Flight test of ARINC 741 configuration low gain SATCOM system on Boeing 747-400 aircraft

The Boeing company conducted a flight test of a SATCOM system similar to the ARINC 741 configuration on a production model 747-400. A flight plan was specifically designed to test the system over a wide variety of satellite elevations and aircraft attitudes as well as over land and sea. Interface bit errors, signal quality and aircraft position and navigational inputs were all recorded as a function of time. Special aircraft maneuvers were performed to demonstrate the potential for shadowing by aircraft structures. Both a compass rose test and the flight test indicated that shadowing from the tail is insignificant for the 747-400. However, satellite elevation angles below the aircraft horizon during banking maneuvers were shown to have a significant deleterious effect on SATCOM communications

Applying lean manufacturing initiatives to naval ship repair centers : implementation and lessons learned

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 2004.Includes bibliographical references (p. 58).The United States Navy is under pressure to reduce the cost of fleet maintenance in order to redirect funds for the construction of new ships and submarines. The Navy looks to private industry for process improvement ideas such as the Theory of Constraints, Six Sigma and Lean Manufacturing Principles. This thesis examines the Lean Manufacturing movement in the private sector of ship repair and how it eventually came to government owned ship repair operations. Recent National Ship Research Program (NSRP) initiatives provide shipyards a strategy of how to select areas of an operation for Lean improvements. The Norfolk Naval Shipyard method is a combination of the Theory of Constraints, Six Sigma and Lean Principles called Lean Sigma. The Lean Sigma methodology for planning, executing and sustaining lean improvement and how to measure success with various metrics is presented. Lean Sigma is implemented into the Electric Motor Rewind and Repair Center as a case study. Before and after assessments, lessons learned, and recommendations from the implementation case study are presented.(cont.) Details of the challenges and pitfalls encountered during the Lean Sigma implementation in the areas of culture, budget, management, metrics and cost benefit measurement, are described throughout the test case. In conclusions key elements for successful Lean transformation and a vision for the future Lean Ship Repair Enterprise are presented.by Brian P. Murphy.S.M

Transient Response of Rotor on Rolling-Element Bearings with Clearance

Internal clearance in rolling element bearings is usually present to allow for radial and axial growth of the rotor-bearing system and to accommodate bearing fit-up. The presence of this clearance also introduces a “dead band” into the load-deflection behavior of the bearing. Previous studies demonstrated that the presence of dead band clearance might have a significant effect on synchronous rotor response. In this work, the authors investigate transient response of a rotor supported on rolling element bearings with internal clearance. In addition, the stiffness of the bearings varies nonlinearly with bearing deflection and with speed. Bearing properties were accurately calculated with a state of the art rolling bearing analysis code. The subsequent rotordynamics analysis shows that for rapid acceleration rates the maximum response amplitude may be less than predicted by steady-state analysis. The presence of clearance may shift the critical speed location to lower speed values. The rotor vibration response exhibits subharmonic components which are more prominent with bearing clearance

Transient Response of Rotor on Rolling-Element Bearings with Clearance

Internal clearance in rolling element bearings is usually present to allow for radial and axial growth of the rotor-bearing system and to accommodate bearing fit-up. The presence of this clearance also introduces a “dead band” into the load-deflection behavior of the bearing. Previous studies demonstrated that the presence of dead band clearance might have a significant effect on synchronous rotor response. In this work, the authors investigate transient response of a rotor supported on rolling element bearings with internal clearance. In addition, the stiffness of the bearings varies nonlinearly with bearing deflection and with speed. Bearing properties were accurately calculated with a state of the art rolling bearing analysis code. The subsequent rotordynamics analysis shows that for rapid acceleration rates the maximum response amplitude may be less than predicted by steady-state analysis. The presence of clearance may shift the critical speed location to lower speed values. The rotor vibration response exhibits subharmonic components which are more prominent with bearing clearance

Making the future a reality: Commitment assurances and time investment in daily life

Relatively little is known about how commitment manifests in couples’ everyday lives in a way that orients couples toward their future together. Building on the Investment Model of Commitment, we propose that, in everyday life, individuals with high levels of commitment are more likely to (a) assure their partners about the future of the relationship and (b) behaviorally invest in that future by spending more time in the partner’s presence. Results from a sample of individuals (N = 100) suggest that relationship commitment is associated with greater time investment in the relationship (i.e., time spent with the partner in daily life); results from a second sample of couple members (N = 269) replicate this effect and suggest that relationship commitment is associated with the use of daily assurances, which mediate the relationship between commitment and time spent co-present with the partner