Simplified structural behaviours of post-tensioned inter-module connection for modular buildings

Seismic behavior of high-rise modular buildings with simplified models of inter-module connections

Revisiting simplified model of a single-well push–pull test for estimating regional flow velocity

In this paper, a simplified aircraft system model is developed correctly emulating the nonlinear dynamics of complex aircraft models under closed-loop control. The simplified model is based on Dubins models used in optimization algorithms for trajectory control of multiple Unmanned Aeriel Vehicles (UAVs). Algorithms optimizing area coverage for reconnaissance based on UAV capabilities, fuel remaining, and time constraints require simple aircraft models providing ecient solutions in near real-time. However, the simplified models should accurately predict UAV dynamics for proper prediction. For this study, a realistic UAV simulation is developed including nonlinear aerodynamics and kinematics. A UAV autonomous navigation algorithm for waypoint-to-waypoint navigation is derived and integrated in the complex UAV simulation. A simplified system model based Dubins model is developed closely matching the full nonlinear UAV simulation. A Rhumb-line navigation algorithm including a velocity-hold and altitude-hold control system is used for closed-loop control. A navigation system utilizing trajectory planning with Dubins curves is also developed. Both control laws are implemented in a simplified Dubins model and tuned to match the full nonlinear simulation under autonomous control including provisions for head and tail wind conditions. Computer simulations are performed demonstrating waypointto-waypoint navigation with desired final heading trajectories for both the full nonlinear UAV model and the simplified Dubins simulation. Simulation time history analysis is used to verify the accuracy of the simplified model compared to the full nonlinear simulation model.

Highly detailed computer models are required for design and development of modern flight control systems, capable of emulating with high accuracy the behaviour of on-board equipment. At the same time, different simplified models are needed, specifically intended for operations such as the optimization of preliminary design and the development of diagnostic or prognostic strategies. These simplified models are required to combine sufficient levels of accuracy and reliability with reduced computational costs, to minimize the computational burden associated with prognostic and optimization algorithms. In this work, we focus on electro-hydraulic actuators, since they are critical subsystems in terms of safety and availability of the aircraft. Advanced monitoring and prognostic algorithms require new numerical models, combining an acceptable computational effort with a satisfying ability to simulate their performance and dynamics. To this purpose, this paper proposes a new simplified numerical model of the servovalve fluid-dynamic behaviour. This numerical algorithm, based on a very compact semi-empirical formulation, is intended to take into account in a simplified but sufficiently accurate way several typical effects related to the SV spool geometry and the operating conditions. To evaluate the approximations introduced by this model into a system-level simulation, it has been integrated into a dedicated numerical model simulating a simple electrohydraulic on-board actuator, and compared with a higher fidelity servovalve model.

Numerical investigation of the shear behaviour of a cable bolt in single shear test

Comparative analysis on the seismic behaviour of unreinforced masonry buildings with flexible diaphragms

Neuroprosthetic devices can be an innovative solution to support subjects suffering from a limb loss. The possibility of restoring tactile sensations by using sensory feedback represents a research area whose outcomes could significantly improve the quality of life of prosthesis users. One of the best techniques to restore close-to-natural and selective tactile sensations is the electrical current stimulation of nerves using neural electrodes. Their interaction with nerves is an important aspect to be studied. The aim of this work is to deepen, in the framework of computational modeling, the possibility of approximating a realistic 3D human median nerve model, based on anatomical imaging, to a simplified model using the hybrid FEM-Neuron approach. Often, a high computational simulation time is also related to the complexity of the model geometry; therefore using a geometrical simplified model can be an important aspect to be analyzed. The simplified model is built approximating inner fascicles shape to simple geometrical shapes, i.e. ellipses. The electrical current stimulation is studied in Comsol environment by using a ds-FILE electrode model implanted in the human median nerve. The results obtained from computational simulations using both anatomical and simplified models, allow concluding that the percentage activation ranges at different distances from the active site obtained by the two models are comparable.

: Stress analyses of lumbar vertebrae were performed by a three dimensional finite element method for the purposes of (i) evaluating simplified models of the vertebrae which are suitable as injury post processors, and (ii) gaining a better understanding of injury mechanisms. The finite element analyses were linear and elastic. Axial and moment loads were applied over the end plates to simulate G sub z impact and on the facets to simulate load transmission between the articular facets and the vertebral bodies. The finite element model predicts that the maximum stresses under axial load are perpendicular to the axis of the vertebral body, which are called axial stresses; this is consistent with the predominance of compressive and wedge fractures. However, the maximum stresses predicted by the finite element model are only about a third of those predicted by the simplified injury model. This discrepancy is due to the fact that a substantial portion of the total load is transmitted through the vertebral centrum which is neglected in the simplified model. Furthermore, the finite element model exhibits a rather complex pattern of deformation even under axial load, which cannot be incorporated easily in a simplified model. The stresses predicted by the finite element model for bending also differ substantially from those given by the simplified model for the same reasons. Good agreement between the finite element model and simplified model is only achieved for torsion loads.

Dependence of the AES backscattering correction factor on the experimental configuration

One method for simplified manipulator model construction and its application in quazioptimal trajectory synthesis

Lateral stiffness evaluation on corner-supported thin walled modular steel structures

The spatial distribution of trapped holes in the gate oxide of MOS exposed to ionizing radiation plays a significant role in the dynamics of the threshold voltage shift with dose, specially when switched bias measurements are considered. In this work, we analyze currently available simplified models stressing out their limitations when dealing with complex measurements. Therefore, we present a simplified model based on the fitting of the evolution with dose of the spatial distribution of trapped holes obtained from a physics-based numerical model. For that, a two-exponential expression was considered, with four fitting parameters. Then, the change with dose of these parameters is considered. The effect the variation of the capture and neutralization rates has on the spatial distribution of trapped holes is analyzed to better understanding radiation effects in MOS devices and also to contribute to the development of simplified numerical models capable of reproducing complex dynamics.

The propulsion subsystem of multi-rotor Unmanned Aerial Vehicles (UAV) is one of the most complex due to the aerodynamic, aero-elastic and electromechanical elements it comprises. Therefore, accurate models of this subsystem can be difficult to work with. Therefore, simplified models are normally used for the design of control and navigation algorithms. Considering this, the effectiveness of these algorithms is heavily dependent on the identification process used for the estimation of the parameters of the simplified propulsion model. On the other hand, the novel method of fuzzy adaptive neurons (FANs) have interesting characteristics that make them attractive for applications in which a fast response and good precision are required. In this article, the identification of the parameters of the propulsion system and the trajectory tracking of a multi-rotor UAV using FANs is explored. The efficient learning algorithm of the FANs is applied to identify the parameters of a simplified model of the propulsion system and to the self-tuning proportional integral derivative (PID) controllers of the trajectory tracking system. The proposed simplified model with the identified parameters is tested with experimental data obtained with low speed wind tunnels. The proposed PID controllers with self-tuning gains defined by the algorithm of the FANs for trajectory tracking system, are verified with simulations in MATLAB/Simulink® environment. The results showed that the parameter identification and trajectory tracking with PID controllers with self-tuning gains defined by the algorithm of the FANs, are suitable for estimating the parameters of the simplified model and track the trajectory with better error reduction than a classical PID controller.

Effects of constructional tolerances on lateral resistance of steel–concrete composite modular buildings with various connection rigidity

The ultraviolet structure of s-channel mediator dark matter simplified models at hadron colliders is considered. In terms of commonly studied s-channel mediator simplified models it is argued that at arbitrarily high energies the perturbative description of dark matter production in high energy scattering can break down. This is analogous to the well documented breakdown of an EFT description of dark matter collider production. With this in mind, to diagnose whether or not the use of simplified models at the LHC is valid, perturbative unitarity of the scattering amplitude in the processes relevant to LHC dark matter searches is studied. The results are as one would expect: at the LHC and future proton colliders the simplified model descriptions of dark matter production are in general valid. As a result of the general discussion, a simple class of ‘Fermiophobic Scalar’ simplified models is proposed, in which a scalar mediator couples to electroweak vector bosons. The Fermiophobic simplified model is well motivated and exhibits interesting collider and direct detection phenomenology.