Managing urban water utilization: A delicate balance

eXecuTiVe Summary Serious water problems-from issues of scarcity and security to poor quality-now affect a large proportion of the world's population. These challenges are particularly intense in regions with high population density, low average precipitation and weak economies. Given the current state of technology and necessarily limited water sources, administering and using water reasonably and efficiently is crucially important now and in the years ahead. This article considers the relationships among water supply stakeholders and several water management strategies including the "5E-principle" related to economic, environmental, equity, efficiency and energy factors. We advance a water management system and framework for meeting urban socio-economic growth challenges while maintaining water utilization sustainability, based on a notable Beijing experience

The crucial importance of air valve characterization to the transient response of pipeline systems

[EN] Air valves are often crucial components in an air management strategy for pressurized water conveyance systems. However, the reliability of characteristic curves of air valves found in product catalogs is quite variable. This paper evaluates the consistency of a selection of product curves to basic air flow principles. Several recurring issues are identified: catalogs that present identical curves for admission and expulsion (they are, in fact, quite distinct); admission curves that are inconsistent with the isentropic inflow model; inflow (admission) curves actually consistent with the shape of the isentropic outflow model; limited validity curves that encompass only part of the subsonic flow regimen; and unclear or unstated specifications regarding the conditions under which the characterization tests were performed or their results displayed. To examine the significance of these representational issues related to air valve capacity on system behaviour, this paper uses a case study involving the simulated transient response arising from a pump trip at the upstream end of a rising water line having a distinct high point fitted with an air valve. It is found that employing inaccurate air valve characteristics in a transient simulation may potentially result in appreciable or even dangerous simulation errors.This study was financed in part by the Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior-Brasil (CAPES)-Finance Code 001.Tasca, E.; Karney, B.; Fuertes-Miquel, VS.; Dalfré Filho, JG.; Luvizotto Jr., E. (2022). The crucial importance of air valve characterization to the transient response of pipeline systems. Water. 14(17):1-13. https://doi.org/10.3390/w14172590113141

Concerning dynamic effects in pipe systems with two-phase flows: pressure surges, cavitation and ventilation

[EN] The risks associated with unsteady two-phase flows in pressurized pipe systems must be considered both in system design and operation. To this end, this paper summarizes experimental tests and numerical analyses that highlight key aspects of unsteady two-phase flows in water pipelines. The essential dynamics of air¿water interactions in unvented lines are first considered, followed by a summary of how system dynamics change when air venting is provided. System behaviour during unsteady two-phase flows is shown to be counter-intuitive, surprising, and complex. The role of air valves as protection devices is considered as is the reasonableness of the usual assumptions regarding air valve behaviour. The paper then numerically clarifies the relevance of cavitation and air valve performance to both the predicted air exchanges through any installed air valves and their role in modifying system behaviour during unsteady flows.This work was supported by Fundacao para a Ciencia e a Tecnologia [grant number SFRH/BD/39502/2007]. This study was financed in part by the Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior-Brasil (CAPES)-Finance Code 001.Ramos, HM.; Fuertes-Miquel, VS.; Tasca, E.; Coronado-Hernández, OE.; Besharat, M.; Zhou, L.; Karney, B. (2022). Concerning dynamic effects in pipe systems with two-phase flows: pressure surges, cavitation and ventilation. Water. 14(15):1-23. https://doi.org/10.3390/w14152376123141

Artesian Landfill Liner System: Optimization and Numerical Analysis

ABSTRACT: Conventional landfill design attempts to control the downward seepage of leachate by using low permeability liners. The rate of leachate seepage into the underlying ground-water system can be controlled by decreasing the permeability of soil liners and/or by using synthetic membranes to form an additional barrier to leachate migration. However, loss of leachate from conventional landfills is likely to occur due to the inherent limitations of natural materials and the inevitable imperfections of installing synthetic liners. The artesian landfill liner system eliminates the downward seepage by reversing the direction of the hydraulic gradient so that seepage occurs into, and not out of, the landfill. A conceptual cost model incorporates the trade-offs between the capital cost of constructing robust liners and the operational costs of supplying recharge water and treating additional leachate produced by the artesian hydraulics. In addition, a two-dimensional, transient finite-element flow model demonstrates that the reverse hydraulic gradient limits the loss of leachate even if the integrity of the landfill liner is imperfect or deteriorates over time

Health behavior change models for HIV prevention and AIDS care: practical recommendations for a multi-level approach

Despite increasing recent emphasis on the social and structural determinants of HIV-related behavior, empirical research and interventions lag behind, partly because of the complexity of social-structural approaches. This article provides a comprehensive and practical review of the diverse literature on multi-level approaches to HIV-related behavior change in the interest of contributing to the ongoing shift to more holistic theory, research, and practice. It has the following specific aims: (1) to provide a comprehensive list of relevant variables/factors related to behavior change at all points on the individual-structural spectrum, (2) to map out and compare the characteristics of important recent multi-level models, (3) to reflect on the challenges of operating with such complex theoretical tools, and (4) to identify next steps and make actionable recommendations. Using a multi-level approach implies incorporating increasing numbers of variables and increasingly context-specific mechanisms, overall producing greater intricacies. We conclude with recommendations on how best to respond to this complexity, which include: using formative research and interdisciplinary collaboration to select the most appropriate levels and variables in a given context; measuring social and institutional variables at the appropriate level to ensure meaningful assessments of multiple levels are made; and conceptualizing intervention and research with reference to theoretical models and mechanisms to facilitate transferability, sustainability, and scalability

Analysis of fluid transients in large distribution networks

It is well known that the pressures generated during transient conditions should be an important consideration when pipeline systems are being designed or constructed. If the size and strength of the required pipe is to be rationally selected, if the surge suppression equipment is to be logically sized and if system operating rules are to be intelligently specified, reliable transient analysis is essential. The aim of this research has been to develop a general, efficient and reliable algorithm for computing the response of large distribution systems to rapid transient conditions. Although further refinement and verification work is still required, it is considered that this goal has been achieved. Significantly, the algorithm is general, since a wider class of networks can be analyzed than was previously possible. The program is also efficient, since the solution of many of the network boundary conditions is made explicit for the first time and because computer storage is conserved in the program implementation. Finally, the program is reliable, since a number of numerical experiments have proven its correctness. Specifically, the solution procedure for obtaining the transient response of large networks includes the following new features: a coupling of the steady and unsteady parts of the analysis avoids duplication and improves program efficiency; a general network and boundary condition classification system which permits networks with any reasonable topology to be analyzed; solution procedures for many common network boundary conditions are made explicit or put in a form which allows efficient numerical calculation; and, finally an automatic algorithm for selecting the time step and dividing the network pipes into an integer number of reaches. All of these elements combine to produce efficient and accurate transient analysis of large distribution systems. In summary, the developed algorithm allows comprehensive transient analysis of networks having arbitrary geometry to be performed. The networks may include any general combinations of hydraulic devices and no restriction is placed on either the number of boundary conditions or pipes that connect to a given node or the number of sections found in any pipe in the network. Procedures have been utilized which keep data requirements to a minimum despite the general nature of the problem being solved. Finally, the program has been carefully tested and compared with known solutions for simple pipelines with very good agreement being observed.Applied Science, Faculty ofCivil Engineering, Department ofGraduat

Measuring the Connection Between Mathematics and Engineering

Mathematics forms the foundation for all the engineering disciplines. Students have trouble transferring this mathematical knowledge from their mathematics classes to the rest of their undergraduate engineering classes. This study is borne out of a desire to ‘be better,' to endeavour always to try to improve, but first, you need to know where one the starting point. The authors are also passionate about mathematics as it relates to engineering. Anecdotally the authors had heard that both students and faculty were disappointed and aggravated with the current status of mathematics teaching in undergraduate engineering. With no known study in Canada looking at how mathematics connects with engineering the authors went down the path to find out how strong the connection between mathematics and undergraduate engineering is at the University of Toronto. Through a mixed-method survey, the goal was to measure respondents’ (i.e. The teaching staff) views on the importance of and students’ competence of both mathematical topics and specific mathematic skills. A survey was administered in the 2017 fall semester to all of those who teach in the Faculty of Applied Science at the University of Toronto. The first part of the survey used a 5-point scale, the second part of the survey had open-ended questions. The responses to the 5-point scale questions demonstrate that the selected mathematic topics and specific skills were all seen as important and that the students’ competence was lower than their rated importance. The open ended-questions asked for respondents definitions and views as they related to abstract, applied, and engineering mathematics

Mind the Gap: A preliminary Investigation into the Gaps Between Faculty and Student Expectations in Engineering Mathematics Instruction

© 2019 American Society for Engineering EducationThe connection between mathematics and engineering, that is the ability for students to transfer their knowledge between mathematics courses and other engineering courses, has been documented as difficult for students (Holmegaard, Madsen, & Ulriksen, 2016; Basitere & Ivala, 2015; Klingbeil, Rattan, Raymer, Reynolds, & Mercer, 2009; Willcox & Bounova, 2004; Harper, Baker, & Grzybowski, 2013). By looking at faculty views regarding the mathematics that is learned while in undergraduate engineering, I argue that mathematics plays an important role in undergraduate engineering, yet faculty often believe that the students are inadequately equipped with the mathematics skills they need, which is essential because mathematics is foundational for engineering design. Through a mixed-methods study over the course of the 2017-2018 academic year, we sought to answer the following questions: To what extent does mathematics play an important role in undergraduate engineering education? Do professors believe that undergraduate engineering students can competently apply mathematic principles in engineering classes? And finally, how should mathematics be taught as it relates to undergraduate engineering? The initial findings suggest faculty believe that mathematics plays an important role in engineering, calculus being the most important, with linear algebra and statistics also playing a significant role. Faculty also believe that mathematics should be taught as a means of communicating (i.e. through mathematical modelling). Faculty also believe that students’ competence ranks lower than the importance of the general and specific mathematics skills. Finally, faculty were unsure if mathematics should be taught toward the abstract or the applied, but in general, believe that it should have some examples that are tied to engineering. Mathematics instruction to engineering students is often taught through two lenses, an abstract or an applied lens. While both categories of mathematics are essential in undergraduate engineering, a third paradigm for teaching is offered, an engineering mathematics lens, which combines both the necessity for an understanding both in abstract and applied mathematics, but relates examples to all facets of engineering. An engineering mathematics lens could offer part of a solution to helping to close the gap in faculty and student expectations as it relates to mathematics instruction in engineering education