Electric machines have broadly been used in many industries including the transportation industry. With the evolving trend of electrification in transportation, electric machines with higher power density and higher efficiency are demanded and, thus, more stringent thermal management requirements are needed for electrified vehicle applications. This study comprehensively presents various important aspects of thermal management in electric machines with the main focus on transportation applications. Design considerations, challenges, and methods for enhanced thermal management are discussed. Fundamental thermal properties of common materials are presented and sources of losses in various parts of machines are explained. Furthermore, typical cooling techniques and thermal analysis approaches for electric machines are reviewed in detail. This study will serve as a reference guideline for machine designers, who are interested in thermal management, and for thermal researchers working on electric machines.
Objective: To date, very few studies investigating neurocognitive deficits in COVID-19 have been published. This case series addresses cognition in post-COVID-19 patient by describing three patients in acute rehabilitation to inform a model of cognitive sequelae of COVID-19. Methods: Three English-speaking inpatients with severe symptoms and long-term intensive care unit (ICU) treatment are described. All patients had a premorbid history of hypertension and hyperlipidemia and experienced delirium and hypoxemia when hospitalized. Patient 1 is a 62-year-old male with 15 years of education with additional history of obstructive sleep apnea and type 2 diabetes. Patient 2 is a 73-year-old female with 12 years of education with a premorbid medical history of alcohol use disorder and Guillain-Barre syndrome. Patient 3 is a 75-year-old male with 14 years of education. No patients had premorbid psychiatric histories. Results: The three patients demonstrated deficits on formal neuropsychological testing, particularly with encoding and verbal fluency. Memory measures improved with a more structured story memory task compared to a lessstructured verbal list-learning task, suggesting executive dysfunction impacted learning. None of the patients demonstrated rapid forgetting of information. Two patients endorsed new depressive and/or anxiety symptoms. Conclusions: The results suggest evidence for neurocognitive deficits after severe COVID-19 infection, particularly in encoding and verbal fluency. These results were interpreted with caution given the limited number of patients and the telephone-based battery. The specific mechanism that caused these cognitive deficits in these individuals remains unclear. A proposed three-stage model of cognitive dysfunction is described to help guide future research.
Diffusion-Induced Recrystallization (DIR) is investigated in size mismatched thin film interdiffusion couples. New grains formed in the diffusion zone are characterized by distinctive composition levels which seem to be characteristic to the interdiffusing materials. In this paper, we analyzed sputter-deposited Ni/Pd films. The lattice mismatch and the driving force are varied by pre-alloying one side of the diffusion couples. Recrystallization was detected after heat treatment by transmission electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffractometry. We determined characteristic concentrations from XRD data. Remarkably, the difference between the concentration inside newly formed grains and that of the parent layers remains practically constant, when initial layer concentration is varied. Also, the characteristic compositions are nearly independent of temperature. A thermo-mechanic model has been derived, which demonstrates that the observed concentration differences are such that the stress in front of the moving grain boundary reaches a maximum close to the ideal strength of the host material.
Purpose: This paper present thermal and microstructural and microchemical analyses
were conducted on the unmodified experimental alloy Al20Si3Cu (B390.1) solidified in
the High Temperature Universal Metallurgical Simulator and Analyser (HT UMSA) under
atmospheric pressure (0.1 MPa) and a relatively low solidification rate (-1.2 K/s just after end
of solidification), for identification of the thermal events during solidification and the phases
in the as-cast structure. Design/methodology/approach: The HT UMSA platform, using a
low thermal mass stainless steel cup, enabled the acquisition of high resolution thermal
analysis data.
Design/methodology/approach: A new approach for de-convolution of the first
derivative thermal curves allowed detailed thermal and microstructural phase histories to be
documented for solidification of Al-Si alloys. Recently developed SEM/EDS methodology
allowed to determine composition and distribution of individual phases that are smaller than
the X–ray volume.
Findings: Simultaneous consideration of thermal microstructural and microchemical
information allowed detailed understanding of the series of events that take place during
solidification of Al casting alloy with complex chemistry. In our hypereutectic alloy we
document growth of Al(1) dendrites and formation of secondary Si(2) and Al(2) phases all at
temperatures higher than the binary equilibrium Al-Si eutectic temperature of 850 K.
Practical implications: Even at this slow solidification rate detailed understanding of
the solidification microstructure requires consideration of non-equilibrium processes during
solidification.
Originality/value: We propose an original set of hypotheses that consistently explain the
observed non-equilibrium solidification behaviour. Proof of these hypotheses is beyond the
scope of this work.
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