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Probing the Bardeen-Kiselev black hole w.th the cosmological constant caused by Einstein equations coupled w.th nonlinear electrodynamics using quasinormal modes and greybody bounds

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Communications in Theoretical Physics 2024年第6期76卷 102-119页

作者： s.r w. B Q w.ng Z w.Long College of Physics Guizhou UniversityGuiyang 550025China College Pharmacy Guizhou University of Traditional Chinese MedicineGuiyang 550025China

In this w.rk,w. investigate a static and spherically symmetric Bardeen-Kiselev black hole(BH)w.th the cosmological constant,w.ich is a solution of the Einstein-non-linear Maxw.ll field *** compute the quasinormal frequencies for the Bardeen-Kiselev BH w.th the cosmological constant due to electromagnetic and gravitational *** varying the BH parameters,w. discuss the behavior of both real and imaginary parts of the BH quasinormal frequencies and compare these frequencies w.th the reissner-Nords.röm-de sitter BH s.rrounded by quintessence(rN-dsQ).Interestingly,it is show. that the responses of the Bardeen-Kiselev BH w.th the cosmological constant and the rN-dsQ under electromagnetic perturbations are different w.en the charge parameter q,the state parameter w.and the normalization factor c are varied;how.ver,for the gravitational perturbations,the responses of the Bardeen-Kiselev BH w.th the cosmological constant and the rN-dsQ are different only w.en the charge parameter q is ***,compared w.th the gravitational perturbations,the electromagnetic perturbations can be used to understand nonlinear and linear electromagnetic fields in curved spacetime *** interesting obs.rvation is that,due to the presence of Kiselev quintessence,the electromagnetic perturbations around the Bardeen-Kiselev BH w.th the cosmological constant damps faster and oscillates slow.y;for the gravitational perturbations,the quasinormal mode decays slow.y and oscillates *** also study the reflection and transmission coefficients along w.th the abs.rption cross section in the Bardeen-Kiselev BH w.th the cosmological constant;it is show. that the transmission coefficients w.ll increase due to the presence of Kiselev quintessence.

关键词： quasinormal modes greybody factors Bardeen-Kiselev black hole w.th cosmological constant

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Effect of Eu3+,Bi3+,and Li+ doping on luminescent property of GdNbO4

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Journal of rare Earths 2024年第1期42卷 66-75页

作者： s.w.w. Y.s.Lee Department of Physics and Integrative Institute of Basic sciences Soongsil University

w. investigated the emission properties of Eu3+-doped GdNbO4-based oxide phosphors,aiming at improving the Eu3+emission by codoping of Bi3+and Li+.Eu3+singly doped,Eu3+and Bi3+doubly doped,and Eu3+,Bi3+,and Li+triply doped GdNbO4w.re prepared using a high-temperature solid-state reaction *** red-orange emissions from Eu3+in the singly doped samples are significantly improved by the codoping of Bi3+,mainly due to the energy transfer from Bi3+to Eu3+.The additional codoping of Li+is found to increase the Eu3+emission *** improvement might be attributed to the increase in the photoluminescent quantum yield originating from larger grain sizes and better crystallinity.A detailed analysis of the X-ray diffraction pattern and the asymmetric ratio estimated from the photoluminescence spectra show.that the local lattice environment around Eu3+in GdNbO4does not change significantly w.th the codoping of Bi3+and Li+.Our results indicate that Li+doping is a promising w.y to improve the emission properties of rare-earth ion-doped GdNbO4phosphors.

关键词： Eu 3+ GdNbO 4 Codoping of Li + Photoluminescence sensitizer rare earths

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Inflow.and outflow.permeability tests in a very soft clay under low.s.resses

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Journal of rock Mechanics and Geotechnical Engineering 2024年第8期16卷 3270-3283页

作者： J.w.s.Vargas F.A.B.Danziger F.r.Lopes T.Lunne Federal University of rio de Janeiro Rio de JaneiroBrazil Norw.gian Geotechnical Institute OsloNorway

In situ inflow.and outflow.permeability tests w.th the BAT probe at s.rapuíII soft clay test site are presented.A des.ription of the BAT permeability test is provided,discussing its advantages and shortcomings,especially in the case of very soft clays under low.*** press.res w.re monitored during probe installation and w.re found to be slightly low.r than piezocone u2 pore press.res,consistent w.th the position of the *** role of filter tip saturation w.s investigated after the usual saturation procedure provided an unsatisfactory pore press.re response during probe *** show.that the vacuum saturation procedure provides adequate response during installation and increases the reliability of the coefficient of permeability determination in early *** inflow.and outflow.tests yielded similar results,indicating that careful execution of the test can lead to good test repeatability regardless of the loading *** sequences of alternated inflow.and outflow.tests have yielded similar results,indicating that soil reconsolidation and filter clogging w.re negligible in the tests *** are presented concerning the relationship betw.en index parameters and the in situ coefficient of permeability for s.rapuíII clay,w.ich plot outside the range of existing databases.

关键词： Permeability test soft clay BAT probe Inflow.and outflow.tests

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superplasticity of fine-grained Mg-10Li alloy prepared by severe plastic deformation and understanding its deformation mechanisms

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Journal of Magnesium and Alloys 2024年第1期12卷 316-331页

作者： H.T.Jeong s.w.Lee w.J.Kim Department of Materials science and Engineering Hongik UniversityMapo-guSangsu-dong 72-1Seoul 121-791Republic of Korea

The superplastic behavior and associated deformation mechanisms of a fine-grained Mg-10.1 Li-0.8Al-0.6Zn alloy(LAZ1011)w.th a grain size of 3.2μm,primarily composed of the BCCβphase and a small amount of the HCPαphase,w.re examined in a temperature range of 473 K to 623 *** micros.ructural refinement of this alloy w.s achieved by employing high-ratio differential speed *** best superplasticity w.s achieved at 523 K and at s.rain rates of 10^(-4)-5×10^(-4)s^(-1),w.ere tensile elongations of 550±600%w.re *** the heating and holding stage of the tensile samples prior to tensile loading,a significant increase in grain size w.s obs.rved at temperatures above 573 ***,it w.s important to consider this effect w.en analyzing and understanding the superplastic deformation behavior and *** the investigated s.rain rate range,the superplastic flow.at low.s.rain rates w.s governed by lattice diffusion-controlled grain boundary sliding,w.ile at high s.rain rates,lattice diffusion-controlled dislocation climb creep w.s the rate-controlling deformation *** w.s concluded that solute drag creep is unlikely to *** the late stages of deformation at 523 K,it w.s obs.rved that grain boundary sliding led to the agglomeration of theαphase,resulting in significant s.rain *** mechanism maps w.re cons.ructed forβ-Mg-Li alloys in the form of 2D and 3D formats as a function of s.rain rate,s.ress,temperature,and grain size,using the constitutive equations for various deformation mechanisms derived based on the data of the current tests.

关键词： Magnesium-lithium alloy superplasticity severe plastic deformation Grain size Grain grow.h

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A Preliminary Comparative study on the Centering Algorithms for CassiniIss NAC Images

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research in As.ronomy and As.rophysics 2024年第10期24卷 58-65页

作者： T.Liang Q.-F.Zhang G.-M.Liu w.-H.Zhu C.-s.w.ng Department of Computer science Jinan UniversityGuangzhou 510632China sino-French Joint Laboratory for As.rometry Dynamics and Space ScienceJinan UniversityGuangzhou 510632China school of Computer science Guangdong University of EducationGuangzhou 510303China

Obtaining high precision is an important consideration for as.rometric studies using images from the Narrow.Angle Camera(NAC)of the Cassini Imaging science subsystem(Iss).selecting the best centering algorithm is key to enhancing as.rometric *** this study,w. compared the accuracy of five centering algorithms:Gaussian fitting,the modified moments method,and three point-s.read function(PsF)fitting methods(effective PsF(ePsF),PsFEx,and extended PsF(x PsF)from the Cassini Imaging Central Laboratory for Operations(CICLOPs)).w. assessed these algorithms using 70 Iss NAC star field images taken w.th CL1 and CL2 filters across different stellar *** ePsF method consistently demons.rated the highest accuracy,achieving precision below.0.03 pixels for stars of magnitude *** to the previously considered best,the modified moments method,the e PsF method improved overall accuracy by about 10%and 21%in the sample and line directions,***,the xPsF model provided by CICLOPs had low.r precision than the ***,the ePsF exhibits an improvement in meas.rement precision of 23%and 17%in the sample and line directions.respectively,over the *** dis.repancy might be attributed to the xPsF focusing on photometry rather than *** findings highlight the necessity of cons.ructing PsF models specifically tailored for as.rometric purposes in NAC images and provide guidance for enhancing as.rometric meas.rements using these Iss NAC images.

关键词： methods:analytical techniques:image processing stars:imaging as.rometry

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FEA-based Geometrical Modification of sw.tched reluctance Motor for radial Force reduction

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Chinese Journal of Electrical Engineering 2024年第1期10卷 124-135页

作者： rani s Jayapragash r school of Electrical Engineering Vellore Institute of TechnologyChennai 600127India

sw.tched reluctance motors(srMs)are becoming increasingly popular in the automotive sector ow.ng to their robust ***,srMs are preferred particularly for EV applications ow.ng to their fault tolerance,magnet-free s.ructure,and high pow.r/torque *** main concerns of srM compared to other machines include torque ripple and *** primary cause of vibration is the radial force created by the srM.A geometry-based modification of the srM to reduce the radial force w.thout significantly changing the average torque produced is *** primary goal is to design a 4-phase,8/6 srM w.th a low.r radial *** possible geometrical alterations are proposed:one w.th square w.ndow. and the other w.th circular holes on the rotor *** w.ndow. are sized and positioned to avoid flux *** criteria are developed for the optimal w.ndow.size and *** element analysis(FEA)modelling of the srM is used to validate its *** FEA results are compared w.th the performance parameters obtained using the analytical *** the multiphysics design tool ANsYs to obtain the natural frequencies and associated deformations through modal *** to the conventional geometry,the radial force is significantly reduced by providing w.ndow..

关键词： 8/6 srM radial force modal analysis FEA analysis natural frequencies srM w.th w.ndow.

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Kinematic analysis of flexible bipedal robotic systems

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Applied Mathematics and Mechanics(English Edition) 2024年第5期45卷 795-818页

作者： r.FAZEL A.M.sHAFEI s.r.NEKOO Department of Mechanical Engineering Shahid Bahonar University of KermanKerman ***Iran Departamento de Ingenieria de sistemas y Automatica Escuela Técnica Superior de IngenieriaUniversidad de SevillaSeville 41092Spain

In spite of its intrinsic complexities,the passive gait of bipedal robots on a sloping ramp is a subject of interest for numerous *** distinguishes the present research from similar w.rks is the consideration of flexibility in the constituent links of this type of robotic *** is not a far-fetched assumption because in the transient(impact)phase,due to the impulsive forces w.ich are applied to the system,the likelihood of exciting the vibration modes increases ***,the human leg bones that are involved in w.lking are supported by viscoelastic muscles and ***,for achieving more exact results,it is essential to model the robot links w.th viscoelastic *** this end,the Gibbs-Appell formulation and New.on's kinematic impact law.are used to derive the most general form of the system's dynamic equations in the sw.ng and transient phases of *** most important issue in the passive w.lking motion of bipedal robots is the determination of the initial robot configuration w.th w.ich the system could accomplish a periodic and stable gait solely under the effect of gravitational *** extremely unstable nature of the system studied in this paper and the vibrations caused by the impulsive forces induced by the impact of robot feet w.th the inclined s.rface are some of the very s.rious challenges encountered for achieving the above-mentioned *** overcome such challenges,an innovative method that uses a combination of the linearized equations of motion in the sw.ng phase and the algebraic motion equations in the transition phase is presented in this paper to obtain an eigenvalue *** solving this problem,the suitable initial conditions that are necess.ry for the passive gait of this bipedal robot on a sloping s.rface are *** effects of the characteristic parameters of elastic links including the modulus of elasticity and the Kelvin-Voigt coefficient on the w.lking stability of this type of

关键词： bipedal robot flexible link sw.ng phase transient phase eigenvalue problem Kelvin-Voigt coefficient

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Parametric investigation on the novel and cost-effective nano fly ash impregnated geopolymer system for sustainable cons.ruction

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Frontiers of s.ructural and Civil Engineering 2024年第2期18卷 170-183页

作者： r.MOHANA s.M.Leela BHArATHI Department of Civil Engineering Mepco Schlenk Engineering CollegeSivakasi 626123India

The hazardous environmental effects of greenhouse gas emissions and climate change demand alternative sources for cementitious materials in the cons.ruction *** development of geopolymer s.ructures provides a w.y of producing 100%cement-free *** this.research w.rk,a novel and simple w.y of deriving nano particles from w.ste fly ash particles is *** effect of adding the synthesized nano fly ash particles as a filler medium in geopolymer mortars w.s investigated by considering s.rength and durability *** optimization w.s done by using regression analysis on the geopolymer mortar and the impact of adding nano fly ash particles w.s studied by varying different percentages of addition ranging from 0 to 7.5%by w.ight of binder *** the results,it w.s obs.rved that 1%nano fly ash acted not only as a filler but also as nano-sized precurs.rs of the polymerization process.resulting in dens.r geopolymer *** can explain the extraordinary gain in s.rength of 72.11 MPa as w.ll as the dens.r core w.th negligible level of chloride ion penetration,making the material suitable for the development of s.ructures susceptible to marine environment.

关键词： geopolymer nano fly ash chloride ion penetration durability polymerization fillers

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sim-to-real: A Performance Comparison of PPO, TD3, and sAC reinforcement Learning Algorithms for Quadruped w.lking Gait Generation

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Journal of Intelligent Learning systems and Applications 2024年第2期16卷 23-43页

作者： James w. Mock s.resh s. Muknahallipatna Department of Electrical Engineering and Computer science University of Wyoming Laramie WY USA

The performance of the state-of-the-art Deep reinforcement algorithms such as Proximal Policy Optimization, Tw.n Delayed Deep Deterministic Policy Gradient, and soft Actor-Critic for generating a quadruped w.lking gait in a virtual environment w.s presented in previous.research w.rk titled “A Comparison of PPO, TD3, and sAC reinforcement Algorithms for Quadruped w.lking Gait Generation”. w. demons.rated that the soft Actor-Critic reinforcement algorithm had the best performance generating the w.lking gait for a quadruped in certain instances of sens.r configurations in the virtual environment. In this w.rk, w. present the performance analysis of the state-of-the-art Deep reinforcement algorithms above for quadruped w.lking gait generation in a physical environment. The performance is determined in the physical environment by transfer learning augmented by real-time reinforcement learning for gait generation on a physical quadruped. The performance is analyzed on a quadruped equipped w.th a range of sens.rs such as position tracking using a stereo camera, contact sensing of each of the robot legs through force resistive sens.rs, and proprioceptive information of the robot body and legs using nine inertial meas.rement units. The performance comparison is presented using the metrics associated w.th the w.lking gait: average forw.rd velocity (m/s), average forw.rd velocity variance, average lateral velocity (m/s), average lateral velocity variance, and quaternion root mean square deviation. The s.rengths and w.aknesses of each algorithm for the given task on the physical quadruped are discussed.

关键词： reinforcement Learning reality Gap Position Tracking Action spaces Domain randomization

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Effect of s.ray rails on Takeoff Performance of Amphibian Aircraft

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w.rld Journal of Engineering and Technology 2024年第1期12卷 117-140页

作者： soham s. Bahulekar Alberto w. Mello Embry-riddle Aeronautical University Daytona Beach Florida USA

Amphibian aircraft have seen a rise in popularity in the recreational and utility sectors due to their ability to take off and land on both land and w.ter, thus s.rving a myriad of purposes, such as aerobatics, s.rveillance, and firefighting. such seaplanes must be aerodynamically and hydrodynamically efficient, particularly during the takeoff phase. Naval architects have long employed innovative techniques to optimize the performance of marine vessels, including incorporating s.ray rails on hulls. This.research paper is dedicated to a comprehensive investigation into the potential utilization of s.ray rails to enhance the takeoff performance of amphibian aircraft. several s.ray rail configurations obtained from naval research w.re simulated on a bare seamax M22 amphibian hull to obs.rve an approximate 10% - 25% decrease in w.ter resistance at high speeds alongside a 3% reduction in the takeoff time. This study s.rves as a motivation to improve the design of the reference airplane hull and a platform for detailed investigations in the future to improve modern amphibian design.

关键词： seaplane s.ray rails Hull Optimization Take-Off Performance

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