An overview of Forward Dynamics Algorithms and their use in Open Source Dynamics Engines

Simulation of real-world dynamics is of major importance in testing and verifying developed industrial concepts and solutions, developing and verifying potential control paradigms, scientific research, learning and training tools, or the entertainment industry as a basis for a game engine. The module of the 3D virtual simulator that achieves simulation of the real-world behaviour such as rigid and elastic body dynamics, particle dynamics, fluid dynamics, electrodynamics, magnetism, etc., is often referred to as a dynamics engine or physics engine. The core of the rigid body dynamics (physics) engine is the solution to the forward dynamics problem, which is defined as finding a rigid body's path, velocity, and acceleration for a given input actuating torque and external forces. The past few decades saw a considerable amount of research in robot dynamics modelling, and there are many methods for robot dynamic model development available in the literature. The most commonly used algorithms for solving robot forward dynamics problem are the Composite-Rigid-Body Algorithm (CRBA) [1] and the Articulated-Body Algorithm (ABA) [2]. CRBA and ABA are reduced coordinate methods where known constraints, such as joints, are embedded in the formulation of the equations of motion. Besides reduced coordinate methods, there are maximal coordinate methods using Lagrange multipliers [3-4] to enforce constraints using constraint reaction forces

Effect of temperature on the physical changes and drying kinetics in plum (Prunus domestica L.) Požegača variety

In this study, drying kinetics of autochthonous variety Požegača plum was examined in a laboratory dryer at three temperatures. The whole plum fruits, together with the kernels were subjected to the drying process. The effect of drying has been examined at temperatures of 55, 60 and 75 °C, with a constant air velocity of 1.1 m s-1. The corresponding experimental results were tested using six nonlinear regression models. Coefficient of determination (R2), standard regression error (SSE), model correlation coeficient (Vy), as well as the maximum absolute error (ΔY) showed that the logaritmic model was in good agreement with the experimental data obtained. During drying of plums, the effective diffusivity was found to be between 5.6×10-9 for 55 °C and 8.9×10-9 m2 s-1 at 75 °C, respectively. The physical characteristics of fresh (length 39.64 mm and width 29.15 mm) and dried (length 37.52 mm and width 22.85 mm) plum fruit were determined. Finally, by chemical analysis, the contents of micro- and macro-elements (Fe, Mn, Cu, B and N, F, K, Ca, Mg and S) in the skin and flesh of the dried product, prunes, has been established

Intelligent dual curve-driven tool path optimization and virtual CMM inspection for sculptured surface CNC machining

This paper investigates the profitability of a dual‐curve driven surface finish tool path under the concept of optimizing crucial machining parameters such as toroidal end‐mill diameter, lead angle and tilt angle. Surface machining error as well as tool path time are treated as optimization objectives under a multi‐criteria sense, whilst a central composite design is conducted to obtain experimental outputs for examination and, finally, fit a full quadratic model considered as the fitness function for process optimization by means of a genetic algorithm. A benchmark sculptured surface given as a second‐order parametric equation was tested and simulated using a cutting‐edge manufacturing modeling software and best parameters recommended by the genetic algorithm were implemented for validation. Further assessment involves the virtual inspection to selected profile sections on the part. It was shown that the approach can produce dual‐curve driven tool trajectories capable of eliminating sharp scallop heights, maximizing machining strip widths as well as maintaining smoothness quality and machining efficiency

Cell-type-specific modulation of feedback inhibition by serotonin in the hippocampus

Midbrain raphe nuclei provide strong serotonergic projections to the hippocampus, in which serotonin (5-HT) exerts differential effects mediated by multiple 5-HT receptor subtypes. The functional relevance of this diversity of information processing is poorly understood. Here we show that serotonin via 5-HT(1B) heteroreceptors substantially reduces synaptic excitation of cholecystokinin-expressing interneurons in area CA1 of the rat hippocampus, in contrast to parvalbumin-expressing basket cells. The reduction is input specific, affecting only glutamatergic synaptic transmission originating from CA1 pyramidal cells. As a result, serotonin selectively decreases feedback inhibition via 5-HT(1B) receptor activation and subsequently increases the integration time window for spike generation in CA1 pyramidal cells. Our data imply an important role for serotonergic modulation of GABAergic action in subcortical control of hippocampal output

The role of hydrogen sulfide in homocysteine-induced cardiodynamic effects and oxidative stress markers in the isolated rat heart

This study aimed to assess the role of H2S in homocysteine-induced cardiodynamic effects in the isolated rat heart. The hearts were retrogradely perfused according to the Langendorff technique. The maximum and minimum rates of pressure in the left ventricle (dp/dt max, dp/dt min), systolic and diastolic left ventricular pressures (SLVP, DLVP), heart rate (HR), and coronary flow (CF) were measured. A spectrophotometrical method was used to measure the following oxidative stress markers: index of lipid peroxidation (thiobarbituric acid reactive substances, TBARS), nitrite level (NO2−), superoxide anion radicals (O2•−), and hydrogen peroxide (H2O2) concentrations. The administration of 10 µmol/l DL-homocysteine (DL-Hcy) alone decreased dp/dt max, SLVP, and CF but did not change any oxidative stress parameters. The administration of 10 µmol/l DL-propargylglycine (DL-PAG) decreased all cardiodynamic parameters and increased the concentration of O2•−. The co-administration of DL-Hcy and DL-PAG induced a significant decrease in all estimated cardiodynamic parameters and decreased the concentration of NO2− and O2•− but increased the levels of TBARS and H2O2. Homocysteine shows a lower pro-oxidative effect in the presence of hydrogen sulfide (H2S), which indicates a potential anti-oxidative capacity of H2S

A protocol for thoracic radiation therapy in patients with cardiac implantable electronic devices

Prolonged lifespan and improved diagnostic and treatment modalities have led to significant progress in the diagnosis and treatment of cardiovascular disease and cancer. A substantial number of patients with malignancies also have cardiovascular disease at the time of cancer treatment. Per literature, over one million implantable cardiac devices are inserted annually. Ionizing radiation, especially in the thoracic area is related to cardiac implantable electronic device (CIED) damage and malfunction. Besides that, CIED can interfere with radiotherapy planning and delivery, as well as patient motivation to undergo radiotherapy treatment. Management of oncology patients, undergoing radiotherapy, for any indication, with a CIED is essential, and safe radiotherapy practice requires minimizing the risk to patients as much as possible, from pretherapy planning to posttherapy follow-up. A collaborative multidisciplinary approach, tailor-made for every single radiotherapy center is imperative to provide effective and safe radiotherapy for these patients. A collaboration of radiation oncologists, medical physicists and cardiologists from the University Clinical Center Kragujevac has created a local protocol for radiotherapy treatment and follow-up for patients receiving radiotherapy at the Center for Radiation Oncology University C linical Center Kragujevac, which provides safe and efficient delivery of an adequate radiotherapy dose to target volumes with appropriate cardiac monitoring.Publishe

Deformation of the Magnetic Skyrmion Lattice in MnSi under Electric Current Flow

Using small-angle neutron scattering (SANS), we investigate the deformation of the magnetic skyrmion lattice in bulk single-crystalline MnSi under electric current flow. A significant broadening of the skyrmion-lattice-reflection peaks was observed in the SANS pattern for current densities greater than a threshold value j_t ~ 1 MA/m^2 (10^6 A/m^2). We show this peak broadening to originate from a spatially inhomogeneous rotation of the skyrmion lattice, with an inverse rotation sense observed for opposite sample edges aligned with the direction of current flow. The peak broadening (and the corresponding skyrmion lattice rotations) remain finite even after switching off the electric current. These results indicate that skyrmion lattices under current flow experience significant friction near the sample edges, and plastic deformation due to pinning effects, these being important factors that must be considered for the anticipated skyrmion-based applications in chiral magnets at the nanoscale

Prototype ATLAS IBL Modules using the FE-I4A Front-End Readout Chip

The ATLAS Collaboration will upgrade its semiconductor pixel tracking detector with a new Insertable B-layer (IBL) between the existing pixel detector and the vacuum pipe of the Large Hadron Collider. The extreme operating conditions at this location have necessitated the development of new radiation hard pixel sensor technologies and a new front-end readout chip, called the FE-I4. Planar pixel sensors and 3D pixel sensors have been investigated to equip this new pixel layer, and prototype modules using the FE-I4A have been fabricated and characterized using 120 GeV pions at the CERN SPS and 4 GeV positrons at DESY, before and after module irradiation. Beam test results are presented, including charge collection efficiency, tracking efficiency and charge sharing.Comment: 45 pages, 30 figures, submitted to JINS