An Efficient Data Structure and Accurate Scheme to Solve Front Propagation Problems

In this paper, we are interested in some front propagation problems coming from control problems in d-dimensional spaces, with d≥2. As opposed to the usual level set method, we localize the front as a discontinuity of a characteristic function. The evolution of the front is computed by solving an Hamilton-Jacobi-Bellman equation with discontinuous data, discretized by means of the antidissipative Ultra Bee scheme. We develop an efficient dynamic storage technique suitable for handling front evolutions in large dimension. Then we propose a fast algorithm, showing its relevance on several challenging tests in dimension d=2,3,4. We also compare our method with the techniques usually used in level set methods. Our approach leads to a computational cost as well as a memory allocation scaling as O(N _nb ) in most situations, where N _nb is the number of grid nodes around the front. Moreover, we show on several examples the accuracy of our approach when compared with level set methods.     

The Changing Capabilities of Cohorts of the Elderly in Russia during 1990–2020: Measurement using a Quantitative Index

Russia has had a high elderly share of its population like the OECD countries, but has had a more turbulent history over the past 100 years, which has caused fluctuations in the capabilities of those turning 60 (measured by education and training, income, enabling environment, medical care, and health status). This article analyses the life experiences and capabilities of five Russian birth cohorts turning 60 over the period 1990–2020. It presents relevant concepts, reviews past research, and evaluates the importance of health factors (health environment, health-related behaviours, medical care, health status) in determining the activities and contributions of older people in Russia. A Human Capabilities of the Elderly in Russia Index (HCERI) with 22 indicators is developed. Russian data are used in the calculation of the HCERI for the cohorts turning 60 in 1990, 1995, 2000, 2010 and 2020. The article then presents evaluations of the experiences and changes in capabilities for each of the five selected cohorts of the elderly in four periods of life: Childhood (1–15 years), Young Adult (16–49), Mature Adult (50–59), and Early Elderly (60–69). The implications of changes in the characteristics of the elderly for Russian government policies are discussed.     

Topological and Variational Properties of a Model for the Reconstruction of Three-Dimensional Transparent Images with Self-Occlusions

We introduce and study a two-dimensional variational model for the reconstruction of a smooth generic solid shape E, which may handle the self-occlusions and that can be considered as an improvement of the 2.1D sketch of Nitzberg and Mumford (Proceedings of the Third International Conference on Computer Vision, Osaka, 1990). We characterize from the topological viewpoint the apparent contour of E, namely, we characterize those planar graphs that are apparent contours of some shape E. This is the classical problem of recovering a three-dimensional layered shape from its apparent contour, which is of interest in theoretical computer vision. We make use of the so-called Huffman labeling (Machine Intelligence, vol. 6, Am. Elsevier, New York, 1971), see also the papers of Williams (Ph.D. Dissertation, 1994 and Int. J. Comput. Vis. 23:93–108, 1997) and the paper of Karpenko and Hughes (Preprint, 2006) for related results. Moreover, we show that if E and F are two shapes having the same apparent contour, then E and F differ by a global homeomorphism which is strictly increasing on each fiber along the direction of the eye of the observer. These two topological theorems allow to find the domain of the functional ℱ describing the model. Compactness, semicontinuity and relaxation properties of ℱ are then studied, as well as connections of our model with the problem of completion of hidden contours.

The Riemannian Geometry of the Space of Positive-Definite Matrices and Its Application to the Regularization of Positive-Definite Matrix-Valued Data

In this paper we present a Riemannian framework for smoothing data that are constrained to live in P(n)mathcal{P}(n), the space of symmetric positive-definite matrices of order n. We start by giving the differential geometry of P(n)mathcal{P}(n), with a special emphasis on P(3)mathcal{P}(3), considered at a level of detail far greater than heretofore. We then use the harmonic map and minimal immersion theories to construct three flows that drive a noisy field of symmetric positive-definite data into a smooth one. The harmonic map flow is equivalent to the heat flow or isotropic linear diffusion which smooths data everywhere. A modification of the harmonic flow leads to a Perona-Malik like flow which is a selective smoother that preserves edges. The minimal immersion flow gives rise to a nonlinear system of coupled diffusion equations with anisotropic diffusivity. Some preliminary numerical results are presented for synthetic DT-MRI data.     

Exploring the use of a mobile robot as an imitation agent with children with low-functioning autism

Unpredictability and complexity of social interactions are important challenges for a low functioning autistic child. The objective of this research is to study how a mobile robot can, by appearing more predictable, appealing and simple than a human being, facilitate reciprocal interaction such as imitative play. By conducting an exploratory study involving four children, we found that forms of shared conventions such as imitation of body movements and of familiar actions are higher with two children paired with a human mediator, compared to two children paired with a robot mediator. However, the two children paired with the robot mediator demonstrated increased shared attention (visual contact, physical proximity) and imitate facial expressions (smile) more than the children paired with the human mediator.

On the Structure of Finite Automata of Which M Is an(Weak)Inverse with Delay τ

In this paper,we first give a method that for any inverse finite automaton M' withdelay τ,all inver tible finite automata with delay τ,of which M' is an inverse with delayτ,can be constructed;and a universal nondeterministic finite automaton,for all finiteautomata of which M' is an inverse with delay τ,can also be constructed.We then give amethod that for any weak inverse finite automaton M' with delay τ,all weaklyinvertible finite automata with delay τ of which M' is a weak inverse with delay,can beconstructed;and a universal nondeterministic finite automaton,for all finiteautomata of which M' is a weak inverse with delay τ,can also be constructed.     

Inferring threats in urban environments with uncertain and approximate data: an agent-based approach

In this article we discuss the problem of inferring threats in an urban environment, where the knowledge of the environment involves multiple types of intelligence and infrastructure data, and is by nature uncertain or approximate. We use a collection of situation-aware agents to infer potential threats in such environments, where agents are responsible for event correlation and situation assessment. We review the weaknesses of a current approach to threat assessment in Homeland Security and then describe our agent-based approach. The key innovations of our agent-based approach are: an ontological commitment to events and situations, fuzzy event correlation, fuzzy situation assessment, adaptability and learning during threat assessment operations, and an enhancement of traditional belief-desire-intention (BDI) agents with situation awareness. We describe the properties of situation-aware BDI agents and discuss the implementation of them on a variety of BDI agent platforms. Lastly, we discuss the interoperability of these platforms and address the issue of scalability through coupling to large-scale peer-to-peer overlays.     

Assessment and improvement of the Cloud Emission and Scattering Index (CESI) – an algorithm for cirrus detection

This study evaluates and improves the cirrus detection of the middle and low peak Weighting Function (WF) Cloud Emission and Scattering Index (CESI) by using the Visible Infrared Imaging Radiometer Suite (VIIRS) cloud mask product. Results show that CESI-3 (peak WF about 890 hPa) accurately detect cirrus with the Probability of detection (POD) value reaching 0.69 during both at day and nighttimes. The CESI-1 (peak WF about 550 hPa) falsely detects cirrus in the Sahara Desert, south of the Saudi Arabia, north of Tibetan Plateau and in Australia during the ascending process. More false alarm rates (FARs) are detected in the northern mid-latitude around 60° N because of the surface type and seasonal effects. Furthermore, the thresholds of middle and low peak WF CESIs for cirrus detection are determined and the performance is satisfactory. In addition, Linear Discriminant Analysis (LDA) is employed to train four combination types (combining CESI-1 and CESI-2, combining CESI-1 and CESI-3, combining CESI-2 and CESI-3, and combining CESI-1, CESI-2, and CESI-3). Accordingly, results elucidate that Comb-1-3 (combining CESI-1 and CESI-3) is appropriate to detect cirrus for the ascending process, increasing the POD by 11.2% as compared to CESI-3. However, Comb-1-2-3 (combining CESI-1, CESI-2 with peak WF around 790 hPa, and CESI-3) is most suitable for cirrus detection in the descending process, increasing the PODs by 8.5%. We also find that the POD of cirrus detection over the land increases relatively higher than over the sea. The most significant improvement of cirrus detection occurs over the land in the summer in the daytime with a 35% POD increase from 0.57 to 0.76.     

Structural analysis of the intervertebral discs adjacent to an interbody fusion using multibody dynamics and finite element cosimulation

This work describes a methodology for the dynamic and structural analysis of complex (bio)mechanical systems that joins both multibody dynamics and finite element domains, in a synergetic way, through a cosimulation procedure that takes benefit of the advantages of each numerical formulation. To accomplish this goal, a cosimulation module is developed based on the gluing algorithm X-X, which is the key element responsible for the management of the information flux between the two software packages (each using its own mathematical formulation and code). The X-X algorithm uses for each cosimulated structure multiple pairs of reference points whose kinematics are solved by the multibody module and prescribed, as initial data, to the finite element counterpart. The finite element module, by its turn, solves the structural problem imposed by the prescribed kinematics, calculates the resulting generalized loads applied over the reference points and return these loads back to the multibody module that uses them to solve the dynamic problem and to calculate new reference kinematics to prescribe to the finite element module in the next time step. The proposed method is applied to study the cervical spine dynamics in a pathologic situation in which an intersomatic fusion is simulated to confirm its potential advantages. Taking into account the proposed simulation scenario, a cervical spine multibody model that includes the rigid vertebrae, the facet joints’ and spinous processes’ contacts, ligaments and the finite element models of the intervertebral discs, and their surrogates is developed. The proposed model is simulated for extension in a forward dynamics perspective.     

Development of an Efficient 3–D CFD Software to Simulate and Visualize the Scavenging of a Two-Stroke Engine

In this paper we want to describe in detail how the task of numerically solving the flow through a two-stroke engine with moving parts is solved in an efficient way. The mathematical model behind the scenes is illuminated and the used numerical schemes are specified. First, the computation of the convective flux function is carried out by the AUSMDV Riemann solver, which has been proven to be very efficient in comparison to other schemes. Then the introduction of the temperature dependency of the material properties of the fluid has augmented the realistic setting within the compression and expansion of the hot gas within the cylinder. This temperature dependency of the heat capacity causes a change in the equation of state. The gas is not polytropic any more but calorically imperfect. Thus, the use of a relaxation method is necessary in order to retain our Riemann solver. To account for the complex geometry, it was necessary to realize a special mesh treatment. The computational domain can be assembled by different meshes that are connected in a mass conservative way. Furthermore, the piston and crankshaft motion is obtained by very efficient algorithms. In order to speed up the computation of the numerical solution, different strategies have been followed. Adaptive local time-stepping has been implemented in a time consistent manner. Additionally, a dynamic local mesh adaption with hanging knots is used to reach a better resolution in critical areas. A further reduction in computational time has been obtained by the parallelization of the numerical scheme and the mesh routines. To handle this parallelization of the mesh treatment, an extended partitioning for the dynamic load balancing has been implemented. Finally, a simulation of flow through a real-world geometry of an existing two-stroke engine has been performed, the results have been validated with measured pressure data for this engine, and the flow has been qualitatively and quantitatively studied.     

Proposal of an Index for the Operator’s Haptic Sensation in a Master-Slave System with Force-Feedback Function

This article proposes an index to estimate the operator’s haptic sensation of the contact between the slave device and the environment in operating master–slave systems with force feedback function. The index value is derived from the velocity information of the master device before and after contact, which is hypothesized to represent the intensity of haptic sensation stimuli presented to the operator. Two characteristics of this index are discussed by means of psychophysics experiment, which are the statistical characteristics of the index value for different operators, and how the change in the operator’s haptic sensation is reflected on the index value. The index is validated by another psychophysics experiment. The experimental results show that the performance of operator’s haptic sensation can be predicted correctly based on the proposed index value. This index is expected to be applied in the parameter design of bilateral-control systems with force feedback function.     

How Constitutive Model Complexity can Affect the Capability to Fit Experimental Data: a Focus on Human Carotid Arteries and Extension/Inflation Data

To perform realistic finite element simulations of cardiovascular surgical procedures (such as balloon angioplasty, stenting or bypass), it is necessary to use appropriate constitutive models able to describe the mechanical behavior of the human arterial wall (in healthy and diseased conditions) as well as to properly calibrate the material parameters involved in such constitutive models. Moving from these considerations, the goal of the present study is to compare the reliability of two isotropic phenomenological models and of four structural invariant-based constitutive models, commonly used to describe the passive mechanical behavior of arteries. The arterial wall is modeled as a thick-wall tube with one- and two- layer structure. Residual stresses inclusion is also considered, to evaluate informations on the stress distribution through the wall thickness. The predictive capability of the investigated models is tested using extension/inflation data on human carotid arteries related by two different experimental works available in the literature. The material parameters involved in the investigated models are computed in the least-square sense thought a best fitting procedure, relying on a multi-start optimization algorithm. The good quality of the optimal solution is validated quantitatively computing proper error measures and comparing the model prediction curves. The final outcome of the paper is a critical review of the six considered constitutive models, comparing their formulation and evidencing the more or less capability of such models to fit the considered experimental data.     

The space of EDF deadlines: the exact region and a convex approximation

It is well known that the performance of computer controlled systems is heavily affected by delays and jitter occurring in the control loops, which are mainly caused by the interference introduced by other concurrent activities. A common approach adopted to reduce delay and jitter in periodic task systems is to decrease relative deadlines as much as possible, but without jeopardizing the schedulability of the task set. In this paper, we formally characterize the region of admissible deadlines so that the system designer can appropriately select the desired values to maximize a given performance index defined over the task set. Finally we also provide a sufficient region of feasible deadlines which is proved to be convex.

The ‘measure of a man’ and the ethos of hospitality: towards an ethical dwelling with technology

In this paper, I argue for the impossible possibility of an ethical dwelling with technology. In arguing for an ethical comportment in our dealing with technology, I am not only arguing for the consideration of the ethical implications of technology (which we already do) but also, and more importantly, for an ethics of technological artefacts qua technology. Thus, I attempt to argue for a decentering (or rather overcoming) of anthropocentric ethics, urging us to move beyond any centre, whatever it may be—anthropological, biological, etc. I argue that if we take ethics seriously we must admit that our measure cannot be that of man. To develop the argument, I use an episode in Star Trek where the fate of the highly sophisticated android Commander Data is to be decided. I show how the moral reasoning about Data remains anthropocentric but hints to other possibilities. I proceed to use the work of Derrida and Levinas (with some help from Heidegger) to suggest a possible way to think (and do) an ethos beyond traditional ethics—an ethics of hospitality in which we dwell in a community of those that have nothing in common.     

Simulation of multibody systems with the use of coupling techniques: a case study

Simulation coupling (or cosimulation) techniques provide a framework for the analysis of decomposed dynamical systems with the use of independent numerical procedures for decomposed subsystems. These methods are often seen as very promising because they enable the utilization of the existing software for subsystem analysis and usually are easy to parallelize, and run in a distributed environment. For example, in the domain of multibody systems dynamics, a general setup for “Gluing Algorithms” was proposed by Wang et al. It was intended to provide a basis for multilevel distributed simulation environments. The authors presented an example where Newton’s method was used to synchronize the responses of subsystem simulators.     

Computationally efficient solutions for tracking people with a mobile robot: an experimental evaluation of Bayesian filters

Modern service robots will soon become an essential part of modern society. As they have to move and act in human environments, it is essential for them to be provided with a fast and reliable tracking system that localizes people in the neighborhood. It is therefore important to select the most appropriate filter to estimate the position of these persons. This paper presents three efficient implementations of multisensor-human tracking based on different Bayesian estimators: Extended Kalman Filter (EKF), Unscented Kalman Filter (UKF) and Sampling Importance Resampling (SIR) particle filter. The system implemented on a mobile robot is explained, introducing the methods used to detect and estimate the position of multiple people. Then, the solutions based on the three filters are discussed in detail. Several real experiments are conducted to evaluate their performance, which is compared in terms of accuracy, robustness and execution time of the estimation. The results show that a solution based on the UKF can perform as good as particle filters and can be often a better choice when computational efficiency is a key issue.     

Approaches to Solve the Problem of Determining the Moments of the Beginning and End of an Object’s Movement Using the Data of a Strapdown Inertial Navigation System

Journal of Computer and Systems Sciences International - The problem of autonomous determination using primary and/or secondary data of a strapdown inertial navigation system of two events is...     

Control and trajectory optimization of an aircraft’s alignment with the desired track

The synthesis of the control with the optimal trajectory length is constructed for the problem of aligning an aircraft with the desired track with the ground speed vector direction along the desired track. The solution is based on the maximum principle and involves the use of numerical methods for solving the boundary value problem and analytical investigations for determining the set of possible extremals and comparing the lengths of the trajectories when selecting the optimal one. As a result of these investigations, the switching and separation lines are determined that bound the regions in the phase space which correspond to different values of the optimal relay control.     

Wordnet as a resource for NLP: Yorick Wilks’ reflections on the ontological debate—and how to cope with ambiguity and vagueness of natural language

The paper argues that Guarino is right that ontologies are different from thesauri and similar objects, but not in the ways he believes: they are distinguished from essentially linguistic objects like thesauri and hierarchies of conceptual relations because they unpack, ultimately, in terms of sets of objects and individuals. However this is a lonely status, and without much application outside strict scientific and engineering disciplines, and of no direct relevance to language processing (NLP). More interesting structures, of NLP relevance, that encode conceptual knowledge, cannot be subjected to the “cleaning up” techniques that Guarino advocates, because his conditions are too strict to be applicable, and because the terms used in such structures retain their language-like features of ambiguity and vagueness, and in a way that cannot be eliminated by reference to sets of objects, as it can be in ontologies in the narrow sense. Wordnet is a structure that remains useful to NLP, and has within it features of both types (ontologies and conceptual hierarchies) and its function and usefulness will remain, properly, resistant to Guarino’s techniques, because those rest on a misunderstanding about concepts. The ultimate way out of such disputes can only come from automatic construction and evaluation procedures for conceptual and ontological structures from data, which is to say, corpora.