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Gravel hardness effect on compaction characteristics of gravelly soil
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作者 SHI Yunfang LI Shengang +1 位作者 JIANG Chen LIU Jinning 《Journal of Mountain Science》 SCIE CSCD 2024年第4期1432-1443,共12页
The compaction characteristics of gravelly soil are affected by gravel hardness.To investigate the evolution and influencing mechanism of different gravel hardness on the compaction characteristics of gravelly soil,he... The compaction characteristics of gravelly soil are affected by gravel hardness.To investigate the evolution and influencing mechanism of different gravel hardness on the compaction characteristics of gravelly soil,heavy compaction tests and crushing tests were conducted on gravelly soils with gravels originated from hard,soft and extremely soft rocks.According to orthogonal experiments and variance analysis,it was found that hardness has a significant impact on the maximum dry density of gravelly soil,followed by gravel content,and lastly,moisture content.For gravel compositions with an average saturated uniaxial compressive strength less than 60 MPa,the order of compacted maximum dry density is soft gravels>hard gravels>extremely soft gravels.Each type of gravelly soil has a threshold for gravel content,with 60%for hard and soft gravels and 50%for extremely soft gravels.Beyond these thresholds,the compacted dry density decreases significantly.There is a certain interaction between hardness,gravel content,and moisture content.Higher hardness increases the influence of gravel content,whereas lower hardness increases the influence of moisture content.Gravelly soils with the coarse aggregate(CA)between 0.7 and 0.8 typically achieve higher dry densities after compaction.In addition,the prediction equations for the particle breakage rate and CA ratio in the Bailey method were proposed to estimate the compaction performance of gravelly soil preliminarily.The results further revealed the compaction mechanism of different gravelly soils and can provide reference for subgrade filling construction. 展开更多
关键词 Gravelly soil hardness Compaction characteristics Crushing characteristics Particle breakage rate Bailey method
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Influence of quenching medium on the dendrite morphology,hardness,and tribological behaviour of cast Cu-Ni-Sn spinodal alloy for defence application 被引量:1
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作者 Bipin Sankar Karthik V Shankar +4 位作者 Vamu Sunil Hemanth Kashyap S Nikhil Nair Adarsh A.Nair Abhinav P M 《Defence Technology(防务技术)》 SCIE EI CAS CSCD 2023年第12期83-100,共18页
Cu-Ni-Sn spinodal alloys(Spinodal bronze)are potential materials with robust applications in components associated with defence applications like bearings,propellers,bushes,and shafts of heavily loaded aircraft,off-ro... Cu-Ni-Sn spinodal alloys(Spinodal bronze)are potential materials with robust applications in components associated with defence applications like bearings,propellers,bushes,and shafts of heavily loaded aircraft,off-road vehicles,and warships.This paper presents a comparative study using water,Brine solution,and SAE 40 oil as the quenching media in regular bronze(Cu-6Sn)and spinodal bronze(Cu-9Ni-6Sn)alloys.Morphological analysis was conducted by optical microscopy,transmission electron microscopy(TEM),and X-ray diffraction technique(XRD)on bronze and spinodal bronze samples immersed in the three different quenching media to understand the grain size and hardness values better.Tribological analysis was performed to analyze the effect of quenching media on the wear aspects of bronze and spinodal bronze samples.The hardness value of the brine-aged spinodal bronze samples was as high as 320 Hv,and the grain size was very low in the range of 60μm.A quantitative comparison between brine-aged regular bronze and brine-aged spinodal bronze showed that the hardness(Hv)was almost 80%higher for brine-aged spinodal bronze.Further,the grain size was approximately 30%finer for spinodal bronze when compared with regular bronze.When the load was increased in spinodal bronze samples,there was an initial dip in wear rate followed by a marginal increase.There was a steady increase in friction coefficient with a rise in load for brine-aged regular bronze and spinodal bronze samples.These results indicate that brine solution is the most effective quenching medium for cast Cu-Ni-Sn spinodal alloys. 展开更多
关键词 Quenching Water BRINE SAE 40 oil Grain size hardness Wear rate Spinodal decomposition CuSn Spinodal alloy CuNiSn
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Study on Hardness of Ion Implantation Layer
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作者 Xu Shiru, Qiu Chengferg, Zhang Qiaogen, Li Zhong Yang Zhigui Electronic Engineering Department of Xi’an Jiaotong University, Xi’an, China 《真空科学与技术学报》 EI CAS CSCD 1992年第Z1期183-186,共4页
The surface layer of beryllium, specimen, has been strengthened by ion implantation. Its microhardness was measured. The hardness of surface layer has been calculated from the microhardness. The experimental data of t... The surface layer of beryllium, specimen, has been strengthened by ion implantation. Its microhardness was measured. The hardness of surface layer has been calculated from the microhardness. The experimental data of the wear rate indirectly Confirmed the reasonableness of the result of calculation. It is shown that the hardness of the surface layer strengthened, by ion implantation is nine times higher than that of beryllium itself. The relation between hardness and implantation dose was analysed and the best dose was obtained. 展开更多
关键词 rate In Study on hardness of Ion Implantation Layer
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Effects of Strain Rate and Deformation Temperature on Microstructures and Hardness in Plastically Deformed Pure Aluminum 被引量:12
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作者 F. Huang N.R. Taot K. Lu 《Journal of Materials Science & Technology》 SCIE EI CAS CSCD 2011年第1期1-7,共7页
The microstructures and hardness of pure Al samples subjected to plastic deformation with different tem- peratures and strain rates were investigated. The results showed that the strain-induced grain refinement is sig... The microstructures and hardness of pure Al samples subjected to plastic deformation with different tem- peratures and strain rates were investigated. The results showed that the strain-induced grain refinement is significantly benefited by increasing strain rate and reducing deformation temperature. The saturated size of refined subgrains in Al can be as small as about 240 nm in cryogenic dynamic plastic deformation (DPD). Grain boundaries of the DPD Al samples are low-angle boundaries due to suppression of dynamic recovery during deformation. Agreement of the measured hardness with the empirical Hall-Petch relation extrapolated from the coarse-grained Al implies that the low-angle boundaries can contribute to strengthening as effective as the conventional grain boundaries. 展开更多
关键词 Dynamic plastic deformation MICROSTRUCTURE hardness Strain rate TEMPERATURE
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Effect of Cooling Rate and Vanadium Content on the Microstructure and Hardness of Medium Carbon Forging Steel 被引量:8
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作者 Weijun Hui Yongjian Zhang +3 位作者 Chengwei Shao Silian Chen Xiaoli Zhao Han Dong 《Journal of Materials Science & Technology》 SCIE EI CAS CSCD 2016年第6期545-551,共7页
This paper reports the effect of cooling rate on the microstructure and hardness of a kind of medium carbon steel microalloyed with two levels of V content (0.15% and 0.28%) after hot deformation by using single com... This paper reports the effect of cooling rate on the microstructure and hardness of a kind of medium carbon steel microalloyed with two levels of V content (0.15% and 0.28%) after hot deformation by using single compression tests on a Gleeble-3800 thermal simulator. The results show that cooling rate has a significant effect on the microstructure and hardness of the tested steels. Both the fraction of pearlite and hardness increase with increasing cooling rate, whereas a further increase of the cooling rate above a critical value promotes the formation of acicular ferrite (AF), and thus leads to a decrease of hardness mainly owing to the decrease of pearlite fraction and replacing it by AF and the less effective precipita- tion strengthening. Increasing V content results in a significant increase of hardness, and this tendency enhances with increasing cooling rate until the formation of AF. Furthermore, increasing V content also significantly enhances the formation of AF structure at a lower cooling rate. The results also suggest that by controlling microstructure, especially the precipitation of fine V(C,N) particles through adjusting post- forging cooling, the strengthening and gradient function in one hot-forging part could be obtained. 展开更多
关键词 Cooling rate Microalloyed steel Vanadium Microstructure hardness Acicular ferrite
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Effect of cooling rate on microstructure, hardness, and residual stress of 0.28C-0.22Ti wear-resistant steel 被引量:2
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作者 Chen Dong Hui-bin Wu Xi-tao Wang 《Journal of Iron and Steel Research International》 SCIE EI CAS CSCD 2019年第8期866-874,共9页
The microstructure, hardness, and residual stress of 0.28C-0.22Ti wear-resistant steel produced with cooling rates varying from 80.0 to 0.3℃/s were determined using a dilatometer, scanning electron microscope, Vicker... The microstructure, hardness, and residual stress of 0.28C-0.22Ti wear-resistant steel produced with cooling rates varying from 80.0 to 0.3℃/s were determined using a dilatometer, scanning electron microscope, Vickers hardness tester, and nanoindentation tester. The results showed that the hardness of martensite decreased at a rate of approximately 0.935 HV/s with carbon diffusion time (the cooldown time required to transition from Ar3, 635-100℃). The range of the residual stress caused by the hard particles decreased with decreasing cooling rate, from - 400-300 MPa (cooling rate 40℃/s) to - 200-100 MPa (cooling rate 0.5℃/s), proving that the TiC particles significantly contributed to the residual stress in the high-titanium steels. 展开更多
关键词 Cooling rate MICROSTRUCTURE hardness TIC particle RESIDUAL stress
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Layer Thickness-Dependent Hardness and Strain Rate Sensitivity of Cu–Al/Al Nanostructured Multilayers
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作者 Ya-Qiang Wang Zhao-Qi Hou +4 位作者 Jin-Yu Zhang Xiao-Qing Liang Gang Liu Guo-Jun Zhang Jun Sun 《Acta Metallurgica Sinica(English Letters)》 SCIE EI CAS CSCD 2016年第2期156-162,共7页
Cu-Al/Al nanostructured metallic multilayers with Al layer thickness hAl varying from 5 to 100 nm were prepared, and their mechanical properties and deformation behaviors were studied by nanoindentation testing. The r... Cu-Al/Al nanostructured metallic multilayers with Al layer thickness hAl varying from 5 to 100 nm were prepared, and their mechanical properties and deformation behaviors were studied by nanoindentation testing. The results showed that the hardness increased drastically with decreasing hAl down to about 20 nm, whereafter the hardness reached a plateau that approaches the hardness of the alloyed Cu-Al monolithic thin films. The strain rate sensitivity (SRS, m), however, decreased monotonically with reducing hAl. The layer thickness-dependent strengthening mechanisms were discussed, and it was revealed that the alloyed Cu-Al nanolayers dominated at hAl≤ 20 nm, while the crystalline Al nanolayers dominated at hAl 〉 20 nm. The plastic deformation was mainly related to the ductile Al nanolayers, which was responsible for the monotonic evolution of SRS with hAl. In addition, the hAFdependent hardness and SRS were quanti- tatively modeled in light of the strengthening mechanisms at different length scales. 展开更多
关键词 Nanostructured films Cu-Al/Al multilayers hardness Strain rate sensitivity Layer thickness dependence
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The effects of deformation parameters and cooling rates on the aging behavior of AZ80+0.4%Ce
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作者 Yongbiao Yang Jinxuan Guo +6 位作者 Cuiying Wang Ting Yan Zhang Wenxuan Jiang Zhimin Zhang Qiang Wang Guojun Li Jun Wang 《Journal of Magnesium and Alloys》 SCIE EI CAS CSCD 2024年第2期639-658,共20页
The extruded AZ80+0.4%Ce magnesium alloy was twisted in the temperature range of 300-380℃by using a Gleeble 3500 thermal simulation test machine with a torsion unit.The deformed cylindrical specimens were cooled at a... The extruded AZ80+0.4%Ce magnesium alloy was twisted in the temperature range of 300-380℃by using a Gleeble 3500 thermal simulation test machine with a torsion unit.The deformed cylindrical specimens were cooled at a cooling rate of 10℃/s or 0.1℃/s,respectively,and aged at 170℃.The microstructure analysis results showed that the grain size decreased with increasing specimen radial position from center(SRPC),and that the strong initial basal texture of the extruded magnesium alloy was weakened.Both continuous and discontinuous dynamic recrystallization mechanisms were involved in contributing to the grain refinement for all specimens investigated.And a novel extension twinning induced dynamic recrystallization mechanism was proposed for specimen deformed at 300℃.For the specimens deformed at 300℃and 340℃followed by a slow cooling rate(0.1℃/s),precipitates of various shapes(β-Mg_(17)Al_(12)),with the dominant precipitates being on the grains boundaries,appeared on the surface section.For specimen deformed at 380℃,lamellar precipitates(LPS)in the interiors of the grains were predominant.After aging,the LPS still dominated for specimens twisted at 380℃;however,the LPS gradually decreased with decreasing deformation temperatures from 380℃to 300℃.Dynamically precipitatedβ,especially those decorating the grain boundaries,changed the competition pictures for the LPS and precipitates of other shapes after aging.Interestingly,LPS dominated the areas for the center section of the specimens after aging regardless of deformation temperatures.Low temperature deformation with high SRPC followed by rapid cooling rate increased the micro hardness of the alloy after aging due to refined grain,reduced precipitates size,decreased lamellar spacing as well as strain hardening. 展开更多
关键词 AZ80+0.4%Ce magnesium alloy Hot torsion Deformation parameters Cooling rate Aging Micro hardness
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Recent Progress in Improving Rate Performance of Cellulose-Derived Carbon Materials for Sodium-Ion Batteries
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作者 Fujuan Wang Tianyun Zhang +2 位作者 Tian Zhang Tianqi He Fen Ran 《Nano-Micro Letters》 SCIE EI CAS CSCD 2024年第8期102-147,共46页
Cellulose-derived carbon is regarded as one of the most promising candidates for high-performance anode materials in sodium-ion batteries;however,its poor rate performance at higher current density remains a challenge... Cellulose-derived carbon is regarded as one of the most promising candidates for high-performance anode materials in sodium-ion batteries;however,its poor rate performance at higher current density remains a challenge to achieve high power density sodium-ion batteries.The present review comprehensively elucidates the structural characteristics of cellulose-based materials and cellulose-derived carbon materials,explores the limitations in enhancing rate performance arising from ion diffusion and electronic transfer at the level of cellulose-derived carbon materials,and proposes corresponding strategies to improve rate performance targeted at various precursors of cellulose-based materials.This review also presents an update on recent progress in cellulose-based materials and cellulose-derived carbon materials,with particular focuses on their molecular,crystalline,and aggregation structures.Furthermore,the relationship between storage sodium and rate performance the carbon materials is elucidated through theoretical calculations and characterization analyses.Finally,future perspectives regarding challenges and opportunities in the research field of cellulose-derived carbon anodes are briefly highlighted. 展开更多
关键词 CELLULOSE Hard carbon Anode materials rate performance Sodium-ion batteries
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High-efficiently doping nitrogen in kapok fiber-derived hard carbon used as anode materials for boosting rate performance of sodium-ion batteries
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作者 Tianyun Zhang Tian Zhang +1 位作者 Fujuan Wang Fen Ran 《Journal of Energy Chemistry》 SCIE EI CAS CSCD 2024年第9期472-482,共11页
The engineering of plant-based precursor for nitrogen doping has become one of the most promising strategies to enhance rate capability of hard carbon materials for sodium-ion batteries;however,the poor rate performan... The engineering of plant-based precursor for nitrogen doping has become one of the most promising strategies to enhance rate capability of hard carbon materials for sodium-ion batteries;however,the poor rate performance is mainly caused by lack of pyridine nitrogen,which often tends to escape because of high temperature in preparation process of hard carbon.In this paper,a high-rate kapok fiber-derived hard carbon is fabricated by cross-linking carboxyl group in 2,6-pyridinedicarboxylic acid with the exposed hydroxyl group on alkalized kapok with assistance of zinc chloride.Specially,a high nitrogen doping content of 4.24%is achieved,most of which are pyridine nitrogen;this is crucial for improving the defect sites and electronic conductivity of hard carbon.The optimized carbon with feature of high nitrogen content,abundant functional groups,degree of disorder,and large layer spacing exhibits high capacity of 401.7 mAh g^(−1)at a current density of 0.05 A g^(−1),and more importantly,good rate performance,for example,even at the current density of 2 A g^(−1),a specific capacity of 159.5 mAh g^(−1)can be obtained.These findings make plant-based hard carbon a promising candidate for commercial application of sodium-ion batteries,achieving high-rate performance with the enhanced pre-cross-linking interaction between plant precursors and dopants to optimize aromatization process by auxiliary pyrolysis. 展开更多
关键词 Kapok fiber Hard carbon Electrode materials rate performance Sodium-ion batteries
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MICROSTRUCTURAL CHARACTERISTICS ASSOCIATED WITH HIGH- STRAIN-RATE PLASTIC DEFORMATION IN THE ELECTROFORMED COPPER LINER OF SHAPED CHARGES 被引量:4
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作者 A.L. Fan W.H. Tian +1 位作者 Q. Suns B.S. Wang 《Acta Metallurgica Sinica(English Letters)》 SCIE EI CAS CSCD 2005年第5期620-626,共7页
The microstructures of electroformed copper liners of shaped charges that had undergone high-strain-rate deformation were observed by optical microscopy (OM) and scanning electron microscopy (SEM). Meanwhile, the ... The microstructures of electroformed copper liners of shaped charges that had undergone high-strain-rate deformation were observed by optical microscopy (OM) and scanning electron microscopy (SEM). Meanwhile, the orientation distribution of the grains in the recovered jet was examined by electron backscattering Kikuchi pattern (EBSP) technique. EBSP analysis reveals that the fibrous texture observed in the as-electroformed copper liners disappeared after explosive detonation deformation. OM observation shows that the microstructure evolves system- atically from the jet center to its perimeter during cooling from high temperatures after explosive detonation deformation. This microstructural characteristic is similar to that of solidification, i.e. there exist equiaxed grains in the center of the jet and significant columnar grains around the equiaxed grains. The result reveals that there is melting-related phenomenon in the jet center. Corresponding microhardness variations from the jet center to its perimeter is also determined. All the phenomena can be explained by a strong gradient of temperature across the section of the jet during plastic deformation at high-strain-rate. 展开更多
关键词 JETTING ELECTROFORMATION microstructure hardness ultra-high strain rate deformation
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Drillability prediction in some metamorphic rocks using composite penetration rate index(CPRI)–An approach 被引量:3
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作者 Gaurav Kumar Srivastava M.S.R.Murthy Vemavarapu 《International Journal of Mining Science and Technology》 SCIE EI CAS CSCD 2021年第4期631-641,共11页
Assessment of drillability of rocks is vital in the selection,operation,and performance evaluation of cutting tools used in various excavation machinery deployed in mining and tunneling.The commonly used rock drillabi... Assessment of drillability of rocks is vital in the selection,operation,and performance evaluation of cutting tools used in various excavation machinery deployed in mining and tunneling.The commonly used rock drillability prediction methods,namely,drilling rate index(DRI)and Cerchar hardness index(CHI)have limitations in predicting the penetration rate due to differential wear of the cutting tool in rocks with varied hardness and abrasivity.Since cutting tools get blunt differently in different rocks,the stress beneath the tip of the bit decreases until it reaches a threshold value beyond which the penetration rate becomes constant.In this research,a new composite penetration rate index(CPRI)is suggested based on the investigations on four metamorphic rocks viz.quartzite,gneiss,schist and phyllite with varied hardness-abrasivity values.The penetration-time behavior was classified into active,moderate,passive,and dormant phases based on the reduction in penetration rate at different stages of drilling.A comparison of predicted penetration rate values using DRI and CPRI with actual penetration rate values clearly establishes the supremacy of CPRI.Micro-structure and hardness-based index was also developed and correlated with CPRI.The new indices can help predict cutting tool penetration and its consumption more accurately. 展开更多
关键词 Abrasivity hardness DRILLABILITY Metamorphic rocks Composite penetration rate index(CPRI)
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Comprehensive study on quasi-static and dynamic mechanical properties and wear behavior of Mg–B4C composite compacted at several loading rates through powder metallurgy 被引量:3
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作者 K.RAHMANI G.H.MAJZOOBI +1 位作者 G.EBRAHIM-ZADEH M.KASHFI 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2021年第2期371-381,共11页
The present study aims to fabricate and evaluate the mechanical properties and wear behavior of Mg metal matrix composite,reinforced by 0,1.5,3,5 and 10 vol.%B4C microparticles.Mg−B4C samples were fabricated at 450℃ ... The present study aims to fabricate and evaluate the mechanical properties and wear behavior of Mg metal matrix composite,reinforced by 0,1.5,3,5 and 10 vol.%B4C microparticles.Mg−B4C samples were fabricated at 450℃ and under different loading rates by using split Hopkinson bar(SHB),drop hammer(DH)and Instron(QS)at strain rates of 1600,800 and 0.008 s–1,respectively.The mechanical properties including microhardness,quasi-static and dynamic compressive strengths and wear behavior of samples were experimentally investigated.The results show that,the hardness of SHB and DH samples is obtained to be 20.2%and 5.7%higher than that of the QS sample,respectively.The wear rate and wear mass loss of Mg–10.0%B4C samples fabricated by SHB were determined lower than those of the QS sample by nearly 33%and 39%,respectively.The quasi-static compressive strengths of Mg−5.0%B4C are improved by 39%,30%and 29%for the SHB,DH and QS samples,respectively,in comparison with the case of pure Mg.Furthermore,it is discovered that the dynamic compressive strength of samples is 51%−110%higher than their quasi-static value with respect to the B4C content. 展开更多
关键词 powder compaction high strain rate Mg−B4C composite hardness mechanical properties wear behavior
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Predicting TBM penetration rate in hard rock condition:A comparative study among six XGB-based metaheuristic techniques 被引量:26
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作者 Jian Zhou Yingui Qiu +4 位作者 Danial Jahed Armaghani Wengang Zhang Chuanqi Li Shuangli Zhu Reza Tarinejad 《Geoscience Frontiers》 SCIE CAS CSCD 2021年第3期201-213,共13页
A reliable and accurate prediction of the tunnel boring machine(TBM)performance can assist in minimizing the relevant risks of high capital costs and in scheduling tunneling projects.This research aims to develop six ... A reliable and accurate prediction of the tunnel boring machine(TBM)performance can assist in minimizing the relevant risks of high capital costs and in scheduling tunneling projects.This research aims to develop six hybrid models of extreme gradient boosting(XGB)which are optimized by gray wolf optimization(GWO),particle swarm optimization(PSO),social spider optimization(SSO),sine cosine algorithm(SCA),multi verse optimization(MVO)and moth flame optimization(MFO),for estimation of the TBM penetration rate(PR).To do this,a comprehensive database with 1286 data samples was established where seven parameters including the rock quality designation,the rock mass rating,Brazilian tensile strength(BTS),rock mass weathering,the uniaxial compressive strength(UCS),revolution per minute and trust force per cutter(TFC),were set as inputs and TBM PR was selected as model output.Together with the mentioned six hybrid models,four single models i.e.,artificial neural network,random forest regression,XGB and support vector regression were also built to estimate TBM PR for comparison purposes.These models were designed conducting several parametric studies on their most important parameters and then,their performance capacities were assessed through the use of root mean square error,coefficient of determination,mean absolute percentage error,and a10-index.Results of this study confirmed that the best predictive model of PR goes to the PSO-XGB technique with system error of(0.1453,and 0.1325),R^(2) of(0.951,and 0.951),mean absolute percentage error(4.0689,and 3.8115),and a10-index of(0.9348,and 0.9496)in training and testing phases,respectively.The developed hybrid PSO-XGB can be introduced as an accurate,powerful and applicable technique in the field of TBM performance prediction.By conducting sensitivity analysis,it was found that UCS,BTS and TFC have the deepest impacts on the TBM PR. 展开更多
关键词 TBM penetration rate Hard rock XGB-based hybrid model Predictive model Metaheuristic optimization
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A Fixed Suppressed Rate Selection Method for Suppressed Fuzzy C-Means Clustering Algorithm 被引量:2
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作者 Jiulun Fan Jing Li 《Applied Mathematics》 2014年第8期1275-1283,共9页
Suppressed fuzzy c-means (S-FCM) clustering algorithm with the intention of combining the higher speed of hard c-means clustering algorithm and the better classification performance of fuzzy c-means clustering algorit... Suppressed fuzzy c-means (S-FCM) clustering algorithm with the intention of combining the higher speed of hard c-means clustering algorithm and the better classification performance of fuzzy c-means clustering algorithm had been studied by many researchers and applied in many fields. In the algorithm, how to select the suppressed rate is a key step. In this paper, we give a method to select the fixed suppressed rate by the structure of the data itself. The experimental results show that the proposed method is a suitable way to select the suppressed rate in suppressed fuzzy c-means clustering algorithm. 展开更多
关键词 HARD C-MEANS CLUSTERING ALGORITHM FUZZY C-MEANS CLUSTERING ALGORITHM Suppressed FUZZY C-MEANS CLUSTERING ALGORITHM Suppressed rate
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Effect of AIBI as Free Radical Initiator on Abrasive-Free Polishing of Hard Disk Substrate
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作者 REN Xiao-yan LEI Hong +1 位作者 CHEN Ru-ling CHEN Yi 《上海大学学报(自然科学版)》 CAS CSCD 北大核心 2014年第6期680-688,共9页
To optimize the existing slurry for abrasive-free polishing(AFP)of hard disk substrate,a water-soluble free radical initiator,2,2-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride(AIBI)is introduced to the H2O2-base... To optimize the existing slurry for abrasive-free polishing(AFP)of hard disk substrate,a water-soluble free radical initiator,2,2-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride(AIBI)is introduced to the H2O2-based slurry.The polishing results show that,the material removal rate(MRR)of hard disk substrate polished with H2O2-based slurry containing AIBI is obviously higher than that without AIBI.The acting mechanism of the improved MRR is investigated.Electron paramagnetic resonances tests show that,by comparison with H2O2 slurry,H2O2-AIBI slurry provides higher concentration of hydroxyl radicals.Auger electron spectrometer analyses further demonstrate that the oxidation ability of H2O2-AIBI slurry is much greater than H2O2 slurry.In addition,potentiodynamic polarization tests show that the corrosion dissolution rate of hard disk substrate in H2O2-AIBI slurry is increased.Therefore that stronger oxidation ability and a higher corrosion dissolution rate of H2O2-AIBI slurry lead to higher MRR can be concluded. 展开更多
关键词 机械摩擦 机械原理 磨损 摩擦
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Influence of B4C and ZrB2 reinforcements on microstructural,mechanical and wear behaviour of AA 2014 aluminium matrix hybrid composites
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作者 Ramesh Babu R Rajendran C +1 位作者 Saiyathibrahim A Rajkumar Velu 《Defence Technology(防务技术)》 SCIE EI CAS CSCD 2024年第10期242-254,共13页
Considering their affordability and high strength-to-weight ratio,lightweight aluminium alloys are the subject of intensive research aimed at improving their properties for use in the aerospace industry.This research ... Considering their affordability and high strength-to-weight ratio,lightweight aluminium alloys are the subject of intensive research aimed at improving their properties for use in the aerospace industry.This research effort aims to develop novel hybrid composites based on AA 2014 alloy through the use of liquid metallurgy stir casting to reinforce dual ceramic particles of Zirconium Diboride(ZrB_(2))and Boron Carbide(B4C).The weight percentage(wt%)of ZrB_(2) was varied(0,5,10,and 15),while a constant 5 wt%of B4C was maintained during this fabrication.The as-cast samples have been assessed using an Optical Microscope(OM)and a Scanning Electron Microscope(SEM)with Energy Dispersive Spectroscopy(EDS).The properties such as hardness,tensile strength,and wear characteristics of stir cast specimens were assessed to examine the impact of varying weight percentages of reinforcements in AA 2014 alloy.In particular,dry sliding wear behaviour was evaluated considering varied loads using a pin-on-disc tribotester.As the weight%of ZrB_(2) grew and B4C was incorporated,hybrid composites showed higher hardness,tensile strength,and wear resistance.Notably,the incorporation of a cumulative reinforcement consisting of 15 wt%ZrB_(2) and 5 wt%B4C resulted in a significant 31.86%increase in hardness and a 44.1%increase in tensile strength compared to AA 2014 alloy.In addition,it has been detected that wear resistance of hybrid composite pin(containing 20 wt%cumulative reinforcement)is higher than that of other stir cast wear test pins during the whole range of applied loads.Fractured surfaces of tensile specimens showed ductile fracture in the AA 2014 matrix and mixed mode for hybrid composites.Worn surfaces obtained employing higher applied load indicated abrasive wear with little plastic deformation for hybrid composites and dominant adhesive wear for matrix alloy.Hence,the superior mechanical and tribological performance of hybrid composites can be attributed to dual reinforcement particles being dispersed well and the effective transmission of load at this specific composition. 展开更多
关键词 AA 2014 alloy Stir casting Hybrid composite hardness Tensile strength Specific wear rate
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3个彩叶紫薇品种的扦插繁殖对比试验
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作者 胡卫霞 邱国金 王红梅 《安徽农业科学》 CAS 2024年第7期99-103,共5页
为获得紫薇硬枝扦插的最佳繁殖方法,以美国红叶紫薇、“红云”紫薇、“农紫1号”紫薇3个品种为试验材料,分别以不同品种、不同激素种类、不同激素浓度为试验因素,对紫薇的硬枝扦插繁殖进行了对比试验。结果表明:春季3月下旬至4月上旬进... 为获得紫薇硬枝扦插的最佳繁殖方法,以美国红叶紫薇、“红云”紫薇、“农紫1号”紫薇3个品种为试验材料,分别以不同品种、不同激素种类、不同激素浓度为试验因素,对紫薇的硬枝扦插繁殖进行了对比试验。结果表明:春季3月下旬至4月上旬进行硬枝扦插,插前将插穗基部在NAA、IBA以及(NAA+IBA)1500 mg/L的溶液中浸泡2 h后进行扦插,30 d后调查发现,3个品种以“农紫1号”紫薇的生根效果最好,生根率最高达92.4%。单独使用NAA、IBA溶液或使用NAA与IBA的混合溶液对扦插效果的影响不显著,对于扦插效果的影响主要体现在浸泡溶液的浓度上,使用1500 mg/L效果最好,与其他水平间均存在显著差异,该浓度下紫薇的平均生根率为91.00%,平均根长为3.00 cm,平均根量为7.93条。 展开更多
关键词 紫薇 硬枝扦插 激素处理 生根率
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胚胎移植女性孕早期睡眠质量及关联因素分析
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作者 万芳芳 高源 +4 位作者 张杰 李爱民 范艳丽 管延彧 刘玲 《解放军医学院学报》 CAS 2024年第7期724-730,745,共8页
背景胚胎移植女性经受了身体和心理的双重挑战,孕早期的生活质量,尤其是睡眠质量会受到较大的影响。目的分析胚胎移植女性孕早期睡眠质量及相关影响因素。方法选取2022年6—12月于河北医科大学第二医院生殖医学科进行体外受精-胚胎移植(... 背景胚胎移植女性经受了身体和心理的双重挑战,孕早期的生活质量,尤其是睡眠质量会受到较大的影响。目的分析胚胎移植女性孕早期睡眠质量及相关影响因素。方法选取2022年6—12月于河北医科大学第二医院生殖医学科进行体外受精-胚胎移植(in vitro fertilization-embryo transfer,IVF-ET)助孕成功的患者,在其移植后45 d返院复查B超时进行问卷调查,调查内容包括匹兹堡睡眠质量指数(Pittsburgh sleep quality index,PSQI)、焦虑自评量表(self-rating anxiety scale,SAS)、抑郁自评量表(self-rating depression scale,SDS)、中文简化版心理弹性量表(Connor Davidson resilience scale,CD-RISC)和社会支持评定量表。以PSQI>7分为判断睡眠障碍的标准,通过多因素Logistic回归模型分析睡眠质量与各个影响因素的关系,并使用信息增益算法对影响睡眠质量的主要因素进行影响程度评估。结果发放问卷336份,回收325份,回收率96.7%。325例IVF-ET孕妇年龄(32.46±4.52)岁,睡眠质量总分为(7.79±3.63)分,其中126例孕妇总分≤7分为睡眠正常组,199例孕妇总分>7分为睡眠障碍组(61.23%,199/325)。相关心理学评估:焦虑自评量表(43.75±8.86)分;抑郁自评量表(50.89±10.54)分;心理弹性量表总分(64.18±11.34),其中坚韧性(32.66±10.28)分,力量性(21.75±6.37)分,乐观性(9.74±3.26)分;社会支持评定量表总分为(42.27±4.93)分,其中客观支持(9.15±2.13)分,主观支持(25.30±4.26)分,对支持的利用度(7.82±1.91)分。Logistic回归结果提示,年龄越大、越焦虑,越容易出现睡眠障碍;文化程度中,以初中及以下人群作为参照,高中或中专学历的人群更不容易出现睡眠障碍;心理弹性水平越高,睡眠障碍出现概率越低(P均<0.05)。信息增益分析结果显示,影响睡眠质量的因素按影响力大小依次为心理弹性中的坚韧性(1.186)、社会支持量表中的主观支持分(0.807)、心理弹性量表中的力量性(0.806)、心理弹性量表中的乐观性(0.510)、社会支持量表中的对支持的利用度(0.422)、文化程度(0.419)、客观支持分(0.391)、职业(0.216)、婆媳关系(0.213)、SAS(0.192)、SDS(0.162)、第几次移植(0.146)、年龄(0.117)、第几次取卵(0.108)、社会支持总分(0.107)、现有子女个数(0.088)、月收入(0.082)、夫妻关系(0.051)、居住地(0.035)。结论胚胎移植女性在孕早期睡眠质量较差;患者的不良心理状态对睡眠有负面影响,而心理弹性和社会支持对睡眠质量则起到了积极的正面影响,临床可以从改善患者心理弹性状态、增加社会支持方向入手,帮助IVF-ET孕妇从孕早期开始改善睡眠质量,从而提高生活质量,保证母婴健康。 展开更多
关键词 体外受精-胚胎移植 孕妇 睡眠质量 心理弹性 社会支持 焦虑 抑郁 信息增益 调查研究
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ESG评级能否提高企业韧性?--基于ESG评级事件的准自然实验
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作者 陈琪 李梦函 《研究与发展管理》 CSSCI 北大核心 2024年第5期132-145,共14页
在充满不确定性的商业环境中,企业韧性成为组织管理和战略规划中的关键议题。以商道融绿公布ESG评级为准自然实验,基于2010—2020年沪深A股上市公司数据,探讨ESG评级对企业韧性的影响。研究发现:ESG评级可以显著增强企业韧性;ESG评级通... 在充满不确定性的商业环境中,企业韧性成为组织管理和战略规划中的关键议题。以商道融绿公布ESG评级为准自然实验,基于2010—2020年沪深A股上市公司数据,探讨ESG评级对企业韧性的影响。研究发现:ESG评级可以显著增强企业韧性;ESG评级通过缓解融资约束、降低信息不对称和提升创新能力来增强企业韧性;对于管理层短视程度较低、破产风险较大和市场关注度较高的企业,ESG评级驱动企业韧性提升的作用更为显著;ESG评级对企业的高绩效增长和低财务波动均具有影响,但对前者的影响具有滞后性;ESG评级对ESG得分较高和较低企业的韧性均有正向影响;ESG评级对企业韧性的增强效应尚未呈现出明显的溢出效应;新冠疫情削弱了ESG评级对企业韧性的增强效应。研究结论为企业提供了在不确定环境中增强韧性的有效途径,也为ESG策略制订和实施提供有力支持。 展开更多
关键词 ESG评级 企业韧性 创新 多期双重差分
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