Design and Validation of A High-Power, High Density All Silicon Carbide Three-Level Inverter

Transportation electrification is clearly the road toward the future. Compared to internal combustion engine, the electrified vehicle has less carbon-dioxide emission, less maintenance costs and less operation costs. It also offers higher efficiency and safety margin. More importantly, it relieves human’s dependence on conventional fossil energy. In the electrification progress, the revolution of electric traction drive systems is one of the most important milestone. The traction system should keep high efficiency to avoid performance reduction. Moreover, the motor drive should be designed within limited space without sacrificing output power rating. Based on the road map from US Drive Electrical and Electronics Technical Team, US Department of Energy, a gap is still there between roadmap target and the state-of-art. To fill the gap, this dissertation performs a systematic research in motor drive system for traction inverters. This paper starts from optimal theoretical design of power converters by using loss model and real-time simulation system. Based on optimal paper design, hardware design is implemented. The component design for converter, such as the laminated busbar, are the focus in this dissertation. The optimized busbar structure can effectively reduce stray inductance in the current-commutation loop, reducing switching overshoots of power modules and increasing semiconductor reliability. The system-level design and trade-off is also analyzed and illustrated by using a 250kW three-level T-type neutral-point clamped converter. The design has reached high efficiency and high-power density. The converter system is also evaluated through comprehensive tests, such as double-pulse tests and continuous tests. The test setup, test condition and test result analysis are discussed in the dissertation. In the end, the dissertation also proposed an improved impedance characterization method for components parasitic inductance measurement in traction drive systems, such as laminated busbar, power module and capacitors. The characterization shares better accuracy and can be customized for device under test with any geometry

Flow Measurement: An Inverse Problem Formulation

This paper proposes a new mathematical formulation for flow measurement based on the inverse source problem for wave equations with partial boundary measurement. Inspired by the design of acoustic Doppler current profilers (ADCPs), we formulate an inverse source problem that can recover the flow field from the observation data on a few boundary receivers. To our knowledge, this is the first mathematical model of flow measurement using partial differential equations. This model is proved well-posed, and the corresponding algorithm is derived to compute the velocity field efficiently. Extensive numerical simulations are performed to demonstrate the accuracy and robustness of our model. Our formulation is capable of simulating a variety of practical measurement scenarios

Melatonin reverses type 2 diabetes-induced cognitive deficits via attenuation of oxidative/nitrosative stress and NF-κB-mediated neuroinflammation in rat hippocampus

Purpose: To evaluate the protective effect of melatonin on diabetes-induced cognitive dysfunction. Methods: Rats were fed a high-fat diet + streptozotocin (HFD + STZ) for 15 weeks to induce type 2 diabetes (HFD + STZ group). At the end of the 15-week induction of diabetes, cognitive function in the diabetic rats was estimated using a Morris water maze and an object recognition task. Next, the diabetic rats were treated with melatonin (10 mg/ kg, po) for 3 weeks. Thereafter, cognitive function was reevaluated in the melatonin-treated diabetic rats (melatonin group). Results: There was a significant (p < 0.01) decrease in the serum glucose and insulin in melatonintreated diabetes type 2 rats compared with that of diabetes type 2 rats exposed to only HFD + STZ. Treatment with melatonin (10 mg/kg, po) for 3 weeks in diabetic type 2 rats also caused a significant increase (p < 0.01) in the time spent in the target quadrant and preference index in diabetic rats compared with the HFD + STZ group. There were significant decreases in reactive oxygen species (ROS), oxido-nitrosative stress markers, including thiobarbituric acid reactive substances (TBARS), nitrite, and depleted glutathione (GSH) level in the hippocampus of melatonin-treated group, compared with the HFD + STZ-treated group. Moreover, the melatonin-treated group showed significant inhibition of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) and reduction in the levels of proinflammatory cytokines. Conclusion: The results demonstrate that melatonin prevents cognitive dysfunction in type 2 diabetic rats by attenuating oxido-nitrosative stress and NF-κB-mediated neuroinflammation. This effect suggests that melatonin may be useful for the management of cognitive dysfunction in patients suffering from diabetes. Keywords: Cognitive dysfunction, Melatonin, Neuroinflammation, Nuclear factor kappa-light-chainenhancer of activated B cells (NF-κB), Oxido-nitrosative stress, Type 2 diabete

Estimating continental river basin discharges using multiple remote sensing data sets

AbstractRivers act as a source of fresh water for terrestrial life, yet the discharges are poorly documented since the existing direct observations are inadequate and some observation stations have been interrupted or discontinued. Discharge estimates using remote sensing thus have a great potential to supplement ground observations. There are remote sensing methods established to estimate discharge based on single parameter derived relationships; however, they are limited to specific sections due to their empirical nature. In this study, we propose an innovative method to estimate daily discharges for continental rivers (with river channel widths >800m (Birkett and Beckley, 2010)) using two satellite derived parameters. Multiple satellite altimetry data and Moderate Resolution Imaging Spectroradiometer (MODIS) data are used to provide a time series of river stages and effective river width. The derived MODIS and altimetry data are then used to optimize unknown parameters in a modified Manning's equation. In situ measurements are used to derive rating curves and to provide assessments of the estimated results. The Nash–Sutcliffe efficiency values for the estimates are between 0.60 and 0.97, indicating the power of the method and accuracy of the estimations. A comparison with a previously developed empirical multivariate equation for estimating river discharge shows that our method produces superior results, especially for large rivers. Furthermore, we found that discharge estimates using both effective river width and stage information consistently outperform those that only use stage data

Depletion of PHD3 protects heart from ischemia/reperfusion injury by inhibiting cardiomyocyte apoptosis

PHD3, a member of a family of Prolyl-4 Hydroxylase Domain (PHD) proteins, has long been considered a pro-apoptotic protein. Although the pro-apoptotic effect of PHD3 requires its prolyl hydroxylase activity, it may be independent of HIF-1α, the common substrate of PHDs. PHD3 is highly expressed in the heart, however, its role in cardiomyocyte apoptosis remains unclear. This study was undertaken to determine whether inhibition or depletion of PHD3 inhibits cardiomyocyte apoptosis and attenuates myocardial injury induced by ischemia-reperfusion (I/R). PHD3 knockout mice and littermate controls were subjected to left anterior descending (LAD) coronary artery ligation for 40 minutes followed by reperfusion. Histochemical analysis using Evan’s Blue, triphenyl-tetrazolium chloride and TUNEL staining, demonstrated that myocardial injury and cardiomyocyte apoptosis induced I/R injury were significantly attenuated in PHD3 knockout mice. PHD3 knockout mice exhibited no changes in HIF-1α protein level, the expression of some HIF target genes or the myocardium capillary density at physiological condition. However, depletion of PHD3 further enhanced the induction of HIF-1α protein at hypoxic condition and increased expression of HIF-1α inhibited cardiomyocyte apoptosis induced by hypoxia. In addition, it has been demonstrated that PHD3 plays an important role in ATR/Chk1/p53 pathway. Consistently, a prolyl hydroxylase inhibitor or depletion of PHD3 significantly inhibits the activation of Chk1 and p53 in cardiomyocytes and the subsequent apoptosis induced by doxorubicin, hydrogen peroxide or hypoxia/re-oxygenation. Taken together, these data suggest that depletion of PHD3 leads to increased stabilization of HIF-1α and inhibition of DNA damage response, both of which may contribute to the cardioprotective effect seen with depletion of PHD3

Mapping evapotranspiration with high-resolution aircraft imagery over vineyards using one- and two-source modeling schemes

Thermal and multispectral remote sensing data from low-altitude aircraft can provide high spatial resolution necessary for sub-field ( 10 m) and plant canopy (1 m) scale evapotranspiration (ET) monitoring. In this study, highresolution (sub-meter-scale) thermal infrared and multispectral shortwave data from aircraft are used to map ET over vineyards in central California with the two-source energy balance (TSEB) model and with a simple model having operational immediate capabilities called DATTUTDUT (Deriving Atmosphere Turbulent Transport Useful To Dummies Using Temperature). The latter uses contextual information within the image to scale between radiometric land surface temperature (TR) values representing hydrologic limits of potential ET and a non-evaporative surface. Imagery from 5 days throughout the growing season is used for mapping ET at the sub-field scale. The performance of the two models is evaluated using tower-based measurements of sensible (H) and latent heat (LE) flux or ET. The comparison indicates that TSEB was able to derive reasonable ET estimates under varying conditions, likely due to the physically based treatment of the energy and the surface temperature partitioning between the soil/cover crop inter-row and vine canopy elements. On the other hand, DATTUTDUT performance was somewhat degraded presumably because the simple scaling scheme does not consider differences in the two sources (vine and inter-row) of heat and temperature contributions or the effect of surface roughness on the efficiency of heat exchange. Maps of the evaporative fraction (EFDLE/(H CLE)) from the two models had similar spatial patterns but different magnitudes in some areas within the fields on certain days. Large EF discrepancies between the models were found on 2 of the 5 days (DOY 162 and 219) when there were significant differences with the tower-based ET measurements, particularly using the DATTUTDUT model. These differences in EF between the models translate to significant variations in daily water use estimates for these 2 days for the vineyards. Model sensitivity analysis demonstrated the high degree of sensitivity of the TSEB model to the accuracy of the TR data, while the DATTUTDUT model was insensitive to systematic errors in TR as is the case with contextual-based models. However, it is shown that the study domain and spatial resolution will significantly influence the ET estimation from the DATTUTDUT model. Future work is planned for developing a hybrid approach that leverages the strengths of both modeling schemes and is simple enough to be used operationally with high-resolution imagery

TGFβ3-mediated induction of Periostin facilitates head and neck cancer growth and is associated with metastasis

The matrix-specific protein periostin (POSTN) is up-regulated in human cancers and associated with cancer growth, metastasis and angiogenesis. Although the stroma of cancer tissues is the main source of POSTN, it is still unclear how POSTN plays a role to facilitate the interplay between cancer cells and cancer-associated fibroblasts (CAFs) in head and neck cancer (HNC), thereby promoting tumorigenesis via modifying the tumor microenvironment. Herein, we have performed studies to investigate POSTN and its role in HNC microenvironment. Our results indicated that POSTN was significantly up-regulated in HNCs, especially in the tissues with lymph node metastasis. Moreover, POSTN was highly enriched in the stroma of cancer tissues and produced mainly by CAFs. More importantly, we have pinpointed TGF-β3 as the major upstream molecular that triggers the induction of POSTN in CAFs. As such, during the interaction between fibroblasts and cancer cells, the increased stromal POSTN induced by TGF-β3 directly accelerated the growth, migration and invasion of cancer cells. Hence, our study has provided a novel modulative role for POSTN on HNC progression and further reveals POSTN as an effective biomarker to predict metastasis as well as a potential cancer therapeutic target