Current Issue : October - December Volume : 2013 Issue Number : 4 Articles : 5 Articles
Piezoelectric transducers have a long history of applications in nondestructive evaluation of material and structure integrity owing\r\nto their ability of transformingmechanical energy to electrical energy and vice versa. As condition basedmaintenance has emerged\r\nas a valuable approach to enhancing continued aircraft airworthiness while reducing the life cycle cost, its enabling structural\r\nhealth monitoring (SHM) technologies capable of providing on-demand diagnosis of the structure without interrupting the aircraft\r\noperation are attracting increasing R&D efforts. Piezoelectric transducers play an essential role in these endeavors. This paper is\r\nset forth to review a variety of ingenious ways in which piezoelectric transducers are used in today�s SHM technologies as a means\r\nof generation and/or detection of diagnostic acoustic waves....
Stationary plasma thrusters are attractive electric propulsion systems for spacecrafts. The usual propellant is xenon. Among the\r\nother suggested propellants, krypton could be one of the best candidates. Most studies have been carried out with a Hall effect\r\nthruster previously designed for xenon.TheATONA-3 developed byMSTUMIREA (Moscow) initially defined for xenon has been\r\noptimized for krypton.The stable high-performanceATONA-3 operation inKr has been achieved after optimization of its magnetic\r\nfield configuration and its optimization in different parameters: length and width of the channel, buffer volume dimensions, mode\r\nof the cathode operation, and input parameters. For a voltage of 400V and the anode mass flow rate of 2.5mg/s the anode efficiency\r\nreaches 60% and the specific impulse reaches 2900 s under A-3 operating with Kr.The achieved performances under operation A-3\r\nwith Kr are presented and compared with performances obtained with Xe....
Bird impact poses serious threats to military and civilian aircrafts as they lead to fatal structural damage to critical aircraft\r\ncomponents. The exposed aircraft components such as windshields, radomes, leading edges, engine structure, and blades are\r\nvulnerable to bird strikes. Windshield is the frontal part of cockpit and more susceptible to bird impact. In the present study,\r\nfinite element (FE) simulations were performed to assess the dynamic response of windshield against high velocity bird impact.\r\nNumerical simulationswere performed by developing nonlinear FEmodel in commercially available explicit FE solverAUTODYN.\r\nAn elastic-plastic material model coupled with maximum principal strain failure criterion was implemented to model the impact\r\nresponse of windshield. Numerical model was validated with published experimental results and further employed to investigate\r\nthe influence of various parameters on dynamic behavior of windshield. The parameters include the mass, shape, and velocity of\r\nbird, angle of impact, and impact location. On the basis of numerical results, the critical bird velocity and failure locations on\r\nwindshield were also determined.The results show that these parameters have strong influence on impact response of windshield,\r\nand bird velocity and impact angle were amongst the most critical factors to be considered in windshield design....
This paper focuses on a hardware-in-the-loop facility aimed at real-time testing of architectures and algorithms of multisensor\r\nsense and avoid systems. It was developed within a research project aimed at flight demonstration of autonomous non-cooperative\r\ncollision avoidance for Unmanned Aircraft Systems. In this framework, an optionally piloted Very Light Aircraft was used as\r\nexperimental platform. The flight system is based onmultiple-sensor data integration and it includes a Ka-band radar, four electrooptical\r\nsensors, and two dedicated processing units. The laboratory test system was developed with the primary aim of prototype\r\nvalidation before multi-sensor tracking and collision avoidance flight tests. System concept, hardware/software components, and\r\noperating modes are described in the paper. The facility has been built with a modular approach including both flight hardware\r\nand simulated systems and can work on the basis of experimentally tested or synthetically generated scenarios. Indeed, hybrid\r\noperating modes are also foreseen which enable performance assessment also in the case of alternative sensing architectures and\r\nflight scenarios that are hardly reproducible during flight tests. Real-time multisensor tracking results based on flight data are\r\nreported, which demonstrate reliability of the laboratory simulation while also showing the effectiveness of radar/electro-optical\r\nfusion in a non-cooperative collision avoidance architecture....
As the Automatic Dependent Surveillance-Broadcast (ADS-B) system has gained wide acceptance, additional exploitations of\r\nthe radioed satellite-based information are topics of current interest. One such opportunity includes the augmentation of the\r\ncommunication ADS-B signal with a random biphase modulation for concurrent use as a radar signal. This paper addresses the\r\nformulation and analysis of a suitable noncooperativemultitarget tracking method for the ADS-B radar system using radar ranging\r\ntechniques and particle filter algorithms. In addition, the low-update-rate measurement due to the ADS-B system specification is\r\ndiscussed in order to provide acceptable estimation results. Simulation results show satisfactory tracking capability up to several\r\nkilometers with acceptable accuracy....
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