期刊文献+
共找到1,084篇文章
< 1 2 55 >
每页显示 20 50 100
Research status and application of artificial intelligence large models in the oil and gas industry
1
作者 LIU He REN Yili +6 位作者 LI Xin DENG Yue WANG Yongtao CAO Qianwen DU Jinyang LIN Zhiwei WANG Wenjie 《Petroleum Exploration and Development》 SCIE 2024年第4期1049-1065,共17页
This article elucidates the concept of large model technology,summarizes the research status of large model technology both domestically and internationally,provides an overview of the application status of large mode... This article elucidates the concept of large model technology,summarizes the research status of large model technology both domestically and internationally,provides an overview of the application status of large models in vertical industries,outlines the challenges and issues confronted in applying large models in the oil and gas sector,and offers prospects for the application of large models in the oil and gas industry.The existing large models can be briefly divided into three categories:large language models,visual large models,and multimodal large models.The application of large models in the oil and gas industry is still in its infancy.Based on open-source large language models,some oil and gas enterprises have released large language model products using methods like fine-tuning and retrieval augmented generation.Scholars have attempted to develop scenario-specific models for oil and gas operations by using visual/multimodal foundation models.A few researchers have constructed pre-trained foundation models for seismic data processing and interpretation,as well as core analysis.The application of large models in the oil and gas industry faces challenges such as current data quantity and quality being difficult to support the training of large models,high research and development costs,and poor algorithm autonomy and control.The application of large models should be guided by the needs of oil and gas business,taking the application of large models as an opportunity to improve data lifecycle management,enhance data governance capabilities,promote the construction of computing power,strengthen the construction of“artificial intelligence+energy”composite teams,and boost the autonomy and control of large model technology. 展开更多
关键词 foundation model large language mode visual large model multimodal large model large model of oil and gas industry pre-training fine-tuning
下载PDF
High-Order DG Schemes with Subcell Limiting Strategies for Simulations of Shocks,Vortices and Sound Waves in Materials Science Problems
2
作者 Zhenhua Jiang Xi Deng +3 位作者 Xin Zhang Chao Yan Feng Xiao Jian Yu 《Fluid Dynamics & Materials Processing》 EI 2024年第10期2183-2204,共22页
Shock waves,characterized by abrupt changes in pressure,temperature,and density,play a significant role in various materials science processes involving fluids.These high-energy phenomena are utilized across multiple ... Shock waves,characterized by abrupt changes in pressure,temperature,and density,play a significant role in various materials science processes involving fluids.These high-energy phenomena are utilized across multiple fields and applications to achieve unique material properties and facilitate advanced manufacturing techniques.Accurate simulations of these phenomena require numerical schemes that can represent shock waves without spurious oscillations and simultaneously capture acoustic waves for a wide range of wavelength scales.This work suggests a high-order discontinuous Galerkin(DG)method with a finite volume(FV)subcell limiting strategies to achieve better subcell resolution and lower numerical diffusion properties.By switching to the FV discretization on an embedded sub-cell grid,the method displays advantages with respect to both DG accuracy and FV shock-capturing ability.The FV scheme utilizes a class of high-fidelity schemes that are built upon the boundary variation diminishing(BVD)reconstruction paradigm.The method is therefore able to resolve discontinuities and multi-scale structures on the subcell level,while preserving the favorable properties of the high-order DG scheme.We have tested the present DG method up to the 6th-order accuracy for both smooth and discontinuous noise problems. 展开更多
关键词 Discontinuous Galerkin finite volume subcell limiting shock associated noise computational aeroacoustics
下载PDF
Effect of leading-edge tubercles on the flow over low-aspect-ratio wings at low Reynolds number
3
作者 Pengxin Yang Yichen Zhu Jinjun Wang 《Theoretical & Applied Mechanics Letters》 CAS CSCD 2023年第1期41-49,共9页
Two-dimensional time-resolved particle image velocimetry(TR-PIV)and stereographic particle image velocimetry(SPIV)techniques were used to investigate the effect of leading-edge tubercles on the flow over low-aspect-ra... Two-dimensional time-resolved particle image velocimetry(TR-PIV)and stereographic particle image velocimetry(SPIV)techniques were used to investigate the effect of leading-edge tubercles on the flow over low-aspect-ratio wing models.The angle of attack is fixed at 10°,and the Reynolds number based on chord length is 5.8×10^(3).It is shown that the leading-edge tubercles can effectively mitigate flow separation in the model and also reduce the contribution of wake vortex to the fluctuating energy of flow.Counter-rotating vortex pairs(CVPs)initiated from the peak of leading-edge tubercles can promote nearby momentum exchange,enhance mixing of the flow and increase the energy contained in the boundary layer,which results in resisting the larger adverse pressure gradient.Therefore,it is concluded that CVPs play an important role in mitigating the flow separation for wings with leading-edge tubercles. 展开更多
关键词 Leading-edge tubercles Low-aspect-ratio Flow separation
下载PDF
A Blind Batch Encryption and Public Ledger-Based Protocol for Sharing Sensitive Data 被引量:1
4
作者 Zhiwei Wang Nianhua Yang +2 位作者 Qingqing Chen Wei Shen Zhiying Zhang 《China Communications》 SCIE CSCD 2024年第1期310-322,共13页
For the goals of security and privacy preservation,we propose a blind batch encryption-and public ledger-based data sharing protocol that allows the integrity of sensitive data to be audited by a public ledger and all... For the goals of security and privacy preservation,we propose a blind batch encryption-and public ledger-based data sharing protocol that allows the integrity of sensitive data to be audited by a public ledger and allows privacy information to be preserved.Data owners can tightly manage their data with efficient revocation and only grant one-time adaptive access for the fulfillment of the requester.We prove that our protocol is semanticallly secure,blind,and secure against oblivious requesters and malicious file keepers.We also provide security analysis in the context of four typical attacks. 展开更多
关键词 blind batch encryption data sharing onetime adaptive access public ledger security and privacy
下载PDF
Surface characteristics,corrosion behavior,and antibacterial property of Ag-implanted NiTi alloy 被引量:18
5
作者 Peng Luo Sheng-Nan Wang +1 位作者 Ting-Ting Zhao Yan Li 《Rare Metals》 SCIE EI CAS CSCD 2013年第2期113-121,共9页
NiTi shape memory alloy was modified by Ag ion implantation with different incident doses to improve its antibacterial property. The atomic force microscopy, auger electron spectroscopy, and X-ray photoelectron spectr... NiTi shape memory alloy was modified by Ag ion implantation with different incident doses to improve its antibacterial property. The atomic force microscopy, auger electron spectroscopy, and X-ray photoelectron spectroscopy show that the surface of NiTi alloy is covered by TiO2 nano-film with embedded pure Ag with a peak concentration of 5.0 at% at the incident dose of 1.5 x10^17 ions.cm-a, and Ni concentration is reduced in the super- ficial surface layer. The surface roughness reaches the maximum value nearly twice higher than the control sample at the incident dose of 1.5x10^17 ions.cm-2. The potentiodynamic anodic polarization curves show that the Ag-implanted NiTi samples possess higher self-corrosion potential (Ecorr) and lower self-corrosion current density (icor0 but lower breakdown potential (Ebr). Therefore, the corrosion resistance of the Ag-NiTi is comparable to, if not better than, the untreated NiTi. The antibacterial tests reveal that there is a distinct reduction of the germ numbers on the Ag-NiTi, which is due to the direct contact between Ag and germ, and enhanced by the leaching Ag ions. 展开更多
关键词 NITI AG Ion implantation CORROSIONRESISTANCE Antibacterial property
下载PDF
Investigation on the Thermal Conductivity of 3-Dimensional and 4-Directional Braided Composites 被引量:24
6
作者 Liu Zhenguo Zhang Haiguo Lu Zixing Li Diansen 《Chinese Journal of Aeronautics》 SCIE EI CAS CSCD 2007年第4期327-331,共5页
It is vital to choose a factual and reasonable micro-structural model of braided composites for improving the calculating precision of thermal property of 3-D braided composites by finite element method (FEM). On th... It is vital to choose a factual and reasonable micro-structural model of braided composites for improving the calculating precision of thermal property of 3-D braided composites by finite element method (FEM). On the basis of new microstructure model of braided composites proposed recently, the model of FEM calculation for thermal conductivity of 3-dimennsional and 4-directional braided composites is set up in this paper. The curves of coefficient of effective thermal conductivity versus fiber volume ratio and interior braiding angle are obtained. Furthermore, comparing the results of FEM with the available experimental data, the reasonability and veracity of calculation are confirmed at the same time. 展开更多
关键词 3-dimennsional and 4-directional braided composites thermal conductivity FEM
下载PDF
FEM Analysis of Spring-backs in Age Forming of Aluminum Alloy Plates 被引量:23
7
作者 Huang Lin Wan Min +1 位作者 Chi Cailou Ji Xiusheng 《Chinese Journal of Aeronautics》 SCIE EI CAS CSCD 2007年第6期564-569,共6页
The age forming technology, characterized by huge spring-backs, has been developed to manufacture large integral wing-skin panel parts, which necessitates devising a method of predicting spring-backs. A 7B04-T7451 alu... The age forming technology, characterized by huge spring-backs, has been developed to manufacture large integral wing-skin panel parts, which necessitates devising a method of predicting spring-backs. A 7B04-T7451 aluminum alloy creep test in tension is accomplished at 155 ℃, and the creep curves are obtained. The material constants of the mechanism-based creep constitutive equations are determined through experiments. The age forming process and the spring-backs of 7B04 aluminum alloy plates are analyzed using the commercial finite element software ABAQUS. The effects of plate thickness and forming time on spring-backs are researched. The spring-backs decrease with the increase of plate thickness and forming time. The test results verify the reliability of the finite element method (FEM) analysis. 展开更多
关键词 aluminum alloy age forming constitutive equation FEM SPRING-BACK
下载PDF
Thermal-hydraulic Modeling and Simulation of Piston Pump 被引量:20
8
作者 李成功 焦宗夏 《Chinese Journal of Aeronautics》 SCIE EI CAS CSCD 2006年第4期354-358,共5页
This paper presents a kind of modeling approach to the study of the thermal-hydraulic piston pump which is used in the airplane comprehensively. A set of lumped parameter mathematical models are developed which are ba... This paper presents a kind of modeling approach to the study of the thermal-hydraulic piston pump which is used in the airplane comprehensively. A set of lumped parameter mathematical models are developed which are based on conservation of energy. Heat transfer analysis for the piston pump is also given in the paper in which the heat flow inside the piston pump is described precisely. The theoretical basis and modeling stratagy are applied in a typical thermal-hydraulic circuit containing the piston pump. Simulation results are presented which show a comparison of model/rig performance and the agreement obtained demonstrates the validity of the modeling approach. 展开更多
关键词 THERMAL-HYDRAULIC piston pump TEMPERATURE MODELLING
下载PDF
INFLUENCE OF NOSE PERTURBATIONS ON BEHAVIORS OF ASYMMETRIC VORTICES OVER SLENDER BODY 被引量:22
9
作者 陈学锐 邓学鉴 +2 位作者 王延奎 刘沛清 顾志福 《Acta Mechanica Sinica》 SCIE EI CAS CSCD 2002年第6期581-593,共13页
The influence of nose perturbations on the behaviors of asymmetric vortices over a slender body with a three-caliber ogive nose is studied in this paper. The tests of a nose-disturbed slender body with surface pressur... The influence of nose perturbations on the behaviors of asymmetric vortices over a slender body with a three-caliber ogive nose is studied in this paper. The tests of a nose-disturbed slender body with surface pressure measurement were conducted at a low speed wind tunnel with subcritical Reynolds number of 1×105 at angle of attack α=50°. The experiment results show that the behaviors and structure of asymmetric vortices over the slender body are mainly controlled by manual perturbation on the nose of body as compared with geometrical minute irregularities on the test model from the machining tolerances. The effect of the perturbation axial location on asymmetric vortices is the strongest if its location is near the model apex. There are four sensitive circumferential locations of manual perturbation at which bistable vortices over the slender body are switched by the perturbation. The flowfield near the reattachment line of lee side is more sensitive to the perturbation, because the saddle point to saddle point topological structure in this reattachment flowfield is unstable. Various types of perturbation do not change the perturbation effect on the behaviors of bistable asymmetric vortices. 展开更多
关键词 asymmetric vortex slender body of revolution bistable flow high angle of attack aerodynamics
下载PDF
ASYMMETRIC VORTICES FLOW OVER SLENDER BODY AND ITS ACTIVE CONTROL AT HIGH ANGLE OF ATTACK 被引量:16
10
作者 邓学蓥 王延奎 《Acta Mechanica Sinica》 SCIE EI CAS CSCD 2004年第6期567-579,共13页
The studies of asymmetric vortices flow over slender body and its active control at high angles of attack have significant importance for both academic field and engineering area.This paper attempts to provide an upda... The studies of asymmetric vortices flow over slender body and its active control at high angles of attack have significant importance for both academic field and engineering area.This paper attempts to provide an update state of art to the investigations on the fields of forebody asymmetric vortices.This review emphasizes the correlation between micro-perturbation on the model nose and its response and evolution behaviors of the asymmetric vortices.The critical issues are discussed, which include the formation and evolution mechanism of asymmetric multi-vortices;main behaviors of asymmetric vortices flow including its deterministic feature and vortices flow structure;the evolution and development of asymmetric vortices under the perturbation on the model nose;forebody vortex active control especially discussed micro-perturbation active control concept and technique in more detail.However present understanding in this area is still very limited and this paper tries to identify the key unknown problems in the concluding remarks. 展开更多
关键词 asymmetric vortex flow control high angle of attack aerodynamics slender body
下载PDF
Elastic Buckling of Bionic Cylindrical Shells Based on Bamboo 被引量:22
11
作者 Jian-feng Ma Wu-yi Chen +1 位作者 Ling Zhao Da-hai Zhao 《Journal of Bionic Engineering》 SCIE EI CSCD 2008年第3期231-238,共8页
High load-bearing efficiency is one of the advantages of biological structures after the evolution of billions of years. Biomimicking from nature may offer the potential for lightweight design. In the viewpoint ofrnec... High load-bearing efficiency is one of the advantages of biological structures after the evolution of billions of years. Biomimicking from nature may offer the potential for lightweight design. In the viewpoint ofrnechanics properties, the culm of bamboo comprises of two types of cells and the number of the vascular bundles takes a gradient of distribution. A three-point bending test was carried out to measure the elastic modulus. Results show that the elastic modulus of bamboo decreases gradually from the periphery towards the centre. Based on the structural characteristics of bamboo, a bionic cylindrical structure was designed to mimic the gradient distribution of vascular bundles and parenchyma cells. The buckling resistance of the bionic structure was compared with that of a traditional shell of equal mass under axial pressure by finite element simulations. Results show that the load-bearing capacity of bionic shell is increased by 124.8%. The buckling mode of bionic structure is global buckling while that of the conventional shell is local buckling. 展开更多
关键词 bionic design bamboo culm thin-walled cylindrical structure BUCKLING load-carrying efficiency
下载PDF
Extremum response surface method of reliability analysis on two-link flexible robot manipulator 被引量:19
12
作者 ZHANG Chun-yi BAI Guang-chen 《Journal of Central South University》 SCIE EI CAS 2012年第1期101-107,共7页
In order to present a new method for analyzing the reliability of a two-link flexible robot manipulator,Lagrange dynamics differential equations of the two-link flexible robot manipulator were established by using the... In order to present a new method for analyzing the reliability of a two-link flexible robot manipulator,Lagrange dynamics differential equations of the two-link flexible robot manipulator were established by using the integrated modal method and the multi-body system dynamics method.By using the Monte Carlo method,the random sample values of the dynamic parameters were obtained and Lagrange dynamics differential equations were solved for each random sample value which revealed their displacement,speed and acceleration.On this basis,dynamic stresses and deformations were obtained.By taking the maximum values of the stresses and the deformations as output responses and the random sample values of dynamic parameters as input quantities,extremum response surface functions were established.A number of random samples were then obtained by using the Monte Carlo method and then the reliability was analyzed by using the extremum response surface method.The results show that the extremum response surface method is an efficient and fast reliability analysis method with high-accuracy for the two-link flexible robot manipulator. 展开更多
关键词 RELIABILITY Monte Carlo method extremum response surface function flexible manipulator dynamic strength dynamicstiffness
下载PDF
Study on the Machining Distortion of Thin-walled Part Caused by Redistribution of Residual Stress 被引量:15
13
作者 王兆峻 陈五一 +2 位作者 张以都 陈志同 刘强 《Chinese Journal of Aeronautics》 SCIE EI CAS CSCD 2005年第2期175-179,共5页
In order to reduce the weight of airplane and increase its mechanical behaviors, more and more large integrated parts are applied in modern aviation industry. When machining thin-walled aeroplane parts, more than 90% ... In order to reduce the weight of airplane and increase its mechanical behaviors, more and more large integrated parts are applied in modern aviation industry. When machining thin-walled aeroplane parts, more than 90% of the materials would be removed, resulting in severe distortion of the parts due to the weakened rigidity and the release of residual stress. This might also lead to stress concentration and damage of the parts. The effect of material removal from residually stressed billet is simulated using FEA software MSC. Marc and the causations of distortion is analyzed. To verify the finite element simulation, a high speed milling test on aluminum alloy 7050T7351 is carried out. The results show that the simulation result is consistent with the experimental one. It is concluded that the release of residual stress is the main cause of machining distortion. 展开更多
关键词 finite element method SIMULATION residual stress machining distortion
下载PDF
Effect of Cr on Microstructure and Fracture Toughness of Nb-20Ti-16Si-xCr Alloys 被引量:11
14
作者 Tang Liang Ma Chaoli Zhao Xinqing 《稀有金属材料与工程》 SCIE EI CAS CSCD 北大核心 2009年第A03期8-12,共5页
The present paper reported the phase stability and microstructures evolution of Nb-20Ti-16Si-xCr (x = 0~20at.%) in-situ composites as function of Cr addition. It was suggested that with the addition of Cr less than 7... The present paper reported the phase stability and microstructures evolution of Nb-20Ti-16Si-xCr (x = 0~20at.%) in-situ composites as function of Cr addition. It was suggested that with the addition of Cr less than 7%, the silicide phase in as-cast Nb-20Ti-16Si alloy was Nb3Si. The silicides changed to be α-Nb5Si3 by the addition of Cr above 7%. It was found that annealing of 1300 ℃ for 100 h could result in the decomposition of Nb3Si to NbSS and α-Nb5Si3 in Cr containing Nb-20Ti-16Si based alloys by means of eutectoid reaction. Whereas in the case of alloy without Cr addition, the Nb3Si in Nb-20Ti-16Si alloy keep good stability during the high temperature annealing. The Cr additions larger than 5% in Nb-20Ti-16Si-xCr alloys could result in the formation of Cr-rich Laves phase. In addition, the influence of Cr addition on the room temperature fracture toughness of the alloys after annealing was reported. 展开更多
关键词 微观结构 硅化物 韧性 合金
下载PDF
Extraction Phase Simulation of Cargo Airdrop System 被引量:16
15
作者 柯鹏 杨春信 杨雪松 《Chinese Journal of Aeronautics》 SCIE EI CAS CSCD 2006年第4期315-321,共7页
To study the characteristics of cargo extraction, the initial phase of airdrop process, a high fidelity and extendibility simulation model with uniform motion equations for all states during extraction is developed on... To study the characteristics of cargo extraction, the initial phase of airdrop process, a high fidelity and extendibility simulation model with uniform motion equations for all states during extraction is developed on the basis of dynamics methods and contact models between cargo and aircraft. Simulation results agree well with tests data. Cargo exit parameters, which contribute to cargo pitch after extraction, are studied. Simplified computation model of dimensionless exit time is developed and used to evaluate the relation between extraction phase and landing accuracy. Safe interval model is introduced to evaluate the safety of extraction process. Also, relations between initial parameters, including pull coefficient, aircraft pitch and CG coefficient, etc, and result parameters, including exit time, cargo safety, pitch, etc, are developed to help design of airdrop system, especially the selection of extraction parachute and cargo deployment. 展开更多
关键词 cargo airdrop system cargo extraction dimensionless exit time safety analysis
下载PDF
AERODYNAMIC FORCE AND FLOW STRUCTURES OF TWO AIRFOILS IN FLAPPING MOTIONS 被引量:13
16
作者 兰世隆 孙茂 《Acta Mechanica Sinica》 SCIE EI CAS CSCD 2001年第4期310-331,共22页
Aerodynamic force and flow structures of two airfoils in a tandem configuration in flapping motions axe studied, by solving the Navier-Stokes equations in moving overset grids. Three typical phase differences between ... Aerodynamic force and flow structures of two airfoils in a tandem configuration in flapping motions axe studied, by solving the Navier-Stokes equations in moving overset grids. Three typical phase differences between the fore- and aft-airfoil flapping cycles are considered. It is shown that: (1) in the case of no interaction (single airfoil), the time average of the vertical force coefficient over the downstroke is 2.74, which is about 3 times as large as the maximum steady-state lift coefficient of a dragonfly wing; the time average of the horizontal force coefficient is 1.97, which is also large. The reasons for the large force coefficients are the acceleration at the beginning of a stroke, the delayed stall and the 'pitching-up' motion near the end of the stroke. (2) In the cases of two-airfoils, the time-variations of the force and moment coefficients on each airfoil are broadly similar to that of the single airfoil in that the vertical force is mainly produced in downstroke and the horizontal force in upstroke, but very large differences exist due to the interaction. (3) For in-phase stroking, the major differences caused by the interaction are that the vertical force on FA in downstroke is increased and the horizontal force on FA in upstroke decreased. As a result, the magnitude of the resultant force is almost unchanged but it inclines less forward. (4) For counter stroking, the major differences are that the vertical force on AA in downstroke and the horizontal force on FA in upstroke are decreased. As a result, the magnitude of the resultant force is decreased by about 20 percent but its direction is almost unchanged. (5) For 90 degrees -phase-difference stroking, the major differences axe that the vertical force on AA in downstroke and the horizontal force on FA in upstroke axe decreased greatly and the horizontal force on AA in upstroke increased. As a result, the magnitude of the resultant force is decreased by about 28% and it inclines more forward. (6) Among the three cases of phase angles, inphase flapping produces the largest vertical force (also the largest resultant force); the 90 degrees -phase-difference flapping results in the largest horizontal force, but the smallest resultant force. 展开更多
关键词 dragonfly flight two airfoils flapping motion Navier-Stokes simulation
下载PDF
Corrosion Inhibition Mechanism of Rare Earth Metal on LC4 Al Alloy with Spilt Cell Technique 被引量:12
17
作者 顾宝珊 刘建华 《Journal of Rare Earths》 SCIE EI CAS CSCD 2006年第1期89-96,共8页
A new method of studying the corrosion inhibition mechanism of rare earth metal(REM) on LC4 Al alloy with the spilt cell technique was studied. The principle and experimental method of the spilt cell technique were ... A new method of studying the corrosion inhibition mechanism of rare earth metal(REM) on LC4 Al alloy with the spilt cell technique was studied. The principle and experimental method of the spilt cell technique were analyzed. By measuring the change of net-electric current between the two electrodes caused by the change of the amount of oxygen in the solution and the addition of CeCl3, the influence of corrosive performance of CeCl3 on LC4 super-power aluminum "alloy in the 0.1 mol· L^-1 NaCl solution was investigated. Meanwhile, the conditional changes of pH values, CeCl3 solution, additire and time of performance were also studied. Finally, the features of electrode surface were revealed by using SEM and X-ray energy-dispersive spectrometry (EDS). By combining these with other electric chemical techniques, such as potential-time curve, polarization curve et al. 展开更多
关键词 spilt cell technique cerium conversion coatings inhibition mechanism aluminum alloys rare earths
下载PDF
Flight Loads and Dynamics of Flexible Air Vehicles 被引量:11
18
作者 吴志刚 杨超 《Chinese Journal of Aeronautics》 SCIE EI CAS CSCD 2004年第1期17-22,共6页
Based on the equations of motion of flexible air vehicles includingrigid-body modes and elastic structural modes, and applying influence coefficients of linearaerodynamics, a set of equations are derived and a method ... Based on the equations of motion of flexible air vehicles includingrigid-body modes and elastic structural modes, and applying influence coefficients of linearaerodynamics, a set of equations are derived and a method is presented for analysis of flight loadsand dynamic characteristics. The problems in the fields of flight mechanics and aeroelasticity suchas static aeroelastic divergence, trim and deformation, aerodynamic loads distribution, flutter andflight dynamics can be solved by the procedure. An airplane with high aspect ratio wings isanalyzed, and the results show that the coupling between rigid -body modes and elastic modes isdistinct and should not be overlooked. 展开更多
关键词 flexible air vehicle aeroelasticity flight dynamics flight load
下载PDF
Grey Relation between Nonlinear Characteristic and Dynamic Uncertainty of Rolling Bearing Friction Torque 被引量:13
19
作者 XIA Xintao WANG Zhongyu 《Chinese Journal of Mechanical Engineering》 SCIE EI CAS CSCD 2009年第2期244-249,共6页
The rolling bearing friction torque which is characterized by its uncertainty and nonlinearity affects heavily the dynamic performance of a system such as missiles, spacecrafts and radars, etc. It is difficult to use ... The rolling bearing friction torque which is characterized by its uncertainty and nonlinearity affects heavily the dynamic performance of a system such as missiles, spacecrafts and radars, etc. It is difficult to use the classical statistical theory to evaluate the dynamic evaluation of the rolling bearing friction torque for the lack of prior information about both probability distribution and trends. For this reason, based on the information poor system theory and combined with the correlation dimension in chaos theory, the concepts about the mean of the dynamic fluctuant range (MDFR) and the grey relation are proposed to resolve the problem about evaluating the nonlinear characteristic and the dynamic uncertainty of the rolling bearing friction torque. Friction torque experiments are done for three types of the rolling bearings marked with HKTA, HKTB and HKTC separately; meantime, the correlation dimension and MDFR are calculated to describe the nonlinear characteristic and the dynamic uncertainty of the friction torque, respectively. And the experiments reveal that there is a certain grey relation between the nonlinear characteristic and the dynamic uncertainty of the rolling bearing friction torque, viz. MDFR will become the nonlinear increasing trend with the correlation dimension increasing. Under the condition of fewer characteristic data and the lack of prior information about both probability distribution and trends, the unitive evaluation for the nonlinear characteristic and the dynamic uncertainty of the rolling bearing friction torque is realized with the grey confidence level of 87.7%-96.3%. 展开更多
关键词 rolling bearing friction torque time series correlation dimension mean of dynamic fluctuant range (MDFR) information poor system theory
下载PDF
Aerodynamic Effects of Corrugation in Flapping Insect Wings in Forward Flight 被引量:11
20
作者 Xueguang Meng Mao Sun 《Journal of Bionic Engineering》 SCIE EI CSCD 2011年第2期140-150,共11页
We have examined the aerodynamic effects of corrugation in model wings that closely mimic the wing movements of a forward flight bumblebee using the method of computational fluid dynamics. Various corrugated wing mode... We have examined the aerodynamic effects of corrugation in model wings that closely mimic the wing movements of a forward flight bumblebee using the method of computational fluid dynamics. Various corrugated wing models were tested (care was taken to ensure that the corrugation introduced zero camber). Advance ratio ranging from 0 to 0.57 was considered. The results shown that at all flight speeds considered, the time courses of aerodynamic force of the corrugated wing are very close to those of the flat-plate wing. The cornlgation decreases aerodynamic force slightly. The changes in the mean location of center of pressure in the spanwise and chordwise directions resulting from the corrugation are no more than 3% of the wing chord length. The possible reason for the small aerodynamic effects of wing corrugation is that the wing operates at a large angle of attack and the flow is separated: the large angle of incidence dominates the corrugation in determining the flow around the wing, and for separated flow, the flow is much less sensitive to wing shape variation. 展开更多
关键词 INSECT FLAPPING forward flight wing corrugation AERODYNAMICS
下载PDF
上一页 1 2 55 下一页 到第
使用帮助 返回顶部