2,938 research outputs found
Comparative feasibility study of a 30 MW disruptive floater solution with a 15 MW PivotBuoy and a benchmark 15 MW semi-submersible floater in the Bay of Biscay
No full textThis paper investigates the technical, life cycle, and economic feasibility of a 30 MW upscaled downwind turbine, comparing it to a 15 MW X1 Wind PivotBuoy downwind turbine and a benchmark 15 MW IEA Umaine VolturnUS-S upwind turbine in the 450 MW Sud de la Bretagne I wind farm site. The study is significant due to the rising energy demand, the potential for decreasing the levelized cost of energy with increased turbine size, and the optimized use of space. The size limit of current upwind turbine designs could be addressed using a downwind turbine solution.The research is conducted by modelling the global dynamic response of the structure using OpenFAST and computing the natural frequencies and stresses using a finite element model. A lifecycle analysis is performed to identify potential pitfalls and bottlenecks by analysing the individual lifecycle phases. The economic feasibility is assessed by simulating the annual energy production using TOPFARM and utilizing structural analysis and lifecycle assessment to quantify capital, operational, and abandonment expenditures. Based on the annual energy production and the performance indicators the levelized cost of energy is calculated.The findings indicate that while the global stability is within boundaries, the stress in members is too high with a simple scale-up of the proposed design. Bottlenecks are found in lifting operations and supply chain readiness. The levelized cost of energy and capital expenditure increased due to substructure self-weight, rendering the proposed 30 MW scale-up currently unfeasible when compared to the other two wind farms.These findings are important as they demonstrate that the 15 MW X1 Wind PivotBuoy is not scalable without design changes. The levelized cost of energy does not decrease with an increased floater solution. The 15 MW X1 Wind PivotBuoy downwind turbine seems more economically viable, making it a more interesting option for future development.Civil Engineerin
Short-circuit characteristics of superconducting permanent magnet generators for 10 MW wind turbines
No full textSuperconducting permanent magnet generators (SCPMGs) are a potential candidate for 10 MW direct-drive wind turbine applications. This paper presents two 10 MW SCPMG designs using MgB<sub>2</sub> cables for the armature winding and investigates the short-circuit characteristics of the designed SCPMGs. The first part of the results shows that the SCPMGs can double the shear stress of a conventional low-speed permanent magnet (PM) generator (from 65 kPa to 130 kPa) whilst avoiding demagnetization of the PMs in rated-load operation. However, the power factor has to drop to a range of 0.7-0.8. The second part of the results shows that during a sudden three-phase short circuit, the superconducting armature winding is prone to quench and the PMs are likely to be demagnetized in both proposed designs.Accepted Author ManuscriptTransport Engineering and Logistic
The impact of single nucleotide polymorphisms in human genes that regulate hepcidin and iron on oral iron absorption and the risk of anaemia in Africans
No full textBackground: Up to 60% of women and children living in low- and middle-income countries (LMICs) are anaemic. Food fortification and iron supplementation are the most common measures employed to combat anaemia. However, these are not effective treatments for anaemias caused by non-nutritional factors. Genome-wide association studies (GWAS) mainly in Europeans and Asians have identified single nucleotide polymorphisms (SNPs) within the hepcidin and iron regulatory genes that are associated with the risk of anaemia. Several of these SNPs are in the TMPRSS6 gene, which encodes matriptase-2, a protein that regulates the expression of hepcidin. This thesis examined the impact of SNPs in the iron regulatory genes previously reported in non-African populations, on the risk of anaemia and on impaired oral iron absorption in Africans. Methods: First, the literature was searched for genetic variants identified in the hepcidin and iron regulatory genes, that are associated with low iron status. Second, we investigated the effects of common TMPRSS6 and transferrin (TF) SNPs on iron status in a cohort of healthy individuals from rural Gambia (n=1315). Third, a recallby- genotype (RbG) study was conducted to investigate the impact of carrying single or multiple alleles at the common TMPRSS6 SNPs on oral iron absorption in healthy individuals from rural Gambia. Results: TMPRSS6 rs855791, rs4820268 and rs2235321, and TF rs3811647 are the most common SNPs that associated with low iron status. We did not find effects of any of the TMPRSS6 SNPs on the risk of anaemia. However, we found that TMPRSS6 rs2235321 was associated with serum hepcidin concentration, with a more substantial effect on individuals with low haemoglobin or ferritin. Also, TF rs3811647 had a significant influence on transferrin and its binding capacity, with a single allele effect of 8-12%. In the RbG study, we did not find any effect of the three TMPRSS6 SNPs on oral iron absorption. However, we found that each of the TMPRSS6 SNPs affects hepcidin, with carriers of major alleles having higher hepcidin compared to minor allele carriers. Also, we found that heterozygotes at both rs2235321 and rs855791 did not alter their hepcidin concentration after an oral iron dose, whereas, individuals in all the other genotype groups did. Conclusions: This thesis confirms the previously observed association between the TF rs3811647 and transferrin in other Africans and Europeans replicates in West Africans. However, we could not demonstrate that the previous associations between TMPRSS6 gene variants and iron status, exist in West Africans. This lack of replication might be due to the high genetic diversity that exists in African populations. We identified an effect of TMPRSS6 rs2235321 on serum hepcidin concentration. In the RbG study, the three TMPRSS6 SNPs studied influenced serum hepcidin levels but not oral iron absorption in healthy individuals. This finding suggests that there might be an alternate pathway of iron regulation independent of hepcidin at the enterocytes. These findings highlight the need to conduct more research on genetic determinants of iron status in African populations. Investigating more genetic markers and in different populations may provide a clearer insight into the role of genetic risk factors on iron deficiency and anaemia in African populations. Identifying the role of genetic risk factors of iron status may pave the way for the formulation of population specific anaemia control measures
An Ultrasonically Powered System Using an AlN PMUT Receiver for Delivering Instantaneous mW-Range DC Power to Biomedical Implants
No full textAluminum Nitride (AlN) Piezoelectric Micromachined Ultrasonic Transducers (PMUTs) are gaining interest for biomedical implant power due to biocompatibility and lowtemperature processing. However, due to the low piezoelectric coefficient of AlN PMUTs, storage capacitors are often used to accumulate ultrasonic power transferred over an extended time. The accumulated energy is then used to power a DC load, which leads to a long start-up time, and insufficient duty cycle for some applications. We present an ultrasonically powered system for biomedical implants capable of delivering mW-range instantaneous power to DC loads, without pre-storing it. The system features a 25 mm2 AlN PMUT, an inductive matching network, and an application-specific power management integrated circuit(ASIC). For an acoustic intensity of 360 mW/cm2 at the surface of the PMUT, an open-circuit voltage of 1.11 V and an aperture efficiency of 30.5 % are measured. Furthermore, by connecting a series-matching inductor to the PMUT, the highest-reported power delivered to the load (PDL) of 6.4 mW is measured over an optimal load of 7.6 Ω. Finally, together with the ASIC and at the intensity of 108 mW/cm2, our system delivers 1.04 mW DC power to a 3.3 kΩ load, which is over two orders of magnitude higher than the previously reported average DC power for AlN PMUTs.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.Bio-ElectronicsElectronic Components, Technology and Material
Inversion of coseismic deformation due to the 8th February 2016, Mw 4.2 earthquake at Los Humeros (Mexico) inferred from DInSAR
No full textOn the 8th of February 2016, a Mw 4.2 earthquake was detected inside the Los Humeros caldera, located in the eastern sector of the Trans-Mexican Volcanic Belt. The event occurred after a sharp increase in the injection rate at the Los Humeros Geothermal Field and it was recorded by the seismic monitoring network of the power plant. The earthquake was felt by the local population and it caused damage in the power plant infrastructure. The focal mechanism solution of a previous study based on seismological data shows a reverse movement with a minor left-lateral component: Mw=4.2, depth=1500m, strike=169°, dip=61°, rake=42°. We have performed a geodetic and geomechanical analysis of the seismic source event based on ground deformation inferred from DInSAR. We used ascending and descending Sentinel-1 differential interferograms to retrieve the horizontal and vertical components of the co-seismic deformation. Subsequently, we inverted the estimated deformation to obtain the solution of an activated fault using the Okada model. These results shed light on the geomechanical aspects of the event and can help to understand the effects of field operations interacting with pre-existing structural features and active tectonic processes in the Los Humeros caldera.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.Mathematical Geodesy and Positionin
Towards a True Author Entry System for CAI
No full textCAI course authors have been faced with the disc tint problem of having to learn an instructional coding language before they can get their courses into the computer. A system has been devised so that an author may easily write his course in English on course planning forms and then a pre-processor will generate the coding which will be input for the machine assembler
A 19.8-mW Eddy-Current Displacement Sensor Interface with Sub-Nanometer Resolution
No full textThis paper presents an eddy-current sensor (ECS) interface intended for sub-nanometer (sub-nm) displacement sensing in hi-tech applications. The interface employs a 126-MHz excitation frequency to mitigate the skin effect, and achieve high resolution and stability. An efficient on-chip sensor offset compensation scheme is introduced which removes sensor-offset proportional to the standoff distance. To assist in the ratiometric suppression of noise and drift of the excitation oscillator, the ECS interface consists of a highly linear amplitude demodulation scheme that employs passive capacitors for voltage-to-current (V2I) conversion. Using a printed circuit board-based pseudo-differential ECS, stability tests were performed which demonstrated a thermal drift of <7.3 nm/°C and long-term drift of only 29.5 nm over a period of 60 h. The interface achieves an effective noise floor of 13.4 pm Hz which corresponds to a displacement resolution of 0.6 nm in a 2-kHz noise bandwidth. The ECS interface is fabricated in TSMC 0.18- μm CMOS technology and dissipates only 19.8 mW from a 1.8-V supply.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.Electronic InstrumentationMicroelectronic
A 0.96-mW dB-Linear Variable Gain Amplifier With 0.4-dB Linearity Error Over a 62.4-dB Gain Tuning Range
No full textThis letter presents a low-power dB-linear variable gain amplifier (VGA) with a small linear-in-dB error over a wide gain tuning range. An exponential current ratio is realized in the linear-in-dB control circuit based on the subthreshold I-V characteristic. The VGA is built with subthreshold common-gate transistors as current steering, accurately replicating the exponential current ratio and forming a tunable gain. Implemented in 55-nm CMOS technology, the proposed VGA occupies a compact active area of 0.011 mm2 excluding the buffer. It achieves a linear-in-dB error of 0.4 dB over a gain tuning range of 62.4 dB, corresponding to the state-of-the-art relative error of 0.6%. The proposed design shows constant 80-MHz bandwidth with a power consumption of 0.96 mW. 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.Electronic Instrumentatio
Exploring Extended Mind-Wandering Through an Interactive Haptic Fidget Object
No full textMind-wandering (MW) and fidgeting are both present as pervasive phenomena in everyday life and can positively impact ideation. Importantly, within the MW experience, MW can manifest in bodily behaviors such as physical fidgeting. Here, we use an extended mind framework to consider fidgeting as a case of extended MW, where (part of) a MW episode is mediated by a fidget object. We position extended MW, fidgeting, and cognition as interrelated processes. We present the design of an interactive haptic fidget object that aims to support introspective self-awareness in MW and aid in idea synthesis. We discuss the results of an exploratory user evaluation in which the fidget object was used by designers during a personally relevant work session combining research, synthesis, and creativity. We close this paper by discussing the initial findings of our research, the implications for extended MW, and additional propositions for future research directions.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.Design AestheticsHuman Information Communication Desig
The Behaviour of the Bridges with the MW Steering Bar
No full textAbstractThe track-bridge interaction is a widely discussed and important topic today, as the modern railway bridges commonly exceed the maximum dilatation lengths allowed for the continuous welded rail. In this case, the Meyer-Wunstorf steering bar is one of the suitable solutions that can move the fixed point of the bridge to the middle of the span and thus exceed the possibility of the application of the continuous welded rail without any rail expansion devices. However, this solution is new in the Czech Republic and its functionality and durability should be verified.The paper deals with the extensive load tests, made on the first Czech railway bridge with the steering bar Meyer-Wunstorf. The two-track railway arch bridge on the Tábor - Sudoměřice track crosses the D3 highway with the span of 100 m. The load tests were focused on the horizontal brake and acceleration forces with the heavy train (totally 1056 t) and four locomotives of weight 318,6 t. During the test, a number of values were measured, such as stresses in the rail and MW system, movements of the MW and the bridge, temperature. The behaviour of the steering bar and the bridge – track interaction is described and compared with the design and theoretical assumptions. The paper also gives the recommendations for the practical design and analysis of the MW system
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