1,657 research outputs found
Advanced Rotorcraft Transmission (ART) program summary
The Advanced Rotorcraft Transmission (ART) Program was initiated to advance the state of the art for rotorcraft transmissions. The goal of the ART Program was to develop and demonstrate the technologies needed to reduce transmission weight by 25 pct. and reduce noise by 10 dB while obtaining a 5000 hr 'mean time between failure'. The research done under the ART Program is summarized. A split path design was selected as best able to meet the program goals. Key part technologies needed for this design were identified, studied, and developed. Two of these technologies are discussed in detail: the load sharing of split path designs including the use of a compliant elastomeric torque splitter and the application of a high ratio, low pitch line velocity gear mesh. Development of an angular contact spherical roller bearing, transmission error analysis, and fretting fatigue testing are discussed. The technologies for a light weight, quiet, and reliable rotorcraft transmission were demonstrated
Spectra for the product of Gaussian noises
Products of Gaussian noises often emerge as the result of non-linear
detection techniques or as a parasitic effect, and their proper handling is
important in many practical applications, including in fluctuation-enhanced
sensing, indoor air or environmental quality monitoring, etc. We use Rice's
random phase oscillator formalism to calculate the power density spectra
variance for the product of two Gaussian band-limited white noises with
zero-mean and the same bandwidth W. The ensuing noise spectrum is found to
decrease linearly from zero frequency to 2W, and it is zero for frequencies
greater than 2W. Analogous calculations performed for the square of a single
Gaussian noise confirm earlier results. The spectrum at non-zero frequencies,
and the variance of the square of a noise, is amplified by a factor two as a
consequence of correlation effects between frequency products. Our analytic
results is corroborated by computer simulations.Comment: submitted for publicatio
Split torque transmission load sharing
Split torque transmissions are attractive alternatives to conventional planetary designs for helicopter transmissions. The split torque designs can offer lighter weight and fewer parts but have not been used extensively for lack of experience, especially with obtaining proper load sharing. Two split torque designs that use different load sharing methods have been studied. Precise indexing and alignment of the geartrain to produce acceptable load sharing has been demonstrated. An elastomeric torque splitter that has large torsional compliance and damping produces even better load sharing while reducing dynamic transmission error and noise. However, the elastomeric torque splitter as now configured is not capable over the full range of operating conditions of a fielded system. A thrust balancing load sharing device was evaluated. Friction forces that oppose the motion of the balance mechanism are significant. A static analysis suggests increasing the helix angle of the input pinion of the thrust balancing design. Also, dynamic analysis of this design predicts good load sharing and significant torsional response to accumulative pitch errors of the gears
Fluctuation-enhanced sensing
We present a short survey on fluctuation-enhanced gas sensing. We compare
some of its main characteristics with those of classical sensing. We address
the problem of linear response, information channel capacity, missed alarms and
false alarms.Comment: Keynote Talk at SPIE's 4th international symposium on Fluctuations
and Noise, Conference Noise and Fluctuations in Circuits, Devices and
Materials, Florence, Italy, May 20-24, 200
Current and voltage based bit errors and their combined mitigation for the Kirchhoff-law-Johnson-noise secure key exchange
We classify and analyze bit errors in the current measurement mode of the
Kirchhoff-law-Johnson-noise (KLJN) key distribution. The error probability
decays exponentially with increasing bit exchange period and fixed bandwidth,
which is similar to the error probability decay in the voltage measurement
mode. We also analyze the combination of voltage and current modes for error
removal. In this combination method, the error probability is still an
exponential function that decays with the duration of the bit exchange period,
but it has superior fidelity to the former schemes.Comment: 9 pages, accepted for publication in Journal of Computational
Electronic
- …