Implementation and Verification of a Pollingbased MAC Layer Protocol for PLC

Prjecte final de carrera realitzat en col.laboració amb Institute of the Industrial Information TechnologyThe aim of this project is to create a Polling-based MAC Layer Protocol for PLC. The first step is to look up some information about how the protocol is and then create the best design. This protocol is inside the Datalink layer, which function is to control the flow of frames inside the network and to make it as efficient as possible. A master/slave typology is used. There is a device (master) that indicates when a slave can transmit a frame. The main advantage of this typology is the low collision risk. The second step is the VHDL implementation which is made in Modelsim. This program is a simulator too, so the functional correctness of the design can be checked with it. Inside this step, there are two stages: firstly the ARQ scheme is made and when it works, the rest of the design is implemented. It is important to simulate the code because all the process, until the result is reached, can be studied, but it does not mean it works in a real device. An Altera kit with a Cyclon III FPGA is used to make the finals tests

Putting socio-cultural theories to work in supporting mathematics teachers' professional development

We discuss the contributions of socio-cultural theories to research and design of interventions directed at the professional development of mathematics teachers. We explain how these theories have been put to work in the field. We also bring to attention specific issues arising in the field for which development and adaptation of socio-cultural theory might be a useful resource

Building learning opportunities in classrooms of disadvantage: rethinking the learning trajectories

Researching learning trajectories in classrooms of disadvantage introduces specific challenges as well as opportunities. Situating our work within design research, we illustrate the power of theoretical approaches in which close attention is paid to both learners' conceptual developments and the means capable of supporting such developments for all learners. We illustrate how considerations of teachers' learning can and should inform the formulation of (students') learning trajectories, if these are to become viable outside of research studies

Reciprocal relations of relative size in the instructional context of fractions as measures

The presented study is part of a bigger design and research enterprise in the teaching of fractions as measures. We analyze extracts of a teaching session with a single fifth grade student, in which he flexibly compared the relative sizes of the lengths of three drinking straws, skillfully using unitary, proper, and improper fractions. We identify aspects of his prior instructional experiences that supported the emergence of his relatively sophisticated ways of reasoning. Findings suggest that supporting students' reasoning about reciprocal relations of relative size can be a viable goal in an instructional agenda on fractions as measures

Resources for teaching: supporting a Mexican teacher’s learning

We analyze the role played by a teaching resource in effectively supporting a professional development collaboration with Irene, a Mexican public-school teacher. The resource is an instructional sequence on fractions that was developed through a series of design experiments in Mexican classrooms. As a result of this collaboration, Irene modified significantly her instructional practices. We discuss how the instructional sequence contributed to Irene’s renewed view of a mathematics classroom by providing her with guidance that was explicit, specific, and achievable

Advanced hybrid system for ammonium valorization as liquid fertilizer from treated urban wastewaters: validation of natural zeolites pretreatment and liquid-liquid membrane contactors at pilot plant scale

This study evaluates a hybrid system combining zeolites as a sorption stage and a hollow fiber membrane contactor (HFMC) for ammonia (NH3) recovery from treated urban wastewater. Ion exchange with zeolites was selected as an advanced pretreatment and concentration step before the HFMC. The system was tested with wastewater treatment plant (WWTP) effluent (mainstream, 50 mg N-NH4/L) and anaerobic digestion centrates (sidestream, 600–800 mg N-NH4/L) from another WWTP. Natural zeolite, primarily clinoptilolite, demonstrated effective desorption of retained ammonium using a 2% NaOH solution in a closed-loop configuration, resulting in an ammonia-rich brine that enabled over 95% NH3 recovery using polypropylene HFMCs. A 1 m3/h demonstration plant processed both urban wastewaters, which were pretreated by ultrafiltration, removing over 90% of suspended solids and 60–65% of COD. The 2% NaOH regeneration brines (2.4–5.6 g N-NH4/L) were treated in a closed-loop HFMC pilot system, producing 10–15% N streams with potential use as liquid fertilizers. The resulting ammonium nitrate was free of heavy metals and organic micropollutants, making it suitable for use as liquid fertilizer. This comprehensive N management solution for urban wastewater applications can contribute to local economies while achieving reduced N discharge and circularity goals.LIFE ENRICH | Ref. LIFE16 ENV/ES/000375Ministerio de Ciencia e Innovación | Ref. PID2020-114401RB-C21Ministerio de Economía y Competitividad | Ref. CTM2017-85346-RGeneralitat de Cataluña | Ref. 2017-SGR-312Ministerio de Ciencia e Innovación | Ref. RYC2021-030966-

Valorisation of N and P from waste water by using natural reactive hybrid sorbents: Nutrients (N,P,K) release evaluation in amended soils by dynamic experiments

The removal of nutrients (nitrogen (N), phosphorous (P)) from waste water has become a resource recovery option in recent regulations worldwide, as observed in the European Union. Although both of these nutrients could be recovered from the sludge line, > 70-75% of the N and P is discharged into the water line. Efforts to improve the nutrient recovery ratios have focused on developing low-cost technologies that use sorption processes. In this study, a natural zeolite (clinoptilolite type) in its potassium (K) form was impregnated with hydrated metal oxides and used to prepare natural hybrid reactive sorbents (HRS) for the simultaneous recovery of ammonium (NH4+) and phosphate (PO43 −) from treated urban waste water. Three unfertile soils (e.g., one acidic and two basic) amended with N-P-K charged HRS were leached with deionized water (e.g. to simulate infiltration in the field) at two- and three-day time intervals over 15 different leaching cycles (equivalent to 15 bed volumes). The N-P-K leaching profiles for the three charged hybrid sorbents exhibited continuous nutrient release, with their values dependent on the composition of minerals in the soils. In the basic soil that is rich in illite and calcite, the release of potassium (K+) and ammonium (NH4+) is favoured by-ion exchange with calcium (Ca2 +) and accordingly diminishes the release of phosphate (PO43 −) due to its limited solubility in saturated calcite solutions (pH 8 to 9). The opposite is true for sandy soils that are rich in albite (both acidic and basic), whereas the release of NH4+ and K+ was limited and the values of both ions measured in the leaching solutions were below 1 mg/L. Their leaching solutions were poor in Ca2 +, and the release of PO43 − was higher (up to 12 mg P-PO43 −/L). The nutrient releases necessary for plant growth were provided continuously and were controlled primarily by the soil mineral dissolution rates fixing the soil aqueous solution composition (e.g. pH and ionic composition; in particular, the presence of calcite is a determinant for nutrient release, especially in alkaline soils). The N-P-K charged HRS sorbents that were used for soil amendment may be an alternative for avoiding nutrient leaching and reaching the goals of soil sustainability in agriculture and reducing the nutrient overloading of surface waters