Metric Regularity of the Sum of Multifunctions and Applications

In this work, we use the theory of error bounds to study metric regularity of the sum of two multifunctions, as well as some important properties of variational systems. We use an approach based on the metric regularity of epigraphical multifunctions. Our results subsume some recent results by Durea and Strugariu.Comment: Submitted to JOTA 37 page

Outage performance analysis of non-orthogonal multiple access with time-switching energy harvesting

In recent years, although non-orthogonal multiple access (NOMA) has shown its potentials thanks to its ability to enhance the performance of future wireless communication networks, a number of issues emerge related to the improvement of NOMA systems. In this work, we consider a half-duplex (HD) relaying cooperative NOMA network using decode-and-forward (DF) transmission mode with energy harvesting (Ell) capacity, where we assume the NOMA destination (D) is able to receive two data symbols in two continuous time slots which leads to the higher transmission rate than traditional relaying networks. To analyse EH, we deploy time-switching (TS) architecture to comprehensively study the optimal transmission time and outage performance at D. In particular, we are going to obtain closed-form expressions for outage probability (OP) with optimal TS ratio for both data symbols with both exact and approximate forms. The given simulation results show that the placement of the relay (R) plays an important role in the system performance.Web of Science253918

Characteristics of integrated mangrove-shrimp farming systems in Ben Tre Province, Vietnam: preliminary findings for organic shrimp production certification

Mangrove forests play a critical role in natural disaster resistance and provide meaningful livelihoods for localcommunities, especially integrated mangrove shrimp farming (IMSF) systems. Organic shrimp certification actuallyincreases the value chains of shrimp farming in addition to ameliorating mangrove–forest management. Identifyingtechnical issues and assessing environmental risks are the leading concerns when considering organic shrimpproduction certification. In this study, the technical practices of 30 households were investigated, and surface waterand sediment samples were collected in the IMSF models and adjacent rivers in the Thua Duc Forest ManagementBoard area, Ben Tre Province. Data collected from shrimp farming ponds and the environmental backgroundwere referred to both the Naturland and National Standards. The results showed that the average mangroveforest and shrimp pond ratio was 56.90:42.70 (%). Two technical issues were highlighted: (i) the use of rotenone,known as a toxin to kill undesirable fish before stocking shrimp, and (ii) annual shrimp pond regeneration causingincreased pollution. The data showed that higher concentrations of TSS and P-PO43- were detected in surroundingrivers, while surface water in either IMSF ponds or adjacent rivers slightly surpassed the permissible levels oftotal Fe concentration. All parameters—including heavy metals; toxic and persistent parameters; oil and greaseand coliforms analysed in surface water, and sediment samples—were lower than the detection and permissiblelevels. The results provided evidence that the IMSF’s practices and environmental characteristics were suitable forrecommending the Naturland Standards. Recommendations and technical interventions for farmers are necessaryto help reduce Fe levels and the safe use of rotenone in IMSF systems. An environmental quality monitoringprogramme at the target area should be applied when launching organic shrimp production

Variational analysis of paraconvex multifunctions

Our aim in this article is to study the class of so-called ρ- paraconvex multifunctions from a Banach space X into the subsets of another Banach space Y. These multifunctions are defined in relation with a modulus function ρ: X→ [0 , + ∞) satisfying some suitable conditions. This class of multifunctions generalizes the class of γ- paraconvex multifunctions with γ> 1 introduced and studied by Rolewicz, in the eighties and subsequently studied by A. Jourani and some others authors. We establish some regular properties of graphical tangent and normal cones to paraconvex multifunctions between Banach spaces as well as a sum rule for coderivatives for such class of multifunctions. The use of subdifferential properties of the lower semicontinuous envelope function of the distance function associated to a multifunction established in the present paper plays a key role in this study. © 2022, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature

Directional metric pseudo subregularity of set-valued mappings: a general model

This paper investigates a new general pseudo subregularity model which unifies some important nonlinear (sub)regularity models studied recently in the literature. Some slope and abstract coderivative characterizations are established. © 2019, Springer Nature B.V

TASK-BASED LANGUAGE TEACHING IN VIETNAM: RESEARCH TRENDS, FINDINGS, AND IMPLICATIONS

It is widely assumed that task-based language teaching (TBLT) has been effectively applied in EFL contexts. In Vietnam, abundant research has been implemented to examine its effects on English proficiency as well as to identify perceptions and attitudes of both teachers and learners towards using this approach in classroom contexts. This paper aims to synthesize trends in research on task-based language teaching in the context by reviewing results extracted from a corpus of 60 studies. Key aspects like effects, challenges, teacher/learner perceptions and attitudes were selected for analysis and synthesis. The results revealed that the research tended to focus more on production skills than receptive skills, and that the implementation of TBLT was reported to cause challenges for teachers, while learners tended to hold positive attitudes toward the approach. Based on the research findings, some lessons were drawn for pedagogy and future research. For successful TBLT implementation, it is suggested that teachers are informed of the effects, engaged in reflections and that exams should be shifted towards communicative competence assessment. Future research could increase sample size and treatment duration, and especially address the challenges teachers, as the main agent, encounter in implementation.  Article visualizations