High-frequency analysis of the efficiency of a local approximate DtN2 boundary condition for prolate spheroidal-shaped boundaries

The performance of the second-order local approximate DtN boundary condition suggested in [4] is investigated analytically when employed for solving high-frequency exterior Helmholtz problems with elongated scatterers. This study is performed using a domain-based formulation and assuming the scatterer and the exterior artificial boundary to be prolate spheroid. The analysis proves that, in the high-frequency regime, the reflected waves at the artificial boundary decay faster than 1/(ka)15/8, where k is the wavenumber and a is the semi-major axis of this boundary. Numerical results are presented to illustrate the accuracy and the efficiency of the proposed absorbing boundary condition, and to provide guidelines for satisfactory performance

Exponential decay of high-order spurious prolate spheroidal modes induced by a local approximate dtn exterior boundary condition

We investigate analytically the asymptotic behavior of high-order spurious prolate spheroidal modes induced by a second-order local approximate DtN absorbing boundary condition (DtN2) when employed for solving high-frequency acoustic scattering problems. We prove that these reflected modes decay exponentially in the high frequency regime. This theoretical result demonstrates the great potential of the considered absorbing boundary condition for solving efficiently exterior high-frequency Helmholtz problems. In addition, this exponential decay proves the superiority of DtN2 over the widely used Bayliss-Gunsburger-Turkel absorbing boundary condition

A modified discontinuous Galerkin method for solving efficiently Helmholtz problems

A new solution methodology is proposed for solving efficiently Helmholtz problems. The proposed method falls in the category of the discontinuous Galerkin methods. However, unlike the existing solution methodologies, this method requires solving (a) well-posed local problems to determine the primal variable, and (b) a global positive semi-definite Hermitian system to evaluate the Lagrange multiplier needed to restore the continuity across the element edges. Illustrative numerical results obtained for two-dimensional interior Helmholtz problems are presented to assess the accuracy and the stability of the proposed solution methodology

Wastewater reuse in agriculture in the outskirts of the city Batna (Algeria)

The study is based on a survey of farmers. The data collected allow us to understand the reasons for the reuse of wastewater. This resource can be an important element in irrigation water management strategy. The possibilities of wastewater reuse in agriculture are significant, as is the case in the Batna region. In this context, the presence of texts establishing the modality of wastewater reuse, are a prerequisite for promotion of wastewater reuse projects. Policymakers are faced with the need to exploit the increase in volumes to meet greater demand. To do this, the integrated management should be considered now as a public / private partnership model and as the best approach for development and efficient and sustainable management.Keywords: Farmers, Irrigation, Management, Public Policy, Text

Air quality in the metropolitan area of Sidi Bel Abbes (Algeria) through the lichens species as bio-indicators

The air quality in towns and cities is increasingly deteriorating as human activities increase but no actions have been taken in Algeria to limit air pollution. There are no regulations for controlling pollutant emissions and no specialist treatment center for treating diseases and allergies caused by  air pollution. To access urban air quality lichens species were used for bio-monitoring   12 stations spread across Sidi Bel Abbés city (Western  Algeria). The use of living organisms, in this case lichens, for evaluating the quality of air is a preferred method.  European lichenologists developed a new environmental quality assessment protocol using mapping lichen diversity and  lichens are very often used as bio- accumulators. The selected species are generally those growing on tree trunks, and having a broad geographic distribution. The lichen species most often used are thallus foliaceus or fruticose forms such as Parmelia caperata, P. sulcata, Hypogymnia physodes, Xanthoria parietina, Evernia prunastri, Pseudevernia furfuracea. These lichens species have large adsorption surfaces for major pollutants.  In this work we evaluate the air quality by applying lichen index based on German environmental engineers to map air pollution  in the city of Sidi Bel Abbes

Individual interactions in a multi-country implementation-focused quality of care network for maternal, newborn and child health: A social network analysis

The Network for Improving Quality of Care for Maternal, Newborn and Child Health (QCN) was established to build a cross-country platform for joint-learning around quality improvement implementation approaches to reduce mortality. This paper describes and explores the structure of the QCN in four countries and at global level. Using Social Network Analysis (SNA), this cross-sectional study maps the QCN networks at global level and in four countries (Bangladesh, Ethiopia, Malawi and Uganda) and assesses the interactions among actors involved. A pre-tested closed-ended structured questionnaire was completed by 303 key actors in early 2022 following purposeful and snowballing sampling. Data were entered into an online survey tool, and exported into Microsoft Excel for data management and analysis. This study received ethical approval as part of a broader evaluation. The SNA identified 566 actors across the four countries and at global level. Bangladesh, Malawi and Uganda had multiple-hub networks signifying multiple clusters of actors reflecting facility or district networks, whereas the network in Ethiopia and at global level had more centralized networks. There were some common features across the country networks, such as low overall density of the network, engagement of actors at all levels of the system, membership of related committees identified as the primary role of actors, and interactions spanning all types (learning, action and information sharing). The most connected actors were facility level actors in all countries except Ethiopia, which had mostly national level actors. The results reveal the uniqueness and complexity of each network assessed in the evaluation. They also affirm the broader qualitative evaluation assessing the nature of these networks, including composition and leadership. Gaps in communication between members of the network and limited interactions of actors between countries and with global level actors signal opportunities to strengthen QCN