214 research outputs found
Supplemental Material - Peritumoral Radiomics for Identification of Telomerase Reverse Transcriptase Promoter Mutation in Patients With Glioblastoma Based on Preoperative MRI
No full textSupplemental Material for Peritumoral Radiomics for Identification of Telomerase Reverse Transcriptase Promoter Mutation in Patients With Glioblastoma Based on Preoperative MRI by Hongbo Zhang, Beibei Zhou, Hanwen Zhang, Yuze Zhang, Yi Lei, and Biao Huang in Canadian Association of Radiologists Journal.</p
Laser directed energy deposition additive manufacturing using friction stir channelling extruded wire
No full textThis paper investigates a new ‘forged’ wire additive manufacturing processing, in which the metal wire is produced as a by-product from stationary shoulder friction stir channelling (SS-FSC) under the severe plastic deformation mechanism (known as CoreFlow®), and then used as the feedstock in directed energy deposition with a laser beam and wire feedstock (DED-LB/w) additive manufacturing. For the first time, the ‘by-products’ produced in the SS-FSC process, which are ‘forged’ 6082 aluminium alloy wire, were tested with built-tracks using DED-LB/w. Process mapping was built to demarcate the melting states, including the stable, dripping, and incomplete melting regimes, over a wide range of laser energy densities (92 to 303 kJ·s·g−1·cm−2). Metallurgy tests were also conducted to reveal the evolution of the microstructure and defect formation of the deposited tracks. It was found that: (i) Stable deposition with a grain size of 9−20μm can be achieved with optimised processing parameters, i.e., energy density 243kJ·s·g−1·cm−2 with a laser power 3.8kW, a scanning speed 0.8cm·s−1 and a wire feed rate 2.0cm·s−1; (ii) The substructure morphology is gradually transitioned from columnar at the track bottom to cellular (8.9±1.8μm) at the top, driven by an increased cooling rate; and (iii) The built track porosity is mainly composed of gas pores that are small (equivalent diameter of 20−50μm) and spherical, primarily resulting from the ambient gas, the SS-FSC extruded wire oxides and contaminations. The study supports resource-efficient, low-carbon manufacturing via reuse of by-products, in alignment with the Net Zero Strategy.</p
Thermodynamic insights into the oxidation mechanisms of CrMnFeCoNi high-entropy alloy using in situ x-ray diffraction
Full text linkThis paper utilizes in situ X-ray diffraction (XRD) to investigate the high-temperature oxidation behaviour of CrMnFeCoNi high-entropy alloy (HEA). We found that (1) Mn is the major oxide-forming element in both vacuum and air environments, leading to the formation of non-protective oxides that deplete the bulk alloy of Mn; (2) no oxides like Cr2O3, Fe2O3, or Fe3O4 were observed during the high-temperature oxidation behaviour of CrMnFeCoNi, which contradicts some previous studies on the isothermal oxidation of CrMnFeCoNi HEA. We also analysed and compared the experimental results with thermodynamic calculations by using ThermoCalc version 2022b software following the CALPHAD method. ThermoCalc predicted spinel oxide in a vacuum environment, along with halite oxides observed in experimental results; also, in an atmospheric environment, it predicted only spinel, indicating the need for further investigation into factors to validate the thermodynamic predictions. Our study shows that the in situ HTXRD technique is a powerful tool to accurately identify time–temperature-dependent phase formation/transformation for studying oxidation behaviours and understanding oxidation mechanisms in HEAs.</p
Il Codice Civile Cinese: bilanci e prospettive
No full textAtti del Convegno internazionale italo-cinese tenuto nel 2022
A meta-analysis study of welfares of genetically modified crops
No full textDue to the controversial debates, skepticism and speculations around Genetic Modified (GM) crops, substantial research has been done on the allocation of welfare implications of GM crops. However, different procedures, various data sources and economic models are used to study commercialized GM crops around the world. Therefore mixed conclusions were conducted. Some papers mentioned benefits from farm producer side; some focused on research of willingness to pay among consumers; while others were asmore interested in market prospect. As a result, is has become difficult to effectively summarize the benefit of adopting GM crops and explain the large study-to-study variations of surplus estimation. This thesis presents a meta-analysis of 58 primary studies with a total of 119 GM crops evaluations, aiming to summarize previous studies on economic surplus of GM crops which are not conditional from a single research study and to identify the determinants of the farmer surplus, GM seed company surplus and consumer surplus of GM crops, from analysis and comparison those broad range data set. This thesis finds that GM seed companies and farmers gained different surplus based on geographic locations. On the other hand, research methods might affect farmer surplus estimation but not GM seed company surplus.M.S.Includes bibliographical referencesby Yuze Shan
Analysis and research on power distribution law of power generation based on HHT transform
No full textIn recent years, tidal current power generation technology has achieved rapid development. On the basis of summarizing the characteristics of tidal current power generation, this paper comprehensively analyzes the distribution law of electric energy in tidal current power generation. Hilbert huang transform was applied to the trend of energy in power quality detection and analysis, the key can power on the trend of the measured data grouping processing, and carried out in accordance with the time period, such as day, month and year of HHT analysis, can get tide power distribution, can verify the HHT analysis in the trend of the power law research in the application feasibility and accuracy
Comprehensive Analytical Modeling of Laser Powder-Bed/Fed Additive Manufacturing Processes and an Associated Magnetic Focusing Module
Full text linkState-of-the-art metal additive manufacturing (AM), mainly laser powder-fed AM (LPF-AM) and laser powder-bed AM (LPB-AM), has been used to produce high-quality, complex-shaped, and end-user metallic parts. To achieve desirable dimensional, microstructural and mechanical features of as-built components through fast process optimization or feedback-control-based adaptive processing adjustment, high fidelity and calculation-efficient processing model is urgently needed. The thesis research has been motivated by the need for time-efficient process models of both LPF-AM and LPB-AM. To this end, comprehensive accelerated models for these processes have been built and experimentally verified.
The comprehensive process model of LPF-AM was built by an innovative analytical approach. Firstly, a mathematical module that couples laser heat flux and powder mass flow was developed, while considering the attenuated laser intensity distribution and the heated powder spatial distribution. Correspondingly, a powder catchment module was built in terms of a three-dimensional (3D) melt pool shape and powder stream spatial distribution. Integrating these physical modules into the thermal modeling, a coupled heat and mass comprehensive model of the LPF-AM process was achieved. Experimental depositions of Inconel 625 proves the model’s high accuracy in predicting as-built deposits’ geometry (a maximum error of ~6.2% for clad width, ~7.8% for clad height) and powder catchment efficiency (maximum error of less than ~6.8%). It was found that the predicted real-time melt pool peak temperatures match well with the experimental results in Stainless Steel (SS) 316L deposition. The calculated micro-hardness has a maximum prediction error of ~16.2% compared with the measured results. The predicted microstructural evolutions show reasonable agreement with the experimental observations for both SS 316L and Inconel 625 depositions. Moreover, sensitivity analysis shows that the powder feed rate has the largest positive effect on the clad height.
The time-efficient process model of LPB-AM was achieved by a novel analytical approach that couples the critical physics of the process, while considering the volume shrinkage and the melting regime. The proposed model can perform a time-efficient prediction of the localized-transient thermal field, melt pool temperature distribution, and multi-track overlapping dimension. The powder bed was treated as a homogeneous medium with effective thermophysical properties derived from the randomly packed rain model. In addition, different melting regimes of the LPB-AM process were considered in the built model. A 3D heat source model with variant penetration depths, together with the varying melting regimes, was utilized to solve the transient thermal field. Moreover, the density and top surface roughness of the final parts were empirically modeled using response surface regression under a Box-Behnken design. Subsequently, the mechanical properties of the part and the in-situ build rates were simultaneously optimized by combining the built analytical models and empirical models with employing a multi-objective genetic algorithm. Experimental results with SS 17-4PH show that the predicted melt pool dimensions have a high degree of accuracy under steady melting regimes, with a maximum of ~14% error for the width prediction and ~15% error for the depth calculation. Furthermore, an optimized parameter solution set was provided based on the built 3D Pareto fronts.
The built models’ calculation time for the localized-transient characteristics for LPF-AM and LPB-AM are ~4 ms and ~1.2 ms, respectively. These findings confirm the great potential of the present research to be used for fast process optimization and in-situ process control.
In addition, a new magnetic concentration approach designed with various configurations was explored. This approach is designed to focus the diverging metal particles in the gas-powder stream of LPF-AM, thereby improving powder catchment and deposition accuracy. It was shown that the proposed permanent-magnet-based configurations may not be suitable for concentrating submillimeter-sized particles. However, an additional development, a doublet-electromagnet-quadrupoles-based configuration with high frequency, may be capable of concentrating the non-ferrous metallic particles (e.g., aluminum particle) with a radius of r_p≥150 μm
Sensor Calibrations with the Improved Picodrift Interferometer
No full textTo meet the growing demand for high precision measurement equipment, sensors with sub-nanometer resolution are becoming readily available. Because of its high precision, traceability and ease of use, the interferometer stands out for high precision measurements. However, the laser beam of an interferometer can be influenced by temperature and pressure fluctuations. Compensation of this error is possible by sensing temperature and pressure fluctuations while performing interferometric measurements. Alternatively, a refractometer running parallel with the interferometer can be used to do the same compensation with a higher accuracy. Additionally, errors caused by external sources such as vibrations, can be compensated by adopting a highly symmetrical design. Picodrift interferometer was developed and upgraded at VSL (Dutch Metrology Institute) as a calibration facility for high-precision sensors. First, the improved design of the picodrift interferometer is evaluated, implemented and tested allowing for a controlled measurement environment and high stability. The design requirements are determined to reduce the uncertainty caused by temperature and pressure fluctuations to picometer level in one hour. Based on those requirements, a vacuum system is implemented and tested to reach a pressure level in the ultra-high vacuum regime. During the implementation, necessary experiments and tests are performed to find leakages and the reasons for an undesired beam drift related to the pressure change. Additionally, an active temperature control system with passive shield is installed. Also, various kinematic coupling mount systems are designed and manufactured to provide a good positioning stability even in a noisy environment caused by a turbo pump. As the number of the interferometer channels has been doubled to perform measurements in both vacuum and atmospheric conditions, a well planned alignment procedure is developed to align the more sophisticated optical path. To characterize the performance of the new interferometer, a dead path measurement is performed. Second, to take advantage of the high precision and traceability, the interferometer is expanded to work as a calibration facility for external sensors of different sizes. A stable symmetrical calibration setup is designed to fit in a limited space for external measurements while minimizing uncertainty caused by temperature fluctuation and misalignment. An alignment procedure for the setup is developed. Eventually an example calibration is performed. <br/
Fast-responsive capsule based on two soluble components for self-healing concrete
No full textDue to low activity or long mineralization time, traditional mineral agents for self-healing concrete generally need a long time to achieve a desired repair efficiency. Inspired by epoxy resin AB glue which can consolidate in a short time when mixing the two components together, a novel type of fast-responsive capsules based on two soluble components was designed for self-healing concrete. Component A (sodium carbonate) and component B (calcium acetate) were encapsulated in two different groups of capsules, respectively, coated with three layers consisting of epoxy resin and fine sands to achieve superior waterproof and alkali resistance properties. After rupture of the capsules, the rapid response with respect to core material dissolution and precipitation can be realized in presence of water, by which the cracks below 200 μm can be healed in 3 days. Super absorbent resin (SAP) embedded in the capsules could expand in contact with water, and further improve the self-healing efficiency of the capsules by blocking the crack.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.Materials and Environmen
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