Browsing by Subject "Vibration"

Now showing 1 - 4 of 4

Open Access
Environmental effects on interferometric fiber optic gyroscope performance
(2021-02) Osunluk, Berk
Today main performance limitations for fiber optic gyroscope technology are its sensitivity to temperature fluctuations and vibration. Shupe error is the main error source for both disturbances. We propose an approach to reduce the thermal sensitivity by controlling the strain inhomogeneity through the fiber coil. The approach is based on advanced fiber coil modeling, which is verified by a series of experiments. Vibration is often a neglected disturbance by the researchers as it highly depends on the integrated platform. We propose a model for bias error formation due to optical power fluctuations under vibration. Model is composed of power fluctuation characteristics, spurious rotation rate formation due to mechanical Shupe error, and the suppression of the rotation rate by the closed-loop operation. Lastly, we introduce the concept of angle random walk performance degradation under vibration due to interferogram nonlinearity.
Open Access
Hydrogenation of naphthalene and methylnaphthalene: modeling and spectroscopy
(Elsevier BV, 2002) Sayan, Ş.; Paul, J.
In situ infrared spectra of 1-methylnaphthalene (1-MeNapht)hydrogenation, over sulfided NiMo/Al2O3-TiO2 catalysts, were compared with theoretically derived properties of methylnaphthalene and its bicyclic products: MeDilin, MeTetralin, MeOctalin and MeDecalin, and with conversion data from literature. Comparisons were also made between the un-substituted and methyl-substituted two-rings, and between the 1- and 5-methyl isomers of 1,4-dihydronaphthalene (dilin) and 1,2,3,4-tetrahydronaphthalene (tetralin). IR spectra of MeNapht adsorption, on the sulfided catalyst, were matched with data for adsorption on the catalyst without sulfidation and the empty support. Surface bound MeNapht is observed below 250°C on all catalysts. MeNapht adsorption suppresses OH groups nondiscriminatory on the empty support and the metal loaded catalyst. We relate the results to previous data on the interaction between the supported metal sulfides and titanium modified aluminas. Calculated total energies, and experimentally derived heats of formation, pointed at decahydronaphthalene (decalin) as the dominant product of naphthalene hydrogenation, with tetralin as an abundant intermediate, and dilin and 1,2,3,4,5,6,7,8-octahydronaphthalene (octalin) as short lived transient stages. The spectroscopic modeling showed that the orbital fingerprints of the five bicyclic compounds were not distinctly different, nor more than marginally modified by methyl substitution or isomerization. The only significant difference came at the highest occupied orbital, where a high naphthalene density of states (DoS) overlapped with the valence bands of metal or metal sulfide catalysts. The vibrational bands for naphthalene, dilin, tetralin and octalin were well separated. Octalin and decalin, alone, have similar vibrational spectra. Upheaval of ring degeneracy for methyl-substituted two-ring structures broadened all infrared bands in a characteristic way.
Open Access
Power dissipation analysis in tapping-mode atomic force microscopy
(American Physical Society, 2003) Balantekin, M.; Atalar, Abdullah
In a tapping-mode atomic force microscope, a power is dissipated in the sample during the imaging process. While the vibrating tip taps on the sample surface, some part of its energy is coupled to the sample. Too much dissipated power may mean the damage of the sample or the tip. The amount of power dissipation is related to the mechanical properties of a sample such as viscosity and elasticity. In this paper, we first formulate the steady-state tip-sample interaction force by a simple analytical expression, and then we derive the expressions for average and maximum power dissipated in the sample by means of sample parameters. Furthermore, for a given sample elastic properties we can determine approximately the sample damping constant by measuring the average power dissipation. Simulation results are in close agreement with our analytical approach.
Open Access
Resonant harmonic response in tapping-mode atomic force microscopy
(American Physical Society, 2004) Sahin, O.; Quate, C. F.; Solgaard, O.; Atalar, Abdullah
Higher harmonics in tapping-mode atomic force microscopy offers the potential for imaging and sensing material properties at the nanoscale. The signal level at a given harmonic of the fundamental mode can be enhanced if the cantilever is designed in such a way that the frequency of one of the higher harmonics of the fundamental mode (designated as the resonant harmonic) matches the resonant frequency of a higher-order flexural mode. Here we present an analytical approach that relates the amplitude and phase of the cantilever vibration at the frequency of the resonant harmonic to the elastic modulus of the sample. The resonant harmonic response is optimized for different samples with a proper design of the cantilever. It is found that resonant harmonics are sensitive to the stiffness of the material under investigation.