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Multifunctional HDPE/Cu biocidal nanocomposites for MEX additive manufactured parts: Perspectives for the defense industry

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Defence Technology（防务技术） 2024年第8期38卷 16-32页

作者： Nectarios Vidakis Nikolaos Michailidis Markos Petousis Nektarios K.Nasikas Vassilios Saltas Vassilis Papadakis Nikolaos Mountakis Apostolos Argyros Mariza Spiridaki Ioannis Valsamos department of mechanical Engineering Hellenic Mediterranean UniversityHeraklion 71410Greece Physical Metallurgy Laboratory Mechanical Engineering DepartmentSchool of EngineeringAristotle University of ThessalonikiThessaloniki 54124Greece Centre for Research&Development of Advanced Materials(CERDAM) Center for Interdisciplinary Research and InnovationBalkan CentreThessaloniki 57001Greece Division of Mathematics and Engineering Sciences Department of Military SciencesHellenic Army AcademyVari GR16673AtticaGreece department of electronic Engineering Hellenic Mediterranean UniversityChania 73133Greece department of Industrial Design and Production Engineering University of West AtticaAthens 12244Greece Institute of electronic Structure and Laser Foundation for Research and Technology-HellasHeraklion 70013Greece

In this study, we investigated the performance improvement caused by the addition of copper(Cu)nanoparticles to high-density polyethylene(HDPE) matrix material. Composite materials, with filler percentages of 0.0, 2.0, 4.0, 6.0, 8.0, and 10.0 wt% were synthesized through the material extrusion(MEX)3D printing technique. The synthesized nanocomposite filaments were utilized for the manufacturing of specimens suitable for the experimental procedure that followed. Hence, we were able to systematically investigate their tensile, flexural, impact, and microhardness properties through various mechanical tests that were conducted according to the corresponding standards. Broadband Dielectric Spectroscopy was used to investigate the electrical/dielectric properties of the composites. Moreover, by employing means of Raman spectroscopy and thermogravimetric analysis(TGA) we were also able to further investigate their vibrational, structural, and thermal properties. Concomitantly, means of scanning electron microscopy(SEM), as well as atomic force microscopy(AFM), were used for the examination of the morphological and structural characteristics of the synthesized specimens, while energy-dispersive Xray spectroscopy(EDS) was also performed in order to receive a more detailed picture on the structural characteristics of the various synthesized composites. The corresponding nanomaterials were also assessed for their antibacterial properties regarding Staphylococcus aureus(S. aureus) and Escherichia coli(E. coli) with the assistance of a method named screening agar well diffusion. The results showed that the mechanical properties of HDPE benefited from the utilization of Cu as a filler, as they showed a notable improvement. The specimen of HDPE/Cu 4.0 wt% was the one that presented the highest levels of reinforcement in four out of the seven tested mechanical properties(for example, it exhibited a 36.7%improvement in the flexural strength, compared to the pure matrix). At the same

关键词： High-density polyethylene(HDPE) Copper(Cu) Material extrusion(MEX) mechanical performance Electrical properties Antibacterial Defense and security

Topological edge and corner states of valley photonic crystals with zipper-like boundary conditions

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Chinese Physics B 2024年第4期33卷 480-491页

作者：沈云峰许孝芳孙铭周文佶常雅箐 School of mechanical Engineering Jiangsu UniversityZhenjiang 212000China School of Optical and electronic Information Suzhou City University&Suzhou Key Laboratory of BiophotonicsSuzhou 215104China

We present a stable valley photonic crystal(VPC)unit cell with C_(3v)symmetric quasi-ring-shaped dielectric columns and realize its topological phase transition by breaking mirror *** on this unit cell structure,topological edge states(TESs)and topological corner states(TCSs)are *** obtain a new type of wave transmission mode based on photonic crystal zipper-like boundaries and apply it to a beam splitter assembled from rectangular photonic crystals(PCs).The constructed beam splitter structure is compact and possesses frequency separation *** addition,we construct a box-shaped triangular PC structures with zipper-like boundaries and discover phenomena of TCSs in the corners,comparing its corner states with those formed by other *** on this,we explore the regularities of the electric field patterns of TESs and TCSs,explain the connection between the characteristic frequencies and locality of TCSs,which helps better control photons and ensures low power consumption of the system.

关键词： valley photonic crystal topological edge states topological corner states higher-order topological insulators topological phase transition

Optimized system for combined production of electricity/green hydrogen for multiple energy pathways:a case study of Egypt

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Clean Energy 2024年第4期8卷 219-236页

作者： Reda Ragab Mohamed HamdiHafez A.El Salmawy Mohamed A.Ismail mechanical Power Engineering department Zagazig UniversityZagazig 44519Egypt mechanical Engineering department College of EngineeringKing Faisal UniversityAl-Ahsa 31982Saudi Arabia

By optimal sizing of a wind/photovoltaic hybrid renewable-energy(RE)system,trimming the surplus capacity to reduce the fluctuations in the electricity supplied to the grid,and using it to produce green hydrogen through electrolysis,a stable output with maximum possible capacity factor(CF)is generated to maintain the electricity grid ***,the trimmed energy is used in a secondary conversion path that minimizes the weighted average cost of the energy generated from the entire *** surplus power-to-gas conversion allows the use of green hydrogen to produce electricity,methanol,or ammonia subject to the resource availability,site characteristics,and financial *** on robust site selection criteria,the best performance is obtained at two sites:Ras Ghareb and Minya,achieving the lowest energy cost with some variance in their *** the Ras Ghareb site,the optimally sized RE plant provided the grid with a quasi-steady capacity of 423 MW with a CF of 80.04%and was capable of injecting 2965.8648 GWh throughout the year with the lowest cost of 2.4355¢/kWh.A surplus of 3.9%of the total energy produced from the plant was directed to produce 1922-ton H_(2)/year,achieving the lowest cost of hydrogen production of$1.9745/kg H_(2).For the other selected site,Minya,the clipped energy is used to produce 3330.47-ton H_(2)/year with an optimized lowest cost of$3.5268/kg H_(2).The difference in hydrogen costs was attributed to the number of full operating hours of the electrolyser in both *** cost is mainly affected by the electricity price and the electrolyser *** both tending to decrease,future forecasts show hydrogen cost reductions.

关键词： hybrid renewable-energy system(HRES) green hydrogen electrolysis power-to-gas methanol ammonia

A novel variable-order fractional chaotic map and its dynamics

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Chinese Physics B 2024年第3期33卷 281-290页

作者：唐周青贺少波王会海孙克辉姚昭吴先明 School of electronic Information Central South UniversityChangsha 410083China School of Automation and electronic Information Xiangtan UniversityXiangtan 411105China School of Physics Central South UniversityChangsha 410083China School of mechanical and Electrical Engineering Guizhou Normal UniversityGuiyang 550025China

In recent years,fractional-order chaotic maps have been paid more attention in publications because of the memory *** paper presents a novel variable-order fractional sine map(VFSM)based on the discrete fractional ***,the order is defined as an iterative function that incorporates the current state of the *** analyzing phase diagrams,time sequences,bifurcations,Lyapunov exponents and fuzzy entropy complexity,the dynamics of the proposed map are investigated comparing with the constant-order fractional sine *** results reveal that the variable order has a good effect on improving the chaotic performance,and it enlarges the range of available parameter values as well as reduces non-chaotic *** coexisting attractors also enrich the dynamics of VFSM and prove its sensitivity to initial ***,the sequence generated by the proposed map passes the statistical test for pseudorandom number and shows strong robustness to parameter estimation,which proves the potential applications in the field of information security.

关键词： chaos fractional difference variable order multistability complexity

Effects of drip and flood irrigation on carbon dioxide exchange and crop growth in the maize ecosystem in the Hetao Irrigation District,China

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Journal of Arid Land 2024年第2期16卷 282-297页

作者： LI Chaoqun HAN Wenting PENG Manman College of mechanical and Electrical Engineering Heze UniversityHeze 274015China College of mechanical and electronic Engineering Northwest A&F UniversityYangling 712100China Institute of Soil and Water Conservation Northwest A&F UniversityYangling 712100China

Drip irrigation and flood irrigation are major irrigation methods for maize crops in the Hetao Irrigation District,Inner Mongolia Autonomous Region,*** research delves into the effects of these irrigation methods on carbon dioxide(CO_(2))exchange and crop growth in this *** experimental site was divided into drip and flood irrigation *** irrigation schedules of this study aligned with the local commonly used irrigation *** employed a developed chamber system to measure the diurnal CO_(2)exchange of maize plants during various growth stages under both drip and flood irrigation *** May to September in 2020 and 2021,two sets of repeated experiments were *** each experiment,a total of nine measurements of CO_(2)exchange were performed to obtain carbon exchange data at different growth stages of maize *** each CO_(2)exchange measurement event,CO_(2)flux data were collected every two hours over a day-long period to capture the diurnal variations in CO_(2)*** each CO_(2)exchange measurement event,the biological parameters(aboveground biomass and crop growth rate)of maize and environmental parameters(including air humidity,air temperature,precipitation,soil water content,and photosynthetically active radiation)were *** results indicated a V-shaped trend in net ecosystem CO_(2)exchange in daytime,reducing slowly at night,while the net assimilation rate(net primary productivity)exhibited a contrasting ***,compared with flood irrigation,drip irrigation demonstrated significantly higher average daily soil CO_(2)emission and greater average daily CO_(2)absorption by maize ***,within the maize ecosystem,drip irrigation appeared more conducive to absorbing atmospheric CO_(2).Furthermore,drip irrigation demonstrated a faster crop growth rate and increased aboveground biomass compared with flood irrigation.A strong linear relationship existed between leaf area index and light utiliza

关键词： carbon dioxide exchange maize growth drip irrigation harvest index net primary productivity Hetao Irrigation District

Laser-Constructing 3D Copper Current Collector with Crystalline Orientation Selectivity for Stable Lithium Metal Batteries

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Energy & Environmental Materials 2024年第6期7卷 129-139页

作者： Hui Li Gang Wang Jin Hu Jun Li Jiaxu Huang Shaolin Xu department of mechanical and Energy Engineering Southern University of Science and TechnologyShenzhen 518000China

The practical application of lithium(Li)metal anodes in high-capacity batteries is impeded by the formation of hazardous Li *** address this challenge,this research presents a novel methodology that combines laser ablation and heat treatment to precisely induce controlled grain growth within laser-structured grooves on copper(Cu)current ***,this approach enhances the prevalence of Cu(100)facets within the grooves,effectively lowering the overpotential for Li nucleation and promoting preferential Li *** approaches that modify the entire surface of collectors,our work focuses on selectively enhancing lithiophilicity within the grooves to mitigate the formation of Li dendrites and exhibit exceptional performance *** half-cell with these collectors maintains a remarkable Coulombic efficiency of 97.42%over 350 cycles at 1 mA cm^(−2).The symmetric cell can cycle stably for 1600 h at 0.5 mA cm^(−2).Furthermore,when integrated with LiFePO4 cathodes,the full-cell configuration demonstrates outstanding capacity retention of 92.39%after 400 cycles at a 1C discharge *** study introduces a novel technique for fabricating selective lithiophilic three-dimensional(3D)Cu current collectors,thereby enhancing the performance of Li metal *** insights gained from this approach hold promise for enhancing the performance of all laser-processed 3D Cu current collectors by enabling precise lithiophilic modifications within complex structures.

关键词： copper current collector heat treatment laser processing lithium metal battery selective crystalline orientation

Effect of cooling media on bead geometry,microstructure,and mechanical properties of wire arc additive manufactured IN718 alloy

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Advances in Manufacturing 2024年第1期12卷 124-149页

作者： Parveen Kumar Satish Kumar Sharma Ratnesh Kumar Raj Singh department of mechanical Engineering Thapar Institute of Engineering and TechnologyPatialaPunjab147004India

This work aims to present and explore thermal management techniques for the wire arc additive manufacturing(WAAM)of IN718 *** heat can be mitigated via air or water *** this study,the material was deposited under four different heat-input conditions with air or water *** air cooling,the layer is deposited in a normal atmospheric air environment,whereas with water cooling,the material is deposited inside a water tank by varying the water *** validate the air and water cooling thermal management techniques,IN718 single-pass and multilayer linear walls were deposited using the bidirectional gas metal arc welding based WAAM setup under four different heat input *** the deposition of single layers,the temperature profiles were recorded,and the geometric and microstructural features were *** multilayer wall structures,the mechanical properties(hardness,tensile strength,and elongation)were determined and assessed using the corresponding microstructural features explored through scanning electron microscopy(SEM),energy dispersive spectroscopy(EDS),and electron backscatter diffraction(EBSD)*** microstructure observed through SEM analysis in the building direction was found to be nonhomogenous compared with that in the deposition ***,water cooling was found to govern bead characteristics,such as wall width and *** grain size and anisotropy of the mechanical properties also decreased in the water-cooled ***,water cooling is an economical and efficient method to mitigate excessive heat accumulation in WAAM-deposited IN718.

关键词： Air cooling Water cooling IN718 Bead characteristics Microstructure Electron backscatter diffraction(EBSD)

A comprehensive review of rectangular duct solar air heaters featuring artificial roughness

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Clean Energy 2024年第5期8卷 186-217页

作者： Ravi Shankar Rajeev Kumar Arun Kumar Pandey Deep Singh Thakur department of mechanical Engineering Rajkiya Engineering College BandaUttar Pradesh 210201India department of mechanical Engineering Institute of Engineering&TechnologyLucknowUttar Pradesh 226021India department of mechanical Engineering Bundelkhand Institute of Engineering&TechnologyJhansiUttar Pradesh 284128India

Solar air heaters(SAHs)are widely used solar thermal systems with applications in diverse ***,its effectiveness is re-strained by low convective heat transfer(HT)coefficients at the absorber plate,leading to inefficient HT,and the elevated temperature of the absorber plate causes significant heat losses,reducing thermal *** study addresses these challenges by introducing ribs or roughness on the absorber plate creating turbulence in the airflow,resulting in significant *** research inves-tigates various rib configurations,the influence of rib parameters,performance methods,and arrangements to evaluate their HT and friction *** these rib configurations,a comparative analysis is done on various factors such as the Nusselt number ratio,thermal enhancement factor,friction factor ratio,and thermal efficiency to optimize distinct roughness parameters and rib ar-rangement *** study also provides valuable recommendations from existing literature,offering insights into the effective design,prospects,and implementation of SAH systems.

关键词： solar air heater artificial roughness low heat transfer heating solar energy

Cooperative Target Fencing of Multiple Vehicles for a General Target with Connectivity Preservation and Collision Avoidance

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Journal of Systems Science & Complexity 2024年第1期37卷 136-151页

作者： PAN Zini CHEN Ben M department of mechanical and Automation Engineering The Chinese University of Hong KongHong KongChina

In this paper,the authors study the cooperative target-fencing problem for n-dimensional systems and a target with a general *** using the velocity of the vehicles,a position feedback control law is proposed to fence the general target into the convex hull formed by the ***,the dynamics of each vehicle is described by a double-integrator *** potential functions are designed to guarantee connectivity preservation of the communication network and collision avoidance among the *** proposed approach can deal with a target whose trajectory is any twice continuously differentiable function of *** effectiveness of the result is verified by a numerical example.

关键词： Multi-agent systems networked systems target fencing