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This study describes the application of a magnetic abrasive finishing process (MAF) to the inner wall of the Co-Cr alloy cardiovascular tube to obtain a fine surface roughness and improve the surface quality. The high-performance spherical iron-based diamond magnetic abrasive powder (MAP) used in the experiments was prepared via combining plasma molten metal powder with sprayed abrasive powder. The experiments were carried out on a MAF machining machine for slender tubes, with permanent slotted magnets as the magnetic field-generating device. The processing mechanism of the MAF on the inner wall of the tube was analyzed, and the magnitude and distribution of the magnetic flux in the processed area were simulated by software. The material removal model for MAF processing of the inner wall of the tube was constructed from mechanical properties of magnetic abrasives and the workpiece and five applied process parameters: finishing time, tube rotational speed, magnetic feed rate, size of MAPs, and filling quantity of MAPs. Single-factor experiments were designed and carried out using surface roughness Ra and quality differences before and after MAF processing as evaluation indicators. The results were used to analyze the relationship between five process parameters and surface roughness Ra and material removal MR. Scanning electron microscopy was used to observe the effect of the MAF process on the surface quality. It shows that the MAF process can effectively remove the defective layer from the workpiece and improve its surface smoothness and quality. The surface roughness Ra of 0.46–0.49 μm before finishing was decreased to 0.093 μm with optimal process parameters. [ABSTRACT FROM AUTHOR]

In this study, a new method of ultrasonic vibration processing of high-speed EDM ultra-fine copper tube electrode is proposed, and the deformation process of copper tube during processing is simulated by finite element analysis, and a prediction model of wall thickness change of ultrasonically processed copper tube electrode is established, and the predicted values are in good agreement with the experimental measurement data. The surface quality of copper tube electrode after ultrasonic processing was improved, and the roughness was reduced from Ra1.28 to Ra0.43 µm, which is important for the automated production of high-quality ultra-fine copper tube electrode. [ABSTRACT FROM AUTHOR]

Using DMDODGA as the carrier, the transportation and separation behavior of Eu(III) and La(III) were studied using a plate-type supported liquid membrane. La(III) and Eu(III) reach their maximum transport rates at feed phase nitric acid concentrations of 2 and 4 mol/L, which are 72.41 (± 2.12)% and 77.80 (± 2.45)%; Increasing the concentration of NO3− in feed phase will promote the transport of both ions. The change of HNO3 concentration in feed phase had major effect on the separation of Eu(III)/La(III), and the co-transport of Eu(III)/La(III) was observed when the concentration of NO3− was 3 mol/L. [ABSTRACT FROM AUTHOR]

In this work, a novel dynamic model with estimating its friction consumptions is developed to study the effect of dynamic behaviors of bearing components on friction consumptions at various structural sizes of cage, which is a novel solution for effectively guiding the structure matching design of bearing components to mitigate the power consumption of ball bearings. Based on this model, the influencing factors for different friction consumptions are analyzed at various structural sizes of cage. The effects of structural sizes of cage on the friction consumptions are revealed. The results indicate that a favorable combination of pocket diameter and large diameter of cage can attain the low friction consumption of ball bearings, also, a compromise between the good dynamic stability of cage and the low friction consumption of ball bearings can be conducted to determine the thickness of cage. [ABSTRACT FROM AUTHOR]

The frozen period interaction of groundwater and lakes is crucial for hydrological properties and aquatic ecology in cold and arid regions. In this study, we investigate the spatial hydrochemical characteristics, influencing factors in the Hulun Lake basin. The hydrochemical type of lake water exhibits Na-HCO3-SO4-Cl, while river shows a primary classification of Na-Ca-HCO3. Groundwater in the eastern and western regions is characterized by Na-SO4-Cl and Na-HCO3, respectively. Silicic acid and ion exchange predominantly influence groundwater chemistry in the western region, whereas evaporation and concentration play a major role in the eastern region. Total dissolved solids, Cl−, and F− emerge as the primary influencing factors of hydrochemical components in the Hulun Lake basin. Ion content decreased from the southern to the northern region, with the lowest value occurring near the Urson River. The high-temperature water body is primarily distributed in the central and southern regions of the lake. Based on characteristic ions and partial characteristics of ice surface temperature, the potential groundwater discharge areas near the inlet of the Xinkai River, the central and southern region are determined. This study reveals the hydrochemical characteristics, vertical ice distribution, and provides a scientific foundation for water resource management in cold and arid regions. [ABSTRACT FROM AUTHOR]

The accuracy of passive localization is impacted by the position of the receiving stations. In practical applications, signal reception is frequently influenced by the emission angle of the target signal, which makes it a challenge to ensure localization accuracy. We present an optimal placement method for TDOA localization with constraints on the signal angle. Firstly, we establish a localization error model based on polar coordinates, which reveals that the localization error is solely dependent on the angular relationships between the target and receiving stations. We determine the optimal locations of the stations without constraints. We then introduce a novel approach where the quarter-angle and one-fifth angle within the emitted beam angle are employed as critical values to determine station placement. Given the constraint of the angle, we use the critical values to evaluate the angular relationship between the station and the target, determining if the station should be positioned on the boundary or on the angle bisector to achieve optimal placement method. Finally, we validate our proposed method through simulations, demonstrating its ability to minimize errors in various scenarios. The method proposed provides an effective solution to the challenge of target localization with constraints on the received signal beam angle. [ABSTRACT FROM AUTHOR]

Inconel 718 offers high oxidation resistance, mechanical strength, and heat resistance, which enables turbofan engines to maintain excellent performance in an operating environment of 1000 °C. However, these properties make Inconel 718 difficult to machine with conventional machining techniques. Water-jet guided laser (WJGL) is a composite processing technology that combines water cooling and laser ablation technology, which is advantageous and promising for processing Inconel 718. While, the water layer on the substrate surface in processing limits WJGL's ability to ablate the metal, which leads to burrs formed when manufacturing groove structures. Therefore, a new method for manufacturing groove structure on Inconel 718 by annular gas-assisted water-jet guided laser (AGAWJGL) is proposed in this paper. In this study, the burr is reduced, and the material removal efficiency is improved by removing the water layer from the substrate surface with a gas-assisted. Then, groove processing experiments are performed on Inconel 718 metal plates with a thickness of 1 mm. The experimental results show that the average size of burrs reduces by 36%, and the depth of grooves increases by 13%. These provide the theoretical foundation for the WJGL machining of Inconel 718. [ABSTRACT FROM AUTHOR]

To explore the correlation between vibration and power consumption of angular contact ball bearings, the evaluation of power consumption was merged into the original nonlinear dynamic model of ball bearings and this model was validated by the experimental method. On this basis, a comprehensive analysis of vibration and power consumption of ball bearings was conducted, then, the variations in the power consumption and vibration at different numbers of balls and groove curvature radii were studied again, their optimal combinations were determined to attain the acceptable power consumption, dynamic stability and vibration in the bearing system. The corresponding results illustrate that reducing the maximum number of balls by one or two can obtain the good dynamic performance of friction consumption, dynamic stability and vibration of ball bearings, besides, the combination of inner and outer groove curvature radii should both strengthen contact loads and effectively guide the motion of the ball to get the favorable comprehensive performances. Compared to existing methods, this innovative approach can effectively guide the structure matching design of bearing components to mitigate the vibration and power consumption of ball bearings, as a result, the experimental cost and period can be significantly reduced in engineering applications. [ABSTRACT FROM AUTHOR]

Operators make profits by publishing information. If they can know the influencing factors in the process of information dissemination, they can provide new insights for practical operations and formulate corresponding operation strategies for different types of accounts. The purpose of this article is to discuss the information dissemination process of WeChat public accounts and what factors will affect the reading rate and sharing rate of the article. In this paper, the "feedback-sympathize-identify participant-share" (FSIPS) two-stage model is used to analyze the characteristics of information dissemination, and the negative binomial regression model is used to analyze which factors have a significant impact on the two stages of the dissemination model. Our data is obtained from a company that specializes in operating WeChat Official Accounts, and the data is authentic and more valuable. We collectively consider the roles of users, message content, interactions between content and individuals, and the context of social media in information dissemination behaviors (i.e., reading and sharing). In this process, some new variables, such as environment-related variables, are involved and incorporated into the two stages of information dissemination for analysis. The results show that the like rate, which is one of the feedback dimensions, has the greatest impact on the reading rate, while the favorite rate has the greatest impact on the sharing rate. Article type also plays a crucial role in the dissemination of information. In addition, the content relevance between the title and the content also largely affects the share rates of the three types. [ABSTRACT FROM AUTHOR]

As the fundamental supporting structure in rotating machinery, the dynamic behaviors of angular contact ball bearings directly affect the operational performances of high-speed machine tools and aero-engine. In this work, a novel dynamic model considers flexible ring and cage motion whirl so that the deformations of flexible rings can change the contacts between balls and raceways to influence the dynamic behaviors of ball bearings, which is a novel solution for the dynamic performance analysis of angular contact ball bearings under different loads, assemblies and bearing structures. Then, the experimental validation conducted by a high-precision instrument demonstrated the reliability of this original model. On this basis, the effects of the clearances between housing and outer ring, the thickness of flexible ring and radial loads on the sliding of the ball, interaction forces between bearing components, vibration of inner ring, and cage whirl motion were investigated. The results show that the thick flexible ring and the minimal clearance can improve the dynamic stability of cage and mitigate the bearing vibration. [ABSTRACT FROM AUTHOR]

Several methods employ weakly supervised technology to highlight the visual sentiment information in images, so as to improve the performance of sentiment analysis. However, the over-focusing of location technology leads to the neglect of the information of some discriminative sentiment regions. In this work, we propose a Weakly Supervised Discriminate Enhancement Network (WSDEN) for visual sentiment analysis to construct a prediction framework of image sentiment. To be specific, firstly, the proposed WSDEN learns sentiment maps with a weakly supervised technology, thus it significantly reduces the annotation burden and encourages features to convey more sentiment information. Secondly, to solve the problem of overemphasis on local information mentioned above, Discriminate Enhancement Map is constructed by spatial weighting and channel weighting, which combines the sentiment map to perform sentiment enhancement on the final deep features of images. Extensive experiments on three benchmark databases show that the proposed method outperforms the state-of-the-art methods of visual sentiment analysis. [ABSTRACT FROM AUTHOR]

This paper presents an experimental study on single particle breakage behavior of crushable weathered sands by a number of single particle uniaxial compression tests to comprehensively investigate the characteristics of single particle breakage, the probability of survival of single particle, and the effects of particle size and weathering on single particle strengths. The behavior of single particle under uniaxial compression falls into the mixed five phases: damage by chipping, elastic deformation, fragmentation by partial fracture, breakage by splitting, and the residuals, demonstrating the complexity and variability of the tensile strengths of single particles. The behavior of single particle breakage was quantified herein by the initial fracture and failure strengths of single particle. The probability of survival decreased as the characteristic stresses increased. An increase in the particle size or weathering number of single particle resulted in a reduction in the probability of survival of single particle. For a given probability of survival, the difference in the initial fracture characteristic stress and failure characteristic stress decreased with increasing particle size but showed a complex change with increasing weathering number. The probability of survival showed greater variability for the normalized initial fracture characteristic stress than for the normalized failure characteristic stress, implying that the initial fracture stresses of single particles diverged more than the failure stresses of the particles. The average initial fracture and failure characteristic stresses, and the initial fracture and failure characteristic stresses corresponding to 1/e (37%) survival of single particles decreased while increasing particle size or weathering number, but the decrease showed a sharper rate for smaller single particles with a lower weathering number. The ln-ln coordinates showed a linear representation of the failure characteristic stress and particle size, verifying the applicability of Weibull theory to single particle breakage. However, weathering resulted in downward translation and slight rotation of the linear relation of the failure characteristic stress and particle size in the ln-ln coordinates. [ABSTRACT FROM AUTHOR]

Water films probably form beneath less-permeable interlayers in liquefiable deposits during an earthquake, further resulting in devastating disasters. However, the development of such water film and its effect on the liquefaction behavior of stratified deposits are still unclear. Herein, a water sedimentation method was developed in laboratory to reproduce the layered structure of sandy soil deposited in water during land reclamation. Undrained cyclic torsional shear tests were conducted to visualize the evolution of localized liquefaction behavior incorporating an image-based measurement technique. The test results indicate that the liquefaction resistance of layered specimens with less-permeable fine layers was similar to that of specimens without fine layer, which was possibly due to the lower liquefaction resistance of the sand layer compared to the fine layer. Large local strains periodically observed at the bottom of fine layer during undrained cyclic shearing implied that pore water concentrated into thin zones, which was also directly proven by the differential pore pressures in the sand and fine layers within the layered specimen. Moreover, large local strains also manifested a relatively lower liquefaction resistance of specimen compared to that evaluated by global strains. As specimen was closely liquefied, a hydraulic gradient significantly higher than its critical value to drive upward particle migration was formed at the fine layer, which overcomes the resultant force of gravity and buoyancy acting on soil particle. This hydraulic gradient and the less-permeable fine layer provided the formation conditions of a subjacent water film. [ABSTRACT FROM AUTHOR]

In order to further study the structure-performance relationship of unsymmetrical diglycolamides. In this work, two types of unsymmetrical diglycolamides (Structure A: N,N'-dimethyl-N,N'-didecyl diglycoamide, LI, N,N'-dimethyl-N,N'-didodecyl diglycoamide, LIII; Structure B: N,N-dimethyl-N',N'-didecyl diglycoamide, LII, N,N-dimethyl-N',N'-didodecyl diglycoamide, LIV), which are geometrical isomers each other, were synthesized, and their extraction performances in 40/60 (v/v)% n-octanol/kerosene were studied and compared. The related results reveal that the size of the alkyl substituents attached on the amide N atoms can influence the extractant performance of the extractant, and the difference in the geometric structure of extractants can lead to the differences in their extraction performances. [ABSTRACT FROM AUTHOR]

The safety of metro tunnels is seriously threatened when protective measures are not well organized during adjacent foundation pit excavations in soft ground. To date, the protective effects obtained from adopting partition excavations and a deep diaphragm wall in large-deep excavations have not been fully understood. In this study, 3D numerical analyses incorporating the hypoplastic constitutive model, which can take into account the small strain stiffness of soil, were performed to reproduce tunnel responses subjected to lateral excavations. The mechanism of crack development in tunnel lining, the protective effects of partition excavations, and diaphragm walls are investigated in sequence. The obtained results indicate that crack development in tunnel lining is mainly dominated by lining deformation in the longitudinal direction, instead of deformations in the radial and circumferential directions. Through firstly excavating the nearest excavation to the tunnel that is small in size, the tunnel displacement and bending moment are reduced, since the system rigidity of the nearest excavation increases significantly after applying supporting structures. By contrast, such reduction is found to be detrimental when the nearest excavation is large in size and is performed at the end. This indicates that a comprehensive consideration of both the order and the size of partition excavations is important. The inhibiting effect on the tunnel displacement caused by increasing the depth of the diaphragm wall is found to function nonlinearly, depending highly on its referred depth. Additionally, this effect is more effective than increasing the width of the diaphragm wall under constant volume conditions. [ABSTRACT FROM AUTHOR]

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N,N'-dimethyl-N,N'-dioctyl diglycolamide (DMDODGA) in 40/60 (V/V)% 1-octanol/kerosene was used to extract 14 lanthanides from nitric acid solution. The effects of the aqueous acidity, the DMDODGA concentration, and the temperature on the distribution ratio of Ln(III) were investigated. The extraction equilibrium constants K and the thermodynamic parameters were determined by the slope analysis method combined with Pitzer model. The IR spectra of the extracted species and pure extractant were recorded and analyzed. Moreover, 0.001 mol/L nitric acid is the suitable stripping agent, and the stripping efficiency of all lanthanides can reach up 90% by three times of stripping. [ABSTRACT FROM AUTHOR]

Gas injection serves as a main enhanced oil recovery (EOR) method in fractured-vuggy carbonate reservoir, but its effect differs among single wells and multi-well groups because of the diverse fractured-vuggy configuration. Many researchers conducted experiments for the observation of fluid flow and the evaluation of production performance, while most of their physical models were fabricated based on the probability distribution of fractures and caves in the reservoir. In this study, a two-dimensional physical model of the karst fault system was designed and fabricated based on the geological model of TK748 well group in the seventh block of the Tahe Oilfield. The fluid flow and production performance of primary gas flooding were discussed. Gas-assisted gravity flooding was firstly introduced to take full use of gas–oil gravity difference, and its feasibility in the karst fault system was examined. Experimental results showed that primary gas flooding created more flow paths and achieved a remarkable increment of oil recovery compared to water flooding. Gas injection at a lower location was recommended to delay gas breakthrough. Gas-assisted gravity flooding achieved more stable gas-displacing-oil because oil production was at a lower location, and thus, the oil recovery was further enhanced. [ABSTRACT FROM AUTHOR]

A revised recurrent neural networks method for the passive source localization is proposed in this paper. The cost function has been designed which makes the transformation from transmitters' localization into the outputs of the settled revised recurrent neural networks through spatial partition. The neural networks are chaotic and stable in convergence. The received signal model is constructed firstly. The parameters of the recurrent neural networks have been trained properly according to the scene. The experiments and analysis display that the revised recurrent neural networks solution not only obtains high precision location, but also has high convergence rate. [ABSTRACT FROM AUTHOR]

The Ag modified transparent Cu2O/ZnO p-n junction films were prepared by a simple magnetron sputtering process. The transparence and photoelectric conversion of these devices were investigated, which exhibited an obvious photoelectric conversion enhancement (PCE of 0.48%, ten times) than those of the unmodified heterojunction. Through analysis, the enhancement of the photoelectric conversion could be attributed to the remarkable Cu2O/ZnO p-n junction and Ag0 nanoparticles with the performances of photoelectron donor and surface enhanced plasmonic absorption. [ABSTRACT FROM AUTHOR]

Carbon quantum dots doped with nitrogen and phosphorus were prepared from adenosine 5′-monophosphate (AMP) in a single simple synthesis step. The nitrogen and phosphorus doped C-dots (N,P-C-dots) were characterized by transmission electron microscopy, Fourier transform infrared spectroscopy, fluorescence spectroscopy, X-ray photoelectron spectroscopy and X-ray powder diffraction. These carbon dots display blue fluorescence, with excitation/emission maxima at 360/430 nm, a quantum yield of 26.5% and an average decay time of 4.3 ns. Fluorescence is strongest at neutral pH values but quenched at very high and very low pH values. It is also quenched by ferric ions which suggests the use of the N,P-C-dots as fluorescent probes for Fe(III). A hemolysis test inferred favorable blood compatibility. The fluorescence of the doped C-dots is excitation wavelength dependent and also is susceptible to 2-photon excitation. The nanoparticles were applied in the fluorescent multicolor bioimaging of A549 (adenocarcinomic alveolar basal epithelial) cells under different excitation wavelengths, typically at 405, 488 and 543 nm. Emission colors ranging from blue to green and red can be adjusted in this way. [ABSTRACT FROM AUTHOR]

3D integrated woven spacer composites with thickened face sheets are fabricated successfully. Static compression and impact behavior are analyzed to evaluate the effect of thickened face sheets. The results show that thickened face sheet is an important influence parameter, warp compression and impact properties have been improved significantly than those of composite without thickened face sheets. Moreover, the damage and failure mechanism is significantly different. The main failure mode under flat compression is an abrupt rigid breakage of core fiber bundles. However, the thickened face sheets reduce the shear stress that transfer to core fibers. For warp compression, there is no face sheets fracture or dislocation, the local shear fracture occurs on the thickened face sheets. In regard to low-velocity impact, the strength of thickened face sheets dominates the failure, the damage is mainly manifested as the penetration of the top and bottom face sheets, matrix cracking, interface debonding, micro-buckling, as well as tearing and breakage of core fibers. [ABSTRACT FROM AUTHOR]

The charpy impact experiments on the 3D integrated woven spacer composites with six types of core heights are performed at room and liquid nitrogen temperatures (as low as −196 °C). Macro-fracture morphology and SEM micrographs are examined to understand the deformation and failure mechanism. The results show that the impact energy increase with the increase of the core height at both room and liquid nitrogen temperatures. Meanwhile, the impact properties at liquid nitrogen temperature have been improved significantly than that at room temperature. Moreover, at room temperature, the penetration fracture of the face sheets, the tearing and pulling out of the core fibers as well as the cracking of the matrix is the main damage and failure patterns. However, at liquid nitrogen temperature, the matrix crushing dominates the failure. Less fibers fracture and brittle fracture feature becomes more obvious. In addition, with the increase of the core heights, the damage of composites has been reduced significantly at room and liquid nitrogen temperatures. [ABSTRACT FROM AUTHOR]

This study was conducted in order to investigate the effects of polymyxin B (PMB) against hepatic ischemia/reperfusion (I/R) injury in rats with obstructive jaundice. Thirty-six Wistar rats (eighteen each) with induced hepatic I/R injury by biliary tract ligation and recanalization were assigned to a control group (reperfused with normal saline) and a PMB group (reperfused with PMB). Indicators involving liver function, oxidation resistance, pro-inflammatory state, and anti-apoptosis effect were determined following the instructions. Compared with normal saline, PMB reperfusion resulted in a significant improvement of liver function (increase of glutathione and reduction of aspartate aminotransferase, alanine aminotransferase, and lactate dehydrogenase), oxidation resistance (decreased malondialdehyde and myeloperoxidase activity), alleviation of pro-inflammatory state (less tumor necrosis factor (TNF)-α, interleukin-1 beta (IL-1β), nuclear factor kappa B (NF-κB) mRNA, and intercellular adhesion molecule (ICAM)-1), and anti-apoptosis effect (more Bcl-2 and less Bax). PMB protects the liver from I/R injury mainly through reducing cellular oncosis and apoptosis and regulating the expression of NF-κB, TNF-α, IL-1β, and ICAM-1. [ABSTRACT FROM AUTHOR]

The surface condition, some properties and ion releasing behavior of cobalt-chromium (Co-Cr) dental alloy formed by selective laser melting (SLM) technique were investigated. Before porcelain fused firing, the surface condition of the Co-Cr alloy was observed using a scanning electron microscope (SEM), and then the density and hardness were examined. After porcelain fused firing, the interface of porcelain and alloy was observed, and then the metal-ion release of the samples was tested. SLM technique provides Co-Cr alloy higher hardness than casting method. After degassing-oxidation procedure and porcelain fused firing, the interface of the alloy and porcelain showed excellent combination. Co ion was more than Cr ion released from SLM Co-Cr alloy, the amounts of Co and Cr ions were safe according to ISO security criterion. Considering the properties before and after porcelain fused sintering process, SLM technique is suitable for dental Co-Cr alloy restoration. [ABSTRACT FROM AUTHOR]

Aim:To determine whether electrical stimulation of caudal medial prefrontal cortex (mPFC) as conditioned stimulus (CS) paired with airpuff unconditioned stimulus (US) was sufficient for establishing eyeblink conditioning in guinea pigs, and whether it was dependent on cerebellar interpositus nucleus.Methods:Thirty adult guinea pigs were divided into 3 conditioned groups, and trained on the delay eyeblink conditioning, short-trace eyeblink conditioning, and long-trace eyeblink conditioning paradigms, respectively, in which electrical stimulation of the right caudal mPFC was used as CS and paired with corneal airpuff US. A pseudo conditioned group of another 10 adult guinea pigs was given unpaired caudal mPFC electrical stimulation and the US. Muscimol (1 μg in 1 μL saline) and saline (1 μL) were infused into the cerebellar interpositus nucleus of the animals through the infusion cannula on d 11 and 12, respectively.Results:The 3 eyeblink conditioning paradigms have been successfully established in guinea pigs. The animals acquired the delay and short-trace conditioned responses more rapidly than long-trace conditioned responses. Muscimol infusion into the cerebellar interpositus nucleus markedly impaired the expression of the 3 eyeblink conditioned responses.Conclusion:Electrical stimulation of caudal mPFC is effective CS for establishing eyeblink conditioning in guinea pigs, and it is dependent on the cerebellar interpositus nucleus. [ABSTRACT FROM AUTHOR]

Rolling resistance is a main consideration in quasi-static shear test simulations of particles via the discrete element method. However, not all rolling resistance models can satisfy the required objectivity and rate independence. A suitable model for spherical particles has been selected from five models in our previous works. In the current study, this model is combined with four normal and tangential contact models to confirm its applicability. After confirmation, the model is generalized to simulate direct shear tests on non-spherical particles. The stress-strain and dilatancy curves are rate-independent, and the relative rolling velocity between particles is objective. Furthermore, objectivity and rate independence for arbitrarily shaped particles are unchanged when normal stresses, volume fractions, or normal and tangential contact models are changed. Simulation results are also consistent with other experiment findings. For comparison, results are calculated for two other rolling resistance models; the shear curve at a single speed is consistent with the experiment, which has three stages: elastoplastic increasing, yielding, and keeping. However, the stress-strain curves at different shear rates do not coincide, which means that the models conflict with the rate independence of quasi-static granular systems. The virtues and defects of the five rolling resistance models are discussed from the perspectives of objectivity and rate independence. These two properties provide criteria for determining the appropriateness of a model, which has been rarely discussed in former studies. [ABSTRACT FROM AUTHOR]