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Magnetic NiFe_(2)O_(4)@FeNi_(3)core-shell nanospheres derived from FeNi-LDH precursor anchoring on rGO nanosheets for enhanced electromagnetic wave absorption

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Journal of Materials science & Technology 2024年第4期171卷 101-114页

作者： Kunyao Cao Yuan Fang Shuai Wang Yue Zhang Jiayue Wen Jun Chen Rui Zhao Weidong Xue School of Materials and energy University of Electronic Science and Technology of ChinaChengdu 610054China

Graphene has been extensively utilized in the domain of electromagnetic wave(EMW)absorption ma-terials because of its excellent electrical ***,the inferior impedance matching per-formance and the single loss mechanism vastly restrict the ***,it’s an effective strat-egy to solve these issues by introducing magnetic ***,layer double hydroxide(LDH)is an appropriate template to obtain magnetic component *** that ferromagnetic met-als such as Fe,Co,Ni,and their corresponding metal oxides are usually treated as magnetic compo-nents which are promising candidates for EMW absorption ***,in this work,a FeNi-layered double hydroxide-reduced graphene oxide(FeNi-LDH-rGO)aerogel was synthesized through a series of processes such as electrostatic self-assembly,hydrothermal,freeze-drying,and *** magnetic NiFe_(2)O_(4)@FeNi_(3)core-shell nanospheres were obtained from FeNi-LDH precursor,anchoring on rGO nanosheets after the annealing ***,the effects of different mass ratios of LDH to GO as well as different annealing temperatures of LDH-rGO aerogel on the EMW absorption prop-erty and impedance matching performance were *** a consequence,the fabricated ultralight 600LDH-rGO 2:1 aerogel shows a broad effective absorption bandwidth(EAB)of 7.04 GHz at a thickness of 2.3 mm with a low filling content of only 6 wt%and a low density of 4.4 mg/cm^(3).In conclusion,the synthetic LDH-rGO aerogels offer an effective strategy for preparing EMW absorption materials that own three-dimensional porous network structure and unique magnetic NiFe_(2)O_(4)@FeNi_(3)core-shell struc-ture nanospheres.

关键词： Electrostatic self-assembly Electromagnetic wave absorption LDH-rGO aerogel Layered double hydroxide Reduced graphene oxide NiFe_(2)O_(4)@FeNi_(3)core-shell structure

Experimental Study on Soot Suppression of Acetylene Diffusion Flame by Acoustic-Excited Oscillation in Rijke-Type Burner

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Journal of Thermal science 2024年第1期33卷 235-248页

作者： ZHU Yibin GUO Hui SUO Yan'ge WU Minle YE Yanghui LI Guoneng ZHANG Zhiguo School of Mechanical and energy Engineering Zhejiang University of Science and TechnologyHangzhou 310023China

This work reports that the flame oscillation induced by acoustic excitation can effectively suppress soot generation in Rijke-type *** the acoustic frequency is close to the natural frequency of the burner system,it can produce resonance resulting in intense oscillation of the *** relationship between the soot suppression efficiency and the acoustic field of standing wave at different flame positions is *** with that under self-excited oscillation,when there is external forced acoustic force introduced to the flame,oscillation combustion occurred in a lager zone in the glass *** fundamental cause of different soot suppression efficiency at different positions is that the standing wave acoustic field causes the particles to move at different speeds in different positions of the glass *** axial particle velocity difference results in the formation of acoustic vortexes and the change of the flame *** high particle velocity causes the air in the glass tube to turn into the turbulent condition and make the flame temperature *** results show that the surface growth rate of soot is reduced,while the oxidation rate of soot is enhanced,which result in the soot suppression under acoustic *** study can provide some reference for the practical application of oscillate combustion in soot suppression.

关键词： soot suppression acetylene diffusion flame acoustic-excited oscillation standing wave

Cooperative game penetration guidance for multiple hypersonic vehicles under safety critical framework

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Chinese Journal of Aeronautics 2024年第1期37卷 247-255页

作者： Jieqing CHEN Ruisheng SUN Yu LU School of energy and Power Engineering Nanjing University of Science and TechnologyNanjing 210094China

The rapid development of the anti-missile weapon technology brings new challenges to the cooperative penetration strategy solution and the guidance law design for Hypersonic Vehicles(HVs).This paper studies the coordinated game penetration guidance problem for multiple hypersonic vehicles faced with space threat areas.A scheme for seeking cooperative game penetration guidance strategy under safety critical control framework is *** this scheme,a multiHV cooperative game model is proposed in a minimum optimization form which can simplify the solving process and accelerate the computing ***,a second-order control barrier function is developed to transform the implicit nonlinear constraints of the proposed model into linear *** order to obtain better performance of guidance strategy,a composite guidance law under the safety critical control framework is presented to allocate guidance strategies appropriately in the whole *** is shown that the proposed scheme can guarantee successful penetration while avoiding threat ***,a comparative simulation with a two-on-three game is conducted to verify the effectiveness of the proposed method.

关键词： Hypersonic vehicles Safety critical control Penetration game Space constraints Cooperative guidance

Numerical and experimental investigation into the evolution of the shock wave when a muzzle jet impacts a constrained moving body

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Defence Technology（防务技术） 2024年第3期33卷 317-326页

作者： Zijie Li Hao Wang Changshun Chen Kun Jiang School of energy and Power Engineering Nanjing University of Science and TechnologyNanjing 210016China

The gun-track launch system is a new special launch device that connects the track outside the *** it is constrained by the track,the characteristics of development of the muzzle jet differ from those of the traditional muzzle ***,it changes from freely developing to doing so in a constrained manner,where this results in an asymmetric direction of flow as well as spatio-temporal coupling-induced interference between various shock waves and the formation of *** this background,the authors of this article formulate and consider the development and characteristics of evolution of the muzzle jet as it impacts a constrained moving *** designed simulations to test the gun-track launch system,and established a numerical model based on the dynamic grid method to explore the development and characteristics of propagation of disturbances when the muzzle jet impacted a constrained moving *** also considered models without a constrained track for the sake of *** results showed that the muzzle jet assumed a circumferential asymmetric shape,and tended to develop in the area above the *** the test platform was close to the ground,the muzzle jet was subjected to reflections from it that enhanced the development and evolution of various forms of shock waves and vortices in the muzzle jet to exacerbate its rate of distortion and asymmetric *** in turn led to significant differences in the changes in pressure at symmetric points that would otherwise have been *** results of a comparative analysis showed that the constrained track could hinder the influence of reflections from the ground on the muzzle jet to some extent,and could reduce the velocity of the shock waves inducing the motion of the muzzle as well as the Mach number of the moving *** work here provides a theoretical basis and the requisite technical support for applications of the gun-track launch *** also sheds light on the

关键词： Shock wave/vortex interference Muzzle jet Constrained boundary Dynamic grid

Effects of Additives on the Microstructure and Tribology Performance of Ta-12W Alloy Micro-Arc Oxidation Coating

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Journal of Wuhan University of Technology(Materials science) 2024年第1期39卷 142-149页

作者：刘玲 HU Changgang CHENG Wendong 刘兴泉 School of Materials and energy University of Electronic Science and Technology of ChinaChengdu 610054China

Oxide ceramic coatings were fabricated on tantalum alloys by micro-arc oxidation (MAO) to improve their hardness and tribological properties. The MAO coatings were manufactured in a mixed silicatephosphate electrolyte containing NaF and/or EDTA (ethylene diamine tetraacetic acid). The surface morphology,cross-sectional view, chemical composition, hardness, and wear performance of the coatings were analysed. As revealed by the scanning electron microscopy, silica-rich nodules appear on the MAO coating obtained in the silicate-phosphate electrolyte, but the formation of nodules is inhibited with NaF and/or EDTA in the ***, they reduce the roughness and improve the compactness of the coatings, which are composed of Ta_(2)O_(5),(Ta, O), and TaO. A thick and hard coating is obtained in the NaF-containing electrolyte, and the tribology performance is effectively improved. With additives, the nodule structure is detached from the coating surface and dissolved in the electrolyte. By using NaF as an electrolyte additive, the abrasion performance of the MAO coating is enhanced by decreasing the nodule structure, increasing the size of micropores, and improving the coating hardness.

关键词： micro-arc oxidation tantalum alloy additives tribology performance

A novel approach towards the selection of regenerators for optimal Stirling engine performance based on energy and exergy analyses

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science China(Technological sciences) 2024年第1期67卷 295-310页

作者： YU MinJie ZHANG MingHui XU Lei CUI HaiChuan LIU ZhiChun LIU Wei School of energy and Power Engineering Huazhong University of Science and TechnologyWuhan 430074China

Regenerators play a vital role in enhancing the overall performance of Stirling ***,this paper performed an energy and exergy analysis to elucidate the significance of regenerator characteristics concerning system performance,contributing to the optimal regenerator’s design and *** relationship between regenerator structure,regenerator exergy destruction,and output power,thermal efficiency,and exergy efficiency for Stirling engines was established by integrating the thermal model of Stirling engines with a mathematical model of *** contrast to cross-flow and parallel-flow regenerators,a novel concept of inclined-flow regenerators,featuring a matrix surface inclined in the direction of gas flow,was developed to achieve higher and more balanced engine output power and energy utilization efficiency.A comprehensive investigation was conducted into the effects of matrix structure types and regenerator geometries on the performance of both regenerators and *** results reveal that,following structural optimization,Stirling engines equipped with the inclined-flow regenerator demonstrate a substantial 16.6%,38.3%,and 37.2%increase in power output,thermal efficiency,and exergy efficiency,respectively,compared to those equipped with cross-flow *** contrast,when compared to engines fitted with parallel-flow regenerators,they experience a 13.5%reduction in power output but achieve remarkable enhancements of 45.4%and 36.7%in thermal and exergy efficiency,*** study introduces new insights into selecting regenerator structures for enhancing the output performance of Stirling engines.

关键词： Stirling engine inclined-flow regenerator adiabatic model exergy analysis

Review on heat-to-power conversion technologies for hypersonic vehicles

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Chinese Journal of Aeronautics 2024年第5期37卷 148-179页

作者： Yinke QI Xiaofeng MA Peixue JIANG Yinhai ZHU Key Laboratory for Thermal science and Power Engineering of Ministry of Education Department of Energy and Power EngineeringTsinghua UniversityBeijing 100084China Beijing Key Laboratory of CO_(2)Utilization and Reduction Technology Department of Energy and Power EngineeringTsinghua UniversityBeijing 100084China

Hypersonic vehicles have enormous military and economic value,while their power and thermal protection demands will increase substantially with the rise in Mach number and *** the tremendous high-quality heat on the vehicle surface and engine wall into electrical energy through heat-to-power technologies will not only play a role in thermal protection,but also supply power for the *** paper provides a comprehensive review of heat-to-power conversion technologies on hypersonic vehicles,including the indirect conversion of Brayton and Rankine cycles,direct conversion of thermoelectric materials,and combined *** the open Brayton cycle with hydrocarbon fuel as the working fluid,the Power-to-Weight Ratio(PWR)can achieve the highest,at around 1.8,due to the high PWR of the hydrocarbon fuel turbine and the few components of the ***,its work capacity is limited by the flow rate of the supplied *** closed Brayton cycle can maintain a relatively high PWR,ranging from 0.2 to 0.8,while achieving relatively high output power and conversion *** Rankine cycle has a higher PWR,its range is close to that of the closed Brayton cycle,peaking at about *** thermoelectric materials technology has a small power generation level,making it more suitable for scenarios with low power *** review provides a basis for selecting and developing heat-to-power conversion technologies on hypersonic vehicles.

关键词： Hypersonic vehicles Heat-to-power conversion Brayton cycle Rankine cycle Thermoelectric materials

Event-triggered sliding mode control of linear repetitive processes and its application in metal rolling process

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science China(Information sciences) 2024年第3期67卷 167-181页

作者： Xinyu LV Yugang NIU James LAM Key Laboratory of Smart Manufacturing in energy Chemical Process (East China University of science and Technology) Ministry of Education department of Mechanical Engineering The University of Hong Kong

This paper investigates the design problem of a sliding mode controller for linear repetitive processes(LRPs) with a finite pass length on each pass. Under limited communication resources, an eventtriggered mechanism is implemented from the sensors to the controller, whose triggered sequence is consistent with the evolution direction of LRPs. To periodically orchestrate communication between the controller and actuator, a round-robin scheduling mechanism is established based on the pass length. A sliding function involving the state and pass profile is constructed, and the sliding mode controller is designed using triggered states and pass profile signals. Feasible controller gains are attained to ensure the stability of the resultant closed-loop system. Finally, the proposed strategy is implemented for a multi-roll metal rolling process.

关键词： event-triggered mechanism linear repetitive processes metal rolling process round-robin scheduling sliding mode control

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Experimental investigation on the gravity driven discharge of cohesive particles from a silo with two outlets

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Particuology 2024年第6期89卷 11-21页

作者： Li Dai Zhulin Yuan Fengxian Fan Conghui Gu School of energy and Power Engineering University of Shanghai for Science and TechnologyShanghai 200093China Key Laboratory of energy Thermal Conversion and Control of Ministry of Education School of Energy and EnvironmentSoutheast UniversityNanjing 210096China Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering University of Shanghai for Science and TechnologyShanghai 200093China School of energy and Power Jiangsu University of Science and TechnologyZhenjiang 212100China

An experimental study on the gravity driven discharge of cohesive particles from a silo with two outlets was *** discharge behaviors under the conditions that a single outlet was open and two outlets were open were investigated by varying the moisture content of the particles and the filling height of the particles in the *** results show that the discharge rate of the cohesive particles increases gradually at the beginning,then almost keeps constant,and finally drops *** discharge rate in case of two openings is around 1.1–1.6 times that in case of a single *** filling height leads to lower discharge rate in case of a single opening but results in higher discharge rate in case of two ***,the avalanche dynamics in case of a single opening was examined,and the mixing behavior of the cohesive particles was *** is observed that the discharge flow is promoted by the avalanche phenomenon in the silo,generating a general trend that the normalized mass of discharge increases with the filling height at higher moisture *** case of a single opening,the transition from mass flow to funnel flow favors the particle mixing,resulting in an increasing mixing index as the moisture content *** general,a better performance of mixing can be achieved in case of a single opening compared with in case of two *** study provides vital information for fundamental understanding of the gravity driven discharge of cohesive particles from the silo with multiple outlets.

关键词： Cohesive particles Moisture content Discharge rate Avalanche Mixing