Multi-Shape Free-Form Deformation Framework for Efficient Data Transmission in AR-Based Medical Training Simulators

Augmented reality medical training simulators can provide a realistic and immersive experience by overlapping the virtual scene on to the real world. Latency in augmented reality (AR) medical training simulators is an important issue as it can lead to motion sickness for users. This paper proposes a framework that can achieve real-time rendering of the 3D scene aligned to the real world using a head-mounted display (HMD). Model deformation in the 3D scene is categorised into local deformation derived from user interaction and global deformation determined by the simulation scenario. Target shapes are predefined by a simulation scenario, and control points are placed to embed the predefined shapes. Free-form deformation (FFD) is applied to multiple shapes to efficiently transfer the simulated model to the HMD. Global deformation is computed by blending a mapping matrix of each FFD with an assigned weighting value. The local and global deformation are then transferred through the control points updated from a deformed surface mesh and its corresponding weighting value. The proposed framework is verified in terms of latency caused by data transmission and the accuracy of a transmitted surface mesh in a vaginal examination (VE) training simulation. The average latency is reduced to 7 ms, less than the latency causing motion sickness in virtual reality simulations. The maximum relative error is less than 3%. Our framework allows seamless rendering of a virtual scene to the real world with substantially reduced latency and without the need for an external tracking system.

Adhesion Percolation Determines Global Deformation Behavior in Biomimetic Emulsions

Characterizing the mechanical properties of tissues is key for the understanding of fundamental biological processes such as morphogenesis or tumor progression. In particular, the intercellular adhesion forces, mediated by transmembrane proteins like cadherins, are expected to control the topology and viscoelastic behavior of tissues under mechanical stress. In order to understand the influence of adhesion in tissues, we use biomimetic emulsions in which droplets mimic cells and adhere to each other through specific bonds. Here, we tune both the binding energy of the adhesive inter-droplets contacts as well as the fraction of contacts that are adhesive, thereby defining a so-called adhesiveness. Our experimental results show that adhesion prevents the emergence of local order in emulsions even at high packing fractions by preventing energetically costly droplet rearrangements. By studying the deformation of droplets within packings with different average adhesiveness values, we reveal the existence of a threshold value of adhesiveness above which all droplets in a packing are deformed as adhesive ones irrespective of their local adhesive properties. We show that this critical adhesiveness coincides with the threshold for percolation of adhesive structures throughout the tissue. From a biological point of view, this indicates that only a fraction of adhesive cells would be sufficient to tune the global mechanical properties of a tissue, which would be critical during processes such as morphogenesis.

Venus internal structure and global deformation

<p>Tidal forces acting on a planet cause a deformation and mass redistribution in its interior, involving surface motions and variation in the gravity field, which may be observed in geodetic experiments. The change in the gravitational field of the planet, due to the influence of an external gravity field, described primarily by its tidal Love number k of degree 2 (denoted by k<sub>2</sub>) can be observed from analysis of a spacecraft radio tracking. The planet’s deformation is linked to its internal structure, most effectively to its density and rigidity. Hence the tidal Love number k<sub>2</sub> can be theoretically approximated for different planetary models, which means comparing the observed and theoretical calculation of k<sub>2</sub> of a planet is a window to its internal structure.</p> <p>The terrestrial planet Venus is reminiscent of the Earth twin planet in size and density, which leads to the assumption that the Earth and Venus have similar internal structures. In this work, with a Venus we investigate the structure and elastic parameters of the planet’s major layers to calculate its frequency dependent tidal Love number k<sub>2</sub>. The calculation of k<sub>2</sub> is done with ALMA, a Fortran 90 program by <em>Spada [2008]</em> for computing the tidal and load Love numbers using the Post-Widder Laplace inversion formula. We test the effect of different parameters in the Venus model (as a layer’s density, rigidity, viscosity and thickness) on the tidal Love numbers k<sub>2 </sub>and different linear and non-linear combinations of k<sub>2</sub> and<sub> </sub>h<sub>2</sub> (as the tidal Love number h<sub>2</sub> describes the radial displacement due to tidal effects).</p>

Myocardial Characterization in Patients with Nonischemic Dilated Cardiomyopathy Combined with Ventricular Arrhythmias: Insights from Cardiovascular Magnetic Resonance Feature Tracking

This study investigated the feasibility of using cardiovascular magnetic resonance feature tracking (CMR-FT) for analysis of left ventricular (LV) strain and strain rate in patients with non-ischemic dilated cardiomyopathy (NIDCM) combined with ventricular arrhythmias (VAs). And evaluated the correlation between the LV global strain and left ventricular ejection (LVEF). We performed a retrospective study in a cohort of 34 consecutive patients with NIDCM combined with VAs who underwent CMR examination in our hospital between January 2016 and December 2019. Global and segmental peak values of LV longitudinal, circumferential, radial strain, and systolic strain rate were analyzed. Pearson analysis was calculated to assess the correlation of LV global deformation and LVEF as well as the correlation of between LV global deformation. Compared with the healthy controls, the global peak radial strain (GPRS), global peak circumferential strain (GPCS), and global peak longitudinal strain (GPLS) were significantly reduced in patients with NIDCM combined with VAs (P < 0.001, respectively). Additionally, Pearson analysis showed GPCS negatively correlated with LVEF (r=-0.946, P < 0.001), GPLS negatively correlated with LVEF (r=-0.860, P < 0.001), and GPRS positively correlated with LVEF (r = 0.920, P < 0.001). CMR-FT is a feasible and promising technique for assessing LV myocardial deformation of patients with NIDCM combined with VAs. And, GPCS was better negatively correlated with LVEF and higher reproducibility of intra-class correlation coefficient (ICC), which can help to guide clinical treatment and have great implication on clinical decision.

Deformations of reducible Galois representations to Hida-families

The global deformation theory of residually reducible Galois representations with fixed auxiliary conditions is studied. We show that [Formula: see text] lifts to a Hida line for which the weights range over a congruence class modulo-[Formula: see text]. The advantage of the purely Galois theoretic approach is that it allows us to construct [Formula: see text]-adic families of Galois representations lifting the actual representation [Formula: see text], and not just the semisimplification.

Rock Triaxial Tests: Global Deformation vs Local Strain Measurements—Implications

Accurate stress–strain measurements in triaxial tests are critical to compute reliable mechanical parameters. We focus on compliance at the interfaces between the specimen and endcaps, and test specimens under various triaxial conditions using different instrumentation protocols. The tested materials include aluminum, Eagle Ford shale, Berea sandstone, and Jubaila carbonate. Results obtained following common practice reveal that surface roughness at the specimen-endcap interfaces leads to marked seating effects, affects all cap-to-cap based measurements and hinders ultrasonic energy transmission. In particular, cap-to-cap deformation measurements accentuate hysteretic behavior, magnify biases caused by bending and tilting (triggered by uneven surfaces and misalignment), and affect the estimation of all rock parameters, from stiffness to Biot’s α-parameter. Higher confining pressure diminishes seating effects. Local measurements using specimen-bonded strain gauges are preferred (Note: mounting strain gauges on sleeves is ill-advised). We confirm that elastic moduli derived from wave propagation measurements are higher than quasi-static moduli determined from local strain measurements using specimen-bonded strain gauges, probably due to the lower strain level in wave propagation and preferential high-velocity travel path for first arrivals.

Influence of DE-cluster refinement on numerical analysis of rockfall experiments

A numerical analysis is validated against a Swiss Federal Commission for Technology and Innovation (CTI)—frame impact experiment conducted by the Swiss Company Geobrugg. The discrete element method is used to simulate the impacting object, while the highly nonlinear structural response is analysed with the finite element method. Both methods are coupled within an open-source multi-physics research code to exchange data and simulate the interaction. The successful practical application of the coupling algorithm is demonstrated with this work, as the numerical results show good agreement with the experimental results. Within this paper the main focus is the appropriate modelling of the impacting objects, which heavily influences the simulation results, while a simplified structural model allows a correct assessment of the global deformation behaviour and reaction forces.

Numerical Investigation of the Damage Mechanism of Offshore Pipeline Impacted by the Lump-Shaped Falling Object

Damage mechanism analysis of the exposed offshore pipeline impacted by lump-shaped falling objects plays a significant role in offshore pipeline design, inspection, maintenance, and protection. A series of three-dimensional (3D) coupling models are established and simulated to investigate mechanical behaviors and responses of exposed offshore pipelines impacted by lump-shaped falling objects. The effects of both offshore pipeline parameters and lump-shaped falling object parameters were discussed under the joint action of internal pressure and external seawater pressure. The results demonstrate that seabed soil could absorb partial impact energy and act as a cushion. Indentation on the pipeline top and stress concentrations on the pipeline bottom starts to appear when the impact velocity is larger than 10 m/s and 14 m/s, respectively. The critical impact energy before pipeline failure is around 9733.339 J. A variation in contact area has a noticeable influence on the dent depth, but a slight influence on the global deformation. An increase in pressure difference mitigates the impact damage. The depression rate increases with the rise of the radius-thickness ratio, and the most severe plastic deformation occurs when the radius-thickness ratio is 40. Besides, the eccentric distance is an essential factor influencing the damage mechanism of the offshore pipeline.