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Showing papers by "General Electric published in 2015"


Journal ArticleDOI
TL;DR: The Multimodal Brain Tumor Image Segmentation Benchmark (BRATS) as mentioned in this paper was organized in conjunction with the MICCAI 2012 and 2013 conferences, and twenty state-of-the-art tumor segmentation algorithms were applied to a set of 65 multi-contrast MR scans of low and high grade glioma patients.
Abstract: In this paper we report the set-up and results of the Multimodal Brain Tumor Image Segmentation Benchmark (BRATS) organized in conjunction with the MICCAI 2012 and 2013 conferences Twenty state-of-the-art tumor segmentation algorithms were applied to a set of 65 multi-contrast MR scans of low- and high-grade glioma patients—manually annotated by up to four raters—and to 65 comparable scans generated using tumor image simulation software Quantitative evaluations revealed considerable disagreement between the human raters in segmenting various tumor sub-regions (Dice scores in the range 74%–85%), illustrating the difficulty of this task We found that different algorithms worked best for different sub-regions (reaching performance comparable to human inter-rater variability), but that no single algorithm ranked in the top for all sub-regions simultaneously Fusing several good algorithms using a hierarchical majority vote yielded segmentations that consistently ranked above all individual algorithms, indicating remaining opportunities for further methodological improvements The BRATS image data and manual annotations continue to be publicly available through an online evaluation system as an ongoing benchmarking resource

3,699 citations


Journal ArticleDOI

906 citations


Journal ArticleDOI
TL;DR: In this paper, the authors summarize the recent advances in Membrane distillation and provide perspectives for its future R&D, including membrane materials, module configurations, process applications and hybrid systems.

716 citations


Journal ArticleDOI
TL;DR: A state-feedback quasi-static SRF-PLL model is proposed, which can identify and quantify the inherent frequency self-synchronization mechanism in the converter control system and explain the PLL instability issues and the related islanding-detection methods in early publications and industry reports.
Abstract: Synchronous reference frame (SRF) phase-locked loop (PLL) is a critical component for the control and grid synchronization of three-phase grid-connected power converters. The PLL behaviors, especially its low-frequency dynamics, influenced by different grid and load impedances as well as operation mode have not been investigated yet, which may not be captured by conventional linear PLL models. In this paper, we propose a state-feedback quasi-static SRF-PLL model, which can identify and quantify the inherent frequency self-synchronization mechanism in the converter control system. This self-synchronization effect is essentially due to the converter interactions with grid impedance and power flow directions. The low-frequency nonlinear behaviors of the PLL under different grid impedance conditions are then analyzed, which forms the framework of evaluating the impacts of the large penetration level of distributed generation units, weak grid, microgrid, and large reactive power consumption in terms of the frequency stability of PLL. Specifically, the PLL behavior of the converter system under islanded condition is investigated to explain the PLL instability issues and the related islanding-detection methods in early publications and industry reports.

482 citations


Journal ArticleDOI
TL;DR: In this article, the authors reviewed recent progress made in the development of polymer dielectrics with high energy storage density, which can potentially lead to significant weight and volume reduction in polymer film capacitors.
Abstract: Polymer film capacitors are critical components in many high-power electrical systems. Because of the low energy density of conventional polymer dielectrics, these capacitors currently occupy significant volume in the entire electrical system. This article reviews recent progress made in the development of polymer dielectrics with high energy storage density, which can potentially lead to significant weight and volume reduction in polymer film capacitors. The increase in energy density is achieved through two approaches, namely (a) the development of novel polymers with high electric polarization and optimized dielectric responses and (b) the development of nanocomposites containing polymer matrixes with high breakdown strength and inorganic nanofillers with high polarization. Promising progress has been made through both strategies, resulting in a maximum energy density of >30 J/cm3, which is at least 5 times higher than those of conventional polymer dielectrics. The state-of-the-art manufacturing method...

467 citations


Journal ArticleDOI
TL;DR: In this article, a LCTM-based transition prediction model for laminar-turbulent transition processes is proposed, where experimental correlations are integrated into standard convection-diffusion transport equations using local variables.
Abstract: A model for the prediction of laminar-turbulent transition processes was formulated. It is based on the LCTM (‘Local Correlation-based Transition Modelling’) concept, where experimental correlations are being integrated into standard convection-diffusion transport equations using local variables. The starting point for the model was the γ-Re θ model already widely used in aerodynamics and turbomachinery CFD applications. Some of the deficiencies of the γ-Re θ model, like the lack of Galilean invariance were removed. Furthermore, the Re θ equation was avoided and the correlations for transition onset prediction have been significantly simplified. The model has been calibrated against a wide range of Falkner-Skan flows and has been applied to a variety of test cases.

335 citations


Journal ArticleDOI
TL;DR: In this article, two new modular multilevel converter (MMC) circuit configurations as well as a hybrid design methodology to embed the dc-fault-handling capability in the MMC-HVDC systems are proposed.
Abstract: The modular multilevel converter (MMC) has become the most promising converter technology for high-voltage direct current (HVDC) transmission systems. However, similar to any other voltage-sourced converter-based HVDC system, MMC-HVDC systems with the half-bridge submodules (SMs) lack the capability of handling dc-side short-circuit faults, which are of severe concern for overhead transmission lines. In this paper, two new SM circuit configurations as well as a hybrid design methodology to embed the dc-fault-handling capability in the MMC-HVDC systems are proposed. By combining the features of various SM configurations, the dc-fault current path through the freewheeling diodes is eliminated and the dc-fault current is enforced to zero. Several MMC configurations based on the proposed hybrid design method and various SM circuits, that is, the half-bridge, the full-bridge, the clamp-double, and the five-level cross-connected SMs, as well as the newly proposed unipolar-voltage full-bridge and three-level cross-connected SMs, are investigated and compared in terms of the dc-fault-handing capability, semiconductor power losses, and component requirements. The studies are carried out based on time-domain simulation in the PSCAD/EMTDC software environment for various SM configurations and dc-fault conditions. The reported study results demonstrate the proposed hybrid-designed MMC-HVDC system based on the combination of the half-bridge and the proposed SM circuits is the optimal design among all evaluated systems in terms of the dc-fault-handing capability, semiconductor power losses, and component requirements.

303 citations


Journal ArticleDOI
TL;DR: In this article, a linear relationship between β1 and the energy of the 2Eg level was established, which made it possible to understand the large variation in the 2 Eg → 4 A2g emission transition that is frequently encountered in the spectroscopy of the Mn 4+ ions in solids.
Abstract: + ( C C0 ) 2 (where (B, C (B0, C0) are the Racah parameters of the Mn 4+ ions in a crystal (free state), respectively) was recently introduced that allows for establishing a linear relationship between β1 and the energy of the 2Eg level. This makes it possible to understand the large variation in the energy of the 2 Eg → 4 A2g emission transition that is frequently encountered in the spectroscopy of the Mn 4+ ions in solids.

239 citations


Journal ArticleDOI
TL;DR: This first-in-human pilot study shows that molecular imaging using an intravenous fluorescent agent specific for c-Met is feasible and safe, and that it may enable the detection of polyps missed by other techniques.
Abstract: Colon cancer prevention currently relies on colonoscopy using white light to detect and remove polyps, but small and flat polyps are difficult to detect and frequently missed when using this technique. Fluorescence colonoscopy combined with a fluorescent probe specific for a polyp biomarker may improve polyp detection. Here we describe GE-137, a water-soluble probe consisting of a 26-amino acid cyclic peptide that binds the human tyrosine kinase c-Met conjugated to a fluorescent cyanine dye. Intravenous administration of GE-137 leads to its accumulation specifically in c-Met-expressing tumors in mice, and it is safe and well tolerated in humans. Fluorescence colonoscopy in patients receiving intravenous GE-137 enabled visualization of all neoplastic polyps that were visible with white light (38), as well as an additional nine polyps that were not visible with white light. This first-in-human pilot study shows that molecular imaging using an intravenous fluorescent agent specific for c-Met is feasible and safe, and that it may enable the detection of polyps missed by other techniques.

230 citations


Journal ArticleDOI
TL;DR: Through extensive empirical studies, it is shown that risk minimization under the 0-1 loss, the sigmoid loss and the ramp loss has much better robustness to label noise when compared to the SVM algorithm.

213 citations


Journal ArticleDOI
TL;DR: While quantitation of analytes in the presence of variable backgrounds is challenging for most sensor arrays, this work shows individual nanofabricated sensors that can be tuned for numerous vapour sensing scenarios in confined areas or as individual nodes for distributed monitoring.
Abstract: Combining vapour sensors into arrays is an accepted compromise to mitigate poor selectivity of conventional sensors. Here we show individual nanofabricated sensors that not only selectively detect separate vapours in pristine conditions but also quantify these vapours in mixtures, and when blended with a variable moisture background. Our sensor design is inspired by the iridescent nanostructure and gradient surface chemistry of Morpho butterflies and involves physical and chemical design criteria. The physical design involves optical interference and diffraction on the fabricated periodic nanostructures and uses optical loss in the nanostructure to enhance the spectral diversity of reflectance. The chemical design uses spatially controlled nanostructure functionalization. Thus, while quantitation of analytes in the presence of variable backgrounds is challenging for most sensor arrays, we achieve this goal using individual multivariable sensors. These colorimetric sensors can be tuned for numerous vapour sensing scenarios in confined areas or as individual nodes for distributed monitoring.

Journal ArticleDOI
TL;DR: In this paper, the authors investigated the shearing mechanisms during single-crystal tensile creep of L12-containing Co- and CoNi-base alloys, and found that the antiphase boundaries formed by shearing of dislocations on octahedral planes.

Journal ArticleDOI
TL;DR: If the number of subsets is too large, the OS-SQS-momentum methods can be unstable, so this paper proposes diminishing step sizes that stabilize the method while preserving the very fast convergence behavior.
Abstract: Statistical X-ray computed tomography (CT) reconstruction can improve image quality from reduced dose scans, but requires very long computation time. Ordered subsets (OS) methods have been widely used for research in X-ray CT statistical image reconstruction (and are used in clinical PET and SPECT reconstruction). In particular, OS methods based on separable quadratic surrogates (OS-SQS) are massively parallelizable and are well suited to modern computing architectures, but the number of iterations required for convergence should be reduced for better practical use. This paper introduces OS-SQS-momentum algorithms that combine Nesterov's momentum techniques with OS-SQS methods, greatly improving convergence speed in early iterations. If the number of subsets is too large, the OS-SQS-momentum methods can be unstable, so we propose diminishing step sizes that stabilize the method while preserving the very fast convergence behavior. Experiments with simulated and real 3D CT scan data illustrate the performance of the proposed algorithms.

Journal ArticleDOI
15 Dec 2015-Energy
TL;DR: In this article, a complex network of energy hubs is modeled and optimized under different scenarios to examine both the financial viability and potential reduction of greenhouse gas emissions, and two case studies consisting of two and three energy hubs within a network are considered.

Journal ArticleDOI
01 Jan 2015
TL;DR: The goals of this paper are to further address issues when CAREX is mounted on human subjects, e.g., generation of continuous cable tension trajectories and demonstrate the feasibility and effectiveness of CAREX on movement training of healthy human subjects and a stroke patient.
Abstract: In recent years, the authors have proposed lightweight exoskeleton designs for upper arm rehabilitation using multi-stage cable-driven parallel mechanism. Previously, the authors have demonstrated via experiments that it is possible to apply “assist-as-needed” forces in all directions at the end-effector with such an exoskeleton acting on an anthropomorphic machine arm. A human–exoskeleton interface was also presented to show the feasibility of CAREX on human subjects. The goals of this paper are to 1) further address issues when CAREX is mounted on human subjects, e.g., generation of continuous cable tension trajectories 2) demonstrate the feasibility and effectiveness of CAREX on movement training of healthy human subjects and a stroke patient. In this research, CAREX is rigidly attached to an arm orthosis worn by human subjects. The cable routing points are optimized to achieve a relatively large “tensioned” static workspace. A new cable tension planner based on quadratic programming is used to generate continuous cable tension trajectory for smooth motion. Experiments were carried out on eight healthy subjects. The experimental results show that CAREX can help the subjects move closer to a prescribed circular path using the force fields generated by the exoskeleton. The subjects also adapt to the path shortly after training. CAREX was also evaluated on a stroke patient to test the feasibility of its use on patients with neural impairment. The results show that the patient was able to move closer to a prescribed straight line path with the “assist-as-needed” force field.

Patent
09 Sep 2015
TL;DR: In this article, a wireless communication device of a vehicle system includes one or more antennas configured to be disposed onboard a first vehicle of the vehicle system, a first modem configured onboard the first vehicle and to communicate a first wireless signal to one of the second vehicles or an off-board device using the antennas, and a second modem configured to communicate the second wireless signal via a different, second type of wireless communication link.
Abstract: A wireless communication device of a vehicle system includes one or more antennas configured to be disposed onboard a first vehicle of the vehicle system, a first modem configured to be disposed onboard the first vehicle and to communicate a first wireless signal to one or more of a second vehicle of the vehicle system or an off-board device using the one or more antennas, and a second modem configured to be disposed onboard the first vehicle and to communicate a second wireless signal to the one or more of the second vehicle or the off-board device using the one or more antennas. The first modem is configured to communicate the first wireless signal via a first type of wireless communication link and the second modem is configured to communicate the second wireless signal via a different, second type of wireless communication link.

Journal ArticleDOI
TL;DR: In this article, chemical fluctuations in the vicinity of superlattice intrinsic stacking faults (SISFs) have been observed via high resolution energy dispersive X-ray spectroscopy (EDS) mapping in new single crystal Co- and CoNi-base superalloys containing γ ′ -(L1 2 ) precipitates.

Journal ArticleDOI
TL;DR: It is shown that the synthesized Cu2S photocatalyst can be efficiently used for the reduction of CO2 to carbon monoxide and methane, achieving formation rates of 3.02 and 0.13 μmol h(-1) g(-1), respectively, and suppressing competing water reduction.
Abstract: Copper(I)-based catalysts, such as Cu2S, are considered to be very promising materials for photocatalytic CO2 reduction. A common synthesis route for Cu2S via cation exchange from CdS nanocrystals requires Cu(I) precursors, organic solvents, and neutral atmosphere, but these conditions are not compatible with in situ applications in photocatalysis. Here we propose a novel cation exchange reaction that takes advantage of the reducing potential of photoexcited electrons in the conduction band of CdS and proceeds with Cu(II) precursors in an aqueous environment and under aerobic conditions. We show that the synthesized Cu2S photocatalyst can be efficiently used for the reduction of CO2 to carbon monoxide and methane, achieving formation rates of 3.02 and 0.13 μmol h(-1) g(-1), respectively, and suppressing competing water reduction. The process opens new pathways for the preparation of new efficient photocatalysts from readily available nanostructured templates.

Journal ArticleDOI
TL;DR: In this paper, the local compositional and structural changes occurring in association with stacking faults in a Ni-base superalloy are characterized and related to the possible rate-controlling processes during creep deformation at intermediate temperatures.

Journal ArticleDOI
TL;DR: Reversibility of a dehydrogenation/hydrogenation catalytic reaction has been an elusive target for homogeneous catalysis and this reactivity suggests a strategy for the development of reversible fuel cell electrocatalysts for partial oxidation of hydroxyl-containing fuels.
Abstract: Reversibility of a dehydrogenation/hydrogenation catalytic reaction has been an elusive target for homogeneous catalysis. In this report, reversible acceptorless dehydrogenation of secondary alcohols and diols on iron pincer complexes and reversible oxidative dehydrogenation of primary alcohols/reduction of aldehydes with separate transfer of protons and electrons on iridium complexes are shown. This reactivity suggests a strategy for the development of reversible fuel cell electrocatalysts for partial oxidation (dehydrogenation) of hydroxyl-containing fuels.

Journal ArticleDOI
19 Nov 2015
TL;DR: The focus is on the emerging wide bandgap semiconductor devices, i.e., silicon carbide (SiC) and gallium nitride (GaN) devices, and their potential impact on future shipboard power conversion and drives.
Abstract: This paper presents some of the key advances in power electronics pertaining to shipboard electric power system applications. The focus is on the emerging wide bandgap semiconductor devices, i.e., silicon carbide (SiC) and gallium nitride (GaN) devices, and their potential impact on future shipboard power conversion and drives. Their benefits on power converter efficiency and power density are explained through a case study of a medium-voltage (MV) class motor drive system. SiC and GaN also enable new applications, including solid-state transformers, while posing new design and application challenges such as gate drive, protection, and interaction with loads. In addition to device related topics, this paper also overviews other important advances in power electronics, including topology, control, passive components, thermal management, filters, and packaging. The significance of power electronics building blocks (PEBBs) concept for shipboard power system development is discussed. Recognizing the growing complexity of shipboard power systems, some system-level technologies related to future MV direct current (dc) system architecture are highlighted.

Journal ArticleDOI
TL;DR: In this article, the authors investigated the principles underlying torque production in a flux-switching permanent-magnet (FSPM) machine and found that the primary torque-producing harmonics in the air-gap flux density waveform are the heterodyned harmonics of the magnetomotive force produced by the stator magnets and the air gap permeance seen by the rotor.
Abstract: This paper investigates the principles underlying torque production in a flux-switching permanent-magnet (FSPM) machine. Because the phase windings and permanent magnets (PMs) in FSPM machines are both located on the stator, the torque production mechanism is not the same as for a conventional PM synchronous machine. Spatial harmonic analysis is applied to examine the frequency components present in the electric and magnetic loading of the machine. Since torque is proportional to the product of the electric and magnetic loading, understanding the source of the principal harmonics in these waveforms yields powerful insights into the components that result in torque production. The analysis is first presented for a specific FSPM machine (12-slot/10-pole) and then extended to a general FSPM machine. The primary torque-producing harmonics in the air-gap flux density waveform are found to be the heterodyned harmonics of the magnetomotive force produced by the stator magnets and the air-gap permeance seen by the stator looking into the rotor. Analytical results are compared to results from finite-element analysis and exhibit good agreement.

Journal ArticleDOI
TL;DR: This is the first, to the authors' knowledge, clinical evaluation of skull bone identification based on a ZTE sequence and the results suggest that proton density–weighted ZTE imaging is an efficient means of obtaining high-resolution maps of bone tissue with sufficient anatomic accuracy for, for example, PET attenuation correction.
Abstract: MR-based attenuation correction is instrumental for integrated PET/MR imaging. It is generally achieved by segmenting MR images into a set of tissue classes with known attenuation properties (e.g., air, lung, bone, fat, soft tissue). Bone identification with MR imaging is, however, quite challenging, because of the low proton density and fast decay time of bone tissue. The clinical evaluation of a novel, recently published method for zero-echo-time (ZTE)–based MR bone depiction and segmentation in the head is presented here. Methods: A new paradigm for MR imaging bone segmentation, based on proton density–weighted ZTE imaging, was disclosed earlier in 2014. In this study, we reviewed the bone maps obtained with this method on 15 clinical datasets acquired with a PET/CT/MR trimodality setup. The CT scans acquired for PET attenuation-correction purposes were used as reference for the evaluation. Quantitative measurements based on the Jaccard distance between ZTE and CT bone masks and qualitative scoring of anatomic accuracy by an experienced radiologist and nuclear medicine physician were performed. Results: The average Jaccard distance between ZTE and CT bone masks evaluated over the entire head was 52% ± 6% (range, 38%–63%). When only the cranium was considered, the distance was 39% ± 4% (range, 32%–49%). These results surpass previously reported attempts with dual-echo ultrashort echo time, for which the Jaccard distance was in the 47%–79% range (parietal and nasal regions, respectively). Anatomically, the calvaria is consistently well segmented, with frequent but isolated voxel misclassifications. Air cavity walls and bone/fluid interfaces with high anatomic detail, such as the inner ear, remain a challenge. Conclusion: This is the first, to our knowledge, clinical evaluation of skull bone identification based on a ZTE sequence. The results suggest that proton density–weighted ZTE imaging is an efficient means of obtaining high-resolution maps of bone tissue with sufficient anatomic accuracy for, for example, PET attenuation correction.

Journal ArticleDOI
TL;DR: Improvements of PL in lesion quantitation accuracy compared to OSEM are demonstrated with a particular improvement in cold background regions such as lungs.
Abstract: Ordered subset expectation maximization (OSEM) is the most widely used algorithm for clinical PET image reconstruction. OSEM is usually stopped early and post-filtered to control image noise and does not necessarily achieve optimal quantitation accuracy. As an alternative to OSEM, we have recently implemented a penalized likelihood (PL) image reconstruction algorithm for clinical PET using the relative difference penalty with the aim of improving quantitation accuracy without compromising visual image quality. Preliminary clinical studies have demonstrated visual image quality including lesion conspicuity in images reconstructed by the PL algorithm is better than or at least as good as that in OSEM images. In this paper we evaluate lesion quantitation accuracy of the PL algorithm with the relative difference penalty compared to OSEM by using various data sets including phantom data acquired with an anthropomorphic torso phantom, an extended oval phantom and the NEMA image quality phantom; clinical data; and hybrid clinical data generated by adding simulated lesion data to clinical data. We focus on mean standardized uptake values and compare them for PL and OSEM using both time-of-flight (TOF) and non-TOF data. The results demonstrate improvements of PL in lesion quantitation accuracy compared to OSEM with a particular improvement in cold background regions such as lungs.

Journal ArticleDOI
Alma Partnership, Ed Fomalont1, Catherine Vlahakis2, Stuartt Corder1  +249 moreInstitutions (36)
TL;DR: The Long Baseline Campaign (LBC) was carried out from 2014 September to late November, culminating in end-to-end observations, calibrations, and imaging of selected Science Verification (SV) targets as discussed by the authors.
Abstract: A major goal of the Atacama Large Millimeter/submillimeter Array (ALMA) is to make accurate images with resolutions of tens of milliarcseconds, which at submillimeter (submm) wavelengths requires baselines up to ~15 km. To develop and test this capability, a Long Baseline Campaign (LBC) was carried out from 2014 September to late November, culminating in end-to-end observations, calibrations, and imaging of selected Science Verification (SV) targets. This paper presents an overview of the campaign and its main results, including an investigation of the short-term coherence properties and systematic phase errors over the long baselines at the ALMA site, a summary of the SV targets and observations, and recommendations for science observing strategies at long baselines. Deep ALMA images of the quasar 3C 138 at 97 and 241 GHz are also compared to VLA 43 GHz results, demonstrating an agreement at a level of a few percent. As a result of the extensive program of LBC testing, the highly successful SV imaging at long baselines achieved angular resolutions as fine as 19 mas at ~350 GHz. Observing with ALMA on baselines of up to 15 km is now possible, and opens up new parameter space for submm astronomy.

Proceedings Article
25 Jul 2015
TL;DR: This paper presents a bandit algorithm for conducting online portfolio choices by effectually exploiting correlations among multiple arms and derives the optimal portfolio strategy that represents the combination of passive and active investments according to a risk-adjusted reward function.
Abstract: The investigation and development of new methods from diverse perspectives to shed light on portfolio choice problems has never stagnated in financial research. Recently, multi-armed bandits have drawn intensive attention in various machine learning applications in online settings. The tradeoff between exploration and exploitation to maximize rewards in bandit algorithms naturally establishes a connection to portfolio choice problems. In this paper, we present a bandit algorithm for conducting online portfolio choices by effectually exploiting correlations among multiple arms. Through constructing orthogonal portfolios from multiple assets and integrating with the upper confidence bound bandit framework, we derive the optimal portfolio strategy that represents the combination of passive and active investments according to a risk-adjusted reward function. Compared with oft-quoted trading strategies in finance and machine learning fields across representative real-world market datasets, the proposed algorithm demonstrates superiority in both risk-adjusted return and cumulative wealth.

Proceedings ArticleDOI
15 Mar 2015
TL;DR: In this paper, the authors presented the latest 1.2kV and 2.7kV SiC MOSFETs designed to maximize SiC device benefits for high-power, medium voltage power conversion applications.
Abstract: This paper presents the latest 1.2kV–2.2kV SiC MOSFETs designed to maximize SiC device benefits for high-power, medium voltage power conversion applications. 1.2kV, 1.7kV and 2.2kV devices with die size of 4.5mm × 4.5mm were fabricated, exhibiting room temperature on-resistances of 34mOhm, 39mOhm and 41mOhm, respectively. The ability to safely withstand single-pulse avalanche energies of over 17J/cm2 is demonstrated. Next, the 1.7kV SiC MOSFETs were used to fabricate half-bridge power modules. The module typical onresistance was 7mOhm at Tj=25°C and 11mOhm at 150°C. The module exhibits 9mJ turn-on and 14mJ turn-off losses at Vds=900V, Id=400A. Validation of GE's SiC MOSFET performance advantages was done through continuous buck-boost operation with three 1.7kV modules per phase leg exhibiting 99.4% efficiency. Device ruggedness and tolerance to terrestrial cosmic radiation was evaluated. Experimental results show that higher voltage devices (2.2kV and 3.3kV) are more susceptible to cosmic radiation, requiring up to 45% derating in order to achieve module failure rate of 100 FIT, while 1.2kV MOSFETs require only 25% derating to deliver similar FIT rate. Finally, the feasibility of medium voltage power conversion based on series connected 1.2kV SiC MOSFETs with body diode is demonstrated.

DOI
Weizhong Yan1, Lijie Yu1
01 Jan 2015
TL;DR: In this paper, the authors used deep learning to hierarchically learn features from the sensor measurements of exhaust gas temperatures and then used the learned features as the input to a neural network classifier for performing combustor anomaly detection.
Abstract: Monitoring gas turbine combustors' health, in particular, early detecting abnormal behaviors and incipient faults, is critical in ensuring gas turbines operating efficiently and in preventing costly unplanned maintenance. One popular means of detecting combustors’ abnormalities is through continuously monitoring exhaust gas temperature profiles. Over the years many anomaly detection technologies have been explored for detecting combustor faults, however, the performance (detection rate) of anomaly detection solutions fielded is still inadequate. Advanced technologies that can improve detection performance are in great need. Aiming for improving anomaly detection performance, in this paper we introduce recently-developed deep learning (DL) in machine learning into the combustors’ anomaly detection application. Specifically, we use deep learning to hierarchically learn features from the sensor measurements of exhaust gas temperatures. And we then use the learned features as the input to a neural network classifier for performing combustor anomaly detection. Since such deep learned features potentially better capture complex relations among all sensor measurements and the underlying combustors’ behavior than handcrafted features do, we expect the learned features can lead to a more accurate and robust anomaly detection. Using the data collected from a real-world gas turbine combustion system, we demonstrated that the proposed deep learning based anomaly detection significantly indeed improved combustors’ anomaly detection performance.Deep learning, one of the breakthrough technologies in machine learning, has attracted tremendous research interests in recent years in the domains such as computer vision, speech recognition and natural language processing.Deep learning, to the best of our knowledge, has not been used for any PHM applications, however. It is our hope that our initial work presented in this paper would shed some light on how deep learning as an advanced machine learning technology can benefit PHM applications and, more importantly, can stimulate more research interests in our PHM community.

Journal ArticleDOI
TL;DR: Thomas et al. as discussed by the authors reported the P-T dependencies of Ti-in-quartz solubility, and there is close agreement among three of the four experimental calibrations.
Abstract: Several studies have reported the P–T dependencies of Ti-in-quartz solubility, and there is close agreement among three of the four experimental calibrations New experiments were conducted in the present study to identify potential experimental disequilibrium, and to determine which Ti-in-quartz solubility calibration is most accurate Crystals of quartz, rutile and zircon were grown from SiO2-, TiO2-, and ZrSiO4-saturated aqueous fluids in an initial synthesis experiment at 925 °C and 10 kbar in a piston-cylinder apparatus A range of quartz crystal sizes was produced in this experiment; both large and small examples were analyzed by electron microprobe to determine whether Ti concentrations are correlated with crystal size Cathodoluminescence images and EPMA measurements show that intercrystalline and intracrystalline variations in Ti concentrations are remarkably small regardless of crystal size The average Ti-in-quartz concentration from the synthesis experiment is 392 ± 1 ppmw Ti, which is within 95 % confidence interval of data from the 10 kbar isobar of Wark and Watson (Contrib Mineral Petrol 152:743–754, 2006) and Thomas et al (Contrib Mineral Petrol 160:743–759, 2010) As a cross-check on the Ti-in-quartz calibration, we also measured the concentration of Zr in rutile from the synthesis experiment The average Zr-in-rutile concentration is 4337 ± 32 ppmw Zr, which is also within the 95 % confidence interval of the Zr-in-rutile solubility calibration of Ferry and Watson (Contrib Mineral Petrol 154:429–437, 2007) The P–T dependencies of Ti solubility in quartz and Zr solubility in rutile were applied as a thermobarometer to the experimental sample The average Ti-in-quartz isopleth calculated from the calibration of Thomas et al (Contrib Mineral Petrol 160:743–759, 2010) and the average Zr-in-rutile isopleth calculated from the calibration of Tomkins et al (J Metamorph Geol 25:703–713, 2007) cross at 95 kbar and 920 °C, which is in excellent agreement with the P–T conditions of the synthesis experiment Separates of the high-Ti quartz from the initial synthesis experiment described above were used as starting material in subsequent experiments at 20 kbar, at which pressure the solubility of Ti in quartz is expected to be significantly lower in the recrystallized quartz These recrystallization experiments were conducted under wet and dry conditions at 925 °C, and under wet conditions at 850 °C Both wet and dry recrystallization experiments produced polycrystalline quartzites Rutile occurs as inclusions in quartz, and as individual crystals dispersed along quartz grain boundaries Quartz that grew during the recrystallization experiments has dark cathodoluminescence indicating substantially lower Ti concentrations The average Ti concentrations in quartz from the recrystallization experiments are within the 95 % confidence interval of a linear fit to the 20 kbar data of Thomas et al (Contrib Mineral Petrol 160:743–759, 2010) Collectively, the results from the synthesis and recrystallization experiments confirm that the Ti-in-quartz concentrations used to calibrate the P–T dependencies of Ti-in-quartz solubility in Thomas et al’s (Contrib Mineral Petrol 160:743–759, 2010) calibration represent the equilibrium concentrations of Ti in quartz

Journal ArticleDOI
TL;DR: In this paper, the effect of number of winding layers on the performance of fractional-slot concentrated-windings is investigated, and it is shown that by going to higher number of layers, there can be significant improvement in efficiency especially at high speeds mainly due to the reduction of the winding factor/magnitude of the most dominant stator mmf subharmonic component.
Abstract: Interior PM machines equipped with fractional-slot concentrated-windings are good candidates for high-speed traction applications. This is mainly due to the higher power density and efficiency that can be achieved. The main challenge with this type of machines is the high rotor losses at high speeds/frequencies. This paper will thoroughly investigate the effect of number of winding layers on the performance of this type of machines. It will be shown that by going to higher number of layers, there can be significant improvement in efficiency especially at high speeds mainly due to the reduction of the winding factor/magnitude of the most dominant stator mmf subharmonic component. It will also be shown that there is significant improvement in torque density. Even though there is reduction in the winding factor of the stator synchronous torque-producing mmf component, this is more than offset by increase in machine saliency and reluctance torque. The paper will provide general guidelines regarding the optimum slot/pole/phase combinations based on torque density and efficiency. Sample designs of various slot/pole combinations are used to quantify the benefit of going to higher number of layers in terms of torque density, efficiency, and torque ripple.