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High temperature oxidation of inoculated high Si/SiMo ductile cast irons in air and combustion atmospheres

China Foundry 2024年第5期21卷 555-562页

作者： Iuliana Stan Mihai Chisamera Robert Lascu Codrut Cariga Eduard Stefan Stelian Stan Denisa Anca Iulian Riposan National university of Science and Technology politehnica bucharest Materials Science and Engineering Faculty313 Splaiul IndependenteiSector 6060042 BucharestRomania

The present work aims to investigate the effect of heating temperature(400,600 and 800°C)and inoculating elements(Ca,Ca-Ba,Ca-RE)on oxidation behavior of ductile irons containing 5.25%Si and 4.8%Si-2.3%Mo in dry air and combustion gas containing water vapour(natural gas burning).The oxidation is influenced by the gas atmosphere type,the iron alloying system,and the inoculating elements depending on the heating *** weight gain increases from 0.001%-0.1%(400°C)to 0.05%-0.70%(600°C)and up to 0.10%-2.15%(800°C).No particular effects of the considered influencing factors are found when heating at 400°C,while at 600°C,mainly the oxidation gas atmosphere type shows a visible *** the highest heating temperature of 800°C,a limited increase of the weight gain is found for dry air atmosphere(up to 0.25%),but it drastically increases for combustion atmospheres(0.65%-2.15%).The water vapour presence in the combustion atmosphere is an important oxidising factor at 600-800°*** alloying system appears to influence the oxidation behavior mainly at a heating temperature of 800°C in the combustion atmosphere,as evidenced by the lower weight gain in 5.25%silicon cast *** effects of inoculating elements increase with the heating temperature,with Ca and Ba-FeSi inoculation generally showing better *** inoculated with CaRE-FeSi exhibit a higher degree of *** results are in good relationship with the previous reported data:Ca-Ba-inoculation system appears to be better than simple Ca for improving the graphite parameters,while RE-bearing inoculant negatively affects the compactness degree of graphite particles in high-Si ductile *** the lower compactness degree is typical for graphite nodules in high-Si ductile irons,which negatively affects the oxidation resistance,it is necessary to employ specific metallurgical treatments to improve nodule ***,in particular,is a potential method to achieve this improvement.

关键词： ductile iron spheroidal graphite Si/SiMo oxidation air/combustion atmospheres FeSiCaMgRE treatment Ca,Ca-Ba,Ca-RE inoculation structure characteristics

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Distributed Energy and Reserve Scheduling in Local Energy Communities Using L-BFGS Optimization

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CSEE Journal of Power and Energy Systems 2024年第3期10卷 942-952页

作者： Mohammad Dolatabadi Alireza Zakariazadeh Alberto Borghetti Pierluigi Siano Department of Management&Innovation Systems University of SalernoSalernoItaly Department of Electrical Electronicand Information EngineeringUniversity of BolognaBolognaItaly university of Science and Technology of Mazandaran BehshahrIran Department of Power Systems National University of Science and Technology POLITEHNICA BucharestBucharestRomania IEEE

Encouraging citizens to invest in small-scale renewable resources is crucial for transitioning towards a sustainable and clean energy *** energy communities(LECs)are expected to play a vital role in this ***,energy scheduling in LECs presents various challenges,including the preservation of customer privacy,adherence to distribution network constraints,and the management of computational *** paper introduces a novel approach for energy scheduling in renewable-based LECs using a decentralized optimization *** proposed approach uses the Limitedmemory Broyden–Fletcher–Goldfarb–Shanno(L-BFGS)method,significantly reducing the computational effort required for solving the mixed integer programming(MIP)*** incorporates network constraints,evaluates energy losses,and enables community participants to provide ancillary services like a regulation reserve to the grid *** assess its robustness and efficiency,the proposed approach is tested on an 84-bus radial distribution *** indicate that the proposed distributed approach not only matches the accuracy of the corresponding centralized model but also exhibits scalability and preserves participant privacy.

关键词： Distributed optimization flexibility services L-BFGS method local energy community renewables reserve

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Dynamic event-triggered fault-tolerant cooperative resilient tracking control with prescribed performance for UAVs

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Science China(Information Sciences) 2024年第8期67卷 67-84页

作者： Rong YUAN Zhengcai AN Shuyi SHAO Mou CHEN Mihai LUNGU College of Automation Engineering Nanjing University of Aeronautics and Astronautics Science and Technology on Electro-optic Control Laboratory Faculty of Electrical Engineering University of Craiova Aerospace Engineering Doctoral School University Politehnica of Bucharest

In this paper, a resilient tracking control scheme with cooperative collision avoidance performance is studied for the fixed-wing unmanned aerial vehicle(UAV) leader-follower formation in the presence of actuator failures and external disturbances. Firstly, based on the control objectives of UAV formation tracking and collision avoidance, the transformation tracking errors are obtained using the prescribed performance control technique. Next, a fault detection mechanism is introduced to determine if there is the actuator fault. Subsequently, the event-triggered resilient fault observers are designed based on a dynamic eventtriggered mechanism to estimate actuator faults. Furthermore, the prescribed performance functions and the H∞ performance index are employed to ensure the UAV formation collision-free and mitigate the impact of disturbances. Moreover, the resilient controller is designed to minimize the effect of the perturbations for the control gain and the fault observer gain on the system. The stability of the system is also proven through the Lyapunov stability analysis, and the controller gains are calculated by solving the linear matrix ***, the validity of the proposed control strategy is demonstrated by the simulation analysis.

关键词： UAV formation cooperative collision avoidance event-triggered fault observer prescribed performance resilient control

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Repeat-pass space-surface bistatic SAR tomography:accurate imaging and first experiment

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Science China(Information Sciences) 2024年第9期67卷 245-262页

作者： Zhiyang CHEN Yuanhao LI Cheng HU Shenglei WANG Xinpeng CHEN Mihai DATCU Andrea Virgilio MONTI-GUARNIERI Radar Technology Research Institute School of Information and Electronics Beijing Institute of Technology Beijing Key Laboratory of Embedded Real-Time Information Processing Technology Beijing Institute of Technology Advanced Technology Research Institute Beijing Institute of Technology CEOSpace Tech University Politehnica of Bucharest Dipartimento di Elettronica Informazione e Bioingegneria Politecnico di Milano

Space-surface bistatic synthetic aperture radar(SS-BiSAR) offers an additional observation angle for monostatic spaceborne SAR, making it a promising technology for high-accuracy deformation retrieval technology in local regions. Repeat-pass SS-BiSAR tomography can accurately estimate the surfaces of buildings and steep areas, effectively removing terrain phases during deformation retrieving. However, inaccuracies in the orbital ephemeris can lead to image geometry distortion, reducing image pair coherence,introducing interferometric phase errors, and consequently deteriorating tomographic precision. This paper precisely models the image geometry distortion and interferometric phase error caused by repeat-pass ephemeris error. We propose an ephemeris correction method based on the chirp-Z transform to address these issues. Furthermore, we introduce an accurate tomography model to improve 3D reconstruction *** first SS-BiSAR tomography experiment, conducted using the Chinese Lutan-1 satellite, demonstrates that the correlation coefficient is improved by 0.16 after ephemeris error correction. Moreover, the density and precision of the tomographic point cloud are improved by 13.7% and 12.1%, respectively.

关键词： space-surface SAR tomography orbit error image distortion Lutan-1

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Granulometry Assessment of Lom Pangar Dam Sediments (East-Cameroon)

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Journal of Geoscience and Environment Protection 2024年第6期12卷 207-231页

作者： Rodrigue Fotie Lele Mihaela Amalia Diminescu Issoufou Ouedraogo Annette Madelene Dăncila Souleymane Pelede Alphonse Emadak Martin Lompo Department of Geology University Joseph Ki Zerbo Ouagadougou Burkina Faso Department of Water and Energy Green Heart International Bafoussam Cameroon Department of Hydraulic Machineries and Environmental Engineering National University of Science and Technology Politehnica Bucharest Bucharest Romania Department of Mining Engineering University Yembila-Abdoulaye-Toguyeni Fada NGourma Burkina Faso Department of Inorganic Chemistry University of Yaound I Yaound Cameroon

The Lom Pangar dam, the largest reservoir in Cameroon with a storage capacity of 6 km3 and a 30 MW hydropower plant, primarily regulates the hydrologic regime of the Sanaga River to maintain hydropower efficiency during dry seasons and enhance downstream hydropower plant performance. Understanding and managing sediments are crucial for the sustainability of dams, as indicated by numerous studies. This study assessed the granulometry of the sediments transported across the reservoir. For that purpose, 6 samples of fresh sediments were collected in the lacustrine and transitional sections of the reservoir using the standard method. Particles size was assessed using the laser diffusion technic after a 3 mm sieving. Various granulometric parameters were derived from the literature to analyze and characterize those sediments. Results show that silts are more than 70% of particles size and range between 2.19 - 60.26 µm. Size distribution also shows the same trend with D75 less than 51 µm. This is confirmed by the low values of Inman Skewness SkΦ (−0.168 to 0.303). The Sorting index S0 ranges from 0.31 to 0.53 µm, showing a very well-sorted sediments, aligning with low values of Krumbein index (0.906 - 1.683) that express the low heterometry of the particles. The consequence on the dam will be a quick clogging of the bottom of the reservoir. Their pH varies from 7.0 to 7.5. It also appears that the sandy fraction trend is higher in the right bank of the dam and reaches 22% on the right bank of Pangar River due to crystalline geology. Fraction greater than 3000 µm is negligible. The management of the dam has to keep attention to these results as siltation may close the safety outlet of the dam, damage turbines, and provoke recurrent technical and safety issues. Further, the clogging of the bottom of the reservoir may lead to an ecological problem with the limitation of hyporheic flow. Thus, water exchange with the underground water table and the natural purification of wate

关键词： Lom Pangar Dam Sediments Granulometry Sustainability Hydropower Dam Safety

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Exploring fs-laser irradiation damage subthreshold behavior of dielectric mirrors via electrical measurements

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High Power Laser Science and Engineering 2024年第2期12卷 24-32页

作者： Petrisor Gabriel Bleotu Radu Udrea Alice Dumitru Olivier Uteza Maria-Diana Mihai Dan Gh Matei Daniel Ursescu Stefan Irimiciuc Valentin Craciun Extreme Light Infrastructure-Nuclear Physics(ELI-NP) Horia Hulubei National Institute for R&D in Physics and Nuclear Engineering(IFIN-HH)MagureleRomania Doctoral School of Physics University of BucharestMagureleRomania LULI-CNRS CEAUniversite SorbonneEcole PolytechniqueInstitut Polytechnique de ParisPalaiseau CEDEXFrance Apel Laser IlfovRomania Aix-Marseille university CNRSLP3 UMR 7341MarseilleFrance Horia Hulubei National Institute for R&D in Physics and Nuclear Engineering(IFIN-HH) MagureleRomania university politehnica of bucharest BucharestRomania National Institute for Lasers Plasma and Radiation Physics MagureleRomania

With ultrafast laser systems reaching presently 10 PW peak power or operating at high repetition rates,research towards ensuring the long-term,trouble-free performance of all laser-exposed optical components is *** work is focused on providing insight into the optical material behavior at fluences below the standardized laser-induced damage threshold(LIDT)value by implementing a simultaneous dual analysis of surface emitted particles using a Langmuir probe(LP)and the target current(TC).HfO_(2) and ZrO_(2) thin films deposited on fused silica substrates by pulsed laser deposition at various O_(2) pressures for defect and stoichiometry control were irradiated by Gaussian,ultrashort laser pulses(800 nm,10 Hz,70 fs)in a wide range of *** TC and LP collected signals were in good agreement with the existing theoretical description of laser–matter interaction at an ultrashort time *** approach for an in situ LIDT monitoring system provides measurable signals for below-threshold irradiation conditions that indicate the endurance limit of the optical surfaces in the single-shot energy scanning *** LIDT value extracted from the LP-TC system is in line with the multipulse statistical analysis done with ISO 21254-2:2011(E).The implementation of the LP and TC as on-shot diagnostic tools for optical components will have a significant impact on the reliability of next-generation ultrafast and high-power laser systems.

关键词： HfO_(2) in situ detection Langmuir probe laser-induced damage threshold target current ZrO_(2)

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Iron casting skin management in no-bake mould – Effects of magnesium residual level and mould coating

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China Foundry 2015年第3期12卷 222-230页

作者： Mihai Chisamera Nicoleta Ivan Iulian Riposan Stelian Stan politehnica university of bucharest

The relative performance of coatings for furan resin sand moulds [P-toluol sulphonic acid(PTSA) as hardener] [FRS-PTSA moulds], was compared by analyzing the surface layer for degenerated graphite in Mg treated iron with 0.020 wt.% to 0.054 wt.% Mgres. It was found that the iron nodularising potential(Mg, Ce, La content) and whether the mould coatings contained S, or were capable of desulphurizing were important factors. These moulds have S in the PTSA binder, which aggravates graphite degeneration in the surface layer, depending strongly on the Mgres with lower Mgres increasing the layer thickness. The application of a mould coating strongly influenced graphite deterioration in the surface layer of castings. It either promoted graphite degeneration to less compact morphologies when using S-bearing coatings, or conversely, limited the surface layer thickness using desulphurization type coatings. Independently of the S-source at the metal – mould interface, the presence of sulphur had an adverse effect on graphite quality at the surface of Mg-treated irons, but its negative effect could also reach the graphite phase within the casting section. If the coatings employed desulphurization materials, such as Mg O, or a mixture(Ca O + Mg O + Talc) or Mgbearing Fe Si, they protected the graphite shape, improving graphite nodularity, at the metal – mould interface, and so decreased the average layer thickness in FRS-PTSA moulds. Fe Si Mg was highly efficient in minimizing the casting skin by improving graphite nodularity. It is presumed that the Mg O or(Mg O + Ca O + Talc) based coatings acted to remove any S released by the mould media. The Mg-Fe Si coatings also reacted with S from the mould but additionally supplemented the Mg nodularising potential prior to solidification. This dual activity is achievable with coatings containing active magnesium derived from fine Mg-Fe Si materials.

关键词： ductile iron compacted graphite iron surface layer graphite degeneration resin bonded sand mould Mg-bearing mould coating S-bearing mould coating

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A paradigm-based evolution of chemical engineering

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Chinese Journal of Chemical Engineering 2016年第5期24卷 553-557页

作者： Alexandru Woinaroschy Department of Chemical and Biochemical Engineering politehnica university bucharest Bucharest 011061Romania

A short presentation of chemical engineering evolution,as guided by its paradigms,is *** first paradigm–unit operations–has emerged as a necessity of systematization due to the explosion of chemical industrial applications at the end of 19th *** birth in the late 1950s of the second paradigm–transport phenomena–was the consequence of the need for a deep,scienti fic knowledge of the phenomena that explain what happens inside of unit *** the second part of 20th century,the importance of chemical product properties and qualities has become essentially in the market ***,it was required with additional and even new fundamental approaches,and product engineering was recognized as the third *** chemical industry,as a huge materials and energy consumer,and with a strong ecological impact,couldn't remain outside of sustainability *** basics of the fourth paradigm–sustainable chemical engineering–are now formulated.

关键词： Paradigms Unit operations Transport phenomena Product engineering Sustainable chemical engineering

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New developments in high quality grey cast irons

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China Foundry 2014年第4期11卷 351-364页

作者： Iulian Riposan Mihai Chisamera Stelian Stan politehnica university of bucharest Romania

The paper reviews original data obtained by the present authors,revealed in recent separate publications,describing specific procedures for high quality grey irons,and reflecting the forecast needs of the worldwide iron foundry *** power,medium frequency coreless induction furnaces are commonly used in electric melting grey iron *** has resulted in low sulphur(1,500°C),contributing to unfavourable conditions for graphite *** wall castings are increasingly produced by these electric melt shops with a risk of greater eutectic undercooling during *** paper focused on two groups of grey cast irons and their specific problems:carbides and graphite morphology control in lower carbon equivalent high strength irons(CE=3.4%-3.8%),and austenite dendrite promotion in eutectic and slightly hypereutectic irons(CE=4.1%-4.5%),in order to increase their strength *** are 3 stages and 3 steps involving graphite formation,iron chemistry and iron processing that appear to be *** concept in the present paper sustains a threestage model for nucleating flake graphite[(Mn,X)S type nuclei].There are three important groups of elements(deoxidizer,Mn/S,and inoculant)and three technological stages in electric melting of iron(superheat,pre-conditioning of base iron,final inoculation).Attention is drawn to a control factor(%Mn)x(%S)ensuring it equals to 0.03–0.06,accompanied by 0.005wt.%–0.010wt.%Al and/or Zr content in inoculated *** was found that iron powder addition promotes austenite dendrite formation in eutectic and slightly eutectic,acting as reinforcement for the eutectic ***,there is an accompanying possible negative influence on the characteristics of the(Mn,X)S type graphite nuclei(change the morphology of nuclei from polygonal compact to irregular polygonal,and therefore promote chill tendency in treat

关键词： grey iron S Al Zr Ti electric melting furnace superheating preconditioning inoculation graphite nucleation graphite morphology carbides dendritic austenite iron powder

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Magnesium-based alloys with adapted interfaces for bone implants and tissue engineering

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Regenerative Biomaterials 2023年第1期10卷 1632-1692页

作者： Iulian Antoniac Veronica Manescu(Paltanea) Aurora Antoniac Gheorghe Paltanea Faculty of Material Science and Engineering National University of Science and Technology POLITEHNICA Bucharest060042 BucharestRomania Academy of Romanian Scientists 050094 BucharestRomania Faculty of Electrical Engineering National University of Science and Technology POLITEHNICA Bucharest060042 BucharestRomania

Magnesium and its alloys are one of the most used materials for bone implants and tissue *** are characterized by numerous advantages such as biodegradability,high biocompatibility and mechanical properties with values close to the human ***,the implant surface must be adequately tuned,or Mg-based alloys must be alloyed with other chemical elements due to their increased corrosion effect in physiological *** article reviews the clinical challenges related to bone repair and regeneration,classifying bone defects and presenting some of the most used and modern therapies for bone injuries,such as Ilizarov or Masquelet techniques or stem cell *** implant interface challenges are related to new bone formation and fracture healing,implant degradation and hydrogen release.A detailed analysis of mechanical properties during implant degradation is extensively described based on different literature studies that included in vitro and in vivo tests correlated with material properties’***-based trauma implants such as plates and screws,intramedullary nails,Herbert screws,spine cages,rings for joint treatment and regenerative scaffolds are presented,taking into consideration their manufacturing technology,the implant geometrical dimensions and shape,the type of in vivo or in vitro studies and fracture *** technologies that modify or adapt the Mg-based implant interfaces are described by presenting the main surface microstructural modifications,physical deposition and chemical conversion *** last part of the article provides some recommendations from a translational perspective,identifies the challenges associated with Mg-based implants and presents some future *** review outlines the available literature on trauma and regenerative bone implants and describes the main techniques used to control the alloy corrosion rate and the cellular environment of the implant.

关键词： adapted interfaces bone tissue engineering fracture healing Mg-based alloys surface modifications

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