Search results for "problems"
showing 10 items of 620 documents
Drops moving in flow with chernical reaction
1994
We propose a free boundary model described by coupled Navier-Stokes and chemical reaction equations with discontinuous coefRcients to simulate the chemical re- ¿ctions in viscous drops moving in a viscous incompressible ûuid. Approximation of the solution by a special ñnite element method (FEM) with a method of mapping is discussed. Several numerical resulùs åre presented.
Usability challenges in digital learning solutions
2015
Usability is a key element in successful software. Ensuring the technical usability of a learning solution enables users to focus on their main task, learning. The purpose of this paper is to demonstrate the results of heuristic usability evaluations of digital learning solutions. Heuristic evaluations were conducted on 24 digital learning solutions from one country (Finland) and two country groups (Asian countries and Spanish speaking countries) concentrating on the usability of the user interface of each evaluated solution. The main results of this study indicate that a few heuristics cover the majority of all usability problems (UPs) observed in learning solutions, but these heuristics c…
A reliable incremental method of computing the limit load in deformation plasticity based on compliance : Continuous and discrete setting
2016
The aim of this paper is to introduce an enhanced incremental procedure that can be used for the numerical evaluation and reliable estimation of the limit load. A conventional incremental method of limit analysis is based on parametrization of the respective variational formulation by the loading parameter ? ? ( 0 , ? l i m ) , where ? l i m is generally unknown. The enhanced incremental procedure is operated in terms of an inverse mapping ? : α ? ? where the parameter α belongs to ( 0 , + ∞ ) and its physical meaning is work of applied forces at the equilibrium state. The function ? is continuous, nondecreasing and its values tend to ? l i m as α ? + ∞ . Reduction of the problem to a finit…
Citizens AND HYdrology (CANDHY) : conceptualizing a transdisciplinary framework for citizen science addressing hydrological challenges
2021
Widely available digital technologies are empowering citizens who are increasingly well informed and involved in numerous water, climate, and environmental challenges. Citizen science can serve many different purposes, from the "pleasure of doing science" to complementing observations, increasing scientific literacy, and supporting collaborative behaviour to solve specific water management problems. Still, procedures on how to incorporate citizens' knowledge effectively to inform policy and decision-making are lagging behind. Moreover, general conceptual frameworks are unavailable, preventing the widespread uptake of citizen science approaches for more participatory cross-sectorial water go…
Mortality risk attributable to wildfire-related PM2·5 pollution: a global time series study in 749 locations
2021
Summary Background Many regions of the world are now facing more frequent and unprecedentedly large wildfires. However, the association between wildfire-related PM2·5 and mortality has not been well characterised. We aimed to comprehensively assess the association between short-term exposure to wildfire-related PM2·5 and mortality across various regions of the world. Methods For this time series study, data on daily counts of deaths for all causes, cardiovascular causes, and respiratory causes were collected from 749 cities in 43 countries and regions during 2000–16. Daily concentrations of wildfire-related PM2·5 were estimated using the three-dimensional chemical transport model GEOS-Chem …
Profiles and Sources of PAHs in Sediments from an Open-Pit Mining Area in the Peruvian Andes
2015
The Peruvian Andes are one of the most productive areas for mining and therefore also one of the most exposed to these sources of pollution. This article reports the characterization of Polycyclic Aromatic Hydrocarbons (PAHs) in sediments of Cerro de Pasco area (Peru) located close to a large open-pit mine and, in recent years, several reports have provided evidence of environmental contamination and related health problems. Investigations were carried out into the fifteen PAHs identified by the US-Environment Protection Agency (US-EPA) as requiring priority monitoring, other non US-EPA listed PAHs and perylene were also investigated in order to obtain further information on their origins. …
Lichens as bio-monitors of trace-elements in Central and Eastern France
2003
Lichens (105 samples, mainly P. sulcata and X parietina) have been used to monitor As, Cd, Co, Cr, Cu, Mg, Ni, Pb, and Zn in Burgundy and in the East of France. When the industrial environment seemed to justify it, other elements were also looked for, such as Ag, Sn and V. Research was carried out on areas with little or moderate pollution and supplemented by studies on three hot spots with health problems. Record and background concentrations in lichens are presented as well as the ratios between those values. In the case of lead, the concentrations in lichens are compared with the results in blood tests.
New facets and an enhanced branch-and-cut for the min-max K -vehicles windy rural postman problem
2011
[EN] The min-max windy rural postman problem is a multiple vehicle version of the windy rural postman problem, WRPP, which consists of minimizing the length of the longest route to find a set of balanced routes for the vehicles. In a previous paper, an ILP formulation and a partial polyhedral study were presented, and a preliminary branch-and-cut algorithm that produced some promising computational results was implemented. In this article, we present further results for this problem. We describe several new facet-inducing inequalities obtained from the WRPP, as well as some inequalities that have to be satisfied by any optimal solution. We present an enhanced branch-and-cut algorithm that t…
Contexto familiar de niños con autismo: Implicaciones en el desarrollo social y emocional
2019
Las familias de niños con trastorno del espectro del autismo (TEA) pueden diferenciarse en función de indicadores sociodemográficos y del clima familiar caracterizado por el nivel de estrés parental, el uso de estrategias de afrontamiento y la búsqueda de apoyo social. El objetivo de este estudio fue analizar las diferencias conductuales, emocionales y sociales de niños con TEA en relación con distintas tipologías de familias caracterizadas en función de los factores de riesgo como de riesgo alto, moderado y bajo. Los participantes fueron 52 madres y sus hijos de entre 7 y 11 años, con TEA sin discapacidad intelectual, que aportaron información del desarrollo socioemocional de los hijos med…
Análisis de variables psicopedagógicas en hijos adolescentes violentos desde el modelo cognitivo
2018
[EN] Parental abuse by sons and daughtersis a reality latent in our society. The present article analyzes the existence or not of psycho-pedagogical variables (academic and occupational) as risk factors in adolescents who exert violence against their parents. Methods used are descriptive, focused on the analysis of studies that contemplate these variables and compare them with research on aggressive offspring. Results suggest that these variables are risk factors for violent behaviors in adolescents due to violence towards parents and they suggest relevant issues to research, prevention and educational intervention. Hereby, from the cognitive model, interaction between intrapersonal and int…