Dynamics research of Fangzhu’s nanoscale surface

In this paper, we mainly focus on a fractal model of Fangzhu’s nanoscale surface for water collection which is established through He’s fractal derivative. Based on the fractal two-scale transform method, the approximate analytical solutions are obtained by the energy balance method and He’s frequency–amplitude formulation method with average residuals. Some specific numerical experiments of the model show that these two methods are simple and effective and can be adopted to other nonlinear fractal oscillators. In addition, these properties of the obtained solution reveal how to enhance the collection rate of Fangzhu by adjusting the smoothness of its surfaces.

Implementation of participatory pre-collection in the sustainable management of household solid waste: case of the district of Douala V in Cameroon

EPI sciences The main objective of this study in the district of Douala V is to set up participatory pre-collection of household solid waste which, by protecting the environment, promotes the recovery of this waste. More specifically, the aim was to make an inventory of solid waste management, to raise awareness of households on participatory pre-collection, to describe the technical organization of the service and to evaluate the parameters of financial analysis for a pre-collection activity. To do this, available documents, direct observations, interviews and survey form were used. The main results of this study showed that the daily production or ratio of one inhabitant of Douala V is 1.05kg/hab/jour; the annual production is estimated at 363,870 tons. The low collection rate of about 23% was observed. With regard to household sensitization, 43% of the households surveyed are willing to pay for the pre-collection service and 52% are against and 5% are uninformed. The provisional financial analysis is based on one year; the investment cost is estimated at 3 327 400 CFA (5079 €). Overall, it appears that the solid waste collection rate in Douala V is below average, so it appears that pre-collection and recovery of household solid waste have a major role to play in the solid waste management system. Cette étude déroulée dans l’arrondissement de Douala V a pour objectif principal de mettre sur pied la pré-collecte participative des déchets solides ménagers qui en protégeant l’environnement, favorise une valorisation de ces déchets. Il s’agissait plus spécifiquement de faire un état de lieux de la gestion des déchets solides, de sensibiliser les ménages sur la pré-collecte participative, décrire l’organisation technique du service et d’évaluer les paramètres d’analyse financière pour une activité de pré-collecte. Pour ce faire, des documents disponibles, observations directes, entretiens et fiche d’enquête ont été utilisés. Les principaux résultats de cette étude ont montré que la production journalière ou ratio d’un habitant de Douala V est de 1,05kg, la production annuelle est estimée à 363 870,45 tonnes. Le taux de collecte faible d’environ 23%. Pour ce qui est de la sensibilisation des ménages, 42,66% des ménages enquêtés sont prêts à payer pour le service de pré-collecte et 52,33% sont contre et 5% sont sans avis. L’analyse financière prévisionnelle est basée sur une année, le coût d’investissement s’estime à deux mille huit cent quatre-vingt-onze Euro (2 891 Euro). Il ressort globalement que le taux de collecte des déchets solides à Douala V est en dessous de la moyenne, il apparait donc que la pré-collecte et la valorisation des déchets solides ménagers ont un rôle majeur à jouer dans le système de gestion des déchets solides.

Numerical and experimental study of droplet-film-interaction for low pressure steam turbine erosion protection applications

One common approach for anti-erosion measures in low pressure steam turbines is to equip a hollow stator vane with slots on the airfoil surface in order to remove the water film by suction and consequently reduce the amount of secondary droplets. The purpose of this paper is to build an understanding of the predominant effects in fluid-film interaction and to examine the suitability of modern numerical methods for the design process of such slots. The performance of a suction slot in terms of collection rate and air leakage is investigated numerically in a flatplate setup with upstream injection of water. In order to model the relevant phenomena (film transport, edge stripping of droplets, transport of droplets in the surrounding fluid, wall impingement of droplets) an unsteady Eulerian-Lagrangian simulation setup is applied. The accuracy of the numerical approach is assessed by comparison with experimental measurements. The comparison of four cases with the measured data demonstrates that the chosen simulation approach is able to predict the main features of film flow and interaction with the surrounding fluid. The collection rate as well as fluid film properties show the same qualitative dependency from water mass flow rate and air velocity.

Residents’ Concerns Regarding Schools Designated as Evacuation Shelters

Objective: The purpose of this study was to investigate the perceptions of residents who are knowledgeable about the schools used as shelters. Methods: The target group was comprised of teachers and guardians of children enrolled in 4 schools, which were selected in the vicinity of District B, which was severely damaged by heavy rain in 2014. A qualitative descriptive study design was used. Results: The number of surveys collected was 1702 (collection rate 62.2%). A total of 1017 clauses were entered, and 85 codes were generated for 7 categories. The guardians and teachers believed that there was a discrepancy between shelter capacity and the real situation; citing a lack of information, and ill preparedness of the schools for disasters as some of the problems. Based on the knowledge and experiences from previous disasters, they responded that there was inadequate management, and evacuees faced difficulty living comfortably in the shelters. Conclusion: In order to use school facilities during any disaster, it is important for residents to recognize the need to solve problems, and to work with local governments to support improvements. This realization reveals a sense of ownership of emergency shelters and prevents confusion among residents. Also, this will help people to prepare for disasters and prevent disruption during evacuation.

Optimizing Water Harvesting on Bioinspired Surfaces: A Mesoscopic Perspective

The water crisis affects the lives of millions over the world. Minimizing water losses in major water-consuming industries like power plants is of utmost importance. Since cooling towers lead to huge amounts of water loss, implementing modifications for recovering a fraction of this lost water in the exhaust has been a topic of active research. These modifications are often inspired by biological species, especially in arid regions, which have adapted in different ways by collecting water from fog, and hence biomimetic has become popular for water harvesting techniques. We revisit the fog collection technique most commonly used in nature and compare the relative merits of the same with surface texture and wettability. Arrays of spines of three different configurations were considered in this study — namely cuboidal, cylindrical and conical shapes. A theoretical model is developed to carry out a comparative analysis of these configurations considered. The effects of Laplace pressure gradient, gravity, topography and tilt angle on droplet transportation along the spines were explored to decipher the most efficient water transport and collection route. The observations are explained by performing extensive Molecular Dynamics (MD) simulations to bring out the interplay of surface tension and roughness at the contact line verifying the proposed formulations. The conical-shaped spines exhibited maximum transport and collection efficiency for zero tilt angle. Both cuboidal and cylindrical shaped spines showed little or no water collection when the spines are oriented horizontally. This is due to the Laplace pressure gradient which arises from varying radii of curvature of the conical shaped spine which drives the water droplets towards the base but is absent for the other two cases considered. On the contrary, when there is some finite tilt angle, the contribution of gravity comes into consideration and the water collection rate of the conical and cylindrical spines becomes comparable. Both Laplace pressure gradient and gravity help in water transport in the conical case whereas only gravity assists the water transport process for cylindrical spines. Still, the water collection rate is almost the same for these two scenarios due to enhanced coalescence of liquid droplets for the cylindrical case as is observed from MD simulations. As the droplets coalesce, they get larger and gravity aids the transport process by overcoming the solid-liquid interaction strength. Cuboidal shaped spines show the least efficiency with only gravity to assist the transport process and no coalescence is observed in this case. Moreover, the geometrical disparity makes the tips of conical spines more hydrophobic compared to the others which further ameliorates the water collection efficiency.

A Novel Design of Hybrid Hydrophilic-Superhydrophobic Surfaces for Fog Harvesting

The continuous growth in the human population and climate change exacerbates the problems related to water scarcity. Harvesting the atmospheric water can mitigate the water scarcity in many regions around the globe. Fog collection using hybrid hydrophilic-superhydrophobic surfaces has the capacity to achieve a higher water collection rate. In this paper, a new method and materials are introduced to create the hybrid surfaces. The method includes additive manufacturing- to make sheets with holes-, mixing and casting polymeric matrix composite, and a controlled spray coating mechanism. The materials comprised of hydrophobic coating on top of the acrylic printed sheet and hydrophilic composite. The ratios of the pitches to diameters of the hydrophilic regions varied during the experiments to obtain the best water generation. The water collection rate for the sample with diameters of 583 um and a pitch of 1600 um has achieved 57% more than the untreated hydrophilic sample. The contrast in wettability accomplished by this novel method has the potential to be implemented on a large scale for atmospheric water harvesting.

Control of Fine Cutting Chips to Improve the Processing Environment in CFRP Drilling

Carbon fiber reinforced plastic (CFRP) is increasingly used in aerospace, automobile, and other industries. With the improvement of carbon fiber reinforced thermoplastic molding technology using thermoplastic resin, it is expected that the applications of CFRP will be expand further. Because of the following issues, CFRP is known as a difficult-to-cut material. i) Machining CFRP is difficult. ii) Its finished surface deteriorates due to delamination and uncut fiber. iii) It has a shortened tool life due to severe tool wear. In addition to these issues, we has been problem presentation of fine cutting chips generated by machining. Because these fine cutting chips may scatter in the atmosphere and adversely affect the human body and machine tools, we have established a chip disposal technology that suppresses these issues to improve the processing environment. A previous study reported that shape of the tool edge is responsible in suppressing the generation of fine cutting chips. Here, we experimentally investigated the effects of tool edge shapes on the chip collection rate and tool life. An attempt was made to determine whether the same effect can be obtained by using the outside dust-collection method which is known that the dust collection efficiency is low. We revealed that the chip collection rate increases if a tool that suppresses the generation of fine cutting chips is used instead of a conventional tool; furthermore, the tool life is insensitive to coating. In contrast, a comparison of our results with previous findings indicates that the tool with a sharpened cutting edge has a longer tool life than the conventional twist drill with honing. A high cutting chip collection rate was obtained, even with the outside dust-collection method, which led to an improvement in the working environment.

Environmental assessment of construction and demolition waste recycling in Bolivia: Focus on transportation distances and selective collection rates

Construction and demolition waste (CDW) management in developing countries is a global concern. The analysis of scenarios and the implementation of life cycle assessment (LCA) support decision-makers in introducing integrated CDW management systems. This paper introduces the application of an LCA in La Paz (Bolivia), where CDW is mainly dumped in open areas. The aim of the research is to evaluate the benefits of inert CDW recycling in function of the selective collection rate, defined as the amount of waste (%wt.) sorted at the source in relation to the total waste amount produced, and the distances from the CDW generation to the material recycling facility. The outcomes of the research suggest that increasing the selective collection rates (5% to 99%) spread the importance of transportation distances planning since it affects the magnitude of the environmental impacts (1.05 tCO2-eq to 20.7 tCO2-eq per km traveled). Transportation limits have been found to be lower than about 40 km in order to make recycling beneficial for all environmental impacts and for all selective collection rate, with the eutrophication potential as the limiting indicator. The theoretical analysis suggests implementing LCA with primary data and involving statistics related to the transportation of virgin materials avoided thanks to recycling. The outcomes of the research support the implementation of CDW recycling in developing countries since it has been found that material recovery is always beneficial.