6061 aluminum alloy is characterized by good comprehensive using properties and thermal processing performance. Traditional numerical simulation of 6061 aluminum alloy's thermal deformation is mostly limited to ma...
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Background: One of the main directions of modern technology in the field of precision machining is high-speed operation. The spindle system is commonly utilized in this kind of operation, and the electric spindle is t...
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Background: One of the main directions of modern technology in the field of precision machining is high-speed operation. The spindle system is commonly utilized in this kind of operation, and the electric spindle is the main preference among high-speed machine tool spindles. Objective: High-speed electric spindle vibration characteristics affect the machining accuracy of the machine tool and the quality of the workpiece, so the research on high-speed electric spindle vibration characteristics has important engineering practical significance. Methods: The research status of high-speed electrospindle at home and abroad has been summarized in this paper. Combined with the patents related to the dynamics modelling of electrospindle, the research on the dynamics modelling of high-speed electrospindle is analyzed. On this basis, the computational and analytical methods for the vibration modelling of the electrospindle, including the transfer matrix method and the finite element method, are investigated, the theoretical foundations of these methods are discussed in depth, and the advantages and disadvantages of the methods are evaluated. The applicability and limitations of the two methods are also compared. Results: The analysis has shown that the current research on the vibration characteristics of high-speed electrospindle is mainly based on mechanical modal analysis and electromagnetic analysis. At present, the dynamic modeling of the electrospindle mainly includes bearing modeling, shaft bearing modeling, spindle-case modeling, electrospindle electromechanical coupling modeling, electrospindle thermal coupling modeling, etc. The correctness of the modelling theory is verified through experimental and simulation results. Although these models tend to be perfected, they are still insufficient in the case of multiple influencing factors coupling and need further development. Conclusion: Finally, through the analysis of the patent and dynamic characteristics related to th
Space manipulators play an important role in the on-orbit services and planetary surface *** the extreme environment of space,space manipulators are susceptible to a variety of unknown *** to have a resilient guarante...
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Space manipulators play an important role in the on-orbit services and planetary surface *** the extreme environment of space,space manipulators are susceptible to a variety of unknown *** to have a resilient guarantee in failure or disturbance is the core capability of its future *** with traditional motion planning,learning-based motion planning has gradually become a hot spot in current ***,no matter what kind of research ideas,the single robotic manipulator is studied as an independent agent,making it unable to provide sufficient flexibility under conditions such as external force disturbance,observation noise,and mechanical ***,this paper puts forward the idea of“discretization of the traditional single manipulator”.Different discretization forms are given through the analysis of the multi-degree-of-freedom single-manipulator joint relationship,and a single-manipulator representation composed of multiple new subagents is ***,to verify the ability of the new multiagent representation to deal with interference,we adopted a centralized multiagent reinforcement learning *** influence of the number of agents and communication distances on learning-based planning results is analyzed in *** addition,by imposing joint locking failures on the manipulator and introducing observation and action interference,it is verified that the“multiagent robotic manipulator”obtained after discretization has stronger antidisturbance resilient capability than the traditional single manipulator.
SLM technology has the advantages of high material utilization, a short processing cycle and a high degree of personalization. 316L stainless steel is widely used in many industrial fields for its excellent various pr...
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The main part of oil-immersed power equipment is oil-paper *** lower ambient temperatures,transformer oil will become *** a result,compared to those at room temperature or operating temperature,the frequency domain di...
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The main part of oil-immersed power equipment is oil-paper *** lower ambient temperatures,transformer oil will become *** a result,compared to those at room temperature or operating temperature,the frequency domain dielectric properties of oil-paper insulation at low temperatures are drastically *** evaluating the insulation condition of electrical equipment,it is essential to accurately determine their dielectric *** paper described the FDS test,the DC conductivity test,and the transformer oil viscosity test,which was carried out in a laboratory environment for different ageing of oil-immersed pressboard and transformer oil at 233–373 *** ef-fects of temperature on the dielectric properties at the competing mechanisms of polarisation and conductivity loss were clarified based on variations of the FDS *** the viscosity change of ageing transformer oil at low temperatures,the Arrhenius and VFT viscosity equations were used to achieve a fitting calculation in the different temperature *** on the molecular/ion transition model in the force field and electric field,the characterisation relationships between the dynamic viscosity,DC conductivity,and test temperature of transformer oil were *** limita-tions of conventional transformer oil equivalent dielectric relaxation models over a wide temperature range were finally clarified by combining the test findings of the DC con-ductivity over a wide temperature range with observed and simulated *** paper provides an essential theoretical reference when using the FDS test to diagnose the insulation performance of oil-immersed power equipment in extremely cold regions.
Phase decomposition can effectively enhance the mechanical properties of carbide ceramics and can overcome the difficulty of enhancing the mechanical properties of single-phase multicomponent carbide *** this work,a s...
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Phase decomposition can effectively enhance the mechanical properties of carbide ceramics and can overcome the difficulty of enhancing the mechanical properties of single-phase multicomponent carbide *** this work,a series of nonstoichiometric(TiZrVNb)Cx ceramics were prepared by spark plasma sintering(SPS)at different *** effects of the carbon content on the phase composition,microstructure evolution,and mechanical properties were investigated in *** decomposition occurred with decreasing carbon *** different solid solutions of(Ti,V)-rich and Zr-rich phases formed from the decomposition of equimolar single-phase solid solutions,namely,the Zr-poor phase and Zr-rich phase,*** distribution of Nb element is relatively *** semicoherent interfaces between the Zr-poor phase and the Zr-rich phase can harden and strengthen effectively under the synergistic effect of grain *** with phase decomposition structures have apparent advantages compared to single-phase high-entropy *** work provides an important train of thought for the microstructure tailoring and properties optimization of multi-component carbide ceramics.
Aiming at the problem of long time-consuming and low accuracy of existing age estimation approaches,a new age estimation method using Gabor feature fusion,and an improved atomic search algorithm for feature selection ...
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Aiming at the problem of long time-consuming and low accuracy of existing age estimation approaches,a new age estimation method using Gabor feature fusion,and an improved atomic search algorithm for feature selection is ***,texture features of five scales and eight directions in the face region are extracted by Gabor wavelet *** statistical histogram is introduced to encode and fuse the directional index with the largest feature value on Gabor ***,a new hybrid feature selection algorithm chaotic improved atom search optimisation with simulated annealing(CIASO-SA)is presented,which is based on an improved atomic search algorithm and the simulated annealing ***,the CIASO-SA algorithm introduces a chaos mechanism during atomic initialisation,significantly improving the convergence speed and accuracy of the ***,a support vector machine(SVM)is used to get classification results of the age *** verify the performance of the proposed algorithm,face images with three resolutions in the Adience dataset are *** the Gabor real part fusion feature at 48�48 resolution,the average accuracy and 1-off accuracy of age classification exhibit a maximum of 60.4%and 85.9%,*** results prove the superiority of the proposed algorithm over the state-of-the-art methods,which is of great referential value for application to the mobile terminals.
With the rapid development of high-speed mobile network technology and high-precision positioning technology,the trajectory information of mobile users has received extensive attention from academia and industry in th...
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With the rapid development of high-speed mobile network technology and high-precision positioning technology,the trajectory information of mobile users has received extensive attention from academia and industry in the field of Location-based Social *** can mine users’trajectories in Location-based Social Networks to obtain sensitive information,such as friendship groups,activity patterns,and consumption ***,mobile users’privacy and security issues have received growing attention in Location-based Social *** is crucial to strike a balance between privacy protection and data *** paper proposes a differential privacy trajectory protection method based on latent interest community detection(DPTP-LICD),ensuring strict privacy protection standards and user data ***,based on the historical trajectory information of users,spatiotemporal constraint information is extracted to construct a potential community strength model for mobile ***,the latent interest community obtained from the analysis is used to identify preferred hot spots on the user’s trajectory,and their priorities are assigned based on a popularity model.A reasonable privacy budget is allocated to prevent excessive noise from being added and rendering the protected trajectory data ***,to prevent privacy leakage,we add Laplace and exponential noise in generating preferred hot spots and recommending user interest *** and effectiveness analysis shows that our mechanism provides effective points of interest recommendations and protects users’privacy from disclosure.
Since first synthesized in 2011, MXenes have attracted extensive attention in many scientific fields as a new two-dimensional(2D) material because of the unique physical and chemical properties. Over the past decade, ...
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Since first synthesized in 2011, MXenes have attracted extensive attention in many scientific fields as a new two-dimensional(2D) material because of the unique physical and chemical properties. Over the past decade, in particular, MXenes have obtained numerous exciting achievements in the field of terahertz applications. In this review, we first briefly introduce the MXene materials, such as the basic structure and main fabrication processes of MXenes. Then, we summarize the recent applications of MXene materials in various terahertz research areas, including terahertz modulation, terahertz absorption, terahertz shielding, terahertz communication, terahertz detection and terahertz generation, in which the representative results are presented. Finally, we give an outlook on the future research directions of MXene materials and their potential applications.
With intelligent terminal devices’widespread adoption and global positioning systems’advancement,Location-based Social Networking Services(LbSNs)have gained considerable *** recommendation mechanism,which revolves a...
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With intelligent terminal devices’widespread adoption and global positioning systems’advancement,Location-based Social Networking Services(LbSNs)have gained considerable *** recommendation mechanism,which revolves around identifying similar users,holds significant importance in *** order to enhance user experience,LbSNs heavily rely on accurate *** mining and analyzing users who exhibit similar behavioral patterns to the target user,LbSNs can offer personalized services that cater to individual ***,trajectory data,a form encompassing various sensitive attributes,pose privacy *** disclosure of users’precise trajectory information can have severe consequences,potentially impacting their daily ***,this paper proposes the Similar User Discovery Method based on Semantic Privacy(SUDM-SP)for trajectory *** approach involves employing a model that generates noise trajectories,maximizing expected noise to preserve the privacy of the original *** users are then identified based on the published noise trajectory ***-SP consists of two key ***,a puppet noise location,exhibiting the highest semantic expectation with the original location,is generated to derive noisesuppressed trajectory ***,a mechanism based on semantic and geographical distance is employed to cluster highly similar users into communities,facilitating the discovery of noise trajectory similarity among *** trials conducted using real datasets,the effectiveness of SUDM-SP,as a recommendation service ensuring user privacy protection is substantiated.
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