Ab inito calculations of Hubbard parameters for NiO and Gd crystals

In this research the Hubbard parameters have been calculated for NiO and Gd crystals, as two strongly correlated systems with partially full 3d and 4f levels, respectively. The calculations were performed within the density functional theory (DFT) using the augmented plane waves plus the local orbitat (APW+lo) method. We constructed a suitable supercell and found that the Hubbard parameters for the NiO and Gd compounds are equal to 5.9 eV and 5.7 eV, respectively. Our results are in good agreement with experimental data and results of other computational methods. Then we used the obtained parameters to study the structural properties of NiO and Gd by means of LDA+U approximation. Our results calculated by the LDA+U method which are in better agreement with the experiment show a significant improvement compared to the GGA approximation. The result shows that our method for calculating U parameter can be considered as a satisfactory method to study a strongly correlated system

Small satellite modelling and three-axis magnetorquer-based stabilisation using fuzzy logical control

Recently small satellites have become increasingly popular because of their ability to provide educational institutes with the chance to design, construct, and test their spacecraft from beginning to the possible launch due to the low launching cost and development of microelectronics (Figure 1). Clearly, using only electromagnetic coils instead of different types of actuators will serve the purpose of weight reduction where every grams counts. But some restrictions described in the paper limit utilising only “Electromagnetic” actuation for 3D stabilisation and adversely affects the efficiency of the controller. However, there are some theories developed recently that have made the aforementioned purpose feasible. In this paper a new control method based on Fuzzy Logic Control (FLC) is presented that keeps the satellite in desired conditions only by electromagnetic coils. More precisely, an approach of Fuzzy control which is incorporated with electromagnetic actuation is presented for the in-orbit attitude control of a small satellite. The design is developed to stabilize the spacecraft against disturbances with a three-axis stabilizing capability. The paper also describes the required hardware and the design and development of the magnetic torquers.Amirhossein Asadabadi and Amir Anva

Small satellite modelling and attitude control using fuzzy logic

Small satellites have become increasingly popular recently as a means of providing educational institutes with the chance to design, construct, and test their spacecraft from beginning to the possible launch due to the low launching cost. This approach is remarkably cost saving because of the weight and size reduction of such satellites. Weight reduction could be realised by utilising electromagnetic coils solely, instead of different types of actuators. This paper describes the restrictions of using only “Electromagnetic” actuation for 3D stabilisation and how to make the magnetorquer based attitude control feasible using Fuzzy Logic Control (FLC). The design is developed to stabilize the spacecraft against gravity gradient disturbances with a three-axis stabilizing capability.Amirhossein Asadabadi, and Amir Anvarhttp://www.waset.org/journals/waset/v72.ph

Flexural Strength Prediction of Welded Flange Plate Connections Based on Slenderness Ratios of Beam Elements Using ANN

The present study was aimed to investigate the strength and ductility of welded flange plate (WFP) connections. Using the FE method, 52 WFP connections with different beam overall depths and beam flanges/web slenderness ratios were analyzed. Fragility curves indicated that, for a WFP connection which is designed based on the seismic codes, its strength is of more concern than its ductility. In addition, limiting the width-to-thickness ratios of the beam flanges and web plates to 0.3E/fy and 2.45E/fy, respectively, may not always lead to the achievement of adequate connection’s strength and ductility. Proposed theoretical formulas and artificial neural network- (ANN-) based models developed in this study were able to adequately predict the connection strength