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Three-dimensional finite element analysis of weakened roots restored with different cements in combination with titanium alloy posts 被引量:26
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作者 LI Li-li WANG Zhong-yi +6 位作者 BAI Zhong-cheng MAO Yong GAO Bo XIN Hai-tao ZHOU Bing ZHANG Yong LIU Bing 《Chinese Medical Journal》 SCIE CAS CSCD 2006年第4期305-311,共7页
Background It is very difficult and relatively unpredictable to preserve and restore severely weakened pulpless roots. To provide much needed benefit basis for clinical practice, this study was carried out to analyze ... Background It is very difficult and relatively unpredictable to preserve and restore severely weakened pulpless roots. To provide much needed benefit basis for clinical practice, this study was carried out to analyze the stress distribution in weakened roots restored with different cements in combination with titanium alloy posts. Finite element analysis (FEA) was employed in the study. Methods A pseudo three-dimensional model of a maxillary central incisor with flared root canal, theoretically restored with titanium alloy posts in combination with different cements, was established. The analysis was performed by use of ANSYS software. The tooth was assumed to be isotropic, homogenous and elastic. A load of 100 N at an angle of 45° to the longitudinal axis was applied at the palatal surface of the crown. The distributions of stresses in weakened roots filled with cements of different elastic modulus were analyzed by the three-dimensional FEA model. Results Several stress trends were observed when the stress cloud atlas obtained in the study was analyzed. With the increase of the elastic modulus of cements from 1.8 GPa to 22.4 GPa, the stress values in dentin decreased from 39.58 MPa to 31.43 MPa and from 24.51 MPa to 20.76 MPa (respectively, for maximum principle stress values and Von Mises stress values). When Panavia F and zinc phosphate cement were used, the stress peak values in dentin were very small with no significant difference observed, and the Von Mises stress values were 20.87 MPa and 20.76 MPa respectively. On the other hand, maximum principle stress value and Von Mises stress value in cement layer increased with the increase of the elastic modulus of cements. Conclusions The result of this study demonstrated that elastic modulus was indeed one of the important parameters to evaluate property of the cements. Our three-dimensional FEA model study also found that the cement with elastic modulus similar to that of dentin could reinforce weakened root and reduce the stress in dentin. Thus, it may be a better choice for the restoration of weakened roots in clinical practice. 展开更多
关键词 weakened root CEMENTS finite element analysis stress distribution
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Survey and clinical considerations of gender identity in lower primary school children 被引量:1
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作者 Ya-Lin Zhang Hong-Mei Zhang +3 位作者 Jing-Xia Xu Qi-Ying Zhou He Wang Xiao-Cheng Pan 《World Journal of Psychiatry》 SCIE 2024年第1期36-43,共8页
BACKGROUND Gender consciousness directly affects the development of gender identity,which is a continuous and lifelong process.Meanwhile,hospitalization is a part of many children's lives and has an impact on thei... BACKGROUND Gender consciousness directly affects the development of gender identity,which is a continuous and lifelong process.Meanwhile,hospitalization is a part of many children's lives and has an impact on their gender development.AIM To investigate the current situation of gender identity in lower primary school children by conducting a survey of 202 hospitalized children in the lower grades and to provide a theoretical basis and foundation for the cultivation of gender identity and medical treatment of children based on the results.This study aims to inspire clinical medical staff to scientifically and reasonably arrange hospital wards for lower primary school children and pay attention to gender protection during the medical treatment process and to help children shape a unified and clear gender identity,which will enable them to better integrate into society and promote their personality development.METHODS The gender consciousness scale for elementary and middle school students was RESULTS Gender identity was already present in lower primary school children.The children's gender roles and gender equality consciousness were strong,exceeding the critical value,but their gender characteristics,gender identity,and gender ideal consciousness were weak.Children aged 6 had the weakest gender identity,and girls had significantly stronger gender identity than boys.CONCLUSION Gender identity is already present in lower primary school children,providing a basis and inspiration for the cultivation of gender identity and medical treatment of lower primary school children.Clinical medical staff should be aware of and understand these results and should scientifically and reasonably arrange hospital wards for lower primary school children. 展开更多
关键词 School-age children Gender consciousness Gender identity HOSPITALIZATION Gender weakening
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Influencing factors analysis of hard limestone reformation and strength weakening under acidic effect
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作者 HOU Ming-xiao HUANG Bing-xiang +2 位作者 ZHAO Xing-long JIAO Xue-jie ZHENG Chen-yang 《Journal of Central South University》 SCIE EI CAS CSCD 2024年第7期2446-2466,共21页
Roof disaster has always been an important factor restricting coal mine safety production.Acidic effect can reform the rock mass structure to weaken the macroscopic strength characteristics,which is an effective way t... Roof disaster has always been an important factor restricting coal mine safety production.Acidic effect can reform the rock mass structure to weaken the macroscopic strength characteristics,which is an effective way to control the hard limestone roof.In this study,the effects of various factors on the reaction characteristics and mechanical properties of limestone were analyzed.The results show that the acid with stronger hydrogen production capacity after ionization(pK_(a)<0)has more prominent damage to the mineral grains of limestone.When pKa increases from−8.00 to 15.70,uniaxial compressive strength and elastic modulus of limestone increase by 117.22%and 75.98%.The influence of acid concentration is manifested in the dissolution behavior of mineral crystals,the crystal defects caused by large-scale acid action will lead to the deterioration of limestone strength,and the strength after 15%concentration reformation can be reduced by 59.42%.The effect of acidification time on limestone has stages and is the most obvious in the initial metathesis reaction stage(within 60 min).The key to the strength damage of acidified limestone is the participation of hydrogen ions in the reaction system.Based on the analytic hierarchy process method,the influence weights of acid type,acid concentration and acidification time on strength are 24.30%,59.54% and 16.16%,respectively.The research results provide theoretical support for the acidification control of hard limestone roofs in coal mines. 展开更多
关键词 hard roof acidic effect structural reformation strength weakening influencing factors
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Dynamic simulation insights into friction weakening effect on rapid long-runout landslides:A case study of the Yigong landslide in the Tibetan Plateau,China
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作者 Zi-zheng Guo Xin-yong Zhou +3 位作者 Da Huang Shi-jie Zhai Bi-xia Tian Guang-ming Li 《China Geology》 CAS CSCD 2024年第2期222-236,共15页
This study proposed a novel friction law dependent on velocity,displacement and normal stress for kinematic analysis of runout process of rapid landslides.The well-known Yigong landslide occurring in the Tibetan Plate... This study proposed a novel friction law dependent on velocity,displacement and normal stress for kinematic analysis of runout process of rapid landslides.The well-known Yigong landslide occurring in the Tibetan Plateau of China was employed as the case,and the derived dynamic friction formula was included into the numerical simulation based on Particle Flow Code.Results showed that the friction decreased quickly from 0.64(the peak)to 0.1(the stead value)during the 5s-period after the sliding initiation,which explained the behavior of rapid movement of the landslide.The monitored balls set at different sections of the mass showed similar variation characteritics regarding the velocity,namely evident increase at the initial phase of the movement,followed by a fluctuation phase and then a stopping one.The peak velocity was more than 100 m/s and most particles had low velocities at 300s after the landslide initiation.The spreading distance of the landslide was calculated at the two-dimension(profile)and three-dimension scale,respectively.Compared with the simulation result without considering friction weakening effect,our results indicated a max distance of about 10 km from the initial unstable position,which fit better with the actual situation. 展开更多
关键词 Rapid long-runout landslide PFC Friction weakening Three-dimension Numerical simulation Tibetan Plateau Hydrogeology Engineering Geological hazards survey engineering
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Borehole stability in naturally fractured rocks with drilling mud intrusion and associated fracture strength weakening:A coupled DFN-DEM approach
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作者 Yaoran Wei Yongcun Feng +4 位作者 Zhenlai Tan Tianyu Yang Xiaorong Li Zhiyue Dai Jingen Deng 《Journal of Rock Mechanics and Geotechnical Engineering》 SCIE CSCD 2024年第5期1565-1581,共17页
Borehole instability in naturally fractured rocks poses significant challenges to drilling.Drilling mud invades the surrounding formations through natural fractures under the difference between the wellbore pressure(P... Borehole instability in naturally fractured rocks poses significant challenges to drilling.Drilling mud invades the surrounding formations through natural fractures under the difference between the wellbore pressure(P w)and pore pressure(P p)during drilling,which may cause wellbore instability.However,the weakening of fracture strength due to mud intrusion is not considered in most existing borehole stability analyses,which may yield significant errors and misleading predictions.In addition,only limited factors were analyzed,and the fracture distribution was oversimplified.In this paper,the impacts of mud intrusion and associated fracture strength weakening on borehole stability in fractured rocks under both isotropic and anisotropic stress states are investigated using a coupled DEM(distinct element method)and DFN(discrete fracture network)method.It provides estimates of the effect of fracture strength weakening,wellbore pressure,in situ stresses,and sealing efficiency on borehole stability.The results show that mud intrusion and weakening of fracture strength can damage the borehole.This is demonstrated by the large displacement around the borehole,shear displacement on natural fractures,and the generation of fracture at shear limit.Mud intrusion reduces the shear strength of the fracture surface and leads to shear failure,which explains that the increase in mud weight may worsen borehole stability during overbalanced drilling in fractured formations.A higher in situ stress anisotropy exerts a significant influence on the mechanism of shear failure distribution around the wellbore.Moreover,the effect of sealing natural fractures on maintaining borehole stability is verified in this study,and the increase in sealing efficiency reduces the radial invasion distance of drilling mud.This study provides a directly quantitative prediction method of borehole instability in naturally fractured formations,which can consider the discrete fracture network,mud intrusion,and associated weakening of fracture strength.The information provided by the numerical approach(e.g.displacement around the borehole,shear displacement on fracture,and fracture at shear limit)is helpful for managing wellbore stability and designing wellbore-strengthening operations. 展开更多
关键词 Borehole stability Naturally fractured rocks Weakening of fracture strength Discrete fracture network Distinct element method
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Experimental investigation on the origin of carbonaceous materials in the fault zone of the Wenchuan earthquake
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作者 Deyang Shi Yaowei Liu Jin Shi 《Earthquake Science》 2024年第3期189-199,共11页
Carbonaceous materials in seismic fault zones may considerably influence seismic fault slip;however,the formation mechanism of carbonaceous materials remains unclear.In this study,we proposed a novel hypothesis for th... Carbonaceous materials in seismic fault zones may considerably influence seismic fault slip;however,the formation mechanism of carbonaceous materials remains unclear.In this study,we proposed a novel hypothesis for the formation of carbonaceous materials in fault gouge.Thus,we conducted a CO_(2) hydrogenation experiment in a high-temperature reactor at a co-seismic temperature,with fault gouge formed during the Wenchuan earthquake as the catalyst.Our experimental results demonstrate that carbonaceous materials in fault zones are formed on the fault gouge during the chemical reaction process,suggesting that the carbonaceous materials are possibly generated from the catalytic hydrogenation of CO_(2),followed by thermal cracking of its products.The results of this study provide a theoretical basis for understanding fault behavior and earthquake physics. 展开更多
关键词 carbon dioxide hydrogenation carbonaceous mineral formation co-seismic temperature fault weakening fault gouge
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Stability analysis of intermittently jointed rock slopes based on the stepped failure mode
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作者 LI Dejian FU Junwen +4 位作者 LI Hekai CHENG Xiao ZHAO Lianheng ZHANG Yingbin PENG Xinyan 《Journal of Mountain Science》 SCIE CSCD 2024年第3期1019-1035,共17页
In practical engineering,due to the noncontinuity characteristics of joints in rock slopes,in addition to plane failure,stepped sliding failure may occur for intermittently jointed rock slopes.Especially for intermitt... In practical engineering,due to the noncontinuity characteristics of joints in rock slopes,in addition to plane failure,stepped sliding failure may occur for intermittently jointed rock slopes.Especially for intermittently bedding jointed rock slopes,the correlation and difference in strength parameters between joints and rock bridges,along with the various failure modes and intermittency of rock bridges,contribute to the complexity of stepped failure modes and the unpredictability of failure regions.Based on the upper-bound limit analysis method and multi-sliders step-path failure mode,considering the shear and tensile failure of rock bridges and the weakened relationship between the strength parameters of rock bridges and jointed surfaces,by introducing the modified M-C failure criterion and the formula for calculating the energy consumption of tensile failure of rock bridges,two failure mechanisms are constructed to obtain the safety factor(F_(s))of intermittently jointed rock slopes.The sequential quadratic programming method is used to obtain the optimal upper-bound solution for F_(s).The influence of multiple key parameters(slope height H,horizontal distance L,Slope angleβ,shear strength parameters of the rock bridgeφr and cr,Dimensionless parameter u,weakening coefficients of the internal friction angle and cohesion between the rock bridges and joint surfaces Kφand Kc)on the stability analysis of intermittently jointed rock slopes under the shear failure mode of rock bridges as well as under the tensile failure mode is also explored.The reliability of the failure mechanisms is verified by comparative analysis with theoretical results,numerical results,and landslide cases,and the variation rules of F_(s)with each key parameter are obtained.The results show that F_(s) varies linearly withφr and cr of the rock bridge and with K_(φ)and K_(c),whereas F_(s)changes nonlinearly with H and L.In particular,with the increase in Kφand Kc,Fs increases by approximately 52.78%and 171.02%on average,respectively.For rock bridge tensile failure,F_(s) shows a nonlinearly positive correlation withφr,cr,Kφand Kc.In particular,with the increase in Kφand Kc,Fs increases by approximately 13%and 61.69%on average,respectively.Fs decreases rapidly with increasing slope gradientβand decreasing dimensionless parameterμ.When Kφand Kc are both less than 1.0,the stepped sliding surface occurs more easily than the plane failure surface,especially in the case of tensile failure of the rock bridge.In addition,rock slopes with higher strength parameters,taller heights,and greater weakening coefficients are prone to rock bridge tension failure with lower Fs,and more attention should be given to the occurrence of such accidents in actual engineering. 展开更多
关键词 Jointed rock slopes Stepped sliding failure Weakening characteristics Modified M‒C failure criterion
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Review of Field Weakening Control Strategies of Permanent Magnet Synchronous Motors
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作者 Runze Jing Gaolin Wang +1 位作者 Guoqiang Zhang Dianguo Xu 《CES Transactions on Electrical Machines and Systems》 EI CSCD 2024年第3期319-331,共13页
Due to high power density,high efficiency,and accurate control performance,permanent magnet synchronous motors(PMSMs)have been widely adopted in equipment manufacturing and energy transformation fields.To expand the s... Due to high power density,high efficiency,and accurate control performance,permanent magnet synchronous motors(PMSMs)have been widely adopted in equipment manufacturing and energy transformation fields.To expand the speed range under finite DC-bus voltage,extensive research on field weakening(FW)control strategies has been conducted.This paper summarizes the major FW control strategies of PMSMs,which are categorized into calculation-based methods,voltage closed-loop control methods,and model predictive control related methods.The existing strategies are analyzed and compared according to performance,robustness,and execution difficulty,which can facilitate the implementation of FW control. 展开更多
关键词 Calculation-based methods Field weakening control Model predictive control Permanent magnet synchronous motor OVERMODULATION Voltage closed-loop control
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SEEPAGE CONTROL OF WEAKENED ROCK FOUNDATION OF GEZHOUBA ERJIANG-SLUICE
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作者 Cao Dun-lu Xu Zhong-sheng Wu Song-gui, Yangtze Research. Institute, wuhan, P.R. China 《Journal of Hydrodynamics》 SCIE EI CSCD 1989年第3期36-46,共11页
It is the presence of weakened intercalations that makes the foundation of Gezhouba Erjiang-Sluice complex. Seepage control installation must be able not only to reduce seepapge pressure, but also to protect weakened ... It is the presence of weakened intercalations that makes the foundation of Gezhouba Erjiang-Sluice complex. Seepage control installation must be able not only to reduce seepapge pressure, but also to protect weakened intercalations from encroachment of seepage. In this paper theoretical analysis has been conducted to prove that well system is highly effective seepage control installation meeting this demand. By means of in-situ monitoring it has been verified that proposed seepage control measure relying mainly on drainage is of success. Seepage stability of weakened intercalations must be considered in employing drains to control seepage, while the seepage deformation of weakened intercalations is different from that of ordinary sand-gravel. Mechanism of seepage deformation of weakened intercalations has been expounded. Seepage wedging is a special type of seepage deformation for weakened intercalations, It is shown clearly that seepage deformation of intercalations does not mean seepage failure of the foundation. In such a foundation as that of Gezhouba sluice, the permeability is distributed randomly. So the seepage field is an unstable, stochastic field. 展开更多
关键词 SEEPAGE CONTROL OF weakened ROCK FOUNDATION OF GEZHOUBA ERJIANG-SLUICE ROCK
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Etiopathogenic theories about long COVID
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作者 Luis Del Carpio-Orantes 《World Journal of Virology》 2023年第3期204-208,共5页
The main etiopathogenic theories of long coronavirus disease(COVID)are listed and a conjunction of them is carried out with the objective of deciphering the pathophysiology of the entity,finally the main lines of trea... The main etiopathogenic theories of long coronavirus disease(COVID)are listed and a conjunction of them is carried out with the objective of deciphering the pathophysiology of the entity,finally the main lines of treatment existing in real life are discussed(Paxlovid,use of antibiotics in dysbiosis,triple anticoagulant therapy,temelimab). 展开更多
关键词 Long COVID Viral persistence Amyloid microthrombosis DYSBIOSIS weakened immune system Paxlovid Triple therapy
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Strength weakening and its micromechanism in water–rock interaction,a short review in laboratory tests 被引量:5
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作者 Cun Zhang Qingsheng Bai +3 位作者 Penghua Han Lei Wang Xiaojie Wang Fangtian Wang 《International Journal of Coal Science & Technology》 EI CAS CSCD 2023年第1期18-32,共15页
Water–rock interaction(WRI)is a topic of interest in geology and geotechnical engineering.Many geological hazards and engineering safety problems are severe under the WRI.This study focuses on the water weakening of ... Water–rock interaction(WRI)is a topic of interest in geology and geotechnical engineering.Many geological hazards and engineering safety problems are severe under the WRI.This study focuses on the water weakening of rock strength and its infuencing factors(water content,immersion time,and wetting–drying cycles).The strength of the rock mass decreases to varying degrees with water content,immersion time,and wetting–drying cycles depending on the rock mass type and mineral composition.The corresponding acoustic emission count and intensity and infrared radiation intensity also weaken accordingly.WRI enhances the plasticity of rock mass and reduces its brittleness.Various microscopic methods for studying the pore characterization and weakening mechanism of the WRI were compared and analyzed.Various methods should be adopted to study the pore evolution of WRI comprehensively.Microscopic methods are used to study the weakening mechanism of WRI.In future work,the mechanical parameters of rocks weakened under long-term water immersion(over years)should be considered,and more attention should be paid to how the laboratory scale is applied to the engineering scale. 展开更多
关键词 Water–rock interaction Weakening mechanism Water content Immersion time Wetting–drying cycles Microscopic methods
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Mechanism of plasticity enhancement of AZ31B magnesium alloy sheet by accumulative alternating back extrusion 被引量:3
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作者 Ye Wang Feng Li +2 位作者 Nan Bian Hua Qiu Du Peng Da Huo 《Journal of Magnesium and Alloys》 SCIE EI CAS CSCD 2023年第5期1791-1801,共11页
Accumulative alternating back extrusion was a potential fine-grain modification method.In this paper,it was an innovative attempt to develop high-performance magnesium alloy sheet by this process.Under the condition o... Accumulative alternating back extrusion was a potential fine-grain modification method.In this paper,it was an innovative attempt to develop high-performance magnesium alloy sheet by this process.Under the condition of 350 K,commercial AZ31 magnesium alloy was made into billet by accumulative alternating back extrusion,and then extruded into fine-grain magnesium alloy sheet.Through a systematic study of its microstructure and mechanical properties,the results showed that the initial state had an important influence on the evolution of the structure during extrusion.After accumulative alternating back extrusion to produce the billet,the grain size of the sheet obtained by extrusion was significantly refined,which was related to the accumulation of deformation and grain refinement during the alternating loading process.Grain refinement caused the proportion of dynamic recrystallization inside the sheet with 2 cycles of accumulative alternating back extrusion to drop to 27%.With the increase of extrusion cycles from 2 to 4,the high density of dislocations led to an increase in the proportion of dynamic recrystallization and finer grains.The texture changed from strong basal texture to weak bimodal texture.The results of uniaxial tensile test show that due to grain refinement and texture change,the yield strength was significantly reduced,and the plasticity was significantly improved.It was verified that accumulative alternating back extrusion was meaningful for subsequent processing,and it also provided scientific guidance for the development of fine-grained magnesium alloy sheet. 展开更多
关键词 Magnesium alloy Alternating back extrusion Microstructure uniformity Bimodal texture Texture weakening Sheet anisotropy
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Super Typhoon Hinnamnor(2022)with a Record-Breaking Lifespan over the Western North Pacific 被引量:2
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作者 Qian WANG Dajun ZHAO +4 位作者 Yihong DUAN Shoude GUAN Lin DONG Hongxiong XU Hui WANG 《Advances in Atmospheric Sciences》 SCIE CAS CSCD 2023年第9期1558-1566,共9页
Super Typhoon Hinnamnor(2022)was a rare and unique western North Pacific typhoon,and throughout its lifespan,it exhibited all of the major features that pose current challenges in typhoon research.Specifically,during ... Super Typhoon Hinnamnor(2022)was a rare and unique western North Pacific typhoon,and throughout its lifespan,it exhibited all of the major features that pose current challenges in typhoon research.Specifically,during different stages of its lifespan,it experienced a sudden change of track,underwent rapid intensification,interacted and merged with another vortex,expanded in size,underwent rapid weakening,produced a strong cold wake,exhibited eyewall replacement,and underwent extratropical transition.Therefore,a timely identification and review of these features of Hinnamnor(2022),as reported in this article,will help update and enrich the case sets for each of these scientific issues and provide a background for more in-depth mechanistic studies of typhoon track,intensity,and structural changes in the future.We also believe that Hinnamnor(2022)can serve as an excellent benchmark to quickly evaluate the overall performance of different numerical models in predicting typhoon’s track,intensity,and structural changes. 展开更多
关键词 sudden track change rapid intensification rapid weakening vortex merging extratropical transition
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A Novel Belief Rule-Based Fault Diagnosis Method with Interpretability 被引量:1
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作者 Zhijie Zhou Zhichao Ming +4 位作者 Jie Wang Shuaiwen Tang You Cao Xiaoxia Han Gang Xiang 《Computer Modeling in Engineering & Sciences》 SCIE EI 2023年第8期1165-1185,共21页
Fault diagnosis plays an irreplaceable role in the normal operation of equipment.A fault diagnosis model is often required to be interpretable for increasing the trust between humans and the model.Due to the understan... Fault diagnosis plays an irreplaceable role in the normal operation of equipment.A fault diagnosis model is often required to be interpretable for increasing the trust between humans and the model.Due to the understandable knowledge expression and transparent reasoning process,the belief rule base(BRB)has extensive applications as an interpretable expert system in fault diagnosis.Optimization is an effective means to weaken the subjectivity of experts in BRB,where the interpretability of BRB may be weakened.Hence,to obtain a credible result,the weakening factors of interpretability in the BRB-based fault diagnosis model are firstly analyzed,which are manifested in deviation from the initial judgement of experts and over-optimization of parameters.For these two factors,three indexes are proposed,namely the consistency index of rules,consistency index of the rule base and over-optimization index,tomeasure the interpretability of the optimizedmodel.Considering both the accuracy and interpretability of amodel,an improved coordinate ascent(I-CA)algorithmis proposed to fine-tune the parameters of the fault diagnosis model based on BRB.In I-CA,the algorithm combined with the advance and retreat method and the golden section method is employed to be one-dimensional search algorithm.Furthermore,the random optimization sequence and adaptive step size are proposed to improve the accuracy of the model.Finally,a case study of fault diagnosis in aerospace relays based on BRB is carried out to verify the effectiveness of the proposed method. 展开更多
关键词 Fault diagnosis belief rule base INTERPRETABILITY weakening factors improved coordinate ascent
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Marginal weakening promoted rift propagation of the Petermann Ice Shelf in northwestern Greenland from 2016 to 2022
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作者 LI Daan JIANG Liming +1 位作者 HUANG Ronggang LU Xi 《Advances in Polar Science》 CSCD 2023年第3期220-231,共12页
Ice-shelf rifts are precursors of glacier calving, and thus they serve as indicators of ice shelf instability, especially under oceanic and atmospheric warming conditions. Therefore, understanding the dynamic processe... Ice-shelf rifts are precursors of glacier calving, and thus they serve as indicators of ice shelf instability, especially under oceanic and atmospheric warming conditions. Therefore, understanding the dynamic processes underlying rift propagation and the associated damage mechanisms is essential to evaluate ice-shelf instability and to predict glacier calving. In this study, we investigated the effect of marginal weakening on rift propagation on the ice shelf of the Petermann Glacier, among the largest in Greenland, during 2016-2022. First, we analyzed satellite optical images to monitor rift growth(length and width) by tracking the tip trajectory of three large rifts identified on the Petermann Ice Shelf. Then, we estimated rift depth using ArcticDEM and ICESat-2 data. Our results indicated consistent increases of the rift widths and depths over the study period, with mean values of 133 m·a^(-1) and 0.3 m·a^(-1), respectively. We also combined remote-sensing observations with an ice-sheet numerical model to calculate the stress and damage fields on the Petermann Ice Shelf and to assess the ice shelf margin stability and strength. We determined that damage and lateral shear in the fracture zone degraded ice shelf integrity by decreasing the contact length with the fjord wall. In conclusion, marginal weakening effectively promoted rift propagation on the Petermann Ice Shelf, increasing the risk of future glacier calving. 展开更多
关键词 rift propagation marginal weakening remote sensing damage mechanism
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The Non-Singular Fast Terminal Sliding Mode Control of Interior Permanent Magnet Synchronous Motor Based on Deep Flux Weakening Switching Point Tracking
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作者 Xiangfei Li Yang Yin +2 位作者 Yang Zhou Wenchang Liu Kaihui Zhao 《Energy Engineering》 EI 2023年第2期277-297,共21页
This paper presents a novel non-singular fast terminal sliding mode control(NFTSMC)based on the deep flux weakening switching point tracking method in order to improve the control performance of permanent interior mag... This paper presents a novel non-singular fast terminal sliding mode control(NFTSMC)based on the deep flux weakening switching point tracking method in order to improve the control performance of permanent interior magnet synchronous motor(IPMSM)drive systems.The mathematical model of flux weakening(FW)control is established,and the deep flux weakening switching point is calculated accurately by analyzing the relationship between the torque curve and voltage decline curve.Next,a second-order NFTSMC is designed for the speed loop controller to ensure that the system converges to the equilibrium state in finite time.Then,an extended sliding mode disturbance observer(ESMDO)is designed to estimate the uncertainty of the system.Finally,compared with both the PI control and sliding mode control(SMC)by simulations and experiments with different working conditions,the method proposed has the merits of accelerating convergence,improving steady-state accuracy,and minimizing the current and torque pulsation. 展开更多
关键词 Interior permanentmagnet synchronousmotor(IPMSM) flux weakening(FW)control non-singular fast terminal sliding mode control(NFTSMC) extended sliding mode disturbance observer(ESMDO)
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Effect of calcium addition on microstructure and texture modification of Mg rolled sheets 被引量:9
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作者 丁汉林 张鹏 +1 位作者 程广萍 Shigeharu KAMADO 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2015年第9期2875-2883,共9页
The mechanical properties and texture of AM60(Mg-6.0Al-0.3Mn,mass fraction %) and ZXM200(Mg-1.6Zn-0.5Ca-0.2Mn) Mg alloys subjected to multi-pass hot rolling were investigated.The finer recrystallized grains usuall... The mechanical properties and texture of AM60(Mg-6.0Al-0.3Mn,mass fraction %) and ZXM200(Mg-1.6Zn-0.5Ca-0.2Mn) Mg alloys subjected to multi-pass hot rolling were investigated.The finer recrystallized grains usually exhibit particular preferred orientations and then alter the total texture feature of rolled sheets.Ca solid solution into Mg matrix serves to the formation of texture component with c-axis rotated away from normal direction towards transverse direction and then weakens the overall texture intensity,resulting in a similar anisotropic characteristic to RE-containing Mg alloys. 展开更多
关键词 Mg sheets hot rolling dynamic recrystallization Ca addition texture weakening
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Seismic performance and comparison of three different I beam to box column joints 被引量:2
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作者 Z.Saneei Nia A.Mazroi +1 位作者 M.Ghassemieh H.Pezeshki 《Earthquake Engineering and Engineering Vibration》 SCIE EI CSCD 2014年第4期717-729,共13页
Despite the inherently advantages of the box column, finding the best option for the I beam to the box column connection is the main challenge in using the box column as a structural member for special moment frames. ... Despite the inherently advantages of the box column, finding the best option for the I beam to the box column connection is the main challenge in using the box column as a structural member for special moment frames. In this paper, the seismic performance of urtreinforced connection, weakened connection and strengthened connection was evaluated through a comprehensive experimental program. The seismic comparisons were fabricated by assessing the strength, ductility and energy dissipation in each configuration. Three full scale tests with several connections were carried out. All the specimens were subjected to cyclic loading and prior to failure by forming a plastic hinge in the beam, all the connections managed to reach an inelastic rotation of more than 6.0% rad. The experimental and analytical results showed that the seismic performance of the strengthened connection with flange and shear plates turned out to be the most effective in the beam to the box column connection. Moreover, the normalized stress distribution of the continuity plates revealed that the possibility of the weld fracture in unreinforced connection is more than other specimens. 展开更多
关键词 box column special moment frame unreinforced connection weakened connection strengthened connection seismic comparison
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Analysis on seismic performance of a new type of joint in steel structures 被引量:1
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作者 Li Xiaodong Ma Guangtian Yan Yinji 《Journal of Southeast University(English Edition)》 EI CAS 2021年第3期290-298,共9页
To examine the seismic performance of a newly fabricated weakened joint at the beam end position,four groups of energy-consuming steel plates with different weakening depths and thicknesses were subjected to horizonta... To examine the seismic performance of a newly fabricated weakened joint at the beam end position,four groups of energy-consuming steel plates with different weakening depths and thicknesses were subjected to horizontal cyclic reciprocating loading tests on beam ends.The tests were designed to evaluate the beams'hysteresis curve,skeleton curve,bearing capacity degradation curve,stiffness degradation curve,and ductility and the nodes'energy dissipation capacity.The test results show that a newly fabricated joint will not undergo brittle damage when the beam-column joint is welded at a displacement of 105 mm.Thus,the hysteresis curve will show an inverse S shape,and an obvious slip phenomenon will occur,which is mainly due to splicing.The diameter of the bolt connecting the slab to the beam flange is slightly smaller than the aperture.Due to the existence of slippage,the skeleton curve has no evident yield point.The joint ductility coefficient is less than 3.0,and the initial rotational stiffness of the joint is also small.The buckling of the splicing panel causes a rapid decrease in the joint bearing capacity.The main approaches,appropriately reducing the weakening depth and increasing the thickness of the splicing plate,can delay the occurrence of buckling and improve the ductility of the joint. 展开更多
关键词 steel structure energy-dissipating members weakened joint seismic performance cyclic loading tests
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Further Political Stability Ahead
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《Contemporary International Relations》 1994年第5期10-10,共1页
General stability will prevail in the new-born country. Not resigned to theirdefeat, some white ultra-rightists and black traditional conservatives willcontinue to provoke troubles, resort to bloodshed and disturb soc... General stability will prevail in the new-born country. Not resigned to theirdefeat, some white ultra-rightists and black traditional conservatives willcontinue to provoke troubles, resort to bloodshed and disturb social security, yetthey have all been greatly weakened and isolated after four years of repeated trial ofstrength in the course of the democratic transition and will be unable to reverse 展开更多
关键词 prevail weakened RESORT unable repeated THINKING PARTY TOWARD hopes ADMINISTRATION
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