Comparison of peak characteristics of F2 ionospheric layer over Tehran region at a low solar activity period with IRI-2001 and IRI-2007 models predictions

In the present work values of peak electron density (NmF2) and height of F2 ionospheric layer (hmF2) over Tehran region at a low solar activity period are compared with the predictions of the International Reference Ionosphere models (IRI-2001 and IRI-2007). Data measured by a digital ionosonde at the ionospheric station of the Institute of Geophysics, University of Tehran from July 2006 to June 2007 are used to perform the calculations. Formulations proposed by  and  are utilized to calculate the hmF2. The International Union of Radio Science (URSI) and International Radio Consultative Committee (CCIR) options are employed to run the IRI-2001 and IRI-2007 models. Results show that both IRI-2007 and IRI-2001 can successfully predict the NmF2 and hmF2 over Tehran region. In addition, the study shows that predictions of IRI-2007 model with CCIR coefficient has closer values to the observations. Furthermore, it is found that the monthly average of the percentage deviation between the IRI models predictions and the values of hmF2 and NmF2 parameters are less than 10% and 21%, respectively.     

Design and fabrication of robotic gripper for grasping in minimizing contact force

This paper presents a new method to improve the kinematics of robot gripper for grasping in unstructured environments, such as space operations. The robot gripper is inspired from the human hand and kept the hand design close to the structure of human fingers to provide successful grasping capabilities. The main goal is to improve kinematic structure of gripper to increase the grasping capability of large objects, decrease the contact forces and makes a successful grasp of various objects in unstructured environments. This research will describe the development of a self-adaptive and reconfigurable robotic hand for space operations through mechanical compliance which is versatile, robust and easy to control. Our model contains two fingers, two-link and three-link, with combining a kinematic model of thumb index. Moreover, some experimental tests are performed to examine the effectiveness of the hand-made in real, unstructured tasks. The results represent that the successful grasp range is improved about 30% and the contact forces is reduced approximately 10% for a wide range of target object size. According to the obtained results, the proposed approach provides an accommodative kinematic model which makes the better grasping capability by fingers geometries for a robot gripper.