Quaternary pulse position modulation electronics for free-space laser communications

The development of a high data-rate communications electronic subsystem for future application in free-space, direct-detection laser communications is described. The dual channel subsystem uses quaternary pulse position modulation (QPPM) and operates at a throughput of 650 megabits per second. Transmitting functions described include source data multiplexing, channel data multiplexing, and QPPM symbol encoding. Implementation of a prototype version in discrete gallium arsenide logic, radiofrequency components, and microstrip circuitry is presented

Providing Attorneys for Children in Dependency and Termination of Parental Rights Proceedings in Florida: The Issue Updated

Florida\u27s system for providing protection and safety to children in the State\u27s child welfare system has changed over the past decade. Regretfully, the changes do not appear to have had a significant impact in two areas: increasing the safety and protection of children in the system\u27 and providing children with independent attorneys to advocate on their behalf. Investigations, lawsuits, grand juries, amendments to court rules, and newspaper articles continue to demonstrate the myriad failures in the Florida system. Two notorious examples hi-lite the shortcomings: the cases of the foster child, Rilya Wilson, who disappeared in 2001, and Gabriel Myers, who was found dead by hanging in his foster home in 2008. Rilya Wilson\u27s disappearance produced articles around the country and a detailed investigation which has exposed serious flaws in Florida\u27s child welfare system. The Wilson case produced legislation, the Rilya Wilson Act, which requires coordination between the Department of Children and Families (DCF) and community-based providers with local school readiness coalitions and licensed early education child care providers. The Act also dramatically increased the prominence and significance of the role of the Guardian Ad Litern Program (GAL Program)

Ultra high bypass Nacelle aerodynamics inlet flow-through high angle of attack distortion test

A flow-through inlet test program was conducted to evaluate inlet test methods and determine the impact of the fan on inlet separation when operating at large angles of attack. A total of 16 model configurations of approximately 1/6 scale were tested. A comparison of these flow-through results with powered data indicates the presence of the fan increased separation operation 3 degrees to 4 degrees over the flow through inlet. Rods and screens located at the fan face station, that redistribute the flow, achieved simulation of the powered-fan results for separation angle of attack. Concepts to reduce inlet distortion and increase angle of attack capability were also evaluated. Vortex generators located on the inlet surface increased inlet angle of attack capability up to 2 degrees and reduced inlet distortion in the separated region. Finally, a method of simulating the fan/inlet aerodynamic interaction using blockage sizing method has been defined. With this method, a static blockage device used with a flow-through model will approximate the same inlet onset of separation angle of attack and distortion pattern that would be obtained with an inlet model containing a powered fan

JT9D engine diagnostics. Task 2: Feasibility study of measuring in-service flight loads

The feasibility of measuring JT9D propulsion system flight inertia loads on a 747 airplane is studied. Flight loads background is discussed including the current status of 747/JT9D loads knowledge. An instrumentation and test plan is formulated for an airline-owned in-service airplane and the Boeing-owned RA001 test airplane. Technical and cost comparisons are made between these two options. An overall technical feasibility evaluation is made and a cost summary presented. Conclusions and recommendations are presented in regard to using existing inertia loads data versus conducting a flight test to measure inertia loads

Expanded study of feasibility of measuring in-flight 747/JT9D loads, performance, clearance, and thermal data

The JT9D jet engine exhibits a TSFC loss of about 1 percent in the initial 50 flight cycles of a new engine. These early losses are caused by seal-wear induced opening of running clearances in the engine gas path. The causes of this seal wear have been identified as flight induced loads which deflect the engine cases and rotors, causing the rotating blades to rub against the seal surfaces, producing permanent clearance changes. The real level of flight loads encountered during airplane acceptance testing and revenue service and the engine's response in the dynamic flight environment were investigated. The feasibility of direct measurement of these flight loads and their effects by concurrent measurement of 747/JT9D propulsion system aerodynamic and inertia loads and the critical engine clearance and performance changes during 747 flight and ground operations was evaluated. A number of technical options were examined in relation to the total estimated program cost to facilitate selection of the most cost effective option. It is concluded that a flight test program meeting the overall objective of determining the levels of aerodynamic and inertia load levels to which the engine is exposed during the initial flight acceptance test and normal flight maneuvers is feasible and desirable. A specific recommended flight test program, based on the evaluation of cost effectiveness, is defined

Computational Study of Fatigue Fracture in Rivet Housing of an Aeronautical Aluminum Alloy 7075-T6

This article describes computerized traction testing through the ANSYS software in aircraft materials, aluminum 7075-T6, which leads to variations of the strength limits with the stress concentration factor in the rivet cavity. However, was performed with a change in the radius of transition from the head to the body of the rivet in order to alleviate the stress concentrations within the rivet bore and improve the strength of the part by 5.25% with no relevant change in part displacement. The fatigue strength limit was higher in the samples without of the burr operation, observing that the geometric trunk of the section generated a decrease of 18.27% in the maximum plate stresses, with better uniformity in the tension distribution of the rivets, with a displacement of 3.125% and a minimum equivalent stress of 2.39% and a maximum of 24%, justifying the cause of the fracture in the riveting region

Combinatorial pulse position modulation for power-efficient free-space laser communications

A new modulation technique called combinatorial pulse position modulation (CPPM) is presented as a power-efficient alternative to quaternary pulse position modulation (QPPM) for direct-detection, free-space laser communications. The special case of 16C4PPM is compared to QPPM in terms of data throughput and bit error rate (BER) performance for similar laser power and pulse duty cycle requirements. The increased throughput from CPPM enables the use of forward error corrective (FEC) encoding for a net decrease in the amount of laser power required for a given data throughput compared to uncoded QPPM. A specific, practical case of coded CPPM is shown to reduce the amount of power required to transmit and receive a given data sequence by at least 4.7 dB. Hardware techniques for maximum likelihood detection and symbol timing recovery are presented