Cylindrical Setup Research Articles

Broadband dark matter axion detection using a cylindrical capacitor

Cosmological axions/axion-like particles can compose a significant part of dark matter; however, the uncertainty of their mass is large. Here, we propose to search the axions using a cylindrical capacitor, in which the static electric field converts dark matter axions into an oscillating magnetic field. Due to the odd CPs, the axions couple to the electric field differently compared to the magnetic field. The axion couples to the electric field via a derivative that carries spatial information of incoming dark matter flux, while the coupling to the magnetic field depends on the dark matter density. This difference could be helpful in searching the axions and studies of the integrity of the theory, especially when the axions are very light, in which case the magnetic field-induced signal is DC-like. Orientation dependence could also be used to reduce the kinetic fluctuation-induced noise when multiple detectors operate simultaneously. In addition, a cylindrical setup shields the electric field to the laboratory and encompasses the axion-induced magnetic field within the capacitor. The induced oscillating magnetic field can then be picked up by a sensitive magnetometer. Adding a superconductor ring-coil system into the scheme can further boost the sensitivity and maintain the axion dark matter inherent bandwidth. This proposed setup could be capable of wide mass range searches.

Qualitative Properties of the Solutions to the Lane–Emden Equation in the Cylindrical Setup

We analyze the Lane–Emden equations in the cylindrical framework. Although the explicit forms of the solutions (which are also called polytropes) are not known, we identify some of their qualitative properties. In particular, possible critical points and zeros of the polytropes are investigated and discussed, leading to possible improvements in the approximation methods which are currently employed. The cases when the critical parameter is odd and even are separately analyzed. Furthermore, we propose a technique to evaluate the distance between a pair of polytropes in small intervals.

Fluid flow of various configurations in a rock-proppant-system

A high rock mass permeability is essential for developing an enhanced geothermal system and commonly achieved through the fracture conductivity. Hydraulic stimulation of fractures in combination with the use of proppants can significantly increase and maintain rock mass permeability. To investigate and quantify the effect of proppants, which are so far not commonly used to enhance deep geothermal reservoirs, on the rock mass hydraulic conductivity we performed various sets of laboratory experiments. We performed long-term creep deformation tests on a stack of rock samples with simultaneous a) fluid flow and b) acidification and fluid flow, in both cases with and without a proppant-filled fracture between the stacked rock samples. A central borehole served as fluid inlet into the lower sample of the stack. Two more boreholes in the lower sample allowed fluid flow. Sample stacks were placed in a Hoek cell at elevated confining pressures to prevent fluid flow along the sidewalls of the cylindrical sample setup. We compared the axial deformation and injection pressures between the experimental setups. The laboratory tests are part of the ZoKrateS Project, which aims at showing the feasibility of enhancing fractured carbonate rock mass by proppant placement for geothermal applications.

Comparing the effects of Cu-Ti/RuO2-IrO2 electrode configuration on the electro-reduction of nitrate.

Nitrate pollution is a global problem as it affects both the environment and human health. The objective of this research was to study the effect of electrode configuration on the electro-reduction of nitrate. Coaxial cylindrical (inner rod and outer tube copper cathodes) and vertical plate parallel copper cathodes paired with Ti/RuO2-IrO2 (rod, tube, and plate) configurations were studied under various current densities and initial nitrate concentrations. The efficiency of each configuration was determined based on the removal efficiency of nitrate, specific energy consumption, mass transfer coefficients, and first order rate constants. Additionally, the overall systems' resistance and geometric factors are discussed. It was found that the performances of the inner rod and outer tube copper cathodes were similar. The vertical plate parallel configuration was superior to the coaxial cylindrical electrode setup, as evident from a higher maximum nitrate removal of 74 and 56% at a current density of 7 mA/cm2 and lower energy consumption of 46.7 × 10-3 and 54.3 × 10-3 kWh/mmol NO3- at 36.4 mA/cm2, respectively. In addition, the mass transfer coefficients and first order rate constants were higher in all conditions tested for the vertical plate parallel configuration.

Legolas: magnetohydrodynamic spectroscopy with viscosity and Hall current

Many linear stability aspects in plasmas are heavily influenced by non-ideal effects beyond the basic ideal magnetohydrodynamics (MHD) description. Here, the extension of the modern open-source MHD spectroscopy code Legolas with viscosity and the Hall current is highlighted and benchmarked on a stringent set of historic and recent findings. The viscosity extension is demonstrated in a cylindrical set-up featuring Taylor–Couette flow and in a viscoresistive plasma slab with a tearing mode. For the Hall extension, we show how the full eigenmode spectrum relates to the analytic dispersion relation in an infinite homogeneous medium. We quantify the Hall term influence on the resistive tearing mode in a Harris current sheet, including the effect of compressibility, which is absent in earlier studies. Furthermore, we illustrate how Legolas mimics the incompressible limit easily to compare with literature results. Going beyond published findings, we emphasise the importance of computing the full eigenmode spectrum, and how elements of the spectrum are modified by compressibility. These extensions allow for future stability studies with Legolas that are relevant to ongoing dynamo experiments, protoplanetary disks or magnetic reconnection.

Model experiments for melt flow in Czochralski growth of silicon

The melt flow plays a key role in the Czochralski (Cz) growth of silicon crystals, and in-situ measurement data are crucial for efficient process development. We present new low-temperature model experiments and numerical simulations for Cz type melt flow studies. A novel cylindrical setup is equipped with a traveling magnetic field (TMF), and with an advanced ultrasound (US) based measurement technique for 2D flow imaging. The setup has been designed for comprehensive flow measurements in a GaInSn melt under well-defined thermal and TMF forcing conditions to generate as exact as possible experimental data to validate flow simulations. The applied numerical models combine time-dependent 3D flow calculations under adjusted heat flux boundary conditions with a 2D treatment of the Lorentz force. The dependence of the buoyant flow on the boundary conditions as well as the interaction between the buoyant flow and a symmetric TMF-forced flow are studied in detail. Special attention is paid to the investigation of flow transitions between symmetric toroidal and non-symmetric roll-like structures. In terms of the dimensionless Grashof (Gr) and magnetic forcing (F) numbers, such transitions are found to occur at around Gr = 3 × 107 and for F < Gr. The results are compared with recent studies in the literature, and a concept to transfer experimental and numerical flow modeling to real Cz growth of silicon is briefly outlined. The observed flow structures may significantly influence the convective heat and mass transport in Cz growth.

Multiple heat transport maxima in confined-rotating Rayleigh–Bénard convection

Moderate rotation and moderate horizontal confinement similarly enhance the heat transport in Rayleigh–Bénard convection (RBC). Here, we systematically investigate how these two types of flow stabilization together affect the heat transport. We conduct direct numerical simulations of confined-rotating RBC in a cylindrical set-up at Prandtl number $\textit {Pr}=4.38$ , and various Rayleigh numbers $2\times 10^{8}\leqslant {\textit {Ra}}\leqslant 7\times 10^{9}$ . Within the parameter space of rotation (given as inverse Rossby number $0\leqslant {\textit {Ro}}^{-1}\leqslant 40$ ) and confinement (given as height-to-diameter aspect ratio $2\leqslant \varGamma ^{-1}\leqslant 32$ ), we observe three heat transport maxima. At lower $ {\textit {Ra}}$ , the combination of rotation and confinement can achieve larger heat transport than either rotation or confinement individually, whereas at higher $ {\textit {Ra}}$ , confinement alone is most effective in enhancing the heat transport. Further, we identify two effects enhancing the heat transport: (i) the ratio of kinetic and thermal boundary layer thicknesses controlling the efficiency of Ekman pumping, and (ii) the formation of a stable domain-spanning flow for an efficient vertical transport of the heat through the bulk. Their interfering efficiencies generate the multiple heat transport maxima.

Fast and Cost-Effective Three-Dimensional Microwave Imaging Using a Cylindrical Setup

In this paper, we propose a fast and low-cost cylindrical microwave imaging system based on the use of arrays of transmitter and receiver antennas and a customized low-cost data acquisition circuit using off-the-shelf components. The complex-valued scattered data captured with the proposed system is processed using near-field holographic image reconstruction. To enhance this technique, standardized minimum norm (SMN) approach is employed to solve the relevant systems of equations. The performance of the proposed imaging technique and the data acquisition system is demonstrated via simulations and experiments.

Fast, Robust, and Low-Cost Microwave Imaging of Multiple Non-Metallic Pipes

The use of non-metallic pipes and composite components that are low-cost, durable, light-weight, and resilient to corrosion is growing rapidly in various industrial sectors such as oil and gas industries in the form of non-metallic composite pipes. While these components are still prone to damages, traditional non-destructive testing (NDT) techniques such as eddy current technique and magnetic flux leakage technique cannot be utilized for inspection of these components. Microwave imaging can fill this gap as a favorable technique to perform inspection of non-metallic pipes. Holographic microwave imaging techniques are fast and robust and have been successfully employed in applications such as airport security screening and underground imaging. Here, we extend the use of holographic microwave imaging to inspection of multiple concentric pipes. To increase the speed of data acquisition, we utilize antenna arrays along the azimuthal direction in a cylindrical setup. A parametric study and demonstration of the performance of the proposed imaging system will be provided.

On the acoustic black-hole effect in waveguides

The acoustic black-hole (ABH) effect is a well-known way of controlling structural vibrations in solid beams and plates. The theory behind this effect is to reduce the velocity of waves by altering the physical properties of the domain according to a power-law profile. For an ideal ABH, this leads to vanishing reflections from the end of the termination. In practice, there will be a truncation in the profile, which leads to some reflections. A well-known way of minimizing this truncation error is to add damping material to the end of the ABH termination. For a waveguide embedding a set of rings with retarding inner radius according to a power-law profile, the velocity of sound waves tends to zero. However, unlike the structural counterpart, experimental results in the literature show that adding damping material to reduce the truncation error is not effective for waveguides. Here, we present a finite element simulation of the considered cylindrical setup. Our results confirm that the addition of damping material to the end of the waveguide is ineffective while suggesting that the local absorption effects at the lateral surface of the cylinder are a primary source of damping to achieve the ABH effect.

Continuous-Flow Flat Jet Setup for Uniform Pulsed Laser Postprocessing of Colloids.

Pulsed laser postprocessing (PLPP) of colloidal nanoparticles and related laser fragmentation in liquid (LFL) using a liquid jet setup have become an acknowledged tool to reduce the nanoparticle diameter down to a few nanometers, alter the crystal phase, or increase the defect density under high-purity and continuous-flow conditions. In recent studies on LFL that were conducted with a cylindrical liquid jet, intensity gradients and related incomplete illumination of the volume element passing through the laser beam path were reported to cause a broadening of the product particle size distribution, melting, and phase segregation. In this paper, we present a new flat jet design, which reduces the deviation of the laser intensity up to 10 times compared to the conventional cylindrical liquid jet. The experimental threshold intensity for gold nanoparticle fragmentation found with the cylindrical setup strongly deviates from the theoretical prediction, while they are in very good agreement for the flat jet setup. Additionally, a narrow product size fraction of 3 ± 2 nm was found for the flat jet, while the main product fraction gained from the cylindrical jet was 10 ± 8 nm in size under the same conditions. Consequently, the flat jet setup allows us not only to study laser fragmentation mechanisms with higher precision but also to gain product particles with narrow particle size distribution at single pulse per particle conditions even at elevated mass concentrations (>50 mg L-1). In future studies, these promising results also render the flat jet setup relevant for the other disciplines of PLPP such as laser melting and defect engineering.

Template-Free Growth of Vertical Poly(3,4-ethylenedioxythiophene) Fiber Array By Alternating Current-Bipolar Electrolysis

Conducting polymers (CPs) play an important role in the field of organic device. Electropolymerization is a very common technique for obtaining CPs, which usually gives a CP film with granular or particulate morphology on the electrode. On the other hand, CP fibers are also of great interest due to their unique properties such as efficient anisotropic carrier mobility. The electropolymerization with a template-modified electrode is regarded as one of the most promising strategies to obtain a CP fiber array. However, the attachment and removal of templates require additional working processes, and the use of a template may hinder other types of surface modification on the substrates. Therefore, a facile way to prepare CP fiber arrays without a template remains a challenging problem.The use of an electric field as a guide for polymer formation is deemed to be efficient to grow CP fibers in a specific direction. We have pioneered the electric field-guided growth of poly(3,4-ethylenedioxythiophene) (PEDOT) fibers. In that system, dendritic PEDOT fibers grew from the terminal of Au wires that were used as bipolar electrodes (BPEs) by the electropolymerization of 3,4-ethylenedioxythiophene (EDOT) under an alternating current (AC).1 Here, we introduce the next progress of a successful template-free fabrication of PEDOT fiber arrays from a flat electrode surface using BPEs under an AC condition (Figure 1).2 An acetonitrile solution containing 50 mM EDOT, 5 mM 1,4-benzoquinone (BQ) and 1 mM Bu4NClO4 was used as an electrolyte. A cylindrical setup with driving electrodes was used here, and a conductive plate acted as a BPE. When an iterative potential was applied to the BPE, the circular anodic or cathodic area appeared alternatively underneath the region covered by the cylinder, with a surrounding cathodic or anodic area simultaneously. A potential difference generated on the BPE surface (Delta V BPE) under an external electric field offers redox reactions on the BPE. When Delta V BPE exceeds Delta V min (1.82 V), the oxidation of EDOT proceeds in the anodic area, while the sacrificial reduction of benzoquinone occurs in the cathodic area.Vertical fiber arrays of PEDOT and its derivatives were successfully grown from the central area of various BPE surfaces by the AC-bipolar electrolysis. The growth of fiber array follows a particle-induced growth mechanism. First, anodic oxidation of EDOT gives a PEDOT film on the BPE surface when the voltage between driving electrodes generates a sufficient Delta V BPE. The film growth proceeds with Stranski-Krastanov (S-K) mode as an induction period to give several particles. Once particles are formed, the deposited particles are considered as nodes to initiate subsequent PEDOT fiber growth.Experimental conditions significantly affected the formation of fiber arrays. Higher applied voltages and shorter gap distances between the BPE and the cylinder were beneficial to form fiber arrays, which was supported by the computational simulation using COMSOL Multiphysics. Higher monomer concentration and lower applied frequency were also in favor of fiber array formation. The choice of solvents and electrolytes also influenced morphology of the fiber arrays. In addition, linear fibers were easily fabricated using a cylinder with a smaller diameter, while branching fibers formed with a larger diameter. This new methodology provides an extremely simple and straightforward way to fabricate uniform fiber arrays without the use of template, which are potentially applicable for sensors and electronic devices. References (1) Y. Koizumi, N. Shida, M. Ohira, H. Nishiyama, I. Tomita, S. Inagi, Nat. Commun., 2016, 7, 10404.(2) Y. Zhou, N. Shida, Y. Koizumi, T. Watanabe, H. Nishiyama, I. Tomita, S. Inagi, J. Mater. Chem. C, 2019, 7, 14745. Figure 1

Holographic Near-Field Microwave Imaging With Antenna Arrays in a Cylindrical Setup

Holographic microwave imaging is fast and robust and it has been adapted for near-field applications such as biomedical imaging and nondestructive testing. While the imaging technique is fast, synthesizing a 2-D aperture by mechanical scanning of the antennas takes time. Here, antenna arrays are used to expedite data acquisition along the azimuthal direction in a cylindrical holographic near-field microwave imaging setup. To deal with the limited and nonuniform samples along the azimuthal direction, three holographic imaging approaches are evaluated, in which, we use interpolation, uniform or nonuniform discrete Fourier transform (DFT), standardized low-resolution brain electromagnetic tomography (sLORETA), and exact low-resolution brain electromagnetic tomography (eLORETA). Besides, to make the system low-cost and portable, off-the-shelf components are used to construct a data acquisition system replacing the vector network analyzers. Simulation and experimental studies are conducted to validate the performance of the proposed imaging system. Structural similarity (SSIM) index is used to assess the quality of the reconstructed images.

Flammability limit behavior of methane with the addition of gaseous fuel at various relative humidities

The lower flammability limit (LFL) of methane is 5 % in volume. Usually, in the relevant industry, the methane leakage monitoring threshold is set on the basis of the LFL from the perspective of safety precautions. When small amounts of other combustible gases coexist with methane, setting the monitoring threshold according to 5% vol may cause a large deviation and lead to a potential explosion accident. To investigate the effects of flammable gases and the relative humidity (RH) on the methane flammability limit behavior, the flammability limits of methane-air mixtures with the addition of gaseous fuels were experimentally measured in a standard cylindrical setup at various relative humidities. A theoretical model based on the adiabatic flame temperature method was employed to obtain reasonable estimates of the flammability limits of binary mixtures of methane and vapor. The combustion hazards of methane-air mixtures were evaluated. The results showed that both the LFL and the upper flammability limit (UFL) of methane were diminished with the addition of gaseous fuel at the same RH, while these parameters increased with an increase in the RH. The flammable range of methane-air mixtures was slightly narrowed by increasing the RH but was extended by the addition of gaseous fuel. The combustion hazard of methane increases as the volume fraction of added gases increases but drops with an increase in the RH. These phenomena were ascribed to the dual roles of water vapor and the influence of the added gaseous fuel on the initial stage of the methane-air chain reactions. The obtained data could supplement the flammability limits database and help to prevent potential explosion hazards.

Experimental setup for bulk susceptibility effect-minimized, multi-orientation MRI of ex vivo tissue samples.

Many conventional ex vivo magnetic resonance imaging (MRI) setups utilize cylindrical or other nonspherical tissue containers which can cause static field (B0 ) inhomogeneity affecting the accuracy of the measurements in an orientation-dependent manner. In this work we demonstrate an experimental method to obtain MRI of ex vivo tissue samples held in a spherical container in order to minimize bulk susceptibility-induced B0 inhomogeneity in arbitrary orientations. B0 inhomogeneity caused by tissue-air susceptibility mismatch can be theoretically eliminated if the surface of susceptibility discontinuity is spherical. This situation can be approximated by putting a tissue sample in a spherical shell filled with materials with tissue-like magnetic susceptibility. We achieved this on an intact monkey brain by (a) holding the brain with a three-dimensional (3D)-printed holder with tissue-like (within 0.5ppm) susceptibility, and (b) enclosing the brain and the holder in an acrylic spherical shell filled with diamagnetic liquid. Furthermore, the sphere and the radio-frequency coil for MRI were mounted on a 3D-printed frame designed to reduce B0 inhomogeneity contributions. The sphere could be rotated freely without disturbing the RF coil to facilitate multi-orientation imaging. We verified our setup by mapping B0 in the monkey brain at 13 different orientations in a human 7T scanner, and measuring orientation-dependent relaxation rates in the white and gray matters of the brain. The results were then compared with a setup where the brain was held inside a cylindrical container. In all orientations, the B0 standard deviation in the brain in the spherical setup (converted to Larmor frequency offset) was less than about 10Hz. This corresponds to two-sigma deviation of B0 of <0.07ppm. The B0 gradient was <9Hz/mm in 95 % of the brain voxels in all orientations. In high-resolution imaging with e.g. voxel size <0.4mm, this corresponds to voxel line broadening of <4Hz (0.013ppm). in the corpus callosum showed distinctly different orientation dependence compared to the gray matter. The B0 uniformity and reliability were much reduced in the cylindrical container setup. We have demonstrated an experimental method to effectively minimize bulk susceptibility-induced B0 perturbation in multi-orientation ex vivo MRI. The method promises to benefit a range of tissue orientation-dependent MR property studies.

Current interruption performance of ultrahigh-pressure nitrogen arc

In this paper, the influence of gas filling pressure on the current interruption performance of different switch configurations with electric arcs burning in nitrogen has been experimentally investigated. A synthetic circuit generating a current of 130 A at 190 Hz is used and the initial rate of rise of recovery voltage just after current zero is varied from 9.8 V/µs to 84.9 V/µs. To evaluate the effect of forced gas flow on current interruption performance, three different test arrangements are investigated: a simple contact configuration with a free-burning arc, a contact and a cylindrical nozzle setup (tube-constricted arc), and finally a self-blast arrangement where the arc is cooled by a gas flow near current zero. In each arrangement, three different filling pressures are mainly studied: 1, 20, and 40 bar, the latter being in the supercritical region. In all cases, the interelectrode gap is fixed at 50 mm. It is observed that the interruption performance deteriorates with increased filling pressure in the absence of forced gas flow. A higher post-arc current is observed for the arcs burning at high filling pressures (i.e. 20 and 40 bar) compared to at atmospheric pressure in cases with no or little forced cooling. On the other hand, a forced gas flow near the current zero reduces the post-arc current and improves the interruption performance also at high filling pressures. Little effect of the supercritical state on the interruption performance of nitrogen is observed. Under the above-mentioned test conditions, the majority of the failures at high filling pressure are observed to be of thermal re-ignition type.

Reliable Antenna Measurements in a Near-Field Cylindrical Setup With a Sparsity Promoting Approach

A novel approach for reliable and effective antenna measurements in cylindrical near-field (NF) setups is presented. Starting from a limited set of NF samples acquired on a finite cylindrical probing surface and by exploiting some a priori information on the class of antennas under test (AUTs) to build an overcomplete dictionary of field bases, the proposed method allows one to accurately extrapolate the data well beyond the physical extension of the NF measurement area. Afterward, a compressive sensing (CS)-based method is successfully applied to retrieve a sparse representation of the actual field distribution over the redundant dictionary at hand. Selected results from a wide numerical analysis are shown to assess the effectiveness and the potentialities of the proposed measurement technique.

Comparison of electron temperature in DC glow discharge and AC glow discharge plasma

Knowing electron temperature and electron density is important for any plasma related applications. In this research, the electron temperature and electron density of argon plasma generated by low frequency AC power supply and a high voltage DC power supply were investigated. The measurements were compared, both experimentally and theoretically. For the experiment, a long glass cylindrical tube was used as a chamber where the electrodes were placed at 37.5 cm apart. A high voltage function generator power supply was operated at various frequencies and it was also used for DC operation. The electron temperatures were measured by Optical Emission Spectroscopy (OES) technique for different operating pressures of 0.1 mbar, 0.6 mbar and 1.1 mbar. For the simulation, both plasma theory and finite element method were used to simulate dynamics of the plasma in the cylindrical setup. From the experiment, the range of breakdown voltage was found to be between 0.80 to 2.3 kV. The length of DC glow discharge dark regions of the plasma decreases due to increasing in both operating pressure and voltage. AC glow discharge shows positive charge and negative charge swing. From the DC discharge, the maximum value of electron temperature was found to be 0.810 eV and the minimum value was 0.610 eV under the operating pressure 0.1 and 0.6 mbar respectively. From AC glow discharge plasma, the maximum electron temperature was 0.907 eV and the minimum was 0.540 eV under operating pressure 0.1 and 1.1 mbar respectively. Collision loss between ions and electrons causes this variation in the results.

A Synthetic Aperture Radar (SAR)-Based Technique for Microwave Imaging and Material Characterization

This contribution presents a simple and fast Synthetic Aperture Radar (SAR)-based technique for microwave imaging and material characterization from microwave measurements acquired in tomographic systems. SAR backpropagation is one of the simplest and fastest techniques for microwave imaging. However, in the case of heterogeneous objects and media, a priori information about the constitutive parameters (conductivity, permittivity) is needed for an accurate imaging. In some cases, a first guess of the constitutive parameters can be extracted from an uncorrected SAR image, and then the estimated parameters can be introduced in a second step to correct the SAR image. The main advantage of this methodology is that there is little or no need for a priori information about the object to be imaged. Besides, calculation time is not significantly increased with respect to conventional SAR, thus allowing real-time imaging capabilities. The methodology has been validated by means of measurements acquired in a cylindrical setup.

Evaluation of AASHTO T 324 Hamburg-Wheel Track Device test

The Hamburg Wheel-Track Device (HWTD) test has recently gained popularity among many state highway departments of transportation (DOTs) for use in hot mix asphalt (HMA) moisture sensitivity evaluation. In this paper, suggestions are presented to improve and provide more consistent and representative results for this test as described in AASHTOT324 – Hamburg Wheel-Track Testing of Compacted Hot Mix Asphalt (HMA). In the AASHTOT324 specification, either a cylindrical or a slab specimen can be tested. Use of a two-dimensional micromechanics finite element (2D-MMFE) analysis has demonstrated significant gap/bonding and specimen shape effects on HWTD test results for the cylindrical specimen setup. In addition, the analysis suggests the best method for defining the “rut depth” to ensure consistent results between two specimen setups. Results of this study have concluded that: (1) slab specimens can provide more reliable test results due to larger size and uniform geometry; (2) two cylindrical specimens (cores) should be glued together to prevent localized failure due to larger peak maximum principal strains when there is no bonding; (3) measurements of average rut depth should be collected from stations near the centers of cylindrical specimens to keep the specimen shape effects to the lowest possible level; and, (4) an agency should not allow both specimen setups to be used interchangeably in the HWTD specifications. The investigation also suggests that the average rut depth evolution curve fitted using a three-stage Weibull approach can define the number of passes to failure and define the stripping initiation point (SIP) better than the visually determined SIP.