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Mechanics and physics under supergravity conditions

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Acta Mechanica Sinica 2024年第6期40卷 1-2页

作者： Chaofeng lü Chao Sun Shengqiang Cai Faculty of Mechanical Engineering and Mechanics Ningbo UniversityNingbo 315211China New Cornerstone Science laboratory Center for Combustion EnergyDepartment of Energy and Power EngineeringTsinghua UniversityBeijing 100084China department of Mechanical and Aerospace Engineering University of CaliforniaSan DiegoLa Jolla CA 92093USA

"Supergravity"refers to the conditions where the effective gravity is greater than that of *** conditions are generally relevant to stellar evolution,geophysical movement,astrophysical flows,and *** also frequently occur in various engineering scenarios involving acceleration,such as the launch of space shuttles,operation of rotor engines,impacts and explosions,chemical separation processes,and overloaded testing *** is already demonstrated in physiological experiments that living organisms of animals or plants could be damaged,either temporarily or permanently,when subjected to *** create supergravity conditions for scientific research on the Earth,centrifugal equipment or rapidly rotating devices are omnipresent in various fields,such as aerospace engineering,geophysical science,chemical and biomedical engineering,nuclear engineering,rotating flows,and physical modeling tests.

关键词： geophysical Earth stellar

A New Proof for Congruent Number’s Problem via Pythagorician divisors

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Advances in Pure Mathematics 2024年第4期14卷 283-302页

作者： léopold dèkpassi Keuméan François Emmanuel Tanoé UFR Mathematics and Computer Science F&#233lix Houphou&#235t Boigny University Abidjan Cote d&#8217Ivoire

Considering Pythagorician divisors theory which leads to a new parameterization, for Pythagorician triplets ( a,b,c )∈ ℕ 3∗ , we give a new proof of the well-known problem of these particular squareless numbers n∈ ℕ ∗ , called congruent numbers, characterized by the fact that there exists a right-angled triangle with rational sides: ( A α ) 2 + ( B β ) 2 = ( C γ ) 2 , such that its area Δ= 1 2 A α B β =n;or in an equivalent way, to that of the existence of numbers U 2 , V 2 , W 2 ∈ ℚ 2∗ that are in an arithmetic progression of reason n;Problem equivalent to the existence of: ( a,b,c )∈ ℕ 3∗ prime in pairs, and f∈ ℕ ∗ , such that: ( a−b 2f ) 2 , ( c 2f ) 2 , ( a+b 2f ) 2 are in an arithmetic progression of reason n;And this problem is also equivalent to that of the existence of a non-trivial primitive integer right-angled triangle: a 2 + b 2 = c 2 , such that its area Δ= 1 2 ab=n f 2 , where f∈ ℕ ∗ , and this last equation can be written as follows, when using Pythagorician divisors: (1) Δ= 1 2 ab= 2 S−1 d e ¯ ( d+ 2 S−1 e ¯ )( d+ 2 S e ¯ )=n f 2;Where ( d, e ¯ )∈ ( 2ℕ+1 ) 2 such that gcd( d, e ¯ )=1 and S∈ ℕ ∗ , where 2 S−1 , d, e ¯ , d+ 2 S−1 e ¯ , d+ 2 S e ¯ , are pairwise prime quantities (these parameters are coming from Pythagorician divisors). When n=1 , it is the case of the famous impossible problem of the integer right-angled triangle area to be a square, solved by Fermat at his time, by his famous method of infinite descent. We propose in this article a new direct proof for the numbers n=1 (resp. n=2 ) to be non-congruent numbers, based on an particular induction method of resolution of Equation (1) (note that this method is efficient too for general case of prime numbers n=p≡a ( ( mod8 ) , gcd( a,8 )=1 ). To prove it, we use a classical proof by induction on k , that shows the non-solvability property of any of the following systems ( t=0 , corresponding to case n=1 (resp. t=1 , corresponding to case n=2 )): ( Ξ t,k ){ X 2 + 2 t ( 2 k Y ) 2 = Z 2 X 2 + 2

关键词： Prime Numbers-diophantine Equations of degree 2 & 4 Factorization Greater Common divisor Pythagoras Equation Pythagorician Triplets Congruent Numbers Inductive demonstration Method Infinite descent BSd Conjecture

Corrosion testing of X52 and X80 steels immersed in stimulated emulsions using a real petroleum sample

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Petroleum Research 2024年第2期9卷 304-316页

作者： l.M.Quej-Ake J.l.Alamilla A.Contreras Instituto Mexicano del Petróleo Eje Central Lázaro CárdenasNorte 152San Bartolo AtepehuacanGustavo A.MaderoCiudad de MéxicoC.P.07730México

The aim of this study is to evaluate the internal corrosion process on X52 and X80 steels/real petroleum interfaces containing condensed hydrocarbon plus oilfield-produced water,which were subjected to stimulated emulsions using 50/50 vol ratio mixtures at 45℃,different hydrodynamic conditions,1 h,and 24 h.A washing process by using deionized water was proposed to simulate and identify the corrosiveness of the hydrocarbon phase after 24 h of exposure *** characterization by electrochemical impedance spectroscopy and the monitoring of the polarization curves indicated that X80 steel/oilfield-produced water interfaces were more susceptible to corrosion than X52 steel exposed to oilfield-produced *** combined speed rotation of 600 rpm using a magnetic stirrer+600 rpm using a rotating disk electrode decreased the corrosion rate on X52 *** stimulated emulsions made of hydrocarbon+oilfield-produced water and hydrocarbon+deionized water at 24 h increased the corrosion rate on X80 steel(0.34 mm/year and 0.43 mm/year,respectively),promoting the formation of erosion and pitting *** types of corrosion depended mainly on the physicochemical properties of the hydrocarbon,oilfield-produced water,exposure times,and hydrodynamic systems in which the hydrocarbon was studied.

关键词： Corrosion Emulsions X52 steel X80 steel

Nonaqueous potassium-ion full-cells:Mapping the progress and identifying missing puzzle pieces

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Journal of Energy Chemistry 2024年第6期93卷 384-399,I0010页

作者： Badre larhrib louiza larbi lénaïc Madec Universite de Pau et des Pays de l’Adour E2S UPPACNRSIPREMPauFrance Universitéde Haute-Alsace Institut de Science des Matériaux de Mulhouse(IS2M)CNRS UMR 7361F-68100 MulhouseFrance Universitéde Strasbourg F-67081 StrasbourgFrance Réseau sur le Stockage Electrochimique de l’Energie CNRS FR3459AmiensFrance Institut des Matériaux Jean Rouxel(IMN) CNRS UMR 6502Univ.Nantes44322 Cedex 3 NantesFrance

This review addresses the growing interest for potassium-ion full-cells(KIFCs)in view of the transition from potassium-ion half-cells(KIHCs)toward commercial K-ion batteries(KIBs).It focuses on the key parameters of KIFCs such as the electrode/electrolyte interfaces challenge,major barriers,and recent advancements in *** strategies for enhancing KIFC performance,including interfaces co ntrol,electrolyte optimization,electrodes capacity ratio,electrode material screening and electrode design,are *** review highlights the need to evaluate KIBs in full-cell configurations as half-cell results are strongly impacted by the K metal *** also emphasizes the importance of understanding solid electrolyte interphase(SEI)formation in KIFCs and explores promising nonaqueous as well as quasiand all-solid-state electrolytes *** review thus paves the way for practical,cost-effective,and scalable KIBs as energy storage systems by offering insights and guidance for future research.

关键词： K-ion full-cells Potassium-ion batteries Cross-talk Solid-state batteries Potassium reactivity Electrolyte design Electrode design

Role of pituitary adenylate cyclase-activating polypeptide in peripheral nerve regeneration:a cellular and molecular perspective

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Neural Regeneration Research 2024年第7期19卷 1429-1430页

作者： Grazia Maugeri Velia d’Agata Section of Anatomy Histology and Movement SciencesDepartment of Biomedical and Biotechnological SciencesUniversity of CataniaCataniaItaly

Neuro regeneration is a very complex phenomenon characterized by the generation of new neurons and synapses,involving connections between adjacent cells and axonal *** supplies additional longterm resources to replace... 详细信息

关键词： replace functional regeneration

Assessment of portable FTIR and Raman spectroscopy for the detection of 2,3-dimethyl-2,3-dinitrobutane(dMdNB)in plastic explosives

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defence Technology（防务技术） 2024年第4期34卷 11-18页

作者： Jacky Cailes Robert dunsmore Kathryn l.linge ChemCentre PO Box 1250PerthAustralia

The Marplex Convention was established to prevent the manufacture of unmarked plastic explosives and stipulates that a volatile detection agent must be added at the time of ***,to-date,laboratory testing remains the internationally accepted practice for identifying and quantifying the taggants stipulated in the *** this project,portable FTIR and Raman instruments were tested for their ability to detect 2,3-dimethyl-2,3-dinitrobutane(dMdNB),the chemical marker incorporated in plastic explosives that are manufactured within *** both FTIR and Raman instruments detected solid dMdNB(98%purity),field analysis of plastic explosives at an Australian defence establishment showed that both FTIR and Raman spectra were matched the relevant explosive(RdX or PETN),rather than the dMdNB *** all three plastic explosives tested,the concentration of dMdNB was measured by SPME-GC-MS to be between 1.8 and 2%,greater than the minimum 1%concentration stipulated by the Marplex *** testing with a plastic explosive analogue confirmed that the minor absorption peaks that would characterize low concentrations of dMdNB were masked by absorption bands from other compounds within the ***,while both FTIR and Raman spectroscopy are suitable for detection of plastic explosives,neither rely on the presence of dMdNB for *** is likely that similar results would be found for other taggants stipulated by the Marplex Convention,given they are also present in concentrations less than 1%.

关键词： Explosive ICAO taggants 2,3-dimethyl-2,3-dinitrobutane(dMdNB) Fourier transform infrared(FTIR) Raman

Guaranteed Cost Attitude Tracking Control for Uncertain Quadrotor Unmanned Aerial Vehicle Under Safety Constraints

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IEEE/CAA Journal of Automatica Sinica 2024年第6期11卷 1447-1457页

作者： Qian Ma Peng Jin Frank l.lewis School of Automation Nanjing University of Science and TechnologyNanjing 210094China UTA Research Institute University of Texas at ArlingtonFort WorthTexas 76118 USA IEEE

In this paper,guaranteed cost attitude tracking con-trol for uncertain quadrotor unmanned aerial vehicle(QUAV)under safety constraints is ***,an augmented system is constructed by the tracking error system and reference *** transformation aims to convert the tracking control prob-lem into a stabilization control ***,control barrier function and disturbance attenuation function are designed to characterize the violations of safety constraints and tolerance of uncertain disturbances,and they are incorporated into the reward function as penalty *** on the modified reward function,the problem is simplified as the optimal regulation problem of the nominal augmented system,and a new Hamilton-Jacobi-Bellman equation is ***,critic-only rein-forcement learning algorithm with a concurrent learning tech-nique is employed to solve the Hamilton-Jacobi-Bellman equa-tion and obtain the optimal *** proposed algorithm can not only ensure the reward function within an upper bound in the presence of uncertain disturbances,but also enforce safety *** performance of the algorithm is evaluated by the numerical simulation.

关键词： Attitude tracking control quadrotor unmanned aerial vehicle(QUAV) reinforcement learning safety constraints uncertain disturbances.

Approximate contact solutions for non-axisymmetric homogeneous and power-law graded elastic bodies:A practical tool for design engineers and tribologists

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Friction 2024年第2期12卷 340-355页

作者： Valentin l.POPOV Qiang lI Emanuel WIllERT Institute of Mechanics Technische Universität BerlinBerlin 10623Germany

In two recent papers,approximate solutions for compact non-axisymmetric contact problems of homogeneous and power-law graded elastic bodies have been suggested,which provide explicit analytical relations for the force–approach relation,the size and the shape of the contact area,as well as for the pressure distribution *** solutions were derived for profiles,which only slightly deviate from the axisymmetric *** the present paper,they undergo an extensive testing and validation by comparison of solutions with a great variety of profile shapes with numerical solutions obtained by the fast Fourier transform(FFT)-assisted boundary element method(BEM).Examples are given with quite significant deviations from axial symmetry and show surprisingly good agreement with numerical solutions.

关键词： normal contact non-axisymmetric indenter extremal principle generalized method of dimensionality reduction(MdR) functional elastic grading

The influence of various grease compositions and silver nanoparticle additives on electrically induced rolling-element bearing damage

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Friction 2024年第4期12卷 796-811页

作者： Samuel BONd Robert l.JACKSON German MIllS department of Chemistry and Biochemistry Auburn UniversityAuburn 36849-5412USA department of Mechanical Engineering Auburn UniversityAuburn 36849-5412USA

leakage currents accelerate surface degradation of metal contacts via small scale arcing across lubricating films,but recent observations suggest that metallic nanoparticle additives in lubricants may be useful to improve contact *** findings prompted a study that examined electrically induced surface pitting of steel contacts in the presence of several lubricating greases including some containing nanometer-sized colloidal silver(Ag)*** rolling sphere-on-disk experiments were conducted under electro-tribological loads employing polyurea greases derived from mineral and synthetic base oils with and without *** forces and electrical resistance were monitored continuously during the tests;surface changes were characterized by means of optical spectroscopy,stylus profilometry,and scanning electron microscopy(SEM)including compositional analysis using energy dispersive spectroscopy(EdS).The observations demonstrate that surface pitting induced by arcing occurs mainly at the points were the rolling motion changes direction and that eroded metal is deposited along the wear ***-sized pits are formed which contain carbon and oxygen indicating that arcing causes decomposition of the hydrocarbon *** findings indicate a significant inhibition of pitting is induced by the Ag nanoparticles;some greases containing other additives exhibit a similar,although less pronounced,effect.

关键词： electric motor bearings wheel bearings electric vehicles arcing electrically induced bearing damage pitting leakage current stray current