Search

Analyzing the landing dynamics response is essential for enhancing the success rate of surface explorations on celestial bodies like Mars, the moon, and asteroids. This paper develops a comprehensive dynamics model for a space lander equipped with four sets of buffer legs. Each set comprises a primary strut, two secondary struts, and a footpad. The compression force of the buffer struts is determined through interpolation of real experimental data, while the contact force between the footpad and the ground is calculated using Archimedes law for granular media. The Lagrange equation of the second kind is employed to construct the dynamical model for the lander with minimal degrees of freedom. The proposed dynamics model is validated through experiments involving touchdowns of a single legged lander and a four legged lander. Moreover, key physical quantities such as the buffer force, energy absorption and body acceleration are computed for both 1-2-1 and 2-2 landing configurations. The results indicate that the buffer strut is capable of absorbing approximately half of the impact energy, leading to a 50-fold reduction in the shock acceleration of the main body in both landing configurations. However, it is observed that the maximum compression of the buffer strut is greater in the 1-2-1 landing configuration than in the 2-2 landing configuration. Furthermore, these simulations can be completed within seconds, enabling extensive simulations for the design and optimization of soft landing processes. [ABSTRACT FROM AUTHOR]

Reducing the dependence on traditional energy sources and shifting towards the utilization of renewable energy sources (RES) of energy in the maritime sector is imperative for reducing greenhouse gas emissions. Inherently, RES sources like solar and wind are intermittent and variable, resulting in inconsistent power availability and hence leading to energy supply fluctuations and potential shortages. In this respect, an efficient control strategy to maintain system stability and address intermittency effectively is essential. This work considers a hybrid marine microgrid with various energy sources like photovoltaics (PV), wind energy conversion system (WECS), marine biodiesel generator, Archimedes wave power generation, solid oxide fuel cell, and batteries. A 2-degree of freedom (2DOF) structure is designed and implemented with the tilt-integral-derivative filter (TIDN) to address frequency variations. Furthermore, an Archimedes optimization algorithm (AOA) is used to optimize the 2DOF-TIDN controller. The stability of the proposed microgrid system is assessed under various combinations of RES availabilities, including real-time data from WECS and PV. The AOA-based 2DOF-TIDN performance is compared to the following algorithms: genetic, Jaya, bat, grasshopper optimization, particle swarm optimization, and moth flame optimization. Simulation results obtained show that the AOA-based 2DOF-TIDN control strategy achieves shorter settling times in mitigating the changes of marine microgrid systems under different dynamic conditions as compared to the other algorithms. Finally, the controller being proposed in this paper was tested for robustness with parameter deviations of +25%, −20%, and − 40% from the nominal values, and proved to be the proposed 2DOF-TIDN controller parameters demonstrate significant robustness in effectively managing the uncertainties and parametric variations. • Maritime Microgrid system is designed for investigations with RE & storage units. • PV, Wind, MBG, AWPG, SOFC, and battery storage units are considered. • 2DOF-TIDN controller is developed to mitigate the changes in the system. • The AOA method is proposed for optimal gains of the 2DOF-TIDN under uncertainties. • Sensitivity analysis, Time delay analysis, and stability analysis are performed [ABSTRACT FROM AUTHOR]

This paper proposes an efficient method for calculating the dynamic behaviour and seismic performance of reciprocal structures by introducing the generalized displacements at the hinge point to describe the displacements of the nodes at the beam ends. The whole structural nodal coding system is condensed by replacing the two codes at the beam end nodes with code at the hinge point based on the traditional space rigid frame matrix displacement method. On the basis of the principle of virtual work, the system natural vibration equation of the structure in the condensed nodal coding system is obtained; from the mode-superposition response spectrum method and the time history analysis method, the system seismic response equation of the structure in the condensed nodal coding system is derived. Then, the dynamic behaviour and seismic performance of the structure can be achieved by solving the obtained system dynamic equations. Finally, two numerical examples, a space L-shaped articulated reciprocal rigid frame and a reciprocal configuration transformed from the 36 type of Archimedes paving, are adopted to demonstrate the effectiveness of the proposed method. From the numerical results, the reciprocal structure transformed from the 36 type of Archimedes paving has a large whole stiffness, and the seismic response generated by vertical earthquake excitation is the most significant, which should be the focus of the seismic design of reciprocal structures. The proposed method effectively reduces the number of computational degrees of freedom of the whole structure and is more efficient in calculating the reciprocal structure. • A new method for dynamic calculation of reciprocal structures is proposed. • The condensed nodal coding system is introduced. • The beam end nodal displacements are described by the generalized displacements at the hinge point. • The natural vibration equation and seismic response equation in the condensed nodal coding system is derived. • The dynamic behaviour and seismic performance of reciprocal structures are investigated. [ABSTRACT FROM AUTHOR]

• A novel MSSAO-ERNN technique is proposed to detect the PTSD symptom from speech. • The MSSAO-ERNN technique efficiently identifies PTSD symptoms from the dataset. • Three datasets namely NNE, FME hospital as well as TIMIT datasets are employed. • PTSD is mental illness that affects people when they experience traumatic events. • Performance is determined by computing various metrics for PTSD identification. Post-traumatic stress disorder (PTSD) is a stress-based disorder that occurs when a person is vulnerable to undesirable traumatic events like injury or harm. Numerous research works reported dissimilar complex issues for detecting PTSD severity in patients which makes the PTSD diagnosis process a complicated task. So, a novel Multi-Strategy Seeker Archimedes Optimization-based Elman Recurrent Neural Network (MSSAO-ERNN) technique to detect PTSD symptoms in earlier stages using speech samples. Our proposed MSSAO-ERNN technique efficiently identifies PTSD symptoms from the dataset and helps the physician to diagnose accurately. The proposed approach constitutes various significant phases that include the pre-processing phase, feature extraction phase, and classification phase to detect the presence of PTSD in the datasets. The performance of the proposed method is determined by computing various metrics for the accurate identification of PTSD. Finally, three different datasets namely the NNE dataset, the FME hospital dataset as well as TIMIT dataset are employed in this paper for PTSD diagnosis. The experimental results revealed that the proposed method attained a superior accuracy of 97% under different PTSD techniques. [ABSTRACT FROM AUTHOR]

With a growing interest on inorganic ceramics based solid-state electrolytes for all-solid-state batteries, there is a need to maximise their density to optimise electrochemical performance and fuel impermeability. In this paper, we demonstrate the sensitivity of terahertz time-domain spectroscopy (THz-TDS) combined with effective medium theory to quantify the porosity or density of sodium superionic conductor (NaSICON)-based solid-state electrolyte (SSEs) pellets prepared at densities in the range of 2.2–2.9 g cm−3, corresponding to 50–90 % relative densities sintered at 900–1150 °C. The results of which, have been validated against complementary Archimedes analysis and mercury porosimetry highlighting the potential of THz-TDS for rapid, contactless, non-destructive electrolyte characterisation. • Demonstrated sensitivity of terahertz radiation to NaSICON-based electrolyte. • NaSICON densities quantified using effective medium theory. • Estimated densities correlates to Archimedes analysis. • Estimated densities agrees with to mercury porosimetry data. [ABSTRACT FROM AUTHOR]