290 research outputs found

    Design of Electrically Excited Synchronous Machines to Achieve Unity Power Factor in Field Weakening for Long-Haul Electric Trucks

    Get PDF
    Electrically excited synchronous machines are a promising candidate for long-haul electric trucks due to excellent capability in field weakening. This study aims at concluding a structural design process of the machine for long-haul electric trucks. A criterion of machine design to achieve unity power factor in field-weakening is derived. With this criterion, a minimum level of field current is decided in the design process. Parametric sweeps are applied to decide the optimum slot geometries for stator and rotor. The optimization of slot geometries is multi-objective. In this study, it is to maximize the peak torque while minimize iron-core losses simultaneously. Pareto frontier is used to identify the optimum solutions. The performance of the finalized design is then evaluated. The high efficiency area is located at high-speed low-torque region which is preferable for long-haul electric trucks. Balance is achieved between copper and iron-core losses during steady-speed intervals of the test cycles which leads to minimum losses in total

    Dynamic Current Control to Compensate for Magnetic Mutual Coupling in Electrically Excited Synchronous Machines

    Get PDF
    Electrically excited synchronous machines have become an attractive solution to electric vehicles. Equipped with a field winding in the rotor, the excitation of the machine is controllable. However, due to the magnetic mutual coupling between the stator and rotor windings, a voltage will be induced in the field winding in case of a current rise in the stator winding and vice versa. In this study, a dynamic current control algorithm with compensation for magnetic mutual coupling is proposed. A first-order response of current rise is expected. To achieve this, the controller consists of three parts. The first part is the feed forward of cross-coupling terms due to Park transform. The second part takes care of the resistances and selfinductances. The third part takes care of the mutual inductances. Finally, the outputs from the three parts are summed up to be the total output from the controller

    MOLECULAR DISSECTION AND FUNCTIONAL DEFINITION OF ESTROGEN-RELATED RECEPTOR ALPHA SIGNALING PATHWAY

    Get PDF
    <p>The estrogen-related receptor alpha (ERR&alpha;) is an orphan nuclear receptor (NR) with no natural ligand identified. Recent studies report that ERR&alpha; expression and activity correlate with poor prognosis in breast cancer. It is also suggested that ERR&alpha; is involved in tumor growth and progression, thus this receptor may be a therapeutic target in the treatment of breast cancer. However, the specific role of ERR&alpha; in breast cancer is not fully understood. Similar to other nuclear receptors, ERR has been suggested to regulate target gene transcription through both classical (direct DNA binding) and non-canonical (tethering mechanisms) to effect various aspects of tumor pathogenesis, such as angiogenesis, regulation of hypoxic response, tumor growth, and migration. Thus, the objective of this dissertation research is to explore the roles of ERR&alpha; in breast cancer by (a) identifying novel ERR&alpha; target genes important for tumor pathogenesis, (b) characterizing the molecular mechanism of non-canonical actions of ERR&alpha;-mediated gene transcription, and (c) examining the structure basis of ERR&alpha; antagonism for future pharmaceutical exploitation. First, we identified an ERR&alpha; target gene, ECM1, which is relevant to breast cancer angiogenesis. The role of ECM1 in angiogenesis was confirmed by endothelial tube formation assay. We further showed that knocking down ECM1 has a dramatic inhibitory effect on tumor xenograft growth. This result, for the first time, directly demonstrates the role of ECM1 in tumor environment and further sheds light on the significance of ERR&alpha-regulated genes in tumors angiogenesis. Next, we explored the molecular mechanism of ERR&alpha; non-canonical pathways using transcriptional reporter assay and ERR&alpha; DNA-binding domain (DBD) mutants. We discovered that the expression of carbonic anhydrase 9 (CA9), a target gene of one of the ERR&alpha; tethering partner hypoxia inducible factor-1 (HIF-1), does not require direct binding of ERR&alpha; to DNA but its DBD is indispensible. These results reflect on the importance of ERR&alpha; DBD even in the non-canonical signaling of ERR&alpha;, which brings challenges to dissecting ERR&alpha; canonical/non-canonical pathways in the future. Finally, to determine the molecular mechanisms underlying ERR&alpha; antagonism, we probed the conformations of ERR&alpha; upon antagonist treatments. M13 phage display was used to screen for ERR&alpha;-interacting peptides. We identified peptides that interact with ERR&alpha; in the activation function 2 (AF2) domain, some of which are able to distinguish the binding of different classes of ERR&alpha; antagonists. Cumulatively, these studies have explored the biological functions of ERR&alpha; and the molecular basis ERR&alpha;-mediated signaling pathways.</p>Dissertatio

    Observations of Field Current and Field Winding Temperature in Electrically Excited Synchronous Machines with Brushless Excitation

    Get PDF
    Electrically excited synchronous machines have become an alternative in electrification of transportations and renewable power generations. To reduce the extra effort in the maintenance of sliprings and brushes for field excitation, brushless excitation has been developed. However, when brushless excitation is adopted, the field winding becomes physically inaccessible when the machine is rotating. To solve this problem, an algorithm is proposed in this study to observe the field current and field winding temperature of an EESM with brushless excitation. The stator currents are measured and then used to correct the machine state predictor. The correction of the state prediction is interpreted to adjust the field winding resistance and temperature value. The algorithm is evaluated in simulations. The estimations of field current and field winding temperature track the measurements successfully

    Convective Heat Transfer Coefficients and Mechanical Loss Evaluation of Oil Splashing in Direct Cooled Electrically Excited Hairpin Motors

    Get PDF
    There in an increasing trend in the use of the direct oil cooling in electric motors for automotive because of the increasing demand of high power/torque density as well as overload capability. One of the most immediate solution is to fill the housing with some oil level and benefit of the heat transfer from the oil splashing. The mechanical losses coming from the rotor rotation are well known and they represent a significant challenge, especially at high speed and high oil level. Therefore, the derivation and prediction of these losses have not been properly investigated leading to a lack in the current literature. Moving Particles Simulation (MPS) method is used in Particleworks to calculate the mechanical losses caused by the oil viscosity and convective heat transfer coefficients (HTC) are extracted for a 250 kW Electrically Excited Synchronous Machine at different speeds and oil levels

    Hybrid Artificial Root Foraging Optimizer Based Multilevel Threshold for Image Segmentation

    Get PDF
    This paper proposes a new plant-inspired optimization algorithm for multilevel threshold image segmentation, namely, hybrid artificial root foraging optimizer (HARFO), which essentially mimics the iterative root foraging behaviors. In this algorithm the new growth operators of branching, regrowing, and shrinkage are initially designed to optimize continuous space search by combining root-to-root communication and coevolution mechanism. With the auxin-regulated scheme, various root growth operators are guided systematically. With root-to-root communication, individuals exchange information in different efficient topologies, which essentially improve the exploration ability. With coevolution mechanism, the hierarchical spatial population driven by evolutionary pressure of multiple subpopulations is structured, which ensure that the diversity of root population is well maintained. The comparative results on a suit of benchmarks show the superiority of the proposed algorithm. Finally, the proposed HARFO algorithm is applied to handle the complex image segmentation problem based on multilevel threshold. Computational results of this approach on a set of tested images show the outperformance of the proposed algorithm in terms of optimization accuracy computation efficiency

    Mechanotransduction regulates inflammation responses of epicardial adipocytes in cardiovascular diseases

    Get PDF
    Adipose tissue is a crucial regulator in maintaining cardiovascular homeostasis by secreting various bioactive products to mediate the physiological function of the cardiovascular system. Accumulating evidence shows that adipose tissue disorders contribute to several kinds of cardiovascular disease (CVD). Furthermore, the adipose tissue would present various biological effects depending on its tissue localization and metabolic statuses, deciding the individual cardiometabolic risk. Crosstalk between adipose and myocardial tissue is involved in the pathophysiological process of arrhythmogenic right ventricular cardiomyopathy (ARVC), cardiac fibrosis, heart failure, and myocardial infarction/atherosclerosis. The abnormal distribution of adipose tissue in the heart might yield direct and/or indirect effects on cardiac function. Moreover, mechanical transduction is critical for adipocytes in differentiation, proliferation, functional maturity, and homeostasis maintenance. Therefore, understanding the features of mechanotransduction pathways in the cellular ontogeny of adipose tissue is vital for underlining the development of adipocytes involved in cardiovascular disorders, which would preliminarily contribute positive implications on a novel therapeutic invention for cardiovascular diseases. In this review, we aim to clarify the role of mechanical stress in cardiac adipocyte homeostasis and its interplay with maintaining cardiac function
    corecore