期刊文献+
共找到968篇文章
< 1 2 49 >
每页显示 20 50 100
Numerical Prediction of Vortex-Induced Vibrations on Top Tensioned Riser in Consideration of Internal Flow 被引量:15
1
作者 郭海燕 李效民 刘晓春 《China Ocean Engineering》 SCIE EI 2008年第4期675-682,共8页
In consideration of the effect of the internal flowing fluid and the external marine environmental condition on the vortex-induced vibration (VIV) of top tensioned riser (Till), the differential equation is derive... In consideration of the effect of the internal flowing fluid and the external marine environmental condition on the vortex-induced vibration (VIV) of top tensioned riser (Till), the differential equation is derived based on work-energy principles and the riser near wake dynamics is modeled by Facchinetti' s wake oscillator model. Then Galerkin' s finite element approximation is implemented to derive the nonlinear matrix equation of the coupled equations and file corresponding numerical programs are compiled which solve the coupled equations directly in the time domain. The comparison of the predicted results with the recent experimental results and the prediction of SHEAR7 is performed. The results show the validity of the proposed method on the prediction of VIV of deep water risers. The effect of internal flow on the dynamic characteristics and dynmnic response of the riser is analyzed and several valuable conelusions are drawn. 展开更多
关键词 top tensioned riser TTR) internal flow vortex-induced vibration V/V) dynamic characteristics dynamic response
下载PDF
Stress Analysis of Top Tensioned Riser Under Random Waves and Vessel Motions 被引量:11
2
作者 LI Xiaomin GUO Haiyan MENG Fanshun 《Journal of Ocean University of China》 SCIE CAS 2010年第3期251-256,共6页
The bending stresses of top tensioned riser(TTR) under combined excitations of currents,random waves and vessel motions are presented in this paper,and the effect of the internal flowing fluid on the riser stresses is... The bending stresses of top tensioned riser(TTR) under combined excitations of currents,random waves and vessel motions are presented in this paper,and the effect of the internal flowing fluid on the riser stresses is also considered.The computation programs which are used to solve the differential equations in the time domain are compiled and the principal factors of concern including the angular movements at the upper and lower ends of the riser,lateral displacements and bending stresses are presented.Then the effects of current velocity,random wave,top tension,vessel mean offset,low frequency motion and internal flow velocity on the bending stresses of the riser are analyzed in detail. 展开更多
关键词 top tensioned riser (TTR) internal flow vessel motion dynamic response
下载PDF
Fatigue Life Assessment of Top Tensioned Risers Under Vortex-Induced Vibrations 被引量:11
3
作者 LI Xiaomin GUO Haiyan MENG Fanshun 《Journal of Ocean University of China》 SCIE CAS 2010年第1期43-47,共5页
The fatigue life of top tensioned risers under vortex-induced vibrations (VIVs) with consideration of the effect of internal flowing fluid on the riser is analyzed in the time domain.The long-term stress histories of ... The fatigue life of top tensioned risers under vortex-induced vibrations (VIVs) with consideration of the effect of internal flowing fluid on the riser is analyzed in the time domain.The long-term stress histories of the riser under VIVs are calculated and the mean stresses,the number of stress cycles and amplitudes are determined by the rainflow counting method.The Palmgren-Miner rule for cumulative damage theory with a specified S-N curve is used to estimate the fatigue life of the riser.The corresponding numerical programs numerical simulation of vortex-induced vibrations (NSVIV) which can be used to calculate the VIV response and fatigue life of the riser are compiled.Finally the influences of the riser's parameters such as flexural rigidity,top tension and internal flow velocity on the fatigue life of the riser are analyzed in detail and some conclusions are drawn. 展开更多
关键词 top tensioned riser (TTR) internal flow vortex-induced vibration (VIV) fatigue life
下载PDF
Nonlinear Coupled in-Line and Cross-Flow Vortex-Induced Vibration Analysis of Top Tensioned Riser 被引量:4
4
作者 李效民 郭海燕 孟凡顺 《China Ocean Engineering》 SCIE EI 2010年第4期749-758,共10页
The fluctuating furces of the fluid exerted on the top terrsioned riser ('FIR) in the in-line and cross-flow directions are both modeled by van del Pol wake oscillator model and the nonlinear coupled dynamics of th... The fluctuating furces of the fluid exerted on the top terrsioned riser ('FIR) in the in-line and cross-flow directions are both modeled by van del Pol wake oscillator model and the nonlinear coupled dynamics of the in-line and cross-flow vortex-induced vibrations (VIV) of the riser are analyzed in time domain in this papar. The numencal shnulation results of the riser's in-line and cross-flow displacements and curvatures are compared with experimental measurements and the comparison shows the validity of this method in modeling some main features of the riser's VIV. Finally, the effects of the riser's top tensions and internal flow velocities on the coupled vibrations of the riser are investigated. 展开更多
关键词 top tensioned riser (TFR) vortex-induced vibration (VIV) wake oscillator model in-line and cross-flowvibration
下载PDF
Design and Analysis of Tapered Stress Joint for Top Tensioned Riser System 被引量:2
5
作者 张日曦 张崎 黄一 《China Ocean Engineering》 SCIE EI 2012年第3期507-520,共14页
Stress Joint (SJ) plays a key role in the Top Tensioned Riser (TTR) system for deep water engineering. A preliminary design method of tapered SJ is proposed in the paper, which could help designers obtain accurate... Stress Joint (SJ) plays a key role in the Top Tensioned Riser (TTR) system for deep water engineering. A preliminary design method of tapered SJ is proposed in the paper, which could help designers obtain accurate design data. After a further sensitive analysis is carried out, the related parameters choice and control methods are recommended in the engineering practice. By taking the extreme environment conditions into consideration, the effects of bending stress reduction and curve control are analyzed, and the 3-D FE models are established by ABQOUS for numerical evaluation to verify the correctness of design results. At last, dynamic analysis and fatigue analysis, based on actual project, are carried out with designed stress joint. The analysis results prove the feasibility and guidance of this method in the practical engineering applications. 展开更多
关键词 stress joint (S J) top tensioned riser (TTR) design method parameters sensitivities dynamic analysis fatigue analysis
下载PDF
ANCHORING EFFECT ANALYSIS OF TENSIONED BOLTS
6
作者 夏建中 《Journal of Coal Science & Engineering(China)》 1997年第1期1-4,共4页
The paper analyses quantitatively the anchoring effect of tensioned bolts on surrounding rock strength, and defines two concepts: one is the surrounding rock strength increased amount Δτ13 and the other is the stren... The paper analyses quantitatively the anchoring effect of tensioned bolts on surrounding rock strength, and defines two concepts: one is the surrounding rock strength increased amount Δτ13 and the other is the strength influence factor k. The anchoring effect of tensioned bolts is considered to increase a strength increased amount Δτ13 where Δτ13 is the product k and ten-sioned load p, i. e. Δτ13 = kp, where k is a function of two variables x and y. The distribu-tive properties both Δτ13 and k are also discussed in the paper, obtaining some useful results for designing bolting support parameters. 展开更多
关键词 tensioned bolt strength increased amount strength influence factor anchoring effect
下载PDF
Thermal instability and dynamic response analysis of a tensioned carbon nanotube under moving uniformly distributed external pressure
7
作者 A.A.Yinusa M.G.Sobamowo 《Nano Materials Science》 CAS CSCD 2021年第1期75-88,共14页
Single-walled carbon nanotubes(SWCNTs)are receiving immense research attention due to their tremendous thermal,electrical,structural and mechanical properties.In this paper,an exact solution of the dynamic response of... Single-walled carbon nanotubes(SWCNTs)are receiving immense research attention due to their tremendous thermal,electrical,structural and mechanical properties.In this paper,an exact solution of the dynamic response of SWCNT with a moving uniformly distributed load is presented.The SWCNT is modelled via the theories of Bernoulli-Euler-thermal elasticity mechanics and solved using Integral transforms.The developed closed-form solution in the present work is compared with existing results and excellent agreements are established.The parametric studies show that as the magnitude of the pressure distribution at the surface increases,the deflection associated with the single walled nanotube increases at any mode whilst a corresponding increase in temperature and foundation parameter have an attenuating effect on deflection.Moreover,an increase in the Winkler parameter,as well as a decrease in the SWCNT mass increases its frequency of vibration.Furthermore,an increase in the speed of the external agent decreases the total external pressure as a result of the removal of dead loads.The present work is envisaged to improve the application of SWCNT as nanodevices for structural,electrical and mechanical systems. 展开更多
关键词 Thermal and moving external uniform pressure tensioned carbon nanotube Dynamic and stability analysis Integral transform
下载PDF
NUMERICAL SIMULATION ANALYSES ON REINFORCEMENT FUNCTION OF THE TENSIONED AND GROUTED BOLTS
8
作者 邹喜正 李华祥 《Journal of Coal Science & Engineering(China)》 1998年第2期29-33,共5页
The purpose of the paper is to calculate the equivalent mechanics parameters of reinforced surroundings, which is based on the assume that the reinforcement of bolts is equivalent to the improvement of mechanics param... The purpose of the paper is to calculate the equivalent mechanics parameters of reinforced surroundings, which is based on the assume that the reinforcement of bolts is equivalent to the improvement of mechanics parameters of surroundings and combines with site engineering practice. Use numerical simulation analysis to study the reinforcement mechanism of full length bolts, thus to provide theoretical bases for bolting design. 展开更多
关键词 numerical simulation analysis tensioned and grouted bolt mechanic parameters
下载PDF
Tensegrities and Tensioned Structures
9
作者 MªDolores Alvarez Elipe 《Journal of Architectural Environment & Structural Engineering Research》 2020年第3期10-16,共7页
“Push-and-pull”efficient structures have been inconceivable between XVIII centuries.It is because of the incapacity of obtain an efficient behaviour of tensioned material.Since XVIII centuries,architecture developed... “Push-and-pull”efficient structures have been inconceivable between XVIII centuries.It is because of the incapacity of obtain an efficient behaviour of tensioned material.Since XVIII centuries,architecture developed some structural knowledge generating novel structural forms in the architecture and engineering that were not known before.Tensegrities and tensioned structures were studied due to the knowledge of geometry and tension.Some investigations about tensegrities and tensioned structures have been developed since that moment.Tensegrities are bar and cable structures that work only in compression or tension efforts.Bars and cables are balanced,but in appearance the growth is disorderly.Most of deployable structures are based on tensegrity systems.The research is focused in presenting a summary of tensegrities and tensioned architectures that have been used in the structural design of novel patterns.The research of adequate materials to tension efforts will be crucial in this study.The investigation presents an important state of the art that provides technical solutions to apply on novel architectures based on tensegrities and tensioned structures.The research is useful to produce the current constructive solutions based on these constructive systems. 展开更多
关键词 TENSEGRITY tensioned GEOMETRY STRUCTURE Compression Tension EFFORT
下载PDF
Tensioned Metastable Fluid Detectors in Nuclear Security for Active Interrogation of Special Nuclear Materials―Part B
10
作者 Jeffrey A. Webster Rusi P. Taleyarkhan 《World Journal of Nuclear Science and Technology》 2011年第3期66-76,共11页
This paper (constituting Part B) addresses active interrogation for detecting Special Nuclear Materials (SN- Ms) and includes description of the transformational Tensioned Metastable Fluid Detector (TMFD) based method... This paper (constituting Part B) addresses active interrogation for detecting Special Nuclear Materials (SN- Ms) and includes description of the transformational Tensioned Metastable Fluid Detector (TMFD) based method for optimal monitoring. One of the greatest difficulties in detection of SNMs by active interrogation is the task of distinguishing between the probing particles and the secondary particles that indicate the presence of SNMs. The TMFD’s selective insensitivity and γ photon blindness features are advantageous for alleviating this problem. The working principle of the TMFD is discussed along with its applications for security. The experimental work to date involving detection of small quantities of uranium with conventional detectors is discussed along with results of fission neutron detection. Statistically significant detection was achieved within 5 minutes of counting to ascertain and measure conclusive evidence for the presence of a 55g sample of uranium containing 235U. Results of simulations of three active detection techniques utilizing a TMFD system are presented. The process for using the TMFD to discriminate active source particles using timing and energy are described. These simulations indicate that it should be possible to utilize the TMFD system for optimal neutron-based interrogation of SNMs. 展开更多
关键词 tensioned METASTABLE FLUID DETECTOR ACTIVE INTERROGATION TMFD SNM Detection
下载PDF
Approach to Determine Corrosion Propensity in Post-Tensioned Tendons with Deficient Grout
11
作者 Juan Carlos Rafols Kingsley Lau +2 位作者 Ivan Lasa Mario Paredes Adel ElSafty 《Open Journal of Civil Engineering》 2013年第3期182-187,共6页
After corrosion failure of post-tensioned tendons was identified in a Florida bridge in early 2011, laboratory tests were conducted in this study on extracted sections from the failed tendons to identify the grout pro... After corrosion failure of post-tensioned tendons was identified in a Florida bridge in early 2011, laboratory tests were conducted in this study on extracted sections from the failed tendons to identify the grout properties and makeup leading to the failure and also to elucidate the mechanism of corrosion. The initial steps in identification of PT tendons with a high propensity for corrosion initiation or damaged included a detailed visual inspection and identification of voids in the grout. Voids in tendon can be a result of bleed water formation or construction problems. General characteristics of the deficient grout and corrosion behavior of steel in the affected bridge gave a first approach to assessing grout deficiency and corrosion susceptibility. However, refinements in the understanding of the mechanisms causing grout segregation and the elucidation of the role of sulfates, oxygen content, and pore water pH in corrosion development are required. 展开更多
关键词 Post tensioned GROUT Dissimilar TENDON CORROSION
下载PDF
Effects of tension on vortex-induced vibration(ⅥⅤ) responses of a long tensioned cylinder in uniform flows 被引量:2
12
作者 Ling Kang Fei Ge +1 位作者 Xiaodong Wu Youshi Hong 《Acta Mechanica Sinica》 SCIE EI CAS CSCD 2017年第1期1-9,共9页
The effects of tension on vortex-induced vibration (VIV) responses for a tension-dominated long cylinder with an aspect ratio of 550 in uniform flows are experimentally investigated in this paper. The results show tha... The effects of tension on vortex-induced vibration (VIV) responses for a tension-dominated long cylinder with an aspect ratio of 550 in uniform flows are experimentally investigated in this paper. The results show that elevated tension suppresses fluctuations of maximum displacement with respect to flow velocity and makes chaotic VIV more likely to appear. With respect to periodic VIV, if elevated tension is applied, the dominant vibration frequency in the in-line (IL) direction will switch from a fundamental vibration frequency to twice the value of the fundamental vibration frequency, which results in a ratio of the dominant vibration frequency in the IL direction to that in the cross-flow direction of 2.0. The suppression of the elevated tension in the fluctuation of the maximum displacement causes the axial tension to become an active control parameter for the VIV maximum displacement of a tension-dominated long riser or tether of an engineering structure in deep oceans. However, the axial tension must be optimized before being used since the high dominant vibration frequency due to the elevated tension may unfavorably affect the fatigue life of the riser or tether. 展开更多
关键词 Tension effect Maximum displacement Dominant vibration frequency CHAOS
下载PDF
Parametric Instability Analysis of Deepwater Top-Tensioned Risers Considering Variable Tension Along the Length 被引量:1
13
作者 ZHANG Jie TANG Yougang 《Journal of Ocean University of China》 SCIE CAS 2015年第1期59-64,共6页
Parametric instability of a riser is caused by fluctuation of its tension in time due to the heave motion of floating platform. Many studies have tackled the problem of parametric instability of a riser with constant ... Parametric instability of a riser is caused by fluctuation of its tension in time due to the heave motion of floating platform. Many studies have tackled the problem of parametric instability of a riser with constant tension. However, tension in the riser actually varies linearly from the top to the bottom due to the effect of gravity. This paper presents the parametric instability analysis of deepwater top-tensioned risers(TTR) considering the linearly varying tension along the length. Firstly, the governing equation of transverse motion of TTR under parametric excitation is established. This equation is reduced to a system of ordinary differential equations by using the Galerkin method. Then the parametric instability of TTR for three calculation models are investigated by applying the Floquet theory. The results show that the natural frequencies of TTR with variable tension are evidently reduced, the parametric instability zones are significantly increased and the maximum allowable amplitude of platform heave is much smaller under the same damping; The nodes and antinodes of mode shape are no longer uniformly distributed along the axial direction and the amplitude also changes with depth, which leads to coupling between the modes. The combination resonance phenomenon occurs as a result of mode coupling, which causes more serious damage. 展开更多
关键词 deepwater risers parametric instability variable tension mode coupling
下载PDF
Nonlinear analysis of pre-tensioned glass wall facade by stability function with initial imperfection
14
作者 Siu-Lai CHAN Yaopeng LIU Andy LEE 《Frontiers of Structural and Civil Engineering》 SCIE EI 2010年第3期376-382,共7页
Pre-tensioned high strength trusses using alloy steel bar are widely used as glass wall supporting systems because of the high degree of transparency.The breakage of glass panes in this type of system occurs occasiona... Pre-tensioned high strength trusses using alloy steel bar are widely used as glass wall supporting systems because of the high degree of transparency.The breakage of glass panes in this type of system occurs occasionally,likely to be due to error in design and analysis in addition to other factors like glass impurity and stress concentration around opening in a spider system.Most design does not consider the flexibility of supports from finite stiffness of supporting steel or reinforced concrete beams.The resistance of lateral wind pressure of the system makes use of high tension force coupled with the large deflection effect,both of which are affected by many parameters not generally considered in conventional structures.In the design,one must therefore give a careful consideration on various effects,such as support settlement due to live loads and material creep,temperature change,pre-tension force,and wind pressure.It is not uncommon to see many similar glass wall systems fail in the wind load test chambers under a design wind speed.This paper presents a rigorous analysis and design of this type of structural systems used in a project in Hong Kong,China.The stability function with initial curvature is used in place of the cubic function,which is only accurate for linear analysis.The considerations and analysis techniques are believed to be of value to engineers involved in the design of the structural systems behaving nonlinearly. 展开更多
关键词 tension system glass wall nonlinear analysis pre-tensioning second-order analysis
原文传递
Neurophysiological, histological, and behavioral characterization of animal models of distraction spinal cord injury: a systematic review 被引量:1
15
作者 Bo Han Weishi Liang +4 位作者 Yong Hai Duan Sun Hongtao Ding Yihan Yang Peng Yin 《Neural Regeneration Research》 SCIE CAS CSCD 2024年第3期563-570,共8页
Distraction spinal cord injury is caused by some degree of distraction or longitudinal tension on the spinal cord and commonly occurs in patients who undergo corrective operation for severe spinal deformity.With the i... Distraction spinal cord injury is caused by some degree of distraction or longitudinal tension on the spinal cord and commonly occurs in patients who undergo corrective operation for severe spinal deformity.With the increased degree and duration of distraction,spinal cord injuries become more serious in terms of their neurophysiology,histology,and behavior.Very few studies have been published on the specific characteristics of distraction spinal cord injury.In this study,we systematically review 22 related studies involving animal models of distraction spinal cord injury,focusing particularly on the neurophysiological,histological,and behavioral characteristics of this disease.In addition,we summarize the mechanisms underlying primary and secondary injuries caused by distraction spinal cord injury and clarify the effects of different degrees and durations of distraction on the primary injuries associated with spinal cord injury.We provide new concepts for the establishment of a model of distraction spinal cord injury and related basic research,and provide reference guidelines for the clinical diagnosis and treatment of this disease. 展开更多
关键词 animal models behavior DISTRACTION heterogeneity HISTOLOGY mechanism NEUROPHYSIOLOGY spinal cord injury systematic review tension
下载PDF
Unveiling the silent link:Normal-tension glaucoma's enigmatic bond with cardiac blood flow 被引量:1
16
作者 Prasanna Venkatesh Ramesh Arvind Kumar Morya +5 位作者 Ajanya K Aradhya Pavithra Pannerselvam Sai Thaejesvi Gopalakrishnan Shruthy Vaishali Ramesh Aji Kunnath Devadas Navaneeth Krishna 《World Journal of Cardiology》 2024年第1期10-15,共6页
This comprehensive review embarks on a captivating journey into the complex relationship between cardiology and normal-tension glaucoma(NTG),a condition that continues to baffle clinicians and researchers alike.NTG,ch... This comprehensive review embarks on a captivating journey into the complex relationship between cardiology and normal-tension glaucoma(NTG),a condition that continues to baffle clinicians and researchers alike.NTG,characterized by optic nerve damage and visual field loss despite normal intraocular pressure,has long puzzled clinicians.One emerging perspective suggests that alterations in ocular blood flow,particularly within the optic nerve head,may play a pivotal role in its pathogenesis.While NTG shares commonalities with its high-tension counterpart,its unique pathogenesis and potential ties to cardiovascular health make it a fascinating subject of exploration.It navigates through the complex web of vascular dysregulation,blood pressure and perfusion pressure,neurovascular coupling,and oxidative stress,seeking to uncover the hidden threads that tie the heart and eyes together in NTG.This review explores into the intricate mechanisms connecting cardiovascular factors to NTG,shedding light on how cardiac dynamics can influence ocular health,particularly in cases where intraocular pressure remains within the normal range.NTG's enigmatic nature,often characterized by seemingly contradictory risk factors and clinical profiles,underscores the need for a holistic approach to patient care.Drawing parallels to cardiac health,we examine into the shared vascular terrain connecting the heart and the eyes.Cardiovascular factors,including systemic blood flow,endothelial dysfunction,and microcirculatory anomalies,may exert a profound influence on ocular perfusion,impacting the delicate balance within the optic nerve head.By elucidating the subtle clues and potential associations between cardiology and NTG,this review invites clinicians to consider a broader perspective in their evaluation and management of this elusive condition.As the understanding of these connections evolves,so too may the prospects for early diagnosis and tailored interventions,ultimately enhancing the quality of life for those living with NTG. 展开更多
关键词 Normal tension glaucoma Vascular dysregulation Ocular blood flow Blood pressure Perfusion pressure Oxidative stress
下载PDF
Versatile fluidity test model for cast superalloys and comparison between IN718 and IN939
17
作者 Jun ZHANG Zi-qi JIE +1 位作者 Miao-nan LIU Min GUO 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2024年第9期2881-2888,共8页
A spiral fluidity test model of superalloys with 10 mm in height and 3 mm in thickness was designed to evaluate the fluidity of two distinct Ni-based superalloys IN718 and IN939.The factors influencing fluidity are as... A spiral fluidity test model of superalloys with 10 mm in height and 3 mm in thickness was designed to evaluate the fluidity of two distinct Ni-based superalloys IN718 and IN939.The factors influencing fluidity are ascertained through comparative analysis utilizing methodologies such as JMat Pro,differential scanning calorimetry and high-temperature confocal laser scanning microscopy.The results show that under identical testing conditions,the fluidity of the IN939 superalloy surpasses that of the IN718 superalloy.When subjected to the same temperature,the melt viscosity and surface tension of IN939 superalloy are considerably reduced relative to those of IN718 superalloy,which is beneficial to improving the melt fluidity.Furthermore,the liquidus temperature and solidification range for the IN939 superalloy are both smaller compared with those of the IN718 superalloy.This condition proves advantageous in delaying dendrite coherency,thereby improving fluidity. 展开更多
关键词 FLUIDITY solidification range SUPERALLOYS surface tension VISCOSITY
下载PDF
Research on Anti-Fluctuation Control of Winding Tension System Based on Feedforward Compensation
18
作者 Yujie Duan Jianguo Liang +4 位作者 Jianglin Liu Haifeng Gao Yinhui Li Jinzhu Zhang Xinyu Wen 《Computer Modeling in Engineering & Sciences》 SCIE EI 2024年第5期1239-1261,共23页
In the fiber winding process,strong disturbance,uncertainty,strong coupling,and fiber friction complicate the winding constant tension control.In order to effectively reduce the influence of these problems on the tens... In the fiber winding process,strong disturbance,uncertainty,strong coupling,and fiber friction complicate the winding constant tension control.In order to effectively reduce the influence of these problems on the tension output,this paper proposed a tension fluctuation rejection strategy based on feedforward compensation.In addition to the bias harmonic curve of the unknown state,the tension fluctuation also contains the influence of bounded noise.A tension fluctuation observer(TFO)is designed to cancel the uncertain periodic signal,in which the frequency generator is used to estimate the critical parameter information.Then,the fluctuation signal is reconstructed by a third-order auxiliary filter.The estimated signal feedforward compensates for the actual tension fluctuation.Furthermore,a time-varying parameters fractional-order PID controller(TPFOPID)is realized to attenuate the bounded noise in the fluctuation.Finally,TPFOPID is enhanced by TFO and applied to control a tension control system considering multi-source disturbances.The stability of the method is analyzed by using the Lyapunov theorem.Finally,numerical simulations verify that the proposed scheme improves the tracking ability and robustness of the system in response to tension fluctuations. 展开更多
关键词 Constant tension control anti-fluctuation strategy tension fluctuation observer time-varying parameters fractional-order PID controller feedforward compensate
下载PDF
Adaptive RISE Control of Winding Tension with Active Disturbance Rejection
19
作者 Junjie Mi Jianyong Yao Wenxiang Deng 《Chinese Journal of Mechanical Engineering》 SCIE EI CAS CSCD 2024年第4期135-145,共11页
A winding system is a time-varying system that considers complex nonlinear characteristics,and how to control the stability of the winding tension during the winding process is the primary problem that has hindered de... A winding system is a time-varying system that considers complex nonlinear characteristics,and how to control the stability of the winding tension during the winding process is the primary problem that has hindered development in this field in recent years.Many nonlinear factors affect the tension in the winding process,such as friction,structured uncertainties,unstructured uncertainties,and external interference.These terms severely restrict the tension tracking performance.Existing tension control strategies are mainly based on the composite control of the tension and speed loops,and previous studies involve complex decoupling operations.Owing to the large number of calculations required for this method,it is inconvenient for practical engineering applications.To simplify the tension generation mechanism and the influence of the nonlinear characteristics of the winding system,a simpler nonlinear dynamic model of the winding tension was established.An adaptive method was applied to update the feedback gain of the continuous robust integral of the sign of the error(RISE).Furthermore,an extended state observer was used to estimate modeling errors and external disturbances.The model disturbance term can be compensated for in the designed RISE controller.The asymptotic stability of the system was proven according to the Lyapunov stability theory.Finally,a comparative analysis of the proposed nonlinear controller and several other controllers was performed.The results indicated that the control of the winding tension was significantly enhanced. 展开更多
关键词 Winding tension Continuous robust integral of the sign of the error(RISE)control Adaptive control Disturbance compensation Extended state observer(ESO) Tension control
下载PDF
Impact of ethanol on the flotation efficiency of imidazolium ionic liquids as collectors:Insights from dynamic surface tension and solvation analysis
20
作者 Qian Cheng Zerui Lei +1 位作者 Guangjun Mei Jianhua Chen 《International Journal of Minerals,Metallurgy and Materials》 SCIE EI CAS CSCD 2024年第12期2645-2656,共12页
To conduct extensive research on the application of ionic liquids as collectors in mineral flotation,ethanol(EtOH)was used as a solvent to dissolve hydrophobic ionic liquids(ILs)to simplify the reagent regime.Interest... To conduct extensive research on the application of ionic liquids as collectors in mineral flotation,ethanol(EtOH)was used as a solvent to dissolve hydrophobic ionic liquids(ILs)to simplify the reagent regime.Interesting phenomena were observed in which EtOH exerted different effects on the flotation efficiency of two ILs with similar structures.When EtOH was used to dissolve 1-dodecyl-3-methylimidazolium chloride(C12[mim]Cl)and as a collector for pure quartz flotation tests at a concentration of 1×10^(−5)mol·L^(−1),quartz recovery increased from 23.77%to 77.91%compared with ILs dissolved in water.However,quartz recovery of 1-dodecyl-3-methylim-idazolium hexafluorophosphate(C12[mim]PF6)decreased from 60.45%to 24.52%under the same conditions.The conditional experi-ments under 1×10^(−5)mol·L^(−1)ILs for EtOH concentration and under 2vol%EtOH for ILs concentration confirmed this difference.After being affected by EtOH,the mixed ore flotation tests of quartz and hematite showed a decrease in the hematite concentrate grade and re-covery for the C12[mim]Cl collector,whereas the hematite concentrate grade and recovery for the C12[mim]PF6 collector increased.On the basis of these differences and observations of flotation foam,two-phase bubble observation tests were carried out.The EtOH promoted the foam height of two ILs during aeration.It accelerated static froth defoaming after aeration stopped,and the foam of C12[mim]PF6 de-foaming especially quickly.In the discussion of flotation tests and foam observation,an attempt was made to explain the reasons and mechanisms behind the diverse phenomena using the dynamic surface tension effect and solvation effect results from EtOH.The solva-tion effect was verified through Fourier transform infrared(FT-IR),X-ray photoelectron spectroscopy(XPS),and Zeta potential tests.Al-though EtOH affects the adsorption of ILs on the ore surface during flotation negatively,it holds an positive value of inhibiting foam mer-ging during flotation aeration and accelerating the defoaming of static foam.And induce more robust secondary enrichment in the mixed ore flotation of the C12[mim]PF6 collector,facilitating effective mixed ore separation even under inhibitor-free conditions. 展开更多
关键词 ionic liquid ETHANOL flotation foam SOLVATION dynamic surface tension
下载PDF
上一页 1 2 49 下一页 到第
使用帮助 返回顶部