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Challenges and opportunities in the production of magnesium parts by directed energy deposition processes

Journal of Magnesium and Alloys 2024年第5期12卷 1663-1686页

作者： Gürel Cam Ali Günen Iskenderun technical University Faculty of Engineering and Natural SciencesDepartment of Mechanical Engineering31200 Iskenderun-HatayTurkey Iskenderun technical University Faculty of Engineering and Natural SciencesDepartment of Metallurgy and Materials Engineering31200 Iskenderun-HatayTurkey

Mg-alloys have gained considerable attention in recent years for their outstanding properties such as lightweight,high specific strength,and corrosion resistance,making them attractive for applications in medical,aerospace,automotive,and other transport ***,their widespread application is hindered by their low formability at room temperature due to limited slip *** Mg-alloys have low mechanical properties due to the presence of casting defects such as porosity and anisotropy in addition to the high *** casting methods benefit from established process optimization techniques for these problems,additive manufacturing methods are increasingly replacing casting methods in Mg alloys as they provide more precise control over the microstructure and allow specific grain orientations,potentially enabling easier optimization of anisotropy properties in certain *** metal additive manufacturing(MAM)technology also results in some manufacturing defects such as inhomogeneous microstructural evolution and porosity and additively manufactured Mg alloy parts exhibit lower properties than the wrought parts,they in general exhibit superior properties than the cast ***,MAM is a promising technique to produce Mg alloy *** energy deposition processes,particularly wire arc directed energy deposition(WA-DED),have emerged as an advantageous additive manufacturing(AM)technique for metallic materials including magnesium alloys,offering advantages such as high deposition rates,improved material efficiency,and reduced production costs compared to subtractive ***,the inherent challenges associated with magnesium,such as its high reactivity and susceptibility to oxidation,pose unique hurdles in the application of this *** review paper delves into the progress made in the application of DED technology to Mg-alloys,its challenges,and ***,the predominant imperfections,notably inhomo

关键词： Additive manufacturing DED processes Arc-DED Wire arc additive manufacturing(WAAM) 3-D printing High deposition rate

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Shape Analysis of Agricultural Parcels for Land Consolidation Priorities in Tekirdag Province,Turkey

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Chinese Geographical Science 2024年第1期34卷 93-105页

作者： Bahadir ALTURK Vocational School of technical sciences Tekirdag Namik Kemal UniversityTekirdag59030Turkey

Shape irregularity,a sub-factor of parcel fragmentation is a problem that hinders sustainable agriculture and is solved using land consolidation *** of the parcel shape degree contributes significantly to spatial prioritization where there is also a high probability of achieving positive effects of consolidation *** study aims to determine the shape degree of the agricultural parcels both at singular and rural county scales in Tekirdag Province,Turkey in 2020 by combining the parcel shape index(PSI) with the minimum bounding geometry index(MBG) to improve parcel ***-spot zones of the highly irregular and near optimum parcels were also determined using Getis-Ord G_(i)^(*) *** parcel degrees were classified into four categories,namely highly irregular,irregular,regular and near *** obtained unweighted scores of the parameters exhibit deviations from the expected *** weighting by pairwise comparison,the values approached ideal *** 346 740 parcels,53% were highly irregular and irregular and 47% were regular and near optimum shapes after weighting whereas these were 70% and 30%,respectively before *** average parcel degree of 63 rural counties was regular while the average parcel degree of the remaining 264 rural counties was *** combined use of PSI and MBG index improved the correctness of the parcel shape *** could be suggested to use as a tool in land consolidation prioritization.

关键词： land consolidation priority parcel shape index(PSI) minimum bounding geometry(MBG) sustainable rural development hot-spot analysis Tekirdag Province Turkey

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Accelerated generation of holograms with ultra-low memory symmetrically high-compressed look-up table

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Chinese Physics B 2024年第4期33卷 466-471页

作者：杨燕朱建英孙敏远毕勇 Applied Laser Research Center Technical Institute of Physics and ChemistryChinese Academy of SciencesBeijing 100190China University of Chinese Academy of sciences Beijing 100049China

Computer-generated holography technology has been widely applied,and as research in this field deepens,the demand for memory and computational power in small AR and VR devices continues to *** paper presents a hologram generation method,i.e.,a symmetrically high-compressed look-up table method,which can reduce memory usage by50%.In offline computing,half of the basic horizontal and vertical modulation factors are stored,halving the memory requirements without affecting inline ***,its potential extends to various holographic applications,including the production of optical diffraction elements.

关键词： computergenerated hologram look-up table holography

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Thermal Performance of a 4 K High-Frequency Pulse Tube Cryocooler with Different Working Fluids

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Journal of Thermal Science 2024年第4期33卷 1468-1479页

作者： GAO Zhaozhao YANG Biao FAN Xiaoyu CHEN Liubiao WANG Junjie Key Laboratory of Cryogenic Science and Technology Technical Institute of Physics and ChemistryChinese Academy of SciencesBeijing100190China University of Chinese Academy of sciences Beijing100049China

The high-frequency pulse tube cryocooler(HPTC)represents a promising miniature cryocooling technology due to its compact structure and the absence of low-temperature moving ***,limited to the non-ideal gas effect of4He,the HPTC is hard to obtain high cooling performance in the liquid helium temperature range.3He as the working fluid can effectively improve the cooling performance of the HPTC,but the high cost hinders its wide *** consideration of both cooling performance and cost-effectiveness,this paper explores the feasibility of utilizing^(3)He-^(4)He mixtures as the working fluid for ***,the experimental results of a developed HPTC based4He are *** a total power consumption of 575 W,the lowest temperature of 3.26 K was *** the measured cooling power at 4.2 K was 20.8 *** the theoretical utmost efficiency of the cryocooler was calculated in terms of the thermophysical properties of the working fluids,using ^(3)He-^(4)He mixtures with different compositions as the working *** whole machine modeling of the HPTC was further carried out,and the influence of the working fluids with different components on the structural parameters such as double-inlet and inertance tube,and operating parameters such as pressure and frequency were *** calculated results show that the cooling power is expected to be increased to36 mW and 53 mW if the equimolar ^(3)He-^(4)He mixture and pure ^(3)He are used,respectively.

关键词： high-frequency pulse tube cryocooler ^(3)He-^(4)He mixture liquid helium temperature thermally coupled

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Exploration of chromene-based BioAIEgens

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National Science Review 2024年第3期11卷 47-48页

作者： Fritz E.Kühn Department of Chemistry&Catalysis Research Center School of Natural Sciences Technical University of Munich

Photoemission efficiency is usually higher in solution than in solid *** compounds however, display a reverse behavior. Such a behavior is called aggregation-induced emission(AIE).

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Enhancement of Solar PV Panel Efficiency Using Double Integral Sliding Mode MPPT Control

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Tsinghua Science and Technology 2024年第1期29卷 271-283页

作者： Immadisetty Rahul Raju Hariharan Department of Electrical and Electronics Engineering Saveetha School of EngineeringSaveetha Institute of Medical and Technical Sciences(SIMATS)Chennai 602105India

The extraction of maximum power from the solar panels,using the sliding mode control scheme,becomes popular for partial weather atmospheric conditions due to its effective dynamic duty cycle ***,the sliding mode control scheme was sophisticated with single integral and double integral sliding mode control scheme,which offer enhanced maximum power extraction and support enhanced solar panel efficiency in partial weather *** operation of the sliding mode control scheme depends on the selection of a sliding surface selection based on the atmospheric weather condition,which enables the effective sliding duty cycle ratio operation for the DC/DC boost *** duty cycle ratio of the sliding mode control resembles the usual dynamic behavior to achieve enhanced efficiency compared to the various maximum power point tracking(MPPT)*** major limitation of the sliding mode control scheme is to achieve the steady state voltage error of the solar panel in minimum settling time *** single integral sliding mode control scheme achieves the expected steady state voltage error limit but fails to achieve minimum settling time ***,the single integral sliding mode control is extended to a double integral sliding mode control scheme to achieve both steady state voltage error limits within the minimum settling time *** double integral sliding mode control scheme allows us to obtain the higher sliding surface duty cycle ratio which acts as the input signal to the boost *** activates the enhanced stable and reliable system operation,and nullifies the lacuna of maximum solar panel efficiency under partial weather ***,this paper aims to present the design and performance operation of the double integral sliding mode(DISM)MPPT control *** validate the performance analysis of the proposed DISM MPPT control scheme,the MATLAB/Simulink model is designed and ***,the performance analysis of the pr

关键词： maximum power point tracking(MPPT)schemes sliding mode controller(SMC) double integral sliding mode controller(DISMC) pulse width modulation(PWM) photovoltaic(PV)system

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Environment-adaptive phase-separation-porous fluorofilm for highperformance passive radiation cooling

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Nano Research 2024年第6期17卷 5636-5644页

作者： Weiming Tang Yong Li Xue Meng Shutao Wang Ziguang Zhao School of Future Technology University of Chinese Academy of SciencesBeijing 100049China CAS Key Laboratory of Bio-inspired Materials and Interfacial Science Technical Institute of Physics and ChemistryChinese Academy of SciencesBeijing 100190China CAS Key Laboratory of Cryogenics Technical Institute of Physics and ChemistryChinese Academy of SciencesBeijing 100190China

Passive radiative cooling is widely recognized as an environmentally sustainable method for achieving significant cooling ***,the mechanical properties and environmental adaptability of current radiative cooling materials are not sufficient to maintain high cooling performance in external *** we reported an environment-adaptive phase-separation-porous fluorofilm for high-performance passive radiation *** to the homogenous fluoro-porous network with limited scattering efficiencies,we modulated the porous structure of the fluorofilm to achieve a strong emissivity of 95.2%(8-13μm)and a high reflectivity of 97.1%(0.3-2.5μm).The fluorofilm demonstrates a temperature drop of 10.5°C and an average cooling power of 81 W·m^(−2)under a sunlight power of 770 W·m^(−2).The high mechanical performance and environmental adaptability of fluorofilms are also *** its significant radiative cooling capability and robust environmental adaptability,the fluorofilm is expected to have a promising future in radiative temperature regulation.

关键词： fluorofilm passive radiation cooling porous optimization thermal regulation

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Absence of BCS–BEC crossover in FeSe0.45Te0.55 superconductor

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Chinese Physics B 2024年第7期33卷 89-96页

作者：贾俊杰谷亚东殷超辉束英杰陈逸雯史聚民张杏陈浩苗泰民任晓琳梁波朱文培蔡能张丰丰张申金杨峰王志敏彭钦军许祖彦毛寒青刘国东任治安赵林周兴江 National Laboratory for Superconductivity Beijing National Laboratory for Condensed Matter PhysicsInstitute of Physics Chinese Academy of Sciences University of Chinese Academy of sciences technical Institute of Physics and Chemistry Chinese Academy of Sciences Songshan Lake Materials Laboratory

In iron-based superconductor Fe（Se,Te）, a flat band-like feature near the Fermi level was observed around the Brillouin zone center in the superconducting state. It is under debate whether this is the evidence on the presence of the BCS–BEC[Bardeen–Cooper–Schrieffer（BCS）, Bose–Einstein condensation（BEC）] crossover in the superconductor. High-resolution laser-based angle-resolved photoemission measurements are carried out on high quality single crystals of FeSe0.45Te0.55superconductor to address the issue. By employing different polarization geometries, we have resolved and isolated the dyz band and the topological surface band, making it possible to study their superconducting behaviors separately. The dyz band alone does not form a flat band-like feature in the superconducting state and the measured dispersion can be well described by the BCS picture. We find that the flat band-like feature is formed from the combination of the dyz band and the topological surface state band in the superconducting state. These results reveal the origin of the flat band-like feature and rule out the presence of BCS-BEC crossover in Fe（Se,Te） superconductor.

关键词： FeSe_(0.45)Te_(0.55) ARPES electronic structure superconducting gap BCS-BEC crossover

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New opportunities for ferroelectric deep-UV nonlinear optical crystals

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Science China Materials 2024年第3期67卷 1004-1005页

作者： Miriding Mutailipu Shilie Pan Research Center for Crystal Materials Xinjiang Technical Institute of Physics and ChemistryChinese Academy of SciencesUrumqi 830011China Center of Materials Science and Optoelectronics Engineering University of Chinese Academy of SciencesBeijing 100049China

Deep-ultraviolet(deep-UV)light with the wavelength below200 nm is one of the most crucial elements of both laser-driven industrial and scientific applications in recent years[1].DeepUV light has been produced using a variety of techniques,such as gas discharge lamps,synchrotron radiation,excimer lasers,free electron lasers,and nonlinear frequency conversion.

关键词： nonlinear optical ferroelectric

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Method for passivation of propellant residues in orbital stage tank of launch vehicle

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Chinese Journal of Aeronautics 2024年第1期37卷 64-76页

作者： Valeriy TRUSHLYAKOV Ivan LESNYAK Alexey PANICHKIN Department of Aviation and Rocket Building Omsk State Technical UniversityOmsk 644050Russia Sobolev Institute of Mathematics of the Siberian Branch of Russian Academy of sciences Novosibirsk 630090Russia

The problem of removing unused liquid propellant residues from the tanks of spent spacecraft and orbital stages of Launch Vehicles(LV)leads to their explosion and the formation of space debris in *** provide a solution to this problem,a method for removing liquid propellant residues from the LV tanks after the mission completion is *** method is based on the gasification of liquid propellant residues in the tanks under acoustic-vacuum exposure and the discharge of the gasification products into the surrounding outer *** investigations were carried out on a Ground-based Experimental Installation(GEI)to determine the coefficient of heat transfer from the surface of an acoustic radiator to a *** obtained coefficient was then used to calculate the energy costs for the gasification of *** estimates are given on the example of the tank with kerosene residues from a spent second stage of the LV“Soyuz-2.1 v”.The optimal discharge rate at which kerosene does not freeze is 0.14 m^(3)/***,the acoustic exposure leads to an increase in the mass of evaporated kerosene over a given time by96.1%,and the energy costs are 1756.7 kJ(approximately 50% of the remaining electrical energy).

关键词： Propellant Weightlessness Liquid evaporation Heat and mass transfer Acoustics Vacuum Vapor bubbles

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