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Dynamic characteristics of coal specimens with varying static preloading levels under low-frequency disturbance load
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作者 WEN Xiao-ze FENG Guo-rui +5 位作者 GUO Jun YU Lu-yang QIAN Rui-peng ZHANG Jie ZHANG Peng-fei FENG Wen-ming 《Journal of Central South University》 SCIE EI CAS CSCD 2024年第8期2644-2657,共14页
The mechanical properties of residual coal pillars under the influence of upward mining disturbances significantly affect the safety of residual mining activities on working faces.This study conducted low-frequency di... The mechanical properties of residual coal pillars under the influence of upward mining disturbances significantly affect the safety of residual mining activities on working faces.This study conducted low-frequency disturbance dynamic uniaxial compression tests on coal specimens using a self-developed dynamic-static load coupling electro-hydraulic servo system,and studied the strength evolutions,surface deformations,acoustic emission(AE)characteristic parameters,and the failure modes of coal specimens with different static preloading levels were studied.The disturbance damage is positively correlated with the coal specimen static preload level.Specifically,the cumulative AE count rates of the initial accelerated damage stage for the coal specimens with static preloading level of 60%and 70%of the uniaxial compressive strength(UCS)were 2.66 and 3.19 times that of the 50%UCS specimens,respectively.Macroscopically,this behaviour manifested as a decrease in the compressive strength,and the mean strengths of the disturbance-damaged coal specimens with 60%and 70%of UCS static preloading decreased by 8.53%and 9.32%,respectively,compared to those of the specimens under pure static loading.The crack sources,such as the primary fissures,strongly control the dynamic response of the coal specimen.The difference between the dynamic responses of the coal specimens and that of dense rocks is significant. 展开更多
关键词 low-frequency disturbance dynamic response coal specimens static preloading level
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Dynamic mechanical characteristics of deep Jinping marble in complex stress environments
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作者 Chendi Lou Heping Xie +6 位作者 Ru Zhang Hai Ren Hao Luo Kun Xiao Yuan Peng Qiang Tan Li Ren 《Journal of Rock Mechanics and Geotechnical Engineering》 SCIE CSCD 2024年第2期630-644,共15页
To reveal the dynamic mechanical characteristics of deep rocks,a series of impact tests under triaxial static stress states corresponding to depths of 300-2400 m were conducted.The results showed that both the strain ... To reveal the dynamic mechanical characteristics of deep rocks,a series of impact tests under triaxial static stress states corresponding to depths of 300-2400 m were conducted.The results showed that both the strain rates and the stress environments in depth significantly affect the mechanical characteristics of rocks.The sensitivity of strain rate to the dynamic strength and deformation modulus shows a negative correlation with depth,indicating that producing penetrative cracks in deep environments is more difficult when damage occurs.The dynamic strength shows a tendency to decrease and then increase slightly,but decreases sharply finally.Transmissivity demonstrates a similar trend as that of strength,whereas reflectivity indicates the opposite trend.Furthermore,two critical depths with high dynamically induced hazard possibilities based on the China Jinping Underground Laboratory(CJPL)were proposed for deep engineering.The first critical depth is 600-900 m,beyond which the sensitivity of rock dynamic characteristics to the strain rate and restraint of circumferential stress decrease,causing instability of surrounding rocks under axial stress condition.The second one lies at 1500-1800 m,where the wave impedance and dynamic strength of deep surrounding rocks drop sharply,and the dissipation energy presents a negative value.It suggests that the dynamic instability of deep surrounding rocks can be divided into dynamic load dominant and dynamic load induced types,depending on the second critical depth. 展开更多
关键词 Rock mechanics Split-Hopkinson pressure bar Coupled staticdynamic loading Different depths Holmquist-Johnson-Cook(HJC)model
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Effects of Fatigue Characteristics on Static and Dynamic Performance of Eucommia Rubber Isolators
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作者 Yongsheng Peng Junfeng Yang +2 位作者 Guopei Pan Jianan Zhang Zhuo Wang 《Journal of Applied Mathematics and Physics》 2023年第7期2165-2177,共13页
This study aimed to investigate the effect of fatigue characteristics on the static and dynamic performance of Eucommia ulmoides gum isolators, and to explore the performance changes of Eucommia ulmoides gum isolators... This study aimed to investigate the effect of fatigue characteristics on the static and dynamic performance of Eucommia ulmoides gum isolators, and to explore the performance changes of Eucommia ulmoides gum isolators with different formulations. For this purpose, we used five formulations of Eucommia ulmoides gum isolators and set different fatigue test methods to study the static and dynamic performance changes of Eucommia ulmoides gum isolators with different formulations by changing the amplitude. The experimental results showed that the addition of Eucommia ulmoides gum had an impact on the performance of the isolator, and the number of fatigue cycles would lead to the hardening of the Eucommia ulmoides gum isolator and changes in its static and dynamic performance. In the range of two million vibrations, the performance change of the isolator was significant in the early stage and then tended to be flat, indicating that the impact of fatigue on the performance of the isolator would not continue to persist. It is worth noting that the study found that the addition of 30% Eucommia ulmoides gum had the least impact on the performance of the isolator under fatigue. Therefore, for long-term use of Eucommia ulmoides gum isolators, attention should be paid to their fatigue characteristics to ensure their stability and reliability. Additionally, this study provides a reference for the design and application of Eucommia ulmoides gum isolators. In summary, this study provides important reference value for a deeper understanding of the fatigue characteristics of Eucommia ulmoides gum isolators and for ensuring their stable and reliable performance. . 展开更多
关键词 Fatigue characteristics Eucommia Rubber Vibration Isolators static Performance dynamic Performance
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Mechanical behavior and failure mechanisms of rock bolts subjected to static-dynamic loads 被引量:1
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作者 Hongpu Kang Guiyang Yuan +4 位作者 Linpo Si Fuqiang Gao Jinfu Lou Jinghe Yang Shuangyong Dong 《International Journal of Mining Science and Technology》 SCIE EI CAS CSCD 2024年第3期281-288,共8页
This study explores the effects of dynamic and static loading on rock bolt performance a key factor in maintaining the structural safety of coal mine roadways susceptible to coal bursts.Employing a housemade load fram... This study explores the effects of dynamic and static loading on rock bolt performance a key factor in maintaining the structural safety of coal mine roadways susceptible to coal bursts.Employing a housemade load frame to simulate various failure scenarios,pretension-impact-pull tests on rock bolts were conducted to scrutinize their dynamic responses under varied static load conditions and their failure traits under combined loads.The experimental results denote that with increased impact energy,maximum and average impact loads on rock bolts escalate significantly under pretension,initiating plastic deformation beyond a certain threshold.Despite minor reductions in the yield load due to impactinduced damage,pretension aids in constraining post-impact deformation rate and fluctuation degree of rock bolts.Moreover,impact-induced plastic deformation causes internal microstructure dislocation,fortifying the stiffness of the rock bolt support system.The magnitude of this fortification is directly related to the plastic deformation induced by the impact.These findings provide crucial guidance for designing rock bolt support in coal mine roadway excavation,emphasizing the necessity to consider both static and dynamic loads for improved safety and efficiency. 展开更多
关键词 Rock bolt PRETENSION static and dynamic load IMPACT
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Energy mechanism of bolt supporting effect to fissured rock under static and dynamic loads in deep coal mines 被引量:1
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作者 Deyuan Fan Xuesheng Liu +2 位作者 Yunliang Tan Xuebin Li Shenglong Yang 《International Journal of Mining Science and Technology》 SCIE EI CAS CSCD 2024年第3期371-384,共14页
The stability control of fissured rock is difficult,especially under static and dynamic loads in deep coal mines.In this paper,the dynamic mechanical properties,strain rate evolution and energy dissipation of fissured... The stability control of fissured rock is difficult,especially under static and dynamic loads in deep coal mines.In this paper,the dynamic mechanical properties,strain rate evolution and energy dissipation of fissured and anchored rocks were respectively obtained by SHPB tests.It was found that bolt can provide supporting efficiency-improving effect for fissured rock against dynamic disturbance,and this effect increased quadratically with decrease in anchoring angles.Then,the energy dissipation mechanism of anchored rock was obtained by slipping model.Furthermore,bolt energy-absorbing mechanism by instantaneous tensile-shear deformation was expressed based on material mechanics,which was the larger the anchoring angle,the smaller the energy absorption,and the less the contribution to supporting efficiency improvement.On this basis,the functional relationship between energy dissipation of anchored rock and energy absorption of bolt was established.Taking the coal-gangue separation system of Longgu coal mine as an example,the optimal anchoring angle can be determined as 57.5°–67.5°.Field monitoring showed fissured rock with the optimal anchoring angle,can not only effectively control the deformation,but also fully exert the energy-absorbing and efficiency-improving effect of bolt itself.This study provides guidance to the stability control and supporting design for deep engineering under the same or similar conditions. 展开更多
关键词 static and dynamic loads Anchored rock Energy absorption Anchoring angle Engineering verification
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Effects of reservoir fluids on sand packs consolidated by furan and epoxy resins:Static and dynamic states
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作者 Mohammad Nabi Tabbakhzadeh Feridun Esmaeilzadeh +1 位作者 Dariush Mowla Reza Zabihi 《Journal of Rock Mechanics and Geotechnical Engineering》 SCIE CSCD 2024年第11期4504-4514,共11页
One of the most effective methods for sand control is the chemical consolidation of sandstone structures.In this paper,the impacts of crude oil and brine in the static state and the impact of the flow rates of the flu... One of the most effective methods for sand control is the chemical consolidation of sandstone structures.In this paper,the impacts of crude oil and brine in the static state and the impact of the flow rates of the fluids in the dynamic state have been assessed at the reservoir conditions.The analyses in this research were Young’s modulus,compressive strength,porosity,and permeability which were done on core samples after and before fluid contact.Samples made with two different resins showed good resistance to crude oil in both states.No considerable change was seen in the analyses even at high crude oil injection rates in the dynamic state.Conversely,brine caused a noticeable change in the analyses in both states.In the presence of brine at the static state,Young’s modulus and compressive strength respectively decreased by 37.5%and 34.5%for epoxy cores,whereas these parameters respectively reduced by 30%and 41%for furan cores.In brine presence at the dynamic state,compressive strength reduction was 10.28 MPa for furan and 6.28 MPa for epoxy samples and their compressive strength reached 16.75 MPa and 26.54 MPa respectively which are higher than the critical point to be known as weak sandstone core.Moreover,Young’s modulus decrease values for furan and epoxy samples were respectively 0.37 GPa and 0.44 GPa.Therefore,brine had a more destructive effect on the mechanical characteristics of samples in the static state than the dynamic one for two resins.In addition,brine injection increased permeability by about 13.6%for furan and 34.8%for epoxy.Also,porosity raised by about 21.8%for furan,and 19%for epoxy by brine injection.The results showed that the chemical sand consolidation weakens in the face of brine production along with crude oil which can lead to increasing cost of oil production and treating wellbore again. 展开更多
关键词 Chemical sand consolidation Brine Flow rate static and dynamic states Crude oil Compressive strength Permeability Young’s modulus
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Influence of static cartoons combined with dynamic virtual environments on preoperative anxiety of preschool-aged children undergoing surgery
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作者 Ya-Lin Zhang Qi-Ying Zhou +3 位作者 Peng Zhang Lin-Feng Huang Li Jin Zhi-Guo Zhou 《World Journal of Clinical Cases》 SCIE 2024年第22期4947-4955,共9页
BACKGROUND Preschoolers become anxious when they are about to undergo anesthesia and surgery,warranting the development of more appropriate and effective interventions.AIM To explore the effect of static cartoons comb... BACKGROUND Preschoolers become anxious when they are about to undergo anesthesia and surgery,warranting the development of more appropriate and effective interventions.AIM To explore the effect of static cartoons combined with dynamic virtual environments on preoperative anxiety and anesthesia induction compliance in preschool-aged children undergoing surgery.METHODS One hundred and sixteen preschool-aged children were selected and assigned to the drug(n=37),intervention(n=40),and control(n=39)groups.All the children received routine preoperative checkups and nursing before being transferred to the preoperative preparation room on the day of the operation.The drug group received 0.5 mg/kg midazolam and the intervention group treatment consisting of static cartoons combined with dynamic virtual environments.The control group received no intervention.The modified Yale Preoperative Anxiety Scale was used to evaluate the children’s anxiety level on the day before surgery(T0),before leaving the preoperative preparation room(T1),when entering the operating room(T2),and at anesthesia induction(T3).Compliance during anesthesia induction(T3)was evaluated using the Induction Compliance Checklist(ICC).Changes in mean arterial pressure(MAP),heart rate(HR),and respiratory rate(RR)were also recorded at each time point.RESULTS The anxiety scores of the three groups increased variously at T1 and T2.At T3,both the drug and intervention groups had similar anxiety scores,both of which were lower than those in the control group.At T1 and T2,MAP,HR,and RR of the three groups increased.The drug and control groups had significantly higher MAP and RR than the intervention group at T2.At T3,the MAP,HR,and RR of the drug group decreased and were significantly lower than those in the control group but were comparable to those in the intervention group.Both the drug and intervention groups had similar ICC scores and duration of anesthesia induction(T3),both of which were higher than those of the control group.CONCLUSION Combining static cartoons with dynamic virtual environments as effective as medication,specifically midazolam,in reducing preoperative anxiety and fear in preschool-aged children.This approach also improve their compliance during anesthesia induction and helped maintain their stable vital signs. 展开更多
关键词 PRESCHOOL Children static cartoons combined with dynamic virtual environments Preoperative anxiety COMPLIANCE Anesthesia induction
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Design,Development and Testing of the JTech Bolt for Use in Static,Quasi-Static and Dynamic Domains
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作者 Trent Roberts 《Journal of Civil Engineering and Architecture》 2024年第6期282-295,共14页
Designing a rock reinforcement element requires knowledge of:geomechanical behaviour,interaction of the reinforcement element with rock mass and the element’s mechanistic response in static and dynamic environments.U... Designing a rock reinforcement element requires knowledge of:geomechanical behaviour,interaction of the reinforcement element with rock mass and the element’s mechanistic response in static and dynamic environments.Using this knowledge the JTech bolt was developed and subjected to a thorough program to test,gather data and validate the bolt performance in varying domains.By conducting FE(finite element)modeling,the simulation reviews the JTech bolt design evaluating the effects of threadbar geometric variation,threadbar and nut engagement results under high stress,coating friction response and effects of thread tolerance extremes on the failure mode.These results determine safety factors,tolerances and quality management criteria.Once manufactured,in-situ system testing,laboratory and underground short encapsulation testing,resin mixing testing,double shear testing and dynamic testing at varying velocity and mass,determine the system’s capacity and effectiveness in static,quasi-static and dynamic mining environments.In this paper,the process and results are described. 展开更多
关键词 Rock reinforcement geomechanical behavior static QUASI-static dynamic domains
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Elimination, Kinetics and Thermodynamics of Fe(II) Ions by Adsorption in Static and Dynamic Conditions on Activated Carbons in Aqueous Media
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作者 Spenseur Bouassa Mougnala Charly Mve Mfoumou +5 位作者 Berthy Lionel Mbouiti Pradel Tonda-Mikiela Francis Ngoye Ferdinand Evoung Evoung Jean Aubin Ondo Guy Raymond Feuya Tchouya 《Journal of Geoscience and Environment Protection》 2024年第10期181-203,共23页
This work investigated the removal, kinetics and thermodynamics of iron(II) ions (Fe(II)) by adsorption in static and dynamic conditions in aqueous media on activated carbons (AC-i30min, AC-i1h, and AC-i24h), prepared... This work investigated the removal, kinetics and thermodynamics of iron(II) ions (Fe(II)) by adsorption in static and dynamic conditions in aqueous media on activated carbons (AC-i30min, AC-i1h, and AC-i24h), prepared from palm nut shells collected in the city of Franceville to Gabon, using potassium hydroxide (KOH) as the activating agent. Results on the elimination of Fe(II) in static and dynamic adsorption on prepared activated carbons (ACs) showed that the AC-i24h adsorbent has the best Fe(II) adsorption capacities at saturation (Qsat). The Qsat obtained on AC-i24h in static and dynamic conditions (17.87 and 10.38 mg/g, respectively) were higher than those of AC-i30min (13.89 and 5.54 mg/g respectively) and AC-i1h (14.92 and 8.64 mg/g respectively). Moreover, the static adsorption was more effective in the removal of Fe(II) ions in aqueous media in our experimental conditions. The percentage removal (%E) of Fe(II) obtained on prepared activated carbons in static conditions was better than those obtained in dynamic conditions, especially on AC-i24h, where the %E was 89.27% in static and 61.56% in dynamic. In kinetics, results showed that the pseudo-second-order kinetic model best described the adsorption mechanisms of Fe(II) on prepared activated carbons in static adsorption, with mainly of chemisorption on the solid surfaces. However, in dynamic conditions, the pseudo-first-order kinetic model was more suitable. In addition to the weak interactions between Fe(II) and the activated carbon surfaces, strong interactions (chemisorption) were also observed. Also, thermodynamic data obtained on AC-i24h in static adsorption indicated that the adsorption of Fe(II) was spontaneous and increased with temperature (ΔG˚ H˚ = 503.54 KJ/mol). 展开更多
关键词 Palm Nut Shells Activated Carbon Removal FE(II) static and dynamic Adsorption KINETICS Thermodynamics
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Theoretical Analysis and Numerical Simulation of the Static and Dynamic Characteristics of Hydrostatic Guides Based on Progressive Mengen Flow Controller 被引量:13
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作者 GAO Dianrong ZHENG Dan ZHANG Zuochao 《Chinese Journal of Mechanical Engineering》 SCIE EI CAS CSCD 2010年第6期709-716,共8页
The oil film thickness of oil hydrostatic guide with constant pressure supply based on capillary restrictor is greatly affected by load, and this kind of hydrostatic guide is usually applied to the machine tools with ... The oil film thickness of oil hydrostatic guide with constant pressure supply based on capillary restrictor is greatly affected by load, and this kind of hydrostatic guide is usually applied to the machine tools with moderate load. The static and dynamic characteristics of the guide have been studied by using some theoretical, numerical and experimental approaches, and some methods and measures have been proposed to improve its performances. The hydrostatic guide based on progressive mengen(PM) flow controller is especially suitable for the heavy numerical control(NC) machine tools. However, few literatures about the research on the static and dynamic characteristics of the hydrostatic guides based on PM flow controller are reported. In this paper, the formulae are derived for analyzing the static and dynamic characteristics of hydrostatic guides with rectangle pockets and PM flow controller according to the theory of hydrostatic bearing. On the basis of the analysis of hydrostatic bearing with circular pocket, some equations are derived for solving the static pressure, volume pressure and squeezing pressure which influence the dynamic characteristics of hydrostatic guides with rectangle pocket. The function and the influencing factors of three pressures are clarified. The formulae of amplitude-frequency characteristics and dynamic stiffness of the hydrostatic guide system are derived. With the help of software MATLAB, programs are coded with C++ language to simulate numerically the static and dynamic characteristics of the hydrostatic guide based on PM flow controller. The simulation results indicate that the sensitive oil volume between the outlet of the PM flow controller and the guide pocket has the greatest influence on the characteristics of the guide, and it should be reduced as small as possible when the field working condition is met. Choosing the oil with a greater viscosity is also helpful in improving the dynamic performance of hydrostatic guides. The research work has instructing significance for analyzing and designing the guide with PM flow controller. 展开更多
关键词 PM flow controller rectangle pocket static characteristics dynamic characteristics hydrostatic guides
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Numerical simulation research on response characteristics of surrounding rock for deep super-large section chamber under dynamic and static combined loading condition 被引量:13
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作者 FAN De-yuan LIU Xue-sheng +3 位作者 TAN Yun-liang SONG Shi-lin NING Jian-guo MA Qing 《Journal of Central South University》 SCIE EI CAS CSCD 2020年第12期3544-3566,共23页
The stability control of surrounding rock for large or super-large section chamber is a difficult technical problem in deep mining condition.Based on the in-site geological conditions of Longgu coal mine,this paper us... The stability control of surrounding rock for large or super-large section chamber is a difficult technical problem in deep mining condition.Based on the in-site geological conditions of Longgu coal mine,this paper used the dynamic module of FLAC3D to study the response characteristics of deep super-large section chamber under dynamic and static combined loading condition.Results showed that under the static loading condition,the maximum vertical stress,deformation and failure range are large,where the stress concentration coefficient is 1.64.The maximum roof-to-floor and two-sides deformations are 54.6 mm and 53.1 mm,respectively.Then,under the dynamic and static combined loading condition:(1)The influence of dynamic load frequency on the two-sides is more obvious;(2)The dynamic load amplitude has the greatest influence on the stress concentration degree,and the plastic failure tends to develop to the deeper;(3)With the dynamic load source distance increase,the response of surrounding rock is gradually attenuated.On this basis,empirical equations for each dynamic load conditions were obtained by using regression analysis method,and all correlation coefficients are greater than 0.99.This research provided reference for the supporting design of deep super-large section chamber under same or similar conditions. 展开更多
关键词 deep mining super-larger section chamber static load dynamic load frequency dynamic load amplitude dynamic load source distance
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Nonlinear Static and Dynamic Stiffness Characteristics of Support Hydraulic System of TBM 被引量:5
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作者 Jianfeng Tao Junbo Lei +1 位作者 Chengliang Liu Wei Yuan 《Chinese Journal of Mechanical Engineering》 SCIE EI CAS CSCD 2019年第6期26-34,共9页
Full-face hard rock tunnel boring machines(TBM)are essential equipment in highway and railway tunnel engineering construction.During the tunneling process,TBM have serious vibrations,which can damage some of its key c... Full-face hard rock tunnel boring machines(TBM)are essential equipment in highway and railway tunnel engineering construction.During the tunneling process,TBM have serious vibrations,which can damage some of its key components.The support system,an important part of TBM,is one path through which vibrational energy from the cutter head is transmitted.To reduce the vibration of support systems of TBM during the excavation process,based on the structural features of the support hydraulic system,a nonlinear dynamical model of support hydraulic systems of TBM is established.The influences of the component structure parameters and operating conditions parameters on the stiffness characteristics of the support hydraulic system are analyzed.The analysis results indicate that the static stiffness of the support hydraulic system consists of an increase stage,stable stage and decrease stage.The static stiffness value increases with an increase in the clearances.The pre-compression length of the spring in the relief valve a ects the range of the stable stage of the static stiffness,and it does not a ect the static stiffness value.The dynamic stiffness of the support hydraulic system consists of a U-shape and reverse U-shape.The bottom value of the U-shape increases with the amplitude and frequency of the external force acting on the cylinder body,however,the top value of the reverse U-shape remains constant.This study instructs how to design the support hydraulic system of TBM. 展开更多
关键词 Tunnel boring machine Support hydraulic system Nonlinear model static stiffness characteristics dynamic stiffness characteristics
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Research on electromagnetic relay's dynamic characteristics disturbed by uniform static magnetic field 被引量:3
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作者 Guo-fu ZHAI Qi-ya WANG Wan-bin REN 《Journal of Zhejiang University-Science A(Applied Physics & Engineering)》 SCIE EI CAS CSCD 2008年第4期577-582,共6页
Electromagnetic relay is a widely used apparatus which usually works in a magnetic disturbance environment. To evaluate its electromagnetic compatibility (EMC) in a static magnetic field, dynamic characteristics of a ... Electromagnetic relay is a widely used apparatus which usually works in a magnetic disturbance environment. To evaluate its electromagnetic compatibility (EMC) in a static magnetic field, dynamic characteristics of a clapper relay in a uniform static magnetic field situation based on the finite element method (FEM) is studied. Influences of the magnetic field on dynamic parameters (delay time, pick-up time, end pressure, and final velocity) as well as a situation in which the relay cannot function normally are analyzed. Simulation reveals that the external magnetic field which weakens the relay’s air-gap field has a greater influence on the relay’s dynamic parameters than the one strengthening the field. The validity of the simulation is verified by measured results of coil current and armature displacement. 展开更多
关键词 dynamic characteristics Uniform static magnetic field Electromagnetic relay Finite element method (FEM) Electromagnetic compatibility (EMC)
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Lateral static and dynamic characteristics of thin-walled box girder 被引量:1
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作者 甘亚南 周广春 《Journal of Harbin Institute of Technology(New Series)》 EI CAS 2009年第1期101-106,共6页
To analyze the static and dynamic behaviors of the thin-walled box girder in its lateral webs in consideration of shear lag effect and shear deformation, an approach based on the minimum potential principle is introdu... To analyze the static and dynamic behaviors of the thin-walled box girder in its lateral webs in consideration of shear lag effect and shear deformation, an approach based on the minimum potential principle is introduced in this paper. Both static and dynamic response equations as well as the corresponding natural boundary conditions of the box girder are deduced. Meanwhile, three generalized displacement functions: w (x) , U(x) and O(x) are employed and their differences in the calculus of variation are quantitatively investigated. The comparison of finite shell element results with analytical results of calculation examples validates the feasibility of the proposed approach. 展开更多
关键词 thin-walled box girder shear lag effect static and dynamic characteristics energy-variation principle
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Advanced Statistical Analysis for Relationships between Particle Morphology (Size and Shape) and Shear (Static and Dynamic) Characteristics of Sands
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作者 Devapriya Chitral Wijeyesekera Alvin John Lim Meng Siang Ahmad Shukri Bin Yahaya 《International Journal of Geosciences》 2013年第10期27-36,共10页
Morphology properties of naturally occurring sandy soil deposits are a consequence of the past geological transport history which gives rise to their different shape and size distributions. Five sand samples with diff... Morphology properties of naturally occurring sandy soil deposits are a consequence of the past geological transport history which gives rise to their different shape and size distributions. Five sand samples with different particle size and shape distributions were analysed statistically. Cluster analysis, performance indicators and probability distributions were used to find a representative shape parameter value. Static and dynamic tests were also contemporarily done to study the shear characteristics of the samples. Dimensionless relationships of the critical shear stress (τcr) normalised with respect to the normal stress (σN) against the representative values are presented. Dynamic testing on the samples showed that the modulus reduction curve (G/Gmax) and damping ratio (D) were also dependent on the morphology characteristics of the sand samples. 展开更多
关键词 Morphology SAND STATISTICS static and dynamic SHEAR
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Static and Dynamic Structure Characteristics of a Trust Network and Formation of User Trust in an Online Society
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作者 Ying Li Hongduo Cao Ying Zhang 《Social Networking》 2018年第4期197-219,共23页
This study investigated the characteristics and formation of the online social trust network of Epinions.com, a general consumer review site. An analysis of the static structure of this social trust network revealed a... This study investigated the characteristics and formation of the online social trust network of Epinions.com, a general consumer review site. An analysis of the static structure of this social trust network revealed a high clustering coefficient, short average path length, and power-law degree distribution;it is therefore a small-world and scale-free trust network. The dynamic evolutionary characteristics of the online social network (OSN) were also examined. The results showed that the scale of the network followed a sigmoidal curve;the average degree of the network was nonconstant and changed into a bell-shaped distribution;the density of the network decreased and subsequently stabilized;and user trust diffusion in the network conformed to the Bass model. Finally, the formation of trust within the network was researched at the overall network (macro) and individual user (micro) levels. Compared with their accumulated contribution and reputation, user activeness had a larger effect on trust formation in OSNs, indicating a “diminishing returns” phenomenon. This phenomenon contrasts with the Matthew effect (i.e. , the more reputation a person has, the more likely he or she is to be trusted) in real-world social networks. 展开更多
关键词 TRUST Network static Structure dynamic Evolution TRUST FORMATION Diminishing Returns
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Static and Dynamic Characterization of High-Speed Silicon Carbide (SiC) Power Transistors
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作者 Johnson A. Asumadu James D. Scofield 《Engineering(科研)》 2010年第9期673-682,共10页
This paper describes the operating characteristics of NPN 4H-SiC (a polytype of silicon carbide) bipolar junction transistor (BJT) and 4H-SiC Darlington Pairs. A large amount of experimental data was collected. The wa... This paper describes the operating characteristics of NPN 4H-SiC (a polytype of silicon carbide) bipolar junction transistor (BJT) and 4H-SiC Darlington Pairs. A large amount of experimental data was collected. The wafer BJTs were able to block over the rated 600 V in the common-emitter configuration and the TO-220 BJTs were able to block over the 1200 V rated voltage. In the thermal analysis, it is found out that at higher temperatures the forward and reverse (blocking) characteristics were stable at 100°C and 200°C. The transistors show positive temperature coefficients of forward voltage (Vf). In general the current gain (β) characteristics obtained (with VCE = 6 V) were approximately as expected for the BJTs. The β‘s were very low (2 to 5 for wafer BJTs, 5 to 20 for the wafer Darlington Pairs, and 5 to 30 for TO-220 BJTs). The large amount of experimental data collected confirms some of the superior properties of the Silicon carbide material when used to fabricate power semiconductor devices, namely high thermal conductivity and high temperature operability. The data presented here will establish the trends and the performance of silicon carbide devices. The silicon carbide BJT has fast switching and recovery characteristics. From the analysis, silicon carbide power devices will be smaller (about 20 times) than a similar silicon power device and with reduced power losses. Silicon carbide will also be very useful for device integration in high densities, as found in integrated chips for current handling capabilities, for applications in instrumentation and measurements. Presently, most of the research is on improving the basic silicon carbide material quality, power device optimization, and applications engineering using devices that have been developed to date. 展开更多
关键词 SILICON CARBIDE static characterISTICS dynamic characterISTICS
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Dynamically triggered seismicity on a tectonic scale:A review 被引量:1
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作者 Chengzhi Qi Mingyang Wang +2 位作者 Gevorg Kocharyan Artem Kunitskikh Zefan Wang 《Deep Underground Science and Engineering》 2024年第1期1-24,共24页
Earthquakes triggered by dynamic disturbances have been confirmed by numerous observations and experiments.In the past several decades,earthquake triggering has attracted increasing attention of scholars in relation t... Earthquakes triggered by dynamic disturbances have been confirmed by numerous observations and experiments.In the past several decades,earthquake triggering has attracted increasing attention of scholars in relation to exploring the mechanism of earthquake triggering,earthquake prediction,and the desire to use the mechanism of earthquake triggering to reduce,prevent,or trigger earthquakes.Natural earthquakes and large‐scale explosions are the most common sources of dynamic disturbances that trigger earthquakes.In the past several decades,some models have been developed,including static,dynamic,quasi‐static,and other models.Some reviews have been published,but explosiontriggered seismicity was not included.In recent years,some new results on earthquake triggering have emerged.Therefore,this paper presents a new review to reflect the new results and include the content of explosion‐triggered earthquakes for the reference of scholars in this area.Instead of a complete review of the relevant literature,this paper primarily focuses on the main aspects of dynamic earthquake triggering on a tectonic scale and makes some suggestions on issues that need to be resolved in this area in the future. 展开更多
关键词 dynamic disturbances dynamic models problems for future research quasi‐static models static models triggered seismicity
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Supporting characteristics analysis of constant resistance bolts under coupled static-dynamic loading
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作者 CHEN Feng TANG Chun-an +2 位作者 SUN Xiao-ming MA Tian-hui DU Yan-hong 《Journal of Mountain Science》 SCIE CSCD 2019年第5期1160-1169,共10页
To study the tensile mechanical properties of constant resistance bolts, the RFPA(Rock Failure Process Analysis) statics software is used to perform a uniaxial tensile test on a constant resistance bolt. The numerical... To study the tensile mechanical properties of constant resistance bolts, the RFPA(Rock Failure Process Analysis) statics software is used to perform a uniaxial tensile test on a constant resistance bolt. The numerical test results show that the plastic strain value is 12 times the magnitude of the elastic strain. During plastic deformation, the fluctuation in the stress magnitude is relatively stable, indicating that the bolt has good constant resistance characteristics. The numerical test results are in good agreement with the laboratory test results of M.C. He, and the accuracy and reliability of the numerical test method are verified. Therefore, the RFPA software with coupled static-dynamic loading is further adopted to study the supporting effects of traditional bolts and constant resistance bolts under coupled staticdynamic loading. The numerical comparison of the test results show that the constant resistance bolts can effectively control the deformation amount and rate of the laneway surrounding rock, reduce the total and rate of increase in the accumulated acoustic emissions,decrease the stress on the units in the model and protect the stability of the laneway. This paper verifies that a constant resistance bolt has better impact resistance mechanical properties than those of a traditional bolt and provides an effective way to control rock burst and soft rock that is prone to large deformation damage. 展开更多
关键词 Rock mechanics COUPLED static-dynamic loading Deep laneway CONSTANT RESISTANCE BOLT RFPA
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Design and Performance Analysis of HMDV Dynamic Inertial Suspension Based on Active Disturbance Rejection Control
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作者 Xiaofeng Yang Wei Wang +2 位作者 Yujie Shen Changning Liu Tianyi Zhang 《Computer Modeling in Engineering & Sciences》 SCIE EI 2024年第8期1485-1506,共22页
This paper addresses the impact of vertical vibration negative effects,unbalanced radial forces generated by the static eccentricity of the hub motor,and road excitation on the suspension performance of Hub Motor Driv... This paper addresses the impact of vertical vibration negative effects,unbalanced radial forces generated by the static eccentricity of the hub motor,and road excitation on the suspension performance of Hub Motor Driven Vehicle(HMDV).A dynamic inertial suspension based on Active Disturbance Rejection Control(ADRC)is proposed,combining the vertical dynamic characteristics of dynamic inertial suspension with the features of ADRC,which distinguishes between internal and external disturbances and arranges the transition process.Firstly,a simulation model of the static eccentricity of the hub motor is established to simulate the unbalanced radial electromagnetic force generated under static eccentricity.A quarter-vehicle model of an HMDV with a controllable dynamic inertial suspension is then constructed.Subsequently,the passive suspension model is studied under different grades of road excitation,and the impact mechanism of suspension performance at speeds of 0–20 m/s is analyzed.Next,the three main components within the ADRC controller are designed for the second-order controlled system,and optimization algorithms are used to optimize its internal parameters.Finally,the performance of the traditional passive suspension,the PID-based controllable dynamic inertial suspension,and the ADRC-based controllable dynamic inertial suspension are analyzed under different road inputs.Simulation results show that,under sinusoidal road input,the ADRC-based controllable dynamic inertial suspension exhibits a 52.3%reduction in the low-frequency resonance peak in the vehicle body acceleration gain diagram compared to the traditional passive suspension,with significant performance optimization in the high-frequency range.Under random road input,the ADRC-based controllable dynamic inertial suspension achieves a 29.53%reduction in the root mean square value of vehicle body acceleration and a 14.87%reduction in dynamic tire load.This indicates that the designed controllable dynamic inertial suspension possesses excellent vibration isolation performance. 展开更多
关键词 HMDV static eccentricity ADRC dynamic inertial suspension road excitation
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