Non-rigid Surface Research Articles

A Programmable Substrate to Study Robots Jumping From Non-Rigid Surfaces

A Programmable Substrate to Study Robots Jumping From Non-Rigid Surfaces

Estimation of human bloodstains time since deposition using ATR-FTIR spectroscopy and chemometrics in simulated crime conditions

Blood in the form of stains is one of the most frequently encountered fluid in crime scene. Estimation of the time since deposition (TSD) is of great importance to guide the police investigation and the clarification of criminal offences. The time elapsed since deposition is usually estimated by modelling the physicochemical degradation of blood biomolecules over time. This work shows an ATR-FTIR spectroscopy and chemometrics study to estimate TSD of bloodstains on various surfaces and under different ambient conditions (indoor and outdoor). For a period from 0 to 212 days, a total of 960 stains were analyzed. Most of the eleven partial least squares regression (PLSR) models obtained showed a good prediction capacity, with a Residual Predictive Deviation (RPD) value higher than 3, and R2 higher than 0.90. Models for non-rigid supports showed better predictive capacity than those for rigid ones. A non-rigid surface model including the various non-rigid surfaces and ambient conditions was elaborated, which might be the most useful one from the criminalistic point of view. These results show that this technique can be a rapid, robust, and trustable tool for in situ determination of the TSD of bloodstains at crime scenes.

Abstract 2009: Computational Modeling Of Long-term Aortic Root Dilatation Following TEVAR Of Type B Aortic Dissection

Objectives: The long-term sequalae of thoracic endovascular aortic repair (TEVAR) are poorly understood. While several failure modes have been identified, the hemodynamic impact of TEVAR in the proximal native ascending aorta has yet to be fully appreciated. This study applies computational modeling tools to investigate a case of long-term aortic root dilatation following TEVAR for acute type B aortic dissection (TBAD). Methods: We investigate a patient who presented with heart failure 4.5 years after initially successful TEVAR. Cross-sectional aortic root diameter was measured in a pre-operative scan and 57 months post-TEVAR. Three-dimensional localized surface dilatation was calculated using pre-operative and post-operative segmentations, followed by a non-rigid surface mapping method of calculating area change in corresponding regions. The hemodynamic impact of TEVAR on the proximal aorta was analyzed with a computational fluid dynamics (CFD) simulation of the post-operative patient geometry. Results: Aortic root diameter increased from 39.2 mm pre-op to 47.1 mm (+ 20.1%) postop and 34.9 mm preop to 40.8 mm (+ 16.9%) postop on axial and coronal images respectively. The three-dimensional area mapping between pre and post-op scans demonstrates a maximum 14% area increase near the aortic root. The CFD simulations show increased velocity and static pressure in the ascending aorta near the aortic root region. Conclusions: Three different computational approaches demonstrate long-term changes in ascending aortic morphology following TEVAR. Computed tomography measurements demonstrate significant aortic root dilatation, and three-dimensional surface mapping shows increasing area in the proximal ascending aorta. The CFD results emphasize localization of increased velocity and stress in the same region. These observations point to potential avenues for further mechanistic investigation.

Comparative Analysis of Non-Rigid Registration Techniques for Liver Surface Registration.

Non-rigid surface-based soft tissue registration is crucial for surgical navigation systems, but its adoption still faces several challenges due to the large number of degrees of freedom and the continuously varying and complex surface structures present in the intra-operative data. By employing non-rigid registration, surgeons can integrate the pre-operative images into the intra-operative guidance environment, providing real-time visualization of the patient's complex pre- and intra-operative anatomy in a common coordinate system to improve navigation accuracy. However, many of the existing registration methods, including those for liver applications, are inaccessible to the broader community. To address this limitation, we present a comparative analysis of several open-source, non-rigid surface-based liver registration algorithms, with the overall goal of contrasting their strength and weaknesses and identifying an optimal solution. We compared the robustness of three optimization-based and one data-driven nonrigid registration algorithms in response to a reduced visibility ratio (reduced partial views of the surface) and to an increasing deformation level (mean displacement), reported as the root mean square error (RMSE) between the pre-and intra-operative liver surface meshed following registration. Our results indicate that the Gaussian Mixture Model - Finite Element Model (GMM-FEM) method consistently yields a lower post-registration error than the other three tested methods in the presence of both reduced visibility ratio and increased intra-operative surface displacement, therefore offering a potentially promising solution for pre- to intra-operative nonrigid liver surface registration.

Real-Time Radiometric Compensation on Deforming Non-Rigid Surfaces using Motion Prediction in Projection Mapping

Real-Time Radiometric Compensation on Deforming Non-Rigid Surfaces using Motion Prediction in Projection Mapping

Bitumen emulsion effect on properties of asphalt-concrete mix for non-rigid road pavements (Tambov) .

During major repairs of non-rigid road surfaces and reconstruction of automobile roads, it is necessary to remove old coating with road cutters. During cold milling of the old coating, the material acquires the form of granules with the surface covered with a bitumen film. Over time, the bitumen film loses its properties, and to reuse the material, it is necessary to restore the binder properties. The introduction of the bitumen emulsion in the composition of asphalt-concrete mix, allows to restore the binder properties affecting not only strength properties of the asphalt-concrete mix, but also deformability and stiffness of the mixture layer under the compressive load.Purpose: Evaluation of the influence of the binder content on deformability and stiffness of the asphalt-concrete mix.Methodology: Asphalt granulate fractions are used in proportions 8 to 16 and 18 to 36 mm with a residual bitumen content of 2%. The bitumen emulsion EBK-2 is used as a binder. The ultimate strength of the asphalt layer is measured according to GOST 12801. Deformation of the mixture layer is measured on a TP-1-1500 hydraulic press.Research findings: The bitumen emulsion effect is shown for deformation and stiffness of the asphalt-concrete mix for the pavement construction.Value: It is shown that the bitumen emulsion in regeneration of asphalt granulate affects deformability and stiffness of the layer subjected to compaction load. The development of deformation and stiffness of the mixture layer under the load with different binder content, particles size, and layer thickness are established. Analytical dependences are suggested for deformation and stiffness of the loaded layer, its thickness during paving, and percentage of bitumen emulsion in the mixture.

Covariations between scapular shape and bone density in B-glenoids: A statistical shape and density modeling-approach.

B-type glenoids arecharacterized by posterior humeral head migration and/or bony-erosion-induced glenoid retroversion. Patients with this type of osteoarthritic glenoids are known to be at increased risk of glenoid component loosening after anatomic total shoulder arthroplasty (aTSA). One of the main challenges in B glenoid surgical planning is to find a balance between correcting the bony shape and maintaining the quality of the bone support. This study aims to systematically quantify variabilities in terms of scapular morphology and bone mineral density in patients with B glenoids and to identify patterns of covariation between these two features. Using computed tomography scan images of 62 patients, three-dimensionalscapular surface models were constructed. Rigid and nonrigid surface registration of the scapular surfaces, followed by volumetric registration and material mapping, enabled us to develop statistical shapemodel(SSM) and statistical density model(SDM). Partial least square correlation (PLSC) was used to identify patterns of covariation. The developed SSM and SDM represented 85.9% and 56.6% of variabilities in terms of scapular morphology and bone density, respectively. PLSC identified four modes of covariation, explaining 66.0% of the correlation between these two variations. Covariation of posterior-inferior glenoid erosion with posterior sclerotic bone formation in association with reduction of bone density in the anterior and central part of the glenoid was detected as the primary mode of covariation. Identification of these asymmetrical distribution of bone density can inform us about possible reasons behind glenoid component loosening in B glenoids and surgical guidelines in terms of the compromise between bony shape correction and bone support quality.

An Energy-Based Framework for Robust Dynamic Bipedal Walking Over Compliant Terrain

Abstract Bipedal locomotion over compliant terrain is an important and largely underexplored problem in the robotics community. Although robot walking has been achieved on some non-rigid surfaces with existing control methodologies, there is a need for a systematic framework applicable to different bipeds that enables stable locomotion over various compliant terrains. In this work, a novel energy-based framework is proposed that allows the dynamic locomotion of bipeds across a wide range of compliant surfaces. The proposed framework utilizes an extended version of the 3D Dual Spring-Loaded Inverted Pendulum (Dual-SLIP) model that supports compliant terrains, while a bioinspired controller is employed to regulate expected perturbations of extremely low ground-stiffness levels. An energy-based methodology is introduced for tuning the bioinspired controller to enable dynamic walking with robustness to a wide range of low ground-stiffness one-step perturbations. The proposed system and controller are shown to mimic the vertical Ground Reaction Force (GRF) responses observed in human walking over compliant terrains. Moreover, they succeed in handling repeated unilateral stiffness perturbations under specific conditions. This work can advance the field of biped locomotion by providing a biomimetic method for generating stable human-like walking trajectories for bipedal robots over various compliant surfaces. Furthermore, the concepts of the proposed framework could be incorporated into the design of controllers for lower-limb prostheses with adjustable stiffness to improve their robustness over compliant surfaces.

Local non-similar solution of radiative and magnetized flow of non-Newtonian liquid over a gravitationally affected porous surface with Newtonian heating effect

A non-similar solution of the generalized Newtonian liquid flow over a vertical non-rigid surface is presented to explore the significance of nonlinear radiation, Newtonian heating, magnetic and gravitational fields. The non-similar dynamical nature with rapid change in size and position is studied by incorporating the ordinate and stream-wise coordinates. The newly formulated mathematical results are presented in the form of partial differential equations (PDEs) which are converted to ordinary differential equations (ODEs) by utilizing the non-similar variables. The governing ODEs are then approximated by one of the collocation methods to explore the characteristic of different physical parameters while using MATLAB. The significant increasing behavior of the velocity profile is determined by the variation in Wessenberg number, bouncy ratio parameter, and suction parameters. On the other hand, the temperature profile is enhanced by uplifting the radiation, Newtonian heating, and heat generation parameters, respectively. The rate of heat transfer and resistive forces are escalating functions of stream-wise coordinate. All the new analysis and applied method are verified by giving a comparison with previous work.

Automated and data-driven plate computation for presurgical cleft lip and palate treatment

PurposePresurgical orthopedic plates are widely used for the treatment of cleft lip and palate, which is the most common craniofacial birth defect. For the traditional plate fabrication, an impression is taken under airway-endangering conditions, which recent digital alternatives overcome via intraoral scanners. However, these alternatives demand proficiency in 3D modeling software in addition to the generally required clinical knowledge of plate design.MethodsWe address these limitations with a data-driven and fully automated digital pipeline, endowed with a graphical user interface. The pipeline adopts a deep learning model to landmark raw intraoral scans of arbitrary mesh topology and orientation, which guides the nonrigid surface registration subsequently employed to segment the scans. The plates that are individually fit to these segmented scans are 3D-printable and offer optional customization.ResultsWith the distance to the alveolar ridges closely centered around the targeted 0.1 mm, our pipeline computes tightly fitting plates in less than 3 min. The plates were approved in 12 out of 12 cases by two cleft care professionals in a printed-model-based evaluation. Moreover, since the pipeline was implemented in clinical routine in two hospitals, 19 patients have been undergoing treatment utilizing our automated designs.ConclusionThe results demonstrate that our automated pipeline meets the high precision requirements of the medical setting employed in cleft lip and palate care while substantially reducing the design time and required clinical expertise, which could facilitate access to this presurgical treatment, especially in low-income countries.

Deformable cardiac surface tracking by adaptive estimation algorithms

This study presents a particle filter based framework to track cardiac surface from a time sequence of single magnetic resonance imaging (MRI) slices with the future goal of utilizing the presented framework for interventional cardiovascular magnetic resonance procedures, which rely on the accurate and online tracking of the cardiac surface from MRI data. The framework exploits a low-order parametric deformable model of the cardiac surface. A stochastic dynamic system represents the cardiac surface motion. Deformable models are employed to introduce shape prior to control the degree of the deformations. Adaptive filters are used to model complex cardiac motion in the dynamic model of the system. Particle filters are utilized to recursively estimate the current state of the system over time. The proposed method is applied to recover biventricular deformations and validated with a numerical phantom and multiple real cardiac MRI datasets. The algorithm is evaluated with multiple experiments using fixed and varying image slice planes at each time step. For the real cardiac MRI datasets, the average root-mean-square tracking errors of 2.61 mm and 3.42 mm are reported respectively for the fixed and varying image slice planes. This work serves as a proof-of-concept study for modeling and tracking the cardiac surface deformations via a low-order probabilistic model with the future goal of utilizing this method for the targeted interventional cardiac procedures under MR image guidance. For the real cardiac MRI datasets, the presented method was able to track the points-of-interests located on different sections of the cardiac surface within a precision of 3 pixels. The analyses show that the use of deformable cardiac surface tracking algorithm can pave the way for performing precise targeted intracardiac ablation procedures under MRI guidance. The main contributions of this work are twofold. First, it presents a framework for the tracking of whole cardiac surface from a time sequence of single image slices. Second, it employs adaptive filters to incorporate motion information in the tracking of nonrigid cardiac surface motion for temporal coherence.

Проблема оптимізації лабораторного ущільнення асфальтобетонних сумішей

The problem of ensuring the durability and operation of asphalt concrete layers of non-rigid road surfaces is closely related to the quality of the materials used, their composition and installation technology. The latter includes two defining stages: moving mixtures and their compaction. At the same time, the prediction of the properties of asphalt concrete should be carried out based on the results of laboratory tests, in the process of which the road, climatic and transport conditions of operation of one or another layer are taken into account. Reliable prediction can be ensured if the conditions of laboratory research and production processes are identical. This mostly applies to the laboratory seal, which must match the production seal. The existing state of affairs does not meet this condition. For many decades, laboratory compaction was carried out by pressing asphalt concrete mixtures under a pressure of 20 MPa with vibration up to 40 MPa. Western European researchers and builders have been aware of this problem for more than 50 years. Due to this, fundamentally new methods of laboratory compaction appeared in the world (impact and vibration-impact type, rolling with metal and pneumatic rollers, displacement with pressure in the case of rotary presses). In Ukrainian practice, such methods are practically not used, despite the fact that the first rolling press was developed in KADI. The results of comparative studies of asphalt concrete compacted by the following methods: pressing, sector rolling, and rotary compaction are presented. Attention to the advantages and disadvantages of each of them is accepted. Keywords: asphalt concrete mixture, compaction by pressing, rolling, rotary shear, kinetics of gradual compaction, bitumen content.

Simulation of the process of milling and grinding cylindrical surfaces by an oriented tool in one setup

Purpose. Improvement of schemes for processing the cylindrical surfaces of the shafts of gearboxes and transmissions of large-sized equipment. Development of modular spatial models of the processes of milling and grinding of the cylindrical surfaces of the shafts of gearboxes and transmissions of military and civil vehicles. Development of a model for dressing a grinding wheel with a diamond tool. Methodology. Creation of general and particular modular mathematical models of the processes of removal of allowance and shaping during rough and finish milling and finishing grinding of non-rigid cylindrical surfaces was carried out using a matrix apparatus for transforming coordinate systems. This made it possible to describe the treatment process using standard matrices. The calculations were carried out in the mathematical package Mathcad. To obtain a graphic display of the mathematical model of the instrumental and machined surfaces, the standard functions of the software package and the developed logical blocks were used. Findings. A technique for processing cylindrical surfaces of revolution with an oriented tool is proposed. Roughing, finishing and polishing are carried out in one setup. Roughing and finishing are carried out with an oriented cutter with replaceable multifaceted carbide inserts. The angle of orientation of the cutter is selected from the condition of maximum loading of the end section. Thus, the roughing stock is removed by the end face and by the finishing periphery, while the maximum component of the cutting force is directed along the axis of the part and does not cause deformations in the radial direction. Final finishing is carried out with a wide grinding wheel. The angle of orientation of the grinding wheel is selected from the condition of uniform distribution of the allowance along the periphery. A scheme for dressing the working surface of a grinding wheel with a diamond pencil with a constant feed is proposed. Originality. Modular spatial models of the processes of milling and grinding of the cylindrical surfaces of the shafts of gearboxes and transmissions of military and civil vehicles were developed. A model for dressing a grinding wheel is proposed. The use of the proposed models makes it possible to conduct a more detailed analysis of the processes of stock removal and shaping. Practical value. Dependencies are proposed for choosing the optimal angles of orientation of the cutter for roughing and finishing milling and the grinding wheel for finishing. The accuracy of parts is increased due to the elimination of the resetting error. The cost of manufacturing is reduced due to the maximum full use of cutting carbide inserts, by turning them and operating the worn finishing edge in the rough milling mode, as well as by increasing the resource of the grinding wheel.

Learning geodesic-aware local features from RGB-D images

Most of the existing handcrafted and learning-based local descriptors are still at best approximately invariant to affine image transformations, often disregarding deformable surfaces. In this paper, we take one step further by proposing a new approach to compute descriptors from RGB-D images (where RGB refers to the pixel color brightness and D stands for depth information) that are invariant to isometric non-rigid deformations, as well as to scale changes and rotation. Our proposed description strategies are grounded on the key idea of learning feature representations on undistorted local image patches using surface geodesics. We design two complementary local descriptors strategies to compute geodesic-aware features efficiently: one efficient binary descriptor based on handcrafted binary tests (named GeoBit), and one learning-based descriptor (GeoPatch) with convolutional neural networks (CNNs) to compute features. In different experiments using real and publicly available RGB-D data benchmarks, they consistently outperforms state-of-the-art handcrafted and learning-based image and RGB-D descriptors in matching scores, as well as in object retrieval and non-rigid surface tracking experiments, with comparable processing times. We also provide to the community a new dataset with accurate matching annotations of RGB-D images of different objects (shirts, cloths, paintings, bags), subjected to strong non-rigid deformations, for evaluation benchmark of deformable surface correspondence algorithms.

The Role of the Double-Layer Potential in Regularised Stokeslet Models of Self-Propulsion

The method of regularised stokeslets is widely used to model microscale biological propulsion. The method is usually implemented with only the single-layer potential, the double-layer potential being neglected, despite this formulation often not being justified a priori due to nonrigid surface deformation. We describe a meshless approach enabling the inclusion of the double layer which is applied to several Stokes flow problems in which neglect of the double layer is not strictly valid: the drag on a spherical droplet with partial-slip boundary condition, swimming velocity and rate of working of a force-free spherical squirmer, and trajectory, swimmer-generated flow and rate of working of undulatory swimmers of varying slenderness. The resistance problem is solved accurately with modest discretisation on a notebook computer with the inclusion of the double layer ranging from no-slip to free-slip limits; the neglect of the double-layer potential results in up to 24% error, confirming the importance of the double layer in applications such as nanofluidics, in which partial slip may occur. The squirming swimmer problem is also solved for both velocity and rate of working to within a small percent error when the double-layer potential is included, but the error in the rate of working is above 250% when the double layer is neglected. The undulating swimmer problem by contrast produces a very similar value of the velocity and rate of working for both slender and nonslender swimmers, whether or not the double layer is included, which may be due to the deformation’s ‘locally rigid body’ nature, providing empirical evidence that its neglect may be reasonable in many problems of interest. The inclusion of the double layer enables us to confirm robustly that slenderness provides major advantages in efficient motility despite minimal qualitative changes to the flow field and force distribution.

A Measurement of ‘Walking-the-Wall’ Dynamics: An Observational Study Using Accelerometry and Sensors to Quantify Risk Associated with Vertical Wall Impact Attenuation in Trampoline Parks

This study illustrates the application of a tri-axial accelerometer and gyroscope sensor device on a trampolinist performing the walking-the-wall manoeuvre on a high-performance trampoline to determine the performer dynamic conditions. This research found that rigid vertical walls would allow the trampolinist to obtain greater control and retain spatial awareness at greater levels than what is achievable on non-rigid vertical walls. With a non-rigid padded wall, the reaction force from the wall can be considered a variable force that is not constrained, and would not always provide the feedback that the trampolinist needs to maintain the balance with each climb up the wall and fall from height. This research postulates that unattenuated vertical walls are safer than attenuated vertical walls for walking-the-wall manoeuvres within trampoline park facilities. This is because non-rigid walls would provide higher g-force reaction feedback from the wall, which would reduce the trampolinist’s control and stability. This was verified by measuring g-force on a horizontal rigid surface versus a non-rigid surface, where the g-force feedback was 27% higher for the non-rigid surface. Control and stability are both critical while performing the complex walking-the-wall manoeuvre. The trampolinist experienced a very high peak g-force, with a maximum g-force of approximately 11.5 g at the bottom of the jump cycle. It was concluded that applying impact attenuation padding to vertical walls used for walking-the-wall and similar activities would increase the likelihood of injury; therefore, padding of these vertical surfaces is not recommended.

A note on the first-order flexes of smooth surfaces which are tangent to the set of all nonrigid surfaces

We prove that first-order flexes of smooth surfaces in Euclidean 3-space, which are tangent to the set of all nonrigid surfaces, can be extended to second-order flexes.

Pheno4D: A spatio-temporal dataset of maize and tomato plant point clouds for phenotyping and advanced plant analysis.

Understanding the growth and development of individual plants is of central importance in modern agriculture, crop breeding, and crop science. To this end, using 3D data for plant analysis has gained attention over the last years. High-resolution point clouds offer the potential to derive a variety of plant traits, such as plant height, biomass, as well as the number and size of relevant plant organs. Periodically scanning the plants even allows for performing spatio-temporal growth analysis. However, highly accurate 3D point clouds from plants recorded at different growth stages are rare, and acquiring this kind of data is costly. Besides, advanced plant analysis methods from machine learning require annotated training data and thus generate intense manual labor before being able to perform an analysis. To address these issues, we present with this dataset paper a multi-temporal dataset featuring high-resolution registered point clouds of maize and tomato plants, which we manually labeled for computer vision tasks, such as for instance segmentation and 3D reconstruction, providing approximately 260 million labeled 3D points. To highlight the usability of the data and to provide baselines for other researchers, we show a variety of applications ranging from point cloud segmentation to non-rigid registration and surface reconstruction. We believe that our dataset will help to develop new algorithms to advance the research for plant phenotyping, 3D reconstruction, non-rigid registration, and deep learning on raw point clouds. The dataset is freely accessible at https://www.ipb.uni-bonn.de/data/pheno4d/.

Modeling of thermal processes in construction of nonrigid pavements using bitumen concrete mixes

The remoteness of the construction site from the production base, large volumes of work, insufficient productivity of asphalt concrete plants for the preparation of hot asphalt concrete mixtures makes urgent the use of cold bitumen concrete mixes for the road construction. The preliminary mix preparation on the production sites with preservation of its properties for several months allows to increase the duration of the construction season. Purpose. Quality improvement of construction of non-rigid road surfaces using cold bitumen concrete mixes. Materials and methods. Models of road pavement structure based on cold bitumen concrete mixes are proposed to clarify the influence of the structural, climatic, technological and thermophysical properties of materials on the pavement quality. Research results. It is shown that the construction of road surfaces using cold bitumen concrete mixes even at positive ambient temperatures, does not provide the required surface quality. Conclusions. To improve the road paving quality using cold bitumen concrete mixes is necessary to heat the base before laying the cold mix. The heating temperature of the base depends on the layer thickness and ambient temperature.

Automatic 3D dense phenotyping provides reliable and accurate shape quantification of the human mandible

Automatic craniomaxillofacial (CMF) three dimensional (3D) dense phenotyping promises quantification of the complete CMF shape compared to the limiting use of sparse landmarks in classical phenotyping. This study assesses the accuracy and reliability of this new approach on the human mandible. Classic and automatic phenotyping techniques were applied on 30 unaltered and 20 operated human mandibles. Seven observers indicated 26 anatomical landmarks on each mandible three times. All mandibles were subjected to three rounds of automatic phenotyping using Meshmonk. The toolbox performed non-rigid surface registration of a template mandibular mesh consisting of 17,415 quasi landmarks on each target mandible and the quasi landmarks corresponding to the 26 anatomical locations of interest were identified. Repeated-measures reliability was assessed using root mean square (RMS) distances of repeated landmark indications to their centroid. Automatic phenotyping showed very low RMS distances confirming excellent repeated-measures reliability. The average Euclidean distance between manual and corresponding automatic landmarks was 1.40 mm for the unaltered and 1.76 mm for the operated sample. Centroid sizes from the automatic and manual shape configurations were highly similar with intraclass correlation coefficients (ICC) of > 0.99. Reproducibility coefficients for centroid size were < 2 mm, accounting for < 1% of the total variability of the centroid size of the mandibles in this sample. ICC’s for the multivariate set of 325 interlandmark distances were all > 0.90 indicating again high similarity between shapes quantified by classic or automatic phenotyping. Combined, these findings established high accuracy and repeated-measures reliability of the automatic approach. 3D dense CMF phenotyping of the human mandible using the Meshmonk toolbox introduces a novel improvement in quantifying CMF shape.