Analytical and flight investigation of the influence of rotor and other high-order dynamics on helicopter flight-control system bandwidth

The increasing use of highly augmented digital flight-control systems in modern military helicopters prompted an examination of the influence of rotor dynamics and other high-order dynamics on control-system performance. A study was conducted at NASA Ames Research Center to correlate theoretical predictions of feedback gain limits in the roll axis with experimental test data obtained from a variable-stability research helicopter. Feedback gains, the break frequency of the presampling sensor filter, and the computational frame time of the flight computer were systematically varied. The results, which showed excellent theoretical and experimental correlation, indicate that the rotor-dynamics, sensor-filter, and digital-data processing delays can severely limit the usable values of the roll-rate and roll-attitude feedback gains

Further analysis of field effects on liquids and solidification

Numerical calculations of the magnitude of external field effects on liquids are presented to describe how external fields can influence the substructure of the field. Quantitative estimates of magnetic and gravitational effects are reported on melts of metals and semiconductors. The results are condensed in tables which contain the input data for calculation of the field effects on diffusion coefficient, solidification rate and for calculation of field forces on individual molecules in the melt

Perfluoro (Imidoylamidine) diamidines

Perfluoroether triazine elastomers having improved properties are prepared from oligomeric imidoylamidines that were in turn, prepared by the process of: (1) reacting a perfluorodinitrile with liquid ammonia to yield a perfluorodiamidine, (2) isolating the perfluorodiamidine, (3) reacting the isolated diamidine with a perfluorodinitrile to yield a perfluoro(imidoylamidine) dinitrile, and then repeating the steps to sequentially grow an oligomer of desired molecular size. The isolated amidine and nitrile intermediates are also disclosed. The elastomers can be fashioned into seals, gaskets, and sealing components and the like

Adsorption/desorption and electrically controlled flipping of ammonia molecules on graphene

In this paper, we evaluate of the adsorption/ desorption of ammonia molecules on a graphene surface by studying the Fermi level shift. Based on a physically plausible model, the adsorption and desorption rates of ammonia molecules on graphene have been extracted from the measured Fermi level shift as a function of exposure time. An electric field-induced flipping behavior of ammonia molecules on graphene is suggested, based on field effect transistor (FET) measurements

Process for preparing perfluorotriazine elastomers and precursors thereof

Perfluoroether triazine elastomers having improved properties and utility in seals, gaskets, sealing components and the like are prepared from oligomeric imidoylamidines that have, in turn, been prepared by the process of (1) reacting a perfluorodinitrile with liquid ammonia to yield a perfluorodiamidine, (2) isolating the perfluorodiamidine, (3) reacting the isolated diamidine with a perfluorodinitrile to yield a perfluoror(imidoylamidine) dinitrile, and then repeating step (1), (2), and (3) to sequentially grow an oligomer of desired molecular size. The isolated amidine and nitrile intermediates are also described

Building a 3.5 m prototype interferometer for the Q & A vacuum birefringence experiment and high precision ellipsometry

We have built and tested a 3.5 m high-finesse Fabry-Perot prototype inteferometer with a precision ellipsometer for the QED test and axion search (Q & A) experiment. We use X-pendulum-double-pendulum suspension designs and automatic control schemes developed by the gravitational-wave detection community. Verdet constant and Cotton-Mouton constant of the air are measured as a test. Double modulation with polarization modulation 100 Hz and magnetic-field modulation 0.05 Hz gives 10^{-7} rad phase noise for a 44-minute integration.Comment: This draft has been presented in the 5th Edoardo Amaldi Conference on Gravitational Wave

Non-ancient solution of the Ricci flow

For any complete noncompact K$\ddot{a}$hler manifold with nonnegative and bounded holomorphic bisectional curvature,we provide the necessary and sufficient condition for non-ancient solution to the Ricci flow in this paper.Comment: seven pages, latex fil

Non-exponential kinetic behavior of confined water

We present the results of molecular dynamics simulations of SPC/E water confined in a realistic model of a silica pore. The single-particle dynamics have been studied at ambient temperature for different hydration levels. The confinement near the hydrophilic surface makes the dynamic behaviour of the liquid strongly dependent on the hydration level. Upon decrease of the number of water molecules in the pore we observe the onset of a slow dynamics due to the ``cage effect''. The conventional picture of a stochastic single-particle diffusion process thus looses its validity