10.1016/j.energy.2017.05.110Abbas, A. T., Benyahia, F., El Rayes, M. M., Pruncu, C., Taha, M. A., & Hegab, H. (2019). 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The M_BH-M_star relation of obscured AGNs at high redshift

We report the detection of broad Halpha emission in three X-ray selected obscured AGNs at z=1-2. By exploiting the Halpha width and the intrinsic X-ray luminosity, we estimate their black hole masses, which are in the range 0.1-3x10^9 Msun. By means of multi-band photometric data, we measure the stellar mass of their host galaxy and, therefore, infer their M_BH/M_star ratio. These are the first obscured AGNs at high-z, selected based on their black hole accretion (i.e. on the basis of their X-ray luminosity), that can be located on the M_BH-M_star relation at high-z. All of these obscured high-z AGNs are fully consistent with the local M_BH-M_star relation. This result conflicts with those for other samples of AGNs in the same redshift range, whose M_BH/M_star ratio departs significantly from the value observed in local galaxies. We suggest that the obscured AGNs in our sample are in an advanced evolutionary stage, have already settled onto the local M_BH-M_star relation, and whose nuclear activity has been temporarily revived by recent galaxy interactions.Comment: 4 pages, 2 figures, accepted for publication in A&A Letters, slightly revised discussion on SMG

Lack of correlation between vertical distribution and carrier frequency, and preference for open spaces in arboreal katydids that use extreme ultrasound, in Gorgona, Colombia (Orthoptera: Tettigoniidae)

Male Tettigoniidae emit sound to attract conspecific females. The sound is produced by stridulation. During stridulation the forewings open and close, but it is during the closing stroke that the scraper contacts the file teeth to generate the predominant sound components, which are amplified by adjacent wing cells specialized in sound radiation. The sounds usually exceed the sonic boundary and might occur above 40 kHz, reaching extreme ultrasonic frequencies of 150kHz in some species. Here we test the hypothesis that Tettigoniidae species should prefer microhabitats that favour efficient signal transmission, i.e. that there is a relationship of sound frequency with the vertical distribution of the species (from ground to canopy) at Gorgona National Natural Park, Colombia. We sampled 16 trees and four different altitudinal levels between 1 and 20m above the understory vegetation. We placed collecting blankets separated by vertical distances of 5m, and knocked insects down using the technique known as fogging. We found no correlation between vertical distribution and carrier frequency, but there was a preference for open spaces (below the canopy and above the understory) in species using extreme ultrasound. This is the first quantitative description of the vertical distribution in neotropical species of the family Tettigoniidae and its relationship to the calling song frequency

Efficiency Centered Maintenance of Preheat Train of a Crude Oil Distillation Unit

Nowadays, maintenance is based on the synergistic integration of operational reliability and timely maintenance, which guarantees the required availability and optimal cost. Operational reliability implies producing more, better performance, longer life, and availability. Timely maintenance involves the least time out of service, fewer maintenance costs, fewer operating costs, and less money. In this work, we study the preheating train of a crude distillation unit of a refinery, which processes 994 m3/h, which presents a formation of a foulinglayer inside it. Among the impacts of fouling is the reduction in the effectiveness of heat transfer, the increase in fuel consumption, the increase in CO2 emissions, the increase in maintenance costs, and the decrease in the profit margin of process. An appropriate cleaning program of the surface of the heat exchanger network is necessary to preserve its key performance parameters, preferably close to design values. This paper presents the maintenance method centered on energy efficiency, to plan the intervention of the preheating train equipment maintenance, which considers the economic energy improvement and the cost of the type of maintenance. The method requires the calculation of the fouling evolution from which the global heat transfer coefficient is obtained, and the heat flux is determined as a function of time. It was observed that, as time passes, the resistance provided by fouling increases and that the overall heat transfer coefficient decreases. The energy efficiency centered maintenance has an indicator of economic justification (factor J) that relates the economic-energy improvement achieved when performing maintenance, taking into account the economic effort invested. Depending on the cost of the type of maintenance to be performed, a threshold should be chosen, from which the maintenance activity is justified. The effectiveness values of the heat exchanger (e) and the J indicator are used to form a criticality matrix, which allows prioritizing maintenance activities in each equipment. The planning of the implementation dates of the maintenance of each heat exchanger, from the maintenance method centered on energy efficiency applied to the crude distillation unit's, preheat train, constitutes a contribution in this specific field. The conceptual design of the maintenance method centered on energy efficiency presented in this work is feasible for other heat transfer equipment used in oil refineries and industry in general. The procedure developed uses real operation values, and with its implementation, a saving of 150000 US dollars was achieved. © 2020 ASME

Parental Involvement between Two Different Urban Communities

Parent involvement is an integral part of a child’s educational progress. In some cases, students’ academic achievement can be directly related to the level of parental involvement exhibited in schools. Families’ perception of roles toward parental involvement in schools may vary among groups from diverse cultures. In today’s urban schools, the increasing diversity of cultures may contribute to differences in levels of parental involvement. The purpose of this research is to address the need to promote parental participation in the educational process of their children. This study will focus on three research questions: Are there differences in levels of parental involvement after participating in a program designed to assist them with their children’s reading skills? Are there changes in the attitudes of families towards parental involvement after participating in the instructional cycle? Is there a relationship between the level of parental involvement and student academic achievement

Changing times, changing diets

Diets are the great equaliser. Depending on who you are, where you live and the amount of resources at your disposal, diets can either hinder or promote human and environmental health. Overall, diets are changing for various reasons, particularly in rapidly transitioning low- and middle-income countries. If trends in these countries follow those in highincome contexts and countries, fragile health systems could be overwhelmed and burdened with a new host of complex diseases. How can low- and middle-income countries leapfrog over the mistakes made in high-income countries and ensure that dietary changes are moving in a direction benefiting both human and planetary health