Advanced transmission studies

The NASA Lewis Research Center and the U.S. Army Aviation Systems Command share an interest in advancing the technology for helicopter propulsion systems. In particular, this paper presents highlights from that portion of the program in drive train technology and the related mechanical components. The major goals of the program are to increase the life, reliability, and maintainability; reduce the weight, noise, and vibration; and maintain the relatively high mechanical efficiency of the gear train. The current activity emphasizes noise reduction technology and analytical code development followed by experimental verification. Selected significant advances in technology for transmissions are reviewed, including advanced configurations and new analytical tools. Finally, the plan for future transmission research is presented

Thinking the Anthropocene

This editorial gives a short introduction to the different strands of the Anthropocene and ties together the contributions of this Special Issue

How to have a successful educational meeting on a public issue

"Revised 1/83/2M""Citizens have the duty and opportunity to help make many group decisions about complex issues. Group decisions are those in which two or more people have a voice or vote. The decision may affect one or more persons individually or as a group. The group decision may be of a local nature such as a change in school tax, or a state problem such as water legislation, or a national issue such as commodity referendum. Increasingly there are issues that relate to broad national programs such as energy, international trade or other complex subjects about which there must be broad public support before much can be accomplished by legislation."--First page.So

Identification and proposed control of helicopter transmission noise at the source

Helicopter cabin interiors require noise treatment which is expensive and adds weight. The gears inside the main power transmission are major sources of cabin noise. Work conducted by the NASA Lewis Research Center in measuring cabin interior noise and in relating the noise spectrum to the gear vibration of the Army OH-58 helicopter is described. Flight test data indicate that the planetary gear train is a major source of cabin noise and that other low frequency sources are present that could dominate the cabin noise. Companion vibration measurements were made in a transmission test stand, revealing that the single largest contributor to the transmission vibration was the spiral bevel gear mesh. The current understanding of the nature and causes of gear and transmission noise is discussed. It is believed that the kinematical errors of the gear mesh have a strong influence on that noise. The completed NASA/Army sponsored research that applies to transmission noise reduction is summarized. The continuing research program is also reviewed

Computerized inspection of gear tooth surfaces

An approach is proposed that uses coordinate measurements of the real surface of spiral bevel gears to determine the actual machine tool setting applied during the gear manufacturing process. The deviations of the real surface from the theoretical one are also determined. Adjustments are then applied by machine tool corrections to minimize these surface deviations. This is accomplished by representing the real surface analytically in the same Gaussian coordinates as the theoretical surface

Elucidation of the functional role of oligopeptide transporters in bacterial virulence

Abstract only availableThe oligopeptide transporter (OPT) family is a relatively poorly characterized family of peptide/modified peptide transporters found in archebacteria, bacteria, fungi and plants. Plant and yeast OPTs were shown to transport tetra- and pentapeptides as well as the modified peptide glutathione. Our database analysis of sequenced bacterial genomes indicated that OPT proteins are encoded in the genomes of important human pathogens such as Pseudomonas aeruginosa, Mycobacterium tuberculosis, Neisseria meningitidis, and Haemophilus influenzae. However, functional analysis of this family of peptide transporters, especially their possible function in bacterial pathogenesis, is lacking. We obtained three P. aeruginosa strains harboring transposon insertions in the PA3934 locus, the gene predicted to encode the putative orthologous OPT protein (OptA) in P. aeruginosa PA01. Two of the optA mutant strains have in-frame fusion between PaOptA and the PhoA protein encoded within the transposon. Expression of OptA-PhoA is induced by the addition of 20 mM arginine, whereas the expression of OptA-PhoA is not affected by iron availability. The lack of iron-regulated expression of optA would indicate that it is unlikely involved in iron nutrition in P. aeruginosa. We also found that 20 mM arginine and 0.4% peptone enhanced biofilm formation by wild type PA01 strain. However, enhanced biofilm formation by arginine was not observed in the optA mutant strains. Addition of 20 mM lysine had no effect on biofilm formation. We also determined the possible function of OptA in the ability of P. aeruginosa to produce pyocyanin. We found that the optA mutant strains produced higher amounts of pyocyanin than the wild type strain. The presence or absence of arginine in the growth medium had no effect on pyocyanin production. Taken together, these results indicate that OptA is important for biofilm formation by P. aeruginosa in response to arginine and peptides, but is unlikely involved in pyocyanin production.NSF grant to G. Stace

Functional/thermal verification and validation of an S-band radio for the nanosatellites

© 2018 COSPAR An S-band radio designed with commercial-grade components for the nanosatellites is functionally and thermally characterized for quiet transmission. The QPSK modulation impairments are minor over −20 °C to +50 °C at 24, 26, 28 and 30 dBm RF levels. The channel response is linear in error vector magnitude, frequency, phase, amplitude and IQ errors. On the average, the stability of amplifier bias and nonlinearity gives −22 dBc maximum upper/lower adjacent channel power and 1.27 MHz occupied channel bandwidth. The acceptable level test results provide good confidence toward robust space-to-earth transmission in variable solar weather at low earth orbital altitudes

SEU Performance of TAG Based Flip Flops

We describe heavy ion test results for two new SEU tolerant latches based on transition nand gates, one for single rail asynchronous and the other for dual rail synchronous designs, implemented in AMI 0.5microprocess

Integration of the Cimosa and high-level coloured Petri net modelling techniques with application in the postal process using hierarchical dispatching rules

Enterprise processes, i.e. business and manufacturing, rely on enterprise modelling and simulation tools to assess the quality of their structure and performance in an unobtrusive and cost-effective way. Each of these processes is a collaboration of inseparable elements such as resources, information, operations, and organization. In order to provide a more complete assessment of enterprise processes, a simulation approach that allows communication and interaction among these elements needs to be provided. The simulation approach requires an analysis of the performance of each element and its influence on other elements in an object-oriented way. It also needs to have the capability to represent the structures and dynamics of the elements mentioned, and to present the performance assessment comprehensively. This will ensure a more holistic simulation modelling task. These simulation requirements have motivated the investigation of the novel integration of two popular enterprise process modelling methods: Cimosa and high-level coloured Petri net. The Cimosa framework is used to formalize the enterprise modelling procedure in the aspects of representing process elements, structure, behaviours, and relationships. The high-level coloured Petri nets method provides the mechanism to simulate the dynamics of objects and their characteristics, and also to enable communication among the objects. The approach is applied on a postal process model, which involves elements from manufacturing processes, i.e. machine processing (sorting), inventory (storage), product flow, and resource planning. Simulation studies based on the hierarchical dispatching rules show that the integrated approach is able to present vital information regarding the communication method, resource management, and the effect of interactions among these manufacturing process elements, which are not provided by the current modelling system in the postal company. The current paper has presented a novel mechanism, i.e. Cimosa—HCTSPN modelling approach, to extract information on process elements and their interactions. It has also presented the novel hierarchical dispatching rules and contributed to the extension of information that can be represented for a postal process