Deformation Tracking Research Articles

Four-dimensional reconstruction and characterization of bladder deformations

Background and ObjectivePelvic floor disorders are prevalent diseases and patient care remains difficult as the dynamics of the pelvic floor remains poorly understood. So far, only 2D dynamic observations of straining exercises at excretion are available in the clinics and 3D mechanical defects of pelvic organs are not well studied. In this context, we propose a complete methodology for the 3D representation of non-reversible bladder deformations during exercises, combined with a 3D representation of the location of the highest strain areas on the organ surface. MethodsNovel image segmentation and registration approaches have been combined with three geometrical configurations of up-to-date rapid dynamic multi-slice MRI acquisitions for the reconstruction of real-time dynamic bladder volumes. ResultsFor the first time, we proposed real-time 3D deformation fields of the bladder under strain from in-bore forced breathing exercises. The potential of our method was assessed on eight control subjects undergoing forced breathing exercises. We obtained average volume deviations of the reconstructed dynamic volume of bladders around 2.5% and high registration accuracy with mean distance values of 0.4 ± 0.3 mm and Hausdorff distance values of 2.2 ± 1.1 mm. ConclusionsThe proposed framework provides proper 3D+t spatial tracking of non-reversible bladder deformations. This has immediate applicability in clinical settings for a better understanding of pelvic organ prolapse pathophysiology. This work can be extended to patients with cavity filling or excretion problems to better characterize the severity of pelvic floor pathologies or to be used for preoperative surgical planning.

Influence of Uneven Subgrade Frost Heave on Deformation and Damage of CRTSIII Slab Track

The problem of uneven frost heave deformation of high-speed railway subgrade in seasonal freezing areas seriously affects the service state and service life of slab track structures and threatens the safe operation of high-speed vehicles. Based on the damage plasticity theory of concrete, in this study, an analytical model is established for CRTSIII slab track with damage plasticity and reinforcement. The influences of various frost heaving parameters on track structure deformation, interlayer seam, as well as the stress and damage behaviors were analyzed in detail. The results show that, as compared with a linear elastic model, the damage plastic model better reflects the softening behavior and stress attenuation of track structure concrete after reaching its tensile strength. The deformation and the interlayer seam reach their maximum values when the frost heaving wave peak acts at the position that is one-sixth of the base length from the edge of the concrete base. When the frost heaving wave peak acts on grooves at the base center, initially, the track structure is seriously damaged. The interlayer seam and damage decrease with an increase in frost heaving wavelength and increase with an increase in frost heaving wave amplitude. The interlayer seam of the track structure is more sensitive to frost heave deformation having a wavelength of less than 10 m. The extent of damage to the concrete base gradually increases with a decrease in the wave/amplitude ratio. It undergoes three stages of damage evolution: (i) no damage, (ii) upper surface bending damage, (iii) reverse bending damage. In order to improve efficiency, it is recommended, during track maintenance, to focus on the position of the central groove of the base and the position that is one-sixth of the base length from the edge of the concrete base.

Assessment of ICESat-2’s Horizontal Accuracy Using an Iterative Matching Method Based on High-Accuracy Terrains

The Ice, Cloud, and Land Elevation Satellite-2 (ICESat-2), launched in September 2018, has been widely used in forestry and surveying. A high-accuracy digital elevation model (DEM)/digital surface model (DSM) for terrain matching can effectively evaluate the ICESat-2 design requirements and provide essential data support for further study. The conventional terrain-matching methods regard the laser ground track as a whole, ignoring the individual differences caused by the interaction of photons during flight. Therefore, a novel terrain-matching method using a two-dimensional affine transformation model was proposed to describe the deformation of laser tracks. The least-square optimizes the model parameters with the high-accuracy terrain data to obtain the best matching result. The results in McMurdo Dry Valley (MDV), Antarctica, and Zhengzhou (ZZ), China, demonstrate that the proposed method can verify geolocation accuracy and indicate that the average horizontal accuracy of ICESat-2 V5 data is about 3.86 m in MDV and 4.67 m in ZZ. It shows that ICESat-2 has good positioning accuracy, even in mountainous areas with complex terrain. Additionally, the random forest (RF) model was calculated to analyze the influence of four factors on geographic location accuracy. The slope and signal-to-noise ratio (SNR) are considered the crucial factors affecting the accuracy of ICESat-2 data.

Effect of operating conditions of mine monorail locomotives on the durability of drive wheel polymeric rims

An increase in the rate of coal mining and a reduction of its prime cost can be ensured by comprehensive mechanization and automation of the system of mine auxiliary transport through the widespread introduction of overhead monorail tracks. The potential use of mine monorail tracks are conditioned by the following factors: low payload ratio of the train; reduction of the mine workings cross-section area due to transfer of auxiliary transport to the upper part of the workings; high operational safety; as well as the possibility of dismantling the track in the unused sections and subsequently installing it in new mine workings. The use of rubberized rollers in the drives of mine monorail locomotives enables the coefficient of adhesion of the wheel with the monorail to be increased. It also reduces dynamic loads and the noise level during operation. The purpose of this research is to assess the durability of polymeric rims of drive wheels for mine monorail locomotives, taking into account their operating conditions. Stress distribution over the contact area of the wheel rim with the monorail was determined, enabling the development of measures to increase the service life of drive wheels of mine monorail locomotives to be developed. It was established that the effect of the monorail track deformation has no significant impact on the durability of drive wheel rims of mine monorail locomotives. A mathematical model was obtained to determine the durability of drive wheel polymeric rims, taking into account the maximum dynamic forces arising during the contact of drive wheels with the monorail. The durability of wheel polymeric rims of mine monorail locomotives was assessed in accordance with the Bailey criterion with regard to the maximum values of dynamic contact loads arising during the monorail train movement. It was also established that an increase in the carriage mass from 20 to 47 kN leads to 32 % less durability of a monorail locomotive drive wheel rim (from 8700 to 5900 hours).

Mechanical deformation properties of Continuous Welded Rail on kilometer-span suspension bridge for high-speed railway

The complex bridge-track interaction between kilometer-span bridges and continuous Welded Rail (CWR) brings great challenges to CWR designing. Taking a suspension bridge with laying CWR as a case, the mechanical properties of CWR on the bridge are analyzed to reveal the sensitive areas of the track, and the design method of CWR and track structures on the beam ends are proposed. The results show that the unidirectional Rail Expansion Joints(REJ) need to be installed on the beam end of the kilometer-span bridge to reduce rail longitudinal force. Due to the bridge characteristics, there is no CWR fixed area on the kilometer-span bridge, and rail longitudinal force on the main span caused by bending loads needs to be concerned. The deformation of track on the beam end is complex, which is the weak area on the kilometer bridge, the large relative displacement between the stock rail of REJ and the main beam can cause poor stability of ballast bed on beam end, small resistance fasteners need to be laid on the sides of stock rail on the main beam to increase the stability of ballast and fasteners on the beam end. To improve the driving safety and comfort of beam end, the Sleeper-Supporting Apparatus (SSA) should be specially designed to ensure the uniform transition of track on beam ends. Temperature and wind loads have a significant impact on track regularity on the kilometer span bridge, the dynamic response of trains and bridges under those loads needs to be attended to.

Interaction Control of a Robotic Manipulator With the Surface of Deformable Object

Robotic manipulation of deformable objects has drawn the attention of researchers over the past few years and is associated with a large spectrum of new application perspectives. In this article, we present an efficient integrated motion planning framework to effectively and accurately control a robotic manipulator executing interactive tasks on the surface of a deformable object. The proposed interactive motion planning framework is based on a mesh representation of the object, integrating three efficient preprocessing algorithmic steps, including visual object segmentation, finite element method deformation tracking, and local mesh parameterization. The use of barycentric coordinates, defined on the mesh triangles, enables the establishment of bijective transformations between the deformable part of an object surface and its planar (static and dynamic) parameterized mapping. By merging these spatial transformations with the preprocessing steps, in combination with an active stiffness scheme for robot manipulator control, we are able to achieve accurate and reactive motion planning of interactive trajectories, even under large and persistent visual occlusions (such as due to the presence of the robot in the visual scene). An extensive experimental evaluation study is presented, involving a robotic manipulator in interaction with a hemispherical model of controllable periodic active deformation, which permits precise ground truth derivation. Motion planning accuracy is evaluated in comparison with our previous direct vision-based approach, showing clearly superior performance of the proposed approach under all experimental conditions. The performance of the proposed framework is also further highlighted in tasks involving physical point tracking, interactive programming by human demonstration, as well as contact force regulation.

Extreme High Step Climbing: Nonlinear Analysis of a Highly-Deformable- Tracked Robot

The mobility on rough terrain is a crucial factor in designing rescue robots. Rubbles scattered across disaster site obstruct the robots, which may limit search areas and disturb rapid rescue. To improve mobility in such situations, we proposed a novel mobile mechanism, called mono-wheel track (MW-track), which is an elastic track driven by a single wheel without passive wheels. This mechanism demonstrated high mobility on step-shaped obstacles by using a self-adaptive track. However, the principle underlying this mechanism is still unclear. Herein, we provide a model of track deformation that estimates step-climbing capability, based on large-deformation analysis of the nonlinear beam. The model was evaluated by comparing 1) the curve geometry of the theoretical track with the actual leaf spring and 2) the theoretical value of the climbable height with the actual value measured by step-climbing tests using a mobile robot with the MW-track mechanism. Furthermore, several tests were conducted under various ground friction and track stiffness conditions to investigate their effect on climbable step height. The mechanism for target step height was determined through the model and tests. The model affords a mechanical procedure to determine design parameters for target obstacles.

Hydration Activates Dual-Confined Shape-Memory Effects of Cold-Reprogrammable Photonic Crystals.

Shape-memory photonic crystals (SMPCs) transform the nanoscale deformation of copolymers into structural color through an undifferentiated response to stimuli; however, activatable selective responses are extremely rare. Herein, activatable dual confined shape-memory effects (CSMEs) derived from the remodeling of the interchain hydrogen bonds (H-bonds) in cold-programmable SMPCs are revealed. The first level is the water-triggered reconstructionof interchain H-bonds, which can activate/lock the collapsed skeleton, showing shape recovery/retention in response to ethanol vapor. The second level is the pressure-induced reorganization ofinterchain H-bonds that results in the recovered skeleton being locked even when exposed to ethanol vapor or water, while the background porous structure can switch between collapse and recovery. Dual CSMEs result from the Laplace pressure difference and the binding effect of interchain H-bonds in the skeleton according to insights of swelling, in situ deformation tracking, multidimensional infrared spectra, and water wetting/evaporation simulations. The signal interference, source code extraction, and color enhancement of structurally colored patterns can be implemented using CSMEs. This work opens up a new method for fabricating activatable responsive structural color and contributes to the expansion of nanophotonic technology in water printing, erasable watermarks, signal amplifiers, and information coding.

Temperature effects of ballastless track and dynamic responses of vehicle-track coupling system on tunnel floor with high temperature

Temperature has a great implication for the structural behavior of the ballastless track, however, there are few studies on the temperature effect of ballastless track and the dynamic responses of vehicle-track coupling system (VTCS) on tunnel floor with high temperature. In this paper, the finite element model is established to investigate this problem. The correctness of the model is verified by the test platform for the temperature field of track slab. The temperature stresses and warp deformations of the ballastless track on tunnel floor with high temperature are investigated, and then the additional irregularities of rail induced by the high temperature are used to study the dynamic responses of the VTCS. The results show that the longitudinal temperature stress of the track bed slab is the largest, and the stress increases nonlinearly with the increase of temperature. The maximum vertical deformation of the rail is less than that of the track bed slab. With the increase of the temperature, the dynamic responses of VTCS enlarge nonlinearly and the running safety index of the vehicle deteriorates. The limit value with 50 ℃ of the temperature difference between the tunnel floor and the environment is recommended. This paper provides the theoretical support for the design, maintenance and repair of the ballastless track in the tunnel with high temperature.

The development of laboratory downscale rail-wheel test rig model with optical sensors

Railway and train condition monitoring are two critical components in assuring passenger safety and comfort during their journey. In this work, a new laboratory downscale rail test rig has been designed and developed for exploring rail-wheel interaction and axle peak detection using fiber Bragg grating (FBG) optical sensors. This paper describes the laboratory setup’s development process which includes numerical analysis of rail model, review of different experimental techniques, followed by 1:3 scaled model, mechanical and functional analysis of the railway setup with the grating sensor. By employing various data processing techniques axle peak detection of train was done and strain/stress transfer was calculated by the train passage to the rail track which was ∼100.86 µɛ. Total wavelength shit in the FBG sensor was 0.133 nm due to wheel load and sensitivity value was calculated approximately 1.36 pm/µɛ for the wavelength/strain changes. Characteristics of 1:3 laboratory rail test rig such as track retention, number of wheels, axle peak detection, rail-wheel rolling contact, stress/strain track deformation can be obtained in real time with fiber Bragg grating sensors.

Investigations on cyclic loading behavior of geocell stabilized tracks with coal overburden refuse recycled as subballast material

An attempt to recycle the massive quantum of mine overburden (OB) waste, generated as a by-product during coal extraction has been made in this study. Experimental and numerical investigations have been carried out to better understand its behavior as a railway subballast material under cyclic loading. On model railway tracks with varying OB-subballast layer thicknesses reinforced with geocells of various pocket sizes, a series of cyclic model tests were conducted. Three-dimensional cyclic FEM models were used to validate the model tests. The validated FEM models served as training data sets for the artificial neural network (ANN) technique, which was used to predict deformations. As the loading cycles increased, the geocells became more effective at reducing track deformation rates. Correspondingly, vertical strains and stresses in the track beds were also reduced in a noticeable way. The findings also supported the use of a shallow OB-subballast thickness in the presence of a geocell, which can withstand track degradations for longer load cycle durations and thus prolong costly track maintenance cycles. The ANN technique, which demonstrated good agreement with the numerical output, can predict the displacements of geocell reinforced tracks in a reliable manner and serve as an efficient deformation prediction tool for railways.

Analysis of existing railway deformation caused by double shield tunnel construction in soil–rock composite stratum

Subway tunnel construction often crosses existing railways, and the soil loss caused by shield construction will inevitably lead to deformation of the surrounding strata and uneven settlement of the adjacent railway tracks, but there are few studies on the existing railway deformation caused by double shield construction in soil–rock composite strata. In this paper, based on the field monitoring data, the deformation analysis of the railway under-crossed by double shield tunnel in soil–rock​ composite stratum was carried out, and the influence law of hard-layer ratio, tunnel burial depth and railway roadbed reinforcement on the railway track deformation was revealed by numerical simulation. Results show that the track settlement mainly occurred in the middle and late stages of the shield crossing the railway. The track settlement showed an obvious trend of decreasing with the increase of hard-layer ratio or tunnel buried depth. The roadbed reinforcement can significantly reduce the settlement of the railway track, the smaller the hard-layer ratio, the better the roadbed reinforcement effect.

Influence of laser-wire interaction on heat and metal transfer in directed energy deposition

In this study, laser metal fusion with feedstock wire is addressed. We investigated how various process parameters affect the fraction of beam energy that is absorbed by the wire and the workpiece and the metal transfer from the feedstock wire to the melt pool. To perform this research, a thermo-fluid dynamic model with tracking of free surface deformation was developed to include the feeding of a solid wire and predict its melting. The fraction of beam energy absorbed by the metal was modeled as a function of local surface curvature and temperature, accounting for multiple Fresnel reflections and absorptions. The model was applied to Titanium alloy (Ti-6Al-4V) with a 1.07 μm laser and a process in conduction mode. Experiments at various wire feeding rates were conducted to evaluate the model’s ability to predict the process and a good agreement was obtained. The different parameters studied were the beam angular position, the wire angular position, the wire feed rate, and the beam-wire offset. The analysis of the simulation results gave a detailed physical understanding of the laser energy use. It highlighted that thermocapillary and Rayleigh-Plateau instabilities can contribute to the transition from continuous to drop metal transfer mode. Damping these instabilities might thus allow using a wider process window.

Tunneling construction technology of shafts and cross-passages under strictly controlling deformation of the existing railway

Underground construction will have more or less adverse effects on adjacent existing buildings with more and more existing buildings above ground. However, this situation has only been reported by a small number of researchers. In view of this, this article takes the existing airport line shaft and horizontal passage project in the western suburb of Beijing Metro Line 12 as the background to study the impact of the construction of subway station and shaft passage on the adjacent existing railway. Based on the above project reality, under the action of pavement load, the effects of different parameters (the distance between the surface measuring point and the middle line of the transverse passage and the substep of construction loading sup step) on the surface settlement and track deformation of the shaft and cross-passage through the existing railway are studied by numerical analysis method. The calculation results show that the construction method of shaft and cross passage is reasonable. The comprehensive reinforcement measures of subgrade, rail and hole are effective, effectively controlling the deformation of subgrade and rail within the standard value (surface settlement ≤60 mm, rail deformation ≤6 mm). In addition, the numerical simulation data can better represent the actual situation as a whole.

Mathematical modeling of the mechanical stabilization of the sub-tie base of railroad tracks in the arctic zone

The practice of construction and operation of railroads in the Arctic zone shows that the greatest share of track deformations occurs in the summer period during the transition of soils of the subgrade from the frozen state to the thawed state. Wetting, freezing-thawing, and vibrodynamic effects of trains have the greatest influence on the properties of clay soils composing the railroad bed. A model of a sub-tie base stabilized by geosynthetic materials is given. The influence of geosynthetic material on redistribution of stresses during thawing and change of shear deformation character is shown.

Embedded System Development for Detection of Railway Track Surface Deformation Using Contour Feature Algorithm

Derailment of trains is not unusual all around the world, especially in developing countries, due to unidentified track or rolling stock faults that cause massive casualties each year. For this purpose, a proper condition monitoring system is essential to avoid accidents and heavy losses. Generally, the detection and classification of railway track surface faults in real-time requires massive computational processing and memory resources and is prone to a noisy environment. Therefore, in this paper, we present the development of a novel embedded system prototype for condition monitoring of railway track. The proposed prototype system works in real-time by acquiring railway track surface images and performing two tasks a) detect deformation (i.e., faults) like squats, shelling, and spalling using the contour feature algorithm and b) the vibration signature on that faulty spot by synchronizing acceleration and image data. A new illumination scheme is also proposed to avoid the sunlight reflection that badly affects the image acquisition process. The contour detection algorithm is applied here to detect the uneven shapes and discontinuities in the geometrical structure of the railway track surface, which ultimately detects unhealthy regions. It works by converting Red, Green, and Blue (RGB) images into binary images, which distinguishes the unhealthy regions by making them white color while the healthy regions in black color. We have used the multiprocessing technique to overcome the massive processing and memory issues. This embedded system is developed on Raspberry Pi by interfacing a vision camera, an accelerometer, a proximity sensor, and a Global Positioning System (GPS) sensors (i.e., multi-sensors). The developed embedded system prototype is tested in real-time onsite by installing it on a Railway Inspection Trolley (RIT), which runs at an average speed of 15 km/h. The functional verification of the proposed system is done successfully by detecting and recording the various railway track surface faults. An unhealthy frame’s onsite detection processing time was recorded at approximately 25.6 ms. The proposed system can synchronize the acceleration data on specific railway track deformation. The proposed novel embedded system may be beneficial for detecting faults to overcome the conventional manual railway track condition monitoring, which is still being practiced in various developing or underdeveloped countries.

A CFD-DEM Based Numerical Investigation of Debris Flow on Ballasted Railway Track

Debris flow occurring in mountainous areas can cause issues to railway tracks. Debris flow may cause large track deformation and even track breakage and introduce server ballast fouling afterwards. After the flash of a debris flow, the fine particles can be retained in the ballast layer and significantly reduce track drainage, leading to lower bearing capacity and a higher risk of track lateral stability problems. Moreover, these solid particles may deposit on the railway surface and endanger the train directly. Unfortunately, those debris flow introduced track issues have not been thoroughly investigated. This study presents a numerical investigation of the impact of the debris flow on the railway track. Various factors governing the debris flow are considered, including particle size and solid fraction. Besides, those factors affecting the ballast are also discussed, such as fouling condition and initial void ratio. A coupled computational fluid dynamics and discrete element method (CFD-DEM) approach is developed to capture the interactions between particles/particles, water/air, and particles/fluid. The results from this study may help the railway to improve track resilience before the debris flow and to improve maintenance strategy after the debris flow flashing.

Study on the threshold for superposed deformation of simply supported bridge creep and track slab upwarp in high-speed railway

Based on long-term inspection data about track geometric irregularity of 32 m-span simply supported girder bridge in China Railway High-Speed for nearly 10 years, it is found that there is continuous periodic track longitudinal level (TLL) with different wavelengths, thereinto, simply supported girder bridges creep and ballastless track slab upwarp are the primary reasons. Moreover, there are two types of variation trends for bridge creep of 32 m simply-supported bridges with ballastless track, that is, stable type and increasing type, and the maximum [Formula: see text] (the peak-to-peak value of track longitudinal level) is 7.1 mm for track longitudinal level caused by bridge creep, and the maximum [Formula: see text] caused by upwarp deformation of ballastless track slab is 3.2 mm. Hence, this paper investigated the effects on running performance and structure service performance of random track irregularity and additional track irregularity caused by bridge creep, track slab upwarp deformation or superposition of both, a three-dimensional finite element model of vehicle-track-bridge for dynamic simulation calculation was established, the threshold values for bridge creep and track slab deformation under 350 km/h were proposed based on running performance and structure service performance. Finally, research results show that bridge creep influences on the ride comfort significantly, but running safety barely. Due to the short wavelength of TLL, the track slab upwarp deformation affects both the ride comfort and running safety heavily. The car bodies are more sensitive to bridge creep and produce mainly low-frequency vibration, but the rate of wheel load reduction is more sensitive to the track deformation and shows the high-frequency vibration. For 32 m simply supported bridges without track slab deformation, the [Formula: see text] caused by bridge creep should be limited to 7 mm, and 9 mm in difficult situations. When the [Formula: see text] caused by bridge creep is small (less than 5 mm), the [Formula: see text] caused by track slab upwarp deformation must be less than 4 mm. When both deformations exist simultaneously, the [Formula: see text] caused by superposition deformations of both should not exceed 10 mm, with track slab upwarp deformation not exceeding 4 mm. In the presence of both structural deficiencies, it is suggested that the track slab deformation must be eliminated when it is difficult to eliminate the bridge creep.

A novel evaluation of train running safety on the HSR bridges under earthquakes based on the observed track deformation rate

Safe operation of the trains on the high-speed railway bridge requires the railway line to have a high level of track regularity. High-speed railway bridges can deform unevenly under horizontal earthquakes, and the solid instantaneous deformation of the track can cause the train to derail. This paper develops a refined nonlinear model of the train-track-bridge coupling vibration subjected to seismic shaking to capture as comprehensively as possible the impact of the transient deformation of the track on the train operation at each moment and position. In addition, the risk factors and derailment characteristics are investigated in depth. The findings showed that the earthquake caused the bridge's girder ends to undergo severe dislocation and rotation, which facilitates the derailment of a train. Moreover, the vibration coupling between the train and the bridge becomes strong after bearing shear pin failure. Based on the statistical results of derailment causes, a novel index for evaluating the train running safety on the high-speed railway bridge is proposed. Besides, the engineering applications of this index are also introduced. Indeed, this new index can be used as the lower limit for evaluating train derailment on HSR bridges during earthquakes.

Multi-instrument observations of the Pajala fireball: Origin, characteristics, and atmospheric implications

Meteor observations provide information about Solar System constituents and their influx onto Earth, their interaction processes in the atmosphere, as well as the neutral dynamics of the upper atmosphere. This study presents optical, radar, and infrasound measurements of a daytime fireball that occurred on 4 December 2020 at 13:30 UTC over Northeast Sweden. The fireball was recorded with two video cameras, allowing a trajectory determination to be made. The orbital parameters are compatible with the Northern Taurid meteor shower. The dynamic mass estimate based on the optical trajectory was found to be 0.6–1.7 kg, but this estimate can greatly vary from the true entry mass significantly due to the assumptions made. The meteor trail plasma was observed with an ionosonde as a sporadic E-like ionogram trace that lasted for 30 min. Infrasound emissions were detected at two sites, having propagation times consistent with a source location at an altitude of 80–90 km. Two VHF specular meteor radars observed a 6 minute long non-specular range spread trail echo as well as a faint head echo. Combined interferometric range-Doppler analysis of the meteor trail echoes at the two radars, allowed estimation of the mesospheric horizontal wind altitude profile, as well as tracking of the gradual deformation of the trail over time due to a prevailing neutral wind shear. This combined analysis indicates that the radar measurements of long-lived non-specular range-spread meteor trails produced by larger meteoroids can be used to measure the meteor radiant by observing the line traveled by the meteor. Furthermore, a multistatic meteor radar observation of these types of events can be used to estimate mesospheric neutral wind altitude profiles.