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1
Keldermann, R. H., K. H. W. J. ten Tusscher, M. P. Nash, R. Hren, P. Taggart, and A. V. Panfilov. "Effect of heterogeneous APD restitution on VF organization in a model of the human ventricles." American Journal of Physiology-Heart and Circulatory Physiology 294, no. 2 (2008): H764—H774. http://dx.doi.org/10.1152/ajpheart.00906.2007.
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The onset of ventricular fibrillation (VF) has been associated with steep action potential duration restitution in both clinical and computational studies. Recently, detailed clinical restitution properties in cardiac patients were reported showing a substantial degree of heterogeneity in restitution slopes at the epicardium of the ventricles. The aim of the present study was to investigate the effect of heterogeneous restitution properties in a three-dimensional model of the ventricles using these clinically measured restitution data. We used a realistic model of the human ventricles, including detailed descriptions of cell electrophysiology, ventricular anatomy, and fiber direction anisotropy. We extended this model by mapping the clinically observed epicardial restitution data to our anatomic representation using a diffusion-based algorithm. Restitution properties were then fitted by regionally varying parameters of the electrophysiological model. We studied the effects of restitution heterogeneity on the organization of VF by analyzing filaments and the distributions of excitation periods. We found that the number of filaments and the excitation periods were both dependent on the extent of heterogeneity. An increased level of heterogeneity leads to a greater number of filaments and a broader distribution of excitation periods, thereby increasing the complexity and dynamics of VF. Restitution heterogeneity may play an important role in providing a substrate for cardiac arrhythmias.
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Shih, Chihhsiong. "Analyzing and Comparing Shot Planning Strategies and Their Effects on the Performance of an Augment Reality Based Billiard Training System." International Journal of Information Technology & Decision Making 13, no. 03 (2014): 521–65. http://dx.doi.org/10.1142/s0219622014500278.
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The shot planning of a cue after it collides with an object ball determines a player's success in a billiard game. This paper proposes three novel gaming strategies to investigate the effect of cue shots planning on gaming performance. The first algorithm considers the nearest pocket for every selected target object ball, seeking optimal post collision positions. The second algorithm considers all pocket and target object ball combinations during both the pre- and post-collision optimal shot selection processes. The third algorithm considers a multi-objective optimization process for optimal shot planning control. The simulations are conducted based on a collision model considering the restitution effects. An augmented reality training facility is devised to guide users in both aiming and cue repositioning control in a real-world billiard game. Experimental results not only prove the reliability of our training device in selecting a proper shot sequence using the all-pocket optimal shot planning algorithm, but it also proves the consistency with the restitution theory.
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Alaci, Stelian, Constantin Filote, Florina-Carmen Ciornei, Oana Vasilica Grosu, and Maria Simona Raboaca. "An Analytical Solution for Non-Linear Viscoelastic Impact." Mathematics 9, no. 16 (2021): 1849. http://dx.doi.org/10.3390/math9161849.
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The paper presents an analytical solution for the centric viscoelastic impact of two smooth balls. The contact period has two phases, compression and restitution, delimited by the moment corresponding to maximum deformation. The motion of the system is described by a nonlinear Hunt–Crossley equation that, when compared to the linear model, presents the advantage of a hysteresis loop closing in origin. There is only a single available equation obtained from the theorem of momentum. In order to solve the problem, in the literature, there are accepted different supplementary hypotheses based on energy considerations. In the present paper, the differential equation is written under a convenient form; it is shown that it can be integrated and a first integral is found—this being the main asset of the work. Then, all impact parameters can be calculated. The effect of coefficient of restitution upon all collision characteristics is emphasized, presenting importance for the compliant materials, in the domain of small coefficients of restitution. The results (variations of approach, velocity, force vs. time and hysteresis loop) are compared to two models due to Lankarani and Flores. For quasi-elastic collisions, the results are practically the same for the three models. For smaller values of the coefficient of restitution, the results of the present paper are in good agreement only to the Flores model. The simplified algorithm for the calculus of viscoelastic impact parameters is also presented. This algorithm avoids the large calculus volume required by solving the transcendental equations and definite integrals present in the mathematical model. The method proposed, based on the viscoelastic model given by Hunt and Crossley, can be extended to the elasto–visco–plastic nonlinear impact model.
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Matthews, Gareth D. K., Laila Guzadhur, Andrew Grace, and Christopher L.-H. Huang. "Nonlinearity between action potential alternans and restitution, which both predict ventricular arrhythmic properties in Scn5a+/− and wild-type murine hearts." Journal of Applied Physiology 112, no. 11 (2012): 1847–63. http://dx.doi.org/10.1152/japplphysiol.00039.2012.
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Electrocardiographic QT- and T-wave alternans, presaging ventricular arrhythmia, reflects compromised adaptation of action potential (AP) duration (APD) to altered heart rate, classically attributed to incomplete Nav1.5 channel recovery prior to subsequent stimulation. The restitution hypothesis suggests a function whose slope directly relates to APD alternans magnitude, predicting a critical instability condition, potentially generating arrhythmia. The present experiments directly test for such correlations among arrhythmia, APD alternans and restitution. Mice haploinsufficient in the Scn5a, cardiac Na+ channel gene ( Scn5a+/−), previously used to replicate Brugada syndrome, were used, owing to their established arrhythmic properties increased by flecainide and decreased by quinidine, particularly in right ventricular (RV) epicardium. Monophasic APs, obtained during pacing with progressively decrementing cycle lengths, were systematically compared at RV and left ventricular epicardial and endocardial recording sites in Langendorff-perfused Scn5a+/− and wild-type hearts before and following flecainide (10 μM) or quinidine (5 μM) application. The extent of alternans was assessed using a novel algorithm. Scn5a+/− hearts showed greater frequencies of arrhythmic endpoints with increased incidences of ventricular tachycardia, diminished by quinidine, and earlier onsets of ventricular fibrillation, particularly following flecainide challenge. These features correlated directly with increased refractory periods, specifically in the RV, and abnormal restitution and alternans properties in the RV epicardium. The latter variables were related by a unique, continuous higher-order function, rather than a linear relationship with an unstable threshold. These findings demonstrate a specific relationship between alternans and restitution, as well as confirming their capacity to predict arrhythmia, but implicate mechanisms additional to the voltage feedback suggested in the restitution hypothesis.
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Dragna, Ionuț-Bogdan, Nicolae Pandrea, and Nicolae-Doru Stănescu. "Simultaneous Collision of the Rigid Body at Two Points." Symmetry 13, no. 10 (2021): 1924. http://dx.doi.org/10.3390/sym13101924.
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We present a new approach based on the notion of inertance for the simultaneous collisions without friction of a rigid solid. The calculations are performed using the screw (plückerian) coordinates, while the results are obtained in matrix form, and they may be easily implemented for different practical situations. One calculates the velocities after collision, the energy of lost velocities, and the loss of the kinetic energy. The general algorithm of calculation is described in the paper. The main assumption is that the normal velocities at the contact points vanish simultaneously. The coefficients of restitution at the contact points may be equal or not. Some completely solved applications are also presented, and the numerical results are discussed. The numerical values depend on which coefficient of restitution is used.
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Yigit, A. S., A. G. Ulsoy, and R. A. Scott. "Dynamics of a Radially Rotating Beam With Impact, Part 1: Theoretical and Computational Model." Journal of Vibration and Acoustics 112, no. 1 (1990): 65–70. http://dx.doi.org/10.1115/1.2930100.
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A model is presented for the dynamics of a radially rotating beam with impact. The model uses a momentum balance method and a coefficient of restitution, and enables one to predict the rigid body motion as well as the elastic motion before and after impact. A computational algorithm is also developed to implement the model. In Part 2 simulation results will be compared with experimental results to investigate the validity of the model.
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CLÉMENT, E., S. LUDING, A. BLUMEN, J. RAJCHENBACH, and J. DURAN. "FLUIDIZATION, CONDENSATION AND CLUSTERIZATION OF A VIBRATING COLUMN OF BEADS." International Journal of Modern Physics B 07, no. 09n10 (1993): 1807–27. http://dx.doi.org/10.1142/s0217979293002602.
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We present numerical and experimental results for the response under external vibration of one-dimensional columns of beads. Such systems are toy-models for dissipative granular materials. We show that a simple algorithm is able to reproduce the basic experimental features. Our main result is that an increase in acceleration leads to a transition from a condensed to a fluidized state of the columns. We discuss this cross-over acceleration as a function of the number of beads and of the restitution coefficient (dissipation) per collision. Also, we show that at high dissipation level clustered states (where all the beads are in contact) exist. The algorithm used by us reproduces well this cluster dynamics.
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Kini, Ananth, Thomas L. Vincent, and Brad Paden. "The Bouncing Ball Apparatus as an Experimental Tool." Journal of Dynamic Systems, Measurement, and Control 128, no. 2 (2005): 330–40. http://dx.doi.org/10.1115/1.2194069.
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The bouncing ball on a sinusoidally vibrating plate exhibits a rich variety of nonlinear dynamical behavior and is one of the simplest mechanical systems to produce chaotic behavior. A computer control system is designed for output calibration, state determination, system identification, and control of a new bouncing ball apparatus designed in collaboration with Magnetic Moments. The experiments described here constitute the first research performed with the apparatus. Experimental methods are used to determine the coefficient of restitution of the ball, an extremely sensitive parameter needed for modeling and control. The coefficient of restitution is estimated using data from a stable one-cycle orbit both with and without using corresponding data from a ball map. For control purposes, two methods are used to construct linear maps. The first map is determined by collecting data directly from the apparatus. The second map is derived analytically using a high bounce approximation. The maps are used to estimate the domains of attraction to a stable one-cycle orbit. These domains of attraction are used to construct a chaotic control algorithm for driving the ball to a stable one-cycle from any initial state. Experimental results based on the chaotic control algorithm are compared and it is found that the linear map obtained directly from the data not only gives a more accurate representation of the domain of attraction, but also results in more robust control of the ball to the stable one-cycle.
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Warzecha, Mariusz, and Rafał Grzejda. "AN IMPROVED APPROACH IN THE APPLICATIONOF AN ELASTIC-PLASTIC CONTACT FORCE MODELIN THE MODELLING OF MULTIPLE IMPACTS." Tribologia 303, no. 1 (2023): 83–95. http://dx.doi.org/10.5604/01.3001.0016.2936.
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This paper presents the modelling of a simultaneous multiple collision occurring between several bodies ofa kinematic chain. An algorithm is proposed that when used with an elastoplastic contact model, allows thephenomena that can occur during a multiple-body collision to be taken into account. These phenomena includethe transition of the collision state from the restitution phase directly to the compression phase or successivecollisions occurring along the same normal. The proposed algorithm can be used with any elastoplastic contactmodel. This paper presents its use with a selected model in a three-body system. Numerical calculations basedon the model have been verified using the Finite Element Method (FEM). The use of the proposed improvedapproach reduces the post-collision velocity prediction error by 2.34% compared to the baseline descriptionof collisions known from the literature.
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Muslim, Hafizh Adam. "NAIVE BAYES ALGORITHM IN HS CODE CLASSIFICATION FOR OPTIMIZING CUSTOMS REVENUE AND MITIGATION OF POTENTIAL RESTITUTION." Journal of Information Technology and Its Utilization 5, no. 1 (2022): 1–9. http://dx.doi.org/10.56873/jitu.5.1.4740.
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The Directorate General of Customs and Excise, as a government revenue collector, must maximise import duty receipts each year. One common issue is the return of unpaid import duty and/or administrative punishments in the form of fines based on the objection judgement document. The Tax Court could help you minimise your gross receipts at the Customs Office. Data mining techniques are intended to provide valuable information regarding the HS Code classification technique, which can assist customs agents in determining duties and/or customs values. This study makes use of data from the Notification of Import of Goods at Customs Regional Office XYZ from 2018 to 2020. The Cross-industry Standard Process for Data Mining (CRISP-DM) model is used in this study, and the Naive Bayes Algorithm in Rapidminer 9.10 is used for data classification. According to the model, the calculation accuracy is 99.97 percent, the classification error value is 0.03 percent, and the Kappa coefficient is 0.999..
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Lis-Gutiérrez, Jenny-Paola, Mercedes Gaitán-Angulo, and Jenny Cubillos-Diaz. "Spending Level of Displaced Population Returned to La Palma, Cundinamarca (2018): A Machine Learning Application." Migration Letters 17, no. 5 (2020): 639–49. http://dx.doi.org/10.33182/ml.v17i5.693.
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This research aims to know the variables allowing to predict the spending level of the displacement victims that returned to La Palma, Cundinamarca. For this purpose, a measurement instrument was divided into four sections: characterisation of the population, restitution of economic rights, patterns of economic distribution and, finally, social innovation initiatives. We applied the instrument to 100 participants, and we use different Machine Learning algorithms to know the variables that allow predicting the level of expenses of the displacement victims that returned to La Palma, Cundinamarca. The findings permitted to observe that, at the aggregate level, the Random Forest and the SMV have a prediction capacity higher than 84%.
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Xie, Liping, Chihua Lu, Zhien Liu, Yawei Zhu, and Weizhi Song. "A method of generating car sounds based on granular synthesis algorithm." Noise Control Engineering Journal 70, no. 4 (2022): 384–93. http://dx.doi.org/10.3397/1/377031.
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The active sound generation technique for automobiles, where car sounds can be synthesized by means of electronic sound production, is one of the effective methods to achieve the target sound. A method for active sound generation of automobile based on the granular synthesis algorithm is put forward here to avoid the broadband beating phenomena that occur due to the mismatch of parameters of sound granular signals. The comparison of the function expression of sound signal and Hilbert transformation is performed based on the principle of overlap and add; moreover, those parameters (phase, frequency and amplitude) of sound signals are interpolated by means of the Hermite interpolation algorithm which can ensure the continuity of the phase, frequency and amplitude curves. Thus, the transition audio is constructed by means of the sound signal function here to splice the adjacent sound granules. Our simulations show that our method can be applied to solve the current broadband beating issue for splicing sound granules and achieve natural continuity of synthesized car sounds. The subjective test results also indicate that our transition audio can produce high quality audio restitution.
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Vu, Pham Loi, and Nguyen Hoan Thanh. "Determination of parameters of axial symmetrical triple stratified medium after the well yield and the water lowering in regard to elastic properties of weakly penetrating layer." Vietnam Journal of Mechanics 8, no. 1 (1986): 25–31. http://dx.doi.org/10.15625/0866-7136/10360.
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This paper considers the problem of axial symmetrical filtration to a well in triple stratified medium, which includes the surface stratum, the weakly penetrating layer and the well penetrating main fall horizon. The Lowering of S1, S0, S2 in these starts sat isfies the system of equations (0.1) with initial and boundary conditions : (0.2), (0.3), (0.4). In this paper the approximate solution of the problem (0.1)- (0.4) with different coefficients water feeding and filtering penetration µ and T1, i = 1, 2 is obtained. The algorithm of restitution for parameters of layer after well yield and water lowering’s is constructed. Using the methods of this work, the results of conculation for example have been presented.
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Marghitu, D. B., and Y. Hurmuzlu. "Three-Dimensional Rigid-Body Collisions With Multiple Contact Points." Journal of Applied Mechanics 62, no. 3 (1995): 725–32. http://dx.doi.org/10.1115/1.2897006.
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This article deals with three-dimensional collisions of rigid, kinematic chains with an external surface while in contact with other surfaces. We concentrate on a special class of kinematic chain problems where there are multiple contact points during the impact process. A differential formulation based algorithm is used to obtain solutions that utilize the kinematic, kinetic, and the energetic definitions of the coefficient of restitution. Planar and spatial collisions of a three-link chain with two contact points are numerically studied to compare the outcomes predicted by each approach. Particular emphasis is placed on the relation between the post and pre-impact energies, slippage and rebounds at the contact points, and differences among planar and nearly planar three-dimensional solutions.
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DRAMAS, FLORIAN, SIMON J. THORPE, and CHRISTOPHE JOUFFRAIS. "ARTIFICIAL VISION FOR THE BLIND: A BIO-INSPIRED ALGORITHM FOR OBJECTS AND OBSTACLES DETECTION." International Journal of Image and Graphics 10, no. 04 (2010): 531–44. http://dx.doi.org/10.1142/s0219467810003871.
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Although artificial vision systems could potentially provide very useful input to assistive devices for blind people, such devices are rarely used outside of laboratory experiments. Many current systems attempt to reproduce the visual image via an alternative sensory modality (often auditory or somatosensory), but this dominant "scoreboard" approach, is often difficult to interpret for the user. Here, we propose to offload the recognition problem onto a separate image processing system that then provides the user with just the essential information about the location of objects in the surrounding environment. Specifically, we show that a bio-inspired image processing algorithm (SpikeNet) can not only robustly, precisely, and rapidly recognize and locate key objects in the image, but also in space if the objects are in a stereoscopic field of view. In addition, the bio-inspired algorithm allows real-time calculation of optic flow. We hence propose that this system, coupled with a restitution interface allowing localization in space (i.e. three-dimensional virtual sounds synthesis) can be used to restore essential visuomotor behaviors such as grasping desired objects and navigating (finding directions, avoiding obstacles) in unknown environments.
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Corral, Eduardo, Raúl Gismeros Moreno, M. J. Gómez García, and Cristina Castejón. "Nonlinear phenomena of contact in multibody systems dynamics: a review." Nonlinear Dynamics 104, no. 2 (2021): 1269–95. http://dx.doi.org/10.1007/s11071-021-06344-z.
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AbstractIn the present work, an introduction to the contact phenomena in multibody systems is made. The different existing approaches are described, together with their most distinctive features. Then, the term of coefficient of restitution is emphasized as a tool to characterize impact events and the algorithm for calculating the relative indentation between two convex-shaped bodies is developed. Subsequently, the main penalty contact models developed in the last decades are presented and developed, analysing their advantages and drawbacks, as well as their respective applications. Furthermore, some models with specific peculiarities that could be useful to the reader are included. The aim of this work is to provide a resource to the novice researcher in the field to facilitate the choice of the appropriate contact model for their work.
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Tamborrini, Giorgio, Martin Schwab, Tamara Hebert, and Viktoria Köhler. "CME-Rheumatologie 20: Parvovirus-B19-induzierte Tenosynovitis?" Praxis 109, no. 1 (2020): 42–46. http://dx.doi.org/10.1024/1661-8157/a003399.
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Zusammenfassung. Wir diskutieren in dieser Fallpräsentation diagnostische Algorithmen und Differenzialdiagnosen bei undifferenzierten Tenosynovitiden. Wir stellen einen Fall eines Patienten mit chronischer Tenosynovitis im 4. Strecksehnenfach vor. Bei unauffälliger Anamnese und aufgrund unauffälliger Laborresultate bestand eine «seronegative (RF), ACPA (CCP)-negative Tenosynovitis ohne Arthritis». Es erfolgte eine diagnostische und therapeutische Tenosynovektomie. Die histologische Aufarbeitung ergab eine positive PCR für Parvovirus B19. Wir erläutern artikuläre und extraartikuläre Manifestationen. Eine Parvovirus-B19-assoziierte Manifestation am Bewegungsapparat ist in der Regel selbstlimitierend. Die Therapie sollte rein symptomatisch durchgeführt werden. Bei unserem Patienten bestand ein ausgeprägter lokaler Befund, sodass die komplette Tenosynovektomie mit anschliessender einmaliger Steroidinjektion zu einer anhaltenden Restitutio ad integrum geführt hat.
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Dorren, L. K. A., F. Berger, and U. S. Putters. "Real-size experiments and 3-D simulation of rockfall on forested and non-forested slopes." Natural Hazards and Earth System Sciences 6, no. 1 (2006): 145–53. http://dx.doi.org/10.5194/nhess-6-145-2006.
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Abstract. Only a few rockfall simulation models take into account the mitigating effect of existing forest cover. The objective of our study was to improve the generic rockfall simulation model RockyFor, which does take the effect of forest stands into account, thereby developing a clear method for quantifying and modelling slope surface characteristics based on quantitative field data. To obtain these data we carried out 218 real-size rockfall experiments on forested and non-forested sites on a mountain slope in the French Alps. On the basis of a polygon map representing different diameter classes of the material covering the slope, we determine the mean obstacle height (MOH) for each homogeneous unit at the experimental sites. We proposed an algorithm for calculating the tangential coefficient of restitution using the MOH. Comparing the simulated and observed data from the real-size rockfall experiments showed that the 3-D combined deterministic-probabilistic rockfall simulation model RockyFor accurately predicted rockfall events on a non-forested (Root Mean Square Error = 17%) and a forested site (Root Mean Square Error = 12%). We conclude that for further improvement of rockfall-forest simulation on different slope types more quantitative data is required on (1) the energy dissipative capacity of shrubs and bushes (e.g. in coppice stands), (2) the effect of the slope material, (3) the rock shape as well as the rock size, and (4) the tangential and normal coefficient of restitution. Based on the presented results we can state that the RockyFor model could contribute to better taking into account the mitigating effect of the existing forest cover when planning protective measures.
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Pandrea, Nicolae, and Nicolae-Doru Stănescu. "A new approach in the study of frictionless collisions using inertances." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 229, no. 12 (2014): 2144–57. http://dx.doi.org/10.1177/0954406214553983.
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This paper presents a complete study on the collision without friction of two rigid bodies with and without bilateral constraints. Our goal is to obtain the same formulae for the impulse, the energy of the lost velocities, and the loss of kinetic energy as in the case of the collision of two particles. The study is performed with the aid of the notion of inertance. The dependence on the constraints is given by the inertances. The calculations are realized using the results from the theory of screws (plückerian coordinates). The obtained formulae are general, written in matrix form, and they may be easily used in any practical problem. We give the general algorithms for the collision of two rigid bodies with and without bilateral constraints. The equality of the coefficients of restitution in the Newton, Poisson, and energetic models is also proved. The numerical examples highlight the theory.
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Atwi, Ali, Antoine Khater, and Abbas Hijazi. "Three-dimensional Monte Carlo simulations of the dynamics of macromolecular particles in solutions flowing in mesopores." Open Chemistry 8, no. 5 (2010): 1009–13. http://dx.doi.org/10.2478/s11532-010-0085-0.
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AbstractNumerical simulations are developed to calculate the dynamic equilibrium probability distribution functions (PDF) for macromolecular rod-like particles suspended in a fluid under hydrodynamic flow inside mesopores. The simulations take into account the effects of Brownian and hydrodynamic forces acting on the particles, as well as diffusive collisions of the particles with the solid surface boundaries. An algorithm is developed for this purpose based on Jeffery’s equations for the dynamics of ellipsoidal objects in bulk fluids, and on a mechanism of restitution for the diffusive collisions. The results are presented with a focus on the depletion layer next to two types of solid boundaries, ideally flat and rough. They demonstrate the significance of numerical simulations in 3D compared to previous results based on a 2D approach. In particular, we are able to obtain a complete topography for the PDFs segmented as a hierarchy in the depletion layer.
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Xiao, Yuan, Zhi Yao, and Xu Zhang. "Comprehensive Penetration Evaluation Method in Collisions between a Supply Ship and a Semi-Submersible Platform." Processes 10, no. 6 (2022): 1212. http://dx.doi.org/10.3390/pr10061212.
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Collisions between ships and offshore platforms frequently occur, with severe consequences. Predicting the collision depth under different conditions is very important to evaluate the severity of the consequences. Considering the time-consuming numerical simulation problem and the accuracy problems of existing approximation algorithms, this paper proposes a comprehensive approach to estimating penetration depths by obtaining two collision coefficients for specific collision structures based on the partial results of numerical simulations and simplified theoretical analysis. In this study, the collision process between a supply ship with a transverse framing stern and an offshore semi-platform was first numerically simulated based on the explicit dynamic method. The changes in ship velocity, impact force, and energy conversion before and after the collision processes were obtained through numerical simulations of the collisions with different speeds and angles. Then, by combining the external dynamics and numerical results, the analytical results of dissipated energy under other collision conditions were obtained using a simulated restitution coefficient. For the following internal dynamics analysis, according to the failure modes of specific structural components in different regions, an appropriate structural energy absorption formula was combined to obtain the relationship between the penetrations and energy absorption in a particular collision area. According to the friction energy ratio derived by the simulation, the penetration depths in the offshore platform were calculated. The results showed that the deviations between the proposed method and direct simulation results were less than 15% in the cases of a medium- to high-energy collision. It can be concluded that the restitution coefficient and friction energy ratio in different collision conditions can be approximately determined for a specific collision system by typical numerical simulations, thus quickly calculating the penetration depths of other conditions.
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Wolf, Johanna, Sebastian Carsch, Clemens Troll, and Jens-Peter Majschak. "Disturbance Simulation in the Packaging Process of Confectionary Using Virtual Commissioning." Machines 8, no. 2 (2020): 19. http://dx.doi.org/10.3390/machines8020019.
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Operator assistance systems can help to reduce disturbance-related machine downtime in food production and packaging processes, especially when combined with machine learning algorithms. These assistance systems analyze the available sensor signals of the process control over time to help operators identify the causes of disturbances. Training such systems requires sufficient test data, which often are hardly available. Thus, this paper presents a study to investigate how test data for teaching machine learning algorithms can be generated by numerical simulation. The potential of using virtual commissioning (VC) software for simulating disturbances of discrete processes is examined, considering the example of a friction and collision-afflicted sub-process from an intermitting wrapping machine for confectionary. In this study the software industrialPhysics (iP) is analyzed regarding accuracy of static and dynamic friction and restitution. The values are verified by setting up virtual substitute tests and comparing the results with analytically determined values. Subsequently, prerecorded disturbances are classified, and seven selected elements are simulated in VC software, recording visual effects and switching the characteristics of sensors. The verification shows that VC software is generally adequate for the assigned task. Restrictions occur regarding the computing power required of the built-in physics engine and the resulting reduction of the machine to be simulated.
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Linder, R., C. Weimar, H. C. Diener, S. J. Pöppl, A. Ziegler, and I. R. König. "Two Models for Outcome Prediction." Methods of Information in Medicine 45, no. 05 (2006): 536–40. http://dx.doi.org/10.1055/s-0038-1634115.
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Summary Objectives: Accurately predicting disease progress from a set of predictive variables is an important aspect of clinical work. For binary outcomes, the classical approach is to develop prognostic logistic regression (LR) models. Alternatively, machine learning algorithms were proposed with artificial neural networks (ANN) having become popular over the last decades. Although some studies have compared predictive accuracies of LR and ANN models, some concerns regarding their methodological quality have been voiced. Our comparison has the advantage of being based on two large independent data sets allowing for elaborate model development and independent validation. Methods: From the German Stroke Database, a learning data set including 1754 prospectively recruited patients with acute ischemic stroke was used. Utilizing LR and ANN, two prognostic models were developed predicting restitution of functional independence and survival after 100 days. The resulting models were applied to classify 1470 patients with acute ischemic stroke; this test data set was collected independently from the learning data. Error fractions in the test data were determined, and differences in error fractions between the algorithms were calculated with 95% confidence intervals. Results: For most prognostic models, error fractions in the test data were below 40%. There was no difference between the algorithms except for the model predicting completely versus incompletely restituted or deceased patients (difference in error fractions = 4.01% [2.10-5.96%], p = 0.0001). Conclusions: The conscientiously applied LR remains the gold standard for prognostic modelling; however, ANN can be an alternative automated “quick and easy” multivariate analysis.
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GRAHOVAC, NENAD, MIODRAG ZIGIC, and DRAGAN SPASIC. "ON IMPACT SCRIPTS WITH BOTH FRACTIONAL AND DRY FRICTION TYPE OF DISSIPATION." International Journal of Bifurcation and Chaos 22, no. 04 (2012): 1250076. http://dx.doi.org/10.1142/s0218127412500769.
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We study the dynamics of a mass, sliding on a dry surface and impacting against a rigid wall through a viscoelastic body, that we model as a straight rod of negligible mass. The problem comprises a constitutive model of the viscoelastic body with fractional derivatives of stress and strain, restrictions on the coefficients that follow from Clausius–Duhem inequality, and discontinuous inequality constraint conditions imposed by the Coulomb friction model. We show that the dynamics of the problem is governed by a single integro-differential inclusion. By use of the slack variable algorithm the problem was solved numerically. The predictions of the model concerning the duration of the impact, maximal values of the impacting force and deformation, as well as the restitution coefficient are determined for several values of system parameters. Depending on the dry friction coefficient three different impact scripts are identified: rebound after the impact, capture in the approaching phase, and capture in the rebound phase.
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Arsenović, D., S. B. Vrhovac, Z. M. Jakšić, Lj Budinski-Petković, and A. Belić. "Simulation Study of Granular Compaction Dynamics under Vertical Tapping." Materials Science Forum 555 (September 2007): 107–12. http://dx.doi.org/10.4028/www.scientific.net/msf.555.107.
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We study by numerical simulation the compaction dynamics of frictional hard disks in two dimensions, subjected to vertical shaking. Shaking is modeled by a series of vertical expansions of the disk packing, followed by dynamical recompression of the assembly under the action of gravity. The second phase of the shake cycle is based on an efficient event−driven molecular−dynamics algorithm. We analyze the compaction dynamics for various values of friction coefficient and coefficient of normal restitution. We find that the time evolution of the density is described by ρ(t)=ρ∞ − ρEα[−(t/τ)α], where Eα denotes the Mittag−Leffler function of order 0<α<1. The parameter τ is found to decay with tapping intensity Γ according to a power law τ ∝ Γ−γ , where parameter γ is almost independent of the material properties of grains. Also, an expression for the grain mobility during compaction process has been obtained.
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Yang, Yukun, Baoqin Wen, Longpeng Ding, Liqiao Li, Xinghua Chen, and Jingbin Li. "Soil Particle Modeling and Parameter Calibration for Use with Discrete Element Method." Transactions of the ASABE 64, no. 6 (2021): 2011–23. http://dx.doi.org/10.13031/trans.14083.
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HighlightsSoil particle shapes were statistically analyzed, and four representative particles were obtained.A particle model was established using three-dimensional non-contact surface topography.This study used a response surface design method to calibrate significant soil parameters.The simulation parameters were verified by rotary tiller experiment.Abstract. The discrete element method (DEM) has broad prospects for application in soil-tool simulations. To ensure the reliability of simulations, appropriate simulation parameters and particle modeling are essential. Therefore, in this article, a method combining simulation and actual tests is proposed to calibrate the critical soil parameters. First, the effect of soil particle shape on particle contact was considered. Soil particle shapes were statistically analyzed using an improved GrabCut algorithm and k-means algorithm. Four representative soil particles were obtained. Second, a soil particle model was established by microscope and three-dimensional non-contact surface topography. Finally, taking the angle of repose as the response value, the three parameters with significant effects on the angle of repose, i.e., soil shear modulus, Hertz-Mindlin with Johnson-Kendall-Roberts contact model (JKR), and soil-soil restitution coefficient, were obtained via a Plackett-Burman experiment. The optimal value intervals of the significant parameters were determined by the steepest climbing test. A polynomial regression model between the angle of repose and the three significant parameters was established with a Box-Behnken experiment using three factors and three levels. The interactions between the three significant parameters were not significant, as revealed by response surface analysis. The optimal values of the significant parameters were obtained by taking the actual angle of repose as the target and resulted in a soil shear module of 9.8 MPa, JKR of 0.063, and soil-soil restitution coefficient of 0.478. To verify the reliability of the calibrated parameters, the soil angles of repose from the simulation and from actual tests were compared and analyzed. For a simulated angle of repose of 38.5°, the actual angle of repose was 38.6°, and the relative error was 0.26%. DEM was also used to simulate a rotary tiller with the calibrated parameters. The maximum error of the simulated soil throwing angle was less than 10% when compared with the actual throwing angle. The experimental results showed that the calibrated parameters were accurate and can provide a reference for the selection of soil discrete element parameters. Keywords: Angle of repose, Numerical simulation, Parameter calibration, Shape survey, Soil.
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Plante, Ianik, Tony Slaba, Zarana Shavers, and Megumi Hada. "A Bi-Exponential Repair Algorithm for Radiation-Induced Double-Strand Breaks: Application to Simulation of Chromosome Aberrations." Genes 10, no. 11 (2019): 936. http://dx.doi.org/10.3390/genes10110936.
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Background: Radiation induces DNA double-strand breaks (DSBs), and chromosome aberrations (CA) form during the DSBs repair process. Several methods have been used to model the repair kinetics of DSBs including the bi-exponential model, i.e., N(t) = N1exp(−t/τ1) + N2exp(−t/τ2), where N(t) is the number of breaks at time t, and N1, N2, τ1 and τ2 are parameters. This bi-exponential fit for DSB decay suggests that some breaks are repaired rapidly and other, more complex breaks, take longer to repair. Methods: The bi-exponential repair kinetics model is implemented into a recent simulation code called RITCARD (Radiation Induced Tracks, Chromosome Aberrations, Repair, and Damage). RITCARD simulates the geometric configuration of human chromosomes, radiation-induced breaks, their repair, and the creation of various categories of CAs. The bi-exponential repair relies on a computational algorithm that is shown to be mathematically exact. To categorize breaks as complex or simple, a threshold for the local (voxel) dose was used. Results: The main findings are: i) the curves for the kinetics of restitution of DSBs are mostly independent of dose; ii) the fraction of unrepaired breaks increases with the linear energy transfer (LET) of the incident radiation; iii) the simulated dose–response curves for simple reciprocal chromosome exchanges that are linear-quadratic; iv) the alpha coefficient of the dose–response curve peaks at about 100 keV/µm.
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Li, Ziwen, Xiangyuan Zeng, Tongge Wen, and Yonglong Zhang. "Numerical Comparison of Contact Force Models in the Discrete Element Method." Aerospace 9, no. 11 (2022): 737. http://dx.doi.org/10.3390/aerospace9110737.
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The discrete element method (DEM) is usually applied in analyzing the scientifical origin/evolution of the asteroids and the landing/sampling of the regolith. In order to manage the contact between the non-spherical granules, the Polygonal Contact Model (PCM) has been introduced into the DEM method. This paper applies four different contact force models in the newly-proposed DEM algorithm to analyze their difference and implication. The four contact force models include one linear model and three nonlinear models derived from the complete Mindlin–Deresiewicz equations. By considering the macroscopical results and calculation efficiency, the single-collision and multiple-collision cases are analyzed by comparing the four contact models. Specifically, the restitution coefficient, the angular velocity, the rebound angle, and the kinetic energy are applied as indicators for the single collision. The multiple-collision case is studied under the Brazil nut effect with ellipsoidal granules. Additionally, the softening feasibility is also discussed by decreasing the Young’s modulus of the material, mainly analyzing the outgoing results and the calculation efficiency.
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Rossi, L., F. Ioli, E. Capizzi, L. Pinto, and M. Reguzzoni. "IMPROVING UAV TELEMETRY POSITIONING FOR DIRECT PHOTOGRAMMETRY." International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLIII-B2-2021 (June 28, 2021): 61–68. http://dx.doi.org/10.5194/isprs-archives-xliii-b2-2021-61-2021.
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Abstract. A fundamental step of UAV photogrammetric processes is to collect Ground Control Points (GCPs) by means of geodetic-quality GNSS receivers or total stations, thus obtaining an absolutely oriented model with a centimetric accuracy. This procedure is usually time-consuming, expensive and potentially dangerous for operators who sometimes need to reach inaccessible areas. UAVs equipped with low-cost GNSS/IMU sensors can provide information about position and attitude of the images. This telemetry information is not enough for a photogrammetric restitution with a centimetric accuracy, but it can be usefully exploited when a lower accuracy is required. The algorithm proposed in this paper aims at improving the quality of this information, in order to introduce it into a direct-photogrammetric process, without collecting GCPs. In particular, the estimation of an optimal trajectory is obtained by combining the camera positions derived from UAV telemetry and from the relative orientation of the acquired images, by means of a least squares adjustment. Then, the resulting trajectory is used as a direct observation of the camera positions into a commercial software, thus replacing the information of GCPs. The algorithm has been tested on different datasets, comparing the classical photogrammetric solution (with GCPs) with the proposed one. These case-studies showed that using the improved trajectory as input to the commercial software (without GCPs) the reconstruction of the three-dimensional model can be improved with respect to the solution computed by using the UAV raw telemetry only.
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Garcia-Romeu-Martinez, M. A., Michael A. Sek, Vincent Rouillard, and V. A. Cloquell-Ballester. "Interpreting Shock Data to Estimate Drop Height Levels During Handling." Applied Mechanics and Materials 7-8 (August 2007): 243–50. http://dx.doi.org/10.4028/www.scientific.net/amm.7-8.243.
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During distribution, consignments undergo numerous handling processes both mechanized and manual. These operations are known to produce drops and impacts of varying severity which have a potential to cause damage to the product. These shocks are the main parameters required for the optimum design of protective packaging systems. The severity of the shocks is often described in terms of their effective (free-fall equivalent) drop height (EDH) and impact orientation, in order to facilitate the laboratory testing conducted on a free-fall apparatus. The preferred approach is to survey the shocks with self-contained tri-axial shock recorders and process the data in such a way that statistical distributions of expected drop heights and orientations are obtained. On the other hand the Real Drop Height (RDH) method, based on the measurement of free fall time, is also used, mainly to discriminate between free-fall events and more commonly occurring complex causes of shocks, primarily for the quality control of distribution environment. The focus of the paper is on the EDH method and on the use of characteristic parameters of the tri-axial acceleration shock pulse to determine the EDH. An accurate estimate of the coefficient of restitution between the instrumented test package and the impact surface must be known and this poses a problem as it cannot always be established for every event during distribution. Consequently, the adopted approach is to calibrate an instrumented test package and obtain an estimate of the coefficient of restitution between the package and a test impact surface which is generally assumed to be hard relative to the cushioned package. The paper addresses the pitfalls and investigates various algorithms of determining the EDH from recorded shock data. It presents an analysis of the influence and errors associated with various methods used to estimate velocity change from characteristic parameters of a shock pulse such as the pulse width, the peak acceleration and its temporal location. The effects of analyzing the orthogonal acceleration vectors separately, as opposed to the resultant vector, are discussed. The results of a number of free-fall experiments, undertaken in controlled conditions, are used to validate and calibrate the proposed method for determining the EDH for free-fall drops on hard surfaces.
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Bai, Xueyu, Qingbing Dong, Han Zheng, and Kun Zhou. "Modelling of Non-Newtonian Starved Thermal-elastohydrodynamic Lubrication of Heterogeneous Materials in Impact Motion." Acta Mechanica Solida Sinica 34, no. 6 (2021): 954–76. http://dx.doi.org/10.1007/s10338-021-00284-2.
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AbstractThis study presents a numerical model for the thermal-elastohydrodynamic lubrication of heterogeneous materials in impact motion, in which a rigid ball bounces on a starved non-Newtonian oil-covered plane surface of an elastic semi-infinite heterogeneous solid with inhomogeneous inclusions. The impact–rebound process and the microscopic response of the subsurface inhomogeneous inclusions are investigated. The inclusions are homogenized according to Eshelby’s equivalent inclusion method. The Elrod algorithm is adopted to determine the lubrication starvation based on the solutions of pressure and film thickness, while the lubricant velocity and shear rate of the non-Newtonian lubricant are derived by using the separation flow method. The dynamic response of the cases subjected to constant impact mass, momentum, and energy is discussed to reveal the influence of the initial drop height on the impact–rebound process. The results imply that the inclusion disturbs the subsurface stress field and affects the dynamic response of the contact system when the surface pressure is high. The impact energy is the decisive factor for the stress peak, maximum hydrodynamic force, and restitution coefficient, while the dynamic response during the early approaching process is controlled by the drop height.
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Reibis, Rona, Annett Salzwedel, Ana Abreu, et al. "The importance of return to work: How to achieve optimal reintegration in ACS patients." European Journal of Preventive Cardiology 26, no. 13 (2019): 1358–69. http://dx.doi.org/10.1177/2047487319839263.
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The vocational reintegration of patients after an acute coronary syndrome is a crucial step towards complete convalescence from the social as well as the individual point of view. Return to work rates are determined by medical parameters such as left ventricular function, residual ischaemia and heart rhythm stability, as well as by occupational requirement profile such as blue or white collar work, night shifts and the ability to commute (which is, in part, determined by physical fitness). Psychosocial factors including depression, self-perceived health situation and pre-existing cognitive impairment determine the reintegration rate to a significant extent. Patients at risk of poor vocational outcomes should be identified in the early period of rehabilitation to avoid a reintegration failure and to prevent socio-professional exclusion with adverse psychological and financial consequences. A comprehensive healthcare pathway of acute coronary syndrome patients is initiated by cardiac rehabilitation, which includes specific algorithms and assessment tools for risk stratification and occupational restitution. As the first in its kind, this review addresses determinants and legal aspects of reintegration of patients experiencing an acute coronary syndrome, and offers practical advice on reintegration strategies particularly for vulnerable patients. It presents different approaches and scientific findings in the European countries and serves as a recommendation for action.
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Fétick, R. J.-L., L. M. Mugnier, T. Fusco, and B. Neichel. "Blind deconvolution in astronomy with adaptive optics: the parametric marginal approach." Monthly Notices of the Royal Astronomical Society 496, no. 4 (2020): 4209–20. http://dx.doi.org/10.1093/mnras/staa1813.
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ABSTRACT One of the major limitations of using adaptive optics (AO) to correct image post-processing is the lack of knowledge about the system’s point spread function (PSF). The PSF is not always available as direct imaging on isolated point-like objects, such as stars. The use of AO telemetry to predict the PSF also suffers from serious limitations and requires complex and yet not fully operational algorithms. A very attractive solution is to estimate the PSF directly from the scientific images themselves, using blind or myopic post-processing approaches. We demonstrate that such approaches suffer from severe limitations when a joint restitution of object and PSF parameters is performed. As an alternative, here we propose a marginalized PSF identification that overcomes this limitation. In this case, the PSF is used for image post-processing. Here we focus on deconvolution, a post-processing technique to restore the object, given the image and the PSF. We show that the PSF estimated by marginalization provides good-quality deconvolution. The full process of marginalized PSF estimation and deconvolution constitutes a successful blind deconvolution technique. It is tested on simulated data to measure its performance. It is also tested on experimental AO images of the asteroid 4-Vesta taken by the Spectro-Polarimetric High-contrast Exoplanet Research (SPHERE)/Zurich Imaging Polarimeter (Zimpol) on the Very Large Telescope to demonstrate application to on-sky data.
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Buurke, Jaap H., Anand V. Nene, Gert Kwakkel, Victorien Erren-Wolters, Maarten J. IJzerman, and Hermie J. Hermens. "Recovery of Gait After Stroke: What Changes?" Neurorehabilitation and Neural Repair 22, no. 6 (2008): 676–83. http://dx.doi.org/10.1177/1545968308317972.
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Background. Little is known about whether changes in coordination patterns of muscle activation after stroke are related to functional recovery of walking. Objective . The present study investigated the longitudinal relationship between changes in neuromuscular activation patterns of paretic muscles in hemiplegic gait and improvement in walking ability after stroke. Methods. Thirteen patients diagnosed with a first unilateral ischemic stroke had their recovery of walking measured by the Rivermead Mobility Index, Functional Ambulation Categories, Barthel Index, Trunk Control Test, Motricity Index, and comfortable walking speed. Surface electromyography (SEMG) of the erector spinae, gluteus maximus, gluteus medius, rectus femoris, vastus lateralis, semitendinosus, gastrocnemius, and tibialis anterior muscles of both legs was used to quantify coordination patterns in comfortable walking mode. All clinical and electromyography-related measurements were taken at 3, 6, 9, 12, and 24 weeks poststroke. Timing parameters of the SEMG patterns were calculated, using an objective burst detection algorithm, and analyzed with the measures of functional recovery. Results . All functional measures, except Trunk Control Test, showed statistically significant improvement over time, whereas SEMG patterns did not change significantly over time. Conclusion. The lack of significant change in SEMG patterns over time suggests that functional gait improvements may be more related to compensatory strategies in muscle activation of the unaffected leg and biomechanical changes than by restitution of muscle coordination patterns in the affected leg.
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Philibert, Alban, Marie Lothon, Julien Amestoy, et al. "CALOTRITON: a convective boundary layer height estimation algorithm from ultra-high-frequency (UHF) wind profiler data." Atmospheric Measurement Techniques 17, no. 6 (2024): 1679–701. http://dx.doi.org/10.5194/amt-17-1679-2024.
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Abstract. Long time series of observations of atmospheric dynamics and composition are collected at the French Pyrenean Platform for Observation of the Atmosphere (P2OA). Planetary boundary layer depth is a key variable of the climate system, but it remains difficult to estimate and analyse statistically. In order to obtain reliable estimates of the convective boundary layer height (Zi) and to allow long-term series analyses, a new restitution algorithm, named CALOTRITON, has been developed. It is based on the observations of an ultra-high-frequency (UHF) radar wind profiler (RWP) from P2OA with the help of other instruments for evaluation. Estimates of Zi are based on the principle that the top of the convective boundary layer is associated with both a marked inversion and a decrease in turbulence. Those two criteria are respectively manifested by larger RWP reflectivity and smaller vertical-velocity Doppler spectral width. With this in mind, we introduce a new UHF-deduced dimensionless parameter which weighs the air refractive index structure coefficient with the inverse of vertical velocity standard deviation to the power of x. We then search for the most appropriate local maxima of this parameter for Zi estimates with defined criteria and constraints such as temporal continuity. Given that Zi should correspond to fair-weather cloud base height, we use ceilometer data to optimize our choice of the power x and find that x=3 provides the best comparisons. The estimates of Zi by CALOTRITON are evaluated using different Zi estimates deduced from radiosounding according to different definitions. The comparison shows excellent results with a regression coefficient of up to 0.96 and a root-mean-square error of 71 m, which is close to the vertical resolution of the UHF RWP of 75 m, when conditions are optimal. In more complex situations, that is when the atmospheric vertical structure is itself particularly ambiguous, secondary retrievals allow us to identify potential thermal internal boundary layers or residual layers and help to qualify the Zi estimations. Frequent estimate errors are observed nevertheless; for example, when Zi is below the UHF RWP first reliable gate or when the boundary layer begins its transition to a stable nocturnal boundary layer.
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Barrile, Vincenzo, Antonino Fotia, Giuliana Bilotta, and Domenico De Carlo. "Integration of geomatics methodologies and creation of a cultural heritage app using augmented reality." Virtual Archaeology Review 10, no. 20 (2019): 40. http://dx.doi.org/10.4995/var.2019.10361.
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<p>3D modelling of archaeological and historical structures is the new frontier in the field of conservation science. Similarly, the identification of buried finds, which enhances their multimedia diffusion and restoration, has gained relevance. As such sites often have a high level of structural complexity and complicated territorial geometries, accuracy in the creation of 3D models and the use of sophisticated algorithms for georadar data analysis are crucial. This research is the first step in a larger project aimed at reclaiming the ancient villages located in the Greek area of southern Italy. The present study focuses on the restoration of the village of Africo (RC), a village hit by past flooding. The survey began with a laser scan of the church of St. Nicholas, using both the Faro Focus3D and the Riegl LMS-Z420i laser scanner. At the same time, georadar analyses were carried out in order to pinpoint any buried objects. In the processing phase, our own MATLAB algorithms were used for both laser scanner and georadar datasets and the results compared with those obtained from the scanners’ respective proprietary software. We are working to develop a tourism app in both augmented and virtual reality environments, in order to disseminate and improve access to cultural heritage. The app allows users to see the 3D model and simultaneously access information on the site integrated from a variety of repositories. The aim is to create an immersive visit, in this case, to the church of St. Nicholas.</p><p><strong>Highlights:</strong></p><ul><li><p>Use of different algorithms for registration of terrestrial laser scans and analysis of the data obtained.</p></li><li><p>3D acquisition, processing and restitution methodology from georadar data.</p></li><li><p>Implementation of a tourist app in both virtual and augmented reality by integrating geomatics methodologies.</p></li></ul>
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Rengifo, Carolina, Jean-Rémy Chardonnet, Hakim Mohellebi, Damien Paillot, and Andras Kemeny. "Driving simulator study of the relationship between motion strategy preference and self-reported driving behavior." SIMULATION 97, no. 9 (2021): 619–33. http://dx.doi.org/10.1177/0037549721999716.
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Faithful motion restitution in driving simulators normally focuses on track monitoring and maximizing the platform workspace by leaving aside the principal component—the driver. Therefore, in this work we investigated the role of the motion perception model on motion cueing algorithms from a user’s viewpoint. We focused on the driving behavior influence regarding motion perception in a driving simulator. Participants drove a driving simulator with two different configurations: (a) using the platform dynamic model and (b) using a supplementary motion perception model. Both strategies were compared and the participants’ data were classified according to the strategy they preferred. To this end, we developed a driving behavior questionnaire aiming at evaluating the self-reported driving behavior influence on participants’ motion cueing preferences. The results showed significant differences between the participants who chose different strategies and the scored driving behavior in the hostile and violations factors. In order to support these findings, we compared participants’ behaviors and actual motion driving simulator indicators such as speed, jerk, and lateral position. The analysis revealed that motion preferences arise from different reasons linked to the realism or smoothness in motion. Also, strong positive correlations were found between hostile and violation behaviors of the group who preferred the strategy with the supplementary motion perception model, and objective measures such as jerk and speed on different road segments. This indicates that motion perception in driving simulators may depend not only on the type of motion cueing strategy, but may also be influenced by users’ self-reported driving behaviors.
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Trizio, I., F. Savini, and A. Giannangeli. "INTEGRATION OF THREE-DIMENSIONAL DIGITAL MODELS AND 3D GIS: THE DOCUMENTATION OF THE MEDIEVAL BURIALS OF AMITERNUM (L’AQUILA, ITALY)." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLII-2 (May 30, 2018): 1121–28. http://dx.doi.org/10.5194/isprs-archives-xlii-2-1121-2018.
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This paper illustrates the results of an experimentation carried out by a multi-disciplinary research group made up of researchers from ITC-CNR of L'Aquila and of archaeologists of the University of L'Aquila. The research project carried out by the team is based on the analysis of the archaeological heritage (in particular, the documentation of some burials found in the medieval site of <i>Amiternum</i>, near L'Aquila). This starts from methods based on digital photogrammetric restitution, based on Structure from Motion (SfM) algorithms, and the generation of photorealistic textures in order to manage, in a 3D GIS environment, complex archaeological and anthropological data. The choice of technology to use is often determined by the specific needs of the survey, the purpose of the project, the budget and experience of the researchers, and the geometric characteristics of the assets, rather than the precision to be achieved. For the survey of the archaeological excavation of the medieval site of <i>Amiternum</i>, it was decided to use digital photogrammetry given that the objective was to document, with a rapid survey compatible with the times of an archaeological excavation the phases of image acquisition, processing and post processing of the site model. Furthermore, thanks to the integration of two technologies, digital photogrammetry and GIS, and the undisputed improvement in the management of 3D data by the GIS, three-dimensionality, in archeology in general, has become an indispensable component for site interpretation and for the documentation of the data.
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MANDEL, P., A. FLEURY, K. DELABRE, and V. HEIM. "La conductivité électrique, témoin opérationnel de la qualité de l’eau dans un réseau de distribution." Techniques Sciences Méthodes 11 (November 21, 2022): 27–37. http://dx.doi.org/10.36904/tsm/202211027.
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Cette étude montre comment les données de conductivité mesurées par des sondes déployées sur un réseau de distribution d’eau potable peuvent être exploitées de manière automatique pour résumer et expliquer les variations spatiales de qualité d’eau. Un algorithme de classification non supervisée est utilisé pour regrouper les sondes dont les profils de conductivité se ressemblent et proposer ainsi des groupes représentant des zones de qualité d’eau homogène. La méthodologie est évaluée sur le réseau du Syndicat des eaux d’Île-de-France (Sedif), à partir des données de 215 sondes mesurant la conductivité toutes les cinq minutes. Deux types de résultats sont présentés : d’une part, l’image d’ensemble de la qualité de l’eau dans le réseau ; d’autre part, une typologie des différents phénomènes mis au jour par la méthode. Les résultats présentés montrent que les différentes zones de qualité d’eau connues par l’expertise métier sont repérées automatiquement, et que de nombreuses sous-zones jusqu’alors inconnues sont identifiées. Ainsi les conséquences des restitutions de réservoir, des interconnexions avec des distributeurs voisins, de l’âge de l’eau, des mélanges d’eaux produites par différentes usines, sont mises en évidence par la méthodologie proposée. Pour le réseau du Sedif, les résultats ont montré que 96 % des sondes pouvaient être affectées à un groupe. Cette méthodologie peut être appliquée à tout réseau équipé de capteurs de conductivité, dès lors qu’il est susceptible d’être alimenté par des eaux de qualités différentes.
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Saadaoui, H., A. Ghennioui, B. Ikken, H. Rhinane, and M. Maanan. "USING GIS AND PHOTOGRAMMETRY FOR ASSESSING SOLAR PHOTOVOLTAIC POTENTIAL ON FLAT ROOFS IN URBAN AREA CASE OF THE CITY OF BEN GUERIR / MOROCCO." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLII-4/W12 (February 26, 2019): 155–66. http://dx.doi.org/10.5194/isprs-archives-xlii-4-w12-155-2019.
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<p><strong>Abstract.</strong> Renewable energy sources are at the forefront of political discussions around the world because of the scarcity of fossil fuels and climate change caused by the accumulation of greenhouse gases. By 2030, Morocco will cover 52% of these energy needs through renewable energies, in order to preserve the environment (COP 22). This paper aims to estimate the potential of photovoltaic solar energy from flat roofs in the city of Ben Guerir, Morocco using remote sensing and GIS data. To achieve this goal, vector orthophoto resulting from the photogrammetric restitution acquired in 2015 were used to generate a 3D model (DSM). The annual solar irradiation is calculated by the analyser of the solar tool. Each roof is calculated based on algorithms for the most common solar panel technologies (mono-si and poly-si). The applicability of this methodology has been demonstrated in the urban area of Benguerir, Morocco, and can be widespread in any other region of the world. The results obtained for a total roofing surface of 135&amp;thinsp;Ha, i.e. more than 345&amp;thinsp;Gwh of electricity annually generate. For an average roof of 60&amp;thinsp;m<sup>2</sup> that could supply 5 to 6 households; A planned investment between 118,218 and 167,296&amp;thinsp;DH, and an annual maintenance charge of 2%. This study may be an initial assessment of solar potential in the city, which can be used to support the management decision regarding investment in the urban solar system.</p>
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Starovoitova, A. S. "A Crypto Loan: Problems of Legal Qualification." Lex Russica 75, no. 10 (2022): 9–16. http://dx.doi.org/10.17803/1729-5920.2022.191.10.009-016.
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The author considers the concept of «digital money». The paper analyzes the legal nature of various types of digital currency. Special attention is paid to the civil law regime of the cryptocurrency and the peculiarities of its property turnover in an information system using blockchain technologies. The paper examines the following complex debatable issues of civil law: 1. possibility of applying provisions on obligations to digital relations; 2. problems of protecting the rights of digital money holders; 3. enforcing restitution in the digital environment. The paper analyzes the design of a crypto loan using a centralized Binance Loan exchange. The author concludes that the actual algorithm for lending cryptocurrencies is similar to the mechanism of traditional transfer of things determined by generic characteristics applied to a loan. The conclusion is reasoned that such legal concepts as «transaction», «legal relationship», «obligation» and «contract» can only be applied to the interaction of participants in actual loan relations in the digital environment with a high degree of conditionality. It has been revealed that attempts to qualify cryptocurrency loan relations without taking into account the position of the legislator are premature. Currently, the actual relationship with cryptocurrency is not a legal relationship and it cannot be formalized by civil contracts. The paper determines the tasks the solution of which, according to the author, will serve to settle loan relations in the digital environment. In particular, the issues concerning legislative determination of the civil law regime of digital money, consolidation of digital legal facts, possibility of applying general provisions on obligations to digital relations need immediate resolution. It is proved that in order to guarantee the proper fulfillment of cyber loan obligations, it is necessary to establish rules for the functioning of information systems at the legislative level, to formalize requirements for their operators and determine the responsibility of the latter for the data safety and reliability of transactions.
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Ebrahimian, Masoud, R. Sean Sanders, and Sina Ghaemi. "Dynamics and wall collision of inertial particles in a solid–liquid turbulent channel flow." Journal of Fluid Mechanics 881 (October 25, 2019): 872–905. http://dx.doi.org/10.1017/jfm.2019.749.
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The dynamics and wall collision of inertial particles were investigated in non-isotropic turbulence of a horizontal liquid channel flow. The inertial particles were $125~\unicode[STIX]{x03BC}\text{m}$ glass beads at a volumetric concentration of 0.03 %. The bead-laden flow and the unladen base case had the same volumetric flow rates, with a shear Reynolds number, $Re_{\unicode[STIX]{x1D70F}}$, of the unladen flow equal to 410 based on the half-channel height and friction velocity. Lagrangian measurements of three-dimensional trajectories of both fluid tracers and glass beads were obtained using time-resolved particle tracking velocimetry based on the shake-the-box algorithm of Schanz et al. (Exp. Fluids, vol. 57, no. 5, 2016, pp. 1–27). The analysis showed that on average the near-wall glass beads decelerate in the streamwise direction, while farther away from the wall, the streamwise acceleration of the glass beads became positive. The ejection motions provided a local maximum streamwise acceleration above the buffer layer by transporting glass beads to high velocity layers and exposing them to a high drag force in the streamwise direction. Conversely, the sweep motion made the maximum contribution to the average streamwise deceleration of glass beads in the near-wall region. The wall-normal acceleration of the beads was positive in the vicinity of the wall, and it became negative farther from the wall. The investigation showed that the glass beads with sweeping motion had the maximum momentum, streamwise deceleration, and wall-normal acceleration among all the beads close to the wall and these values increased with increasing their trajectory angle. The investigation of the beads that collided with the wall showed that those with shallow impact angles (less than $1.5^{\circ }$) typically slide along the wall. The sliding beads had a small streamwise momentum exchange of ${\sim}5\,\%$ during these events. The duration of their sliding motion could be as much as five times the inner time scale of the unladen flow. The wall-normal velocity of these beads after sliding was greater than their wall-normal velocity before sliding, and was associated with the rotation induced lift force. Beads with impact angles greater than $1.5^{\circ }$ had shorter interaction times with the wall and smaller streamwise and wall-normal restitution ratios.
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Belcore, Elena, Stefano Angeli, Elisabetta Colucci, Maria Angela Musci, and Irene Aicardi. "Precision Agriculture Workflow, from Data Collection to Data Management Using FOSS Tools: An Application in Northern Italy Vineyard." ISPRS International Journal of Geo-Information 10, no. 4 (2021): 236. http://dx.doi.org/10.3390/ijgi10040236.
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In the past decades, technology-based agriculture, also known as Precision Agriculture (PA) or smart farming, has grown, developing new technologies and innovative tools to manage data for the whole agricultural processes. In this framework, geographic information, and spatial data and tools such as UAVs (Unmanned Aerial Vehicles) and multispectral optical sensors play a crucial role in the geomatics as support techniques. PA needs software to store and process spatial data and the Free and Open Software System (FOSS) community kept pace with PA’s needs: several FOSS software tools have been developed for data gathering, analysis, and restitution. The adoption of FOSS solutions, WebGIS platforms, open databases, and spatial data infrastructure to process and store spatial and nonspatial acquired data helps to share information among different actors with user-friendly solutions. Nevertheless, a comprehensive open-source platform that, besides processing UAV data, allows directly storing, visualising, sharing, and querying the final results and the related information does not exist. Indeed, today, the PA’s data elaboration and management with a FOSS approach still require several different software tools. Moreover, although some commercial solutions presented platforms to support management in PA activities, none of these present a complete workflow including data from acquisition phase to processed and stored information. In this scenario, the paper aims to provide UAV and PA users with a FOSS-replicable methodology that can fit farming activities’ operational and management needs. Therefore, this work focuses on developing a totally FOSS workflow to visualise, process, analyse, and manage PA data. In detail, a multidisciplinary approach is adopted for creating an operative web-sharing tool able to manage Very High Resolution (VHR) agricultural multispectral-derived information gathered by UAV systems. A vineyard in Northern Italy is used as an example to show the workflow of data generation and the data structure of the web tool. A UAV survey was carried out using a six-band multispectral camera and the data were elaborated through the Structure from Motion (SfM) technique, resulting in 3 cm resolution orthophoto. A supervised classifier identified the phenological stage of under-row weeds and the rows with a 95% overall accuracy. Then, a set of GIS-developed algorithms allowed Individual Tree Detection (ITD) and spectral indices for monitoring the plant-based phytosanitary conditions. A spatial data structure was implemented to gather the data at canopy scale. The last step of the workflow concerned publishing data in an interactive 3D webGIS, allowing users to update the spatial database. The webGIS can be operated from web browsers and desktop GIS. The final result is a shared open platform obtained with nonproprietary software that can store data of different sources and scales.
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Cingolani, Elisa, and Gabriele Fangi. "Spherical Panoramas, and non Metric Images for Long Range Survey, the San Barnaba Spire, Sagrada Familia, Barcelona, Spain." Geoinformatics FCE CTU 6 (December 21, 2011): 109–17. http://dx.doi.org/10.14311/gi.6.15.
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The Sagrada Familia by Gaudi in Barcelona about 80 years after the death of its creator is going quickly to take its final shape as well as, maintain its original form as Gaudi would have wanted, the actual builders say. Complicated and elaborated forms, following the construction layout of the Chapel of Colonia Guell in Santa Coloma, tend to reproduce, on a gigantic scale, the organic forms of trees going to draw the charming and attractive complex of the small church derived from the model of wires used by Gaudi for its design. It has been long debated, and still it is debated on this approach as "camouflage", how it is consistent with the attitude of Gaudi architecture in the sense that he saw a sort of self-generating form of architecture during its own construction gradually responding to the stress placed by the same growth of structures, shapes, and materials. ("We do not reproduce the forms but we are able to reproduce a character owing its spirit,” A. Gaudi). But beyond this, the reality remains of the gradual suppression of what Gaudi realized until his death. Basically the sole facade of the Nativity, with its striking features and ending with four original towers as hyperboloids pinnacles with glittering glazed mosaics, is the only one that was finished by Gaudi himself, in particular the San Barnaba’s spire. In this action of progressive “destruction”, it is very important to analyze, survey and plot what realized by Gaudi for recovering the original forms and keeping them in their Gaudian formal and constructive features. The spire of St. Barnabas is one of the most architecturally significant occurrence of the whole building and its survey poses major technical problems: their possible solution represented by the experience here shown, has been already experimented in the previous 90 years as one of the first applications of expeditious photogrammetric techniques of survey (Clini, Fangi,1990). The technical problems consist basically in the difficulty given by its height above the street level, about 100 meters. Long focal lenses have to be used to get a suitable resolution and accuracy. We wanted to repeat now the survey using a different photogrammetric technique from the old one, that was DLT algorithm for non-metric images. The new technique is the Spherical Photogrammetry. Multi-image Spherical Photogrammetry makes use as sensor of a pseudo-image that is the spherical panorama, composed by the images taken from the same station point. For details of Spherical Photogrammetry see (Fangi, 2,3,4,9). A particular procedure appropriate for the orientation of very narrow field of view lenses panorama has been already set up and used for the orientation and plotting of the three minarets of the Great Mosque of Omayyad’s in Damascus, Syria. Their heights range from 60 to 80 meters above the courtyard pavement of the mosque. The technique consists in taking different focal lengths panorama from the same station point (Fangi, New Castle, 2010), one with WA wide angle and another one with NA Narrow Angle, adding to the stability of WA panorama the resolution of NA panorama. The same approach has been used in the Sagrada Familia, for the survey of San Barnaba’s spire. In 1990 the A. made a survey of the same spire. But in comparison to the years 90, there is one difficulty more: now the rear of the spire is not visible because of the construction of the roof of the church, while it was visible in 1990. The solution has been then to use the original images taken in the years 90 for the rear of the spire and the spherical panoramas for the rest, i.e. the part toward the façade, using the original control points. Then we had to make a combined adjustment of non metric images using DLT approach and spherical photogrammetry algorithms. The restitution has been indeed carried out using both type of imagery, spherical panorama and non metric images. The results are satisfactory in the sense that the principles of quick photogrammetry have been respected: short surveying times, simple and inexpensive tools, reaching in a ny case suitable outcome.
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Merino del Río, Rebeca. "Opportunities and precautions in the implementation of GIS-based analysis tools to cultural landscape restoration." Abstracts of the ICA 2 (October 9, 2020): 1–2. http://dx.doi.org/10.5194/ica-abs-2-44-2020.
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Abstract. The protection of cultural and natural heritage has been extended to the surrounding landscape in the last decades. This tendency has been corroborated by a series of International Charters and the European Landscape Convention (ELC) of 2000. Despite protection, management and planning proposed by ELC some structural aspects of the territory have been disregarded because of the frantic enlargement of cities throughout the Twentieth Century. In many cases, urban investments and planning associated to the expansion of the metropolitan areas have overlooked a territorial heritage that is necessary to ensure the cultural landscape regeneration. Cultural itineraries are presented as a landscape architecture strategy for valorising the territorial heritage. Well-targeted design of these itineraries can also contribute to restore the dynamics of cultural landscape formation. Research is focused on the definition of a method for designing cultural itineraries able to restore the dynamics of cultural landscape formation. Particular attention is paid to the areas around the archaeological sites. Because of the territorial scale of the intervention, software based on Geographical Information Systems (GIS) turns out to be the most suitable for representing and analysing complex spatial phenomena. This paper explores the opportunities and precautions that must be taken into account to integrate a GIS-based analysis into the design of a landscape architecture like the cultural itinerary.A systematic review of the scientific literature indexed in those databases with a wider international impact is elaborated in order to analyse the range of opportunities offered by GIS-based software in the area of theoretical and practical research on cultural landscapes. This review allows us to determine the state of the art, as well as to discover those applications and strategies that are generally used for each research field or intended aim. Knowledge of the recent discussions on the matter can be useful in that it can be integrated into the different phases of a method for designing cultural itineraries in an attempt to increase its level of technological innovation.In first place, a sample must be extracted. To this end, a series of parameters must be determined beforehand. It is considered a valid sample that formed by more than one hundred entries, which is representative of the state of the art observed. The sample is examined afterwards in quantitative and qualitative terms. The systematic review is conducted according to the methodology proposed by Gough, Oliver and Thomas (2012, 2013). The databases used to elaborate the systematic review of the scientific literature are Web of Science and Scopus. The definite search is based on the combination in groups of three of four elements: GIS, the component archaeo*, the operation (route OR path) and the expression “cultural landscape”.The questions that are meant to be clarified by means of this systematic review are the following ones. First, to what discipline does the entries belong? Second, what is the research field? Third, what is the scope of application of GIS? And, fourth, what GIS-based functionalities are prevalent? Then the criteria for inclusion and exclusion are determined. The details of the flow of the review process can be observed in the diagram on the slide.The distribution of the results by discipline allows us to observe how most of the articles and papers mainly belongs to the disciplines of archaeology and history. The significative but scant collection of writings that could be identified as belonging to the disciplines of architecture or civil engineering, may be due to the fact that the number of specific journals indexed in those databases is smaller in comparison with other disciplines. Most of the entries that were ruled out, because of the thematic dispersion, belong to the discipline of natural sciences and fail in considering human activity as fundamental in cultural landscape formation. The reduced number of entries belonging to the disciplines of architecture and civil engineering is considered here to be indicative of an unexplored research field.Following a thorough review, it is concluded that the main research field in relation to architecture and civil engineering concerns the technological innovation. In this sense, scientific literature review allows us to conclude that the main field of application of GIS in relation to architecture and civil engineering, when referring to cultural landscapes, is the development of protection, management and planning actions and cataloguing. The qualitative review of these entries has been useful to outline a possible integration of GIS-based functionalities into a method for designing cultural itineraries, as well as to prevent us from following some apparently innovative paths that sometimes lack of a solid scientific basis or that are far from the intended aim.None of the articles and papers focused on the technological innovation in which the scope of application of GIS is the protection, management and planning of cultural landscapes, is centred on the design of cultural itineraries as a landscape architecture strategy. Neither were they focused on the definition of a conceptual framework to guide the design of the cultural itineraries. This allows us to verify the opportunity of a research in which GIS and, more concretely, their analysis tools assist the landscape architect when design is aimed to restore the dynamics of cultural landscape formation.Having detected the main analysis tools that can contribute to cultural itineraries design and having considered in which way they are distributed by field of knowledge, research field and scope of application of GIS, we can then suggest a hypothesis to integrate GIS into our three-step method for designing cultural itineraries. In order to guide the design actions towards the restoration of the dynamics of cultural landscape formation, the methodological approach to the ecological design of settlements set up by different authors of the Società dei Territorialisti/e is taken as a reference. The synthetical structural descriptions that constitute the first part of the method, can benefit from the use of GIS-based analysis tools as they can assist landscape architect in the elaboration and refinement of the narratives about the evolution of the territorial heritage. The use of advanced spatial analysis tools should not be encouraged, however, in the elaboration of the interpretations. GIS software is used, both in the identity interpretations and the strategic scenario (the second and third phases of the method), as a visualisation and graphic representation tool. Basic functionalities allow us to manipulate and simultaneously observe different georeferenced datasets that can support the architect’s interpretative work of synthesis. As so many qualitative and sensitive factors should be taken into account when interpreting the process of cultural landscape formation, landscape architect’s design cannot rely on the abstract result of a GIS-based advanced spatial analysis. Although the use of algorithms is defended to lead to more precise results based on quantitative indicators, under no circumstances may the design of a landscape architecture be constrained by them, as identity features that have determined cultural landscape formation can hardly be codified.After an in-depth review, it is concluded that the success and efficiency of the method depends on the careful balance between the designer’s interpretation and the scope of application of the information technologies. It is defended that the automated result of applying advanced spatial analysis tools cannot supply the required interpretative work of the architect who pursues to restore the dynamics of cultural landscape formation through the design of cultural itineraries. Like any other operation of restauro, this restitution is subjective as it entails a revision of the past that should be necessarily interpretative. Thus, the use of predictive models based on the application of algorithms are discouraged in the interpretative phases because of the structural and historical complexity associated to the construction of the territory and landscape. Also, reluctance to ground the method on the implementation of GIS-based analysis tools lies in the fact that the highest levels of efficiency are meant to be obtained by focusing on the methodological innovation rather than on the technological one. GIS-based analysis tools integration into the different phases of the method for designing cultural itineraries mainly follows to ease the visualisation and comprehension of complex spatial processes that take place on the territory and it is always subsumed to the designer’s interpretative work.
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Huang, Ying H., Vadim Alexeenko, Gary Tse, Christopher L. H. Huang, Celia M. Marr, and Kamalan Jeevaratnam. "ECG Restitution Analysis and Machine Learning to Detect Paroxysmal Atrial Fibrillation: Insight from the Equine Athlete as a Model for Human Athletes." Function 2, no. 1 (2020). http://dx.doi.org/10.1093/function/zqaa031.
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Abstract Atrial fibrillation is the most frequent arrhythmia in both equine and human athletes. Currently, this condition is diagnosed via electrocardiogram (ECG) monitoring which lacks sensitivity in about half of cases when it presents in paroxysmal form. We investigated whether the arrhythmogenic substrate present between the episodes of paroxysmal atrial fibrillation (PAF) can be detected using restitution analysis of normal sinus-rhythm ECGs. In this work, ECG recordings were obtained during routine clinical work from control and horses with PAF. The extracted QT, TQ, and RR intervals were used for ECG restitution analysis. The restitution data were trained and tested using k-nearest neighbor (k-NN) algorithm with various values of neighbors k to derive a discrimination tool. A combination of QT, RR, and TQ intervals was used to analyze the relationship between these intervals and their effects on PAF. A simple majority vote on individual record (one beat) classifications was used to determine the final classification. The k-NN classifiers using two-interval measures were able to predict the diagnosis of PAF with area under the receiving operating characteristic curve close to 0.8 (RR, TQ with k ≥ 9) and 0.9 (RR, QT with k ≥ 21 or TQ, QT with k ≥ 25). By simultaneously using all three intervals for each beat and a majority vote, mean area under the curves of 0.9 were obtained for all tested k-values (3–41). We concluded that 3D ECG restitution analysis can potentially be used as a metric of an automated method for screening of PAF.
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V, Sarasvathi, Snehanshu Saha, N. Ch S. N. Iyengar, and Mahalaxmi Koti. "Coefficient of Restitution based Cross Layer Interference Aware Routing Protocol in Wireless Mesh Networks." International Journal of Communication Networks and Information Security (IJCNIS) 7, no. 3 (2022). http://dx.doi.org/10.17762/ijcnis.v7i3.1358.
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In Multi-Radio Multi-Channel (MRMC) Wireless Mesh Networks (WMN), Partially Overlapped Channels (POC) has been used to increase the parallel transmission. But adjacent channel interference is very severe in MRMC environment; it decreases the network throughput very badly. In this paper, we propose a Coefficient of Restitution based cross layer interference aware routing protocol (CoRCiaR) to improve TCP performance in Wireless Mesh Networks. This approach comprises of two-steps: Initially, the interference detection algorithm is developed at MAC layer by enhancing the RTS/CTS method. Based on the channel interference, congestion is identified by Round Trip Time (RTT) measurements, and subsequently the route discovery module selects the alternative path to send the data packet. The packets are transmitted to the congestion free path seamlessly by the source. The performance of the proposed CoRCiaR protocol is measured by Coefficient of Restitution (COR) parameter. The impact of the rerouting is experienced on the network throughput performance. The simulation results show that the proposed cross layer interference aware dynamic routing enhances the TCP performance on WMN.
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Jia, Yan-Bin, and Feifei Wang. "Analysis and Computation of Two Body Impact in Three Dimensions." Journal of Computational and Nonlinear Dynamics 12, no. 4 (2017). http://dx.doi.org/10.1115/1.4035411.
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A formal impulse-based analysis is presented for the collision of two rigid bodies at single contact point under Coulomb's friction in three dimensions (3D). The tangential impulse at the contact is known to be linear in the sliding velocity whose trajectory, parametrized with the normal impulse and referred to as the hodograph, is governed by a generally nonintegrable ordinary differential equation (ODE). Evolution of the hodograph is bounded by rays in several invariant directions of sliding in the contact plane. Exact lower and upper bounds are derived for the number of such invariant directions, utilizing the established positive definiteness of the matrix defining the governing ODE. If the hodograph reaches the origin, it either terminates (i.e., the contact sticks) or continues in a new direction (i.e., the contact resumes sliding) whose existence and uniqueness, only assumed in the literature, are proven. Closed-form integration of the ODE becomes possible as soon as the sliding velocity turns zero or takes on an invariant direction. Assuming Stronge's energy-based restitution, a complete algorithm is described to combine fast numerical integration (NI) with a case-by-case closed-form analysis. A number of solved collision instances are presented. It remains open whether the modeled impact process will always terminate under Coulomb's friction and Stronge's (or Poisson's) restitution hypothesis.
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Dasí, Albert, Aditi Roy, Rafael Sachetto, Julia Camps, Alfonso Bueno-Orovio, and Blanca Rodriguez. "In-silico drug trials for precision medicine in atrial fibrillation: From ionic mechanisms to electrocardiogram-based predictions in structurally-healthy human atria." Frontiers in Physiology 13 (September 15, 2022). http://dx.doi.org/10.3389/fphys.2022.966046.
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Atrial fibrillation (AF) inducibility, sustainability and response to pharmacological treatment of individual patients are expected to be determined by their ionic current properties, especially in structurally-healthy atria. Mechanisms underlying AF and optimal cardioversion are however still unclear. In this study, in-silico drug trials were conducted using a population of human structurally-healthy atria models to 1) identify key ionic current properties determining AF inducibility, maintenance and pharmacological cardioversion, and 2) compare the prognostic value for predicting individual AF cardioversion of ionic current properties and electrocardiogram (ECG) metrics. In the population of structurally-healthy atria, 477 AF episodes were induced in ionic current profiles with both steep action potential duration (APD) restitution (eliciting APD alternans), and high excitability (enabling propagation at fast rates that transformed alternans into discordant). High excitability also favored 211 sustained AF episodes, so its decrease, through prolonged refractoriness, explained pharmacological cardioversion. In-silico trials over 200 AF episodes, 100 ionic profiles and 10 antiarrhythmic compounds were consistent with previous clinical trials, and identified optimal treatments for individual electrophysiological properties of the atria. Algorithms trained on 211 simulated AF episodes exhibited &gt;70% accuracy in predictions of cardioversion for individual treatments using either ionic current profiles or ECG metrics. In structurally-healthy atria, AF inducibility and sustainability are enabled by discordant alternans, under high excitability and steep restitution conditions. Successful pharmacological cardioversion is predicted with 70% accuracy from either ionic or ECG properties, and it is optimal for treatments maximizing refractoriness (thus reducing excitability) for the given ionic current profile of the atria.
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Guerin, Nathan, Henry Childs, Pei Zhou, and Bruce R. Donald. "DexDesign: an OSPREY-based algorithm for designing de novo D-peptide inhibitors." Protein Engineering, Design and Selection 37 (2024). http://dx.doi.org/10.1093/protein/gzae007.
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Abstract With over 270 unique occurrences in the human genome, peptide-recognizing PDZ domains play a central role in modulating polarization, signaling, and trafficking pathways. Mutations in PDZ domains lead to diseases such as cancer and cystic fibrosis, making PDZ domains attractive targets for therapeutic intervention. D-peptide inhibitors offer unique advantages as therapeutics, including increased metabolic stability and low immunogenicity. Here, we introduce DexDesign, a novel OSPREY-based algorithm for computationally designing de novo D-peptide inhibitors. DexDesign leverages three novel techniques that are broadly applicable to computational protein design: the Minimum Flexible Set, K*-based Mutational Scan, and Inverse Alanine Scan. We apply these techniques and DexDesign to generate novel D-peptide inhibitors of two biomedically important PDZ domain targets: CAL and MAST2. We introduce a framework for analyzing de novo peptides—evaluation along a replication/restitution axis—and apply it to the DexDesign-generated D-peptides. Notably, the peptides we generated are predicted to bind their targets tighter than their targets' endogenous ligands, validating the peptides' potential as lead inhibitors. We also provide an implementation of DexDesign in the free and open source computational protein design software OSPREY.