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The establishment of cellular identity is driven by transcriptional and epigenetic regulators of the chromatin proteome - the chromatome. Comprehensive analyses of the chromatome composition and dynamics can therefore greatly improve our understanding of gene regulatory mechanisms. Here, we developed an accurate mass spectrometry (MS)-based proteomic method called Chromatin Aggregation Capture (ChAC) followed by Data-Independent Acquisition (DIA) and analyzed chromatome reorganizations during major phases of pluripotency. This enabled us to generate a comprehensive atlas of proteomes, chromatomes, and chromatin affinities for the ground, formative and primed pluripotency states, and to pinpoint the specific binding and rearrangement of regulatory components. These comprehensive datasets combined with extensive analyses identified phase-specific factors like QSER1 and JADE1/2/3 and provide a detailed foundation for an in-depth understanding of mechanisms that govern the phased progression of pluripotency. The technical advances reported here can be readily applied to other models in development and disease.

The establishment of cellular identity is driven by transcriptional and epigenetic regulation exerted by the components of the chromatin proteome - the chromatome. However, chromatome composition and its dynamics in functional phases of pluripotency have not been comprehensively analyzed thus limiting our understanding of these processes. To address this problem, we developed an accurate mass spectrometry (MS)-based proteomic method called Chromatin Aggregation Capture (ChAC) followed by Data-Independent Acquisition (DIA) to analyze chromatome reorganizations during the transition from ground to formative and primed pluripotency states. This allowed us to generate a comprehensive atlas of proteomes, chromatomes, and chromatin affinities for the three pluripotency phases, revealing the specific binding and rearrangement of regulatory complexes. The technical advances, the comprehensive chromatome atlas, and the extensive analysis reported here provide a foundation for an in-depth understanding of mechanisms that govern the phased progression of pluripotency and changes of cellular identities in development and disease.

This article proposes a new complete condition monitoring method which can independently monitor both the threshold voltage drift and the packaging degradation accurately by monitoring only the reverse body diode voltage drop at different gate bias levels. The SiC MOSFETs are aged through an accelerated aging method and the corresponding changes in electrical parameters are periodically measured to assess their correlation with the state of the device's health. It has been revealed that the on -state resistance reveals the combination of gate oxide and package-related degradation while the threshold voltage mainly depicts gate oxide-related issues. Unlike these two parameters, the body diode voltage drop is found to independently indicate the state of device health both for package and gate oxide. This is caused by a unique secondary conduction mode of SiC MOSFETs in third-quadrant operation which is clearly disclosed with transition boundaries by a proposed body diode transfer characterization curve. In order to have a detailed condition information of the device with a simple circuit, monitoring the reverse body diode voltage drop at 0 and $-$ 5 V gate bias is proposed. The proposed condition monitoring method is implemented on a gate drive circuit and experimental results are given for two artificially degraded devices. The experimental results confirm that the proposed method can independently monitor both the gate oxide and packaging degradations accurately by monitoring a single precursor parameter. The proposed method can be integrated into the gate driver or converter itself to monitor SiC devices.

In order to prevent catastrophic failures in power electronic systems, multiple failure precursors have been identified to characterize the degradation of power devices. However, there are some practical challenges in determining the suitable failure precursor, which supports the high-accuracy prediction of remaining useful life (RUL). This article proposes a method to formulate a composite failure precursor (CFP) by taking full advantage of potential failure precursors (PFPs), where CFP is directly optimized in terms of the degradation model to improve the prediction performance. The RUL estimations of the degradation model are explicitly derived to facilitate the precursor quality calculation. For CFP formulation, a genetic programming method is applied to integrate the PFPs in a nonlinear way. As a result, a framework that can formulate a superior failure precursor for the given RUL prediction model is elaborated. The proposed method is validated with the power cycling testing results of SiC MOSFETs.

Condition monitoring of power devices is highly critical for safety and mission-critical power electronics systems. Typically, these systems are subjected to noise in harsh operational environment contaminating the degradation measurements. In dynamic applications, the system duty cycle may not be periodic and results in aperiodic degradation measurements. Both these factors negatively affect the health assessment performance. In order to address these challenges, this article proposes a health state estimation and remaining useful life prediction method for power devices in the presence of noisy and aperiodic degradation measurements. For this purpose, three-source uncertainties in the degradation modeling, including the temporal uncertainty, measurement uncertainty, and device-to-device heterogeneity, are formulated in a Gamma state-space model to ensure health assessment accuracy. In order to learn the device degradation behavior, a model parameter estimation method is developed based on a stochastic expectation-maximization algorithm. The accuracy and robustness of the proposed method are verified by numerical analysis under various noise levels. Finally, the findings are justified using SiC metal-oxide-semiconductor field-effect transistors (MOSFETs) accelerated aging test data.

Liquid-liquid phase separation (LLPS) mediated formation of membraneless organelles has been proposed to coordinate biological processes in space and time. Previously, the formation of phase-separated droplets was described as a unique property of HP1 alpha. Here, we demonstrate that the positive net charge of the intrinsically disordered hinge region (IDR-H) of HP1 proteins is critical for phase separation and that the exchange of four acidic amino acids is sufficient to confer LLPS properties to HP1 beta. Surprisingly, the addition of mono-nucleosomes promoted H3K9me3-dependent LLPS of HP1 beta which could be specifically disrupted with methylated but not acetylated H3K9 peptides. HP1 beta mutants defective in H3K9me3 binding were less efficient in phase separationin vitro and failed to accumulate at heterochromatin in vivo. We propose that multivalent interactions of HP1 beta with H3K9me3-modified nucleosomes via its chromodomain and dimerization via its chromoshadow domain enable phase separation and contribute to the formation of heterochromatin compartments in vivo.

The long-term reliability concerns regarding the latest power devices, e.g., silicon carbide (SiC) MOSFETs, need to be well understood for their rapid and widespread deployment in industrial applications. As an effective reliability assessment, the dc power cycling test is one of the most realistic procedures providing accelerated lifetime tests. In this paper, a dc power cycling setup for SiC power MOSFETs is proposed, and the design methodology is generalized for practicing engineers. At first, the aging-independent junction temperature measurement method is identified to eliminate the laborious recalibration process. Specifically, the electrical parameter changes of commercial SiC MOSFETs are evaluated in a power cycling test. It is observed experimentally that the body diode’s voltage drop at low current and negative gate bias is unaffected by the device/package degradation. Therefore, it is selected for $T_{j}$ measurement in the proposed setup. Following that, the design considerations regarding precise parameter measurement of the device’s parameter are presented. The transient behavior of the proposed test setup is analyzed, and a simulation model is built in LTspice. Based on the model, the effects of gate timing control and paralleled capacitors are investigated for realizing accurate measurements, and the simulation results are verified experimentally in a prototype. In addition, considering the measurement delay in the conditioning circuits and the common-mode noise, the practical issues affecting the measurement accuracy in a multiple-phase setup are investigated in the experiment. Experimental results show that an accurate measurement can be achieved with the design considerations.

The temperature-sensitive electrical parameters (TSEPs) have been used in silicon carbide (SiC) mosfets junction temperature measurement for over-temperature protection and condition monitoring. However, the device aging can affect the TSEPs and thus leads to false ${\boldsymbol{T}}_{\boldsymbol{j}}$ measurement. In this article, the aging's impacts on various TSEPs are comprehensively investigated. Specifically, utilizing the dc power cycling test, both the gate oxide instability and package degradation are considered. Then the commercial devices with different structures are aged, and their temperature-dependent static and switching characteristics are evaluated at different aging cycles. Both the positive gate bias-induced threshold voltage shift and package degradation are observed, and their impacts on each TSEP are evaluated independently. Based on the evaluation results at various operating conditions, the temperature measurement errors due to different aging mechanisms are well summarized for each TSEP. From the dc power cycling test result, the package degradation's impact on TSEPs is found to be more significant than the gate oxide instability. It is pointed out that the aging's effect on TSEPs is an important factor that needs to be considered for accurate ${\boldsymbol{T}}_{\boldsymbol{j}}$ measurement in SiC mosfets .

This paper presents an silicon carbide (SiC) MOSFET health condition monitoring method based on the switching transient measurements. Specifically, the device's turn -on time is used as the aging precursor, and a detection circuit is developed with picosecond resolution to detect the variations of the turn -on time. For this purpose, power cycles with constant junction temperature swings are applied on sample devices to accelerate their thermally triggered degradation. Over the aging process, device parameters are measured periodically using automated curve tracer to observe degradation-related changes. Also, a double pulse tester is used to evaluate devices’ switching transient changes throughout aging. Based on these results, both the theoretical discussions and experimental results imply that device turn -on time is a viable aging precursor and can be used to monitor device health at system start-up. High-resolution capture module of readily available system microcontroller is employed to measure the turn -on time through a simple auxiliary interface circuit on a buck converter. Experimental results show that onboard device aging can successfully be achieved during systems start-up in the order of microseconds.

In this article, an in situ SiC mosfet degradation monitoring method using readily available converter sensors is presented. Device's drain-source resistance in saturation and ohmic regions are employed as aging precursors to, respectively, indicate die and package-related degradations. The presented findings in this article are essential for low-cost and practical early warning systems in power electronics applications. To verify the effectiveness of the proposed method, a number of power-cycling tests are conducted to analyze aging process and fatigue mechanism. Device static parameters are measured throughout accelerated aging tests and the physical causes behind them are discussed in detail. It is shown that the drain-source resistance within saturation region at low gate bias can be used to indicate die-related degradation. Similarly, at full positive gate bias, device on -state drain-source resistance can be used to detect package-related degradation. In order to find out optimal variables such as applied gate bias, pulse duration, etc., a comprehensive single pulse test is conducted and the results are reported. Finally, the proposed degradation monitoring method is experimentally validated in the context of a three-phase inverter considering different sensor configurations and load types.

The genetic code of mammalian cells can be expanded to allow the incorporation of non-canonical amino acids (ncAAs) by suppressing in-frame amber stop codons (UAG) with an orthogonal pyrrolysyl-tRNA synthetase (PylRS)/tRNAPylCUA (PylT) pair. However, the feasibility of this approach is substantially hampered by unpredictable variations in incorporation efficiencies at different stop codon positions within target proteins. Here, we apply a proteomics-based approach to quantify ncAA incorporation rates at hundreds of endogenous amber stop codons in mammalian cells. With these data, we compute iPASS (Identification of Permissive Amber Sites for Suppression; available at www.bultmannlab.eu/tools/iPASS), a linear regression model to predict relative ncAA incorporation efficiencies depending on the surrounding sequence context. To verify iPASS, we develop a dual-fluorescence reporter for high-throughput flow-cytometry analysis that reproducibly yields context-specific ncAA incorporation efficiencies. We show that nucleotides up- and downstream of UAG synergistically influence ncAA incorporation efficiency independent of cell line and ncAA identity. Additionally, we demonstrate iPASS-guided optimization of ncAA incorporation rates by synonymous exchange of codons flanking the amber stop codon. This combination of in silico analysis followed by validation in living mammalian cells substantially simplifies identification as well as adaptation of sites within a target protein to confer high ncAA incorporation rates, Nucleic Acids Research, 49 (11), ISSN:1362-4962, ISSN:0301-5610

Silicon carbide (SiC) power mosfet s are promising alternatives to Si devices in high-voltage, high-frequency, and high-temperature applications. The rapid and widespread deployment of SiC devices raises long-term reliability concerns, particularly for mission and safety critical systems due to limited field data and potential uncertainties. Therefore, it is essential to investigate progressive degradations and parameter shifts in SiC devices to develop system integrated degradation monitoring tools for self-monitoring converters, which can recognize failure precursors at the earliest stage and prevent catastrophic failures. This paper presents a comprehensive long-term reliability analysis of commercially available SiC mosfet s under high temperature operation and high temperature swing, degradation related key precursors, and possible causes behind them. For this purpose, discrete SiC devices are power cycled and all datasheet parameters are recorded at certain intervals with the aid of the curve tracer. Variation of electrical parameters throughout the tests is presented in order to assess their correlation with the aging/degradation state of the switch. Among them, gate oxide charge trapping related threshold voltage drift and corresponding on state resistance variation has been observed for all samples. For some samples, bond wire heel cracking is found to be the root cause of sudden on state resistance and body diode voltage increases. The discussions regarding aging precursors are supported by failure analysis obtained through the decapsulation of failed devices. Finally, the findings are evaluated in order to define the suitability of electrical parameters as an aging precursor parameter under the light of practical implementation related issues.

Fault diagnosis and failure prognosis of power electronics systems are essential for various mission critical applications, where safety, continuity, and survivability of the system are of paramount importance. With the recent advances in power device failure precursor identification and lifetime estimation, it is possible to extend the lifetime of the power devices, and thereby converters through secondary control schemes. The essence of the lifetime extension strategies relies on either reducing the power loss on the degraded device(s) and shifting it to other parts, or decreasing the total power loss of the converter. As the power converters are optimized for efficiency and total harmonic distortion (THD) requirements, these secondary control strategies can result in operations above the design limits. This paper proposes a hybrid secondary lifetime extension control scheme for three-phase inverters based on the identified failure precursors, which dynamically changes the modulation scheme and adjusts the switching frequency. In the content of this paper, the tradeoff between the THD and achievable lifetime extension is addressed, and a control algorithm is proposed, which maximizes the lifetime with feasible lowest THD.

Today, power conversion in automotive industry depends heavily on the reliable operation of insulated-gate bipolar transistors (IGBTs). Condition monitoring of IGBTs and reporting imminent faults to driver dashboard are critical for avoiding any fatal accidents. In this study, first, a comprehensive comparison is carried out between on-state collector–emitter drop ( $V_{ce,on}$ ) with gate threshold voltage ( V th), as two reliable aging precursors. In order to enrich current understanding of IGBT aging prognosis, accelerated aging methods are applied under a wide variety of thermal stresses. Aging mechanisms and physical phenomena responsible for variation in both $V_{ce,on}$ and V th have been methodically investigated. These explanations are also supported by detailed failure analysis. Based on the extensive result sets for tested samples from different manufacturers with different structural types, it is found that $V_{ce,on}$ show different trends at different stress levels, whereas under the same test conditions V th provides more consistent and robust state-of-health information. Finally, an example experiment has been performed in which continuous $V_{ce,on}$ measurements coupled with V th information has been used to provide more insight about the device aging as well as faults in an automobile's sub-systems.

This paper presents a comprehensive study on degradation monitoring of silicon carbide mosfet s and proposes an early warning method to detect aging. The proposed plug-in tool can be integrated to smart gate drivers or directly to power converters. During the accelerated aging tests (power cycling within safe operating area), several electrical parameters are monitored to find out critical signatures and precursors of failure. Among those, gate leakage current is identified as the most practical precursor, which exhibits consistent changes in all aged devices and is relatively easy to monitor. Due to its simple scheme and low cost, it can potentially be embedded into commercial gate drivers featuring improved reliability options.

A Correction to this paper has been published: https://doi.org/10.1038/s41467-020-20453-0

Biotin proximity labeling has largely extended the toolbox of mass spectrometry-based interactomics. To date, BirA, engineered BirA variants, or other biotinylating enzymes have been widely applied to characterize protein interactions. By implementing chromatin purification-based methods the genome-wide interactome of proteins can be defined. However, acquiring a high-resolution interactome of a single genomic locus preferably by multiplexed measurements of several distinct genomic loci in parallel remains challenging. We recently developed CasID, a novel approach where the catalytically inactive Cas9 (dCas9) is coupled to the promiscuous biotin ligase BirA (BirA∗). With CasID, first the local proteome at repetitive telomeric, major satellite, and minor satellite regions was determined. With more efficient biotin ligases and sensitive mass spectrometry, others have successfully identified the chromatin composition at even smaller genomic, non-repetitive regions of a few hundred base pairs in length. Here, we summarize the most recent developments towards interactomics at a single genomic locus and provide a step-by-step protocol based on the CasID approach.

Biotin proximity labeling has largely extended the toolbox of mass spectrometry-based interactomics. To date, BirA, engineered BirA variants, or other biotinylating enzymes have been widely applied to characterize protein interactions. By implementing chromatin purification-based methods the genome-wide interactome of proteins can be defined. However, acquiring a high-resolution interactome of a single genomic locus preferably by multiplexed measurements of several distinct genomic loci in parallel remains challenging. We recently developed CasID, a novel approach where the catalytically inactive Cas9 (dCas9) is coupled to the promiscuous biotin ligase BirA (BirA∗). With CasID, first the local proteome at repetitive telomeric, major satellite, and minor satellite regions was determined. With more efficient biotin ligases and sensitive mass spectrometry, others have successfully identified the chromatin composition at even smaller genomic, non-repetitive regions of a few hundred base pairs in length. Here, we summarize the most recent developments towards interactomics at a single genomic locus and provide a step-by-step protocol based on the CasID approach.

The long-term device and package degradations in SiC MOSFETs can affect the power converter’s performance. In this paper, the aging’s effect on the device’s conduction and switching loss is evaluated experimentally. A DC power cycling test is implemented to age the commercial SiC MOSFETs. From the experimental results, the conduction loss is observed to increase by ~9.7%. Both the gate trap induced threshold voltage shift and package degradation contribute to the on-resistance increase. In terms of the switching loss, the turn-on loss also increases after aging, and the increment depends on the operating conditions. Specifically, at high current level and low gate resistance, the turn-on loss increase is more significant. In the experimental result with 0 Ω gate resistance, more than 36% turn-on loss increase is observed at 600 V/ 20 A. From the switching transient waveforms, the turn-on loss variation mainly occurs during the turn-on current rise period and is caused by the package degradation. During the voltage falling period, a slight turn-on loss increase is observed because of the positive V th shift. In contrast, the turn-off loss variation after aging is not significant.

Harsh operating environment and high temperature swings introduce die and packaging related degradations in SiC MOSFETs causing potential system failures. This paper proposes a new SiC MOSFET state-of-health monitoring approach based on Miller plateau voltage sensing. To age the SiC devices in a short time, power cycling test is applied. During the aging process, the device's static parameters and switching transients are evaluated. From the comprehensive assessment results, the Miller plateau voltage is found to be a promising aging precursor for SiC devices. Targeting at aging detection, a practical monitoring circuit is proposed for Miller plateau voltage measurement. Experimental results reveal that the proposed method is valid for on-board SiC MOSFET aging detection during system start-up within microseconds.

In this paper, a monitoring method is proposed for SiC MOSFETs based power converter/inverter topologies. Device's drain current and drain-source resistance in the saturation region are selected as the aging precursors. By applying fixed low V gs within microseconds at system start-up, on-board SiC MOSFET degradation monitoring can be achieved by excluding device junction temperature effect. In this study, readily available inverter current and dc bus voltage sensors are used to measure drain-source resistance shift throughout device degradation, and no extra sensing circuit is required. In order to verify the proposed method, power cycling tests are applied to devices under test (DUT) to observe progressive degradation and corresponding parameter shifts. Based on the identified aging signatures, the effect of variables like saturation gate voltage, pulse duration on the proposed technique are evaluated and discussed by means of single pulse test. The proposed degradation monitoring method is then experimentally validated in the context of a 3-phase inverter for case study. It is shown in the experimental results that device drain-source resistance in saturation region shows increasing trend over aging, can be used to monitor progressive SiC MOSFET degradation within microseconds at system start-up.

In this paper, a high-performance DC power cycling setup dedicated for SiC power MOSFETs is presented. Different from the previous DC power cycling setup designs focusing on circuit topology and operation principle, this paper discusses the detailed design considerations to ensure the measurement accuracy and control the voltage spikes within the safe voltage range of the data acquisition (DAQ) equipment. Specifically, the transient behavior of the circuit is analyzed, and a simulation model is built in LTspice to facilitate the design. From the simulation result, it is observed that the gate timing control is critical to limit the measurement spikes. In addition, adding decoupling capacitors helps to attenuate the ringing noise in the voltage measurement. A prototype is built, and the experimental results indicate that a precise measurement can be realized with the proposed DC power cycling setup under various conditions.

To process the power in hybrid energy systems using a reduced part count, researchers have proposed several multi-input dc-dc power converter topologies to transfer power from different input voltage sources to the output. This paper proposes a novel bidirectional nonisolatedmulti-input converter (MIC) topology for hybrid systems to be used in electric vehicles composed of energy storage systems (ESSs) with different electrical characteristics. The proposed converter has the ability to control the power of ESSs by allowing active power sharing. The voltage levels of utilized ESSs can be higher or lower than the output voltage. The inductors of the converter are connected to a single switch; therefore, the converter requires only one extra active switch for each input, unlike its counterparts, hence resulting in reduced element count. The proposed MIC topology is compared with its counterparts concerning various parameters. It is analyzed in detail, and then, this analysis is validated by simulation and through a 1-kWprototype based on a battery/ ultracapacitor hybrid ESS.

In this paper, thermally triggered SiC MOSFET aging effect on SiC based boost PFC converter's conducted EMI is investigated. Existing EMI evaluation and suppression studies are mostly based on power devices at healthy state. This study provides a comprehensive EMI evaluation at different state of health of SiC MOSFET used in continuous conduction mode (CCM) Boost PFC converter. For this purpose, SiC MOSFET samples are exposed to accelerated aging and the corresponding device degradations are triggered by thermal stresses. To study device characteristics at different state of health, devices under test (DUT) electrical parameters and switching transients are evaluated over aging to support SiC based AC/DC converter's conducted EMI discussion. Respectively, device aging effect on differential mode (DM) noise and common mode (CM) noise changes are discussed in detail. An 800W single phase CCM Boost PFC prototype is built to evaluate both DM and CM noise in band B frequency range (150kHz~30MHz) with experimental testing results. According to the study, high frequency noise decrement is observed after SiC MOSFET is thermally aged.

In this paper, the performance degradation of enhancement-mode (E-mode) GaN HEMFs under accelerated aging is presented in detail. A real-time degradation monitoring tool is essential to prevent costly shutdowns and minimize safety concerns. Specifically, a DC power cycling setup is first designed which operates within the safe operating area (SOA) of the device to mimic the field operation and accelerate the aging process. The E-mode GaN devices are mounted on a custom designed PCB adaptor to accommodate the curve tracer where all the parasitics are carefully controlled to minimize the measurement errors. Using the curve tracer, the parameter shifts are periodically monitored at certain aging cycles. From the experimental results, it is observed that the on-state resistance and the threshold voltage are gradually increasing over the aging cycles, which makes it potential failure precursors. Meanwhile, a variation in the transfer characteristics is observed, and the transconductance decreases as the device is aged. Finally, a detailed theoretical analysis is provided to explain this parameter shift in experiments.

Gallium Nitride (GaN) devices are becoming an attractive option in industry to achieve high-power-density and high-efficiency converter design. However, the dynamic on-resistance of GaN devices still remains a major concern. In this paper, a new dynamic on-resistance measurement circuit is proposed for fast-switching GaN power HEMTs. Simple circuit design, fast sensing speed, and accurate measurement can be realized with exclusively passive components. Compared with existing circuits, detailed component selection guidelines to realize fast sensing speed is discussed considering the switching transients. Simulation results show an accurate tracking of on-resistance in 48.3 ns after the drain current reaches the load current in the turn-on process. The proposed circuit is implemented in a double-pulse test for a 650 V GaN device. Experiment results demonstrate that the proposed circuit can work effectively at various gate resistance, dc-link voltage and load current. At 300 V/15 A turn-on process with R g,on = 20 Ω, the circuit can accurately obtain the dynamic on-state voltage within 49.6 ns after the load current is reached. Under the same switching condition with R g,on = 0 Ω, a faster sensing speed is achieved, and the circuit is able to track the dynamic on-resistance in 47.6 ns after the drain current starts to rise.

Genome-wide DNA demethylation is a unique feature of mammalian development and naïve pluripotent stem cells. So far, it was unclear how mammals specifically achieve global DNA hypomethylation, given the high conservation of the DNA (de-)methylation machinery among vertebrates. We found that DNA demethylation requires TET activity but mostly occurs at sites where TET proteins are not bound suggesting a rather indirect mechanism. Among the few specific genes bound and activated by TET proteins was the naïve pluripotency and germline markerDppa3(Pgc7, Stella), which undergoes TDG dependent demethylation. The requirement of TET proteins for genome-wide DNA demethylation could be bypassed by ectopic expression ofDppa3. We show that DPPA3 binds and displaces UHRF1 from chromatin and thereby prevents the recruitment and activation of the maintenance DNA methyltransferase DNMT1. We demonstrate that DPPA3 alone can drive global DNA demethylation when transferred to amphibians (Xenopus) and fish (medaka), both species that naturally do not have aDppa3gene and exhibit no post-fertilization DNA demethylation. Our results show that TET proteins are responsible for active and - indirectly also for - passive DNA demethylation; while TET proteins initiate local and gene-specific demethylation in vertebrates, the recent emergence of DPPA3 introduced a unique means of genome-wide passive demethylation in mammals and contributed to the evolution of epigenetic regulation during early mammalian development.

Silicon carbide (SiC) power MOSFETs have been becoming a strong alternative to silicon (Si) technology in high-voltage, high-frequency, and high-temperature applications. Despite their growing market share, limited field information is available regarding the aging facts under thermal stress and long term reliability of discrete SiC MOSFETs. In this paper, discrete SiC devices are thermally aged through a custom designed high temperature power cycling setup controlled by TI 28335 microcontroller. On-state resistance variation of devices is continuously monitored and stored in each cycle, while other electrical parameters are captured at certain intervals by utilizing an automated curve tracer. Variation of electrical parameters throughout the cycles is presented in order to assess their correlation with the aging/degradation state of the switch. The discussions regarding aging precursors are supported by structural changes obtained through scanning acoustic microscopy (SAM) and cross-sectioning.

The goal of this work is to develop a real time degradation monitoring tool for Silicon Carbide (SiC) power MOSFETs. The conventional methods for prognosis and reliability monitoring are mostly based on parametric measurements as on state resistance, threshold voltage, leakage currents etc. The change in switching characteristics of aged devices and the root cause analysis behind this change are also worth exploring for degradation monitoring. In this paper, a real-time monitoring procedure is proposed using readily available system microcontroller. For this purpose, an accelerated aging test bench is utilized to actively swing the junction temperature through power cycles in order to trigger device degradation. A number of parametric measurement results are presented for degradation discussion and turn on time variation are captured by proposed degradation monitoring approach.

In this paper, performance degradation of thermally aged cascode GaN devices is presented in detail. For this purpose, an accelerated aging setup is designed which operates within safe operating area (SOA) to mimic the power cycling in real applications as much as possible. The parametric variations are measured via a curve tracer at certain intervals to find out critical signatures for incipient fault diagnostics. Among those, the on-state resistance gradually increases throughout the power cycles, which can be identified as one of the most reliable failure precursor. Devices with different failure modes are decapsulated to investigate the causes of the failures. Some of failed cascode GaN devices show a high drain-source leakage current, gate-source leakage current and different reverse conduction characteristic compared to other thermally aged single die devices. Through measuring the two detached dies, a failure model is built in LTspice to simulate the failed device characteristics. Finally, weak points of the devices are pointed out based on the failure analysis.

In this paper, a model based signal processing method is proposed to diagnose two faults under different load condition for permanent magnet synchronous machines. This method captures the spectrum of stator current in a compact representation. Then, its dimensionality is reduced using the discriminant analysis. Finally a support vector machine automatically classifies the health state of the system. For testing the method, a customized test rig is built and data from different loads and faults are collected. An average accuracy of 93% in a 10-fold cross validation is obtained.

In this paper, a comprehensive analysis on near field electromagnetic radiation (EMR) of SiC power devices throughout aging is studied. To realize thermally triggered degradation, an accelerated test bench has been built to actively apply power cycles, swing junction temperature and trigger device degradation. The junction temperature of the devices under test (DUT) exposed to 30°C to 170°C swing and after each 250 thermal cycles, the devices are plugged into a Synchronous-Buck converter operating in continuous conduction mode. Device near field EMR is recorded by a fixed-to-clipper near field probe and a spectrum analyzer. In parallel, DUT electrical parameter shifts are measured by curve tracer as well. Possible causes of SiC MOSFET degradation are discussed under the light of the experimental result.

The recent advances and reports on failure precursors of power switches have led to estimation of lifetime as well as developing secondary control schemes to increase the lifetime of the converters. In this study, a secondary control scheme to extend the lifetime of the converter based on the identified failure precursors such as the on-state resistance variation for power MOSFETs and collector emitter voltage variation for IGBTs is proposed for three-phase converters. The controller switches the modulation scheme from SVPWM to discontinuous PWM, and adjusts the switching frequency, once the tracked failure precursor reaches to the defined threshold value. The tradeoff between the total harmonic distortion and lifetime extension at different modulation techniques and switching frequencies are addressed.

Lately, interest in renewable sources, especially wind and solar energy, has shown a significant increase in all over the world that mostly depends on climate-threatening conventional fossil fuels. Besides, hybrid use of these power sources with suitable back-up units provides many advantages compared to sole use of these sources. In this regard, a hybrid system consisting of a wind turbine for utilizing the wind energy, photovoltaic panels for solar energy, fuel cell for providing back-up power and a battery unit for storing the possible excess energy production and supplying the transient load is considered in this study. Experimental assessment of this system in different case studies including the real time measured dynamic power demand of an office block is realized. The collaborative actions of the proposed hybrid system with a fuzzy logic based energy management strategy during fluctuations of renewable-based power production are investigated. Thus, results of this study may be valuable for evaluating the feasibility of stand-alone hybrid renewable energy units for future power systems.

Photovoltaic (PV) systems are considered as a support unit and eco-friendly energy source for the electric vehicles. If the surface of the electric vehicle is covered by PV cells, it is possible to store considerable amount of energy in the battery system. In this study, different maximum power point trackers (MPPT) with different maximum power point (MPP) tracking algorithms have been tested on a PV structure moving according to a predefined motion loop. Compatibility of each algorithm to moving systems, such as electric vehicles, is presented in a real experimental environment. As a result of these experiments, positive factors in each algorithm have been defined and a new MPP tracking algorithm convenient for moving vehicle has been proposed. The proposed MPPT algorithm shows a better performance than other MPPT algorithms under fast varying radiations. However, proposed algorithm brings slightly higher costs compared to usage of other MPPT algorithms since it requires the measurement of solar irradiance. The developed algorithm is described in detail and comparative analysis and performance evaluation with other algorithms are presented.

Bidirectional dc-dc converters are widely used in applications requiring bidirectional power flow. Control of these converters in a more suitable way and modeling and analyzing of them in a simpler method is still a research topic. In this paper different small signal modeling methods for bidirectional dc-dc converters are compared. Mathematical averaged small signal modeling and ac sweep tool on PSIM simulation software are used to obtain ac response of the converter. These results are compared in terms of bode plots to evaluate accuracy and convenience of the modeling techniques. Step-by-step calculations and simulations are presented together with detailed comparison of simulation results.

Recently, ideas like smart cities, smart buildings/homes has been widely used under smart grid concept, which is a new research area that combines power systems and information technology (IT). The basic building block of the smart grid can be considered as “smart home”. Smart grid infrastructure with smart homes will allow to monitor electrical demand of a city or a residential customer and to achieve better utilization of existing grid through the use of streaming demand data. In addition, it will be easier to integrate renewable energy sources into existing grid. Experimental demonstrations are important for promoting smart grid concept. Thus, a renewable energy supplied smart home project with a budget of $0.5 million has been completed at Yildiz Technical University (YTU), Istanbul, Turkey. This paper first introduces the constructed smart home in detail. Then, the benefit of smart home operation on carbon emission reduction with appliance control through smart plugs is analysed by a simulation study in Matlab/Simulink.

Small-scale wind turbines are promising renewable energy devices driven by the aim of carbon savings at energy generation. However, the use of small-scale wind turbines in residential areas is still very narrow because of low wind speeds, high turbulence intensity, and the perception of high aerodynamic noise produced by wind turbines. Furthermore, their high cost make it essential to assess the turbines carefully before deciding to purchase so that the optimum performance and costs can be obtained. In this study, power curves of bestselling small scale wind turbines in Turkey are compared using experimentally collected one year wind data for the use in a smart home environment at Davutpasa Campus, Istanbul. The total annual energy production of the wind turbines and financial payback periods are calculated. With the results of performed analysis, it is possible to define the most profitable small wind turbine to be used in related applications in Istanbul and in areas where wind speed is similar.

Photovoltaic systems have been a prominent option as an additional energy source for vehicles. Maximum power point trackers (MPPTs) should be used to increase efficiency and power output of solar panels under changing environmental factors. There are several different algorithms in the literature developed for maximum power point tracking. However, energy performances of MPPT algorithms are not clarified for vehicle applications that cause rapid changes of environmental factors. In this study, three popular MPPT algorithms, i.e. P&O, IC and OC, are compared at real ambient conditions by couples. For comparison, PV modules are mounted on a moving platform designed to simulate insulation received by solar systems on a moving vehicle. Experimental results obtained from comparison of algorithms by a motion loop are presented and discussed.

In this study, a battery and ultra-capacitor (UC) hybrid electric vehicular system is proposed. The battery supplies the long term energy requirements of the vehicle while UC is employed for picking up the transient load variations that can seriously damage the electrochemical structure of the battery. An experimental assessment of the constructed vehicle prototype of such hybrid structure is realized under a real time drive cycle. The proposed system provides the advantages of eliminating of the supervisory control system necessity as well as realizing a more reliable local control approach based on voltage regulation compared to current based control approaches.

Sensorless control strategies for brushless DC motors (BLDC) offer cost-effective and fault-tolerant operation through replacing expensive position sensors with low-cost circuit components or taking advantage of on-board components. These drives mainly focus on two individual issues; first one is finding the initial rotor position at standstill, and the second one is driving BLDC at high speeds. Most of the studies focus on these two cases separately, proposing different circuit for each of them which adds to cost of the system. Therefore, it is desired to have control over all speed ranges including zero speed with same circuit elements if possible. This manuscript proposes a sensorless control method that combines initial position estimation by analyzing the stator core saturation and detection of zero crossings of back emf voltage by utilizing low pass filters with the same circuit topology. Results verify that a cost-effective drive can be achieved with proposed add-on resistor configuration and control method.

For vehicular systems, fuel cells (FCs) are considered as a potential long term alternative to replace conventional combustion engines. However, high cost and slow dynamic response of FC are still the main challenges for wider applications. To overcome this problem, an auxiliary power system with adequate power capacity has to be incorporated. Ultra-capacitors (UCs) can provide an applicable solution in this aspect. Thus, a test bench of FC/UC hybrid configuration that can be suitable for vehicular systems is presented in this paper. In addition, an improved power conditioning unit (PCU) that can enhance fuel economy compared to conventional converter topologies is provided. Two different hybridization topologies are examined from different aspects. A test bench performance verification of a fuzzy logic based energy management strategy that was discussed in earlier simulation-based studies of the authors is investigated. Experimental results with small-scale devices, namely, a PEMFC (1200 W, 46 A) manufactured by the Ballard Power System Company, and four UC modules (58 F, 15 V) manufactured by the Maxwell Technologies Company, illustrate the performance analysis of both the applied PCUs and employed energy-management scheme during load cycles.

DNA methylation (5-methylcytosine (5mC)) is critical for genome stability and transcriptional regulation in mammals. The discovery that ten-eleven translocation (TET) proteins catalyze the oxidation of 5mC to 5-hydroxymethylcytosine (5hmC), 5-formylcytosine (5fC), and 5-carboxylcytosine (5caC) revolutionized our perspective on the complexity and regulation of DNA modifications. However, to what extent the regulatory functions of TET1 can be attributed to its catalytic activity remains unclear. Here, we use genome engineering and quantitative multi-omics approaches to dissect the precise catalytic vs. non-catalytic functions of TET1 in murine embryonic stem cells (mESCs). Our study identifies TET1 as an essential interaction hub for multiple chromatin modifying complexes and a global regulator of histone modifications. Strikingly, we find that the majority of transcriptional regulation depends on non-catalytic functions of TET1. In particular, we show that TET1 is critical for the establishment of H3K9me3 and H4K20me3 at endogenous retroviral elements (ERVs) and their silencing that is independent of its canonical role in DNA demethylation. Furthermore, we provide evidence that this repression of ERVs depends on the interaction between TET1 and SIN3A. In summary, we demonstrate that the non-catalytic functions of TET1 are critical for regulation of gene expression and the silencing of endogenous retroviruses in mESCs.