39 research outputs found

    Pan-cancer analysis of whole genomes

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    Cancer is driven by genetic change, and the advent of massively parallel sequencing has enabled systematic documentation of this variation at the whole-genome scale(1-3). Here we report the integrative analysis of 2,658 whole-cancer genomes and their matching normal tissues across 38 tumour types from the Pan-Cancer Analysis of Whole Genomes (PCAWG) Consortium of the International Cancer Genome Consortium (ICGC) and The Cancer Genome Atlas (TCGA). We describe the generation of the PCAWG resource, facilitated by international data sharing using compute clouds. On average, cancer genomes contained 4-5 driver mutations when combining coding and non-coding genomic elements; however, in around 5% of cases no drivers were identified, suggesting that cancer driver discovery is not yet complete. Chromothripsis, in which many clustered structural variants arise in a single catastrophic event, is frequently an early event in tumour evolution; in acral melanoma, for example, these events precede most somatic point mutations and affect several cancer-associated genes simultaneously. Cancers with abnormal telomere maintenance often originate from tissues with low replicative activity and show several mechanisms of preventing telomere attrition to critical levels. Common and rare germline variants affect patterns of somatic mutation, including point mutations, structural variants and somatic retrotransposition. A collection of papers from the PCAWG Consortium describes non-coding mutations that drive cancer beyond those in the TERT promoter(4); identifies new signatures of mutational processes that cause base substitutions, small insertions and deletions and structural variation(5,6); analyses timings and patterns of tumour evolution(7); describes the diverse transcriptional consequences of somatic mutation on splicing, expression levels, fusion genes and promoter activity(8,9); and evaluates a range of more-specialized features of cancer genomes(8,10-18).Peer reviewe

    Dynamic Wireless Charging of Electric Vehicles

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    As a more convenient alternative to conductive charging technology, wireless charging is seen as a key technology drive for transportation electrification. In electric vehicle (EV) battery charging applications, wireless power is transferred through a magnetic link, so it is referred to as inductive power transfer (IPT). One advantage of IPT technology is that the charging of EVs can be fully automated. The recharge of traction batteries can start automatically when the EV stops where its receiver (Rx) coil is coupled with a transmitter (Tx) coil of an IPT charger. Apart from static charging applications, IPT technology can also be used to build dynamic charging roads where EVs can get charged in motion and the capacity of onboard batteries can be reduced. This thesis studied four challenges that should be addressed before dynamic IPT becomes mature enough for commercial use. The research topics focus on magnetic coupler design, prediction and control of transient behaviors, reduction of power fluctuation, and detection of EVs and foreign objects (FOs). Magnetic coupler designThe key performance indicators of an IPT system include power transfer capability, power density, power efficiency, and misalignment tolerance. Due to conflicts among these performance indicators, it is indispensable to formulate the design of IPT charging pads as a multi-objective optimization (MOO) problem. By using finite element (FE) models, the magnetic field property of a coupler can be computed. However, calculating the aligned and misaligned power losses at the rated power requires not only the magnetic field property but also the compensation strategy. The compensation strategy determines the load match method which is used to calculate the optimal load condition and the rated winding currents. Therefore, compensation strategy should also be considered for the magnetic coupler design. With the magnetic field distribution known, the power losses in the AC link can be calculated through the existing analytical method. This thesis develops a MOO method that can find the performance space from the design search space of magnetic couplers. In the performance space, Pareto fronts can be obtained under different conflicting optimization objectives. The study shows that analytically calculating the AC link power efficiency is possible when the magnetic field is accurately computed at the rated condition. More importantly, the DC-DC power efficiency of the final prototype reaches 97.2%97.2\% which proves that the MOO design is vital to make full use of IPT technology.Prediction and control of transient behaviorsIPT systems require capacitive/inductive components to form resonant circuits on both sides to improve the power transfer capability and power efficiency, while the compensation components also make the resonant stage of a high order. As a result, the analytical dynamic models of IPT systems are complex and mostly impossible to solve in the time domain. This thesis proposes a new reduced-order dynamic modeling method that describes the transient behavior of a resonant stage from the energy point of view. The order of the resultant dynamic model is one-fourth that of conventional ones for SS compensated IPT systems. Also, a MPC controller is designed based on the proposed dynamic model. It is proven that simplifying the dynamic model is helpful in explaining how circuit parameters influence transient behaviors and also in facilitating the application of advanced control strategies in IPT systems. Reduction of power fluctuationThe most obvious difference between static and dynamic IPT is the change in magnetic coupling. In DIPT applications, the magnetic coupling fluctuates from the maximum to a usable level as EVs move, so one of the main challenges of DIPT is to stabilize the pick-up power, especially for DIPT systems using segmented Tx coils where magnetic coupling changes more frequently. The conventional methods are either to overlap Tx coils or to add extra sets of the Rx sides, which are expensive in building costs.This thesis presents the design of a segmented DIPT system using a multiphase Tx side. The Rx coil consists of two sub-windings connected in series with a relatively large spatial offset in the EV moving direction. One advantage of the proposed design is that the Tx coils are deployed loosely so the building cost can be reduced. The other advantage is that the pick-up power is seamless with a small ripple. The pick-up power demonstrates a 24.9%24.9\% ripple by experiments. Detection of EVs and FOsTo minimize the Tx side power losses and magnetic field radiation, the detection of EVs and FOs should be implemented in DIPT systems. Considering the integration of the detection equipment into the charging pads, PCB coils become the most suitable candidate to sense the magnetic field for detection purposes. However, the detection of EVs and FOs are mostly discussed separately in the literature. There is a need to achieve these two detection functions within one set of PCB coils.This thesis presents the design of detection equipment consisting of PCB coils installed onto charging pads and the detection resonant circuit (DRC) connected to Tx side PCB coils. It can be concluded that the detection of EVs and FOs can both be realized by measuring the variation of the magnetic field caused by their intrusion, and PCB coils demonstrate good performances in measuring the change of magnetic field together with DRC to amplify the detection signals.DC systems, Energy conversion & Storag

    Dynamics of Energy System Behaviour and Emissions of Trailing Suction Hopper Dredgers

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    Reducing fuel consumption from dredge vessels is always one of the priorities of the ship builder and the dredge contractor. In addition there is an increased awareness worldwide regarding exhaust emissions. CO2, NOx and SOx currently are or will in future be regulated strictly by international legislation and local authorities. Looking at a dredge cycle of a Trailing Suction Hopper Dredger (TSHD), every stage is far from stationary and in fact the dynamic variations are very severe.. Its performance is strongly influenced by weather condition, hydrological condition, river/sea bed profiles, soil types and characteristics, discharge method and discharge pipeline configuration. Although, nowadays, sophisticated automation is employed on subsystems for optimizing the dredging process, the dredger is still mainly under control of operators. The knowledge, the skill, the attitude of the dredge operators determine the performance of a TSHD and make it even more dynamic. In order to reduce fuel consumption and exhaust emissions, the impact from said dynamics need to be taken into account. This research is therefore conducted in order to know, capture, understand and be able to predict the behaviour of the energy system of a TSHD under dynamic load. Comprehensive onboard measurements have been executed to collect real time data on the energy system behaviour and exhaust emissions. After post-processing, consisting of signal synchronization, correction of the NOx-sensor time lag, filtering, signal organization and unit conversion, the results are presented the very first time. It is observed that, at constant nominal engine speed transient loads push the fuel consumption, air consumption and NOx emission away from the stationary lines. However seen at a larger time scale (in the order of stages per dredging cycle), the effects from transient loads are neutralized. The most important conclusion is: that in terms of total fuel consumption and total exhaust emissions, a dynamic loading of the energy system is not resulting in a penalty. Nonlinear time domain simulation models of a TSHD energy system (for dredging and sailing) are built in Matlab/Simulink®. The main system components and their dynamics are included, which makes the scope of the simulation models wide enough to cover all required energy systems. By means of matching and validation, the precision of the simulation models is ensured on both component and system level. Most of the components are modelled based on first principle concepts. They provide the required level of detail for understanding the system behaviour and emissions. In addition, the simulation models are well structured, providing easy removal of non-needed components, addition of new components and improvement of existing components. Through onboard measurements and simulation models, the dynamics of the behaviour of energy systems and in particular the emissions of a TSHD was thoroughly investigated in the time domain. Using normalization and linearization, the response of the energy systems to external disturbances and control commands are also investigated in the frequency domain. The linear model requires only a limited number of normalized derivatives and time constants and they are relatively independent of physical dimensions of the components. In a block diagram as presented in the thesis it can be easily traced how the disturbances propagate through the energy system and the sensitivities of involved parameters can be judged. The linear model has several advantages when compared to the nonlinear model. In the first place a linear model is generic. Further the required normalized derivatives and time constants can often easily be estimated beforehand, also because their first principle origin is made explicit. So this makes it possible that the order of magnitude of the frequency bands of any system can be grasped, even before there is an actual design. Finally the dynamic response can be explored using classical control methods. This would be useful in deciding whether a control system is needed and to determine what kind of control strategy would be effective. In summary, the three approaches (onboard measurement, non-linear simulation model and linear model) presented in this thesis provide an exclusive database and practical tools to know, to capture, to understand and to be able to predict the behaviour of the energy system and emissions of a TSHD. By further development, such as: measurement from more vessels, extending the scope of the model, increasing the precision of the model and increasing the level of details of the model, these methods can eventually be used for optimizing the design of a TSHD and reducing operational cost (fuel and emissions).MTT-SPDOMechanical, Maritime and Materials Engineerin

    Positron Annihilation Studies on Thin Film Solar Cells: CdSe and PbSe Quantum Dot Thin Films and Cu(In1-xGax)Se2 Layered Systems

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    High efficiency, low cost, and long stability are three key factors for the wide application of photovoltaics (PV) which are currently intensively studied in order to meet the increasing global renewable energy demand. Currently, the PV market is mainly based on silicon. However, solar cells based on silicon may not be capable to meet the long-term global energy demand due to their relatively high costs and high energy required for the synthesis of silicon wafers, opening the door to conventional thin films (such as Cu(In1-xGax)Se2 (CIGS)) and innovative thin films (e.g. semiconductor quantum dots (QDs), based on PbS, PbSe, CdSe QDs). The advantages of QDs as solar cell materials are the low-temperature synthesis process, the tunable band gap via control of the composition and size, and the promise of physical mechanisms that may increase efficiency above the Shockley-Queisser limit, such as multiple exciton generation (MEG), in which more than one exciton is created from a single photon. However, the low efficiency, with a current laboratory record just above 10%, and the durability are still limitations on their widespread application in the PV market. It is very important to understand the surface structure and surface-ligand interactions in order to improve the efficiency and stability of QD solar cells. For CIGS solar cells, research-cell efficiencies have reached 22.6%, which is just below the efficiencies of Si-based solar cells. Besides, various deposition approaches have been developed that can supply high-efficiency, low-cost and large-area solar cell devices. However, it is still a challenge to guarantee long-term stability of CIGS modules. CIGS solar cells can be well protected by sealing into glass plates, but this in turn increases the manufacturing cost. Therefore, understanding of the degradation mechanism is necessary.Positron techniques are powerful tools to study the surface composition of QDs and to determine the types of open space deficiencies in thin film materials. For QDs, previous studies provided indications that positrons can trap and annihilate at the surfaces of semiconductor QDs and can effectively probe the surface composition and electronic structure of colloidal semiconductor QDs. For CIGS, previous depth-sensitive positron experiments indicated the sensitivity of positrons to probe the types of vacancy-related defects in CIGS.RST/Fundamental Aspects of Materials and Energ

    Detecting changes in extreme precipitation and extreme streamflow in the Dongjiang River Basin in southern China

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    International audienceExtreme hydro-meteorological events have become the focus of more and more studies in the last decade. Due to the complexity of the spatial pattern of changes in precipitation processes, it is still hard to establish a clear view of how precipitation has changed and how it will change in the future. In the present study, changes in extreme precipitation and streamflow processes in the Dongjiang River Basin in southern China are investigated with several nonparametric methods, including one method (Mann-Kendall test) for detecting trend, and three methods (Kolmogorov?Smirnov test, Levene's test and quantile test) for detecting changes in probability distribution. It was shown that little change is observed in annual extreme precipitation in terms of various indices, but some significant changes are found in the precipitation processes on a monthly basis, which indicates that when detecting climate changes, besides annual indices, seasonal variations in extreme events should be considered as well. Despite of little change in annual extreme precipitation series, significant changes are detected in several annual extreme flood flow and low-flow series, mainly at the stations along the main channel of Dongjiang River, which are affected significantly by the operation of several major reservoirs. To assess the reliability of the results, the power of three non-parametric methods are assessed by Monte Carlo simulation. The simulation results show that, while all three methods work well for detecting changes in two groups of data with large sample size (e.g., over 200 points in each group) and large differences in distribution parameters (e.g., over 100% increase of scale parameter in Gamma distribution), none of them are powerful enough for small data sets (e.g., less than 100 points) and small distribution parameter difference (e.g., 50% increase of scale parameter in Gamma distribution). The result of the present study raises the concern of the robustness of statistical change-detection methods, shows the necessity of combined use of different methods including both exploratory and quantitative statistical methods, and emphasizes the need of physically sound explanation when applying statistical test methods for detecting changes

    Integrated Solution for Electric Vehicle and Foreign Object Detection in the Application of Dynamic Inductive Power Transfer

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    One of the challenges with the dynamic inductive power transfer (DIPT) technique is the electric vehicle detection (EVD) that helps the DIPT system to control the power supply of the transmitter. The EVD method applying auxiliary coils is a promising candidate because the flat shape of the auxiliary coils is suitable for the compact design. However, the EVD may fail when the metallic foreign object (MFO) is present. Therefore, the desire emerges in the integration design of the EVD and foreign object detection (FOD). The FOD can ensure the reliability of the EVD as well as the highly efficient operation of the DIPT system without MFOs. In this context, this paper proposes an integrated solution to the EVD and FOD well suited for DIPT systems. The integrated solution utilizes both passive coil sets (PCSs) and active coil sets (ACSs). Additionally, a novel detection resonant circuit (DRC) is proposed to realize EVD and FOD using the same coil sets and to amplify the measurement sensitivity. The operation mechanisms, the detection coil sets architecture, the design of the proposed resonant circuits and the detection procedure are detailed. Finally, a printed circuit board based prototype is built to validate the integrated functionality of the EVD and FOD in a DIPT prototype processing 1 kW output. Experiments considering the practical DIPT application scenarios are conducted, and the proposed detection method is able to achieve advantageously high sensitivity and no blind zone.Accepted Author ManuscriptDC systems, Energy conversion & Storag

    NbN hot electron bolometer mixer at 5.3 THz

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    We report the sensitivity of a superconducting NbN hot electron bolometer mixer integrated with a tight spiral antenna at 5.3 THz. Using a measurement setup with black body calibration sources and a beam splitter in vacuo, and an antireflection coated Si lens, we obtained a double sideband receiver noise temperature of 1150 K, which is 4.5 times h?/kB (quantum limit). Our experimental results in combination with an antenna-to-bolometer coupling simulation suggest that HEB mixer can work well at least up to 6 THz, suitable for next generation of high-resolution spectroscopic of the neutral atomic oxygen (OI) line at 4.7 THz.Kavli Institute of NanoscienceApplied Science

    Analysis of Magnetic Field Emissions in Inductive Power Transfer EV Chargers Following Reference Designs in SAE J2954/2019

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    This paper aims to investigate the radiated magnetic field by 11 kW inductive power transfer (IPT) systems used for the charging of electric vehicles. Two reference designs suggested by SAE J2954 are studied. Both designs are analysed to obtain the coils winding currents, and 3D FEM models are built in COMSOL without considering the car chassis, which constitutes a conservative approach. The magnetic field intensity at specific distances from the IPT coupler are calculated. Finally, the simulation results are compared with the respective magnetic field limits defined in the international standards SAE J2954, IEC 61980-1 and ICNIRP. The results show that the magnetic field radiations at 10 meters points are significantly lower than the limits established in the SAE J2954, while the emissions at 0.9 meters points are only slightly below the limits defined by ICNIRP.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.DC systems, Energy conversion & Storag

    Detection of Metallic Foreign Objects and Electric Vehicles Using Auxiliary Coil Sets for Dynamic Inductive Power Transfer Systems

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    This paper proposes a new method of electric vehicles detection (EVD) and foreign objects detection (FOD) for dynamic inductive power transfer (DIPT) systems. The proposed detection method applies both passive coil sets (PCSs) and active coil sets (ACSs) to achieve both EVD and FOD with a high detection sensitivity. The operation mechanisms and design of the detection coil sets topology and resonant circuits are elaborated. Finally, both circuit and magnetic field simulation are carried out. The results verify the feasibility and sensitivity of the proposed detection method.Virtual/online event due to COVID-19 Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.DC systems, Energy conversion & Storag

    Coils’ Current Distortion Due to Variable Series Compensation Capacitance in EV Wireless Charging for a Constant Optimum Load

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    When considering EV wireless charging that uses inductive power transfer with magnetic resonance, the coils’ current distortion must be minimized to guarantee compliance with the electromagnetic compatibility limits on the radiated magnetic field set by the relevant industrial standards. This paper analyzes the current distortion caused by switch-controlled capacitors (SCCs) used as series compensation to achieve constant optimum load (COL) matching at different coils’ alignments. First, the proposed COL charging method is explained where the SCCs have either the half-wave or the full-wave modulation. Their impact on the measured coils’ current distortion has been analyzed up to 30MHz by computing the fast Fourier transform (FFT). Additionally, the currents’ FFT from the half-wave modulation has been compared to those resulting from the conventional series-series compensation with fixed capacitance. The SCCs using the half-wave modulation result in the highest total-lumped distortion. However, the individual amplitudes corresponding to the critical frequencies of the radiated magnetic field’s limit from SAE J2954 are comparable or lower than those resulting from the other implementations. Finally, the radiated magnetic field resulting from each strategy has been evaluated using the finite element method. All results are well within the SAE J2954 recommended limits at 10 m. Moreover, a minimum distance of 25 cm from the outer sides of the coupled coils ensures a safe exposure to both the general public and implanted medical devices according to the ICNIRP reference levels.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.DC systems, Energy conversion & Storag
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