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Uncertainties of geological structural geometry constructed based on seismic reflections can stem from data acquisition, processing, analysis, or interpretation. Especially uncertainties arising from structural interpretations and subsequent estimates of geological slip have been little quantified and discussed. To illustrate the implications of interpretation uncertainties for seismic potential and structural evolution, I use an example of a shear fault-bend fold in the Central Himalaya. I apply a simple solution from the kinematic model of shear fault-bend folding to resolve the geological input slip of given structure, and then compare the result with a previous study to show how differences in structural interpretations could impact dependent conclusions. The findings show that only a little variance in interpretations owing to subjectivity or an unclear seismic image could yield geological slip rates differing by up to ~10 mm/yr, resulting in significantly different scenarios of seismic potential. To reduce unavoidable subjectivity, this study also suggests that the epistemic uncertainty in raw data should be included in interpretations and conclusions. [ABSTRACT FROM AUTHOR]

Experiments of a sphere oblique impact with and without an initial spin have been carried out to obtain properties of the impact interface. The contact surface is recorded with a piece of thin carbon paper. The interfacial parameters measured are expressed as axis length, contact area and slip ratio. It is found that for the impact between steels the forward spin can make geometrical sizes of the contact surface increase compared with the case of no initial spin, however, just the reverse for the backward spin. The effect of the initial spin becomes more apparent for the impact with a rubber cushion. Whether the initial spin promotes or hinders the sphere sliding depends on the parameters of tangential velocity and force at the interface. [ABSTRACT FROM AUTHOR]

Repeating earthquakes, earthquakes that rupture the same fault patch more than once, are playing an important role in the study of source processes and fault behavior, and have the potential to improve hazard assessment and earthquake forecast. They are believed to represent brittle failure of a stuck patch (asperity) on an otherwise creeping fault, and as such may offer insight into slip behavior at depth. We carried out a systematic analysis in search for repeating earthquakes in northern California between 1984 and 2014 by identifying events that are co‐located, are of similar size, and share similar waveforms. We find 27,675 events in 7,713 repeating earthquake sequences (RES) that include between 2 and 32 events with magnitudes between −0.5 and 6.5. Temporal behavior of the events within each RES ranges between random and quasi‐periodic over the 30‐year observation period, and includes temporal clustering (bursts). The RESs occur throughout northern California, with some of the largest and most periodic sequences predominately, but not exclusively, along faults within the San Andreas Fault system that exhibit surface creep. Piecewise periodic RESs are found near large earthquakes where they are modulated by transient stress. Slip rates inferred from the new data, while generally consistent with published estimates from geodetic and surface data, offer a high‐resolution image of subsurface creep along individual fault strands and resolve slip partitioning across wider zones of deformation. Plain Language Summary: Repeating earthquakes are earthquakes that rupture the same fault patch more than once, often numerous times and with surprising periodicity. They are believed to represent stuck patches on a fault surface that otherwise creeps in response to tectonic stress. This makes them ideal for studying processes that cause earthquakes and control fault behavior. Because we can use repeating earthquake sequences as slip meters at depth, they are also playing an important role in the assessment of seismic hazard. In this study we carried out a systematic search for repeating earthquakes in northern California by mining 30 years of earthquake data. We find 27,675 repeating earthquakes included in 7,713 sequences that locate throughout northern California, predominately, but not exclusively, along faults within the San Andreas Fault system that exhibit creep at the surface. The pattern of event timing in each sequence ranges from random to quasi‐periodic. That pattern is disturbed by transient stresses in cases where a sequence locates close to a large earthquake. Slip rates inferred from the new data offer a high‐resolution view of subsurface creep along individual fault strands and resolve slip partitioning across wider zones of deformation. Key Points: We identify 27,675 repeating earthquakes in 7,713 sequences based on waveform similarity, co‐location, and size of the eventsThe sequences are widespread, with temporal behavior of events ranging from random to quasi‐periodic over the 30‐year observation periodThe new data imply aseismic slip partitioning across many major and minor faults within the San Andreas Fault system [ABSTRACT FROM AUTHOR]

A new global optimization method is used to determine the distribution of earthquakes on a complex, connected fault system. The method, integer programming, has been advanced in the field of operations research but has not been widely applied to geophysical problems until recently. In this application, we determine the optimal distribution of earthquakes on mapped faults to minimize the global misfit in slip rates for multifault ruptures. Integer programming solves for a decision vector composed of every possible location that a sample of earthquakes can occur on every fault, subject to slip rate uncertainty constraints. Step over connections are straightforward to include, whereas branching fault connections are not. To include branching ruptures, we distinguish between individual multifault rupture paths, as opposed to formulating the integer programming problem based on individual faults as in previous studies. The new method is applied to the complex fault system in the San Francisco Bay Area as a case study. Results from the integer programming method are compared to those from a local optimization method, termed the greedy-sequential method. Several experiments using these two methods indicate that shape of the on-fault magnitude distributions and which branching faults are involved in multifault ruptures depend on how much emphasis is placed on fitting the target slip rate. In cases where the underlying data are not strong enough to warrant chasing the target slip rate, it is better to focus on the distribution of feasible results that better represents the uncertainty in the solutions imposed by the data. [ABSTRACT FROM AUTHOR]

This paper is concerned with the problem of constraint control for an Antilock Braking System (ABS) with asymmetric slip ratio constraints. A nonlinear backstepping control method based on Barrier Lyapunov Function (BLF) is proposed not only to track the optimal slip ratio but also to guarantee no violation on the slip ratio constraints. A second order slip rate model is established based on a quarter vehicle braking model and a Burckhardt's tire model. The Asymmetric Barrier Lyapunov Function (ABLF) is introduced into the backstepping controller for solving the asymmetric slip ratio constraint problems. The proposed controller can implement ABS zero steady state error tracking of the optimal wheel slip ratio and make slip ratio constraints flexible for various runway surfaces and runway transitions. Simulation results show that the control scheme can guarantee no violation on slip ratio constraints and avoid self-locking. [ABSTRACT FROM AUTHOR]

The injection‐induced slip of a fault containing along‐the‐fault geometrical complexities such as permeable cracks, dilational jogs and branches, was studied numerically using a plane‐strain hydraulic fracture model. The fault is modeled by placing complexities evenly spaced on either side of the inlet where fluid coming from a steady source is injected at a constant rate. The fault slip obeys the Coulomb friction law with slip weakening of the coefficient of friction. The applied shear stress is less than the residual fault strength, corresponding to a situation where a fault undergoes stable slip behind a slowly advancing rupture front. The numerical results show that the segments of complexity may not only delay slip zone extension and fluid flow, but temporarily increase slip rates. Short‐term faster slip rates occur after cracks and jogs are pressurized. The slip rate can reach values typical of microearthquake events, accompanied by rising and then dropping pressure and producing a stress release. Especially, the discontinuous slip sources are separated by the right‐angle jogs that do not slip. The slip on branches can be activated by fluid invasion and an associated normal effective stress reduction, and the slow slip sources eventually move from the fault to the branches. Even if a hydraulic fracturing treatment presents a low risk of generating dynamic slip, when fractures intersect faults containing geometrical complexities, fast slip events may be induced. The spatiotemporally varying slip rates and patterns presented provide an alternative interpretation for recorded seismic slip signals. Key Points: Along‐the‐fault geometrical complexities affect the slip location and rate.Short‐term fast slip rates can be generated by along‐the‐fault dilational segments.Fast slip duration and spatial pattern from seismicity may provide an estimate of rupture geometries. [ABSTRACT FROM AUTHOR]

The slip ratio, which is the ratio of the slip speed to the driving speed, is an essential input in tire models for vehicle-driving analysis. At a driving speed of zero, because the denominator of the slip ratio is zero, singularity is crucial for stable numerical analysis for examining the low-speed dynamic behavior of vehicles. A lagged slip ratio is widely adopted in most commercial software to prevent such failures, but this causes oscillation and requires a tuning parameter. Moreover, it increases the computational complexity because differential equations are employed to define the slip. To overcome this, researchers proposed a modified slip ratio without a differential equation; however, a tuning parameter was still required. Herein, we propose an advanced slip-ratio calculation method that allows stable simulation without the use of a differential equation or tuning parameter in the explicit integration. The accuracy and stability of the proposed slip ratio were verified against other methods via braking simulation. The proposed method showed very stable results compared to conventional methods and did not fail even with explicit integration. Furthermore, in the case of implicit integration, it prevented step-size reduction. [ABSTRACT FROM AUTHOR]

This paper proposes a novel control strategy to improve the stability performance for four-wheel independent drive electric vehicles in critical cornering by introducing the supervision mechanism for yaw moment control and slip ratio regulation simultaneously. The proposed control strategy is a three-level structure: the first level is composed of a yaw moment controller and a longitudinal velocity controller; the second level is made up of a tyre force distributor; and the third level consists of a slip ratio regulator. To begin with, the supervision mechanism is developed to supervise vehicle driving states and determine whether the yaw moment controller should be activated. After that, the tyre force distributor is presented to assign the resultant force/moment generated by the first level to the four independent wheels, in which average distribution, dynamic load distribution, and optimal distribution schemes are separately discussed for comparison. Also, the slip ratio regulator is designed to regulate the slip ratio within the threshold. In the end, simulations performed on a nonlinear vehicle model with eight degree of freedom validated the effectiveness of the proposed control strategy and approaches. [ABSTRACT FROM AUTHOR]

The accurate predictions of void fraction and gas volume fraction are important in characterizing wet gas flow, as they are the basic input for determining other key flow parameters, such as flow velocity and flow rate of each phase. In previous studies, empirical relationships were used to predict void fraction and gas volume fraction, which have limited applicability due to the lack of detailed structural and dynamic information involved in two-phase flow. Hence, in this work, attempts are being made to develop a model based on a simplified two-phase interfacial structure. A slip ratio based equal-diameter double-circle model is proposed to predict the void fraction and gas volume fraction using gamma ray attenuation method for high-pressure wet gas conditions. Model predictions were verified against experiments in a 172.0 mm inner diameter horizontal pipe. Nitrogen and kerosene were used as the test fluids with gas volume fractions ranging from 92% to 100%. The relative errors in the line-averaged void fraction predicted by the slip ratio based model were within ± 2 % . In addition, this model can be used to explain the relationship between the key flow parameters and further to predict the optimal measuring angle of the gamma rays. The line-averaged void fraction measured by the gamma ray attenuation method at a proper angle predicted by the model is equal to the gas volume fraction for these high-pressure wet gas conditions, with an average relative error of 0.2%. [ABSTRACT FROM AUTHOR]

In this paper, the phase redistribution of refrigerant two-phase flow at a horizontal branch T-junction was investigated experimentally. The T-junction had equal-sized inlet and outlet tubes (internal diameter 8.0 mm). During the experiments, three refrigerants, namely R134a, R600a and R245fa were considered. The inlet mass flux and quality were varied from 200 to 500 kg m −2 s −1 and from 0.1 to 0.9, respectively. Meanwhile, the mass flux of the branch was regulated by keeping the mass flow ratios to 0.3, 0.5 and 0.7. Under these experimental conditions, intermittent and annular flows at the T-junction inlet were identified and predicted. After analyzing the experimental data, it was found that the vapor is preferred to flow into the branch. As the inlet quality increases, the fraction of vapor extracted into the branch decreases, whereas the mass flux has little influence on the phase redistribution of refrigerant under the same flow pattern. Furthermore, a higher vapor fraction can be obtained by a larger mass flow ratio. For the effect of refrigerant on the phase separation, the vapor faction of the branch satisfies the following order: R245fa > R600a > R134a. The product of momentum ratio and viscosity ratio between vapor and liquid is defined to characterize the phase separation degree of refrigerant qualitatively. In order to test the applicability of the published models in the literature, the present data are compared with the predicted values. The results show that the models for air-water are not appropriate to predict the phase redistribution of refrigerant two-phase flow at the T-junction. A separation model for refrigerant should be proposed by coupling with the pressure drop. [ABSTRACT FROM AUTHOR]

This paper proposes an experimental method of predicting the traction performance of a small tracked mobile robot. Firstly, a track-terrain interaction model based on terramechanics is built. Then, an experimental platform of the tracked robot is established, on which the measurement methods of the parameters that influencing the accuracy of the prediction model are introduced and the data post-processing are improved, including drawbar pull, slip ratio, sinkage, track deformation and so on. Based on the experimental data, several key terrain parameters are identified. With the tracked robot platform, the drawbar pull-slip ratio relationship is tested, and the effects on drawbar pull considering different kinds of terrain and the influence of the grousers are analyzed as well. The research results provide a reference for the experimental study on the traction performance of small tracked robots. [ABSTRACT FROM AUTHOR]

The recurrence period of maximum magnitude earthquake in a seismogenically active formation along the Kopili Fault has been estimated having adequate dependence on the slip rate, moment rate and its seismicity pattern. Here, the frequency–magnitude cum fault area–maximum magnitude relations play a key role with input parameters pertinent to the Kopili Fault zone. Subsequently, where the fault slip rate estimates are not available, the seismic activity is studied from the seismic moment release. The results of this study show that the return period has a strong relation with the fault length, slip rate, strain drop and rigidity. This study ascertains the activity rate in terms of the return period as ∼50 ± 5 years with the moment release of 2.12E+23 dyne-cm from the most active 80-km fault length consideringMw5.5 as reference magnitude under the Kopili Fault zone that may produce a maximum magnitude ofMw∼ 7.6. Finally, we conclude that these models can be used to study the rate of seismicity of the active faults in Northeast India which will provide us prime inputs for seismic hazard analysis of the region and is especially significant for estimating expected return period for poorly known faults or blind faults that lack surface expression. [ABSTRACT FROM AUTHOR]

In this research work, the hydrodynamic behavior of a Kühni extraction column has been investigated for determination of slip velocity and characteristic velocity for three different liquid–liquid systems with and without mass transfer conditions and toluene–water system with the presence of silica nanoparticles. The effects of the agitation speed, dispersed as well as continuous phase velocity, and interfacial tension were studied. The findings revealed that an increase in agitation speed and continuous phase velocity led to the reduction of slip velocity while it increased with increasing dispersed phase velocity. More buoyancy and faster upward movement of larger drops accelerate the slip velocity in the dispersed to continuous phase mass transfer condition as compared with the case of no mass transfer. In addition, the slip velocity decreased in the experimental conditions with nanoparticles because of the decrease in Sauter mean drop diameter and the increase in the holdup. Empirical correlations for prediction of slip and characteristic velocities are recommended. The results of the proposed correlations were compared with the experimental data obtained from the literature and the present investigation. Findings of this study demonstrated that the proposed correlations gave accurate predictions for slip velocity and characteristic velocity. [ABSTRACT FROM AUTHOR]

Wheeled mobile robots (WMRs) often suffer from the longitudinal slipping when moving on the loose soil of the surface of the moon during exploration. Longitudinal slip is the main cause of WMRs' delay in trajectory tracking. In this paper, a nonlinear extended state observer (NESO) is introduced to estimate the longitudinal velocity in order to estimate the slip ratio and the derivative of the loss of velocity which are used in modelled disturbance compensation. Owing to the uncertainty and disturbance caused by estimation errors, a multi-objective controller using the mixed H 2 / H ∞ method is employed to ensure the robust stability and performance of the WMR system. The final inputs of the trajectory tracking consist of the feedforward compensation, compensation for the modelled disturbances and designed multi-objective control inputs. Finally, the simulation results demonstrate the effectiveness of the controller, which exhibits a satisfactory tracking performance. [ABSTRACT FROM AUTHOR]

Here peristalsis of Sisko nanoliquid with gyrotactic microorganism in a curved channel is investigated. Channel boundaries comprises the wall properties and second order slip conditions for velocity. Consideration of Newtonian heat, mass and gyrotactic microorganisms aspects characterizes the heat, mass and motile density transfer processes. Flow formulation is established utilizing constitutive relations of Sisko fluid. Lubrication theory is employed for the simplification of governing expressions. Further numerical solution is carried out for velocity, temperature, concentration and motile density gyrotactic microorganisms. The numerical solution is justified through graphical results. Graphical discussion determined that velocity has opposite behavior for first and second order velocity slip parameters. Interestingly Sisko fluid parameter has opposite impact on velocity for both shear thinning and shear thickening cases. It is seen that temperature enhances for Newtonian heating whereas concentration and gyrotactic microorganism reduces for Newtonian mass and Newtonian gyrotactic microorganisms. [ABSTRACT FROM AUTHOR]

In this paper, an optimal longitudinal slip ratio system for real-time identification of electric vehicle (EV) with motored wheels is proposed based on the adhesion between tire and road surface. First and foremost, the optimal longitudinal slip rate torque control can be identified in real time by calculating the derivative and slip rate of the adhesion coefficient. Secondly, the vehicle speed estimation method is also brought. Thirdly, an ideal vehicle simulation model is proposed to verify the algorithm with simulation, and we find that the slip ratio corresponds to the detection of the adhesion limit in real time. Finally, the proposed strategy is applied to traction control system (TCS). The results showed that the method can effectively identify the state of wheel and calculate the optimal slip ratio without wheel speed sensor; in the meantime, it can improve the accelerated stability of electric vehicle with traction control system (TCS). [ABSTRACT FROM AUTHOR]

Magic Formula (MF) tyre model is widely used for the analysis of tyre behavior in different driving situations. The model is mostly used to fit the simulation and experimental data slip curves. As there are many modifications of the MF, this paper presents a literature analysis of MF application and fitting techniques. A short review of other empirical tyre models was also made. At the end, a simple least squares minimisation technique was used to fit the experimental data of longitudinal tyre performance on ice. Measurements were performed with the inner drum test rig in the laboratory. In general, the fitting showed a very good accuracy. [ABSTRACT FROM AUTHOR]

In this study the flow field of a nonlocal, diffusive upper convected Maxwell fluid in a solvent undergoing shearing motion is revisited for pressure driven planar channel flow and the free boundary problem of a liquid layer on a solid substrate is investigated. For large ratios of the zero shear polymer viscosity to the solvent viscosity, channel flows exhibit boundary layers at the channel walls. In addition, for increasing stress diffusion the flow field away from the boundary layers undergoes a transition from a parabolic to a plug flow. Corresponding flow structures and transitions are found for the free boundary problem of a thin layer sheared along a solid substrate. Matched asymptotic expansions are used to first derive sharp-interface models describing the bulk flow with expressions for an apparent slip for the boundary conditions, obtained by matching to the flow in the boundary layers. For a thin-film geometry several asymptotic regimes are identified in terms of the order of magnitude of the stress diffusion, and corresponding new thin-film models with a slip boundary condition are derived. [ABSTRACT FROM AUTHOR]

In petroleum industries, the demand for effective design and operation of the oil-water transport systems is very high, and holdup of each phase is one of the important hydrodynamic parameters needed for such design and operation. This parameter can be affected by several factors one of which is the presence of the drag-reducing polymers in the oil-water flow. Therefore, the focus of this experimental study is on the effect of the drag-reducing polymer on the holdups and by extension, velocity ratios of the oil-water flow. Specifically, the investigation of the holdups and velocity ratios of the oil-water flow before and after the addition of the drag-reducing polymer was carried out in horizontal (0 ᴼ ) and different inclined (−5 ᴼ , +5 ᴼ and +10 ᴼ ) acrylic pipe with 30.6-mm ID. The investigation was conducted using flow conditions of 0.4, 0.8 and 1.6 m/s mixture velocities and 0.1–0.9 input oil volume fractions at each inclination. In each experimental run, the holdup of each phase was measured after steady flow was achieved using quick closing valves. Thereafter, the master solution of the polymer which was prepared at 2000 ppm water was injected at controlled flow rates to provide 40 ppm of the polymer in the water phase and the measurement was repeated. It was found generally that the water holdups and hence, the velocity ratios were increased after the addition of the polymer particularly in water-dominated flow regions. The velocity ratios also increased with the increase in the mixture velocities at these same flow regions. Finally, water was found to flow faster for separated flow at 0.4 m/s while for the dispersed flow regions at higher mixture velocities, the dispersed phase was in general the faster flowing phase. [ABSTRACT FROM AUTHOR]

In this paper, a numerical investigation on the effects of variable viscosity, slip velocity and heat generation or absorption on power-law fluids with heat and mass transfer over a moving permeable surface is carried out. The transformation of the governing boundary layer equations into ordinary differential equations has been performed by applying similarity transformations. The transformed governing equations are numerically solved by using MATLAB BVP solver bvp4c. The obtained results are presented graphically and discussed for various values of the viscosity parameter, the slip parameter, the heat generation or absorption parameter, the Eckert number and Lewis number. The result shows that, the variable viscosity parameter θc → ∞, it is confirmed that the local skin-friction coefficient decreases while heat and mass transfer rates increases. The heat and mass transfer rates increases rapidly on increasing the Prandtl number. The rate of mass transfer is rapidly increased when the Lewis number increased. [ABSTRACT FROM AUTHOR]

The paper investigates gradient effects, which relate to how highly stressed regions should be dealt with in fatigue design analyses. In particular stress gradients in rolling contact are investigated with a focus on differences in response between full and partial slip conditions. To this end the multiaxial state of stress beneath a wheel–rail contact featuring full or partial slip is quantified using a multiaxial equivalent stress criterion. A comparative study shows that the significant differences in peak interfacial shear stress magnitudes between full and partial slip conditions are significantly reduced when translated to equivalent stress magnitudes. An innovative procedure to quantify the gradient effects by comparing the multiaxial contact stress field to uniaxial conditions is developed and employed. For the studied cases stress gradients beneath the frictional contact were found to be similar to stress gradients outside a uniaxially loaded large plate featuring a small hole with a radius in the order of 0.5–0.7 mm. The study concludes that the use of local magnitudes of interfacial shear stress in the analysis of surface initiated rolling contact fatigue under partial slip conditions is conservative. The analysis framework established in the current study can be used to estimate the level of conservativeness. [ABSTRACT FROM AUTHOR]

The objective of this study is to evaluate the effect of slip ratio on the wear and rolling contact fatigue (RCF) of wheel/rail materials using a rolling–sliding wear testing apparatus. The results indicate that two wear types are presented in terms of wear rate: type I (mild wear) and type II (severe wear). In type I wear, cracks propagate parallel to the surface. While in type II, the peeling is aggravated and spalling can be observed. With the slip ratio increasing, the wear mechanism of rollers transforms from slight oxidation wear and peeling to severe fatigue wear and spalling. Due to the mild wear and light plastic deformation in type I, the angle and depth of cracks show no obvious differences between the wheel and rail rollers. The crack depth and angle increase in type II wear owing to severe plastic deformation, while the depth is smaller on the wheel rollers. The size of flake wear debris presents an increasing trend and the main composition is Fe 2 O 3 and metallic iron, and the content of iron diminishes with increasing oxidation. [ABSTRACT FROM AUTHOR]

The slip velocity between particle size classes in a homogeneous bidisperse gas-solid flow is quantified using particle-resolved direct numerical simulation (PR-DNS). This slip velocity is the key characteristic of size segregation in industrial devices. The ability of current gas-particle drag models to predict this slip velocity is examined by simultaneously solving the mean momentum equations for the gas phase and dispersed phases. PR-DNS of fixed particle assemblies is then used to validate and improve the bidisperse gas-particle drag model. The drag model inferred from bidisperse fixed beds is compared with the drag force measured from PR-DNS of freely evolving bidisperse suspensions. The ability of this new model to predict the slip velocity between particle size classes in a bidisperse gas-solid flow is also examined. [ABSTRACT FROM AUTHOR]

The paper aims at the investigation of the effect of slip ratio on the rolling contact fatigue (RCF) performance of Fe-based alloy coatings. A double-roll test machine is employed to perform the experiment. The result shows that slip ratio has a significant influence on the RCF performance of Fe-based coating. With the increment of the slip ratio, the RCF failure life keeps decreasing but the shape parameter β of Weibull mode decreases first, then increases. The failure mechanism under pure rolling contact condition is the accumulation of micro-pits and the propagation of fatigue cracks within the coating. However, under nonzero slip ratio condition, failure is controlled by the coupling of the cyclic loading action and of the friction force. [ABSTRACT FROM AUTHOR]

Experimental results of a series of laboratory pullout tests on a new screw soil nail are presented. A review of the literature for the screw soil nails as well as a comparison of its performance with other conventional types of soil nails is discussed. The present investigation also examines the fundamental interface mechanism and attempts to define the associated rupture zones in cohesionless material with the aid of thin vertical bands of coloured sand cast in a large distinctly fabricated pullout box. The philosophy behind the design and development of the new screw nail is briefly described first followed by presentation of the laboratory testing procedure and its instrumentation. The results of the testings indicate that the slip mechanism, which controls the pullout behaviour, is rather different to the conventional soil nails and the resultant pullout capacity is higher when compared to this type soil nails. This effect is attributed to the geometry of the screw nail and the installation processes that result in the development of different soil stresses around the soil nail. In addition, the experimental pullout results demonstrate, contrary to the conventional soil nail, that the screw nail pullout capacity is dependent on the overburden pressure and that the failure planes extends out a certain radial distance from the soil–nail interface. From the test results, it is shown that the failure of the screw nail satisfies the Mohr–Coulomb failure condition, which is similar behaviour seen in the conventional soil nail tests. [ABSTRACT FROM AUTHOR]

The development of highly efficient nanofluidic devices necessitates means for enhancing and controlling fluid transport under confinement. Here, it is shown experimentally that significant interfacial drag reduction in nanoscale channels can be obtained with hydrophobic arrays of conical textures tapering to a radius of less than 10 nanometers at their tip. This geometry maximizes interfacial slippage by trapping a highly resilient air layer at the solid/liquid interface. Further, it is revealed that the composite liquid/solid-air interface bears an electrostatic charge density comparable to that of a flat hydrophobic solid. Altogether these properties render the nanotextured surfaces highly attractive for efficient nanofluidic transport both in pressure-driven and electroosmotic flow. [ABSTRACT FROM AUTHOR]

An analysis of micropolar and power law fluid–lubricated partial slip–partial slip texture slider and journal bearings is presented. The nondimensional pressure and shear stress expressions for a partial slip texture configuration are analyzed using narrow groove theory. The parameters used in the analysis are nondimensional partial slip length, nondimensional partial slip–partial slip texture length, nondimensional depth of recess, ratio of land with slip to recess, nondimensional slip coefficient, coupling number; ratio of characteristic length to film gap, and power law index. A partial slip configuration with a higher slip coefficient yields an improvement in load capacity and reduction in coefficient of friction compared to a partial slip texture configuration for micropolar and power law shear thinning (pseudoplastic) fluid-lubricated slider and journal bearings. [ABSTRACT FROM PUBLISHER]

Under complicated situations, such as the low slippery road surface and split-μ road surface, traction control system is the key issue to improve the performance of vehicle acceleration and stability. In this paper, a novel control strategy with engine controller and active pressure controller is presented. First and foremost, an ideal vehicle model is proposed for simulation; then a method for the calculation of optimal slip ratio is also brought. Finally, the scheme of control method with engine controller and active brake controller is presented. From the results of simulation and road tests, it can be concluded that the acceleration performance and stability of a vehicle equipped with traction control system (TCS) can be improved. [ABSTRACT FROM AUTHOR]

A method is presented for the online prediction of the terrain-shearing parameters for a wheeled Unmanned Ground Vehicles (UGVs) traversing on an unknown terrain. The method uses a trained multiple-output least squares support vector machine (LS_SVM) to map engineering data and predict the terrain-shearing parameters such as cohesion, internal friction angle and shear deformation modulus without requiring information on wheel sinkage. The predicted terrain-shearing parameters can be used to predict vehicle drawbar pull which can be used for trafficability prediction, traction control and performance optimization. Experiments were performed using a single-wheel soil bin to measure the sinkage, drawbar pull and torque for a griddle net wheel under different slip ratio. An additional experiment was performed under a continuous slip ratio from 0.2 to 0.6 with a wheel load of 50 N to validate the method. The experimental results show that the multiple output LS_SVM model can accurately predict the terrain-shearing parameters using the slip ratio, torque and wheel load without the need of wheel sinkage. [ABSTRACT FROM AUTHOR]

The earthquake slip distribution self-similarity is investigated in this study. We complied finite fault slip models for earthquakes in the Taiwan orogenic belt and global earthquakes to determine the slip distribution self-similarity. Forty-one earthquakes (19 Taiwan earthquakes and 22 global earthquakes) in the Mw = 4.6 - 8.9 magnitude range were examined. The fault slip exhibited self-similar scaling between the rupture slip and area. The average area ratio (Rs) and slip ratio (Rd) follows a scaling of Rs = 10a-n(Rd) . Slip self-similarity implies that a fault rupture exhibits fractal behavior. The scaling exponent can be considered as a measure for the roughness degree of the slip distribution on the fault surface. This study suggests that the slip distribution for large earthquakes (Mw > 7.0) tends to have a more homogeneous slip. Scaling exponents can provide insight into earthquake rupture mechanics and the scaling of heterogeneous slips on the fault surface provides a basis for ground motion simulation for a finite fault for an earthquake scenario, particularly for near-fault motion. [ABSTRACT FROM AUTHOR]

This study proposes a novel approach to evaluating and controlling the traction force of a wheel directly driven by an electric motor on different road surfaces. Instead of slip ratio measurements, the database of the motor called the current-RPM-torque database can evaluate the traction force of the wheel. The feedback of the measured current and the rotational speed can assist the autonomous traction controller synthesized from this database by the neural network approach when one traction wheel of the vehicle is traveling on different kinds of road surfaces. The adequate gains which are the training data for the neural network control synthesis have to satisfy the assigned specifications in time domain for different slip ratios. This paper also finds that the adequate gains mainly depend on slip ratio slope rather than slip ratio. Based on a scenario similar to real situations, the simulated results in this study show that it is feasible to evaluate and control the traction force through the motor database by the feedback of the current and the RPM. [ABSTRACT FROM AUTHOR]

In gas-liquid two-phase flow, void fraction is the most unique parameter which influences all the transport processes. In the most general case, though the void fraction varies non-linearly with the channel length, many practical simulations make use of the "system mean void fraction." The present investigation makes a critical assessment of different system mean void fraction models for a wide range of slip velocity and density difference between the phases. To this end, different correlations for slip ratio have been considered and, for all the cases, closed form expression for the system mean void fraction has been presented. The local as well as the system mean void fractions have also been estimated numerically from a heat transfer based model. Predictions from the heat transfer based model and the slip ratio based model have been compared. As an application, the slip ratio based system mean void fraction is used in to build the moving boundary model for phase-change heat exchangers. The prediction of startup transients for both an evaporator and a condenser of an automotive air conditioning system (AACS) agrees well with the experimental results. INSET: 0. [ABSTRACT FROM AUTHOR]

Measurement of tyre longitudinal slip-ratio is often estimated from three independent measurements devices namely wheel rotation speed, vehicle speed and tyre rolling radius. This produces an expensive measurement system to indirectly determine the slip-ratio. This paper presents a method by which the slip-ratio is determined from a video camera using digital image correlation techniques. The camera, mounted in such a way that the contact patch region is captured, enables the system to measure the tyre tread speed and ground speed at the contact patch. The slip-ratio is then determined from these two measurements. [ABSTRACT FROM AUTHOR]

Wheeled exploration robots (WERs) used for applications such as planetary exploration have to traverse loose terrain, often, during which time they may suffer longitudinal slip and side slip owing to the interaction between their rigid wheels and the loose soil. Longitudinal slip and side slip are the main causes for WERs delay or deviate from the ideal trajectory. But the presented work is indeed focused on longitudinal slip. By analyzing and simplifying the wheel–soil interaction terramechanics model for this case, the algorithm for an adaptive fuzzy control law based on slip ratio optimization is designed to optimize the tractive efficiency and minimize energy consumption. Its stability is proved, and conditions for control parameters are derived. Analytical and simulation results demonstrate that the proposed control system significantly improves the mobile performance of the WER. [ABSTRACT FROM AUTHOR]

While the kinematics of Anatolia plate and the North Anatolian Fault System (NAFS) has been studied extensively, the slip rate and locking depth along the NAFS are usually assumed constant in the analyses due to the lack of sufficient data. This is also partly due to the reasonably good fit of Euler small circle and partly due to the lack of spatial resolution of observations to determine slip rates independently from locking depths. On the other hand, recent geodetic studies show a contrast for locking depth between Marmara and other parts of the NAFS, implying a non-uniform locking depth across the NAFS. In this study, we analyse new GPS data and homogenously combine available data sets covering the eastern part of the NAFS to form the most complete data set. In particular, we incorporate the first results of Turkish Real-Time Kinematic GPS Network (CORS-TR) into our data set. A detailed analysis of three profiles within the NAFS reveals an increase of locking depth in the middle profile to 19.1 ± 3.4 km from 11.9 ± 3.5 km in the easternmost profile while the slip rate is nearly constant (20-22 mm yr-1), which implies a variation of strain rate of ~100 nanostrain yr-1. Assuming a constant locking depth throughout whole NAFS gives an average locking depth of 14.3 ± 1.7 km. Our best estimates of slip rates in block modelling which takes the variation of locking depths into account are in the range between 22.5 and 22.8 mm yr-1 over eastern part of the NAFS. [ABSTRACT FROM AUTHOR]

This paper proposes a model-based range extension control system for electric vehicles. The proposed system optimizes the front and rear driving–braking force distributions by considering the slip ratio of the wheels and the motor loss. The optimal distribution depends solely on vehicle acceleration and velocity. Therefore, this system is effective not only at constant speeds but also in acceleration and deceleration modes. Bench tests were conducted for more precise evaluation and to realize experimental results with high reproducibility. The effectiveness of the proposed system was verified through field and bench tests. [ABSTRACT FROM PUBLISHER]

This paper presents an acceleration slip regulation strategy for distributed drive electric vehicles with two motors on the front axle. The tasks of the strategy include controlling the slip ratio to make full use of the road grip and controlling the yaw rate to eliminate the lateral movement due to the difference between motor torques. The rate of the slip ratio change can be controlled by controlling the motor torque, so that the slip ratio can be controlled by applying a proportional-integral control strategy to control the rate of the slip ratio change. The yaw rate can be controlled to almost zero by applying torque compensation based on yaw rate feedback. A coordination control strategy for the slip ratio control and yaw rate control is proposed based on analysis of the priorities and features of the two control processes. Simulations were carried out using MATLAB/Simulink, and experiments were performed on a hardware-in-loop test bench with actual motors. The results of the simulations and experiments showed that the proposed strategy could improve the longitudinal driving performance and straight line driving stability of the vehicle. [ABSTRACT FROM AUTHOR]

To investigate and improve the mobility of the Lunar Roving Vehicle (LRV), it is necessary to consider the mechanical properties of the interaction between the wheels and the ground. In this paper, a new solution method, the forced-slip solution method, which uses a semi-empirical approach, was presented. That is, given the wheel’s vertical load and drawbar pull or driving torque as known input values, the unknown slip ratio can be resolved. The alternative method involves predicting the mechanics for a given slip ratio. The proposed method correlates better with actual wheel movements, and by studying a single wheel, this solution method can also be used to resolve the mechanical properties of the front and rear wheels in a four-wheel-drive (4WD) LRV configuration. It can also be used to consider the multi-pass effect of the rear wheels on lunar soil. The calculation results show that the 4WD LRV driving efficiency varies with the position of the center of mass. Thus, the LRV driving efficiency can be optimized by adjusting the position of its center of mass. [ABSTRACT FROM AUTHOR]

The running parameters of lunar rover locomotion system often varies during running. The traditional control method cannot be used to gain the optimal control effect in any case. The variable structure control with sliding mode (VSS) is a special non-linear control method and has strong robustness. The method is easy to be realized. The control logic and algorithm of lunar rover slip-ratio control are established based on the dynamic model of lunar rover and the variable structure control system with sliding mode theory. The control characteristics of VSS are analyzed in details. VSS is applied in slip-ratio control of the lunar rover locomotion system successfully. The simulation is conducted. The simulation results show that the control method has good control effect. [ABSTRACT FROM AUTHOR]

The electric vehicle with four direct-driven in-wheel motors is an over actuated system. A three-level control strategy of electronic stability control (ESC) is proposed to achieve optimal torque distribution for four in-wheel motors. The first level is a gain-scheduled linear quadratic regulator which is designed to generate the desired yaw moment command for ESC. Control allocation is the second level which is used to distribute the desired longitudinal tire forces according to the yaw moment command while satisfying the driver's intent for acceleration and deceleration. The associated weighting matrix is designed using the work load ratio at each wheel to prevent saturating the tire. The third level is slip ratio control (SRC) which is employed at each wheel to generate the desired longitudinal tire force based on a combined-slip tire model. Simulation results show that the proposed method can enhance the ESC performance for the test maneuvers. Since the tire model is often unknown for practical implementation, the effectiveness of the SRC is studied using the sine with dwell test. It is found that the SRC is not crucial for achieving performance similar to the proposed method with SRC, if the slip ratio can be maintained in the stable region using traction control system/anti-lock braking system. [ABSTRACT FROM AUTHOR]

Abstract: We describe a kinematic approach to simulate folds above listric propagating thrusts. The model is based on a pre-defined circular thrust geometry with a maximum central angle beyond which the thrust is planar, inclined shear above the circular thrust, and trishear in front of the thrust. Provided the trajectory of thrust propagation is established, the model can be run forward and backwards. We use this last feature to implement a global simulated annealing, inverse modeling strategy. This inverse modeling strategy is applied to synthetic folds as well as two real examples in offshore Venezuela and the Niger Delta toe-thrust system. These three examples illustrate the benefits of the algorithm, particularly in predicting the possible range of models that can fit the structures. Thrust geometry, depth to detachment level, and backlimb geometry have high impact in model parameters such as backlimb shear angle and fault slip; while forelimb geometry is critical to constrain parameters such as fault propagation to fault slip ratio and trishear angle. Steep to overturned beds in forelimb areas are often not imaged by seismic, so in the absence of additional well data, considering all possible thrust-fold geometries is critical for the modeling and whatever prediction (e.g. hydrocarbon trap integrity) is made from it. [Copyright &y& Elsevier]

Highlights: [•] The effect of inclination on distribution parameter and drift velocity is studied. [•] Slug behaviors in different flow regions are investigated. [•] Inclination influences the void fraction and slip ratio. [•] Drift flux models for calculating void fraction are evaluated. [•] Correlations of frictional pressure drop are evaluated in different flow regions. [ABSTRACT FROM AUTHOR]

Slip at the interface between immiscible polymer melts remains poorly understood. A method that relies solely on rheological measurements to obtain the interfacial slip velocity uses the slip-induced deviation in the flow variables. To use the method, accurate estimates of the flow variables under the assumption of no-slip are necessary. Although such estimates can be easily derived under some cases, in general, this is not straightforward. Therefore, methods to determine the interfacial slip velocity without using estimates for the flow variables under no-slip conditions are desirable. In this work, we focus on investigations of slip at the interface between two immiscible polymer melts undergoing two-phase coaxial flow. To enable such investigations, we have adapted the Mooney method, usually used to investigate wall slip, to investigate polymer/polymer interfacial slip. Using this method, we have measured the slip velocity at the interface between polypropylene and polystyrene as a function of the interfacial stress. To determine the validity of the modified Mooney method, we also determine the slip velocity using the slip-induced deviation in the flow variables. To enable this determination, we use polypropylene and polystyrene with almost identical shear rate-dependent viscosities over a range of shear rates. The slip velocity obtained from the modified Mooney method displayed excellent agreement with that determined using the deviation from no-slip. In agreement with prior work, the dependence of the slip velocity on the interfacial stress is a power-law. Our investigation spans a sufficiently wide range of interfacial stress to enable the direct observation of two power-law regimes and also the transition between the two regimes. We also find that the power-law exponent of approximately 3 at low stresses decreases to approximately 2 at high stresses. [ABSTRACT FROM AUTHOR]

A challenging problem faced by wheeled mobile robots (WMRs) such as planetary rovers traversing loose sloped terrain is the inevitable longitudinal slip suffered by the wheels, which often leads to their deviation from the predetermined trajectory, reduced drive efficiency, and possible failures.This study investigates this problem using terramechanics analysis of the wheel-soil interaction. First, a slope-based wheel-soil interaction terramechanics model is built, and an online slip coordinated algorithm is designed based on the goal of optimal drive efficiency. An equation of state is established using the coordinated slip as the desired input and the actual slip as a state variable. To improve the robustness and adaptability of the control system, an adaptive neural network is designed. Analytical results and those of a simulation using Vortex demonstrate the significantly improved mobile performance of the WMR using the proposed control system. [ABSTRACT FROM AUTHOR]

Abstract: A novel technique for the identification of the tire–road grip conditions is presented. This is based on the use of strain information inside the tire, from which relevant characteristics of the tire–road contact can be extracted also through a factor named area slip ratio. This process forms the basis of a technology for grip identification that requires a new model of the tire dynamics. The model permits to determine closed form analytical relationships between the measured strain and the area slip ratio. On this basis, a procedure that can extract the contact kinematic parameter from the time history of the internal strain of the rolling tire is presented. Numerical simulations offer the chance to validate the identification algorithm. [Copyright &y& Elsevier]

In gas–liquid two-phase flow, the prediction of two-phase density and hence the hydrostatic pressure drop relies on the void fraction and is sensitive to the error in prediction of void fraction. The objectives of this study are to analyze dependence of two-phase density on void fraction and to examine slip ratio and drift flux model-based correlations for their performance in prediction of void fraction and two-phase densities for the two extremes of two-phase flow conditions, that is, bubbly and annular flow or, alternatively, the low and high region of the void fraction. It is shown that the drift flux model-based correlations perform better than the slip ratio model-based correlations in prediction of void fraction and hence the two-phase mixture density. Another objective of this study is to verify performance of different two-phase dynamic viscosity models in prediction of two-phase frictional pressure drop. Fourteen two-phase dynamic viscosity models are assessed for their performance against 616 data points consisting of 10 different pipe diameters in annular flow regime. It is found that none of these two-phase dynamic viscosity models are able to predict the frictional pressure drop in annular flow regime for a range of pipe diameters. The correlations that are successful for small pipe diameters fail for large pipe diameters and vice versa. [ABSTRACT FROM AUTHOR]

A high-resolution digital elevation model (DEM, 1 ms spacing) derived from an airborne light detection and ranging (LiDAR) campaign was used in an attempt to characterize the structural and erosive elements of the geometry of the Pettino fault, a seismogenic normal fault in Central Apennines (Italy). Four 90- to 280 m-long fault scarp segments were selected and the surface between the base and the top of the scarps was analyzed through the statistical analysis of the following DEM-derived parameters: altitude, height of the fault scarp, and distance along strike, slope, and aspect. The results identify slopes of up to 40° in faults lower reaches interpreted as fresh faces, 34° up the faces. The Pettino fault maximum long-term slip rate (0.6–1.1 mm/yr) was estimated from the scarp heights, which are up to 12–19 m in the selected four segments, and the age (ca. 18 ka) of the last glacial erosional phase in the area. The combined analysis of the DEM-derived parameters allows us to (a) define aspects of three-dimensional scarp geometry, (b) decipher its geomorphological significance, and (c) estimate the long-term slip rate. [ABSTRACT FROM PUBLISHER]

Slip ratio control of a ground vehicle is an important concern for the development of antilock braking system (ABS) to avoid skidding when there is a transition of road surfaces. In the past, the slip ratio models of such vehicles were derived to implement ABS. It is found that the dynamics of the hybrid electric vehicle (HEV) is nonlinear, time varying and uncertain as the tire-road dynamics is a nonlinear function of road adhesion coefficient and wheel slip. Sliding mode control (SMC) is a robust control paradigm which has been extensively used successfully in the development of ABS of a HEV. But the SMC performance is influenced by the choice of sliding surface. This is due to the discontinuous switching of control force arising in the vicinity of the sliding surface that produces chattering. This paper presents a detailed study on the effects of different sliding surfaces on the performances of sliding mode based adaptive slip ratio control applied to a HEV. [ABSTRACT FROM AUTHOR]