Losses Analysis of Induction Motors under Ambient and Cryogenic Conditions

Cryogenic induction machines have been re-emerging as a potential solution to increase the current power density for challenging specific power applications. Compared with an ambient temperature operation, cryogenic conditions allow higher power density and increased efficiency due to the decrease of electric resistivity of conducting materials and increased cooling capability. This work focuses on the losses analysis of induction machines immersed in liquid nitrogen. Under ambient and cryogenic conditions, experimental tests are performed and presented for two induction machines, a 90 W 40 V induction machine, and a 550 W 400 V induction machine, to evaluate the mechanical, iron and residual losses, and the change of their equivalent circuit parameters

A Comparison of Cryogenic-Cooled and Superconducting Electrical Machines

This paper compares the steady-state operation of air-cooled, cryogenic-cooled and superconducting induction machines. The aim is to investigate the impact of a very low temperature and the influence of a superconducting rotor cage on the performances of standard designed, air-cooled machines. The research work includes a review of the state of the art of cryogenic-cooled and superconducting induction machines for various applications. The performances of the machines are assessed analytically by solving the single-phase equivalent circuit and considering the influence of the temperature, the skin-effect and the nonlinear behavior of superconductors. The analytical results are validated by experiments on a fractional kilowatt induction motor. The experimental activities include the characterization of the core losses at cryogenic temperature

From fiber curls to mesh waves:a platform for the fabrication of hierarchically structured nanofibers mimicking natural tissue formation

\u3cp\u3eBioinstructive scaffolds for regenerative medicine are characterized by intrinsic properties capable of directing cell response and promoting wound healing. The design of such scaffolds requires the incorporation of well-defined physical properties that mimic the native extracellular matrix (ECM). Here, inspired by epithelial tissue morphogenesis, we present a novel approach to code nanofiber materials with controlled hierarchical wavy structures resembling the configurations of native EMC fibers through using thermally shrinking materials as substrates onto which the fibers are deposited. This approach could serve as a platform for fabricating functional scaffolds mimicking various tissues such as trachea, iris, artery wall and ciliary body. Modeling affirms that the mechanical properties of the fabricated wavy fibers could be regulated through varying their wavy patterns. The nanofibrous scaffolds coded with wavy patterns show an enhanced cellular infiltration. In addition, we further investigated whether the wavy patterns could regulate transforming growth factor-beta (TGF-β) production, a key signalling pathway involved in connective tissue development. Our results demonstrated that nanofibrous scaffolds coded with wavy patterns could induce TGF-β expression without the addition of a soluble growth factor. Our new approach could open up new avenues for fabricating bioinstructive scaffolds for regenerative medicine.\u3c/p\u3

Electrical behaviour of the pump working as turbine in off grid operation

[EN] The use of pumps working as turbines (PATs) connected to the electric system, in the replacement of pressure reduction valves to reduce the excessive pressure in water distribution networks, have been studied for the last years. The introduction of PATs is very important in the water-energy nexus to promote the increase of the energy savings. As consequence, the majority of the water systems does not have access to the electrical grid and, therefore, the need to study the PATS operation off-grid is necessary. In this line, the novelty of this research is the application and optimization of a PAT in water systems when the recovery solution is off-grid type. To operate correctly, the induction machine requires an external source of reactive power, which is typically provided by the electrical grid. To supply the required reactive power, a bank of capacitors is installed at the machine terminals, so-called self-excited induction generator (SEIG). The analytical model, simulation and experimental works were performed, to analyse the SEIG behaviour. The results were applied in a SEIG-PAT system obtaining the global efficiency of the system for different speeds and loads. The global efficiency decreases 47% when off-grid operation, showing the need to optimize the electrical parameters of the generator to operate as off- grid with acceptable efficiency levels. In this framework, a tuning methodology for the SEIG capacitor bank values was developed to be automatically adjusted according to the operating point of the PAT to maximize its efficiency.This research is supported by Academic program career of the faculty of the Universitat Politecnica de Valencia 2016/2017 in the project "Maximization of the global efficiency in PATs in laboratory facility" and by FCT, through IDMEC, under LAETA, project UID/EMS/50022/2013. Besides, the authors wish to thank to the project REDAWN (Reducing Energy Dependency in Atlantic Area Water Networks) EAPA_198/2016 from INTERREG ATLANTIC AREA PROGRAMME 2014-2020 and CERIS (CEHIDRO-IST), the Hydraulic Laboratory, for the support in the conceptual work and in experiments on PATs.Capelo, B.; Pérez-Sánchez, M.; Fernandes, JFP.; Ramos, HM.; López Jiménez, PA.; Costa Branco, PJ. (2017). Electrical behaviour of the pump working as turbine in off grid operation. Applied Energy. 208:302-311. https://doi.org/10.1016/j.apenergy.2017.10.039S30231120

Electro-Hydraulic Transient Regimes in Isolated Pumps Working as Turbines with Self-Excited Induction Generators

[EN] The use of pumps working as turbines (PATs) is a sustainable technical measure that contributes to the improvement of energy efficiency in water systems. However, its performance analysis in off-grid recovery systems is a complex task that must consider both hydraulic (PAT) and electrical machines (typically a self-excited induction generator-SEIG). Aside from several kinds of research that analyze the PAT-SEIG behavior under steady-state constant hydraulic and electrical conditions, this research focuses on the analysis of PAT-SEIG transient regimes, by analyzing their variation when a sudden change occurs in the hydraulic or electrical components. Analytical models were developed to represent the operation of SEIG, PAT, and the PAT-SEIG coupled system. Hydraulic and electromechanical experimental tests validated these models. An excellent fit was obtained when analytical and experimental values were compared. With these models, the impact on the operation of the PAT-SEIG system was examined when sudden change occurred in the excitation capacitances, resistive loads, or recovered head. With a sudden increase of resistive load, the hydraulic power and SEIG stator current remain almost constant. However, there is an increase of SEIG reactive power, decreasing the PAT-SEIG efficiency. Also, with a sudden increase of SEIG capacitors or PAT hydraulic head, the SEIG stator current increases once and not again, while PAT-SEIG efficiency decreases, but the induction generator can be overloaded. The development of this research is key to the advancement of future models which can analyze the coupling of micro-hydropower solutions.This research received some support from the project REDAWN (Reducing Energy Dependency in Atlantic Area Water Networks) EAPA_198/2016 from INTERREG ATLANTIC AREA.Madeira, FC.; Fernandes, JFP.; Pérez-Sánchez, M.; López Jiménez, PA.; Ramos, HM.; Costa Branco, PJ. (2020). Electro-Hydraulic Transient Regimes in Isolated Pumps Working as Turbines with Self-Excited Induction Generators. Energies. 13(17):1-23. https://doi.org/10.3390/en13174521S1231317Postacchini, M., Darvini, G., Finizio, F., Pelagalli, L., Soldini, L., & Di Giuseppe, E. (2020). Hydropower Generation Through Pump as Turbine: Experimental Study and Potential Application to Small-Scale WDN. Water, 12(4), 958. doi:10.3390/w12040958Capelo, B., Pérez-Sánchez, M., Fernandes, J. F. P., Ramos, H. M., López-Jiménez, P. A., & Branco, P. J. C. (2017). Electrical behaviour of the pump working as turbine in off grid operation. Applied Energy, 208, 302-311. doi:10.1016/j.apenergy.2017.10.039Fecarotta, O., Aricò, C., Carravetta, A., Martino, R., & Ramos, H. M. (2014). Hydropower Potential in Water Distribution Networks: Pressure Control by PATs. Water Resources Management, 29(3), 699-714. doi:10.1007/s11269-014-0836-3Ramos, H., & Borga, A. (1999). Pumps as turbines: an unconventional solution to energy production. Urban Water, 1(3), 261-263. doi:10.1016/s1462-0758(00)00016-9Fernandes, J. F. P., Pérez-Sánchez, M., da Silva, F. F., López-Jiménez, P. A., Ramos, H. M., & Branco, P. J. C. (2019). Optimal energy efficiency of isolated PAT systems by SEIG excitation tuning. Energy Conversion and Management, 183, 391-405. doi:10.1016/j.enconman.2019.01.016Yi, Y., Zhang, Z., Chen, D., Zhou, R., Patelli, E., & Tolo, S. (2017). State feedback predictive control for nonlinear hydro-turbine governing system. Journal of Vibration and Control, 107754631774001. doi:10.1177/1077546317740013Khan, M. F., & Khan, M. R. (2016). Analysis of voltage build-up and speed disturbance ride through capability of a self-excited induction generator for renewable energy application. International Journal of Power and Energy Conversion, 7(2), 157. doi:10.1504/ijpec.2016.076521Han, Y., & Tan, L. (2020). Dynamic mode decomposition and reconstruction of tip leakage vortex in a mixed flow pump as turbine at pump mode. Renewable Energy, 155, 725-734. doi:10.1016/j.renene.2020.03.142Pérez-Sánchez, M., Sánchez-Romero, F. J., López-Jiménez, P. A., & Ramos, H. M. (2018). PATs selection towards sustainability in irrigation networks: Simulated annealing as a water management tool. Renewable Energy, 116, 234-249. doi:10.1016/j.renene.2017.09.060Pérez-Sánchez, M., López-Jiménez, P., & Ramos, H. (2018). PATs Operating in Water Networks under Unsteady Flow Conditions: Control Valve Manoeuvre and Overspeed Effect. Water, 10(4), 529. doi:10.3390/w1004052

A labelling strategy to define airtightness performance ranges of naturally ventilated dwellings: An application in southern Europe

Energy efficiency and indoor air quality are frequently-two conflicting objectives when establishing the air change rate (ACH) of a dwelling. In Europe, the northern countries have a clear focus on energy conservation, leading to an obvious awareness of the importance of airtightness, which translates into a high level of regulation and implementation. Meanwhile, the southern counterparts experience a more com-plex challenge by having predominantly passive ventilation strategies and milder climates, which often results in a more permissive approach. This work proposes an innovative labelling methodology to classify the performance of naturally ventilated dwellings. A representative sample of a southern European national built stock is used in a stochastic process to create a pool of 43,200 unique dwellings. The simulation period refers to a month of the typical heating season in the southern European mild conditions. The results test the labelling methodology. With feature selection, ACH limits, and a labelling strategy, dwellings classify according to their ability to provide adequate ACHs. The terrain was the best splitter of the dataset from the applied categorical variables. Regarding continuous variables, the airtightness was the one explaining most of the variability of the outputted ACHs, followed by the floor area. From the best performing dwellings labelled as compliant (Com), the average airtightness level was 5.3 h(-1), with 4.9 h(-1) and 5.8 h(-1) in rural and urban locations. (C) 2022 Elsevier B.V. All rights reserved.This work was financially supported by: Base Funding - UIDB/04708/2020 and Programmatic Funding - UIDP/04708/2020 of the CONSTRUCT - Instituto de I&D em Estruturas e Construcoes - funded by national funds through the FCT/MCTES (PIDDAC). The author would like to acknowledge the support of FCT - Fundacao para a Ciencia e a Tecnologia, the funding of the Doctoral Grant PD/BD/135162/2017, through the Doctoral Programme EcoCoRe. This work is supported by the European Social Fund (ESF), through the North Portugal Regional Operational Programme (Norte 2020) [Funding Reference: NORTE-06-3559-FSE-000176]. The authors also acknowledge Dr. Ricardo Deus and the Portuguese Institute for Sea and Atmosphere, I.P. (IPMA, IP) for providing the meteorological dataset for this work

Towards an airtightness compliance tool based on machine learning models for naturally ventilated dwellings

Physical models and probabilistic applications often guide the study and characterization of natural phenomena in engineering. Such is the case of the study of air change rates (ACHs) in buildings for their complex mechanisms and high variability. It is not uncommon for the referred applications to be costly and impractical in both time and computation, resulting in the use of simplified methodologies and setups. The incorporation of airtightness limits to quantify adequate ACHs in national transpositions of the Energy Performance Building Directive (EPBD) exemplifies the issue. This research presents a roadmap for developing an alternative instrument, a compliance tool built with a Machine Learning (ML) framework, that overcomes some simplification issues regarding policy implementation while fulfilling practitioners' needs and general societal use. It relies on dwellings' terrain, geometric and airtightness characteristics, and meteorological data. Results from previous work on a region with a mild heating season in southern Europe apply in training and testing the proposed tool. The tool outputs numerical information on the air change rates performance of the building envelope, and a label, accordingly. On the test set, the best regressor showed mean absolute errors (MAE) below 1.02% for all the response variables, while the best classifier presented an average accuracy of 97.32%. These results are promising for the generalization of this methodology, with potential for application at regional, national, and European Union levels. The developed tool could be a complementary asset to energy certification programmes of either public or private initiatives. (c) 2023 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).This work was financially supported by: Base Funding - UIDB/04708/2020 and Programmatic Funding - UIDP/04708/2020 of the CONSTRUCT - Instituto de I & D em Estruturas e Construcoes - funded by national funds through the FCT/MCTES (PIDDAC). The author would like to acknowledge the support of FCT - Fundacao para a Ciencia e a Tecnologia, the funding of the Doctoral Grant PD/BD/135162/2017, through the Doctoral Programme EcoCoRe. This work is supported by the European Social Fund (ESF), through the North Portugal Regional Operational Programme (Norte 2020) [Funding Reference: NORTE-06-3559-FSE-000176]

Effects of a Supraseasonal Drought on the Ecological Attributes of Plagioscion squamosissimus (Heckel, 1840) (Pisces, Sciaenidae) in a Brazilian Reservoir

The aim of this study was to evaluate the effect of a supraseasonal drought on the ecological attributes of Plagioscion squamosissimus. The fish were caught quarterly from February 2010 to November 2014 using gill nets in the reservoir of Santa Cruz, Rio Grande do Norte, Brazil. The abundance of the species was evaluated with the catch per unit effort (CPUE) metric and then correlated with the accumulated rainfall and water volume of the reservoir. The diet of the fish was evaluated using the feeding index (IAi). The proportional similarity index (PS i ) was used to evaluate the variation in the niches of the fish. The body condition was inferred through the relative condition factor, and its variation was assessed with ANOVA. A reduction in the abundance of the species that were positively correlated with the reservoir water volume was observed. The diet of the fish comprised shrimp, gastropods, fish, insects, shrimp larvae, and vegetable matter, with shrimp being the major component. PS i showed the occurrence of individual specialization during November 2013 and November 2014. The relative condition factor was not correlated with a reduction in the water volume of the reservoir. The supraseasonal drought did not affect the relative condition factor, diet, and the trophic niche, but it did affect the species abundance

Polymeric nanoparticles loaded with the 3,5,3'-triiodothyroacetic acid (Triac), a thyroid hormone: factorial design, characterization, and release kinetics

This present investigation deals with the development and optimization of polymeric nanoparticle systems loaded with 3,5,3′-triiodothyroacetic acid (Triac). A '2 POT. 11-6' fractional factorial design and another '2 POT. 2' factorial design were used to study the contrasts on particle size distribution, morphology, surface charge, drug content, entrapment efficiency, and in vitro drug release profiles. The independent variables were the concentration of Triac, type and quantity of both polymer and oil, quantity of Span™ 60 and Tween® 80, volume of solvent and water, and velocity of both magnetic stirring and the transfer of the organic phase into the aqueous solution. The results of optimized formulations showed a narrow size distribution with a polydispersity index lower than 0.200. The particle sizes were on average 159.6 nm and 285.6 nm for nanospheres and nanocapsules, respectively. The zeta potential was higher than 20 mV (in module) and the entrapment efficiency was nearly 100%. A high-performance liquid chromatography method was developed, validated, and efficiently applied to Triac quantification in colloidal suspension. The main independent variables were the type and quantity of the polymer and oil. In vitro drug release profile depicted several features to sustain Triac release. Different formulations showed various release rates indicating an interaction between Triac and other formulation compounds such as polymer and/or oil quantity. Two different models were identified (biexponential and monoexponential) that allowed the control of both the release rate and Triac concentration. Thus, the prepared nanoparticles described here may be of clinical importance in delivering Triac for thyroid treatment.CNPqFAPES