Implementation and Use of a Convergence Test for Iterative Wind Tunnel Balance Load Predictions

A modified and extended version of a convergence test for wind tunnel strain-gage balance load iterations was implemented. The test uses an upper bound of the Lipschitz constant to assess convergence characteristics of balance load predictions if the Iterative Method is applied. Convergence is expected within the use envelope of the balance whenever this upper bound is less than the threshold of one. It is explained in great detail how the convergence test can be applied to the two load iteration equation types that are currently being used in the aerospace testing community. In addition, the application of the test to balances with bi-directional output characteristics is discussed. It is also shown how numerical differentiation can be used in order to obtain partial derivatives that are needed for the calculation of the Lipschitz constant. Finally, machine calibration data of NASA's MC60E six-component force balance is selected to demonstrate both implementation and use of the convergence test

Kinetics of exciton photoluminescence in type-II semiconductor superlattices

The exciton decay rate at a rough interface in type-II semiconductor superlattices is investigated. It is shown that the possibility of recombination of indirect excitons at a plane interface essentially affects kinetics of the exciton photoluminescence at a rough interface. This happens because of strong correlation between the exciton recombination at the plane interface and at the roughness. Expressions that relate the parameters of the luminescence kinetics with statistical characteristics of the rough interface are obtained. The mean height and length of roughnesses in GaAs/AlAs superlattices are estimated from the experimental data.Comment: 3 PostScript figure

Interesting magnetic properties of Fe1−x_{1-x}Cox_xSi alloys

Solid solution between nonmagnetic narrow gap semiconductor FeSi and diamagnetic semi-metal CoSi gives rise to interesting metallic alloys with long-range helical magnetic ordering, for a wide range of intermediate concentration. We report various interesting magnetic properties of these alloys, including low temperature re-entrant spin-glass like behaviour and a novel inverted magnetic hysteresis loop. Role of Dzyaloshinski-Moriya interaction in the magnetic response of these non-centrosymmetric alloys is discussed.Comment: 11 pages and 3 figure

GATAC - A generic framework for multi-parameter optimization of flight trajectories

Simulations in different scenarios requires the use of various models, the interfacing of which typically requires extensive effort and programming resources that may not be readily available in most industrial and academic environments. This paper discusses the development of GATAC - a generic framework that was developed for simulation and multiparameter optimization purposes allowing users to easily set up a simulation by making use of models developed using different technologies with different interfaces.peer-reviewe

A flexible framework for configurable real-time flight simulators

This paper presents the design and development of a Simulation and Integration Framework for use in research and teaching simulators. The design of the framework facilitates the integration of different simulation models of various formats without the need of software programming skills in a simulation environment. This is achieved through a Graphical User Interface (GUI) allowing the user to easily set up a flight simulator utilizing models programmed in different languages and having different interfaces. The framework allows for dynamic parallel processing over a distributed system providing the capability of concurrent model processing.peer-reviewe

Design and validation of a detailed aircraft performance model for trajectory optimisation

A key component in flight optimization studies is the aircraft performance model. This must be capable of representing to a high degree of fidelity the performance of the aircraft over its typical flight envelope if meaningful conclusions are to be made from the optimization studies. Flexibility is also required in order to facilitate robust trajectory definition and interoperability with secondary multidisciplinary tools. This paper describes the structure and main features of an Aircraft Performance Model (APM) specifically designed for use within a multi-disciplinary optimization environment. A validation exercise has been carried out against data generated with another aircraft performance model designed using the Base of Aircraft Data coefficients. Climb, cruise and descent phases have been investigated for the comparison. The performance of the aircraft predicted by the two models has been compared and found to compare well, with most cases resulting in less than a 0.5% mean variation between the two models.peer-reviewe

Trailblazer: Proof of Concept CubeSat Mission for SPA-1

The Space Plug-and-play Architecture (SPA) concept of rapid satellite development has progressed exponentially over the past several years. The team at the Configurable Space Microsystems Innovations and Applications Center (COSMIAC) in conjunction with the Space Dynamics Laboratory (SDL) and the Air Force Research Laboratory have trained over 500 individuals on this rapid bus architecture related to satellite development. This paper will outline the first CubeSat satellite proof of concept flight for a SPA only spacecraft. The Trailblazer mission is designed to fly a 1U CubeSat that is based entirely on a SPA bus implementation. Trailblazer will consist of Commercial Off The Shelf (COTS) parts converted to be SPA compliant. This allows not only a demonstration of the bus reliability in a space environment, but also the ease in converting existing components to be SPA compliant. With the dimensional constraints and power budget of Trailblazer, we have elected to use the SPA-1 standard. SPA-1 is the most recent addition to the AFRL SPA family. The SPA-1 data transfer protocol is based on 400 kbit/s I2C making it the lowest power, and lowest bandwidth option for SPA. Given the power constraints of typical satellite architecture, it is generally advantageous to interface devices/modules which do not require high data transfer rates to a SPA network via the SPA-1 Applique Sensor Interface Module (ASIM). This ASIM is logic that enables SPA Plug-and-Play for hardware components. It contains all the information needed for the system to automatically discover and automatically configure the hardware component. SPA-1 ASIMs can be any microcontroller that supports I2C and has enough memory to contain the needed logic. This allows the standard to remain open to a variety of dynamic implementations. The Trailblazer mission is being launched under the National Aeronautics and Space Administration (NASA) Educational Launch of Nanosatellite (ELaNA) program. This NASA program is designed to provide affordable access to space through collaborative efforts with academic institutions. The ELaNA program provides manifesting and launch of CubeSats for $30,000 per 1U module. The proposed orbit is 325 km with an inclination of 51 degrees for a launch in 2011