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RISS 인기검색어
- 검색키워드
- 저자 : Jose Maia (검색결과 4 건)
- 무료
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- 유료
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Nonisentropic Phenomenological Model of a Reciprocating Compressor
Willian Moreira Duarte,Juan Jose Garcia Pabon,Antônio Augusto Torres Maia,LUIZ MACHADO 대한설비공학회 2019 International Journal Of Air-Conditioning and Refr Vol.27 No.4
This paper presents the development of a numerical, iterative and nonisentropic model for the thermodynamic processes of a reciprocating compressor of a refrigeration system operating at steady state. The mathematical model was implemented using the scientific software Engineering Equation Solver (EES) and it is based on the application of the energy equations in four regions of the compressor: inlet duct and chambers of pre-compression, compression, and post-compression. The model was validated with experimental data collected from an open-drive reciprocating compressor, operating with the refrigerant R-134a at different suction and discharge pressures and with different compressor rotational speeds. Model validation was made comparing the values of the mass flow rate and the discharge temperature of the compressor generated by the model with their corresponding experimental values for 33 experimental tests, the mean relative difference was − 0.2% for the discharge temperature and 2.9% for mass flow rate. In this validation, the output variables of the model were calculated considering the uncertainties from the input variables. The theoretical mean standard uncertainty is 2% for discharge temperature and 6% for mass flow rate. An analysis of the capacitive and thermal performance of the compressor was made using the model, which demonstrates a decrease in the capacitive and thermal efficiencies for increasing the pressure ratio or clearance volume.
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Detection and Diagnosis Solutions for Fault-Tolerant VSI
Cordeiro, Armando,Palma, Joao C.P.,Maia, Jose,Resende, Maia J. The Korean Institute of Power Electronics 2014 JOURNAL OF POWER ELECTRONICS Vol.14 No.6
This paper presents solutions for fault detection and diagnosis of two-level, three phase voltage-source inverter (VSI) topologies with IGBT devices. The proposed solutions combine redundant standby VSI structures and contactors (or relays) to improve the fault-tolerant capabilities of power electronics in applications with safety requirements. The suitable combination of these elements gives the inverter the ability to maintain energy processing in the occurrence of several failure modes, including short-circuit in IGBT devices, thus extending its reliability and availability. A survey of previously developed fault-tolerant VSI structures and several aspects of failure modes, detection and isolation mechanisms within VSI is first discussed. Hardware solutions for the protection of power semiconductors with fault detection and diagnosis mechanisms are then proposed to provide conditions to isolate and replace damaged power devices (or branches) in real time. Experimental results from a prototype are included to validate the proposed solutions.
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Detection and Diagnosis Solutions for Fault-Tolerant VSI
Armando Cordeiro,Joao C. P. Palma,Jose Maia,Maia J. Resende 전력전자학회 2014 JOURNAL OF POWER ELECTRONICS Vol.14 No.6
This paper presents solutions for fault detection and diagnosis of two-level, three phase voltage-source inverter (VSI) topologies with IGBT devices. The proposed solutions combine redundant standby VSI structures and contactors (or relays) to improve the fault-tolerant capabilities of power electronics in applications with safety requirements. The suitable combination of these elements gives the inverter the ability to maintain energy processing in the occurrence of several failure modes, including short-circuit in IGBT devices, thus extending its reliability and availability. A survey of previously developed fault-tolerant VSI structures and several aspects of failure modes, detection and isolation mechanisms within VSI is first discussed. Hardware solutions for the protection of power semiconductors with fault detection and diagnosis mechanisms are then proposed to provide conditions to isolate and replace damaged power devices (or branches) in real time. Experimental results from a prototype are included to validate the proposed solutions.
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Inclusion of bioclimatic variables in genetic evaluations of dairy cattle
Negri, Renata,Aguilar, Ignacio,Feltes, Giovani Luis,Machado, Juliana Dementshuk,Neto, Jose Braccini,Costa-Maia, Fabiana Martins,Cobuci, Jaime Araujo Asian Australasian Association of Animal Productio 2021 Animal Bioscience Vol.34 No.2
Objective: Considering the importance of dairy farming and the negative effects of heat stress, more tolerant genotypes need to be identified. The objective of this study was to investigate the effect of heat stress via temperature-humidity index (THI) and diurnal temperature variation (DTV) in the genetic evaluations for daily milk yield of Holstein dairy cattle, using random regression models. Methods: The data comprised 94,549 test-day records of 11,294 first parity Holstein cows from Brazil, collected from 1997 to 2013, and bioclimatic data (THI and DTV) from 18 weather stations. Least square linear regression models were used to determine the THI and DTV thresholds for milk yield losses caused by heat stress. In addition to the standard model (SM, without bioclimatic variables), THI and DTV were combined in various ways and tested for different days, totaling 41 models. Results: The THI and DTV thresholds for milk yield losses was THI = 74 (-0.106 kg/d/THI) and DTV = 13 (-0.045 kg/d/DTV). The model that included THI and DTV as fixed effects, considering the two-day average, presented better fit (-2logL, Akaike information criterion, and Bayesian information criterion). The estimated breeding values (EBVs) and the reliabilities of the EBVs improved when using this model. Conclusion: Sires are re-ranking when heat stress indicators are included in the model. Genetic evaluation using the mean of two days of THI and DTV as fixed effect, improved EBVs and EBVs reliability.
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