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Effect of feeding parameters on ingot segregation and shrinkage pore in vacuum arc remelting

Journal of Iron and Steel Research International 2023年第6期30卷 1268-1278页

作者： Dong-bin Jiang Fu-zhong Yang Jian Zhang Yang Zhou Li-feng Zhang School of Metallurgy and Ecological Engineering University of Science and Technology BeijingBeijing 100083China Chengdu Advanced Metal Materials Industrial Technology Institute Chengdu 610303SichuanChina School of Mechanical and Materials Engineering North China University of TechnologyBeijing 100144China

The feeding parameters in the final stage of vacuum arc remelting process obviously affect the solute segregation and shrinkage pore *** with the electromagnetic field,fluid flow,and solute transport,a numerical model was built to investigate the effect of feeding parameters on the ingot solidification *** Nb segregation and shrinkage pore depth in the solidified ingot were *** results show that the liquid moves along the solidification front and the vertex flow is formed in the liquid pool,which promotes solute *** the solidified ingot,the Nb segregation in the lower part is negative,while that in the upper part is *** the differential electrode applied,the positive segregation is slightly reduced but the segregation distribution remains *** the feeding current decreases,the positive segregation zone moves toward the ingot top surface,due to the final solidification position moving *** the feeding time extended,the positive segregation moves to the top surface and the shrinkage pore depth is *** the feeding time is set at 12 min,the shrinkage pore depth can be reduced to 21 mm.

关键词： Vacuum arc remelting Feeding parameter Macrosegregation Shrinkage pore Solidification

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Experimental investigation of mechanical responses of helmeted headforms under the ballistic impact 4

Experimental investigation of mechanical responses of helmet...

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4th International Conference on Defence technology, ICDT 2024

作者： Harmukh, Atul Ganpule, Shailesh Department of Mechanical and Industrial Engineering Indian Institute of Technology Roorkee Roorkee India Department of Design Indian Institute of Technology Roorkee Roorkee India

Ballistic impact induced head injury is a massive concern in contemporary asymmetric warfare. The performance of the ballistic helmets and the associated mechanical responses of headforms against ballistic impact are highly sought. The ballistic assessment of the helmet is traditionally evaluated based on the perforation of the helmet and back face deformation (BFD) of the helmet. However, the link between BFD and head injury remains unclear. Toward this end, we have investigated the mechanical responses (BFD, head kinematics (linear and angular)) using rigid headform and flexible headform under the ballistic impact with using 9 mm bullet (bullet velocities: 430 ± 15 m/s). The front, oblique (30ºto the sagittal axis), right, back, and left orientations were considered for the ballistic impact. Our results indicate that the flexible headform influenced head kinematics significantly, although the differences in BFD between the rigid and flexible headforms were minimal. Overall, these findings offer insights and new data on the ballistic performance of helmeted headforms. This information is crucial for designing and developing next-generation helmets and for improving testing protocols to better evaluate the effectiveness of ballistic helmets. © 2024 Published under licence by IOP Publishing Ltd.

关键词： Ballistics

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A modified maxwell-pulse thermoplastic constitutive model of in-situ Ta-particle reinforced Zr-based bulk metallic glass composites

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Progress in Natural Science:Materials International 2024年第4期34卷 753-766页

作者： Pan Gong Zhuang Wang Guoqing Yu Maojun Li Xin Zhuo Xuefeng Tang Mao Zhang Lei Deng Junsong Jin A.A.Churakova Xinyun Wang State Key Laboratory of Materials Processing and Die & Mould Technology School of Materials Science and Engineering Huazhong University of Science and Technology State Key Laboratory of Advanced Design and Manufacturing Technology for Vehicle Hunan University Institute of Molecule and Crystal Physics Ufa Federal Research Center RAS

The impact of different Ta contents on the mechanical properties and thermoplastic forming ability of in-situ Taparticle reinforced Zr–Cu–Al–Ni bulk metallic glass composites was studied. The composition(Zr55Cu30Al10-Ni5)94Ta6with the best comprehensive performance was chose for a systematic investigation into its thermoplastic behavior in the supercooled liquid region（SLR）, with quantitative analysis conducted by the strain rate sensitivity index and activation volume. The steady-state flow stress and the stress overshoot intensity were augmented with deformation temperature decreasing, strain rate increasing, and the addition of the secondary phase, leading to a transition from Newtonian to non-Newtonian flow regime. The addition of the secondary phase deteriorated the rheological properties of the material. To solve the problem that the Maxwell-Pulse constitutive model showed an inability to accurately describe the steady-state flow process. A modified constitutive relationship, introducing the effect of the volume fraction of Ta particles on viscosity and elastic modulus in the steady-state flow process which was ignored in Maxwell-pulse model, was established. The fitting results of the true stress-strain curves of the modified Maxwell-pulse constitutive model were in better agreement with the experimental date than those of the Maxwell-pulse constitutive model, with higher prediction accuracy. The modified constitutive model well predicted the thermoplastic deformation behavior of(Zr55Cu30Al10Ni5)*** influence mechanism of Ta particles on the flow behavior was explained that Ta particles increased the viscosity of amorphous matrix, thereby hindering its flow and ultimately leading to an increase in flow stress.

关键词： Bulk metallic glass composites Supercooled liquid region Thermoplastic deformation Constitutive model Influence mechanism

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Holographic Terahertz Imaging for Breast Cancer Detection

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Journal of engineering and Science in Medical Diagnostics and Therapy 2024年第1期7卷 011010页

作者： Wang, Lulu Al-Rawi, Mohammad Biomedical Device Innovation Center Shenzhen Technology University Shenzhen518118 China Centre for Engineering and Industrial Design Waikato Institute of Technology Hamilton3240 New Zealand

Terahertz (THz) imaging is a promising technology that can accurately detect breast tumors during breast-conserving surgery. Researchers have studied THz imaging and spectroscopy techniques to improve breast tumor detection for the past 20 years. This paper presents the recent development of the holographic THz imaging (HTI) method for identifying breast tumors. To evaluate the effectiveness of this new approach, we have developed a numerical system that includes realistic breast models and an imaging processing model. Through various experiments, we have successfully used the proposed holographic THz imaging method to identify breast tumors. Our results have shown that this method can reconstruct high-quality breast images and accurately detect small tumor inclusions, providing the correct size and location information. Based on these promising results, further investigation is warranted to explore the potential of this approach for breast tumor detection in a faster and more cost-effective manner. © 2024 American Society of Mechanical Engineers (ASME). All rights reserved.

关键词： Microwave holography

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PLASTIC DEFORMATION CAPACITY OF STEEL BEAM-COLUMN DETERMINED BY IN-PLANE INSTABILITY

Journal of Structural and Construction Engineering

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Journal of Structural and Construction engineering 2022年第794期87卷 381-392页

作者： Sato, Atsushi Fujiwara, Ukyo Graduate School of Engineering Nagoya Institute of Technology Japan Dept. Architecture Design Civil Engineering and Industrial Management Engineering Nagoya Institute of Technology Japan

Numerical analysis, which considers the material and geometrical nonlinearity, was conducted to understand the structural behavior of the steel beam-column in this study. Axial force, member length, cross-sectional shape, and end moment ratio were selected as the parameters to gather sufficient data. As a result, the design formula that can be used to guaranty the beam-columns ductility was proposed. Moreover, quantitative formula to predict the plastic deformation capacity was proposed. Finally, the ultimate limit state determined by local buckling or in-plane instability was studied;the border where the mode will change was verified with the existing test results. © 2022 Architectural institute of Japan. All rights reserved.

关键词： Steel beams and girders

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Enhanced Resource Orchestration in Near-Field and Far-Field NOMA Communications for Emergency IoT Applications

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IEEE Internet of Things Journal 2025年第12期12卷 18520-18531页

作者： Zhang, Chaofeng Hou, Jia Chen, Caijuan Li, Gaolei Advanced Institute of Industrial Technology Department of Information and Electronic Engineering Tokyo Japan Soochow University Department of Communication Engineering Jiangsu China Tokyo Japan Shanghai Jiao Tong University School of Electronic Information and Electrical Engineering Shanghai China

In the face of escalating public crises such as geological disasters and pandemics, there is an urgent need for enhanced communication strategies within the Internet of Things (IoT) to ensure effective emergency response. This paper introduces a novel approach utilizing hybrid Near-Field and Far-Field Non-Orthogonal Multiple Access (NOMA) to address the challenges of increased device density and bandwidth demand in emergency scenarios. Our proposed resource orchestration framework optimally balances throughput, energy, and Quality of Service (QoS), employing power and device matching algorithms for equitable PD-NOMA access. We introduce a dynamic Actor-Critic model for real-time multi-objective optimization, ensuring fair resource allocation among IoT devices. Experimental results show marked improvements in throughput and system stability, underscoring the model's efficacy in advanced emergency communications. © 2014 IEEE.

关键词： Near field communication

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Role of solute elements in Mg-Mg_(2)Ni hydrogen storage alloys:A first-principles calculation study

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Journal of Magnesium and Alloys 2024年第11期12卷 4574-4593页

作者： Min-Seok Yoon Jae Hur Seo-Hui Park Ui-Jong Lee Guanglong Xu Hyung-Ki Park Byeong-Chan Suh Young Min Kim Won-Seok Ko Department of Materials Science and Engineering Inha UniversityIncheon 22212Republic of Korea College of Materials Science and Engineering Nanjing Tech UniversityNanjing 211816China Functional Materials and Components R&D Group Korea Institute of Industrial TechnologyGangneung 25440Republic of Korea Advanced Metals Division Korea Institute of Materials ScienceChangwon 51508Republic of Korea Advanced Materials Engineering University of Science and TechnologyDaejeon 34113Republic of Korea

The effects of various alloying elements on the performance of Mg-Mg_(2)Ni hydrogen storage alloys were investigated by performing firstprinciples density functional theory *** examined the important characteristics of hydrogen storage alloys by considering both Mg-based solid solution and Mg_(2)Ni-based intermetallic compound phases,where the hydride forms are Mg H2and Mg_(2)NiH4,*** particular,qualitatively valid information for predicting changes in plateau pressures in the pressure-composition-temperature(PCT)curve was provided by calculating changes in the energy of related hydrogenation *** effects of alloying elements on volume changes due to hydrogenation reactions were also obtained to provide additional criteria for the practical use of hydrogen storage *** the Mg_(2)Ni-based intermetallic compound,we examined the site preference of each alloying element,considering the designated stoichiometry of the base *** on the revealed site preferences,the effects of various possible alloying elements on the properties of Mg_(2)Ni-based hydrides were also *** structure analyses were further conducted to elucidate the detailed mechanisms underlying the role of the additional solute elements.

关键词： Mg-Mg_(2)Ni alloys Density functional theory Hydrogen storage alloys Metal hydrides

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Topological magnetoelectric response in ferromagnetic axion insulators

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National Science Review 2024年第2期11卷 8-14页

作者： Yuhao Wan Jiayu Li Qihang Liu Department of Physics and Shenzhen Institute for Quantum Science and Engineering(SIQSE) Southern University of Science and Technology Shenzhen Key Laboratory of Advanced Quantum Functional Materials and Devices Southern University of Science and Technology Guangdong Provincial Key Laboratory for Computational Science and Material Design Southern University of Science and Technology

The topological magnetoelectric effect （TME） is a hallmark response of the topological field theory,which provides a paradigm shift in the study of emergent topological ***,its direct observation is yet to be realized due to the demanding magnetic configuration required to gap all surface ***,we theoretically propose that axion insulators with a simple ferromagnetic configuration,such as the MnBi2Te4/（Bi2Te3）nfamily,provide an ideal playground to realize the *** the designed triangular prism geometry,all the surface states are magnetically *** a vertical electric field,the surface Hall currents give rise to a nearly half-quantized orbital moment,accompanied by a gapless chiral hinge mode circulating in ***,the orbital magnetization from the two topological origins can be easily distinguished by reversing the electric *** work paves the way for direct observation of the TME in realistic axion-insulator materials.

关键词： topological magnetoelectric effect axion insulator magnetic topological materials

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Explicit and Computational Fluid Dynamics Analysis of a Novel Polo Helmet design: A Parametric Study

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Journal of engineering and Science in Medical Diagnostics and Therapy 2024年第2期7卷 021009页

作者： Al-Rawi, Mohammad Zheng, Li Best, Russ Centre for Engineering and Industrial Design Te Pūkenga—Waikato Institute of Technology Hamilton3240 New Zealand Faculty of Engineering Chemical and Materials Engineering The University of Auckland Auckland1010 New Zealand

Polo is a popular sport in New Zealand, Australia, the United Kingdom, and many other countries. Polo is a vigorous sport involving players and horses moving at speed and can result in head injuries caused by falls. Helmets play a vital role in the safety and protection of Polo players. This study investigates different hemispheric bumper shapes of the helmet to improve the impact resistance performance using finite element analysis (FEA) and explicit dynamics analysis (EDA). The aerodynamic performance of the proposed helmet is investigated using computational fluid dynamics (CFD) to account for drag impact on the Polo player’s speed. These are investigated for impact resistance and the drag coefficient under different speeds. The EDA results show that the new proposed bumper will absorb the impact and reduce the energy transferred to the inside foam at a relative impact speed of 6.2 m/s, as recommended by the U.S. Consumer Product Safety Commission (CPSC), with a maximum total deformation of 4.42 mm compared to 4.19 mm and 3.85 mm for impact speeds of 5.9 m/s by the European standard PAS015:2011 helmets for equestrian use and 5.42 m/s BS EN 1078 helmets for bicyclists’ use, respectively. Additionally, under speeds ranging from 15 km/h to 65 km/h, the new helmet demonstrated a drag coefficient of 0.454, similar to that of the national team helmet, at 0.423. Copyright © 2024 by ASME.

关键词： Computational fluid dynamics

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Polygon formation of multiple nonholonomic mobile robots with double-level-control collision avoidance scheme

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Journal of Control and Decision 2023年第3期10卷 301-313页

作者： A.Widyotriatmo E.Joelianto A.M.Burohman J.J.Damanik Y.Y.Nazaruddin Instrumentation and control research group faculty of industrial technologyinstitut teknologi bandungbandungindonesia engineering and technology institute groningen university of groningengroningenthe netherlands caerospace engineering korea advanced institute of science and technologydaejeonsouth korea

This paper considers a polygon formation control of multiple robots with nonholonomic constraintsenclosing a goal target and double-level-control collision avoidance scheme. Doublelevel-control scheme consisted of upper-level and lower-level controls are proposed for trajectorygeneration and tracking control of multi-robot systems. Both upper-level and lower-levelcontrols operate collision avoidance mechanisms based on potential functions. The proposedcontrol scheme guarantees that the group of robots are kept in the polygon formation and drivento a goal, while avoiding collisions during the travel. Moreover, the designed interaction betweenthe upper- and lower-level controls guarantees that the mobile robots are not trapped in localminima or deadlock case. Experiments of the formation of three-robots are conducted to showthe performance of the mobile robots in accomplishing a polygon formation while achieving thegoal without any collision and no local minima.

关键词： Artificial potential function collision avoidance formation control multi-robot systems polygon formation

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